Atara Biotherapeutics (ATRA) 10-K 28 Feb 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 18, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Trading Symbol	ATRA
Entity Registrant Name	ATARA BIOTHERAPEUTICS, INC.
Entity Central Index Key	0001604464
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		93,097,679
Entity Public Float			$ 1,149,785,847
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity File Number	001-36548
Entity Tax Identification Number	46-0920988
Entity Address, Address Line One	611 Gateway Blvd.
Entity Address, Address Line Two	Suite 900
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	278-8930
Entity Incorporation, State or Country Code	DE
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Security Exchange Name	NASDAQ
Entity Interactive Data Current	Yes
Document Annual Report	true
Document Transition Report	false
ICFR Auditor Attestation Flag	true
Auditor Firm ID	34
Auditor Name	DELOITTE & TOUCHE LLP
Auditor Location	San Francisco, California
Documents Incorporated by Reference	Portions of the Registrant’s definitive proxy statement relating to its 2022 Annual Meeting of Stockholders are incorporated by reference into Part III of this Report where indicated. Such proxy statement will be filed with the U.S. Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 106,084	$ 200,404
Short-term investments	264,984	300,255
Restricted cash - short-term	194	194
Accounts receivable	986	1,250
Prepaid expenses and other current assets	12,373	21,170
Total current assets	384,621	523,273
Property and equipment, net	53,780	50,517
Operating lease assets	26,159	12,303
Restricted cash - long-term	1,200	1,200
Other assets	2,367	827
Total assets	468,127	588,120
Current liabilities:
Accounts payable	17,368	7,118
Accrued compensation	25,150	20,458
Accrued research and development expenses	13,451	15,813
Deferred revenue	40,760	33,455
Other current liabilities	9,057	6,057
Total current liabilities	105,786	82,901
Deferred revenue - long-term	55,708	27,795
Operating lease liabilities - long-term	25,518	13,041
Other long-term liabilities	1,501	2,044
Total liabilities	188,513	125,781
Commitments and contingencies (Note 9)
Stockholders’ equity:
Common stock—$0.0001 par value, 500,000 shares authorized as of December 31, 2021 and 2020, respectively; 91,671 and 83,372 shares issued and outstanding as of December 31, 2021 and 2020, respectively	9	8
Additional paid-in capital	1,744,695	1,586,616
Accumulated other comprehensive (loss) income	(368)	296
Accumulated deficit	(1,464,722)	(1,124,581)
Total stockholders’ equity	279,614	462,339
Total liabilities and stockholders’ equity	$ 468,127	$ 588,120

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	91,671,000	83,372,000
Common stock, shares outstanding	91,671,000	83,372,000

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
License and collaboration revenue	$ 20,340	$ 0	$ 0
Operating expenses:
Research and development	282,001	244,650	216,097
General and administrative	78,801	64,402	79,584
Total operating expenses	360,802	309,052	295,681
Loss from operations	(340,462)	(309,052)	(295,681)
Interest and other income, net	367	2,447	4,717
Loss before provision for income taxes	(340,095)	(306,605)	(290,964)
Provision for income taxes	46	15	12
Net loss	(340,141)	(306,620)	(290,976)
Other comprehensive (loss) gain:
Unrealized (loss) gain on available-for-sale securities	(664)	76	560
Comprehensive loss	$ (340,805)	$ (306,544)	$ (290,416)
Net loss per common share:
Basic and diluted net loss per common share	$ (3.63)	$ (4.15)	$ (5.67)
Weighted-average shares outstanding used to calculate basic and diluted net loss per common share	93,670	73,973	51,308

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	At The Market Offering	Underwritten Public Offering	Common Stock	Common StockAt The Market Offering	Common StockUnderwritten Public Offering	Additional Paid-in Capital	Additional Paid-in CapitalAt The Market Offering	Additional Paid-in CapitalUnderwritten Public Offering	Accumulated Other Comprehensive (Loss) Income	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ 339,221			$ 5			$ 866,541			$ (340)	$ (526,985)
Beginning balance (in shares) at Dec. 31, 2018				45,951
Issuance of common stock, net of offering costs, values			$ 140,716			$ 1			$ 140,715
Issuance of common stock, net Of offering costs, shares						6,872
Issuance of common stock, net of commissions and offering costs, value		$ 48,909						$ 48,909
Issuance of common stock, net of commissions and offering costs, shares					3,135
RSU settlements, net of shares withheld	(6,695)						(6,695)
RSU settlements, net of shares withheld, shares				361
Issuance of common stock pursuant to employee stock awards	7,350						7,350
Issuance of common stock pursuant to employee stock awards, shares				487
Stock-based compensation expense	51,696						51,696
Net loss	(290,976)										(290,976)
Unrealized (loss) gain on available-for-sale securities	560									560
Ending balance at Dec. 31, 2019	290,781			$ 6			1,108,516			220	(817,961)
Ending balance (in shares) at Dec. 31, 2019				56,806
Issuance of common stock and pre-funded warrants, net of offering costs			$ 353,588			$ 2			$ 353,586
Issuance of common stock and pre-funded warrants, net of offering costs, shares						20,060
Issuance of common stock, net of commissions and offering costs, value		68,004						68,004
Issuance of common stock, net of commissions and offering costs, shares					4,786
Exercise of pre-funded warrants, shares				57
RSU settlements, net of shares withheld	(1,521)						(1,521)
RSU settlements, net of shares withheld, shares				1,112
Issuance of common stock pursuant to employee stock awards	6,680						6,680
Issuance of common stock pursuant to employee stock awards, shares				551
Stock-based compensation expense	51,351						51,351
Net loss	(306,620)										(306,620)
Unrealized (loss) gain on available-for-sale securities	76									76
Ending balance at Dec. 31, 2020	462,339			$ 8			1,586,616			296	(1,124,581)
Ending balance (in shares) at Dec. 31, 2020				83,372
Issuance of common stock, net of commissions and offering costs, value		$ 98,697			$ 1			$ 98,696
Issuance of common stock, net of commissions and offering costs, shares					6,241
RSU settlements, net of shares withheld	(1,244)						(1,244)
RSU settlements, net of shares withheld, shares				1,492
Issuance of common stock pursuant to employee stock awards	6,762						6,762
Issuance of common stock pursuant to employee stock awards, shares				566
Stock-based compensation expense	53,865						53,865
Net loss	(340,141)										(340,141)
Unrealized (loss) gain on available-for-sale securities	(664)									(664)
Ending balance at Dec. 31, 2021	$ 279,614			$ 9			$ 1,744,695			$ (368)	$ (1,464,722)
Ending balance (in shares) at Dec. 31, 2021				91,671

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - Common Stock - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Underwritten Public Offering
Stock issuance, discounts, commissions and offering costs		$ 583	$ 284
At The Market Offering
Stock issuance, discounts, commissions and offering costs	$ 2,501	$ 1,887	$ 1,553

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating activities
Net loss	$ (340,141)	$ (306,620)	$ (290,976)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	53,865	51,351	51,696
Depreciation and amortization expense	9,345	8,332	7,070
Non-cash operating lease expense	1,948	1,457	964
Amortization (accretion) of investment premiums (discounts)	1,769	828	(1,330)
Loss on disposals of property and equipment	21	130	1,027
Asset retirement obligation accretion expense	87	78	71
Changes in operating assets and liabilities:
Accounts receivable	264	(1,250)	0
Prepaid expenses and other current assets	8,182	(8,666)	(998)
Operating lease assets	0	886	239
Other assets	(1,727)	(219)	322
Accounts payable	9,067	(815)	4,213
Accrued compensation	4,692	5,752	4,070
Accrued research and development expenses	(2,362)	7,472	(10,869)
Other current liabilities	1,618	(187)	(394)
Deferred revenue	35,218	61,250	0
Operating lease liabilities	(1,859)	(1,316)	(731)
Other long-term liabilities	(509)	778	0
Net cash used in operating activities	(220,522)	(180,759)	(235,626)
Investing activities
Purchases of short-term investments	(301,129)	(425,868)	(270,230)
Proceeds from maturities and sales of short-term investments	333,967	309,653	336,261
Purchases of property and equipment	(10,580)	(4,513)	(5,733)
Proceeds from sale of property and equipment	0	0	161
Net cash provided by (used in) investing activities	22,258	(120,728)	60,459
Financing activities
Proceeds from sale of common stock and pre-funded warrants in underwritten offerings, net	0	353,780	140,888
Proceeds from issuance of common stock through ATM facilities, net	98,697	69,189	47,729
Proceeds from employee stock awards	6,762	6,680	7,350
Taxes paid related to net share settlement of restricted stock units	(1,244)	(1,521)	(6,695)
Principal payments on finance and capital lease obligations	(254)	(389)	(486)
Other financing activities, net	(17)	(165)	0
Net cash provided by financing activities	103,944	427,574	188,786
Increase (decrease) in cash, cash equivalents and restricted cash	(94,320)	126,087	13,619
Cash, cash equivalents and restricted cash at beginning of period	201,798	75,711	62,092
Cash, cash equivalents and restricted cash at end of period	107,478	201,798	75,711
Non-cash investing and financing activities
Property and equipment purchases included in accounts payable and other accrued liabilities	2,139	326	276
Accrued costs related to underwritten public offering	0	192	172
Accrued costs related to ATM facility	87	0	0
Proceeds from issuance of common stock through ATM facilities not yet received	0	0	1,185
Supplemental cash flow disclosure
Cash paid for interest	32	62	50
Cash paid for income taxes	$ 15	$ 10	$ 0

