0001564590-22-007672 | 10-K | XBRL Viewer

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income (loss)	$ 121,190	$ (10,947)	$ (14,034)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities
Stock-based compensation expense	39,621	7,457	624
Depreciation and amortization expense	29	19	17
Changes in operating assets and liabilities
Unbilled accounts receivable		(5,815)
Prepaid expenses and other current assets	(483)	(7,296)	(43)
Other assets	(161)		0
Accounts payable	10,289	(488)	157
Accrued expenses and other liabilities	43,877	12,437	450
Deferred revenue	(301,367)	301,367
Net cash provided by (used in) operating activities	(87,005)	296,734	(12,829)
Cash flows from investing activities
Additions to property and equipment	(4)	(26)	(2)
Net cash used in investing activities	(4)	(26)	(2)
Cash flows from financing activities
Net proceeds from issuance of convertible preferred stock		214,116
Proceeds from issuance of common stock	1,465	27
Net proceeds from initial public offering of common stock		317,605
Net cash provided by financing activities	1,465	531,748
Net increase (decrease) in cash, cash equivalents and restricted cash	(85,544)	828,456	(12,831)
Cash, cash equivalents and restricted cash at the beginning of period	850,224	21,768	34,599
Cash, cash equivalents and restricted cash at the end of period	764,680	850,224	21,768
Cash, cash equivalents and restricted cash at the end of period
Cash and cash equivalents	764,375	850,117	21,661
Restricted cash	305	107	107
Cash, cash equivalents and restricted cash at the end of period	$ 764,680	850,224	$ 21,768
Supplemental disclosure of non-cash financing activities
Conversion of preferred stock to common stock upon closing of initial public offering		$ 283,230

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Options Activity

The following summarizes stock option activity:


	Number of Shares			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value ($000s)
Outstanding at January 1, 2021		7,917,783		$	6.68		8.6	$	277,894
Granted		3,561,295		$	55.14
Exercised		(665,793	)	$	2.20
Cancelled		(296,313	)	$	24.64
Outstanding at December 31, 2021		10,516,972		$	22.87		8.1	$	31,239
Options exercisable at December 31, 2021		4,561,016		$	11.33		7.2	$	23,500
Vested or expected to vest at December 31, 2021		10,516,972		$	22.87		8.1	$	31,239

Summary of Assumptions Used to Estimate Fair Value of Award

The fair value of each award was estimated using Black-Scholes based on the following assumptions:

	For the Year Ended December 31,
	2021			2020			2019
Risk-free interest rate		0.80	%	0.31 - 0.56%			1.61 - 2.02%
Expected term	5.99 years			6.25 years			5.52 - 10.0 years
Expected volatility		85.0	%	80.0% - 91.7%			49.2% - 78.0%
Expected dividend yield		0	%		0	%		0	%

Schedule of Stock-based Compensation Expense

Stock-based compensation expense is classified as follows:

	For the Year Ended December 31,
	2021		2020		2019
Research and development expense	$	18,127	$	3,565	$	255
General and administrative		21,494		3,892		369
Total stock-based compensation expense	$	39,621	$	7,457	$	624

Summary of Components of Stock-based Compensation Expense

The components of stock-based compensation expense were:

	For the Year Ended December 31,
	2021		2020		2019
Restricted common stock	$	—	$	657	$	—
Stock options		39,621		6,800		624
Total stock-based compensation expense	$	39,621	$	7,457	$	624

Collaboration Revenue

12 Months Ended

Dec. 31, 2021

Revenue From Contract With Customer [Abstract]

Collaboration Revenue

3. Collaboration Revenue

Background

In October 2020, the Company licensed to Roche ex-US rights to develop and commercialize certain of the Company’s compounds, including bemnifosbuvir.

On November 12, 2021, Roche provided the Company with a notice of termination of the Roche License Agreement. Under the terms of the Roche License Agreement, the termination was effective in February 2022. Upon termination, the rights and licenses granted by the Company to Roche under the Roche License Agreement were returned to the Company, and the Company has full rights to continue the clinical development and future commercialization of bemnifosbuvir worldwide. Global development plan activities and related cost sharing between the parties continued through the effective date of the termination.

The Company was responsible for completing certain ongoing clinical and non-clinical and manufacturing activities at its own expense. These obligations are referred to as the Atea Ongoing Studies and the Atea Manufacturing Obligations, respectively. Through the agreement termination in February 2022, the parties were collaboratively executing a global development plan intended to support regulatory approvals and were sharing joint development costs equally.

The Roche License Agreement provided for a nonrefundable upfront payment of $350,000 which the Company received in November 2020. In addition, the Roche License Agreement further provided that Roche was obligated to pay the Company up to $330,000 in the aggregate upon the achievement of certain development and regulatory milestone events; up to $320,000 in the aggregate upon the achievement of certain sales-based milestone events; and tiered royalties based on annual net sales of the products covered by the agreement, ranging between low double-digits and mid-twenties, subject to certain adjustments and limitations. The Company achieved a development milestone in the amount of $50,000 in the quarter ended June 30, 2021. Further, under the Roche License Agreement, the Company had a one-time option to request that Roche co-promote with the Company in the United States products covered by the Roche License Agreement that were successfully developed and commercialized. Roche had the right to terminate the Roche License Agreement for convenience pursuant to the terms of the agreement.

Accounting Analysis

The Company concluded that the Roche License Agreement was under the scope of ASC 808 as both parties were actively participating in a joint operating activity and were exposed to significant risks and rewards that depended on the activity’s commercial success. ASC 808 provides that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606 when the collaborative arrangement participant is a customer in the context of a unit of account. In those situations, all of the guidance in ASC 606 should be applied, including recognition, measurement, presentation, and disclosure requirements related to such unit of account. The unit-of-account guidance in ASC 808, which aligns with the guidance in ASC 606 (that is, a distinct good or service) is used when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of ASC 606. Based on the Company’s analysis, it concluded that the delivery of the license to Roche, the performance of the Atea Ongoing Studies and the Atea Manufacturing Obligations should be accounted for under ASC 606. The Company’s efforts under the global development plan and certain Atea Manufacturing Obligations in the initial year of the contract, were accounted for under ASC 808.

The Company concluded that the provision of the license to Roche, the performance of the Atea Ongoing Studies and the Atea Manufacturing Obligations should be combined as one performance obligation (“Combined Performance Obligation”) as Roche could receive the benefit of each promise without the other promises. Specifically, Roche was dependent on the Company’s expertise and ability to complete

the Atea Ongoing Studies and the Atea Manufacturing Obligations, which could not be performed by other third parties, in order to exploit the value from the license.

The initial transaction price was $350,000 which consisted of the upfront payment. During the quarter ended June 30, 2021, the transaction price was increased to $400,000 which included the $350,000 upfront payment and $50,000 related to the development milestone payment achieved during the quarter ended June 30, 2021. The Company concluded that all other forms of variable consideration, including future development and regulatory milestones should be constrained. As part of this conclusion, the Company assessed the stage of development and risk associated with remaining development required to achieve each milestone, including whether the achievement of certain milestones was outside the control of the Company. Sales based milestone payments and royalty payments qualified for the sales-based royalty exception and would have been recognized when the underlying sale transactions have occurred.

The transaction price was being recognized as collaboration revenue over the period in which the Company performs the Atea Ongoing Studies and the Atea Manufacturing Obligations. The Company concluded that an inputs method based on costs incurred compared to total estimated costs-to-complete approach most faithfully depicts the Company’s progress towards completion.

The Company concluded that the notice of termination represents a contract modification for accounting purposes. The Company further concluded that upon receipt of the notice of termination, the Combined Performance Obligation had been completely satisfied. As a result, the Company recognized all remaining deferred revenue as collaboration revenue within the consolidated statements of operations and comprehensive income for the year ended December 31, 2021.

The activities to complete the global development plan were accounted for under ASC 808. Expenses incurred and reimbursements made or received from Roche are accounted for pursuant to ASC 730, Research and Development. As such, the Company was expensing costs as incurred, including any reimbursements made to Roche, and recognizing reimbursement received from Roche as a reduction of research and development expense through the effective date of the termination.

