UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2023

OR

Commission File Number 001-39661

ATEA PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its Charter)

Registrant’s telephone number, including area code: (857) 284-8891

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. YES ☐ No ☒

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. YES ☐ No ☒

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ NO ☐

Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ NO ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☐

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant's executive officers during the relevant recovery period pursuant to §240.10D-1(b). ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). YES ☐ NO ☒

As of June 30, 2023, the aggregate market value of the voting and non-voting common equity held by non-affiliates of the registrant, based on the last reported sales price for the registrant’s common stock, par value $0.001 per share, on the Nasdaq Global Select Market on such date, was approximately $283.7 million.

The number of shares of Registrant’s Common Stock outstanding as of February 25, 2024 was 84,164,545.

Table of Contents

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K contains forward-looking statements. We make such forward-looking statements pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 and other federal securities laws. Forward-looking statements are neither historical facts nor assurances of future performance. Instead, they are based on our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, our clinical development timelines and results and other future conditions. The words “aim,” “anticipate,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “goal,” “intend,” “may,” "objective," "on track," “plan,” “possible,” “potential,” “predict,” “project,” “seek,” “should,” “target,” “will,” “would” or the negative of these terms or other similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.

These forward-looking statements include, among other things, statements about:

These forward-looking statements are based on management’s current expectations, estimates, forecasts and projections about our business and the industry in which we operate. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements. Factors that may cause actual results to differ materially from current expectations include the initiation, execution

and completion of clinical trials, uncertainties surrounding the timing of availability of data from our clinical trials, ongoing discussions with and actions by regulatory authorities, our development activities and those other factors we discuss in Part I, Item 1A. “Risk Factors.” You should read these risk factors and the other cautionary statements made in this report as being applicable to all related forward-looking statements wherever they appear in this report. The risk factors are not exhaustive and other sections of this report may include additional factors which could adversely impact our business and financial performance.

Drug development and commercialization involve a high degree of risk, and only a small number of research and development programs result in commercialization of a product. Preliminary and interim results from any trial and results in early-stage clinical trials may not be indicative of full results or results from later stage or larger scale clinical trials and do not ensure regulatory approval. Moreover, we operate in a very competitive and rapidly changing environment. New risk factors emerge from time to time, and it is not possible for our management to predict all risk factors nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in, or implied by, any forward-looking statements.

Given these uncertainties, you should not rely on these forward-looking statements as predictions of future events. Except as required by law, we assume no obligation to update or revise these forward-looking statements for any reason, even if new information becomes available in the future.

As used in this Annual Report on Form 10-K, unless otherwise specified or the context otherwise requires, the terms “we,” “our,” “us,” and the “Company” refer to Atea Pharmaceuticals, Inc. and its subsidiary. All brand names or trademarks appearing in this Annual Report on Form 10-K are the property of their respective owners.

SUMMARY RISK FACTORS

Our business is subject to numerous risks and uncertainties, including those described in Part I, Item 1A. “Risk Factors” in this Annual Report on Form 10-K. The principal risks and uncertainties affecting our business include the following:

PART I

Item 1. Business.

Overview

We are a clinical-stage biopharmaceutical company leveraging our deep understanding of antiviral drug development, medicinal chemistry, biology, biochemistry and virology to discover and develop novel orally administered product candidates to treat serious viral diseases. Currently, we are developing our lead product candidate, bemnifosbuvir, in a global Phase 3 clinical trial as a monotherapy for the treatment of COVID-19, and in a global Phase 2 clinical trial as part of a combination therapy with ruzasvir, an NS5A inhibitor, for the treatment of HCV infection.

Bemnifosbuvir

Derived from our internal discovery program, bemnifosbuvir (AT-527), is an investigational, novel, orally administered guanosine nucleotide analog polymerase inhibitor that combines a unique nucleotide scaffold with novel double prodrugs for the intended purpose of inhibiting the enzymes central to viral replication. We believe that utilizing this double prodrug moiety approach allows us to maximize formation of the active metabolite potentially resulting in an oral antiviral product candidate that is selective for and highly effective at preventing replication and transcription of SARS-CoV-2, the causative agent of COVID-19, HCV and other single stranded RNA (“ssRNA”) viruses while avoiding toxicity to host cells.

COVID-19 – Our Strategy and Objective

More than four years after emerging as a global pandemic and public health crisis, COVID-19 remains a persistent and serious health threat because of continued variant fueled surges of infection. The SARS-CoV-2 virus is accumulating mutations with amino acid substitutions faster than any other endemic ssRNA virus and the constant evolution of new variants has resulted in continued waves of infections globally.

Our COVID-19 strategy is focused on the development of bemnifosbuvir for the treatment of COVID-19. We believe that oral antivirals protecting against the development of severe infection and transmission remain urgently needed particularly for high-risk patients who currently have few or no treatment options due to limitations of currently available vaccines and therapeutics. High-risk patients include those who are unvaccinated, patients who fail to respond to available vaccines, vaccinated patients with waning efficacy, which can occur between three to six months after immunization, and patients for whom current treatments are contraindicated. Without suitable treatments, high-risk patients remain vulnerable to severe COVID-19 and associated hospitalization and death.

As COVID-19 continues to persist as a global endemic disease, we believe that the global COVID-19 therapeutic market, and in particular the US market, will remain a multi-billion-dollar commercial opportunity for many years to come. Further, as the commercialization of COVID-19 therapeutics enters more fully into traditional distribution and reimbursement channels in 2024 and after, we anticipate that a major consideration for third-party payers will be a cost/value analysis that is driven in part by the economic burden of hospitalization, especially for high-risk populations.

The objective of our COVID-19 development program is to address the current unmet medical needs of high-risk patients who remain vulnerable to hospitalization and death from COVID-19 by developing bemnifosbuvir, as a safe, effective, convenient, oral antiviral without the key limitations of current treatment options, including drug-drug interactions, tolerability and other safety concerns. The FDA has granted Fast Track designation for the investigation of bemnifosbuvir to treat COVID-19. Currently, we are evaluating bemnifosbuvir in SUNRISE-3, a global Phase 3 clinical trial that is enrolling high-risk patients with mild to moderate COVID-19.

For COVID-19, bemnifosbuvir targets the SARS-CoV-2 RNA polymerase (Nsp12), a highly conserved enzyme that is unlikely to change as the virus mutates and new variants continue to emerge. The RNA polymerase complex is responsible for both replication and transcription of SARS-CoV-2. Bemnifosbuvir

has a unique dual mechanism of action at both the RNA-dependent RNA polymerase ("RdRp") and nidovirus RdRp associated nucleotidyltransferase ("NiRAN") active sites on the highly conserved SARS-CoV-2 RNA polymerase, which has the potential to create a high barrier to resistance. In vitro data have shown that bemnifosbuvir was active with similar activity against all SARS-CoV-2 variants of concern ("VOC") and variants of interest ("VOI") that have been tested to date, including Omicron subvariants BA.4, BA.5 and XBB and EG.5.1.

HCV – Our Strategy and Objective

Despite the availability of direct acting antiviral oral combination treatment regimens, HCV continues to be a serious viral disease in the US and globally. Approximately 58 million people globally are living with chronic HCV infection. The World Health Organization ("WHO") estimates a global incidence of 1.5 million new infections and 290,000 deaths per year.

In the US, HCV is recognized as a health crisis with approximately 2.4 million individuals estimated to be infected. Prevalence of HCV in the US is expected to remain constant over the coming years as rising HCV incidence is largely attributable to the opioid crisis, IV drug use, and HCV reinfection, especially among younger adults, offsets the number of new patients treated.

Our HCV strategy focuses on the development of bemnifosbuvir in combination with ruzasvir, an HCV NS5A inhibitor, a product candidate which we have exclusively licensed from MSD International GmbH, an affiliate of Merck & Co, Inc. ("Merck"). Combination therapy utilizing two or more direct acting antivirals with different mechanisms of action is a scientifically and clinically well-established approach that is utilized by currently available human immunodeficiency virus, hepatitis B virus and HCV treatment regimens.

The objective of our HCV development program is to improve upon the current standard of care ("SOC") by offering, if successfully developed, the combination of bemnifosbuvir and ruzasvir, as a potentially differentiated eight-week duration, pan-genotypic protease inhibitor-free regimen for HCV-infected patients with or without cirrhosis. Currently, we are conducting a Phase 2 clinical trial of bemnifosbuvir in combination with ruzasvir in treatment naïve HCV infected patients, either without cirrhosis or with compensated cirrhosis.

For HCV, the combination of bemnifosbuvir and ruzasvir targets the HCV non-structural protein 5B (“NS5B”) and the HCV non-structural protein 5A (“NS5A”), respectively, and is designed to inhibit these enzymes which are essential for HCV replication. Both bemnifosbuvir and ruzasvir have individually demonstrated potent, pan-genotypic, antiviral activity against HCV and the combination of bemnifosbuvir and ruzasvir has exhibited synergistic activity against HCV in vitro.

Key Clinical Trials

COVID-19 – SUNRISE-3: Global Phase 3 Clinical Trial of Bemnifosbuvir

SUNRISE-3, is a currently ongoing global, multicenter, randomized, double-blind, placebo-controlled Phase 3 clinical trial that is evaluating bemnifosbuvir (550 mg twice-daily ("BID") for five days) in high-risk non-hospitalized patients with mild or moderate COVID-19. SUNRISE-3 is designed to evaluate bemnifosbuvir as monotherapy (primary analysis) but it is also exploring the effect of combination therapy in a smaller sub-set of patients who receive a compatible antiviral drug along with bemnifosbuvir (secondary analysis).

The trial consists of two study populations derived from the type of SOC received: 1) a “supportive care population” (those patients who do not qualify for another antiviral treatment or where other antivirals are not locally available) which is assessing bemnifosbuvir given as monotherapy (primary analysis) and 2) a “combination antiviral population” which is assessing combination therapy if the SOC includes treatment with other compatible antiviral drugs against COVID-19 (secondary analysis). Patients are being randomized 1:1 to receive either bemnifosbuvir 550 mg BID plus locally available SOC or placebo BID plus locally available SOC for five days.

The primary endpoint of the SUNRISE-3 study is all-cause hospitalization or death through Day 29 in approximately 2,200 patients in the supportive care monotherapy population. Secondary endpoints in each of the supportive care monotherapy patient population and the combination antiviral population

include COVID-19 related hospitalization or death, COVID-19 complications, medically attended visits, symptom rebound/relapse and viral load rebound.

The trial is enrolling patients who are ≥70 years old (regardless of other risk factors), patients ≥55 years old with one or more risk factors, patients ≥50 years old with two or more risk factors and patients ≥18 years old with certain risk factors including immunocompromised conditions, all regardless of COVID-19 vaccination status. We believe that this population encompasses those patients who currently remain at high-risk for progression of COVID-19 to severe disease and associated hospitalization and death.

In January and February 2024, we announced the enrollment of more than 650 patients and more than 1,350 patients, respectively, in the supportive care monotherapy cohort. Each of these patient enrollment milestones triggers an interim analysis by an independent data safety monitoring board (“DSMB”) principally for safety and futility after the respective patient group has completed Day 29 post treatment. As a result, we currently anticipate that the first interim analysis by the DSMB will occur in March of 2024 and the second interim analysis by the DSMB will occur in the second quarter of 2024. Patient enrollment in the SUNRISE-3 trial, which has currently surpassed 1,400 patients in the supportive care monotherapy population, continues and topline data from the trial are anticipated in the second half of 2024.

HCV – Global Phase 2 Clinical Trial of the Combination of Bemnifosbuvir and Ruzasvir

Currently, we are conducting a global Phase 2 clinical trial of bemnifosbuvir in combination with ruzasvir in treatment-naïve, HCV-infected patients either without cirrhosis or with compensated cirrhosis. This study is designed to evaluate the safety and efficacy of eight weeks of treatment with the combination consisting of once daily bemnifosbuvir 550 mg and ruzasvir 180 mg. Up to approximately 280 HCV-infected, treatment-naïve patients across HCV genotypes (“GT”), including a lead-in cohort of 60 patients without cirrhosis, are expected to be enrolled in this Phase 2 clinical trial. The primary endpoints of the study are safety and sustained virologic response ("SVR") at Week 12 post-treatment (“SVR12”). Other virologic endpoints include virologic failure, SVR at Week 24 post-treatment (“SVR24”) and resistance.

In February 2024, we announced final results from the full lead-in cohort in which a 98% SVR at Week 4 post-treatment ("SVR4") rate was observed [58 of 59 subjects achieved SVR4 with one patient who did not return for post-treatment follow-up]. The one patient who did not achieve SVR4 had poor adherence, and was infected with HCV GT-2. These results are consistent with the initial results announced in January 2024. The SVR4 rate exceeded the protocol-defined efficacy criterion of ≥90% SVR4 for continuing the study. As a result, in January 2024 we commenced enrolling up to an additional 220 patients in the study, including patients with cirrhosis. In the lead-in cohort, very rapid kinetics were observed with viral load for each patient near or below the lower limit of quantification ("LLOQ") at four weeks of treatment, which we believe is supportive of an eight-week treatment regimen for the combination of bemnifosbuvir and ruzasvir. All 60 patients in the lead-in cohort achieved viral load below the LLOQ by the end of the eight-week treatment regimen.

The combination of bemnifosbuvir and ruzasvir in the lead-in cohort was generally safe and well tolerated and there were no drug related serious adverse events ("SAEs"), no treatment discontinuations and adverse events ("AEs") were mostly mild. Final SVR12 results from all 280 patients enrolled in the global Phase 2 study are anticipated in the second half of 2024.

If the Phase 2 study is successfully completed, subject to discussion and alignment with regulatory authorities, we anticipate initiating a Phase 3 clinical development program in the second half of 2024.

Our Corporate Strategy

Our corporate goal is to become a global leader in the discovery, development, and commercialization of novel oral antiviral therapies for serious viral infections. We intend to achieve this goal by pursuing the following strategies:

Our Development Pipeline

The following table summarizes our orally administered antiviral product candidate pipeline. We have full global rights to commercialize all our product candidates in all indications.

Antiviral Therapy

Viral Polymerase as an Antiviral Target

The viral polymerase, which is the single protein present in all RNA viruses, is a key enzyme in the replication of viruses making it an attractive target for antiviral therapeutics. Among other things, the core structural features of viral polymerase are highly conserved, making drugs targeted to the polymerase less susceptible to the effects of viral mutation and resistance. Among RNA viruses, there are two types of viral polymerase:

Advances in technology have enabled intensive structural and functional studies of viral RNA polymerase including the identification, in the case of SARS-CoV-2, of NiRAN and have opened avenues for the development of new and more effective antiviral therapies.

Viral Resistance and Variants – Challenges to the Development of Antiviral Therapeutics

A major challenge to the development of direct acting antivirals is the emergence of viral resistance. Resistance is a function of a virus’ ability to genetically mutate which can make them less susceptible to certain antiviral therapies over time. In the case of RNA viruses, which generally lack proofreading abilities, the rate of mutation is substantially higher than DNA viruses and can occur at six orders of magnitude greater than the rate of mutation of host cells.

Another anticipated and naturally recurring consequence of viral mutations is the emergence of new variants. Variants are new strains of the original virus with genetic codes that are unique from the original virus. As a result of the unique genetic code, variants may have more or less transmissibility or virulence and may result in more severe disease than the original virus. Additionally, because of the changes in the genetic code of the variant, the effectiveness of vaccines and therapeutics may be reduced to the point of obsolescence.

Our Lead Antiviral Candidate - Bemnifosbuvir

Bemnifosbuvir is an investigational, novel, proprietary, orally administered double prodrug of a guanosine nucleotide analog which has been derived from our internal discovery program. More specifically, bemnifosbuvir is the hemisulfate salt of a phosphoramidate protide, AT-511, that is metabolized after multistep activation to the active 5’-triphosphate metabolite, AT-9010, which is an inhibitor of SARS-CoV-2 and HCV replication.

Our medicinal chemists designed bemnifosbuvir with the following critical elements to achieve the objectives noted below:

We believe that these modifications together with the double prodrug approach impart the following potentially advantageous characteristics and features to bemnifosbuvir:

Our Development Programs

Bemnifosbuvir for the Treatment of COVID-19

COVID-19 – Disease Overview and Limitation of Current Standard of Care

COVID-19, the disease caused by infection with SARS-CoV-2 and its variants, gave rise to a global pandemic that swept rapidly throughout the world beginning in 2020. In 2023, public health emergencies

declared by each of the WHO and Centers for Disease Control and Prevention ("CDC") ended, however, SARS-CoV-2 continues to cause vast rates of infection and in many cases serious COVID-19 disease due to waning immunity and continued emergence of SARS-CoV-2 variants. The COVID-19 surge in the US and globally during the winter of 2023 / 2024 demonstrates that newly emerged variants such as JN.1 continue to thrive and become dominant despite the availability of treatments and updated vaccines.

In the US, COVID-19 remains a major cause of respiratory virus-associated hospitalizations and is a continuing threat, particularly for those most vulnerable to severe disease. Older adults and individuals who have risk factors or who are immunocompromised are at a higher risk for developing more serious complications from COVID-19, leading to hospitalization and death.

At the outset of the pandemic, unprecedented progress was made with both COVID-19 vaccines and treatment options. Despite this progress, substantial limitations remain to currently available vaccines and therapies, including waning immunity to both naturally acquired and vaccine generated immunity, failure of certain populations to mount an adequate immune response to vaccines and lack of efficacy of currently available monoclonal antibodies to currently circulating SARS-CoV-2 subvariants.

Limitations of current oral antivirals include drug-drug interactions with many commonly prescribed medications including anti-seizure medications, anti-psychotics, anti-coagulants and other safety concerns. As a result, many high-risk patients currently do not have suitable outpatient therapies and as a result, are also more likely to be hospitalized because of severe disease.

With the ongoing evolution of the SARS-CoV-2 virus and the continuing emergence of new variants, there remains an urgent need to develop new oral therapies that are safe, efficacious, convenient and with low risk of drug-drug interactions for the treatment of COVID-19 that can be utilized as monotherapy and potentially as part of a combination therapy. We believe that oral therapies protecting against the development of severe infection and transmission remain urgently needed particularly for vulnerable patients who currently have limited or no treatment options. This includes patients who are unvaccinated, patients who fail to respond to available vaccines, vaccinated patients with waning efficacy, which can occur between three to six months after immunization, and patients for whom vaccines and existing treatments are contraindicated. As COVID-19 remains endemic with continued variant fueled pandemic surges, we believe that this need will continue for years.

Vaccines for Prevention

Several vaccines are either approved or authorized under an emergency use authorization ("EUA") and additional vaccines are in development to prevent COVID-19 infection.

The ability of vaccines to produce durable immunity protection against disease and transmission is currently limited due to multiple factors, including:

Monoclonal Antibodies ("mAbs") for the treatment and prevention of COVID-19

Starting in November 2020 and into 2022, the FDA granted EUAs to several mAbs for the prophylaxis and/or treatment of COVID-19. The use of mAbs for the treatment of COVID-19 was subsequently limited and is currently not authorized in the US for the following reasons:

Even if future mAbs are developed, the continued emergence of new SARS-CoV-2 variants may make even these new mAbs ineffective for the treatment of COVID-19.

Project NextGen

In 2023, the US federal government announced the Project NextGen initiative with the purpose to accelerate and streamline the rapid development of the next generation of vaccines and treatments through public-private collaborations. Based at the Department of Health and Human Services (“HHS”) and seeded with an initial investment of $5 billion, Project NextGen is coordinating across the US federal government and the private sector to fund and advance a pipeline of new, innovative vaccines and mAbs into clinical trials and potential review by the FDA. Project NextGen is focusing on:

Antivirals for the treatment of COVID-19

Antiviral therapies, which are complementary to vaccines, have been approved or authorized for the treatment of COVID-19. In the US, Veklury® (remdesivir), an RdRp inhibitor, is approved for the treatment of COVID-19 in adults and certain pediatric patients who are hospitalized or outpatients at high-risk of progression to severe COVID-19. Lagevrio™ (molnupiravir), an orally administered direct-acting antiviral for the treatment of adults with mild to moderate COVID-19 in the outpatient setting is authorized for use under an EUA in the US. Paxlovid™ is approved in the US for adults with mild to moderate COVID-19 in the outpatient setting and is available under EUA for pediatric patients 12 years and older weighing at least 40 kg. All three antiviral therapies are approved or authorized for use in many additional countries globally. Other oral antiviral therapies are approved in other countries including Xocova® (enstirelvir), a protease inhibitor which is approved in Japan.

Limitations of currently authorized or approved antiviral therapies include:

Our Development of COVID-19 Product Candidates

We are developing bemnifosbuvir, an investigational, orally administered, novel antiviral product candidate, for the treatment of COVID-19. We believe bemnifosbuvir as a monotherapy has the potential

to address the key limitations of current therapies and the continued unmet medical need particularly for high-risk patients with limited treatment options. SUNRISE-3 is a global Phase 3 randomized, double-blind, placebo-controlled clinical trial that is currently evaluating bemnifosbuvir (550 mg BID for 5 days) in high-risk non-hospitalized patients with mild or moderate COVID-19.

While SUNRISE-3 is principally designed to evaluate bemnifosbuvir as monotherapy (primary analysis) in approximately 2,200 patients, it is also designed to explore the effect of combination therapy in a smaller sub-set of patients who receive a compatible antiviral drug along with bemnifosbuvir (secondary analysis). We intend to use data from the smaller subset of patients who receive combination therapy to inform our development plans to evaluate bemnifosbuvir as combination therapy for the treatment of COVID-19.

In parallel with conducting SUNRISE-3, we are engaging in efforts to identify and advance a protease inhibitor product candidate for the treatment of COVID-19. We are seeking a protease inhibitor that is highly potent, well tolerated with limited drug-drug interactions and does not require a pharmacokinetic ("PK") booster (e.g., ritonavir). The optimization of lead compounds is ongoing.

Targeting SARS-COV-2 NiRAN/RdRp to treat COVID-19

The RNA polymerase complex of SARS-CoV and SARS-CoV-2 supports the transcription and replication of their approximately 30,000-nucleotide viral RNA genomes. It is the largest and most complex RNA synthesis machinery among RNA viruses. As shown in the illustration below, the multi-subunit SARS-CoV polymerase complex is composed of a number of non-structural proteins ("Nsp") including viral RdRp ("Nsp12"), processivity factors ("Nsp7", "Nsp8"), a proofreading exonuclease, a N7-methyl transferase ("Nsp14"), and a helicase ("Nsp13"). The Nsp12 protein contains two domains, an RdRp core, which is the catalytic subunit incorporating ribonucleotides into RNA templates, and an N-terminal NiRAN domain, the function of which was previously unknown.

We have investigated the mechanism by which SARS-CoV initiates viral RNA synthesis and have discovered that there are two distinct pathways: one protein-primed and mediated by the NiRAN through the UMPylation of Nsp8, and the other through de novo synthesis of dinucleotide primers in a NiRAN-independent manner. Importantly, both functions can be inhibited by AT-9010, the active triphosphate metabolite of bemnifosbuvir. Furthermore, we have obtained a 2.98 Å cryo-EM quaternary structure of Nsp12/7/8/RNA/AT-9100, which confirms that AT-9010 not only bound to the NiRAN active site but also was incorporated by the RdRp and functions as a chain terminator. We believe this unique dual mechanism of bemnifosbuvir creates a potentially higher barrier to resistance compared to other direct acting antiviral inhibitors.

SARS-CoV-2 Variants

SARS-CoV-2 has proven to be able to mutate quickly with more than seven million variants identified since fall 2020 and more than one million identified in 2023 alone. A number of these variants have been designated by the WHO and CDC as VOI because there is evidence of increased transmissibility, more

severe disease, reduced effectiveness of vaccines or antibodies, or diagnostic detection failures. The WHO and CDC have also identified several VOCs which express similar attributes to VOIs but are more likely to be responsible for greater disease severity across the globe. Previously identified VOCs included Alpha, Beta, Gamma, and Delta while the currently circulating VOC is Omicron, which includes BA.1, BA.2, BA.3 BA.4, BA.5, XBB, EG.5.1, JN.1 and descendent lineages.

In the US, as of February 17, 2024, JN.1 is estimated to account for over 90% of all currently circulating SARS-CoV-2 variants.

Given the mutagenic nature of SARS-CoV-2, we expect that the evolution of the virus will continue with more variants emerging and presenting new and varied health challenges. The continued emergence of dominant SARS-CoV-2 variants is a key contributor to COVID-19 remaining as an endemic threat where the virus will still be circulating, with surges from time to time.

Potent in vitro inhibition of SARS-CoV-2 replication across variants

Since bemnifosbuvir targets viral RNA polymerase, a highly conserved enzyme critical to viral replication and transcription, we expect it will maintain its antiviral activity even against the recently emerged variants with mutations in the spike (S) protein responsible for the receptor recognition and host cell membrane fusion process.

We have assessed the in vitro potency of AT-511 (free base of bemnifosbuvir) against SARS-CoV-2 VOC and VOI. The data from these studies are summarized in the table below showing that AT-511 maintained its potency against all major VOC and VOI tested. These data support the key mechanistic advantage of the compound, which targets the highly conserved viral RNA polymerase.

Non-mutagenic

Results from non-clinical studies indicated that bemnifosbuvir was non-mutagenic and non-teratogenic and it has shown no reproductive toxicity.

More specifically, analysis of SARS-CoV-2 infected Huh7.5 cells treated with AT-511 (the free base of bemnifosbuvir) by next generation sequencing ("NGS") showed that bemnifosbuvir was not a mutagen (which is consistent with the lack of genotoxicity observed in the preclinical in vitro and in vivo studies) and did not introduce mutations in the viral genome.

In addition to the standard battery of preclinical safety, pharmacology and repeat dose toxicity studies, which showed no adverse effects of bemnifosbuvir treatment in rats and non-human primates at respective doses up to 650 and 1000 mg/kg/day for 13 weeks, completed preclinical studies have demonstrated that bemnifosbuvir did not affect male or female fertility in treated rats, did not affect early embryo-fetal development in treated pregnant rats or rabbits, and did not affect the pre- or post-natal development, reproductive capability, or behavioral assessments of the offspring of rats treated prior to and during mating (males) and prior to mating through pregnancy and lactation (females).

Clinical Development

Summary

At the outset of the COVID-19 pandemic, we initiated our COVID-19 program with a global Phase 2 clinical trial of bemnifosbuvir in hospitalized patients. This was followed by the initiation, together with our former collaborator, F. Hoffmann-LaRoche Ltd. and Genentech, Inc. (together, “Roche”), of MOONSONG, a Phase 2 outpatient clinical trial, MORNINGSKY, a Phase 3 outpatient clinical trial and MEADOWSPRING, a Phase 3 six-month follow-up study for patients who had been enrolled in MORNINGSKY.

Together with Roche, we completed the Phase 2 outpatient MOONSONG clinical trial in October 2021 and, due to the complexities and time required to effect the transfer of study sponsorship from Roche to us following the termination of the collaboration, the very dynamic COVID-19 landscape in which SARS-CoV-2 was rapidly evolving and the introduction of the original vaccines and antivirals, after careful consideration, each of the Phase 3 MORNINGSKY and MEADOWSPRING clinical trials were discontinued after careful consideration prior to completion in December 2021 and March 2022, respectively. We leveraged the key clinical data obtained from these patient studies, including clinical efficacy data from MORNINGSKY, with additional supporting Phase 1 and clinical pharmacology studies conducted in healthy subjects, to support the design of SUNRISE-3, the currently ongoing Phase 3 clinical trial of bemnifosbuvir for the treatment of COVID-19.

SUNRISE-3 – Global Phase 3 clinical trial

In 2023, the FDA granted Fast Track designation for the investigation of bemnifosbuvir for the treatment of COVID-19. In SUNRISE-3, we are targeting the patient population whom we believe are at the greatest risk for disease progression to severe COVID-19 or mortality, and for whom there are currently the fewest treatment options.

In January and February 2024, we announced the enrollment of more than 650 patients and more than 1,350 patients, respectively, in the supportive care monotherapy cohort of the trial. As a result, we currently anticipate that the first interim analysis by the DSMB will occur in March of 2024 and the second interim analysis by the DSMB will occur in the second quarter of 2024. At each interim analysis, we anticipate the DSMB will evaluate the data principally for safety and futility. Patient enrollment in the SUNRISE-3 trial, which has currently surpassed 1,400 patients in the supportive care monotherapy population, continues and topline data from the trial are anticipated in the second half of 2024.

MORNINGSKY - Global Phase 3 clinical trial

The Phase 3 MORNINGSKY study was a global, randomized, placebo-controlled study across 50 centers globally in non-hospitalized adult and adolescent patients with mild or moderate COVID-19 who were at high-risk or standard risk for disease progression regardless of vaccination. Due to the complexities and time required to effect the transfer of study sponsorship from Roche to us following the termination of the collaboration, and the very dynamic COVID-19 landscape including the rapid evolution of SARS-CoV-2 and the introduction and availability of the original vaccines and antivirals, after careful consideration, MORNINGSKY was discontinued prior to completion in December 2021.

Patients were randomized (2:1; active:placebo) to receive bemnifosbuvir 550 mg BID or placebo for five days. The primary endpoint was time to alleviation/improvement of COVID-19 symptoms. Secondary endpoints included the proportion of patients requiring hospitalization, all-cause mortality, and change in viral load. At the time of discontinuation, 216 patients had been randomized, with 207 patients included in efficacy analyses. The study enrolled a broad outpatient population, including 47% with high-risk factors, 28% who received ≥1 doses of vaccine against COVID-19, and 56% who were seropositive for SARS-CoV-2 at baseline. Because the study was prematurely discontinued, no formal statistical comparisons were made.

While the primary endpoint of the MORNINGSKY study, time to symptom alleviation, was not achieved, the results from MORNINGSKY showed that non-hospitalized adult and adolescent patients who received bemnifosbuvir (n=137) experienced a 71% relative reduction in risk of hospitalization (2.9% versus 10%) (p=0.047, unadjusted, exploratory; secondary endpoint) versus placebo (n=70), regardless of vaccination status. In an exploratory analysis, an 82% reduction in risk of hospitalization was seen in a subset of patients greater than 40 years of age in the bemnifosbuvir arm. In another ad hoc analysis, the proportion

of patients who were considered standard risk experienced a similar relative reduction in risk of hospitalization as those who were considered high-risk (75% versus 69%).

Error bars denote the 97.5% Confidence Interval

No deaths were observed during the study. No clear differences in any of the virology end points between the bemnifosbuvir and placebo arms were observed. Overall, bemnifosbuvir was well tolerated. There were no drug-related SAEs reported, and proportions of patients with AEs leading to study drug discontinuation were low (2.8% in the bemnifosbuvir arm vs 7.0% in the placebo arm).

The MEADOWSPRING trial, originally designed as a six-month follow-up study of patients previously enrolled in MORNINGSKY, was closed out in March 2022 after enrolling only 72 patients. As a result, firm conclusions about the long-term symptoms of COVID-19 could not be drawn from this study.

Hospitalized Patients - Global Phase 2 clinical trial

This Phase 2 study was a randomized, double-blind, placebo-controlled, study that evaluated bemnifosbuvir in hospitalized/confined patients with moderate COVID-19 versus placebo. The study was initially designed to assess the treatment effect of bemnifosbuvir (550 mg BID; Part A) on a primary endpoint of proportion of subjects with Progressive Respiratory Insufficiency ("PRI"). However, low background rates of disease progression precluded completion of the study as initially planned. The protocol was amended to explore higher doses of bemnifosbuvir (1100 mg BID; Part B), however the study was prematurely discontinued in January 2022. Only two subjects (both receiving placebo) had been enrolled in Part B.

Rates for reduction of PRI were low in 550 mg BID patients and no difference was seen between treatment groups (Intent To Treat [ITT] population: 3/41 7.3% bemnifosbuvir patients and 4/40 10.0% placebo patients). The all-cause mortality for the Part A 550 mg BID subjects was 0/41 in the bemnifosbuvir group and 5.0% (2/40) in the placebo group. In addition, one placebo patient in the Part B 1100 mg BID group died.

Virology results indicated that treatment with bemnifosbuvir rapidly reduced the SARS-CoV-2 viral load from baseline, as measured by PCR of nasopharyngeal swabs. Compared with placebo, participants on bemnifosbuvir had a 0.61 log10 (95% CI: -1.38–0.16) greater mean reduction from baseline viral load on Day 2, and this trend was sustained through Day 8.

Bemnifosbuvir’s SARS-CoV-2 antiviral activity was also observed in patients with baseline viral loads above the median of 5.36 log10 as compared to placebo. In this subset, those in the bemnifosbuvir arm achieved SARS-CoV-2 clearance as early as Day 2 (in 6% of patients), Day 8 (in 13% of patients) Day 10 (in 33% of patients), and Day 12 (in 31% of patients) compared to 0% of patients in the placebo arm at the same timepoints. By Day 14 (last viral sampling study day), 50% of patients in the bemnifosbuvir arm and 23% in the placebo arm had no detectable RNA virus.

After dosing with 550 mg BID for five days, bemnifosbuvir was generally well tolerated and there were no drug-related SAEs. AEs were equally distributed across treatment arms. Most were mild-to-moderate in severity and assessed as not related to bemnifosbuvir.

MOONSONG - Global Phase 2 clinical trial

This Phase 2 study was a randomized, double-blind, multi-center, placebo-controlled trial, that evaluated the antiviral activity, safety, efficacy and PK of bemnifosbuvir in adult outpatients with mild or moderate COVID-19. Patients were randomized 1:1 to bemnifosbuvir 550 mg or placebo (Cohort A) and 3:1 to bemnifosbuvir 1,100 mg or placebo (Cohort B); all doses were given BID for 5 days. The modified intent-to-treat infected population comprised 100 patients (bemnifosbuvir 550 mg, n = 30; bemnifosbuvir 1,100 mg, n = 30; cohort A placebo, n = 30; cohort B placebo, n = 10). Treatment with bemnifosbuvir in this study did not meet the primary endpoint of showing a reduction in SARS-CoV-2 viral load in the overall population of patients compared to placebo, of whom approximately two thirds were low-risk with mild symptoms.

However, in high-risk patients with underlying health conditions, a reduction of viral load of approximately 0.5 log10 at Day 7 was observed with administration of 550 mg BID as compared to placebo (prespecified subgroup analysis Cohort A n=7; placebo n=10) and with administration of 1,100 mg BID as compared to placebo (exploratory subgroup analysis Cohort B; n=14; placebo n=7).

Bemnifosbuvir was generally well tolerated in this study. The proportion of patients experiencing any AE was 28% in the placebo group, 20% in the bemnifosbuvir 550 mg BID group and 33% in the bemnifosbuvir 1100 mg BID group. There were three non-drug related SAEs in each of the treatment groups and all other AEs were grade 1 or 2. Gastrointestinal ("GI")-related AEs were the most commonly reported AEs: 8% in the placebo group; 7% in the bemnifosbuvir 550 mg BID group; 20% in the bemnifosbuvir 1100 mg BID group, with mild to moderate nausea/vomiting resulting in premature study drug discontinuation of 3% in the placebo group, 0% in the bemnifosbuvir 550 mg BID group and 17% in the bemnifosbuvir 1100 mg BID group. No clinically significant differences in laboratory abnormalities were observed in the treatment arms as compared to placebo.

Other Studies

Supporting Phase 1 and clinical pharmacology studies, including a bronchoalveolar lavage ("BAL") study, multiple drug-drug interaction studies and a mass balance study, have been conducted and completed since we initiated our COVID-19 program. In these studies, the safety and PK of bemnifosbuvir has been evaluated at doses up to 1100 mg BID for five days in healthy subjects.

Results from the BAL study in healthy subjects demonstrated that bemnifosbuvir was efficiently delivered to the lungs (epithelial lining fluid), the primary site of SARS-CoV-2 infection. Five clinical drug-drug interaction studies were completed with results demonstrating an overall low drug-drug interaction potential associated with bemnifosbuvir.

Phase 1 – Drug-Drug Interaction Studies

A series of Phase 1 studies demonstrated an overall low drug-drug interaction potential associated with bemnifosbuvir, including no dosage adjustment needed for co-administration of bemnifosbuvir with drugs that are CYP3A substrates or for drugs that are sensitive substrates of efflux and hepatic uptake transporters. CYP3A is an enzyme that metabolizes many classes of medicines and supplements, and the sensitive substrates of efflux and hepatic uptake transporters regulate cellular trafficking of drugs that are commonly prescribed among high-risk COVID-19 patients.

In these studies, bemnifosbuvir was administered with index drugs for CYP3A4 (midazolam), P-glycoprotein (digoxin, cyclosporine, carbamazepine), breast cancer resistance protein and organic anion transporter polypeptide 1B1 (rosuvastatin). Based on low potential for drug interaction, we believe bemnifosbuvir has the potential to be co-administered with commonly prescribed therapeutics that are often taken for other conditions, especially in vulnerable patient populations who are at high-risk for disease progression to severe COVID-19.

Bemnifosbuvir has been generally well tolerated in healthy subjects. Consistent with the results from the MOONSONG Phase 2 outpatient clinical trial, an increased incidence of mild to moderate GI-related adverse events, specifically nausea and vomiting, were observed at doses greater than 550 mg BID in healthy subjects. As 550 mg BID has been well tolerated for up to ten days, the 550 mg BID dose for five days was selected for the Phase 3 SUNRISE-3 study.

In addition, other completed clinical pharmacology studies supporting a potentially favorable PK and safety profile for bemnifosbuvir include a study in healthy Japanese subjects as well as a study assessing the effects of bemnifosbuvir on cardiac repolarization in healthy adult subjects. Other supporting clinical pharmacology studies in special populations (e.g., subjects with hepatic and renal impairment) are ongoing.

Bemnifosbuvir and Ruzasvir for the Treatment of HCV

HCV – Disease Overview and Current Standard of Care

HCV is a blood-borne, positive sense, ssRNA virus, primarily infecting cells of the liver. HCV is a leading cause of chronic liver disease and liver transplants and spreads via blood transfusion, hemodialysis, and needle sticks. In the US, injection drug use accounts for approximately 60% of all new cases of HCV. Diagnosis of HCV is made through blood tests, including molecular tests that allow for the detection, quantification and analysis of viral genomes and the classification of an infection into specific viral GTs. Hepatitis C becomes chronic Hepatitis C in 55% to 85% of acute cases, with an incubation period lasting from two to 26 weeks.

HCV is classified into seven GTs (GT-1 through GT-7) and 67 subtypes, with HCV GT-1 being responsible for more than 70% of HCV cases in the US. Patients with HCV are also classified by liver function status: compensated cirrhosis (liver scarring) denotes those patients that do not yet have impaired liver function, while decompensated cirrhosis describes patients with moderate to severe liver function impairment.

According to the WHO, an estimated 58 million people globally have chronic HCV infection, with about 1.5 million new infections occurring per year. The most recently published CDC HCV surveillance report showed a continuing increase in HCV infections in the US. The WHO estimated that approximately 290,000 people died in 2019 from HCV related liver diseases, with the majority of deaths related to cirrhosis and hepatocellular carcinoma.

The CDC HCV surveillance report also showed a continuing increase in HCV infections in the US and new and reinfection rates exceeding cures on a yearly basis with the number of reported cases of acute HCV in the US more than doubling between 2014 and 2021 (129% increase). However, there is a wide gap between the number of reported cases versus estimated cases. Most individuals who become infected with HCV remain unaware that they are infected because HCV can go undetected until the condition progresses to symptomatic disease or until specific clinical tests are performed to confirm diagnosis. Consequently, cases are unreported, skewing actual disease prevalence rates. The burden of underreporting is realized when high medical expenditures (comorbid treatment costs, liver transplants) and mortality rates from advanced chronic liver disease do not proportionally align with reported prevalence rates.

Increasing Incidence of HCV in the US

Source: CDC. 2021 Viral Hepatitis Published September 2022.

Despite significant advances in treatment beginning in 2013, there remains a large, underserved, HCV patient population in the US. The US HCV prevalence is expected to continue to remain steady over the coming years as rising HCV incidence offsets the number of new patients treated. It is estimated that a substantial global market for HCV therapeutics will exist for the foreseeable future. The HCV commercial market is expected to remain large. Reported global net sales exceeded $3.0 billion in 2023, with the US contributing about 50% of these sales.

The US HCV prevalence is expected to continue to remain steady over the coming years as rising HCV incidence offsets the number of new patients treated. It is estimated that a substantial global market for HCV therapeutics will exist to 2050 and beyond. The HCV commercial market is large and expected to remain large. Reported global net sales exceeded $3.0 billion in 2023, with about 50% attributable to the US.

Antivirals for the treatment of HCV

No vaccine exists for the prevention of HCV but beginning in 2013 several sequentially introduced and improved oral antiviral therapeutics have boosted SVR rates to over 95% in a majority of patients, with treatment durations of eight to 12 weeks depending upon the regimen and patient population. The leading HCV products are combination therapies comprised of agents with differing mechanisms of action and therapeutic targets: NS3/4A protease inhibitors, NS5A inhibitors, and NS5B nucleos(t)ide polymerase inhibitors. A patient’s GT, cirrhotic status, and prior treatment failures determine the appropriate antiviral therapeutic used in treatment. In the US, currently the two leading therapeutics for treatment of chronic HCV are:

Epclusa® (sofosbuvir and velpatasvir): an orally administered, fixed dose combination regimen consisting of an HCV nucleotide analog NS5B polymerase inhibitor and an HCV NS5A inhibitor, was first approved by the FDA in 2016. It is indicated for the treatment of adults and pediatric patients ≥3 years with chronic HCV GT-1, -2, -3, -4, -5 or -6 infection, either without cirrhosis or with compensated cirrhosis. For patients with decompensated cirrhosis, Epclusa is approved for use in combination with ribavirin. Patients on Epclusa require 12 weeks of treatment.

Mavyret® (glecaprevir and pibrentasvir): an orally administered, fixed dose combination regimen consisting of an HCV NS3/4A protease inhibitor and an HCV NS5A inhibitor was first approved by the FDA in 2017. It is indicated for the treatment of adults and pediatric patients ≥3 years with

chronic HCV GT-1, -2, -3, -4, -5 or -6 infection, without cirrhosis or with compensated cirrhosis. Mavyret is also approved for HCV patients with GT-1 infection who have been previously treated with a regimen either containing an HCV NS5A inhibitor or an NS3/4A protease inhibitor (but not both). Mavyret was the first eight-week treatment approved for HCV GT-1, -2, -3, -4, -5 or -6 in adult patients without cirrhosis and with compensated cirrhosis who have not been previously treated. Longer treatment durations (up to 16 weeks) are indicated for some treatment-experienced populations. Mavyret is not approved for use in patients with decompensated cirrhosis.

Even with the presence and availability of these currently approved direct acting antivirals, only 6% of the prescribers of HCV therapeutic products who participated in quantitative market research we recently conducted indicated that there are no unmet medical needs with current treatments. The key unmet medical needs identified in this market research included the need for treatments with fewer contradictions than exist with current options, including in particular fewer drug-drug interactions, and the need for treatments with shorter treatment durations given that respondents estimated approximately 17% of patients fail to complete current regimens. This research was conducted by an independent market research consulting firm who surveyed 157 US healthcare providers including hepatologists, infectious disease specialists, gastroenterologists and primary care physicians each of whom, within the 12 months prior to the participation in the project, had treated at least 25 HCV patients, initiated more than 15 patients on direct acting antivirals and prescribed Epclusa or Mavyret to at least 50% of their eligible patients.

Our Development of HCV Product Candidates

We are developing bemnifosbuvir in combination with ruzasvir for the treatment of HCV. Bemnifosbuvir is an investigational oral, potent inhibitor of HCV NS5B RdRp. Ruzasvir is an investigational oral, potent, pan‑genotypic NS5A inhibitor that we licensed from Merck in December 2021. Based on our preclinical and clinical data to date, we believe that this combination, if approved, could offer the following potential benefits:

Rationale supporting the combination of bemnifosbuvir and ruzasvir for HCV

With the antiviral potency observed with bemnifosbuvir, especially in more difficult to treat GT-3 infected patients, we believe that the combination of bemnifosbuvir and ruzasvir has the potential to improve on the SVR12 rates observed in the prior studies conducted by Merck.

To further support our clinical development of the combination of bemnifosbuvir and ruzasvir, we have conducted in vitro synergy experiments in HCV GT-1b replicon assays. As shown in the figure below, these experiments demonstrated that the combination resulted in substantially greater inhibition of HCV replication than with either agent alone, suggesting a synergistic antiviral effect between the two inhibitors.

