Gritstone bio (GRTSQ) 10-Q 5 May 22 2022 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	May 03, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Document Quarterly Report	true
Document Transition Report	false
Trading Symbol	GRTS
Entity Registrant Name	Gritstone bio, Inc.
Entity Central Index Key	0001656634
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	true
Entity Small Business	true
Entity Ex Transition Period	true
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	001-38663
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	47-4859534
Entity Address, Address Line One	5959 Horton Street
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	Emeryville
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94608
City Area Code	510
Local Phone Number	871-6100
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		72,812,833

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 69,158	$ 93,287
Marketable securities	103,004	108,346
Restricted cash, current	9,395	11,285
Prepaid expenses and other current assets	10,946	7,672
Total current assets	192,503	220,590
Long-term restricted cash	5,290	6,005
Property and equipment, net	22,283	21,622
Lease right-of-use assets	21,832	22,920
Deposits and other long-term assets	1,564	2,352
Long-term marketable securities	0	4,617
Total assets	243,472	278,106
Current liabilities:
Accounts payable	5,641	4,230
Accrued compensation	4,285	6,925
Accrued liabilities	1,350	411
Accrued research and development expenses	3,601	3,706
Lease liabilities, current portion	6,886	7,483
Deferred revenue, current portion	12,324	17,201
Total current liabilities	34,087	39,956
Lease liabilities, net of current portion	18,689	18,936
Deferred revenue, net of current portion	1,505	3,128
Total liabilities	54,281	62,020
Commitments and contingencies (Notes 6 and 8)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding at March 31, 2022 and December 31, 2021	0	0
Common stock, $0.0001 par value; 300,000,000 shares authorized at March 31, 2022 and December 31, 2021; 72,779,508 and 69,047,878 shares issued and outstanding at March 31, 2022 and December 31, 2021, respectively	20	20
Additional paid-in capital	619,862	617,523
Accumulated other comprehensive loss	(391)	(73)
Accumulated deficit	(430,300)	(401,384)
Total stockholders’ equity	189,191	216,086
Total liabilities and stockholders’ equity	$ 243,472	$ 278,106

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
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	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	72,779,508	69,047,878
Common stock, shares outstanding	72,779,508	69,047,878

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Total revenues	$ 7,191	$ 39,693
Operating expenses:
Research and development	28,199	24,856
General and administrative	7,955	6,941
Total operating expenses	36,154	31,797
Income (Loss) from operations	(28,963)	7,896
Interest income, net	47	27
Net Income (loss)	(28,916)	7,923
Other comprehensive loss:
Unrealized loss on marketable securities	(318)	(3)
Net and comprehensive income (loss)	$ (29,234)	$ 7,920
Net income (loss) per share, basic	$ (0.34)	$ 0.10
Weighted-average number of shares used in computing net loss per share, basic	86,277,599	75,987,372
Net income (loss) per share, diluted	$ (0.34)	$ 0.10
Weighted-average number of shares used in computing net income (loss) per share, diluted	86,277,599	77,464,356
Collaboration and license revenues [Member]
Total revenues	$ 4,745	$ 39,693
Grant Revenues [Member]
Total revenues	$ 2,446	$ 0

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	ATM Equity Offering Program [Member]	Common Stock [Member]	Common Stock [Member]Private Investment In Public Equity [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Gain (Loss) [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2020	$ 166,739		$ 18		$ 493,023		$ (326,302)
Balance, shares at Dec. 31, 2020			47,552,693
Unrealized loss on marketable securities	(3)					(3)
Offering costs related to the sale of common stock and pre-funded warrants	(451)				(451)
Issuance of common stock under Sales Purchase Agreement, net of issuance costs	$ 20,839				20,839
Issuance of common stock under Sales Purchase Agreement, shares			1,169,591
Issuance of common stock, net of issuance costs, shares	1,169,591
Issuance of common stock under employee stock purchase plan (“ESPP”)	$ 279				279
Issuance of common stock under employee stock purchase plan (“ESPP”), shares			109,564
Issuance of common stock upon exercise of stock options	1,824				1,824
Issuance of common stock upon exercise of stock options, shares			365,980
Stock-based compensation	2,201				2,201
Net income (loss)	7,923						7,923
Balance at Mar. 31, 2021	199,351		$ 18		517,715	(3)	(318,379)
Balance, shares at Mar. 31, 2021			49,197,828
Balance at Dec. 31, 2020	$ 166,739		$ 18		493,023		(326,302)
Balance, shares at Dec. 31, 2020			47,552,693
Issuance of common stock, net of issuance costs, shares	3,990,869
Balance at Dec. 31, 2021	$ 216,086		$ 20		617,523	(73)	(401,384)
Balance, shares at Dec. 31, 2021			69,047,878
Unrealized loss on marketable securities	(318)					(318)
Issuance of common stock upon restricted stock units vesting, net of shares withheld, Shares				215,350
Tax payments related to shares withheld for vested restricted stock units	(890)				(890)
Issuance of common stock, net of issuance costs, shares		0
Issuance of common stock for warrant exercises, Value	34				34
Issuance of common stock for warrant exercises, shares			3,442,567
Issuance of common stock upon exercise of stock options	$ 64				64
Issuance of common stock upon exercise of stock options, shares	73,713		73,713
Stock-based compensation	$ 3,131				3,131
Net income (loss)	(28,916)						(28,916)
Balance at Mar. 31, 2022	$ 189,191		$ 20		$ 619,862	$ (391)	$ (430,300)
Balance, shares at Mar. 31, 2022			72,779,508

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Common Stock [Member] | Follow On Public Offering [Member]
Payment for issuance cost under Sales Purchase Agreement	$ 330

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Operating activities
Net income (loss)	$ (28,916)	$ 7,923
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,589	1,595
Net amortization of premiums and discounts on marketable securities	196	107
Stock-based compensation	3,131	2,201
Non-cash operating lease expense	2,332	1,900
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(3,273)	(182)
Deposits and other long-term assets	787	(7)
Accounts payable	1,861	1,637
Accrued compensation	(2,640)	(2,510)
Accrued and other non-current liabilities	121	(51)
Accrued research and development expenses	(105)	505
Lease liability	(2,034)	(1,950)
Deferred revenue	(6,500)	(514)
Net cash provided by (used in) operating activities	(33,451)	10,654
Investing activities
Purchase of marketable securities	(28,342)	(89,610)
Maturities of marketable securities	26,573	1,000
Sales of marketable securities	11,215	0
Purchase of property and equipment	(1,812)	(990)
Net cash provided by (used in) investing activities	7,634	(89,600)
Financing activities
Payments of financing costs	(69)	(5,878)
Payments of financing lease	(56)	0
Tax payments related to shares withheld for vested restricted stock units	(890)	0
Net cash provided by (used in) financing activities	(917)	17,395
Net decrease in cash, cash equivalents and restricted cash	(26,734)	(61,551)
Cash, cash equivalents and restricted cash at beginning of period	110,577	171,048	$ 171,048
Cash, cash equivalents and restricted cash at end of period	83,843	109,497	110,577
Supplemental disclosures of non-cash investing and financing information
Property and equipment purchases accrued but not yet paid	1,182	509
Financing costs included in accrued liabilities and accounts payable	0	46
Remeasurement of operating lease right-of-use asset for lease modification	228	0
Public Offering [Member]
Financing activities
Proceeds from issuance of common stock	0	21,170
Stock Options, Warrants and Other [Member]
Financing activities
Proceeds from issuance of common stock	98	1,824
ATM Equity Offering Program [Member]
Financing activities
Proceeds from issuance of common stock			$ 9,800
ESPP [Member]
Financing activities
Proceeds from issuance of common stock	$ 0	$ 279

Organization

Organization	3 Months Ended
	Mar. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Description of Business Gritstone bio, Inc. (“Gritstone” or the “Company”) is a clinical-stage bio technology company developing next generation vaccines for solid tumors and viral diseases. The Company was incorporated in the state of Delaware in August 2015, and is headquartered in Emeryville, California with a site in Cambridge, Massachusetts and a manufacturing facility in Pleasanton, California. The Company operates in one segment. Liquidity The Company has incurred operating losses and has an accumulated deficit as a result of ongoing efforts to develop drug product candidates, including conducting preclinical and clinical trials and providing general and administrative support for these operations. The Company had a net loss of $ 28.9 million for the three months ended March 31, 2022 and net income of $ 7.9 million for the three months ended March 31, 2021. During the three months ended March 31, 2022, cash used by operating activities was $ 33.5 million. During the three months ended March 31, 2021, cash provided by operating activities was $ 10.7 million. The Company had an accumulated deficit of $ 430.3 million and $ 401.4 million as of March 31, 2022 and December 31, 2021, respectively. To date, none of the Company’s product candidates have been approved for sale and therefore the Company has not generated any revenue from sales of commercial products. Management expects operating losses to continue for the foreseeable future. The Company has funded its operations to date primarily through private placements of its convertible preferred stock, the sale of common stock in public offerings and under an “at the market offering”, the private placement of common stock and pre-funded warrants, and through proceeds received from its collaboration arrangements. As of March 31, 2022, the Company had cash, cash equivalents and marketable securities of $ 172.2 million , which the Company believes will be sufficient to fund its planned operations for a period of at least twelve months following the filing date of this report.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying interim condensed consolidated financial statements are unaudited and are comprised of the consolidation of the Company and its wholly-owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation. The Company has no unconsolidated subsidiaries or investments accounted for under the equity method. The accompanying interim condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) and the rules and regulations of the Securities and Exchange Commission (the “SEC”) for interim reporting. The interim condensed consolidated financial statements are unaudited and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, necessary for the fair presentation for interim reporting. The results of operations for any interim period are not necessarily indicative of results of operations for any future period. Certain information and footnote disclosures typically included in annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements as of and for the year ended December 31, 2021, which are included in the Company’s Annual Report on Form 10-K, as filed with the SEC on March 10, 2022 . Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the reported amounts of assets and liabilities and disclosures of contingent liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates. Fair Value of Financial Instruments U.S. GAAP establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances. Fair value is established as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, an established three-tier fair value hierarchy distinguishes between the following: • Level 1 inputs are quoted prices in active markets that are accessible at the market date for identical assets or liabilities. • Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. • Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the assets or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value instrument. The carrying amounts reflected on the condensed consolidated balance sheets for cash and cash equivalents, prepaid expenses and other current assets, accounts payable, accrued compensation and accrued liabilities approximate their fair values due to their short-term nature. Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist of cash, cash equivalents and marketable securities. Cash, cash equivalents and marketable securities are invested through banks and other financial institutions in the United States. Such deposits may be in excess of federally insured limits. The Company maintains cash equivalents and marketable securities with various high-credit-quality and capitalized financial institutions. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. The Company’s investment policy limits investments to certain types of securities issued by the U.S. government, its agencies, and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents and marketable securities and issuers of marketable securities to the extent recorded on the condensed consolidated balance sheets. As of March 31, 2022, the Company has no off-balance sheet concentrations of credit risk. Other Risks and Uncertainties The Company is subject to a number of risks similar to those of other clinical-stage biotechnology companies, including dependence on key individuals; the need to develop commercially viable therapeutics; competition from other companies, many of which are larger and better capitalized; and the need to obtain adequate additional financing to fund the development of its products. The Company currently depends on third-party suppliers for key materials and services used in its research and development manufacturing process and is subject to certain risks related to the loss of these third-party suppliers or their inability to supply the Company with adequate materials and services. In March 2020, the World Health Organization declared the global novel coronavirus disease (“COVID-19”) outbreak a pandemic. To date, the Company’s business has not been materially impacted by the COVID-19 pandemic. However, the Company has experienced slowing of patient recruitment and sample collection in its ongoing clinical trials and cannot at this time predict the specific extent, duration, or full impact that the COVID-19 pandemic will have on its financial condition and operations, including ongoing and planned clinical trials. The impact of the COVID-19 pandemic on the financial performance of the Company will depend on future developments, including the duration and spread of the outbreak and related governmental advisories and restrictions. These developments and the impact of COVID-19 on the financial markets and the overall economy are highly uncertain. If the financial markets and/or the overall economy are impacted for an extended period, the Company’s results may be adversely affected. Cash, Cash Equivalents and Restricted Cash Cash equivalents, which consist primarily of highly liquid investments with original maturities of three (3) months or less when purchased, are stated at fair value. These assets include investments in money market funds that invest in U.S. Treasury obligations and certificates of deposit, which are stated at fair value. The Company has issued letters of credit under certain lease agreements that have been collateralized by cash deposits for an equal amount and are recorded within short-term restricted cash and deposits and other long-term assets on the condensed consolidated balance sheets based on the term of the underlying lease. Additionally, the Company’s restricted cash includes payments received under the Coalition for Epidemic Preparedness Innovations (“CEPI”) Funding Agreement, dated as of August 14, 2021 (the “CEPI Funding Agreement”) and the Gates Foundation Grant Agreement (see Note 8). The Company will utilize the CEPI and Gates Foundation funds as it incurs expenses for services performed under the agreements. The following table provides a reconciliation of cash, cash equivalents and short-term and long-term restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows (in thousands): March 31, December 31, 2022 2021 Cash and cash equivalents $ 69,158 $ 93,287 Restricted cash 9,395 11,285 Long-term restricted cash 5,290 6,005 Total cash, cash equivalents and restricted cash $ 83,843 $ 110,577 Leases The Company determines whether the arrangement is or contains a lease at the inception of the arrangement and if such a lease is classified as a financing lease or operating lease. The majority of the Company’s leases are classified as operating leases. Leases with a term greater than one year are included in operating lease ROU Assets, lease liabilities, current portion, and lease liabilities, net of current portion in the Company’s condensed consolidated balance sheets as of March 31, 2022 and December 31, 2021. The Company has elected not to recognize on the condensed consolidated balance sheets leases with terms of one year or less. Lease liabilities and their corresponding ROU Assets are recorded based on the present value of lease payments over the expected lease term. In determining the net present value of lease payments, the interest rate implicit in lease contracts is typically not readily determinable. As such, the Company estimates the appropriate incremental borrowing rate, which is the rate that would be incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. Certain adjustments to the ROU Assets may be required for items such as initial direct costs paid or incentives received and impairment charges if we determine the ROU Asset is impaired. The Company considers a lease term to be the non-cancelable period that it has the right to use the underlying asset, including any periods where it is reasonably assured the Company will exercise the option to extend the contract. Periods covered by an option to extend are included in the lease term if the lessor controls the exercise of that option. The Company recognizes lease expense on a straight-line basis over the expected lease term. The Company has elected not to separate lease and non-lease components for its leased assets and accounts for all lease and non-lease components of its agreements as a single lease component. The lease components resulting in a ROU Asset have been recorded on the condensed consolidated balance sheets and amortized as lease expense on a straight-line basis over the lease term. Revenue Recognition The Company performs research and development under collaboration, license, grant, and clinical development agreements. The Company’s revenue primarily consists of collaboration agreements and grant agreements. At contract inception, the Company analyzes a revenue arrangement to determine the appropriate accounting under U.S. GAAP. Currently, the Company’s revenue arrangements represent customer contracts within the scope of ASC Topic 606, Revenue from Contracts with Customers (Topic 606) (“ASC 606”) or are subject to the contribution guidance in ASC Topic 958-605, Not-for-Profit Entities – Revenue Recognition (“ASC 958-605”), which applies to business entities that receive contributions within the scope of ASC 958-605. For collaboration agreements, the Company analyzes to assess 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 dependent on the commercial success of such activities. This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. For collaboration arrangements that are considered to be in the scope of the collaboration guidance and that contain multiple elements, the Company first determines which elements of the collaboration are deemed to be within the scope of the collaboration guidance and those that are more reflective of a vendor-customer relationship and, therefore, within the scope of the revenue with contracts with customers guidance. Elements of collaboration arrangements that are reflective of a vendor-customer relationship are accounted for pursuant to the revenue from contracts with customers guidance. The terms of the licensing and collaboration agreements entered into typically include payment of one or more of the following: non-refundable, up-front fees; development, regulatory, and commercial milestone payments; payments for manufacturing supply services; and royalties on net sales of licensed products. Each of these payments results in license, collaboration and other revenues, except for revenues from royalties on net sales of licensed products, which are classified as royalty revenues. The core principle of the accounting for revenue from contracts with customers guidance is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received in exchange for those goods or services. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s condensed consolidated balance sheets. If the related performance obligation is expected to be satisfied within the next twelve (12) months, this will be classified in current liabilities. Amounts recognized as revenue prior to receipt are recorded as contract assets in the Company’s condensed consolidated balance sheets. If the Company expects to have an unconditional right to receive consideration in the next twelve (12) months, this will be classified in current assets. A net contract asset or liability is presented for each contract with a customer. At contract inception, the Company assesses the goods or services promised in a contract with a customer and identifies those distinct goods and services that represent a performance obligation. A promised good or service may not be identified as a performance obligation if it is immaterial in the context of the contract with the customer, if it is not separately identifiable from other promises in the contract (either because it is not capable of being separated or because it is not separable in the context of the contract), or if the performance obligation does not provide the customer with a material right. The Company considers the terms of the contract and its customary business practices to determine the transaction price. The transaction price is the amount of consideration to which the Company expects to be entitled in exchange for transferring promised goods or services to a customer. The consideration promised in a contract with a customer may include fixed amounts, variable amounts, or both. Variable consideration will only be included in the transaction price when it is not considered constrained, which is when it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur. If it is determined that multiple performance obligations exist, the transaction price is allocated at the inception of the agreement to all identified performance obligations, based on the relative standalone selling prices. The relative selling price for each performance obligation is estimated using objective evidence if it is available. If objective evidence is not available, the Company uses its best estimate of the selling price for the performance obligation. Revenue is recognized when, or as, the Company satisfies a performance obligation by transferring a promised good or service to a customer. An asset is transferred when, or as, the customer obtains control of that asset, which for a service is considered to be as the services are received and used. The Company recognizes revenue over time by measuring the progress toward complete satisfaction of the relevant performance obligation, using an appropriate input or output method based on the nature of the good or service promised to the customer. After contract inception, the transaction price is reassessed at every period end and updated for changes, such as resolution of uncertain events. Any change in the transaction price is allocated to the performance obligations on the same basis as at contract inception. Management may be required to exercise considerable judgment in estimating revenue to be recognized. Judgment is required in identifying performance obligations, estimating the transaction price, estimating the stand-alone selling prices of identified performance obligations (which may include forecasted revenue, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success) and estimating the progress towards satisfaction of performance obligations. For grant funding agreements, grant revenue is recognized during the period that the research and development services occur, as qualifying expenses are incurred. The Company concluded that payments received under these grants represent nonreciprocal contributions, as described in ASC 958, Not-for-Profit Entities, and that the grants are not within the scope of ASC 606 as the organization providing the grant does not meet the definition of a customer. Grant revenue relates primarily to the CEPI and Gates Funding Agreements (see Note 8). Income Taxes On March 18, 2020, the Families First Coronavirus Response Act (the “FFCR Act”), and on March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) were each enacted in response to the COVID-19 pandemic. The FFCR Act and the CARES Act contain numerous income tax provisions relating to refundable payroll tax credits, deferment of employer side social security payments, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property. On June 29, 2020, Assembly Bill 85 (“A.B. 85”) was signed into California law. A.B. 85 provides for a three-year suspension of the use of net operating losses for medium and large businesses and a three-year cap on the use of business incentive tax credits to offset no more than $ 5.0 million of tax per year. A.B. 85 suspends the use of net operating losses for taxable years 2020 and 2021 for certain taxpayers with taxable income of $ 1.0 million or more. The carryover period for any net operating losses that are suspended under this provision will be extended. A.B. 85 also requires that business incentive tax credits, including carryovers, may not reduce the applicable tax by more than $ 5.0 million for taxable years 2020 and 2021. The FFCR Act, CARES Act and A.B. 85 did not have a material impact on the Company’s condensed consolidated financial statements as of March 31, 2022; however, the Company continues to examine the impacts the FFCR Act, CARES Act and A.B. 85 may have on its business, results of operations, financial condition, liquidity and related disclosures. Recently Adopted Accounting Pronouncements In October 2020, the FASB issued ASU No. 2020-10, Codification Improvements (“ASU 2020-10”). The standard contains improvements to the FASB Accounting Standards Codification (the “Codification”) by ensuring that all guidance that requires or provides an option for an entity to provide information in the notes to financial statements is codified in the disclosure section of the Codification. The standard also improves various topics in the Codification so that entities can apply guidance more consistently on codifications that are varied in nature where the original guidance may have been unclear. The amendments in ASU 2020-10 are effective for the Company for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption is permitted. We adopted ASU 2020-10 on January 1, 2022 and the adoption did not have a material impact on the Company's condensed consolidated financial statements and related disclosures. Recently Issued Accounting Pronouncements Not Yet Adopted In August 2020, the FASB issued ASU No. 2020-06, Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (“ASU 2020-06”). The standard eliminates the beneficial conversion and cash conversion accounting models for convertible instruments. It also amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions. In addition, the standard modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted EPS computation. The amendments in ASU 2020-06 are effective for the Company as defined by the SEC for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted, but not earlier than fiscal years beginning after December 15, 2020. The Company does not expect the adoption of ASU 2020-06 to have a material impact on its condensed consolidated financial statements and related disclosures.