The Company classifies all revenues recognized under the Roche License Agreement as collaboration revenues within the accompanying consolidated statements of operations and comprehensive income (loss). For the years ended December 31, 2021 and 2020, the Company recognized collaboration revenue of $351,367 and $48,633, respectively, related to the Combined Performance Obligation. As of December 31, 2021 and 2020, the Company recorded Deferred Revenue of $0 and $301,367, respectively, related to the Roche License Agreement. Deferred Revenue is classified in current liabilities in the accompanying balance sheet as of December 31, 2020 as the Combined Performance Obligation associated with the deferred revenue as of December 31, 2020 was expected to be completed within twelve months.

For the years ended December 31, 2021 and 2020, costs reimbursable by Roche which are reflected as a reduction to operating expenses were $7,264 and $7,901, respectively. The Company recorded research and development expense of $76,567 and $2,086 during the years ended December 31, 2021 and 2020, respectively, related to its share of costs incurred by Roche. As of December 31, 2021, the Company recorded accrued expenses of $10,417 related to amounts payable to Roche. As of December 31, 2020 the Company had recorded unbilled other receivable of $5,815 related to amounts due from Roche. This amount was offset against amounts payable to Roche for costs incurred during 2021.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

+ Details

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Convertible Preferred Stock	Series D Convertible Preferred Stock	Series D-1 Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings (Accumulated Deficit)
Balance at Dec. 31, 2018	$ (36,161)				$ 10	$ 4,008	$ (40,179)
Balance, shares at Dec. 31, 2018		33,645,447
Balance at Dec. 31, 2018		$ 69,114
Balance, shares at Dec. 31, 2018					10,091,100
Stock-based compensation expense	624					624
Net income (loss)	(14,034)						(14,034)
Balance at Dec. 31, 2019	(49,571)				$ 10	4,632	(54,213)
Balance, shares at Dec. 31, 2019		33,645,447
Balance at Dec. 31, 2019		$ 69,114
Balance, shares at Dec. 31, 2019					10,091,100
Issuance of convertible preferred stock, net of issuance costs			$ 106,631	$ 107,485
Issuance of convertible preferred stock, net of issuance costs, shares			15,313,382	8,973,261
Issuance of common stock for exercise of stock options	27					27
Issuance of common stock for exercise of stock options, shares					18,747
Stock-based compensation in connection with vesting of restricted stock	657					657
Stock-based compensation in connection with vesting of restricted stock, shares					20,000
Initial public offering, net of issuance costs of $3,245	317,605				$ 14	317,591
Initial public offering, net of issuance costs of $3,245, shares					14,375,000
Conversion of preferred stock into common stock	283,230				$ 58	283,172
Conversion of preferred stock into common stock, shares		(57,932,090)
Conversion of preferred stock into common stock	283,230	$ (283,230)
Conversion of preferred stock into common stock, shares					57,932,090
Stock-based compensation expense	6,800					6,800
Net income (loss)	(10,947)						(10,947)
Balance at Dec. 31, 2020	547,801				$ 82	612,879	(65,160)
Balance, shares at Dec. 31, 2020					82,436,937
Issuance of common stock for exercise of stock options	$ 1,465				$ 1	1,464
Issuance of common stock for exercise of stock options, shares	665,793				665,793
Stock-based compensation expense	$ 39,621					39,621
Net income (loss)	121,190						121,190
Balance at Dec. 31, 2021	$ 710,077				$ 83	$ 653,964	$ 56,030
Balance, shares at Dec. 31, 2021					83,102,730

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation and Use of Estimates

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America, or GAAP.

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and in these accompanying notes. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors and assumptions that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates, which include but are not limited to estimates of revenue, accrued research and development expenses, the valuation of common stock in connection with the issuance of stock-based awards prior to the completion of the IPO, and income taxes. Changes in estimates are recorded in the period in which they become known.

Principles of Consolidation

The consolidated financial statements include the accounts of Atea Pharmaceuticals, Inc. and its wholly- owned subsidiary, Atea Pharmaceuticals Securities Corporation. All intercompany amounts have been eliminated in consolidation.

Revenue Recognition

Through December 31, 2021, all of the Company’s revenue was collaboration revenue generated from the Roche License Agreement.

Until receipt in November 2021 of the notice from Roche that Roche was terminating the Roche License Agreement effective February 2022, the Company recognized collaboration revenue over the expected performance period based on its measure of progress towards the completion of certain activities referred to as its Combined Performance Obligation. The Company concluded that the notice of termination represents a contract modification for accounting purposes. The Company further concluded that upon receipt of the notice of termination, the Combined Performance Obligation has been completely satisfied. As a result, the Company recognized all remaining deferred revenue as collaboration revenue within the consolidated statements of operations and comprehensive income for the year ended December 31, 2021 (see Note 3, Collaboration Revenue, for a detailed discussion).

The Company analyzes its collaboration arrangements to assess whether they are within the scope of Accounting Standards Codification ASC Topic 808, Collaborative Arrangements (“ASC 808”), to determine whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards that are dependent on the commercial success of such activities. If the Company concludes that some or all aspects of the arrangement are within the scope of ASC 808 and do not represent a transaction with a customer, the Company recognizes its allocation of the shared costs incurred with respect to the jointly conducted activities pursuant to ASC 730, Research and Development. As such, the Company will expense costs as incurred, including any reimbursements made, and recognize reimbursements received as a reduction of research and development expense. If the Company concludes that some or all aspects of the arrangement represent a transaction with a customer, the Company accounts for those aspects of the arrangement within the scope of ASC 606, Revenue from Contracts with Customers (“ASC 606”).

To determine the appropriate amount of revenue to be recognized for arrangements that the Company determines are within the scope of ASC 606, it performs the following steps: (i) identify the contract(s) with the customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) each performance obligation is satisfied. ASC 606 requires significant judgment and estimates and results in changes to, but not limited to: (i) the determination of the transaction price, including estimates of variable consideration, (ii) the allocation of the transaction price, including the

determination of estimated selling price, and (iii) the pattern of recognition, including the application of proportional performance as a measure of progress on service-related promises and application of point-in-time recognition for supply-related promises.

The transaction price is generally comprised of an upfront payment due at contract inception and variable consideration in the form of payments for the Company’s services and materials and milestone payments due upon the achievement of specified events. Other payments the Company could be entitled to include tiered royalties earned when customers recognize net sales of licensed products. The Company considers the existence of any significant financing component within its arrangements and has determined that a significant financing component does not exist in its arrangements as substantive business purposes exist to support the payment structure other than to provide a significant benefit of financing. The Company measures the transaction price based on the amount of consideration to which it expects to be entitled in exchange for transferring the promised goods and/or services to the customer. The Company utilizes either the expected value method or the most likely amount method to estimate the amount of variable consideration, depending on which method is expected to better predict the amount of consideration to which the Company will be entitled. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. With respect to arrangements that include payments for a development or regulatory milestone payment, the Company evaluates whether the associated event is considered probable of achievement and estimate the amount to be included in the transaction price using the most likely amount method. Milestone payments that are not within the Company’s control or the customer’s, such as those dependent upon receipt of regulatory approval, are not considered to be probable of achievement until the triggering event occurs. At the end of each reporting period, the Company re-evaluates the probability of achievement of each milestone and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenue and net loss in the period of adjustment. For arrangements that include sales-based royalties, including milestone payments based upon the achievement of a certain level of product sales, wherein the license is deemed to be the sole or predominant item to which the payments relate, the Company recognizes revenue upon the later of: (i) when the related sales occur or (ii) when the performance obligation to which some or all of the payment has been allocated has been satisfied (or partially satisfied). Consideration that would be received for optional goods and/or services is excluded from the transaction price at contract inception.