In vitro Synergy: Assay performed in HCV GT1b replicon

Viral resistance has emerged as an important consideration since it may impact the effectiveness of antiviral treatments for HCV infection. We profiled the antiviral activity of AT-511, the free base of bemnifosbuvir, and ruzasvir against major HCV NS5A and NS5B Resistance-Associated Variants ("RAVs") selected in vitro or identified in HCV patients with hard-to-treat sub-genotypes who have failed treatment with currently available direct acting antivirals.

In these in vitro studies, AT-511 was approximately 10-fold more active than sofosbuvir against a panel of laboratory strains and clinical isolates of HCV GTs tested (GT-1, -2, -3, -4, -5)) and bemnifosbuvir was not resistant to known sofosbuvir RAVs such as S282T and L159F/S282T. AT-511 also retained antiviral activity against all HCV GT-1a and HCV GT-3a NS5A RAVs tested. In GT-1a, ruzasvir was 10 times more active than velpatasvir, a direct acting antiviral, and retained single-digit picomolar potency against a panel of RAVs selected by previous NS5A inhibitors and was 10 times more potent than velpatasvir against selected double mutants. In HCV GT-3a, one of the most difficult to treat HCV GTs, ruzasvir was six times more active than velpatasvir and retained sub-nanomolar potency against select NS5A RAVs which were treatment-emergent in HCV GT-3 patients failing direct acting antivirals.

Ruzasvir and a panel of other NS5A inhibitors were profiled for antiviral activity against seven difficult-to-treat HCV sub-genotypes using the HCV GT-1b replicon backbone. Both ruzasvir and velpatasvir maintained picomolar potency over the majority of these difficult-to-treat sub-genotypes such as HCV GT-1l, -4r, and -6v. All tested NS5A inhibitors exhibited 100- to 1000-fold EC50 shifts for HCV GT-3b and GT-3g.

In a 13-week combination toxicity study in rats, bemnifosbuvir and ruzasvir were well tolerated when administered orally at 500 mg/kg/day alone or in combination. No test article-related adverse effects were noted for any of the three dose groups. Systemic exposures of bemnifosbuvir, its metabolites, and ruzasvir were similar when dosed alone or in combination, suggesting no significant drug-drug interactions between the two drugs.

Clinical Development

Summary

To date, we have completed two clinical trials of bemnifosbuvir in HCV infected patients to support the treatment of chronic HCV infection and have one on-going, global Phase 2 clinical study.

Open Label Study – Ongoing Global Phase 2 clinical trial

In June 2023, we initiated enrollment of a Phase 2 clinical trial of bemnifosbuvir in combination with ruzasvir in treatment-naïve, HCV-infected patients either without cirrhosis or with compensated cirrhosis. This study is designed to evaluate the safety and efficacy of eight weeks of treatment with the pan-genotypic combination consisting of once daily bemnifosbuvir 550 mg and ruzasvir 180 mg. Up to 280 HCV-infected, treatment-naive patients across all GTs, including a lead-in cohort of approximately 60 patients are expected to be enrolled in this Phase 2 clinical trial. The primary endpoints of the study are safety and SVR12. Other virologic endpoints include virologic failure, SVR24 and resistance.

Phase 2 Open Label Study of Bemnifosbuvir + Ruzasvir in HCV Patients

In February 2024, we announced final results from the full lead-in cohort in which a 98% SVR4 rate was observed [58 of 59 subjects achieved SVR4 with one patient who did not return for post-treatment follow-up]. The one patient who did not achieve SVR4 had poor adherence, and was infected with HCV GT-2. These results are consistent with the initial results announced in January 2024. The SVR4 rate exceeded the protocol-defined efficacy criterion of ≥90% SVR4 for continuing the study. As a result, in January 2024 we commenced enrolling up to an additional 220 patients in the study, including patients with cirrhosis.

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Proportion of Patients with HCV RNA <LLOQ by Study Visit with Eight Weeks of Treatment with the Combination of Bemnifosbuvir and Ruzasvir

In the lead-in cohort, very rapid kinetics were observed with viral load for each patient near or below the LLOQ at four weeks of treatment, which we believe is supportive of an eight-week treatment regimen for the combination of bemnifosbuvir and ruzasvir. All 60 patients in the lead-in cohort achieved viral load below the LLOQ by the end of the eight-week treatment regimen.

On-Treatment Viral Kinetics – Individual HCV RNA Levels in Patients Receiving Combination of Bemnifosbuvir and Ruzasvir for Eight Weeks

In the lead in cohort, the combination treatment was generally safe and well tolerated. There were no drug related SAEs, no treatment discontinuations and AEs were mostly mild.

If the Phase 2 study is successfully completed, subject to discussion and alignment with regulatory authorities, we anticipate initiating a Phase 3 clinical development program in the second half of 2024. Currently, we expect these initial Phase 3 studies will target a population of HCV-infected patients either without cirrhosis or with compensated cirrhosis that is similar to the patients being enrolled in the Phase 2 clinical trial.

Bemnifosbuvir in combination with daclatasvir - Phase 2 clinical trial

We conducted a Phase 2, open-label clinical trial to evaluate bemnifosbuvir in combination with daclatasvir, an approved commercially available HCV NS5A inhibitor, in HCV-infected subjects. Ten treatment-naïve, non-cirrhotic HCV GT-1 infected subjects received 553 mg free base bemnifosbuvir and 60 mg daclatasvir once daily for a period of eight or 12 weeks. The primary efficacy endpoint of the study was SVR12 (a sustained viral response, defined as HCV RNA < LLOQ at 12 weeks after end of treatment (“EOT”)). Secondary efficacy endpoints included HCV RNA< LLOQ, and Target Not Detected (“TND”) (an assessment of virologic response that is more rigorous than LLOQ), by study visit, virologic failure, and appearance of RAVs to either of the study drugs.

Despite the use of a less potent first-generation HCV NS5A inhibitor, daclatasvir, all subjects achieved HCV RNA < LLOQ and TND at the EOT and nine of the ten subjects achieved SVR12. One subject who was TND by week two received eight weeks of treatment, achieved SVR4, and then experienced likely virologic relapse at post-treatment week 12. The single subject who relapsed with GT 1b virus had the following multiple RAVs/variants both at baseline and at the SVR12 timepoint: NS5A: R30Q; NS5B: L159F/A218S/C316N. Phenotypic analysis demonstrated that bemnifosbuvir retained the same potency against clinical isolates obtained from this relapsed subject at baseline and SVR12 (only a 1.1 and 0.8-fold shift, respectively, in EC50 compared to reference). Compared to sofosbuvir, the EC50 and EC90m values for bemnifosbuvir were ~10-fold lower. Thus, the significance of the RAVs in this case is unclear. No other subjects had pre-existing NS5A RAVs at baseline.

As shown in the graph below, viral load decreased rapidly after initiation of study drugs, with 70% of subjects achieving plasma HCV RNA < LLOQ by week two (and 50% achieving TND by week 2).

Proportion (%) of subjects achieving HCV RNA <LLOQ and TND by study visit with bemnifosbuvir in combination with daclatasvir

We believe that the rapid early clearance of HCV RNA observed in the Phase 2 clinical trial evaluating bemnifosbuvir in combination with daclatasvir supported continued evaluation of bemnifosbuvir in shortened treatment regimens, ideally with a more potent, next-generation HCV NS5A inhibitor. This has led us to conduct the currently ongoing Phase 2 clinical trial evaluating bemnifosbuvir in combination with ruzasvir.

Bemnifosbuvir in combination with ruzasvir – Phase 1 clinical trial

A Phase 1 clinical study in healthy subjects was conducted in first quarter of 2023 to evaluate the potential drug-drug interaction between bemnifosbuvir and ruzasvir and the effect of food on the PK of the agents. The study drugs were well-tolerated and plasma PK profiles were not substantially affected by food nor concomitant dosing, the latter indicating lack of drug-drug interaction between bemnifosbuvir and ruzasvir. These data supported the evaluation of the combination in HCV-infected patients.

Bemnifosbuvir as a single agent – Phase 1 clinical trial

We conducted a Phase 1 trial to evaluate single and multiple doses of bemnifosbuvir as a single agent in healthy and HCV-infected subjects for up to seven days. All HCV-infected subjects were treatment-naïve with HCV RNA ≥5 log10 IU/mL. The objectives of the trial were to assess safety, tolerability, PK and antiviral activity.

The trial evaluated single oral doses of bemnifosbuvir up to 400 mg salt form (369 mg free base) in healthy subjects (Part A), single doses up to 600 mg salt form (553 mg free base) in non-cirrhotic HCV-infected subjects (Part B), and multiple doses up to 600 mg salt form (553 mg free base) once daily for seven days in non-cirrhotic HCV GT-1b infected subjects (Part C). Additional cohorts evaluated 600 mg salt form (553 mg free base) once daily for seven days in non-cirrhotic GT-3, (Part D) and Child-Pugh A cirrhotic GT -1, -2, -3, HCV-infected subjects (Part E). The tables below show the dosage and mean maximum HCV RNA reductions for each treatment cohort.

A total of 88 subjects were dosed across all parts of the trial, with 72 subjects who received active drug and 16 subjects who received placebo. In this trial, bemnifosbuvir showed equivalent pan-genotypic antiviral activity in both cirrhotic and non-cirrhotic HCV infected patients. The mean maximum HCV reduction after a single dose (Part B) was 2.3 log10IU/mL, and the mean maximum HCV RNA reduction after seven days of dosing with bemnifosbuvir at 553 mg free base was 4.6 log10IU/mL. Data also showed a mean maximum HCV RNA reduction of 4.4 log10IU/mL after seven days of dosing of bemnifosbuvir at 553 mg free base in non-cirrhotic GT-1b HCV-infected subjects, and a mean reduction of 4.5 log10IU/mL after seven days of dosing in non-cirrhotic GT-3 HCV-infected subjects. The PK data in cirrhotic subjects was similar to non-cirrhotic subjects. Emax modeling predicted that a dose of 553 mg free base of bemnifosbuvir once daily would result in maximum viral load reduction.

Maximum HCV RNA change in Part B (single dose in non-cirrhotic, HCV GT-1 infected subjects)

Maximum HCV RNA change in Part C (multiple dose in non-cirrhotic, HCV GT-1 infected subjects)

Maximum HCV RNA change in Part D (multiple dose in non-cirrhotic, HCV GT-3 infected subjects) and Part E (multiple dose in cirrhotic HCV-infected subjects)

* SD = standard deviation

** QD = once daily

Bemnifosbuvir HCV safety

No SAEs, dose-limiting toxicities or AEs leading to trial discontinuation were observed in the HCV Phase 1 or Phase 2 clinical trials of bemnifosbuvir that we have completed to date. The most common side effects observed were headache and small increases in blood lipid levels, with no consistent patterns in other reported effects. Most side effects were not severe and were not thought to be related to bemnifosbuvir.

Ruzasvir

Ruzasvir is an investigational oral, pan-genotypic NS5A inhibitor that we licensed from Merck in December 2021. In studies conducted by Merck, ruzasvir demonstrated in vitro potent antiviral activity with an EC50 in the sub- to low picomolar range against all GTs (<10 pM against GTs 1-7). The antiviral activity of ruzasvir was evaluated in a proof-of-concept ("POC") study in HCV-infected patients, where viral load reductions >3 log10 were observed in HCV GT-1, GT-2 and GT-3 infected patients after treatment with monotherapy. This clinical antiviral activity is on par with what was achieved, as single

agents, with pibrentasvir and velpatasvir, the NS5A inhibitor components of Mavyret and Epclusa, respectively. These POC data supported evaluation of ruzasvir in larger phase 2 multiple drug combination studies (including two and three drug regimens) previously conducted by Merck. These studies included treatment-naïve and interferon-experienced patients with or without compensated cirrhosis. In general, high SVR12 rates (>90%) were observed in two-drug combination studies (ruzasvir plus uprifosbuvir, a pyrimidine nucleotide prodrug, for 12 weeks) conducted by Merck in GT-1, -2, -4 and -6-infected patients (C-Breeze 1 and 2). A lower SVR12 rate was observed in GT-3 subjects with compensated cirrhosis (40% SVR12; C-Breeze 1). We believe this lower rate is attributed to the reduced antiviral activity associated with the nucleotide uprifosbuvir in GT-3 cirrhotic subjects as an increase in ruzasvir dose to 180 mg substantially increased the SVR12 rate in this population (68% SVR12; C-Breeze 2), highlighting the observed dose-related clinical antiviral activity of ruzasvir in GT-3 subjects with cirrhosis.

In studies conducted by Merck, over 1,200 HCV-infected participants received ruzasvir at daily doses up to 180 mg for durations up to 12 weeks as part of 2-drug and 3-drug regimens with or without ribavirin. The overall safety data indicates that ruzasvir was generally well-tolerated with no consistent treatment-related changes in laboratory, vital signs, or electrocardiogram parameter values. SAEs and discontinuations due to AEs were rare in all studies conducted by Merck.

Dengue

In February 2023, after advancing AT-752 into a Phase 2 clinical trial, we decided not to pursue further clinical development of AT-752 for the treatment and prophylaxis of dengue. This action was taken due to the long timelines anticipated for patient enrollment, expected clinical operational challenges, including the challenge of successfully administering an antiviral very shortly after infection which is not feasible with the current diagnostic tests, and the estimated resource burdens, including substantial costs, associated with the further clinical development of an antiviral for each of the treatment and prophylaxis of dengue.

Roche License Agreement

In October 2020, we entered into a license agreement (“Roche License Agreement”) with Roche in connection with the global development, manufacture and commercialization of bemnifosbuvir, products containing bemnifosbuvir or AT-511, the free base of bemnifosbuvir, and related companion diagnostics.

As partial consideration for the rights we granted to Roche under the Roche License Agreement, Roche paid us an upfront payment of $350 million in November 2020. Additionally, upon realization of a development milestone in June 2021, we received an additional $50 million from Roche.

During the term of the Roche License Agreement, Roche and we jointly developed bemnifosbuvir for COVID-19 on a worldwide-basis and equally shared the costs associated with such development activities. On February 10, 2022, the Roche License Agreement terminated.

As a result of the Roche License Agreement termination, we regained worldwide exclusive rights from Roche to research, develop, manufacture and commercialize bemnifosbuvir, products containing bemnifosbuvir or AT-511, the free base of bemnifosbuvir and related companion diagnostics in all fields of use.

Merck License Agreement

In December 2021, we entered into a license agreement with Merck (“Merck License Agreement”) for the development, manufacture and commercialization of ruzasvir. Ruzasvir is the NS5A inhibitor we are developing in combination with bemnifosbuvir for the treatment of HCV.

Pursuant to the terms of the Merck License Agreement, we obtained from Merck an exclusive (subject to certain reserved rights to conduct internal research), sublicensable, and worldwide license under certain Merck patents and know-how to research, develop, manufacture, have manufactured, use, import, export, sell, offer for sale, and otherwise commercialize ruzasvir (“Compound"), or products containing the Compound (each a “Product”) for all therapeutic or prophylactic uses in humans (“Field”).

In consideration for the rights we acquired under the Merck License Agreement, we paid Merck an upfront payment in the amount of $25 million and we will be required to pay Merck milestone payments up to $135 million in the aggregate upon our achievement of certain development and regulatory milestones

and up to $300 million in the aggregate upon our achievement of certain sales-based milestones. The first potential milestone, in the amount of $5.0 million, would be payable upon the commencement of a Phase 3 clinical trial. Additionally, we have agreed to pay Merck tiered royalties based on annual net sales of Products ranging from high single digit to mid-teens percentages, subject to certain adjustments. Our royalty payment obligations will continue on a country-by-country and Product-by-Product basis until the later of (i) the expiration of the last to expire valid claim of a licensed Merck patent claiming such Product and (ii) a period of years after the first commercial sale of such Product in such country.

Under the terms of the Merck License Agreement, we are obligated to use commercially reasonable efforts to develop and commercialize at least one Product in the Field in certain countries.

The term of the Merck License Agreement will continue, on a Product-by-Product and country-by-country basis, until expiration of all royalty payment obligations arising under the Merck License Agreement. We may terminate the Merck License Agreement for convenience upon 90 days prior written notice. Each party has the right to terminate the Merck License Agreement in the event of the other party’s material breach of the terms of the Merck License Agreement subject to a 60-day cure period and in the event of the other party’s bankruptcy or insolvency. Merck has the right to terminate the Merck License Agreement immediately if we commence any interference or opposition proceeding or other challenge to the validity or enforceability of any Merck patent licensed to us under the Merck License Agreement or if we otherwise oppose any extension of, or the grant of any supplementary protection certificate with respect to, any such Merck patent.

Upon any termination of the Merck License Agreement, the license granted to us by Merck will terminate. Upon termination of the Merck License Agreement by us for convenience other than as a result of a safety issue, or upon any termination by Merck, Merck will have an exclusive, fully paid, perpetual, sublicensable license to certain of our patents and know-how that are reasonably necessary to develop, manufacture or commercialize a Product that contains ruzasvir as the sole active agent, as such Product exists at termination. Additionally, if requested by Merck, during a period of time after delivery of the notice of termination of the Merck License Agreement by Merck or by us for convenience other than as a result of a safety issue, we will have the obligation to negotiate with Merck for the grant to Merck of a non-exclusive, royalty bearing license to certain of our patents and know-how that are reasonably necessary to develop, manufacture or commercialize a Product that is comprised of the combination of ruzasvir and bemnifosbuvir, as such Product exists at termination, with certain license terms pre-specified in the Merck License Agreement.

Manufacturing

We do not currently own or operate manufacturing facilities for the production of preclinical or clinical product candidates, nor do we have plans to develop or operate our own manufacturing operations in the future. We currently rely upon third-party contract manufacturing organizations (“CMOs”) to produce our product candidates for both preclinical and clinical use and anticipate to rely upon these or other CMOs or other third parties for commercial supply if any of our product candidates is successfully developed and approved for sale. While we expect that we will be able to enter into such arrangements, we do not currently have long term agreements in place for manufacture of product at commercial scale quantities. As a result, there are no assurances that our manufacturing and supply chain infrastructure will remain uninterrupted and reliable or that our CMOs or other third parties will be able to satisfy demand in a timely manner. While there are a limited number of companies that can produce raw materials and active pharmaceutical ingredients in the quantities and with the quality and purity that we require for our product candidates, based on our diligence to date, we believe our current network of manufacturing partners are able to fulfill these requirements, and are capable of continuing to expand capacity as needed. Additionally, we have, and will continue to evaluate further relationships with additional suppliers to increase overall capacity as well as further reduce risks associated with reliance on a limited number of suppliers for manufacturing.

Our employees who have extensive manufacturing and supply chain experience oversee the relationships with our CMOs.

Competition

As a clinical-stage biopharmaceutical company, we face competition from a wide array of companies in the pharmaceutical and biotechnology industries. These include both small companies and large

companies with much greater financial and technical resources and far longer operating histories than our own. We may also compete with the intellectual property, technology, and product development efforts of academic, governmental, and private research institutions.

Our competitors may have significantly greater financial resources, established presence in the market, expertise in research and development, manufacturing, preclinical and clinical testing, obtaining regulatory approvals and reimbursement, and marketing approved products than we do. These competitors also compete with us in recruiting and retaining qualified scientific, sales, marketing, and management personnel, establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies.

The key competitive factors affecting the success of any product candidates that we develop, if approved, are likely to be their efficacy, safety, convenience, price, and the availability of reimbursement from government and other third-party payors. The commercial opportunity for any product candidate we develop, if any are approved, could be reduced or eliminated if such product fails to achieve market acceptance from patients, prescribers and payors, our competitors develop and commercialize products that are more effective, have fewer or less severe side effects, are more convenient, or are less expensive than any products that we may develop. Our competitors also may obtain FDA or other regulatory approval for their products more rapidly than we may obtain approval for ours and may commercialize products more quickly than we are able to.

SARS-CoV-2

Many therapies and vaccines are approved or authorized for emergency use for the treatment and prevention, respectively of COVID-19 in the US and multiple additional countries. In addition to approved or authorized products, there are other agents in development for the treatment of COVID-19 both within and outside the US.

Direct acting antiviral therapies for the treatment of COVID-19 that are currently approved or authorized by the FDA for use include:

These antiviral therapies are also approved or authorized for use in many countries outside the US.

In addition to bemnifosbuvir, other orally administered antiviral agents that are currently in later stage development in the US for the treatment of COVID-19 include:

In addition to the antivirals listed above, both within and outside the US, several monoclonal antibodies were previously authorized for emergency use for the prophylaxis or treatment of COVID-19. While these authorizations were rescinded in the US, it is possible that monoclonal antibodies which have effectiveness against future SARS-CoV-2 variants may be developed and authorized or approved for the treatment of COVID-19.

Vaccines that are approved or authorized for emergency use for the prevention of COVID-19 in the US include:

The potential treatments and vaccines for COVID-19 continue to evolve and the lists above are not comprehensive lists of every or all treatments and vaccines that are in development for COVID-19. These lists include the products or product candidates approved or authorized for emergency use and the direct acting antivirals in late stage clinical development in the US as of the date of this Annual Report on Form 10-K that we believe would be the most competitive with bemnifosbuvir.

HCV

Since 2014, many direct-acting antiviral therapies have been approved for use for the treatment of HCV in the US and globally. Orally administered, FDA-approved treatments for patients with chronic HCV include:

In addition to the branded products, Gilead Sciences, Inc. markets authorized generic copies of Epclusa and Harvoni through its subsidiary, Asegua Therapeutics, LLC. We are not aware of any investigational agents in late-stage development in the US although there may be other investigational agents for HCV in various stages of clinical development in other parts of the world.

Commercialization

We currently believe that we can maximize the value of our product portfolio by retaining global development rights to our product candidates. However, to further maximize the value of product candidates that are authorized or approved for sale, we may seek collaborations that allow us to access and leverage commercialization expertise and resources of collaborators in certain markets. To assist in the commercialization in the US of any product candidates we successfully develop, we may enter into arrangements with third parties that have existing commercial infrastructure including primary care sales force and expertise in managed care. Outside the US, we anticipate that commercialization of our products, if approved or authorized for use, would be undertaken by third party collaborators. Currently, we do not have any sales, marketing or commercial product distribution infrastructure and we do not have any existing arrangements with third parties to commercialize our product candidates in the US or elsewhere.

Intellectual Property

Our commercial success depends in part on our ability to obtain and maintain proprietary protection for our nucleotide therapeutic products for viral diseases, including our purine nucleotide compounds for SARS-CoV-2 and HCV. We seek to protect our proprietary compounds and methods of treatment for viral diseases using our nucleotide compounds, alone and in combination with other therapeutic agents, in addition to dosage forms, dosing regimens and formulations for their administration. We also seek protection on the manufacturing process for the production of our nucleotide compounds. Our success also depends on our ability to operate without infringing, misappropriating or otherwise violating the proprietary rights of others and to prevent others from infringing, misappropriating or otherwise violating our proprietary rights.

Our policy is to seek to protect our proprietary position by filing US and foreign patent applications covering our proprietary technologies, inventions, and improvements that are important to the development and implementation of our business. In addition, we currently plan to seek patent term adjustments, restorations, and/or patent term extensions where applicable in the US, Europe and other jurisdictions. We also rely on trade secrets, know-how, continuing technological innovation and potential in-licensing opportunities to develop and maintain our proprietary position. Additionally, we expect to benefit, where appropriate, from statutory frameworks in the US, Europe and other countries that provide a period of regulatory data exclusivity to compensate for the time required for regulatory approval of our drug products.

As of February 1, 2024, we are the sole owner of fourteen patent families covering our product candidates and proprietary nucleotide compounds, which include composition of matter, pharmaceutical compositions, methods of use, and processes of manufacture as described in more detail below. Our owned patent estate as of February 1, 2024, on a worldwide basis, includes more than 300 pending, granted, or allowed patent applications with eighteen issued US patents, nine pending US non-provisional applications, two pending international patent applications filed under the Patent Cooperation Treaty (“PCT”), and more than 250 pending or granted patent applications that have entered the national phase of prosecution in countries outside the US.

As of February 1, 2024, we are the exclusive licensee of three patent families from Merck covering composition of matter, process of preparation, and formulations of the NS5A inhibitor ruzasvir (MK-8408), which collectively include two issued US patents, granted patents in France, Great Britain, and Germany and one pending US patent application and one pending patent application in the European Patent Office ("EPO").

The exclusivity terms of our patents depend upon the laws of the countries in which they are obtained. In the countries in which we currently file, the patent term is 20 years from the earliest date of filing of a non-provisional patent application. The term of a US patent may be extended to compensate for the time required to obtain regulatory approval to sell a drug (a patent term extension) or by delays encountered during patent prosecution that are caused by the US Patent and Trademark Office (referred to as patent term adjustment). For example, the Drug Price Competition and Patent Term Restoration Act of 1984, referred to as the Hatch-Waxman Act, permits a patent term extension for FDA-approved new chemical entity drugs of up to five years beyond the expiration of the patent. The length of the patent term extension is related to the length of time the drug is under regulatory review and diligence during the review process. Patent term extensions in the US cannot extend the term of a patent beyond a total of 14 years from the date of product approval, only one patent covering an approved drug, or its method of use may be extended, and only those claims covering the approved drug, or an approved method for using it may be extended. A similar kind of patent extension, referred to as a Supplementary Protection Certificate, is available in the European Union ("EU"). Legal frameworks are also available in certain other jurisdictions to extend the term of a patent. We currently intend to seek patent term extensions on any of our issued patents in any jurisdiction where we have a qualifying patent and the extension is available; however, there is no guarantee that the applicable regulatory authorities, including the FDA in the US, will agree with our assessment of whether such extensions should be granted, and even if granted, the length of such extensions. Further, even if our patent is extended, the patent, including the extended portion of the patent, may be held invalid or unenforceable by a court of final jurisdiction in the US or a foreign country.

Current issued patents and patent applications covering the composition of matter for our present clinical candidates AT-511 and bemnifosbuvir will expire on dates ranging from 2036 to 2038, if the applications are issued and held valid by a court of final jurisdiction if challenged, and without regard to any possible patent term adjustments or extensions. Current patent applications covering the use of AT-511 and bemnifosbuvir for the treatment of SARS-CoV-2 will expire on dates ranging from 2040 to 2041, if the applications are issued and held valid by a court of final jurisdiction if challenged, and without regard to any possible patent term adjustments or extensions. Current issued patents and patent applications covering the use of AT-511 and bemnifosbuvir for the treatment of HCV will expire on dates ranging from 2036 to 2042, if the applications are issued and held valid by a court of final jurisdiction if challenged, and without regard to any possible patent term adjustments or extensions.

However, any of our patents, including patents that we may rely on to protect our market for approved products, may be held invalid or unenforceable by a court of final jurisdiction. Alternatively, we may decide that it is in our interest to settle a litigation in a manner that affects the term or enforceability of our patent. Changes in either the patent laws or in interpretations of patent laws in the US and other jurisdictions may diminish our ability to protect our inventions and enforce our intellectual property rights. Accordingly, we cannot predict the breadth or enforceability of claims that have been or may be granted on our patents or on third-party patents. The pharmaceutical and biotechnology industries are characterized by extensive litigation regarding patents and other intellectual property rights. Our ability to obtain and maintain our proprietary position for our nucleotide compounds and the use of these compounds will depend on our success in enforcing patent claims that have been granted or may grant.

We do not know whether any of the pending patent applications that we have filed or may file or license from third parties will result in the issuance of any additional patents. The issued patents that we own or may receive in the future may be challenged, invalidated, or circumvented, and the rights granted under any issued patents may not provide us with sufficient protection or competitive advantages against competitors with similar technology. Furthermore, our competitors may be able to independently develop and commercialize drugs with similar mechanisms of action and/or duplicate our methods of treatments or strategies without infringing our patents. Because of the extensive time required for clinical development and regulatory review of a drug we may develop, it is possible that, before any of our drugs can be commercialized, any related patent may expire or remain in force for only a short period following commercialization, thereby reducing any advantage of any such patent. For more information regarding risks relating to intellectual property, see Part I, Item 1A. “Risk Factors—Risks Related to Intellectual Property.”

Our patent families, as of February 1, 2024, are further described below.

AT-511 and bemnifosbuvir

We own a first patent family that describes AT-511 or a pharmaceutically acceptable salt thereof (for example, bemnifosbuvir), pharmaceutical compositions of AT-511 or the pharmaceutical salts thereof, and methods to treat HCV using AT-511 or a salt thereof. This family consists of seven issued US patents (US Pat. Nos. 9,828,410; 10,000,523; 10,005,811; 10,239,911; 10,815,266; 10,870,672; 10,870,673) covering AT-511 or a pharmaceutically acceptable salt thereof, related compounds and their pharmaceutical compositions. This patent family is now also in the national stage of prosecution or granted in the African Regional Intellectual Property Organization (“ARIPO”), Australia, Brazil, Canada, China, Colombia, the Eurasian Patent Office (“EAPO”), Egypt, the EPO, Georgia, Hong Kong, Indonesia, Israel, India, Japan, Korea, Mexico, Macao, Malaysia, Nigeria, New Zealand, the Philippines, Russia, Saudi Arabia, Singapore, Thailand, Vietnam, Ukraine, South Africa, and the United Arab Emirates. We have more than 30 foreign patents granted or allowed, and more than 20 pending patent applications. The expected year of expiration for this patent family, where issued, valid and enforceable, is 2036, without regard to any extensions, adjustments, or restorations of term that may be available under national law.

We also own a second patent family that specifically covers bemnifosbuvir (the hemisulfate salt for AT-511), pharmaceutical compositions, process of preparation, and methods to treat HCV using bemnifosbuvir. This family includes two issued US patents (US Pat. No. 10,519,186, and US Patent No. 10,906,938,) and one allowed US application covering bemnifosbuvir. This family is currently in the national phase of prosecution in Argentina, ARIPO, Australia, Brazil, Canada, China, Colombia, the EAPO, the EPO, Georgia, Hong Kong, Indonesia, Israel, India, Japan, Korea, Mexico, Malaysia, Nigeria, New Zealand, the Philippines, Russia, Singapore, Taiwan, Thailand, Vietnam, Ukraine, Uzbekistan, and South Africa. We have over 25 granted foreign patents and over 25 pending applications. The expected year of expiration for this patent family, if issued, valid and enforceable, is 2038, without regard to any extensions, adjustments, or restorations of term that may be available under US or other national laws.

We own two patent families that disclose methods for the treatment of SARS-CoV-2 using AT-511 or bemnifosbuvir. These families include four granted US patents (US Patent Nos. 10,874,687, 11,707,480, 11,783,038, and 11,813,278) and two pending US applications. A patent application in this family has been allowed in Japan and applications are pending in Argentina, ARIPO, Australia, Bahrain, Brazil, Canada, Chile, China, Columbia, Ecuador, Egypt, the EPO, the EAPO, Georgia, India, Israel, Japan, Jordan, Kuwait, Libya, Malaysia, Mexico, Morocco, New Zealand, Nicaragua, Nigeria, Oman, Philippines, Russia, Saudi Arabia, Singapore, South Africa, South Korea, Taiwan, Thailand, Tunisia, Uzbekistan, and Vietnam. The expected year of expiration for patents issued from these families, if valid and enforceable, is 2040 or 2041, without regard to any extensions, adjustments, or restorations of term that may be available under US or other national laws.

We own a fifth patent family that discloses the use of AT-511 or a pharmaceutically acceptable salt thereof for the treatment or prevention of a positive-stranded RNA virus infection, including a Flaviviridae viral infection such as dengue, West Nile, or yellow fever. This family consists of one allowed application and one issued patent (US Patent No. 10,946,033) and is currently pending or granted in Australia, Brazil, Canada, China, the EAPO, the EPO, Hong Kong, Indonesia, Japan, Korea, Malaysia, Nigeria, Russia,

Singapore, Thailand, Vietnam, and South Africa. We have over 30 foreign patents granted and over 20 pending patent applications. The expected year of expiration for this patent family, if issued, valid and enforceable, is 2037, without regard to any extensions, adjustments, or restorations of term that may be available under US or other national laws.

We own a sixth patent family that discloses the use of AT-511 and bemnifosbuvir for the treatment of HCV in patients with cirrhosis of the liver. This family includes one granted US application (US Patent No. 11,690,860). The expected year of expiration for this patent family, if issued, valid and enforceable, is 2039, without regard to any extensions, adjustments, or restorations of term that may be available under US or other national laws.

We own a seventh patent family that describes methods to treat mutant or resistant forms of the SARS-CoV-2 virus. This family consists of pending applications in the US, the EPO, Japan, Canada and Hong Kong, as well as one application in Argentina and one application in Taiwan. The expected year of expiration for patents issued from non-provisional patent applications filed on the basis of this patent application, if valid and enforceable, is 2041, without regard to adjustments of term that may be available under US or other national laws.

We also own an eighth patent family that discloses methods for manufacturing AT-511 and bemnifosbuvir. This family consists of one pending US application. The expected year of expiration for patents issued from non-provisional patent applications filed on the basis of these provisional patent applications, if valid and enforceable, is 2041, without regard to adjustments of term that may be available under US or other national laws.

We also own a ninth patent family that discloses additional processes for the manufacture of AT-511 and bemnifosbuvir. This family consists of one pending patent application in the US in addition to pending applications in Argentina, Australia, Canada, China, the EPO Hong Kong, India, Japan, Korea, Mexico, New Zealand, and Taiwan. The expected year of expiration for patents issuing from these non-provisional patent applications, if valid and enforceable, is 2041, without regard to any adjustments of term that may be available under US or other national law.

We also own a tenth patent family that discloses new morphic forms of bemnifosbuvir. This family consists of one pending patent application in the US, as well as pending applications in Australia, Brazil, Canada, China, the EAPO, the EPO, Israel, India, Japan, Korea, Mexico, Russia, and Taiwan. The expected year of expiration for patents issued from non-provisional patent applications filed on the basis of this patent application, if valid and enforceable, is 2042, without regard to adjustments of term that may be available under US or other national laws.

Ruzasvir

We have exclusively licensed three patent families from Merck covering composition of matter, process of preparation, and formulations of ruzasvir (MK-8408), a pan-genotype NS5A inhibitor to treat HCV. The family covering the composition of matter includes one granted US patent (US Patent No. 9,555,038), and granted patents in France, Great Britain, and Germany. The expected expiration date is in 2034. The family describing a process of preparation includes one granted US patent (US Patent No. 10,457,690), with an expected expiration date in 2036. The family describing formulations includes one pending US patent application and one pending patent application in the EPO, which if granted, is expected to expire in 2039.

We also solely own a patent family covering the combination of bemnifosbuvir and ruzasvir. This family consists of one patent application in the US, in addition to patent applications in the United Arab Emirates, Argentina, Australia, Brazil, Canada, China, Colombia, the EAPO, the EPO, Indonesia, Israel, India, Japan, Korea, Mexico, Malaysia, New Zealand, the Philippines, Qatar, Russia, Saudi Arabia, Singapore, Thailand, Taiwan, and South Africa. These patent applications, if granted, will have an expiration date in 2042.

Government Regulation and Product Approval

Government authorities in the US, at the federal, state and local level, and other countries extensively regulate, among other things, the research, development, testing, manufacture, quality control, approval, labeling, packaging, storage, record-keeping, promotion, advertising, distribution, marketing and export and import of products such as those we are developing. A new drug must be approved by the FDA through the new drug application (“NDA”), process before it may be legally marketed in the US.

US Drug Development Process

In the US, the FDA regulates drugs under the Federal Food, Drug and Cosmetic Act (“FDCA”) and its implementing regulations. The process of obtaining regulatory approvals and the subsequent compliance with appropriate federal, state, local and foreign statutes and regulations require the expenditure of substantial time and financial resources.

The process required by the FDA before a drug may be marketed in the US generally involves the following:

Prior to beginning the first clinical trial with a product candidate in the US, a sponsor must submit an IND to the FDA. An IND is a request for allowance from the FDA to administer an investigational drug product to humans. The central focus of an IND submission is on the general investigational plan and the protocol(s) for clinical studies. The IND also includes results of animal and in vitro studies assessing the toxicology, pharmacokinetics, pharmacology, and pharmacodynamic characteristics of the investigational product; chemistry, manufacturing, and controls information; and any available human data or literature to support the use of the investigational product. An IND must become effective before human clinical trials may begin. Once submitted, the IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA, within the 30- day time period, raises safety concerns or questions about the proposed clinical trial. In such a case, the IND may be placed on clinical hold and the IND sponsor and the FDA must resolve any outstanding concerns or questions before the clinical trial can begin. Submission of an IND therefore may or may not result in FDA allowance to begin a clinical trial.

Clinical trials involve the administration of the investigational product to human subjects under the supervision of qualified investigators in accordance with GCPs, which among other things include the requirement that all research subjects provide their informed consent for their participation in any clinical

study. Clinical trials are conducted under protocols detailing, among other things, the objectives of the study, the parameters to be used in monitoring safety and the effectiveness criteria to be evaluated. A separate submission to the existing IND must be made for each successive clinical trial conducted during product development and for any subsequent protocol amendments. While the IND is active, progress reports summarizing the results of the clinical trials and nonclinical studies performed since the last progress report, among other information, must be submitted at least annually to the FDA, and written IND safety reports must be submitted to the FDA and investigators for serious and unexpected suspected adverse events, findings from other studies suggesting a significant risk to humans exposed to the same or similar drugs, findings from animal or in vitro testing suggesting a significant risk to humans, and any clinically important increased incidence of a serious suspected adverse reaction compared to that listed in the protocol or investigator brochure.

Furthermore, an independent IRB or ethics committee for each site proposing to conduct the clinical trial must review and approve the plan for any clinical trial and its informed consent form before the clinical trial begins at that site and must monitor the study until completed. Some studies also include oversight by an independent group of qualified experts organized by the clinical study sponsor, known as a data safety monitoring board, which provides authorization for whether or not a study may move forward at designated check points based on access to certain data from the study and may halt the clinical trial if it determines that there is an unacceptable safety risk for subjects or other grounds, such as no demonstration of efficacy. The FDA or the sponsor may suspend a clinical trial at any time on various grounds, including a finding that the research subjects or patients are being exposed to an unacceptable health risk. Similarly, an IRB can suspend or terminate approval of a clinical trial at its institution if the clinical trial is not being conducted in accordance with the IRB’s requirements or if the investigational product has been associated with unexpected serious harm to patients.

Human clinical trials are typically conducted in three sequential phases that may overlap or be combined:

Post-approval trials, sometimes referred to as Phase 4 studies, may be conducted after initial marketing approval. These trials are used to gain additional experience from the treatment of patients in the intended therapeutic indication. In certain instances, the FDA may mandate the performance of Phase 4 clinical trials as a condition of approval of an NDA.

During the development of a new drug, sponsors are given opportunities to meet with the FDA at certain points. These points may be prior to submission of an IND, at the end of Phase 2, and before an NDA is submitted. Meetings at other times may be requested. These meetings can provide an opportunity for the sponsor to share information about the data gathered to date, for the FDA to provide advice, and for the sponsor and the FDA to reach alignment on the next phase of development.

Concurrent with clinical trials, companies usually complete additional animal studies and must also develop additional information about the chemistry and physical characteristics of the drug and finalize a process for manufacturing the product in commercial quantities in accordance with cGMP requirements.

The manufacturing process must be capable of consistently producing quality batches of the product candidate and, among other things, the manufacturer must develop methods for testing the identity, strength, quality and purity of the final drug. In addition, appropriate packaging must be selected and tested, and stability studies must be conducted to demonstrate that the product candidate does not undergo unacceptable deterioration over its shelf life.

US Review and Approval Process

Assuming successful completion of all required testing in accordance with all applicable regulatory requirements, the results of product development, including results from preclinical and other non-clinical studies and clinical trials, along with descriptions of the manufacturing process, analytical tests conducted on the chemistry of the drug, proposed labeling and other relevant information are submitted to the FDA as part of an NDA requesting approval to market the product. The submission of an NDA is subject to the payment of substantial user fees; a waiver of such fees may be obtained under certain limited circumstances. Additionally, no user fees are assessed on NDAs for products designated as orphan drugs, unless the product also includes a non-orphan indication.

In addition, the Pediatric Research Equity Act (“PREA”), requires a sponsor to conduct pediatric clinical trials for most drugs, for a new active ingredient, new indication, new dosage form, new dosing regimen or new route of administration. Under PREA, original NDAs and certain supplements must contain a pediatric assessment unless the sponsor has received a deferral or waiver. The required assessment must evaluate the safety and effectiveness of the product for the claimed indications in all relevant pediatric subpopulations and support dosing and administration for each pediatric subpopulation for which the product is deemed safe and effective. The sponsor or FDA may request a deferral of pediatric clinical trials for some or all of the pediatric subpopulations. A deferral may be granted for several reasons, including a finding that the drug is ready for approval for use in adults before pediatric clinical trials are complete or that additional safety or effectiveness data needs to be collected before the pediatric clinical trials begin. The FDA must send a non-compliance letter to any sponsor that fails to submit the required assessment, keep a deferral current or fails to submit a request for approval of a pediatric formulation.

The FDA conducts a preliminary review of all NDAs within the first 60 days after submission, before accepting them for filing, to determine whether they are sufficiently complete to permit substantive review. The FDA may request additional information rather than accept an NDA for filing. In this event, the NDA must be resubmitted with additional information. The resubmitted application also is subject to review before the FDA accepts it for filing. Once filed, the FDA reviews an NDA to determine, among other things, whether a product is safe and effective for its intended use and whether its manufacturing is cGMP-compliant to assure and preserve the product’s identity, strength, quality and purity. Under the Prescription Drug User Fee Act (“PDUFA”), guidelines that are currently in effect, the FDA has a goal of ten months from the date of “filing” of a standard NDA for a new molecular entity to review and act on the submission. This review typically takes twelve months from the date the NDA is submitted to FDA because the FDA has approximately two months to make a “filing” decision after it the application is submitted.

The FDA may refer an application for a novel drug to an advisory committee. An advisory committee is a panel of independent experts, including clinicians and other scientific experts, that reviews, evaluates and provides a recommendation as to whether the application should be approved and under what conditions. The FDA is not bound by the recommendations of an advisory committee, but it considers such recommendations carefully when making decisions.

Before approving an NDA, the FDA will typically inspect the facility or facilities where the product is manufactured. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMP and adequate to assure consistent production of the product within required specifications. Additionally, before approving a NDA, the FDA may inspect one or more clinical sites to assure compliance with GCPs.

After the FDA evaluates an NDA, it will issue an approval letter or a Complete Response Letter ("CRL"). An approval letter authorizes commercial marketing of the drug with prescribing information for specific indications. A CRL indicates that the review cycle of the application is complete, and the application will not be approved in its present form. A CRL usually describes the specific deficiencies in the NDA

identified by the FDA and may require additional clinical data, such as an additional clinical trials or other significant and time-consuming requirements related to clinical trials, nonclinical studies or manufacturing. If a CRL is issued, the sponsor must resubmit the NDA addressing all of the deficiencies identified in the letter or withdraw the application. Even if such data and information are submitted, the FDA may decide that the NDA does not satisfy the criteria for approval.

If regulatory approval of a product is granted, such approval will be granted for particular indications and may entail limitations or restrictions on the indicated uses for which such product may be marketed. For example, the FDA may approve the NDA with a Risk Evaluation and Mitigation Strategy (“REMS”), to ensure the benefits of the product outweigh its risks. A REMS is a safety strategy to manage a known or potential serious risk associated with a medicine and to enable patients to have continued access to such medicines by managing their safe use, and could include medication guides, physician communication plans, or elements to assure safe use, such as restricted distribution methods, patient registries, and other risk minimization tools. The FDA also may condition approval on, among other things, changes to proposed labeling or the development of adequate controls and specifications. The FDA may also require one or more post-approval studies and surveillance to further assess and monitor the product’s safety and effectiveness after commercialization and may limit further marketing of the product based on the results of these post-approval studies.