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2021
Description Of Business [Abstract]
Description of Business	1. Description of Business Atara Biotherapeutics, Inc. (“Atara”, “we”, “our” or “the Company”) was incorporated in August 2012 in Delaware. Atara is a pioneer in T-cell immunotherapy, leveraging its novel allogeneic EBV T-cell platform to develop transformative therapies for patients with serious diseases, including solid tumors, hematologic cancers and autoimmune disease. We have several T-cell immunotherapies in clinical development and are progressing multiple next-generation allogeneic chimeric antigen receptor T-cell (“CAR T”) programs. Our most advanced T-cell immunotherapy program, tab-cel ® ® ® We have licensed rights to T-cell product candidates from Memorial Sloan Kettering Cancer Center (“MSK”), rights related to our next-generation CAR T programs from MSK and from H. Lee Moffitt Cancer Center (“Moffitt”), and rights to know-how and technology from the Council of the Queensland Institute of Medical Research (“QIMR Berghofer”). See Note 6 for further information.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation We prepare our consolidated financial statements in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and follow the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”). Principles of Consolidation The consolidated financial statements include the accounts of Atara and our wholly owned subsidiaries. All intercompany balances and transactions are eliminated in consolidation. Segment and Geographic Information We operate and manage our business as one operating and reportable segment, which is the business of developing and commercializing therapeutics. Our Chief Executive Officer, who is our chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. Substantially all of our assets are located in the U.S. Of the $20.3 million license and collaboration revenue recognized in 2021, $19.8 million related to our agreements with Bayer, a German company, and $0.5 million related to our agreements with Pierre Fabre, a French company. Liquidity Risk We have incurred significant operating losses since inception and have relied primarily on public and private equity financings and receipts from license and collaboration agreements to fund our operations. As we continue to incur losses, our transition to profitability will depend on the successful development, approval and commercialization of product candidates and on the achievement of sufficient revenues to support our cost structure. We may never achieve profitability, and unless and until we do, we will need to continue to raise additional capital. We expect that existing cash, cash equivalents and short-term investments as of December 31, 2021 will be sufficient to fund our planned operations for at least the next twelve months from the date of issuance of these financial statements. Concentration of Credit Risk and Other Uncertainties We place cash and cash equivalents in the custody of financial institutions that management believes are of high credit quality, the amount of which at times, may be in excess of the amount insured by the Federal Deposit Insurance Corporation. We also make short-term investments in money market funds; U.S. Treasury, government agency and corporate debt obligations; commercial paper; certificates of deposit; and asset-backed securities, which can be subject to certain credit risk. However, we mitigate the risks by investing in high-grade instruments, limiting our exposure to any one issuer and monitoring the ongoing creditworthiness of the financial institutions and issuers. We are subject to certain risks and uncertainties and believe that changes in any of the following areas could have a material adverse effect on future financial position or results of operations: our ability to obtain future financing; regulatory approval and market acceptance of, and reimbursement for, our product candidates, if approved by applicable regulatory authorities; our ability to collect amounts due from our collaboration partners, future customers or distribution partners; performance of third-party clinical research organizations and manufacturers upon which we rely; development of sales channels; protection of our intellectual property; litigation or claims against us based on intellectual property, patent, product, regulatory or other factors; and our ability to attract and retain employees necessary to support our growth. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates, assumptions and judgments that affect the amounts reported in the financial statements and accompanying notes. Significant estimates relied upon in preparing these financial statements include estimates related to revenue recognition, clinical study and other accruals, stock-based compensation expense and income taxes. Actual results could differ materially from those estimates. Foreign Currency Transactions and monetary assets and liabilities that are denominated in a foreign currency are translated into U.S. dollars at the current exchange rate on the transaction date and as of each balance sheet date, respectively, with gains or losses on foreign exchange changes recognized in interest and other income (expense), net in the consolidated statements of operations and comprehensive loss. Foreign currency-denominated monetary assets and liabilities as of December 31, 2021 were not material. Cash Equivalents and Short-Term Investments Cash equivalents are defined as short-term, highly liquid investments with original maturities of 90 days or less at the date of purchase, and generally consist of money market funds, U.S. Treasury, government agency and corporate debt obligations, and commercial paper. Investments with original maturities of greater than 90 days are classified as short-term investments on the balance sheet, and consist primarily of U.S. Treasury, government agency and corporate debt obligations, commercial paper and asset-backed securities. As our entire investment portfolio is considered available for use in current operations, we classify all investments as available-for-sale and as current assets, even though the stated maturity may be more than one year from the current balance sheet date. Available-for-sale securities are carried at fair value, with unrealized gains and losses reported in accumulated other comprehensive loss, which is a separate component of stockholders’ equity in the consolidated balance sheet. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity, which are both recorded to interest and other income (expense), net in the consolidated statements of operations and comprehensive loss. Changes in the fair value of available-for-sale securities impact the consolidated statements of operations and comprehensive loss only when such securities are sold, if an allowance for credit losses is recognized or if an impairment is recognized. Realized gains and losses on the sale of securities are determined by specific identification of each security’s cost basis. We regularly review our investment portfolio to determine if any security is impaired, which would require us to record an allowance for credit losses or impairment charge in the period any such determination is made. In making this judgment, we evaluate, among other things, the duration and extent to which the fair value of a security is less than its cost, our intent to sell or whether it is more likely than not that we will be required to sell the security before recovery of its amortized cost basis, the financial condition of the issuer and any changes thereto, and, as necessary, the portion of a decline in fair value that is credit-related. This assessment could change in the future due to new developments or changes in assumptions related to any particular security. Realized gains and losses, allowances for credit losses and impairments on available-for-sale securities, if any, are recorded to interest and other income, net in the statements of operations and comprehensive loss . Fair Value Measurement The carrying amounts of certain of our financial instruments including cash equivalents, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued liabilities approximate fair value due to their short maturities. Short-term investments are comprised of available-for-sale securities, which are carried at fair value. Fair Value of Financial Instruments Our financial assets are measured at fair value on a recurring basis using the following hierarchy to prioritize valuation inputs, Level 1: Quoted prices in active markets for identical assets or liabilities that we have the ability to access Level 2: Observable market-based inputs or unobservable inputs that are corroborated by market data such as quoted prices, interest rates and yield curves Level 3: Inputs that are unobservable data points that are not corroborated by market data We review the fair value hierarchy classification on a quarterly basis. Changes in the ability to observe valuation inputs may result in a reclassification of levels of certain securities within the fair value hierarchy. We recognize transfers into and out of levels within the fair value hierarchy in the period in which the actual event or change in circumstances that caused the transfer occurs. There have been no transfers between Level 1, Level 2, and Level 3 in any periods presented. Financial assets and liabilities are considered Level 2 when their fair values are determined using inputs that are observable in the market or can be derived principally from or corroborated by observable market data such as pricing for similar securities, recently executed transactions, cash flow models with yield curves, and benchmark securities. In addition, Level 2 financial instruments are valued using comparisons to like-kind financial instruments and models that use readily observable market data as their basis. U.S. Treasury, government agency and corporate debt obligations, commercial paper and asset-backed securities are valued primarily using market prices of comparable securities, bid/ask quotes, interest rate yields and prepayment spreads and are included in Level 2. Financial assets and liabilities are considered Level 3 when their fair values are determined using pricing models, discounted cash flow methodologies, or similar techniques, and at least one significant model assumption or input is unobservable. We have no Level 3 financial assets or liabilities. Property and Equipment, net Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets, ranging from three to five years. Costs incurred to acquire, construct or install property and equipment during the construction stage of a capital project or costs incurred to purchase and develop internal use software during the application development stage are recorded as construction in progress. Leasehold improvements are amortized over the lesser of the life of the leasehold improvements or the lease term. Maintenance and repairs are charged to operations as incurred. Long-lived Assets We evaluate the carrying amount of our long-lived assets whenever events or changes in circumstances indicate that the assets may not be recoverable. An impairment loss would be recognized when estimated future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount of the asset. To date, there have been no such impairment losses. Asset Retirement Obligations (“ARO”) ARO are legal obligations associated with the retirement of long-lived assets pertaining to leasehold improvements. These liabilities are initially recorded at fair value and the related asset retirement costs are capitalized by increasing the carrying amount of the related assets by the same amount as the liability. Asset retirement costs are subsequently depreciated over the useful lives of the related assets. Subsequent to initial recognition, the Company records period-to-period changes in the ARO liability resulting from the passage of time and revisions to either the timing or the amount of the original estimate of undiscounted cash flows. The Company derecognizes ARO liabilities when the related obligations are settled. Leases We determine if an arrangement is a lease at inception in accordance with Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) Lease assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. The lease term includes renewal options that we are reasonably certain of exercising as of the commencement date. None of the lease terms used to calculate the future minimum lease payments at commencement date include renewal options. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. The incremental borrowing rate for our leases is determined based on lease term and currency in which lease payments are made, adjusted for impacts of collateral. Lease assets also includes any lease payments made and excludes lease incentives and initial direct costs incurred. Operating lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. Finance lease assets are amortized over the shorter of the lease term or the asset’s estimated useful life. Our facilities and equipment operating leases have lease and non-lease components and we have made a policy election to account for the lease and non-lease components as a single lease component. Revenue Recognition At inception, we determine whether contracts are within the scope of Accounting Standards Codification Topic 606 (ASU No. 2014-09), Revenue from Contracts with Customers Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct and are distinct in the context of the contract. To the extent a contract includes multiple promised goods and services, we apply judgment to determine whether promised goods and services are both capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation. The transaction price is determined based on the consideration to which we will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, we estimate the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method, depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in our judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. Determining the transaction price requires significant judgment, which is discussed in further detail for our out-license agreements in Note 7. Our out-license agreements do not contain a significant financing component. If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation. The consideration to be received is allocated among the separate performance obligations based on relative standalone selling prices. We typically determine standalone selling prices using an adjusted market assessment approach model. We satisfy performance obligations either over time or at a point in time. Revenue is recognized over time if either (i) the customer simultaneously receives and consumes the benefits provided by our performance, (ii) our performance creates or enhances an asset that the customer controls as the asset is created or enhanced or (iii) our performance does not create an asset with an alternative use to the entity and we have an enforceable right to payment for performance completed to date. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. If we do not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring control of a promised good or service to a customer. As of December 31, 2021, our deferred revenue is related to the Bayer Agreements and the Pierre Fabre Commercialization Agreement, which are both within the scope of ASC 606. As discussed in further detail in Note 7, the terms of these arrangements include potential payments to us for some or all of the following: nonrefundable, upfront fees; development, regulatory, and commercial milestone payments; research and development funding payments; and royalties on the net sales of licensed products. These payments relate to promised goods or services for which revenue will be recognized upon our satisfaction of the underlying performance obligations. Licenses of intellectual property : If the license of our intellectual property is determined to be distinct from the other performance obligations identified in an arrangement, we recognize revenues from consideration allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are combined with other promises, we utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. Upfront payments Milestone payments Royalties Certain judgments affect the application of our revenue recognition policy. For example, we record short-term and long-term deferred revenue based on our best estimate of when such revenue will be recognized. Short-term deferred revenue consists of amounts that are expected to be recognized as revenue in the next 12 months, and long-term deferred revenue consists of amounts that we do not expect will be recognized in the next 12 months. This estimate is based on our current operating plan and, if our operating plan should change in the future, we may recognize a different amount of deferred revenue over the next 12-month period. Contract Balances We receive payments from our customers based on billing schedules established in each contract. Amounts payable to us are recorded as accounts receivable when our right to consideration is unconditional. Our contract liabilities consist of deferred revenue. Stock-Based Compensation Expense We account for stock-based compensation expense, including the expense of restricted common stock awards (“RSAs”), grants of restricted stock units (“RSUs”), and stock options that may be settled in shares of our common stock, based on the fair values of the equity instruments issued. The fair value is determined on the measurement date, which is generally the date of grant. The fair value of our RSUs is measured at the closing market price of our common stock on the measurement date. The fair value for our stock option awards is determined at the grant date using the Black-Scholes valuation model. For awards with performance-based vesting criteria, we assess the probability of the achievement of the performance conditions at the end of each reporting period and begin to recognize the share-based compensation costs when it becomes probable that the performance conditions will be met. For awards that are subject to both service and performance conditions, no expense is recognized until it is probable that performance conditions will be met. Stock-based compensation expense for awards with time-based vesting criteria is recognized as expense on a straight-line basis over the requisite service period. Stock-based compensation expense for awards with performance and other vesting criteria is recognized as expense under an accelerated graded vesting model. Key assumptions used in the Black-Scholes valuation model used for employee stock awards include: Expected term – We derived the expected term using the “simplified” method (the expected term is determined as the average of the time-to-vesting and the contractual life of the options), as we have limited historical information to develop expectations about future exercise patterns and post vesting employment termination behavior. Expected volatility – Prior to 2021, expected volatility was estimated using comparable public companies’ volatility for similar terms. Beginning in 2021, volatility is estimated using an average of Atara’s historical volatility and comparable public companies’ volatility for similar terms. Expected dividend – We have not historically declared or paid dividends to our stockholders and have no plans to pay dividends; therefore, we assumed an expected dividend yield of 0%. Risk-free interest rate – The risk-free interest rate is based on the yield on U.S. Treasury securities with the expected term of the associated award. The fair value of our common stock is measured at the closing market price on the measurement date. We account for forfeitures of stock-based awards as they occur. Research and Development Expense Research and development expense consists of costs incurred in performing research and development activities, including compensation and benefits for research and development employees, including stock-based compensation; expenses incurred under agreements with contract research organizations and investigative sites that conduct clinical and preclinical studies; the costs of acquiring and manufacturing clinical study materials and other supplies; payments under licensing and research and development agreements; other outside services and consulting costs, and facilities, information technology and overhead expenses. Research and development costs are expensed as incurred. Clinical Study Accruals Costs for preclinical studies, clinical studies and manufacturing activities are recognized based on an evaluation of our vendors’ progress towards completion of specific tasks, using data such as patient enrollment, clinical site activations or information provided to us by our vendors regarding their actual costs incurred. Payments for these activities are based on the terms of individual contracts and payment timing may differ significantly from the period in which the services are performed. We determine accrual estimates through reports from and discussions with applicable personnel and outside service providers as to the progress or state of completion of studies, or the services completed. Our estimates of accrued expenses as of each balance sheet date are based on the facts and circumstances known at the time. Costs that are paid in advance of performance are deferred as a prepaid expense and amortized over the service period as the services are provided. Defined Contribution Plan We have one qualified 401(k) plan covering all eligible employees. Under the plan, employees may contribute up to the statutory allowable amount for any calendar year. We make matching contributions, equal to 50% of each dollar contributed up to the first 6% of an individual’s eligible earnings, up to the annual IRS maximum. For the years ended December 31, 2021, 2020, and 2019 we recorded matching contributions of approximately $2.6 million, $2.1 million, and $1.6 million, respectively. Other Current Liabilities Other current liabilities consisted of the following as of each period end: December 31, December 31, 2021 2020 (in thousands) Accrued operating expenses $ 5,960 $ 3,016 Current portion of operating lease liabilities 2,582 1,730 Current portion of finance lease liabilities 171 255 Other accrued liabilities 344 1,056 Total other current liabilities $ 9,057 $ 6,057 Income Taxes We use the asset and liability method to account for income taxes. We record deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial statement carrying amounts and the tax basis of assets and liabilities using enacted tax rates expected to be in effect when the differences are expected to reverse. Valuation allowances are provided when necessary to reduce net deferred tax assets to the amount that is more likely than not to be realized. Based on the available evidence, we are unable, at this time, to support the determination that it is more likely than not that our deferred tax assets will be utilized in the future. Accordingly, we recorded a full valuation allowance as of December 31, 2021 and 2020. We intend to maintain valuation allowances until sufficient evidence exists to support their reversal. Tax benefits related to uncertain tax positions are recognized when it is more likely than not that a tax position will be sustained during an audit. Interest and penalties related to unrecognized tax benefits are included within the provision for income tax. Comprehensive Income (Loss) Comprehensive income (loss) is defined as a change in equity of a business enterprise during a period resulting from transactions from non-owner sources. Our other comprehensive income (loss) is comprised solely of unrealized gains (losses) on available-for-sale securities and is presented net of taxes. We have not recorded any reclassifications from other comprehensive income (loss) to net loss during any period presented. Recent Accounting Pronouncements We consider the applicability and impact of any recent ASU issued by the Financial Accounting Standards Board (“FASB”). Based on our assessment, the ASUs were determined to be either not applicable or are expected to have minimal impact on our condensed consolidated financial statements.

Net Loss per Common Share

Net Loss per Common Share	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Net Loss per Common Share	3. Net Loss per Common Share Basic net loss per common share is calculated by dividing net loss by the weighted-average number of shares of common stock and pre-funded warrants outstanding during the period, without consideration of common share equivalents. Diluted net loss per common share is computed by dividing net loss by the weighted-average number of shares of common stock, pre-funded warrants and common share equivalents outstanding for the period. The pre-funded warrants are included in the computation of basic and diluted net loss per common share as the exercise price is negligible and the pre-funded warrants are fully vested and exercisable. Common share equivalents are only included in the calculation of diluted net loss per common share when their effect is dilutive. Potential dilutive securities, which include unvested restricted stock units (“RSUs”), unvested performance-based RSUs for which established performance criteria have been achieved as of the end of the respective periods, vested and unvested options to purchase common stock and shares to be issued under our employee stock purchase plan (“ESPP”), have been excluded from the computation of diluted net loss per share as the effect is antidilutive. Therefore, the denominator used to calculate both basic and diluted net loss per common share is the same in all periods presented . The following table represents the potential common shares issuable pursuant to outstanding securities as of the related period end dates that were excluded from the computation of diluted net loss per common share, as their inclusion would have an antidilutive effect: As of December 31, 2021 2020 2019 Unvested RSUs 5,253,347 2,868,407 1,910,764 Vested and unvested options 9,200,337 7,832,386 6,934,262 ESPP share purchase rights 27,238 26,349 20,438 Total 14,480,922 10,727,142 8,865,464

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2021
Financial Instruments Disclosure [Abstract]
Financial Instruments	4. Financial Instruments The following tables summarize the estimated fair value and related valuation input hierarchy of our available-for-sale securities as of each period end: Total Total Total Total Amortized Unrealized Unrealized Estimated As of December 31, 2021: Input Level Cost Gain Loss Fair Value (in thousands) Money market funds Level 1 $ 89,738 $ — $ — $ 89,738 U.S. Treasury obligations Level 2 111,832 1 (138 ) $ 111,695 Government agency obligations Level 2 21,346 — (23 ) $ 21,323 Corporate debt obligations Level 2 99,757 6 (190 ) $ 99,573 Commercial paper Level 2 36,993 — — $ 36,993 Asset-backed securities Level 2 10,174 1 (25 ) $ 10,150 Total available-for-sale securities 369,840 8 (376 ) 369,472 Less: amounts classified as cash equivalents (104,488 ) $ (104,488 ) Amounts classified as short-term investments $ 265,352 $ 8 $ (376 ) $ 264,984 Total Total Total Total Amortized Unrealized Unrealized Estimated As of December 31, 2020: Input Level Cost Gain Loss Fair Value (in thousands) Money market funds Level 1 $ 168,343 $ — $ — $ 168,343 U.S. Treasury obligations Level 2 230,239 113 (6 ) 230,346 Government agency obligations Level 2 22,537 22 (3 ) 22,556 Corporate debt obligations Level 2 50,080 166 (1 ) 50,245 Commercial paper Level 2 17,990 — — 17,990 Asset-backed securities Level 2 9,860 10 (5 ) 9,865 Total available-for-sale securities 499,049 311 (15 ) 499,345 Less: amounts classified as cash equivalents (199,090 ) — — (199,090 ) Amounts classified as short-term investments $ 299,959 $ 311 $ (15 ) $ 300,255 The amortized cost and fair value of our available-for-sale securities by contractual maturity were as follows: As of December 31, 2021 As of December 31, 2020 Amortized Estimated Amortized Estimated Cost Fair Value Cost Fair Value (in thousands) (in thousands) Maturing within one year $ 278,457 $ 278,354 $ 434,828 $ 435,023 Maturing in one to five years 91,383 91,118 64,221 64,322 Total available-for-sale securities $ 369,840 $ 369,472 $ 499,049 $ 499,345 As of December 31, 2021, no significant facts or circumstances were present to indicate a deterioration in the creditworthiness of the issuers of the available-for-sale securities we hold, and the Company has no requirement or intention to sell these securities before maturity or recovery of their amortized cost basis. We considered the current and expected future economic and market conditions surrounding the COVID-19 pandemic and determined that our investments were not significantly impacted. For all securities with a fair value less than its amortized cost basis, we determined the decline in fair value below amortized cost basis to be immaterial and non-credit related, and therefore no allowance for losses has been recorded. During the years ended , 2020 and 2019, we did not recognize any impairment losses on our investments. We have elected the practical expedient to exclude the applicable accrued interest from both the fair value and the amortized cost basis of our available-for-sale securities for purposes of identifying and measuring an impairment. We present accrued interest receivable related to our available-for-sale securities in prepaid expenses and other current assets, separate from short-term investments on our consolidated balance sheet. As of December 31, 2021 and 2020, accrued interest receivable was $0.8 million and $0.7 million, respectively. Our accounting policy is to not measure an allowance for credit losses for accrued interest receivables and to write-off any uncollectible accrued interest receivable as a reversal of interest income in a timely manner, which we consider to be in the period in which we determine the accrued interest will not be collected by us. We have not written off any accrued interest receivables for the years ended December 31, 2021, 2020 and 2019. In addition, restricted cash collateralized by money market funds is a financial asset measured at fair value and is a Level 1 financial instrument under the fair value hierarchy. As of December 31, 2021 and 2020, restricted cash totaled $1.4 million. The following table provides a reconciliation of cash, cash equivalents and restricted cash within the consolidated balance sheets that sum to the total of the same such amounts in the consolidated statement of cash flows: December 31, December 31, 2021 2020 (in thousands) Cash and cash equivalents $ 106,084 $ 200,404 Restricted cash - short-term 194 194 Restricted cash - long-term 1,200 1,200 Total cash, cash equivalents and restricted cash $ 107,478 $ 201,798