The Company generally allocates the transaction price to each performance obligation based on a relative standalone selling price basis. The Company develops assumptions that require judgment to determine the standalone selling price for each performance obligation in consideration of applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated research and development costs. However, in certain instances, the Company allocates variable consideration entirely to one or more performance obligation if the terms of the variable consideration relate to the satisfaction of the respective performance obligation and the amount allocated is consistent with the amount the Company would expect to receive for the satisfaction of the respective performance obligation.

The Company recognizes revenue based on the amount of the transaction price that is allocated to each respective performance obligation when or as the performance obligation is satisfied by transferring a promised good or service to the customer. For performance obligations that are satisfied at a point in time, the Company recognizes revenue when control of the goods and/or services is transferred to the customer. For performance obligations that are satisfied over time, the Company recognizes revenue by measuring the progress toward complete satisfaction of the performance obligation using a single method of measuring progress which depicts the performance in transferring control of the associated goods and/or services to the customer. The Company generally uses input methods to measure the progress toward the complete satisfaction of performance obligations satisfied over time. With respect to arrangements containing a license to its intellectual property that is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from amounts allocated to the license when the license is transferred to the licensee and the licensee is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes

judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. Significant management judgment is required in determining the level of effort required under an arrangement and the period over which the Company is expected to complete its performance obligations under an arrangement. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenue and net loss in the period of adjustment.

Contract costs

The Company recognizes as an asset the incremental costs of obtaining a contract with a customer if the costs are expected to be recovered. The Company has elected the practical expedient in ASC 340, Other Assets and Deferred Costs, wherein it recognizes the incremental costs of obtaining a contract as an expense when incurred if, at inception, the expected amortization period of the asset that the Company otherwise would have recognized is one year or less. In connection with the Roche License Agreement, the Company incurred an incremental cost of $7,000, which was included in general and administrative costs in the accompanying statement of operations and comprehensive loss for the year ended December 31, 2020.

Cash and Cash Equivalents

The Company considers all highly-liquid investments purchased with maturities of 90 days or less at acquisition to be cash equivalents. Cash and cash equivalents include bank demand deposits and money market funds that invest in U.S. government and U.S. government agency obligations. Cash equivalents are reported at fair value.

Concentrations of Credit Risk and Significant Suppliers

Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash and cash equivalents. The Company maintains its cash and cash equivalents with a financial institution that management believes is creditworthy. The Company’s investment policy includes guidelines on the quality of the financial institutions and financial instruments and defines allowable investments that the Company believes minimizes the exposure to concentration of credit risk.

The Company is dependent on third-party manufacturers to supply products for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs.

Fair Value Measurements

Assets and liabilities recorded at fair value on a recurring basis in the consolidated balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows:

Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 2—Observable inputs (other than quoted prices included in Level 1) that are either directly or indirectly observable for the asset or liability. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active.

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determination of fair value of the assets or liabilities.

Cash, cash equivalents and restricted cash are Level 1 assets which are comprised of funds held in checking and money market accounts. Cash, cash equivalents and restricted cash were recorded at fair value as disclosed in Note 4. The carrying amounts of accounts payable, accrued expenses and unbilled other receivables approximate their fair values due to their short-term maturities.

Property and Equipment

Property and equipment are stated at cost, less accumulated depreciation and amortization. Property and equipment are depreciated using the straight-line method over the estimated useful lives of the asset. The Company estimates the useful life of its assets as follows:

Asset		Estimated useful life
Laboratory equipment		Five years
Office furniture and fixtures		Five years
Computer hardware		Two years
Leasehold improvements		Shorter of useful life or remaining lease term

Maintenance and repairs that do not improve or extend the life of the respective asset are expensed to operations as incurred. Upon disposal of an asset, the related cost and accumulated depreciation are removed from the accounts and any resulting gain or loss is included in the consolidated statements of operations.

Other Assets

Other assets consist of a right-of-use asset of $161 and bank deposits of $305, classified as restricted cash, to collateralize two letters of credit.

Impairment of Long-lived Assets

The Company reviews long-lived assets when events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Recoverability is measured by comparing the book value of the assets to the estimated undiscounted future net cash flows that the asset is expected to generate. If the estimated undiscounted future net cash flows are less than the book value, the asset is impaired, and the impairment loss to be recognized in income is measured as the amount by which the book value of the asset exceeds its fair value, which is measured based on the estimated discounted future net cash flows that the asset is expected to generate. No impairment losses were recorded during the years ended December 31, 2021, 2020 and 2019.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development expenses consist principally of costs associated with outsourced research and development activities, including preclinical and clinical development, manufacturing and research conducted by contract research organizations and academic institutions, employee compensation, including stock-based compensation and consulting expenses together with related expenses, professional fees and facility and overhead costs. Facility and overhead costs primarily include the allocation of rent, utility and office-related expenses attributable to research and development personnel. In circumstances where amounts have been paid in advance or in excess of costs incurred, the Company records a prepaid expense, which is expensed as services are performed or goods are delivered.

The Company has entered into various research and development contracts with third parties. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase of completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent Costs

Costs to secure and maintain the Company’s patents are expensed as incurred and are classified as general and administrative expenses in the Company’s consolidated statements of operations.

Stock-based Compensation

Stock-based compensation expense is classified in the consolidated statement of operations in the same manner in which the award recipient’s payroll costs or service payments are classified. Stock-based awards granted to employees and non-employees are measured based on the estimated fair value of the awards using the Black-Scholes option pricing model (“Black-Scholes”). Stock-based compensation expense with respect to awards with service conditions is recognized using the straight-line method over the service period. Stock-based compensation with respect to awards with performance conditions is recognized when satisfaction of the performance conditions is probable. Stock-based compensation is based on awards ultimately expected to vest and, as such, it is reduced by forfeitures. The Company accounts for forfeitures as they occur.

Black-Scholes requires the use of subjective assumptions which determine the fair value of stock-based awards. These assumptions include:

Fair value of common stock

Prior to the IPO, because there was no public market for the Company’s common stock, the fair value of the Company’s common stock underlying stock-based awards was estimated on each grant date by the board of directors. The Company developed an estimate on each grant date of the fair value of its common stock based on valuations from an independent third-party valuation firm using information known to the Company on the date of grant and a review of any recent events and their potential impact on the estimated fair value per share of the common stock. The third-party valuations of the Company’s common stock were determined in accordance with the guidelines outlined in the American Institute of Certified Public Accountants Practice Aid, Valuation of Privately-Held-Company Equity Securities Issued as Compensation, or the Practice Aid. The assumptions used to determine the estimated fair value of the Company’s common stock were based on numerous objective and subjective factors, combined with management judgment, including:

•	external market conditions affecting the pharmaceutical and biotechnology industry and trends within the industry;

•	the Company’s stage of development and business strategy;

•	the rights, preferences and privileges of the Company’s then-outstanding redeemable convertible preferred stock relative to those of its common stock;

•	the prices at which the Company sold shares of its then-outstanding redeemable convertible preferred stock;

•	the Company’s financial condition and operating results, including its levels of available capital resources;

•	the progress of the Company’s research and development efforts;

•	equity market conditions affecting comparable public companies; and

•	general U.S. market conditions and the lack of marketability at the time of the Company’s common stock.

The Practice Aid identifies various available methods for allocating enterprise value across classes and series of capital stock to determine the estimated fair value of common stock at each valuation date. In accordance with the Practice Aid, the Company considered the following methods:

•

Option Pricing Method. Under the option pricing method (“OPM”), shares are valued by creating a series of call options with exercise prices based on the liquidation preferences and conversion terms of each equity class. The estimated fair values of the then-outstanding preferred stock and common stock were inferred by analyzing these options.

•

Probability-Weighted Expected Return Method. The probability-weighted expected return method (“PWERM”), is a scenario-based analysis that estimates value per share based on the probability-weighted present value of expected future investment returns, considering each of the possible outcomes available to the Company, as well as the economic and control rights of each share class.