Emergency Use Authorization

The Commissioner of the FDA, under delegated authority from the Secretary of HHS may, under certain circumstances in connection with a declared public health emergency, allow for the marketing of a product that does not otherwise comply with FDA regulations by issuing an EUA for such product. Before an EUA may be issued by HHS, the Secretary must declare an emergency based a determination that public health emergency exists that effects or has the significant potential to affect, national security, and that involves a specified biological, chemical, radiological, or nuclear agent or agents (“CBRN”), or a specified disease or condition that may be attributable to such CBRN. On February 4, 2020, the HHS Secretary determined that there is such a public health emergency that involves SARS-CoV-2, the virus that causes the COVID-19 infection. Once the determination of the threat or emergency has been made, the Secretary of HHS must then declare that an emergency exists justifying the issuance of EUAs for certain types of products (referred to as EUA declarations). On March 27, 2020, the Secretary of HHS declared on the basis of his determination of a public health emergency that has the potential to affect national security or the health and security of US citizens living abroad that involves SARS-CoV-2 that circumstances exist justifying authorization of drugs and biologics during the COVID-19 pandemic, subject to the terms of any EUA that is issued.

Once an EUA declaration has been issued, the FDA can issue EUAs for products that fall within the scope of that declaration. To issue an EUA, the FDA Commissioner must conclude that (1) the CBRN that is referred to in the EUA declaration can cause serious or life-threatening diseases or conditions; (2) based on the totality of scientific evidence available, it is reasonable to believe that the product may be effective in diagnosing, treating, or preventing the disease or condition attributable to the CBRN and that the product’s known and potential benefits outweigh its known and potential risks; and (3) there is no adequate, approved, and available alternative to the product. Products subject to an EUA must still comply with the conditions of the EUA, including labeling and marketing requirements. Moreover, the authorization to market products under an EUA is limited to the period of time the EUA declaration is in effect, and the FDA can revoke an EUA in certain circumstances.

Expedited Development and Review Programs

The FDA offers a number of expedited development and review programs for qualifying product candidates. For example, the FDA Fast Track program is intended to expedite or facilitate the process for reviewing product candidates that meet certain criteria. Specifically, investigational drugs are eligible for Fast Track designation if they are intended to treat a serious or life-threatening disease or condition and demonstrate the potential to address unmet medical needs for the disease or condition. The sponsor of a Fast Track product candidate has opportunities for more frequent interactions with the applicable FDA review team during product development and, once an NDA is submitted, the application may be eligible for priority review. With regard to a Fast Track product candidate, the FDA may consider for review sections of the NDA on a rolling basis before the complete application is submitted, if the sponsor

provides a schedule for the submission of the sections of the NDA, the FDA agrees to accept sections of the NDA and determines that the schedule is acceptable, and the sponsor pays any required user fees upon submission of the first section of the NDA.

A product candidate intended to treat a serious or life-threatening disease or condition may also be eligible for Breakthrough Therapy designation to expedite its development and review. A product candidate can receive Breakthrough Therapy designation if preliminary clinical evidence indicates that the product candidate, alone or in combination with one or more other drugs or biologics, may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. The designation includes all of the Fast Track program features, as well as more intensive FDA interaction and guidance beginning as early as Phase 1 and an organizational commitment to expedite the development and review of the product candidate, including involvement of senior managers.

Any marketing application for a drug submitted to the FDA for approval, including a product with a Fast Track designation or Breakthrough Therapy designation, may also be eligible for other types of FDA programs intended to expedite development and review, such as priority review. An NDA is eligible for priority review if the product candidate is designed to treat a serious condition, and if approved, would provide a significant improvement in safety or effectiveness compared to marketed products. The FDA will attempt to direct additional resources to the evaluation of an NDA designated for priority review in an effort to facilitate the review. The FDA endeavors to review applications with priority review designations within six months of the filing date as compared to ten months for review of new molecular entity NDAs under its current PDUFA review goals.

In addition, depending on the design of the applicable clinical trials, a product candidate may be eligible for accelerated approval. Product candidates intended to treat serious or life-threatening diseases or conditions may be eligible for accelerated approval upon a determination that the product candidate has an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity, or prevalence of the condition and the availability or lack of alternative treatments. As a condition of approval, the FDA generally requires that a sponsor of a drug receiving accelerated approval perform adequate and well-controlled confirmatory clinical trials to verify and describe the predicted clinical benefit and may require that such confirmatory trials be underway prior to granting any accelerated approval. Products receiving accelerated approval may be subject to expedited withdrawal procedures if the sponsor fails to conduct the required clinical trials in a timely manner, or if such trials fail to verify the predicted clinical benefit. In addition, the FDA currently requires pre-approval of promotional materials as a condition for accelerated approval, which could adversely impact the timing of the commercial launch of the product.

Fast Track designation, Breakthrough Therapy designation, priority review and accelerated approval do not change the standards for approval but may expedite the development or approval process. Even if a product qualifies for one or more of these programs, the FDA may later decide that the product no longer meets the conditions for qualification or decide that the time period for FDA review or approval will not be shortened.

Post-approval Requirements

Any products manufactured or distributed pursuant to FDA approvals are subject to pervasive and continuing regulation by the FDA, including, among other things, requirements relating to record-keeping, reporting of adverse experiences, periodic reporting, product sampling and distribution, and advertising and promotion of the product. After approval, most changes to the approved product, such as adding new indications or other labeling claims, are subject to prior FDA review and approval. There also are continuing, annual program fees for any marketed products.

Drug manufacturers and their subcontractors are required to register their establishments with the FDA and certain state agencies and are subject to periodic unannounced inspections by the FDA and certain state agencies for compliance with cGMP, which impose certain procedural and documentation requirements upon drug manufacturers. Changes to the manufacturing process are strictly regulated,

and, depending on the significance of the change, may require prior FDA approval before being implemented. FDA regulations also require investigation and correction of any deviations from cGMP and impose reporting requirements upon NDA holders and any third-party manufacturers that NDA holders may decide to use. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain compliance with cGMP and other aspects of regulatory compliance.

The FDA may withdraw approval if compliance with regulatory requirements and standards is not maintained or if problems occur after the product reaches the market. Later discovery of previously unknown problems with a product, including adverse events of unanticipated severity or frequency, or with manufacturing processes, or failure to comply with regulatory requirements, may result in revisions to the approved labeling to add new safety information, imposition of post-market studies or clinical studies to assess new safety risks, or imposition of distribution restrictions or other restrictions under a REMS program. Other potential consequences include, among other things:

The FDA closely regulates the marketing, labeling, advertising and promotion of drug products. A company can make only those claims relating to safety and efficacy, purity and potency that are approved by the FDA and in accordance with the provisions of the approved label. The FDA and other agencies actively enforce the laws and regulations prohibiting the promotion of off label uses. Failure to comply with these requirements can result in, among other things, adverse publicity, warning letters, corrective advertising and potential civil and criminal penalties. Physicians may prescribe, in their independent professional medical judgment, legally available products for uses that are not described in the product’s labeling and that differ from those tested and approved by the FDA. Physicians may believe that such off-label uses are the best treatment for many patients in varied circumstances. The FDA does not regulate the behavior of physicians in their choice of treatments. The FDA does, however, restrict marketers’ communications on the subject of off-label use of their products. The federal government has levied large civil and criminal fines against companies for alleged improper promotion of off-label use and has enjoined companies from engaging in off-label promotion. The FDA and other regulatory agencies have also required that companies enter into consent decrees or permanent injunctions under which specified promotional conduct is changed or curtailed. However, companies may share truthful and not misleading information that is otherwise consistent with a product’s FDA-approved labelling.

Marketing Exclusivity

Marketing exclusivity provisions authorized under the FDCA can delay the submission or the approval of certain marketing applications. The FDCA provides a five-year period of non-patent data exclusivity within the US to the first applicant to obtain approval of an NDA for a new chemical entity. A drug is a new chemical entity if the FDA has not previously approved any other new drug containing the same active moiety, which is the molecule or ion responsible for the action of the drug substance. During the

exclusivity period, the FDA may not approve or even accept for review an abbreviated new drug application (“ANDA”), or an NDA submitted under Section 505(b)(2) (“505(b)(2) NDA”), submitted by another company for another drug based on the same active moiety, regardless of whether the drug is intended for the same indication as the original innovative drug or for another indication, where the applicant does not own or have a legal right of reference to all the data required for approval. However, an application may be submitted after four years if it contains a certification of patent invalidity or non-infringement to one of the patents listed with the FDA by the innovator NDA holder.

The FDCA alternatively provides three years of non-patent exclusivity for an NDA, or supplement to an existing NDA if new clinical investigations, other than bioavailability studies, that were conducted or sponsored by the applicant are deemed by the FDA to be essential to the approval of the application, for example new indications, dosages or strengths of an existing drug. This three-year exclusivity covers only the modification for which the drug received approval on the basis of the new clinical investigations and does not prohibit the FDA from approving ANDAs or 505(b)(2) NDAs for drugs containing the active agent for the original indication or condition of use. Five-year and three-year exclusivity will not delay the submission or approval of a full NDA. However, an applicant submitting a full NDA would be required to conduct or obtain a right of reference to any preclinical studies and adequate and well-controlled clinical trials necessary to demonstrate safety and effectiveness.

Pediatric exclusivity is another type of marketing exclusivity available in the US. Pediatric exclusivity provides for an additional six months of marketing exclusivity attached to any existing periods of regulatory exclusivity or patent terms if a sponsor conducts clinical trials in children in response to a written request from the FDA. The issuance of a written request does not require the sponsor to undertake the described clinical trials, and a grant of pediatric exclusivity does not require the sponsor to obtain approval for the product candidate for pediatric use.

Other Healthcare Laws

Pharmaceutical companies are subject to additional healthcare regulation and enforcement by the federal government and by authorities in the states and foreign jurisdictions in which they conduct their business. Such laws include, without limitation, US federal and state anti-kickback, fraud and abuse, false claims, pricing reporting, and physician payment transparency laws and regulations regarding drug pricing and payments or other transfers of value made to physicians and other licensed healthcare professionals as well as similar foreign laws in the jurisdictions outside the US. Such foreign laws and regulations may be broader in scope than the provisions described above and may apply regardless of payor. These laws and regulations may differ from one another in significant ways, thus further complicating compliance efforts. For instance, in the EU, many EU member states have adopted specific anti-gift statutes that further limit commercial practices for medicinal products, in particular vis-à-vis healthcare professionals and organizations. Additionally, there has been a recent trend of increased regulation of payments and transfers of value provided to healthcare professionals or entities and many EU member states have adopted national “Sunshine Acts” which impose reporting and transparency requirements (often on an annual basis), similar to the requirements in the US, on pharmaceutical companies. Certain countries also mandate implementation of commercial compliance programs, or require disclosure of marketing expenditures and pricing information. Violation of any of such laws or any other governmental regulations that apply may result in significant penalties, including, without limitation, administrative civil and criminal penalties, damages, disgorgement fines, additional reporting requirements and oversight obligations, contractual damages, the curtailment or restructuring of operations, exclusion from participation in governmental healthcare programs and/ or imprisonment.

Coverage and Reimbursement

Significant uncertainty exists as to the coverage and reimbursement status of any product candidate for which we may seek regulatory approval. Sales in the US and in foreign jurisdictions will depend, in part, on the availability of sufficient coverage and adequate reimbursement from third-party payors, which include government health programs such as Medicare, Medicaid, TRICARE and the Veterans Administration, as well as managed care organizations and private health insurers. Prices at which we or our customers seek reimbursement for our product candidates can be subject to challenge, reduction or denial by third-party payors.

The process for determining whether a third-party payor will provide coverage for a product is typically separate from the process for setting the reimbursement rate that the payor will pay for the product. In the US, there is no uniform policy among payors for coverage or reimbursement. Decisions regarding whether to cover any of a product, the extent of coverage and amount of reimbursement to be provided are made on a plan-by-plan basis. Third-party payors often rely upon Medicare coverage policy and payment limitations in setting their own coverage and reimbursement policies, but also have their own methods and approval processes. Therefore, coverage and reimbursement for products can differ significantly from payor to payor. As a result, the coverage determination process is often a time-consuming and costly process that can require manufacturers to provide scientific and clinical support for the use of a product to each payor separately, with no assurance that coverage and adequate reimbursement will be applied consistently or obtained in the first instance.

Third-party payors are increasingly challenging the price and examining the medical necessity and cost-effectiveness of medical products and services, in addition to their safety and efficacy. Adoption of price controls and cost-containment measures, and adoption of more restrictive policies in jurisdictions with existing controls and measures, could further limit sales of any product that receives approval. Third-party payors may not consider our product candidates to be medically necessary or cost-effective compared to other available therapies, or the rebate percentages required to secure favorable coverage may not yield an adequate margin over cost or may not enable us to maintain price levels sufficient to realize an appropriate return on our investment in drug development. Additionally, decreases in third-party reimbursement for any product or a decision by a third-party payor not to cover a product could reduce physician usage and patient demand for the product.

Healthcare Reform

In the US and in foreign jurisdictions, there has been, and continues to be, several legislative and regulatory changes and proposed changes regarding the healthcare system that could prevent or delay marketing approval of product candidates, restrict or regulate post-approval activities, and affect the profitable sale of product candidates.

Among policy makers and payors in the US, there is significant interest in promoting changes in healthcare systems with the stated goals of containing healthcare costs, improving quality and/or expanding access. In the US, the pharmaceutical industry has been a particular focus of these efforts and has been significantly affected by major legislative initiatives. In March 2010, the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act (collectively, the “ACA”) was passed, which substantially changed the way healthcare is financed by both governmental and private insurers, and significantly affected the pharmaceutical industry. The ACA increased the minimum level of Medicaid rebates payable by manufacturers of brand name drugs from 15.1% to 23.1%; required collection of rebates for drugs paid by Medicaid managed care organizations; required manufacturers to participate in a coverage gap discount program, in which manufacturers must agree to offer point-of-sale discounts off negotiated prices of applicable brand drugs to eligible beneficiaries during their coverage gap period, as a condition for the manufacturer’s outpatient drugs to be covered under Medicare Part D; imposed a non-deductible annual fee on pharmaceutical manufacturers or importers who sell certain “branded prescription drugs” to specified federal government programs, implemented a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for drugs that are inhaled, infused, instilled, implanted, or injected; expanded eligibility criteria for Medicaid programs; created a new Patient-Centered Outcomes Research Institute to oversee, identify priorities in, and conduct comparative clinical effectiveness research, along with funding for such research; and established a Center for Medicare and Medicaid Innovation at the Centers for Medicare & Medicaid Services (“CMS”) to test innovative payment and service delivery models to lower Medicare and Medicaid spending, potentially including prescription drug spending.

Since its enactment, there have been judicial and political challenges to certain aspects of the ACA. On June 17, 2021, the US Supreme Court dismissed the most recent judicial challenge to the ACA without specifically ruling on the constitutionality of the ACA. In addition, other legislative changes have been proposed and adopted since the ACA was enacted. These changes included aggregate reductions to Medicare payments to providers, which went into effect on April 1, 2013 and, due to subsequent legislative amendments to the statute, will remain in effect through 2032, with the exception of a

temporary suspension from May 1, 2020 through March 31, 2022, unless additional Congressional action is taken. In addition, on January 2, 2013, the American Taxpayer Relief Act of 2012 was signed into law, which, among other things, reduced Medicare payments to several providers, including hospitals, and increased the statute of limitations period for the government to recover overpayments to providers from three to five years. In addition, on March 11, 2021, the American Rescue Plan Act of 2021 was signed into law, which eliminated the statutory Medicaid drug rebate cap, beginning January 1, 2024. The rebate was previously capped at 100% of a drug’s average manufacturer price.

Moreover, there has recently been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in several Congressional inquiries and proposed and enacted federal and state legislation designed to, among other things, bring more transparency to product pricing, review the relationship between pricing and manufacturer patient programs, and reform government program reimbursement methodologies for pharmaceutical products. On August 16, 2022, the Inflation Reduction Act of 2022, or ("IRA"), was enacted into law. Among other things, the IRA requires manufacturers of certain drugs to engage in price negotiations with Medicare (beginning in 2026), imposes rebates under Medicare Part B and Medicare Part D to penalize price increases that outpace inflation (first due in 2023), and replaces the Part D coverage gap discount program with a new discounting program (beginning in 2025). The IRA permits the Secretary of HHS to implement many of these provisions through guidance, as opposed to regulation, for the initial years. On August 29, 2023, HHS announced the list of the first ten drugs that will be subject to price negotiations. HHS has issued and will continue to issue guidance implementing the IRA, although the Medicare drug price negotiation program is currently subject to legal challenges. While the impact of the IRA on the pharmaceutical industry cannot yet be fully determined, it is likely to be significant.

Individual states in the US have also become increasingly active in implementing regulations designed to control pharmaceutical product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing. In addition, certain individual states as well as regional healthcare authorities and individual hospitals are increasingly using bidding procedures to determine which drugs and suppliers will be included in their healthcare programs. The states of Louisiana and Washington used bidding procedures in 2019 and more recently Minnesota did so in 2021 to secure contracts with suppliers of HCV antiviral therapeutics for certain populations including those covered by Medicare and those in correctional institutions. Other states are currently engaged in similar discussions. Furthermore, there has been increased interest by third party payors and governmental authorities in reference pricing systems and publication of discounts and list prices.

In the EU, on December 13, 2021, Regulation No 2021/2282 on Health Technology Assessment (“HTA”) was adopted. While the Regulation entered into force in January 2022, it will only begin to apply from January 2025 onwards, with preparatory and implementation-related steps to take place in the interim. Once applicable, it will have a phased implementation depending on the concerned products. The Regulation intends to boost cooperation among EU member states in assessing health technologies, including new medicinal products, and provide the basis for cooperation at the EU level for joint clinical assessments in these areas. It will permit EU member states to use common HTA tools, methodologies, and procedures across the EU, working together in four main areas, including joint clinical assessment of the innovative health technologies with the highest potential impact for patients, joint scientific consultations whereby developers can seek advice from HTA authorities, identification of emerging health technologies to identify promising technologies early, and continuing voluntary cooperation in other areas. Individual EU member states will continue to be responsible for assessing non-clinical (e.g., economic, social, ethical) aspects of health technology, and making decisions on pricing and reimbursement.

We expect that additional state, federal and foreign healthcare reform measures will be adopted in the future, any of which could limit the amounts that federal and state governments will pay for drug products and healthcare services, which could result in reduced demand for our product candidates once approved or additional pricing pressures.

Data Privacy and Security

Numerous state and federal laws, regulations and standards govern the collection, use, access to, confidentiality and security of health-related and other personal information and could apply now or in the future to our operations or the operations of our partners. In the US, numerous federal and state laws and regulations, including data breach notification laws, health information privacy and security laws and consumer protection laws and regulations govern the collection, use, disclosure, and protection of health-related and other personal information. Further, certain foreign laws govern the privacy and security of personal data, including health-related data. Privacy and security laws, regulations, and other obligations are constantly evolving, may conflict with each other to complicate compliance efforts, and can result in investigations, proceedings, or actions that lead to significant civil and/or criminal penalties and restrictions on data processing. For additional information, see Part I, Item 1A, “Risk Factors”.

Government Regulation Outside of the US

In addition to regulations in the US, we are subject to a variety of regulations in other jurisdictions, such as the EU, governing, among other things, clinical trials, marketing authorization and any commercial sales and distribution of our products once approved. Whether or not we obtain FDA approval for a product candidate, we must obtain the requisite approvals from regulatory authorities in foreign countries prior to the commencement of clinical trials or marketing of the product in those countries. The requirements and processes governing the conduct of clinical trials, approval process, product licensing, pricing and reimbursement vary from country to country. Failure to comply with applicable foreign regulatory requirements may be subject to, among other things, fines, suspension or withdrawal of regulatory approvals, product recalls, seizure of products, operating restrictions and criminal prosecution.

Non-clinical studies and clinical trials

Similar to the US, the various phases of non-clinical and clinical research in the EU are subject to significant regulatory controls.

Non-clinical studies are performed to demonstrate the health or environmental safety of new chemical or biological substances. Non-clinical (pharmaco-toxicological) studies must be conducted in compliance with the principles of good laboratory practice (“GLP”) as set forth in EU Directive 2004/10/EC (unless otherwise justified for certain particular medicinal products – e.g., radio-pharmaceutical precursors for radio-labelling purposes). In particular, non-clinical studies, both in vitro and in vivo, must be planned, performed, monitored, recorded, reported and archived in accordance with the GLP principles, which define a set of rules and criteria for a quality system for the organizational process and the conditions for non-clinical studies. These GLP standards reflect the Organization for Economic Co-operation and Development requirements.

Clinical trials of medicinal products in the EU must be conducted in accordance with EU and national regulations and the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (“ICH”) guidelines on Good Clinical Practices (“GCP”) as well as the applicable regulatory requirements and the ethical principles that have their origin in the Declaration of Helsinki. If the sponsor of the clinical trial is not established within the EU, it must appoint an EU entity to act as its legal representative. The sponsor must take out a clinical trial insurance policy, and in most EU member states, the sponsor is liable to provide ‘no fault’ compensation to any study subject injured in the clinical trial.

The regulatory landscape related to clinical trials in the EU has been subject to recent changes. The EU Clinical Trials Regulation (“CTR”) which was adopted in April 2014 and repeals the EU Clinical Trials Directive, became applicable on January 31, 2022. Unlike directives, the CTR is directly applicable in all EU member states without the need for member states to further implement it into national law. The CTR notably harmonizes the assessment and supervision processes for clinical trials throughout the EU via a Clinical Trials Information System, which contains a centralized EU portal and database.

While the EU Clinical Trials Directive required a separate clinical trial application (“CTA”) to be submitted in each member state in which the clinical trial takes place, to both the competent national health authority and an independent ethics committee, much like the FDA and IRB respectively, the CTR introduces a centralized process and only requires the submission of a single application for multi-center

trials. The CTR allows sponsors to make a single submission to both the competent authority and an ethics committee in each member state, leading to a single decision per member state. The CTA must include, among other things, a copy of the trial protocol and an investigational medicinal product dossier containing information about the manufacture and quality of the medicinal product under investigation.

The assessment procedure of the CTA has been harmonized as well, including a joint assessment by all member states concerned, and a separate assessment by each member state with respect to specific requirements related to its own territory, including ethics rules. Each member state’s decision is communicated to the sponsor via the centralized EU portal. Once the CTA is approved, clinical study development may proceed.

The CTR foresees a three-year transition period. The extent to which ongoing and new clinical trials will be governed by the CTR varies. Clinical trials for which an application was submitted (i) prior to January 31, 2022 under the EU Clinical Trials Directive, or (ii) between January 31, 2022 and January 31, 2023 and for which the sponsor has opted for the application of the EU Clinical Trials Directive remain governed by said Directive until January 31, 2025. After this date, all clinical trials (including those which are ongoing) will become subject to the provisions of the CTR.

Medicines used in clinical trials must be manufactured in accordance with Good Manufacturing Practice (“GMP”). Other national and EU-wide regulatory requirements may also apply.

Marketing Authorization

In order to market our future product candidates in the EU and many other foreign jurisdictions, we must obtain separate regulatory approvals. More concretely, in the EU, medicinal product candidates can only be commercialized after obtaining a marketing authorization (“MA”). To obtain regulatory approval of a product candidate under EU regulatory systems, we must submit a MA application (“MAA”). The process for doing this depends, among other things, on the nature of the medicinal product. There are two types of MAs:

Under the centralized procedure the maximum timeframe for the evaluation of a MAA by the EMA is 210 days.

In the EU, innovative products that target an unmet medical need and are expected to be of major public health interest may be eligible for a number of expedited development and review programs, such as the

PRIority MEdicines (“PRIME”) scheme, which provides incentives similar to the breakthrough therapy designation in the US. In March 2016, the EMA launched an initiative, the PRIME scheme, a voluntary scheme aimed at enhancing the EMA’s support for the development of medicines that target unmet medical needs. It is based on increased interaction and early dialogue with companies developing promising medicines, to optimize their product development plans and speed up their evaluation to help them reach patients earlier. Product developers that benefit from PRIME designation can expect to be eligible for accelerated assessment, but this is not guaranteed. Many benefits accrue to sponsors of product candidates with PRIME designation, including but not limited to, early and proactive regulatory dialogue with the EMA, frequent discussions on clinical trial designs and other development program elements, and accelerated MAA assessment once a dossier has been submitted. Importantly, a dedicated contact and rapporteur from the CHMP is appointed early in the PRIME scheme facilitating increased understanding of the product at EMA’s committee level. An initial meeting initiates these relationships and includes a team of multidisciplinary experts at the EMA to provide guidance on the overall development and regulatory strategies.

Moreover, in the EU, a “conditional” MA may be granted in cases where all the required safety and efficacy data are not yet available. The conditional MA is subject to conditions to be fulfilled for generating the missing data or ensuring increased safety measures. It is valid for one year and has to be renewed annually until fulfillment of all the conditions. Once the pending studies are provided, it can become a “standard” MA. However, if the conditions are not fulfilled within the timeframe set by the EMA, the MA ceases to be renewed. Furthermore, MA may also be granted “under exceptional circumstances” when the applicant can show that it is unable to provide comprehensive data on the efficacy and safety under normal conditions of use even after the product has been authorized and subject to specific procedures being introduced. This may arise in particular when the intended indications are very rare and, in the present state of scientific knowledge, it is not possible to provide comprehensive information, or when generating data may be contrary to generally accepted ethical principles. This MA is close to the conditional MA as it is reserved to medicinal products to be approved for severe diseases or unmet medical needs and the applicant does not hold the complete data set legally required for the grant of a MA. However, unlike the conditional MA, the applicant does not have to provide the missing data and will never have to. Although the MA “under exceptional circumstances” is granted definitively, the risk-benefit balance of the medicinal product is reviewed annually, and the MA is withdrawn in case the risk-benefit ratio is no longer favorable.

Under the above-described procedures, in order to grant the MA, the EMA or the competent authorities of the EU member states make an assessment of the risk benefit balance of the product on the basis of scientific criteria concerning its quality, safety and efficacy. MAs have an initial duration of five years. After these five years, the authorization may be renewed for an unlimited period on the basis of a reevaluation of the risk-benefit balance.

Data and Marketing Exclusivity

The EU also provides opportunities for data and market exclusivity. Upon receiving MA, reference products generally receive eight years of data exclusivity and an additional two years of market exclusivity. If granted, the data exclusivity period prevents generic or biosimilar applicants from relying on the pre-clinical and clinical trial data contained in the dossier of the reference product when applying for a generic or biosimilar MA in the EU during a period of eight years from the date on which the reference product was first authorized in the EU. The market exclusivity period prevents a successful generic or biosimilar applicant from commercializing its product in the EU until 10 years have elapsed from the initial MA of the reference product in the EU. The overall 10-year market exclusivity period can be extended to a maximum of eleven years if, during the first eight years of those 10 years, the MA holder obtains an authorization for one or more new therapeutic indications which, during the scientific evaluation prior to their authorization, are held to bring a significant clinical benefit in comparison with existing therapies. However, there is no guarantee that a product will be considered by the EU’s regulatory authorities to be a new chemical entity, and products may not qualify for data exclusivity.

Pediatric Development

In the EU, MAAs for new medicinal products have to include the results of studies conducted in the pediatric population, in compliance with a pediatric investigational plan ("PIP") agreed with the EMA’s Pediatric Committee ("PDCO"). The PIP sets out the timing and measures proposed to generate data to support a pediatric indication of the drug for which MA is being sought. The PDCO can grant a deferral of the obligation to implement some or all of the measures of the PIP until there are sufficient data to demonstrate the efficacy and safety of the product in adults. Further, the obligation to provide pediatric clinical trial data can be waived by the PDCO when these data is not needed or appropriate because the product is likely to be ineffective or unsafe in children, the disease or condition for which the product is intended occurs only in adult populations, or when the product does not represent a significant therapeutic benefit over existing treatments for pediatric patients. Once the MA is obtained in all the EU member states and study results are included in the product information, even when negative, the product is eligible for six months’ supplementary protection certificate extension (if any is in effect at the time of approval) or, in the case of orphan pharmaceutical products, a two-year extension of the orphan market exclusivity is granted.

The aforementioned EU rules are generally applicable in the European Economic Area (“EEA”) which consists of the 27 EU member states plus Norway, Liechtenstein and Iceland.

Failure to comply with EU and member state laws that apply to the conduct of clinical trials, manufacturing approval, MA of medicinal products and marketing of such products, both before and after grant of the MA, manufacturing of pharmaceutical products, statutory health insurance, bribery and anti-corruption or with other applicable regulatory requirements may result in administrative, civil or criminal penalties. These penalties could include delays or refusal to authorize the conduct of clinical trials, or to grant MA, product withdrawals and recalls, product seizures, suspension, withdrawal or variation of the MA, total or partial suspension of production, distribution, manufacturing or clinical trials, operating restrictions, injunctions, suspension of licenses, fines and criminal penalties.

Brexit and the Regulatory Framework in the United Kingdom

Since the end of the Brexit transition period on January 1,2021, Great Britain (England, Scotland and Wales) has not been directly subject to EU laws, however under the terms of the Ireland/Northern Ireland Protocol, EU laws generally apply to Northern Ireland. The EU laws that have been transposed into United Kingdom (“UK”) law through secondary legislation remain applicable in Great Britain, however, new legislation such as the EU CTR is not applicable in Great Britain (“GB”). Under the Medicines and Medical Devices Act 2021, the Secretary of State or an ‘appropriate authority’ has delegated powers to amend or supplement existing regulations in the area of medicinal products and medical devices. This allows new rules to be introduced in the future by way of secondary legislation, which aims to allow flexibility in addressing regulatory gaps and future changes in the fields of human medicines, clinical trials and medical devices.

Since January 1, 2021, the Medicines and Healthcare products Regulatory Agency (“MHRA”) has been the UK’s standalone medicines and medical devices regulator. As a result of the Northern Ireland protocol, different rules will apply in Northern Ireland than in GB; broadly, Northern Ireland will continue to follow the EU regulatory regime, but its national competent authority will remain the MHRA.

The UK regulatory framework in relation to clinical trials is derived from existing EU legislation (as implemented into UK law, through secondary legislation). On January 17, 2022, the MHRA launched an eight-week consultation on reframing the UK legislation for clinical trials which aimed to streamline clinical trials approvals, enable innovation, enhance clinical trials transparency, enable greater risk proportionality, and promote patient and public involvement in clinical trials. The MHRA responded to the consultation on March 21, 2023 and confirmed that it would bring forward changes to the legislation. The final legal texts introduced by the UK Government will ultimately determine the extent to which the UK clinical trials framework aligns with or diverges from the EU CTR.

The MHRA has introduced changes to national licensing procedures, including procedures to prioritize access to new medicines that will benefit patients, including a 150-day assessment and a rolling review procedure. All existing EU MAs for centrally authorized products were automatically converted or grandfathered into UK MAs, effective in GB (only), free of charge on January 1, 2021, unless the MA

holder opted out. In order to use the centralized procedure to obtain a MA that will be valid throughout the EEA, companies must be established in the EEA. Therefore, since Brexit, companies established in the UK can no longer use the EU centralized procedure and instead an EEA entity must hold any centralized MAs. In order to obtain a UK MA to commercialize products in the UK, an applicant must be established in the UK and must follow one of the UK national authorization procedures or one of the remaining post-Brexit international cooperation procedures to obtain an MA to commercialize products in the UK. A new international recognition framework has been in place from January 1, 2024, whereby the MHRA will have regard to decisions on the approval of MAs made by the EMA and certain other regulators when determining an application for a new GB MA.

There is no pre-MA orphan designation. Instead, the MHRA will review applications for orphan designation in parallel to the corresponding MA application. The criteria are essentially the same, but have been tailored for the market, i.e., the prevalence of the condition in GB, rather than the EU, must not be more than five in 10,000. Should an orphan designation be granted, the period of market exclusivity will be set from the date of first approval of the product in GB.

Human Capital Resources

As of February 28, 2024, we had 75 full-time employees, including 22 employees with M.D., Ph.D. or Pharm.D. degrees. Of these full-time employees, 53 employees are engaged in research and development activities. None of our employees is represented by a labor union or covered by a collective bargaining agreement. We consider our relationship with our employees to be good.

Our human capital resource priorities include attracting, recruiting, retaining, incentivizing and integrating our existing and new employees. The principal purpose of our competitive equity and cash compensation and benefits programs is to promote and support these priorities. We consider our human capital resources strategy to be comprehensive and built to foster our core way of working which is grounded on the principles of scientific rigor in a collaborative, entrepreneurial, and results-oriented manner. We plan to continue to evaluate our suite of human capital resources as we grow.

Organization

Atea Pharmaceuticals, Inc. was incorporated in July 2012 and began principal operations in March 2014. Our principal office facilities are in Boston, Massachusetts. Atea Pharmaceuticals Securities Corporation, a Massachusetts corporation incorporated in 2016, is a wholly owned subsidiary of Atea Pharmaceuticals, Inc. Our website is www.ateapharma.com. Information that is contained on, or that can be accessed through, our website is not incorporated by reference into this Annual Report on Form 10-K, and you should not consider information on our website to be part of this Annual Report on Form 10-K.

Available Information

We make available free of charge on the investor relations portion of our website our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, Proxy Statements for our annual meetings of stockholders, and amendments to those reports, as soon as reasonably practicable after we file such material with, or furnish it to, the Securities and Exchange Commission (“SEC”). These filings are available for download free of charge on the investor relations portion of our website located at https://ir.ateapharma.com. The SEC also maintains a website that contains reports, proxy statements and other information that we and other issuers file electronically with the SEC. The address of that website is https://www.sec.gov.

Information about our Executive Officers and Directors

The following table sets forth the name, age and position of each of our executive officers and directors as of the date of this Annual Report on Form 10-K.

(1) Member of the Audit Committee.

(2) Member of the Compensation Committee.

(3) Member of the Nominating and Corporate Governance Committee.

(4) Member of the Strategy and Public Policy Committee.

Executive Officers

Jean-Pierre Sommadossi, Ph.D., is the founder of our company and has served as our President and Chief Executive Officer and as Chairman of our Board since July 2012. Prior to that, he co-founded and held several roles at Idenix Pharmaceuticals, Inc., a biopharmaceutical company, from 1998 to 2010, including Principal Founder and Chief Executive Officer and Chairman. Dr. Sommadossi also co-founded Pharmasset, Inc., a biopharmaceutical company, in 1998. Dr. Sommadossi has also served on the board of directors of ABG Acquisition Corporation since February 2021, as Chairman of the board of directors of Panchrest, Inc., a marketing authorized representative in healthcare, since 2013, and Chairman of the board of directors of Biothea Pharma, Inc., a biotechnology company since 2021. Dr. Sommadossi has also served as a member of the board of directors of The BioExec Institute since 2004. Previously, Dr. Sommadossi served as Chairman of the board of directors of Kezar Life Sciences, Inc., a biopharmaceutical company, from June 2015 to May 2022, Vice Chairman of the board of directors of Rafael Pharmaceuticals, Inc., a biopharmaceutical company, from October 2016 to November 2020 and as Chair of the board of directors of PegaOne, Inc., a biopharmaceutical company from September 2020 to January 2021. Dr. Sommadossi also served as a member of the Harvard Medical School Discovery Council from 2010 to 2021 Dr. Sommadossi received his Ph.D. and Pharm.D. degrees from the University of Marseilles in France. We believe that Dr. Sommadossi’s extensive scientific, operational, strategic and management experience in the biotech industry qualifies him to serve on our Board.

Andrea Corcoran has served as our Chief Financial Officer since October 2020, our Secretary since September 2014 and our Executive Vice President, Legal since December 2013. Ms. Corcoran also served as Executive Vice President, Administration from September 2014 to October 2020. Prior to joining us, Ms. Corcoran served as Senior Vice President, Strategy and Finance at iBio, Inc., a biotechnology company, from 2011 to 2012, as General Counsel and Secretary at Tolerx, Inc., a biopharmaceutical company, from 2007 to 2011, and as Executive Vice President of Idenix Pharmaceuticals, Inc. from 1998 to 2007. Ms. Corcoran received her J.D. from Boston College Law School and her B.S. from Providence College.

Janet Hammond, M.D., Ph.D., has served as our Chief Development Officer since August 2020. Prior to joining us, Dr. Hammond served at AbbVie, Inc., a biopharmaceutical company, from November 2016 to August 2020 as Vice President and Therapeutic Area Head for General Medicine and Infectious Disease Development and at F. Hoffmann-La Roche from March 2011 to November 2016 as Senior Vice President, Global Head of Infectious Diseases and Head of Pharmaceutical Research and Early Development China. Dr. Hammond received her M.D. and Ph.D. from the University of Cape Town, South Africa, and her Sc.M. in Clinical Investigation from Johns Hopkins University School of Hygiene and Public Health.

Maria Arantxa Horga, M.D., has served as our Chief Medical Officer since January 2021 and previously served as our Acting Chief Medical Officer since October 2020 and as Executive Vice President, Clinical Sciences since August 2020. Prior to joining us, Dr. Horga served as Vice President, Pharmacovigilance and Medical Affairs at Biohaven Pharmaceuticals from October 2019 to August 2020. Prior to that, Dr. Horga served as Vice President, Global Head of Clinical Program Execution, Site Head of the Roche NY Innovation Center from July 2017 to August 2019, and as Global Head of Translational Medicine, Infectious Diseases at F. Hoffmann-La Roche from 2012 to 2016. Dr. Horga received her M.D. from the Santander School of Medicine and completed her residency in Pediatrics and a fellowship in Pediatric Infectious Diseases at the Mount Sinai School of Medicine.

John Vavricka has served as our Chief Commercial Officer since October 2018. Prior to joining us, Mr. Vavricka co-founded and served as the Chief Executive Officer of Biothea Pharma, Inc., a biotechnology company, from March 2018 to June 2021. Prior to that Mr. Vavricka founded and served as the Chief Executive Officer and President of Iroko Pharmaceuticals, Inc., a global pharmaceuticals company, from 2007 to 2015. Mr. Vavricka received his B.S. from Northwestern University.

Wayne Foster has served as our Executive Vice President, Finance and Chief Accounting Officer since January 2022 and previously served as Senior Vice President, Finance and Administration from December 2019 to January 2022. Prior to joining us, Mr. Foster served as Vice President of Finance at Mersana Therapeutics, Inc., a biopharmaceutical company, from January 2012 to September 2019. Mr. Foster received his B.B.A. from the University of Massachusetts Amherst.

Directors

Franklin Berger has served as a member and the Lead Director of our Board since September 2019. Mr. Berger has served as Founder and Managing Director at FMB Research LLC, a consulting firm, since June 2005. Mr. Berger also has served on the boards of directors of ESSA Pharma Inc. since March 2015, Kezar Life Sciences, Inc. since January 2016, Atreca Inc. since October 2014, Rain Therapeutics Inc. since May 2020 and as lead director of Rain Therapeutics Inc. since April 2021. Mr. Berger previously served on the boards of directors of BELLUS Health, Inc. from May 2010 to June 2023, Tocagen, Inc. from October 2014 to December 2020, of Proteostasis Therapeutics, Inc. from February 2016 to December 2020, and of Five Prime Therapeutics, Inc. from October 2014 to April 2021. Mr. Berger received his B.A. and M.A. from Johns Hopkins University and his M.B.A. from Harvard Business School. We believe that Mr. Berger’s financial background and experience as an equity analyst in the biotechnology industry combined with his experience serving on the boards of directors of multiple public companies qualifies him to serve on our Board.

Jerome Adams, M.D., has served as a member of our Board since May 2021. Dr. Adams also has served as Director of Health Equity Initiatives at Purdue University since October 2021. Dr. Adams served as the 20th Surgeon General of the US from September 2017 to January 2021, where he focused on the opioid epidemic and was a member of the COVID-19 Task Force. Prior to that, Dr. Adams served as the State Health Commissioner for the State of Indiana from November 2014 to September 2017, where he presided over Indiana’s efforts to deal with state-wide, unprecedented HIV outbreak. Before beginning his public service in 2014, Dr. Adams was a practicing anesthesiologist and Associate Professor in the Department of Anesthesiology at Indiana University from January 2008 to September 2017. Earlier in his career, Dr. Adams was a Clinical Research Assistant at Eli Lilly and Company. He has served in leadership positions at a number of professional organizations, including the American Medical Association, the Indiana State Medical Association, and the Indiana Society of Anesthesiologists. Dr. Adams received his B.S. in Biochemistry and B.A. in Psychology from the University of Maryland, Baltimore County, his M.D. from the Indiana University School of Medicine and his M.P.H. from the

University of California, Berkeley. We believe that Dr. Adams’ extensive public sector experience, including his work on the COVID-19 Task Force, qualifies him to serve on our board.

Barbara Duncan has served as a member of our Board since October 2020. Ms. Duncan served at Intercept Pharmaceuticals, Inc. as Chief Financial Officer and Treasurer from May 2009 to June 2016. Ms. Duncan also has served as Chair of the board of directors of Fusion Pharmaceuticals Inc. since November 2020, and on the boards of directors of Ovid Therapeutics, Inc. since June 2017, and Halozyme, Inc. since February 2023. Previously, Ms. Duncan served on the boards of directors of Jounce Therapeutics, Inc. from June 2016 to May 2023, Adaptimmune Therapeutics plc from June 2016 to June 2023, Immunomedics, Inc. from March 2019 to October 2020, Innoviva, Inc., from November 2016 through April 2018, Aevi Genomic Medicine, Inc., from June 2015 through January 2020, and ObsEva S.A. from November 2016 to May 2021. Ms. Duncan received her B.A. from Louisiana State University and her M.B.A. from the Wharton School, University of Pennsylvania. We believe Ms. Duncan is qualified to serve on our Board due to her experience in the biotechnology industry and with public companies.

Bruno Lucidi has served as a member of our Board since September 2014. Mr. Lucidi has served as an independent consultant to biotechnology companies since July 2013. Mr. Lucidi served as a Life Sciences Expert at Wallonia Trade and Foreign Investment Agency, an economic development agency, from January 2017 to June 2020. From October 2017 to September 2019, Mr. Lucidi was Chief Executive Officer at AgenTus Therapeutics, a pre-clinical stage biopharmaceutical company. Mr. Lucidi has more than 35 years of experience in the pharmaceutical industry. He held Senior Executive positions at Bristol-Myers Squibb, Johnson and Johnson and GSK and he has been CEO and Chairman of the board of several biopharmaceutical companies in Europe and the US. Mr. Lucidi was trained in Oncology at the Gustave Roussy Institute, Villejuif, France, in Marketing and Strategic Management of Companies at the Ecole Superieure de Commerce, Paris, France, and in Finance, Merger and Acquisitions at the Investment Banking Institute in New York. We believe Mr. Lucidi is qualified to serve on our Board due to his extensive experience in the life sciences industry.

Polly A. Murphy, D.V.M., Ph.D.has served as a member of our Board since August 2020. Dr. Murphy has served as Chief Business Officer at UroGen Pharma, Inc. since August 2020. Prior to that, Dr. Murphy served in various leadership roles at Pfizer, Inc. from September 2008 to August 2020, including as Vice President and Head of Commercial Development Pfizer Oncology Business Unit from January 2019 to August 2020, Vice President and Head of Global Marketing and Commercial Development Pfizer Oncology Business Unit from June 2017 to December 2018, and as Vice President and Head of Strategy and Business Development for Pfizer China from November 2013 to May 2018. Dr. Murphy has served on the board of directors of Celcuity Inc. since September 2022. Dr. Murphy received her D.V.M. and Ph.D. from Iowa State University. We believe Dr. Murphy is qualified to serve on our Board due to her experience in the pharmaceutical industry in business development and commercialization.

Bruce Polsky, M.D., has served as a member of our Board since November 2014. Dr. Polsky is the chair of the Department of Medicine at NYU Langone Hospital – Long Island in Mineola, New York, where he has practiced since May 2015. He also has served as professor and Chair of the Department of Medicine at NYU Long Island School of Medicine and as an Associate Dean at NYU Long Island School of Medicine since February 2019. Dr. Polsky is a leading clinical virologist who played an active role in clinical investigations of HIV/AIDS, HBV, HCV and other viral infections. From December 1998 to May 2015, Dr. Polsky was at Mount Sinai St. Luke’s and Mount Sinai Roosevelt Hospitals, where he served as Chair of the Department of Medicine and as Chief of the Division of Infectious Diseases, among other positions. Dr. Polsky received his M.D. from Wayne State University. We believe Dr. Polsky is qualified to serve on our Board due to his extensive clinical experience in the life sciences industry.

Item 1A. Risk Factors.