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2021
Property Plant And Equipment [Abstract]
Property and Equipment	5. Property and Equipment Property and equipment consisted of the following as of each period end: December 31, December 31, 2021 2020 (in thousands) Leasehold improvements $ 50,142 $ 50,132 Lab equipment 14,060 8,033 Machinery and equipment 5,228 5,023 Computer equipment and software 4,245 4,060 Furniture and fixtures 2,518 2,066 Construction in progress 6,325 879 Property and equipment, gross 82,518 70,193 Less: accumulated depreciation and amortization (28,738 ) (19,676 ) Property and equipment, net $ 53,780 $ 50,517 Depreciation and amortization expense was $9.3 million, $8.3 million and $7.1 million for the years ended December 31, 2021 , 2020 and 2019

In-license and Manufacturing Ag

In-license and Manufacturing Agreements	12 Months Ended
	Dec. 31, 2021
In License And Manufacturing Agreements [Abstract]
In-license and Manufacturing Agreements	6. In-license and Manufacturing Agreements MSK Agreements In June 2015, we entered into an exclusive license agreement with MSK for three clinical stage T-cell therapies. We are required to make as well as future sales of products resulting from the development of the licensed product candidates, if any. In addition, under certain circumstances, we are required to make certain minimum annual royalty payments to MSK, which are creditable against earned royalties owed for the same annual period. We are also required to pay a low double-digit percentage of any consideration we receive for sublicensing the licensed rights. The license agreement expires on a product-by-product and country-by-country basis on the latest of: (i) expiration of the last licensed patent rights related to each licensed product, (ii) expiration of any market exclusivity period granted by law with respect to each licensed product, and (iii) a specified number of years after the first commercial sale of the licensed product in each country. Upon expiration of the license agreement, Atara will retain non-exclusive rights to the licensed products. In May and December 2018, we licensed additional technology from MSK. We are obligated to make additional milestone payments based on achievement of specified development, regulatory and sales-related milestones as well as mid-single-digit percentage tiered royalty payments based on future sales of products resulting from the development of the licensed product candidates, if any. In March 2021, we amended and restated our license agreement with MSK to: (i) terminate our license to certain rights related to WT1 and cytomegalovirus (“CMV”); and (ii) license additional know-how rights not otherwise covered by our existing agreements. QIMR Berghofer Agreements In October 2015, we entered into an exclusive license agreement and a research and development collaboration agreement with QIMR Berghofer. Under the terms of the license agreement, we obtained an exclusive, worldwide license to develop and commercialize allogeneic T-cell therapy programs utilizing technology and know-how developed by QIMR Berghofer. In September 2016, the exclusive license agreement and research and development collaboration agreement were amended and restated. Under the amended and restated agreements, we obtained an exclusive, worldwide license to develop and commercialize additional T-cell programs, as well as the option to license additional technology that we exercised in June 2018. We further amended and restated our license agreement and research and development collaboration agreements with QIMR Berghofer in August 2019 to terminate our license to certain rights related to CMV and again in August 2020 to terminate our license to certain rights related to BK polyomavirus and JC polyomavirus. Our current license agreement also provides for various milestone and royalty payments to QIMR Berghofer based on future product sales, if any. Under the terms of our current research and development collaboration agreement, we are also required to reimburse the cost of agreed-upon development activities related to programs developed under the collaboration. These payments are expensed on a straight-line basis over the related development periods. The agreement also provides for various milestone payments to QIMR Berghofer based on achievement of certain developmental and regulatory milestones. Other In-license and Collaboration Agreements From time to time, we have entered into other license and collaboration agreements with other parties. For example, we licensed additional rights related to our MSK-partnered next-generation CAR T programs from MSK in May 2018 and we licensed rights related to our next-generation CAR T programs from Moffitt Cancer Center in August 2018, and we agreed to collaborate through sponsored research in connection with each of these licenses. We also licensed rights related to our MSK-partnered next-generation CAR T programs from the National Institutes of Health in December 2018. Milestones and royalties under each of the above agreements are contingent upon future events and will be recorded as expense when it is probable that the milestones will be achieved or royalties are due. As of December 31, 2021 and 2020, there were no outstanding obligations for milestones and royalties under our license and collaboration agreements. Cognate Manufacturing Agreement In December 2019, we entered into a Commercial Manufacturing Services Agreement (the “Manufacturing Agreement”) with Cognate Bioservices, Inc. (“Cognate”). Pursuant to the Manufacturing Agreement, Cognate provides manufacturing services for certain of our product candidates. The initial term of the Manufacturing Agreement, as amended, runs until May 31, 2022. We may terminate the Manufacturing Agreement for convenience on six months’ written notice to Cognate, or immediately if Cognate is unable to perform the services under the Manufacturing Agreement or fails to obtain or maintain certain necessary approvals.

Out-license Agreements

Out-license Agreements	12 Months Ended
	Dec. 31, 2021
Research And Development [Abstract]
Out-license Agreements	7. Out-license Agreements Bayer Agreements Research, Development and License Agreement In December 2020, we entered into the Bayer License Agreement to develop mesothelin-directed CAR T-cell therapies for the treatment of solid tumors, pursuant to which we granted to Bayer an exclusive, field-limited license under the applicable patents and know-how owned or controlled by us and our affiliates covering or related to ATA2271 and ATA3271 (the “Licensed Products”). Under the terms of the Bayer License Agreement, we will be responsible at our cost for all mutually agreed preclinical and clinical activities for ATA2271 through the first in human Phase 1 clinical study in collaboration with MSK, following which Bayer will be responsible for the further development of ATA2271 at its cost. Bayer will be responsible for the development of ATA3271, except for certain mutually agreed preclinical, translational, manufacturing and supply chain activities to be performed by us relating to ATA3271, in each case at Bayer’s cost. Bayer will also be solely responsible for commercializing the Licensed Products at its cost. In December 2020, we received an upfront cash payment of $45.0 million from Bayer for the exclusive license grant, net of applicable withholding taxes, which were fully recovered in August 2021, and an additional $15.0 million upfront reimbursement payment for certain research and process development activities to be performed by us. We are also entitled to receive (i) up to $5.0 million for additional, specified translational activities under the Bayer License Agreement, of which we have invoiced $1.3 million, and (ii) an aggregate of up to $610.0 million in milestone payments upon achieving certain development, regulatory and commercial milestones relating to the Licensed Products. In addition, we are eligible to receive from Bayer tiered royalties at percentages up to low double digits on worldwide net product sales of the Licensed Products on a country-by-country and product-by-product basis until the later of 12 years after the first commercial sale in such country or the expiration of specified patent rights in such country, subject to certain reductions and aggregate minimum floors. Bayer and we have formed a joint steering committee (“JSC”) that will provide oversight, decision making and implementation guidance regarding the collaboration activities covered under the agreement. We assessed this arrangement in accordance with ASC 606 and concluded that the promises in the Bayer License Agreement represent transactions with a customer. We concluded that the Bayer License Agreement contains the following promises: (i) a development and commercialization license; (ii) performance of early-stage research and development (“R&D”) services, including technology transfer services; (iii) JSC participation; and (iv) chemistry, manufacturing and control (“CMC”) services. In accordance with ASC 606, we determined that the license, early-stage R&D and CMC services were not distinct from each other, as the license, early-stage R&D and CMC services are highly interdependent upon one another. Participation on the JSC to oversee the research and development activities are combined into the single performance obligation as these activities are highly interdependent with the other R&D and CMC services. Accordingly, we determined that these promises should be combined into a single performance obligation. The transaction price at inception consisted of a $45.0 million upfront payment for the license, $15.0 million for certain research and process development activities and the $5.0 million for additional specified translational activities, and this amount was allocated to the single performance obligation. The potential development and commercial milestone payments that we are eligible to receive were excluded from the transaction price, as all milestone amounts were fully constrained based on the probability of achievement. None of the future royalty and sales-based milestone payments were included in the transaction price, as the potential payments represent sales-based consideration. We will reevaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, adjust our estimate of the transaction price. Technology Transfer Agreement In March 2021, we entered into a Technology Transfer Agreement with Bayer (the “Bayer Tech Transfer Agreement”), which was contemplated as part of the Bayer License Agreement, to transfer to Bayer the ATA3271 manufacturing process being developed as part of the CMC services in the Bayer License Agreement. Upon entering into the agreement, we invoiced Bayer 20 percent We assessed this arrangement in accordance with ASC 606 and concluded that the promises in the Bayer Tech Transfer Agreement represent transactions with a customer. We concluded that the Bayer Tech Transfer Agreement should be combined with the Bayer License Agreement and accounted for as a modification of that agreement and that the Bayer Tech Transfer Agreement contains the following promises: (i) technology transfer services and (ii) supply of materials required for the technology transfer services. In accordance with ASC 606, we determined that the technology transfer services and supply of materials required for the technology transfer services were not distinct from each other, as they are highly interdependent upon one another. In addition, we concluded that the technology transfer services and supply of materials required for the technology transfer services were highly interdependent with the license, early-stage R&D and CMC services identified in the Bayer License Agreement. Accordingly, we determined that these promises should be combined into a single performance obligation. Under the Bayer Tech Transfer Agreement, in order to evaluate the appropriate transaction price, we determined that the $15.3 million fee constituted the entire consideration to be included in the transaction price, and this amount was allocated to the single performance obligation as identified under the Bayer License Agreement. We utilize a cost-based input method to recognize revenue based on the amount of actual costs incurred relative to the total budgeted costs expected to be incurred for the combined performance obligation. Manufacturing and Supply Agreement In March 2021, we entered into a Manufacturing and Supply Agreement with Bayer (the “Bayer Manufacturing Agreement”), which was contemplated as part of the Bayer License Agreement, to manufacture Phase 1 and 2 allogeneic mesothelin-directed CAR T-cell therapies for Bayer to use in clinical trials at a price based on our costs plus a reasonable margin, which is consistent with our standalone selling price. Under the Bayer Manufacturing Agreement, we will also provide storage and distribution services to Bayer at a price that is consistent with our standalone selling price for these services. Upon entering into the Bayer Manufacturing Agreement, Bayer submitted, and we approved, a binding purchase order for manufacturing services and storage services. Any fees for the manufacturing services will be invoiced as follows: (i) 50 percent upon written acceptance by us of the binding purchase order, and (ii) the remainder upon delivery of the certification of analysis of such lots to Bayer. Storage and distribution services are billed monthly as those services are provided to Bayer. In March 2021, we invoiced Bayer 50 percent of the total estimated supply price of $13.1 million for manufacturing services under the initial purchase order for the supply of six lots, or $6.6 million, which we received in the second quarter of 2021. The remainder of the supply price will be billed upon the release of the lots ordered by Bayer. We assessed this arrangement in accordance with ASC 606 and concluded that the promises in the manufacturing and supply agreement represent transactions with a customer. We concluded that the Bayer Manufacturing Agreement contains the following promises: (i) manufacturing services; (ii) storage services provided on a month-to-month basis; and (iii) distribution services. In accordance with ASC 606, we determined that the manufacturing services for the initial purchase order of six lots, that are expected to be provided prior to completion of the technology transfer, are not distinct as they are highly interdependent on the manufacturing process being developed and transferred under the Bayer License Agreement and the Bayer Tech Transfer Agreement. Accordingly, we determined that these promises should be combined into a single performance obligation. We also determined that each of the other services were distinct and separate performance obligations. We determined that the initial binding order for the manufacture and supply of six lots should be combined with the Bayer License Agreement and accounted for as a modification of that agreement along with the Bayer Tech Transfer Agreement. We also concluded that a binding purchase order from Bayer, together with the Bayer Manufacturing Agreement, form the contract for manufacturing services and storage services and a shipping order from Bayer forms the contract for distribution services. We also determined that the storage services provided on a month-to-month basis and distribution services are distinct and separate performance obligations. All the performance obligations identified above are priced at their standalone selling price. Under the Bayer Manufacturing Agreement, in order to evaluate the appropriate transaction price, we determined that the $13.1 million fee constituted the entire consideration to be included in the transaction price, and this amount was allocated to the single performance obligation as identified under the Bayer License Agreement. Revenue for the manufacturing services for the initial six lots will be recognized based on the amount of actual costs incurred relative to the total budgeted costs expected to be incurred for the combined performance obligation. Revenue for the storage services will be recognized over time as those services are provided. Revenue for the distribution services will be recognized at a point in time when the product is delivered to a clinical site designated by Bayer. Bayer Revenue Recognition We utilize a cost-based input method to recognize revenue based on the amount of actual costs incurred relative to the total budgeted costs expected to be incurred for the combined performance obligation. For the year ended December 31, 2021, we recognized license and collaboration revenue of $19.8 million under the Bayer License Agreement, Bayer Tech Transfer Agreement and Bayer Manufacturing Agreement, collectively, the Bayer Agreements. We did not recognize any license and collaboration revenue in 2020 under Bayer License Agreement. Deferred revenue related to the Bayer Agreements aggregated to $51.5 million and $61.3 million as of December 31, 2021 and 2020, respectively. Of the $51.5 million of deferred revenue as of December 31, 2021, $40.8 million is included in current liabilities and $10.7 million is included in long-term liabilities. This revenue is expected to be recognized over approximately the next three years. No development or sales-based milestone payments have been earned or received through December 31, 2021. Pierre Fabre Commercialization Agreement In October 2021, we entered into the Pierre Fabre Commercialization Agreement, pursuant to which, we granted to Pierre Fabre an exclusive, field-limited license to commercialize and distribute tab-cel ® ® We are responsible at our cost for the conclusion of the ongoing Phase 3 ALLELE clinical study and the Phase 2 multi-cohort clinical study. We will also be responsible at our cost for certain other activities directed to obtaining regulatory approval for tab-cel ® ® Pierre Fabre paid us an upfront cash payment of $45.0 million for the exclusive license grant in October 2021. We are also entitled to receive an aggregate of up to $318.0 million in milestone payments upon achieving certain regulatory and commercial milestones. In addition, we are eligible to receive double-digit tiered royalties as a percentage of net sales of tab-cel ® We will negotiate a separate manufacturing and supply agreement with Pierre Fabre for us to manufacture tab-cel ® ® We are also responsible for cell selection services at our cost until January 1, 2024 unless the parties agree to transfer the related cell selection technology to Pierre Fabre prior to this date. From January 1, 2024 onwards, if we agree to continue to provide cell selection services, it shall be at the sole expense of Pierre Fabre. Pierre Fabre and we have formed a joint steering committee (“JSC”) that will provide oversight, decision making and implementation guidance regarding the commercialization activities covered under the agreement. We assessed this arrangement in accordance with ASC 606 and concluded that the promises in the Pierre Fabre Commercialization Agreement represent transactions with a customer. We concluded that the Pierre Fabre Commercialization Agreement includes transfer of intellectual property rights in the form of a license, the potential to manufacture and supply tab-cel ® Under the Pierre Fabre Commercialization Agreement, in order to evaluate the appropriate transaction price, we determined that the $45 million upfront payment, constituted the entire consideration to be included in the transaction price at the outset of the arrangement. Revenue associated with the upfront fee for the single performance obligation will be deferred until the initial delivery of services related to the manufacture and supply and cell selection and then recognized over the contract performance period​. We did not recognize any of the $45.0 million upfront payment as revenue in 2021. All of the $45.0 million of deferred revenue as of December 31, 2021 is included in long-term liabilities. The potential development and commercial milestone payments that we are eligible to receive were excluded from the transaction price, as all milestone amounts were fully constrained based on the probability of achievement. None of the future royalty and sales-based milestone payments were included in the transaction price, as the potential payments represent sales-based consideration. We will reevaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and, if necessary, adjust our estimate of the transaction price. No development or commercial milestone payments have been earned or received through December 31, 2021.

