UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2022

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, 2022, 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 $537,283,731.

The number of shares of Registrant’s Common Stock outstanding as of February 25, 2023 was 83,341,574.

Table of Contents

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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,” "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:

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These forward-looking statements are based on management’s current expectations. 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. 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.

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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:

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PART I

Item 1. Business.

Overview

We are a clinical-stage biopharmaceutical company focused on discovering, developing, and commercializing antiviral therapeutics to improve the lives of patients suffering from serious viral infections. We are developing our lead product candidate, bemnifosbuvir, for the treatment of COVID-19, the disease caused by infection with Severe Acute Respiratory Syndrome Coronavirus 2 ("SARS-CoV-2") and its variants. We are also developing bemnifosbuvir in combination with ruzasvir for the treatment of Hepatitis C ("HCV").

COVID-19 has caused a global health crisis resulting in millions of deaths and lingering medical issues for many survivors. While there have been many rapid advances in the prevention and treatment of COVID‑19, due to the limitations of the current vaccine and treatment options, there remains a significant unmet medical need for large numbers of high-risk individuals both in the US and globally. Our COVID-19 strategy is centered on the development of bemnifosbuvir as a monotherapy and potentially as a part of a COVID-19 therapy that combines bemnifosbuvir with another antiviral agent and focuses on these high-risk patients for whom current vaccines and treatments remain inadequate. Our goal is to deliver a safe, effective, and convenient treatment option for individuals that remain vulnerable to hospitalization and death as a result of infection with SARS-CoV-2.

Even with the availability of vaccines and therapeutics, COVID-19 is the third leading cause of mortality in the US after only heart disease and cancer. As of February 15, 2023, the CDC reported that more than 400 persons a day are dying in the US from COVID-19 or related complications. More than 75% of these persons are 65 years and older. Additionally, it has been reported as recently as February 15, 2023, persons 60 years and older account for ~70% of current US hospitalizations associated with COVID-19.

While the US government has recently announced plans to end the declaration of a public health emergency associated with COVID-19, COVID-19 is expected to remain a serious endemic threat for an indefinite future period. The reasons contributing to the likelihood of COVID-19 remaining an endemic threat include: (1) viral transmission before symptom onset; (2) uneven global rollout of vaccinations; (3) ongoing vaccine hesitancy; (4) limited duration of immunity conferred by both natural infection and vaccination; (5) limited vaccine efficacy against certain SARS-CoV-2 variants; (6) limitations of current oral antivirals such as drug-drug interactions, safety concerns and tolerability; (7) uncertain impact of vaccines on transmission; (8) continuing evolution of the virus evading endogenous and vaccine-induced immunity; and (9) diminution of virus transmission mitigation behaviors, such as wearing masks and social distancing.

The continued emergence of SARS-CoV-2 variants that may have greater transmissibility and may cause more severe disease, combined with the diminution of virus mitigation behaviors among others in the general population, together with the consequences that are expected to associate with the end of the public health emergency leave patients for whom current therapeutics are limited particularly vulnerable to the virus and related disease. In view of these factors, we are developing bemnifosbuvir as a potential therapy to meet the needs of these vulnerable patients.

As COVID-19 continues to persist as a serious global endemic disease, we believe that the COVID-19 therapeutic market will remain a multi-billion-dollar opportunity for many years to come with the US continuing to comprise the most significant commercial market. In the US, we anticipate that the COVID-19 commercial market will soon transition from a single government payer to more traditional payer channels such as Medicare, Medicaid and private commercial insurance. 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.

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Bemnifosbuvir

We utilized our team’s expertise and experience, gained from decades of developing innovative antiviral treatments, to design bemnifosbuvir, an investigational, proprietary, potent, and selective, nucleotide polymerase inhibitor, which may be developed as each of a monotherapy and in combination with other antiviral agents. Bemnifosbuvir (AT-527) has been derived from our internal discovery program that combines unique nucleotide scaffolds with novel double prodrugs for the purpose of inhibiting the enzymes central to viral replication. Utilizing this double prodrug moiety approach, we believe that we have been able to maximize formation of the active metabolite of bemnifosbuvir thereby creating an oral antiviral product candidate that is designed to prevent replication of single stranded RNA (“ssRNA”) viruses while avoiding toxicity to host cells. In nonclinical studies we have demonstrated that bemnifosbuvir has a unique mechanism of action that includes both RNA-dependent RNA polymerase (“RdRp”) chain termination and inhibition of the nidovirus RdRp associated nucleotidyltransferase (“NiRAN”) of the SARS-CoV-2 virus and variants. By targeting these highly conserved sites through this unique dual mechanism of action, bemnifosbuvir has the potential to create a high barrier to resistance. Additionally, in in vitro studies we have conducted, bemnifosbuvir maintained its antiviral activity across COVID-19 variants of concern ("VOC"), including all Omicron subvariants tested.

COVID-19 Clinical Studies

In November 2022, we initiated SUNRISE-3, a global, multicenter, randomized, double-blind, placebo-controlled Phase 3 clinical trial. SUNRISE-3 is evaluating bemnifosbuvir (550 mg twice-daily ("BID") for five days) in at least 1500 high-risk non-hospitalized patients with mild or moderate COVID-19. The trial will be conducted at clinical trial sites in the US, Europe, Japan, and other regions of the world. The patient population will consist of those at the highest risk for disease progression, including patients ≥ 80 years old, patients ≥ 65 years old with one or more major risk factors, and immunocompromised patients ≥ 18 years old, all regardless of COVID-19 vaccination status.

SUNRISE-3 is designed to evaluate bemnifosbuvir as monotherapy (primary analysis) but will also explore the effect of combination therapy in a smaller sub-set of patients who receive an antiviral drug along with bemnifosbuvir (secondary analysis). The trial will include two populations derived from the type of standard of care ("SOC") received: 1) “supportive care population” (those patients who do not qualify for an approved antiviral treatment or where antivirals are not locally available) which will assess bemnifosbuvir given as monotherapy (primary analysis) and 2) “combination antiviral population” which will assess 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 at least 1,300 patients in the supportive care population and is powered to detect a clinically meaningful reduction in hospitalization/death versus placebo in this population. By enriching the patients enrolling in the trial with those who are at the highest risk for disease progression, we are targeting rates of hospitalization/death of ~4-6%. An interim analysis will be conducted by an independent data safety monitoring board ("DSMB") after 60% patient enrollment in the arm of the study enrolling the supportive care population. Secondary endpoints in each of the supportive care patient population and the combination antiviral population include COVID-19 complications, medically attended visits, symptom rebound/relapse and viral load rebound.

Data from prior studies of bemnifosbuvir that we have relied upon to support the design of SUNRISE-3 includes results from the Phase 3 clinical trial referred to as MORNINGSKY that was closed out early along with results from Phase 1 drug-drug interaction ("DDI") studies. While the primary endpoint of the MORNINGSKY study, time to symptom alleviation, was not achieved, the results from MORNINGSKY demonstrated a 71% reduction in hospitalization (2.9% versus 10%) (p=0.047, unadjusted, exploratory; secondary endpoint) in the bemnifosbuvir arm (n=137) versus placebo (n=70). The patients enrolled in the MORNINGSKY trial consisted of a broad outpatient population including 47% who were high risk, 28% who were vaccinated, and 56% who were seropositive at baseline. In a subgroup analysis in

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patients greater than 40 years old, the reduction in hospitalization in the bemnifosbuvir arm of the MORNINGSKY trial was even greater at 82%.

To date, five clinical DDI studies have been completed and demonstrated an overall low DDI 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 many drugs that are commonly prescribed to patients at high risk for COVID-19.

In these DDI 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.

In parallel to conducting our SUNRISE-3 clinical trial, we are engaging in efforts to discover a protease inhibitor product candidate that we may combine with bemnifosbuvir for the treatment of specific COVID-19 patient populations that are unable to mount immune response and require combination therapy. We have conducted in vitro studies that have demonstrated an additive antiviral effect when bemnifosbuvir was combined with antivirals from the protease inhibitor class, including nirmatrelvir. The data that we anticipate obtaining from the SUNRISE-3 clinical trial in the subset of patients who receive combination therapy will be, we believe, the first clinical data evaluating the combination of bemnifosbuvir and certain other currently authorized antiviral treatments.

Combination Therapy

Combination therapy utilizing multiple direct acting antivirals with differing mechanisms of action is an established strategy that has been historically successful in treating many life-threatening viral diseases, including human immunodeficiency virus (“HIV”), hepatitis B virus (“HBV”) and HCV. Nucleos(t)ide analogs are the backbone of many of these successful combination therapies. Advantageously, drug combinations can simultaneously target multiple points in the viral replication cycle with the effect of increasing antiviral activity and can also combat resistance that may develop over time with use of single agent drugs.