You should carefully consider the risks and uncertainties described below, as well as the other information in this Annual Report on Form 10-K, including our consolidated financial statements and the related notes and “Management’s Discussion and Analysis of Results of Operations and Financial Condition.” Our business, financial condition, results of operations or prospects could be materially and adversely affected if any of these risks occurs, and as a result, the market price of our common stock could decline and you could lose all or part of your investment. Our actual results could differ materially and adversely from those anticipated in these forward-looking statements as a result of certain factors, including those set forth below as well as other events that we do not currently anticipate or other events that we currently deem immaterial.

Risks Related to the Development of Product Candidates for the Treatment of COVID-19

There is significant uncertainty around our development of bemnifosbuvir as a potential treatment for COVID-19.

Since the start of the COVID-19 pandemic, we have focused substantive efforts on the development of bemnifosbuvir for the treatment of COVID-19. We may not succeed in developing, securing market authorization or approval, or commercializing bemnifosbuvir as a potential treatment for COVID-19.

In October 2020, we entered into the Roche License Agreement with Roche under which we granted to Roche an exclusive license to development and commercialization rights related to certain of our compounds, including bemnifosbuvir, outside of the US (other than for certain HCV uses). In November 2021, Roche notified us that it was terminating the Roche License Agreement effective February 10, 2022. In December 2021, due to the changing COVID-19 treatment landscape, including the availability of new oral antiviral treatment regimens, and the termination of the collaboration with Roche, we determined to discontinue each of the Phase 3 MORNINGSKY and MEADOWSPRING clinical trials. We did not enroll a sufficient number of patients in either Phase 3 study to conduct prespecified statistical analyses. In January 2022 we determined to close out the Phase 2 clinical trial in hospitalized patients.

Nonetheless, we are advancing the development of bemnifosbuvir for the treatment of COVID-19 in high-risk non-hospitalized patients pursuing both a mono- and combination therapy strategy. We do not know if either monotherapy or combination therapy approach will be successful.

Currently, we are conducting SUNRISE-3, a global, multicenter, randomized, double blind, placebo-controlled Phase 3 clinical trial evaluating bemnifosbuvir (550 mg BID for 5 days) in high-risk non-hospitalized patients with mild or moderate COVID-19. For the description of this trial, please see Part 1, Item 1, "Business". There are two interim analyses for review by the DSMB principally for safety and futility after approximately 650 and 1,350 patients in the supportive care monotherapy cohort have completed Day 29. We currently anticipate that the first interim analysis by the DSMB will occur in March of 2024 and that the second interim analysis by the DSMB will occur in the second quarter of 2024. At either interim analysis, the DSMB may determine that there are safety concerns or that the study as currently designed is futile. In this instance, we would be required to either discontinue the study or if recommended by the DSMB make amendments to the study. If feasible to implement, it is possible that such amendments, would make the trial more difficult to complete, if possible at all, and the time and cost for completion of the trial would be expected to increase.

In parallel with the conduct of SUNRISE-3, we are also engaging in efforts to identify a proprietary protease inhibitor product candidate that could potentially be combined with bemnifosbuvir for the treatment of COVID-19. Our efforts to develop a potential protease inhibitor to evaluate in combination with bemnifosbuvir are at a very early stage and we do not know if such efforts will be successful, or if successful, when such a protease inhibitor product candidate we identify may be permitted to enter clinical development. Before we can begin clinical development of a newly identified protease inhibitor product candidate, or any other product candidate, we will need to complete extensive preclinical studies to support the submission of an IND to the FDA or CTA to a comparable regulatory authority outside the US.

Alternatively, we may in-license or acquire the rights to develop and commercialize a protease inhibitor drug candidate from a third-party. Proposing, negotiating and implementing acquisition or in-license of a

protease inhibitor or any other product candidate that may be combined with bemnifosbuvir for the potential treatment of COVID-19 may be a lengthy and complex process. Other companies, including those with substantially greater financial, marketing and sales resources, may compete with us for the acquisition of such product candidates. We may not be able to acquire the rights to additional product candidates on terms that we find acceptable, if at all.

In addition, clinical trials evaluating combination regimens are subject to additional costs, time and risks, including the requirement to sufficiently demonstrate the effect, if any, of each constituent component of the combination regimen to the satisfaction of the FDA or other regulatory authorities. For example, we expect that we will be required to conduct early-stage clinical trials evaluating the safety of any newly discovered protease inhibitor candidate before we can conduct later stage clinical trials evaluating the combination of bemnifosbuvir with such protease inhibitor.

We have committed and plan to continue to commit significant financial and personnel resources to the development of bemnifosbuvir as a monotherapy, to the discovery of a protease inhibitor candidate to combine with bemnifosbuvir and to the combination of bemnifosbuvir and a protease inhibitor candidate for the treatment for COVID-19 (each, a “bemnifosbuvir COV19 product candidate”). If we are unable to successfully develop one or more bemnifosbuvir COV19 product candidates, we will have taken resources away from other development programs and may not be able to recuperate the resources dedicated to developing bemnifosbuvir COV19 product candidates, which could have a material adverse impact on our business.

If we are unable to complete the SUNRISE-3 clinical trial in the manner or on the timeline we anticipate or if data from our Phase 3 SUNRISE-3 clinical trial and other clinical trials are not supportive of further development or commercialization of one or more bemnifosbuvir COV19 product candidates, or the investor community otherwise has a negative reaction to any of the design of our clinical trial, expected time to complete our clinical trial or the clinical trial data, the demand for our common stock could decrease significantly, and the price of our common stock could decline substantially, which could result in significant losses for our stockholders.

Further, while we believe there is currently an urgent need for additional oral antiviral treatments for COVID-19, the longevity and extent of future market demand for new oral antiviral treatments is uncertain. If the serious health consequences associated with COVID-19 and infection with SARS-CoV-2 variants or subvariants were to dissipate for all persons, including those currently at high-risk for severe disease, the need for new treatments could decrease significantly. This reduction in incidence of serious health consequences could occur as a result of multiple factors including a significant and sustained decrease in the number or severity of new infections, an increase in the uptake and effectiveness of current and future vaccines and the introduction of other treatment options. If the need for a new treatment decreases before or soon after commercialization of a bemnifosbuvir COV19 product candidate, if successfully developed and approved, our business would be adversely impacted.

A bemnifosbuvir COV19 product candidate, even if successfully developed and approved, is expected to face significant competition from other treatments and vaccines for COVID-19 which have been authorized or approved for use or are in development.

Many biotechnology and pharmaceutical companies have and are continuing to develop treatments for COVID-19 or vaccines against SARS-CoV-2, the virus that causes COVID-19. Many of these companies, which include large pharmaceutical companies, have greater resources for development and established commercialization capabilities.

Currently in the US and elsewhere, there are therapeutics available for the treatment of COVID-19 including two oral antiviral therapies, Paxlovid™ developed by Pfizer which has been approved by the FDA, and Lagevrio™ developed by Merck and Ridgeback Therapeutics, which is authorized by FDA for emergency use for the treatment of high-risk COVID-19 patients. Additionally, Veklury®, a nucleotide prodrug developed by Gilead Sciences, is approved for the treatment of COVID-19 in adults and pediatric patients who are hospitalized or if not hospitalized have mild to moderate COVID-19 and are at high-risk for progression to severe COVID-19, including hospitalization and death. In Japan, the oral protease inhibitor, ensitrelvir, branded Xocova® developed and marketed by Shionogi, has been granted special approval for emergency use in patients with mild to moderate SARS-CoV-2 infection.

In the US and other territories outside Japan, Shionogi continues to develop ensitrelvir and is currently conducting a global development program including four Phase 3 trials evaluating ensitrelvir for the treatment of COVID-19. Additionally, Pfizer is conducting development of a second generation oral protease inhibitor. Other companies developing oral direct acting antivirals for treatment of COVID-19 include Junshi Biosciences, Jiangsu Simcere Pharmaceuticals, and SyneuRx. Efforts to develop new mAbs for the treatment of COVID-19 are also ongoing and being conducted by Regeneron Pharmaceuticals Inc. and Invivyd, Inc. among others.

In addition to therapeutics, in the US and elsewhere, vaccines indicated for active immunization to prevent COVID-19 and associated vaccine updates which are intended to extend the immunizing effect initiated with the administration of the initial vaccine have been approved or authorized for emergency use. Vaccine manufacturers, including Pfizer and BioNTech SE and Moderna, Inc., are continuing to develop new vaccines and vaccine updates that may have greater and longer immunizing effects against current and future variants of SARS-CoV-2.

In 2023, the US federal government announced the Project NextGen initiative with the purpose to accelerate and streamline the rapid development of the next generation of vaccines and treatments through public-private collaborations. Based at HHS and seeded with an initial investment of $5 billion, Project NextGen is coordinating across the US federal government and the private sector to fund and advance a pipeline of new, innovative vaccines and mAbs into clinical trials and potential review by the FDA. Project NextGen is focusing on mucosal vaccines, vaccines that provide broader protection against variants of concern and a longer duration of protection, pan-coronavirus vaccines, new mAbs that are more durable and resilient against new variants, and advancing new technologies that will improve access and enable faster, cheaper, rapid and more flexible production of vaccines and therapeutics.

Given the products currently approved or authorized for use as well as those in development by others, any treatment we may develop could face significant competition. If we are unable to develop a treatment that can be distinguished based on efficacy, safety, cost or other factors from the growing number of treatments for COVID-19 or if any treatment becomes the standard of care, can be administered more conveniently or at a lower cost, or any entity is more successful at commercializing an authorized or approved treatment, even if a bemnifosbuvir COV19 product candidate is approved, we may not be able to successfully commercialize such a product for the treatment of COVID-19, or compete with other treatments or vaccines, which would adversely impact our business and operations.

Our business, operations and financial results may be adversely affected by the continuing evolution of COVID-19.

The evolving and constantly changing impact of COVID-19, which was declared a global pandemic by the WHO in March 2020, will directly affect the potential commercial prospects of our product candidates for the treatment of COVID-19. In May 2023, three years into the pandemic, the WHO determined that COVID-19 no longer fit the definition of the public health emergency of international concern. While noting that this determination did not mean that the pandemic itself is ended, the WHO concluded that the global emergency COVID-19 has caused is ended for the time being. In reaching this conclusion, the WHO considered evidence of reducing risks to human health driven mainly by high population-level immunity from infection, vaccination or both; consistent virulence of currently circulating SARS-CoV-2 Omicron sub-lineages and improved clinical case management. Further, the WHO considered that these factors have contributed to a decline in the weekly number of COVID-19 related deaths and hospitalizations since the beginning of the pandemic and that while SARS-CoV-2 continues to evolve, the currently circulating variants do not appear to be associated with increased severity. The WHO currently classifies COVID-19 as an established and ongoing health issue.

The rates of infection, severity of the disease, the availability, administration and acceptance of vaccines, monoclonal antibodies, antiviral agents and other therapies, potential vaccine mandate policies, and “herd immunity” by the global population if achieved and sustained may materially affect the design and will impact the enrollment of our clinical trials, the potential regulatory authorization or approval of our bemnifosbuvir COV19 product candidates and the commercialization of our bemnifosbuvir COV19 product candidates, if authorized or approved.

Pandemics, epidemics or outbreaks of an infectious disease may materially and adversely impact our business, including our preclinical studies and clinical trials.

If other pandemics, epidemics or outbreaks of infectious disease occur in the future, we may experience disruptions that could severely impact our business, preclinical studies and clinical trials, including:

If we or any of the third parties with whom we engage were to experience shutdowns or other business disruptions due to pandemics, epidemics or outbreaks of infectious disease, our ability to conduct our business in the manner and on the timelines presently planned could be materially and negatively impacted.

Risks Related to Our Financial Condition and Capital Requirements

We have a limited operating history and no history of successfully developing or commercializing any approved antiviral products, which may make it difficult to evaluate the success of our business to date and to assess the prospects for our future viability.

We are a clinical-stage biopharmaceutical company. Our operations to date have been limited to financing and staffing our company, developing our technology, and identifying and developing our product candidates. Our prospects must be considered in light of the uncertainties, risks, expenses and difficulties frequently encountered by biopharmaceutical companies in their early stages of operations. We have not yet demonstrated an ability to complete any late-stage or pivotal clinical trials, obtain marketing approval, manufacture a product at commercial-scale, or conduct sales and marketing activities necessary for successful product commercialization, or have third parties to do these activities on our behalf. Consequently, predictions about our future success or viability may not be as accurate as they could be if we had a longer operating history or a history of successfully developing, obtaining marketing approval for and commercializing antiviral therapies.

In addition, we may encounter unforeseen expenses, difficulties, complications, delays and other known and unknown obstacles in developing or commercializing our products. For example, in November 2022, we initiated SUNRISE-3, the Phase 3 clinical trial evaluating bemnifosbuvir for the treatment of high risk outpatients with mild or moderate COVID-19. Our initial SUNRISE-3 study design and sample size

contemplated that the rate of hospitalization in the placebo cohort would be at least 4%. Since the initiation of the study, there has been a decline in the observed rate of hospitalization in the general population to below 4%. To address this, in August 2023, we amended the SUNRISE-3 clinical trial protocol to, among other things, take into account this lower rate of hospitalization with the effect that the study sample size was increased to approximately 2,200 patients in the supportive care monotherapy population in comparison to our initial target sample size of 1,300 patients in the supportive care monotherapy population. With the current sample size of 2,200 patients in the supportive care monotherapy population, we believe that the study is adequately powered for target rates of hospitalization and death of approximately 2 to 3% in patients who are at high-risk for disease progression. If the actual rate of hospitalization in the placebo cohort of patients is less, the DSMB evaluating the data at either of two interim analyses may determine that the study as currently designed is futile. In this instance, we would be required to either discontinue the study or if recommended by the DSMB make amendments to the study. If feasible to implement, it is possible that such amendments, would make the trial more difficult to complete, if possible at all, and the time and cost for completion of the trial would be expected to increase.

As the COVID-19 landscape has evolved, rates of testing, diagnosis and hospitalization for COVID-19 have varied and continue to vary substantially. Reported rates of hospitalization in many geographic regions have and may continue to fluctuate significantly. Additionally, we believe that the current rate of testing is substantially lower than the rate of testing occurring throughout earlier phases of the COVID-19 pandemic. Further, it is uncertain what effect the migration of government provided therapeutics, testing kits and other related items to more traditional health channels will have on rates of testing and diagnoses among other things. Even the perception that patients will now incur costs associated with the testing for and treatment of COVID-19 may result in rates of testing and treatment to further decline.

If we successfully develop and obtain approval of any product candidate, we will need to transition from a company with a research and development focus to a company capable of supporting commercial activities. We may not be successful in this transition.

As we continue to build our business, we expect our financial condition and operating results may fluctuate significantly from quarter to quarter and year to year due to a variety of factors, many of which are beyond our control. Accordingly, you should not rely upon the results included in this report or reports for any other particular prior quarterly or annual period as indications of future operating performance.

We have incurred significant operating expenses since inception and expect to incur significant additional operating expenses for the foreseeable future. We have no products that have generated any commercial revenue. We expect to incur operating losses in 2024 and for the foreseeable future.

We have incurred significant operating expenses since our inception. For the years ended December 31, 2023 and 2022, our operating expenses were $164.2 million and $130.7 million, respectively. As of December 31, 2023, we had an accumulated deficit of $195.8 million.

We have not commercialized any products and have never generated any revenue from product sales. We have devoted almost all of our financial resources to research and development, including our clinical trials and preclinical development activities. We expect to continue to incur significant additional operating expenses and to incur operating losses for the foreseeable future as we seek to advance product candidates through clinical development, continue preclinical development, expand our research and development activities, discover or acquire and develop product candidates, including any product candidate we may seek to combine with bemnifosbuvir for the potential treatment of COVID-19, complete preclinical studies and clinical trials, seek regulatory approval and, if we receive regulatory approval, commercialize our products.

In order to obtain the FDA’s or a foreign regulatory authority’s approval to market any product candidate in the US or abroad, respectively, we must submit to the FDA an NDA or similar application to the foreign regulatory authority demonstrating to the FDA’s or foreign regulatory authority’s satisfaction that the product candidate is safe and effective for its intended use(s). This demonstration requires significant research and extensive data from animal tests, which are referred to as nonclinical or preclinical studies, as well as human tests, which are referred to as clinical trials.

Furthermore, the costs of advancing product candidates into each succeeding clinical phase tend to increase substantially over time. The total costs to advance any of our product candidates to marketing approval in even a single jurisdiction would be substantial and difficult to accurately predict. Because of the numerous risks and uncertainties associated with the development of drug products, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to begin generating revenue from the commercialization of products or again achieve profitability. As we advance clinical development activities, particularly our Phase 3 SUNRISE-3 clinical trial for the treatment of high-risk outpatients with mild or moderate COVID-19 and our Phase 2 clinical trial evaluating the combination of bemnifosbuvir and ruzasvir for the treatment of HCV, our expenses have increased and we expect will continue to increase substantially. Additionally, our expenses will also increase substantially if or as we:

Furthermore, our ability to successfully develop, commercialize and license any products and generate product revenue is subject to substantial additional risks and uncertainties. Each of our product candidates and any future product candidate we may discover, license or otherwise acquire, will require additional preclinical and/or clinical development, regulatory approval in not less than one jurisdiction, the securing of manufacturing supply, capacity, distribution channels and expertise, the use of external vendors, the building of or other access to a commercial organization, substantial investment and significant marketing efforts before we generate any revenue from product sales. As a result, we expect to continue to use cash for operating activities and incur operating expenses and operating losses for the foreseeable future. The use of cash and incurrence of operating expenses and operating losses has had, and we expect will continue to have, an adverse effect on our working capital.

The amount of future expenses or losses and our ability to achieve or maintain profitability in future years, if ever, are uncertain. We have no products that have generated any commercial revenue, do not expect to generate revenues from the commercial sale of products in the near term, and might never generate revenues from the sale of products. Our ability to generate product revenue and maintain profitability will

depend on, among other things, successful completion of the clinical development of our product candidates; obtaining necessary regulatory approvals from the FDA and foreign regulatory authorities; establishing manufacturing and sales capabilities; market acceptance of our products, if approved, and establishing marketing infrastructure or otherwise arranging to commercialize our product candidates for which we obtain approval; and raising sufficient funds to finance our activities. We might not succeed at any of these undertakings. If we are unsuccessful at some or all of these undertakings, our business, prospects, and results of operations may be materially adversely affected.

We maintain our cash at financial institutions, often in balances that exceed federally insured limits.

The majority of our cash is held in accounts at US banking institutions. Cash held in depository accounts may exceed the Federal Deposit Insurance Corporation (“FDIC”) standard deposit insurance limit of $250,000. If such banking institutions were to fail, such as Silicon Valley Bank when the FDIC took control in March 2023, we could lose all or a portion of those amounts held in excess of such insured amounts. In the future, our access to our cash in amounts adequate to finance our operations could be significantly impaired if the financial institutions with which we have arrangements encounter liquidity constraints or failures. Any future limitation on timely access to our funds or any material loss that we may experience in the future could have a material adverse effect on our financial condition and could materially impact our ability to pay our operating expenses or make other payments.

We will require substantial additional financing, which may not be available on acceptable terms, or at all. A failure to obtain this necessary capital when needed could force us to delay, limit, reduce or terminate our product development or commercialization efforts.

Since inception, we have incurred substantial operating expenses. We expect to incur substantial expenses in connection with our current and planned business activities, particularly the conduct of the Phase 3 SUNRISE-3 clinical trial for the treatment of high-risk outpatients with mild or moderate COVID-19, our Phase 2 clinical trial evaluating the combination of bemnifosbuvir and ruzasvir for the treatment of HCV, and if the Phase 2 clinical trial is successful, Phase 3 clinical development of this HCV combination product candidate. Additionally, we anticipate that we will incur substantial expenses in connection with the discovery, license or other acquisition and potential development of a combination bemnifosbuvir COV19 product candidate and in connection with the discovery, acquisition and development of other product candidates.

We will continue to need additional capital to fund future clinical trials and preclinical development, which we may raise through equity offerings, debt financings, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements or other sources. Additional sources of financing might not be available on favorable terms, if at all. If we do not succeed in raising additional funds on acceptable terms, we might be unable to initiate or complete planned clinical trials or seek regulatory approvals of any of our product candidates from the FDA, or any foreign regulatory authorities, and could be forced to discontinue product development. In addition, attempting to secure additional financing could divert the time and attention of our management from day-to-day activities and may harm our product candidate development efforts.

Based on our current operating plan, we believe that our cash and cash equivalents as of December 31, 2023 will be sufficient to fund our operating expenses and capital expenditure requirements through 2026. This estimate is based on assumptions that may prove to be wrong, and we could use our available capital resources sooner than we currently expect. We will require significant additional funds in order to launch and commercialize our current and any future product candidates to the extent that such launch and commercialization are not the responsibility of a collaborator. In addition, other unanticipated costs may arise in the course of our development efforts. Because the design and outcome of our planned and anticipated clinical trials is highly uncertain, we cannot reasonably estimate the actual amounts necessary to successfully complete the development and, if approved, commercialization of any product candidate we develop.

The timing and amount of our future capital requirements will depend on many factors, including but not limited to:

Currently, we do not have any committed external source of funds or other support and we cannot be certain that additional funding will be available on acceptable terms, or at all. Our ability to access potential sources of future liquidity and raise funds will depend upon financial, economic and geopolitical conditions and other factors, many of which are beyond our control. These external factors, including high rates of interest and inflation, will also impact and may increase substantially costs we incur in connection with any potential fundraising. If we are unable to raise additional capital in sufficient amounts, on terms acceptable to us, or on a timely basis, we may have to significantly delay, scale back or discontinue the development or commercialization of our product candidates or other research and development initiatives.

We have not generated any revenue from product sales and may not be able to achieve profitability.

We incurred a net loss of $136.0 million and $115.9 million for the years ended December 31, 2023 and 2022, respectively. Our ability to achieve and sustain future profitability depends upon our ability to

generate revenue from product sales. We have not generated product revenue and we do not expect to generate product revenue unless or until we successfully complete clinical development and obtain regulatory approval of, and then successfully commercialize, at least one of our product candidates. Our product candidates are in varying stages of development, which is expected to necessitate additional preclinical studies in some cases and in all cases will require additional clinical development as well as regulatory review and approval, substantial investment in and access to sufficient commercial manufacturing capacity and significant marketing efforts before we can generate any revenue from product sales. Currently, we do not anticipate generating revenue from product sales for at least the next few years. Our ability to generate revenue depends on a number of factors, including, but not limited to:

Many of the factors listed above are beyond our control, and could cause us to experience significant delays, incur substantially greater expenses than anticipated or prevent us from obtaining regulatory approvals or commercializing our product candidates. Even if we are able to commercialize our product candidates, we may not be able to achieve and maintain profitability after generating product sales or meet outside expectations for our profitability. If we are unable to achieve or sustain profitability or to meet outside expectations for our profitability, the value of our common stock will be materially adversely affected. In addition, if we are unable to generate sufficient revenue through the sale of any products, we may be unable to continue operations.

Our ability to use our net operating loss carryforwards and other tax attributes to offset taxable income may be subject to certain limitations.

As of December 31, 2023, we had US federal net operating loss carryforwards (“NOLs”), of $31.4 million, which may be available to offset future taxable income, if any, of which $0.4 million begin to expire in 2034 and of which $31.0 million do not expire but are limited in their usage in future tax years to an annual deduction equal to 80% of annual taxable income. In addition, as of December 31, 2023, we had state NOLs of $55.3 million, which may be available to offset future taxable income, if any, and begin to expire in 2042.

In general, under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended (“Code”), a corporation that undergoes an “ownership change,” which is generally defined as a greater than 50% change by value in its equity ownership over a three-year period, is subject to limitations on its ability to utilize its pre-change NOLs and its research and development credit carryforwards to offset future taxable income. Our NOLs and research and development credit carryforwards may be subject to limitations arising from previous ownership changes, and if we undergo an ownership change, our ability to utilize NOLs (to the extent not previously utilized) and research and development credit carryforwards could be further limited by Sections 382 and 383 of the Code.

For each of the years ended December 31, 2023 and 2022, we have completed a Section 382 study, the results of which indicated that no ownership shift occurred during such respective period. However, this conclusion could be challenged by tax authorities. In addition, future changes in our stock ownership, some of which might be beyond our control, could result in an ownership change under Sections 382 and 383 of the Code. For these reasons, we may not be able to utilize existing NOLs or research and development credit carryforwards or net operating losses and research and development credits that may be generated in the future.

We may delay, suspend or terminate the development of a product candidate at any time if we believe the perceived market or commercial opportunity does not justify further investment or for other strategic business, financial or other reasons, which could materially harm our business and adversely affect our stock price.

Even if the results of preclinical studies and clinical trials that we have conducted or may conduct in the future may support further development of one or more of our product candidates, we may delay, suspend or terminate the future development of a product candidate at any time for strategic, business, financial or other reasons, including the determination or belief that the emerging profile of the product candidate is such that it may not receive regulatory approvals in key markets, gain meaningful market acceptance, otherwise provide any competitive advantages in its intended indication or market or generate a significant return to stockholders. For example, in February 2023, after advancing AT-752 into a Phase 2 clinical trial, we decided not to pursue further clinical development of AT-752 for the treatment and prophylaxis of dengue. This action was taken due to the anticipated long timelines and other challenges associated with the clinical development of an antiviral for the treatment of dengue. This action and any other similar delays, suspensions or terminations of other clinical programs or product candidates could materially harm our business, results of operations or financial condition.

Risks Related to the Discovery, Development, Preclinical and Clinical Testing, Manufacturing and Regulatory Approval of Our Product Candidates

Our business is highly dependent on our ability to develop one or more bemnifosbuvir COV19 product candidates. If we are not successful in developing a bemnifosbuvir COV19 product candidate, our business will be harmed. Our business is also highly dependent on the success of

our other most advanced product candidates, including the combination of bemnifosbuvir and ruzasvir for the treatment of HCV, which will require significant additional clinical testing, including Phase 3 clinical testing, before we can seek regulatory approval and potentially launch commercial sales. If these product candidates fail in clinical development, do not receive regulatory approval or are not successfully commercialized, or are significantly delayed in doing so, our business will be harmed.

A substantial portion of our business and future success depends on our ability to develop, obtain regulatory approval for and successfully commercialize one or more bemnifosbuvir COV19 product candidates and the combination of bemnifosbuvir and ruzasvir for the treatment of HCV. We currently have no products that are approved for commercial sale and have not completed the development of any of our product candidates, and we may never be able to develop marketable products.

During the near term we expect that a substantial portion of our efforts and expenditures will continue to be devoted to developing a potential bemnifosbuvir COV19 product candidate. Among other things, this effort will require the successful completion of our Phase 3 SUNRISE-3 clinical trial for the treatment of high-risk outpatients with mild to moderate COVID-19 and additional nonclinical and clinical development and the incurrence of expenses related to discovering, acquiring or in-licensing and then developing a drug or drug candidate to combine with bemnifosbuvir for the treatment of COVID-19.

There have been a large number of programs developing therapeutics for COVID-19 that have not succeeded. This includes the development of obeldesivir (GS-5245), an oral nucleoside prodrug, that was being developed by Gilead Sciences in two Phase 3 clinical trials. In February 2024, Gilead Sciences announced that its Phase 3 clinical trial of obeldesivir which had enrolled standard risk patients failed to meet its primary endpoint of alleviation of symptoms. Previously, in September 2023, Gilead Sciences announced that, based upon lower-than-expected COVID-19 incidence rates and related hospitalizations or all cause deaths, it was discontinuing enrollment in its Phase 3 clinical trial in non-hospitalized patients at high-risk of progression. These or similar factors may also adversely impact our SUNRISE-3 Phase 3 clinical trial, our ability to submit an NDA or other marketing authorization for or obtain marketing approval of bemnifosbuvir for the treatment of high-risk patients with COVID-19 or any other bemnifosbuvir COV19 product candidate.

COVID-19 is unpredictable and therapies, including any bemnifosbuvir COV19 product candidate, may be adversely impacted up to the point of obsolescence by the emergence of new variants or subvariants as well as by the development and authorization and approval of new vaccines, vaccine updates and therapeutics.

Additionally, we expect that a substantial portion of our efforts and expenditures over the next few years will be devoted to developing the combination of bemnifosbuvir and ruzasvir for the treatment of HCV which will require additional clinical development, management of clinical, medical affairs and manufacturing activities, obtaining regulatory approvals in multiple jurisdictions, securing of manufacturing supply, building of or otherwise accessing a commercial organization, substantial investment and significant marketing efforts.

We can not be certain that any of our current or future product candidates will be successful in clinical trials, receive regulatory approval or be successfully commercialized even if we receive regulatory approval. Further, our development of any product candidate may be delayed or suspended, which may affect our ability to successfully commercialize such product candidate. Additionally, our ability to successfully commercialize a product will also be dependent upon our ability to timely manufacture at commercial scale the quantities of product that will satisfy market demand.

If our competitors develop products to treat diseases and, if applicable, specified patient populations which our current or future product candidates are being developed to treat, before we are able to successfully develop a product candidate, or if our competitors develop any products that are superior to our product candidates, our potential market share could become smaller or non-existent. Even if we receive approval to market any product candidate, we cannot be certain that our product candidates will be as or more effective than other commercially available alternatives, successfully commercialized or widely accepted in the marketplace. For each of COVID-19 and HCV, there are currently approved and marketed oral antiviral products against which we would be required to compete.

We can not be certain that, if approved, the safety and efficacy profile of any product will be consistent with the results observed in clinical trials, or in the case of a bemnifosbuvir COV19 product candidate, that it will demonstrate efficacy against continuing mutations of the SARS-COV-2 virus, the causative agent of COVID-19. If we are not successful in the clinical development of a bemnifosbuvir COV19 product candidate or our other most advanced product candidates, the required regulatory approvals for these product candidates are not obtained, there are significant delays in the development or approval of these product candidates, supplying on an uninterrupted basis commercial quantities of approved products or any approved products are otherwise not commercially successful, our business, financial condition and results of operations may be materially harmed.

The regulatory approval processes of the FDA and comparable foreign regulatory authorities are lengthy, expensive, time-consuming, and inherently unpredictable. If we are ultimately unable to obtain regulatory approval for our product candidates, we will be unable to generate product revenue and our business will be seriously harmed.

We are not permitted to commercialize, market, promote or sell any product candidate in the US without obtaining marketing approval from the FDA. Foreign regulatory authorities impose similar requirements. The time required to obtain approval by the FDA and comparable foreign regulatory authorities is unpredictable, typically takes many years following the commencement of clinical trials and depends upon numerous factors, including the type, complexity and novelty of the product candidates involved and the disease or condition for which the product candidate is intended.

In addition, approval policies, regulations or the type and amount of clinical data necessary to gain approval may change during the course of a product candidate’s clinical development particularly with respect to COVID-19, which continues to evolve rapidly, and may vary among jurisdictions, which may cause delays in the approval or the decision not to approve an application.

In the early stages of the COVID-19 pandemic when there were no available countermeasures, initial COVID-19 vaccines, therapeutic antibodies and other therapeutics that demonstrated positive clinical trial results moved rapidly through the regulatory review and EUA process of the FDA and regulatory authorities in other jurisdictions, including the EU. The speed at which all parties acted to create, develop and review these countermeasures, including therapeutics for COVID-19, was exceptional. With COVID-19 countermeasures, including oral antivirals, now available and COVID-19 moving from pandemic to endemic status, these exceptional and extraordinary dynamics have lessened and evolving priorities within the FDA and the regulatory authorities in other jurisdictions, including changes based on new data regarding potential therapeutics of others, new variants of the virus, preferred clinical development pathways and clinical trial endpoints may significantly affect the regulatory timeline for further authorizations or approvals for additional COVID-19 therapeutics including bemnifosbuvir. Even with Fast Track designation, and the conduct of SUNRISE-3 under a US IND, uncertainty remains regarding the timelines and regulatory processes required for the authorization or approval of new treatments for COVID-19, including bemnifosbuvir.

Regulatory authorities have substantial discretion in the approval process and may refuse to accept any application or may decide that our data are insufficient for approval and require additional preclinical, clinical or other studies. Approval by any one regulatory authority does not ensure approval by any other regulatory authority.

We have not submitted an NDA for, or obtained regulatory approval of, any product candidate. We must complete additional clinical development in each case and in some cases additional preclinical or nonclinical development to demonstrate the safety and efficacy of our product candidates in humans to the satisfaction of the regulatory authorities before we will be able to obtain these approvals, and it is possible that none of our existing product candidates or any product candidates we may seek to develop in the future will ever obtain regulatory approval. Applications for our product candidates could fail to receive regulatory approval for many reasons, including but not limited to the following:

This lengthy approval process, as well as the unpredictability of the results of clinical trials, may result in our failing to obtain regulatory approval to market any of our product candidates, which would seriously harm our business. In addition, even if we were to obtain approval, regulatory authorities may approve any of our product candidates for fewer or more limited indications than we request, may impose significant limitations in the form of narrow indications, warnings, or a REMS or similar risk management measures. Regulatory authorities may not approve the price we intend to charge for products we may develop, may grant approval contingent on the performance of costly post-marketing clinical trials, or may approve a product candidate with a label that does not include the labeling claims necessary or desirable for the successful commercialization of that product candidate. Any of the foregoing scenarios could seriously harm our business.

Clinical development, including enrollment of patients in clinical trials, is an expensive, lengthy and uncertain process. We may encounter substantial delays and costs in our clinical trials, or may not be able to conduct or complete our clinical trials on the timelines we expect, if at all.

Before obtaining marketing approval from the FDA or other comparable foreign regulatory authorities for the sale of our product candidates, we must complete preclinical development and extensive clinical trials to demonstrate the safety and efficacy of our product candidates. Clinical testing is expensive, time-consuming and subject to uncertainty. A failure of one or more clinical trials can occur at any stage of the process, such as the failure in October 2021 of bemnifosbuvir to meet the primary endpoint in the overall patient population in the Phase 2 MOONSONG clinical trial. The outcome of preclinical studies and early-stage clinical trials may not be predictive of the success of later clinical trials. This may be particularly true in the development of therapeutics for the treatment of COVID-19, including our development of bemnifosbuvir COV19 product candidates, where the evolution of the virus and disease have occurred at such a rapid rate that product candidates in development have the potential to become obsolete before clinical development is completed. Moreover, preclinical and clinical data, particularly the analysis of exploratory endpoints and analysis of data derived from patient subgroups, such as the data from the MORNINGSKY study upon which we have relied to initiate the Phase 3 SUNRISE-3 clinical trial and continue clinical development of bemnifosbuvir for the treatment of COVID-19, as well as the data from the lead-in cohort in our HCV Phase 2 clinical trial of the combination of bemnifosbuvir and ruzasvir, are often susceptible to varying interpretations, and many companies that have believed their product candidates performed satisfactorily in preclinical studies and clinical trials have nonetheless failed to obtain marketing approval of their drugs.

To date, we have not completed any late-stage or pivotal clinical trials for any of our product candidates. We cannot guarantee that any of our planned or ongoing clinical trials will be initiated or conducted as planned or completed on schedule, if at all. We also cannot be sure that submission of any future IND or similar application will result in the FDA or other regulatory authority, as applicable, allowing future clinical trials to begin in a timely manner, if at all. Moreover, even if these trials begin, issues may arise that could

cause regulatory authorities to suspend or terminate such clinical trials. A failure of one or more clinical trials can occur at any stage of testing, and our future clinical trials may not be successful.

Events that may prevent successful or timely initiation or completion of clinical trials include but are not limited to:

In addition, events, occurrences and disruptions caused by the continuing evolution of COVID-19 may increase the likelihood that we encounter difficulties or delays in initiating, enrolling, conducting or completing our planned and ongoing clinical trials. In particular, the rate of incidence, testing and diagnosis of COVID-19, rates of hospitalization and death, changes in the SOC for the treatment of COVID-19, which continues to evolve due to the mutation of the virus and increasing knowledge being obtained by healthcare providers, rates and durability of vaccines and population immunity, and availability of therapeutic options, may impact the successful completion of our Phase 3 SUNRISE-3 clinical trial and other COVID-19-related clinical trials we may initiate.

Any inability to successfully complete our Phase 3 SUNRISE-3 clinical trial, our Phase 2 clinical trial evaluating the combination of bemnifosbuvir and ruzasvir for the treatment of HCV or the completion of any other planned clinical trials we may initiate could result in additional costs to us or impair our ability to generate revenue from product sales. In addition, if we make manufacturing or formulation changes to our product candidates, we may be required to or we may elect to conduct additional studies to bridge our modified product candidates to earlier versions. Clinical trial delays could also shorten any periods during which any approved products have patent protection and may allow our competitors to further strengthen the market position of their current products or bring new products to market before we do, which could impair our ability to successfully commercialize our product candidates and may seriously harm our business.

We could also encounter delays if a clinical trial is suspended or terminated by us, by the DSMB for such trial, or by the FDA or any other regulatory authority, or if the IRBs of the institutions at which such trials are being conducted suspend or terminate the participation of their clinical investigators and sites subject to their review. Such authorities may suspend or terminate a clinical trial due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or trial site by the FDA or other regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a product candidate, changes in governmental regulations or administrative actions or lack of adequate funding to continue the clinical trial.

Further, conducting clinical trials in foreign countries, as we are currently doing and otherwise expect to continue doing for other product candidates, presents additional risks that may delay completion of our clinical trials. These risks include the failure of enrolled patients in foreign countries to adhere to clinical protocol as a result of differences in healthcare services or cultural customs, managing additional administrative burdens associated with foreign regulatory schemes, as well as political and economic risks relevant to such foreign countries.

Moreover, principal investigators for our clinical trials may serve as scientific advisors or consultants to us from time to time and receive compensation in connection with such services. Under certain circumstances, we may be required to report some of these relationships to the FDA or comparable

foreign regulatory authorities. The FDA or comparable foreign regulatory authority may conclude that a financial relationship between us and a principal investigator has created a conflict of interest or otherwise affected interpretation of the study. The FDA or comparable foreign regulatory authority may therefore question the integrity of the data generated at the applicable clinical trial site and the utility of the clinical trial itself may be jeopardized. This could result in a delay in approval, or rejection, of our marketing applications by the FDA or comparable foreign regulatory authority, as the case may be, and may ultimately lead to the denial of marketing approval of one or more of our product candidates.

Delays in the completion of any clinical trial of our product candidates will increase our costs, slow down our product candidate development and approval process and delay or potentially jeopardize our ability to commence product sales and generate product revenue. In addition, many of the factors that cause, or lead to, a delay in the commencement or completion of clinical trials may also ultimately lead to the denial of regulatory approval of our product candidates. Any delays to our clinical trials that occur as a result could shorten any period during which we may have the exclusive right to commercialize our product candidates and our competitors may be able to further strengthen the market position of their current products or bring new or additional products to market before we do, which could significantly reduce the commercial viability of our product candidates. Any of these occurrences may harm our business, financial condition and prospects significantly.

In addition, the FDA’s and other regulatory authorities’ policies with respect to clinical trials may change and additional government regulations may be enacted. For instance, the regulatory landscape related to clinical trials in the EU recently evolved. The EU CTR which was adopted in April 2014 and repeals the EU Clinical Trials Directive (“Clinical Trial Directive”), became applicable on January 31, 2022. While the EU Clinical Trials Directive required a separate CTA to be submitted in each member state in which the clinical trial takes place, to both the competent national health authority and an independent ethics committee, the CTR introduces a centralized process and only requires the submission of a single application for multi-center trials. The CTR allows sponsors to make a single submission to both the competent authority and an ethics committee in each member state, leading to a single decision per member state. The assessment procedure of the CTA has been harmonized as well, including a joint assessment by all member states concerned, and a separate assessment by each member state with respect to specific requirements related to its own territory, including ethics rules. Each member state’s decision is communicated to the sponsor via the centralized EU portal. Once the CTA is approved, clinical study development may proceed. The CTR foresees a three-year transition period. The extent to which ongoing and new clinical trials will be governed by the CTR varies. Clinical trials for which an application was submitted (i) prior to January 31, 2022 under the EU Clinical Trials Directive, or (ii) between January 31, 2022 and January 31, 2023 and for which the sponsor has opted for the application of the EU Clinical Trials Directive remain governed by said Directive until January 31, 2025. After this date, all clinical trials (including those which are ongoing) will become subject to the provisions of the CTR. Through January 31, 2023, submissions of CTAs that we made in connection with each of our SUNRISE-3 Phase 3 clinical trial and our Phase 2 HCV clinical trial were made using the EU Clinical Trial Directive. We have submitted CTAs under the CTR since February 1, 2023. Our experience with submissions under the CTR is limited. Compliance with the CTR requirements by us and our third-party service providers, such as CROs, may impact our developments plans.

It is currently unclear to what extent the UK will seek to align its regulations with the EU. While the MHRA has confirmed that it will bring forward changes to the legislation post-Brexit, the final legislation has not yet been introduced by the UK Government and it therefore remains uncertain as to the extent to which the UK clinical trials framework will align with or diverge from the EU CTR. A decision by the UK not to closely align its regulations with the new approach that has been adopted in the EU may have an effect on the cost of conducting clinical trials in the UK as opposed to other countries.

If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies governing clinical trials, our development plans may also be impacted.

We are developing certain of our product candidates in combination with other therapies, which exposes us to additional risks.

Combination therapies are commonly used for the treatment of viral infections. Developing combination therapies exposes us to additional clinical risks, such as the requirement that we demonstrate the safety and efficacy of each active component of any combination regimen we may develop.

For the treatment of HCV, we are currently developing bemnifosbuvir in combination with ruzasvir, a product candidate that has not yet been approved for marketing by the FDA or similar foreign regulatory authorities.

If the FDA or similar foreign regulatory authorities do not approve the combination agents or revoke their approval thereof, or if safety, efficacy, manufacturing, or supply issues arise with the drugs we choose to evaluate in combination with our product candidates, we may be unable to obtain approval of or market our product candidates for combination therapy regimens.

Additionally, if the third-party manufacturers of therapies or therapies in development used in combination with our product candidates are unable to produce sufficient quantities for clinical trials or for commercialization of our product candidates, or if the cost of combination therapies are prohibitive, our development and commercialization efforts would be impaired, which would have an adverse effect on our business, financial condition, results of operations and growth prospects.

Our product candidates may be associated with serious adverse events, undesirable side effects or have other properties that could halt their clinical development, prevent their regulatory approval, limit their commercial potential or result in significant negative consequences.

Adverse events or other undesirable side effects caused by our product candidates could cause us, our collaborators, any DSMB for a trial, or regulatory authorities to interrupt, delay or halt clinical trials and could result in a more restrictive label or the delay or denial of regulatory approval by the FDA or other comparable foreign regulatory authorities.

During the conduct of clinical trials, patients report changes in their health, including illnesses, injuries, and discomforts, to their study doctor. Often, it is not possible to determine whether or not the product candidate being studied caused these conditions. It is possible that as we test our product candidates in larger, longer and more extensive clinical trials, or as use of these product candidates becomes more widespread if they receive regulatory approval, illnesses, injuries, discomforts and other adverse events that were observed in previous trials, as well as conditions that did not occur or went undetected in previous trials, will be reported by patients. Many times, side effects are only detectable after investigational products are tested in large-scale clinical trials or, in some cases, after they are made available to patients on a commercial scale following approval.

If any serious adverse events occur, clinical trials or commercial distribution of any product candidates or products we develop could be suspended or terminated, and our business could be seriously harmed. Treatment-related side effects could also affect patient recruitment and the ability of enrolled patients to complete the trial or result in potential liability claims. Regulatory authorities could order us to cease further development of, deny approval of, or require us to cease selling any product candidates or products for any or all targeted indications. If we are required to delay, suspend or terminate any clinical trial or commercialization efforts, the commercial prospects of such product candidates or products may be harmed, and our ability to generate product revenues from them or other product candidates that we develop may be delayed or eliminated. Additionally, if one or more of our product candidates receives marketing approval and we or others later identify undesirable side effects or adverse events caused by such products, a number of potentially significant negative consequences could result, including but not limited to:

Any of these events could prevent us from achieving or maintaining market acceptance of the particular product candidate, if approved, and could seriously harm our business, financial condition and results of operations.

If we encounter difficulties enrolling patients in our clinical trials, our clinical development activities could be delayed or otherwise adversely affected.