Based on the Company’s early stage of development and other relevant factors, the Company determined that OPM method as well as a hybrid approach of the OPM and the PWERM methods were the most appropriate methods for allocating its enterprise value to determine the estimated fair value of its common stock. In determining the estimated fair value of the Company’s common stock, its board of directors also considered the fact that its stockholders could not freely trade its common stock in the public markets. Accordingly, the Company applied discounts to reflect the lack of marketability of its common stock based on the weighted-average expected time to liquidity. The estimated fair value of the Company’s common stock at each grant date reflected a non-marketability discount partially based on the anticipated likelihood and timing of a future liquidity event.

Upon the completion of the Company’s initial public offering, the fair value of its common stock is based on the daily closing quoted market price of its common stock.

Risk-free interest rate—The risk-free interest rate is based on the U.S. Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term of a stock-based award.

Expected term—The expected term represents the period that stock-based awards are expected to be outstanding. Given the Company’s lack of specific history, the expected term for option grants is determined using the simplified method. The simplified method deems the term to be the average of the time-to-vesting and the contractual life of the stock-based awards.

Expected volatility—Since the Company was privately held through October 29, 2020 and did not have any trading history for its common stock, the expected volatility was estimated based on the average volatility for comparable publicly traded biotechnology companies over a period equal to the expected term of the stock-based awards. The comparable companies were chosen based on their similar size, stage in the life cycle or area of specialty. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available.

Expected dividend yield —The Company has never paid dividends on its common stock and has no plans to pay dividends on its common stock. Therefore, the Company used an expected dividend yield of zero.

The Company also accounts for any modifications to share based payments in accordance with ASC Topic 718, Compensation – Stock Compensation (ASC 718).

Income Taxes

The Company uses the asset and liability method of accounting for income taxes. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax base. Deferred tax assets are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Deferred tax expense or benefit is the result of changes in the deferred tax assets and liabilities. Valuation allowances are established to reduce deferred tax assets where, based upon the available evidence, the Company concludes that it is more-likely-than-not that the deferred tax assets will not be realized. In evaluating its ability to recover deferred tax assets, the Company considers all available positive and negative evidence, including its operating results, ongoing tax planning and forecasts of future taxable income.

Reserves are provided for tax benefits for which realization is uncertain. Such benefits are only recognized when the underlying tax position is considered more-likely-than-not to be sustained on examination by a taxing authority. Interest and penalties related to uncertain tax positions are recognized in the provision of income taxes.

Comprehensive Income (Loss)

Comprehensive income (loss) includes net income (loss) as well as other changes in stockholders’ equity (deficit) that result from transactions and economic events other than those with equity holders. The Company did not have any items of comprehensive income or loss other than net income (loss) for the years ended December 31, 2021, 2020 and 2019.

Net Income (Loss) Per Share Attributable to Common Stockholders

Basic net income (loss) per share attributable to common stockholders is computed by dividing the net income (loss) attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net income per share attributable to common stockholders is computed by dividing the diluted net income attributable to common stockholders by the weighted average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of outstanding stock options.

Prior to the Company’s IPO, basic and diluted net loss per share attributable to common stockholders was determined using the two-class method, which is required for participating securities. The Company considered its convertible preferred stock to be participating securities as, in the event a dividend is paid on common stock, the holders of convertible preferred stock would be entitled to receive dividends on a basis consistent with the common stockholders. Under the two-class method, the net loss attributable to common stockholders is not allocated to the convertible preferred stock as the holders of the convertible preferred stock do not have a contractual obligation to share in losses.

Under the two-class method, basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock. Due to net losses for the years ended December 31, 2020 and 2019, basic and diluted net loss per share attributable to common stockholders were the same, as the effect of all potentially dilutive securities would have been anti-dilutive.

In-process Research and Development Assets

In-process research and development assets that are acquired in a transaction that does not qualify as a business combination under GAAP and that do not have an alternative future use are expensed in the period in which the assets are acquired.

Segments

Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the chief operating decision maker (the “CODM”), in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s CODM is its chief executive officer, who manages and allocates resources to the operations on a total company basis. Accordingly, there is a single operating segment and one reportable segment.

SEC Filing Status

Based on its public float as of June 30, 2021, the Company became a large accelerated filer, and lost emerging growth company status, as of December 31, 2021. As of December 31, 2021, the Company is required to adopt new or revised accounting standards when they are applicable to public companies that are not emerging growth companies and is required to comply with the auditor attestation requirements Section 404(b) of the Sarbanes-Oxley Act.

Recently Issued Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the Financial Accounting Standard Board (“FASB”) or other standard setting bodies that the Company adopts as of the specified effective date. Unless otherwise disclosed below, the Company does not believe that the adoption of recently issued standards have or may have a material impact on its consolidated financial statements and disclosures.

Recently Adopted Accounting Pronouncements

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (“ASU 2016-02” or “ASC 842”), which requires a lessee to record a right-of-use asset and a corresponding lease liability on the balance sheet for all leases with terms longer than 12 months. A modified retrospective transition approach is required for lessees for capital and operating leases existing at, or entered into after, the

beginning of the earliest comparative period presented in the financial statements, with certain practical expedients available.

In July 2018, an amendment was made that allows companies the option of using the effective date of the new standard as the initial application date (at the beginning of the period in which the new standard is adopted, rather than at the beginning of the earliest comparative period). This update includes a short-term lease exception for leases with a term of 12 months or less, in which a lessee can make an accounting policy election not to recognize the associated lease assets and lease liabilities on its balance sheet.

Additionally, in March 2019, the FASB issued ASU 2019-01 (“ASU No. 2019-01”). ASU No. 2019-01 clarifies the transition guidance related to interim disclosures provided in the year of adoption. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases, using classification criteria that are substantially similar to the previous guidance. For lessees, the recognition, measurement, and presentation of expenses and cash flows arising from a lease did not significantly change from previous U.S. GAAP. The modified retrospective method includes several optional practical expedients that entities may elect to apply, as well as transition guidance specific to nonstandard leasing transactions.

The Company adopted the new standard effective January 1, 2021 using the modified retrospective method as of the beginning of the period of the adoption. The Company has elected the package of practical expedients permitted in ASC Topic 842. Accordingly, the Company accounted for its existing operating lease as an operating lease under the new guidance, without reassessing (a) whether the contracts contain a lease under ASC Topic 842, (b) whether classification of the operating leases would be different in accordance with ASC Topic 842, or (c) whether the unamortized initial direct costs would have met the definition of initial direct costs in ASC Topic 842 at lease commencement.

The adoption of this standard resulted in the recording of operating lease liabilities and right-of-use assets on the Company’s consolidated balance sheet (see Note 7). The adoption of the standard did not have a material effect on the Company’s consolidated statements of operations and comprehensive income (loss), consolidated statements of cash flows or consolidated statements of convertible preferred stock and stockholders’ equity (deficit).

In July 2017, the FASB issued ASU No. 2017-11, Earnings Per Share (Topic 260), Distinguishing Liabilities from Equity (Topic 480), Derivatives and Hedging (Topic 815) I. Accounting for Certain Financial Instruments with Down Round Features II. Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception (“ASU 2017-11”). Part I applies to entities that issue financial instruments such as warrants, convertible debt or convertible preferred stock that contain down-round features. Part II replaces the indefinite deferral for certain mandatorily redeemable noncontrolling interests and mandatorily redeemable financial instruments of nonpublic entities contained within ASC Topic 480 with a scope exception and does not impact the accounting for these mandatorily redeemable instruments. The standard was effective for the Company beginning January 1, 2021, with early adoption permitted. The adoption of this standard did not have a material impact on the Company’s consolidated financial position and results of operations.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Statements. The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The Company adopted the standard effective December 31, 2021. The adoption of this standard did not have a material impact on the Company’s consolidated financial position and results of operations.

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, which is intended to simplify the accounting for income taxes. ASU 2019-12 removes certain exceptions to the general principles in Topic 740 and also clarifies and amends existing guidance to improve consistent application. The Company adopted the standard effective

January 1, 2021. The adoption of the standard did not have a material effect on the Company’s consolidated balance sheets, consolidated statements of operations and comprehensive income (loss), consolidated statements of cash flows or consolidated statement of stockholders’ equity (deficit).