Hepatitis C Virus (HCV) Clinical Studies

For the treatment of chronic HCV infection, we are advancing the combination of bemnifosbuvir and ruzasvir, an investigational NS5A inhibitor. Approximately 58 million people globally, including ~2.4 million in the US, are living with chronic HCV infection. The World Health Organization ("WHO") reports a global incidence of 1.5 million cases per year and 399,000 deaths per year. The US HCV prevalence is expected to remain constant over the coming years as rising HCV incidence offsets the number of new patients treated.

We believe that the combination of bemnifosbuvir and ruzasvir has the potential to improve upon the current standard of care by offering a differentiated short duration, pan-genotypic protease-sparing regimen for HCV-infected patients with or without cirrhosis.

During the second quarter of 2023, we plan to initiate 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 the pan-genotypic combination consisting of 550 mg once daily ("QD") of bemnifosbuvir and 180 mg QD of ruzasvir after eight weeks of treatment. Approximately 280 HCV-infected, treatment-naïve patients across all genotypes, 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 sustained virologic response ("SVR") at Week 12 post-treatment. Other virologic endpoints include virologic failure, SVR at Week 24 post-treatment and resistance.

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Our Development Pipeline

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

Dengue and RSV

In February 2023, after advancing AT-752 to a Phase 2 clinical trial, we have determined 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 estimated resource burdens, including substantial costs, associated with the further clinical development of an antiviral for each of the treatment and prophylaxis of dengue.

We have also recently determined not to further pursue our discovery efforts to identify a product candidate for the treatment of respiratory syncytial virus ("RSV"). This action was taken to facilitate enhanced focus of our management team and to deploy our other resources on those therapeutic indications where our programs are more advanced.

We believe we are well capitalized to advance our current programs. We had $646.7 million in cash, cash equivalents and marketable securities at December 31, 2022. 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 into 2026.

Our Strategy

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

Deploy our expertise and experience particularly our depth of knowledge with respect to nucleos(t)ide analogs to discover and develop novel or differentiated direct acting antivirals that have the potential to meet unmet medical needs or improve the current standard of care. We have assembled and are utilizing the expertise and experience of a team with a demonstrated track

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record of efficiently and successfully discovering, developing, obtaining global regulatory approvals and commercializing innovative direct acting oral antiviral therapeutics. Our team has very specific expertise in the identification of unmet patient needs, virology, medicinal chemistry, particularly nucleos(t)ide chemistry and optimization, drug discovery, preclinical and clinical development, regulatory affairs and commercialization. We have relied on that expertise to:

Additionally, we are using that expertise to:

Develop bemnifosbuvir (AT-527) as monotherapy for COVID-19 to address key limitations of current therapies and explore combination therapy for specific patient populations. Bemnifosbuvir, is an investigational, orally administered, non-mutagenic, non-teratogenic, direct-acting antiviral agent being evaluated in our Phase 3 SUNRISE-3 clinical trial as monotherapy and in combination with other antivirals as a part of the locally available SOC. Supportive data from MORNINGSKY showed a 71% lower risk of hospitalization in the bemnifosbuvir arm versus placebo (p=0.047, unadjusted, exploratory; secondary endpoint). In a subgroup analysis in patients greater than 40 years old, the reduction in hospitalization was even greater at 82%.

We are developing bemnifosbuvir for COVID-19 to address the current highest unmet medical need. Specifically, we are targeting the most vulnerable patient populations who are at the greatest risk for disease progression to severe COVID-19 or mortality, and for whom there are currently the fewest treatment options. With currently available oral antivirals, there are serious limitations that minimize or eliminate the suitability of use in certain patient populations and monoclonal antibodies are no longer effective against COVID-19 variants and subvariants. These limitations include DDIs with commonly prescribed medications such as seizure medications, anti-psychotics and anti-coagulants. In addition, currently available vaccines have also presented limitations, including waning immunity and failure to mount immune response in specific populations.

We believe the potential product profile we are targeting for bemnifosbuvir with potential low risk for DDIs would fulfill an unmet need for an oral antiviral for COVID-19. If realized in clinical studies and if bemnifosbuvir is approved, we believe this potential profile may enable bemnifosbuvir to become a cornerstone of both monotherapy and combination oral therapy for the treatment of COVID-19.

In addition to the development of bemnifosbuvir as a monotherapy, we are advancing the development of COVID-19 combination therapy for specific immunocompromised populations. In vitro combinations of bemnifosbuvir with authorized direct acting antivirals, including protease inhibitors, have demonstrated additive antiviral activity and we continue to advance our internal protease inhibitor program for future combination therapy with bemnifosbuvir.

Advance a pan-genotypic regimen of bemnifosbuvir and ruzasvir for HCV that has the potential to improve the standard of care. Despite the availability of direct acting antiviral oral combination regimens for the treatment of HCV, there remains a large, underserved, HCV patient population which continues to grow in the US. A large portion of this increase in incidence is attributable to the opioid crisis, IV drug use, and HCV reinfection, especially among younger adults. Clinical studies that Merck conducted with ruzasvir and clinical studies of bemnifosbuvir we have conducted each demonstrated potent antiviral activity and were well tolerated by HCV-infected patients. Synergy of the combination of bemnifosbuvir and ruzasvir in inhibiting HCV replication has also been observed in vitro. We expect to initiate enrollment

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of a Phase 2 clinical trial evaluating the combination of bemnifosbuvir and ruzasvir during the second quarter of 2023. We believe that the combination of bemnifosbuvir and ruzasvir with a short treatment duration and protease inhibitor-free regimen, if successfully developed and approved, has the potential to benefit the expanding populations of HCV-infected patients in the US and globally.

Maximize the value of our product candidates by retaining rights and selectively seeking advantageous collaborations to enhance our global commercialization reach. We generally intend to retain global development and commercialization rights to our product candidates, which we believe will allow us to retain the greatest potential value of our product portfolio. However, we may opportunistically enter into commercialization license agreements or collaborations when and where we believe there is an opportunity, particularly outside the US, to gain specific market expertise and other commercialization resources without requiring us to build significant commercial infrastructure.

Remain opportunistic for in-licensing opportunities to augment our pipeline. In addition to our internal research activities which are currently focused on the potential discovery and preclinical development of a second-generation protease inhibitor product candidate, we plan to remain opportunistic in the evaluation of third party clinical-stage antiviral drug candidates that we may in-license to augment our existing pipeline. Utilizing our scientific expertise, we will continue to evaluate in-licensing opportunities that would allow us to address significant unmet medical need or where we anticipate we could substantively improve upon the current standard of care.

Our Team

Our management team has significant experience discovering, developing, and commercializing antiviral therapies for life-threatening viral infections. Our Founder, Chairman, and Chief Executive Officer, Jean-Pierre Sommadossi, Ph.D., has over 30 years of scientific, operational, strategic, and management experience in the biopharmaceutical industry. Dr. Sommadossi has authored over 180 peer-reviewed publications and holds more than 135 US patents related to antiviral and cancer therapeutics. Dr. Sommadossi was the principal founder of Idenix Pharmaceuticals, Inc. (“Idenix”), which was acquired by Merck in 2014, and a co-founder of Pharmasset, Inc. (“Pharmasset”), which was acquired by Gilead Sciences, Inc. in 2012.

We have assembled an experienced management and scientific team with a track record of success in the field of antiviral drug development, many of whom have worked together previously. Our team has significant expertise in nucleos(t)ide chemistry, biochemistry and virology and has applied that expertise towards the discovery and development of innovative antiviral treatments, including Epivir, Sovaldi, Tyzeka, Valtrex, Wellferon, Videx, Reyataz, Sustiva, Mavyret, Xofluza, Relenza, Zerit, Zepatier, Epclusa, Harvoni and Veklury. Members of our team have held senior positions at AstraZeneca plc, Merck, GlaxoSmithKline plc, Chiron, Novartis International AG, Biogen, F. Hoffmann La Roche, Abbvie, Bristol Myers Squibb, Shire, Biohaven Pharma, Pharmasset, Idenix, Valeant Pharmaceuticals International, Gilead Sciences, Inc. and Alnylam Pharmaceuticals.

Antiviral Therapy

Background on viruses

Viruses are cellular parasites that lack the machinery required to survive and replicate on their own and can only replicate using a host cell’s replication process. Unlike living organisms, such as humans, that use DNA as the basis for their genetic material, viruses can use either DNA or RNA. Approximately 70% of all viruses are RNA viruses. RNA viruses can be single stranded (ssRNA) viruses or double-stranded (dsRNA), viruses, depending on the type of RNA used as the genetic material.

Viruses have two primary components: nucleic acid (single or double stranded RNA or DNA) and a protective shell (the capsid). Some viruses may also have a lipid bilayer (the envelope) surrounding the capsid, an additional membrane derived from host cell membranes that contains viral proteins. A virus encased within a lipid bilayer is known as an enveloped virus, while a virus without this bilayer is called a non-enveloped virus. Enveloped ssRNA viruses are the more prevalent cause of severe human viral disease. Each of SARS-CoV-2, a coronavirus belonging to the coronaviridae family, and hepatitis C virus, a flavivirus, are enveloped ssRNA viruses.