We may experience difficulties in patient enrollment in our clinical trials for a variety of reasons. The timely completion of clinical trials in accordance with their protocols depends, among other things, on our ability to enroll a sufficient number of patients who remain in the trial until its conclusion. The enrollment of patients depends on many factors, including but not limited to:

Particularly with respect to our COVID-19 clinical trials and most notably with respect to SUNRISE-3, we have observed that the rate of enrollment varies significantly based upon the rate of transmissibility and severity of disease associated with newly emerged SARS-CoV-2 variants. To the extent waves of infection with variants causing severe disease decline prior to the time we complete enrollment of the study we anticipate that the rate of enrollment in the SUNRISE-3 clinical trial is also likely to lessen. This occurrence could have the effect of delaying the completion of the trial which currently requires the enrollment of approximately 2,200 patients in the supportive care monotherapy cohort. A delay in the completion of the study would also delay our ability to seek regulatory approval to commercialize bemnifosbuvir.

In addition, our clinical trials will compete with other clinical trials sponsored by third parties, including potential competitors, that are in the same or substantially similar therapeutic areas as our product candidates, and this competition may reduce the number and types of patients available to us because some patients who might have opted to enroll in our trials may instead opt to enroll in a trial being conducted by one of our competitors. For example, we are aware of other clinical trials sponsored by our

potential competitors, including Shionogi, that are recruiting patients in clinical trials evaluating oral antivirals for the treatment of high-risk outpatients with mild to moderate COVID-19, the same patient population that we are seeking to enroll in SUNRISE-3. Since the number of qualified clinical investigators is limited, it is possible that we will conduct some of our clinical trials at the same clinical trial sites that some of our competitors use, which will reduce the number of patients who are available for our clinical trials at such clinical trial sites.

Delays in patient enrollment as a result of competition, or in the case of COVID-19 in particular, evolution of the disease and treatment paradigms as well as rates of infection, testing, diagnoses, hospitalizations and deaths, or for other reasons, may result in increased costs or may affect the timing or outcome of our ongoing and planned clinical trials, which could prevent completion or commencement of these trials and adversely affect our ability to advance the development of our product candidates. For example, we are aware that Gilead Sciences in September 2023 discontinued the enrollment of high-risk outpatients in the COVID-19 Phase 3 clinical trial of its product candidate, obeldesivir, an oral nucleoside prodrug. The stated reasons for the discontinuation of enrollment prior to completion of the trial was the observation by Gilead Sciences of lower-than-expected COVID-19 incidence rates and related hospitalizations or all cause deaths in countries where patients were being enrolled. These or similar factors may also impact our SUNRISE-3 Phase 3 clinical trial of bemnifosbuvir for the treatment of high-risk patients with COVID-19.

A Fast Track designation by the FDA may not lead to a faster development or regulatory review or approval process, and does not increase the likelihood that our product candidates will receive marketing approval.

If a product candidate is intended for the treatment of a serious or life-threatening condition and the product candidate demonstrates the potential to address unmet medical needs for such condition, the product candidate sponsor may apply for Fast Track designation. In April 2023, the FDA granted Fast Track designation for the investigation of bemnifosbuvir for the treatment of COVID-19. As the sponsor of a product candidate that has received Fast Track designation, we may have opportunities for more frequent interactions with the FDA review team during product development and, once a NDA is submitted, the NDA may be eligible for priority review. An NDA for a Fast Track designated product candidate may also be eligible for rolling review, where the FDA may consider review of sections of the NDA on a rolling basis before the complete NDA is submitted.

The FDA has broad discretion whether or not to grant Fast Track designation to any particular product candidate. As a result, we may seek such Fast Track designation for other product candidates, but cannot assure you that the FDA would decide to grant it. Even though a Fast Track designation has been received for the investigation of bemnifosbuvir to treat COVID-19, we may not experience a faster development process, review or approval compared to conventional FDA procedures. The FDA may withdraw Fast Track designation if it believes that the designation is no longer supported by data from our clinical development program. Many product candidates that have received Fast Track designation have nevertheless failed to obtain approval.

We currently conduct clinical trials, and may in the future choose to conduct additional clinical trials, of our product candidates in sites outside the US, and the FDA may not accept data from trials conducted in foreign locations.

We currently conduct, and expect in the future to conduct, clinical trials outside the US for our product candidates. The acceptance of study data from clinical trials conducted outside the US or another jurisdiction by the FDA or comparable foreign regulatory authorities may be subject to certain conditions or may not be accepted at all. In cases where data from foreign clinical trials are intended to serve as the sole basis for marketing approval in the US, the FDA will generally not approve the application on the basis of foreign data alone unless (i) the data are applicable to the US population and US medical practice; (ii) the trials were performed by clinical investigators of recognized competence and pursuant to GCP regulations; and (iii) the data may be considered valid without the need for an on-site inspection by the FDA, or if the FDA considers such inspection to be necessary, the FDA is able to validate the data through an on-site inspection or other appropriate means. In addition, even where the foreign study data are not intended to serve as the sole basis for approval, if the study was not otherwise subject to an IND, the FDA will not accept the data as support for an application for marketing approval unless the study was

conducted in accordance with GCP requirements and the FDA is able to validate the data from the study through an onsite inspection if deemed necessary. Many foreign regulatory authorities have similar approval requirements. In addition, such foreign trials would be subject to the applicable local laws of the foreign jurisdictions where the trials are conducted. There can be no assurance that the FDA or any comparable foreign regulatory authority will accept data from trials conducted outside of the US or the applicable jurisdiction. If the FDA or any comparable foreign regulatory authority does not accept such data, it would result in the need for additional trials, which could be costly and time-consuming, and which may result in current or future product candidates that we may develop not receiving approval for commercialization in the applicable jurisdiction.

In addition, there are risks inherent in conducting clinical trials in multiple jurisdictions, inside and outside of the US, such as:

Interim, “topline” and preliminary data from our clinical trials that we announce or publish from time to time may change as more patient data become available and are subject to audit and verification procedures that could result in material changes in the final data.

From time to time, we may publicly disclose preliminary or top-line data from our preclinical studies and clinical trials, which is based on a preliminary analysis of then-available data. For example, in January and February 2024, we have announced preliminary, then-available data from the 60 patients lead-in cohort in our Phase 2 clinical trial evaluating the combination of bemnifosbuvir and ruzasvir for the treatment of HCV. Similar to all preliminary and then-available data, these results and related findings and conclusions are subject to change as additional data becomes available or following a more comprehensive review of the data related to the particular study or trial. We also make assumptions, estimations, calculations and conclusions as part of our analyses of data, and we may not have received or had the opportunity to fully and carefully evaluate all data. Consequently, the top-line or preliminary data that we report may differ from final results reported from the same studies, or different conclusions or considerations may qualify such preliminary or topline data, once additional data have been received and fully evaluated. Top-line and preliminary data also remain subject to audit and verification procedures that may result in the final results being materially different from the preliminary or topline data we previously published. As a result, top-line data should be viewed with caution until the final data are available.

From time to time, we may also disclose interim data from our preclinical studies and clinical trials. Interim data from clinical trials that we may subsequently complete are subject to the risk that one or more of the clinical outcomes may materially change as patient enrollment continues and more patient data become available or as patients from our clinical trials continue other treatments for their disease. Adverse differences between preliminary or interim data and final results could significantly harm our business prospects. Further, disclosure of interim data by us or by our competitors could result in volatility in the price of our common stock.

Further, others, including regulatory agencies, may not accept or agree with our assumptions, estimates, calculations, conclusions or analyses or may interpret or weigh the importance of data differently, which could impact the value of the particular program, the approvability or commercialization of the particular product candidate or product and our company in general.

In addition, the information we choose to publicly disclose regarding a particular study or clinical trial is based on what is typically extensive information, and you or others may not agree with what we determine is material or otherwise appropriate information to include in our disclosure. If the interim,

top-line, or preliminary data that we report differ from actual results, or if others, including regulatory authorities, disagree with the conclusions reached, our ability to obtain approval for, and commercialize, our product candidates may be harmed, which could harm our business, operating results, prospects or financial condition.

We may not be successful in our efforts to identify and successfully develop additional product candidates.

Part of our strategy involves identifying novel product candidates. For example, we are currently engaged in internal efforts to identify a protease inhibitor product candidate that we may be able to combine with bemnifosbuvir for the treatment of COVID-19. These efforts and any subsequent discovery efforts we initiate to identify other novel product candidates may fail to yield product candidates for clinical development for a number of reasons, including those discussed in these risk factors and also:

If we are unable to identify and successfully develop and commercialize additional suitable product candidates, this would adversely impact our business strategy and our financial position.

We may focus on potential product candidates that may prove to be unsuccessful and we may have to forego opportunities to develop other product candidates that may prove to be more successful.

We may choose to focus our efforts and resources on one or more potential product candidates that ultimately prove to be unsuccessful, or to license or purchase a marketed product that does not meet our financial expectations. As a result, we may fail to capitalize on viable commercial products or profitable market opportunities, be required to forego or delay pursuit of opportunities with other product candidates or other diseases that may later prove to have greater commercial potential.

Furthermore, we have limited financial and personnel resources and are placing significant focus on the development of our lead product candidates, particularly our bemnifosbuvir COV19 product candidate and bemnifosbuvir in combination with ruzasvir for the treatment of HCV, and as such, we may forgo or delay pursuit of opportunities with other future product candidates that later prove to have greater commercial potential. Our resource allocation decisions may cause us to fail to capitalize on viable commercial products or profitable market opportunities. Our spending on current and future research and development programs and other future product candidates for specific indications may not yield any commercially viable future product candidates. If we do not accurately evaluate the commercial potential or target market for a particular future product candidate, we may relinquish valuable rights to those future product candidates through collaboration, licensing or other royalty arrangements in cases in which it

would have been more advantageous for us to retain sole development and commercialization rights to such future product candidates.

We may attempt to secure FDA approval of certain product candidates through the use of the accelerated approval pathway or similar expedited approval pathways outside the US. If we are unable to obtain such approval, we may be required to conduct additional preclinical studies or clinical trials beyond those that we contemplate, which could increase the expense of obtaining, and delay the receipt of, necessary marketing approvals. Even if we receive accelerated approval from the FDA or similar expedited approval by foreign regulatory authorities, if our confirmatory trials do not verify clinical benefit, or if we do not comply with rigorous post-marketing requirements, the FDA or foreign regulatory authorities may seek to withdraw accelerated approval or similar conditional approval.

We are developing our product candidates for the treatment of serious conditions, and therefore may decide to seek approval of such product candidates under the FDA’s accelerated approval pathway. A product candidate may be eligible for accelerated approval if it is designed to treat a serious or life-threatening disease or condition and generally provides a meaningful advantage over available therapies, upon a determination that the product candidate has an effect on a surrogate endpoint or intermediate clinical endpoint that is reasonably likely to predict clinical benefit. The FDA considers a clinical benefit to be a positive therapeutic effect that is clinically meaningful in the context of a given disease, such as irreversible morbidity or mortality. For the purposes of accelerated approval, a surrogate endpoint is a marker, such as a laboratory measurement, radiographic image, physical sign, or other measure that is thought to predict clinical benefit, but is not itself a measure of clinical benefit. An intermediate clinical endpoint is a clinical endpoint that can be measured earlier than an effect on irreversible morbidity or mortality that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit.

The accelerated approval pathway may be used in cases in which the advantage of a new drug over available therapy may not be a direct therapeutic advantage, but is a clinically important improvement from a patient and public health perspective. If granted, accelerated approval is usually contingent on the sponsor’s agreement to conduct, in a diligent manner, confirmatory studies to verify and describe the drug’s clinical benefit. If the sponsor fails to conduct such studies in a timely manner, or if such confirmatory studies fail to verify the drug’s predicted clinical benefit, the FDA may withdraw its approval of the drug on an expedited basis. In addition, in December 2022, President Biden signed an omnibus appropriations bill to fund the U.S. government through fiscal year 2023. Included in the omnibus bill is the Food and Drug Omnibus Reform Act of 2022, which among other things, provided FDA new statutory authority to mitigate potential risks to patients from continued marketing of ineffective drugs previously granted accelerated approval. Under these provisions, the FDA may require a sponsor of a product seeking accelerated approval to have a confirmatory trial underway prior to such approval being granted

In the EU, a “conditional” marketing authorization may be granted in cases where all the required safety and efficacy data are not yet available. A conditional marketing authorization is subject to conditions to be fulfilled for generating missing data or ensuring increased safety measures. A conditional marketing authorization is valid for one year and has to be renewed annually until fulfillment of all relevant conditions. Once the applicable pending studies are provided, a conditional marketing authorization can become a “standard” marketing authorization. However, if the conditions are not fulfilled within the timeframe set by the EMA, the marketing authorization will cease to be renewed. Furthermore, marketing authorizations may also be granted “under exceptional circumstances” when the applicant can show that it is unable to provide comprehensive data on the efficacy and safety under normal conditions of use even after the product has been authorized and subject to the introduction of specific procedures. This may arise when the intended indications are very rare and, in the present state of scientific knowledge, it is not possible to provide comprehensive information, or when generating data may be contrary to generally accepted ethical principles. This type of marketing authorization is close to a conditional marketing authorization as it is reserved to medicinal products to be approved for severe diseases or unmet medical needs and the applicant does not hold the complete data set legally required for the grant of a marketing authorization. However, unlike a conditional marketing authorization, the applicant does not have to provide the missing data and will never have to. Although a marketing authorization “under exceptional circumstances” is granted definitively, the risk-benefit balance of the medicinal product is reviewed

annually and the marketing authorization may be withdrawn where the risk-benefit ratio is no longer favorable.

The competent regulatory authorities in the EU have broad discretion whether to grant such a conditional marketing authorization or marketing authorization under exceptional circumstances, and, even if such assessment or authorization is granted, we may not experience a faster development process, review or authorization compared to conventional procedures. Moreover, the removal or threat of removal of such marketing authorizations may create uncertainty or delay in the clinical development of our product candidates and threaten the commercialization prospects of our products and product candidates, if approved. Such an occurrence could materially impact our business, financial condition and results of operations.

If we decide to submit an NDA seeking accelerated approval or receive an expedited regulatory designation for our product candidates, there can be no assurance that such submission or application will be accepted or that any expedited development, review or approval will be granted on a timely basis, or at all. Failure to obtain accelerated approval or any other form of expedited development, review or approval for a product candidate would result in a longer time period prior to commercialization of such product candidate, if any, and could increase the cost of development of such product candidate, which could harm our competitive position in the marketplace.

Even if we complete the necessary preclinical studies and clinical trials, the marketing approval process is expensive, time-consuming and uncertain and may prevent us or any future collaboration partners from obtaining approvals for the commercialization of any product candidate we develop.

Any product candidates we may develop and the activities associated with their development and commercialization, including their design, testing, manufacture, safety, efficacy, recordkeeping, labeling, storage, approval, advertising, promotion, sale and distribution, are subject to comprehensive regulation by the FDA and other regulatory authorities in the US and by comparable authorities in other countries. Any product candidates we develop may not be effective, may be only moderately effective, or may prove to have undesirable or unintended side effects, toxicities or other characteristics that may preclude our obtaining marketing approval or prevent or limit commercial use. Failure to obtain marketing approval for a product candidate will prevent us from commercializing the product candidate in a given jurisdiction. We have not received approval to market any product candidates from regulatory authorities in any jurisdiction. It is possible that none of the product candidates we are developing or that we may seek to develop in the future will ever obtain regulatory approval. We, as a company, have no experience in filing and supporting the applications necessary to gain marketing approvals and expect to rely on third-party CROs, suppliers, vendors or regulatory consultants to assist us in this process. Securing regulatory approval requires the submission of extensive preclinical and clinical data and supporting information to the various regulatory authorities for each therapeutic indication to establish the product candidate’s safety and efficacy. Securing regulatory approval also requires the submission of information about the product manufacturing process to, and inspection of manufacturing facilities by, the relevant regulatory authority.

The process of obtaining marketing approvals, both in the US and abroad, is expensive, may take many years if numerous clinical trials are required, if approval is obtained at all, and can vary substantially based upon a variety of factors, including the type, complexity and novelty of the product candidates involved. Changes in marketing approval policies during the development period, changes in or the enactment of additional statutes or regulations, or changes in regulatory review for each submitted product application, may cause delays in the approval or rejection of an application. For instance, the EU pharmaceutical legislation is currently undergoing a complete review process, in the context of the Pharmaceutical Strategy for Europe initiative, launched by the European Commission in November 2020. The European Commission's proposal for revision of several legislative instruments related to medicinal products (potentially reducing the duration of regulatory data protection, revising the eligibility for expedited pathways, etc.) was published on April 26, 2023. The proposed revisions have yet to be agreed and adopted by the European Parliament and European Council and the proposal may therefore be substantially revised before adoption, which is not anticipated before early 2026. The revisions may however have a significant impact on the pharmaceutical industry and our business in the long term.

The FDA and comparable authorities in other countries have substantial discretion in the approval process and may refuse to accept any application or may decide that our data are insufficient for approval and require additional preclinical, clinical or other studies. In addition, varying interpretations of the data obtained from preclinical and clinical testing could delay, limit or prevent marketing approval of a product candidate. Any marketing approval we ultimately obtain may be limited or subject to restrictions or post-approval commitments that render the approved product not commercially viable.

If we experience delays in obtaining approval or if we fail to obtain approval of any product candidates we may develop, the commercial prospects for those product candidates may be harmed, and our ability to generate product revenue will be materially impaired.

We may seek an EUA from the FDA or comparable emergency use authorizations from foreign regulatory authorities with respect to our bemnifosbuvir COV19 product candidates in development for the treatment of COVID-19, and if we fail to obtain or maintain such authorizations, we may be required to pursue a more lengthy clinical development process than we expect, and our business may be harmed.

If available at the time we have sufficient data from our Phase 3 SUNRISE-3 clinical trial, we may seek an EUA from the FDA or comparable emergency use authorizations from foreign regulatory authorities with respect to our bemnifosbuvir COV19 product candidates. The FDA has the authority to issue an EUA, pursuant to the Federal FDCA and a declaration by the HHS Secretary, that circumstances exist justifying the issuance of EUAs for certain types of products (referred to as EUA declarations). On March 27, 2020, the Secretary of HHS declared that circumstances then existed that justified authorization of drugs and biologics during the COVID-19 pandemic, subject to the terms of any EUA that subsequently issued for a specific product. Once an EUA declaration has been issued and remains in place, the FDA can issue EUAs for products that fall within the scope of that declaration. To issue an EUA, the FDA Commissioner must conclude that (1) the CBRN, that is referred to in the EUA declaration can cause serious or life-threatening diseases or conditions; (2) based on the totality of scientific evidence available, it is reasonable to believe that the product may be effective in diagnosing, treating, or preventing the disease or condition attributable to the CBRN and that the product’s known and potential benefits outweigh its known and potential risks; and (3) there is no adequate, approved, and available alternative to the product.

Since December 2021, in the US two oral direct acting antivirals Paxlovid™ (nirmatrelvir and ritonavir) and Lagevrio™ (molnupiravir) have been authorized for emergency use for high-risk COVID-19 patients. While Lagevrio remains available under the emergency use authorization, following the submission of a NDA, Paxlovid has been approved for use for the treatment of mild-to-moderate COVID-19 in adults at high-risk for progression to severe COVID-19.

The FDA’s standards for granting an EUA are lower than for approving NDAs in accordance with traditional review procedures, and even if we seek and obtain an EUA for one or more of our product candidates, we cannot assure you that the FDA would approve a NDA for such product candidate, if such approval is required. Accordingly, even if we obtain an EUA for a bemnifosbuvir COV19 product candidate, we may be required to conduct additional clinical trials before we are able to submit an NDA or comparable marketing applications for such product candidate.

The authorization to market products under an EUA is limited to the period of time the EUA declaration is in effect. If the Secretary of HHS determines that the circumstances justifying the issuance of EUAs have also lapsed, the HHS Secretary will provide advance notice that the EUA declaration will be terminated. After an EUA declaration is terminated, all EUAs issued under that declaration also terminate and therefore emergency use of all products under the EUA declaration is no longer authorized. The FDA can also revoke an EUA in certain circumstances even if the EUA declaration has not been terminated.

The FDA’s policies regarding an EUA can change unexpectedly. We cannot predict how long any authorization, if obtained, will remain in place. The FDA’s policies regarding vaccines and other products used to diagnose, treat or mitigate COVID-19 remain in flux as the FDA responds to new and evolving public health information and clinical evidence. Moreover, the federal government has taken steps to terminate distinct emergency authorizations related to COVID-19. For example, following the expiration on May 11, 2023 of the COVID-19 public health emergency under the Public Health Service Act, although

the FDA has maintained its authority to grant EUAs to qualifying products, certain FDA policies and operational procedures related to COVID-19 expired, and the FDA has continued to return to normal operations, including a potential transition of products marketed under EUAs, to the conventional FDA requirements, including premarket authorization requirements. Changes in COVID-19 pandemic related policies and procedures and resumption of pre-pandemic operations are also occurring at regulatory agencies outside the US. Among other things, these changes include a return to longer periods for review of CTAs than was occurring during the pandemic.

Therefore, even if we believe the data from our Phase 3 SUNRISE-3 clinical trial and any other COVID-19 clinical trials we may initiate are positive, we may be unable to obtain an EUA or other emergency authorizations for a bemnifosbuvir COV19 product candidate at all or in a timely manner. Moreover, even if we do obtain an EUA or comparable emergency authorization, it is possible that such EUA or other authorizations may be revoked and we may be required to cease any commercialization activities, until, if ever, we receive NDA approval for such product. Any cessation of commercialization activities would adversely impact our business, financial condition and results of operations.

Even if we obtain FDA approval of any of our product candidates, we may never obtain approval or commercialize such products outside of the US, which would limit our ability to realize their full market potential.

In order to market any products outside of the US, we must establish and comply with numerous and varying regulatory requirements of other countries regarding safety and efficacy. Clinical trials conducted in one country may not be accepted by regulatory authorities in other countries, and regulatory approval in one country does not mean that regulatory approval will be obtained in any other country. Approval procedures vary among countries and can involve additional product testing and validation and additional administrative review periods. Seeking foreign regulatory approvals could result in significant delays, difficulties and costs for us and may require additional preclinical studies or clinical trials which would be costly and time-consuming. Regulatory requirements can vary widely from country to country and could delay or prevent the introduction of our products in those countries. Satisfying these and other regulatory requirements is costly, time-consuming, uncertain and subject to unanticipated delays. In addition, our failure to obtain regulatory approval in any country may delay or have negative effects on the process for regulatory approval in other countries. We do not have any product candidates approved for sale in any jurisdiction, including international markets, and as an organization we do not have experience in obtaining regulatory approval in international markets. If we fail to comply with regulatory requirements in international markets or to obtain and maintain required approvals, our ability to realize the full market potential of our products will be harmed.

Even if a current or future product candidate receives marketing approval, it may fail to achieve the degree of market acceptance by physicians, patients, third-party payors and others in the medical community necessary for commercial success.

If any current or future product candidate we develop receives marketing approval, whether as a single agent or in combination with other therapies, it may nonetheless fail to gain sufficient market acceptance by physicians, patients, third-party payors and others in the medical community. For example, current approved antiviral products are well established in the medical community for the treatment of HCV and in the US, two oral antivirals, Paxlovid and Lagevrio, are currently approved and authorized, respectively, for the treatment of COVID-19, and doctors may continue to rely on these therapies.

If the product candidates we develop do not achieve an adequate level of acceptance, we may not generate significant product revenues and we may not become profitable. The degree of market acceptance of any product candidate, if approved for commercial sale, will depend on a number of factors, including but not limited to:

If the market opportunities for our product candidates are smaller than we believe they are or any approval we obtain is based on a narrower definition of the patient population, our business may suffer.

We currently focus on the discovery and development of product candidates for the treatment of serious viral diseases. Our eligible patient population, pricing estimates and available coverage and reimbursement may differ significantly from the actual market addressable by our product candidates. Our estimates of the number of people who have these diseases, the subset of people with these diseases who have the potential to benefit from treatment with our product candidates, and the market demand for our product candidates are based on our beliefs and analyses. These estimates have been derived from a variety of sources, including the scientific literature, current third-party data regarding prescriptions dispensed, and market research, and may prove to be incorrect. Further, new trials may change the estimated incidence or prevalence of the diseases we are targeting. The number of patients may turn out to be lower than expected. Likewise, the potentially addressable patient population for each of our product candidates may be limited or may not be receptive to treatment with our product candidates, and new patients may become increasingly difficult to identify or access. Additionally, the availability of superior or competitive therapies from our competitors could negatively impact or eliminate market demand for our product candidates. If the market opportunities for our product candidates are smaller than we estimate, it could have an adverse effect on our business, financial condition, results of operations and prospects.

Disruptions at the FDA and foreign regulatory authorities caused by funding shortages or global health concerns could hinder their ability to hire, retain or deploy key leadership and other personnel, or otherwise prevent new or modified products from being developed, approved or commercialized in a timely manner or at all, which could negatively impact our business.

The ability of the FDA and foreign regulatory authorities to review or approve new products can be affected by a variety of factors, including government budget and funding levels, statutory, regulatory, and policy changes, the FDA’s or foreign regulatory authorities’ ability to hire and retain key personnel and accept the payment of user fees, and other events that may otherwise affect the FDA’s or foreign regulatory authorities’ ability to perform routine functions including a rapid substantial influx of applications from numerous sponsors as occurred with COVID-19. Average review times at the FDA and foreign regulatory authorities have fluctuated in recent years as a result. In addition, government funding of other government agencies that fund research and development activities is subject to the political process, which is inherently fluid and unpredictable. Disruptions at the FDA and other agencies may also slow the time necessary for new drugs to be reviewed and/or approved by necessary government agencies, which would adversely affect our business. For example, over the last several years, the US government has shut down several times and certain regulatory agencies, such as the FDA, have had to furlough critical FDA employees and stop critical activities.

Separately, in response to the COVID-19 pandemic, the FDA postponed most inspections of domestic and foreign manufacturing facilities at various points. Even though the FDA has since resumed standard inspection operations of domestic facilities where feasible, any reoccurrence of a public health emergency may lead to further administrative or inspectional delays.

If a prolonged government shutdown occurs, or if global health concerns prevent the FDA or other regulatory authorities from conducting their regular inspections, reviews, or other regulatory activities, it

could significantly impact the ability of the FDA or other regulatory authorities to timely review and process our regulatory submissions, which could have a material adverse effect on our business.

Our insurance policies are expensive and protect us only from some business risks, which leaves us exposed to significant uninsured liabilities.

Though we have insurance coverage for clinical trial product liability, we do not carry insurance for all categories of risk that our business may encounter. Some of the additional policies we currently maintain include general liability, property, auto, workers’ compensation, cybersecurity, umbrella, and directors’ and officers’ insurance.

As a part of the clinical trial regulatory submission process, in many countries, we are required to provide local insurance coverage covering claims that persons associated with the clinical trial may assert if they are or believe they are injured as a result of participation in the clinical trial or contact with the investigational product candidate being studied in the clinical trial. These local insurance policies can be time consuming to obtain which may delay the anticipated start of a clinical trial in a particular country. Additionally, these local insurance policies may not cover all the claims an injured party may assert and may be insufficient to cover the losses associated with our defense of the claim and any judgment against us that may result.

Any additional product liability insurance coverage we acquire in the future may not be sufficient to reimburse us for any expenses or losses we may suffer. Moreover, insurance coverage is becoming increasingly expensive and in the future we may not be able to maintain insurance coverage at a reasonable cost or in sufficient amounts to protect us against losses due to liability. If we obtain marketing approval for any of our product candidates, we intend to acquire insurance coverage to include the sale of commercial products; however, we may be unable to obtain product liability insurance on commercially reasonable terms or in adequate amounts. A successful product liability claim or series of claims brought against us could cause our stock price to decline and, if judgments are for claims not covered by or are in amounts that exceed our insurance coverage, could adversely affect our results of operations and business, including preventing or limiting the development and commercialization of any product candidates we develop. We do not carry specific biological or hazardous waste insurance coverage, and our property, casualty and general liability insurance policies specifically exclude coverage for damages and fines arising from biological or hazardous waste exposure or contamination. Accordingly, in the event of contamination or injury from biological or hazardous waste, we could be held liable for damages or be penalized with fines in an amount exceeding our resources, and our clinical trials or regulatory approvals could be suspended.

Operating as a public company has in the past and may in the future make it more difficult and more expensive for us to obtain director and officer liability insurance, and we may be required to accept reduced policy limits and coverage or incur substantially higher costs to obtain the same or similar coverage. As a result, it may be more difficult for us to attract and retain qualified people to serve on our board of directors, our board committees or as executive officers. We do not know, however, if we will be able to maintain existing insurance with adequate levels of coverage. Any significant uninsured liability may require us to pay substantial amounts, which would adversely affect our cash and cash equivalents position and results of operations.

Our business and operations may suffer in the event of information technology system failures, cyberattacks, or deficiencies, which could materially affect our results.

Our information technology systems, as well as those of our CROs and other contractors and consultants, are vulnerable to attack, failure and damage from computer viruses and other malware (e.g., ransomware), unauthorized access or other cybersecurity attacks, malfeasance by external or internal parties, human error (e.g., social engineering, phishing), natural disasters (including hurricanes), terrorism, war, fire and telecommunication or electrical failures. In the ordinary course of our business, we directly or indirectly collect, store and transmit sensitive data, including intellectual property, confidential information, preclinical and clinical trial data, proprietary business information, personal data and personally identifiable health information of our clinical trial subjects and employees, in our data centers and on our networks, or on those of third parties. The secure processing, maintenance and transmission of this information is critical to our operations.

Despite security measures that we and our critical third parties (e.g., collaborators) implement, our information technology systems may be vulnerable to attacks by hackers or internal bad actors, or breached due to human error, a technical vulnerability, malfeasance or other disruptions. The risk of a security breach or disruption, particularly through cyber-attacks or cyber intrusion, including by computer hackers, foreign governments, and cyber terrorists, has generally increased as the number, level of persistence, intensity and sophistication of attempted attacks and intrusions from around the world have increased. We also face increased cybersecurity risks due to our reliance on internet technology and the number of our employees who are working remotely, which may create additional opportunities for cybercriminals to exploit vulnerabilities. We may not be able to anticipate all types of security threats, nor may we be able to implement preventive measures effective against all such security threats. The techniques used by cybercriminals change frequently, may not be recognized until launched and can originate from a wide variety of sources, including outside groups such as external service providers, organized crime affiliates, terrorist organizations or hostile foreign governments or agencies. Because of this, we may also experience security breaches that may remain undetected for an extended period. Even if identified, we may be unable to adequately investigate or remediate incidents or breaches due to attacks increasingly using tools and techniques that are designed to circumvent controls, to avoid detection, and to remove or obfuscate forensic evidence. We cannot assure you that our data protection efforts and our investment in information technology will prevent significant breakdowns, data leakages or breaches in our systems or those of our CROs and other contractors and consultants or that any such significant breakdowns, data leakages or breaches will be timely discovered, disclosed (if applicable) and remediated.

We and certain of our service providers are from time to time subject to cyberattacks and security incidents. While we do not believe that we have experienced any significant system failure, accident or security breach to date, if such an event were to occur and cause interruptions in our operations, it could result in a material disruption of our product candidate development programs. For example, the loss data from completed, ongoing or planned preclinical studies or clinical trials could result in delays in our regulatory approval efforts and significantly increase our costs to recover or reproduce the data. To the extent that any disruption or security breach were to result in a loss of or damage to our data or applications, or inappropriate disclosure of personal, confidential or proprietary information, we could incur liability and the further development of our product candidates could be delayed.

If a security breach or other incident were to result in the unauthorized access to or unauthorized use, disclosure, release or other processing of personal information, it may be necessary to notify individuals, governmental authorities, supervisory bodies, the media and other parties pursuant to privacy and security laws. Any such access, disclosure or other loss of information could result in legal claims or proceedings, liability under laws that protect the privacy of personal information and significant regulatory penalties, and such an event could disrupt our operations, damage our reputation and cause a loss of confidence in us and our ability to conduct clinical trials, which could adversely affect our reputation and delay our clinical development of our product candidates. Further, our insurance coverage may not be sufficient to cover the financial, legal, business or reputational losses that may result from an interruption or breach of our systems.

Risks Related to Healthcare Laws and Other Legal Compliance Matters

We are subject to extensive and costly government regulation.

Our product candidates will be subject to extensive and rigorous domestic government regulation, including regulation and oversight by the FDA, the CMS, other divisions of HHS, the US Department of Justice, state and local governments, and their respective equivalents outside of the US. The FDA regulates the research, development, preclinical and clinical testing, manufacture, safety, effectiveness, record-keeping, reporting, labeling, packaging, storage, approval, advertising, promotion, sale, distribution, import and export of pharmaceutical products. If our products are marketed abroad, they will also be subject to extensive regulation by foreign governments, whether or not they have obtained FDA approval. Such foreign regulation may be equally or more demanding than corresponding US regulation.

Government regulation substantially increases the cost and risk of researching, developing, manufacturing and, if approved, selling our products. The regulatory review and approval process, which includes preclinical testing and clinical trials of each product candidate, is lengthy, expensive and

uncertain. We must obtain and maintain regulatory authorization to conduct clinical trials. We must obtain regulatory approval for each product we intend to market, and the manufacturing facilities used for the products must be inspected and meet legal requirements. Securing regulatory approval requires the submission of extensive preclinical and clinical data and other supporting information for each proposed therapeutic indication in order to establish the product’s safety and efficacy, potency and purity, for each intended use. The development and approval process takes many years, requires substantial resources, and may never lead to the approval of a product.

Even if we are able to obtain regulatory approval for a particular product, the approval may limit the indicated medical uses for the product, may otherwise limit our ability to promote, sell and distribute the product, may require that we conduct costly post-marketing surveillance, and/or may require that we conduct ongoing post-marketing studies. Material changes to an approved product, such as, for example, manufacturing changes or revised labeling, may require further regulatory review and approval. Once obtained, any approvals may be withdrawn, including, for example, if there is a later discovery of previously unknown problems with the product, such as a previously unknown safety issue.

If we, our consultants, CMOs, CROs or other vendors, fail to comply with applicable regulatory requirements at any stage during the regulatory process, such noncompliance could result in, among other things, delays in the approval of applications or supplements to approved applications; refusal of a regulatory authority, including the FDA, to review pending market approval applications or supplements to approved applications; warning letters; fines; import and/or export restrictions; product recalls or seizures; injunctions; total or partial suspension of production; civil penalties; withdrawals of previously approved marketing applications or licenses; recommendations by the FDA or other regulatory authorities against governmental contracts; and/or criminal prosecutions.

Enacted and future healthcare legislation and policies may increase the difficulty and cost for us to commercialize our product candidates and could adversely affect our business.

In the US, the EU and other jurisdictions, there have been, and we expect there will continue to be, a number of legislative and regulatory changes and proposed changes to the healthcare system that could prevent or delay marketing approval of our product candidates, restrict or regulate post-approval activities involving any product candidates for which we obtain marketing approval, impact pricing and reimbursement and impact our ability to sell any such products profitably. In particular, there have been and continue to be a number of initiatives at the US federal and state levels that seek to reduce healthcare costs and improve the quality of healthcare. In addition, new regulations and interpretations of existing healthcare statutes and regulations are frequently adopted.

In March 2010, the Patient Protection and ACA, was enacted, which substantially changed the way healthcare is financed in the US by both governmental and private insurers. Among the provisions of the ACA, those of greatest importance to the pharmaceutical and biotechnology industries include the following:

Since its enactment, there have been judicial, Congressional and executive challenges to certain aspects of the ACA. On June 17, 2021, the US Supreme Court dismissed the most recent judicial challenge to the ACA brought by several states without specifically ruling on the constitutionality of the ACA.

In addition, other legislative changes have been proposed and adopted in the US since the ACA was enacted. In August 2011, the Budget Control Act of 2011 imposed aggregate reductions of Medicare payments to providers, effective April 1, 2013 which, due to subsequent legislative amendments, will stay in effect through 2032. Further, on March 11, 2021 the American Rescue Plan Act of 2021 was signed into law, which eliminated the statutory Medicaid drug rebate cap, beginning January 1, 2024. The rebate was previously capped at 100% of a drug’s average manufacturer price.

Moreover, payment methodologies may be subject to other changes in healthcare legislation and regulatory initiatives. For example, CMS may develop new payment and delivery models, such as outcomes-based reimbursement. In addition, recently there has been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in several US Congressional inquiries and proposed and enacted federal legislation designed to, among other things, bring more transparency to drug pricing, reduce the cost of prescription drugs under Medicare, and review the relationship between pricing and manufacturer patient programs. Most recently, on August 16, 2022, the IRA was signed into law. Among other things, the IRA requires manufacturers of certain drugs to engage in price negotiations with Medicare (beginning in 2026), with prices that can be negotiated subject to a cap; imposes rebates under Medicare Part B and Medicare Part D to penalize price increases that outpace inflation (first due in 2023); and replaces the Part D coverage gap discount program with a new discounting program (beginning in 2025). The IRA permits the HHS Secretary to implement many of these provisions through guidance, as opposed to regulation, for the initial years. HHS has and will continue to issue and update guidance as these programs are implemented. On August 29, 2023, HHS announced the list of the first ten drugs that will be subject to price negotiations, although the Medicare drug price negotiation program is currently subject to legal challenges. For that and other reasons, it is currently unclear how the IRA will be effectuated. We expect that additional US federal healthcare reform measures will be adopted in the future, any of which could limit the amounts that the US federal government will pay for healthcare products and services, which could result in reduced demand for our product candidates or additional pricing pressures.

Individual states in the US have also increasingly passed legislation and implemented regulations designed to control pharmaceutical and biological product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access, and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing. Legally mandated price controls on payment amounts by third-party payors or other restrictions could harm our business, results of operations, financial condition and prospects. In addition, states and other regional healthcare authorities and individual hospitals are increasingly using bidding procedures to determine what pharmaceutical products and which suppliers will be included in their prescription drug and other healthcare programs. This could reduce the ultimate demand for our product candidates or put pressure on our product pricing.

In the EU, similar political, economic and regulatory developments may affect our ability to profitably commercialize our product candidates, if approved. In addition to continuing pressure on prices and cost containment measures, legislative developments at the EU or member state level may result in significant additional requirements or obstacles that may increase our operating costs. The delivery of healthcare in the EU, including the establishment and operation of health services and the pricing and reimbursement

of medicines, is almost exclusively a matter for national, rather than EU, law and policy. National governments and health service providers have different priorities and approaches to the delivery of healthcare and the pricing and reimbursement of products in that context. In general, however, the healthcare budgetary constraints in most EU member states have resulted in restrictions on the pricing and reimbursement of medicines by relevant health service providers. Coupled with ever-increasing EU and national regulatory burdens on those wishing to develop and market products, this could prevent or delay marketing approval of our product candidates, restrict or regulate post-approval activities and affect our ability to commercialize our product candidates, if approved.

In markets outside of the US and the EU, reimbursement and healthcare payment systems vary significantly by country, and many countries have instituted price ceilings on specific products and therapies.

Enacted and future legislation and policies may increase the difficulty and cost for us to obtain marketing approval of our product candidates and could adversely affect our business.

In the US, legislative and regulatory proposals have been made to expand post-approval requirements and restrict sales and promotional activities for pharmaceutical products. We cannot be sure whether additional legislative changes will be enacted, or whether the FDA’s regulations, guidance or interpretations will be changed, or what the impact of such changes on the marketing approvals of our product candidates, if any, may be. In addition, increased scrutiny by Congress of the FDA’s approval process may significantly delay or prevent marketing approval, as well as subject us to more stringent product labeling and post-marketing testing and other requirements.

We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative action in the US, the EU or any other jurisdiction. If we or any third parties we may engage are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we or such third parties are not able to maintain regulatory compliance, we may be subject to enforcement action and we may not achieve or sustain profitability.

Even if we obtain regulatory approval for a product candidate, our products will remain subject to regulatory scrutiny and post-marketing requirements.

Any regulatory approvals that we may receive for our product candidates will require the submission of reports to regulatory authorities and surveillance to monitor the safety and efficacy of the product candidate, may contain significant limitations related to use restrictions for groups specified by, among other things, age or medical condition, warnings, precautions or contraindications, and may include burdensome post-approval study or risk management requirements. For example, the FDA may require a REMS in order to approve our product candidates, which could entail requirements for a medication guide, physician training and communication plans or additional elements to ensure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. In addition, if any of our product candidates is approved, it will be subject to ongoing regulatory requirements for manufacturing, labeling, packaging, storage, advertising, promotion, sampling, record-keeping, conduct of post-marketing studies and submission of safety, efficacy, and other post-market information, including both federal and state requirements in the US and requirements of comparable foreign regulatory authorities. Manufacturers and manufacturers’ facilities are required to comply with extensive FDA and comparable foreign regulatory authority requirements, including ensuring that quality control and manufacturing procedures conform to cGMP and similar regulations. As such, we and our contract manufacturers will be subject to continual review and inspections to assess compliance with cGMP and similar requirements and adherence to commitments made in any approved marketing application. Accordingly, we and others with whom we work must continue to expend time, money and effort in all areas of regulatory compliance, including manufacturing, production and quality control.

If the FDA or another regulatory authority discovers previously unknown problems with a product, such as adverse events of unanticipated severity or frequency, or problems with the facility where the product is manufactured, or disagrees with the promotion, marketing or labeling of a product, such regulatory authorities may impose restrictions on that product or us, including requiring withdrawal of the product from the market. If we fail to comply with applicable regulatory requirements, a regulatory authority or enforcement authority may, among other things:

Any government investigation of alleged violations of law could require us to expend significant time and resources in response and could generate negative publicity. Any failure to comply with ongoing regulatory requirements may adversely affect our ability to commercialize and generate revenue from our products. If regulatory sanctions are applied or if any regulatory approval is withdrawn, our business will be seriously harmed.

Moreover, the policies of the FDA and of other regulatory authorities may change, and additional government regulations may be enacted that could prevent, limit or delay regulatory approval of our product candidates. We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative or executive action, either in the US or abroad. If we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, we may be subject to enforcement action, and we may not achieve or sustain profitability.

The FDA and other regulatory agencies actively enforce the laws and regulations prohibiting the promotion of off-label uses.

If any of our product candidates are approved and we are found to have improperly promoted off-label uses of those products, we may become subject to significant liability. The FDA and other regulatory agencies strictly regulate the promotional claims that may be made about prescription products, such as our product candidates, if approved. In particular, a product may not be promoted for uses that are not approved by the FDA or such other regulatory agencies as reflected in the product’s approved labeling. If we receive marketing approval for a product candidate, physicians may nevertheless prescribe it to their patients in a manner that is inconsistent with the approved label. If we are found to have promoted such off-label uses, we may become subject to significant liability. The US federal government has levied large civil and criminal fines against companies for alleged improper promotion of off-label use and has enjoined several companies from engaging in off-label promotion. The FDA has also requested that companies enter into consent decrees or permanent injunctions under which specified promotional conduct is changed or curtailed. If we cannot successfully manage the promotion of our product candidates, if approved, we could become subject to significant liability, which would materially adversely affect our business and financial condition.

Our business operations and current and future relationships with clinical trial investigators, healthcare professionals, consultants, third-party payors, patient organizations and customers will be subject to applicable healthcare regulatory laws, which could expose us to penalties.

Our business operations and current and future arrangements with clinical trial investigators, other healthcare professionals, consultants, third-party payors, patient organizations and customers, may expose us to broadly applicable fraud and abuse and other healthcare laws and regulations. These laws may constrain the business or financial arrangements and relationships through which we conduct our operations, including how we research, and if approved, market, sell and distribute our product candidates. Such laws include but are not limited to:

Ensuring that our internal operations and future business arrangements with third parties comply with applicable healthcare laws and regulations will involve substantial costs. It is possible that governmental authorities will conclude that our business practices, including our relationships with physicians and other healthcare providers, some of whom are compensated in the form of stock or stock options for services provided to us and may be in the position to influence the ordering of or use of our product candidates, if approved, may not comply with current or future statutes, regulations, agency guidance or case law involving applicable fraud and abuse or other healthcare laws and regulations. If our operations are found to be in violation of any of the laws described above or any other governmental laws and regulations that may apply to us, we may be subject to significant penalties, including civil, criminal and administrative penalties, damages, fines, exclusion from government-funded healthcare programs, such as Medicare and Medicaid or similar programs in other countries or jurisdictions, integrity oversight and reporting obligations to resolve allegations of non-compliance, disgorgement, individual imprisonment, contractual damages, reputational harm, diminished profits and the curtailment or restructuring of our operations. If any of the physicians or other providers or entities with whom we expect to do business are found to not be in compliance with applicable laws, they may be subject to criminal, civil or administrative sanctions, including exclusions from government funded healthcare programs and imprisonment, which could affect our ability to operate our business. Further, defending against any such actions can be costly, time-consuming and may require significant personnel resources. Therefore, even if we are successful in defending against any such actions that may be brought against us, our business may be impaired.

