0001564590-21-024572 | 10-Q | XBRL Viewer

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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2021	May 03, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
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 Common Stock, Shares Outstanding		49,197,828
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

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 108,505	$ 170,056
Marketable securities	89,501	1,002
Prepaid expenses and other current assets	4,507	4,332
Total current assets	202,513	175,390
Property and equipment, net	21,693	22,105
Operating lease right-of-use assets	19,997	21,344
Deposits and other long-term assets	2,736	2,728
Total assets	246,939	221,567
Current liabilities:
Accounts payable	6,368	9,578
Accrued compensation	3,821	6,331
Accrued liabilities	571	677
Accrued research and development expenses	1,558	1,053
Lease liabilities, current portion	6,075	5,874
Deferred revenue, current portion	3,386	3,475
Total current liabilities	21,779	26,988
Other non-current liabilities	395	395
Lease liabilities, net of current portion	17,619	19,225
Deferred revenue, net of current portion	7,795	8,220
Total liabilities	47,588	54,828
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	0	0
Common stock, $0.0001 par value; 300,000,000 shares authorized at March 31, 2021 and December 31, 2020; 49,197,828 and 47,552,693 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	18	18
Additional paid-in capital	517,715	493,023
Accumulated other comprehensive loss	(3)	0
Accumulated deficit	(318,379)	(326,302)
Total stockholders’ equity	199,351	166,739
Total liabilities and stockholders’ equity	$ 246,939	$ 221,567

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
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	49,197,828	47,552,693
Common stock, shares outstanding	49,197,828	47,552,693

Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Total revenues	$ 39,693	$ 1,262
Revenue from Contract with Customer, Product and Service [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember
Operating expenses:
Research and development	$ 24,856	$ 22,468
General and administrative	6,941	5,465
Total operating expenses	31,797	27,933
Income (loss) from operations	7,896	(26,671)
Interest income, net	27	465
Net income (loss)	7,923	(26,206)
Other comprehensive loss:
Unrealized loss on marketable securities	(3)	(44)
Net and comprehensive income (loss)	$ 7,920	$ (26,250)
Net income (loss) per share, basic	$ 0.10	$ (0.71)
Weighted-average number of shares used in computing net income (loss) per share, basic	75,987,372	36,798,562
Net income (loss) per share, diluted	$ 0.10	$ (0.71)
Weighted-average number of shares used in computing net income (loss) per share, diluted	77,464,356	36,798,562

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	ATM Equity Offering Program [Member]	Common Stock [Member]	Common Stock [Member] ATM Equity Offering Program [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] ATM Equity Offering Program [Member]	Accumulated Other Comprehensive Gain (Loss) [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2019	$ 134,344		$ 17		$ 355,291		$ 24	$ (220,988)
Balance, shares at Dec. 31, 2019			36,332,956
Issuance of common stock, net of issuance costs		$ 5,577				$ 5,577
Issuance of common stock, net of issuance costs, shares				568,369
Unrealized loss on marketable securities	(44)						(44)
Lapse of repurchase rights related to common stock issued pursuant to early exercises	8				8
Lapse of repurchase rights related to common stock issued pursuant to early exercises, shares			23,732
Issuance of common stock upon exercise of stock options	91				91
Issuance of common stock upon exercise of stock options, shares			60,682
Stock-based compensation	1,619				1,619
Net income (loss)	(26,206)							(26,206)
Balance at Mar. 31, 2020	115,389		$ 17		362,586		(20)	(247,194)
Balance, shares at Mar. 31, 2020			36,985,739
Balance at Dec. 31, 2019	134,344		$ 17		355,291		24	(220,988)
Balance, shares at Dec. 31, 2019			36,332,956
Issuance of common stock, net of issuance costs, shares		1,160,193
Balance at Dec. 31, 2020	166,739		$ 18		493,023			(326,302)
Balance, shares at Dec. 31, 2020			47,552,693
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, net of issuance costs, shares			1,169,591
Issuance of common stock, net of issuance costs, shares		0
Unrealized loss on marketable securities	(3)						(3)
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		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

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Common Stock [Member]
Payment for issuance cost under Sales Purchase Agreement	$ 330
Common Stock [Member] \| ATM Equity Offering Program [Member]
Payment for issuance cost	$ 4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Operating activities
Net income (loss)	$ 7,923	$ (26,206)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	1,595	1,626
Net amortization of premiums and discounts on marketable securities	107	(78)
Stock-based compensation	2,201	1,619
Non-cash operating lease expense	1,900	1,850
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(182)	32
Deposits and other long-term assets	(7)	83
Accounts payable	1,637	865
Accrued compensation	(2,510)	(1,825)
Accrued and other non-current liabilities	(51)	(38)
Accrued research and development expenses	505	532
Lease liability	(1,950)	(520)
Deferred revenue	(514)	(917)
Net cash provided by (used in) operating activities	10,654	(22,977)
Investing activities
Purchase of marketable securities	(89,610)	(3,805)
Maturities of marketable securities	1,000	17,167
Sales of marketable securities	0	3,021
Purchase of property and equipment	(990)	(1,609)
Net cash provided by (used in) investing activities	(89,600)	14,774
Financing activities
Proceeds from issuance of common stock, net of issuance costs	2,103	5,659
Payments of deferred financing costs	(5,878)	(4)
Net cash provided by financing activities	17,395	5,655
Net decrease in cash, cash equivalents and restricted cash	(61,551)	(2,548)
Cash, cash equivalents and restricted cash at beginning of period	171,048	58,400	$ 58,400
Cash, cash equivalents and restricted cash at end of period	109,497	55,852	$ 171,048
Supplemental disclosures of non-cash investing and financing information
Property and equipment purchases accrued but not yet paid	509	946
Deferred financing costs included in accrued liabilities and accounts payable	46	0
Public Offering [Member]
Financing activities
Proceeds from issuance of common stock, net of issuance costs	$ 21,170	$ 0

Organization

3 Months Ended

Mar. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization

1.	Organization

Description of Business

Gritstone bio, Inc. (“Gritstone” or the “Company”), previously known as “Gritstone Oncology, Inc.”, is a biotechnology company developing targeted immunotherapies for cancer and infectious disease. The Company was incorporated in the state of Delaware in August 2015, and is based in Emeryville, California and Cambridge, Massachusetts, with 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. During the three months ended March 31, 2021, the Company had net income of $7.9 million and $10.7 million of cash provided by operating activities. The Company had an accumulated deficit of $318.4 million as of March 31, 2021. 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, under an “at the market offering” (the “ATM Offering Program”) and private placement of common stock and pre-funded warrants, as well as proceeds from its collaboration arrangements. As of March 31, 2021, the Company had cash, cash equivalents and marketable securities of $198.0 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 Quarterly Report on Form 10-Q.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2021

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 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 financial statements as of and for the year ended December 31, 2020, which are included in the Company’s Annual Report on Form 10-K, as filed with the SEC on March 11, 2021.

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. On an ongoing basis, management evaluates its estimates, including those related to preclinical and clinical study trial accruals, fair value of assets and liabilities, the fair value of right-of-use assets (“ROU Assets”) and lease liabilities, fair value of pre-funded warrants, revenue recognition, and the fair value of stock-based compensation awards. 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.