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Viral infection occurs and the viral replication process begins when a virus attaches itself to a specific receptor site on the host-cell membrane through attachment proteins. The viral replication mechanism is dependent upon whether the virus is an RNA or DNA virus. Most DNA viruses use host cell proteins and enzymes to make additional DNA that is used to copy the viral genome or is transcribed to messenger RNA (“mRNA”). RNA viruses use their RNA as a template for synthesis of viral genomic RNA and mRNAs. The mRNAs encode both nonstructural proteins responsible for viral replication and transcription and structural proteins responsible for viral assembly. Finally, the newly created virus particles (“virions”), are released from the host cell in order to repeat the infection and replication cycle. RNA viruses can be particularly challenging to treat, as the error rates around the viral RNA polymerase directed RNA synthesis cause high mutation rates during replication, creating variants and resistance challenges for antiviral therapies.

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 across different viruses, making drugs targeted to the polymerase less susceptible to the effects of viral mutation and resistance. There are four types of viral polymerase, depending upon the virus and its genomic makeup:

As viral RNA polymerase-based synthesis does not occur in human host cells, antiviral drug development for RNA viruses focuses on identifying selective drug-like molecules that target viral RNA 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 nidovirus RdRp associated nucleotidyltransferase (NiRAN) and have opened avenues for the development of new and more effective antiviral therapies.

Viral resistance and variants

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 and become less susceptible to certain antiviral therapies over time. In the case of RNA viruses, which 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.

SARS-CoV-2 has proven to be able to mutate quickly with more than six million variants identified since fall 2020. A number of these variants have been designated by WHO and Centers for Disease Control and Prevention ("CDC") as Variants of Interest ("VOI") because there is evidence of increased transmissibility, more severe disease, reduced effectiveness of vaccines or antibodies, or diagnostic detection failures. However, these strains may only appear in isolated regions and have not yet spread to

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other countries. WHO and CDC have also identified a number of VOC 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 and descendent lineages.

Globally, from January 10, 2023 to February 6, 2023 it was reported that 99.6% of SARS-CoV-2 sequences were the Omicron VOC. Among the Omicron VOC, BA.5 and its descendent lineages dominated globally, accounting for 53.9% prevalence of all submitted sequences during the January 16 to January 22 January 2023 timeframe. In light of the widespread transmission of the Omicron VOC across the globe, WHO has added a new category to its variant tracking system, “Omicron subvariants under monitoring,” which may require prioritized attention and monitoring. Current Omicron subvariants under monitoring include BF.7, BQ.1, BA.2.75, CH.1.1, XBB, XBB.1.5, and XBF.

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 evolving from a pandemic to an endemic threat where the virus will still be circulating, with surges from time to time.

Nucleos(t)ide analogs and prodrugs

Nucleic acids are composed of naturally occurring chemical compounds termed nucleosides and nucleotides and are the main information-carrying molecules of the cell that determine the inherited characteristics of human and viral genetic material by directing the process of protein synthesis. The two main classes of nucleic acids are DNA and RNA. Nucleos(t)ide analogs are synthetic compounds that mimic the structure of naturally occurring nucleosides and nucleotides that target the viral polymerase directly so that it mistakenly incorporates these analogs into nascent nucleic acids, causing inhibition of viral replication. Nucleos(t)ide analogs, compared to other classes of antiviral therapies, have a high barrier to viral resistance due to the conservation of the structure of the polymerase that is required to produce viable virions.

Prodrugs are biologically inactive compounds which are employed to improve drug delivery, bypass rate limiting activation steps, decrease toxicity, and improve the oral bioavailability and permeation of cell membranes by the nucleos(t)ide analog. Prodrugs of nucleos(t)ide analogs have become the backbone of single-drug and combination-drug therapies to treat life threatening viral infections, including HIV, HBV, and HCV.

Bemnifosbuvir

Bemnifosbuvir is an investigational, novel, proprietary, orally administered double prodrug of a guanosine nucleotide analog. More specifically, it 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 in an effort to achieve the objectives noted below:

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

Because bemnifosbuvir targets viral RNA polymerase, a highly conserved enzyme critical to viral replication and transcription, via a dual mechanism, we expect it to maintain antiviral activity against emerging variants with mutations in the spike protein which is responsible for the receptor recognition and host cell membrane fusion process. In fact, the few amino acid substitutions (Y273H, P323L, and G671S) in the polymerase that emerged in past and present VOCs are all remote from the nucleoside triphosphate ("NTP") binding site and nucleos(t)ide analogs resistance sites. They belong to functionally distinct clusters providing general adaptation to the evolving virus in its human host, unlikely to confer drug resistance. Additionally, since all the enzymes involved in the metabolic pathway of bemnifosbuvir to the active triphosphate are ubiquitous host cell enzymes and not virally encoded proteins, we believe that the high rate of viral mutation does not affect the activation of bemnifosbuvir.

Development Programs

SARS-CoV-2

Background

SARS-CoV-2 is a coronavirus, belonging to the coronaviridae family, and is an enveloped virus with a positive sense ssRNA genome which encodes 29 viral proteins. It is one of six other human coronaviruses that exist, with four responsible for one third of common cold infections.

SARS-CoV-2 is structurally similar to two other life-threatening coronaviruses: SARS-CoV and Middle East Respiratory Syndrome coronavirus (“MERS-CoV-1”).

SARS-CoV-2 is a spherical virus that carries four different structural proteins: spike protein, envelope protein, membrane glycoprotein and nucleocapsid protein. As shown in the illustration below, the infection cycle begins when the spike proteins bind to the angiotensin-converting enzyme 2 cellular receptor (“ACE2”), on the surface of the target cells. A second cell surface protein, transmembrane serine protease 2 (“TMPRSS2”), enables the virion to enter the cell, where it releases its RNA. Some of this RNA is translated into new proteins using the host cell’s machinery—these proteins include the four structural proteins, as well as a number of Non-structural proteins (“Nsps”), that form the replication complex. Within this complex, RdRps catalyze the synthesis of the approximately 30,000-nucleotide RNA viral genome. The proteins and RNA are then assembled into a new virion in the Golgi and released through exocytosis.

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COVID-19 – Disease Overview

Coronavirus disease 2019 ("COVID-19"), the disease caused by infection with SARS-CoV-2 and its variants, has given rise to a global pandemic that swept rapidly throughout the world beginning in 2020 and continues to cause infection and disease due to waning immunity and continued emergence of SARS-CoV-2 variants. As of February 15, 2023 according to the CDC, there have been more than 100 million confirmed cases reported and over 1.1 million deaths in the US alone and the WHO reported more than 754 million confirmed cases of COVID-19 and over 7 million deaths worldwide. In 2022, the CDC reported that COVID-19 was the third leading cause of death in the US after only heart disease and cancer with the majority of deaths occurring in patients aged 65 and older. Older adults and individuals who have risk factors are at a higher risk for developing more serious complications from COVID-19 leading to hospitalization and death.

Infection with SARS-CoV-2 may be asymptomatic or it may cause a wide spectrum of illness ranging from a mild upper respiratory tract infection to severe life-threatening sepsis and multiorgan failure. Commonly reported symptoms include fever, cough, shortness of breath, loss of taste or smell, sore throat, fatigue, headaches, muscle aches, and gastrointestinal ("GI") disturbance. Symptoms typically last two to three weeks, but many patients continue to experience symptoms for many weeks or develop new symptoms, which is now recognized as the post-acute COVID-19 syndrome, or Long COVID. COVID-19 affects people of all ages; however, people who are immunocompromised, elderly, or have certain underlying medical conditions (e.g., chronic heart, lung, and kidney disease; diabetes, obesity, and cancer) are at increased risk of poor outcomes.

The elderly (with or without comorbidities) and the immunocompromised at any age, are well documented to be unlikely to be able to mount an adequate immune response to the virus, and also seem to be unsuccessful in mounting an adequate antibody response even when vaccinated. Furthermore, many of these people are likely to be receiving concomitant medications which are recognized to have drug-drug interactions with ritonavir, meaning that they are contraindicated to receive nirmatrelvir/ritonavir. In this same population, there is considerable reluctance to use molnupiravir because of its mutagenicity and the perceived downstream consequences that may induce. With the ongoing evolution of the virus and the continual emergence of new variants, the utility of monoclonal antibodies has also been abrogated. The net result of this is that these patients currently have no access to effective outpatient therapies, are likely to need intravenous remdesivir as therapy and are also more likely to be hospitalized because of more severe disease.