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	3 Months Ended
	Mar. 31, 2022
Cash and Cash Equivalents [Abstract]
Cash Equivalents and Marketable Securities	3. Cash Equivalents and Marketable Securities The amortized costs, unrealized gains and losses and fair values of cash equivalents and marketable securities were as follows (in thousands): March 31, 2022 Description Amortized Unrealized Unrealized Fair Cash equivalents: Money market funds $ 45,083 $ — $ — $ 45,083 Commercial paper 2,999 — — 2,999 U.S. treasuries 5,000 — — 5,000 Asset backed securities 1,001 1,001 Total cash equivalents 54,083 — — 54,083 Short-term marketable securities: Certificates of deposit 4,650 — ( 33 ) 4,617 Commercial paper 35,451 — ( 136 ) 35,315 Corporate debt securities 21,212 — ( 94 ) 21,118 U.S. treasuries 34,792 — ( 100 ) 34,692 U.S. government debt securities 2,000 — ( 4 ) 1,996 Asset backed securities 5,290 — ( 24 ) 5,266 Total short-term marketable securities 103,395 — ( 391 ) 103,004 Total $ 157,478 $ — $ ( 391 ) $ 157,087 December 31, 2021 Description Amortized Unrealized Unrealized Fair Cash equivalents: Money market funds $ 79,281 $ — $ — $ 79,281 Commercial paper 1,000 — — 1,000 Corporate debt securities 1,031 — — 1,031 Total cash equivalents 81,312 — — 81,312 Short-term marketable securities: Certificates of deposit 5,600 — ( 6 ) 5,594 Commercial paper 44,990 — ( 16 ) 44,974 Corporate debt securities 26,976 — ( 23 ) 26,953 U.S. treasuries 12,277 — ( 8 ) 12,269 U.S. government debt securities 2,000 — ( 1 ) 1,999 Asset backed securities 16,565 — ( 8 ) 16,557 Total short-term marketable securities 108,408 — ( 62 ) 108,346 Long-term marketable securities: Corporate debt securities 1,637 — ( 6 ) 1,631 U.S. treasuries 2,991 — ( 5 ) 2,986 Total long-term marketable securities 4,628 — ( 11 ) 4,617 Total $ 194,348 $ — $ ( 73 ) $ 194,275 All marketable securities held as of March 31, 2022 had contractual maturities of less than one year . There have been no material realized gains or losses on marketable securities for the periods presented. As of March 31, 2022, the Company did no t hold any individual securities in an unrealized loss position for 12 months or greater . The Company has the ability and intent to hold all marketable securities that have been in a continuous loss position until maturity or recovery. No significant facts or circumstances have arisen to indicate that there has been any significant deterioration in the creditworthiness of the issuers of the securities held by us. The Company considered the current and expected future economic and market conditions and determined that the estimate of credit losses was not significantly impacted. Thus, no credit loss existed as of or for the three months ended March 31, 2022 or December 31, 2021. The Company will continue to assess the current and expected future economic and market conditions as further development arises. See Note 4 for further information regarding the fair value of the Company’s financial instruments.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The Company’s financial assets subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands): March 31, 2022 Description Total Level 1 Level 2 Level 3 Cash equivalents: Money market funds $ 45,083 $ 45,083 $ — $ — Commercial paper 2,999 — 2,999 — U.S. treasuries 5,000 5,000 — — Asset backed securities 1,001 — 1,001 — Total cash equivalents 54,083 50,083 4,000 — Short-term marketable securities: Certificates of deposit 4,617 — 4,617 — Commercial paper 35,315 — 35,315 — Corporate debt securities 21,118 — 21,118 — U.S. treasuries 34,692 34,692 — — U.S. government debt securities 1,996 — 1,996 — Asset backed securities 5,266 — 5,266 — Total short-term marketable securities 103,004 34,692 68,312 — Total $ 157,087 $ 84,775 $ 72,312 $ — December 31, 2021 Description Total Level 1 Level 2 Level 3 Cash equivalents: Money market funds $ 79,281 $ 79,281 $ — $ — Commercial paper 1,000 — 1,000 — Corporate debt securities 1,031 — 1,031 — Total cash equivalents 81,312 79,281 2,031 — Short-term marketable securities: Certificates of deposit 5,594 — 5,594 — Commercial paper 44,974 — 44,974 — Corporate debt securities 26,953 — 26,953 — U.S. treasuries 12,269 12,269 — — U.S. government debt securities 1,999 — 1,999 — Asset backed securities 16,557 — 16,557 — Total short-term marketable securities 108,346 12,269 96,077 — Long-term marketable securities: Corporate debt securities 1,631 — 1,631 — U.S. treasuries 2,986 2,986 — — Total long-term marketable securities 4,617 2,986 1,631 — Total $ 194,275 $ 94,536 $ 99,739 $ — The Company measures the fair value of money market funds based on quoted prices in active markets for identical securities. Commercial paper, corporate debt securities, certificates of deposits, asset backed securities, and U.S. government debt securities are valued taking into consideration valuations obtained from third-party pricing services. These pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of, and broker/dealer quotes on, the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs. There were no transfers between Level 1 and Level 2 during the periods presented. See Note 3 for further information regarding the amortized cost of our financial instruments.

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2022
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	5. Property and Equipment, Net Property and equipment and related accumulated depreciation and amortization are as follows (in thousands): March 31, December 31, 2022 2021 Computer equipment and software $ 997 $ 987 Furniture and fixtures 2,113 2,113 Laboratory equipment 25,057 24,679 Leasehold improvements 14,128 14,128 42,295 41,907 Less accumulated depreciation and amortization ( 23,837 ) ( 22,276 ) Construction-in-progress 3,825 1,991 Total property and equipment, net $ 22,283 $ 21,622 Depreciation and amortization expense was $ 1.6 million and $ 1.6 million for the three months ended March 31, 2022 and 2021, respectively.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies Leases The Company leases office, laboratory and storage space in facilities at several locations: Emeryville Lease The Company’s principal executive offices in Emeryville, California, consisting of office and laboratory space, are leased pursuant to a 120-month operating lease (the “Emeryville Lease”), which the Company entered into in January 2019, with the obligation to pay rent commencing in November 2019. In conjunction with signing the Emeryville Lease, the Company paid a cash security deposit of $ 0.6 million, which is recorded as a deposit on the Company’s condensed consolidated balance sheet as of March 31, 2022. The Emeryville Lease includes a free rent period, an escalation clause for increased rent and a renewal provision allowing the Company to extend this lease for an additional two five-year periods at the then market rental rate. The lessor provided the Company a tenant improvement allowance for a total of $ 4.0 million to complete the laboratory and office renovation. The Company has determined the tenant improvements to be lessee owned and therefore has recorded a $ 8.6 million ROU Asset and a $ 13.6 million lease liability on the condensed consolidated balance sheet as of March 31, 2022. The Company recorded a $ 8.7 million ROU Asset and a $ 13.9 million lease liability on the condensed consolidated balance sheet as of December 31, 2021. Pleasanton Leases The Company leases 42,620 square feet of office, cleanroom, and laboratory support manufacturing space in Pleasanton, California pursuant to a non-cancelable operating lease (the “Pleasanton Lease”), which the Company entered into in March 2017, with the obligation to pay rent commencing in December 2017. The Pleasanton Lease includes a free rent period, escalating rent payments and a term that expires on November 30, 2024 . The Company may extend the lease term for a period of five years at the then market rental rate. The Company obtained an irrevocable letter of credit in March 2017 in the initial amount of approximately $ 1.0 million as a security deposit to the Pleasanton Lease, which may be drawn down by the landlord in the event the Company fails to fully and faithfully perform its obligations under the Pleasanton lease. The letter of credit may be reduced based on certain levels of cash and cash equivalents the Company holds. As of March 31, 2022, none of the irrevocable letter of credit amount had been drawn. The Pleasanton Lease further provides that the Company is obligated to pay to the landlord its proportionate share of certain basic operating costs, including taxes and operating expenses. In connection with the Pleasanton Lease, the Company received a tenant improvement allowance of $ 1.2 million from the landlord for the costs associated with the design, development and construction of tenant improvements. The unamortized tenant improvement balance is recognized as a component of operating lease ROU Assets on the condensed consolidated balance sheets as of March 31, 2022 and December 31, 2021. In addition, in May 2019, the Company entered into a 64-month non-cancelable operating lease for additional office space in Pleasanton, California, with an obligation to pay rent commencing in August 2019. In January 2022, the Company amended the lease to add additional leased space and extend the lease expiration date to February 2027. Cambridge Leases The Company leases laboratory, office and storage space in several facilities in Cambridge, Massachusetts, pursuant to three separate agreements: The Company’s facility located at 40 Erie Street in Cambridge, Massachusetts is leased pursuant to a 67-month non-cancelable operating lease (the “40 Erie Lease”), which the Company entered into in February 2016, with an obligation to pay rent commencing in October 2016. The lessor provided the Company a tenant improvement allowance for a total of $ 2.1 million to complete the laboratory and office renovation. In September 2021, the Company executed an amendment to the 40 Erie Lease, which extends its term through April 2025 and provides for monthly base rent amounts, subject to annual increases over the term of the lease. The Company’s facility located at 21 Erie Street in Cambridge, Massachusetts is leased pursuant to a 24-month non-cancelable operating lease (the “21 Erie Lease”), which the Company entered into in September 2018. The 21 Erie Lease has since been amended three times, as a result of which the lease term extends through January 2023 . In March 2021, the Company entered into a 17-month operating lease (the “Cambridge Storage Lease”) for additional office and laboratory storage space in Cambridge, Massachusetts, which commenced on April 1, 2021 . The Company also paid an insignificant cash security deposit. In conjunction with the 40 Erie Lease, the 21 Erie Lease and the Cambridge Storage Lease, each as amended (if applicable), the Company has paid certain cash security deposits, which in each case included amounts for the applicable last month’s rent and has been classified as part of the operating lease ROU Assets. Of the $ 0.7 million security deposits, $ 0.4 million was recorded in prepaids and other assets on the Company's condensed consolidated balance sheet and the remaining $ 0.3 million was recorded in deposits and other long-term assets on the Company's condensed consolidated balance sheet as of March 31, 2022. Security deposits of $ 0.7 million are recorded in deposits and other long-term assets on the Company's condensed consolidated balance sheet as of December 31, 2021. Boston Lease The Company plans to occupy a newly-built facility in Boston, Massachusetts, with office and laboratory space, in 2023 pursuant to a 120-month operating lease (the “Boston Lease”), which the Company entered into in September 2021. The Boston Lease includes a free rent period, an escalation clause for increased rent and a renewal provision allowing the Company to extend the Boston Lease for two additional five-year periods at the then market rental rate. The landlord provided the Company with a tenant improvement allowance of up to approximately $ 19.1 million for costs relating to the design, permitting and construction of improvements. The Company’s obligation to pay rent is expected to commence in the second half of 2023, subject to free rent periods of three and six months with respect to certain premises. The Company expects to be provided early access to the premises to install fixtures and equipment 60 days prior to the anticipated rent commencement date. The Boston Lease is expected to expire in 2033. The Boston Lease further provides that the Company is obligated to pay to the landlord its proportionate share of certain basic operating costs, including taxes and operating expenses. In connection with the Boston Lease and as a security deposit thereunder, the Company has provided the landlord an irrevocable letter of credit in the amount of approximately $ 4.6 million, which is collateralized by a restricted cash deposit of $ 4.7 million, and which may be reduced in the fifth and seventh years of the Boston Lease. As of March 31, 2022, none of the irrevocable letter of credit amount had been drawn. As of March 31, 2022, the Company has not recognized a ROU Asset or lease liability for the Boston Lease as it did not control the underlying assets at any time in the three months ended March 31, 2022. Under the Boston Lease, the Company is obligated to make minimum lease payments of approximately $ 79.1 million for the years from 2023 to 2033, which includes rent abatement during the free rent periods. The Company’s operating leases include various covenants, indemnities, defaults, termination rights, security deposits and other provisions customary for lease transactions of this nature. The components of lease costs, which were included in our condensed consolidated statements of operations and comprehensive income (loss), were as follows (in thousands): Three Months Ended March 31, 2022 2021 Lease cost Operating lease cost $ 2,253 $ 1,900 Total lease cost $ 2,253 $ 1,900 Supplemental information related to leases was as follows: Three Months Ended March 31, 2022 2021 Cash paid for amounts included in the measurement of Operating cash flows from operating leases $ 2,034 $ 1,950 New right-of-use assets obtained in exchange for lease Operating leases $ 781 $ — Weighted-average remaining lease term (years): Operating leases 5.3 6.1 Weighted-average discount rate: Operating leases 7.4 % 9.0 % As of March 31, 2022, minimum annual rental payments under the Company’s lease agreements are as follows (in thousands): Lease Financing Year ending December 31, 2022 (remaining nine months) $ 7,621 2023 6,837 2024 12,527 2025 10,658 2026 10,376 Thereafter 62,814 Total minimum payments 110,833 Less: Amounts representing interest expense ( 6,144 ) Less: Amounts representing lease payments under the Boston Lease ( 79,114 ) Present value of future minimum lease payments 25,575 Less: Current portion of lease liability ( 6,886 ) Noncurrent portion of lease liability $ 18,689 Agreements with CROs In September 2017, the Company entered into a contract research and development agreement with a third-party contract research organization (“CRO”) to provide research, analysis and antibody samples to further the Company’s development of its antibody drug candidates. The Company is also obligated to pay the CRO certain milestone payments of up to an aggregate of $ 36.4 million on achievement of specified events. None of these events had occurred as of March 31, 2022. During the three months ended March 31, 2022, the Company had no research and development expense under the agreement. During the three months ended March 31, 2021, the Company had immaterial research and development expense under the agreement. In May 2019, the Company entered into a contract research and testing agreement with another third-party CRO to provide antibody discovery related services. In March 2022, the Company notified that CRO of its intent to terminate the agreement effective in May 2022. Until the effective date of the termination, the Company is obligated to pay the CRO certain milestone payments of up to $ 34.8 million on achievement of specified events. None of these events had occurred as of March 31, 2022. No research and development expense was recorded under the agreement during the three months ended March 31, 2022 and 2021. Guarantees and Indemnifications The Company, as permitted under Delaware law and in accordance with its certificate of incorporation and bylaws, and pursuant to indemnification agreements with certain of its officers and directors, indemnifies its officers and directors for certain events or occurrences, subject to certain limits, with respect to which the officer or director is or was serving at the Company’s request in such capacity. The term of the indemnification period lasts as long as an officer or director may be subject to any proceeding arising out of acts or omissions of such officer or director in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company currently holds director and officer liability insurance. This insurance limits the Company’s exposure and may enable it to recover a portion of any future amounts paid. The Company believes that the fair value of these indemnification obligations is minimal. Accordingly, the Company has not recognized any liabilities relating to these obligations for any period presented.