We are subject to governmental regulation and other legal obligations, particularly related to privacy, data protection and information security, and we are subject to consumer protection laws that regulate our marketing practices and prohibit unfair or deceptive acts or practices. Our actual or perceived failure to comply with such obligations could harm our business.

We are subject to diverse laws and regulations relating to data privacy and security. New privacy rules are being enacted in the US and globally, and existing ones are being updated and strengthened. For example, the California Consumer Privacy Act (“CCPA”) went into effect on January 1, 2020 and creates individual privacy rights for California consumers, increases the privacy and security obligations of entities handling certain personal information, requires new disclosures to California individuals and affording such individuals new abilities to opt out of certain sales of personal information, and provides for civil penalties for violations as well as a private right of action for data breaches that has increased the likelihood of, and risks associated with data breach litigation. Further, the California Privacy Rights Act (“CPRA”), which generally went into effect on January 1, 2023, significantly amends the CCPA and imposes additional data protection obligations on covered businesses, including additional consumer rights processes, limitations on data uses, new audit requirements for higher risk data, and opt outs for

certain uses of sensitive data. It has also created a new California data protection agency authorized to issue substantive regulations and could result in increased privacy and information security enforcement, additional compliance investment and potential business process changes may be required. Similar laws have passed in other states, and are continuing to be proposed at the state and federal level, reflecting a trend toward more stringent privacy legislation in the US. The enactment of such laws could have potentially conflicting requirements that would make compliance challenging. Any liability from failure to comply with the requirements of applicable data privacy and data protection laws could adversely affect our financial condition.

Complying with these numerous, complex and often changing regulations is expensive and difficult, and failure to comply with any privacy laws or data security laws or any security incident or breach involving the misappropriation, loss or other unauthorized processing, use or disclosure of sensitive or confidential patient, consumer or other personal information, whether by us, one of our CROs or business associates or another third-party, could adversely affect our business, our operations abroad, financial condition and results of operations. Such adverse effects may include, but are not limited to: investigation costs; material fines and penalties; compensatory, special, punitive and statutory damages; litigation; consent orders regarding our privacy and security practices; requirements that we provide notices, credit monitoring services and/or credit restoration services or other relevant services to impacted individuals; adverse actions against our licenses to do business; reputational damage; and injunctive relief.

Our operations abroad may also be subject to increased scrutiny or attention from data protection authorities. For example, the EU General Data Protection Regulation ("GDPR") went into effect in May 2018, and imposes strict requirements for processing the personal data of individuals within the EEA or in the context of our activities in the EEA. The GDPR and related implementing laws in individual EU member states govern the collection and use of health data and other personal data in the EU including the personal data processed by companies outside the EU in connection with the offering of goods or services to individuals in the EU or the monitoring of their behavior (including in the context of clinical trials). Companies that must comply with the GDPR face increased compliance obligations and risk, including more robust regulatory enforcement of data protection requirements and potential fines for noncompliance of up to €20 million or 4% of the annual global revenues of the noncompliant company, whichever is greater. In addition to the foregoing, a breach of the GDPR could result in regulatory investigations, reputational damage, orders to cease / change our processing of our data, enforcement notices, and/ or assessment notices (for a compulsory audit). Companies may also face civil claims including representative actions and other class action type litigation (where individuals have suffered harm), potentially amounting to significant compensation or damages liabilities, as well as associated costs, diversion of internal resources, and reputational harm.

Among other requirements, the GDPR regulates transfers of personal data subject to the GDPR to third countries that have not been found to provide adequate protection to such personal data, including the US, and the efficacy and longevity of current transfer mechanisms between the EEA, and the US remains uncertain. On July 10, 2023, the European Commission adopted its Adequacy Decision in relation to the new EU-US Data Privacy Framework (“DPF”), rendering the DPF effective as a GDPR transfer mechanism to U.S. entities self-certified under the DPF. As supervisory authorities issue further guidance on personal data export mechanisms, including circumstances where the SCCs cannot be used, and/or start taking enforcement action, we could suffer additional costs, complaints and/or regulatory investigations or fines, and/or if we are otherwise unable to transfer personal data between and among countries and regions in which we operate, it could affect the manner in which we conduct our business, the geographical location or segregation of our relevant systems and operations, and could adversely affect our financial results.

In addition, since January 1, 2021, after the end of the transition period following the UK’s departure from the EU, we are also subject to the UK data protection regime (the UK GDPR and UK Data Protection Act 2018), which imposes separate but similar obligations to those under the GDPR and comparable penalties, including fines of up to £17.5 million or 4% of a noncompliant company’s global annual revenue for the preceding financial year, whichever is greater. On October 12, 2023, the UK Extension to the DPF came into effect (as approved by the UK Government), as a data transfer mechanism from the UK to US entities self-certified under the DPF. As we continue to expand into other foreign countries and

jurisdictions, we may be subject to additional laws and regulations that may affect how we conduct business.

We cannot assure you that our CROs or other third-party service providers with access to our or our suppliers’, trial patients’, investigators and clinical site employees’ personally identifiable and other sensitive or confidential information in relation to which we are responsible will not breach contractual obligations imposed by us, or that they will not experience data security breaches or attempts thereof, which could have a corresponding effect on our business, including putting us in breach of our obligations under privacy laws and regulations and/or which could in turn adversely affect our business, results of operations and financial condition. We cannot assure you that our contractual measures and our own privacy and security-related safeguards will protect us from the risks associated with the third-party processing, use, storage and transmission of such information. Any of the foregoing could have a material adverse effect on our business, financial condition, results of operations, and prospects.

We face potential liability related to the privacy of health information we obtain from clinical trials sponsored by us.

Most healthcare providers in the US, including research institutions from which we obtain patient health information, are subject to privacy and security regulations promulgated under HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act. We do not believe that we are currently acting as a covered entity or business associate under HIPAA and thus are not directly subject to its requirements or penalties. However, any person may be prosecuted under HIPAA’s criminal provisions either directly or under aiding-and-abetting or conspiracy principles. Consequently, depending on the facts and circumstances, we could face substantial criminal penalties if we knowingly receive individually identifiable health information from a HIPAA-covered healthcare provider or research institution that has not satisfied HIPAA’s requirements for disclosure of individually identifiable health information. Even when HIPAA does not apply, according to the Federal Trade Commission (“FTC”), failing to take appropriate steps to keep consumers’ personal information secure constitutes unfair acts or practices in or affecting commerce in violation of the Federal Trade Commission Act. The FTC expects a company’s data security measures to be reasonable and appropriate in light of the sensitivity and volume of consumer information it holds, the size and complexity of its business, and the cost of available tools to improve security and reduce vulnerabilities. Individually identifiable health information is considered sensitive data that merits stronger safeguards.

We, our CROs and third-party service providers receive and maintain sensitive information, including health-related information, that we receive throughout the clinical trial process, in the course of our research collaborations. As such, we may also be subject to state laws, requiring notification of affected individuals and state regulators in the event of a breach of personal information, which is a broader class of information than the health information protected by HIPAA. Our clinical trial programs outside the US may implicate international data protection laws, including the UK GDPR, GDPR and legislation of the EU member states implementing it. In addition, the EU imposes obligations on the use of data generated from clinical trials and enables European patients to have the opportunity to access their personal data processed in the context of clinical trials.

Our activities outside the US impose additional compliance requirements and generate additional risks of enforcement for noncompliance. Failure by our CROs and other third-party contractors to comply with the strict rules on the transfer of personal data outside of the EU into the US may result in the imposition of criminal and administrative sanctions on such collaborators, which could adversely affect our business. Furthermore, certain health privacy laws, data breach notification laws, consumer protection laws and genetic testing laws may apply directly to our operations and/or those of our collaborators and may impose restrictions on our collection, use and dissemination of individuals’ health information.

Moreover, patients about whom we or our collaborators obtain health information, as well as the providers who share this information with us, may have statutory or contractual rights that limit our ability to use and disclose the information. We may be required to expend significant capital and other resources to ensure ongoing compliance with applicable privacy and data security laws. Claims that we have violated individuals’ privacy rights or breached our contractual obligations, even if we are not found liable, could be expensive and time-consuming to defend and could result in adverse publicity that could harm our business.

If we or third-party CMOs, CROs or other contractors or consultants fail to comply with applicable federal, state or foreign regulatory privacy requirements, we could be subject to a range of regulatory actions that could affect our or our contractors’ ability to develop and commercialize our product candidates and could harm or prevent sales of any affected products that we are able to commercialize, or could substantially increase the costs and expenses of developing, commercializing and marketing our products. Any threatened or actual government enforcement action could also generate adverse publicity and require that we devote substantial resources that could otherwise be used in other aspects of our business. Increasing use of social media could give rise to liability, breaches of data security or reputational damage. Any of the foregoing could have a material adverse effect on our business, financial condition, results of operations and prospects.

We are subject to environmental, health and safety laws and regulations, and we may become exposed to liability and substantial expenses in connection with environmental compliance or remediation activities.

Our operations, including our development, testing and manufacturing activities, are subject to numerous environmental, health and safety laws and regulations. These laws and regulations govern, among other things, the controlled use, handling, release and disposal of and the maintenance of a registry for, hazardous materials and biological materials, such as chemical solvents, human cells, carcinogenic compounds, mutagenic compounds and compounds that have a toxic effect on reproduction, laboratory procedures and exposure to blood-borne pathogens. If we fail to comply with such laws and regulations, we could be subject to fines or other sanctions. Moreover, certain environmental laws may impose liability without regard to fault or legality of the action at the time of its occurrence.

As with other companies engaged in activities similar to ours, we face a risk of environmental liability inherent in our current and historical activities, including liability relating to releases of or exposure to hazardous or biological materials. Environmental, health and safety laws and regulations are becoming more stringent. We may be required to incur substantial expenses in connection with future environmental compliance or remediation activities, in which case, the production efforts of our third-party manufacturers or our development efforts may be interrupted or delayed.

We and our employees are increasingly utilizing social media tools as a means of communication both internally and externally.

Despite our efforts to monitor evolving social media communication guidelines and comply with applicable rules, there is risk that the use of social media by us or our employees to communicate about our product candidates or business may cause us to be found in violation of applicable requirements. In addition, our employees may knowingly or inadvertently make use of social media in ways that may not comply with applicable laws and regulations, our policies and other legal or contractual requirements, which may give rise to regulatory enforcement action, liability, lead to the loss of trade secrets or other intellectual property or result in public exposure of personal information of our employees, clinical trial patients, customers and others. Furthermore, negative posts or comments about us or our product candidates in social media could seriously damage our reputation, brand image and goodwill. Any of these events could have a material adverse effect on our business, prospects, operating results and financial condition and could adversely affect the price of our common stock.

Risks Related to Commercialization

Developments by competitors may render our products or technologies obsolete or non-competitive or may reduce the size of our markets.

Our industry is characterized by extensive research and development efforts, rapid developments in technologies, intense competition and a strong emphasis on proprietary products. We expect our product candidates to face intense competition with existing products and increasing competition as new products enter the relevant markets and advanced technologies become available. We face potential competition from many different sources, including pharmaceutical, biotechnology and specialty pharmaceutical companies. Academic research institutions, governmental agencies and public and private institutions are also potential sources of competitive products and technologies. Our competitors may have or may develop superior technologies or approaches, which may provide them with competitive advantages. Many of these competitors have products already approved or in development in the therapeutic

categories that we are targeting with our product candidates. Either alone or together with their collaborative partners, many of these competitors operate larger research and development programs and have substantially greater financial resources and access to larger pools of capital, including in some cases US government funding, than we do.

Additionally, many of these competitors have greater experience in:

If these competitors access the marketplace before we do with safer, more effective, or less expensive therapeutics or vaccines, our product candidates, if approved for commercialization, may not be profitable to sell or worthwhile to continue to develop. Technology in the pharmaceutical industry has undergone rapid and significant change, and we expect that it will continue to do so. Any compounds, products or processes that we develop may become obsolete or uneconomical before we recover any expenses incurred in connection with their development. The success of our product candidates will depend upon factors such as product efficacy, safety, reliability, availability, timing, scope of regulatory approval, acceptance and price, among other things. Other important factors to our success include speed in developing product candidates, completing clinical development and laboratory testing, obtaining regulatory approvals and manufacturing and selling commercial quantities of potential products.

For the diseases that we are targeting, significant competition exists from approved and authorized oral treatments as well as other treatments in development. The approved drugs, particularly for HCV and increasingly for COVID-19, are well-established products and are widely accepted by physicians, patients and third-party payors. For a description of approved and authorized vaccines and therapeutics, as well as competing treatments in clinical development, please see Part I, Item1 "Business".

Our product candidates, if approved, are expected to compete directly or indirectly with existing products and products currently in development. Even if approved and commercialized, our product candidates may fail to achieve market acceptance with hospitals, physicians, patients or third-party payors. Hospitals, physicians, patients or third-party payors may conclude that our products are less safe or effective or otherwise less attractive than existing drugs. If our product candidates do not receive market acceptance for any reason, our revenue potential would be diminished, which would materially adversely affect our ability to become profitable.

Many of our competitors have substantially greater capital resources, access to larger pools of capital, robust product candidate pipelines, established presence in the market, deep and broad commercial infrastructures and greater expertise in research and development, manufacturing, preclinical and clinical testing, obtaining regulatory approvals and reimbursement and marketing approved products than we do. As a result, our competitors may achieve product commercialization or patent or other intellectual property protection earlier than we can. For example, in May 2023, Gilead Sciences was granted a patent in the US that may cover our compound bemnifosbuvir. If Gilead Sciences asserts this patent, we may not be successful in invalidating it. If we are not successful, we will need to obtain a license from Gilead, which may not be available on reasonable terms, if at all.

Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies. These competitors also compete with us in recruiting and retaining qualified clinical, regulatory, scientific, sales, marketing and management personnel and establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs. Our commercial opportunity could be reduced or eliminated if our competitors develop and commercialize products that are safer, more effective, have fewer or less severe side effects, are more convenient, or are less expensive than

any products that we may develop or that would render any products that we may develop obsolete or noncompetitive, which would have a material adverse effect on our business and operations.

The successful commercialization of our product candidates will depend in part on the extent to which governmental authorities and health insurers establish coverage, adequate reimbursement levels and pricing policies. Failure to obtain or maintain coverage and adequate reimbursement for our product candidates, if approved, could limit our ability to market those products and decrease our ability to generate product revenue.

There is significant uncertainty related to the insurance coverage and reimbursement of newly approved products. Our ability to successfully commercialize our product candidates will depend in part on the extent to which coverage and adequate reimbursement for these products and related treatments will be available from government health administration authorities, private health insurers and other organizations. Government authorities and other third-party payors, such as private health insurers and health maintenance organizations, decide which medications they will pay for and establish reimbursement levels. The availability of coverage and extent of reimbursement by governmental and private payors is essential for most patients to be able to afford treatments.

Third-party payors increasingly are challenging prices charged for pharmaceutical products and services, and many third-party payors may refuse to provide coverage and reimbursement for particular drugs and biologics when an equivalent generic drug, biosimilar or a less expensive therapy is available. It is possible that a third-party payor may consider our product candidates as substitutable and only offer to reimburse patients for the less expensive product. Even if we show improved efficacy or improved convenience of administration with our product candidates, pricing of existing third-party therapeutics may limit the amount we will be able to charge for our product candidates. These payors may deny or revoke the reimbursement status of a given product or establish prices for new or existing marketed products at levels that are too low to enable us to realize an appropriate return on our investment in our product candidates. If reimbursement is not available or is available only at limited levels, we may not be able to successfully commercialize our product candidates and may not be able to obtain a satisfactory financial return on our product candidates.

In the US, third-party payors, including private and governmental payors, such as the Medicare and Medicaid programs, play an important role in determining the extent to which new drugs and biologics will be covered and reimbursed. The Medicare program is increasingly used as a model for how private and other governmental payors develop their coverage and reimbursement policies for new drugs. However, no uniform policy for coverage and reimbursement for products exists among third-party payors in the US. Therefore, coverage and reimbursement for products can differ significantly from payor to payor. As a result, the coverage determination process is often a time-consuming and costly process that will require us to provide scientific and clinical support for the use of our product candidates to each payor separately, with no assurance that coverage and adequate reimbursement will be applied consistently or obtained in the first instance. Some third-party payors may require pre-approval of coverage for new or innovative drug therapies before they will reimburse healthcare providers who use such therapies. Furthermore, rules and regulations regarding reimbursement change frequently, in some cases on short notice, and we believe that changes in these rules and regulations are likely. We cannot predict at this time what third-party payors will decide with respect to the coverage and reimbursement for our product candidates.

Outside the US, international operations are generally subject to extensive governmental price controls and other market regulations, and we believe the increasing emphasis on cost-containment initiatives in the EU and other jurisdictions have and will continue to put pressure on the pricing and usage of our product candidates. In many countries, the prices of medical products are subject to varying price control mechanisms as part of national health systems. Other countries allow companies to fix their own prices for medical products, but monitor and control company profits. Additional foreign price controls or other changes in pricing regulation could restrict the amount that we are able to charge for our product candidates. Accordingly, in markets outside the US, the reimbursement for our product candidates may be reduced compared with the US and may be insufficient to generate commercially reasonable revenue and profits.

Moreover, increasing efforts by governmental and third-party payors in the US and abroad to cap or reduce healthcare costs may cause such organizations to limit both coverage and the level of

reimbursement for newly approved products and, as a result, they may not cover or provide adequate payment for our product candidates. For example, the future value of the US HCV market may be impacted by payors obtaining additional discounts from manufacturers and by payor contracting dynamics. Individual state Medicaid agencies may enact HCV treatment subscription models where manufacturers provide unrestricted access to their antiviral medication for a capitated total price. Contract duration and restrictions of such agreements could impact the ability of the non-awarded HCV oral antivirals to compete. In addition, future US government sponsored HCV eradication initiatives could impact the HCV market opportunity. While future US government sponsored HCV programs could significantly expand the number of HCV infected patients being treated, it also could negatively impact market value and access to many HCV oral antivirals.

We expect to experience pricing pressures in connection with the sale of our product candidates due to the presence of approved, and in the case of HCV, authorized generic, products already in many marketplaces, the trend toward managed healthcare, the increasing influence of health maintenance organizations and additional legislative changes resulting from legislative actions, including the recently enacted IRA. The downward pressure on healthcare costs in general, particularly prescription drugs and biologics and surgical procedures and other treatments, has become intense. As a result, increasingly high barriers are being erected to the entry of new products.

In addition, beginning in March 2020, the US federal government has been the primary purchaser of COVID-19 therapeutics, vaccines and diagnostics. In October 2023, the Administration for Strategic Preparedness & Response, an agency of the US Public Health Service within HHS released new guidance sunsetting the US federal government COVID-19 Therapeutics Distribution Program. The guidance effectively ended the distribution of US federal government procured oral antivirals through the Federal Retail Pharmacy Therapeutics Program. As a result of the guidance, Paxlovid and Lagevrio officially entered the commercial market in November 2023 ending the role of the US federal government as the single payer for COVID-19 oral antivirals. Patients insured through federally funded programs such as Medicaid and Medicare may continue to access Paxlovid free of charge through 2028. Beginning in 2025, we expect that US patient reimbursement for COVID-19 oral antivirals will become subject to traditional payer dynamics for commercial, Medicare and Medicaid patients. We anticipate a major consideration for determining reimbursement by these third-party payers will be a cost/value analysis that is driven in part by the economic burden of hospitalization, especially for at-risk populations. The effect of third-party payers managing patient access to COVID-19 oral antivirals and patient’s co-insurance amounts may impact future demand and patient uptake of COVID-19 oral antiviral medications

If we are unable to establish sales, marketing and distribution capabilities either on our own or in collaboration with third parties, we may not be successful in commercializing any of our product candidates, if approved, and we may not be able to generate any product revenue.

We have limited personnel and limited infrastructure for the sales, marketing or distribution of products, and no experience as a company in commercializing a product candidate. The cost of building and maintaining such an organization may exceed the cost-effectiveness of doing so.

Currently, we anticipate to establish our own commercial organization in the US to commercialize, together with a collaborator, our COVID-19 and HCV product candidates, if approved. Outside the US, we anticipate to rely on a collaborator to commercialize our COVID-19 and HCV products candidates if approved. We do not currently have any commercialization arrangements in place with any collaborator either within or outside the US and we may be unable to enter into acceptable arrangements to do so.

There are significant expenses and risks involved with building our own sales, marketing and distribution capabilities, including our ability to hire, retain and appropriately incentivize qualified individuals, generate sufficient sales leads, provide adequate training to sales and marketing personnel, and effectively manage a geographically dispersed sales and marketing team. Any failure or delay in the development of our internal sales, marketing and distribution capabilities could delay the product launch, and adversely impact the commercialization of our product candidates, if approved. Additionally, if the commercial launch of our product candidates for which we recruit a sales force and establish marketing capabilities is delayed or does not occur for any reason, we would have prematurely or unnecessarily incurred these commercialization expenses. This may be costly, and our investment would be lost if we cannot retain or reposition our sales and marketing personnel.

Factors that may inhibit our efforts to commercialize our product candidates on our own include but are not limited to:

In those territories where we engage a collaborator to commercialize our products in whole or in part our sales will depend on the collaborator’s strategic interest in the product and such collaborator’s ability to successfully commercialize the product.

If we are unable to build our own sales force or access a collaborative relationship for the commercialization of any of our product candidates, we may be forced to delay the potential commercialization of our product candidates or reduce the scope of our sales or marketing activities for such product candidates. If we elect to increase our expenditures to fund additional commercialization activities ourselves, we will need to obtain additional capital, which may not be available to us on acceptable terms, or at all. We could enter into arrangements with collaborative partners at an earlier stage than otherwise would be ideal and we may be required to relinquish rights to any of our product candidates or otherwise agree to terms unfavorable to us, any of which may have an adverse effect on our business, operating results and prospects.

If we are unable to establish adequate sales, marketing and distribution capabilities, either on our own or in collaboration with third parties, we will not be successful in commercializing our product candidates and may not become profitable and may incur significant additional losses. We will be competing with many companies, including large pharmaceutical companies, including Pfizer in COVID-19 and Gilead Sciences and AbbVie in HCV, that have extensive and well-funded marketing and sales operations. Without a robust internal team or the support of third-parties to perform marketing and sales functions, we may be unable to compete successfully against these more established companies.

In addition, even if we do establish adequate sales, marketing and distribution capabilities, the progress of general industry trends with respect to pricing models, supply chains and delivery mechanisms, among other things, could deviate from our expectations. If these or other industry trends change in a manner which we do not anticipate or for which we are not prepared, we may not be successful in commercializing our product candidates or become profitable.

Our future growth may depend, in part, on our ability to penetrate foreign markets, where we would be subject to additional regulatory burdens and other risks and uncertainties.

Our future profitability may depend, in part, on our ability to commercialize our product candidates in foreign markets for which we currently anticipate to rely on collaboration with third parties. We do not currently have any collaborator for the commercialization of any of our product candidates in foreign markets. We are evaluating the opportunities for the commercialization of our product candidates in foreign markets. Neither we or any third party with which we may collaborate is permitted to market or promote any of our product candidates before regulatory approval of such product candidate is received from the applicable regulatory authority in that foreign market, and such regulatory approval for any of our product candidates may never result. To obtain regulatory approvals in countries outside the US, it will be

necessary to comply with numerous and varying regulatory requirements of such countries regarding the safety and efficacy of our product candidates and governing, among other things, clinical trials and commercial sales, pricing and distribution of our product candidates, and we cannot predict success in these jurisdictions. If we obtain approval of our product candidates and ultimately commercialize our product candidates in foreign markets, we would be subject to additional risks and uncertainties, including but not limited to:

Foreign sales of any product for which we obtain approval could also be adversely affected by the imposition of governmental controls, political and economic instability, trade restrictions and changes in tariffs.

If any of our product candidates is approved for commercialization, we currently anticipate to selectively partner with third parties to market such product candidate both within and outside the US. If we or a collaborator market a product candidate outside the US, we expect that we will be subject to additional risks related to international pharmaceutical operations, including but not limited to:

As an organization, we have no prior experience in these areas. In addition, we will need to comply with complex regulatory, tax, labor and other legal requirements imposed by both the EU and many of the individual member states in the EU as well as in other global territories. Many US-based biotechnology

and biopharmaceutical companies have found the process of marketing products outside of North America to be very challenging.

Certain legal and political risks are also inherent in foreign operations without regard to whether these activities are conducted by us in whole or in part or by a collaborator. There is a risk that foreign governments may nationalize private enterprises in certain countries where we or any collaborator with which we are collaborating may operate. In certain countries or regions, terrorist activities and the response to such activities may threaten our operations more than in the US. Social and cultural norms in certain countries may not support compliance with our corporate policies, including those that require compliance with substantive laws and regulations. Also, changes in general economic and political conditions in countries where we may operate are a risk to our financial performance and future growth.

Additionally, the need to identify financially and commercially strong partners for commercialization outside the US who will comply with the high manufacturing and legal and regulatory compliance standards we require is a risk to our financial performance. As we operate our business globally, our success will depend, in part, on our ability to anticipate and effectively manage these and other related risks. There can be no assurance that the consequences of these and other factors relating to our international operations will not have an adverse effect on our business, financial condition or results of operations.

In many countries outside the US, particularly in the EU, the pricing of prescription pharmaceuticals is subject to governmental control. In these countries, pricing negotiations with governmental authorities can take considerable time after the receipt of marketing approval for a drug. To obtain reimbursement or pricing approval in some countries, we may be required to conduct clinical trials that compare the cost-effectiveness of our product candidates to other available therapies. If reimbursement of our products is unavailable or limited in scope or amount, or if pricing is set at unsatisfactory levels, our business could be harmed, possibly materially.

Potential product liability lawsuits against us could cause us to incur substantial liabilities and limit commercialization of any products that we may develop.

Currently, we face an inherent risk of product liability claims as a result of the testing our product candidates and we will face product liability risks if we, or a collaborator, commercialize any of our product candidates that are approved. Product liability claims might be brought against us by consumers, healthcare providers, pharmaceutical companies or others selling or otherwise coming into contact with our products. On occasion, large judgments have been awarded in class action lawsuits based on products that had unanticipated adverse effects. If we cannot successfully defend against product liability claims, we could incur substantial liability and costs, which may not be covered by insurance. In addition, regardless of merit or eventual outcome, product liability claims may result in:

Failure to obtain or retain sufficient product liability insurance at an acceptable cost to protect against potential product liability claims could prevent or inhibit the commercialization of products we develop, alone or with commercial collaborators. To date, we have not sought and do not yet have any experience securing product liability insurance for a product that is being commercialized. Currently, we have clinical trial insurance to cover the use of our product candidates in the clinical trials we are conducting. However, these insurance policies have various exclusions, and we may be subject to a product liability claim for which we have no coverage. We may have to pay any amounts awarded by a court or negotiated in a settlement that exceed our coverage limitations or that are not covered by our insurance, and we may not have, or be able to obtain, sufficient capital to pay such amounts. Even if our agreements with any future commercial collaborators entitle us to indemnification against product liability claims and associated losses, such indemnification may not be available or adequate should any claim or loss arise.

Risks Related to Manufacturing and our Dependence on Third Parties

We rely and expect to continue to rely on third parties for the manufacture of materials for our research programs, preclinical studies and clinical trials and we do not have long-term contracts with any of these parties. This reliance on third parties increases the risk that we will not have sufficient quantities of such materials or any product candidates that we may develop and, if approved, commercialize, or that such supply will not be available to us at an acceptable cost, which could delay, prevent, or impair our development or commercialization efforts.

We rely and expect to continue to rely on third parties for the manufacture of materials for our clinical trials, research activities and preclinical development. We expect to rely on third parties for commercial manufacture if any of our product candidates receive marketing approval. We do not currently have long-term agreements with any of the third-party manufacturers we currently use to provide preclinical and clinical trial materials, and we purchase any required materials on a purchase order basis. Certain of these manufacturers are critical to our production and the loss of these manufacturers, or an inability to obtain quantities at an acceptable cost or quality, could delay, prevent or impair our ability to timely conduct preclinical studies or clinical trials, and would materially and adversely affect our development and commercialization efforts.

We may be unable to maintain or establish required agreements with third-party manufacturers or to do so on acceptable terms. Even if we are able to establish agreements with third-party manufacturers, reliance on third-party manufacturers entails additional risks, including but not limited to:

For ruzasvir, we have a sole supplier located in China for our active pharmaceutical ingredient, and for all our product candidates, including bemnifosbuvir, all suppliers of the regulatory starting materials for the respective manufacturing processes are located in China. We expect to continue to use such third-party manufacturers. Any disruption in production or inability of our manufacturers in China to produce adequate quantities to meet our needs, including as a result of COVID-19, a natural disaster, other public health crises, trade disruptions, changes in the US trade policies, could impair our ability to operate our business on a day-to-day basis and adversely impact our ability to continue the research and development of our product candidates.

We do not have complete control over all aspects of the manufacturing process of, and are dependent on, our contract manufacturing partners for compliance with cGMP regulations and similar regulatory requirements for manufacturing both active drug substances and finished drug products. Third-party manufacturers may not be able to comply with cGMP regulations or similar regulatory requirements outside of the US. If our contract manufacturers cannot successfully manufacture material that conforms to our specifications and the strict regulatory requirements of the FDA and other applicable regulatory authorities, they will not be able to secure and/or maintain authorization for their manufacturing facilities. In addition, we do not have control over the ability of our contract manufacturers to maintain adequate quality control, quality assurance and qualified personnel. If the FDA or a comparable foreign regulatory authority does not authorize these facilities for the manufacture of our product candidates or if it withdraws any such authorization in the future, we may need to find alternative manufacturing facilities, which would significantly impact our ability to develop, obtain marketing approval for or, if approved, market our product candidates. Our failure, or the failure of our third-party manufacturers, to comply with applicable regulations could result in sanctions being imposed on us, including fines, injunctions, civil penalties, delays, suspension or withdrawal of approvals, license revocation, seizures or recalls of product candidates or drugs, operating restrictions and criminal prosecutions, any of which could significantly and adversely affect supplies of our product candidates or drugs and harm our business and results of operations.

Our third-party manufacturers may be unable to successfully scale up manufacturing of our product candidates in sufficient quality and quantity in a timely manner, if at all, which may impair the clinical advancement and commercialization of our product candidates.

In order to conduct clinical trials of our product candidates and commercialize any approved product, our manufacturers need to manufacture them in large quantities. However, they may be unable to successfully increase the manufacturing capacity for any of our product candidates or products in a timely or cost-effective manner, or at all. In addition, quality issues may arise during scale-up activities. If we, or any manufacturers are unable to successfully scale up the manufacture of our product candidates in sufficient quality and quantity in a timely manner, the development, testing and clinical trials of these product candidates may be delayed or infeasible, and regulatory approval or commercial launch and sustained commercialization of any resulting products may be delayed or not obtained, which could significantly harm our business. Supply sources could be interrupted from time to time and, if interrupted, would disrupt our manufacturers’ ability to manufacture our product candidates at the scale required. If we are unable to meet the clinical or commercial supply need for our product candidates, or to do so on commercially reasonable terms, we may not be able to develop our product candidates and commercialize our products successfully.

We do not have multiple sources of supply for all of the components used in our product candidates, nor long-term supply contracts, and certain of our suppliers are critical to our production. If we were to lose a critical supplier, it could have a material adverse effect on our ability to complete the development of our product candidates. If we obtain regulatory approval

for any of our product candidates, we would need to expand the supply of their components in order to commercialize them.

We do not have multiple sources of supply for all of the components used in the manufacture of bemnifosbuvir or ruzasvir. For ruzasvir, we have a sole supplier located in China for our active pharmaceutical ingredient, and for all our product candidates, including bemnifosbuvir, all suppliers of the regulatory starting materials for the respective manufacturing processes are located in China. We do not have long-term supply agreements with any of our component suppliers. We may not be able to establish additional sources of supply for our product candidates, or may be unable to do so on acceptable terms. Manufacturing suppliers are subject to cGMP and comparable foreign quality standards and requirements covering manufacturing, testing, quality control and record keeping relating to our product candidates and subject to ongoing inspections by applicable regulatory authorities. Manufacturing suppliers are also subject to local, state and federal regulations and licensing requirements. Failure by any of our suppliers to comply with all applicable regulations and requirements may result in long delays and interruptions in supply.

The number of suppliers of the components of our product candidates is limited. In the event it is necessary or desirable to acquire supplies from alternative suppliers, we might not be able to obtain them on commercially reasonable terms, if at all. It could also require significant time and expense to redesign our manufacturing processes to work with another manufacturer and redesign of processes can trigger the need for conducting additional clinical studies such as comparability or bridging studies. Additionally, certain of our suppliers are critical to our production, and the loss of these suppliers to one of our competitors or otherwise would materially and adversely affect our development and commercialization efforts.

As part of any application for marketing approval, regulatory authorities generally conduct inspections that must be satisfactory prior to the approval of the product. Failure of manufacturing suppliers to successfully complete these regulatory inspections could result in delays or prevent the approval of our product candidates. In addition, if supply from the supplier of an approved product is interrupted, there could be a significant disruption in commercial supply. An alternative vendor would need to be qualified through a NDA amendment or supplement, which could result in further delay. The FDA or other regulatory authorities outside of the US may also require additional studies if a new supplier is relied upon for commercial production. Switching vendors may involve substantial costs and is likely to result in a delay in our desired clinical and commercial timelines.

If we are unable to obtain the supplies we need at a reasonable price or on a timely basis, it could have a material adverse effect on our ability to complete the development of our product candidates or, if we obtain regulatory approval for our product candidates, to commercialize them.

We rely on third parties to conduct our preclinical studies and clinical trials. Any failure by a third-party to conduct the clinical trials according to GCPs and in a timely manner may delay or prevent our ability to seek or obtain regulatory approval for or commercialize our product candidates.

We are dependent on third parties to conduct critical aspects of our Phase 3 SUNRISE-3 clinical trial, our Phase 2 clinical trial evaluating the combination of bemnifosbuvir and ruzasvir, our preclinical studies and our other clinical trials and we expect to rely on third parties to conduct future clinical trials and preclinical studies for our product candidates. Specifically, we have used and relied on, and intend to continue to use and rely on, medical institutions, clinical investigators, CROs and consultants to conduct our clinical trials in accordance with our clinical protocols and regulatory requirements. These CROs, investigators and other third parties play a significant role in the conduct and timing of these trials and subsequent collection and analysis of data. While we have agreements governing the activities of our third-party contractors, we have limited influence over their actual performance. Nevertheless, we are responsible for ensuring that each of our clinical trials is conducted in accordance with the applicable protocol and legal, regulatory and scientific standards, and our reliance on the CROs and other third parties does not relieve us of our regulatory responsibilities. We and our CROs are required to comply with GCP requirements, which are regulations and guidelines enforced by the FDA and comparable foreign regulatory authorities for all of our product candidates in clinical development. Regulatory authorities enforce these GCPs through periodic inspections of trial sponsors, principal investigators and trial sites. If we or any of our CROs or trial sites fail to comply with applicable GCPs, the clinical data generated in our clinical trials

may be deemed unreliable, and the FDA or comparable foreign regulatory authorities may require us to perform additional clinical trials before approving our marketing applications. We cannot assure you that upon inspection by a given regulatory authority, such regulatory authority will determine that any of our clinical trials or research activities complies with GCP regulations. In addition, our clinical trials must be conducted with product produced under cGMP or similar regulations outside the US. Our failure to comply with these regulations may require us to repeat clinical trials, which would delay the regulatory approval process.

Any third parties conducting our clinical trials or preclinical studies are not and will not be our employees and, except for remedies available to us under our agreements with such third parties, we cannot guarantee that any such CROs, investigators or other third parties will devote adequate time and resources to such trials or perform as contractually required. If any of these third parties fail to meet expected deadlines, adhere to our clinical protocols or meet regulatory requirements, or otherwise performs in a substandard manner, our clinical trials may be extended, delayed or terminated. In addition, many of the third parties with whom we contract may also have relationships with other commercial entities, including our competitors, for whom they may also be conducting clinical trials or other drug development activities that could harm our competitive position. In addition, principal investigators for our clinical trials may serve as scientific advisors or consultants to us from time to time and may receive cash and cash equivalents or equity compensation in connection with such services. If these relationships and any related compensation result in perceived or actual conflicts of interest, or the FDA or foreign regulatory authorities conclude that the financial relationship may have affected the interpretation of the trial, the integrity of the data generated at the applicable clinical trial site may be questioned, and the utility of the clinical trial itself may be jeopardized, which could result in the delay or rejection of any NDA or similar applications we submit to the FDA or foreign regulatory authorities. Any such delay or rejection could prevent us from commercializing our product candidates.

Our CROs have the right to terminate their agreements with us in the event of an uncured material breach. In addition, some of our CROs and substantially all our clinical trial sites have an ability to terminate their respective agreements with us if it can be reasonably demonstrated that the safety of the subjects participating in our clinical trials warrants such termination.

If any of our relationships with these third parties terminate, we may not be able to enter into arrangements with alternative third parties or do so on commercially reasonable terms. Switching or adding additional CROs, investigators and other third parties involves additional cost and requires management time and focus. In addition, there is a natural transition period when a new CRO commences work. As a result, delays occur, which could materially impact our ability to meet our desired clinical development timelines. Though we carefully manage our relationships with our CROs, investigators and other third parties, there can be no assurance that we will not encounter challenges or delays in the future or that these delays or challenges will not have a material adverse impact on our business, financial condition and prospects.

We currently expect that we may collaborate with third parties in connection with the commercialization of our product candidates, if approved. We may not succeed in establishing and maintaining collaborative relationships, which may significantly limit our ability to develop and commercialize our product candidates successfully, if at all.

For commercialization of any of our product candidates that may be approved, our current strategy includes the potential establishment of collaborative relationships with third parties. As a result of entering into collaborative arrangements with third parties, we become dependent on the amount and timing of resources that our collaborators dedicate to the development or potential commercialization of any product candidates we may seek to develop or commercialize with them. Our ability to generate product revenue from any collaborations will depend on our collaborators’ abilities to successfully perform the functions assigned to them. We cannot predict the success of any collaboration that we enter into.

Collaborations involving our product candidates involve many risks, including:

For example, in February 2022, the Roche License Agreement, under which we exclusively granted to Roche certain rights to develop bemnifosbuvir and certain rights to commercialize bemnifosbuvir outside of the US, terminated. As a result, substantially all activities that Roche was conducting in connection with the development and manufacture of bemnifosbuvir, including global manufacture of clinical trial material and certain operations necessary for the conduct of clinical trials, ceased. Substantially all of these activities are necessary for the continued and ongoing global development of a bemnifosbuvir COV19 product candidate and since February 2022, we have been and remain solely responsible for the conduct and cost of such activities.

We may face significant competition in seeking appropriate collaborations. Business combinations among biotechnology and pharmaceutical companies have resulted in a reduced number of potential collaborators. In addition, the negotiation process is time-consuming and complex, and we may not be able to negotiate collaborations on a timely basis, on acceptable terms, or at all. If we are unable to do so, we may have to curtail the development of the product candidate for which we are seeking to collaborate or delay its potential commercialization or reduce the scope of any sales, marketing or distribution activities, or increase our expenditures and undertake development, manufacture or commercialization activities at our own expense. If we elect to increase our expenditures to fund development, manufacture or commercialization activities on our own, we may need to obtain additional capital, which may not be available to us on acceptable terms or at all. If we do not have sufficient funds, we may not be able to further develop product candidates or bring them to market and generate product revenue.

If we enter into collaborations to develop, manufacture and potentially commercialize any product candidates, we may not be able to realize the benefit of such transactions if we or our collaborator elect not to exercise the rights granted under the agreement or if we or our collaborator are unable to successfully integrate a product candidate into existing operations. In addition, if our agreement with any of our collaborators terminates, our access to technology and intellectual property licensed to us by that collaborator may be restricted or terminate entirely, which may delay our continued development of our product candidates utilizing the collaborator’s technology or intellectual property or require us to stop development of those product candidates completely. For example, if the license agreement with Merck was terminated, we would be required to discontinue the development, manufacture and commercialization of ruzasvir in combination with bemnifosbuvir, our lead product candidate for the treatment of HCV, unless we could enter into another agreement with Merck potentially on terms less favorable to us. We may also find it more difficult to find a suitable replacement collaborator or attract new collaborators, and our development programs may be delayed or the perception of us in the business and financial communities could be adversely affected. Any collaborator may also be subject to many of the risks relating to product development, regulatory approval, and commercialization described in this “Risk Factors” section, and any negative impact on our collaborators may adversely affect us.

Data provided by collaborators and others upon which we rely that have not been independently verified could turn out to be false, misleading or incomplete.

We rely on third-party vendors, such as CROs, CMOs, investigators, scientists and other service providers to provide us with significant data and other information related to our programs, preclinical studies or clinical trials and our business. If such third parties provide inaccurate, misleading or incomplete data, our business, prospects and results of operations could be materially adversely affected.

Our employees and independent contractors, including principal investigators, CROs, consultants, vendors and any third parties we may engage in connection with research, development, regulatory, manufacturing, quality assurance and other pharmaceutical functions and commercialization may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements, which could have a material adverse effect on our business.

Misconduct by our employees and independent contractors, including principal investigators, CROs, consultants, vendors and any third parties we may engage in connection with research, development, regulatory, manufacturing, quality assurance and other pharmaceutical functions and commercialization, could include intentional, reckless or negligent conduct or unauthorized activities that violate: (i) the laws and regulations of the FDA, and other similar regulatory authorities, including those laws that require the reporting of true, complete and accurate information to such authorities; (ii) manufacturing standards; (iii) data privacy, security, anti-corruption, fraud and abuse and other healthcare laws and regulations; or (iv) laws that require the reporting of true, complete and accurate financial information and data. Specifically, sales, marketing and business arrangements in the healthcare industry are subject to extensive laws and regulations intended to prevent fraud, misconduct, kickbacks, self-dealing and other abusive practices. These laws and regulations may restrict or prohibit a wide range of pricing, discounting, marketing and promotion, sales commission, customer incentive programs and other business arrangements. Activities subject to these laws could also involve the improper use or misrepresentation of information obtained in the course of preclinical studies or clinical trials, creation of fraudulent data in preclinical studies or clinical trials or illegal misappropriation of drug product, which could result in regulatory sanctions and cause serious harm to our reputation. It is not always possible to identify and deter misconduct by employees and other third parties, and the precautions we take to detect and prevent this activity may not be effective in controlling unknown or unmanaged risks or losses or in protecting us from governmental investigations or other actions or lawsuits stemming from a failure to comply with such laws or regulations. Additionally, we are subject to the risk that a person or government could allege such fraud or other misconduct, even if none occurred. If any such actions are instituted against us, and we are not successful in defending ourselves or asserting our rights, those actions could have a significant impact on our business and results of operations, including the imposition of significant civil, criminal and administrative penalties, damages, monetary fines, disgorgements, possible exclusion from participation in Medicare, Medicaid, other US federal healthcare programs or healthcare programs in other jurisdictions, integrity oversight and reporting obligations to resolve allegations of non-compliance, individual imprisonment, other sanctions, contractual damages, reputational harm, diminished profits and future earnings, and curtailment of our operations.

If our CMOs and CROs use hazardous materials in a manner that causes injury or violates applicable law, we may be liable for damages.

Our research and development activities involve the controlled use of potentially hazardous substances, including chemical materials by our CMOs and medical and biological materials by our CROs. Our CMOs and CROs are subject to federal, state and local laws and regulations in the US and in the countries in which they operate governing the use, manufacture, storage, handling and disposal of hazardous materials. Although we believe that our CMOs’ and CROs’ procedures for using, handling, storing and disposing of these materials comply with legally prescribed standards, we cannot completely eliminate the risk of contamination or injury resulting from chemical, medical, biological or other potentially hazardous materials. As a result of any such contamination or injury, we may incur liability or local, city, state or federal authorities may curtail the use of these materials and interrupt our business operations. In the event of an accident, we could be held liable for damages or penalized with fines, and the liability could exceed our resources. Generally, we do not have any insurance for liabilities arising from the improper handling of chemical, medical, biological or other potentially hazardous materials. Compliance with applicable environmental laws and regulations is expensive, and current or future environmental regulations may impair our research, development and production efforts, which could harm our business, prospects, financial condition or results of operations.