While the US government has recently announced plans to end the declaration of a public health emergency associated with COVID-19, COVID-19 is expected to remain a serious endemic threat for an indefinite future period. The reasons contributing to the likelihood of COVID-19 remaining an endemic threat, include (1) viral transmission before symptom onset; (2) uneven global rollout of vaccinations; (3) ongoing vaccine hesitancy; (4) limited duration of immunity conferred by both natural infection and vaccination; (5) limited vaccine efficacy against certain SARS-CoV-2 variants; (6) limitations of current

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oral antivirals such as drug-drug interactions, safety concerns and tolerability; (7) uncertain impact of vaccines on transmission; (8) continuing evolution of the virus evading endogenous and vaccine-induced immunity; and (9) diminution of virus transmission mitigation behaviors, such as wearing masks and social distancing.

Current Approaches for Prevention and Treatment of COVID-19 and Their Limitations

At the outset of the COVID-19 pandemic, unprecedented progress was made with both vaccines and treatment options for this novel disease. Despite this progress, there remain substantial limitations 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 (which have increased transmissibility and the ability to evade neutralizing antibodies). Limitations of current oral antivirals include DDIs with commonly prescribed medications such as seizure medications, anti-psychotics, anti-coagulants and more, and safety concerns.

As a result, there remains a continued urgent need to develop novel, safe, efficacious, convenient, oral, therapies with low risk of drug-drug interaction 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 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 becomes endemic with the potential for 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. Approved and authorized vaccines include, among others, mRNA vaccines such as Pfizer/BioNTech’s Comirnaty and Moderna’s mRNA-1273, each monovalent vaccines which, were approved for the prevention of symptomatic COVID-19 caused by the original strain. These vaccines have been available in the US and globally since December 2020. More recently, in August 2022, bivalent mRNA vaccines from each of Pfizer/BioNTech and Moderna were authorized by the FDA for the prevention of symptomatic COVID-19 caused by the Omicron subvariants BA.4 or BA.5.

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

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Monoclonal Antibodies ("mAbs") for the treatment 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. However, the use of mAbs for the treatment of COVID-19 has been limited and is currently not authorized in the US for the following reasons:

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 including the treatment of outpatients at high risk of progression to severe COVID-19. Additionally, each of Lagevrio™ (molnupiravir), an orally administered direct-acting antiviral for the treatment of adults with mild to moderate COVID-19 in the outpatient setting, and Paxlovid™ (ritonavir boosted nirmatrelvir), an orally administered protease inhibitor for the treatment of adults with mild to moderate COVID-19 in the outpatient setting are authorized for use under an EUA in the US and many additional countries globally.

Limitations of currently authorized or approved antiviral therapies include:

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Our COVID-19 strategy

We are developing bemnifosbuvir, an investigational, orally administered, novel antiviral product candidate, for the treatment of COVID-19.

Data from the Phase 3 MORNINGSKY clinical trial that was closed out early did not meet the primary endpoint of time to symptom alleviation but the results demonstrated a 71% reduction in hospitalization (2.9% versus 10%) (p=0.047, unadjusted, exploratory; secondary endpoint) in the bemnifosbuvir arm (n=137) versus placebo (n=70). The patients enrolled in the MORNINGSKY trial consisted of a broad outpatient population including 47% who were high risk, 28% who were vaccinated, and 56% who were seropositive at baseline. In a subgroup analysis in patients greater than 40 years old, the reduction in hospitalization in the bemnifosbuvir arm of the MORNINGSKY trial was even greater at 82%. There was also a trend for clinical benefit (all-cause mortality) observed in the global phase 2 study in hospitalized patients. Although low background rates of disease progression precluded completion of the study as initially designed, all three deaths in the study occurred in placebo recipients compared to no deaths in patients receiving bemnifosbuvir. Additionally, bemnifosbuvir has demonstrated low risk of DDIs in five phase 1 clinical studies, antiviral activity against all tested VOC in in vitro studies, no mutagenicity or teratogenicity in in vitro studies and, given its mechanism of action, a high barrier to resistance.

We believe bemnifosbuvir as 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. We have initiated SUNRISE-3, a global Phase 3 randomized, double-blind, placebo-controlled clinical trial evaluating bemnifosbuvir (550 mg BID for 5 days) in at least 1500 high-risk non-hospitalized patients with mild or moderate COVID-19.

While SUNRISE-3 is principally designed to evaluate bemnifosbuvir as monotherapy (primary analysis) it is also designed to explore of 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 also advancing an internal discovery program focused on identifying a second generation protease inhibitor that we may potentially combine with bemnifosbuvir for combination treatment of COVID-19. We are seeking to discover a protease inhibitor that is highly potent and well tolerated with limited DDIs and does not require a Pharmacokinetic ("PK") booster (e.g., ritonavir). The optimization of lead compounds is ongoing with a target of late 2023 to submit an IND for the selected clinical candidate.

Our rationale for advancing this potential combination is based upon both historical precedents for treating serious viral diseases with combination treatments that include agents with different mechanisms of action targeting different points in the viral replication cycle and the results from the in vitro study we have conducted in an HCoV-229E surrogate model. In this in vitro study, we evaluated the antiviral activity of AT-511, the free base of bemnifosbuvir in combination with the protease inhibitor, nirmatrelvir, and the results showed an additive antiviral effect.

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We believe these data suggest a potential benefit of the combination of bemnifosbuvir and a protease inhibitor for the treatment of SARS-CoV-2 infection.

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 Nsps 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, a 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.

SARS-CoV RNA Polymerase

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

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mechanism of bemnifosbuvir creates a potentially higher barrier to resistance compared to other direct acting antiviral inhibitors.

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. Current COVID-19 variants have lessened the effectiveness of vaccines and eliminated the effectiveness of monoclonal antibodies due to the mutations in the viral spike protein. It is expected that future variants may also impact the effectiveness of vaccines and monoclonal antibodies.

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

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.

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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 history

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 with the termination of the Roche License Agreement in November 2021, we prematurely discontinued each of the Phase 3 MORNINGSKY and MEADOWSPRING clinical trials 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 the SUNRISE-3 Phase 3 clinical trial of bemnifosbuvir for the treatment of COVID-19.

SUNRISE-3 – Global Phase 3 clinical trial

SUNRISE-3 is a global, multicenter, randomized, double-blind, placebo-controlled Phase 3 clinical trial evaluating bemnifosbuvir (550 mg BID for 5 days) in at least 1,500 high-risk non-hospitalized patients with mild or moderate COVID-19. The trial will be conducted at clinical trial sites in the US, Europe, Japan, and other regions of the world. The patient population will consist of those at the highest risk for disease progression, including patients ≥ 80 years old, patients ≥ 65 years old with one or more major risk factors, and immunocompromised patients ≥ 18 years old, all regardless of COVID-19 vaccination status.

The trial is designed to evaluate bemnifosbuvir as monotherapy (primary analysis) but will also explore the impact of combination therapy in a smaller sub-set of patients who receive a compatible antiviral drug along with bemnifosbuvir (secondary analysis). The trial will include two populations derived from the type of standard of care received 1) “supportive care population” (patients who do not qualify for an approved antiviral treatment or where antivirals are not locally available) which will assess bemnifosbuvir given as monotherapy (primary analysis) and 2) “combination antiviral population” which will assess 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 twice-daily plus locally available SOC or placebo BID plus locally available SOC for five days.

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The primary endpoint of the SUNRISE-3 study is all-cause hospitalization or death through Day 29 in at least 1,300 patients in the supportive care population and is powered to detect a clinically meaningful reduction in hospitalization/death versus placebo in this population. By enriching the patients enrolling in the trial with those who are at the highest risk for disease progression, we are targeting rates of hospitalization/death of ~4-6%. An interim analysis will be conducted by a DSMB after 60% patient enrollment in the arm of the study enrolling the supportive care population. Secondary endpoints in each of the supportive care patient population and the combination antiviral population include COVID-19 complications, medically attended visits, symptom rebound/relapse and viral load rebound.

MORNINGSKY - Global Phase 3 trial

The Phase 3 MORNINGSKY study was a randomized, placebo-controlled study 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. The study, which was initiated in collaboration with Roche, was discontinued in December 2021 prior to completion as a result of the termination of the collaboration with Roche. Patients were randomized (2:1) to receive 550 mg BID bemnifosbuvir or placebo for five days. The primary endpoint was time to alleviation/improvement of COVID-19 symptoms. Secondary endpoints included hospitalization, all-cause mortality, and change in viral load. At the time of discontinuation, 216 patients had been randomized (2:1; active:placebo), with 207 patients who comprised the efficacy evaluable population. The study enrolled a broad outpatient population, including 47% who were high risk, 28% who were vaccinated, and 56% who were seropositive 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 demonstrated a 71% reduction in hospitalization (2.9% versus 10%) (p=0.047, unadjusted, exploratory; secondary endpoint) in the bemnifosbuvir arm (n=137) versus placebo (n=70). In a subgroup analysis in patients greater than 40 years old, the reduction in hospitalization in the bemnifosbuvir arm of the MORNINGSKY trial was even greater at 82%.