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Leases	8 . Leases We lease our corporate headquarters in South San Francisco, California under a non-cancellable lease agreement. In December 2021, we entered into a second amendment with the landlord to extend the lease term through May 2025 I n March 2021, we entered into a new lease agreement for approximately 33,659 square feet of office, lab and warehouse space in Thousand Oaks, California. We have the option to extend this lease for two additional five-year In February 2017, we entered into a lease agreement for approximately 90,580 square feet of office, lab and cellular therapy manufacturing space in Thousand Oaks, California. The initial 15-year term of the lease commenced on February 15, 2018, upon the substantial completion of landlord’s work as defined under the agreement. The contractual obligations during the initial term are $16.4 million in aggregate. We have the option to extend the lease for two additional periods of ten and nine years, respectively, after the initial term. In connection with the lease, we were required to issue a letter of credit in the amount of $1.2 million to the landlord, which is recorded as long-term restricted cash in our consolidated balance sheet. In November 2018, we entered into a lease agreement for additional office space in Thousand Oaks, California that expires in February 2026 April 2024 The maturities of lease liabilities under our operating and finance leases as of December 31, 2021 were as follows: Operating Leases Finance Leases Years Ending December 31, (in thousands) 2022 5,171 $ 181 2023 5,265 29 2024 5,183 — 2025 4,806 — 2026 3,257 — Thereafter 19,004 — Total lease payments $ 42,686 $ 210 Less: amount representing interest (14,586 ) (10 ) Present value of lease liabilities $ 28,100 $ 200 Balance as of December 31, 2021 Other current liabilities $ 2,582 $ 171 Operating lease liabilities - long-term 25,518 — Other long-term liabilities — 29 Total $ 28,100 $ 200 The components of lease cost were as follows: Year Ended Year Ended Year Ended December 31, 2021 December 31, 2020 December 31, 2019 (in thousands) (in thousands) Operating lease cost: Operating lease cost $ 3,827 $ 3,020 $ 2,578 Short-term lease cost 836 987 770 Total operating lease cost $ 4,663 $ 4,007 $ 3,348 Finance lease cost: Amortization expense $ 244 $ 389 $ 324 Interest on lease liabilities 29 60 56 Total finance lease cost $ 273 $ 449 $ 380 Other information related to leases was as follows: Year Ended Year Ended Year Ended December 31, 2021 December 31, 2020 December 31, 2019 (in thousands, except lease term and discount rate) Supplemental Cash Flows Information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 3,738 $ 2,878 $ 2,346 Operating cash flows for finance leases 32 62 50 Financing cash flows for finance leases 254 389 486 Operating lease assets obtained in exchange for lease obligations: $ 13,427 $ — $ 838 Finance lease assets obtained in exchange for lease obligations: — 281 323 Non-cash increase to operating lease assets due to remeasurement of lease liabilities: 1,760 639 Weighted Average Remaining Lease Term Operating leases 9.2 years 9.4 years 10.3 years Finance leases 1.0 years 1.7 years 2.5 years Weighted Average Discount Rate Operating leases 9.6 % 10.3 % 10.4 % Finance leases 9.7 % 9.7 % 10.0 % Asset Retirement Obligation The Company’s ARO consists of a contractual requirement to remove the tenant improvements at our manufacturing facility in Thousand Oaks, California and restore the facility to a condition specified in the lease agreement. The Company records an estimate of the fair value of its ARO in long-term liabilities in the period incurred. The fair value of the ARO is also capitalized in property and equipment, net and depreciated over the lease term. The fair value of our ARO was estimated by discounting projected cash flows over the estimated life of the related assets using our credit adjusted risk-free rate. The following table presents the activity for our ARO liabilities: ARO Liability (In thousands) Balance as of December 31, 2020 $ 866 Accretion expense 87 Balance as of December 31, 2021 $ 953

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9 . Commitments and Contingencies License and Collaboration Agreements Potential payments related to our license and collaboration agreements, including milestone and royalty payments, are detailed in Note 6. Other Research and Development Agreements We may enter into contracts in the normal course of business with clinical research organizations for clinical trials, with contract manufacturing clinical supplies, and with other vendors for preclinical studies, supplies and other services for our operating purposes. These contracts generally provide for termination on Indemnification Agreements In the normal course of business, we enter into contracts and agreements that contain a variety of representations and warranties and provide for indemnification for certain liabilities. The exposure under these agreements is unknown because it involves claims that may be made against us in the future but have not yet been made. To date, we have not paid any claims or been required to defend any action related to our indemnification obligations. However, we may record charges in the future as a result of these indemnification obligations. We also have indemnification obligations to our directors and executive officers for specified events or occurrences, subject to some limits, while they are serving at our request in such capacities. There have been no claims to date and we consider the fair value of these indemnification agreements to be minimal. Accordingly, we did not record liabilities for these agreements as of December 31, 2021 and 2020. Contingencies From time to time, we may be involved in legal proceedings, as well as demands, claims and threatened litigation, which arise in the normal course of our business or otherwise. The ultimate outcome of any litigation is uncertain and unfavorable outcomes could have a negative impact on our results of operations and financial condition. Regardless of outcome, litigation can have an adverse impact on us because of the defense costs, diversion of management resources and other factors. We are not currently involved in any material legal proceedings.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stockholders' Equity	10 . Stockholders’ Equity Our authorized capital stock consists of 520,000,000 shares, all with a par value of $0.0001 per share, of which 500,000,000 shares are designated as common stock and 20,000,000 shares are designated as preferred stock. There were no shares of preferred stock outstanding as of . Equity Offerings In July 2019, we issued and sold 6,871,727 shares of common stock at a public offering price of $15.28 per share and pre-funded warrants to purchase 2,945,026 shares of common stock at an offering price of $15.2799 per warrant in an underwritten public offering pursuant to a shelf registration on Form S-3. The gross proceeds from this offering were $150.0 million, resulting in aggregate net proceeds of $140.7 million, after deducting underwriting discounts and commissions and offering expenses payable by us. Each pre-funded warrant entitles the holder to purchase one share of common stock at an exercise price of $0.0001 per share and expires seven years from the date of issuance. These warrants were recorded as a component of stockholders’ equity within additional paid-in capital. Per the terms of the warrant agreement, a holder of the outstanding warrants is not entitled to exercise any portion of any pre-funded warrant if, upon exercise of the warrant, the holder’s ownership (together with its affiliates) of our common stock or combined voting power of our securities beneficially owned by such holder (together with its affiliates) would exceed 9.99% after giving effect to the exercise (“Maximum Ownership Percentage”). Upon at least 61 days’ prior notice to us by the holder, any holder may increase or decrease the Maximum Ownership Percentage to any other percentage not to exceed 19.99%. As of December 31, 2021, 2,888,526 of the pre-funded warrants from the July 2019 offering were outstanding. In the second quarter of 2020, we issued and sold 12,633,039 shares of common stock at a public offering price of $11.32 per share and pre-funded warrants to purchase 2,866,961 shares of common stock at a public offering price of $11.3199 per warrant in an underwritten public offering pursuant to a shelf registration on Form S-3. We granted the underwriters an option to purchase up to 2,325,000 additional shares of our common stock at a public offering price of $11.32, less underwriting discounts and commissions. The full option was exercised by the underwriters in June 2020. The gross proceeds from this public offering were $201.8 million, resulting in net proceeds of $189.3 million, after deducting underwriting discounts and commissions and offering expenses payable by us. The terms of the pre-funded warrants issued and sold as part of this public offering were similar to those above. In December 2020, we issued and sold 5,102,041 shares of common stock at a public offering price of $24.50 per share and pre-funded warrants to purchase 2,040,816 shares of common stock at a public offering price of $24.4999 per warrant in an underwritten public offering pursuant to a shelf registration on Form S-3. The gross proceeds from this public offering were $175.0 million, resulting in net proceeds of $164.3 million, after deducting underwriting discounts and commissions and estimated offering expenses payable by us. As of December 31, 2021, all of the pre-funded warrants issued and sold as part of the 2020 underwritten public offerings were outstanding. ATM Facilities In February 2019, we entered into a sales agreement (the “2019 ATM Facility”) with Cowen, which provided for the sale, in our sole discretion, of shares of our common stock having an aggregate offering price of up to $100.0 million through Cowen, as our sales agent. In February 2020, we entered into a sales agreement (the “2020 ATM Facility”) with Cowen, which provides for the sale, in our sole discretion, of shares of our common stock having an aggregate offering price of up to $100.0 million through Cowen, as our sales agent. The 2020 ATM Facility is separate from and did not replace the 2019 ATM Facility in any way. We paid a commission of up to 3.0% of gross sales proceeds of any common stock sold under the 2020 ATM Facility. In November 2021, we entered into a sales agreement (the “2021 ATM Facility”) with Cowen, which provides for the sale, in our sole discretion, of shares of our common stock having an aggregate offering price of up to $100.0 million through Cowen, as our sales agent. The 2021 ATM Facility is separate from and does not replace the 2020 ATM Facility in any way. We pay a commission of up to 3.0% of gross sales proceeds of any common stock sold under the 2021 ATM Facility. During the fiscal year ended December 31, 2020 During the fiscal year ended December 31, 2021 The issuance and sale of these shares by us pursuant to the ATM facilities are deemed “at the market” offerings as defined in Rule 415 under the Securities Act of 1933, as amended (the “Securities Act”), and are registered under the Securities Act. As of December 31, 2021 fully utilized the 2019 ATM Facility, and the 2020 ATM Facility and we had remaining and available to be sold under the 2021 ATM Facility. From January 1, 2022 through February 15, 2022, we sold an additional 1,319,878 shares of common stock under the 2021 ATM Facility, at an average price of $15.88 per share, for gross proceeds of $21.0 million and net proceeds of $20.5 million, after deducting commissions and other offering expenses payable by us. As of February 15, 2022, we had $57.4 million of common stock remaining and available to be sold under the 2021 ATM Facility, subject to certain conditions as specified in the agreement. Equity Incentive Plans In March 2014, we adopted the 2014 Equity Incentive Plan (“2014 EIP”), which was amended and restated on October 15, 2014 upon the pricing of our initial public offering (“IPO”). The 2014 EIP provides for annual increases in the number of shares available for issuance thereunder on the first business day of each fiscal year, beginning with 2015 and ending in 2024, equal to five percent of the number of shares of the Company’s common stock outstanding as of such date or a lesser number of shares as determined by our board of directors. Under the terms of the 2014 EIP, we may grant stock options, RSAs and RSUs to employees, directors, consultants and other service providers. RSUs generally vest over four years. In 2020, we granted performance-based awards to certain of our employees that provide for the issuance of common stock if specified Company performance criteria related to our clinical programs are achieved. The number of performance-based awards that ultimately vests depends upon if, when and which performance criteria are achieved, as well as the employee’s continuous service, as defined in the 2014 EIP, through the date of vesting. The fair value of RSUs, including those with performance conditions, is determined as the closing stock price on the date of grant. Stock options are granted with exercise prices at no less than 100% of the estimated fair value of the shares on the date of grant as determined by the board of directors, provided, however, that the exercise price of an option granted to a 10% shareholder cannot be less than 110% of the estimated fair value of the shares on the date of grant. The estimated fair value is generally equal to the closing market price of the Company’s common stock on the measurement date. Options granted generally vest over four years and expire in seven to ten years. As of December 31, 2021, a total of 16,086,987 shares of common stock were reserved for issuance under the 2014 EIP, of which 4,018,597 shares were available for future grant and 12,068,390 shares were subject to outstanding options and RSUs, including performance-based awards. In February 2018, we adopted the 2018 Inducement Plan (“Inducement Plan”), under which we may grant options, stock appreciation rights, RSAs and RSUs to new employees. In September 2020, we amended the Inducement Plan to reserve an additional 1,500,000 shares of the Company’s common stock for issuance under the Inducement Plan, and in September 2021 we made a further amendment to reserve an additional 1,500,000 shares of the Company’s common stock for issuance under the Inducement Plan. As of December 31, 2021 Restricted Stock Units The weighted average grant date fair value of RSUs granted during the years ended December 31, 2021 December 31, 2021 December 31, 2021 December 31, 2021 The following is a summary of RSU activity under our 2014 EIP and Inducement Plan: RSUs Shares Weighted Average Grant Date Fair Value Balance as of December 31, 2020 3,829,620 $ 15.91 Granted 4,624,257 $ 16.42 Forfeited (1,307,626 ) $ 14.64 Vested (1,553,893 ) $ 17.41 Balance as of December 31, 2021 5,592,358 $ 16.22 Under our RSU settlement procedures, for some of the RSUs granted to our employees, we withhold shares at settlement to cover the estimated payroll withholding tax obligations. During 2021, we settled 1,553,893 shares underlying RSUs, of which 154,341 shares underlying RSUs were net settled by withholding 61,385 shares. The value of the shares underlying RSUs withheld was $1.2 million, based on the closing price of our common stock on the settlement date. During 2020, we settled 1,218,945 shares underlying RSUs, of which 276,822 shares underlying RSUs were net settled by withholding 106,459 shares. The value of the shares underlying RSUs withheld was $1.5 million, based on the closing price of our common stock on the settlement date. The value of RSUs withheld in each period was remitted to the appropriate taxing authorities and has been reflected as a financing activity in our consolidated statements of cash flows. Stock Options The following is a summary of stock option activity under our 2014 EIP and Inducement Plan. The table below also includes the activity relating to options for 275,000 shares of our common stock which were issued in 2017 outside of these plans: Shares Weighted Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Balance as of December 31, 2020 7,851,886 $ 22.89 6.4 $ 26,834 Granted 2,643,378 15.97 Exercised (246,867 ) 13.97 Forfeited or expired (1,028,560 ) 25.92 Balance as of December 31, 2021 9,219,837 $ 20.81 6.4 $ 12,810 Vested and expected to vest as of December 31, 2021 9,219,837 $ 20.81 6.4 $ 12,810 Exercisable as of December 31, 2021 5,073,289 $ 24.36 4.8 $ 5,496 Aggregate intrinsic value represents the difference between the closing stock price of our common stock on December 31, 2021 December 31, 2021 Options for 246,867, 268,938 and 347,716 shares of our common stock were exercised during the years ended December 31, 2021 The fair value of each option issued was estimated at the date of grant using the Black-Scholes valuation model. The following table summarizes the weighted-average assumptions used as inputs to the Black-Scholes model and resulting weighted-average grant date fair values of stock options granted during the periods indicated: Year ended December 31, 2021 2020 2019 Assumptions: Expected term (years) 6.0 6.0 5.9 Expected volatility 75.9 % 76.8 % 76.1 % Risk-free interest rate 0.9 % 0.8 % 2.1 % Expected dividend yield 0.0 % 0.0 % 0.0 % Fair Value: Weighted-average estimated grant date fair value per share $ 10.52 $ 7.96 $ 18.06 Options granted 2,643,378 2,641,125 2,535,425 Total estimated grant date fair value $ 27,808,000 $ 21,023,000 $ 45,790,000 The estimated fair value of stock options that vested in the years ended December 31, 2021 Employee Stock Purchase Plan In May 2014, we adopted the 2014 Employee Stock Purchase Plan (“2014 ESPP”), which became effective on October 15, 2014 upon the pricing of our IPO. The 2014 ESPP permits eligible employees to purchase common stock at a discount through payroll deductions during defined offering periods. Eligible employees can purchase shares of the Company’s common stock at 85% of the lower of the fair market value of the common stock at (i) the beginning of a 12-month offering period, or (ii) at the end of one of the two related 6-month purchase periods. No participant in the 2014 ESPP may purchase shares of common stock valued at more than $25,000 per calendar year. The first offering under the 2014 ESPP commenced on June 1, 2016, and subsequent offerings commence on each anniversary of this date. The Company recorded $1.7 million, $1.8 million and $1.3 million of expense related to the 2014 ESPP in the years ended December 31, 2021, December 31, 2021 As of December 31, 2021, there was $0.6 million of unrecognized stock-based compensation expense related to the ESPP that is expected to be recognized by the end of second quarter of 2022. The 2014 ESPP provides for annual increases in the number of shares available for issuance thereunder on the first business day of each fiscal year, beginning with 2015 and ending in 2024, equal to the lower of (i) one percent of the number of shares of our common stock outstanding as of such date, (ii) 230,769 shares of our common stock, or (iii) a lesser number of shares as determined by our board of directors. As of December 31, 2021, there were 1,817,511 shares authorized under the 2014 ESPP. Reserved Shares The following shares of common stock were reserved for future issuance under our equity incentive plans as of December 31, 2021 Total Shares Reserved 2014 Equity Incentive Plan 16,086,987 2018 Inducement Plan 4,022,184 2014 Employee Stock Purchase Plan 862,382 Total reserved shares of common stock 20,971,553 Stock-based Compensation Expense Total stock-based compensation expense related to all stock awards was as follows: Year Ended December 31, 2021 2020 2019 (in thousands) Research and development $ 32,063 $ 31,527 $ 26,773 General and administrative 21,802 19,824 24,923 Total stock-based compensation expense $ 53,865 $ 51,351 $ 51,696