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 consolidated balance sheets. As of March 31, 2021, 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 immunotherapy 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 a letter of credit under a lease agreement that has been collateralized by a cash deposit for an equal amount and is recorded within deposits and other long-term assets on the condensed consolidated balance sheets based on the term of the underlying lease. The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same amounts shown in the statements of cash flows (in thousands):

	March 31,		December 31,
	2021		2020
Cash and cash equivalents	$	108,505	$	170,056
Restricted cash		992		992
Total cash, cash equivalents and restricted cash	$	109,497	$	171,048

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. All 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 at March 31, 2021 and December 31, 2020. 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 to not 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 analyzes its collaboration agreements 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 vender-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.

Income Taxes

On March 18, 2020, the Families First Coronavirus Response Act (“FFCR Act”), and on March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“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, 2021 and 2022 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, 2021 and 2022.

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, 2021; 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 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 is currently evaluating the impact of ASU 2020-06 on its condensed consolidated financial statements and related disclosures.

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. The Company does not expect the adoption of ASU 2020-10 to have a material impact on its condensed consolidated financial statements and related disclosures.

Cash Equivalents and Marketable Securities

3 Months Ended

Mar. 31, 2021

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, 2021
Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	51,940	$	—	$	—		$	51,940
Commercial paper		6,000		—		—			6,000
Corporate debt securities		4,143		—		(1	)		4,142
Total cash equivalents		62,083		—		(1	)		62,082
Short-term marketable securities:
Commercial paper		31,724		2		(2	)		31,724
Corporate debt securities		17,444		—		(9	)		17,435
U.S. treasuries		40,335		7		—			40,342
Total short-term marketable securities		89,503		9		(11	)		89,501
Total	$	151,586	$	9	$	(12	)	$	151,583

	December 31, 2020
Description	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Cash equivalents:
Money market funds	$	36,801	$	—	$	—	$	36,801
Total cash equivalents		36,801		—		—		36,801
Short-term marketable securities:
U.S. treasuries		1,002		—		—		1,002
Total short-term marketable securities		1,002		—		—		1,002
Total	$	37,803	$	—	$	—	$	37,803

All marketable securities held as of March 31, 2021 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, 2021, the Company did not 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 surrounding the COVID-19 pandemic 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, 2021. The Company will continue to assess the current and expected future economic and market conditions surrounding the COVID-19 pandemic, as further development arises.

See Note 4 for further information regarding the fair value of the Company’s financial instruments.

Fair Value Measurements

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurements

4.	Fair Value Measurements

The Company determines the fair value of financial and non-financial assets and liabilities based on the assumptions that market participants would use in pricing the asset or liability in an orderly transaction between market participants at the measurement date. The identification of market participant assumptions provides a basis for determining what inputs are to be used for pricing each asset or liability. A fair value hierarchy has been established, which gives precedence to fair value measurements calculated using observable inputs over those using unobservable inputs. This hierarchy prioritizes the inputs into three broad levels, as follows:

•

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.

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.

The Company’s financial assets and liabilities 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, 2021
Description	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	51,940	$	51,940	$	—	$	—
Commercial paper		6,000		—		6,000		—
Corporate debt securities		4,142		—		4,142		—
Total cash equivalents		62,082		51,940		10,142		—
Short-term marketable securities:
U.S. treasuries		38,229		38,229		—		—
U.S. government securities		2,113		—		2,113		—
Commercial paper		31,724		—		31,724		—
Corporate debt securities		17,435		—		17,435		—
Total short-term marketable securities		89,501		38,229		51,272		—
Total	$	151,583	$	90,169	$	61,414	$	—

	December 31, 2020
Description	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	36,801	$	36,801	$	—	$	—
Total cash equivalents		36,801		36,801		—		—
Short-term marketable securities:
U.S. treasuries		1,002		1,002		—		—
Total short-term marketable securities		1,002		1,002		—		—
Total	$	37,803	$	37,803	$	—	$	—

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, and U.S. government 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.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Property and Equipment, Net

3 Months Ended

Mar. 31, 2021

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,
	2021			2020
Computer equipment and software	$	971		$	971
Furniture and fixtures		2,054			2,054
Laboratory equipment		23,321			22,213
Leasehold improvements		13,770			13,726
		40,116			38,964
Less accumulated depreciation and amortization		(18,516	)		(16,925	)
Construction-in-progress		93			66
Total property and equipment, net	$	21,693		$	22,105

Depreciation and amortization expense was $1.6 million for each of the three months ended March 31, 2021 and 2020.

Commitments and Contingencies

3 Months Ended

Mar. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

6.	Commitments and Contingencies

Leases

In January 2019, the Company entered into a 120-month operating lease for a new facility in Emeryville, California, with office and laboratory space for the Company’s new principal executive offices. In conjunction with signing the 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, 2021 and December 31, 2020. The lease agreement 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’s obligation to pay rent commenced on November 1, 2019. The Company has determined the tenant improvements to be lessee owned and therefore has recorded a $9.2 million ROU Asset and a $14.5 million lease liability on the condensed consolidated balance sheet as of March 31, 2021.

In February 2016, the Company entered into a 67-month non-cancelable operating lease effective October 2016 for a facility in Cambridge, Massachusetts, with laboratory and office space. In conjunction with signing the lease, the Company paid a cash security deposit of $0.3 million, which is recorded in deposits and other long-term assets on the Company’s condensed consolidated balance sheet as of March 31, 2021. The lease agreement includes an escalation clause for increased rent and a renewal provision allowing the Company to extend this lease for an additional three years at the prevailing rental rate. The lessor provided the Company a tenant improvement allowance for a total of $2.1 million to complete the laboratory and office renovation.

In March 2017, the Company entered into a non-cancelable operating lease (the “Pleasanton Lease”) to lease 42,620 square feet of office, cleanroom, and laboratory support manufacturing space in Pleasanton, California (the “Pleasanton Facility”). Subsequently, in April 2017, the Company took possession of the space. The Pleasanton Lease includes a free rent period, escalating rent payments and a term that expires on November 30, 2024. The Company has the option to extend the lease term for a period of five years at the then market rental rate. The Company’s obligation to pay rent commenced in December 2017. 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 all of its obligations. The letter of credit may be reduced based on certain levels of cash and cash equivalents the

Company holds. As of March 31, 2021, 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 for the Pleasanton Facility. 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, 2021 and December 31, 2020.

In September 2018, the Company entered into a 24-month non-cancelable operating lease for an additional facility in Cambridge, Massachusetts with laboratory and office space. The Company also paid a cash security deposit of $0.3 million, which included $0.1 million for the last month’s rent and has been classified as part of the operating lease ROU assets on the condensed consolidated balance sheets as of March 31, 2021 and December 31, 2020. The remaining security deposit is recorded in deposits and other long-term assets on the Company’s condensed consolidated balance sheet as of March 31, 2021.

In July 2019, the Company amended its Cambridge, Massachusetts laboratory and office space facility lease. The amendment extended the original 24-month lease term ending in August 2020 by another 12 months through August 2021 and added additional leased laboratory and office space. Upon six months written notice, the Company has the right to terminate the amended lease agreement. The amendment provides for annual base rent of approximately $3.4 million, effective July 2019. In conjunction with signing the lease amendment, the Company prepaid an additional twelve months base rent for both the original leased space and the additional leased space in the amount of $3.2 million, which was reclassified to operating lease right-of-use assets on the condensed consolidated balance sheets. The Company also paid a cash security deposit of $0.3 million, which included $0.1 million for the last month’s rent and has been classified as part of the operating lease right-of-use assets on the condensed consolidated balance sheets as of March 31, 2021 and December 31, 2020. The remaining security deposit is recorded in deposits and other long-term assets on the Company’s condensed consolidated balance sheets as of March 31, 2021 and December 31, 2020.