Risks Related to Intellectual Property

If we are unable to obtain, maintain, enforce and adequately protect our intellectual property rights with respect to our technology and product candidates, or if the scope of the patent or other intellectual property protection obtained is not sufficiently broad, our competitors could develop and commercialize technology and products similar or identical to ours, and our ability to successfully develop and commercialize our technology and product candidates may be adversely affected.

We rely upon a combination of patents, trade secret protection and confidentiality agreements to protect our intellectual property and prevent others from duplicating AT-511 (the free base of bemnifosbuvir), bemnifosbuvir and our in-licensed compound ruzasvir and their use or manufacture, or any of our other pipeline product candidates and any future product candidates. Our success depends in large part on our ability to obtain and maintain patent protection in the US and other countries with respect to such product candidates.

The patent prosecution process is expensive, time-consuming, and complex, and we may not be able to file, prosecute, maintain, enforce, or license all necessary or desirable patents or patent applications at a reasonable cost or in a timely manner. Although we enter into confidentiality agreements with parties who have access to confidential or patentable aspects of our research and development output, such as our employees, CROs, consultants, scientific advisors and other contractors, any of these parties may breach the agreements and disclose such output before a patent application is filed, thereby jeopardizing our ability to seek patent protection. In addition, publications of discoveries in the scientific literature often lag behind the actual discoveries, and patent applications in the US and other jurisdictions are typically not published until 18 months after filing, and some remain so until issued. Therefore, we cannot be certain that we were the first to make the inventions claimed in our patents or pending patent applications, or that we were the first to file any patent application related to an invention or product candidate. Further, if we encounter delays in regulatory approvals, the period of time during which we could market a product candidate under patent protection could be reduced.

The strength of patents in the pharmaceutical field involves complex legal, factual and scientific questions and can be uncertain. It is possible that we will fail to identify patentable aspects of our research and development output before it is too late to obtain patent protection. The patent applications that we own may fail to result in issued patents with claims that cover our product candidates in the US or in other foreign countries. There is no assurance that all of the potentially relevant prior art relating to our patents and patent applications has been found, which can invalidate a patent or prevent a patent from issuing from a pending patent application. Even if patents do successfully issue and even if such patents cover our product candidates, third parties may challenge the inventorship, ownership, validity, enforceability or scope of such patents, which may result in such patents being narrowed or invalidated, or being held unenforceable. Our pending and future patent applications may not result in patents being issued which protect our technology or product candidates or which effectively prevent others from commercializing competitive technologies and product candidates. Additionally, any US provisional patent application that we file is not eligible to become an issued patent until, among other things, we file a non-provisional patent application within 12 months of filing the related provisional patent application. If we do not timely file any non-provisional patent application, we may lose our priority date with respect to the provisional patent application and any patent protection on the inventions disclosed in the provisional patent application.

Furthermore, even if they are unchallenged, our patents and patent applications may not adequately protect our intellectual property, provide exclusivity for our product candidates or prevent others from designing around our claims. In addition, no assurances can be given that third parties will not create similar or alternative products or methods that achieve similar results without infringing upon our patents. Any of these outcomes could impair our ability to prevent competition from third parties, which may have an adverse impact on our business.

If the patent applications we hold with respect to our programs or product candidates fail to issue, if the breadth or strength of protection of our current or future issued patents is threatened, or if they fail to provide meaningful exclusivity for our product candidates, it could dissuade companies from collaborating with us to develop product candidates, or threaten our ability to commercialize our current or future product candidates. Several patent applications covering our product candidates have been filed recently

by us. We cannot offer any assurances about which, if any, will result in issued patents, the breadth of any such patents or whether any issued patents will be found invalid or unenforceable or will be threatened by third parties. Any successful opposition to these patents or any other patents owned by us could deprive us of rights necessary for the successful commercialization of any product candidates that we may develop.

The issuance of a patent is not conclusive as to its inventorship, ownership, scope, validity or enforceability, and our patents may be challenged in courts or patent offices in the US and abroad. In addition, the issuance of a patent does not give us the right to practice the patented invention, as third parties may have blocking patents that could prevent us from marketing our product candidate, if approved, or practicing our own patented technology.

Wide-ranging patent reform legislation in the US, including the Leahy-Smith America Invents Act of 2011 (“Leahy-Smith Act”), may increase the uncertainty of the strength or enforceability of our intellectual property and the cost to defend it. The Leahy-Smith Act includes a number of significant changes to US patent law, including provisions that affect the way patent applications are prosecuted and also affect patent litigation. Under the Leahy-Smith Act, the US transitioned from a “first-to-invent” to a “first-to-file” system for deciding which party should be granted a patent when two or more patent applications are filed by different parties claiming the same invention. This will require us to be prompt going forward during the time from invention to filing of a patent application and to be diligent in filing patent applications, but circumstances could prevent us from promptly filing or prosecuting patent applications on our inventions. The Leahy-Smith Act also enlarged the scope of disclosures that qualify as prior art. Furthermore, if a third-party filed a patent application before effectiveness of applicable provisions of the Leahy-Smith Act, on March 16, 2013, an interference proceeding in the US can be initiated by a third-party to determine if it was the first to invent any of the subject matter covered by the claims of our patent applications. We may also be subject to a third-party preissuance submission of prior art to the US Patent and Trademark Office (“USPTO”).

The Leahy-Smith Act created for the first time new procedures to challenge issued patents in the US, including post-grant review, inter partes review and derivation proceedings, which are adversarial proceedings conducted at the USPTO, which some third parties have been using to cause the cancellation of selected or all claims of issued patents of competitors. For a patent with a priority date of March 16, 2013 or later, which all of our patent filings have, a petition for post-grant review can be filed by a third-party in a nine-month window from issuance of the patent. A petition for inter partes review can be filed immediately following the issuance of a patent if the patent was filed prior to March 16, 2013. A petition for inter partes review can be filed after the nine-month period for filing a post-grant review petition has expired for a patent with a priority date of March 16, 2013 or later. Post-grant review proceedings can be brought on any ground of challenge, whereas inter partes review proceedings can only be brought to raise a challenge based on published prior art. These adversarial actions at the USPTO include review of patent claims without the presumption of validity afforded to US patents in lawsuits in US federal courts. The USPTO issued a final rule effective November 13, 2018 announcing that it will now use the same claim construction standard currently used in the US federal courts to interpret patent claims in USPTO proceedings, which is the plain and ordinary meaning of words used. If any of our patents are challenged by a third-party in such a USPTO proceeding, there is no guarantee that we will be successful in defending the patent, which would result in a loss of the challenged patent right to us, including loss of exclusivity, or in patent claims being narrowed, invalidated, or held unenforceable, which could limit our ability to stop others from using or commercializing similar or identical technology and products, or limit the duration of the patent protection of our technology and product candidates. Such proceedings also may result in substantial cost and require significant time from our scientists and management, even if the eventual outcome is favorable to us.

As a result of all of the foregoing, the issuance, scope, validity, enforceability and commercial value of our patent rights are highly uncertain, which could have a material adverse effect on our business, financial condition, results of operations, and prospects.

Third-party claims of intellectual property infringement, misappropriation or other violation may result in substantial costs or prevent or delay our development and commercialization efforts.

Our commercial success depends in part on our avoiding actual and allegations of infringement, misappropriation or other violation of the patents and other proprietary rights of third parties. There is a substantial amount of litigation, both within and outside the US, involving patent and other intellectual property rights in the pharmaceutical industry, including patent infringement lawsuits, interferences, oppositions, re-examination, and post-grant and inter partes review proceedings before the USPTO and similar proceedings in foreign jurisdictions, such as oppositions before the EPO. Numerous US and foreign issued patents and pending patent applications, which are owned by third parties, exist in the fields in which we are pursuing development candidates. Many companies in intellectual property-dependent industries, including the pharmaceutical industry, have employed intellectual property litigation as a means to gain an advantage over their competitors. As the pharmaceutical industry expands and more patents are issued, and as third parties become more aware of our product pipeline, the risk increases that our product candidates may be subject to claims of infringement of the patent rights of third parties.

For example, in March 2021, Gilead Sciences first presented a patent claim to the USPTO that purports to cover bemnifosbuvir. On May 9, 2023, the USPTO issued US Patent No. 11,642,361 (“ ‘361 patent”) with an amended claim (“Claim”) to Gilead Sciences that still purports to cover bemnifosbuvir. We believe that the ‘361 patent, if valid and enforceable, will expire in mid-2028. On August 7, 2023, we filed a Post Grant Review Petition with the USPTO Patent Trial and Appeal Board (“PTAB”), challenging the issuance of the Claim to Gilead, on the basis that the Claim is not supported by the written description of the ‘361 patent and that the ‘361 patent does not have an enabling disclosure for the Claim. In February 2024, the PTAB denied to exercise its discretion to institute the post grant proceeding. This denial does not stop us from making the same or similar arguments, or additional arguments, nor from bringing the same or new evidence of invalidity or unenforceability in court if Gilead Sciences files an infringement suit. However, while we believe this Claim is invalid and unenforceable, a trial court or an appellate court may disagree and uphold the Claim of the '361 patent, which would require us, prior to commercialization of a bemnifosbuvir product candidate to obtain a license from Gilead Sciences to the ‘361 patent. Such a license may not be available on reasonable terms or at all.

Third party claimants may have substantially greater resources than we do and may be able to sustain the costs of complex intellectual property litigation to a greater degree and for longer periods of time than we could. In addition, patent holding companies that focus solely on extracting royalties and settlements by enforcing patent rights may target us.

Third parties may assert that we are employing their proprietary technology without authorization. There may be third-party patents or patent applications with claims to composition of matter, drug delivery, methods of manufacture or methods for treatment related to the use or manufacture of our product candidates. We cannot guarantee that our technologies, products, compositions and their uses do not or will not infringe, misappropriate or otherwise violate third-party patent or other intellectual property rights. Because patent applications can take many years to issue, there may be currently pending patent applications which may later result in issued patents that our product candidates may infringe. In addition, third parties may obtain patents in the future and claim that use of our technologies infringes upon these patents. Pending patent applications that have been published can, or subject to certain limitations, later present claims in a manner that could cover our product candidates or the use of our product candidates. After issuance, the scope of patent claims remains subject to construction as determined by an interpretation of the law, the written disclosure in a patent and the patent’s prosecution history.

Our interpretation of the relevance or the scope of a patent or a pending application may be incorrect, which may negatively impact our ability to market our product candidates. In order to successfully challenge the validity of a US patent, we would need to initiate an action either in federal court or at the PTAB as we have done against the '361 patent. An action brought before the PTAB must be timely submitted within nine months of the issuance of the patent we are seeking to challenge. In either a PTAB or federal court proceeding, there is no assurance that the PTAB or a court of competent jurisdiction would invalidate the claims of any such US patent or, if a PTAB decision is appealed, that a federal court would uphold a PTAB determination of invalidity. If any third-party patents were held by a court of competent jurisdiction to cover the composition of matter of any of our product candidates, the manufacturing process of any of our product candidates or the method of use for any of our product candidates, the holders of any such patents may be able to block our ability to commercialize such

product candidate unless we obtain a license under the applicable patents, which may not be available at all or on commercially reasonable terms, or until such patents expire.

Litigation and contested proceedings can be expensive and time-consuming, and our adversaries in these proceedings may have the ability to dedicate greater resources to prosecuting these legal actions than we can. The risks of being involved in such litigation and proceedings may increase if and as our product candidates near commercialization and as we gain the greater visibility associated with being a public company. Third parties may assert infringement claims against us based on existing patents or patents that may be granted in the future, regardless of the merit of such claims. We may not be aware of all intellectual property rights potentially relating to our technology and product candidates and their uses, or we may incorrectly conclude that third-party intellectual property is invalid or that our activities and product candidates do not infringe, misappropriate or otherwise violate such intellectual property. Thus, we do not know with certainty that our technology and product candidates, or our development and commercialization thereof, do not and will not infringe, misappropriate or otherwise violate any third-party’s intellectual property.

Parties making claims against us may obtain injunctive or other equitable relief, which could if granted effectively block our ability to further develop and commercialize one or more of our product candidates and/or harm our reputation and financial results. Defense of these claims, regardless of their merit, could involve substantial litigation expense and could be a substantial diversion of management and employee resources from our business. In addition, there could be public announcements of the results of hearings, motions, or other interim proceedings or developments, and if securities analysts or investors perceive these results to be negative, it could have a substantial adverse effect on the price of our common stock. In the event of a successful claim of infringement against us, we may have to pay substantial damages, including treble damages and attorneys’ fees for willful infringement, pay royalties, redesign our infringing products, in the case of claims concerning registered trademarks, rename our product candidates, or obtain one or more licenses from third parties, which may require substantial time and monetary expenditure, and which might be impossible or technically infeasible. Furthermore, we may not be able to obtain any required license on commercially reasonable terms or at all. Even if we were able to obtain a license, it could be non-exclusive, thereby giving our competitors and other third parties access to the same technologies licensed to us; alternatively or additionally it might include terms that impede or destroy our ability to compete successfully in the commercial marketplace. Any of the foregoing could have a material adverse effect on our business, financial condition, results of operations, and prospects.

A number of companies and universities file and obtain patents in the same area as our products, which are nucleotide prodrugs, and these patent filings could be asserted against us, which may affect our business, and if successful, could lead to expensive litigation, affect the profitability of our products and/or prohibit the sale of a product or its use.

Our product candidates are predominantly nucleotide prodrugs, or nucleotide phosphoramidates. A number of companies and universities have patent applications and issued patents in this general area, including for viral indications, such as, for example, Gilead Pharmasset, LLC; Gilead Sciences; Merck & Co.; Bristol Myers Squibb; Roche; University of Cardiff; University College Cardiff Consultants; NuCana, plc; Janssen Pharmaceutical Companies; Medivir AB; and others. If any of these companies or universities, or others, assert that a patent it holds is infringed by any of our product candidates or their use or manufacture, we may be drawn into expensive litigation, which may affect our business, take the time of and distract the attention of our employees, and if the litigation is successful, could affect the profitability of our products or prohibit their sale.

For example, we note that Gilead Sciences has obtained the U.S. '361 patent that includes a Claim that purportedly covers bemnifosbuvir. We requested the PTAB Board to institute a post grant review of this patent and it declined to exercise its discretion to do so. This denial does not stop us from making the same or similar arguments, or additional arguments, nor from bringing the same or new evidence of invalidity or unenforceability in court if Gilead files an infringement suit. While we believe this Claim is invalid and unenforceable, a trial court or an appellate court may disagree and uphold the Claim of the '361 patent, which would require us, prior to commercialization of a bemnifosbuvir product candidate to obtain a license from Gilead Sciences to the ‘361 patent. Such a license may not be available on reasonable terms or at all.

Our products are subject to The Drug Price Competition and Patent Term Restoration Act of 1984, as amended (also referred to as the Hatch-Waxman Act), in the US, that can increase the risk of litigation with generic companies trying to sell our products, and may cause us to lose patent protection.

Because our clinical candidates are pharmaceutical molecules reviewed by the Center for Drug Evaluation and Research of the FDA, after commercialization they will be subject in the US to the patent litigation process of the Hatch-Waxman Act, as currently amended, which allows a generic company to submit an Abbreviated New Drug Application ("ANDA") to the FDA to obtain approval to sell our drug using bioequivalence data only. Under the Hatch-Waxman Act, we will have the opportunity to list our patents that cover our drug product or its method of use in the FDA’s compendium of “Approved Drug Products with Therapeutic Equivalence Evaluation,” sometimes referred to as the FDA’s Orange Book.

Currently, in the US, the FDA may grant five years of exclusivity for new chemical entities (“NCEs”) for which all of our products may qualify. An NCE is a drug that contains no active moiety that has been approved by the FDA in any other NDA. A generic company can submit an ANDA to the FDA four years after approval of our product. The submission of an ANDA by a generic company is considered a technical act of patent infringement. The generic company can certify that it will wait until the natural expiration date of our listed patents to sell a generic version of our product or can certify that one or more of our listed patents are invalid, unenforceable or not infringed. If the latter, we will have 45 days to bring a patent infringement lawsuit against the generic company. This will initiate a challenge to one or more of our Orange Book-listed patents based on arguments from the generic company that our listed patents are invalid, unenforceable or not infringed. Under the Hatch-Waxman Act, if a lawsuit is brought, the FDA is prevented from issuing a final approval on the generic drug until 30 months after the end of our data exclusivity period, or a final decision of a court holding that our asserted patent claims are invalid, unenforceable or not infringed. If we do not properly list our relevant patents in the Orange Book, do not timely file a lawsuit in response to a certification from a generic company under an ANDA, or if we do not prevail in the resulting patent litigation, we can lose our proprietary protection, and our product can rapidly become generic. Further, even if we do correctly list our relevant patents in the Orange Book, bring a lawsuit in a timely manner and prevail in that lawsuit, the generic litigation may be at a very significant cost to us of attorneys’ fees and employee time and distraction over a long period. Further, it is common for more than one generic company to try to sell an innovator drug at the same time, and so we may be faced with the cost and distraction of multiple lawsuits. We may also determine it is necessary to settle the lawsuit in a manner that allows the generic company to enter our market prior to the expiration of our patent or otherwise in a manner that adversely affects the strength, validity or enforceability of our patent.

A number of pharmaceutical companies have been the subject of intense review by the FTC or a corresponding agency in another country based on how they have conducted or settled drug patent litigation, and certain reviews have led to an allegation of an antitrust violation, sometimes resulting in a fine or loss of rights. We cannot be sure that we would not also be subject to such a review or that the result of the review would be favorable to us, which could result in a fine or penalty.

The FTC has brought a number of lawsuits in federal court in the past few years to challenge Hatch-Waxman Act ANDA litigation settlements between innovator companies and generic companies as anti-competitive. As an example, the FTC has taken an aggressive position that anything of value is a payment, whether money is paid or not. Under its approach, if an innovator as part of a patent settlement agrees not to launch or delay launch of an authorized generic during the 180-day period granted to the first generic company to challenge an Orange Book-listed patent covering an innovator drug, or negotiates a delay in entry without payment, the FTC may consider it an unacceptable reverse payment. The pharmaceutical industry argues that such agreements are rational business decisions to dismiss risk and are immune from antitrust attack if the terms of the settlement are within the scope of the exclusionary potential of the patent. In 2013, the US Supreme Court, in a five-to-three decision in FTC v. Actavis, Inc., rejected both the pharmaceutical industry’s and FTC’s arguments with regard to so-called reverse payments, and held that whether a “reverse payment” settlement involving the exchange of consideration for a delay in entry is subject to an anticompetitive analysis depends on five considerations: (a) the potential for genuine adverse effects on competition; (b) the justification of payment; (c) the patentee’s ability to bring about anticompetitive harm; (d) whether the size of the payment is a workable

surrogate for the patent’s weakness; and (e) that antitrust liability for large unjustified payments does not prevent litigating parties from settling their lawsuits, for example, by allowing the generic to enter the market before the patent expires without the patentee’s paying the generic. Furthermore, whether a reverse payment is justified depends upon its size, its scale in relation to the patentee’s anticipated future litigation costs, its independence from other services for which it might represent payment, as was the case in Actavis, and the lack of any other convincing justification. The Court held that reverse payment settlements can potentially violate antitrust laws and are subject to the standard antitrust rule-of-reason analysis, with the burden of proving that an agreement is unlawful on the FTC, leaving to lower courts the structuring of such rule of reason analysis. If we are faced with drug patent litigation, including Hatch-Waxman Act litigation with a generic company, we could be faced with such an FTC challenge based on that activity, including how or whether we settle the case, and even if we strongly disagree with the FTC’s position, we could face a significant expense or penalty.

Patent terms may be inadequate to protect our competitive position on our products for an adequate amount of time.

The term of any individual patent depends on applicable law in the country where the patent is granted. In the US, provided all maintenance fees are timely paid, a patent generally has a term of 20 years from its application filing date or earliest claimed non-provisional filing date. Extensions may be available under certain circumstances, but the life of a patent and, correspondingly, the protection it affords is limited. Given the amount of time required for the development, testing and regulatory review of new product candidates, patents protecting such candidates might expire before or shortly after such candidates are commercialized. For patents that are eligible for extension of patent term, we expect to seek extensions of patent terms in the US and, if available, in other countries, however there can be no assurance that we will be granted any patent term extension we seek, or that any such patent term extension will provide us with any competitive advantage.

The Hatch-Waxman Act in the US provides for the opportunity to seek a patent term extension on one selected patent for each of our products, and the length of that patent term extension, if at all, is subject to review and approval by the USPTO and the FDA.

In the US, the Hatch-Waxman Act permits one patent term extension of up to five years beyond the normal expiration of one patent per product, which if a method of treatment patent, is limited to the approved indication (or any additional indications approved during the period of extension). The length of the patent term extension is typically calculated as one half of the clinical trial period plus the entire period of time during the review of the NDA by the FDA, minus any time of delay by us during these periods. There is also a limit on the patent term extension to a term that is no greater than fourteen years from drug approval. Therefore, if we select and are granted a patent term extension on a recently filed and issued patent, we may not receive the full benefit of a possible patent term extension, if at all. We might also not be granted a patent term extension at all, because of, for example, failure to apply within the applicable period, failure to apply prior to the expiration of relevant patents or otherwise failure to satisfy any of the numerous applicable requirements. Moreover, the applicable authorities, including the FDA and the USPTO in the US, and any equivalent regulatory authorities in other countries, may not agree with our assessment of whether such extensions are available, may refuse to grant extensions to our patents, or may grant more limited extensions than we request. If this occurs, our competitors may be able to obtain approval of competing products following our patent expiration by referencing our clinical and preclinical data and launch their product earlier than might otherwise be the case. If this were to occur, it could have a material adverse effect on our ability to generate product revenue.

In 1997, as part of the Food & Drug Administration Modernization Act, (“FDAMA”), Congress enacted a law that provides incentives to drug manufacturers who conduct studies of drugs in children. The law, which provides six months of exclusivity in return for conducting pediatric studies, is referred to as the pediatric exclusivity provision. If clinical studies are carried out by us that comply with the FDAMA, we may receive an additional six-month term added to our regulatory data exclusivity period and our patent term extension period, if received, on our product. However, if we choose not to carry out pediatric studies that comply with the FDAMA, or are not accepted by the FDA for this purpose, we would not receive this additional six-month exclusivity extension to our data exclusivity or our patent term extension.

In Europe, supplementary protection certificates are available to extend a patent term up to five years to compensate for patent term lost during regulatory review, and can be extended for an additional six months if data from clinical trials is obtained in accordance with an agreed-upon pediatric investigation plan. Although all countries in Europe must provide supplementary protection certificates, there is no unified legislation among European countries and so supplementary protection certificates must be applied for and granted on a country-by-country basis. This can lead to a substantial cost to apply for and receive these certificates, which may vary among countries or not be provided at all.

If we are unable to obtain licenses from third parties on commercially reasonable terms or at all, or fail to comply with our obligations under such agreements, our business could be harmed.

It may be necessary for us to use the patented or other proprietary technology of third parties to commercialize our products, in which case we would be required to obtain a license from these third parties. If we are unable to license such technology, or if we are forced to license such technology on unfavorable terms, our business could be materially harmed. If we are unable to obtain a necessary license, we may be unable to develop or commercialize the affected product candidates, which could materially harm our business and the third parties owning or otherwise controlling such intellectual property rights could seek either an injunction prohibiting our sales or an obligation on our part to pay royalties and/or other forms of compensation. Even if we are able to obtain a license, it may be non-exclusive, thereby giving our competitors and other third parties access to the same technologies licensed to us. The licensing or acquisition of third-party intellectual property rights is a competitive area, and several more established companies may pursue strategies to license or acquire third-party intellectual property rights that we may consider attractive or necessary. These established companies may have a competitive advantage over us due to their size, capital resources and greater clinical development and commercialization capabilities. In addition, companies that perceive us to be a competitor may be unwilling to assign or license rights to us.

If we are unable to obtain rights to required third-party intellectual property rights or maintain the existing intellectual property rights we have, we may be required to expend significant time and resources to redesign our technology, product candidates or the methods for manufacturing them or to develop or license replacement technology, all of which may not be feasible on a technical or commercial basis. If we are unable to do so, we may be unable to develop or commercialize the affected technology and product candidates, which could harm our business, financial condition, results of operations and prospects significantly.

Additionally, if we fail to comply with our obligations under any future license agreements, our counterparties may have the right to terminate these agreements, in which event we might not be able to develop, manufacture or market, or may be forced to cease developing, manufacturing or marketing, any product that is covered by these agreements or may face other penalties under such agreements. Such an occurrence could materially adversely affect the value of the product candidate being developed under any such agreement. Termination of these agreements or reduction or elimination of our rights under these agreements, or restrictions on our ability to freely assign or sublicense our rights under such agreements when it is in the interest of our business to do so, may result in our having to negotiate new or reinstated agreements with less favorable terms, cause us to lose our rights under these agreements, including our rights to important intellectual property or technology, or impede, or delay or prohibit the further development or commercialization of one or more product candidates that rely on such agreements.

Litigation and adversarial proceedings are expensive, time-consuming and if unsuccessful, can adversely affect our ability to sell our products when commercialized.

Competitors and other third parties may infringe, misappropriate or otherwise violate our or our future licensors’ patents, trademarks, copyrights or other intellectual property. As a result, we may need to file infringement, misappropriation or other intellectual property-related claims against third parties. To counter infringement or other unauthorized use, we may be required to file claims on a country-by-country basis, which can be expensive and time-consuming and divert the time and attention of our management and scientific personnel. There can be no assurance that we will have sufficient financial or other resources to file and pursue such claims, which often last for years before they are concluded.

Any claims we assert against third parties could also provoke these parties to assert counterclaims against us alleging that we infringe, misappropriate or otherwise violate their intellectual property. In addition, in a patent infringement proceeding, such parties could counterclaim that the patents we have asserted are invalid or unenforceable, or both. In patent litigation in the US, defendant counterclaims alleging invalidity or unenforceability are commonplace. Grounds for a validity challenge could be an alleged failure to meet any of several statutory requirements, including lack of novelty, obviousness or non-enablement. Grounds for an unenforceability assertion could be an allegation that someone connected with prosecution of the patent withheld relevant information from the USPTO, or made a misleading statement, during prosecution. Third parties may institute such claims before administrative bodies in the US or abroad, even outside the context of litigation. Such mechanisms include re-examination, post-grant review, inter partes review, interference proceedings, derivation proceedings and equivalent proceedings in foreign jurisdictions (e.g., opposition proceedings). The outcome following legal assertions of invalidity and unenforceability is unpredictable.

In any such proceeding, a court may decide that a patent of ours, or a patent that we in-license, is not valid, is unenforceable and/or is not infringed, or may construe such patent’s claims narrowly or refuse to stop the other party from using the technology at issue on the grounds that our patents do not cover the technology in question. An adverse result in any litigation or defense proceedings could put one or more of our patents at risk of being invalidated, interpreted narrowly or held unenforceable in whole or in part, could put our patent applications at risk of not issuing, and could limit our ability to assert those patents against those parties or other competitors and curtail or preclude our ability to exclude third parties from making and selling similar or competitive products. Similarly, if we assert trademark infringement claims, a court may determine that the marks we have asserted are invalid or unenforceable, or that the party against whom we have asserted trademark infringement has superior rights to the marks in question. In this case, we could ultimately be forced to cease use of such trademarks, which could materially harm our business and negatively affect our position in the marketplace.

Even if we establish infringement, misappropriation or other violation of our intellectual property, the court may decide not to grant an injunction against further such activity and instead award only monetary damages, which may or may not be an adequate remedy. Furthermore, because of the substantial amount of discovery required in connection with intellectual property litigation, there is a risk that some of our confidential information could be compromised by disclosure during this type of litigation. There could also be public announcements of the results of hearings, motions or other interim proceedings or developments. If securities analysts or investors perceive these results to be negative, it could have a material adverse effect on the price of our common stock. Any of the foregoing could have a material adverse effect on our business, financial condition, results of operations, and prospects.

On June 3, 2019, we received an anonymous third-party Observation filed in connection with our international Patent Cooperation Treaty patent application for our second patent family, which covers the hemisulfate salt form of AT-511, or bemnifosbuvir. The Observation generally challenges the patentability of the hemisulfate salt bemnifosbuvir over the free base AT-511 described in our first patent family. On August 1, 2019, we filed a response to the Observation describing that the bemnifosbuvir hemisulfate salt of AT-511 is not obvious in view of the AT-511 free base because bemnifosbuvir disproportionately concentrates in the liver over the heart, as shown in vivo in a dog model, which can provide an increased therapeutic effect to treat HCV, and decreased toxicity because HCV is a disease of the liver. Further, while not raised in the response to the Observation, we have now also shown that bemnifosbuvir has a longer half-life and higher concentration in the lung than in the liver in vivo in monkeys, which is relevant to our COVID-19 indication. The Observations by anonymous third parties as well as our responses are placed in the file and available to be read and considered by any country examining our respective patent applications.

In December 2019, the US Patent Office issued a patent to us covering the composition of matter of bemnifosbuvir. Our composition of matter patent on bemnifosbuvir has also been granted in China, Japan, Korea, Australia, Brazil, Eurasia, Canada, Israel, New Zealand, South Africa, Russia and Mexico, and is pending in certain other countries and regions, including Europe.

Our patent on AT-511 or its pharmaceutically acceptable salt, which includes bemnifosbuvir, has been granted in United States, China, Japan, Korea, Australia, Eurasia, Canada, Israel, Singapore, Malaysia,

Indonesia, Georgia, Russia, Ukraine, Columbia and Mexico, and is also pending in certain other countries and regions, including Europe.

We may not be aware of patent claims that are currently or may in the future be pending that affect our business by the competitors working in this area. Patent applications are typically published between six and eighteen months from filing, and the presentation of new claims in already pending applications can sometimes not be visible to the public, including to us, for a period of time, or if publicly available, not yet seen by us. We cannot provide any assurance that a third-party practicing in the general area of our technology will not present a patent claim that covers one or more of our products or their methods of use or manufacture at any time, including before or during this registration period. If that does occur, we may have to take steps to try to invalidate such patent or application, and we may either choose not to or may not be successful in such attempt. A license to the patent or application may not be available on commercially reasonable terms or at all.

On April 12, 2022, we received notification of a Pre-Grant Opposition from the Controller General of Patents, Designs, and Trademarks at the Indian Patent Office. The Opposition was filed by Sankalp Rehabilitation Trust and challenges our pending patent claims to AT-511 or a pharmaceutically acceptable salt thereof. In February 2023, we responded to this Pre-Grant Opposition. We are currently awaiting further action on this matter by the Indian Patent Office. In addition to the Pre-Grant Opposition related to AT-511, we have received notification of a second Pre-Grant Opposition filed by the Sankalp Rehabilitation Trust. This second Pre-Grant Opposition challenges our pending patent claims to bemnifosbuvir. In October 2023, we responded to this second Pre-Grant Opposition. While we intend to vigorously defend our patent claims on AT-511 and bemnifosbuvir and their use to treat HCV in India, we cannot guarantee that the Indian Patent Office will decide in our favor with respect to either or both Pre-Grant Oppositions and allow our patent claims to either AT-511 or bemnifosbuvir to grant. In addition, Pre-Grant Oppositions in India can proceed very slowly, and therefore these proceedings may not be resolved for several years. Our patent applications will not issue as a patent on AT-511 or bemnifosbuvir or their use to treat HCV in India unless and until these Pre-Grant Oppositions are resolved in our favor. If it is not resolved in our favor, we may not receive patents on AT-511, bemnifosbuvir or their use to treat HCV in India.

Changes in patent laws and enforcement by courts and other authorities in the US and other jurisdictions may impact our ability to protect our patents.

The US Supreme Court and lower courts have issued opinions in patent cases in the last few years that many consider may weaken patent protection in the US, either by narrowing the scope of patent protection available in certain circumstances, holding that certain kinds of innovations are not patentable or generally otherwise making it easier to invalidate patents in court. Additionally, there have been recent proposals for additional changes to the patent laws of the US and other countries that, if adopted, could impact our ability to obtain patent protection for our proprietary technology or our ability to enforce our proprietary technology. Depending on future actions by the US Congress, the US courts, the USPTO and the relevant law-making and other bodies in other countries, the laws and regulations governing patents could change in unpredictable ways that would weaken our ability to obtain new patents or to enforce and defend our existing patents and patents that we might obtain in the future.

In June 2023, the European Unitary Patent system and the European Unified Patent Court (“UPC”) were launched. European patent applications now have the option, upon grant of a patent, of becoming a Unitary Patent which is subject to the jurisdiction of the UPC. In addition, conventional European patents, both already granted at the time the new system began and granted thereafter, are subject to the jurisdiction of the UPC, unless actively opted out. This was a significant change in European patent practice and deciding whether to opt-in or opt-out of Unitary Patent practice entail strategic and cost considerations. The UPC provides our competitors with a new forum to centrally revoke our European patents and makes it possible for a competitor to obtain pan-European injunctions against us. It will be several years before we will understand the scope of patent rights that will be recognized and the strength of patent remedies that will be provided by the UPC. While we have the right to opt our patents out of the UPC over the first seven years of the court’s existence, doing so may preclude us from realizing the benefits of the UPC. Moreover, the decision whether to opt-in or opt-out of Unitary Patent status will require coordinating with co-applicants, if any, adding complexity to any such decision.

The laws of some foreign jurisdictions do not protect intellectual property rights to the same extent as in the US and many companies have encountered significant difficulties in protecting and defending such rights in foreign jurisdictions. If we encounter such difficulties in protecting or are otherwise precluded from effectively protecting our intellectual property rights in foreign jurisdictions, our ability to compete and our business prospects in such marketplaces could be substantially harmed. For example, we have been notified that two Pre-Grant Opposition have been filed with the Controller General of Patents, Designs and Trademarks at the Indian Patent Office relating to our pending patent claims to AT-511, bemnifosbuvir and their use to treat HCV in India. While we intend to defend our patent claims for AT-511, bemnifosbuvir and their use to treat HCV, we cannot provide any assurance that we will succeed or that the Indian patent office will allow the patent claims to grant. The cost of foreign adversarial proceedings can also be substantial, and in many foreign jurisdictions, the losing party must pay the attorney fees of the winning party.

Obtaining and maintaining our patent protection depends on compliance with various procedural, document submission, fee payment and other requirements imposed by governmental patent agencies, and our patent protection could be reduced or eliminated for non-compliance with these requirements.

The USPTO, EPO and other patent agencies require compliance with a number of procedural, documentary, fee payment and other similar provisions during the patent application process. Periodic maintenance fees, renewal fees, annuity fees and various other governmental fees on patents and/or applications will be due to be paid to the USPTO and various governmental patent agencies outside of the US in several stages over the lifetime of the patents and/or applications. We have systems in place to remind us to pay these fees, and we employ an outside firm and rely on our outside counsel to pay such fees due to non-US patent agencies. While, in many cases, an inadvertent lapse can be cured by payment of a late fee or by other means in accordance with the applicable rules, there are situations in which non-compliance can result in abandonment or lapse of the patent or patent application, resulting in partial or complete loss of patent rights in the relevant jurisdiction. In such an event, our competitors or other third parties might be able to enter the market with similar or identical products or technology, which could have a material adverse effect on our business, financial condition, results of operations, and prospects.

We may not be able to enforce our intellectual property rights throughout the world.

Filing, prosecuting and defending patents on our product candidates in all countries throughout the world would be prohibitively expensive. Therefore, we may choose not to pursue or maintain protection for certain intellectual property in certain jurisdictions. The requirements for patentability may differ in certain countries, particularly in developing countries. Competitors may use our technologies in jurisdictions where we have not obtained patent protection to develop their own products and, further, may export otherwise infringing products to territories where we may obtain patent protection, but where patent enforcement is not as strong as that in the US. These products may compete with our products in jurisdictions where we do not have any issued or licensed patents and any future patent claims or other intellectual property rights may not be effective or sufficient to prevent them from so competing.

Moreover, our ability to protect and enforce our intellectual property rights may be adversely affected by changes in foreign intellectual property laws. Additionally, laws of some countries outside of the US and Europe do not afford intellectual property protection to the same extent as the laws of the US and Europe. Many companies have encountered significant problems in protecting and defending intellectual property rights in certain foreign jurisdictions. The legal systems of some countries, including India, China and other developing countries, may not favor the enforcement of our patents and other intellectual property rights.

This could make it difficult for us to stop the infringement of our patents or the misappropriation or other violation of our other intellectual property rights. A number of foreign countries have stated that they are willing to issue compulsory licenses to patents held by innovator companies on approved drugs to allow the government or one or more third-party companies to sell the approved drug without the permission of the innovator patentee where the foreign government concludes it is in the public interest. India, for example, has used such a procedure to allow domestic companies to make and sell patented drugs without innovator approval. There is no guarantee that patents covering any of our drugs will not be

subject to a compulsory license in a foreign country, or that we will have any influence over if or how such a compulsory license is granted. Further, Brazil allows its regulatory agency ANVISA to participate in deciding whether to grant a drug patent in Brazil, and patent grant decisions are made based on several factors, including whether the patent meets the requirements for a patent and whether such a patent is deemed in the country’s interest. In addition, several other countries have created laws that make it more difficult to enforce drug patents than patents on other kinds of technologies. Further, under the treaty on the Trade-Related Aspects of Intellectual Property, as interpreted by the Doha Declaration, countries in which drugs are manufactured are required to allow exportation of the drug to a developing country that lacks adequate manufacturing capability. Therefore, our drug markets in the US or foreign countries may be affected by the influence of current public policy on patent issuance, enforcement or involuntary licensing in the healthcare area.

The WTO is currently considering a waiver of intellectual property rights for COVID-19 vaccines and the US government has taken a stance in support of the waiver. The current proposal is for a temporary waiver of intellectual property rights that cover COVID-19 vaccines, however, the ultimate timing and scope of the waiver, if approved, is unknown. The scope and timing of such waiver will likely be subject to extensive negotiations given the complexity of the matter, which may result in prolonged uncertainty and therefore could adversely affect our business. If a waiver is approved and covers COVID-19 treatments, such as bemnifosbuvir, our ability to successfully commercialize bemnifosbuvir and protect our related technology could be adversely affected.

We rely on our ability to stop others from competing by enforcing our patents, however some jurisdictions may require us to grant licenses to third parties. Such compulsory licenses could be extended to include some of our product candidates, which may limit our potential revenue opportunities.

Many foreign countries have compulsory licensing laws under which a patent owner must grant licenses to third parties, in certain circumstances. For example, compulsory licensing, or the threat of compulsory licensing, of life-saving products and expensive products is becoming increasingly popular in developing countries, either through direct legislation or international initiatives. Compulsory licenses could be extended to include some of our product candidates, if they receive marketing approval, which may limit our potential revenue opportunities. Consequently, we may not be able to prevent third parties from practicing our inventions in certain countries outside the US and Europe. Competitors may also use our technologies in jurisdictions where we have not obtained patent protection to develop their own products and, further, may export otherwise infringing products to territories where we have patent protection, if our ability to enforce our patents to stop infringing activities is inadequate. These products may compete with our products, and our patents or other intellectual property rights may not be effective or sufficient to prevent them from competing. Proceedings to enforce our patent rights in foreign jurisdictions, whether or not successful, could result in substantial costs and divert our efforts and resources from other aspects of our business. Furthermore, while we intend to protect our intellectual property rights in major markets for our products where such patent rights exist, we cannot ensure that we will be able to initiate or maintain similar efforts in all jurisdictions in which we may wish to market our products. Accordingly, our efforts to protect our intellectual property rights in such countries may be inadequate.

In addition, some countries limit the enforceability of patents against government agencies or government contractors. In these countries, the patent owner may be limited to monetary relief and may be unable to enjoin infringement if a government is the infringer, which could materially diminish the value of the patent.

If we are unable to protect the confidentiality of our trade secrets, our business and competitive position would be harmed.

In addition to the protection afforded by patents, we rely on trade secret protection and confidentiality agreements to protect proprietary know-how that is either not patentable or that we elect not to patent, processes for which patents are difficult to enforce and any other elements of our product candidate discovery and development processes that involve proprietary know-how, information or technology that is not covered by patents. However, trade secrets can be difficult to protect. We seek to protect our proprietary technology and processes, in part, by entering into confidentiality agreements with parties who have access to them, such as our employees, CROs, consultants, scientific advisors and other

contractors. We cannot guarantee that we have entered into such agreements with each party that may have or have had access to our trade secrets or proprietary technology and processes. We also seek to preserve the integrity and confidentiality of our data and trade secrets by maintaining physical security of our premises and physical and electronic security of our information technology systems. While we have confidence in these individuals, organizations and systems, agreements or security measures may be breached and our trade secrets could be disclosed, and we may not have adequate remedies for any such breach. Enforcing a claim that a party illegally disclosed or misappropriated a trade secret is difficult, expensive and time-consuming, and the outcome is unpredictable. In addition, some courts inside and outside the US are less willing or unwilling to protect trade secrets. Misappropriation or unauthorized disclosure of our trade secrets or other confidential proprietary information could cause us to lose trade secret protection, impair our competitive position and have a material adverse effect on our business. Additionally, if the steps taken to maintain our trade secrets or other confidential proprietary information are deemed inadequate, we may have insufficient recourse against third parties for misappropriating the trade secret or other confidential proprietary information.

Further, we cannot provide any assurances that competitors or other third parties will not otherwise gain access to our trade secrets and other confidential proprietary information or independently discover or develop substantially equivalent technology and processes. If we are unable to prevent disclosure of the trade secrets and other non-patented intellectual property related to our product candidates and technologies to third parties, there is no guarantee that we will have any such enforceable trade secret protection and we may not be able to establish or maintain a competitive advantage in our market, which could materially adversely affect our business, results of operations and financial condition.

We may be subject to claims that our employees, consultants or independent contractors have wrongfully used or disclosed confidential information of third parties, that our employees have wrongfully used or disclosed alleged trade secrets of their former employers, or asserting ownership of what we regard as our own intellectual property.

We have employed, and may in the future employ, individuals who were previously employed at universities or other biotechnology or pharmaceutical companies, including our competitors or potential competitors. Although we try to ensure that our employees, consultants and independent contractors do not use the proprietary information or know-how of others in their work for us, we may be subject to claims that we or our employees, consultants or independent contractors have inadvertently or otherwise used or disclosed intellectual property, including trade secrets or other proprietary information, of any of such individuals’ former employers or other third parties. Litigation may be necessary to defend against these claims. If we fail in defending any such claims, in addition to paying monetary damages, we may lose valuable intellectual property rights or personnel, or our ability to hire personnel, which, in any case of the foregoing, could adversely impact our business. Even if we are successful in defending against such claims, litigation could result in substantial costs and be a distraction to management and other employees.

Although it is our policy to require all of our employees and consultants to assign their inventions to us, to the extent that employees or consultants use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting know-how and inventions. We may also be unsuccessful in executing such an agreement with each party who, in fact, conceives or develops intellectual property that we regard as our own. The assignment of intellectual property rights may not be self-executing, or the assignment agreements may be breached, and we may be forced to bring claims against third parties, or defend claims that they may bring against us, to determine the ownership of what we regard as our intellectual property. Such claims could have a material adverse effect on our business, financial condition, results of operations, and prospects.

Our proprietary rights may not adequately protect our technologies and product candidates, and intellectual property rights do not necessarily address all potential threats to our competitive advantage.

The degree of future protection afforded by our intellectual property rights is uncertain because intellectual property rights have limitations, and may not adequately protect our business, or permit us to maintain our competitive advantage. The following examples are illustrative:

Should any of these events occur, they could have a material adverse effect on our business, financial condition, results of operations, and prospects.

Risks Related to Employee Matters, Managing Growth and Other Risks Related to Our Business

We will need to expand our organization, and we may experience difficulties in managing this growth, which could disrupt our operations.