Stock-based Compensation - Summary of Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Number of Shares
Number of Shares, Outstanding	7,917,783
Number of Shares, Granted	3,561,295
Number of Shares, Exercised	(665,793)
Number of Shares, Cancelled	(296,313)
Number of Shares, Outstanding	10,516,972	7,917,783
Number of Shares, Options exercisable	4,561,016
Number of Shares, Vested or expected to vest	10,516,972
Weighted Average Exercise Price Per Share
Weighted Average Exercise Price Per Share, Outstanding	$ 6.68
Weighted Average Exercise Price Per Share, Granted	55.14
Weighted Average Exercise Price Per Share, Exercised	2.20
Weighted Average Exercise Price Per Share, Cancelled	24.64
Weighted Average Exercise Price Per Share, Outstanding	22.87	$ 6.68
Weighted Average Exercise Price Per Share, Options exercisable	11.33
Weighted Average Exercise Price Per Share, Vested or expected to vest	$ 22.87
Weighted Average Remaining Contractual Term and Aggregate Intrinsic Value
Weighted Average Remaining Contractual Term (years), Outstanding	8 years 1 month 6 days	8 years 7 months 6 days
Weighted Average Remaining Contractual Term (years), Options exercisable	7 years 2 months 12 days
Weighted Average Remaining Contractual Term (years), Vested or expected to vest	8 years 1 month 6 days
Aggregate Intrinsic Value, Outstanding	$ 31,239	$ 277,894
Aggregate Intrinsic Value, Options exercisable	23,500
Aggregate Intrinsic Value, Vested or expected to vest	$ 31,239

Commitments and Contingencies

12 Months Ended

Dec. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

7. Commitments and Contingencies

Operating Lease Agreements

The Company leases an office facility under a non-cancelable operating lease that expires July 2022. The office lease includes commitments obligating the Company to pay a pro rata share of certain building operating costs and annual rent escalations which will result in higher lease payments in future years.

As of January 1, 2021, the date of adoption of ASC 842, the Company utilized operating classification for its facility lease and recorded a right-of-use asset and lease liability.

The following assets and liabilities are recorded on the Company’s consolidated balance sheet as of December 31, 2021.

	As of December 31,
	2021
Right-of-use asset	$	161
Current lease liability		197
Non-current lease liability		—

The right-of-use asset is included in other assets, the current lease liability is included in accrued expenses and other current liabilities and the non-current lease liability is included in other liabilities, respectively.

The components of the lease allocated between the general and administrative and the research and development expenses on the consolidated statement of operations for the year ended December 31, 2021 were as follows:

	Year Ended
	December 31, 2021
Operating lease costs	$	281
Variable lease costs		37
Total lease costs	$	318

The variable lease costs for the year ended December 31, 2021 include common area maintenance and other operating charges associated with the Company’s lease of its principal office facilities in Boston, MA. As the Company’s lease does not provide an implicit rate, the Company utilized its incremental borrowing rate to discount lease payments, which reflects the fixed rate at which the Company could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment.

	As of December 31,
	2021
Remaining lease term (in years)		0.5
Discount rate		7	%

On July 19, 2021, the Company entered into a sublease (the “Sublease”) pursuant to which the Company leases additional office space in Boston, Massachusetts (the “Premises”). The term of the Sublease commenced on January 1, 2022 (the “Commencement Date”) and will end on December 31, 2026.

The Sublease provides that the initial base rent for the Premises is $66 per month, subject to upward adjustment of 2% each year starting on the first anniversary of the Commencement Date. In addition to base rent, the Company is required to pay certain operating expenses and taxes associated with the Premises as well as certain utilities supplied to the Premises.

As of December 31, 2021, future minimum payments for operating leases are as follows:

2022		989
2023		805
2024		821
2025		838
2026		855
Total future minimum lease payments	$	4,308

Rent expense recognized under all operating leases was $318, $303 and $305 for the years ended December 31, 2021, 2020 and 2019, respectively.

The Company is required to maintain letters of credit for the duration of the office leases. The Company maintains bank deposits of $305, to collateralize the letters of credit which are classified as restricted cash and a long-term asset in the consolidated balance sheets as of December 31, 2021 and 2020.

License Agreement

Background

In December 2021, the Company entered into a license agreement with MSD International GmbH, an affiliate of Merck & Co, Inc. (“Merck”) (the “Merck License Agreement”) for the development, manufacture and commercialization of ruzasvir (the “Compound”). Ruzasvir is the NS5A inhibitor the Company is developing in combination with bemnifosbuvir for the treatment of HCV.

Pursuant to the terms of the Merck License Agreement, the Company 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 the Compound, or products containing the Compound (each a “Product”) for all therapeutic or prophylactic uses in humans (the “Field”).

In consideration for the rights the Company acquired under the Merck License Agreement, the Company paid Merck a non-refundable upfront payment in the amount of $25,000 in February 2022 and will be required to pay Merck milestone payments up to $135,000 in the aggregate upon its achievement of certain development and regulatory milestones and up to $300,000 in the aggregate upon its achievement of certain sales-based milestones. Additionally, the Company will pay Merck tiered royalties based on annual net sales of Products ranging from high single digits to mid-teens percentages. The Company’s royalty payment obligations will continue until the later of (i) the expiration of the last to expire valid claim of a licensed Merck patent claiming such Product (or a Compound contained in such Product) and (ii) a period of years after the first commercial sale of such Product in such country. The Company may terminate the Merck License Agreement for convenience upon prior written notice. The first potential milestone would be payable upon the commencement of a Phase 3 clinical trial.

The Company recognized, as research and development expense, the $25,000 non-refundable upfront payment amount as a cost of the asset acquired in the year ended December 31, 2021 because the in-process research and development asset does not have an alternative future use. The upfront payment, payable in February 2022, is included in accrued expenses as of December 31, 2021.

Contingent Consulting Fee

The Company has an agreement with a consultant that requires payment of a success fee calculated as a percentage of certain product sales, subject to a cumulative maximum payout of $5.0 million. This success payment is contingent upon the occurrence of future events and the timing and likelihood of such payment is neither probable nor estimable.

Indemnification

The Company enters into certain types of contracts that contingently requires the Company to indemnify various parties against claims from third parties. These contracts primarily relate to (i) the Company’s

bylaws, under which the Company must indemnify directors and executive officers, and may indemnify other officers and employees, for liabilities arising out of their relationship, (ii) contracts under which the Company must indemnify directors and certain officers and consultants for liabilities arising out of their relationship, and (iii) procurement, service or license agreements under which the Company may be required to indemnify vendors, service providers or licensees for certain claims, including claims that may be brought against them arising from the Company’s acts or omissions with respect to the Company’s products, technology, intellectual property or services.

From time to time, the Company may receive indemnification claims under these contracts in the normal course of business. In the event that one or more of these matters were to result in a claim against the Company, an adverse outcome, including a judgment or settlement, may cause a material adverse effect on the Company’s future business, operating results or financial condition. It is not possible to determine the maximum potential amount payable under these contracts since the Company has no history of prior indemnification claims and the unique facts and circumstances involved in each particular claim will be determinative.