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	7. Balance Sheet Components Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): March 31, December 31, 2022 2021 Prepaid research and development-related expenses $ 5,728 $ 2,672 Net contract asset — 1,385 Collaboration receivable 2,235 688 Prepaid insurance 1,314 1,769 Interest and other receivables 224 292 Facilities-related deposits 455 — Other 990 866 Total prepaid expenses and other current assets $ 10,946 $ 7,672 Deposits and Other Long-Term Assets Deposits and other long-term assets consist of the following (in thousands): March 31, December 31, 2022 2021 Lease security deposits $ 934 $ 1,305 Prepaid research and development-related expenses 630 1,047 Total deposits and other long-term assets $ 1,564 $ 2,352

Collaboration and License Agree

Collaboration and License Agreements and Grant Revenue	3 Months Ended
	Mar. 31, 2022
Collaborative And License Agreements [Abstract]
Collaboration and License Agreements	8. Collaboration and License Agreements and Grant Revenue 2seventy bio, Inc. In August 2018, the Company entered into a Research Collaboration and License Agreement with bluebird bio, Inc. (“bluebird”). In November 2021, bluebird assigned the Research Collaboration and License Agreement (the “2seventy Agreement”), to its affiliate, 2seventy bio, Inc. (“2seventy”), in connection with bluebird's restructuring and subsequent spin-out of 2seventy. Under the terms of the 2seventy Agreement, the Company provides to 2seventy tumor-specific targets across several tumor types and, in certain cases, T cell receptors (TCR) directed to those targets. The Company received a non-refundable upfront payment of $ 20.0 million, and 2seventy also concurrently acquired 768,115 shares of the Company’s Series C convertible preferred stock for $ 10.0 million at $ 13.04 per share. Per the 2seventy Agreement, 2seventy was also provided an option to acquire shares of the Company’s common stock at the same price as all other investors in connection with the Company’s initial public offering (“IPO”). In October 2018, 2seventy purchased 666,667 shares of the Company’s common stock at the price to the public of $ 15.00 per share for a total of $ 10.0 million. Under the terms of the 2seventy Agreement, the Company is eligible to earn development, regulatory, and sales-based milestones in an amount of up to $ 1.2 billion, and single-digit royalties on sales of products that utilize the technology subject to the 2seventy Agreement. None of these events had occurred as of December 31, 2021, and no royalties were due from the sale of licensed products. In August 2019, the Company entered into a First Amendment to the 2seventy Agreement, which extended the timeline for the Company and 2seventy to execute a Patient Selection Services Agreement from within one year to within two years after the Effective Date of the 2seventy Agreement. In August 2020, the Company entered into a Second Amendment, which extended the timeline of the Patient Selection Services Agreement to within three years and also extended the Tissue Analysis Period from February 28, 2021 to June 30, 2021. In April 2021, the Company entered into a Third Amendment, which removed the Patient Selection Services Agreement in its entirety and extended the Tissue Analysis Period from June 30, 2021 to December 31, 2021. The amendments were entered into for administrative purposes, and the Company determined the amendments were not a modification of contract under the contract with customers guidance. 2seventy may terminate the 2seventy Agreement by giving a 120 -day prior written notice to the Company at any time after the effective date of the agreement. Unless terminated early, the agreement has a term that ends upon the last payment owed by the Company on a licensed product. The 2seventy Agreement may be terminated for cause by either party based on uncured material breach by the other party or bankruptcy of the other party. Upon early termination, all ongoing activities under the agreement and all mutual collaboration, development and commercialization licenses and sublicenses will terminate. The licenses granted by the Company to 2seventy under the licensed intellectual property will remain in effect in accordance with their respective terms. Additionally, all of 2seventy’s payment obligations that have not yet accrued related to future milestone and royalty payments will be reduced by 50 % for the remainder of the agreement term. The Company concluded that 2seventy is a customer, and the contract is not subject to guidance on collaborative arrangements. This is because the Company granted to 2seventy a license to its intellectual property and provided research and development services, all of which are outputs of the Company’s ongoing activities, in exchange for consideration. The Company identified the following three material promises under the 2seventy Agreement: (i) transfer of a license to intellectual property and related technology know-how (“License and Know-How”); (ii) the obligation to perform target selection and TCR generation services (“Research and Development Services”); and (iii) participation on the Joint Steering Committee (the “JSC”). The Company provided to 2seventy standard indemnification and protection of licensed intellectual property, which is part of assurance that the license meets the contract’s specifications and is not an obligation to provide goods or services. The Company considered that the License and Know-How has standalone functionality, was considered to be functional intellectual property, and is capable of being distinct. However, the Company determined that the License and Know-How is not distinct from the Research and Development Services or participation on the JSC within the context of the 2seventy Agreement, because 2seventy is dependent on the Company to execute the Research and Development Services and participate on the JSC in order for 2seventy to benefit from the License and Know-How. As such, the License and Know-How is combined with the Research and Development Services and participation on the JSC into a single performance obligation, and the transaction price under this arrangement will be allocated to this single performance obligation. The Company has also determined that all other goods or services that are contingent upon 2seventy reaching various milestones are not considered performance obligations at the inception of the arrangement. The transaction price at the inception of the 2seventy Agreement consisted of the upfront payment of $ 20.0 million and the $ 10.0 million received from 2seventy for the purchase of the Company’s Series C convertible preferred stock. The sale of the Series C convertible preferred stock was not considered to be a performance obligation, as it was a separate financing component of the transaction. Accordingly, $ 10.0 million of the transaction price was allocated to the issuance of 768,115 shares of Series C convertible preferred stock at fair value of $ 13.04 per share and recorded in stockholders’ equity. The variable consideration related to the remaining development, regulatory, and sales-based milestones payments has not been included in the initial transaction price and continues to be fully constrained as of December 31, 2021. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon initiation of clinical trials for early-stage targets and 2seventy’s development efforts. Any variable consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur, as they were determined to relate predominantly to the License and Know-How granted to 2seventy. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. For revenue recognition purposes, the Company determined that the duration of the 2seventy Agreement began on the effective date in August 2018 and ends upon completion of the Research and Development Services, which is also when the participation on the JSC is no longer an obligation. The contract duration is defined as the period in which parties to the contract have present enforceable rights and obligations. The Company also analyzed the impact of 2seventy terminating the agreement prior to August 2023 and determined, considering both quantitative and qualitative factors, that there were substantive non-monetary penalties to 2seventy for doing so. Revenue is recognized when, or as, the Company satisfies its performance obligation by transferring the promised services to 2seventy. Revenue is being recognized over time using a cost-based input method, based on internal labor cost effort to perform the research services, since the internal labor cost incurred over time is thought to best reflect the transfer of services to 2seventy. In applying a cost-based input method of revenue recognition, we use actual costs incurred relative to budgeted costs to fulfill the combined performance obligation. A cost-based input method of revenue recognition requires us to make estimates of costs to complete the performance obligation. The cumulative effect of any revisions to estimated costs to complete the performance obligation will be recorded in the period in which changes are identified and amounts can be reasonably estimated. A significant change in these assumptions and estimates could have a material impact on the timing and amount of revenue recognized in future periods. During the three months ended March 31, 2022 and 2021, the Company recognized $ 4.0 million and $ 0.7 million, respectively, in collaboration revenue under the 2seventy Agreement. The amount of collaboration revenue recognized during the three months ended March 31, 2022 included a cumulative catch-up adjustment increasing contribution revenue by $ 3.5 million due to revisions to estimated costs to complete the remaining performance obligation. Deferred revenue of $ 4.7 million and $ 8.7 million was recorded on the condensed consolidated balance sheets in both current and long-term liabilities as of March 31, 2022 and December 31, 2021, respectively. Deferred revenue relates to the performance obligations identified under the 2seventy Agreement and will be recognized over the period the performance obligations are expected to be satisfied, which is currently estimated to be through September 2023 . Changes in the deferred revenue balance during the three months ended March 31, 2022 for the 2seventy Agreement are as follows (in thousands): Deferred Revenue Balance at December 31, 2021 $ 8,725 Additions — Deductions ( 3,994 ) Balance at March 31, 2022 $ 4,731 There were no receivables or net contract assets recorded as of March 31, 2022 and December 31, 2021 associated with the 2seventy Agreement. Gilead Sciences, Inc. In January 2021, the Company entered into a Collaboration, Option and License Agreement (the “Gilead Collaboration Agreement”) with Gilead Sciences, Inc. (“Gilead”) to research and develop a vaccine-based immunotherapy as part of Gilead’s efforts to find a curative treatment for HIV infection. Under the terms of the Gilead Collaboration Agreement, the Company granted to Gilead an exclusive, worldwide license to develop and commercialize a HIV-specific therapeutic vaccine utilizing the Company’s technology. Gilead is responsible for conducting all development and commercialization activities beginning with a Phase 1 study, and the Company is responsible for contributing to preclinical research studies and participation in a joint steering committee (collectively, “research and development activities”). Concurrently with execution of the Gilead Collaboration Agreement, the Company and Gilead entered into a Supply Agreement (the “Gilead Supply Agreement”) under which the Company will supply research product and GMP product (“Product Supply”) that may be required under the Gilead Collaboration Agreement until Gilead completes its first GMP product batch, and the Company will participate in a joint manufacturing team (collectively, “product supply activities”). In addition, the Company also concurrently entered into a Stock Purchase Agreement (the “Gilead Stock Purchase Agreement”) under which Gilead acquired, in a private placement transaction, 1,169,591 shares of the Company’s common stock. The common shares were issued to Gilead with certain registration rights and certain standstill and market stand-off provisions. The Company determined that these concurrent contracts represent a combined arrangement (“the Gilead Arrangement”). Under the Gilead Collaboration Agreement, the Company received a non-refundable upfront payment of $ 30.0 million. Under the Gilead Collaboration Agreement and the Gilead Supply Agreement, the Company will receive additional reimbursement payments for expenses incurred in the research and development activities and product supply activities. Under the Gilead Stock Purchase Agreement, the common shares were sold at a price of $ 25.65 per share for a total of $ 30.0 million. The Company’s common stock at fair value on closing was $ 18.10 per share. If Gilead decides to move forward with development beyond the initial Phase 1 study (the “Option”), the Company will receive a $ 40.0 million non-refundable option fee and will be eligible to receive up to an aggregate of $ 685.0 million if certain clinical, regulatory and commercial milestones are achieved, as well as tiered royalties ranging from the mid-single digits to low double-digits on net sales of a therapeutic product utilizing its technology. None of these events had occurred as of March 31, 2022 and no royalties were due from the sale of licensed products. Gilead may terminate the Gilead Collaboration Agreement for convenience by giving a 90 -day prior written notice to the Company at any time after the effective date of the agreement. Unless terminated early, the agreement has a term that ends upon the expiration of the royalty term, or, if the Option is not exercised, by the end of the Option term. The Gilead Collaboration Agreement may be terminated for cause by either party based on uncured material breach by the other party, insolvency of the other party, or patent challenge. Upon early termination, all ongoing activities under the agreement and all mutual collaboration, development and commercialization licenses and sublicenses will terminate. The licenses granted by the Company to Gilead under the licensed intellectual property will remain in effect in accordance with their respective terms. Additionally, if terminated early by Gilead for convenience or by the Company for material breach or insolvency, all of Gilead’s payment obligations for reimbursable costs or for future milestone and royalty payments remain. If terminated early by Gilead for material breach or insolvency, all of Gilead’s unaccrued payment obligations related to future milestone and royalty payments will be reduced by 50% for the remainder of the agreement term. Furthermore, Gilead may terminate the Gilead Supply Agreement without cause by giving six months prior written notice and any active orders with 60-day notice without terminating the agreement, and either party may terminate based on an uncured material breach, insolvency of the other party, or in the event that the Gilead Collaboration Agreement is terminated. Upon termination, the Company will deliver all supply products that have been produced and destroy, reimburse or deliver materials that Gilead has reimbursed, and Gilead must pay for any manufacturing costs that the Company has actually incurred or committed to pay, including any cancellation costs owed to subcontractors. The Company concluded that Gilead is a customer and therefore revenue recognition should be accounted for in accordance with ASC 606, because the Company granted to Gilead licenses to its intellectual property and will provide research and development services and Supply of Product, as defined below, all of which are outputs of the Company’s ongoing activities, in exchange for consideration. The Option, if exercised by Gilead, will be considered a modification that increases the scope of the arrangement beyond the Option Term. The Company identified the following performance obligations under the Gilead Collaboration Agreement: (i) licenses including an exclusive (in the HIV field), royalty-free, worldwide collaboration license and transfer of know-how and an exclusive (in the HIV field) worldwide, royalty-bearing development and commercial license subject to restrictions on its use during the Option Term and an exclusive option to release such restrictions; (ii) preclinical research and development