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There were no deaths in the study. There was no meaningful difference in the change from baseline in viral load between the bemnifosbuvir arm and the placebo arm. The 550 mg BID dose was generally well tolerated compared to placebo. There were no drug-related SAEs reported, and proportions of patients with adverse events 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 also closed out in March 2022 after enrolling only 72 patients that had taken part in MORNINGSKY, a smaller number of patients than planned. As a result, firm conclusions about the long-term symptoms of COVID-19 could not be drawn from this study.

Global Phase 2 study in hospitalized patients with COVID-19

This 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 impact of bemnifosbuvir (550 mg BID; Part A) on Progressive Respiratory Insufficiency (PRI), however, low background rates of disease progression precluded completion of the study as initially designed. The protocol was amended to explore higher doses of bemnifosbuvir (1100 mg BID; Part B), however the study was prematurely discontinued in January 2022 due to the changing COVID-19 treatment landscape. 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.

After bemnifosbuvir 550 mg BID dosing for five days, rapid reduction in viral load levels were observed. At Day 2, patients receiving bemnifosbuvir experienced a 0.6 log10 greater mean reduction from baseline viral load versus placebo. A sustained difference in viral load reduction was maintained through Day 8.

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Bemnifosbuvir’s SARS-CoV-2 antiviral activity was also observed in patients with baseline viral loads above the median of 5.35log10 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 12% 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 serious adverse events. Non-serious adverse events were equally distributed across treatment arms. Most were mild-to-moderate in severity and assessed as not related to bemnifosbuvir.

MOONSONG - Global Phase 2 trial

This study was a randomized, double-blind, multi-center, placebo-controlled trial, that evaluated the antiviral activity, safety and pharmacokinetics of sequential doses of bemnifosbuvir 550 mg (Cohort A, n=30) and 1,100 mg (Cohort B, n=30) with BID dosing in adult outpatients with mild or moderate COVID-19 versus placebo (n=40). 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 pooled 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 adverse event ("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 serious adverse events ("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.

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Other Studies

In addition to the MORNINGSKY Phase 3 clinical trial and the Phase 2 clinical trials, supporting Phase 1 and clinical pharmacology studies, including a bronchoalveolar lavage study, multiple DDI 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 5 days in healthy subjects.

Results from the bronchoalveolar lavage 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 DDI studies were completed with topline results demonstrating an overall low DDI potential associated with bemnifosbuvir.

Phase 1 - DDI Studies

A series of Phase 1 studies suggest a favorable drug-interaction profile, 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 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 may be co-administered with commonly prescribed therapeutics that are often taken for other conditions by 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, supporting clinical pharmacology studies in special populations (e.g., subjects with hepatic and renal impairment) are ongoing.

Phase 1 - PK Study – Second-generation bemnifosbuvir tablet

In the SUNRISE-3 clinical trial, we are using a second-generation formulation 275 mg tablet of bemnifosbuvir. We have evaluated this formulation in a Phase 1 study in healthy subjects who were administered bemnifosbuvir (fasted and with a low-fat meal) for ten days at 550 mg BID (2 x 275 mg). The results of this study demonstrated that the second-generation tablet had higher plasma exposures of AT-273, the active surrogate metabolite of bemnifosbuvir, than the plasma exposures obtained with the first-generation tablet which was used in the MORNINGSKY study. Additionally, the second-generation tablet achieved higher plasma trough concentrations of AT-273 (> EC90 of bemnifosbuvir in inhibiting SARS-CoV-2 replication) without food effect and regardless of fat content. In this study, bemnifosbuvir was generally well-tolerated in healthy subjects.

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Bemnifosbuvir and Ruzasvir for the Treatment of Hepatitis C

Hepatitis C virus (HCV)

Background

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 genotypes. Hepatitis C becomes chronic Hepatitis C in 75% to 85% of acute cases, with an incubation period lasting from two to 26 weeks.

HCV is classified into seven genotypes and 67 subtypes, with genotype 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. Approximately 290,000 people die every year from HCV related liver diseases, with the majority of deaths related to cirrhosis and hepatocellular carcinoma.

The incidence rate of acute HCV has more than doubled since 2013 (124% 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.

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Increasing Incidence of HCV in the US

Despite significant advances in treatment beginning in 2013, there remains a large, underserved, HCV patient population which continues to grow dramatically in the US. While a portion of this rise in incidence results from increased diagnosis of HCV that began following the 2013 CDC issuance of guidelines for screening of all Americans born between the years 1945 and 1965, a large portion of this increase in incidence is attributable to the opioid crisis, IV drug use and HCV reinfection.

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. Estimated at approaching $4 billion in global sales in 2022, with approximately 50% attributable to the US, the HCV market remains large.

Current treatment landscape

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 genotype, 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/velpatasvir): a combination regimen consisting of an NS5B inhibitor and an 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 genotype one through six infection, either without cirrhosis or with compensated cirrhosis. For patients with decompensated cirrhosis, Epclusa is approved for use in combination with ribavirin (a purine nucleoside analog). Patients on Epclusa require 12 weeks of treatment.

Mavyret® (glecaprevir/pibrentasvir): a combination regimen consisting of a NS3/4A protease inhibitor and an 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 genotype one through six infection, without cirrhosis or with compensated cirrhosis. Mavyret is also approved for HCV patients with genotype 1 infection who have been previously treated with a regimen either containing an NS5A inhibitor or an NS3/4A protease inhibitor (but not both). Mavyret was the first eight-week treatment approved for HCV genotypes one through six in adult patients without cirrhosis and with compensated cirrhosis who have not been

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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.

Our approach – seeking to improve the standard of care

We are developing bemnifosbuvir in combination with ruzasvir for the treatment of HCV. Bemnifosbuvir is a potent inhibitor of the HCV nonstructural protein 5B ("NS5B") RdRp. Ruzasvir is an investigational oral, potent, pan‑genotypic nonstructural protein 5A ("NS5A") inhibitor for the treatment of chronic HCV infection 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:

Clinical development

To date, we have completed two clinical trials of bemnifosbuvir to support the treatment of chronic HCV infection.

Phase 1 clinical trial of bemnifosbuvir as a single agent

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 genotype 1b (“GT1”), HCV-infected subjects (Part C). Additional cohorts evaluated 600 mg salt form (553 mg free base) once daily for seven days in non-cirrhotic genotype 3 (“GT3”), (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 log10 IU/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 genotype 1b (“GT1b”), HCV-infected subjects, and a mean reduction of 4.5 log10 IU/mL after seven days of dosing in non-cirrhotic GT3 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, GT1 HCV-infected subjects)

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Maximum HCV RNA change in Part C (multiple dose in non-cirrhotic, GT1 HCV-infected subjects)

Maximum HCV RNA change in Part D (multiple dose in non-cirrhotic, GT3 HCV-infected subjects) and Part E (multiple dose in cirrhotic HCV-infected subjects)

* SD = standard deviation

** QD = once daily

Phase 2 clinical trial of bemnifosbuvir in combination with daclatasvir

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 GT1 HCV-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 < lower limit of quantitation ("LLOQ") at 12 weeks after end of treatment ("EOT")). Secondary efficacy endpoints included HCV RNA< Lower Limit Of Quantitation (“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 resistance-associated variants ("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 end of treatment; 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 EC90values 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). We believe that the rapid early clearance of HCV RNA observed in this trial supports continued evaluation of bemnifosbuvir in shortened treatment regimens, ideally with a more potent, next-generation HCV NS5A inhibitor.

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

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Bemnifosbuvir HCV safety

There were no serious adverse events, dose-limiting toxicities or adverse events leading to trial discontinuation observed in our HCV Phase 1 or Phase 2 clinical trials of bemnifosbuvir. 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 EC50in the sub- to low picomolar range against all HCV genotypes (<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 GT1, GT2 and GT3-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 GT1, GT2, GT4 and GT6-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 preserved dose-related clinical antiviral activity of ruzasvir in GT-3 subjects with cirrhosis.

Over 1200 HCV-infected participants have received ruzasvir at daily doses up to 180 mg for durations up to 24 weeks as part of 2-drug and 3-drug regimens with or without ribavirin. The overall safety data indicates that ruzasvir has been generally well-tolerated with no consistent treatment-related changes in labs, vital signs, or ECG parameter values. Serious adverse events and discontinuations due to adverse events were rare in all studies conducted by Merck.

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Rationale supporting the combination of bemnifosbuvir and ruzasvir for HCV

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

To further support our development of the combination of bemnifosbuvir and ruzasvir in patients, we have conducted in vitro synergy experiments in HCV GT1b replicon assays (Huh-luc/neo-ET), where HCV replicon cells were treated with multiple concentrations of AT-511, the free base of bemnifosbuvir, and ruzasvir either alone or in combination. As shown in the figure below, these experiments demonstrated that the combination resulted in substantially greater inhibition of HCV replication than either agent alone, suggesting a synergistic antiviral effect between the two inhibitors.

In vitro Synergy: Assay performed in HCV GT1b replicon (Huh-luc/neo-ET)

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.

Collectively, these data support the clinical development of bemnifosbuvir and ruzasvir used in combination for the treatment of chronic HCV infection.