Stock-based Compensation

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based Compensation

10. Stock-based Compensation

In October 2020, the Company’s shareholders approved the Company’s 2020 Incentive Award Plan (the “2020 Plan”), which became effective in connection with the Company’s IPO. The 2020 Plan provides for the issuance of up to 7,924,000 shares of common stock and for the grant of incentive stock options or other incentive awards to employees, members of the board of directors and consultants of the Company. The number of shares of common stock that may be issued under the 2020 Plan is also subject to increase on the first day of each calendar year equal to the lesser of i) 5% of the aggregate number of shares of common stock outstanding on the final day of the immediately preceding calendar year or ii) such smaller number of shares as is determined by the board of directors. In January 2021, the shares available under the plan were increased by 4,130,847 shares. As of December 31, 2021 there were 7,963,829 shares of common stock remaining available for future issuance under the 2020 Plan. In January 2022, the shares available under the plan were increased by 4,155,136 shares

The 2020 Plan replaced and is the successor of the Company’s 2013 Equity Incentive Plan, as amended (the “2013 Plan”), which provided for the grant of incentive stock options, non-qualified stock options, restricted common stock awards and other awards for up to 7,807,200 shares of common stock to employees, officers, directors and consultants of the Company. Upon the closing of the Company’s IPO the 2013 Plan was terminated and no further awards will be made under the 2013 Plan. Any cancellation of outstanding awards at the time of the Company’s IPO under the 2013 Plan will be made available for grant under the 2020 Plan.

Restricted Common Stock

Restricted stock awards generally include vesting and risk of forfeiture provisions that lapse upon satisfaction of performance conditions or over time periods commencing on the grant date and concluding on the third or fourth anniversary of the grant date. As of December 31, 2021, there were no unvested shares of restricted stock.

Employee Stock Purchase Plan

In October 2020, the Company’s shareholders approved the 2020 Employee Stock Purchase Plan (the “ESPP”), which became effective in connection with the Company’s IPO. A total of 1,187,000 shares of common stock are reserved for issuance under this plan. As of December 31, 2021 the Company had not commenced any offering under the ESPP and no shares have been issued.

Stock Options

The following summarizes stock option activity:


	Number of Shares			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value ($000s)
Outstanding at January 1, 2021		7,917,783		$	6.68		8.6	$	277,894
Granted		3,561,295		$	55.14
Exercised		(665,793	)	$	2.20
Cancelled		(296,313	)	$	24.64
Outstanding at December 31, 2021		10,516,972		$	22.87		8.1	$	31,239
Options exercisable at December 31, 2021		4,561,016		$	11.33		7.2	$	23,500
Vested or expected to vest at December 31, 2021		10,516,972		$	22.87		8.1	$	31,239

The aggregate intrinsic value of options granted is calculated as the difference between the exercise price of the options and the estimated fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock.

Option grants generally vest over a service period of three or four years and have a contractual term of ten years. As of December 31, 2021, total unrecognized compensation expense related to stock option

awards was $128,036, which amount is being recognized over a remaining weighted average period of 2.7 years.

The weighted average grant date fair value per option granted during the years ended December 31, 2021, 2020 and 2019 was $39.10, $14.93 and $1.19, respectively. The fair value of each award was estimated using Black-Scholes based on the following assumptions:

	For the Year Ended December 31,
	2021			2020			2019
Risk-free interest rate		0.80	%	0.31 - 0.56%			1.61 - 2.02%
Expected term	5.99 years			6.25 years			5.52 - 10.0 years
Expected volatility		85.0	%	80.0% - 91.7%			49.2% - 78.0%
Expected dividend yield		0	%		0	%		0	%

Stock-based Compensation Expense

Stock-based compensation expense is classified as follows:

	For the Year Ended December 31,
	2021		2020		2019
Research and development expense	$	18,127	$	3,565	$	255
General and administrative		21,494		3,892		369
Total stock-based compensation expense	$	39,621	$	7,457	$	624

The components of stock-based compensation expense were:

	For the Year Ended December 31,
	2021		2020		2019
Restricted common stock	$	—	$	657	$	—
Stock options		39,621		6,800		624
Total stock-based compensation expense	$	39,621	$	7,457	$	624

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 764,375	$ 850,117
Unbilled other receivable		5,815
Prepaid expenses and other current assets	8,028	7,545
Total current assets	772,403	863,477
Property and equipment, net	23	48
Other assets	466	107
Total assets	772,892	863,632
Current liabilities
Accounts payable	4,534	60
Accrued expenses and other current liabilities	52,349	14,368
Deferred revenue		301,367
Total current liabilities	56,883	315,795
Other liabilities	5,932	36
Total liabilities	62,815	315,831
Commitments and contingencies (see Note 7)
Stockholders’ equity:
Preferred stock, $0.001 par value per share; 10,000,000 shares authorized; no shares issued and outstanding as of December 31, 2021 and 2020
Common stock, $0.001 par value; 300,000,000 shares authorized; 83,102,730 and 82,436,937 shares issued and outstanding as of December 31, 2021 and 2020	83	82
Additional paid-in capital	653,964	612,879
Retained earnings (accumulated deficit)	56,030	(65,160)
Total stockholders’ equity	710,077	547,801
Total liabilities and stockholders’ equity	$ 772,892	$ 863,632

Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Collaboration revenue	$ 351,367	$ 48,633
Operating expenses
Research and development	167,205	38,023	$ 10,170
General and administrative	45,785	21,640	4,438
Total operating expenses	212,990	59,663	14,608
Income (loss) from operations	138,377	(11,030)	(14,608)
Interest income and other, net	213	83	574
Income (loss) before income taxes	138,590	(10,947)	(14,034)
Income taxes	17,400
Net income (loss) and comprehensive income (loss)	$ 121,190	$ (10,947)	$ (14,034)
Net income (loss) per share attributable to common stockholders
Basic	$ 1.46	$ (0.51)	$ (1.39)
Diluted	$ 1.37	$ (0.51)	$ (1.39)
Weighted-average number of common shares used in computing net income (loss) per share attributable to common stockholders
Basic	82,820,037	21,592,441	10,091,100
Diluted	88,249,243	21,592,441	10,091,100

Income Taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

11. Income Taxes

For the year ended December 31, 2021, the Company recorded a provision for income taxes for $17,400. During the years ended December 31, 2020 and 2019, the Company did not record a current or deferred income tax expense or benefit.

The reconciliation of federal statutory income tax rate to the Company’s effective income tax rate is as follows:

	For the Year Ended December 31,
	2021				2020				2019
Expected income tax benefit at the federal statutory rate		21.0		%		21.0		%		21.0		%
State and local taxes		3.2				(2.6	)			6.2
Research and development credits		(4.1	)			12.5				0.9
Stock-based compensation		—				(13.6	)			—
Foreign derived intangible income		(6.1	)			—				—
Uncertain tax positions		4.3				—				—
Other		(1.4	)			—				(0.5	)
Change in valuation allowance		(4.4	)			(17.3	)			(27.6	)
Total		12.5		%		0.0		%		0.0		%

Deferred income taxes reflect the net effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The principal components of the Company’s deferred tax assets consisted of the following:

	December 31,
	2021			2020
Deferred tax assets (liabilities)
Net operating loss carryforwards	$	—		$	14,069
License agreement		6,261			—
Stock-based compensation		5,643			1,072
Research and development credits		—			1,791
Other		256			53
Prepaid expenses		(1,256	)		—
Gross deferred tax assets (liabilities)		10,904			16,985
Less: valuation allowance		(10,904	)		(16,985	)
Net deferred tax assets (liabilities)	$	—		$	—

As of December 31, 2021, the Company had federal net operating losses of $377 and state net operating loss carryforwards of $9, which may be used to offset future tax liabilities. The federal net operating losses and research and development tax credits begin to expire in 2034. The Company utilized net operating losses and research and development tax credit carryforwards of $52,820 and $665, respectively.

Management has evaluated the positive and negative evidence bearing upon the realizability of the Company’s deferred tax assets. Based on the Company’s projected net operating losses for 2022 and beyond, the Company determined that it is more likely than not that it will not recognize the benefits of the deferred tax assets. As a result, the Company has recorded a full valuation allowance of approximately $10,904 at December 31, 2021. The Company recorded a net decrease of $6,081 to its valuation allowance for the year ended December 31, 2021 as a result of utilization of certain net operating loss and research and development credit carryforwards during 2021 and in order to maintain a full valuation allowance against its remaining deferred tax assets.

Under the provisions of Sections 382 and 383 of the Internal Revenue Code (the “IRC”), net operating loss and credit carryforwards and other tax attributes may be subject to limitation if there has been a significant change in ownership of the Company, as defined by the IRC.