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	1 1 . Income Taxes Losses before provision for income taxes were as follows in each period presented: Year Ended December 31, 2021 2020 2019 (in thousands) United States $ (340,301 ) $ (306,758 ) $ (291,049 ) Foreign 206 153 85 Total loss before provision for income taxes $ (340,095 ) $ (306,605 ) $ (290,964 ) The components of provision for (benefit from) income taxes were as follows in each period presented: Year Ended December 31, 2021 2020 2019 (in thousands) Current provision for (benefit from) income taxes: State 4 2 — Foreign 42 13 12 Total current provision for (benefit from) income taxes $ 46 $ 15 $ 12 A reconciliation of statutory tax rates to effective tax rates were as follows in each of the periods presented: Year Ended December 31, 2021 2020 2019 Federal income taxes at statutory rate 21.0 % 21.0 % 21.0 % Impact of stock compensation (2.0 %) (2.4 %) 0.1 % Non-deductible executive compensation (0.2 %) (0.1 %) (0.7 %) Other (0.1 %) 0.3 % (0.2 %) Change in valuation allowance (18.7 %) (18.8 %) (20.2 %) Effective tax rate 0.0 % 0.0 % 0.0 % Deferred tax assets and liabilities reflect the net tax effect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our deferred tax assets and liabilities were as follows for each of the dates presented: As of December 31, 2021 2020 (in thousands) Deferred tax assets: Net operating losses $ 308,997 $ 237,010 Stock-based compensation 24,181 20,672 Capitalized expenses 10,499 12,590 License fees 8,716 8,159 Operating lease liabilities 7,972 4,251 Legal fees 2,366 2,136 Tax credits 1,580 1,580 Deferred Revenue 12,133 — Other 7,048 5,360 Total deferred tax assets 383,492 291,758 Valuation allowance (376,071 ) (287,349 ) Total deferred tax assets 7,421 4,409 Deferred tax liabilities: Operating lease assets (7,421 ) (3,541 ) Other — (868 ) Total deferred tax liabilities (7,421 ) (4,409 ) Net deferred tax assets (liabilities) $ — $ — We recognize deferred income taxes for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes, as well as for tax attribute carryforwards. We regularly evaluate the positive and negative evidence in determining the realizability of our deferred tax assets. Based upon the weight of available evidence, which includes our historical operating performance and reported cumulative net losses since inception, we maintained a full valuation allowance on the net deferred tax assets as of December 31, 2021 December 31, 2021 In response to the COVID-19 pandemic, the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) was signed into law on March 27, 2020, providing companies with various tax relief provisions and other stimulus measures. Such measures include, but are not limited to, temporary changes regarding the prior and future utilization of net operating losses, technical corrections to prior tax legislation for tax depreciation of certain qualified improvement property, acceleration of AMT credit refunds, and changes to business interest limitations. The Consolidated Appropriations Act was also signed into law on December 27, 2020 to provide further relief measures and renew various expiring tax provisions. Additionally, the IRS issued final regulations and proposed regulations on calculating the limitation on business interest expense, the allowance for the first-year depreciation deduction under IRC Section 168(k), as amended by the Tax Cuts and Jobs Act (the “Tax Act”), for qualified property acquired and placed in service after September 27, 2017, and meals and entertainment deductions. Based on our evaluation, these regulations did not have a material impact on the income tax provision for the years ended December 31, 2021, 2020 and 2019. Under the Tax Act, federal net operating losses generated in tax years beginning on or after January 1, 2018 and in future years may be carried forward indefinitely, but the utilization of such federal net operating losses is limited to 80% of current year taxable income. The CARES Act temporarily suspends this 80% taxable income limitation, allowing a net operating loss carryforward to fully offset taxable income in tax years beginning before January 1, 2021. It is uncertain if, and to what extent, various states will conform to the Tax Act or the CARES Act. As of December 31, 2021 Under Section 382 of the Internal Revenue Code of 1986, as amended, our ability to utilize net operating loss carryforwards or other tax attributes in any taxable year may be limited if we have experienced an “ownership change.” Generally, a Section 382 “ownership change” occurs if one or more stockholders or groups of stockholders who owns at least 5% of a corporation’s stock increases its ownership by more than 50 percentage points over its lowest ownership percentage within a specified testing period. Similar rules may apply under state tax laws. We have performed a Section 382 analysis of transactions in our stock through December 31, 2021. We have experienced ownership changes since inception and our utilization of net operating loss carryforwards will be subject to annual limitations. However, it is not expected that the annual limitations will result in the expiration of tax attribute carryforwards prior to utilization . The changes in the balance of gross unrecognized tax benefits, which excludes interest and penalties, for the years ended December 31, 2019, 2020 and 2021 are as follows: (In thousands) Balance as of January 1, 2019 $ 41,074 Gross increases for tax positions related to current year 22,800 Gross increases for tax positions related to prior year 22,126 Gross decreases for tax positions related to prior year — Balance as of December 31, 2019 86,000 Gross increases for tax positions related to current year 24,648 Gross increases for tax positions related to prior year — Gross decreases for tax positions related to prior year (47 ) Balance as of December 31, 2020 110,601 Gross increases for tax positions related to current year 28,171 Gross increases for tax positions related to prior year 5,295 Gross decreases for tax positions related to prior year — Balance as of December 31, 2021 $ 144,067 The Company currently has a full valuation allowance against its U.S. net deferred tax assets, which would impact the timing of the effective tax rate benefit should any uncertain tax position be favorably settled in the future. For 2021, 2020, and 2019 total unrecognize benefits in the amount of $144.1 million, $110.6 million, and $86.0 million, respectively, no amount, if recognized, would affect the Company’s effective tax rate. The Company’s policy is to account for interest and penalties related to uncertain tax positions as a component of the income tax provision. The Company has not accrued interest and penalties as of December 31, 2021 due to available tax losses. Our significant jurisdictions are the U.S. federal jurisdiction and the California state jurisdiction. All of our tax years remain open to examination by the U.S. federal and California tax authorities. We also file in other state, local and foreign jurisdictions in which we operate, and such tax years remain open to examination. The 2017 Tax Act imposed a mandatory transition tax on accumulated foreign earnings and generally eliminated U.S. taxes on foreign subsidiary distribution. As of December 31, 2021, the Company is not permanently reinvested with respect to its foreign earnings and has not recorded deferred income taxes and withholding taxes as these taxes are immaterial to the financial statements.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	12. Subsequent Events On January 26, 2022, the Company announced it has entered into an asset purchase agreement with FUJIFILM Diosynth Biotechnologies California, Inc. and, for certain limited purposes, FUJIFILM Holdings America Corporation, to sell all of the Company’s right, title and interest in and to certain assets related to the Atara T-Cell Operations and Manufacturing facility located at 2430 Conejo Spectrum Street, Thousand Oaks, California for $100 million in cash, plus or minus certain closing adjustments pursuant to the asset purchase agreement. The closing of the proposed transaction is expected to occur in the quarter ending June 30, 2022, subject to certain closing conditions, including clearance of the transaction under the Hart-Scott-Rodino Antitrust Improvements Act of 1976.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation We prepare our consolidated financial statements in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and follow the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”).
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of Atara and our wholly owned subsidiaries. All intercompany balances and transactions are eliminated in consolidation.
Segment and Geographic Information	Segment and Geographic Information We operate and manage our business as one operating and reportable segment, which is the business of developing and commercializing therapeutics. Our Chief Executive Officer, who is our chief operating decision maker, reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. Substantially all of our assets are located in the U.S. Of the $20.3 million license and collaboration revenue recognized in 2021, $19.8 million related to our agreements with Bayer, a German company, and $0.5 million related to our agreements with Pierre Fabre, a French company.
Liquidity Risk	Liquidity Risk We have incurred significant operating losses since inception and have relied primarily on public and private equity financings and receipts from license and collaboration agreements to fund our operations. As we continue to incur losses, our transition to profitability will depend on the successful development, approval and commercialization of product candidates and on the achievement of sufficient revenues to support our cost structure. We may never achieve profitability, and unless and until we do, we will need to continue to raise additional capital. We expect that existing cash, cash equivalents and short-term investments as of December 31, 2021 will be sufficient to fund our planned operations for at least the next twelve months from the date of issuance of these financial statements.
Concentration of Credit Risk and Other Uncertainties	Concentration of Credit Risk and Other Uncertainties We place cash and cash equivalents in the custody of financial institutions that management believes are of high credit quality, the amount of which at times, may be in excess of the amount insured by the Federal Deposit Insurance Corporation. We also make short-term investments in money market funds; U.S. Treasury, government agency and corporate debt obligations; commercial paper; certificates of deposit; and asset-backed securities, which can be subject to certain credit risk. However, we mitigate the risks by investing in high-grade instruments, limiting our exposure to any one issuer and monitoring the ongoing creditworthiness of the financial institutions and issuers. We are subject to certain risks and uncertainties and believe that changes in any of the following areas could have a material adverse effect on future financial position or results of operations: our ability to obtain future financing; regulatory approval and market acceptance of, and reimbursement for, our product candidates, if approved by applicable regulatory authorities; our ability to collect amounts due from our collaboration partners, future customers or distribution partners; performance of third-party clinical research organizations and manufacturers upon which we rely; development of sales channels; protection of our intellectual property; litigation or claims against us based on intellectual property, patent, product, regulatory or other factors; and our ability to attract and retain employees necessary to support our growth.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates, assumptions and judgments that affect the amounts reported in the financial statements and accompanying notes. Significant estimates relied upon in preparing these financial statements include estimates related to revenue recognition, clinical study and other accruals, stock-based compensation expense and income taxes. Actual results could differ materially from those estimates.
Foreign Currency	Foreign Currency Transactions and monetary assets and liabilities that are denominated in a foreign currency are translated into U.S. dollars at the current exchange rate on the transaction date and as of each balance sheet date, respectively, with gains or losses on foreign exchange changes recognized in interest and other income (expense), net in the consolidated statements of operations and comprehensive loss. Foreign currency-denominated monetary assets and liabilities as of December 31, 2021 were not material.
Cash Equivalents and Short-Term Investments	Cash Equivalents and Short-Term Investments Cash equivalents are defined as short-term, highly liquid investments with original maturities of 90 days or less at the date of purchase, and generally consist of money market funds, U.S. Treasury, government agency and corporate debt obligations, and commercial paper. Investments with original maturities of greater than 90 days are classified as short-term investments on the balance sheet, and consist primarily of U.S. Treasury, government agency and corporate debt obligations, commercial paper and asset-backed securities. As our entire investment portfolio is considered available for use in current operations, we classify all investments as available-for-sale and as current assets, even though the stated maturity may be more than one year from the current balance sheet date. Available-for-sale securities are carried at fair value, with unrealized gains and losses reported in accumulated other comprehensive loss, which is a separate component of stockholders’ equity in the consolidated balance sheet. The amortized cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity, which are both recorded to interest and other income (expense), net in the consolidated statements of operations and comprehensive loss. Changes in the fair value of available-for-sale securities impact the consolidated statements of operations and comprehensive loss only when such securities are sold, if an allowance for credit losses is recognized or if an impairment is recognized. Realized gains and losses on the sale of securities are determined by specific identification of each security’s cost basis. We regularly review our investment portfolio to determine if any security is impaired, which would require us to record an allowance for credit losses or impairment charge in the period any such determination is made. In making this judgment, we evaluate, among other things, the duration and extent to which the fair value of a security is less than its cost, our intent to sell or whether it is more likely than not that we will be required to sell the security before recovery of its amortized cost basis, the financial condition of the issuer and any changes thereto, and, as necessary, the portion of a decline in fair value that is credit-related. This assessment could change in the future due to new developments or changes in assumptions related to any particular security. Realized gains and losses, allowances for credit losses and impairments on available-for-sale securities, if any, are recorded to interest and other income, net in the statements of operations and comprehensive loss .
Fair Value Measurement	Fair Value Measurement The carrying amounts of certain of our financial instruments including cash equivalents, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued liabilities approximate fair value due to their short maturities. Short-term investments are comprised of available-for-sale securities, which are carried at fair value.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Our financial assets are measured at fair value on a recurring basis using the following hierarchy to prioritize valuation inputs, Level 1: Quoted prices in active markets for identical assets or liabilities that we have the ability to access Level 2: Observable market-based inputs or unobservable inputs that are corroborated by market data such as quoted prices, interest rates and yield curves Level 3: Inputs that are unobservable data points that are not corroborated by market data We review the fair value hierarchy classification on a quarterly basis. Changes in the ability to observe valuation inputs may result in a reclassification of levels of certain securities within the fair value hierarchy. We recognize transfers into and out of levels within the fair value hierarchy in the period in which the actual event or change in circumstances that caused the transfer occurs. There have been no transfers between Level 1, Level 2, and Level 3 in any periods presented. Financial assets and liabilities are considered Level 2 when their fair values are determined using inputs that are observable in the market or can be derived principally from or corroborated by observable market data such as pricing for similar securities, recently executed transactions, cash flow models with yield curves, and benchmark securities. In addition, Level 2 financial instruments are valued using comparisons to like-kind financial instruments and models that use readily observable market data as their basis. U.S. Treasury, government agency and corporate debt obligations, commercial paper and asset-backed securities are valued primarily using market prices of comparable securities, bid/ask quotes, interest rate yields and prepayment spreads and are included in Level 2. Financial assets and liabilities are considered Level 3 when their fair values are determined using pricing models, discounted cash flow methodologies, or similar techniques, and at least one significant model assumption or input is unobservable. We have no Level 3 financial assets or liabilities.
Property and Equipment, Net	Property and Equipment, net Property and equipment are stated at cost and depreciated using the straight-line method over the estimated useful lives of the assets, ranging from three to five years. Costs incurred to acquire, construct or install property and equipment during the construction stage of a capital project or costs incurred to purchase and develop internal use software during the application development stage are recorded as construction in progress. Leasehold improvements are amortized over the lesser of the life of the leasehold improvements or the lease term. Maintenance and repairs are charged to operations as incurred.
Long-lived Assets	Long-lived Assets We evaluate the carrying amount of our long-lived assets whenever events or changes in circumstances indicate that the assets may not be recoverable. An impairment loss would be recognized when estimated future cash flows expected to result from the use of the asset and its eventual disposition are less than the carrying amount of the asset. To date, there have been no such impairment losses.
Asset Retirement Obligations ("ARO")	Asset Retirement Obligations (“ARO”) ARO are legal obligations associated with the retirement of long-lived assets pertaining to leasehold improvements. These liabilities are initially recorded at fair value and the related asset retirement costs are capitalized by increasing the carrying amount of the related assets by the same amount as the liability. Asset retirement costs are subsequently depreciated over the useful lives of the related assets. Subsequent to initial recognition, the Company records period-to-period changes in the ARO liability resulting from the passage of time and revisions to either the timing or the amount of the original estimate of undiscounted cash flows. The Company derecognizes ARO liabilities when the related obligations are settled.
Leases	Leases We determine if an arrangement is a lease at inception in accordance with Accounting Standards Update (“ASU”) No. 2016-02, Leases (Topic 842) Lease assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. The lease term includes renewal options that we are reasonably certain of exercising as of the commencement date. None of the lease terms used to calculate the future minimum lease payments at commencement date include renewal options. As most of our leases do not provide an implicit rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. The incremental borrowing rate for our leases is determined based on lease term and currency in which lease payments are made, adjusted for impacts of collateral. Lease assets also includes any lease payments made and excludes lease incentives and initial direct costs incurred. Operating lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. Finance lease assets are amortized over the shorter of the lease term or the asset’s estimated useful life. Our facilities and equipment operating leases have lease and non-lease components and we have made a policy election to account for the lease and non-lease components as a single lease component.
Revenue Recognition	Revenue Recognition At inception, we determine whether contracts are within the scope of Accounting Standards Codification Topic 606 (ASU No. 2014-09), Revenue from Contracts with Customers Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct and are distinct in the context of the contract. To the extent a contract includes multiple promised goods and services, we apply judgment to determine whether promised goods and services are both capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation. The transaction price is determined based on the consideration to which we will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, we estimate the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method, depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in our judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. Determining the transaction price requires significant judgment, which is discussed in further detail for our out-license agreements in Note 7. Our out-license agreements do not contain a significant financing component. If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation. The consideration to be received is allocated among the separate performance obligations based on relative standalone selling prices. We typically determine standalone selling prices using an adjusted market assessment approach model. We satisfy performance obligations either over time or at a point in time. Revenue is recognized over time if either (i) the customer simultaneously receives and consumes the benefits provided by our performance, (ii) our performance creates or enhances an asset that the customer controls as the asset is created or enhanced or (iii) our performance does not create an asset with an alternative use to the entity and we have an enforceable right to payment for performance completed to date. We evaluate the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. If we do not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring control of a promised good or service to a customer. As of December 31, 2021, our deferred revenue is related to the Bayer Agreements and the Pierre Fabre Commercialization Agreement, which are both within the scope of ASC 606. As discussed in further detail in Note 7, the terms of these arrangements include potential payments to us for some or all of the following: nonrefundable, upfront fees; development, regulatory, and commercial milestone payments; research and development funding payments; and royalties on the net sales of licensed products. These payments relate to promised goods or services for which revenue will be recognized upon our satisfaction of the underlying performance obligations. Licenses of intellectual property : If the license of our intellectual property is determined to be distinct from the other performance obligations identified in an arrangement, we recognize revenues from consideration allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are combined with other promises, we utilize judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. Upfront payments Milestone payments Royalties Certain judgments affect the application of our revenue recognition policy. For example, we record short-term and long-term deferred revenue based on our best estimate of when such revenue will be recognized. Short-term deferred revenue consists of amounts that are expected to be recognized as revenue in the next 12 months, and long-term deferred revenue consists of amounts that we do not expect will be recognized in the next 12 months. This estimate is based on our current operating plan and, if our operating plan should change in the future, we may recognize a different amount of deferred revenue over the next 12-month period.
Contract Balances	Contract Balances We receive payments from our customers based on billing schedules established in each contract. Amounts payable to us are recorded as accounts receivable when our right to consideration is unconditional. Our contract liabilities consist of deferred revenue.
Stock-Based Compensation Expense	Stock-Based Compensation Expense We account for stock-based compensation expense, including the expense of restricted common stock awards (“RSAs”), grants of restricted stock units (“RSUs”), and stock options that may be settled in shares of our common stock, based on the fair values of the equity instruments issued. The fair value is determined on the measurement date, which is generally the date of grant. The fair value of our RSUs is measured at the closing market price of our common stock on the measurement date. The fair value for our stock option awards is determined at the grant date using the Black-Scholes valuation model. For awards with performance-based vesting criteria, we assess the probability of the achievement of the performance conditions at the end of each reporting period and begin to recognize the share-based compensation costs when it becomes probable that the performance conditions will be met. For awards that are subject to both service and performance conditions, no expense is recognized until it is probable that performance conditions will be met. Stock-based compensation expense for awards with time-based vesting criteria is recognized as expense on a straight-line basis over the requisite service period. Stock-based compensation expense for awards with performance and other vesting criteria is recognized as expense under an accelerated graded vesting model. Key assumptions used in the Black-Scholes valuation model used for employee stock awards include: Expected term – We derived the expected term using the “simplified” method (the expected term is determined as the average of the time-to-vesting and the contractual life of the options), as we have limited historical information to develop expectations about future exercise patterns and post vesting employment termination behavior. Expected volatility – Prior to 2021, expected volatility was estimated using comparable public companies’ volatility for similar terms. Beginning in 2021, volatility is estimated using an average of Atara’s historical volatility and comparable public companies’ volatility for similar terms. Expected dividend – We have not historically declared or paid dividends to our stockholders and have no plans to pay dividends; therefore, we assumed an expected dividend yield of 0%. Risk-free interest rate – The risk-free interest rate is based on the yield on U.S. Treasury securities with the expected term of the associated award. The fair value of our common stock is measured at the closing market price on the measurement date. We account for forfeitures of stock-based awards as they occur.
Research and Development Expense	Research and Development Expense Research and development expense consists of costs incurred in performing research and development activities, including compensation and benefits for research and development employees, including stock-based compensation; expenses incurred under agreements with contract research organizations and investigative sites that conduct clinical and preclinical studies; the costs of acquiring and manufacturing clinical study materials and other supplies; payments under licensing and research and development agreements; other outside services and consulting costs, and facilities, information technology and overhead expenses. Research and development costs are expensed as incurred.
Clinical Study Accruals	Clinical Study Accruals Costs for preclinical studies, clinical studies and manufacturing activities are recognized based on an evaluation of our vendors’ progress towards completion of specific tasks, using data such as patient enrollment, clinical site activations or information provided to us by our vendors regarding their actual costs incurred. Payments for these activities are based on the terms of individual contracts and payment timing may differ significantly from the period in which the services are performed. We determine accrual estimates through reports from and discussions with applicable personnel and outside service providers as to the progress or state of completion of studies, or the services completed. Our estimates of accrued expenses as of each balance sheet date are based on the facts and circumstances known at the time. Costs that are paid in advance of performance are deferred as a prepaid expense and amortized over the service period as the services are provided.
Defined Contribution Plan	Defined Contribution Plan We have one qualified 401(k) plan covering all eligible employees. Under the plan, employees may contribute up to the statutory allowable amount for any calendar year. We make matching contributions, equal to 50% of each dollar contributed up to the first 6% of an individual’s eligible earnings, up to the annual IRS maximum. For the years ended December 31, 2021, 2020, and 2019 we recorded matching contributions of approximately $2.6 million, $2.1 million, and $1.6 million, respectively.
Other Current Liabilities	Other Current Liabilities Other current liabilities consisted of the following as of each period end: December 31, December 31, 2021 2020 (in thousands) Accrued operating expenses $ 5,960 $ 3,016 Current portion of operating lease liabilities 2,582 1,730 Current portion of finance lease liabilities 171 255 Other accrued liabilities 344 1,056 Total other current liabilities $ 9,057 $ 6,057
Income Taxes	Income Taxes We use the asset and liability method to account for income taxes. We record deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial statement carrying amounts and the tax basis of assets and liabilities using enacted tax rates expected to be in effect when the differences are expected to reverse. Valuation allowances are provided when necessary to reduce net deferred tax assets to the amount that is more likely than not to be realized. Based on the available evidence, we are unable, at this time, to support the determination that it is more likely than not that our deferred tax assets will be utilized in the future. Accordingly, we recorded a full valuation allowance as of December 31, 2021 and 2020. We intend to maintain valuation allowances until sufficient evidence exists to support their reversal. Tax benefits related to uncertain tax positions are recognized when it is more likely than not that a tax position will be sustained during an audit. Interest and penalties related to unrecognized tax benefits are included within the provision for income tax.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) is defined as a change in equity of a business enterprise during a period resulting from transactions from non-owner sources. Our other comprehensive income (loss) is comprised solely of unrealized gains (losses) on available-for-sale securities and is presented net of taxes. We have not recorded any reclassifications from other comprehensive income (loss) to net loss during any period presented.
Recent Accounting Pronouncements	Recent Accounting Pronouncements We consider the applicability and impact of any recent ASU issued by the Financial Accounting Standards Board (“FASB”). Based on our assessment, the ASUs were determined to be either not applicable or are expected to have minimal impact on our condensed consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Other Current Liabilities	Other current liabilities consisted of the following as of each period end: December 31, December 31, 2021 2020 (in thousands) Accrued operating expenses $ 5,960 $ 3,016 Current portion of operating lease liabilities 2,582 1,730 Current portion of finance lease liabilities 171 255 Other accrued liabilities 344 1,056 Total other current liabilities $ 9,057 $ 6,057