activities, manufacturing-related activities, and participation on a Joint Steering Committee; and (iii) product supply, including research and GMP product, until Gilead completes its first GMP batch, and participation on a Joint Manufacturing Team. The Company considered that the licenses and know-how have standalone functionality, are considered to be functional intellectual property and are capable of being distinct. The Company also determined that the research and development activities and product supply by Gritstone could be provided by resources otherwise available to Gilead and thus are capable of being distinct. The Company has also determined that the pricing for optional goods and services and release of license restrictions upon exercise of the Option do not constitute material rights and are not a potential performance obligation. The Company evaluated whether there is an interdependence between the promises and determined that the licenses are a combined solution and the predominant performance obligation, while the other promises are separately identifiable in the context of the contract; however, the research and development activities are dependent on the research product supply, which is accounted for as a combined performance obligation. As a result, the Company identified three performance obligations in the Gilead Arrangement: (i) exclusive licenses and know-how, (ii) research and development activities and product supply, and (iii) GMP product supply. The transaction price at the inception of the Gilead Collaboration Agreement consisted of the upfront payment of $ 30.0 million and the $ 30.0 million received for the sale of the Company’s common stock. The sale of the common stock was not considered to be a performance obligation, as it was a separate financing component of the transaction. Accordingly, $ 21.2 million of the transaction price was allocated to the issuance of 1,169,591 shares of the Company’s common stock at fair value on closing of $ 18.10 per share and recorded in stockholders’ equity. The remaining $ 8.8 million of the common stock purchase price in excess of the fair value of the shares received is added to the transaction price for the Gilead Collaboration Agreement. In addition, the initial transaction price includes estimated variable consideration for budgeted reimbursement of research and development costs and product supply. The variable consideration related to reimbursable costs and product supply has been constrained as of March 31, 2022 based on the current research and development plan forecast. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. The Company determined that the variable consideration for the $ 40.0 million option exercise fee and for the development, regulatory, and sales-based milestones payments were probable of significant revenue reversal as their achievement was highly dependent on factors outside the Company’s control. As a result, these payments were fully constrained and were not included in the transaction price. Any variable consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur, as they were determined to relate predominantly to the exclusive licenses and know-how granted to Gilead. The transaction price is allocated to the performance obligation based upon relative standalone selling prices, which were determined for the exclusive licenses and know-how using an adjusted market approach and for the research and development activities and product supply using a cost plus reasonable margin approach. Variable consideration is allocated to the specific performance obligations to which it relates. For revenue recognition purposes, the Company determined that the duration of the contract began on the effective date in January 2021 and ends upon (i) the completion of the Option term, which is expected to end two to four years after the effective date, if the Option is not exercised or (ii) the expiration of the royalty-term on a product-by-product and country-by-country basis. The Company also analyzed the impact of Gilead terminating the agreement prior to the end of the Option term and determined, considering both quantitative and qualitative factors, that there were substantive non-monetary penalties to Gilead for doing so. Revenue for the exclusive licenses and know-how was recognized on the effective date of the Gilead Collaboration Agreement at the point in time that the licenses are effective. The research and development activities and product combined performance obligation and the GMP product supply performance obligation are recognized over time when, or as, the Company transfers the promised goods and services to Gilead. Research and development service and product supply revenues will be recognized over time using a cost-based input method, based on internal and external labor cost effort to perform the services, costs to acquire research materials, and costs of product supply, since the costs incurred over time are thought to best reflect the transfer of goods and services to Gilead. In applying a cost-based input method of revenue recognition, we use actual costs incurred relative to estimated total costs to fulfill each performance obligation. A cost-based input method of revenue recognition requires us to make estimates of costs to complete the performance obligation. The cumulative effect of any revisions to estimated costs to complete the performance obligation and associated variable consideration will be recorded in the period in which changes are identified and amounts can be reasonably estimated. A significant change in these assumptions and estimates could have a material impact on the timing and amount of revenue recognized in future periods. For the three months ended March 31, 2022, the Company did not record any license revenue and recorded $ 0.7 million as collaboration revenue as a result of satisfying its performance obligations by transferring the promised goods and services estimated by the costs incurred for the Gilead Collaboration Agreement. For the three months ended March 30, 2021, the Company recognized $ 38.6 million as license revenue and $ 0.3 million as collaboration revenue as a result of satisfying its performance obligations by transferring the promised goods and services estimated by the costs incurred for the Gilead Collaboration Agreement. There was no contract asset recorded on the condensed consolidated balance sheet as of March 31, 2022. A contract asset of $ 1.4 million was recorded on the condensed consolidated balance sheet as of December 31, 2021 for supply costs that were incurred during the year ended December 31, 2021, but not billable until future periods when the asset is released. The contract asset relates to the performance obligations yet to be satisfied identified under the Gilead Collaboration Agreement. There was $ 0.1 million recorded as deferred revenue as of March 31, 2022 and no deferred revenue as of December 31, 2021 associated with the Gilead Collaboration Agreement. Changes in the contract asset and deferred revenue balance during the three months ended March 31, 2022 for the Gilead Collaboration Agreement are as follows (in thousands): Contract Asset Deferred Revenue Balance at December 31, 2021 $ 1,385 $ — Additions 123 99 Deductions ( 1,508 ) — Balance at March 31, 2022 $ — $ 99 There was $ 2.2 million and $ 0.7 million of receivables recorded on the condensed consolidated balance sheet as a current asset in the prepaid expenses and other current assets balance as of March 31, 2022 and December 31, 2021, respectively, associated with the Gilead Collaboration Agreement. The Company deferred $ 0.1 million in incremental costs to acquire the Gilead Collaboration Agreement in the first quarter of 2021 allocated to performance obligations recognized over time, which will be recognized over time in each period proportionate to revenue recognition. As of March 31, 2022, deferred contract acquisition costs were zero . Deferred contract acquisition costs amortized during the three months ended March 31, 2022 and 2021 were negligible. Arbutus Biopharma Corporation In October 2017, the Company entered into an Exclusive License Agreement with Arbutus Biopharma Corporation (“Arbutus”) and its wholly-owned subsidiary, Protiva Biotherapeutics Inc. Certain terms of the agreement were modified by amendment in July 2018 (such amended license agreement, the Arbutus License Agreement). Under the Arbutus License Agreement, Arbutus granted the Company exclusive license rights under certain intellectual property related to Arbutus’ lipid nanoparticle (LNP) technology . During the three months ended March 31, 2022 and 2021, the Company had no research and development expense under the Arbutus License Agreement. The Company is obligated to pay Arbutus certain milestone payments up to $ 123.5 million on achievement of specified events, and royalties on sales of its licensed products. Following the acceptance of our investigational new drug application for GRANITE by the U.S. Food and Drug Administration (the “FDA”), the Company made a $ 2.5 million development milestone payment to Arbutus in September 2018 that was recorded as research and development expense. In August 2019, a milestone was met following the initial patient treatment of SLATE in the Company’s GO-005 clinical trial. In 2019, the Company recorded $ 3.0 million as research and development expense in connection with the milestone. None of the other events had occurred as of March 31, 2022, and no royalties were due from the sale of licensed products. Non-Profit Hospital Cancer Center In January 2016, the Company entered into an Exclusive License Agreement with a non-profit hospital cancer center. Under the license agreement, the Company has an exclusive license to utilize certain patents and know-how relating to immunotherapy for an insignificant upfront payment, cash milestone payments on achievement of specified events, and a low single digit royalty on sales of licensed products. The achievement of the milestones and payment of royalties is dependent upon obtaining regulatory approval. Upon achievement of a milestone related to the Company’s Phase 1 clinical trial for GRANITE, GO-004, in December 2018 the Company recorded an insignificant amount to research and development expense for amounts owed to the Hospital Cancer Center, which was paid to the hospital in February 2019. None of the other milestone events had occurred as of March 31, 2022 and no royalties were due from the sales of licensed products. Genevant Sciences GmbH In October 2020, the Company entered into an Option and License and Development Agreement (the “2020 Genevant License Agreement”) with Genevant Sciences GmbH (“Genevant”), pursuant to which Genevant granted the Company exclusive license rights under certain intellectual property related to Genevant’s LNP technology for a single therapeutic indication, and the Company agreed to pay Genevant an initial payment of $ 2.0 million, up to an aggregate of $ 71.0 million in specified development, regulatory, and commercial milestones, and low to mid-single digit royalties on net sales of licensed products. The upfront payment of $ 2.0 million was included in research and development expense for the year ended December 31, 2020. The 2020 Genevant License Agreement expands Gritstone’s intellectual property rights to such LNP technology originally obtained pursuant to the Company’s license agreement with Arbutus. Genevant is a spin-off of Arbutus. Prior to the 2020 Genevant License Agreement, the Company licensed Arbutus’ LNP technology for indications in the oncology space. The remainder of Arbutus’ IP portfolio was transferred to Genevant in the spin-off. In March 2022, a milestone in the amount of $ 1.0 million was met, which was included in research and development expense for the three months ended March 31, 2022. Pursuant to the 2020 Genevant License Agreement, Genevant also granted the Company certain options to license the LNP technology for additional therapeutic indications of up to $ 1.5 million for each indication and $ 1.0 million to extend the option term. The 2020 Genevant License Agreement continues in effect until the last to expire royalty term or early termination. It is terminable by the Company for convenience with 90 days prior written notice or immediately if based on certain product safety or efficacy or regulatory criteria. Either party may terminate the agreement for material breach, subject to a cure period, and Genevant may terminate the agreement if the Company challenges a licensed patent. In January 2021, the Company entered into a Non-Exclusive License and Development Agreement (the “2021 Genevant License Agreement”) with Genevant. Pursuant to the 2021 Genevant License Agreement, the Company obtained a nonexclusive license to Genevant’s LNP technology to develop and commercialize self-amplifying RNA (“samRNA”) vaccines against SARS-CoV-2, the virus that causes COVID-19. Under the 2021 Genevant License Agreement, the Company made a $ 1.5 million upfront payment to Genevant, and Genevant is eligible to receive from the Company up to an aggregate of $ 141.0 million in contingent milestone payments per product, plus certain tiered royalties, upon achievement of development and commercial milestones. In certain scenarios, in lieu of milestones and royalties, Genevant will be entitled to a percentage of amounts that the Company receives from sublicenses under the 2021 Genevant License Agreement, subject to certain conditions. In March 2021, a milestone in the amount of $ 1.0 million was met following the initial patient treatment in the Phase 1 clinical trial conducted through the NIAID-supported Infectious Diseases Clinical Research Consortium (“IDCRC”). Both the $ 1.5 million upfront and $ 1.0 million milestone payments were recorded as research and development expense for the three months ended March 31, 2021. None of the other milestone events had occurred as of March 31, 2022. Coalition for Epidemic Preparedness Innovations On August 14, 2021, the Company entered into the CEPI Funding Agreement with CEPI, under which CEPI agreed to provide funding of up to $ 20.6 million to the Company to advance the Company’s program, which is developing a second-generation COVID-19 vaccine, with an initial clinical trial in South Africa. Under the terms of the agreement, CEPI will fund a multi-arm Phase 1 study evaluating the CORAL program’s samRNA vaccine in naïve, convalescent, and HIV+ patients. The study will evaluate two different samRNA vaccine constructs that each target both the spike protein and other SARS-CoV-2 targets and are designed to drive both robust B and T cell immune responses. The funding will also support pre-clinical studies, scale-up and formulation development to enable manufacturing of large quantities of stable vaccine product. Under the terms of the CEPI Funding Agreement, among other things, the Company and CEPI agreed on the importance of global equitable access to the vaccine produced pursuant to the CEPI Funding Agreement. The vaccine, if approved, is expected to be made available to the COVAX Facility for procurement and allocation. The COVAX Facility aims to deliver equitable access to COVID-19 vaccines for all countries, at all levels of development, that wish to participate. The scope and continuation of the CEPI Funding Agreement may be amended depending on ongoing developments of the COVID-19 outbreak and the success of the Company’s COVID-19 vaccine candidate developed under the CEPI Funding Agreement relative to other third-party COVID-19 vaccine candidates or treatments. If the World Health Organization (WHO), CEPI or a regulatory authority having jurisdiction over a clinical trial performed under the CEPI Funding Agreement determines that a third-party product candidate has substantially greater potential than the Company’s COVID-19 vaccine candidate developed under the CEPI Funding Agreement and should be prioritized instead for a particular trial, the Company must consider in good faith any written request of CEPI not to proceed with a clinical trial of such COVID-19 vaccine candidate (the determination of whether to proceed or not with such trial shall be made by the Company in its sole discretion). In addition, CEPI has the right to unilaterally terminate the CEPI Funding Agreement upon prior written notice if CEPI determines that (i) there are material safety, regulatory, scientific misconduct or ethical issues with the project undertaken by the Company under