The Company performed an analysis through December 31, 2020 pursuant to Section 382 of the IRC to determine whether any limitations might exist on the utilization of net operating losses and other tax attributes. Based on this analysis, the Company has determined that ownership changes occurred in 2014, resulting in an annual limitation of $169 on the use of its net operating losses and other tax attributes generated prior to the ownership change. In addition, based on publicly available statements of acquisition of beneficial ownership, the Company identified an ownership change on December 31, 2021 which did not have an impact on the Company’s consolidated financial statements. The Company is in the process of completing a Section 382 study for the fiscal year 2021, the results of which could indicate that the ownership shift occurred prior to December 31, 2021. Should a shift have occurred prior to December 31, 2021, any resulting limitation is not expected to have a material impact on the Company’s consolidated financial statements. To the extent that the Company raises additional equity financing or other changes in the ownership interest of significant stockholders occurs, additional tax attributes may become subject to an annual limitation. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities.

The Company files federal and various state income tax returns. The statute of limitations for assessment by the Internal Revenue Service (the “IRS”), and state tax authorities remains open for all tax years ended since the inception of the Company. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the IRS or state tax authorities to the extent utilized in a future period. No federal or state tax audits are currently in process.

The Company evaluates tax positions for recognition using a more-likely-than-not recognition threshold, and those tax positions eligible for recognition are measured as the largest amount of tax benefit that is greater than 50% likely of being realized upon the effective settlement with a taxing authority that has full knowledge of all relevant information. During the year ended December 31, 2021, the Company recorded an unrecognized tax benefit of $5,932 related to certain tax positions which is included in other liabilities in the consolidated balance sheet. The Company did not have any unrecognized tax benefits prior to the year ended December 31, 2021.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

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Stock-based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Jan. 31, 2022	Jan. 31, 2021	Oct. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance				19,667,801	16,163,783
Unrecognized compensation expense				$ 128,036
Remaining weighted average period for recognize compensation expense				2 years 8 months 12 days
Weighted average grant date fair value per option granted				$ 39.10	$ 14.93	$ 1.19
Fair value assumptions, method used				Black-Scholes
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested shares				0
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting contractual term				10 years
2020 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of shares of common stock Outstanding			5.00%
Increased number of shares available under incentive plan		4,130,847
Common stock, capital shares reserved for future issuance				7,963,829
2020 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance			1,187,000
Shares issued				0
Subsequent Event \| 2020 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increased number of shares available under incentive plan	4,155,136
Maximum \| Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting service period				4 years
Maximum \| 2020 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for grant			7,924,000
Maximum \| 2013 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for grant							7,807,200
Minimum \| Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting service period				3 years

Net Income (Loss) Per Share Attributable to Common Stockholders - Summary of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net income (loss)	$ 121,190	$ (10,947)	$ (14,034)
Weighted average common shares outstanding, basic	82,820,037	21,592,441	10,091,100
Dilutive effect of outstanding stock options	5,429,206
Weighted average common shares outstanding, diluted	88,249,243	21,592,441	10,091,100
Net income (loss) per share, basic	$ 1.46	$ (0.51)	$ (1.39)
Net income (loss) per share, diluted	$ 1.37	$ (0.51)	$ (1.39)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2021

Accounting Policies [Abstract]

Basis of Presentation and Use of Estimates

The accompanying consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America, or GAAP.

Principles of Consolidation

Revenue Recognition

Through December 31, 2021, all of the Company’s revenue was collaboration revenue generated from the Roche License Agreement.

Contract costs

Cash and Cash Equivalents

Concentrations of Credit Risk and Significant Suppliers

Fair Value Measurement

Fair Value Measurements

Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determination of fair value of the assets or liabilities.

Property and Equipment

Asset		Estimated useful life
Laboratory equipment		Five years
Office furniture and fixtures		Five years
Computer hardware		Two years
Leasehold improvements		Shorter of useful life or remaining lease term

Other Assets

Other assets consist of a right-of-use asset of $161 and bank deposits of $305, classified as restricted cash, to collateralize two letters of credit.

Impairment of Long-lived Assets

Research and Development Costs

Patent Costs

Costs to secure and maintain the Company’s patents are expensed as incurred and are classified as general and administrative expenses in the Company’s consolidated statements of operations.

Stock-based Compensation

Black-Scholes requires the use of subjective assumptions which determine the fair value of stock-based awards. These assumptions include:

Fair value of common stock

•	external market conditions affecting the pharmaceutical and biotechnology industry and trends within the industry;

•	the Company’s stage of development and business strategy;

•	the rights, preferences and privileges of the Company’s then-outstanding redeemable convertible preferred stock relative to those of its common stock;

•	the prices at which the Company sold shares of its then-outstanding redeemable convertible preferred stock;

•	the Company’s financial condition and operating results, including its levels of available capital resources;

•	the progress of the Company’s research and development efforts;

•	equity market conditions affecting comparable public companies; and

•	general U.S. market conditions and the lack of marketability at the time of the Company’s common stock.

•

Upon the completion of the Company’s initial public offering, the fair value of its common stock is based on the daily closing quoted market price of its common stock.

The Company also accounts for any modifications to share based payments in accordance with ASC Topic 718, Compensation – Stock Compensation (ASC 718).

Income Taxes

Comprehensive Income (Loss)

Net Income (Loss) Per Share Attributable to Common Stockholders

In-process Research and Development Assets

Segments

SEC Filing Status

Recently Issued Accounting Pronouncements and Recently Adopted Accounting Pronouncements

Recently Issued Accounting Pronouncements

Recently Adopted Accounting Pronouncements

beginning of the earliest comparative period presented in the financial statements, with certain practical expedients available.

Convertible Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Oct. 31, 2020	May 31, 2020	Dec. 31, 2020	Dec. 31, 2021	Nov. 03, 2020	Dec. 31, 2019	Dec. 31, 2018
Class Of Stock [Line Items]
Preferred stock, shares authorized			10,000,000	10,000,000
Preferred stock, shares issued			0	0
Net proceeds from issuance of preferred stock			$ 214,116
Convertible Preferred Stock
Class Of Stock [Line Items]
Shares authorized						33,645,447
Shares issued						33,645,447
Shares outstanding						33,645,447	33,645,447
Series A Preferred
Class Of Stock [Line Items]
Shares authorized						20,000,000
Shares issued						20,000,000
Shares outstanding						20,000,000
Preferred stock purchase price						$ 1.00
Series B Preferred
Class Of Stock [Line Items]
Shares authorized						7,592,830
Shares issued						7,592,830
Shares outstanding						7,592,830
Preferred stock purchase price						$ 3.03
Series C Preferred
Class Of Stock [Line Items]
Shares authorized						6,052,617
Shares issued						6,052,617
Shares outstanding						6,052,617
Preferred stock purchase price						$ 4.56
Series D Preferred
Class Of Stock [Line Items]
Shares authorized		15,313,382
Shares issued		15,313,382
Net proceeds from issuance of preferred stock		$ 106,631
Series D-1 Preferred
Class Of Stock [Line Items]
Shares authorized		8,973,261
Shares issued	8,973,261
Preferred stock purchase price	$ 11.98
Net proceeds from issuance of preferred stock	$ 107,485
Common Stock \| IPO
Class Of Stock [Line Items]
Convertible preferred stock converted into shares					57,932,090

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Summary of Reconciliation of Federal Statutory Income Tax Rate to Effective Income Tax Rate

The reconciliation of federal statutory income tax rate to the Company’s effective income tax rate is as follows:

	For the Year Ended December 31,
	2021				2020				2019
Expected income tax benefit at the federal statutory rate		21.0		%		21.0		%		21.0		%
State and local taxes		3.2				(2.6	)			6.2
Research and development credits		(4.1	)			12.5				0.9
Stock-based compensation		—				(13.6	)			—
Foreign derived intangible income		(6.1	)			—				—
Uncertain tax positions		4.3				—				—
Other		(1.4	)			—				(0.5	)
Change in valuation allowance		(4.4	)			(17.3	)			(27.6	)
Total		12.5		%		0.0		%		0.0		%