In May 2020, the Company executed an additional amendment to its Cambridge, Massachusetts laboratory and office space facility lease. The amendment extended the lease term by an additional 12 months through August 2022. Upon six months written notice, the Company has the right to terminate the amended lease agreement. The amendment provides for annual base rent of approximately $3.6 million, effective September 2021. This amendment resulted in an increase to the ROU Assets and lease liabilities of $3.1 million.

In May 2019, the Company entered into a 64-month non-cancelable operating lease for additional office space in Pleasanton, California. The lessor provided the Company a tenant improvement allowance for a total of $0.1 million to complete the office renovation. The Company’s obligation to pay rent commenced on August 1, 2019. The Company has determined the tenant improvements to be lessee owned and therefore has recorded a $0.3 million ROU Asset and a $0.4 million lease liability on the condensed consolidated balance sheets as of March 31, 2021.

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,
	2021		2020
Lease cost
Operating lease cost	$	1,900	$	1,850
Short-term lease cost		—		8
Total lease cost	$	1,900	$	1,858

Supplemental information related to leases was as follows (in thousands):

	Three Months Ended March 31,
	2021			2020
Cash paid for amounts included in the measurement of lease liabilities (in thousands):
Operating cash flows from operating leases	$	1,950		$	1,053
New right-of-use assets obtained in exchange for lease obligations (in thousands):
Operating leases	$	—		$	—
Weighted average remaining lease term (years):
Operating leases		6.1			6.9
Weighted average discount rate:
Operating leases		9.0	%		9.0	%

As of March 31, 2021, minimum annual rental payments under the Company’s operating lease agreements are as follows (in thousands):

	Lease Financing Obligation
Year ending December 31,
2021 (remaining nine months)	$	5,912
2022		5,836
2023		3,459
2024		3,459
2025		2,456
Thereafter		10,076
Total minimum payments		31,198
Less: Amounts representing interest expense		(7,504	)
Present value of future minimum lease payments		23,694
Less: Current portion of lease liability		(6,075	)
Noncurrent portion of lease liability	$	17,619

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 drug candidates. The Company is also obligated to pay the CRO certain milestone payments of up to $36.4 million on achievement of specified events. None of these events had occurred as of March 31, 2021. During the three months ended March 31, 2021, the Company had immaterial research and development expense under the agreement. The Company had no research and development expense under the agreement during the three months ended March 31, 2020.

In May 2019, the Company entered into a contract research and testing agreement with a third-party contract research organization to provide antibody discovery related services. The Company is also 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, 2021. No research and development expense was recorded under the agreement during the three months ended March 31, 2021. During the three months ended March 31, 2020, the Company recognized an insignificant amount of research and development expense under the agreement.

Guarantees and Indemnifications

The Company, as permitted under Delaware law and in accordance with its certification 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

3 Months Ended

Mar. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [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,
	2021		2020
Prepaid insurance	$	988	$	1,480
Prepaid research and development-related expenses		2,757		2,584
Interest and other receivables		249		8
Other		513		260
Total prepaid expenses and other current assets	$	4,507	$	4,332

Deposits and Other Long-Term Assets

Deposits and other long-term assets consist of the following (in thousands):

	March 31,		December 31,
	2021		2020
Lease security deposits	$	1,225	$	1,218
Prepaid research and development-related expenses		519		518
Restricted cash		992		992
Total deposits and other long-term assets	$	2,736	$	2,728

Collaboration and License Agreements

3 Months Ended

Mar. 31, 2021

Collaborative And License Agreements [Abstract]

Collaboration and License Agreements

8.	Collaboration and License Agreements

bluebird bio, Inc.

In August 2018, the Company entered into a Research Collaboration and License Agreement (the “bluebird Collaboration Agreement”) with bluebird bio, Inc. (“bluebird”). Under the terms of the bluebird Collaboration Agreement, the Company will provide to bluebird 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 bluebird 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 bluebird Collaboration Agreement, bluebird 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 IPO. In October 2018, bluebird 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 bluebird Collaboration 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 bluebird Collaboration Agreement. None of these events had occurred as of March 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 bluebird Collaboration Agreement, which extended the timeline for the Company and bluebird to execute a Patient Selection Services Agreement from within one year to within two years after the Effective Date of the bluebird Collaboration 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. Both 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.

bluebird may terminate the bluebird Collaboration 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 Gritstone on a licensed product. The bluebird Collaboration 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 bluebird under the licensed intellectual property will remain in effect in accordance with their respective terms. Additionally, all of bluebird’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 bluebird is a customer, and the contract is not subject to guidance on collaborative arrangements. This is because the Company granted to bluebird 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 bluebird Collaboration Agreement: 1) transfer of a license to intellectual property and related technology know-how (“License and Know-How”); 2) the obligation to perform target selection and TCR generation services (“Research and Development Services”); and 3) participation on the Joint Steering Committee (the “JSC”). The Company provided to bluebird 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 bluebird Collaboration Agreement, because bluebird is dependent on the Company to execute the Research and Development Services and participate on the JSC in order for bluebird 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 bluebird reaching various milestones are not considered performance obligations at the inception of the arrangement.

The transaction price at the inception of the bluebird Collaboration Agreement consisted of the upfront payment of $20.0 million and the $10.0 million received from bluebird 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 March 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 bluebird’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 bluebird. 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 contract 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 bluebird terminating the agreement prior to August 2023 and determined, considering both quantitative and qualitative factors, that there were substantive non-monetary penalties to bluebird for doing so.

Revenue is recognized when, or as, the Company satisfies its performance obligation by transferring the promised services to bluebird. Revenue will be 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 bluebird. 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, 2021 and 2020, the Company recognized $0.7 million and $0.9 million, respectively, in collaboration revenue under the bluebird Collaboration Agreement. Deferred revenue of $11.0 million and $11.7 million was recorded on the condensed consolidated balance sheets in both current and long-term liabilities as of March 31, 2021, and December 31, 2020, respectively. Deferred revenue relates to the performance obligations identified under the bluebird Collaboration Agreement and will be recognized over the period the performance obligations are expected to be satisfied, which is currently estimated to be through mid-2023.

Changes in the deferred revenue balance during the three months ended March 31, 2021 for the bluebird Collaboration Agreement are as follows (in thousands):

	Deferred Revenue
Balance at December 31, 2020	$	11,695
Additions		—
Deductions		(693	)
Balance at March 31, 2021	$	11,002

Gilead Sciences, Inc.

In January 2021, the Company entered into a Collaboration, Option and License Agreement (the “Gilead Collaboration Agreement”) with Gilead Sciences, Inc., or 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 this 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”). In addition, the Company and Gilead entered into a Supply Agreement (the “Gilead Supply Agreement”) under which Gritstone 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”). Concurrently, the Company also entered into a 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 Gilead agreed to 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 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, 2021 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 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. Further, 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 actually incurred or committed to pay by the Company 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 right is provided in the original contract, so Gilead’s decision to exercise the Option will not be considered a modification.