We expect to experience significant growth over time in the number of our employees and the scope of our operations, particularly in the areas of product candidate development, regulatory and clinical affairs and sales, marketing and distribution. To manage our growth activities, we must continue to implement and improve our managerial, operational and financial systems, expand our facilities and continue to recruit and train additional qualified personnel. Due to our limited financial resources and the limited experience of our management team, as a group, in managing a company with such anticipated growth, we may not be able to effectively manage the expansion of our operations or recruit and train additional qualified personnel. As we expand our company, we may have difficulty identifying, hiring and integrating new personnel. Future growth would impose significant additional responsibilities on our management, including but not limited to:

Also, our management may need to divert a disproportionate amount of its attention away from our day-to-day activities and devote a substantial amount of time to managing these growth activities. We may not be able to effectively manage the expansion of our operations, which may result in weaknesses in our infrastructure, give rise to operational mistakes, loss of business opportunities, loss of employees and reduced productivity among remaining employees. Our expected growth, including the potential establishment of a commercial infrastructure and commercialization of product candidates, if any, that are approved for sale will require significant capital expenditures and may divert financial resources from other projects, such as the development of other product candidates. If our management is unable to effectively manage our growth, our expenses may increase more than expected, our ability to generate and/or grow product revenues, if any, could be reduced, and we may not be able to implement our business strategy. Our future financial performance and our ability to commercialize any approved products and compete effectively will depend, in part, on our ability to effectively manage any future growth.

We currently rely, and for the foreseeable future will continue to rely, in substantial part on certain independent organizations, advisors and consultants to provide certain services, including substantially all aspects of clinical trial conduct and execution, international regulatory affairs activities and manufacturing. There can be no assurance that the services of independent organizations, advisors and consultants will continue to be available to us on a timely basis when needed, or that we can find qualified replacements. In addition, if we are unable to effectively manage our outsourced activities or if the quality or accuracy of the services provided by independent organizations, advisors or consultants is compromised for any reason, our clinical trials may be extended, delayed or terminated, and we may not be able to obtain regulatory approval of our product candidates or otherwise advance our business. There can be no assurance that we will be able to manage our existing independent organizations, advisors or consultants or find other competent outside independent organizations, advisors and consultants on economically reasonable terms, or at all. If we are not able to effectively expand our organization by hiring new employees and expanding our groups of advisors and consultants, or we are not able to effectively maintain or obtain facilities to accommodate this expansion, we may not be able to successfully implement the tasks necessary to further develop and commercialize our product candidates and, accordingly, may not achieve our research, development and commercialization goals.

Many of the biotechnology and pharmaceutical companies that we compete against for qualified personnel and consultants have greater financial and other resources, different risk profiles and a longer history in the industry than we do. If we are unable to continue to attract and retain high-quality personnel and consultants, the rate and success at which we can discover and develop product candidates and operate our business will be limited.

We only have a limited number of employees to manage and operate our business.

As of February 25, 2024, we had 75 full-time employees. Our focus on the clinical development of product candidates in two distinct disease indications requires us to manage and operate our business in a highly efficient manner. We cannot assure you that we will be able to hire and/or retain adequate staffing levels to develop our product candidates or run our operations and/or to accomplish all of the objectives that we otherwise would seek to accomplish.

If we lose key management or scientific personnel, cannot recruit qualified employees, directors, officers or other significant personnel or experience increases in our compensation costs, our business may materially suffer.

We are highly dependent on our officers, directors and key employees. Due to the specialized knowledge each of our officers, directors and key employees possesses with respect to our product candidates and our operations, the loss of service of any of one or more of our officers, directors or key employees could seriously delay, harm or prevent the planning and execution of clinical trials and other key activities required for the successful advancement of our business. Although we have employment agreements with our executive officers, in general, these agreements do not prevent our executive officers from terminating their employment with us at any time.

We do not carry key person life insurance on any officers or directors.

In addition to retaining the continued service of our officers, directors and key employees, our future success and growth will depend in part on our ability to identify, hire and retain additional personnel.

Our ability to identify, hire and retain additional personnel and, if necessary, replace departed executive officers and key employees may be difficult or costly and may take an extended period of time because of the limited number of individuals in our industry with the breadth of skills and experience required to discover or otherwise identify and develop product candidates and gain regulatory approval of and commercialize products successfully. Competition to hire from this limited pool is intense, and we may be unable to hire, train, retain or effectively incentivize these additional key personnel on acceptable terms given the competition among numerous pharmaceutical and biotechnology companies for similar personnel. We also experience competition for the hiring of scientific and clinical personnel from universities and research institutions. In addition, we rely on consultants and advisors, including scientific and clinical advisors, to assist us in formulating our research and development and commercialization strategy. Our consultants and advisors may be engaged by entities other than us and may have commitments under consulting or advisory contracts with other entities that may limit their availability to us. If we are unable to continue to attract and retain high quality personnel, our ability to develop and commercialize product candidates will be limited.

Many of our key officers, directors and employees are vested in a substantial amount of our common stock or options to purchase our common stock. Our employees, including many of our officers and key employees, may be more likely to leave us if the shares they own have significantly fluctuated in value relative to the original purchase prices of the shares, or if the exercise prices of the options that they hold are significantly below or above the market price of our common stock.

Unstable market and economic conditions may have serious adverse consequences on our business, financial condition and share price.

The global economy, including credit and financial markets, has recently experienced extreme volatility and disruptions, including severely diminished liquidity and credit availability, declines in consumer confidence, declines in economic growth, increases in unemployment rates, increases in interest rates, increases in inflation rates and uncertainty about economic stability. For example, the COVID-19 pandemic resulted in widespread unemployment, economic slowdown and extreme volatility in the capital markets. Similarly, international conflicts, terrorism and political instability have created extreme volatility in the capital markets. These conditions may make any necessary debt or equity financing more difficult to obtain in a timely manner or on favorable terms, more costly or more dilutive. In addition, there is a risk that one or more of our CROs, suppliers, CMOs or other third-party providers may not survive an economic downturn. As a result, our business, results of operations and price of our common stock may be adversely affected.

Our business could face adverse consequences as a result of the actions of activist shareholders.

We have in the past and may in the future be subject to unsolicited attempts to gain control of our company, proxy contests, and other forms of shareholder activism. For example, in May 2023, our board of directors received an unsolicited proposal from a stockholder to acquire all outstanding shares of our common stock. Our Board of Directors carefully reviewed and evaluated the proposal in consultation with our independent financial and legal advisors and decided not to approve the proposal. If in the future, a stockholder, by itself or in conjunction with other stockholders or as part of a group, engages in activist activities with respect to us, our business could be adversely affected because responding to an unsolicited offer, proxy contest or other actions by activist stockholders can be costly and time-consuming, disruptive to our operations and divert the attention of management and our employees from the execution of our strategy. In addition, actual or perceived uncertainties as to our future direction caused by activist activities may cause or appear to cause instability, potentially making it more difficult to attract and retain qualified personnel and collaborators or leading to the loss of collaboration opportunities, and if individuals are elected to our board of directors with a specific agenda, it may adversely affect our ability to effectively and timely implement our strategic plans. Activist stockholder activities may also cause significant fluctuations in our stock price based on temporary or speculative market perceptions, or other factors that do not necessarily reflect the fundamental underlying value of

our business. Finally, we might experience a significant increase in legal fees and administrative and associated costs incurred in connection with responding to an unsolicited offer, proxy contest or related action. These actions could also negatively affect the price of our common stock.

Risks Related to Our Common Stock

If securities or industry analysts do not publish research or reports about our business, or if they issue an adverse or misleading opinion regarding our stock, our stock price and trading volume could decline, even if our business is doing well.

The trading market for our common stock is influenced by the research and reports that industry or securities analysts publish about us or our business. We currently have limited research coverage by securities and industry analysts. If any of the analysts who cover us, or may cover us, downgrades our common stock or issues an adverse or misleading opinion regarding us, our business model, our intellectual property or our stock performance, or if our preclinical studies or clinical trials and operating results fail to meet the expectations of analysts, our stock price would likely decline. If one or more of these analysts ceases coverage of us or fails to publish reports on us regularly, we could lose visibility in the financial markets, which in turn could cause our stock price or trading volume to decline.

Provisions in our restated certificate of incorporation and amended and restated bylaws and under Delaware law could make an acquisition of our Company, which may be beneficial to our stockholders, more difficult and may prevent attempts by our stockholders to replace or remove our current management.

Provisions in our restated certificate of incorporation and our amended and restated bylaws may discourage, delay or prevent a merger, acquisition or other change in control of our company that stockholders may consider favorable, including transactions in which you might otherwise receive a premium for your shares. These provisions may also limit the price that investors are willing to pay in the future for shares of our common stock, thereby depressing the market price of our common stock. In addition, because our board of directors is responsible for appointing the members of our management team, these provisions may frustrate or prevent any attempts by our stockholders to replace or remove our current management by making it more difficult for stockholders to replace members of our board of directors. Among other things, these provisions include those establishing:

Moreover, because we are incorporated in Delaware, we are governed by the provisions of Section 203 of the General Corporation Law of the State of Delaware, which prohibits a person who owns in excess of 15% of our outstanding voting stock from merging or combining with us for a period of three years after the date of the transaction in which the person acquired in excess of 15% of our outstanding voting stock, unless the merger or combination is approved in a prescribed manner.

Our restated certificate of incorporation designates specific courts as the exclusive forum for certain litigation that may be initiated by our stockholders, which could limit our stockholders’ ability to obtain a favorable judicial forum for disputes with us.

Our restated certificate of incorporation, specifies that, unless we consent in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware will be the sole and exclusive forum for most legal actions involving claims brought against us by stockholders, other than suits brought to enforce any liability or duty created by the Exchange Act or any other claim for which the federal courts have exclusive jurisdiction and any action that the Court of Chancery of the State of Delaware has dismissed for lack of subject matter jurisdiction, which may be brought in another state or federal court sitting in the State of Delaware. Our restated certificate of incorporation also specifies that unless we consent in writing to the selection of an alternate forum, the federal district courts of the US shall be the exclusive forum for the resolution of any complaint asserting a cause of action arising under the Securities Act of 1933. Any person or entity purchasing or otherwise acquiring any interest in shares of our capital stock shall be deemed to have notice of and to have consented to the provisions of our restated certificate of incorporation described above.

We believe this provision benefits us by providing increased consistency in the application of Delaware law by chancellors particularly experienced in resolving corporate disputes or federal judges experienced in resolving Securities Act disputes, efficient administration of cases on a more expedited schedule relative to other forums and protection against the burdens of multi-forum litigation. However, the provision may have the effect of discouraging lawsuits against our directors, officers, employees and agents as it may limit any stockholder’s ability to bring a claim in a judicial forum that such stockholder finds favorable for disputes with us or our directors, officers, employees or agents. The enforceability of similar choice of forum provisions in other companies’ certificates of incorporation has been challenged in legal proceedings, and it is possible that, in connection with any applicable action brought against us, a court could find the choice of forum provisions contained in our restated certificate of incorporation to be inapplicable or unenforceable in such action. If a court were to find the choice of forum provision contained in our restated certificate of incorporation to be inapplicable or unenforceable in an action, we may incur additional costs associated with resolving such action in other jurisdictions, which could adversely affect our business, financial condition or results of operations.

General Risk Factors

Raising additional capital may cause additional dilution to our stockholders, restrict our operations, require us to relinquish rights to our technologies or product candidates, and could cause our share price to fall.

Until such time, if ever, as we can generate substantial revenue from product sales, we may finance our cash needs through a combination of equity offerings, debt financings, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements. In addition, we may seek additional capital due to favorable market conditions or strategic considerations, even if we believe that we have sufficient funds for our current or future operating plans.

To the extent that we raise additional capital through the sale of equity or convertible debt securities, your ownership interest will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect your rights as a common stockholder. Debt financing and preferred equity financing, if available, may involve agreements that include covenants limiting or restricting our

operations, our ability to take specific actions, such as incurring additional debt, making capital expenditures, declaring dividends, redeeming our stock, making certain investments and engaging in certain merger, consolidation or asset sale transactions, among other restrictions. If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may be required to relinquish valuable rights to our technologies, future revenue streams or product candidates or grant licenses on terms that may not be favorable to us. If we are unable to raise additional funds through equity or debt financings when needed, we may be required to delay, limit, reduce or terminate our product development or future commercialization efforts or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

We may engage in acquisitions or strategic collaborations that could disrupt our business, cause dilution to our stockholders, reduce our financial resources, cause us to incur debt or assume contingent liabilities, and subject us to other risks.

In the future, we may enter into transactions to acquire other businesses, products or technologies or enter into strategic collaborations, including licensing transactions. If we do identify suitable acquisition or collaboration candidates, we may not be able to complete such acquisitions or collaborations on favorable terms, or at all. Any acquisitions or collaborations may not strengthen our competitive position, and these transactions may be viewed negatively by stock research analysts or investors, and we may never realize the anticipated benefits of such acquisitions or collaborations. We may decide to incur debt in connection with an acquisition or issue our common stock or other equity securities to the stockholders of the acquired company, which would reduce the percentage ownership of our existing stockholders. We could incur losses resulting from undiscovered liabilities of the acquired business or collaboration that are not covered by the indemnification we may obtain from the seller or our collaborator. In addition, we may not be able to successfully integrate any acquired personnel, technologies and operations into our existing business in an effective, timely and non-disruptive manner. Acquisitions or collaborations may also divert management attention from day-to-day responsibilities, lead to a loss of key personnel, increase our expenses and reduce our cash and cash equivalents available for operations and other uses. We cannot predict the number, timing or size of future acquisitions or collaborations or the effect that any such transactions might have on our operating results.

We or the third parties upon whom we depend may be adversely affected by natural disasters or pandemics and our business continuity and disaster recovery plans may not adequately protect us from a serious disaster.

Natural disasters (including, but not limited to earthquakes, fires, storms, floods, droughts, and extreme temperatures) or pandemics, other than or in addition to COVID-19, could severely disrupt our operations and have a material adverse effect on our business, results of operations, financial condition and prospects. Climate change has increased, and is expected to continue to increase the frequency or intensity of such events. Moreover, climate change may result in various chronic changes in the physical environment, such as changes in temperature or precipitation patterns or sea-level rise, as well as changes to the availability of certain natural resources, that may also have an adverse impact on our operations. If a natural disaster, power outage, pandemic, such as the COVID-19 pandemic, or other event occurred that prevented us from using all or a significant portion of our headquarters or the virtual network capabilities upon which our employees depend to collaborate and access critical business records, that damaged critical infrastructure, such as the manufacturing facilities on which we rely, or that otherwise disrupted operations, it may be difficult or, in certain cases, impossible for us to continue our business for a substantial period of time. The disaster recovery and business continuity plans we have in place may prove inadequate in the event of a serious disaster or similar event. We may incur substantial expenses as a result of the limited nature of our disaster recovery and business continuity plans, which could have a material adverse effect on our business.

Increased attention to, and evolving expectations for ESG initiatives could increase our costs, harm our reputation, or otherwise adversely impact our business.

Companies across industries are facing increasing scrutiny from a variety of stakeholders related to their ESG and sustainability practices. Expectations regarding voluntary ESG initiatives and disclosures may result in increased costs (including but not limited to increased costs related to compliance, stakeholder

engagement, contracting and insurance), enhanced compliance or disclosure obligations, or other adverse impacts to our business, financial condition, or results of operations.

While we may at times engage in voluntary initiatives (such as voluntary disclosures, certifications, or goals, among others) to improve the ESG profile of our Company and/or product candidates and if approved, our products, such initiatives may be costly and may not have the desired effect. Moreover, we may not be able to successfully complete such initiatives due to factors that are within or outside of our control. Even if this is not the case, our actions may subsequently be determined to be insufficient by various stakeholders, and we may be subject to investor or regulator engagement on our ESG efforts, even if such initiatives are currently voluntary.

Certain market participants, including major institutional investors and capital providers, use third-party benchmarks and scores to assess companies’ ESG profiles in making investment or voting decisions. Unfavorable ESG ratings or other reputational issues could result in various negative impacts, including negative investor sentiment, decreased interest in our shares, changes in the availability or cost of capital, or our ability to attract/retain employees, customers, or business partners. Simultaneously, some parties are seeking to restrict or eliminate companies’ attention to ESG matters. Both advocates and opponents to certain ESG matters are increasingly resorting to a range of activism forms, including media campaigns and litigation, to advance their perspectives. To the extent we are subject to such activism, it may require us to incur costs or otherwise adversely impact our business.

In addition, we expect there will likely be increasing levels of regulation, disclosure-related and otherwise, with respect to ESG matters. For example, various policymakers, including the SEC and the State of California, have adopted or are considering adopting requirements for significantly expanded climate-related disclosures, which may require us to incur significant additional costs to comply, including the implementation of significant additional internal controls processes and procedures regarding matters that have not been subject to such controls in the past, and impose increased oversight obligations on our management and board of directors. These and other changes in stakeholder expectations will likely lead to increased costs as well as scrutiny that could heighten all of the risks identified in this risk factor. Additionally, many of our customers and suppliers may be subject to similar expectations, which may augment or create additional risks, including risks that may not be known to us.

Litigation against us could be costly and time-consuming to defend and could result in additional liabilities.

We may from time to time be subject to legal proceedings and claims that arise in the ordinary course of business or otherwise, such as claims brought by third parties in connection with commercial disputes and employment claims made by our current or former employees. Claims may also be asserted by or on behalf of a variety of other parties, including government agencies, patients or vendors of our customers, or stockholders. In the past, securities class action litigation has often been brought against a company following a decline in the market price of its securities.

Any litigation involving us may result in substantial costs, operationally restrict our business, and may divert management’s attention and resources, which may seriously harm our business, overall financial condition and results of operations. Insurance may not cover existing or future claims, be sufficient to fully compensate us for one or more of such claims, or continue to be available on terms acceptable to us. A claim brought against us that is uninsured or underinsured could result in unanticipated costs, thereby adversely impacting our results of operations and resulting in a reduction in the trading price of our stock.

The market price of our common stock has been volatile and may fluctuate substantially.

Our stock price has been and is likely to remain volatile. Extreme fluctuations have occurred in our stock price. Additionally, the stock market in general, and The Nasdaq Global Select Market-listed companies and biopharmaceutical companies in particular have experienced extreme volatility in trading volume that exacerbates, is disproportionate to or in some cases has been unrelated to the operating performance of particular companies. As a result of this volatility, you may not be able to sell your common stock at a profit. The market price for our common stock may be influenced by many factors, including but not limited to:

Broad market and industry factors may negatively affect the market price of our common stock, regardless of our actual operating performance. In the past, securities class action litigation has often been instituted against companies following periods of volatility in the market price of a company’s securities. This type of litigation, if instituted, could result in substantial costs and a diversion of management’s attention and resources, which would harm our business, financial condition and results of operations.

If we fail to maintain effective internal control over financial reporting and effective disclosure controls and procedures, we may not be able to accurately report our financial results in a timely manner or prevent fraud, which may adversely affect investor confidence in our company.

We are required to comply with the SEC’s rules implementing Sections 302 and 404 of the Sarbanes-Oxley Act, which require management to certify financial and other information in our quarterly and annual reports and provide an annual management report on the effectiveness of controls over financial reporting. In addition, we have in the past and may for future fiscal years beginning January 1, 2024 and after be required to include an attestation report on internal control over financial reporting issued by our independent registered public accounting firm and our independent registered public accounting firm has in the past and may be required to attest to the effectiveness of our internal control over financial reporting pursuant to Section 404 for future fiscal years beginning January 1, 2024 and after. Our independent registered public accounting firm may issue a report that is adverse in the event material weaknesses have been identified in our internal control over financial reporting. For the year ended December 31, 2023, our independent registered public accounting firm was not required to issue an attestation report on internal control over financial reporting or attest to the effectiveness of our internal control over financial reporting pursuant to Section 404.

To comply with the requirements of Section 404, we may need to undertake additional actions, such as implementing new internal controls and procedures and hiring additional accounting or internal audit staff. We will need to continue to dedicate internal resources, engage outside consultants, adopt a detailed work plan to assess and document the adequacy of internal control over financial reporting, continue steps to improve control processes as appropriate, validate through testing whether such controls are functioning as documented, and implement a continuous reporting and improvement process for internal control over financial reporting. Testing and maintaining internal control can divert our management’s attention from other matters that are also important to the operation of our business. Despite our efforts, there is a risk that we will not be able to conclude, within the prescribed timeframe or at all, that our internal control over financial reporting is effective as required by Section 404. When evaluating our internal control over financial reporting, we may identify material weaknesses that we may not be able to remediate in time to meet the applicable deadline imposed upon us for compliance with the requirements of Section 404. If we identify any material weaknesses in our internal controls over financial reporting or we are unable to comply with the requirements of Section 404 in a timely manner or assert that our internal control over financial reporting is effective, or if our independent registered public accounting firm, if required, is unable to express an opinion as to the effectiveness of our internal control over financial reporting, investors may lose confidence in the accuracy and completeness of our financial reports. As a result, the market price of our common stock could be materially adversely affected.

Our disclosure controls and procedures may not prevent or detect all errors or acts of fraud.

We are subject to the periodic reporting requirements of the Exchange Act. We are continuing to refine our disclosure controls and procedures to provide reasonable assurance that information we must

disclose in reports we file or submit under the Exchange Act is accumulated and communicated to management, and recorded, processed, summarized and reported within the time periods specified in the rules and forms of the SEC. We believe that any disclosure controls and procedures, no matter how well-conceived and operated, can provide only reasonable, not absolute, assurance that the objectives of the control system are met.

These inherent limitations include the realities that judgments in decision-making can be faulty, and that breakdowns can occur because of simple error or mistake. Additionally, controls can be circumvented by the individual acts of some persons, by collusion of two or more people or by an unauthorized override of the controls. Accordingly, because of the inherent limitations in our control system, misstatements due to error or fraud may occur and not be detected.

Because we do not anticipate paying any cash dividends on our common stock in the foreseeable future, capital appreciation, if any, is likely to be your sole source of gain.

We have never declared or paid any cash dividends on our common stock. We currently anticipate that we will retain all available funds and future earnings for the development, operation and expansion of our business and do not anticipate declaring or paying any cash dividends for the foreseeable future. As a result, capital appreciation, if any, of our common stock is likely to be your sole source of gain on an investment in our common stock for the foreseeable future.

Item 1B. Unresolved Staff Comments.

Not applicable.

Item 1C. Cybersecurity.

Cybersecurity Risk Management and Strategy

We have developed and implemented a cybersecurity risk management program intended to protect the confidentiality, integrity, and availability of our critical systems and information. Our cybersecurity risk management program includes a cybersecurity incident response plan.

We design and assess our program based on the National Institute of Standards and Technology Cybersecurity Framework (NIST CSF). This does not imply that we meet any particular technical standards, specifications, or requirements, only that we use the NIST CSF as a guide to help us identify, assess, and manage cybersecurity risks relevant to our business.

Our cybersecurity risk management program is integrated into our overall enterprise risk management program, and shares common methodologies, reporting channels and governance processes that apply across the enterprise risk management program to other legal, compliance, strategic, operational, and financial risk areas.

Our cybersecurity risk management program includes:

We have not identified risks from known cybersecurity threats, including as a result of any prior cybersecurity incidents, that have materially affected or are reasonably likely to materially affect us, including our operations, business strategy, results of operations, or financial condition. For more information, see the section titled “Risk Factors — Our business and operations may suffer in the event of information technology system failures, cyberattacks, or deficiencies, which could materially affect our results.”

Cybersecurity Governance

Our Board considers cybersecurity risk as part of its risk oversight function and has delegated to the Audit Committee (the “Audit Committee”) oversight of cybersecurity and other IT risks. The Committee oversees management’s implementation of our cybersecurity risk management program.

The Audit Committee receives periodic reports from management on our cybersecurity risks and would be notified between such regular updates regarding any significant cybersecurity threat or incident, if applicable. The Audit Committee reports to the full Board regarding its activities, including those related to cybersecurity.

Our IT team, which includes both our internal staff and retained consultants with IT and cybersecurity expertise, is led by our executive director of IT. The IT team has responsibility for, among other things, developing and implementing practices, procedures and controls designed to identify, assess and manage cybersecurity programs and risks. The IT team supervises efforts to prevent, detect, mitigate, and remediate cybersecurity risks and incidents through various means, which may include briefings from internal security personnel; threat intelligence and other information obtained from governmental, public or private sources, including external consultants engaged by us; and alerts and reports produced by security tools deployed in the IT environment. Our IT team is supplemented by a security committee, comprised of representatives from key functional areas of our business and includes both our CFO and our Sr. VP of Human Resources to whom the executive director of IT reports. Combined, members of our security committee and our internal IT team have more than 25 years of risk management experience, including with respect to IT and cybersecurity systems.

Item 2. Properties.

Our principal office is located at 225 Franklin Street, Boston, Massachusetts, where we lease 17,544 square feet of office space. We lease this space under a sublease agreement, with the term January 1, 2022 through December 31, 2026. We believe that our facilities are sufficient to meet our current needs and that suitable additional space will be available as and when needed.

Item 3. Legal Proceedings.

We are not subject to any material legal proceedings.

Item 4. Mine Safety Disclosures.

Not applicable.

PART II

Item 5. Market for Registrant’s Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities.

Certain Information Regarding the Trading of Our Common Stock

Our common stock has been listed on The Nasdaq Global Select Market under the symbol “AVIR” since October 30, 2020.

Holders of Our Common Stock

As of February 28, 2024 there were 18 stockholders of record of our common stock, which does not reflect stockholders whose shares were held in nominee or street name by brokers.

Dividends

We have never declared or paid any cash dividends on our common stock. We currently intend to retain all available funds and any future earnings to fund the development and expansion of our business, and therefore do not anticipate paying cash dividends in the foreseeable future. Any future determination to pay dividends will be at the discretion of our board of directors and will depend on our financial condition, results of operations, capital requirements, business prospects, contractual arrangements, any limitations on payment of dividends present in any future debt agreements and other factors that our board of directors may deem relevant, and will be subject to the restrictions contained in any future financing instruments.

Use of Proceeds

On November 3, 2020, we completed the initial public offering (“IPO”) of our common stock pursuant to which we issued and sold 14,375,000 shares of our common stock at a price to the public of $24.00 per share.

All shares issued and sold in the initial public offering were registered under the Securities Act pursuant to a Registration Statement on Form S-1 (File No.333-249404), as amended (“Registration Statement”), declared effective by the SEC on October 29, 2020.

We received net proceeds of approximately $317.6 million after deducting underwriting discounts and commissions and offering expenses.

The net proceeds from our IPO have been invested primarily in money market accounts and marketable securities. There has been no material change in the expected use of the net proceeds from our IPO as described in our Prospectus filed pursuant to Rule 424(b)(4) under the Securities Act with the SEC on October 29, 2020.

Item 6. Reserved

Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations.

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our financial statements and the related notes to those statements included elsewhere in this Annual Report on Form 10-K. In addition to historical financial information, the following discussion and analysis contains forward-looking statements that involve risks, uncertainties and assumptions. Our actual results and timing of selected events may differ materially from those anticipated in these forward-looking statements as a result of many factors, including those discussed in Part I, Item 1A, “Risk Factors” and elsewhere in this Annual Report on Form 10-K. See “Special Note Regarding Forward-Looking Statements.”

Overview

We are a clinical-stage biopharmaceutical company leveraging our deep understanding of antiviral drug development, medicinal chemistry, biology, biochemistry and virology to discover and develop novel orally administered product candidates to treat serious viral diseases. Currently, we are developing our lead product candidate, bemnifosbuvir, in a global Phase 3 clinical trial as a monotherapy for the treatment of COVID-19, and in a global Phase 2 clinical trial as part of a combination therapy with ruzasvir, an NS5A inhibitor, for the treatment of HCV infection.

Bemnifosbuvir

Derived from our internal discovery program, bemnifosbuvir (AT-527), is an investigational, novel, orally administered guanosine nucleotide analog polymerase inhibitor that combines a unique nucleotide scaffold with novel double prodrugs for the intended purpose of inhibiting the enzymes central to viral replication. We believe that utilizing this double prodrug moiety approach allows us to maximize formation of the active metabolite potentially resulting in an oral antiviral product candidate that is selective for and highly effective at preventing replication and transcription of SARS-CoV-2, the causative agent of COVID-19, HCV and other single ssRNA viruses while avoiding toxicity to host cells.

COVID-19 – Our Strategy and Objective

More than four years after emerging as a global pandemic and public health crisis, COVID-19 remains a persistent and serious health threat because of continued variant fueled surges of infection. The SARS-CoV-2 virus is accumulating mutations with amino acid substitutions faster than any other endemic ssRNA virus and the constant evolution of new variants has resulted in continued waves of infections globally.

Our COVID-19 strategy is focused on the development of bemnifosbuvir for the treatment of COVID-19. We believe that oral antivirals protecting against the development of severe infection and transmission remain urgently needed particularly for high-risk patients who currently have few or no treatment options due to limitations of currently available vaccines and therapeutics. High-risk patients include those who are unvaccinated, patients who fail to respond to available vaccines, vaccinated patients with waning efficacy, which can occur between three to six months after immunization, and patients for whom current treatments are contraindicated. Without suitable treatments, high-risk patients remain vulnerable to severe COVID-19 and associated hospitalization and death.

As COVID-19 continues to persist as a global endemic disease, we believe that the global COVID-19 therapeutic market, and in particular the US market, will remain a multi-billion-dollar commercial opportunity for many years to come. Further, as the commercialization of COVID-19 therapeutics enters more fully into traditional distribution and reimbursement channels in 2024 and after, we anticipate that a major consideration for third-party payers will be a cost/value analysis that is driven in part by the economic burden of hospitalization, especially for high-risk populations.

The objective of our COVID-19 development program is to address the current unmet medical needs of high-risk patients who remain vulnerable to hospitalization and death from COVID-19 by developing bemnifosbuvir, as a safe, effective, convenient, oral antiviral without the key limitations of current treatment options, including drug-drug interactions, tolerability and other safety concerns. The FDA has granted Fast Track designation for the investigation of bemnifosbuvir to treat COVID-19. Currently, we

are evaluating bemnifosbuvir in SUNRISE-3, a global Phase 3 clinical trial that is enrolling high-risk patients with mild to moderate COVID-19.

For COVID-19, bemnifosbuvir targets the SARS-CoV-2 RNA polymerase (Nsp12), a highly conserved enzyme that is unlikely to change as the virus mutates and new variants continue to emerge. The RNA polymerase complex is responsible for both replication and transcription of SARS-CoV-2. Bemnifosbuvir has a unique dual mechanism of action at both the RdRp and nidovirus RdRp associated NiRAN active sites on the highly conserved SARS-CoV-2 RNA polymerase, which has the potential to create a high barrier to resistance. In vitro data have shown that bemnifosbuvir was active with similar activity against all SARS-CoV-2 VOC and VOI that have been tested to date, including Omicron subvariants BA.4, BA.5 and XBB and EG.5.1.

HCV – Our Strategy and Objective

Despite the availability of direct acting antiviral oral combination treatment regimens, HCV continues to be a serious viral disease in the US and globally. Approximately 58 million people globally are living with chronic HCV infection. The WHO estimates a global incidence of 1.5 million new infections and 290,000 deaths per year.

In the US, HCV is recognized as a health crisis with approximately 2.4 million individuals estimated to be infected. Prevalence of HCV in the US is expected to remain constant over the coming years as rising HCV is incidence largely attributable to the opioid crisis, IV drug use, and HCV reinfection, especially among younger adults, offsets the number of new patients treated.

Our HCV strategy focuses on the development of bemnifosbuvir in combination with ruzasvir, an HCV NS5A inhibitor, a product candidate which we have exclusively licensed from Merck. Combination therapy utilizing two or more direct acting antivirals with different mechanisms of action is a scientifically and clinically well-established approach that is utilized by currently available human immunodeficiency virus, hepatitis B virus and HCV treatment regimens.

The objective of our HCV development program is to improve upon the current SOC by offering, if successfully developed, the combination of bemnifosbuvir and ruzasvir, as a potentially differentiated eight-week duration, pan-genotypic protease inhibitor-free regimen for HCV-infected patients with or without cirrhosis. Currently, we are conducting a Phase 2 clinical trial of bemnifosbuvir in combination with ruzasvir in treatment naïve HCV infected patients, either without cirrhosis or with compensated cirrhosis.

For HCV, the combination of bemnifosbuvir and ruzasvir targets the HCV NS5B and the HCV NS5A, respectively, and is designed to inhibit these enzymes which are essential for HCV replication. Both bemnifosbuvir and ruzasvir have individually demonstrated potent, pan-genotypic, antiviral activity against HCV and the combination of bemnifosbuvir and ruzasvir has exhibited synergistic activity against HCV in vitro.

Key Clinical Trials

COVID-19 – SUNRISE-3: Global Phase 3 Clinical Trial of Bemnifosbuvir

SUNRISE-3, is a currently ongoing global, multicenter, randomized, double-blind, placebo-controlled Phase 3 clinical trial that is evaluating bemnifosbuvir (550 mg BID) for five days) in high-risk non-hospitalized patients with mild or moderate COVID-19. SUNRISE-3 is designed to evaluate bemnifosbuvir as monotherapy (primary analysis) but it is also exploring the effect of combination therapy in a smaller sub-set of patients who receive a compatible antiviral drug along with bemnifosbuvir (secondary analysis).

The trial consists of two study populations derived from the type of SOC received: 1) a “supportive care population” (those patients who do not qualify for another antiviral treatment or where other antivirals are not locally available) which is assessing bemnifosbuvir given as monotherapy (primary analysis) and 2) a “combination antiviral population” which is assessing combination therapy if the SOC includes treatment with other compatible antiviral drugs against COVID-19 (secondary analysis). Patients are being randomized 1:1 to receive either bemnifosbuvir 550 mg BID plus locally available SOC or placebo BID plus locally available SOC for five days.

The primary endpoint of the SUNRISE-3 study is all-cause hospitalization or death through Day 29 in approximately 2,200 patients in the supportive care monotherapy population. Secondary endpoints in each of the supportive care monotherapy patient population and the combination antiviral population include COVID-19 related hospitalization or death, COVID-19 complications, medically attended visits, symptom rebound/relapse and viral load rebound.

The trial is enrolling patients who are ≥70 years old (regardless of other risk factors), patients ≥55 years old with one or more risk factors, patients ≥50 years old with two or more risk factors and patients ≥18 years old with certain risk factors including immunocompromised conditions, all regardless of COVID-19 vaccination status. We believe that this population encompasses those patients who currently remain at high-risk for progression of COVID-19 to severe disease and associated hospitalization and death.

In January and February 2024, we announced the enrollment of more than 650 patients and more than 1,350 patients, respectively, in the supportive care monotherapy cohort. Each of these patient enrollment milestones triggers an interim analysis by an independent DSMB principally for safety and futility after the respective patient group has completed Day 29 post treatment. As a result, we currently anticipate that the first interim analysis by the DSMB will occur in March of 2024 and the second interim analysis by the DSMB will occur in the second quarter of 2024. Patient enrollment in the SUNRISE-3 trial, which has currently surpassed 1,400 patients in the supportive care monotherapy population, continues and topline data from the trial are anticipated in the second half of 2024.

HCV – Global Phase 2 Clinical Trial of the Combination of Bemnifosbuvir and Ruzasvir

Currently, we are conducting a global Phase 2 clinical trial of bemnifosbuvir in combination with ruzasvir in treatment-naïve, HCV-infected patients either without cirrhosis or with compensated cirrhosis. This study is designed to evaluate the safety and efficacy of eight weeks of treatment with the combination consisting of once daily bemnifosbuvir 550 mg and ruzasvir 180 mg. Up to approximately 280 HCV-infected, treatment-naïve patients across HCV GTs, including a lead-in cohort of 60 patients without cirrhosis, are expected to be enrolled in this Phase 2 clinical trial. The primary endpoints of the study are safety and SVR12. Other virologic endpoints include virologic failure, SVR24 and resistance.

In February 2024, we announced final results from the full lead-in cohort in which a 98% SVR4 rate was observed [58 of 59 subjects achieved SVR4 with one patient who did not return for post-treatment follow-up]. The one patient who did not achieve SVR4 had poor adherence, and was infected with HCV GT-2. These results are consistent with the initial results announced in January 2024. The SVR4 rate exceeded the protocol-defined efficacy criterion of ≥90% SVR4 for continuing the study. As a result, in January 2024 we commenced enrolling up to an additional 220 patients in the study, including patients with cirrhosis. In the lead-in cohort, very rapid kinetics were observed with viral load for each patient near or below the LLOQ at four weeks of treatment, which we believe is supportive of an eight-week treatment regimen for the combination of bemnifosbuvir and ruzasvir. All 60 patients in the lead-in cohort achieved viral load below the LLOQ by the end of the eight-week treatment regimen.

The combination of bemnifosbuvir and ruzasvir in the lead-in cohort was generally safe and well tolerated and there were no drug related SAEs, no treatment discontinuations and adverse events AEs were mostly mild. Final SVR12 results from all 280 patients enrolled in the global Phase 2 study are anticipated in the second half of 2024.

If the Phase 2 study is successfully completed, subject to discussion and alignment with regulatory authorities, we anticipate initiating a Phase 3 clinical development program in the second half of 2024.

Dengue

After conducting a Phase 2 clinical trial, in February 2023, we decided not to pursue further clinical development of AT-752 for the treatment and prophylaxis of dengue. This action was taken due to the long timelines anticipated for patient enrollment, expected clinical operational challenges, including the challenge of successfully identifying patients shortly after infection which is not feasible with the diagnostic tests that are currently readily available in endemic countries, and the estimated resource burdens, including substantial costs, associated with the further clinical development of an antiviral for each of the treatment and prophylaxis of dengue.

Financial Resources

We believe we are well capitalized to advance our current programs. We had $578.1 million in cash, cash equivalents and marketable securities at December 31, 2023. Based on our current plans, we anticipate these financial resources will allow us to advance our current and planned clinical programs to and through key inflection points and to fund our activities through 2026. We have based this estimate on assumptions that may prove to be wrong and we could exhaust our available capital resources sooner than we expect.

Roche License Agreement

In October 2020, with Roche, we entered into the Roche License Agreement in connection with the global development, manufacture and commercialization of bemnifosbuvir, products containing bemnifosbuvir or AT-511, the free base of bemnifosbuvir, and related companion diagnostics. During the term of the Roche License Agreement, Roche and we jointly developed bemnifosbuvir for COVID-19 on a worldwide-basis and equally shared the costs associated with such development activities.

The Roche License Agreement terminated on February 10, 2022, and, accordingly, our obligations to share costs with Roche also ended. As a result of the termination of the Roche License Agreement, we regained worldwide exclusive rights from Roche to research, develop, manufacture and commercialize bemnifosbuvir, products containing bemnifosbuvir and related companion diagnostics in all fields of use.

Merck License Agreement

In December 2021, we entered into the Merck License Agreement for the development, manufacture and commercialization of ruzasvir. Ruzasvir is an investigational NS5A inhibitor we are developing in combination with bemnifosbuvir for the treatment of HCV.

Pursuant to the terms of the Merck License Agreement, we obtained from Merck an exclusive (subject to certain reserved rights to conduct internal research), sublicensable, and worldwide license under certain Merck patents and know-how to research, develop, manufacture, have manufactured, use, import, export, sell, offer for sale, and otherwise commercialize a Product for all therapeutic or prophylactic uses in humans.

In addition to a non-refundable upfront payment that we made in February 2022, we will be required to pay Merck milestone payments upon our achievement of certain development, regulatory and sales-based milestones. Additionally, we will pay Merck tiered royalties based on annual net sales of Products ranging from high single digits to mid-teens percentages. Our royalty payment obligations will continue until the later of (i) the expiration of the last to expire valid claim of a licensed Merck patent claiming such Product and (ii) a period of years after the first commercial sale of such Product in such country. We may terminate the Merck License Agreement for convenience upon prior written notice. The first potential milestone, in the amount of $5.0 million, would be payable upon the commencement of a Phase 3 clinical trial.

Financial Operations Overview

As of December 31, 2023, we had cash, cash equivalents and marketable securities of $578.1 million. Net cash used in operating activities was $85.4 million for the year ended December 31, 2023.

We expect that our net cash used in operating activities will increase significantly as we advance our product candidates through preclinical and clinical development, seek regulatory approval, and prepare for and, if approved, proceed to commercialization; acquire, discover, validate and develop additional product candidates; obtain, maintain, protect and enforce our intellectual property portfolio; and hire additional personnel. In addition, we may incur additional costs as we continue to operate as a public company. We believe that our available cash and cash equivalents will be sufficient to fund our planned operations through 2026. We have based this estimate on assumptions that may prove to be wrong and we could exhaust our available capital resources sooner than we expect.

We do not have any products approved for sale and have not generated any product revenue since inception. We do not anticipate generating any revenue from product sales for the foreseeable future. Our

ability to generate product revenue will depend on the successful development, regulatory approval and eventual commercialization of one or more of our product candidates. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through private or public equity or debt financings, collaborative or other arrangements with third parties, or through other sources of financing. Adequate funding may not be available to us on acceptable terms, or at all. If we fail to raise capital or enter into such agreements as and when needed, we may have to significantly delay, scale back or discontinue the development and commercialization of our product candidates.

We plan to continue to use third-party service providers, including CROs to carry out our preclinical and clinical development, and CMOs to manufacture and supply the materials used during the development of our product candidates. Additionally, we expect to rely on CMOs for the manufacture of commercial supply of any product candidate we may successfully develop.

As we continue to advance our programs, we expect to incur significantly higher expenses over the next several years. We anticipate that our expenses will increase significantly in connection with our ongoing activities, as we:

Components of Results of Operations

Revenue

We do not have any products approved for sale and we have not generated any revenue in the periods presented.

If our development efforts for our product candidates are successful and result in commercialization, we may generate revenue in the future from product sales. Additionally, we may generate revenue from collaboration or license agreements that we may enter into with third parties.

Operating Expenses

Research and Development Expenses

Substantially all of our research and development expenses consist of expenses incurred in connection with the discovery and development of our product candidates. These expenses include external costs consisting of fees paid to third parties, including CROs and CMOs, to conduct certain research and development activities on our behalf and consulting costs, as well as internal costs consisting of payroll

and personnel-related expenses, including salaries and bonuses, employee benefit costs and stock-based compensation expenses for our research and product development employees and allocated overhead, including rent, equipment, depreciation, information technology costs and utilities attributable to our research and development personnel. We expense both internal and external research and development expenses as they are incurred. In circumstances where amounts have been paid in advance or in excess of costs incurred, we record a prepaid expense, which is expensed as services are performed or goods are delivered.

A significant portion of our research and development costs have been external costs, which we track by therapeutic area. We have not historically tracked our internal research and development expenses by therapeutic area as they are deployed across multiple programs.

As discussed in Note 3 to our consolidated financial statements, during the term of the Roche License Agreement which terminated in February 2022, we and Roche shared certain manufacturing and clinical development costs on a 50/50 basis. Billings to us by Roche for our percentage share of such expenses were recorded in research and development expenses. During the year ended December 31, 2023, we recorded a net reduction to research and development expenses of $18.6 million related to credits received from Roche. During the year ended December 31, 2022, we recorded a net reduction to research and development expenses of $6.9 million related to credits received from Roche. These credits were the result, following the termination of the Roche License Agreement, of changes and adjustments by Roche in estimated amounts of expenses reported by Roche during the period in which we and Roche shared costs associated with the development of bemnifosbuvir.

The following table summarizes our external research and development expenses by indication and internal research and development expenses:

We are focusing substantially all of our resources on the development of our product candidates, particularly bemnifosbuvir for the treatment of COVID-19 and the combination of bemnifosbuvir and ruzasvir for the treatment of HCV. We expect our research and development expenses to continue to increase substantially for at least the next few years, as we seek to complete our current clinical programs which in the case of HCV, is expected to include a Phase 3 clinical trial if our Phase 2 clinical trial is successful, pursue regulatory approval of our product candidates and prepare for the possible commercialization of these product candidates. Predicting the timing or cost to complete our clinical programs, validate our commercial manufacturing and supply processes and manufacture of product at commercial scale is difficult and delays may occur because of many factors, including factors outside of our control. For example, if the FDA or other regulatory authorities were to require us to conduct clinical trials beyond those that we currently anticipate or the time to complete planned clinical trials is extended due to delays in enrollment or otherwise, we could be required to expend significant additional financial resources and time on the completion of clinical development. Furthermore, we are unable to predict with any certainty when our product candidates, if ever, will receive regulatory approval with any certainty, if ever.

General and Administrative Expenses

General and administrative expenses consist principally of payroll and personnel expenses, including salaries and bonuses, benefits and stock-based compensation expenses, professional fees for legal, consulting, accounting and tax services, allocated overhead, including rent, equipment, depreciation,