Summary of Principal Components of Deferred Tax Assets

The principal components of the Company’s deferred tax assets consisted of the following:

	December 31,
	2021			2020
Deferred tax assets (liabilities)
Net operating loss carryforwards	$	—		$	14,069
License agreement		6,261			—
Stock-based compensation		5,643			1,072
Research and development credits		—			1,791
Other		256			53
Prepaid expenses		(1,256	)		—
Gross deferred tax assets (liabilities)		10,904			16,985
Less: valuation allowance		(10,904	)		(16,985	)
Net deferred tax assets (liabilities)	$	—		$	—

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Initial Public Offering
Stock issuance costs	$ 3,245
Series D Convertible Preferred Stock
Stock issuance costs	869
Series D-1 Convertible Preferred Stock
Stock issuance costs	$ 15

Stock-based Compensation - Summary of Assumptions Used to Estimate Fair Value of Award (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.80%
Risk-free interest rate, Minimum		0.31%	1.61%
Risk-free interest rate, Maximum		0.56%	2.02%
Expected term	5 years 11 months 26 days	6 years 3 months
Expected volatility	85.00%
Expected volatility, Minimum		80.00%	49.20%
Expected volatility, Maximum		91.70%	78.00%
Expected dividend yield	0.00%	0.00%	0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term			5 years 6 months 7 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term			10 years

Commitments and Contingencies - Summary of Assets and Liabilities Recorded on Consolidated Balance Sheet (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Commitments And Contingencies Disclosure [Abstract]
Right-of-use asset	$ 161
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	us-gaap:OtherAssets
Current lease liability	$ 197
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	us-gaap:OtherLiabilitiesCurrent

Collaboration Revenue - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended	12 Months Ended
	Nov. 30, 2020	Oct. 31, 2020	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation Of Revenue [Line Items]
Collaboration revenue				$ 351,367,000	$ 48,633,000
Unbilled other receivable					5,815,000
Research and development				167,205,000	38,023,000	$ 10,170,000
Accrued expenses and other current liabilities				52,349,000	14,368,000
Roche License Agreement
Disaggregation Of Revenue [Line Items]
Non-refundable upfront payment received	$ 350,000,000
Development Milestone Achieved			$ 50,000,000
Initial transaction price			$ 400,000,000	350,000,000
Collaboration revenue				351,367,000	48,633,000
Deferred revenue				0	301,367,000
Costs reimbursed amount				7,264,000	7,901,000
Unbilled other receivable					5,815,000
Research and development				76,567,000	$ 2,086,000
Accrued expenses and other current liabilities				$ 10,417,000
Roche License Agreement \| Maximum \| Development and Regulatory
Disaggregation Of Revenue [Line Items]
Milestones receivable upon achievement aggregate		$ 330,000,000
Roche License Agreement \| Maximum \| Sales Based
Disaggregation Of Revenue [Line Items]
Milestones receivable upon achievement aggregate		$ 320,000,000

Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment, at cost	$ 184	$ 180
Less: accumulated depreciation and amortization	(161)	(132)
Property and equipment, net	23	48
Laboratory Equipment
Property Plant And Equipment [Line Items]
Total property and equipment, at cost	5	5
Office Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment, at cost	13	13
Computer Hardware
Property Plant And Equipment [Line Items]
Total property and equipment, at cost	37	37
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment, at cost	$ 129	$ 125

Income Taxes - Summary of Principal Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets (liabilities)
Net operating loss carryforwards		$ 14,069
License agreement	$ 6,261
Stock-based compensation	5,643	1,072
Research and development credits		1,791
Other	256	53
Prepaid expenses	(1,256)
Gross deferred tax assets (liabilities)	10,904	16,985
Less: valuation allowance	(10,904)	(16,985)
Net deferred tax assets (liabilities)	$ 0	$ 0

Commitments and Contingencies - Summary of Future Minimum Payments under Operating Leases (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2022	$ 989
2023	805
2024	821
2025	838
2026	855
Total future minimum lease payments	$ 4,308

Related Party Transactions - Additional Information (Details) - Consulting Agreement - Director $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)
Related Party Transaction [Line Items]
Number of company directors in control of related party entity	one
Annual retainer	$ 110
Related party transaction expense	$ 67

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	83,102,730	82,436,937
Common stock, shares outstanding	83,102,730	82,436,937

Commitments and Contingencies - Summary of Remaining Lease Term and Discount Rate (Details)	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Remaining lease term (in years)	6 months
Discount rate	7.00%

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021 USD ($) Segment	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Accounting Policies [Line Items]
Recognition method for costs of obtaining a contract	The Company has elected the practical expedient in ASC 340, Other Assets and Deferred Costs, wherein it recognizes the incremental costs of obtaining a contract as an expense when incurred if, at inception, the expected amortization period of the asset that the Company otherwise would have recognized is one year or less.
Incremental cost included in general and administration costs	$ 45,785,000	$ 21,640,000	$ 4,438,000
Right-of-use asset	161,000
Impairment losses	$ 0	$ 0	$ 0
Expected dividend yield	0.00%	0.00%	0.00%
Comprehensive income or loss	$ 0	$ 0	$ 0
Number of operating segments \| Segment	1
Number of reportable segments \| Segment	1
Other Assets
Accounting Policies [Line Items]
Bank deposits, restricted cash	$ 305,000
Right-of-use asset	161,000
Incremental Cost \| Roche License
Accounting Policies [Line Items]
Incremental cost included in general and administration costs	$ 7,000,000

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Research and development, including manufacturing and clinical expenditures	$ 18,080	$ 10,546
License fee	25,000
Income taxes	2,572
Payroll and payroll related	4,209	2,743
Professional fees and other	2,488	1,079
Total accrued expenses and other current liabilities	$ 52,349	$ 14,368

Commitments and Contingencies - Additional Information (Details) - USD ($)		1 Months Ended	12 Months Ended
	Jul. 19, 2021	Feb. 28, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Loss Contingencies [Line Items]
Location of the additional office space	Boston, Massachusetts
Expected commencement date of sublease	Jan. 01, 2022
Expected end date of sublease	Dec. 31, 2026
Sublease monthly base rent	$ 66,000
Sublease monthly base rent, upward adjustment	2.00%
Rent expense			$ 318,000	$ 303,000	$ 305,000
Research and development			167,205,000	$ 38,023,000	$ 10,170,000
Maximum \| Business Development Consulting Agreements
Loss Contingencies [Line Items]
Success fee			5,000,000.0
Merck License Agreement \| Maximum \| Development and Regulatory
Loss Contingencies [Line Items]
Milestone payments			135,000,000
Merck License Agreement \| Maximum \| Sales-based
Loss Contingencies [Line Items]
Milestone payments			300,000,000
Merck License Agreement \| Subsequent Event
Loss Contingencies [Line Items]
Non-refundable upfront payment paid license agreement		$ 25,000,000
Other Assets \| Letter of Credit
Loss Contingencies [Line Items]
Bank deposits, restricted cash			305,000
Non-refundable Upfront Payment Accrued \| Merck License Agreement
Loss Contingencies [Line Items]
Research and development			$ 25,000,000

Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Cash equivalents
Total cash equivalents	$ 731,767	$ 846,701
Level 1
Cash equivalents
Total cash equivalents	731,767	846,701
Money Market Funds
Cash equivalents
Total cash equivalents	731,767	846,701
Money Market Funds \| Level 1
Cash equivalents
Total cash equivalents	$ 731,767	$ 846,701

Common Stock - Additional Information (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Equity [Abstract]
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	83,102,730	82,436,937
Common stock, shares outstanding	83,102,730	82,436,937
Common stock voting rights per share	On all matters to be voted upon by the holders of common stock, holders of common stock are entitled to one vote per share.

Benefit Plan - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan recognized expense related to matching contributions	$ 272
Maximum
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percentage	4.00%