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Stockholders' Equity	9. Stockholders’ Equity The Company’s amended and restated certificate of incorporation provides for 300,000,000 shares of common stock and 10,000,000 shares of preferred stock authorized for issuance, each with a par value of $ 0.0001 per share. As of March 31, 2022 and December 31, 2021, no shares of preferred stock were issued and outstanding. As of March 31, 2022 and December 31, 2021, there were 72,779,508 and 69,047,878 shares of common stock issued and outstanding, respectively. Holders of the Company’s common stock are entitled to one vote per share. Sale of Common Stock and Pre-Funded Warrants In October 2019, the Company filed a Registration Statement on Form S-3 (the “2019 Shelf Registration Statement”) with the SEC, covering the offering of up to $ 250.0 million of common stock, preferred stock, debt securities, warrants and units. The 2019 Shelf Registration Statement included a prospectus supplement covering the issuance and sale of up to $ 75.0 million of the Company’s common stock, from time to time, through the “ at-the-market" offering program (the “2019 ATM Offering Program”) under the Securities Act of 1933, as amended (the “Securities Act”). The SEC declared the 2019 Shelf Registration Statement effective on November 8, 2019. In connection with the 2019 ATM Offering, in October 2019, the Company entered into a sales agreement (the “2019 Sales Agreement”) with Cowen and Company, LLC (“Cowen”), pursuant to which Cowen acts as its sales agent and, from time to time, offers and sells shares of the Company’s common stock having an aggregate offering price of up to $ 75.0 million. Cowen is entitled to compensation for its services equal to up to 3.0 % of the gross proceeds of any shares of common stock sold under the 2019 Sales Agreement. In addition, the Company agreed to reimburse a portion of Cowen’s expenses in connection with the 2019 ATM Offering up to $ 50,000 . During the year ended December 31, 2021, the Company issued and sold 3,990,869 shares of its common stock through its 2019 ATM Offering Program and received net proceeds of approximately $ 9.8 million, net of commissions and other offering costs. During the three months ended March 31, 2022, there have been no sales of shares of the Company's common stock through its 2019 ATM Offering Program. In December 2020, the Company entered into two private placement financing transactions (collectively, the “First PIPE Financing”), as follows: (i) to sell 5,543,351 shares of its common stock at a price of $ 3.34 per share and pre-funded warrants (the “Warrants”) to purchase 27,480,719 shares of common stock at a price of $ 3.34 per share (of which $ 3.33 per share was prepaid by each purchaser) , and (ii) to sell an additional 4,043,127 shares of its common stock at a price per share of $ 3.71 . In connection with the First PIPE Financing, the Company received aggregate net proceeds of approximately $ 119.8 million. The Warrants are exercisable upon issuance at an exercise price of $ 0.01 per share. The outstanding Warrants generally may not be exercised if the holder’s aggregate beneficial ownership would be more than 9.99 % of the total issued and outstanding shares of the Company’s common stock following such exercise. The exercise price and number of shares of common stock issuable upon the exercise of the Warrants (the “Warrant Shares”) are subject to adjustment in the event of any stock dividends and splits, reverse stock split, recapitalization, reorganization or similar transaction, as described in the Warrant agreements. Under certain circumstances, the Warrants may be exercisable on a “cashless” basis. In connection with the issuance and sale of the common stock and Warrants, the Company granted the purchasers certain registration rights with respect to the Warrants and the Warrant Shares. The Warrants were classified as a component of permanent stockholders’ equity within additional paid-in-capital and were recorded at the issuance date using a relative fair value allocation method. The Warrants are equity classified because they are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, are immediately exercisable, do not embody an obligation for the Company to repurchase its shares, permit the holders to receive a fixed number of common shares upon exercise, are indexed to the Company’s common stock and meet the equity classification criteria. In addition, such Warrants do not provide any guarantee of value or return. The Company valued the Warrants at issuance, concluding their sales price approximated their fair value, and allocated net proceeds from the sale proportionately to the common stock and Warrants, of which $ 87.7 million, net of issuance costs, was allocated to the Warrants and recorded as a component of additional paid-in-capital. In September 2021, the Company completed a PIPE financing transaction, in which it sold 5,000,000 shares of its common stock at a price of $ 11.00 per share pursuant to a securities purchase agreement entered into on September 16, 2021 (the “Second PIPE Financing”). The Company received aggregate net proceeds of approximately $ 52.7 million after deducting placement agent commissions and offering expenses payable by the Company. In connection with the issuance and sale of the common stock, the Company filed a registration statement with the SEC registering the resale of the shares of common stock issued in the Second PIPE Financing. In March 2022, the Company filed a Registration Statement on Form S-3 with the SEC (the “2022 Shelf Registration Statement”), covering the offering of up to $ 250.0 million of common stock, preferred stock, debt securities, warrants and units. The 2022 Shelf Registration Statement included a prospectus supplement covering the issuance and sale of up to $ 100.0 million of the Company’s common stock, from time to time, through the ”at-the-market" offering program (the “2022 ATM Offering Program”) under the Securities Act. As of May 3, 2022, the SEC has not yet declared the 2022 Shelf Registration Statement effective. In connection with the 2022 ATM Offering, in March 2022, the Company also entered into a sales agreement (the “2022 Sales Agreement”) with Cowen, pursuant to which Cowen will act as its sales agent and, from time to time, offer and sell shares of the Company’s common stock having an aggregate offering price of up to $ 100.0 million. Cowen is entitled to compensation for its services equal to up to 3.0 % of the gross proceeds of any shares of common stock sold under the 2022 Sales Agreement. In addition, the Company agreed to reimburse a portion of Cowen’s expenses in connection with the 2022 ATM Offering up to $ 50,000 . As of March 31, 2022, there have been no sales of shares of the Company's common stock under the 2022 ATM Offering Program. Common Stock Warrants As of March 31, 2022, the following warrants to purchase shares of the Company’s common stock were issued and outstanding: Issue Date Expiration Date Exercise Price Number of Warrants Outstanding December 28, 2020 None $ 0.01 13,573,704 During the three months ended March 31, 2022, there were 3,442,567 warrants exercised resulting in the Company issuing 3,442,567 shares of common stock. There were no warrants exercised during the three months ended March 31, 2021.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	10. Stock-Based Compensation Award Incentive Plans In August 2015, the Company’s board of directors approved the 2015 Equity Incentive Plan (“2015 Plan”). In connection with the Company’s IPO and the effectiveness of the 2018 Award Incentive Plan (“2018 Plan”), discussed below, the 2015 Plan terminated. The 92,815 shares of common stock that were then unissued and available for future issuance under the 2015 Plan became available under the 2018 Plan. In September 2018, the Company’s board of directors approved the 2018 Plan. Under the 2018 Plan, a total of 2,690,000 shares of common stock were initially reserved for issuance under the 2018 Plan, plus the number of shares remaining available for future awards under the 2015 Plan, as of the effective date of the 2018 Plan. The number of shares of common stock reserved for issuance under the 2018 Plan will automatically increase on January 1 of each year, beginning on January 1, 2019 and continuing through and including January 1, 2028, by 4 % of the total number of shares of the Company’s outstanding stock on December 31 of the preceding calendar year, or a lesser number of shares determined by the Company’s board of directors. The 2018 Plan provides, among others, for the grant of options, stock appreciation rights, restricted stock awards, restricted stock unit awards and performance bonus awards. The maximum number of shares that may be issued upon the exercise of stock options under the 2018 Plan is 45,000,000 . The Company’s board of directors has the authority to determine to whom options will be granted, the number of shares, the term, and the exercise price. If an individual owns stock representing 10 % or more of the outstanding shares, the price of each share shall be at least 110 % of the fair market value, as determined by the board of directors. Options granted have a term of up to 10 years and generally vest over a 4 -year period with a straight-line vesting. Material Features of the 2021 Employment Inducement Incentive Award Plan In April 2021, the Company’s board of directors adopted the 2021 Employment Inducement Incentive Award Plan (the “2021 Plan”), pursuant to Nasdaq Listing Rule 5635(c)(4). The principal purpose of the 2021 Plan is to enhance our ability to attract, retain and motivate employees who are expected to make important contributions to us by providing such individuals with equity ownership opportunities. Awards granted under the 2021 Plan are intended to constitute “employment inducement awards” under Nasdaq Listing Rule 5635(c)(4), and, as such, the 2021 Plan is intended to be exempt from the Nasdaq Listing Rules regarding shareholder approval of stock option and stock purchase plans. A total of 790,400 shares of our common stock ("Share Limit") were initially reserved for issuance under the 2021 Plan. The Share Limit may be increased by the Company's board of directors. The 2021 Plan provides for the grant of non-qualified stock options, restricted stock units, restricted stock awards, stock appreciation rights, and other stock-based and cash-based awards. The 2021 Plan does not provide for the grant of incentive stock options. Awards under the 2021 Plan may be granted to eligible employees who are either new employees or who are commencing employment with the Company or one of its subsidiaries following a bona fide period of non-employment with the Company, and for whom such awards are granted as a material inducement to commencing employment with the Company or one of its subsidiaries. Awards under the 2021 Plan may not be granted to the Company's consultants or non-employee directors. The 2021 Plan is administered by our board of directors and, to the extent the Company's board of directors delegates its authority to it, the Company's compensation committee. In the event of a change in control in which the Company's successor refuses to assume or substitute any outstanding award under the 2021 Plan, the vesting of such award will accelerate in full. The Company's board of directors may terminate, amend, or modify the 2021 Plan at any time, provided that no termination or amendment may materially impair any rights under any outstanding award under the 2021 Plan without the consent of the holder. Stock Option Activity A summary of the 2018 Plan and 2021 Plan activity is as follows: Options Outstanding Number of Number Weighted- Weighted- Aggregate Balance at December 31, 2021 3,459,187 5,107,335 $ 9.82 8.13 $ 17,153 Authorized 2,761,915 — $ — Granted ( 2,550,341 ) 2,200,168 $ 5.61 Exercised — ( 73,713 ) $ 0.87 Cancelled 338,523 ( 302,640 ) $ 10.21 Balance at March 31, 2022 4,009,284 6,931,150 $ 8.56 8.53 $ 1,016 Vested and exercisable at 2,329,666 $ 8.94 7.20 $ 996 Vested and expected to vest at 6,076,920 $ 8.65 8.40 $ 1,013 For the three months ended March 31, 2022 and 2021, the total intrinsic value of stock option awards exercised was $ 0.3 million and $ 3.9 million, respectively, determined at the date of option exercise, and the total cash received upon exercise of stock options was not significant for either period. The aggregate intrinsic value was calculated as the difference between the exercise prices of the underlying stock option awards and the estimated fair value of the common stock on the date of exercise. As of March 31, 2022, $ 22.3 million of total unrecognized compensation cost related to non-vested employee and consultant options is expected to be recognized over a weighted-average period of 2.6 years. The total fair value of shares vested during the three months ended March 31, 2022 was $ 4.0 million. Stock-based compensation expense and awards granted to non-employees were immaterial for the three months ended March 31, 2022 and 2021. Restricted Stock Units We have granted restricted stock unit awards under the 2018 Equity Plan. Our restricted stock unit awards have a term of up to 10 years and generally vest over a 1 or 2 -year period. The following table summarizes our restricted stock unit activity during the three months ended March 31, 2022: Number of Shares Weighted- Outstanding, unvested at December 31, 2021 708,800 $ 5.29 Issued 350,173 $ 5.46 Vested ( 353,300 ) $ 5.29 Canceled/Forfeited ( 35,883 ) $ 5.31 Outstanding, unvested at March 31, 2022 669,790 $ 5.38 Stock-Based Compensation Expense Total stock-based compensation for all awards granted to employees, consultants and our 2018 Employee Stock Purchase Plan (“ESPP”), before taxes, is as follows (in thousands): Three Months Ended March 31, 2022 2021 Research and development expenses $ 1,745 $ 1,481 General and administrative expenses 1,386 720 Total $ 3,131 $ 2,201

Net Loss Per Common Share

Net Loss Per Common Share	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Net Income (Loss) Per Common Share	11. Net Income (Loss) Per Common Share Basic net income (loss) per share is calculated by dividing the net income (loss) by the weighted-average number of shares of common stock outstanding during the period, without consideration for common stock equivalents. The following table sets forth the computation of the basic and diluted net income (loss) per share (in thousands, except for share and per share amounts): Three Months Ended March 31, 2022 2021 Numerator: Net income (loss) $ ( 28,916 ) $ 7,923 Denominator: Weighted-average common shares outstanding, basic 86,277,599 75,987,372 Effect of dilutive shares — 1,476,984 Weighted-average common shares outstanding, diluted 86,277,599 77,464,356 Net income (loss) per share, basic $ ( 0.34 ) $ 0.10 Net income (loss) per share, diluted $ ( 0.34 ) $ 0.10 In December 2020, the Company issued and sold Warrants to purchase 27,480,719 shares of common stock at a nominal exercise price of $ 0.01 per share (see Note 9). The shares of common stock into which the Warrants may be exercised are considered outstanding for the purposes of computing earnings per share, because the shares may be issued for little or no consideration, they are fully vested and the Warrants are immediately exercisable upon their issuance date. During a period of net loss, basic net loss per share is the same as diluted net loss per share, as the inclusion of all potential common shares outstanding would have been anti-dilutive. Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: March 31, 2022 2021 Options issued and outstanding and ESPP shares issuable and outstanding 7,038,660 1,416,794 Restricted stock subject to future vesting 669,790 340 Total 7,708,450 1,417,134