Planned clinical development

In the second quarter of 2023, we plan to initiate enrollment of a Phase 2 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 the pan-genotypic combination consisting of 550 mg QD of bemnifosbuvir and 180 mg QD of ruzasvir after eight weeks of treatment. Approximately 280 HCV-infected, direct-acting antiviral naive patients across all genotypes, including a lead-in cohort of approximately 60 patients are expected to be enrolled in this Phase 2 study. The primary endpoints of the study are safety and SVR at Week 12 post-treatment. Other virologic endpoints include virologic failure, SVR at Week 24 post-treatment and resistance.

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Results from this study, if positive, may support future larger studies of bemnifosbuvir in combination with ruzasvir in broad patient populations for treatment durations of eight weeks or potentially less (six weeks) as well as in patients with decompensated cirrhosis for treatment durations of 12 weeks without ribavirin.

Currently we are conducting a Phase 1 clinical study in healthy subjects to evaluate the potential DDI between bemnifosbuvir and ruzasvir and the effect of food on the PK of the agents.

Roche License Agreement

In October 2020, we entered into a License Agreement with F. Hoffmann-La Roche Ltd and Genentech, Inc. (“Roche License Agreement”) in connection with the global development, manufacture and commercialization of bemnifosbuvir, AT-511, their backup compounds (including AT-752) (“Licensed Compounds”), products containing any Licensed Compound (“Licensed Products”), and related companion diagnostics (“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 following our receipt of notice of termination from Roche in November 2021. As of the termination date, our obligations under the cost sharing arrangement with Roche associated with the development of bemnifosbuvir also ended.

As a result of the termination of the Roche License Agreement, we have regained worldwide exclusive rights from Roche to research, develop, manufacture and commercialize the Licensed Compounds, the Licensed Products and the Companion Diagnostics in all fields of use.

License Agreement with Merck

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.

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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. 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 (or a Compound contained in 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. Although we rely on CMOs, we also have personnel with extensive manufacturing experience that can oversee the relationship with our manufacturing partners. We believe that any materials required for the manufacture of our product candidates could be obtained from more than one source.

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.

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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. Our commercial opportunity for any of our product candidates could be reduced or eliminated if 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.

We are aware of the following competitors in the areas that we are currently targeting:

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 a number of other agents in development for the treatment of COVID-19.

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

Other orally administered investigational agents that are currently in development for the treatment of COVID-19 include:

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In addition to the antivirals listed above, a number of monoclonal antibodies were previously authorized for emergency use for the prophylaxis or treatment of COVID-19. While these authorizations have been currently 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 and associated vaccine boosters that are approved or authorized for emergency use for the prevention of COVID-19 include:

The potential treatments and vaccines for COVID-19 continue to evolve. The list above addresses the products or product candidates approved or authorized for emergency use or under clinical development in the US as of the date of this Annual Report on Form 10-K that we believe could be the most competitive with a bemnifosbuvir therapy but is not a comprehensive list of every treatment that is in development for COVID-19.

HCV

FDA-approved treatments for patients with chronic HCV include Epclusa®, an orally administered fixed dose combination of sofosbuvir, an NS5B inhibitor, and velpatasvir, an NS5A inhibitor, Harvoni®, a fixed dose combination sofosbuvir and ledipasvir, an NS5A inhibitor, Vosevi®, a fixed dose triple combination of

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sofosbuvir, velpatasvir and voxilaprevir, a NS3/4A protease inhibitor, and Sovaldi®, an NS5B inhibitor marketed by Gilead Sciences, Inc., Mavyret®, the combination of glecaprevir, a NS3/4A protease inhibitor, and pibrentasvir, a NS5A inhibitor, marketed by AbbVie Inc., and Zepatier®, the combination of elbasvir, a NS5A inhibitor and grazoprevir, a NS3/4A protease inhibitor, marketed by Merck & Co., Inc., In addition to the branded products, Gilead launched and 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 co-promotion arrangements with third parties that have existing commercial infrastructure. Outside the US, we may enter into commercial license agreements. 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 on 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, 2023, we are the sole owner of fifteen 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, 2023, on a worldwide basis, includes more than 250 pending, granted, or allowed patent applications with fourteen issued US patents, eight pending US non-provisional applications, four pending US provisional applications, five pending international patent applications filed under the Patent Cooperation Treaty (“PCT”), and more than 200pending or granted patent applications that have entered the national phase of prosecution in countries outside the US.

As of February 1, 2023, we are the exclusive licensee of three patent families from MSD International GmbH (Merck, Sharp & Dohme Corp.) 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 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

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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 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, bemnifosbuvir, AT-281 (the free base of AT-752), and AT-752 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. Current patent applications covering the use of AT-281 and AT-752 for the treatment of dengue fever will expire on dates ranging from 2036 to 2043, 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.”

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Our patent families, as of February 1, 2023, 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) and one pending US applications 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 European Patent Office (“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 20 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, pharmaceutical compositions, 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 pending 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 ten 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 one granted US patent (US Patent No. 10,874,687), three pending US applications and applications 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 pending 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 pending US application. This family is currently in the national phase of prosecution in China, the EPO, Hong Kong, Japan, Korea, Russia, and Taiwan. 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 one international application filed under the PCT, as well as one

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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 international application field under the PCT. 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 international application filed under the PCT, as well as one pending application in Canada. 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.

AT-281 and AT-752

The first patent family described above also describes AT-281, a pharmaceutically acceptable salt thereof (for example, AT-752) and pharmaceutical compositions of AT-281 or a pharmaceutical salt thereof and their use to treat HCV infection, including issued US Patent No. 10,875,885.

The second patent family described above also describes AT-752 and pharmaceutical compositions of AT-752, including in US Patent No. 10,906,928. One of these pending US applications in this patent family covers AT-752 and pharmaceutical compositions of AT-752.

The fifth patent family described above also includes a disclosure of the use of AT-281 or a pharmaceutically acceptable salt thereof for the treatment or prevention of an RNA viral infection, including dengue fever (US Patent No. 10,946,033), yellow fever, and Zika virus. Therefore, we have three patent families that describe AT-281 or AT-752 and methods of treatment for viral infections using AT-281 or AT-752.

We own another patent family that consists of three provisional US applications that disclose advantageous dosage forms of AT-752, dosage regimens of AT-752, and combination therapies comprising AT-752 for the treatment of dengue fever. The expected year of expiration for patents issuing from these non-provisional patent applications, if valid and enforceable, is 2043, without regard to any adjustments of term that may be available under US or other national law.

Ruzasvir

We have exclusively licensed three patent families from MSD International GmbH (Merck, Sharp & Dohme Corp.) 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 an international application filed under the PCT covering the combination of bemnifosbuvir and ruzasvir, which if granted, will have an expiration date in 2042.

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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 authorization from the FDA to administer an IND 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 authorization 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 include the requirement that all research subjects provide their informed consent for their participation in any clinical study. Clinical trials

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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:

Phase 1: The product candidate is initially introduced into healthy human subjects, and in some cases, patients with the target disease or condition. These studies are designed to test the safety, dosage tolerance, absorption, metabolism and distribution of the investigational product in humans, the side effects associated with increasing doses, and, if possible, to gain early evidence on effectiveness.

Phase 2: The product candidate is administered to a limited patient population with a specified disease or condition to evaluate the preliminary efficacy, optimal dosages and dosing schedule and to identify possible adverse side effects and safety risks. Multiple Phase 2 clinical trials may be conducted to obtain information prior to beginning larger and more expensive Phase 3 clinical trials.

Phase 3: The product candidate is administered to an expanded patient population to further evaluate dosage, to provide statistically significant evidence of clinical efficacy and to further test for safety, generally at multiple geographically dispersed clinical trial sites. These clinical trials are intended to establish the overall risk/benefit ratio of the investigational product and to provide an adequate basis for product approval.

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 agreement on the next phase of development. Sponsors typically use the meeting at the end of the Phase 2 trial to discuss Phase 2 clinical results and present plans for the pivotal Phase 3 clinical trials that they believe will support approval of the new drug.

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.

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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, 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.

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 the 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

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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. Once approved, the FDA may withdraw the product approval if compliance with pre- and post-marketing requirements is not maintained or if problems occur after the product reaches the marketplace. The FDA may also require one or more Phase 4 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. In addition, new government requirements, including those resulting from new legislation, may be established, or the FDA’s policies may change, which could impact the timeline for regulatory approval or otherwise impact ongoing development programs.

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 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 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.

Emergency Use Authorization

The Commissioner of the FDA, under delegated authority from the Secretary of Health and Human Services (“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, new 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. With regard to a Fast Track

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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 and accelerated approval. 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, 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. 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

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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

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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 marketing 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 another period of exclusivity 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.