Net Loss per Common Share (Tabl

Net Loss per Common Share (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Antidilutive Securities Excluded From Computation of Diluted Net Loss per Common Share	The following table represents the potential common shares issuable pursuant to outstanding securities as of the related period end dates that were excluded from the computation of diluted net loss per common share, as their inclusion would have an antidilutive effect: As of December 31, 2021 2020 2019 Unvested RSUs 5,253,347 2,868,407 1,910,764 Vested and unvested options 9,200,337 7,832,386 6,934,262 ESPP share purchase rights 27,238 26,349 20,438 Total 14,480,922 10,727,142 8,865,464

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2021
Financial Instruments Disclosure [Abstract]
Summary of Estimated Fair Value and Related Valuation Input Hierarchy of Available-for-Sale Securities	The following tables summarize the estimated fair value and related valuation input hierarchy of our available-for-sale securities as of each period end: Total Total Total Total Amortized Unrealized Unrealized Estimated As of December 31, 2021: Input Level Cost Gain Loss Fair Value (in thousands) Money market funds Level 1 $ 89,738 $ — $ — $ 89,738 U.S. Treasury obligations Level 2 111,832 1 (138 ) $ 111,695 Government agency obligations Level 2 21,346 — (23 ) $ 21,323 Corporate debt obligations Level 2 99,757 6 (190 ) $ 99,573 Commercial paper Level 2 36,993 — — $ 36,993 Asset-backed securities Level 2 10,174 1 (25 ) $ 10,150 Total available-for-sale securities 369,840 8 (376 ) 369,472 Less: amounts classified as cash equivalents (104,488 ) $ (104,488 ) Amounts classified as short-term investments $ 265,352 $ 8 $ (376 ) $ 264,984 Total Total Total Total Amortized Unrealized Unrealized Estimated As of December 31, 2020: Input Level Cost Gain Loss Fair Value (in thousands) Money market funds Level 1 $ 168,343 $ — $ — $ 168,343 U.S. Treasury obligations Level 2 230,239 113 (6 ) 230,346 Government agency obligations Level 2 22,537 22 (3 ) 22,556 Corporate debt obligations Level 2 50,080 166 (1 ) 50,245 Commercial paper Level 2 17,990 — — 17,990 Asset-backed securities Level 2 9,860 10 (5 ) 9,865 Total available-for-sale securities 499,049 311 (15 ) 499,345 Less: amounts classified as cash equivalents (199,090 ) — — (199,090 ) Amounts classified as short-term investments $ 299,959 $ 311 $ (15 ) $ 300,255
Amortized Cost and Fair Value of Available for Sale Securities by Contractual Maturity	The amortized cost and fair value of our available-for-sale securities by contractual maturity were as follows: As of December 31, 2021 As of December 31, 2020 Amortized Estimated Amortized Estimated Cost Fair Value Cost Fair Value (in thousands) (in thousands) Maturing within one year $ 278,457 $ 278,354 $ 434,828 $ 435,023 Maturing in one to five years 91,383 91,118 64,221 64,322 Total available-for-sale securities $ 369,840 $ 369,472 $ 499,049 $ 499,345
Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash within the consolidated balance sheets that sum to the total of the same such amounts in the consolidated statement of cash flows: December 31, December 31, 2021 2020 (in thousands) Cash and cash equivalents $ 106,084 $ 200,404 Restricted cash - short-term 194 194 Restricted cash - long-term 1,200 1,200 Total cash, cash equivalents and restricted cash $ 107,478 $ 201,798

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2021
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consisted of the following as of each period end: December 31, December 31, 2021 2020 (in thousands) Leasehold improvements $ 50,142 $ 50,132 Lab equipment 14,060 8,033 Machinery and equipment 5,228 5,023 Computer equipment and software 4,245 4,060 Furniture and fixtures 2,518 2,066 Construction in progress 6,325 879 Property and equipment, gross 82,518 70,193 Less: accumulated depreciation and amortization (28,738 ) (19,676 ) Property and equipment, net $ 53,780 $ 50,517

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Schedule of Maturities of Lease Liabilities Under Operating and Finance Leases	The maturities of lease liabilities under our operating and finance leases as of December 31, 2021 were as follows: Operating Leases Finance Leases Years Ending December 31, (in thousands) 2022 5,171 $ 181 2023 5,265 29 2024 5,183 — 2025 4,806 — 2026 3,257 — Thereafter 19,004 — Total lease payments $ 42,686 $ 210 Less: amount representing interest (14,586 ) (10 ) Present value of lease liabilities $ 28,100 $ 200 Balance as of December 31, 2021 Other current liabilities $ 2,582 $ 171 Operating lease liabilities - long-term 25,518 — Other long-term liabilities — 29 Total $ 28,100 $ 200
Components of Lease Cost	The components of lease cost were as follows: Year Ended Year Ended Year Ended December 31, 2021 December 31, 2020 December 31, 2019 (in thousands) (in thousands) Operating lease cost: Operating lease cost $ 3,827 $ 3,020 $ 2,578 Short-term lease cost 836 987 770 Total operating lease cost $ 4,663 $ 4,007 $ 3,348 Finance lease cost: Amortization expense $ 244 $ 389 $ 324 Interest on lease liabilities 29 60 56 Total finance lease cost $ 273 $ 449 $ 380
Summary of Other Information Related to Leases	Other information related to leases was as follows: Year Ended Year Ended Year Ended December 31, 2021 December 31, 2020 December 31, 2019 (in thousands, except lease term and discount rate) Supplemental Cash Flows Information Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows for operating leases $ 3,738 $ 2,878 $ 2,346 Operating cash flows for finance leases 32 62 50 Financing cash flows for finance leases 254 389 486 Operating lease assets obtained in exchange for lease obligations: $ 13,427 $ — $ 838 Finance lease assets obtained in exchange for lease obligations: — 281 323 Non-cash increase to operating lease assets due to remeasurement of lease liabilities: 1,760 639 Weighted Average Remaining Lease Term Operating leases 9.2 years 9.4 years 10.3 years Finance leases 1.0 years 1.7 years 2.5 years Weighted Average Discount Rate Operating leases 9.6 % 10.3 % 10.4 % Finance leases 9.7 % 9.7 % 10.0 %
Summary of Activity for ARO Liabilities	The following table presents the activity for our ARO liabilities: ARO Liability (In thousands) Balance as of December 31, 2020 $ 866 Accretion expense 87 Balance as of December 31, 2021 $ 953