The Company identified the following performance obligations under the Gilead Collaboration Agreement: 1) 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; 2) preclinical research and development activities, manufacturing related activities, and participation on a Joint Steering Committee; and 3) 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 does not constitute a material right and is not a potential performance obligation. The Company evaluated if there is an interdependence between the promises and determined that the licenses are the predominant performance obligation and that the other promises are separable 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, 2021 based on the current research and development plan budget. 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 based 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 is 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 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, 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. Deferred revenue of $0.2 million was recorded on the condensed consolidated balance sheets as a current liability as of March 31, 2021. Deferred revenue relates to the performance obligations identified under the Gilead Collaboration Agreement and will be recognized over the period the performance obligations are expected to be satisfied, which is currently estimated to be through March 2022. There was no deferred revenue as of December 31, 2020.

Changes in the deferred revenue balance during the three months ended March 31, 2021 for the Gilead Collaboration Agreement are as follows (in thousands):

	Deferred Revenue
Balance at December 31, 2020	$	—
Additions		220
Deductions		(41	)
Balance at March 31, 2021	$	179

There were no receivables or net contract assets recorded as of March 31, 2021 or December 31, 2020 associated with the bluebird Collaboration Agreement or 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, 2021, deferred contract acquisition costs

were $0.1 million. Deferred contract acquisition costs amortized during the three months ended March 31, 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. Under the license agreement, the Company has an exclusive license to utilize certain Arbutus intellectual property, including patents and know-how relating to immunotherapy. During the three months ended March 31, 2021 and 2020, the Company had no research and development expense under the 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, 2021, 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, 2021 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 lipid nanoparticle, or 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 this 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.

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 (“SAM”) 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 $191.0 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.

Stockholders' Equity

3 Months Ended

Mar. 31, 2021

Equity [Abstract]

Stockholders' Equity

9.	Stockholders’ Equity

In connection with the completion of its IPO, in October 2018, the Company’s certificate of incorporation was amended and restated to provide for 300,000,000 authorized shares of common stock with a par value of $0.0001 per share and 10,000,000 authorized shares of preferred stock with a par value of $0.0001 per share.

The Company has 10,000,000 shares of preferred stock authorized for issuance, par value of $0.0001 per share. As of March 31, 2021 and December 31, 2020, no shares of preferred stock were issued and outstanding.

The Company has 300,000,000 shares of common stock authorized for issuance, par value $0.0001 per share. Holders of the Company’s common stock are entitled to one vote per share. As of March 31, 2021 and December 31, 2020, there were 49,197,828 and 47,552,693 shares of common stock issued and outstanding, respectively.

Sale of Common Stock, Preferred Stock and Pre-Funded Warrants

In October 2019, the Company filed a Registration Statement on Form S-3 (the “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 Shelf Registration Statement included a prospectus covering the offering, issuance and sale of up to $75.0 million of the Company’s common stock from time to time through the ATM Offering Program under the Securities Act of 1933, as amended (the “Securities Act”). The SEC declared the Shelf Registration Statement effective on November 8, 2019.

In October 2019, the Company also entered into the Sales Agreement with Cowen and Company, LLC (“Cowen”) to sell shares of the Company’s common stock, from time to time, with aggregate gross sales proceeds of up to $75.0 million, through an “at the market offering” under which Cowen will act as its sales agent. 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 through Cowen under the Sales Agreement. In addition, the Company has agreed to reimburse a portion of the expenses of Cowen in connection with the offering up to a maximum of $50,000. During the year ended December 31, 2020, the Company issued and sold 1,160,193 shares of its common stock through its ATM Offering Program and received net proceeds of approximately $9.8 million, after deducting commissions of $0.3 million and other offering expenses of $0.1 million. During the three months ended March 31, 2021, there was no sale of shares of the Company’s common stock through its ATM Offering Program.

In December 2020, the Company entered into an agreement 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 public offering price of $3.33 per share in a private placement transaction, or PIPE, financing. The Company received aggregate net proceeds of approximately $110.0 million after deducting placement agent commissions and offering expenses payable by the Company. 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 (“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 December 2020, the Company entered into an additional stock purchase agreement pursuant to which it sold an additional 4,043,127 shares of its common stock in a PIPE financing at a price per share of $3.71 for aggregate gross proceeds of $15.0 million. No additional Warrants were issued in connection with this second PIPE financing. The placement agent commissions and legal fees of $5.2 million related to these two PIPE financing transactions were included in accounts payable and accrued liabilities on the condensed consolidated balance sheets as of December 31, 2020.

Common Stock Warrants

As of March 31, 2021, 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		$	3.34				27,480,719

There were no warrants exercised during the three months ended March 31, 2021. There were no warrants issued or outstanding for the three months ended March 31, 2020.

Stock-Based Compensation

3 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [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”), the 2015 Plan terminated and no further awards will be granted under the 2015 Plan. 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 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 promote

the success and enhance the value of the Company by inducing new employees to commence employment with us, and by aligning the individual interests of new employees with the interests of our stockholders. Awards granted under the 2021 Plan are intended to constitute “employment inducement awards” under Nasdaq Listing Rule 5635(c)(4), and, therefore, 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 were initially reserved for issuance under the 2021 Plan. 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 us or one of our subsidiaries following a bona fide period of non-employment with us, and for whom such awards are granted as a material inducement to commencing employment with us or one of our subsidiaries. Awards under the 2021 Plan may not be granted to our consultants or non-employee directors.

The 2021 Plan is administered by our board of directors and, to the extent our board of directors delegates its authority, our compensation committee. In the event of a change in control in which the successor corporation refuses to assume or substitute any outstanding award under the 2021 Plan, the vesting of such award will accelerate in full. Our 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 2015 Plan and 2018 Plan activity is as follows:

				Options Outstanding
	Number of Shares Available for Issuance			Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2020		3,108,412			4,166,441		$	8.13		8.15	$	2,092
Authorized		1,902,107			—
Granted		(1,311,250	)		1,311,250		$	13.86
Exercised		—			(365,980	)	$	4.98
Cancelled		41,023			(41,023	)	$	13.53
Balance at March 31, 2021		3,740,292			5,070,688		$	9.79		8.49	$	7,103
Vested and exercisable – March 31, 2021					1,805,272		$	7.59		7.41	$	5,117
Vested and expected to vest – March 31, 2021					4,611,349		$	9.62		8.41	$	6,891

For the three months ended March 31, 2021 and 2020, the total intrinsic value of stock option awards exercised was $3.9 million and $0.4 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.

At March 31, 2021, $22.9 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 2.8 years. The total fair value of shares vested during the period ended March 31, 2021 was $1.4 million.

Stock-based compensation expense and awards granted to non-employees were immaterial for the three months ended March 31, 2021 and 2020.

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 2-year period. The following table summarizes our restricted stock unit activity during the three months ended March 31, 2021:

	Number of Shares			Weighted- Average Grant Date Fair Value
Outstanding, unvested at December 31, 2020		—		$	—
Issued		880,600		$	5.29
Canceled/Forfeited		(32,000	)	$	5.29
Outstanding, unvested at March 31, 2021		848,600		$	5.29

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,
	2021		2020
Research and development expenses	$	1,481	$	1,028
General and administrative expenses		720		591
Total	$	2,201	$	1,619

Net Income (Loss) Per Common Share

3 Months Ended

Mar. 31, 2021

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. Diluted net income (loss) per share is the same as basic net income (loss) per share, since the effects of potentially dilutive securities are antidilutive given the net income (loss) for each period presented.