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

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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. Prior to the Supreme Court’s decision, President Biden issued an executive order to initiate a special enrollment period from February 15, 2021 through August 15, 2021 for purposes of obtaining health insurance coverage through the ACA marketplace. The executive order also instructed certain governmental agencies to review and reconsider their existing policies and rules that limit access to health care, including among others, reexamining Medicaid demonstration projects and waiver programs that include work requirements, and policies that create unnecessary barriers to obtaining access to health insurance coverage through Medicaid or the ACA.

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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 eliminates the statutory Medicaid drug rebate cap, currently set at 100% of a drug’s average manufacturer price, beginning January 1, 2024.

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. For that and other reasons, it is currently unclear how the IRA will be effectuated.

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 the Regulation becomes applicable, it will have a phased implementation depending on the concerned products. This regulation intends to boost cooperation among EU member states in assessing health technologies, including new medicinal products, and providing the basis for cooperation at the EU level for joint clinical assessments in these areas. The regulation 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 most potential impact for patients, joint scientific consultations whereby developers can seek advice from HTA authorities, identification of m 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.

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Data Privacy & 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. 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.

Further, certain foreign laws govern the privacy and security of personal data, including health-related data. For example, the EU General Data Protection Regulation ("GDPR") imposes strict requirements for processing the personal data of individuals within the European Economic Area. 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. Further, from January 1, 2021, companies have had to comply with the GDPR and also the UK GDPR, which, together with the amended UK Data Protection Act 2018, retains the GDPR in UK national law. The UK GDPR mirrors the fines under the GDPR, i.e., fines up to the greater of €20 million (£17.5 million) or 4% of global turnover.

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 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 process 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

Similarly 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 Conference on Harmonization (“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

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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 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 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:

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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.

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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, under the Retained EU Law (Revocation and Reform) Bill 2022, which is currently before the UK parliament, any retained EU law not expressly preserved and “assimilated” into domestic law or extended by ministerial regulations (to no later than 23 June 2026) will automatically expire and be revoked by December 31, 2023. 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

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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 England, Wales, and Scotland, together, 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. The consultation closed on March 14, 2022 and aims 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 outcome of the consultation is being closely watched and will determine whether the UK chooses to align with the (EU) CTR or diverge from it to maintain regulatory flexibility.

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.

There will be 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 20, 2023, we had 70 full-time employees, including 23 employees with M.D., Ph.D. or Pharm.D. degrees. Of these full-time employees, 49 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. The Company is located in Boston, Massachusetts. Atea Pharmaceuticals Securities Corporation, a Massachusetts corporation incorporated in 2016, is a wholly owned subsidiary of Atea Pharmaceuticals, Inc.

Available Information

We file or furnish electronically with the Securities and Exchange Commission (“SEC”) our annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K, proxy statements and other information, as well as amendments to those reports. These and other SEC filings are available to the public over the Internet at the SEC's website at http://www.sec.gov. We make available on our website at

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https://ateapharma.com, under “Investors,” free of charge, copies of these reports as soon as reasonably practicable after filing or furnishing these reports with the SEC.

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

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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 cofounded 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 BELLUS Health, Inc. since May 2010, 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 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 until 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

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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, on the board of directors of Jounce Therapeutics, Inc. since June 2016, Adaptimmune Therapeutics plc since June 2016, Ovid Therapeutics, Inc. since June 2017, and Halozyme, Inc. since February 2023. Previously, Ms. Duncan served on the boards of directors of 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.

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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.

Risks Related to COVID-19

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

Our development of bemnifosbuvir for the treatment of COVID-19 is in its early stages, and we may not be successful in our development of bemnifosbuvir as a potential treatment for COVID-19. In October 2020, we entered into a license agreement (as amended, “Roche License Agreement”) with F. Hoffmann-LaRoche Ltd. and Genentech, Inc. (together, “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). Together with Roche, in April 2021, we initiated a randomized, double blind, multi-center, placebo-controlled Phase 3 MORNINGSKY clinical trial to study bemnifosbuvir in adult and adolescent patients with mild or moderate COVID-19 in the outpatient setting and we subsequently initiated MEADOWSPRING, a Phase 3 six month follow-up study, to assess the impact of bemnifosbuvir treatment on long-term sequelae of COVID-19 in the patients previously enrolled in MORNINGSKY. Phase 3 clinical trials were begun while two Phase 2 clinical trials evaluating bemnifosbuvir in patients with COVID-19 were ongoing. One of these Phase 2 clinical trials enrolled hospitalized patients and the other Phase 2 MOONSONG clinical trial enrolled outpatients. In October 2021, we, together with Roche, completed MOONSONG, and we announced that we did not meet the primary endpoint of reduction from baseline in the amount of SARS-CoV-2 virus in patients with mild or moderate COVID-19 compared to placebo in the overall study population, of which approximately two-thirds of enrolled patients were low-risk with mild symptoms. 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, 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 strategy. We do not know if either monotherapy or combination therapy approach will be successful. In November 2022, we initiated SUNRISE-3, a global, multicenter, randomized, double blind, placebo-controlled Phase 3 clinical trial evaluating bemnifosbuvir (550 mg BID for 5 days) in at least 1500 high-risk non-hospitalized patients with mild or moderate COVID-19.

In parallel with the conduct of SUNRISE-3, we are also engaging in efforts to discover a proprietary protease inhibitor that could potentially be combined with bemnifosbuvir for the treatment of COVID-19. Our efforts to internally discover and 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 a protease inhibitor product candidate generated from our discovery efforts may be permitted to enter clinical development. Before we can begin clinical development of a newly discovered 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.

Conducting preclinical testing of any product candidate and the related manufacture of sufficient quantities of material that can be used in clinical trials, is a complex, lengthy, time consuming and

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expensive process. As a result, we cannot be certain that we will be able to submit such INDs or CTAs on the timelines we expect, if at all, and we cannot be certain that regulatory authorities will allow clinical trials of a protease inhibitor that we newly discover to begin.

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 such as the one we are proposing with the combination of bemnifosbuvir and a protease inhibitor 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 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 oral antiviral treatments for COVID-19, the longevity and extent of the ongoing COVID-19 pandemic is uncertain and it is unclear whether SARS-CoV-2 will become an endemic human coronavirus that may circulate in the human population after the current pandemic has subsided. If the pandemic were to dissipate, whether due to a significant decrease in the number or severity of new infections, the effectiveness of vaccines, the effectiveness of other treatment options, or otherwise, the need for treatments could decrease significantly. 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 there are several vaccines and associated vaccine boosters approved or authorized for use for COVID-19 and there are therapeutics available for the treatment of COVID-19 including two oral antiviral therapies, Paxlovid™ developed by Pfizer Inc., and Lagevrio™ developed by Merck and Ridgeback Therapeutics, each of which are authorized for emergency use for 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

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moderate COVID-19 and are at high risk for progression to severe COVID-19, including hospitalization and death. Treatments in development for COVID-19 include GS-5245, an oral nucleoside prodrug, that is being developed by Gilead Sciences and is currently being evaluated in a randomized, double-blind placebo controlled Phase 3 clinical trial in non-hospitalized COVID patients who are at high risk of progression to hospitalization.

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

Additional vaccines and therapeutics are in development by other pharmaceutical and biopharmaceutical companies. Other companies developing oral direct acting antivirals for treatment of COVID-19 include Enanta Pharmaceuticals, Inc., Shionogi & Co., Ltd., Pardes Biosciences, Inc., Junshi Biosciences, Jiangsu Simcere Pharmaceuticals, and SyneuRx.

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.

The COVID-19 pandemic may materially and adversely affect our business and financial results.

The global emergence of variants and subvariants of SARS-CoV-2 has resulted in an increasing number of infections, including breakthrough infections in persons who have been vaccinated against the infection. Travel bans, stay-at-home orders and other measures implemented by governments to reduce the transmission of COVID-19 in response to the initial outbreak of COVID-19 in 2020 caused widespread disruption in global business operations and economic activity. Future resurgences in cases may result in renewal of measures, many of which are currently relaxed, that are intended to reduce the spread of COVID-19. In response to the public health directives and to help minimize the risk of COVID-19 for our employees, we took and continue to maintain precautionary measures, including permitting work-from-home policies for all our employees. Many of our third-party collaborators, such as our CMOs, clinical research organizations (“CROs”), suppliers and others, took and continue to maintain similar precautionary measures. At times during the pandemic, these measures disrupted our business and delayed certain of our clinical programs and timelines. For example, in 2020 our hepatitis C virus clinical development program was paused when clinical trial sites closed due to COVID-19 precautions by the countries and medical facilities where the clinical trial was to be conducted. In 2023, we are planning to re-initiate HCV clinical trials.

The impact to our operations due to elongation or resurgence of the COVID-19 pandemic could be severe and could negatively affect our business, financial condition, and results of operations. For example, the recent relaxation of government lockdown measures in China has resulted in widespread outbreak of COVID-19. If continuing or new waves of COVID-19 infection disrupt business activities in China, our ability to source and manufacture critical components of our clinical trial material could be adversely impacted. To the extent that the COVID-19 pandemic adversely affects our business and financial results, it may also have the effect of heightening many of the other risk factors described in this “Risk Factors” section, such as those relating to our clinical trial timelines, our ability to enroll subjects for clinical trials and obtain materials that are required for the manufacture of our product candidates, and our ability to raise capital.