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of RSU Activity	The following is a summary of RSU activity under our 2014 EIP and Inducement Plan: RSUs Shares Weighted Average Grant Date Fair Value Balance as of December 31, 2020 3,829,620 $ 15.91 Granted 4,624,257 $ 16.42 Forfeited (1,307,626 ) $ 14.64 Vested (1,553,893 ) $ 17.41 Balance as of December 31, 2021 5,592,358 $ 16.22
Summary of Stock Option Activity	The following is a summary of stock option activity under our 2014 EIP and Inducement Plan. The table below also includes the activity relating to options for 275,000 shares of our common stock which were issued in 2017 outside of these plans: Shares Weighted Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Balance as of December 31, 2020 7,851,886 $ 22.89 6.4 $ 26,834 Granted 2,643,378 15.97 Exercised (246,867 ) 13.97 Forfeited or expired (1,028,560 ) 25.92 Balance as of December 31, 2021 9,219,837 $ 20.81 6.4 $ 12,810 Vested and expected to vest as of December 31, 2021 9,219,837 $ 20.81 6.4 $ 12,810 Exercisable as of December 31, 2021 5,073,289 $ 24.36 4.8 $ 5,496
Summary of Options Estimated with Weighted Average	The fair value of each option issued was estimated at the date of grant using the Black-Scholes valuation model. The following table summarizes the weighted-average assumptions used as inputs to the Black-Scholes model and resulting weighted-average grant date fair values of stock options granted during the periods indicated: Year ended December 31, 2021 2020 2019 Assumptions: Expected term (years) 6.0 6.0 5.9 Expected volatility 75.9 % 76.8 % 76.1 % Risk-free interest rate 0.9 % 0.8 % 2.1 % Expected dividend yield 0.0 % 0.0 % 0.0 % Fair Value: Weighted-average estimated grant date fair value per share $ 10.52 $ 7.96 $ 18.06 Options granted 2,643,378 2,641,125 2,535,425 Total estimated grant date fair value $ 27,808,000 $ 21,023,000 $ 45,790,000
Schedule of Common Stock Reserved for Future Issuance Under Equity Incentive Plans	The following shares of common stock were reserved for future issuance under our equity incentive plans as of December 31, 2021 Total Shares Reserved 2014 Equity Incentive Plan 16,086,987 2018 Inducement Plan 4,022,184 2014 Employee Stock Purchase Plan 862,382 Total reserved shares of common stock 20,971,553
Schedule of Stock-based Compensation Related to Stock Awards	Total stock-based compensation expense related to all stock awards was as follows: Year Ended December 31, 2021 2020 2019 (in thousands) Research and development $ 32,063 $ 31,527 $ 26,773 General and administrative 21,802 19,824 24,923 Total stock-based compensation expense $ 53,865 $ 51,351 $ 51,696

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Losses Before Provision for Income Taxes	Losses before provision for income taxes were as follows in each period presented: Year Ended December 31, 2021 2020 2019 (in thousands) United States $ (340,301 ) $ (306,758 ) $ (291,049 ) Foreign 206 153 85 Total loss before provision for income taxes $ (340,095 ) $ (306,605 ) $ (290,964 )
Components of Provision for (Benefit from) Income Taxes	The components of provision for (benefit from) income taxes were as follows in each period presented: Year Ended December 31, 2021 2020 2019 (in thousands) Current provision for (benefit from) income taxes: State 4 2 — Foreign 42 13 12 Total current provision for (benefit from) income taxes $ 46 $ 15 $ 12
Reconciliation of Statutory Tax Rates to Effective Tax Rates	A reconciliation of statutory tax rates to effective tax rates were as follows in each of the periods presented: Year Ended December 31, 2021 2020 2019 Federal income taxes at statutory rate 21.0 % 21.0 % 21.0 % Impact of stock compensation (2.0 %) (2.4 %) 0.1 % Non-deductible executive compensation (0.2 %) (0.1 %) (0.7 %) Other (0.1 %) 0.3 % (0.2 %) Change in valuation allowance (18.7 %) (18.8 %) (20.2 %) Effective tax rate 0.0 % 0.0 % 0.0 %
Components of Deferred Tax Assets and Liabilities	Significant components of our deferred tax assets and liabilities were as follows for each of the dates presented: As of December 31, 2021 2020 (in thousands) Deferred tax assets: Net operating losses $ 308,997 $ 237,010 Stock-based compensation 24,181 20,672 Capitalized expenses 10,499 12,590 License fees 8,716 8,159 Operating lease liabilities 7,972 4,251 Legal fees 2,366 2,136 Tax credits 1,580 1,580 Deferred Revenue 12,133 — Other 7,048 5,360 Total deferred tax assets 383,492 291,758 Valuation allowance (376,071 ) (287,349 ) Total deferred tax assets 7,421 4,409 Deferred tax liabilities: Operating lease assets (7,421 ) (3,541 ) Other — (868 ) Total deferred tax liabilities (7,421 ) (4,409 ) Net deferred tax assets (liabilities) $ — $ —
Reconciliation of Beginning and Ending Amount of Gross Unrecognized Tax Benefits	The changes in the balance of gross unrecognized tax benefits, which excludes interest and penalties, for the years ended December 31, 2019, 2020 and 2021 are as follows: (In thousands) Balance as of January 1, 2019 $ 41,074 Gross increases for tax positions related to current year 22,800 Gross increases for tax positions related to prior year 22,126 Gross decreases for tax positions related to prior year — Balance as of December 31, 2019 86,000 Gross increases for tax positions related to current year 24,648 Gross increases for tax positions related to prior year — Gross decreases for tax positions related to prior year (47 ) Balance as of December 31, 2020 110,601 Gross increases for tax positions related to current year 28,171 Gross increases for tax positions related to prior year 5,295 Gross decreases for tax positions related to prior year — Balance as of December 31, 2021 $ 144,067

Description of Business (Detail

Description of Business (Detail)	12 Months Ended
	Dec. 31, 2021
Description Of Business [Abstract]
Entity incorporation state	DE
Entity incorporation date	Aug. 1, 2012

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2021USD ($)Segment	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Significant Accounting Policies [Line Items]
Number of reportable segments | Segment	1
Number of operating segments | Segment	1
License and collaboration revenue	$ 20,340,000	$ 0	$ 0
Cash and cash equivalents maturity period	90 days
Investment maturity period	90 days
Impairment of long-lived assets	$ 0
Expected dividend yield	0.00%	0.00%	0.00%
Defined contribution plan, plan name	401(k)
Defined contribution plan, matching contribution percentage	50.00%
Defined contribution plan, maximum percentage of an individual's eligible earnings	6.00%
Defined contribution plan contributions by employer	$ 2,600,000	$ 2,100,000	$ 1,600,000
Minimum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	3 years
Maximum
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life	5 years
Bayer Agreements
Significant Accounting Policies [Line Items]
License and collaboration revenue	$ 19,800,000	$ 0
Pierre Fabre Commercialization Agreement
Significant Accounting Policies [Line Items]
License and collaboration revenue	$ 500,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounting Policies [Abstract]
Accrued operating expenses	$ 5,960	$ 3,016
Current portion of operating lease liabilities	2,582	1,730
Current portion of finance lease liabilities	171	255
Other accrued liabilities	344	1,056
Total other current liabilities	$ 9,057	$ 6,057

Net Loss per Common Share - Ant

Net Loss per Common Share - Antidilutive Securities Excluded From Computation of Diluted Net Loss per Common Share (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	14,480,922	10,727,142	8,865,464
Unvested RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	5,253,347	2,868,407	1,910,764
Vested and Unvested Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	9,200,337	7,832,386	6,934,262
ESPP Share Purchase Rights
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	27,238	26,349	20,438

Financial Instruments - Summary

Financial Instruments - Summary of Estimated Fair Value and Related Valuation Input Hierarchy of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Total Fair Value	$ 369,472	$ 499,345
Fair Value, Measurements, Recurring
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	369,840	499,049
Total Unrealized Gain	8	311
Total Unrealized Loss	(376)	(15)
Total Fair Value	369,472	499,345
Fair Value, Measurements, Recurring | Money Market Funds | Level 1
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	89,738	168,343
Total Unrealized Gain	0	0
Total Unrealized Loss	0	0
Total Fair Value	89,738	168,343
Fair Value, Measurements, Recurring | U.S. Treasury Obligations | Level 2
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	111,832	230,239
Total Unrealized Gain	1	113
Total Unrealized Loss	(138)	(6)
Total Fair Value	111,695	230,346
Fair Value, Measurements, Recurring | Government Agency Obligations | Level 2
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	21,346	22,537
Total Unrealized Gain	0	22
Total Unrealized Loss	(23)	(3)
Total Fair Value	21,323	22,556
Fair Value, Measurements, Recurring | Corporate Debt Obligations | Level 2
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	99,757	50,080
Total Unrealized Gain	6	166
Total Unrealized Loss	(190)	(1)
Total Fair Value	99,573	50,245
Fair Value, Measurements, Recurring | Commercial Paper | Level 2
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	36,993	17,990
Total Unrealized Gain	0	0
Total Unrealized Loss	0	0
Total Fair Value	36,993	17,990
Fair Value, Measurements, Recurring | Asset-Backed Securities | Level 2
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	10,174	9,860
Total Unrealized Gain	1	10
Total Unrealized Loss	(25)	(5)
Total Fair Value	10,150	9,865
Fair Value, Measurements, Recurring | Amounts Classified As Cash Equivalents
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	(104,488)	(199,090)
Total Unrealized Gain	0	0
Total Unrealized Loss	0	0
Total Fair Value	(104,488)	(199,090)
Fair Value, Measurements, Recurring | Amounts Classified As Short-Term Investments
Schedule of Available-for-sale Securities [Line Items]
Total Amortized Cost	265,352	299,959
Total Unrealized Gain	8	311
Total Unrealized Loss	(376)	(15)
Total Fair Value	$ 264,984	$ 300,255

Financial Instruments - Amortiz

Financial Instruments - Amortized Cost and Fair Value of Available-for-Sale Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Amortized cost
Maturing within one year, Amortized cost	$ 278,457	$ 434,828
Maturing in one to five years, Amortized cost	91,383	64,221
Total available-for-sale securities, Amortized cost	369,840	499,049
Estimated Fair value
Maturing within one year, Estimated fair value	278,354	435,023
Maturing in one to five years, Estimated fair value	91,118	64,322
Total available-for-sale securities, Estimated fair value	$ 369,472	$ 499,345

Financial Instruments - Additio

Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financial Instruments Disclosure [Abstract]
Accrued interest receivable	$ 800,000	$ 700,000
Write off, of accrued interest receivable	0	0	$ 0
Restricted Cash	$ 1,400,000	$ 1,400,000

Financial Instruments - Reconci

Financial Instruments - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financial Instruments Disclosure [Abstract]
Cash and cash equivalents	$ 106,084	$ 200,404
Restricted cash - short-term	194	194
Restricted cash - long-term	1,200	1,200
Total cash, cash equivalents and restricted cash	$ 107,478	$ 201,798	$ 75,711	$ 62,092

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 82,518	$ 70,193
Less: accumulated depreciation and amortization	(28,738)	(19,676)
Property and equipment, net	53,780	50,517
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	50,142	50,132
Lab Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	14,060	8,033
Machinery and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	5,228	5,023
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	4,245	4,060
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	2,518	2,066
Construction in Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 6,325	$ 879

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment Net By Type [Abstract]
Depreciation and amortization expense	$ 9,345	$ 8,332	$ 7,070

In-License and Manufacturing _2

In-License and Manufacturing Agreements - Additional Information (Detail) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
License Collaboration And Manufacturing Agreements [Abstract]
Contractual obligations due to Bayer, MSK and QIMR	$ 0	$ 0

Out-license Agreements - Additi

Out-license Agreements - Additional Information (Detail) - USD ($)	1 Months Ended				12 Months Ended
	Jan. 31, 2022	Oct. 31, 2021	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
License, Collaboration and Manufacturing Agreements [Line Items]
License and collaboration revenue					$ 20,340,000	$ 0	$ 0
Years of manufacturing and supplying cost					7 years
Bayer License Agreement
License, Collaboration and Manufacturing Agreements [Line Items]
Upfront cash payment received				$ 45,000,000
Additional upfront reimbursement payment for research and process development				15,000,000
Additional upfront cash payment entitle to receive for translational activities, invoiced amount				$ 1,300,000		1,300,000
Royalty eligible to receive term after first commercial sale				12 years
Determined upfront payment for license in order to evaluate transaction price				$ 45,000,000
Determined research and process development activities in order to evaluate transaction price				15,000,000
Determined additional specified translational activities in order to evaluate transaction price				5,000,000
Determined fee constituted entire consideration included in transaction price					$ 13,100,000
Deferred revenue					51,500,000
Development or sales-based milestone payments earned or received					0
Bayer License Agreement | Current Liabilities
License, Collaboration and Manufacturing Agreements [Line Items]
Deferred revenue					40,800,000
Bayer License Agreement | Long-Term Liabilities
License, Collaboration and Manufacturing Agreements [Line Items]
Deferred revenue					$ 10,700,000
Bayer License Agreement | Maximum
License, Collaboration and Manufacturing Agreements [Line Items]
Additional upfront cash payment entitle to receive for translational activities				5,000,000		5,000,000
Aggregate milestone payments entitle to receive upon achieving certain development, regulatory and commercial milestones				610,000,000		610,000,000
Bayer Technology Transfer Agreement
License, Collaboration and Manufacturing Agreements [Line Items]
License agreement percentage			20.00%
License agreement amount			$ 3,100,000
License agreement total fee			$ 15,300,000
Technology transfer agreements fee remainder					The remainder of the fee will be billed as follows: (i) 20 percent in January 2023 and (ii) 20 percent upon the technology transfer completion
Transaction fee price					$ 15,300,000
Bayer Technology Transfer Agreement | Subsequent Event
License, Collaboration and Manufacturing Agreements [Line Items]
License agreement percentage	40.00%
License agreement amount	$ 6,100,000
Bayer Manufacturing Agreement
License, Collaboration and Manufacturing Agreements [Line Items]
License agreement percentage			50.00%
Written acceptance of binding purchase order percentage					50.00%
Bayer Manufacturing Agreement | Maximum
License, Collaboration and Manufacturing Agreements [Line Items]
Manufacturing services			$ 13,100,000
Bayer Manufacturing Agreement | Minimum
License, Collaboration and Manufacturing Agreements [Line Items]
Manufacturing services			$ 6,600,000
Bayer Agreements
License, Collaboration and Manufacturing Agreements [Line Items]
License and collaboration revenue					$ 19,800,000	0
Deferred revenue				$ 61,300,000	51,500,000	$ 61,300,000
Pierre Fabre Commercialization Agreement
License, Collaboration and Manufacturing Agreements [Line Items]
Upfront cash payment received		$ 45,000,000
Royalty eligible to receive term after first commercial sale		12 years
License and collaboration revenue					500,000
Development or sales-based milestone payments earned or received					0
Determined upfront payment constituted entire consideration included in transaction price		$ 45,000,000
Upfront payment recognized					0
Pierre Fabre Commercialization Agreement | Long-Term Liabilities
License, Collaboration and Manufacturing Agreements [Line Items]
Deferred revenue					$ 45,000,000
Pierre Fabre Commercialization Agreement | Maximum
License, Collaboration and Manufacturing Agreements [Line Items]
Aggregate milestone payments entitle to receive upon achieving certain regulatory and commercial milestones		$ 318,000,000
Pierre Fabre Commercialization Agreement | Minimum
License, Collaboration and Manufacturing Agreements [Line Items]
Years of potential to manufacturing and supply					7 years
Years of potential to perform cell-selection services					3 years

Out-license Agreements - Addi_2

Out-license Agreements - Additional Information (Detail 1)	Dec. 31, 2021
Bayer Technology Transfer Agreement | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
License, Collaboration and Manufacturing Agreements [Line Items]
Revenue expected to be recognized over period	3 years