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events The 2021 Plan Share Limit Increase On April 21, 2022, the Company’s board of directors approved a share limit increase of 700,000 shares under the 2021 Plan.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying interim condensed consolidated financial statements are unaudited and are comprised of the consolidation of the Company and its wholly-owned subsidiary. All intercompany balances and transactions have been eliminated in consolidation. The Company has no unconsolidated subsidiaries or investments accounted for under the equity method. The accompanying interim condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“U.S. GAAP”) and the rules and regulations of the Securities and Exchange Commission (the “SEC”) for interim reporting. The interim condensed consolidated financial statements are unaudited and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, necessary for the fair presentation for interim reporting. The results of operations for any interim period are not necessarily indicative of results of operations for any future period. Certain information and footnote disclosures typically included in annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the Company’s audited financial statements as of and for the year ended December 31, 2021, which are included in the Company’s Annual Report on Form 10-K, as filed with the SEC on March 10, 2022 .
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the reported amounts of assets and liabilities and disclosures of contingent liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Fair Value Of Financial Instruments	Fair Value of Financial Instruments U.S. GAAP establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability and are developed based on the best information available in the circumstances. Fair value is established as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, an established three-tier fair value hierarchy distinguishes between the following: • Level 1 inputs are quoted prices in active markets that are accessible at the market date for identical assets or liabilities. • Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. • Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the assets or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value instrument. The carrying amounts reflected on the condensed consolidated balance sheets for cash and cash equivalents, prepaid expenses and other current assets, accounts payable, accrued compensation and accrued liabilities approximate their fair values due to their short-term nature.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist of cash, cash equivalents and marketable securities. Cash, cash equivalents and marketable securities are invested through banks and other financial institutions in the United States. Such deposits may be in excess of federally insured limits. The Company maintains cash equivalents and marketable securities with various high-credit-quality and capitalized financial institutions. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. The Company’s investment policy limits investments to certain types of securities issued by the U.S. government, its agencies, and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents and marketable securities and issuers of marketable securities to the extent recorded on the condensed consolidated balance sheets. As of March 31, 2022, the Company has no off-balance sheet concentrations of credit risk.
Other Risks and Uncertainties	Other Risks and Uncertainties The Company is subject to a number of risks similar to those of other clinical-stage biotechnology companies, including dependence on key individuals; the need to develop commercially viable therapeutics; competition from other companies, many of which are larger and better capitalized; and the need to obtain adequate additional financing to fund the development of its products. The Company currently depends on third-party suppliers for key materials and services used in its research and development manufacturing process and is subject to certain risks related to the loss of these third-party suppliers or their inability to supply the Company with adequate materials and services. In March 2020, the World Health Organization declared the global novel coronavirus disease (“COVID-19”) outbreak a pandemic. To date, the Company’s business has not been materially impacted by the COVID-19 pandemic. However, the Company has experienced slowing of patient recruitment and sample collection in its ongoing clinical trials and cannot at this time predict the specific extent, duration, or full impact that the COVID-19 pandemic will have on its financial condition and operations, including ongoing and planned clinical trials. The impact of the COVID-19 pandemic on the financial performance of the Company will depend on future developments, including the duration and spread of the outbreak and related governmental advisories and restrictions. These developments and the impact of COVID-19 on the financial markets and the overall economy are highly uncertain. If the financial markets and/or the overall economy are impacted for an extended period, the Company’s results may be adversely affected.
Cash, Cash Equivalents, and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Cash equivalents, which consist primarily of highly liquid investments with original maturities of three (3) months or less when purchased, are stated at fair value. These assets include investments in money market funds that invest in U.S. Treasury obligations and certificates of deposit, which are stated at fair value. The Company has issued letters of credit under certain lease agreements that have been collateralized by cash deposits for an equal amount and are recorded within short-term restricted cash and deposits and other long-term assets on the condensed consolidated balance sheets based on the term of the underlying lease. Additionally, the Company’s restricted cash includes payments received under the Coalition for Epidemic Preparedness Innovations (“CEPI”) Funding Agreement, dated as of August 14, 2021 (the “CEPI Funding Agreement”) and the Gates Foundation Grant Agreement (see Note 8). The Company will utilize the CEPI and Gates Foundation funds as it incurs expenses for services performed under the agreements. The following table provides a reconciliation of cash, cash equivalents and short-term and long-term restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows (in thousands): March 31, December 31, 2022 2021 Cash and cash equivalents $ 69,158 $ 93,287 Restricted cash 9,395 11,285 Long-term restricted cash 5,290 6,005 Total cash, cash equivalents and restricted cash $ 83,843 $ 110,577
Leases	Leases The Company determines whether the arrangement is or contains a lease at the inception of the arrangement and if such a lease is classified as a financing lease or operating lease. The majority of the Company’s leases are classified as operating leases. Leases with a term greater than one year are included in operating lease ROU Assets, lease liabilities, current portion, and lease liabilities, net of current portion in the Company’s condensed consolidated balance sheets as of March 31, 2022 and December 31, 2021. The Company has elected not to recognize on the condensed consolidated balance sheets leases with terms of one year or less. Lease liabilities and their corresponding ROU Assets are recorded based on the present value of lease payments over the expected lease term. In determining the net present value of lease payments, the interest rate implicit in lease contracts is typically not readily determinable. As such, the Company estimates the appropriate incremental borrowing rate, which is the rate that would be incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. Certain adjustments to the ROU Assets may be required for items such as initial direct costs paid or incentives received and impairment charges if we determine the ROU Asset is impaired. The Company considers a lease term to be the non-cancelable period that it has the right to use the underlying asset, including any periods where it is reasonably assured the Company will exercise the option to extend the contract. Periods covered by an option to extend are included in the lease term if the lessor controls the exercise of that option. The Company recognizes lease expense on a straight-line basis over the expected lease term. The Company has elected not to separate lease and non-lease components for its leased assets and accounts for all lease and non-lease components of its agreements as a single lease component. The lease components resulting in a ROU Asset have been recorded on the condensed consolidated balance sheets and amortized as lease expense on a straight-line basis over the lease term.
Revenue Recognition	Revenue Recognition The Company performs research and development under collaboration, license, grant, and clinical development agreements. The Company’s revenue primarily consists of collaboration agreements and grant agreements. At contract inception, the Company analyzes a revenue arrangement to determine the appropriate accounting under U.S. GAAP. Currently, the Company’s revenue arrangements represent customer contracts within the scope of ASC Topic 606, Revenue from Contracts with Customers (Topic 606) (“ASC 606”) or are subject to the contribution guidance in ASC Topic 958-605, Not-for-Profit Entities – Revenue Recognition (“ASC 958-605”), which applies to business entities that receive contributions within the scope of ASC 958-605. For collaboration agreements, the Company analyzes to assess 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 dependent on the commercial success of such activities. This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. For collaboration arrangements that are considered to be in the scope of the collaboration guidance and that contain multiple elements, the Company first determines which elements of the collaboration are deemed to be within the scope of the collaboration guidance and those that are more reflective of a vendor-customer relationship and, therefore, within the scope of the revenue with contracts with customers guidance. Elements of collaboration arrangements that are reflective of a vendor-customer relationship are accounted for pursuant to the revenue from contracts with customers guidance. The terms of the licensing and collaboration agreements entered into typically include payment of one or more of the following: non-refundable, up-front fees; development, regulatory, and commercial milestone payments; payments for manufacturing supply services; and royalties on net sales of licensed products. Each of these payments results in license, collaboration and other revenues, except for revenues from royalties on net sales of licensed products, which are classified as royalty revenues. The core principle of the accounting for revenue from contracts with customers guidance is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received in exchange for those goods or services. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s condensed consolidated balance sheets. If the related performance obligation is expected to be satisfied within the next twelve (12) months, this will be classified in current liabilities. Amounts recognized as revenue prior to receipt are recorded as contract assets in the Company’s condensed consolidated balance sheets. If the Company expects to have an unconditional right to receive consideration in the next twelve (12) months, this will be classified in current assets. A net contract asset or liability is presented for each contract with a customer. At contract inception, the Company assesses the goods or services promised in a contract with a customer and identifies those distinct goods and services that represent a performance obligation. A promised good or service may not be identified as a performance obligation if it is immaterial in the context of the contract with the customer, if it is not separately identifiable from other promises in the contract (either because it is not capable of being separated or because it is not separable in the context of the contract), or if the performance obligation does not provide the customer with a material right. The Company considers the terms of the contract and its customary business practices to determine the transaction price. The transaction price is the amount of consideration to which the Company expects to be entitled in exchange for transferring promised goods or services to a customer. The consideration promised in a contract with a customer may include fixed amounts, variable amounts, or both. Variable consideration will only be included in the transaction price when it is not considered constrained, which is when it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur. If it is determined that multiple performance obligations exist, the transaction price is allocated at the inception of the agreement to all identified performance obligations, based on the relative standalone selling prices. The relative selling price for each performance obligation is estimated using objective evidence if it is available. If objective evidence is not available, the Company uses its best estimate of the selling price for the performance obligation. Revenue is recognized when, or as, the Company satisfies a performance obligation by transferring a promised good or service to a customer. An asset is transferred when, or as, the customer obtains control of that asset, which for a service is considered to be as the services are received and used. The Company recognizes revenue over time by measuring the progress toward complete satisfaction of the relevant performance obligation, using an appropriate input or output method based on the nature of the good or service promised to the customer. After contract inception, the transaction price is reassessed at every period end and updated for changes, such as resolution of uncertain events. Any change in the transaction price is allocated to the performance obligations on the same basis as at contract inception. Management may be required to exercise considerable judgment in estimating revenue to be recognized. Judgment is required in identifying performance obligations, estimating the transaction price, estimating the stand-alone selling prices of identified performance obligations (which may include forecasted revenue, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success) and estimating the progress towards satisfaction of performance obligations. For grant funding agreements, grant revenue is recognized during the period that the research and development services occur, as qualifying expenses are incurred. The Company concluded that payments received under these grants represent nonreciprocal contributions, as described in ASC 958, Not-for-Profit Entities, and that the grants are not within the scope of ASC 606 as the organization providing the grant does not meet the definition of a customer. Grant revenue relates primarily to the CEPI and Gates Funding Agreements (see Note 8).
Income Taxes	Income Taxes On March 18, 2020, the Families First Coronavirus Response Act (the “FFCR Act”), and on March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) were each enacted in response to the COVID-19 pandemic. The FFCR Act and the CARES Act contain numerous income tax provisions relating to refundable payroll tax credits, deferment of employer side social security payments, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property. On June 29, 2020, Assembly Bill 85 (“A.B. 85”) was signed into California law. A.B. 85 provides for a three-year suspension of the use of net operating losses for medium and large businesses and a three-year cap on the use of business incentive tax credits to offset no more than $ 5.0 million of tax per year. A.B. 85 suspends the use of net operating losses for taxable years 2020 and 2021 for certain taxpayers with taxable income of $ 1.0 million or more. The carryover period for any net operating losses that are suspended under this provision will be extended. A.B. 85 also requires that business incentive tax credits, including carryovers, may not reduce the applicable tax by more than $ 5.0 million for taxable years 2020 and 2021. The FFCR Act, CARES Act and A.B. 85 did not have a material impact on the Company’s condensed consolidated financial statements as of March 31, 2022; however, the Company continues to examine the impacts the FFCR Act, CARES Act and A.B. 85 may have on its business, results of operations, financial condition, liquidity and related disclosures.
Recently Issued Accounting Pronouncements Adopted and Not Yet Adopted	Recently Adopted Accounting Pronouncements In October 2020, the FASB issued ASU No. 2020-10, Codification Improvements (“ASU 2020-10”). The standard contains improvements to the FASB Accounting Standards Codification (the “Codification”) by ensuring that all guidance that requires or provides an option for an entity to provide information in the notes to financial statements is codified in the disclosure section of the Codification. The standard also improves various topics in the Codification so that entities can apply guidance more consistently on codifications that are varied in nature where the original guidance may have been unclear. The amendments in ASU 2020-10 are effective for the Company for fiscal years beginning after December 15, 2021, and interim periods within fiscal years beginning after December 15, 2022. Early adoption is permitted. We adopted ASU 2020-10 on January 1, 2022 and the adoption did not have a material impact on the Company's condensed consolidated financial statements and related disclosures. Recently Issued Accounting Pronouncements Not Yet Adopted In August 2020, the FASB issued ASU No. 2020-06, Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (“ASU 2020-06”). The standard eliminates the beneficial conversion and cash conversion accounting models for convertible instruments. It also amends the accounting for certain contracts in an entity’s own equity that are currently accounted for as derivatives because of specific settlement provisions. In addition, the standard modifies how particular convertible instruments and certain contracts that may be settled in cash or shares impact the diluted EPS computation. The amendments in ASU 2020-06 are effective for the Company as defined by the SEC for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted, but not earlier than fiscal years beginning after December 15, 2020. The Company does not expect the adoption of ASU 2020-06 to have a material impact on its condensed consolidated financial statements and related disclosures.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Schedule of Cash and Cash Equivalents	The following table provides a reconciliation of cash, cash equivalents and short-term and long-term restricted cash reported within the condensed consolidated balance sheets that sum to the total of the same amounts shown in the condensed consolidated statements of cash flows (in thousands): March 31, December 31, 2022 2021 Cash and cash equivalents $ 69,158 $ 93,287 Restricted cash 9,395 11,285 Long-term restricted cash 5,290 6,005 Total cash, cash equivalents and restricted cash $ 83,843 $ 110,577

Cash Equivalents and Marketab_2

Cash Equivalents and Marketable Securities (Tables)	3 Months Ended
	Mar. 31, 2022
Cash and Cash Equivalents [Abstract]
Cash Equivalents and Marketable Securities	The amortized costs, unrealized gains and losses and fair values of cash equivalents and marketable securities were as follows (in thousands): March 31, 2022 Description Amortized Unrealized Unrealized Fair Cash equivalents: Money market funds $ 45,083 $ — $ — $ 45,083 Commercial paper 2,999 — — 2,999 U.S. treasuries 5,000 — — 5,000 Asset backed securities 1,001 1,001 Total cash equivalents 54,083 — — 54,083 Short-term marketable securities: Certificates of deposit 4,650 — ( 33 ) 4,617 Commercial paper 35,451 — ( 136 ) 35,315 Corporate debt securities 21,212 — ( 94 ) 21,118 U.S. treasuries 34,792 — ( 100 ) 34,692 U.S. government debt securities 2,000 — ( 4 ) 1,996 Asset backed securities 5,290 — ( 24 ) 5,266 Total short-term marketable securities 103,395 — ( 391 ) 103,004 Total $ 157,478 $ — $ ( 391 ) $ 157,087 December 31, 2021 Description Amortized Unrealized Unrealized Fair Cash equivalents: Money market funds $ 79,281 $ — $ — $ 79,281 Commercial paper 1,000 — — 1,000 Corporate debt securities 1,031 — — 1,031 Total cash equivalents 81,312 — — 81,312 Short-term marketable securities: Certificates of deposit 5,600 — ( 6 ) 5,594 Commercial paper 44,990 — ( 16 ) 44,974 Corporate debt securities 26,976 — ( 23 ) 26,953 U.S. treasuries 12,277 — ( 8 ) 12,269 U.S. government debt securities 2,000 — ( 1 ) 1,999 Asset backed securities 16,565 — ( 8 ) 16,557 Total short-term marketable securities 108,408 — ( 62 ) 108,346 Long-term marketable securities: Corporate debt securities 1,637 — ( 6 ) 1,631 U.S. treasuries 2,991 — ( 5 ) 2,986 Total long-term marketable securities 4,628 — ( 11 ) 4,617 Total $ 194,348 $ — $ ( 73 ) $ 194,275

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2022
Fair Value Disclosures [Abstract]
Assets Measured at Fair Value	The Company’s financial assets subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands): March 31, 2022 Description Total Level 1 Level 2 Level 3 Cash equivalents: Money market funds $ 45,083 $ 45,083 $ — $ — Commercial paper 2,999 — 2,999 — U.S. treasuries 5,000 5,000 — — Asset backed securities 1,001 — 1,001 — Total cash equivalents 54,083 50,083 4,000 — Short-term marketable securities: Certificates of deposit 4,617 — 4,617 — Commercial paper 35,315 — 35,315 — Corporate debt securities 21,118 — 21,118 — U.S. treasuries 34,692 34,692 — — U.S. government debt securities 1,996 — 1,996 — Asset backed securities 5,266 — 5,266 — Total short-term marketable securities 103,004 34,692 68,312 — Total $ 157,087 $ 84,775 $ 72,312 $ — December 31, 2021 Description Total Level 1 Level 2 Level 3 Cash equivalents: Money market funds $ 79,281 $ 79,281 $ — $ — Commercial paper 1,000 — 1,000 — Corporate debt securities 1,031 — 1,031 — Total cash equivalents 81,312 79,281 2,031 — Short-term marketable securities: Certificates of deposit 5,594 — 5,594 — Commercial paper 44,974 — 44,974 — Corporate debt securities 26,953 — 26,953 — U.S. treasuries 12,269 12,269 — — U.S. government debt securities 1,999 — 1,999 — Asset backed securities 16,557 — 16,557 — Total short-term marketable securities 108,346 12,269 96,077 — Long-term marketable securities: Corporate debt securities 1,631 — 1,631 — U.S. treasuries 2,986 2,986 — — Total long-term marketable securities 4,617 2,986 1,631 — Total $ 194,275 $ 94,536 $ 99,739 $ —

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2022
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment and related accumulated depreciation and amortization are as follows (in thousands): March 31, December 31, 2022 2021 Computer equipment and software $ 997 $ 987 Furniture and fixtures 2,113 2,113 Laboratory equipment 25,057 24,679 Leasehold improvements 14,128 14,128 42,295 41,907 Less accumulated depreciation and amortization ( 23,837 ) ( 22,276 ) Construction-in-progress 3,825 1,991 Total property and equipment, net $ 22,283 $ 21,622

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Schedule of Components of Lease Costs	The components of lease costs, which were included in our condensed consolidated statements of operations and comprehensive income (loss), were as follows (in thousands): Three Months Ended March 31, 2022 2021 Lease cost Operating lease cost $ 2,253 $ 1,900 Total lease cost $ 2,253 $ 1,900
Schedule of Supplemental Information Related to Leases	Supplemental information related to leases was as follows: Three Months Ended March 31, 2022 2021 Cash paid for amounts included in the measurement of Operating cash flows from operating leases $ 2,034 $ 1,950 New right-of-use assets obtained in exchange for lease Operating leases $ 781 $ — Weighted-average remaining lease term (years): Operating leases 5.3 6.1 Weighted-average discount rate: Operating leases 7.4 % 9.0 %
Schedule of Minimum Annual Rental Payments Under Operating Lease Agreements	As of March 31, 2022, minimum annual rental payments under the Company’s lease agreements are as follows (in thousands): Lease Financing Year ending December 31, 2022 (remaining nine months) $ 7,621 2023 6,837 2024 12,527 2025 10,658 2026 10,376 Thereafter 62,814 Total minimum payments 110,833 Less: Amounts representing interest expense ( 6,144 ) Less: Amounts representing lease payments under the Boston Lease ( 79,114 ) Present value of future minimum lease payments 25,575 Less: Current portion of lease liability ( 6,886 ) Noncurrent portion of lease liability $ 18,689

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Schedule of Deposits and Other Long-Term Assets	Deposits and other long-term assets consist of the following (in thousands): March 31, December 31, 2022 2021 Lease security deposits $ 934 $ 1,305 Prepaid research and development-related expenses 630 1,047 Total deposits and other long-term assets $ 1,564 $ 2,352
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): March 31, December 31, 2022 2021 Prepaid research and development-related expenses $ 5,728 $ 2,672 Net contract asset — 1,385 Collaboration receivable 2,235 688 Prepaid insurance 1,314 1,769 Interest and other receivables 224 292 Facilities-related deposits 455 — Other 990 866 Total prepaid expenses and other current assets $ 10,946 $ 7,672

Collaboration and License Agr_2

Collaboration and License Agreements and Grant Revenue (Tables)	3 Months Ended
	Mar. 31, 2022
Collaboration Agreement [Member] | 2 Seventy [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Schedule of Changes in Contract Asset and Deferred Revenue Balance	Changes in the deferred revenue balance during the three months ended March 31, 2022 for the 2seventy Agreement are as follows (in thousands): Deferred Revenue Balance at December 31, 2021 $ 8,725 Additions — Deductions ( 3,994 ) Balance at March 31, 2022 $ 4,731
Collaboration, Option and License Agreement [Member] | Gilead Sciences Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Schedule of Changes in Contract Asset and Deferred Revenue Balance	Changes in the contract asset and deferred revenue balance during the three months ended March 31, 2022 for the Gilead Collaboration Agreement are as follows (in thousands): Contract Asset Deferred Revenue Balance at December 31, 2021 $ 1,385 $ — Additions 123 99 Deductions ( 1,508 ) — Balance at March 31, 2022 $ — $ 99
Grant Agreement [Member] | Gates Foundation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Schedule of Changes in Contract Asset and Deferred Revenue Balance	Changes in the deferred revenue balance during the three months ended March 31, 2022 for the Gates Grant Agreement are as follows (in thousands): Deferred Revenue Balance at December 31, 2021 $ 2,225 Additions — Deductions ( 190 ) Balance at March 31, 2022 $ 2,035
Funding Agreement [Member] | CEPI [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Schedule of Changes in Contract Asset and Deferred Revenue Balance	Changes in the deferred revenue balance during the three months ended March 31, 2022 for the CEPI Funding Agreement are as follows (in thousands): Deferred Revenue Balance at December 31, 2021 $ 9,379 Additions — Deductions ( 2,415 ) Balance at March 31, 2022 $ 6,964

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Schedule of Issued and Outstanding Warrants to Purchase Shares of the Company's Common Stock	As of March 31, 2022, the following warrants to purchase shares of the Company’s common stock were issued and outstanding: Issue Date Expiration Date Exercise Price Number of Warrants Outstanding December 28, 2020 None $ 0.01 13,573,704

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [Abstract]
Schedule of Stock Options Activity	A summary of the 2018 Plan and 2021 Plan activity is as follows: Options Outstanding Number of Number Weighted- Weighted- Aggregate Balance at December 31, 2021 3,459,187 5,107,335 $ 9.82 8.13 $ 17,153 Authorized 2,761,915 — $ — Granted ( 2,550,341 ) 2,200,168 $ 5.61 Exercised — ( 73,713 ) $ 0.87 Cancelled 338,523 ( 302,640 ) $ 10.21 Balance at March 31, 2022 4,009,284 6,931,150 $ 8.56 8.53 $ 1,016 Vested and exercisable at 2,329,666 $ 8.94 7.20 $ 996 Vested and expected to vest at 6,076,920 $ 8.65 8.40 $ 1,013
Summary of Restricted Stock Unit Activity	The following table summarizes our restricted stock unit activity during the three months ended March 31, 2022: Number of Shares Weighted- Outstanding, unvested at December 31, 2021 708,800 $ 5.29 Issued 350,173 $ 5.46 Vested ( 353,300 ) $ 5.29 Canceled/Forfeited ( 35,883 ) $ 5.31 Outstanding, unvested at March 31, 2022 669,790 $ 5.38
Schedule of Stock Based Compensation Expense	Total stock-based compensation for all awards granted to employees, consultants and our 2018 Employee Stock Purchase Plan (“ESPP”), before taxes, is as follows (in thousands): Three Months Ended March 31, 2022 2021 Research and development expenses $ 1,745 $ 1,481 General and administrative expenses 1,386 720 Total $ 3,131 $ 2,201

Net Loss Per Common Share (Tabl

Net Loss Per Common Share (Tables)	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss Per Share	The following table sets forth the computation of the basic and diluted net income (loss) per share (in thousands, except for share and per share amounts): Three Months Ended March 31, 2022 2021 Numerator: Net income (loss) $ ( 28,916 ) $ 7,923 Denominator: Weighted-average common shares outstanding, basic 86,277,599 75,987,372 Effect of dilutive shares — 1,476,984 Weighted-average common shares outstanding, diluted 86,277,599 77,464,356 Net income (loss) per share, basic $ ( 0.34 ) $ 0.10 Net income (loss) per share, diluted $ ( 0.34 ) $ 0.10
Computation of Potentially Anti-Dilutive Securities	During a period of net loss, basic net loss per share is the same as diluted net loss per share, as the inclusion of all potential common shares outstanding would have been anti-dilutive. Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: March 31, 2022 2021 Options issued and outstanding and ESPP shares issuable and outstanding 7,038,660 1,416,794 Restricted stock subject to future vesting 669,790 340 Total 7,708,450 1,417,134

Organization - Additional Infor

Organization - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2022USD ($)Segment	Mar. 31, 2021USD ($)	Dec. 31, 2021USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments | Segment	1
Net income (loss)	$ (28,916)	$ 7,923
Net cash used in operating activities	(33,451)	$ 10,654
Accumulated deficit	430,300		$ 401,384
Cash, cash equivalents and marketable securities	$ 172,200

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 69,158	$ 93,287
Restricted cash	9,395	11,285
Long-term restricted cash	5,290	6,005
Total cash, cash equivalents and restricted cash	$ 83,843	$ 110,577

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	Jun. 29, 2020	Dec. 31, 2021	Dec. 31, 2020
Summary Of Significant Accounting Policies [Line Items]
Use of net operating losses suspension period for medium and large business under AB 85	3 years
Use of business incentive tax credits period cap under AB 85	3 years
Taxable Years Two Thousand and Twenty and Two Thousand Twenty One [Member]
Summary Of Significant Accounting Policies [Line Items]
Minimum amount of taxable income where use of net operating losses is suspended	$ 1
Taxable Years Two Thousand And Twenty Two [Member]
Summary Of Significant Accounting Policies [Line Items]
Business incentive tax credits to offset against taxes	$ 5	$ 5	$ 5

Cash Equivalents and Marketab_3

Cash Equivalents and Marketable Securities - Schedule of Amortized Cost, Unrealized Gains and Losses and Fair Value of Cash Equivalent and Marketable Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Cash equivalents and marketable securities [Line Items]
Cash and cash equivalents	$ 69,158	$ 93,287
Amortized Cost	157,478	194,348
Unrealized Gains	0	0
Unrealized Losses	(391)	(73)
Fair Value	157,087	194,275
Cash Equivalents [Member]
Cash equivalents and marketable securities [Line Items]
Cash and cash equivalents	54,083	81,312
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	54,083	81,312
Cash Equivalents [Member] | Money Market Funds [Member]
Cash equivalents and marketable securities [Line Items]
Cash and cash equivalents	45,083	79,281
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	45,083	79,281
Cash Equivalents [Member] | Corporate Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Cash and cash equivalents		1,031
Unrealized Gains		0
Unrealized Losses		0
Fair Value		1,031
Cash Equivalents [Member] | Commercial Paper [Member]
Cash equivalents and marketable securities [Line Items]
Cash and cash equivalents	2,999	1,000
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	2,999	1,000
Cash Equivalents [Member] | U.S. Treasuries [Member]
Cash equivalents and marketable securities [Line Items]
Cash and cash equivalents	5,000
Unrealized Gains	0
Unrealized Losses	0
Fair Value	5,000
Cash Equivalents [Member] | Asset Backed Securities [Member]
Cash equivalents and marketable securities [Line Items]
Cash and cash equivalents	1,001
Short-Term Marketable Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	103,395	108,408
Unrealized Gains	0	0
Unrealized Losses	(391)	(62)
Fair Value	103,004	108,346
Short-Term Marketable Securities [Member] | Corporate Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	21,212	26,976
Unrealized Gains	0	0
Unrealized Losses	(94)	(23)
Fair Value	21,118	26,953
Short-Term Marketable Securities [Member] | Certificates of Deposit [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	4,650	5,600
Unrealized Gains	0	0
Unrealized Losses	(33)	(6)
Fair Value	4,617	5,594
Short-Term Marketable Securities [Member] | Commercial Paper [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	35,451	44,990
Unrealized Gains	0	0
Unrealized Losses	(136)	(16)
Fair Value	35,315	44,974
Short-Term Marketable Securities [Member] | U.S. Treasuries [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	34,792	12,277
Unrealized Gains	0	0
Unrealized Losses	(100)	(8)
Fair Value	34,692	12,269
Short-Term Marketable Securities [Member] | U.S. Government Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	2,000	2,000
Unrealized Gains	0	0
Unrealized Losses	(4)	(1)
Fair Value	1,996	1,999
Short-Term Marketable Securities [Member] | Asset Backed Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	5,290	16,565
Unrealized Gains	0	0
Unrealized Losses	(24)	(8)
Fair Value	$ 5,266	16,557
Long-term Marketable Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost		4,628
Unrealized Gains		0
Unrealized Losses		(11)
Fair Value		4,617
Long-term Marketable Securities [Member] | Corporate Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost		1,637
Unrealized Gains		0
Unrealized Losses		(6)
Fair Value		1,631
Long-term Marketable Securities [Member] | U.S. Treasuries [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost		2,991
Unrealized Gains		0
Unrealized Losses		(5)
Fair Value		$ 2,986

Cash Equivalents and Marketab_4

Cash Equivalents and Marketable Securities - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2022USD ($)Security
Cash equivalents and marketable securities [Line Items]
Realized gains or losses on marketable securities	no material realized gains or losses
Number of individual securities in an unrealized loss position for 12 months or greater | Security	0
Credit loss | $	$ 0
Period of unrealized loss position	12 months or greater
Maximum [Member]
Cash equivalents and marketable securities [Line Items]
Marketable securities contractual maturities period	1 year

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets Subject To Fair Value Measurements on a Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	$ 157,087	$ 194,275
U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	5,000
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	84,775	94,536
Fair Value, Inputs, Level 1 [Member] | U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	5,000
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	72,312	99,739
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Cash Equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	54,083	81,312
Cash Equivalents [Member] | Asset Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	1,001
Cash Equivalents [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	45,083	79,281
Cash Equivalents [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	2,999	1,000
Cash Equivalents [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		1,031
Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	50,083	79,281
Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Asset Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0
Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	45,083	79,281
Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	4,000	2,031
Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Asset Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	1,001
Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	2,999	1,000
Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		1,031
Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Asset Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0
Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Short-Term Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	103,004	108,346
Short-Term Marketable Securities [Member] | U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	1,996	1,999
Short-Term Marketable Securities [Member] | Asset Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	5,266	16,557
Short-Term Marketable Securities [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	35,315	44,974
Short-Term Marketable Securities [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	21,118	26,953
Short-Term Marketable Securities [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	4,617	5,594
Short-Term Marketable Securities [Member] | U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	34,692	12,269
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	34,692	12,269
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Asset Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	34,692	12,269
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	68,312	96,077
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	1,996	1,999
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Asset Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	5,266	16,557
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	35,315	44,974
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	21,118	26,953
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	4,617	5,594
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Government Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Asset Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0	0
Short-Term Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	$ 0	0
Long-term Marketable Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		4,617
Long-term Marketable Securities [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		1,631
Long-term Marketable Securities [Member] | U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		2,986
Long-term Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		2,986
Long-term Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Long-term Marketable Securities [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		2,986
Long-term Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		1,631
Long-term Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		1,631
Long-term Marketable Securities [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Long-term Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Long-term Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		0
Long-term Marketable Securities [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value		$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) $ in Thousands	Mar. 31, 2022USD ($)
Fair Value Disclosures [Abstract]
Fair Value, Assets, Level 1 to Level 2 Transfers	$ 0
Fair Value, Liabilities, Level 1 to Level 2 Transfers	0
Fair Value, Assets, Level 2 to Level 1 Transfers	0
Fair Value, Liabilities, Level 2 to Level 1 Transfers	$ 0

Property and Equipment, Net - S

Property and Equipment, Net - Summary of Property and Equipment and Related Accumulated Depreciation and Amortization (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 42,295	$ 41,907
Less accumulated depreciation and amortization	(23,837)	(22,276)
Total property and equipment, net	22,283	21,622
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	997	987
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,113	2,113
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	25,057	24,679
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	14,128	14,128
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, net	$ 3,825	$ 1,991

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 1,589	$ 1,595

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended					3 Months Ended
	Sep. 30, 2021USD ($)RenewalTerm	Jan. 31, 2019USD ($)RenewalTerm	Sep. 30, 2018	Mar. 31, 2017USD ($)ft²	Feb. 29, 2016	Mar. 31, 2022USD ($)	Mar. 31, 2021USD ($)	Dec. 31, 2021USD ($)	May 31, 2019USD ($)	Sep. 30, 2017USD ($)	Feb. 28, 2016USD ($)
Commitments and Contingencies Disclosure [Line Items]
Operating lease cash security deposit						$ 934,000		$ 1,305,000
Lease right-of-use assets						21,832,000		22,920,000
Lease liability						25,575,000
Research and Development Expense						28,199,000	$ 24,856,000
Contract Research Organization [Member]
Commitments and Contingencies Disclosure [Line Items]
Maximum milestone payments									$ 34,800,000	$ 36,400,000
Research and Development Expense						0	$ 0
Emeryville lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term		120 months
Operating leases number of renewal terms | RenewalTerm		2
Operating leasing renewal option to extend lease		5 years
Operating lease cash security deposit						600,000
Tenant improvement allowance		$ 4,000,000
Lease right-of-use assets						8,600,000		8,700,000
Lease liability						13,600,000		13,900,000
Pleasanton Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing renewal option to extend lease				5 years
Tenant improvement allowance				$ 1,200,000
Net rentable area | ft²				42,620
Lease expiration date				Nov. 30, 2024
Letters of credit outstanding, amount				$ 1,000,000
Withdrawal from irrevocable letters of credit						0
Pleasanton Lease [Member] | Additional Office Space [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term									64 months
Cambridge Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term			24 months				17 months				67 months
Operating lease cash security deposit						700,000		$ 700,000
Tenant improvement allowance											$ 2,100,000
Operating lease termination date			2023-01		2025-04
Storage space commenced							Apr. 1, 2021
Cambridge Lease [Member] | Prepaid and other assets [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating lease cash security deposit						400,000
Cambridge Lease [Member] | Deposits and other long term assets [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating lease cash security deposit						300,000
Boston Lease [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term	120 months
Operating leases number of renewal terms | RenewalTerm	2
Operating leasing renewal option to extend lease	5 years
Minimum Lease Payments						79,100,000
Letters of credit outstanding, amount						4,600,000
Withdrawal from irrevocable letters of credit						0
Restricted cash deposit used as collateral for letter of credit						$ 4,700,000
Boston Lease [Member] | Maximum [Member]
Commitments and Contingencies Disclosure [Line Items]
Tenant improvement allowance	$ 19,100,000

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Components of Lease Costs (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Lease cost
Operating lease cost	$ 2,253	$ 1,900
Total lease cost	$ 2,253	$ 1,900

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Supplemental Information Related to Leases (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash paid for amounts included in the measurement of lease liabilities (in thousands):
Operating cash flows from operating leases	$ 2,034	$ 1,950
New right-of-use assets obtained in exchange for lease obligations (in thousands):
Operating leases	$ 781	$ 0
Weighted-average remaining lease term (years):
Operating leases	5 months 9 days	6 months 3 days
Weighted-average discount rate:
Operating leases	7.40%	9.00%

Commitments and Contingencies_4

Commitments and Contingencies - Schedule of Minimum Annual Rental Payments Under Operating Lease Agreements (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Operating Leases
2022 (remaining nine months)	$ 7,621
2023	6,837
2024	12,527
2025	10,658
2026	10,376
Thereafter	62,814
Total minimum payments	110,833
Less: Amounts representing interest expense	(6,144)
Less: Amounts representing lease payments under the Boston Lease	(79,114)
Present value of future minimum lease payments	25,575
Less: Current portion of lease liability	(6,886)	$ (7,483)
Noncurrent portion of lease liability	$ 18,689	$ 18,936

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid research and development-related expenses	$ 5,728	$ 2,672
Net contract asset	0	1,385
Collaboration receivable	2,235	688
Prepaid insurance	1,314	1,769
Interest and other receivables	224	292
Facilities-related deposits	455	0
Other	990	866
Total prepaid expenses and other current assets	$ 10,946	$ 7,672

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Deposits and Other Long-Term Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Deposits And Other Long Term Assets Disclosure [Abstract]
Lease security deposits	$ 934	$ 1,305
Prepaid research and development-related expenses	630	1,047
Total deposits and other long-term assets	$ 1,564	$ 2,352

Collaboration and License Agr_3

Collaboration and License Agreements - Additional Information (Detail) - USD ($)	Aug. 14, 2021	Nov. 30, 2021	Jan. 31, 2021	Oct. 31, 2020	Oct. 31, 2018	Sep. 30, 2018	Aug. 31, 2018	Mar. 31, 2022	Sep. 30, 2021	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2019	Dec. 31, 2020	Oct. 31, 2017
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock shares issued								0			0
Contract with Customer, Liability, Current								$ 12,324,000			$ 17,201,000
Number of common shares sold										1,169,591	3,990,869
Increase in contribution revenue								(6,500,000)		$ (514,000)
Revenue								$ 7,191,000		39,693,000
Common stock, shares issued								72,779,508			69,047,878
Research and development								$ 28,199,000		24,856,000
Restricted cash, current								9,395,000			$ 11,285,000
Restricted Cash								9,395,000			11,285,000
License Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue								4,745,000		39,693,000
Grant Revenues [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue								2,446,000		0
Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from Issuance of Common Stock								100,000,000
Gilead Sciences Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred Contract Acquisition Costs								0
Coalition for Epidemic Preparedness Innovations [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Restricted Cash Current								$ 7,000,000			9,400,000
Blue Bird Bio Inc to 2seventy [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Future Milestone And Royalty Payments, Reduction Percentage								50.00%
Collaboration Agreement [Member] | Bluebird Bio Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from issuance of convertible preferred stock, net of issuance costs							$ 10,000,000
Offering price per share					$ 15
Proceeds from Issuance of Common Stock					$ 10,000,000
Number of common shares sold					666,667
Maximum development, regulatory, and commercial milestones							$ 1,200,000,000
Collaboration agreement early termination notice period								120 days
Early termination reduction of future milestone and royalty payments, description								Additionally, all of 2seventy’s payment obligations that have not yet accrued related to future milestone and royalty payments will be reduced by 50% for the remainder of the agreement term.
Collaboration Agreement [Member] | Bluebird Bio Inc [Member] | Series C [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock shares issued							768,115
Offering price per share							$ 13.04
Collaboration Agreement [Member] | Blue Bird Bio Inc to 2seventy [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment							$ 20,000,000
Revenue recognition contract start month year								2018-08
Revenue recognition contract end month year								2023-08
Collaboration and license revenue								$ 4,000,000		700,000
Increase in contribution revenue								3,500,000
Deferred revenue								4,700,000			8,700,000
Contract assets								0			0
Receivables								$ 0			0
Collaboration Agreement [Member] | 2 Seventy [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment							20,000,000
Proceeds from issuance of convertible preferred stock, net of issuance costs							$ 10,000,000
Revenue recognition contract end month year								2023-09
Collaboration Agreement [Member] | 2 Seventy [Member] | Series C [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock shares issued							768,115
Offering price per share							$ 13.04
Issuance of convertible preferred stock, Transaction price							$ 10,000,000
Collaboration Agreement [Member] | Arbutus Biopharma Corporation and Protiva Biotherapeutics Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Maximum milestone consideration payable														$ 123,500,000
Milestone payment included in research and development expense						$ 2,500,000						$ 3,000,000
Research and development								$ 0		0
Collaboration, Option and License Agreement [Member] | Gilead Sciences Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment			$ 30,000,000
Offering price per share			$ 25.65
Proceeds from Issuance of Common Stock			$ 30,000,000
Collaboration agreement early termination notice period			90 days
Early termination reduction of future milestone and royalty payments, description								Additionally, if terminated early by Gilead for convenience or by the Company for material breach or insolvency, all of Gilead’s payment obligations for reimbursable costs or for future milestone and royalty payments remain. If terminated early by Gilead for material breach or insolvency, all of Gilead’s unaccrued payment obligations related to future milestone and royalty payments will be reduced by 50% for the remainder of the agreement term.
Revenue recognition contract start month year								2021-01
Deferred revenue								$ 99,000			0
Contract assets								0			1,385,000
Receivables								$ 2,200,000			700,000
Maximum aggregate contingent milestone payment			$ 685,000,000
Proceeds from equity investment			$ 30,000,000
Common stock fair value closing price per share			$ 18.10
Non-refundable option fee			$ 40,000,000
Collaboration agreement termination term								Gilead may terminate the Gilead Supply Agreement without cause by giving six months prior written notice and any active orders with 60-day notice without terminating the agreement, and either party may terminate based on an uncured material breach, insolvency of the other party, or in the event that the Gilead Collaboration Agreement is terminated. Upon termination, the Company will deliver all supply products that have been produced and destroy, reimburse or deliver materials that Gilead has reimbursed, and Gilead must pay for any manufacturing costs that the Company has actually incurred or committed to pay, including any cancellation costs owed to subcontractors.
Transaction price allocated to shares of common stock at fair value			$ 21,200,000
Common stock, shares issued			1,169,591
Common stock purchase price in excess of fair value			$ 8,800,000
Collaboration and license revenue										300,000
Deferred incremental costs to acquire contract										100,000
Collaboration, Option and License Agreement [Member] | Gilead Sciences Inc [Member] | License Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration and license revenue								$ 700,000		$ 38,600,000
Collaboration, Option and License Agreement [Member] | Gilead Sciences Inc [Member] | Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition contract end period										2 years
Collaboration, Option and License Agreement [Member] | Gilead Sciences Inc [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition contract end period										4 years
Option and License and Development Agreement [Member] | Genevant Sciences GmbH [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment				$ 2,000,000
Amount to extend the option term								1,000,000					$ 1,000,000
Option and License and Development Agreement [Member] | Genevant Sciences GmbH [Member] | Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment													$ 2,000,000
Option and License and Development Agreement [Member] | Genevant Sciences GmbH [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate payment in specified development regulatory and commercial milestone				71,000,000
Payments for options to license for each indication				$ 1,500,000
Non-Exclusive License and Development Agreement [Member] | Genevant Sciences GmbH [Member] | Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payments			1,500,000							$ 1,500,000
Maximum aggregate contingent milestone payments to be made by company			141,000,000
Milestone payments			$ 1,000,000							$ 1,000,000
Funding Agreement [Member] | Coalition for Epidemic Preparedness Innovations [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Agreement Total Funding											25,600,000
Deferred revenue								6,964,000			9,379,000
Additional Funding											5,000,000
Collaboration and license revenue								2,200,000			1,500,000
Total Grant Amount	$ 20,600,000
First tranche of funding received									$ 11,300,000
Grant Agreement [Member] | Gates Foundation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment		$ 2,200,000
Contract with Customer, Liability, Current								2,000,000
Future Funding Expected		1,000,000
Deferred revenue								2,035,000			$ 2,225,000
Revenue								$ 200,000
Total Grant Amount		$ 3,200,000

Collaboration and License Agr_4

Collaboration and License Agreements - Schedule of Changes in Contract Asset and Deferred Revenue Balance (Detail)	3 Months Ended
	Mar. 31, 2022USD ($)
Research Collaboration and License Agreement [Member] | Blue Bird Bio Inc to 2seventy [Member]
Deferred Revenue
Balance at December 31, 2021	$ 8,725,000
Additions	0
Deductions	3,994,000
Balance at March 31, 2022	4,731,000
Collaboration, Option and License Agreement [Member] | Gilead Sciences Inc [Member]
Contract Asset
Balance at December 31, 2021	1,385,000
Additions	123,000
Deductions	(1,508,000)
Balance at March 31, 2022	0
Deferred Revenue
Balance at December 31, 2021	0
Additions	99,000
Deductions	0
Balance at March 31, 2022	99,000
C E P I Funding Agreement [Member] | Coalition for Epidemic Preparedness Innovations [Member]
Deferred Revenue
Balance at December 31, 2021	9,379,000
Additions	0
Deductions	(2,415,000)
Balance at March 31, 2022	6,964,000
Grant Agreement [Member] | Gates Foundation [Member]
Deferred Revenue
Balance at December 31, 2021	2,225,000
Additions	0
Deductions	(190,000)
Balance at March 31, 2022	$ 2,035,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended			3 Months Ended		12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020	Oct. 31, 2019	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Subsidiary Sale Of Stock [Line Items]
Common stock, shares authorized				300,000,000		300,000,000
Common stock, par value				$ 0.0001		$ 0.0001
Preferred stock, shares authorized				10,000,000		10,000,000
Preferred stock, par value				$ 0.0001		$ 0.0001
Preferred stock, shares issued				0		0
Preferred stock, shares outstanding				0		0
Common stock, shares issued				72,779,508		69,047,878
Common stock, shares outstanding				72,779,508		69,047,878
Common stock voting rights				Holders of the Company’s common stock are entitled to one vote per share.
Common stock, preferred stock, debt securities, warrants and units covered in Registration Statement			$ 250,000,000	$ 250,000,000
Maximum offering expense agreed to be reimbursed			$ 50,000
Stock Issued During Period, Shares, New Issues					1,169,591	3,990,869
Warrant exercise price				$ 0.01
Warrants exercised				3,442,567
Warrants issued					$ 0
Common Stock and Warrants [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares issued				3,442,567
Common Stock [Member]
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock for warrant exercises, Share				3,442,567
Maximum [Member]
Subsidiary Sale Of Stock [Line Items]
Net proceeds from issuance of stock				$ 100,000,000
Maximum [Member] | March 2022 Registration Statement [Member]
Subsidiary Sale Of Stock [Line Items]
Net proceeds from issuance of stock				$ 100,000,000
Amended and Restated Certificate of Incorporation [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock, shares authorized				300,000,000
Common stock, par value				$ 0.0001
Preferred stock, shares authorized				10,000,000
Preferred stock, par value				$ 0.0001
ATM Equity Offering Program [Member]
Subsidiary Sale Of Stock [Line Items]
Net proceeds from issuance of stock						$ 9,800,000
Percentage of gross proceeds as underwriter compensation			3.00%
Stock Issued During Period, Shares, New Issues				0
ATM Equity Offering Program [Member] | Maximum [Member]
Subsidiary Sale Of Stock [Line Items]
Net proceeds from issuance of stock			$ 75,000,000
2022 At The Market Equity Offering Program [Member]
Subsidiary Sale Of Stock [Line Items]
Percentage of gross proceeds as underwriter compensation				3.00%
Maximum offering expense agreed to be reimbursed				$ 50,000
Stock Issued During Period, Shares, New Issues				0
Private Investment In Public Equity [Member]
Subsidiary Sale Of Stock [Line Items]
Issuance of pre-funded warrants, net of issuance costs							$ 87,700,000
Private Investment In Public Equity [Member] | Common Stock and Warrants [Member]
Subsidiary Sale Of Stock [Line Items]
Sale of common stock		5,543,351
Shares issued price per share		$ 3.34					$ 3.34
Proceed from issuance of stock and pre-funded warrants		$ 119,800,000
Sale Of Stock, Price Per Share Prepaid By Purchaser		$ 3.33					3.33
Warrant exercise price		0.01					0.01
Offering price per share		$ 3.34					3.34
Pre-funded warrants to purchase shares of common stock		27,480,719
Maximum percentage of common stock ownership to exercise warrant		9.99%
Private Investment In Public Equity [Member] | Common Stock and Warrants [Member] | Additional Shares [Member]
Subsidiary Sale Of Stock [Line Items]
Stock Issued During Period, Shares, New Issues		4,043,127
Shares issued price per share		$ 3.71					$ 3.71
Private Investment In Public Equity [Member] | Common Stock [Member]
Subsidiary Sale Of Stock [Line Items]
Net proceeds from issuance of stock	$ 52,700,000
Stock Issued During Period, Shares, New Issues	5,000,000
Shares issued price per share	$ 11

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Issued and Outstanding Warrants to Purchase Shares of the Company's Common Stock (Detail)	3 Months Ended
	Mar. 31, 2022$ / sharesshares
Equity [Abstract]
Issue Date	Dec. 28, 2020
Expiration Date	None
Warrant exercise price | $ / shares	$ 0.01
Number of warrants outstanding | shares	13,573,704

Stock Based Compensation - Addi

Stock Based Compensation - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021	Apr. 30, 2021	Sep. 30, 2018	Aug. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance	4,009,284		3,459,187
Intrinsic value of stock option awards exercised	$ 0.3	$ 3.9
Unrecognized compensation cost related to non-vested employee and consultant options	$ 22.3
Recognition period of unrecognized compensation cost related to non-vested employee and consultant	2 years 7 months 6 days
Fair value of shares vested	$ 4
Restricted Stock Unit Awards under 2018 Equity Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation by shared based payment award, description	We have granted restricted stock unit awards under the 2018 Equity Plan. Our restricted stock unit awards have a term of up to 10 years and generally vest over a 1 or 2-year period.
Restricted Stock Unit Awards under 2018 Equity Plan | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting period	2 years
Option granted expiration period	10 years
Restricted Stock Unit Awards under 2018 Equity Plan | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting period	1 year
2018 Award Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance						92,815
Number of shares available for issuance					2,690,000
Increase in shares available for issuance	4.00%
Maximum number of shares authorized	45,000,000
Minimum percentage of outstanding shares held by individual	10.00%
Minimum percentage fair market value of share price	110.00%
Option vesting period	4 years
Share based compensation by shared based payment award, description	If an individual owns stock representing 10% or more of the outstanding shares, the price of each share shall be at least 110% of the fair market value, as determined by the board of directors. Options granted have a term of up to 10 years and generally vest over a 4-year period with a straight-line vesting.
2018 Award Incentive Plan [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option granted expiration period	10 years
2021 Employment Inducement Incentive Award Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance				790,400

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Number of Shares Available for Issuance
Number of options beginning balance	3,459,187
Authorized	2,761,915
Granted	(2,550,341)
Exercised	0
Cancelled	338,523
Number of options ending balance	4,009,284	3,459,187
Number of Shares
Outstanding at beginning of period	5,107,335
Granted	2,200,168
Exercised	(73,713)
Cancelled	(302,640)
Outstanding at end of period	6,931,150	5,107,335
Options Outstanding, Number of Shares, Vested and exercisable	2,329,666
Options Outstanding, Number of Shares, Vested and expected to vest	6,076,920
Weighted-Average Exercise Price
Beginning Balance	$ 9.82
Granted	5.61
Exercised	0.87
Cancelled	10.21
Ending Balance	8.56	$ 9.82
Weighted-Average Exercise Price, Vested and exercisable	8.94
Weighted-Average Exercise Price, Vested and expected to vest	$ 8.65
Options Outstanding, Weighted-Average Remaining Contractual Term (in years)	8 years 6 months 10 days	8 years 1 month 17 days
Options Outstanding, Weighted-Average Remaining Contractual Term, Vested and exercisable (in years)	7 years 2 months 12 days
Options Outstanding, Weighted-Average Remaining Contractual Term, Vested and expected to vest (in years)	8 years 4 months 24 days
Options Outstanding, Aggregate Intrinsic Value	$ 1,016	$ 17,153
Options Outstanding, Aggregate Intrinsic Value, Vested and exercisable	996
Options Outstanding, Aggregate Intrinsic Value, Vested and expected to vest	$ 1,013

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Restricted Stock Unit Activity (Detail)	3 Months Ended
	Mar. 31, 2022$ / sharesshares
Number of Shares
Outstanding, unvested beginning balance | shares	708,800
Issued | shares	350,173
Vested | shares	(353,300)
Canceled/Forfeited | shares	(35,883)
Outstanding, unvested ending balance | shares	669,790
Weighted Average Grant Date Fair Value
Outstanding, unvested beginning balance | $ / shares	$ 5.29
Issued | $ / shares	5.46
Vested | $ / shares	5.29
Canceled/Forfeited | $ / shares	5.31
Outstanding, unvested ending balance | $ / shares	$ 5.38

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock Based Compensation Expense	$ 3,131	$ 2,201
Research and Development Expense [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock Based Compensation Expense	1,745	1,481
General and Administrative Expense [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock Based Compensation Expense	$ 1,386	$ 720

Net Loss Per Common Share - Com

Net Loss Per Common Share - Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Numerator:
Net income (loss)	$ (28,916)	$ 7,923
Denominator:
Weighted-average common shares outstanding, basic	86,277,599	75,987,372
Effect of dilutive shares	0	1,476,984
Weighted-average common shares outstanding, diluted	86,277,599	77,464,356
Net income (loss) per share, basic	$ (0.34)	$ 0.10
Net income (loss) per share, diluted	$ (0.34)	$ 0.10

Net Loss Per Common Share - Add

Net Loss Per Common Share - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2020
Earnings Per Share Basic [Line Items]
Warrants exercised	3,442,567
Stock issued upon exercise of stock options	$ 64	$ 1,824
Number of warrants outstanding	13,573,704
Common Stock and Pre-funded Warrants [Member]
Earnings Per Share Basic [Line Items]
Outstanding warrants to purchase common stock			27,480,719
Class of warrant nominal exercise price			$ 0.01

Net Loss Per Common Share - C_2

Net Loss Per Common Share - Computation of Potentially Anti-dilutive Securities (Detail) - shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities that were not included in the diluted per share calculations	7,708,450	1,417,134
Options Issued and Outstanding and ESPP Shares Issuable and Outstanding [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities that were not included in the diluted per share calculations	7,038,660	1,416,794
Restricted Stock Subject to Future Vesting [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities that were not included in the diluted per share calculations	669,790	340

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ in Millions	Apr. 21, 2022	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Subsequent Event [Line Items]
Issuance of common stock, net of issuance costs, shares			1,169,591	3,990,869
At The Market Equity Offering Program [Member]
Subsequent Event [Line Items]
Issuance of common stock, net of issuance costs, shares		0
Net proceeds from issuance of stock				$ 9.8
Subsequent Event [Member] | 2021 Employment Inducement Incentive Award Plan [Member]
Subsequent Event [Line Items]
Share limit increase	700,000