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,
	2021		2020
Numerator:
Net income (loss)	$	7,923	$	(26,206	)
Denominator:
Weighted-average common shares outstanding, basic		75,987,372		36,798,562
Effect of dilutive shares		1,476,984		—
Weighted-average common shares outstanding, diluted		77,464,356		36,798,562
Net income (loss) per share, basic	$	0.10	$	(0.71	)
Net income (loss) per share, diluted	$	0.10	$	(0.71	)

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 they 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,		March 31,
	2021		2020
Options issued and outstanding and ESPP shares issuable and outstanding		1,416,794		4,647,441
Restricted stock subject to future vesting		340		—
Early exercised common stock subject to future vesting		—		7,142
Total		1,417,134		4,654,583

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates

Concentrations of Credit Risk

Other Risks and Uncertainties

Cash, Cash Equivalents, and Restricted Cash

	March 31,		December 31,
	2021		2020
Cash and cash equivalents	$	108,505	$	170,056
Restricted cash		992		992
Total cash, cash equivalents and restricted cash	$	109,497	$	171,048

Leases

The Company recognizes lease expense on a straight-line basis over the expected lease term.

Revenue Recognition

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.

Income Taxes

periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property.

Recently Issued Accounting Pronouncements Not Yet Adopted

Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

Cash, Cash Equivalents, and Restricted Cash

The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same amounts shown in the statements of cash flows (in thousands):

	March 31,		December 31,
	2021		2020
Cash and cash equivalents	$	108,505	$	170,056
Restricted cash		992		992
Total cash, cash equivalents and restricted cash	$	109,497	$	171,048

Cash Equivalents and Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2021

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, 2021
Description	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Cash equivalents:
Money market funds	$	51,940	$	—	$	—		$	51,940
Commercial paper		6,000		—		—			6,000
Corporate debt securities		4,143		—		(1	)		4,142
Total cash equivalents		62,083		—		(1	)		62,082
Short-term marketable securities:
Commercial paper		31,724		2		(2	)		31,724
Corporate debt securities		17,444		—		(9	)		17,435
U.S. treasuries		40,335		7		—			40,342
Total short-term marketable securities		89,503		9		(11	)		89,501
Total	$	151,586	$	9	$	(12	)	$	151,583

	December 31, 2020
Description	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Cash equivalents:
Money market funds	$	36,801	$	—	$	—	$	36,801
Total cash equivalents		36,801		—		—		36,801
Short-term marketable securities:
U.S. treasuries		1,002		—		—		1,002
Total short-term marketable securities		1,002		—		—		1,002
Total	$	37,803	$	—	$	—	$	37,803

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Assets and Liabilities Measured at Fair Value

The Company’s financial assets and liabilities 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, 2021
Description	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	51,940	$	51,940	$	—	$	—
Commercial paper		6,000		—		6,000		—
Corporate debt securities		4,142		—		4,142		—
Total cash equivalents		62,082		51,940		10,142		—
Short-term marketable securities:
U.S. treasuries		38,229		38,229		—		—
U.S. government securities		2,113		—		2,113		—
Commercial paper		31,724		—		31,724		—
Corporate debt securities		17,435		—		17,435		—
Total short-term marketable securities		89,501		38,229		51,272		—
Total	$	151,583	$	90,169	$	61,414	$	—

	December 31, 2020
Description	Total		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	36,801	$	36,801	$	—	$	—
Total cash equivalents		36,801		36,801		—		—
Short-term marketable securities:
U.S. treasuries		1,002		1,002		—		—
Total short-term marketable securities		1,002		1,002		—		—
Total	$	37,803	$	37,803	$	—	$	—

Property and Equipment, Net (Tables)

3 Months Ended

Mar. 31, 2021

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,
	2021			2020
Computer equipment and software	$	971		$	971
Furniture and fixtures		2,054			2,054
Laboratory equipment		23,321			22,213
Leasehold improvements		13,770			13,726
		40,116			38,964
Less accumulated depreciation and amortization		(18,516	)		(16,925	)
Construction-in-progress		93			66
Total property and equipment, net	$	21,693		$	22,105

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2021

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,
	2021		2020
Lease cost
Operating lease cost	$	1,900	$	1,850
Short-term lease cost		—		8
Total lease cost	$	1,900	$	1,858

Schedule of Supplemental Information Related to Leases

Supplemental information related to leases was as follows (in thousands):

	Three Months Ended March 31,
	2021			2020
Cash paid for amounts included in the measurement of lease liabilities (in thousands):
Operating cash flows from operating leases	$	1,950		$	1,053
New right-of-use assets obtained in exchange for lease obligations (in thousands):
Operating leases	$	—		$	—
Weighted average remaining lease term (years):
Operating leases		6.1			6.9
Weighted average discount rate:
Operating leases		9.0	%		9.0	%

Schedule of Minimum Annual Rental Payments Under Operating Lease Agreements

As of March 31, 2021, minimum annual rental payments under the Company’s operating lease agreements are as follows (in thousands):

	Lease Financing Obligation
Year ending December 31,
2021 (remaining nine months)	$	5,912
2022		5,836
2023		3,459
2024		3,459
2025		2,456
Thereafter		10,076
Total minimum payments		31,198
Less: Amounts representing interest expense		(7,504	)
Present value of future minimum lease payments		23,694
Less: Current portion of lease liability		(6,075	)
Noncurrent portion of lease liability	$	17,619

Balance Sheet Components (Tables)

3 Months Ended

Mar. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following (in thousands):

	March 31,		December 31,
	2021		2020
Prepaid insurance	$	988	$	1,480
Prepaid research and development-related expenses		2,757		2,584
Interest and other receivables		249		8
Other		513		260
Total prepaid expenses and other current assets	$	4,507	$	4,332

Schedule of Deposits and Other Long-Term Assets

Deposits and other long-term assets consist of the following (in thousands):

	March 31,		December 31,
	2021		2020
Lease security deposits	$	1,225	$	1,218
Prepaid research and development-related expenses		519		518
Restricted cash		992		992
Total deposits and other long-term assets	$	2,736	$	2,728

Collaboration and License Agreements (Tables)

3 Months Ended

Mar. 31, 2021

Collaboration Agreement [Member] | Bluebird Bio Inc [Member]

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Schedule of Changes in Deferred Revenue Balance

Changes in the deferred revenue balance during the three months ended March 31, 2021 for the bluebird Collaboration Agreement are as follows (in thousands):

	Deferred Revenue
Balance at December 31, 2020	$	11,695
Additions		—
Deductions		(693	)
Balance at March 31, 2021	$	11,002

Collaboration, Option and License Agreement [Member] | Gilead Sciences Inc [Member]

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Schedule of Changes in Deferred Revenue Balance

Changes in the deferred revenue balance during the three months ended March 31, 2021 for the Gilead Collaboration Agreement are as follows (in thousands):

	Deferred Revenue
Balance at December 31, 2020	$	—
Additions		220
Deductions		(41	)
Balance at March 31, 2021	$	179

Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2021

Equity [Abstract]

Schedule of Issued and Outstanding Warrants to Purchase Shares of the Company's Common Stock

As of March 31, 2021, 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		$	3.34				27,480,719

Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Stock Options Activity

A summary of the 2015 Plan and 2018 Plan activity is as follows:

				Options Outstanding
	Number of Shares Available for Issuance			Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2020		3,108,412			4,166,441		$	8.13		8.15	$	2,092
Authorized		1,902,107			—
Granted		(1,311,250	)		1,311,250		$	13.86
Exercised		—			(365,980	)	$	4.98
Cancelled		41,023			(41,023	)	$	13.53
Balance at March 31, 2021		3,740,292			5,070,688		$	9.79		8.49	$	7,103
Vested and exercisable – March 31, 2021					1,805,272		$	7.59		7.41	$	5,117
Vested and expected to vest – March 31, 2021					4,611,349		$	9.62		8.41	$	6,891

Summary of Restricted Stock Unit Activity

	Number of Shares			Weighted- Average Grant Date Fair Value
Outstanding, unvested at December 31, 2020		—		$	—
Issued		880,600		$	5.29
Canceled/Forfeited		(32,000	)	$	5.29
Outstanding, unvested at March 31, 2021		848,600		$	5.29

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,
	2021		2020
Research and development expenses	$	1,481	$	1,028
General and administrative expenses		720		591
Total	$	2,201	$	1,619

Net Income (Loss) Per Common Share (Tables)

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Computation of Basic and Diluted Net Income (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,
	2021		2020
Numerator:
Net income (loss)	$	7,923	$	(26,206	)
Denominator:
Weighted-average common shares outstanding, basic		75,987,372		36,798,562
Effect of dilutive shares		1,476,984		—
Weighted-average common shares outstanding, diluted		77,464,356		36,798,562
Net income (loss) per share, basic	$	0.10	$	(0.71	)
Net income (loss) per share, diluted	$	0.10	$	(0.71	)

Computation of Potentially Anti-Dilutive Securities

	March 31,		March 31,
	2021		2020
Options issued and outstanding and ESPP shares issuable and outstanding		1,416,794		4,647,441
Restricted stock subject to future vesting		340		—
Early exercised common stock subject to future vesting		—		7,142
Total		1,417,134		4,654,583

Organization - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) Segment	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of operating segments \| Segment	1
Net income (loss)	$ 7,923	$ (26,206)
Net cash provided by operating activities	10,654	$ (22,977)
Accumulated deficit	318,379		$ 326,302
Cash, cash equivalents and marketable securities	$ 198,000

- Definition

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

+ References

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+ Details

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 108,505	$ 170,056
Restricted cash	992	992
Total cash, cash equivalents and restricted cash	$ 109,497	$ 171,048

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	Jun. 29, 2020 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Use of net operating losses suspension period for medium and large business	3 years
Use of business incentive tax credits period cap	3 years
Taxable Years 2020, 2021 and 2022 [Member]
Summary Of Significant Accounting Policies [Line Items]
Minimum amount of taxable income where use of net operating losses is suspended	$ 1.0
Taxable Years 2020, 2021 and 2022 [Member] \| Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Business incentive tax credits to offset against taxes	$ 5.0

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, 2021	Dec. 31, 2020
Cash equivalents and marketable securities [Line Items]
Amortized Cost	$ 108,505	$ 170,056
Amortized Cost	151,586	37,803
Unrealized Gains	9	0
Unrealized Losses	(12)	0
Fair Value	151,583	37,803
Cash Equivalents [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	62,083	36,801
Unrealized Gains	0	0
Unrealized Losses	(1)	0
Fair Value	62,082	36,801
Cash Equivalents [Member] \| Money Market Funds [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	51,940	36,801
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	51,940	36,801
Cash Equivalents [Member] \| Corporate Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	4,143
Unrealized Gains	0
Unrealized Losses	(1)
Fair Value	4,142
Cash Equivalents [Member] \| Commercial Paper [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	6,000
Unrealized Gains	0
Unrealized Losses	0
Fair Value	6,000
Short-Term Marketable Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	89,503	1,002
Unrealized Gains	9	0
Unrealized Losses	(11)	0
Fair Value	89,501	1,002
Short-Term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	17,444
Unrealized Gains	0
Unrealized Losses	(9)
Fair Value	17,435
Short-Term Marketable Securities [Member] \| Commercial Paper [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	31,724
Unrealized Gains	2
Unrealized Losses	(2)
Fair Value	31,724
Short-Term Marketable Securities [Member] \| U.S. Treasuries [Member]
Cash equivalents and marketable securities [Line Items]
Amortized Cost	40,335	1,002
Unrealized Gains	7	0
Unrealized Losses	0	0
Fair Value	$ 40,342	$ 1,002

Cash Equivalents and Marketable Securities - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2021 USD ($) Security
Cash equivalents and marketable securities [Line Items]
Realized gains or losses on marketable securities, description	no material realized gains or losses
Number of individual securities in an unrealized loss position for 12 months or less \| Security	0
Credit loss \| $	$ 0
Maximum [Member]
Cash equivalents and marketable securities [Line Items]
Marketable securities contractual maturities period	1 year

Fair Value Measurements - Additional Information (Detail) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value, Assets, Level 1 to Level 2 Transfers	$ 0	$ 0
Fair Value, Liabilities, Level 1 to Level 2 Transfers	0	0
Fair Value, Assets, Level 2 to Level 1 Transfers	0	0
Fair Value, Liabilities, Level 2 to Level 1 Transfers	$ 0	$ 0

Property and Equipment, Net - Summary of Property and Equipment and Related Accumulated Depreciation and Amortization (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 40,116	$ 38,964
Less accumulated depreciation and amortization	(18,516)	(16,925)
Total property and equipment, net	21,693	22,105
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	971	971
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,054	2,054
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	23,321	22,213
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	13,770	13,726
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment, net	$ 93	$ 66

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 1,595	$ 1,626

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended					3 Months Ended
	May 31, 2020 USD ($)	Jul. 31, 2019 USD ($)	Jan. 31, 2019 USD ($) renewal_term	Sep. 30, 2018 USD ($)	Mar. 31, 2017 USD ($) ft²	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	May 31, 2019 USD ($)	Sep. 30, 2017 USD ($)	Feb. 28, 2016 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Operating lease cash security deposit						$ 1,225,000		$ 1,218,000
Operating lease right-of-use assets						19,997,000		21,344,000
Lease liability						23,694,000
Research and Development Expense						24,856,000	$ 22,468,000
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 California [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term			120 months
Operating leases number of renewal terms \| renewal_term			2
Operating leasing renewal option to extend lease			5 years
Operating lease cash security deposit						600,000		$ 600,000
Tenant improvement allowance			$ 4,000,000.0
Operating lease right-of-use assets						9,200,000
Lease liability						14,500,000
Cambridge Massachusetts [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term		24 months		24 months							67 months
Operating leasing renewal option to extend lease	12 months	12 months									3 years
Operating lease cash security deposit		$ 300,000		$ 300,000							$ 300,000
Tenant improvement allowance											$ 2,100,000
Operating lease right-of-use assets	$ 3,100,000
Lease liability	3,100,000
Operating leases rent expense		100,000		$ 100,000
Annual base rent	$ 3,600,000	$ 3,400,000
Operating lease termination date	2022-08	2021-08		2020-08
Base rent paid for the year		$ 3,200,000
Pleasanton [Member]
Commitments and Contingencies Disclosure [Line Items]
Operating leasing term									64 months
Operating leasing renewal option to extend lease					5 years
Tenant improvement allowance					$ 1,200,000				$ 100,000
Operating lease right-of-use assets						300,000
Lease liability						400,000
Net rentable area \| ft²					42,620
Lease expiration date					Nov. 30, 2024
Letters of credit outstanding, amount					$ 1,000,000.0
Withdrawal from irrevocable letters of credit						$ 0

Commitments and Contingencies - Schedule of Components of Lease Costs (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Lease cost
Operating lease cost	$ 1,900	$ 1,850
Short-term lease cost	0	8
Total lease cost	$ 1,900	$ 1,858

Commitments and Contingencies - Schedule of Supplemental Information Related to Leases (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash paid for amounts included in the measurement of lease liabilities (in thousands):
Operating cash flows from operating leases	$ 1,950	$ 1,053
Weighted average remaining lease term (years):
Operating leases	6 years 1 month 6 days	6 years 10 months 24 days
Weighted average discount rate:
Operating leases	9.00%	9.00%

Commitments and Contingencies - Schedule of Minimum Annual Rental Payments Under Operating Lease Agreements (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Operating Leases
2021 (remaining nine months)	$ 5,912
2022	5,836
2023	3,459
2024	3,459
2025	2,456
Thereafter	10,076
Total minimum payments	31,198
Less: Amounts representing interest expense	(7,504)
Present value of future minimum lease payments	23,694
Less: Current portion of lease liability	(6,075)	$ (5,874)
Noncurrent portion of lease liability	$ 17,619	$ 19,225

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Prepaid Expense And Other Assets Current [Abstract]
Prepaid insurance	$ 988	$ 1,480
Prepaid research and development-related expenses	2,757	2,584
Interest and other receivables	249	8
Other	513	260
Total prepaid expenses and other current assets	$ 4,507	$ 4,332

Balance Sheet Components - Schedule of Deposits and Other Long-Term Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Deposit Assets And Other Assets Noncurrent Disclosure [Abstract]
Lease security deposits	$ 1,225	$ 1,218
Prepaid research and development-related expenses	519	518
Restricted cash	992	992
Total deposits and other long-term assets	$ 2,736	$ 2,728

Collaboration and License Agreements - Additional Information (Detail) - USD ($)	1 Months Ended					3 Months Ended		12 Months Ended
	Jan. 31, 2021	Oct. 31, 2019	Oct. 31, 2018	Sep. 30, 2018	Aug. 31, 2018	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Oct. 31, 2020
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Preferred stock shares issued						0		0
Proceeds from purchase of Company's common stock						$ 2,103,000	$ 5,659,000
Common stock shares issued						49,197,828		47,552,693
Deferred revenue						$ 3,386,000		$ 3,475,000
Research and development						$ 24,856,000	22,468,000
Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from purchase of Company's common stock		$ 75,000,000.0
Gilead Sciences Inc [Member] \| Collaboration, Option and License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment	$ 30,000,000.0
Proceeds from purchase of Company's common stock	30,000,000.0
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 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.
Revenue recognition contract start month year						2021-01
Deferred revenue						$ 179,000
Upfront payments	30,000,000.0
Maximum aggregate contingent milestone payment	685,000,000.0
Non-refundable option fee	40,000,000.0
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 actually incurred or committed to pay by the Company including any cancellation costs owed to subcontractors.
Transaction price	$ 21,200,000
Common stock shares issued	1,169,591
Common stock purchase price in excess of fair value	$ 8,800,000
Deferred incremental costs						$ 100,000
Deferred contract acquisition costs						$ 100,000
Gilead Sciences Inc [Member] \| Collaboration, Option and License Agreement [Member] \| Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition contract end period						2 years
Gilead Sciences Inc [Member] \| Collaboration, Option and License Agreement [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognition contract end period						4 years
Gilead Sciences Inc [Member] \| Collaboration, Option and License Agreement [Member] \| Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Offering price per share	$ 18.10
Gilead Sciences Inc [Member] \| Stock Purchase Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Offering price per share	$ 25.65
Proceeds from equity investment	$ 30,000,000.0
Common stock fair value closing price per share	$ 18.10
Gilead Sciences Inc [Member] \| Stock Purchase Agreement [Member] \| Private Placement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Number of common shares sold	1,169,591
Genevant Sciences GmbH [Member] \| Non-Exclusive License and Development Agreement [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 payment	191,000,000.0
Milestone payments	$ 1,000,000.0					1,000,000.0
Bluebird Bio Inc [Member] \| Collaboration Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from non refundable upfront payment					$ 20,000,000.0
Proceeds from issuance of preferred stock					$ 10,000,000.0
Offering price per share			$ 15.00
Proceeds from purchase of Company's common stock			$ 10,000,000.0
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 bluebird’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.
Revenue recognition contract start month year						2018-08
Revenue recognition contract end month year						2023-08
Collaboration and license revenue						$ 700,000	900,000
Deferred revenue						11,002,000		11,695,000
Receivables						0		0
Contract assets						0		0
Bluebird Bio Inc [Member] \| Collaboration Agreement [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
Gilead Sciences Inc [Member] \| Collaboration, Option and License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration and license revenue						300,000
Deferred revenue						200,000
Receivables						0		0
Contract assets						0		0
Gilead Sciences Inc [Member] \| Collaboration, Option and License Agreement [Member] \| License Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration and license revenue						38,600,000
Arbutus Biopharma Corporation and Protiva Biotherapeutics Inc [Member] \| Collaboration Agreement [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					$ 3,000,000.0
Research and development						$ 0	$ 0
Genevant Sciences GmbH [Member] \| Option and License and Development Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment										$ 2,000,000.0
Amount to extend the option term								1,000,000.0
Genevant Sciences GmbH [Member] \| Option and License and Development Agreement [Member] \| Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment								2,000,000.0
Genevant Sciences GmbH [Member] \| Option and License and Development Agreement [Member] \| Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate payment in specified development regulatory and commercial milestone										$ 71,000,000.0
Payments for options to license for each indication								$ 1,500,000

Collaboration and License Agreements - Schedule of Changes in Deferred Revenue Balance (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)
Gilead Sciences Inc [Member] \| Collaboration, Option and License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additions	$ 220
Deductions	(41)
Balance at March 31, 2021	179
Bluebird Bio Inc [Member] \| Collaboration Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Balance at December 31, 2020	11,695
Additions	0
Deductions	(693)
Balance at March 31, 2021	$ 11,002

Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended		12 Months Ended
	Dec. 31, 2020	Oct. 31, 2019	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Oct. 31, 2018
Subsidiary Sale Of Stock [Line Items]
Common stock, shares authorized	300,000,000		300,000,000		300,000,000
Common stock, par value	$ 0.0001		$ 0.0001		$ 0.0001
Preferred stock, shares authorized	10,000,000		10,000,000		10,000,000
Preferred stock, par value	$ 0.0001		$ 0.0001		$ 0.0001
Preferred stock, shares issued	0		0		0
Preferred stock, shares outstanding	0		0		0
Common stock, shares issued	47,552,693		49,197,828		47,552,693
Common stock, shares outstanding	47,552,693		49,197,828		47,552,693
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		$ 250,000,000.0
Net proceeds from issuance of stock			$ 2,103,000	$ 5,659,000
Percentage of gross proceeds as underwriter compensation		3.00%
Maximum offering expense agreed to be reimbursed		$ 50,000
Warrant exercise price			$ 3.34
Issuance of pre-funded warrants, net of issuance costs			$ 87,700,000
Class of warrant issued			0
Warrants exercised			0
Warrants outstanding			$ 0
Maximum [Member]
Subsidiary Sale Of Stock [Line Items]
Net proceeds from issuance of stock		$ 75,000,000.0
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
Stock issued, number of shares			0		1,160,193
Payment of commissions on sale of shares					$ 300,000
Payment for issuance cost					$ 100,000
ATM Equity Offering Program [Member] \| Common Stock [Member]
Subsidiary Sale Of Stock [Line Items]
Stock issued, number of shares				568,369
Payment for issuance cost				$ 4,000
Private Placement [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	$ 110,000,000.0
Warrant exercise price	$ 0.01				0.01
Offering price per share	$ 3.33				3.33
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 \| Common Stock [Member]
Subsidiary Sale Of Stock [Line Items]
Stock issued, number of shares	4,043,127
Shares issued price per share	$ 3.71				$ 3.71
Gross proceeds from issuance of stock	$ 15,000,000.0
Class of warrant issued	0				0
Placement agent commissions and legal fees	$ 5,200,000

Stockholders' Equity - Schedule of Issued and Outstanding Warrants to Purchase Shares of the Company's Common Stock (Detail)	3 Months Ended
	Mar. 31, 2021 $ / shares shares
Equity [Abstract]
Issue Date	Dec. 28, 2020
Expiration Date	None
Warrant exercise price \| $ / shares	$ 3.34
Number of Warrants Outstanding \| shares	27,480,719

Stock Based Compensation - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Apr. 30, 2021	Dec. 31, 2020	Sep. 30, 2018	Aug. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance	3,740,292			3,108,412
Intrinsic value of stock option awards exercised	$ 3.9	$ 0.4
Unrecognized compensation cost related to non-vested employee and consultant options	$ 22.9
Recognition period of unrecognized compensation cost related to non-vested employee and consultant	2 years 9 months 18 days
Fair value of shares vested	$ 1.4
Restricted Stock Unit Awards under 2018 Equity Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting period	2 years
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 2-year period.
Maximum [Member] \| Restricted Stock Unit Awards under 2018 Equity Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option granted expiration period	10 years
2018 Award Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance					2,690,000	92,815
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] \| Subsequent Event [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance			790,400

Stock-Based Compensation - Schedule of Stock Options Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Number of Shares Available for Issuance
Number of options beginning balance	3,108,412
Authorized	1,902,107
Granted	(1,311,250)
Exercised	0
Cancelled	41,023
Number of options ending balance	3,740,292	3,108,412
Number of Shares
Outstanding at beginning of period	4,166,441
Granted	1,311,250
Exercised	(365,980)
Cancelled	(41,023)
Outstanding at end of period	5,070,688	4,166,441
Options Outstanding, Number of Shares, Vested and exercisable	1,805,272
Options Outstanding, Number of Shares, Vested and expected to vest	4,611,349
Weighted-Average Exercise Price
Beginning Balance	$ 8.13
Granted	13.86
Exercised	4.98
Cancelled	13.53
Ending Balance	9.79	$ 8.13
Weighted-Average Exercise Price, Vested and exercisable	7.59
Weighted-Average Exercise Price, Vested and expected to vest	$ 9.62
Options Outstanding, Weighted-Average Remaining Contractual Term (in years)	8 years 5 months 26 days	8 years 1 month 24 days
Options Outstanding, Weighted-Average Remaining Contractual Term, Vested and exercisable (in years)	7 years 4 months 28 days
Options Outstanding, Weighted-Average Remaining Contractual Term, Vested and expected to vest (in years)	8 years 4 months 28 days
Options Outstanding, Aggregate Intrinsic Value	$ 7,103	$ 2,092
Options Outstanding, Aggregate Intrinsic Value, Vested and exercisable	5,117
Options Outstanding, Aggregate Intrinsic Value, Vested and expected to vest	$ 6,891

Stock-Based Compensation - Summary of Restricted Stock Unit Activity (Detail)	3 Months Ended
	Mar. 31, 2021 $ / shares shares
Number of Shares
Issued \| shares	880,600
Canceled/Forfeited \| shares	(32,000)
Outstanding, unvested ending balance \| shares	848,600
Weighted Average Grant Date Fair Value
Issued \| $ / shares	$ 5.29
Canceled/Forfeited \| $ / shares	5.29
Outstanding, unvested ending balance \| $ / shares	$ 5.29

Stock-Based Compensation - Schedule of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock Based Compensation Expense	$ 2,201	$ 1,619
Research and Development Expense [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock Based Compensation Expense	1,481	1,028
General and Administrative Expense [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock Based Compensation Expense	$ 720	$ 591

Net Income (Loss) Per Common Share - Computation of Basic and Diluted Net Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net income (loss)	$ 7,923	$ (26,206)
Denominator:
Weighted-average common shares outstanding, basic	75,987,372	36,798,562
Effect of dilutive shares	1,476,984	0
Weighted-average common shares outstanding, diluted	77,464,356	36,798,562
Net income (loss) per share, basic	$ 0.10	$ (0.71)
Net income (loss) per share, diluted	$ 0.10	$ (0.71)

- Definition

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

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- Definition

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

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+ Details

- Definition

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

+ References

+ Details

Net Income (Loss) Per Common Share - Additional Information (Detail) - Common Stock and Pre-funded Warrants [Member]	Dec. 31, 2020 $ / shares shares
Earnings Per Share Basic [Line Items]
Common stock called by warrants \| shares	27,480,719
Class of warrant nominal exercise price \| $ / shares	$ 0.01

Net Income (Loss) Per Common Share - Computation of Potentially Anti-dilutive Securities (Detail) - shares	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities that were not included in the diluted per share calculations	1,417,134	4,654,583
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	1,416,794	4,647,441
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	340	0
Early Exercised Common 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	0	7,142

Fair Value Measurements - Financial Assets and Liabilities Subject To Fair Value Measurements on a Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	$ 151,583	$ 37,803
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	90,169	37,803
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	61,414	0
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	62,082	36,801
Cash Equivalents [Member] \| Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	51,940	36,801
Cash Equivalents [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	6,000
Cash Equivalents [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	4,142
Cash Equivalents [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	51,940	36,801
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	51,940	36,801
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
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	10,142	0
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	6,000
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	4,142
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] \| 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
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	89,501	1,002
Short-Term Marketable Securities [Member] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	31,724
Short-Term Marketable Securities [Member] \| Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	17,435
Short-Term Marketable Securities [Member] \| U.S. Treasuries [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	38,229	1,002
Short-Term Marketable Securities [Member] \| U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	2,113
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	38,229	1,002
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
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
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	38,229	1,002
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	0
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	51,272	0
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	31,724
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	17,435
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 2 [Member] \| U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	2,113
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] \| Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	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
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
Short-Term Marketable Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets fair value	$ 0