Leases - Additional Information

Leases - Additional Information (Detail) $ in Millions	Feb. 15, 2018USD ($)ft²	Mar. 31, 2021USD ($)ft²	Dec. 31, 2021USD ($)
South San Francisco California
Lessee Lease Description [Line Items]
Lease expiration date			May 31, 2025
South San Francisco California | Line of Credit
Lessee Lease Description [Line Items]
Letter of credit maintained			$ 0.1
Letter of credit renewal term			12 months
Letter of credit, decrease from prior lease agreement			$ 0.1
Restricted cash related to letter of credit			$ 0.2
Thousand Oaks California
Lessee Lease Description [Line Items]
Lease agreement area of square feet of office, lab and warehouse space | ft²		33,659
Lease initial term	15 years	10 years 6 months
Contractual obligations	$ 16.4	$ 21
Percentage of annual increase in base rent		3.00%
Operating lease, option to extend		0
Lease option to extend additional term		5 years
Lease agreement area of office, lab and cellular therapy manufacturing space | ft²	90,580
Lease commencement date	Feb. 15, 2018
Lease extension term, option one	10 years
Lease extension term, option two	9 years
Thousand Oaks California | Additional Office Space
Lessee Lease Description [Line Items]
Lease expiration date			Feb. 28, 2026
Operating lease, option to extend			we have the option to extend the lease for an additional period of five years after the initial term.
Lease option to extend additional term			5 years
Operating lease, existence of option to extend [true false]			true
Thousand Oaks California | Line of Credit
Lessee Lease Description [Line Items]
Letter of credit issued, classified as long-term restricted cash	$ 1.2
Aurora Colorado
Lessee Lease Description [Line Items]
Lease expiration date			Apr. 30, 2024
Incremental contractual obligations under lease amendment			$ 0.2

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Lease Liabilities Under Operating and Finance Leases (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating leases, 2022	$ 5,171
Operating leases, 2023	5,265
Operating leases, 2024	5,183
Operating leases, 2025	4,806
Operating leases, 2026	3,257
Operating leases, Thereafter	19,004
Operating leases, Total minimum payments	42,686
Less: amount representing interest	(14,586)
Present value of lease liabilities	28,100
Other current liabilities	$ 2,582	$ 1,730
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities
Operating lease liabilities - long-term	$ 25,518	13,041
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other long-term liabilities
Total	$ 28,100
Finance leases, 2022	181
Finance leases, 2023	29
Finance leases, 2024	0
Finance leases, 2025	0
Finance leases, 2026	0
Finance leases, Thereafter	0
Finance leases, Total minimum payments	210
Less: amount representing interest	(10)
Present value of lease liabilities	200
Other current liabilities	$ 171	$ 255
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Other current liabilities
Other long-term liabilities	$ 29
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Other long-term liabilities
Total	$ 200

Leases - Components of Lease Co

Leases - Components of Lease Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating lease cost:
Operating lease cost	$ 3,827	$ 3,020	$ 2,578
Short-term lease cost	836	987	770
Total operating lease cost	4,663	4,007	3,348
Finance lease cost:
Amortization expense	244	389	324
Interest on lease liabilities	29	60	56
Total finance lease cost	$ 273	$ 449	$ 380

Leases - Summary of Other Infor

Leases - Summary of Other Information Related to Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$ 3,738	$ 2,878	$ 2,346
Operating cash flows for finance leases	32	62	50
Financing cash flows for finance leases	254	389	486
Operating lease assets obtained in exchange for lease obligations:	13,427	0	838
Finance lease assets obtained in exchange for lease obligations:	0	281	323
Non-cash increase to operating lease assets due to remeasurement of lease liabilities:	$ 1,760	$ 639	$ 0
Weighted Average Remaining Lease Term
Operating leases	9 years 2 months 12 days	9 years 4 months 24 days	10 years 3 months 18 days
Finance leases	1 year	1 year 8 months 12 days	2 years 6 months
Weighted Average Discount Rate
Operating leases	9.60%	10.30%	10.40%
Finance leases	9.70%	9.70%	10.00%

Leases - Summary of Activity fo

Leases - Summary of Activity for ARO Liabilities (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Leases [Abstract]
Balance as of December 31, 2020	$ 866
Accretion expense	87
Balance as of December 31, 2021	$ 953

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Accrued termination charges	$ 0	$ 0
Liabilities related to indemnification agreements	$ 0	$ 0

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	Jul. 31, 2019	Jul. 18, 2019	Nov. 30, 2021	Dec. 31, 2020	Feb. 29, 2020	Feb. 28, 2019	Feb. 15, 2022	Jun. 30, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Authorized capital stock									520,000,000
Common stock, par value				$ 0.0001					$ 0.0001	$ 0.0001
Common stock, shares authorized				500,000,000					500,000,000	500,000,000
Preferred stock, par value									$ 0.0001
Preferred stock, shares authorized									20,000,000
Preferred stock, shares outstanding				0					0	0
Stock option granted description terms									the exercise price of an option granted to a 10% shareholder cannot be less than 110% of the estimated fair value of the shares on the date of grant. The estimated fair value is generally equal to the closing market price of the Company’s common stock on the measurement date. Options granted generally vest over four years and expire in seven to ten years.
Ownership percent									10.00%
Shares of common stock, reserved for issuance									20,971,553
Additional shares of common stock, reserved for issuance													1,500,000
Common stock, shares exercised									246,867	268,938	347,716
Option intrinsic value, exercised									$ 800,000	$ 1,000,000	$ 3,800,000
Net tax benefits related to exercised options									0
Estimated fair value of stock option, vested									26,600,000	29,400,000	31,600,000
Stock-based compensation expense									$ 53,865,000	$ 51,351,000	$ 51,696,000
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value per share									$ 16.42	$ 12.19	$ 27.04
Estimated fair value, vested in period									$ 27,100,000	$ 23,600,000	$ 13,800,000
Unrecognized stock-based compensation expense									$ 75,700,000
Unrecognized stock-based compensation weighted average recognition period									2 years 9 months 18 days
Aggregate intrinsic value									$ 88,100,000
Restricted stock units, settled									1,553,893	1,218,945
RSU settlements, net of shares withheld, shares									154,341	276,822
Restricted stock units withheld for tax obligations									61,385	106,459
Restricted stock units withheld for tax obligations, value									$ 1,200,000	$ 1,500,000
Restricted Stock Units (RSUs) | From Date Of Grant
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation, vesting period									4 years
Employees And Non Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation, vesting period									4 years
Vested and Unvested Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation weighted average recognition period									2 years 6 months
Stock options, issued												275,000
Unrecognized stock-based compensation									$ 41,900,000
2014 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Annual increase in EIP/ESPP, subject to other limitations									5.00%
Shares of common stock, reserved for issuance									16,086,987
Shares of common stock, reserved for issuance									4,018,597
Outstanding options and RSUs									12,068,390
Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock, reserved for issuance									4,022,184
Shares of common stock, reserved for issuance									1,278,379
Outstanding options and RSUs									2,743,805
Additional shares of common stock, reserved for issuance														1,500,000
2014 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of employees purchase price of common stock									85.00%
Shares of common stock, reserved for issuance									862,382
Unrecognized stock-based compensation expense									$ 600,000
Employee stock purchase plan effective date									Oct. 15, 2014
Employee stock purchase plan description									(i) the beginning of a 12-month offering period, or (ii) at the end of one of the two related 6-month purchase periods
Employee stock purchase plan offering commenced start date									Jun. 1, 2016
Stock-based compensation expense									$ 1,700,000	$ 1,800,000	$ 1,300,000
Shares purchased									319,190	282,514	139,466
Aggregate number of shares authorized									1,817,511
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of employees purchase price of common stock									100.00%
Minimum | 10% Shareholder
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of employees purchase price of common stock									110.00%
Minimum | Employees And Non Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation award expiration period									7 years
Maximum | Employees And Non Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation award expiration period									10 years
Maximum | 2014 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Annual increase in EIP/ESPP, subject to other limitations									1.00%
Stock may be issued or transferred, value									$ 25,000
Maximum increase in number of shares available for issuance									230,769
Underwritten Public Offering
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares issued	6,871,727			5,102,041				12,633,039
Shares issued, price per share	$ 15.28			$ 24.50				$ 11.32		$ 24.50
Proceeds from sale of common stock, gross	$ 150,000,000			$ 175,000,000				$ 201,800,000
Proceeds from sale of common stock, net	$ 140,700,000			$ 164,300,000				$ 189,300,000
Warrants outstanding									2,888,526
Option price to purchase shares								$ 11.32
Underwritten Public Offering | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares of our common stock								2,325,000
Underwritten Public Offering | Warrant
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of warrants issued	2,945,026			2,040,816				2,866,961		2,040,816
Warrant, price per share	$ 15.2799			$ 24.4999				$ 11.3199		$ 24.4999
Number of securities called by each warrant		1
Warrants, exercise price		$ 0.0001
Warrants, term		7 years
Maximum ownership Percentage		9.99%
Underwritten Public Offering | Warrant | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Prior notice period		61 days
Underwritten Public Offering | Warrant | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum ownership Percentage		19.99%
At The Market Offering | Cowen
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, shares issued							1,319,878		6,240,601	4,785,514
Proceeds from sale of common stock, gross							$ 21,000,000		$ 101,300,000	$ 69,900,000
Proceeds from sale of common stock, net							$ 20,500,000		$ 98,900,000	$ 68,000,000
Common stock average price							$ 15.88		$ 16.23	$ 14.60
Common stock value available to be sold							$ 57,400,000		$ 78,300,000
At The Market Offering | Maximum | Cowen
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock aggregate offering price			$ 100,000,000		$ 100,000,000	$ 100,000,000
Percentage of commission to be paid on gross sales proceeds of common stock sold			3.00%		3.00%	3.00%

Stockholders' Equity - Summary

Stockholders' Equity - Summary of RSU Activity (Detail) - Unvested RSUs - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Unvested as of December 31, 2020	3,829,620
Shares, Granted	4,624,257
Shares, Forfeited	(1,307,626)
Shares, Vested	(1,553,893)
Shares, Outstanding as of December 31, 2021	5,592,358	3,829,620
Weighted Average Grant Date Fair Value, Unvested as of December 31, 2020	$ 15.91
Weighted Average Grant Date Fair Value, Granted	16.42	$ 12.19	$ 27.04
Weighted Average Grant Date Fair Value, Forfeited	14.64
Weighted Average Grant Date Fair Value, Vested	17.41
Weighted Average Grant Date Fair Value, Outstanding as of December 31, 2021	$ 16.22	$ 15.91

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Shares	2,643,378	2,641,125	2,535,425
Exercised, Shares	(246,867)	(268,938)	(347,716)
2014 EIP and Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding, Shares, beginning balance	7,851,886
Granted, Shares	2,643,378
Exercised, Shares	(246,867)
Forfeited or expired, Shares	(1,028,560)
Outstanding, Shares, ending balance	9,219,837	7,851,886
Vested and expected to vest, Shares	9,219,837
Exercisable, Shares	5,073,289
Outstanding, Weighted Average Exercise Price, beginning balance	$ 22.89
Granted, Weighted Average Exercise Price	15.97
Exercised, Weighted Average Exercise Price	13.97
Forfeited or expired, Weighted Average Exercise price	25.92
Outstanding, Weighted Average Exercise Price, ending balance	20.81	$ 22.89
Stock options vested and expected to vest, Weighted Average Exercise Price	20.81
Exercisable, Weighted Average Exercise Price	$ 24.36
Outstanding, Weighted Average Remaining Contractual Term	6 years 4 months 24 days	6 years 4 months 24 days
Stock options vested and expected to vest, Weighted Average Remaining Contractual Term	6 years 4 months 24 days
Exercisable, Weighted Average Remaining Contractual Term	4 years 9 months 18 days
Aggregate intrinsic value	$ 12,810	$ 26,834
Vested and expected to vest, Aggregate Intrinsic Value	12,810
Exercisable, Aggregate Intrinsic Value	$ 5,496

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of Estimated Weighted-Average Assumptions (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected term (years)	6 years	6 years	5 years 10 months 24 days
Expected volatility	75.90%	76.80%	76.10%
Risk-free interest rate	0.90%	0.80%	2.10%
Expected dividend yield	0.00%	0.00%	0.00%
Weighted-average estimated grant date fair value per share	$ 10.52	$ 7.96	$ 18.06
Options granted	2,643,378	2,641,125	2,535,425
Total estimated grant date fair value	$ 27,808,000	$ 21,023,000	$ 45,790,000

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Common Stock Reserved for Future Issuance Under Equity Incentive Plans (Detail)	Dec. 31, 2021shares
Class Of Stock [Line Items]
Total reserved shares of common stock	20,971,553
2014 Equity Incentive Plan
Class Of Stock [Line Items]
Total reserved shares of common stock	16,086,987
2018 Inducement Plan
Class Of Stock [Line Items]
Total reserved shares of common stock	4,022,184
2014 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Total reserved shares of common stock	862,382

Stockholders' Equity - Schedu_2

Stockholders' Equity - Schedule of Stock-based Compensation Related to Stock Awards (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 53,865	$ 51,351	$ 51,696
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	32,063	31,527	26,773
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 21,802	$ 19,824	$ 24,923

Income Taxes - Losses Before Pr

Income Taxes - Losses Before Provision for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
United States	$ (340,301)	$ (306,758)	$ (291,049)
Foreign	206	153	85
Loss before provision for income taxes	$ (340,095)	$ (306,605)	$ (290,964)

Income Taxes - Components of Pr

Income Taxes - Components of Provision for (Benefit from) Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current provision for (benefit from) income taxes:
State	$ 4	$ 2	$ 0
Foreign	42	13	12
Total current provision for (benefit from) income taxes	$ 46	$ 15	$ 12

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Statutory Tax Rates to Effective Tax Rates (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Federal income taxes at statutory rate	21.00%	21.00%	21.00%
Impact of stock compensation	(2.00%)	(2.40%)	0.10%
Non-deductible executive compensation	(0.20%)	(0.10%)	(0.70%)
Other	(0.10%)	0.30%	(0.20%)
Change in valuation allowance	(18.70%)	(18.80%)	(20.20%)
Effective tax rate	0.00%	0.00%	0.00%

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating losses	$ 308,997	$ 237,010
Stock-based compensation	24,181	20,672
Capitalized expenses	10,499	12,590
License fees	8,716	8,159
Operating lease liabilities	7,972	4,251
Legal fees	2,366	2,136
Tax credits	1,580	1,580
Deferred Revenue	12,133	0
Other	7,048	5,360
Total deferred tax assets	383,492	291,758
Valuation allowance	(376,071)	(287,349)
Total deferred tax assets	7,421	4,409
Deferred tax liabilities:
Operating lease assets	(7,421)	(3,541)
Other	0	(868)
Total deferred tax liabilities	(7,421)	(4,409)
Net deferred tax assets (liabilities)	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Increase in valuation allowance tax	$ 88,700
Net operating loss carryforwards, federal	1,064,400
Research and development tax credit carryforwards	$ 94,500
Research and development tax credit carryforwards, expiration year	2035
Net operating loss carryforwards, state	$ 1,045,500
Tax credit carryforwards	$ 2,000
Tax credit carryforwards, expiration year	2024
Unrecognized tax benefits	$ 144,067	$ 110,601	$ 86,000	$ 41,074
Unrecognized tax benefits if recognized would impact effective tax rate	$ 0
Other States
Income Taxes [Line Items]
Net tax operating losses, expiration	begins to expire in 2030
Net operating loss carryforwards, state	$ 226,600
Domestic
Income Taxes [Line Items]
Net operating loss carryforwards subject to expiration	$ 65,200
Net tax operating losses, expiration	begin to expire in 2032
Net operating loss carryforwards not subject to expiration	$ 999,200
Research and development tax credit carryforwards	$ 18,000
Research and development tax credit carryforwards, expiration year	2032
State
Income Taxes [Line Items]
Net tax operating losses, expiration	begin to expire in 2032
Research and development tax credit carryforwards	$ 30,400

Income Taxes - Reconciliation_2

Income Taxes - Reconciliation of Beginning and Ending Amount of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Beginning Balance	$ 110,601	$ 86,000	$ 41,074
Gross increases for tax positions related to current year	28,171	24,648	22,800
Gross increases for tax positions related to prior year	5,295	0	22,126
Gross decreases for tax positions related to prior year	0	(47)	0
Ending Balance	$ 144,067	$ 110,601	$ 86,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ in Millions	Jan. 26, 2022USD ($)
Subsequent Event
Subsequent Event [Line Items]
Amount of closing adjustment related to asset purchase agreement	$ 100