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The evolution of the COVID-19 pandemic or occurrence of any other public health crises may materially and adversely affect our clinical trials.

As a result of the evolution of the COVID-19 pandemic or the occurrence of any other public health crises, we may experience additional disruptions that could severely impact our clinical trials, including but not limited to:

The symptoms, progression, and transmission of COVID-19 resulting from infection with a particular variant or subvariant differ in multiple ways including severity of symptoms and rate of transmissibility. This rapid and continuing emergence of variants and the evolution of disease manifestation presents additional challenges for the conduct of our clinical trials in COVID-19 patients. For example, COVID-19 patients have presented with a wide range of symptoms and side effects, which may make it more difficult for clinical trial investigators to determine whether any adverse events observed in our clinical trials are related to bemnifosbuvir or are consistent with the underlying disease. Any increase in the severity or

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incidence of adverse events deemed to be related to bemnifosbuvir or any combination regimen we seek to develop could delay or prevent its regulatory approval, which could have a material adverse effect on our business, financial condition and results of operations. In addition, efficacy and antiviral results from a COVID-19 clinical trial may be affected by, among other things, which variant or variants cause the infection, resulting transmissibility and severity of disease and related hospitalizations and deaths. As a result, response rates occurring throughout the duration of a clinical trial may be variable over time as the pandemic progresses.

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. For example, due to changes in the COVID-19 landscape, we discontinued our Phase 3 MORNINGSKY trial in December 2021 and have only recently initiated a subsequent Phase 3 clinical trial, SUNRISE-3, evaluating bemnifosbuvir for the treatment of high risk outpatients with mild or moderate COVID-19. The primary endpoint of the SUNRISE-3 trial is all cause hospitalization or death through day 29 in the population of enrolled patients who receive only bemnifosbuvir or placebo without co-administration of the local standard care therapeutic. Our current study design and sample size contemplates that the rate of hospitalization in the placebo cohort will be at least 4%. If the actual rate of hospitalization in the placebo cohort of patients is less, the sample size and number of patients enrolling overall in the trial may need to be increased. This would make the trial more difficult to complete, if 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 and continue to vary substantially. Reported rates of hospitalization in many geographic regions have and may continue to fluctuate significantly including being reported below 4% for the overall patient population in specific regions.

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. For example, the decision by Roche to terminate the Roche License Agreement also terminated Roche’s obligation, after February 10, 2022, the effective date of the termination of the Roche License Agreement, to share with us costs associated with the development of bemnifosbuvir for the treatment of COVID-19.

Additionally, as a further result of the termination of the Roche License Agreement, we will not receive any other revenue from Roche beyond the upfront payment we received in 2020 and the milestone payment we received in 2021. 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

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generated any commercial revenue and we do not expect to maintain profitability in 2022 and for the foreseeable future.

We have incurred significant operating expenses since our inception. For the year ended December 31, 2022 and the year ended December 31, 2021, our operating expenses were $130.7 million and $213.0 million, respectively. In 2021, as a result of the termination by Roche of the Roche License Agreement, which resulted in the recognition of revenue for accounting purposes associated with the deferred revenue balance associated with upfront payment and the milestone payment we received from Roche, we recorded operating income for the year ended December 31, 2021. For the year ended December 31, 2022, we did not record any operating income and we do not expect to realize operating income in 2023 or for the foreseeable future.

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, we expect our expenses will increase substantially. Additionally, our expenses will also increase substantially if or as we:

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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 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 foreseeable future, 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 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 and our Phase 2 clinical trial evaluating the combination of bemnifosbuvir and ruzasvir for the treatment of HCV. Additionally, we anticipate that we will incur substantial expenses in connection with the 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.

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Based on our current operating plan, we believe that our cash and cash equivalents as of December 31, 2022 will be sufficient to fund our operating expenses and capital expenditure requirements into 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.

Our future capital requirements 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. The COVID-19 pandemic, including the evolution of new and existing variants of COVID-19, and geopolitical events, including civil or political unrest (such as the ongoing war between Ukraine and Russia), have resulted in a significant disruption of global financial markets. In addition, recent or future market volatility, increased inflation and higher interest rates, if sustained, may increase our cost of financing and may restrict our access to

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potential sources of future liquidity. 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.

Due to the recognition of revenue for accounting purposes of certain payments we received under the terminated Roche License Agreement, we recognized operating income for the year ended December 31, 2021. However, following the termination of the Roche License Agreement, we have received no incremental payments from Roche or any other third party that were recognized as revenue. As a result we incurred an operating loss in the amount of $130.7 million for the year ended December 31, 2022. Our ability to achieve and sustain future profitability depends upon our ability to generate revenue from product sales. Other than from the Roche License Agreement, we have not generated any revenue and 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, 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 several years. Our ability to generate revenue depends on a number of factors, including, but not limited to:

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Many of the factors listed above are beyond our control, and could cause us to experience significant delays 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 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, 2022, we had US federal net operating loss carryforwards (“NOLs”), of $19.4 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 $19.0 million do not expire but are limited in their usage (for taxable years beginning after December 31, 2022) to an annual deduction equal to 80% of annual taxable income. In addition, as of December 31, 2022, we had state NOLs of $30.0 million, which may be available to offset future taxable income, if any, and begin to expire in 2042. During the year ending December 31, 2021, we utilized each of federal and state NOLs of approximately $52.8 million and $52.6 million, respectively, and federal and state research and development credit carryforwards of $0.7 million and $0.3 million, respectively.

In general, under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended (“Code”), a corporation that undergoes an “ownership change,” 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 the year ended December 31, 2021, we have completed a Section 382 study, the results of which indicated that no ownership shift occurred during such 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 are in the process of completing a Section 382 study for the year ended December 31, 2022.

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,

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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. In February 2023, after advancing AT-752 to Phase 2 clinical trial, we suspended the 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. We have also recently terminated our efforts to discover a product candidate for the treatment of RSV. This action was taken to facilitate enhanced focus of our management team and resources for therapeutic indications where our programs are more advanced. These actions 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 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 a drug or drug candidate to combine with bemnifosbuvir for the treatment of COVID-19. COVID-19, while currently a global pandemic, 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 boosters 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 a commercial organization, substantial investment and significant marketing efforts. We cannot 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.

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. Nor can we 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

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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, or any approved products are 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, particularly with respect to COVID-19, which continues to evolve rapidly. 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 and may vary among jurisdictions, which may cause delays in the approval or the decision not to approve an application.

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. We have not submitted an NDA for, or obtained regulatory approval of, any product candidate. We must complete additional preclinical or nonclinical studies and clinical trials 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

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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 Risk Evaluation and Mitigation Strategy (“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 continue clinical development, 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:

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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, changes in the standard of care for the treatment of COVID-19, which is rapidly evolving due to the mutation of the virus, rapidly increasing knowledge being obtained by healthcare providers, rates and durability of vaccines, and availability of an increasing number of therapeutic options,

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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 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 bring 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 in 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 bring 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 European Union (“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 Clinical Trials Directive required a separate CTA to be submitted in each member state, 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 to all member states concerned. 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

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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. For clinical trials whose CTA was made under the Clinical Trials Directive before January 31, 2022, the Clinical Trials Directive will continue to apply on a transitional basis for three years. Clinical trials for which an application was submitted (i) prior to January 31, 2022 under the 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 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 Clinical Trial Directive. We have only begun submitting 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 clinical research organizations (“CROs”), may impact our developments plans.

It is currently unclear to what extent the UK will seek to align its regulations with the EU. 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 UK Medicines and Healthcare products Regulatory Agency (“MHRA”) launched an eight-week consultation on reframing the UK legislation for clinical trials. The consultation closed on March 14, 2022 and aims 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 outcome of the consultation is being closely watched and will determine whether the UK chooses to align with the CTR or diverge from it to maintain regulatory flexibility. 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 intend to develop 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. We are currently planning to develop combination therapies for the treatment of COVID-19 and HCV. 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 COVID-19 patients, in addition to our development of bemnifosbuvir as a monotherapy, we anticipate that we will develop a combination product consisting of bemnifosbuvir and an investigational protease inhibitor that is currently the subject of internal discovery efforts. For the treatment of HCV, we are currently pursuing development of bemnifosbuvir in combination with ruzasvir, a product candidate that has not yet been approved for marketing by the FDA or similar foreign regulatory authorities. We may not be able to market and sell any product candidate we develop in combination with any such unapproved therapies that do not ultimately obtain marketing approval.

If the FDA or similar foreign regulatory authorities do not approve these other combination agents or revoke their approval thereof, or if safety, efficacy, manufacturing, or supply issues arise with the drugs or biologics 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.

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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.

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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: