Lyell Immunopharma (LYEL) 10-K 29 Mar 22 2021 FY Annual report Financial data

Cover

Cover - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Mar. 25, 2022	Jun. 30, 2021
Cover [Abstract]
Entity Central Index Key	0001806952
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-40502
Entity Registrant Name	Lyell Immunopharma, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	83-1300510
Entity Address, Address Line One	201 Haskins Way
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	695-0677
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	LYEL
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 2,741,432
Entity Common Stock, Shares Outstanding		245,388,050
Documents Incorporated by Reference	Portions of the registrant's Proxy Statement for the 2022 Annual Meeting of Stockholders are incorporated herein by reference in Part III of this Annual Report on Form 10-K to the extent stated herein. Such proxy statement will be filed with the Securities and Exchange Commission within 120 days of the registrant's fiscal year ended December 31, 2021.

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2021
Audit Information [Abstract]
Auditor Name	Ernst & Young LLP
Auditor Location	Redwood City, California
Auditor Firm ID	42

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 293,828	$ 140,406
Marketable securities	320,966	472,213
Prepaid expenses and other current assets	11,492	4,928
Total current assets	626,286	617,547
Restricted cash	466	466
Marketable securities, non-current	283,531	79,995
Other investments	47,001	83,448
Property and equipment, net	120,098	77,045
Operating lease right-of-use assets	46,541	47,010
Other non-current assets	3,483	2,769
Total assets	1,127,406	908,280
Current liabilities:
Accounts payable	3,207	9,396
Accrued liabilities and other current liabilities	29,057	28,021
Success payment liabilities	9,486	5,773
Deferred revenue	4,988	6,095
Total current liabilities	46,738	49,285
Operating lease liabilities, non-current	66,650	50,957
Deferred revenue, non-current	79,665	89,066
Other non-current liabilities	4,566	532
Total liabilities	197,619	189,840
Commitments and contingencies (Note 16)
Convertible preferred stock, $0.0001 par value; zero and 195,021 shares authorized at December 31, 2021 and 2020, respectively; zero and 194,474 shares issued and outstanding at December 31, 2021 and 2020, respectively	0	1,010,968
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value; 10,000 and zero shares authorized at December 31, 2021 and 2020, respectively; zero shares issued and outstanding at December 31, 2021 and 2020	0	0
Common stock, $0.0001 par value; 500,000 and 264,905 shares authorized at December 31, 2021 and 2020, respectively; 242,738 and 15,570 shares issued and outstanding at December 31, 2021 and 2020, respectively	24	2
Additional paid-in capital	1,515,748	41,357
Accumulated other comprehensive (loss) income	(1,623)	256
Accumulated deficit	(584,362)	(334,143)
Total stockholders’ equity (deficit)	929,787	(292,528)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 1,127,406	$ 908,280

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock authorized (in shares)	0	195,021,000
Convertible preferred stock issued (in shares)	0	194,474,000
Convertible preferred stock outstanding (in shares)	0	194,474,000
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock authorized (in shares)	10,000,000	0
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock authorized (in shares)	500,000,000	264,905,000
Common stock issued (in shares)	242,738,000	15,570,000
Common stock outstanding (in shares)	242,738,350	15,569,788

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Revenue	$ 10,650	$ 7,756	$ 657
Operating expenses (income):
Research and development	138,693	182,243	63,595
General and administrative	89,057	46,881	39,151
Other operating income, net	(2,324)	(9,431)	0
Total operating expenses	225,426	219,693	102,746
Loss from operations	(214,776)	(211,937)	(102,089)
Interest income, net	1,165	5,939	8,121
Other (expense) income, net	(161)	1,526	(35,409)
Impairment of other investments	(36,447)	0	0
Total other (loss) income, net	(35,443)	7,465	(27,288)
Net loss	(250,219)	(204,472)	(129,377)
Other comprehensive (loss) gain:
Net unrealized (loss) gain on marketable securities	(1,879)	(198)	454
Comprehensive loss	(252,098)	(204,670)	(128,923)
Net loss attributed to common stockholders:
Net loss	(250,219)	(204,472)	(129,377)
Deemed dividends upon issuance or repurchase of convertible preferred stock	0	(3,582)	(1,144)
Net loss attributed to common stockholders	$ (250,219)	$ (208,054)	$ (130,521)
Net loss per common share, basic (in dollars per share)	$ (1.84)	$ (15.69)	$ (24.04)
Net loss per common share, diluted (in dollars per share)	$ (1.84)	$ (15.69)	$ (24.04)
Weighted-average shares used to compute net loss per common share, basic (in shares)	135,918	13,258	5,429
Weighted-average shares used to compute net loss per common share, diluted (in shares)	135,918	13,258	5,429

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Total	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Series AA Convertible Preferred Stock	Series C Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive (Loss) Income	Retained Earnings (Accumulated Deficit)
Beginning balance, (in shares) at Dec. 31, 2018	74,406,000
Beginning balance at Dec. 31, 2018	$ 120,296
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of convertible preferred stock, net of issuance costs (in shares)		23,527,000	23,930,000	30,253,000
Issuance of convertible preferred stock, net of issuance costs		$ 89,380	$ 162,018	$ 146,325
Deemed dividends on issuance of Series A convertible preferred stock		1,144
Ending balance, (in shares) at Dec. 31, 2019	152,116,000
Ending balance at Dec. 31, 2019	$ 519,163
Beginning balance (in shares) at Dec. 31, 2018						1,092,000
Beginning balance at Dec. 31, 2018	850					$ 0	$ 826	$ 0	$ 24
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Deemed dividends on issuance of Series A convertible preferred stock	(1,144)						(826)		(318)
Issuance of common stock to strategic partners (in shares)						910,000
Issuance of common stock to strategic partners	2,562						2,562
Repurchase of common stock	(185)						(185)
Stock-based compensation (in shares)						9,179,000
Stock-based compensation	15,732					$ 1	15,731
Other comprehensive loss	454							454
Net loss	(129,377)								(129,377)
Ending balance (in shares) at Dec. 31, 2019						11,181,000
Ending balance at Dec. 31, 2019	$ (111,108)					$ 1	18,108	454	(129,671)
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of convertible preferred stock, net of issuance costs (in shares)					42,905,000
Issuance of convertible preferred stock, net of issuance costs					$ 492,467
Repurchase of convertible preferred stock (in shares)	(547,000)
Repurchase of convertible preferred stock	$ (662)	$ (700)
Ending balance, (in shares) at Dec. 31, 2020	194,474,000
Ending balance at Dec. 31, 2020	$ 1,010,968
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock to strategic partners (in shares)						275,000
Issuance of common stock to strategic partners	1,004						1,004
Issuance of common stock for asset acquisition (in shares)						688,000
Issuance of common stock for asset acquisition	4,000						4,000
Issuance of common stock upon exercise of stock options (in shares)						113,000
Issuance of common stock upon exercise of stock options	373						373
Repurchase of convertible preferred stock	(3,582)						(3,582)
Repurchase of common stock (in shares)						(2,032,000)
Repurchase of common stock	(11,806)						(11,806)
Stock-based compensation (in shares)						5,345,000
Stock-based compensation	33,261					$ 1	33,260
Other comprehensive loss	(198)							(198)
Net loss	(204,472)								(204,472)
Ending balance (in shares) at Dec. 31, 2020						15,570,000
Ending balance at Dec. 31, 2020	$ (292,528)					$ 2	41,357	256	(334,143)
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of convertible preferred stock to common stock (in shares)	(194,474,000)
Conversion of convertible preferred stock to common stock	$ (1,010,968)
Ending balance, (in shares) at Dec. 31, 2021	0
Ending balance at Dec. 31, 2021	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from initial public offering, net of issuance costs (in shares)						25,000,000
Proceeds from initial public offering, net of issuance costs	391,802					$ 2	391,800
Conversion of convertible preferred stock to common stock (in shares)						194,474,000
Conversion of convertible preferred stock to common stock	$ 1,010,968					$ 20	1,010,948
Issuance of common stock upon exercise of stock options (in shares)	2,750,380					2,750,000
Issuance of common stock upon exercise of stock options	$ 9,442						9,442
Stock-based compensation (in shares)						4,944,000
Stock-based compensation	62,201						62,201
Other comprehensive loss	(1,879)							(1,879)
Net loss	(250,219)								(250,219)
Ending balance (in shares) at Dec. 31, 2021						242,738,000
Ending balance at Dec. 31, 2021	$ 929,787					$ 24	$ 1,515,748	$ (1,623)	$ (584,362)

Consolidated Statements of Co_2

Consolidated Statements of Convertible Preferred Stock and Stockholders’ Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Series A Convertible Preferred Stock
Stock issuance costs	$ 29
Series B Convertible Preferred Stock
Stock issuance costs	133
Series AA Convertible Preferred Stock
Stock issuance costs	$ 101

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (250,219)	$ (204,472)	$ (129,377)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Stock-based compensation expense	62,201	33,261	15,732
Impairment of other investments	36,447	0	0
Depreciation and amortization	13,624	4,294	1,256
Change in fair value of success payment liabilities	3,713	5,337	436
Change in fair value of warrants	256	(1,323)	0
Lease expense, net of gain on lease remeasurement	911	3,181	3,127
Non-cash expense in connection with asset acquisition	0	3,529	0
Net amortization or accretion on marketable securities	1,901	539	(1,518)
Loss on remeasurement of convertible preferred stock tranche liabilities	0	0	35,444
Expense in connection with equity issuances	0	0	3,566
Loss (gain) on property and equipment disposals	1,210	(4,884)	0
Gain on net operating lease liability disposal	(308)	0	0
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(6,987)	(1,388)	(5,767)
Accounts payable	91	(278)	1,709
Accrued liabilities and other current liabilities	4,542	6,120	9,755
Deferred revenue	(10,508)	(7,756)	102,917
Operating lease liabilities, non-current	13,202	2,966	2,194
Other non-current liabilities	3,675	0	0
Net cash (used in) provided by operating activities	(126,249)	(160,874)	39,474
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(65,504)	(51,481)	(16,047)
Purchases of marketable securities	(673,465)	(864,909)	(610,842)
Sales and maturities of marketable securities	617,396	686,322	238,456
Purchases of other investments	0	(43,448)	(34,000)
Net cash used in investing activities	(121,573)	(273,516)	(422,433)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from initial public offering, net of issuance costs	391,802	0	0
Proceeds from issuance of convertible preferred stock, net of issuance costs	0	492,467	351,341
Proceeds from exercise of stock options	9,442	373	0
Payments for the repurchase of common stock	0	(11,806)	(185)
Payments for the repurchase of convertible preferred stock	0	(4,244)	0
Net cash provided by financing activities	401,244	476,790	351,156
Net increase (decrease) in cash, cash equivalents and restricted cash	153,422	42,400	(31,803)
Cash, cash equivalents and restricted cash at beginning of period	140,872	98,472	130,275
Cash, cash equivalents and restricted cash at end of period	294,294	140,872	98,472
Represented by:
Cash and cash equivalents	293,828	140,406	96,674
Restricted cash	466	466	1,798
Total	294,294	140,872	98,472
SUPPLEMENTAL CASH FLOW INFORMATION
Cash received for amounts related to tenant improvement allowances	13,295	2,966	2,194
Cash paid for amounts included in the measurement of lease liabilities	8,546	5,147	1,464
Non-cash investing and financing activities:
Conversion of convertible preferred stock to common stock upon closing of initial public offering	1,010,968	0	0
Purchases of property and equipment included in accounts payable and accrued liabilities	4,605	12,740	3,185
Operating lease right-of-use assets obtained in exchange for lease obligations	0	30,475	23,656
Remeasurement of operating lease right-of-use asset for lease modification	3,873	(8,958)	0
Other investments received for sale of assets	0	6,000	0
Non-cash deemed dividends on convertible preferred stock	$ 0	$ 0	$ 1,144

Organization

Organization	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Lyell Immunopharma, Inc. (the “Company”) was incorporated in Delaware in June 2018. The Company is a T‑cell reprogramming company dedicated to the mastery of T cells to cure patients with solid tumors. The Company is building a multi-modality product pipeline. The Company’s primary activities since incorporation have been to develop T‑cell therapies, perform research and development, enter into strategic collaboration and license arrangements, enable manufacturing activities in support of its product candidate development efforts, acquire technology, organize and staff the Company, conduct business planning, establish its intellectual property portfolio, raise capital and provide general and administrative support for these activities. Initial Public Offering

Basis of Presentation and Signi

Basis of Presentation and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies	Basis of Presentation and Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The consolidated financial statements include the accounts of Lyell Immunopharma, Inc. and its wholly-owned subsidiary. All significant intercompany transactions and balances are eliminated in consolidation. Certain prior period amounts in the consolidated financial statements and accompanying notes have been reclassified to conform to the current period’s presentation. Liquidity and Management’s Plan The Company is currently working on a number of long-term development projects that involve experimental technologies. The projects may require several years and substantial expenditures to complete and ultimately may be unsuccessful. The Company plans to finance operations with available cash resources or from the issuance of equity or debt securities. The Company believes that its available cash, cash equivalents and marketable securities as of December 31, 2021 will be adequate to fund its operations at least through the next 12 months from the date these consolidated financial statements are issued. The Company will require substantial additional financial resources to complete the development and commercialization of its product candidates. Additional capital may not be available on terms acceptable to the Company, or at all. If adequate funds are not available, or if the terms of potential funding sources are unfavorable, the Company’s business and ability to develop its technology and therapeutic products would be harmed. Furthermore, any sales of additional equity securities may result in dilution to the Company’s stockholders, and any debt financing may include covenants that restrict the Company’s business. Summary of Significant Accounting Policies Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with GAAP requires management to make judgments, estimates and assumptions that affect reported amounts and related disclosures. Specific accounts that require management estimates include, but are not limited to, stock-based compensation, valuation of success payments, revenue recognition and accrued expenses. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results could differ materially from those estimates. Comprehensive Loss Comprehensive loss includes net loss and certain changes in stockholders’ equity (deficit) that are excluded from net loss. For the years ended December 31, 2021, 2020, and 2019 this was comprised of net unrealized gains and losses on the Company’s marketable securities. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts. Restricted cash is cash held in bank accounts and is used as collateral for letters of credits issued in conjunction with the Company’s lease agreements and collateral associated with the Company’s corporate credit card program. Marketable Securities The Company generally invests its excess cash in investment grade short- to intermediate-term fixed income securities. Such investments are classified as available-for-sale and are carried at fair value, with the unrealized gains and losses reported as a component of comprehensive loss. Realized gains and losses on available-for-sale securities are included in other (expense) income, net. The cost of investments sold is based on the specific-identification method. The Company classifies those investments that are not required for use in current operations and that mature in more than 12 months as non-current marketable securities in the accompanying consolidated balance sheets. Each reporting period, the Company evaluates whether declines in fair value below carrying value are due to expected credit losses, as well as the Company’s ability and intent to hold the investment until a forecasted recovery occurs. Expected credit losses are recorded as an allowance through other (expense) income, net. Other Investments The Company determines at the inception of each arrangement whether an investment or other interest is considered a variable interest entity (“VIE”). If the investment or other interest is determined to be a VIE, the Company evaluates whether it is considered the primary beneficiary. The primary beneficiary of a VIE is the party that meets both of the following criteria: (i) has the power to direct the activities that most significantly impact the VIE’s economic performance; and (ii) has the obligation to absorb losses or the right to receive benefits from the VIE. For investments in VIEs in which the Company is considered the primary beneficiary, the assets, liabilities and results of operations of the VIE are included in its consolidated financial statements. As of December 31, 2021 and 2020, there were no VIEs for which the Company was the primary beneficiary. The Company accounts for its strategic equity interests in non-publicly traded companies for which it does not have the ability to exercise significant influence in accordance with Accounting Standards Codification (“ASC”) 321, Investments – Equity Securities (“ASC 321”). Upon acquisition, these investments are measured at cost, which represents the then fair value. Under ASC 321, the Company can elect to subsequently measure the investments at initial cost, minus impairment and any changes, plus or minus, resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. This election must be made for each investment separately. The Company has made this election for all investments in this category and will continue to measure these investments using this method until they no longer qualify to be measured in accordance with this method. Changes in the carrying value of other investments are recognized through net loss. Each reporting period, the Company performs a qualitative assessment to evaluate whether the investment is impaired. The Company’s assessment includes a review of recent operating results and trends, recent sales/acquisitions of the investee securities and other factors that raise concerns about the investee’s ability to continue as a going concern. If the investment is impaired, an impairment charge is recognized in the amount by which the carrying amount of the investment exceeds the estimated fair value of the investment, with the impairment charge recognized through net loss. See Note 5, Other Investments , for details related to an investment impairment recognized during the year ended December 31, 2021. Additionally, the Company holds an investment in equity warrants giving it the right to acquire stock of a non‑publicly traded company. Equity warrant investments are recorded within other assets at the estimated fair value, with gains and losses recognized in other (expense) income, net. Property and Equipment, Net Property and equipment primarily consist of laboratory equipment, computer equipment and software, furniture and fixtures and leasehold improvements. Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method based on the estimated useful lives of the related assets, which are generally three Valuation of Long-lived Assets Long-lived assets are reviewed each reporting period for impairment or whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable, which may warrant adjustments to carrying values or estimated useful lives. Recoverability is measured by comparison of the carrying amount of an asset group to the future net undiscounted cash flows that the assets are expected to generate. If the carrying amount of an asset group exceeds its estimated future cash flows, an impairment charge is recognized in the amount by which the carrying amount of the asset group exceeds the fair value of the asset group. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the projected discounted future net cash flows arising from the asset. There has been no impairment of long-lived assets for any of the periods presented. Acquisitions The Company evaluates acquisitions of assets and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen to determine if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If the screen is met, the transaction is accounted for as an asset acquisition. If the screen is not met, further determination is required as to whether or not the Company has acquired inputs and processes that have the ability to create outputs which would meet the requirements of a business in which case the transaction is accounted for using the acquisition method of accounting, which requires, among other things, that assets acquired and liabilities assumed be recognized at their estimated fair values as of the acquisition date, and that the fair value of acquired intangibles be recorded on the balance sheet. Transaction costs are expensed as incurred. Any excess of the purchase price over the assigned fair values of the net assets acquired is recorded as goodwill. If the Company determines an acquisition does not meet the definition of a business combination under the acquisition method of accounting, the transaction is accounted for as an asset acquisition. In an asset acquisition, upfront payments allocated to in-process research and development (“IPR&D”) are recorded in research and development expense if it is determined that there is no alternative future use, and subsequent milestone payments are recorded in research and development expense when achieved for technology that has not yet met product feasibility. Leases The Company leases certain office, laboratory and manufacturing spaces. In addition to minimum rent, the leases require payment of real estate taxes, insurance, common area maintenance charges and other executory costs. At inception of a contract, the Company determines whether an arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. For all leases, the Company determines the classification of the lease as either operating or financing. As of December 31, 2021 and 2020, all of the Company’s leases were classified as operating leases. The Company recognizes right-of-use (“ROU”) assets and lease liabilities at the lease commencement date based on the present value of future lease payments over the lease term. As the Company’s leases do not provide an implicit rate, an incremental borrowing rate at each lease commencement date is used to determine the present value of future lease payments. The incremental borrowing rate is the rate of interest that the Company would pay to borrow equivalent funds on a collateralized basis at the lease commencement date. To estimate the incremental borrowing rate, a credit rating applicable to the Company is estimated using a synthetic credit rating analysis since the Company does not currently have a rating agency-based credit rating. The ROU asset includes any lease payments made prior to the lease commencement date and is reduced by any lease incentives received or deemed payable to the Company. The lease term may include options to extend or terminate the lease when it is reasonably certain that a lease option will be exercised. Lease expense is recognized on a straight-line basis over the lease term within operating expenses on the consolidated statements of operations and comprehensive loss. The Company has elected the practical expedient to not separate lease and non-lease components for real estate leases. Additionally, the Company has elected the short-term lease recognition exemption for all short-term leases and as a result, lease liabilities and ROU assets are not included on the consolidated balance sheets for leases with an initial term of 12 months or less. Fair Value Measurements The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs: Level 1 – Quoted prices in active markets for identical assets or liabilities. Level 2 – Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 3 – Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. The Company’s financial instruments, in addition to those presented in Note 6, Fair Value Measurements , include cash, restricted cash, other investments, accounts payable and accrued liabilities and other current liabilities. The carrying amount of cash, restricted cash, accounts payable and accrued liabilities and other current liabilities approximate fair value because of the short-term nature of these instruments. As described in Note 5, Other Investments , other investments are carried at cost, minus impairment and any changes, plus or minus, resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. Deemed Dividends Upon Issuance or Repurchase of Convertible Preferred Stock In March 2020, 546,806 shares of the Company’s Series A convertible preferred stock were repurchased by the Company at the then estimated fair value of $7.76 per share, which was higher than the carrying value of those shares. See Note 10, Convertible Preferred Stock . As a result, the Company recorded deemed dividends of $3.6 million for the year ended December 31, 2020. The transaction decreased convertible preferred stock by $0.7 million and reduced additional paid-in capital by $3.6 million. The deemed dividends increased the net loss attributed to common stockholders by $3.6 million. Revenue Recognition The Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements within the scope of ASC 606, Revenue from Contracts with Customers , ( “ ASC 606 ” ) the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the performance obligation is satisfied. In applying the ASC 606 framework, the Company must apply judgment to determine the nature of the promises within a revenue contract and whether those promises represent distinct performance obligations. In determining the transaction price, the Company does not include amounts subject to uncertainties unless it is probable that there will be no significant reversal of cumulative revenue when the uncertainty is resolved. Milestone and other forms of variable consideration that the Company may earn are subject to significant uncertainties of research and development related achievements, which generally are deemed not probable until such milestones are actually achieved. For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Additionally, the Company develops assumptions that require judgment to determine the standalone selling price of each performance obligation identified in the contract. The Company then allocates the total transaction price to each performance obligation based on the estimated standalone selling prices of each performance obligation, for which it recognizes revenue as or when the performance obligations are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the variable consideration and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis. Under the Company’s license agreements, the Company grants the license to a customer as it exists at the point of transfer and the nature of the license is a right to use the Company’s intellectual property as transferred. If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, upfront fees 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 bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time. Research and Development Expense The Company records expense for research and development costs as incurred. Research and development expenses consist of costs incurred by the Company for the discovery and development of its technology platforms and product candidates and includes costs incurred in connection with strategic collaborations, costs to license technology, personnel-related costs, including stock-based compensation expense, facility and technology related costs, research and laboratory expenses, as well as other expenses, which include consulting fees and other costs. Upfront payments and milestones paid to third parties in connection with technology platforms, which have not reached technological feasibility and do not have an alternative future use are expensed as incurred. General and Administrative Expense General and administrative costs are expensed as incurred and include personnel-related expenses, including stock-based compensation expense for personnel in executive, legal, finance and other administrative functions, legal costs, transaction costs related to collaboration and licensing agreements, as well as fees paid for accounting and tax services, consulting fees and facilities costs not otherwise included in research and development expenses. Legal costs include those related to corporate and patent matters. Success Payments The Company granted rights to success payments to Fred Hutchinson Cancer Research Center (“Fred Hutch”) and The Board of Trustees of the Leland Stanford Junior University (“Stanford”) pursuant to the terms of its research and collaboration agreements with each of those entities. Pursuant to the terms of these agreements, on each contractually prescribed measurement date, the Company may be required to make success payments based on increases in the estimated per share fair value of the Company’s common stock. See Note 3, Collaboration, License and Success Payment Agreements . The success payments are accounted for under ASC 718, Compensation – Stock Compensation , with the expense being recorded in research and development expenses. Once the service period is complete, the instrument will be accounted for under ASC 815, Derivatives and Hedging , and continue to be remeasured each reporting period with all changes in value recognized immediately in other (expense) income, net. The success payment liability is estimated at fair value at inception and at each reporting period, and the expense is accreted over the service period of the research and collaboration agreement. To determine the estimated fair value of the success payments, the Company uses a Monte Carlo simulation methodology which models the future movement of stock prices based on several key variables combined with empirical knowledge of the process governing the behavior of the stock price. The following variables were incorporated in the estimated fair value of the success payment liability: estimated fair value of the Company’s common stock, expected volatility, risk-free interest rate and the estimated number and timing of valuation measurement dates on the basis of which payments may be triggered. The computation of expected volatility was estimated based on available information about the historical volatility of stocks of similar publicly traded companies for a period matching the expected term assumption. Concentrations of Credit Risk and Off-balance Sheet Risk The Company maintains its cash, cash equivalents and restricted cash with high quality, accredited financial institutions. These amounts, at times, may exceed federally insured limits. The Company also makes short-term investments in money market funds, U.S. Treasury securities, U.S. government agency securities and corporate debt securities, which can be subject to certain credit risk. However, the Company mitigates the risks by investing in high-grade instruments, limiting exposure to any one issuer or type of investment and monitoring the ongoing creditworthiness of the financial institutions and issuers. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to significant risk on these funds. The Company has no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements. Claims and Contingencies From time to time, the Company may become involved in litigation and proceedings relating to claims arising from the ordinary course of business. The Company accrues a liability if the likelihood of an adverse outcome is probable and the amount is estimable. If the likelihood of an adverse outcome is only reasonably possible (as opposed to probable), or if an estimate is not determinable, the Company provides disclosure of a material claim or contingency. Stock-based Compensation Under ASC 718, the Company measures and recognizes expense for restricted stock awards (“RSAs”) and stock options granted to employees, directors and consultants based on the fair value of the awards on the date of grant. The fair value of stock options is estimated using the Black-Scholes option pricing model, which requires the use of subjective assumptions and for management to apply judgment and make estimates including: stock price volatility, the expected life of stock options, the risk-free interest rate, expected dividend, and the fair value of the underlying common stock on the date of grant. The expected volatility is based on the historical volatility of the stock of similar entities within the Company’s industry over periods commensurate with the Company’s expected term assumption. The expected term of stock option grants represents the weighted-average period the options are expected to remain outstanding and is based on the “simplified” method where the expected term is the midpoint between the vesting date and the end of the contractual term for each option. The Company bases the risk-free interest rate on the interest rate payable on U.S. Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected option term. In reference to the expected dividend yield assumption, the Company has not historically paid, and does not expect for the foreseeable future to pay, a dividend. The Company utilizes significant estimates and assumptions in determining the fair value of its common stock for financial reporting purposes. Prior to the closing of the IPO, the Company recorded expense for RSAs and stock options at prices not less than the fair market value of its common stock as determined by the board of directors, taking into consideration input from management and an independent third-party valuation analysis, and in accordance with the American Institute of Certified Public Accountants (“AICPA”) Accounting and Valuation Guide, Valuation of Privately-Held Company Equity Securities Issued as Compensation . Following the closing of the IPO, the fair value of the Company’s common stock is based on its closing price as reported on the NASDAQ Global Select Market on the date of grant. Stock-based compensation expense for RSAs and stock options is recognized on a straight-line basis over the requisite service period, which is generally the vesting period of the respective award. The Company accounts for forfeitures as they occur. The Company also granted stock options that vest in conjunction with certain performance conditions to certain key employees. At each reporting date, the Company is required to evaluate whether achievement of the performance conditions is probable. Compensation expense is recorded over the appropriate service period based upon the Company’s assessment of accomplishing each performance provision. Income Taxes The Company determines its deferred tax assets and liabilities based on the differences between the financial reporting and tax basis of assets and liabilities. The deferred tax assets and liabilities are measured using the enacted tax rates that will be in effect when the differences are expected to reverse. A valuation allowance is recorded when it is more likely than not that the deferred tax asset will not be recovered. The Company applies judgment in the determination of the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The Company recognizes any material interest and penalties related to unrecognized tax benefits in income tax expense. Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment and one reportable segment. Recent Accounting Pronouncements Recently Adopted Income Taxes In December 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2019-12, Income Taxes – Simplifying the Accounting for Income Taxes (“ASU 2019-12”). The guidance removes exceptions to the general principles in Income Taxes (Topic 740) for allocating tax expense between financial statement components, accounting basis differences stemming from an ownership change in foreign investments and interim period income tax accounting for year-to-date losses that exceed projected losses. The guidance became effective for annual reporting periods beginning after December 15, 2020 and interim periods within those fiscal years with early adoption permitted. Effective January 1, 2019, the Company early adopted ASU 2019-12. The adoption of this standard did not have a material impact on the Company ’ s consolidated financial statements. Credit Losses In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) (“ASU 2016-13”). ASU 2016-13 implements an impairment model, known as the current expected credit loss model, that is based on expected losses rather than incurred losses. Under the new guidance, an entity will recognize as an allowance its estimate of expected credit losses. On January 1, 2020, the Company early adopted this standard by using a modified retrospective approach. The adoption did not have a material impact on the Company’s consolidated financial statements. Collaborative Arrangements In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 (“ASU 2018-18”), which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC 606 when the counterparty is a customer. In addition, ASU 2018-18 precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. On January 1, 2020, the Company early adopted this standard on a retrospective basis to the date of initial application of ASC 606. The adoption did not have a material impact on the Company’s consolidated financial statements. Cloud Computing Arrangements In August 2018, the FASB issued ASU No. 2018-15, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract

Collaboration, License and Succ

Collaboration, License and Success Payment Agreements	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration, License and Success Payment Agreements	Collaboration, License and Success Payment Agreements Fred Hutch License Agreement – In 2018, the Company entered into a license agreement with Fred Hutch that grants the Company an exclusive, worldwide, sublicensable license under certain patent rights, and a non-exclusive, worldwide, sublicensable license for certain technology, to research, develop, manufacture, improve and commercialize products and processes covered by such patent rights or incorporating such technology for all therapeutic uses for the treatment of human cancer. The Company is also required to pay Fred Hutch annual license maintenance payments of $50,000 on the second anniversary of the effective date, and each anniversary of the effective date thereafter until the first commercial sale of a licensed product. Collaboration – In 2018, the Company entered into a research and collaboration agreement with Fred Hutch (“Fred Hutch Collaboration Agreement”), focused on research and development of cancer immunotherapy products. The Company funded aggregate research performed by Fred Hutch of $12.0 million under the Fred Hutch Collaboration Agreement and the research is conducted in accordance with a research plan and budget approved by the parties. The Fred Hutch Collaboration Agreement has a six-year term. During the year-ended December 31, 2021, one of the research plans on which the success payment service term is based, was extended from January 31, 2022 to December 31, 2022. The Company incurred $4.2 million, $4.1 million and $3.7 million in expense in connection with the Fred Hutch Collaboration Agreement for the years ended December 31, 2021, 2020 and 2019, respectively. Success Payments – In 2018, the Company granted Fred Hutch rights to certain success payments, pursuant to the terms of the Fred Hutch Collaboration Agreement. The potential payments for the Fred Hutch success payments are based on multiples of increased value ranging from 10x to 50x based on a comparison of the estimated per share fair value of the Series A convertible preferred stock, or any security into which such stock has been converted or for which it has been exchanged, relative to its original $1.83 per share issuance price. Upon the closing of the IPO, all shares of Series A convertible preferred stock then outstanding converted into an equivalent number of shares of common stock. The aggregate success payments to Fred Hutch are not to exceed $200.0 million, which would only occur upon a 50 times increase in value. Each threshold is associated with a success payment, ascending from $10.0 million at $18.29 per share to $200.0 million at $91.44 per share, payable if such threshold is reached during the measurement period. Any previous success payments made are credited against the success payment owed as of any valuation date, such that Fred Hutch does not receive multiple success payments in connection with the same threshold. The term of the success payment agreement ends on the earlier to occur of (i) the nine year anniversary of the date of the agreement and (ii) a change in control transaction. The following table summarizes the aggregate potential success payments, which are payable to Fred Hutch in cash or cash equivalents, or at the Company’s discretion, publicly-tradeable shares of the Company’s common stock: Multiple of initial equity value at issuance 10x 20x 30x 40x 50x Per share common stock price required for payment $ 18.29 $ 36.58 $ 54.86 $ 73.15 $ 91.44 Aggregate success payment(s) (in millions) $ 10 $ 40 $ 90 $ 140 $ 200 The success payments will be owed if the per share fair value of the Company’s common stock on the contractually specified valuation measurement dates during the term of the success payment agreement equals or exceeds the above outlined multiples. The valuation measurement dates are triggered by the following events: the one-year anniversary of the Company ’ s IPO and each two-year anniversary of the Company ’ s IPO thereafter, the closing of a change in control transaction and the last day of the term of the success payment agreement, unless the term has ended due to the closing of a change of control transaction. The estimated fair values of the success payments to Fred Hutch as of December 31, 2021 and 2020 were $8.5 million a nd $8.0 million, respectively. The success payment liability is estimated at fair value at inception and at each subsequent reporting period and the expense is accreted over the service period of the Fred Hutch Collabor ation Agreement. The success payment liability was $6.4 million and $5.2 million as of December 31, 2021 and 2020, respectively. With respect to Fred Hutch success payment obligations, the Company recognized expense of $1.2 million, $4.8 million, and $0.4 million for the years ended December 31, 2021, 2020, and 2019 respectively. Stanford License Agreement – In 2019, the Company entered into a license agreement with Stanford to license specified patent rights. The Company is also required to pay Stanford annual license maintenance payments of $50,000 on the second anniversary of the effective date, and each anniversary of the effective date thereafter until the date of the first commercial sale of a licensed product. Milestone payments to Stanford of up to a maximum of $3.7 million per target are payable upon achievement of certain specified clinical and regulatory milestones. The Company is also obligated to pay Stanford $2.5 million collectively for all licensed products upon the achievement of a certain commercial milestone. Additionally, low single-digit tiered royalties based on annual net sales of the licensed products are payable to Stanford. Collaboration Agreement – In October 2020, the Company entered into a research and collaboration agreement with Stanford (“Stanford Collaboration Agreement”), focused on research and development of cellular immunotherapy products. The Stanford Collaboration Agreement has a four-year term. The Company is committed to fund aggregate research performed by Stanford of $12.0 million under the Stanford Collaboration Agreement, and the research will be conducted in accordance with a research plan and budget approved by the parties. The Company incurred $3.0 million and $0.8 million in expense in connection with the Stanford Collaboration Agreement for the years ended December 31, 2021 and 2020, respectively. Success Payments – In October 2020, the Company granted Stanford rights to certain success payments, pursuant to the terms of the Stanford Collaboration Agreement. The potential payments for the Stanford success payments are based on multiples of increased value ranging from 10x to 50x based on a comparison of the estimated per share fair value of the Series A convertible preferred stock, or any security into which such stock has been converted or for which it has been exchanged, relative to its original $1.83 per share issuance price. At the closing of the IPO, all shares of Series A convertible preferred stock then outstanding converted into an equivalent number of shares of common stock. The aggregate success payments to Stanford are not to exceed $200.0 million, which would only occur upon a 50 times increase in value. Each threshold is associated with a success payment, ascending from $10.0 million at $18.29 per share to $200.0 million at $91.44 per share, payable if such threshold is reached during the measurement period. Any previous success payments made are credited against the success payment owed as of any valuation date, so that Stanford does not receive multiple success payments in connection with the same threshold. The term of each success payment agreement ends on the earlier to occur of (i) the nine year anniversary of the date of the agreement and (ii) a change in control transaction. The following table summarizes the aggregate potential success payments, which are payable to Stanford in cash or cash equivalents, or at the Company’s discretion, publicly-tradeable shares of the Company’s common stock: Multiple of initial equity value at issuance 10x 20x 30x 40x 50x Per share common stock price required for payment $ 18.29 $ 36.58 $ 54.86 $ 73.15 $ 91.44 Aggregate success payment(s) (in millions) $ 10 $ 40 $ 90 $ 140 $ 200 The success payments will be owed if the per share fair value of the Company’s common stock on the contractually specified valuation measurement dates during the term of the success payment agreement equals or exceeds the above outlined multiples. The valuation measurement dates are triggered by the following events: the one-year anniversary of the Company ’ s IPO and each two-year anniversary of the Company ’ s IPO thereafter, the closing of a change in control transaction and the last day of the term of the success payment agreement, unless the term has ended due to the closing of a change of control transaction. The estimated fair value of the success payments to Stanford as of December 31, 2021 and 2020 was $9.9 million and $8.9 million, respectively. The success payment liability is estimated at fair value at inception and at each subsequent reporting period and the expense is accreted over the service period of the Stanford Collaboration Agreement. The success payment liability was $3.1 million and $0.6 million as of December 31, 2021 and 2020, respectively. With respect to Stanford success payment obligations, the Company recognized expe nse of $2.5 million and $0.6 million for the years ended December 31, 2021 and 2020, respectively. GSK In 2019, the Company entered into a Collaboration and License Agreement, amended in June 2020 and December 2021 (“GSK Agreement”) with GlaxoSmithKline Intellectual Property (No. 5) Limited and Glaxo Group Limited (together, “GSK”) for potential T-cell therapies that apply the Company’s platform technologies and cell therapy innovations with T-cell receptors (“TCRs”) or chimeric antigen receptors (“CARs”) under distinct collaboration programs. The GSK Agreement has defined two initial collaboration targets and allows GSK to nominate seven additional targets through July 2024. The Company is expected to perform research and development services for each selected target up until a defined point (the “GSK Option Point”), at which time GSK will decide whether or not to exercise an option to obtain a license from the Company (“License Option”) and take over the future development and commercialization. For each selected target, both parties will determine whether it will be developed under a Proof of Concept (“PoC”) Development Program or Component Development Program. For a PoC Development Program, the Company is expected to conduct both preclinical and clinical development for the target and present clinical trial data to GSK in connection with their evaluation of whether to exercise the License Option. For a Component Development Program, the Company is obligated to perform preclinical studies only. Along with the research activities, the Company appoints three representatives to the joint steering committee (“JSC”) and is responsible for the manufacture of all compounds and products necessary for its research and development activities. The Company received a non-refundable upfront payment of $45.0 million under the GSK Agreement. In addition to the upfront payment, the Company is eligible to receive up to two one-time payments, totaling up to approximately $200.0 million in aggregate for technology validation of the Company’s cell therapy innovations. For each cell therapy target for which there has been a joint collaboration program, the Company also could receive up to approximately $400.0 million in aggregate in development and sales milestones if the target is already within GSK’s pipeline and meets certain criteria, up to approximately $900.0 million in aggregate in development and sales milestones for all other targets, and tiered royalties on a per-product basis ranging from low to high single digits for targets that are already within GSK’s pipeline and meet certain criteria, or from high single digit to low teens for all other targets. Milestones are paid once per target, even if there is more than one of the Company’s innovations applied to a T-cell therapy directed to that target. Any amounts received from GSK are generally non-refundable unless the Company terminates a collaboration target for safety or feasibility reasons and the funding received from GSK exceeds the costs incurred for the terminated target. In connection with the GSK Agreement, in May 2019, the Company also entered into a Stock Purchase Agreement with GSK (the “GSK Stock Purchase Agreement”), pursuant to which the Company agreed to sell 30,253,189 shares of Series AA convertible preferred stock at a price of $6.78 per share, which was above the issuance date estimated fair value of $4.84 per share. The difference between the per share values resulted in $58.6 million additional deemed consideration, bringing the total upfront payment of the GSK Agreement to $103.6 million. Research and Development Services The GSK Agreement was deemed to be within the scope of ASC 606 because GSK engaged the Company to initially provide research and development services, which are outputs of its ongoing activities, in exchange for consideration. The Company identified the following two distinct performance obligations: (i) research and development services related to the two initial collaboration targets, inclusive of the JSC participation and the manufacture of compounds necessary for providing the research and development services and (ii) a material right for GSK to nominate seven additional collaboration targets for which the Company will perform research and development services until the GSK Option Point. To allocate revenue among the performance obligations, the Company determined standalone selling prices (“SSP”) of each obligation. For the research and development services, the SSP was calculated using a cost-plus margin approach. For the material right, SSP was calculated by reference to the underlying research and development services expected to be provided and the corresponding expected consideration. All amounts included in the transaction price are allocated to performance obligations proportionate to their SSPs. As of December 31, 2020, the transaction price was deemed to be $103.6 million, consisting of the upfront payment of $45.0 million under the GSK Agreement and the $58.6 million allocated from the GSK Stock Purchase Agreement. Other than the upfront payment and the amounts allocated from the GSK Stock Purchase Agreement, all other contingent consideration that may be earned under the GSK Agreement is subject to uncertainties including but not limited to target addition, research and investigational new drug enabling studies, initiation of clinical trials, and other related achievements. Consequently, the transaction price currently does not include any such contingent consideration that, if included, could result in a probable significant reversal of cumulative revenue when related uncertainties become resolved. The Company will re-evaluate the transaction price at each reporting period. If and when contingent consideration is included in the transaction price, it will be allocated to the two performance obligations proportionate to their SSPs and a cumulative catch up in revenue will be recorded for the portion of the services already completed. The remaining amounts will be deferred and recognized as the services are rendered. The research and development services are transferred as the services are performed, with cost used as the measure of progress compared to total estimated cost to complete. Incurred cost represents work performed, which corresponds with, and thereby best depicts, the transfer of control to the customer. The determination of the percentage of completion requires the Company to estimate the costs to complete the project. The Company makes a detailed estimate of the costs to complete, which is reassessed every reporting period based on the latest project plan and discussions with project teams. If a change in facts or circumstances occurs, the estimate will be adjusted, and the revenue will be recognized based on the revised estimate. The difference between the cumulative revenue recognized based on the previous estimate and the revenue recognized based on the revised estimate would be recognized as an adjustment to revenue in the period in which the change in estimate occurs. The Company recognized revenue related to the research and development services related to the two initial targets of $10.5 million, $7.8 million and $0.7 million for the years ended December 31, 2021, 2020 and 2019 respectively. Changes in deferred revenue during the year ended December 31, 2021 were as follows: Deferred revenue balance at December 31, 2020 $ 95,161 Revenue recognized during the period previously recorded in deferred revenue (10,508) Deferred revenue balance at December 31, 2021 $ 84,653 Exercise of the License Option In April 2021, GSK exercised the License Option on NY-ESO-1 TCR with Gen-R, a Component Development Program, and will assume sole responsibility for future development and commercialization of the program at its own cost and expense. The Company is entitled to the remaining development and sales milestones up to an aggregate of approximately $400.0 million as well as the tiered royalties on future sales of all such products covered by the license granted pursuant to the License Option. The exercise of the License Option was accounted for as a separate license contract for revenue recognition purposes. The Company identified one performance obligation, which was the license delivered to GSK upon the exercise of the License Option and transfer of information and data associated with the license. The Company concluded that the development milestone payments are solely dependent on GSK’s performance and achievement of the specified events and are deemed to be not probable until such development milestones are actually achieved. Therefore, the remaining development milestones are fully constrained and excluded from the transaction price until the respective milestone is achieved. The Company also concluded that sales milestones and royalties relate predominantly to the license granted to GSK. Therefore, they also have been excluded from the transaction price and will be recognized when the related sales occur. At the end of each reporting period, the Company will update its assessment of whether an estimate of variable consideration is constrained and update the estimated transaction price accordingly. As of December 31, 2021, there were no contract assets or contract liabilities related to the license contract. None of the costs to obtain or fulfill the contract were capitalized. No license revenue was recognized for the year ended December 31, 2021. PACT In June 2020, the Company entered into an agreement (“PACT Agreement”) with PACT Pharma, Inc. (“PACT”) to jointly develop and test a next generation personalized anti-cancer T-cell therapy against solid tumors. The Company paid PACT an upfront non-refundable payment of $50.0 million upon execution of the PACT Agreement. In November 2020, the parties agreed to suspend research and development activity under the PACT Agreement, and neither party would be required to conduct any further work under the development plan (including manufacturing development) nor incur any financial obligations (including milestone payments) that might otherwise arise, for as long as the parties continued to negotiate in good faith to resolve the issues that have arisen between them relating to the PACT Agreement. In June 2020 in connection with the entry into the PACT Agreement, the Company also entered into a stock purchase agreement with PACT (“PACT SPA”), pursuant to which the Company purchased 17,806,901 shares of PACT Series C-1 convertible preferred stock at a purchase price of $2.81 per share. As of the purchase date, the estimated fair value of the Series C-1 convertible preferred stock was $2.05 per share, and the difference between the estimated fair value of the preferred stock as of the purchase date and the purchase price of $13.6 million was deemed to be additional consideration for the PACT Agreement and recognized as research and development expense. As a result, the total upfront payment paid in connection with the PACT Agreement was $63.6 million and was included in research and development expense. The remaining $36.4 million associated with the PACT Series C-1 convertible preferred stock was recorded in other investments. In the fourth quarter of 2021, the Company fully impaired the remaining balance of $36.4 million. See Note 5, Other Investments , for additional details regarding the PACT investment impairment. In February 2021, the Company filed a demand for arbitration seeking, among other things, rescission of the PACT Agreement and the PACT SPA and recovery of the consideration paid thereunder. An arbitration hearing occurred in March 2022. The Company expects to receive the outcome of the arbitration panel in June 2022. NCI In December 2020, the Company entered into a license agreement with the National Cancer Institute (“NCI”) to access certain intellectual property for the development of treatment of human cancers. In connection with this agreement, the Company paid $100,000 upfront, which was recorded as research and development expense for the year ended December 31, 2020. The Company is also required to pay NCI annual maintenance payments which may be credited against earned royaltie s. The Company incurred $75,000 and $3,100 in maintenance fees for the years ended December 31, 2021 and 2020, respectively. Under the agreement, the Company may also be required to make certain prespecified development milestone payments up to an aggregate of $3.1 million, and prespecified commercial milestone payments up to a maximum aggregate of $12.0 million for all licensed products. In June 2021, the Company entered into an amendment to the license agreement with NCI to include additional intellectual property and one additional inventor. In connection with this amendment, the Company paid $25,000 upfront, which was recorded in research and development expense. Under the amendment, the Company may also be required to pay prespecified additional development milestone payments that total $75,000.

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	12 Months Ended
	Dec. 31, 2021
Cash and Cash Equivalents [Abstract]
Cash Equivalents and Marketable Securities	Cash Equivalents and Marketable Securities The fair value and amortized cost of cash equivalents and marketable securities by major security type as of December 31, 2021 and 2020 are presented in the following tables (in thousands): December 31, 2021 Amortized Gross Gross Fair Value Money market funds $ 206,245 $ — $ — $ 206,245 U.S. Treasury securities 290,909 2 (1,205) 289,706 U.S. government agency securities 93,864 2 (240) 93,626 Corporate debt securities 285,338 — (182) 285,156 Total cash equivalents and marketable securities $ 876,356 $ 4 $ (1,627) $ 874,733 Classified as: Fair Value Cash equivalents $ 270,236 Marketable securities 320,966 Marketable securities, non-current 283,531 Total cash equivalents and marketable securities $ 874,733 December 31, 2020 Amortized Gross Gross Fair Value Money market funds $ 50,513 $ — $ — $ 50,513 U.S. Treasury securities 202,674 27 — 202,701 U.S. government agency securities 205,558 207 (1) 205,764 Corporate debt securities 211,086 34 (11) 211,109 Total cash equivalents and marketable securities $ 669,831 $ 268 $ (12) $ 670,087 Classified as: Fair Value Cash equivalents $ 117,879 Marketable securities 472,213 Marketable securities, non-current 79,995 Total cash equivalents and marketable securities $ 670,087 As of December 31, 2021 and 2020, the fair value of securities held by the Company in an unrealized loss position was $602.9 million and $132.6 million, respectively, and as of December 31, 2021 and 2020, securities held by the Company in an unrealized loss position have been in the continuous loss position for less than 12 months. The Company determined that there was no material change in the credit risk of the above investments during the years ended December 31, 2021 and 2020. As such, an allowance for credit losses has not been recognized. The Company does not intend to sell these securities nor does the Company believe that it will be required to sell these securities before recovery of their amortized cost basis. Gross realized gains and losses were de minimis for the years ended December 31, 2021 and 2020 and as a result, amounts reclassified out of accumulated other comprehensive (loss) income for the years ended December 31, 2021 and 2020 were also de minimis . As of December 31, 2021 and 2020, all of the Company’s marketable securities had a maturity date of two years or less, were available for use, and were classified as available-for-sale. See Note 6, Fair Value Measurements , for additional information regarding cash equivalents and marketable securities.

Other Investments

Other Investments	12 Months Ended
	Dec. 31, 2021
Investments, All Other Investments [Abstract]
Other Investments	Other Investments From time to time, the Company makes minority ownership strategic investments. As of December 31, 2021 and 2020, the aggregate carrying amounts of the Company’s strategic investments in non-publicly traded companies were $47.0 million and $83.4 million , respectively. These investments are measured at initial cost, minus impairment, if any, and plus or minus changes, resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. In connection with the preparation of the financial statements for 2021, the Company performed a qualitative assessment of potential indicators of impairment and determined that indicators exist for its $36.4 million investment in PACT Series C-1 convertible preferred stock . While there was no single event or factor, the Company considered PACT’s operating cash flow requirements over the next year and liquid asset balances to fund those requirements and PACT’s inability to raise funds as indicators of impairment. Due to these indicators, the Company assessed the valuation of the investment in PACT as of December 31, 2021 and determined the fair value to be negligible and the impairment to be other-than-temporary in nature. As a result, the Company recorded a $36.4 million impairment expense for the PACT investment in the fourth quarter of 2021. The impairment charge was recorded within impairment of other investments on the Consolidated Statement of Operations and Comprehensive Loss and as a reduction to the investment balance within other investments on the Consolidated Balance Sheet. Aside from the investment in PACT, no other investments were impaired for the year ended December 31, 2021. In November 2020, the Company made a strategic equity investment of $13.0 million in Outpace Bio, Inc. (“Outpace”), a privately-held company, which represented a minority ownership interest at the time of the strategic investment. Outpace is engaged in the research and development of protein and cell technology platforms and has financed its activities via issuances of preferred stock. The Company determined that Outpace is a VIE and the at-risk equity holders, as a group, lack the characteristics of a controlling financial interest. The Company does not have majority voting rights, representation on Outpace’s board of directors or the power to direct the activities of this entity, and therefore it is not the primary benefic iary. As of both December 31, 2021 and 2020, the carrying value of the Company’s investment in Outpace was $13.0 million, which is recorded in other investments.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The following table sets forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands): December 31, 2021 Level 1 Level 2 Level 3 Total Financial assets: Money market funds $ 206,245 $ — $ — $ 206,245 U.S. Treasury securities — 289,706 — 289,706 U.S. government agency securities — 93,626 — 93,626 Corporate debt securities — 285,156 — 285,156 Equity warrant investment — — 1,067 1,067 Total financial assets $ 206,245 $ 668,488 $ 1,067 $ 875,800 Financial liabilities: Success payment liabilities $ — $ — $ 9,486 $ 9,486 Total financial liabilities $ — $ — $ 9,486 $ 9,486 December 31, 2020 Level 1 Level 2 Level 3 Total Financial assets: Money market funds $ 50,513 $ — $ — $ 50,513 U.S. Treasury securities — 202,701 — 202,701 U.S. government agency securities — 205,764 — 205,764 Corporate debt securities — 211,109 — 211,109 Equity warrant investment — — 1,323 1,323 Total financial assets $ 50,513 $ 619,574 $ 1,323 $ 671,410 Financial liabilities: Success payment liabilities $ — $ — $ 5,773 $ 5,773 Total financial liabilities $ — $ — $ 5,773 $ 5,773 The Company measures the fair value of money market funds based on quoted prices in active markets for identical assets or liabilities. The Level 2 marketable securities include U.S. Treasury securities, government agency securities and corporate debt securities. The Company’s Level 2 securities are valued using third-party pricing sources. The pricing services utilize industry standard valuation models. Inputs utilized include market pricing based on real-time trade data for the same or similar securities and other significant inputs derived from or corroborated by observable market data. The Level 3 financial instruments include an equity warrant investment and the success payment liabilities. The Company’s Level 3 financial instruments are valued using valuation models which include the Black-Scholes model for valuing the equity warrant investment and a Monte Carlo simulation for the success payment liabilities. To determine the estimated fair value of the success payment liabilities, the Company uses a Monte Carlo simulation methodology that models the future movement of stock prices based on several key variables combined with empirical knowledge of the process governing the behavior of the stock price. The following variables were incorporated in the estimated fair value of the success payment liabilities: fair value of the Company ’ s common stock (Series A convertible preferred stock, prior to IPO), expected volatility, risk-free interest rate and the estimated number and timing of valuation measurement dates on the basis of which payments may be triggered. The computation of expected volatility was estimated based on available information about the historical volatility of stocks of similar publicly traded companies for a period matching the expected term assumption. The following assumptions were incorporated into the calculation of the estimated fair value of the Fred Hutch success payment liability: December 31, 2021 2020 Fair value of common stock (Series A convertible preferred stock) $ 7.74 $ 9.07 Risk-free interest rate 0.19% - 1.88% 0.10% - 1.52% Expected volatility 75 % 80 % Expected term (in years) 0.46 - 5.97 1.00 - 6.97 The following assumptions were incorporated into the calculation of the estimated fair value of the Stanford success payment liability: December 31, 2021 2020 Fair value of common stock (Series A convertible preferred stock) $ 7.74 $ 9.07 Risk-free interest rate 0.19% - 1.88% 0.10% - 1.53% Expected volatility 75 % 80 % Expected term (in years) 0.46 - 7.75 1.00 - 8.75 The Company utilizes estimates and assumptions in determining the estimated success payment liabilities and associated expense. A small change in the valuation of the Company’s common stock may have a relatively large change in the estimated fair value of the success payment liability and associated expense. The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial assets and liabilities (in thousands): Equity Warrant Success Payment Balance at December 31, 2019 $ — $ 436 Additions 1,380 — Change in fair value (1) (57) 5,337 Balance at December 31, 2020 1,323 5,773 Change in fair value (1) (256) 3,713 Balance at December 31, 2021 $ 1,067 $ 9,486 __________ (1) The change in fair value associated with the equity warrant investment held is recorded in other (expense) income, net and the change in fair value associated with success payments liabilities is recorded in research and development expense.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net, consisted of the following (in thousands): December 31, 2021 2020 Leasehold improvements $ 95,001 $ 8,452 Laboratory equipment 27,039 17,083 Computer equipment and software 1,610 724 Furniture and fixtures 384 178 Construction in progress 10,577 55,712 Property and equipment, at cost 134,611 82,149 Less: Accumulated depreciation and amortization (14,513) (5,104) Total property and equipment, net $ 120,098 $ 77,045

Accrued Liabilities and Other C

Accrued Liabilities and Other Current Liabilities	12 Months Ended
	Dec. 31, 2021
Accrued Liabilities and Other Liabilities [Abstract]
Accrued Liabilities and Other Current Liabilities	Accrued Liabilities and Other Current Liabilities Accrued liabilities and other current liabilities consisted of the following (in thousands): December 31, 2021 2020 Accrued compensation and related benefits $ 17,296 $ 14,850 Accrued property and equipment 4,055 5,910 Accrued legal 2,619 412 Accrued research and development expenses 2,449 2,575 Current lease liabilities 1,169 3,617 Other 1,469 657 Total accrued liabilities and other current liabilities $ 29,057 $ 28,021

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Leases	Leases The Company’s lease portfolio is comprised of operating leases for laboratory, office and manufacturing facilities located in South San Francisco, California, and Seattle and Bothell, Washington with contractual periods expiring between December 2028 and March 2031. In addition to minimum rent, the leases require payment of real estate taxes, insurance, common area maintenance charges and other executory costs. These additional charges are considered variable costs and are recognized in the period in which the costs are incurred. In 2018, the Company entered into an operating lease for approximately 34,000 square feet of office and laboratory space in Seattle, Washington, with an initial lease term expiring in December 2028. The Company has two five-year options to extend the lease, which are not reasonably assured. In 2019, the Company entered into an operating lease for approximately 34,000 square feet of office and laboratory space in South San Francisco, California. In December 2020, the Company exercised its early termination right and remeasured the remaining consideration in the contract, resulting in a gain of $2.9 million, which was recognized in other operating income, net. The lease termination was effective October 2021, resulting in a gain of $0.3 million, which was recognized in other operating income, net. Additionally, the Company recognized a loss of $0.6 million at lease termination on leasehold improvements unable to be moved to its new corporate headquarters in South San Francisco, California, which was recognized in other operating income, net. In 2019, the Company entered into two operating lease agreements for a combined approximately 73,000 square feet of space to develop a cell therapy manufacturing facility located in Bothell, Washington, with initial terms expiring in May 2030. The Company has two 90-month options to extend the leases, which are not reasonably assured. In 2019, the Company entered into an operating lease agreement for approximately 108,000 square feet of office and laboratory space located in South San Francisco, California. The initial lease term expires in January 2031 with the option to extend the term for another 10 years, which is not reasonably assured. In January 2021, the Company amended the lease term to extend the lease expiration to March 2031, which resulted in an increase to the right of use asset and lease liability of $4.2 million. The following table summarizes the Company’s future minimum operating lease commitments, including expected lease incentives to be received, as of December 31, 2021 (in thousands): Year Ending December 31: 2022 $ 9,807 2023 11,018 2024 11,347 2025 11,859 2026 12,209 Thereafter 48,094 Total undiscounted lease payments 104,334 Less: imputed interest (31,754) Less: tenant improvement allowances (4,761) Total operating lease liabilities $ 67,819 Reported as of December 31, 2021: Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities) $ 1,169 Operating lease liabilities, non-current 66,650 Total $ 67,819 The operating lease costs for all operating leases were $9.4 million, $11.2 million and $4.6 million for the years ended December 31, 2021, 2020 and 2019, respectively. The operating lease costs and total commitments for short-term leases were de minimis f or the years ended December 31, 2021, 2020 and 2019. Variable lease costs for operating leases were $4.1 million, $2.1 million and $1.0 million for the years ended December 31, 2021, 2020 and 2019, respectively. The weighted-average remaining lease terms for operating leases were 8.8 and 9.0 years as of December 31, 2021 and 2020, respectively. The weighted-average discount rates for operating leases were 8.4% and 9.6% as of December 31, 2021 and 2020, respectively. In May 2021, the Company entered into a sublease, whereby the Company agreed to sublease approximately 11,000 square feet of its space in South San Francisco, California currently leased by the Company. The sublease is classified as an operating lease and will expire in March 2031. The monthly fixed payment due to the Company is $0.1 million, subject to annual rent increases in accordance with the contract. In September 2021, the Company entered into a sublease with Sonoma Biotherapeutics, Inc. ( “ Sonoma”), a related party, whereby the Company agreed to sublease approximately 18,000 square feet of space in South San Francisco, California currently leased by the Company. See Note 17, Related-Party Transactions . As a part of the sublease, in September 2021, the Company received a $4.6 million tenant improvement contribution payment, which will be recognized over the term of the sublease. The sublease is classified as an operating lease and will expire in March 2031. The monthly fixed payment due to the Company is $0.1 million , subject to annual rent increases in accordance with the contract.

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Convertible Preferred Stock	Convertible Preferred Stock In March 2020, the Company sold 42,905,042 shares of its Series C convertible preferred stock at a price of $11.49 per share for proceeds of $492.5 million, net of issuance costs of $0.5 million. In March 2020, the Company repurchased 546,806 shares of its Series A convertible preferred stock from a related party for a purchase price of $4.2 million. Upon the closing of the IPO, 194,474,431 shares of convertible preferred stock then outstanding converted into an equal number of shares of common stock. As of December 31, 2021, no shares of convertible preferred stock were outstanding.

Stockholders_ Equity (Deficit)

Stockholders’ Equity (Deficit)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Stockholders’ Equity (Deficit)	Stockholders’ Equity (Deficit) The Company amended and restated its certificate of incorporation effective June 2021, increasing the number of shares the Company has the authority to issue to 510.0 million shares, of which 500.0 million are common shares and 10.0 million shares are preferred stock. Preferred Stock The Company is authorized to issue 10.0 million shares of preferred stock, par value $0.0001 per share. As of December 31, 2021, no shares of preferred stock were outstanding. Common Stock As of December 31, 2021 and 2020, there wer e 242,738,350 shares and 15,569,788 shares of the Company’s common stock outstanding, respectively, excluding 2,600,002 s hares and 7,562,503 shares, respectively, of RSAs outstanding that are subject to vesting requirements. In March 2020, the Company repurchased 2,032,166 shares of its common stock from a related party for a purchase price of $11.8 million .

Stock-based Compensation

Stock-based Compensation	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Stock-based Compensation	Stock-based Compensation 2021 Equity Incentive Plan In June 2021, the Company adopted the 2021 Equity Incentive Plan (“2021 Plan”), which on the date of the underwriting agreement related to the Company’s IPO became effective with an initial reserve of 26,662,087 shares, plus any shares subject to outstanding awards granted under the 2018 Equity Incentive Plan (“2018 Plan”) that, on or after the effectiveness of the 2021 Plan, terminate or expire before exercise or settlement, are not issued because the award is settled in cash, are forfeited because of the failure to vest or are reacquired or withheld (or not issued) to satisfy a tax withholding obligation or the purchase or exercise price. In addition, the number of shares reserved for issuance under the 2021 Plan will automatically increase on January 1 of each year for a period of ten years, beginning on January 1, 2022 and continuing through January 1, 2031, in an amount equal to (1) 5% of the total number of shares of the Company’s common stock outstanding on December 31 of the immediately preceding year, or (2) a lesser number of shares determined by the Company's board of directors no later than December 31 of the immediately preceding year. Under the 2021 Plan, the Company may grant incentive stock options, non-statutory stock options, RSAs, restricted stock units, stock appreciation rights, performance awards and other stock-based awards. Terms of stock awards, including vesting requirements, are determined by the Company’s board of directors or by a committee authorized by the Company’s board of directors, subject to provisions of the 2021 Plan. The term of any stock option granted under the 2021 Plan cannot exceed ten years. Generally, awards granted by the Company vest over four years, but may be granted with different vesting terms. In conjunction with adopting the 2021 Plan, the Company discontinued the 2018 Plan with respect to new equity awards. As of December 31, 2021 , 24.7 million shares were available for future issuance pursuant to the 2021 Plan. 2021 Employee Stock Purchase Plan In June 2021, the Company adopted the 2021 Employee Stock Purchase Plan (“2021 ESPP”), which became effective immediately prior to the execution of the underwriting agreement related to the Company’s IPO with an initial reserve of 2,470,000 shares. The 2021 ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their earnings, subject to plan limitations. Unless otherwise determined by the Company’s board of directors, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first date of an offering or on the purchase date. The number of shares of the Company’s common stock reserved for issuance under the 2021 ESPP will automatically increase on January 1 of each year for a period of ten years, beginning on January 1, 2022 and continuing through January 1, 2031, by the lesser of (1) 1% of the total number of shares of the Company’s common stock outstanding on December 31 of the immediately preceding year, and (2) 4,940,000 shares; provided, however, that the Company’s board of directors may act to provide a lesser increase in number of shares. The Company may specify offerings with durations not more than 27 months and may specify shorter purchase periods within each offering. No shares have been issued under the 2021 ESPP as of December 31, 2021. 2018 Equity Incentive Plan In 2018, the Company established the 2018 Plan under which it may grant incentive stock options, non-statutory stock options, RSAs, restricted stock units, stock appreciation rights, and other stock-based awards. Terms of stock awards, including vesting requirements, are determined by the board of directors or by a committee authorized by the Company’s board of directors, subject to provisions of the 2018 Plan. The term of any stock option granted under the 2018 Plan cannot exceed ten years. Generally, awards granted by the Company vest over four years, but may be granted with different vesting terms. Pursuant to the terms of the 2021 Plan, any shares subject to outstanding options originally granted under the 2018 Plan that terminate, expire or lapse for any reason without the delivery of shares to the holder thereof shall become available for issuance pursuant to awards granted under the 2021 Plan. While no shares are available for future issuance under the 2018 Plan, it continues to govern outstanding equity awards granted thereunder. Stock-based Compensation Expense Stock-based compensation expense by classification included within the consolidated statements of operations and comprehensive loss was as follows (in thousands): Year Ended December 31, 2021 2020 2019 Research and development $ 15,328 $ 14,977 $ 4,926 General and administrative 46,873 18,284 10,806 Total stock-based compensation expense $ 62,201 $ 33,261 $ 15,732 Stock-based compensation expense for the year ended December 31, 2021 includes the impact of awards accelerated in connection with the Company’s IPO of $2.6 million. Stock Options and RSA Modifications Stock-based compensation expense includes costs related to stock option and RSA modifications in the years ended December 31, 2021 and 2020. The modifications were due to the reduction in the service level for certain employees, including the former chief executive officer (“CEO”), changes in vesting schedules and an increase to certain awards’ post-termination exercise periods. The modifications impacted both vested and unvested awards. Expense associated with vested awards was recognized in the period of the modification and expense associated with unvested awards is recognized over the remaining service life of the options or RSAs. The following is a summary of the incremental stock-based compensation expense recognized during the years ended December 31, 2021 and 2020, as well as expense to be recognized in future periods as a result of the modifications (in thousands): Year Ended December 31, Future Total 2021 2020 Expense 2021 Equity Modifications: Former CEO - Options $ 21,948 $ 4,105 $ — $ 17,843 Other - Options 1,019 1,019 — — Former CEO - RSA 10,908 3,237 — 7,671 2020 Equity Modifications: Former CEO - Options 15,052 6,044 2,755 6,253 Other - Options 4,717 1,153 2,954 610 Former CEO - RSA 20,799 10,168 4,701 5,930 Other - RSA 9,029 1,975 7,054 — Total $ 83,472 $ 27,701 $ 17,464 $ 38,307 Repricing Stock-based compensation expense includes the impact of the Company repricing certain stock options in December 2019 by canceling all existing outstanding option grants with a per share exercise price at, and higher than, $4.78 in exchange for new option grants at an exercise price of $3.65 per share. Except for the change in exercise price, the new options had the same terms and conditions as the original options, including the contractual term, vesting schedule and vesting start date. The total amount of incremental stock-based compensation expense associated with the repricing was $3.3 million, of which $0.3 million, $0.7 million and $0.6 million were recognized for the years ended December 31, 2021, 2020 and 2019, respectively. Amounts relating to options that were already vested were recorded on the date of the modification and amounts relating to options that were unvested are expensed over the remaining vesting term of the new options. Stock-based compensation expense also includes the impact of the accelerated vesting of certain RSAs in 2019, resulting in an incremental expense of $8.6 million, which was recorded for the year ended December 31, 2019. At December 31, 2021, total stock-based compensation cost related to unvested awards not yet recognized was $136.8 million, which is expected to be recognized over a remaining weighted-average period of 2.33 years. Restricted Stock Awards A summary of the Company’s RSAs activity were as follows: Number of Shares Weighted-Average Unvested shares as of December 31, 2020 7,562,503 $ 0.0001 Vested (4,943,751) $ 0.0001 Forfeited (18,750) $ 0.0001 Unvested shares as of December 31, 2021 2,600,002 $ 0.0001 The fair value of RSAs vested during the years ended December 31, 2021, 2020 and 2019 was $57.1 million, $29.4 million and $33.5 million, respectively. Stock Options A summary of the Company’s stock option activity were as follows: Number of Weighted- Average Exercise Price Per Share Weighted- Aggregate Options outstanding as of December 31, 2020 34,413,889 $ 3.33 8.67 $ 100,223 Granted 12,947,501 $ 9.09 Exercised (2,750,380) $ 3.43 Canceled or forfeited (2,835,831) $ 4.19 Options outstanding as of December 31, 2021 41,775,179 $ 5.05 7.84 $ 142,076 Options exercisable as of December 31, 2021 23,716,000 $ 3.39 7.08 $ 110,520 The fair value of stock options granted to employees, directors and consultants was estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions: Year Ended December 31, 2021 2020 2019 Risk-free interest rate 0.80 % 0.79 % 1.91 % Expected volatility 79 % 75 % 75 % Expected term (in years) 6.10 6.11 6.08 Expected dividend yield 0 % 0 % 0 % The weighted-average grant date fair value of options granted for the years ended December 31, 2021, 2020 and 2019 was $6.59 per share, $3.36 per share and $2.24 per share, respectively. The intrinsic value of options exercised during the years ended December 31, 2021 and 2020 was $16.1 million a nd $0.3 million, respectively. No options were exercised for the year ended December 31, 2019 .

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company has reported pre-tax operating losses for all periods presented. The Company’s net losses are derived solely from within the U.S. The Company has not reflected any benefit for corresponding tax net operating loss carryforwards in the accompanying consolidated financial statements. The Company has established a full valuation allowance against its deferred tax assets due to the uncertainty surrounding the realization of such assets. As of December 31, 2021 and 2020, the Company had U.S. federal net operating loss (“NOL”) carryforwards of approximately $271.0 million and $116.1 million, respectively, which were available to reduce future taxable income and do not expire. The Company also had U.S. state NOL carryforwards of $199.4 million that begin to expire in 2038. The Company had gross U.S. federal and state tax credits of $9.8 million and $5.7 million as of December 31, 2021 and 2020, respectively, which may be used to offset future tax liabilities. The federal NOL carryforward period is indefinite, while the tax credits will begin to expire in 2039. The attributed carryforwards may become subject to annual limitations in the event of certain cumulative changes in the ownership interest of significant stockholders. This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. A reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations follows: Year Ended December 31, 2021 2020 2019 Federal statutory tax 21.00 % 21.00 % 21.00 % State tax, net of federal benefit 6.39 4.71 0.52 Valuation allowance (22.43) (24.60) (15.27) Convertible preferred stock tranche liabilities — — (5.75) Stock-based compensation (5.92) (1.77) (1.69) Tax credits 0.99 0.95 1.24 Other (0.03) (0.29) (0.05) Effective income tax rate 0.00 % 0.00 % 0.00 % The principal components of the Company’s net deferred tax assets were as follows (in thousands): Year Ended December 31, 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 70,855 $ 28,692 Tax credit carryforwards 8,338 4,980 Accrued liabilities & allowances 3,879 3,518 Deferred revenue 8,224 8,997 Amortization 15,961 14,375 Investment basis difference 13,587 3,334 Lease liability 18,429 13,421 Stock-based compensation 2,872 5,175 Other 2,613 1,454 Gross deferred tax assets 144,758 83,946 Valuation allowance (127,226) (71,093) Deferred tax assets, net of valuation allowance 17,532 12,853 Deferred tax liabilities: Operating lease right-of-use assets (12,647) (11,221) Property and equipment (4,885) (1,632) Deferred tax liabilities (17,532) (12,853) Net deferred tax assets $ — $ — The Company maintains a full valuation allowance on its net U.S. deferred tax assets. The assessment regarding whether a valuation allowance is required considers the evaluation of both positive and negative evidence when concluding whether it is more likely than not that deferred tax assets are realizable. In making this assessment, significant weight is given to evidence that can be objectively verified. In its evaluation, the Company considered its cumulative loss in recent years and its forecasted losses in the near-term as significant negative evidence. Based upon a review of the four sources of income identified within ASC 740, Accounting for Income Taxes (“ASC 740”), the Company determined that the negative evidence outweighed the positive evidence and a full valuation allowance on its U.S. net deferred tax assets will be maintained. The valuation allowance relates primarily to net U.S. deferred tax assets from net operating loss carryforwards, research and development tax credit carryforwards, research and development expenses capitalized and amortized for tax but deducted for GAAP and stock-based compensation. The Company will continue to assess the realizability of its deferred tax assets and adjust the valuation allowance as required by ASC 740. The increase in the valuation allowance was $56.1 million and $50.4 million for the years ended December 31, 2021 and 2020, respectively. The Company evaluates its uncertain tax positions based on a determination of whether it is more likely than not such position will be sustained based upon its technical merits and upon examination by the relevant income tax authorities with all facts known. The Company applies judgment in its measurement of an uncertain tax position recorded in its consolidated financial statements and tax return. As of December 31, 2021 and 2020, there are no penalties or accrued interest recorded in the consolidated financial statements. The Company is generally subject to examination by the U.S. federal and local income tax authorities for all tax years in which a loss carryforward is available. The Company is currently not under examination by the Internal Revenue Service or other jurisdictions for any tax years. The following tab le summarized changes to the Company’s unrecognized tax benefits (in thousands): Year Ended December 31, 2021 2020 Beginning balance $ — $ — Additions based on tax position related to the current year 396 — Additions based on prior year tax positions 400 — Ending balance $ 796 $ —

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share Basic and diluted net loss per share attributed to common stockholders is calculated by dividing net loss attributed to common stockholders by the weighted average number of common shares outstanding during the period, without consideration for common stock equivalents. The Company’s potentially dilutive shares, which include preferred stock, unvested RSAs and options to purchase common stock, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The amounts in the table below were excluded from the calculation of diluted net loss per share attributed to common stockholders for the periods indicated due to their anti-dilutive effect: Year Ended December 31, 2021 2020 2019 Convertible preferred stock — 194,474,431 152,116,195 Unvested RSAs 2,600,002 7,562,503 13,663,338 Options to purchase common stock 41,775,179 34,413,889 27,028,217 Total 44,375,181 236,450,823 192,807,750

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Employee Benefit Plan	Employee Benefit PlanIn January 2019, the Company adopted a 401(k) retirement and savings plan (the “401(k) Plan”) covering all of its employees. The 401(k) Plan allows employees to make pre- and post-tax contributions up to the maximum allowable amount set by the IRS. As of December 31, 2021, the Company had not made any matching contributions to the 401(k) Plan on behalf of participants.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Collaboration and License Agreements The Company has entered into certain collaboration and license agreements, including those identified in Note 3, Collaboration, License and Success Payment Agreements above, with third parties that include the funding of certain development, manufacturing and commercialization efforts with the potential for future milestone and royalty payments upon the achievement of pre-established developmental, regulatory and/or commercial milestones. The Company’s obligation to fund these efforts is contingent upon continued involvement in the programs and/or the lack of any adverse events that could cause the discontinuance of the programs. Due to the nature of these agreements, the future potential payments are inherently uncertain, and accordingly no amounts had been recorded for the potential future achievement of these targets as of December 31, 2021 and 2020.

Related-Party Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2021
Related Party Transactions [Abstract]
Related-Party Transactions	Related-Party Transactions In September 2021, the Company entered into a sublease with Sonoma, with whom the Company has common stockholders with board seats. As a part of the sublease, a $4.6 million tenant improvement contribution payment was made by Sonoma, which will be recognized over the term of the sublease. As of December 31, 2021, accrued liabilities and other current liabilities of $0.5 million a nd other non-current lia bilities of $4.0 million we re in connection with the sublease with Sonoma. Incom e of $1.8 million w as recognized in other operating income, net for the year ended December 31, 2021. See Note 9, Leases , for more detail on the Sonoma sublease. The Company is party to the GSK Agreement, who is a holder of more than 10% of the Company’s equity. See Note 3, Collaboration, License and Success Payment Agreements . Deferred revenue of $5.0 million and $6.1 million as of December 31, 2021 and 2020, respectively, and deferred revenue, net of current portion of $79.7 million and $89.1 million as of December 31, 2021 and 2020, respectively, were in connection with the GSK Agreement. Revenue recognized in connection with the GSK agreement was $10.5 million, $7.8 million and $0.7 million for the years ended December 31, 2021, 2020 and 2019, respectively. In March 2020, the Company repurchased 546,806 shares of its Series A convertible preferred stock and 2,032,166 shares of its common stock from a related party. See Note 10, Convertible Preferred Stock and Note 11, Stockholders’ Equity (Deficit) .

Asset Acquisition

Asset Acquisition	12 Months Ended
	Dec. 31, 2021
Business Combination and Asset Acquisition [Abstract]
Asset Acquisition	Asset Acquisition In May 2020, the Company completed the acquisition of 100% of the outstanding equity of Immulus, Inc. (“Immulus”), a company focused on developing technology platforms that enable the development and production of cell therapeutics. As consideration for the acquisition, the Company paid $3.5 million in cash and issued an aggregate of 688,463 shares of its common stock, with an estimated fair value of $4.0 million. The Company also incurred $0.5 million of direct expenses, for total consideration of $8.0 million. The Company concluded the acquisition did not meet the accounting definition of a business as inputs were acquired, but no processes or outputs were acquired. Consequently, the Company accounted for the transaction as an asset acquisition with the value concentrated in IPR&D. The following table summarizes the fair value of assets acquired (in thousands): Other assets $ 487 In-process research and development (IPR&D) 7,528 Total assets acquired $ 8,015 The amount allocated to the IPR&D asset was charged to research and development expenses for the year ended December 31, 2020 as this asset had no alternative future use at the time of the acquisition transaction. In addition, the Company is also required to make milestone payments of up to $37.0 million to the former stockholders of Immulus upon successful completion of specified development milestones. Triggering of these milestones payments was not considered probable as of the date of the acquisition, and no expense has been recorded for these milestones for the years ended December 31, 2021 and 2020.

Basis of Presentation and Sig_2

Basis of Presentation and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of PresentationThe accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The consolidated financial statements include the accounts of Lyell Immunopharma, Inc. and its wholly-owned subsidiary.
Consolidations	All significant intercompany transactions and balances are eliminated in consolidation. Certain prior period amounts in the consolidated financial statements and accompanying notes have been reclassified to conform to the current period’s presentation.
Use of Estimates	Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with GAAP requires management to make judgments, estimates and assumptions that affect reported amounts and related disclosures. Specific accounts that require management estimates include, but are not limited to, stock-based compensation, valuation of success payments, revenue recognition and accrued expenses. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results could differ materially from those estimates.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss and certain changes in stockholders’ equity (deficit) that are excluded from net loss. For the years ended December 31, 2021, 2020, and 2019 this was comprised of net unrealized gains and losses on the Company’s marketable securities.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted CashThe Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market accounts.Restricted cash is cash held in bank accounts and is used as collateral for letters of credits issued in conjunction with the Company’s lease agreements and collateral associated with the Company’s corporate credit card program.
Marketable Securities	Marketable Securities The Company generally invests its excess cash in investment grade short- to intermediate-term fixed income securities. Such investments are classified as available-for-sale and are carried at fair value, with the unrealized gains and losses reported as a component of comprehensive loss. Realized gains and losses on available-for-sale securities are included in other (expense) income, net. The cost of investments sold is based on the specific-identification method. The Company classifies those investments that are not required for use in current operations and that mature in more than 12 months as non-current marketable securities in the accompanying consolidated balance sheets. Each reporting period, the Company evaluates whether declines in fair value below carrying value are due to expected credit losses, as well as the Company’s ability and intent to hold the investment until a forecasted recovery occurs. Expected credit losses are recorded as an allowance through other (expense) income, net.
Other Investments	Other Investments The Company determines at the inception of each arrangement whether an investment or other interest is considered a variable interest entity (“VIE”). If the investment or other interest is determined to be a VIE, the Company evaluates whether it is considered the primary beneficiary. The primary beneficiary of a VIE is the party that meets both of the following criteria: (i) has the power to direct the activities that most significantly impact the VIE’s economic performance; and (ii) has the obligation to absorb losses or the right to receive benefits from the VIE. For investments in VIEs in which the Company is considered the primary beneficiary, the assets, liabilities and results of operations of the VIE are included in its consolidated financial statements. As of December 31, 2021 and 2020, there were no VIEs for which the Company was the primary beneficiary. The Company accounts for its strategic equity interests in non-publicly traded companies for which it does not have the ability to exercise significant influence in accordance with Accounting Standards Codification (“ASC”) 321, Investments – Equity Securities (“ASC 321”). Upon acquisition, these investments are measured at cost, which represents the then fair value. Under ASC 321, the Company can elect to subsequently measure the investments at initial cost, minus impairment and any changes, plus or minus, resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer. This election must be made for each investment separately. The Company has made this election for all investments in this category and will continue to measure these investments using this method until they no longer qualify to be measured in accordance with this method. Changes in the carrying value of other investments are recognized through net loss. Each reporting period, the Company performs a qualitative assessment to evaluate whether the investment is impaired. The Company’s assessment includes a review of recent operating results and trends, recent sales/acquisitions of the investee securities and other factors that raise concerns about the investee’s ability to continue as a going concern. If the investment is impaired, an impairment charge is recognized in the amount by which the carrying amount of the investment exceeds the estimated fair value of the investment, with the impairment charge recognized through net loss. See Note 5, Other Investments , for details related to an investment impairment recognized during the year ended December 31, 2021. Additionally, the Company holds an investment in equity warrants giving it the right to acquire stock of a non‑publicly traded company. Equity warrant investments are recorded within other assets at the estimated fair value, with gains and losses recognized in other (expense) income, net.
Property and Equipment, Net	Property and Equipment, Net Property and equipment primarily consist of laboratory equipment, computer equipment and software, furniture and fixtures and leasehold improvements. Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method based on the estimated useful lives of the related assets, which are generally three
Valuation of Long-lived Assets	Valuation of Long-lived AssetsLong-lived assets are reviewed each reporting period for impairment or whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable, which may warrant adjustments to carrying values or estimated useful lives. Recoverability is measured by comparison of the carrying amount of an asset group to the future net undiscounted cash flows that the assets are expected to generate. If the carrying amount of an asset group exceeds its estimated future cash flows, an impairment charge is recognized in the amount by which the carrying amount of the asset group exceeds the fair value of the asset group. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the projected discounted future net cash flows arising from the asset.
Acquisitions	Acquisitions The Company evaluates acquisitions of assets and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen to determine if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If the screen is met, the transaction is accounted for as an asset acquisition. If the screen is not met, further determination is required as to whether or not the Company has acquired inputs and processes that have the ability to create outputs which would meet the requirements of a business in which case the transaction is accounted for using the acquisition method of accounting, which requires, among other things, that assets acquired and liabilities assumed be recognized at their estimated fair values as of the acquisition date, and that the fair value of acquired intangibles be recorded on the balance sheet. Transaction costs are expensed as incurred. Any excess of the purchase price over the assigned fair values of the net assets acquired is recorded as goodwill. If the Company determines an acquisition does not meet the definition of a business combination under the acquisition method of accounting, the transaction is accounted for as an asset acquisition. In an asset acquisition, upfront payments allocated to in-process research and development (“IPR&D”) are recorded in research and development expense if it is determined that there is no alternative future use, and subsequent milestone payments are recorded in research and development expense when achieved for technology that has not yet met product feasibility.
Leases	Leases The Company leases certain office, laboratory and manufacturing spaces. In addition to minimum rent, the leases require payment of real estate taxes, insurance, common area maintenance charges and other executory costs. At inception of a contract, the Company determines whether an arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. For all leases, the Company determines the classification of the lease as either operating or financing. As of December 31, 2021 and 2020, all of the Company’s leases were classified as operating leases. The Company recognizes right-of-use (“ROU”) assets and lease liabilities at the lease commencement date based on the present value of future lease payments over the lease term. As the Company’s leases do not provide an implicit rate, an incremental borrowing rate at each lease commencement date is used to determine the present value of future lease payments. The incremental borrowing rate is the rate of interest that the Company would pay to borrow equivalent funds on a collateralized basis at the lease commencement date. To estimate the incremental borrowing rate, a credit rating applicable to the Company is estimated using a synthetic credit rating analysis since the Company does not currently have a rating agency-based credit rating. The ROU asset includes any lease payments made prior to the lease commencement date and is reduced by any lease incentives received or deemed payable to the Company. The lease term may include options to extend or terminate the lease when it is reasonably certain that a lease option will be exercised. Lease expense is recognized on a straight-line basis over the lease term within operating expenses on the consolidated statements of operations and comprehensive loss. The Company has elected the practical expedient to not separate lease and non-lease components for real estate leases. Additionally, the Company has elected the short-term lease recognition exemption for all short-term leases and as a result, lease liabilities and ROU assets are not included on the consolidated balance sheets for leases with an initial term of 12 months or less.
Fair Value Measurements	Fair Value Measurements The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs: Level 1 – Quoted prices in active markets for identical assets or liabilities. Level 2 – Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. Level 3 – Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. The Company’s financial instruments, in addition to those presented in Note 6, Fair Value Measurements , include cash, restricted cash, other investments, accounts payable and accrued liabilities and other current liabilities. The carrying amount of cash, restricted cash, accounts payable and accrued liabilities and other current liabilities approximate fair value because of the short-term nature of these instruments. As described in Note 5, Other Investments , other investments are carried at cost, minus impairment and any changes, plus or minus, resulting from observable price changes in orderly transactions for the identical or a similar investment of the same issuer.
Revenue Recognition	Revenue Recognition The Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements within the scope of ASC 606, Revenue from Contracts with Customers , ( “ ASC 606 ” ) the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the performance obligation is satisfied. In applying the ASC 606 framework, the Company must apply judgment to determine the nature of the promises within a revenue contract and whether those promises represent distinct performance obligations. In determining the transaction price, the Company does not include amounts subject to uncertainties unless it is probable that there will be no significant reversal of cumulative revenue when the uncertainty is resolved. Milestone and other forms of variable consideration that the Company may earn are subject to significant uncertainties of research and development related achievements, which generally are deemed not probable until such milestones are actually achieved. For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Additionally, the Company develops assumptions that require judgment to determine the standalone selling price of each performance obligation identified in the contract. The Company then allocates the total transaction price to each performance obligation based on the estimated standalone selling prices of each performance obligation, for which it recognizes revenue as or when the performance obligations are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the variable consideration and any related constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis. Under the Company’s license agreements, the Company grants the license to a customer as it exists at the point of transfer and the nature of the license is a right to use the Company’s intellectual property as transferred. If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, upfront fees 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 bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time.
Research and Development Expense	Research and Development Expense The Company records expense for research and development costs as incurred. Research and development expenses consist of costs incurred by the Company for the discovery and development of its technology platforms and product candidates and includes costs incurred in connection with strategic collaborations, costs to license technology, personnel-related costs, including stock-based compensation expense, facility and technology related costs, research and laboratory expenses, as well as other expenses, which include consulting fees and other costs. Upfront payments and milestones paid to third parties in connection with technology platforms, which have not reached technological feasibility and do not have an alternative future use are expensed as incurred.
General and Administrative Expense	General and Administrative Expense General and administrative costs are expensed as incurred and include personnel-related expenses, including stock-based compensation expense for personnel in executive, legal, finance and other administrative functions, legal costs, transaction costs related to collaboration and licensing agreements, as well as fees paid for accounting and tax services, consulting fees and facilities costs not otherwise included in research and development expenses. Legal costs include those related to corporate and patent matters.
Success Payments	Success Payments The Company granted rights to success payments to Fred Hutchinson Cancer Research Center (“Fred Hutch”) and The Board of Trustees of the Leland Stanford Junior University (“Stanford”) pursuant to the terms of its research and collaboration agreements with each of those entities. Pursuant to the terms of these agreements, on each contractually prescribed measurement date, the Company may be required to make success payments based on increases in the estimated per share fair value of the Company’s common stock. See Note 3, Collaboration, License and Success Payment Agreements . The success payments are accounted for under ASC 718, Compensation – Stock Compensation , with the expense being recorded in research and development expenses. Once the service period is complete, the instrument will be accounted for under ASC 815, Derivatives and Hedging , and continue to be remeasured each reporting period with all changes in value recognized immediately in other (expense) income, net. The success payment liability is estimated at fair value at inception and at each reporting period, and the expense is accreted over the service period of the research and collaboration agreement. To determine the estimated fair value of the success payments, the Company uses a Monte Carlo simulation methodology which models the future movement of stock prices based on several key variables combined with empirical knowledge of the process governing the behavior of the stock price. The following variables were incorporated in the estimated fair value of the success payment liability: estimated fair value of the Company’s common stock, expected volatility, risk-free interest rate and the estimated number and timing of valuation measurement dates on the basis of which payments may be triggered. The computation of expected volatility was estimated based on available information about the historical volatility of stocks of similar publicly traded companies for a period matching the expected term assumption.
Concentrations of Credit Risk	Concentrations of Credit Risk and Off-balance Sheet Risk The Company maintains its cash, cash equivalents and restricted cash with high quality, accredited financial institutions. These amounts, at times, may exceed federally insured limits. The Company also makes short-term investments in money market funds, U.S. Treasury securities, U.S. government agency securities and corporate debt
Off-balance Sheet Risk	The Company has no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements.
Claims and Contingencies	Claims and Contingencies From time to time, the Company may become involved in litigation and proceedings relating to claims arising from the ordinary course of business. The Company accrues a liability if the likelihood of an adverse outcome is probable and the amount is estimable. If the likelihood of an adverse outcome is only reasonably possible (as opposed to probable), or if an estimate is not determinable, the Company provides disclosure of a material claim or contingency.
Stock-based Compensation	Stock-based Compensation Under ASC 718, the Company measures and recognizes expense for restricted stock awards (“RSAs”) and stock options granted to employees, directors and consultants based on the fair value of the awards on the date of grant. The fair value of stock options is estimated using the Black-Scholes option pricing model, which requires the use of subjective assumptions and for management to apply judgment and make estimates including: stock price volatility, the expected life of stock options, the risk-free interest rate, expected dividend, and the fair value of the underlying common stock on the date of grant. The expected volatility is based on the historical volatility of the stock of similar entities within the Company’s industry over periods commensurate with the Company’s expected term assumption. The expected term of stock option grants represents the weighted-average period the options are expected to remain outstanding and is based on the “simplified” method where the expected term is the midpoint between the vesting date and the end of the contractual term for each option. The Company bases the risk-free interest rate on the interest rate payable on U.S. Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected option term. In reference to the expected dividend yield assumption, the Company has not historically paid, and does not expect for the foreseeable future to pay, a dividend. The Company utilizes significant estimates and assumptions in determining the fair value of its common stock for financial reporting purposes. Prior to the closing of the IPO, the Company recorded expense for RSAs and stock options at prices not less than the fair market value of its common stock as determined by the board of directors, taking into consideration input from management and an independent third-party valuation analysis, and in accordance with the American Institute of Certified Public Accountants (“AICPA”) Accounting and Valuation Guide, Valuation of Privately-Held Company Equity Securities Issued as Compensation . Following the closing of the IPO, the fair value of the Company’s common stock is based on its closing price as reported on the NASDAQ Global Select Market on the date of grant. Stock-based compensation expense for RSAs and stock options is recognized on a straight-line basis over the requisite service period, which is generally the vesting period of the respective award. The Company accounts for forfeitures as they occur. The Company also granted stock options that vest in conjunction with certain performance conditions to certain key employees. At each reporting date, the Company is required to evaluate whether achievement of the performance conditions is probable. Compensation expense is recorded over the appropriate service period based upon the Company’s assessment of accomplishing each performance provision.
Income Taxes	Income Taxes The Company determines its deferred tax assets and liabilities based on the differences between the financial reporting and tax basis of assets and liabilities. The deferred tax assets and liabilities are measured using the enacted tax rates that will be in effect when the differences are expected to reverse. A valuation allowance is recorded when it is more likely than not that the deferred tax asset will not be recovered. The Company applies judgment in the determination of the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The Company recognizes any material interest and penalties related to unrecognized tax benefits in income tax expense.
Segments	Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment and one reportable segment.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Income Taxes In December 2019, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2019-12, Income Taxes – Simplifying the Accounting for Income Taxes (“ASU 2019-12”). The guidance removes exceptions to the general principles in Income Taxes (Topic 740) for allocating tax expense between financial statement components, accounting basis differences stemming from an ownership change in foreign investments and interim period income tax accounting for year-to-date losses that exceed projected losses. The guidance became effective for annual reporting periods beginning after December 15, 2020 and interim periods within those fiscal years with early adoption permitted. Effective January 1, 2019, the Company early adopted ASU 2019-12. The adoption of this standard did not have a material impact on the Company ’ s consolidated financial statements. Credit Losses In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) (“ASU 2016-13”). ASU 2016-13 implements an impairment model, known as the current expected credit loss model, that is based on expected losses rather than incurred losses. Under the new guidance, an entity will recognize as an allowance its estimate of expected credit losses. On January 1, 2020, the Company early adopted this standard by using a modified retrospective approach. The adoption did not have a material impact on the Company’s consolidated financial statements. Collaborative Arrangements In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 (“ASU 2018-18”), which clarifies that certain transactions between participants in a collaborative arrangement should be accounted for under ASC 606 when the counterparty is a customer. In addition, ASU 2018-18 precludes an entity from presenting consideration from a transaction in a collaborative arrangement as revenue from contracts with customers if the counterparty is not a customer for that transaction. On January 1, 2020, the Company early adopted this standard on a retrospective basis to the date of initial application of ASC 606. The adoption did not have a material impact on the Company’s consolidated financial statements. Cloud Computing Arrangements In August 2018, the FASB issued ASU No. 2018-15, Intangibles – Goodwill and Other – Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract

Collaboration, License and Su_2

Collaboration, License and Success Payment Agreements (Tables)	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Aggregate Potential Success Payments	The following table summarizes the aggregate potential success payments, which are payable to Fred Hutch in cash or cash equivalents, or at the Company’s discretion, publicly-tradeable shares of the Company’s common stock: Multiple of initial equity value at issuance 10x 20x 30x 40x 50x Per share common stock price required for payment $ 18.29 $ 36.58 $ 54.86 $ 73.15 $ 91.44 Aggregate success payment(s) (in millions) $ 10 $ 40 $ 90 $ 140 $ 200 The following table summarizes the aggregate potential success payments, which are payable to Stanford in cash or cash equivalents, or at the Company’s discretion, publicly-tradeable shares of the Company’s common stock: Multiple of initial equity value at issuance 10x 20x 30x 40x 50x Per share common stock price required for payment $ 18.29 $ 36.58 $ 54.86 $ 73.15 $ 91.44 Aggregate success payment(s) (in millions) $ 10 $ 40 $ 90 $ 140 $ 200
Schedule of Changes in Deferred Revenue	Changes in deferred revenue during the year ended December 31, 2021 were as follows: Deferred revenue balance at December 31, 2020 $ 95,161 Revenue recognized during the period previously recorded in deferred revenue (10,508) Deferred revenue balance at December 31, 2021 $ 84,653

Cash Equivalents and Marketab_2

Cash Equivalents and Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2021
Cash and Cash Equivalents [Abstract]
Schedule of Fair Value and Amortized Cost of Cash Equivalents	The fair value and amortized cost of cash equivalents and marketable securities by major security type as of December 31, 2021 and 2020 are presented in the following tables (in thousands): December 31, 2021 Amortized Gross Gross Fair Value Money market funds $ 206,245 $ — $ — $ 206,245 U.S. Treasury securities 290,909 2 (1,205) 289,706 U.S. government agency securities 93,864 2 (240) 93,626 Corporate debt securities 285,338 — (182) 285,156 Total cash equivalents and marketable securities $ 876,356 $ 4 $ (1,627) $ 874,733 Classified as: Fair Value Cash equivalents $ 270,236 Marketable securities 320,966 Marketable securities, non-current 283,531 Total cash equivalents and marketable securities $ 874,733 December 31, 2020 Amortized Gross Gross Fair Value Money market funds $ 50,513 $ — $ — $ 50,513 U.S. Treasury securities 202,674 27 — 202,701 U.S. government agency securities 205,558 207 (1) 205,764 Corporate debt securities 211,086 34 (11) 211,109 Total cash equivalents and marketable securities $ 669,831 $ 268 $ (12) $ 670,087 Classified as: Fair Value Cash equivalents $ 117,879 Marketable securities 472,213 Marketable securities, non-current 79,995 Total cash equivalents and marketable securities $ 670,087
Schedule of Fair Value and Amortized Cost of Marketable Securities	The fair value and amortized cost of cash equivalents and marketable securities by major security type as of December 31, 2021 and 2020 are presented in the following tables (in thousands): December 31, 2021 Amortized Gross Gross Fair Value Money market funds $ 206,245 $ — $ — $ 206,245 U.S. Treasury securities 290,909 2 (1,205) 289,706 U.S. government agency securities 93,864 2 (240) 93,626 Corporate debt securities 285,338 — (182) 285,156 Total cash equivalents and marketable securities $ 876,356 $ 4 $ (1,627) $ 874,733 Classified as: Fair Value Cash equivalents $ 270,236 Marketable securities 320,966 Marketable securities, non-current 283,531 Total cash equivalents and marketable securities $ 874,733 December 31, 2020 Amortized Gross Gross Fair Value Money market funds $ 50,513 $ — $ — $ 50,513 U.S. Treasury securities 202,674 27 — 202,701 U.S. government agency securities 205,558 207 (1) 205,764 Corporate debt securities 211,086 34 (11) 211,109 Total cash equivalents and marketable securities $ 669,831 $ 268 $ (12) $ 670,087 Classified as: Fair Value Cash equivalents $ 117,879 Marketable securities 472,213 Marketable securities, non-current 79,995 Total cash equivalents and marketable securities $ 670,087

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table sets forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands): December 31, 2021 Level 1 Level 2 Level 3 Total Financial assets: Money market funds $ 206,245 $ — $ — $ 206,245 U.S. Treasury securities — 289,706 — 289,706 U.S. government agency securities — 93,626 — 93,626 Corporate debt securities — 285,156 — 285,156 Equity warrant investment — — 1,067 1,067 Total financial assets $ 206,245 $ 668,488 $ 1,067 $ 875,800 Financial liabilities: Success payment liabilities $ — $ — $ 9,486 $ 9,486 Total financial liabilities $ — $ — $ 9,486 $ 9,486 December 31, 2020 Level 1 Level 2 Level 3 Total Financial assets: Money market funds $ 50,513 $ — $ — $ 50,513 U.S. Treasury securities — 202,701 — 202,701 U.S. government agency securities — 205,764 — 205,764 Corporate debt securities — 211,109 — 211,109 Equity warrant investment — — 1,323 1,323 Total financial assets $ 50,513 $ 619,574 $ 1,323 $ 671,410 Financial liabilities: Success payment liabilities $ — $ — $ 5,773 $ 5,773 Total financial liabilities $ — $ — $ 5,773 $ 5,773
Summary of Estimated Fair Value of Success Payment Liability Assumptions	The following assumptions were incorporated into the calculation of the estimated fair value of the Fred Hutch success payment liability: December 31, 2021 2020 Fair value of common stock (Series A convertible preferred stock) $ 7.74 $ 9.07 Risk-free interest rate 0.19% - 1.88% 0.10% - 1.52% Expected volatility 75 % 80 % Expected term (in years) 0.46 - 5.97 1.00 - 6.97 The following assumptions were incorporated into the calculation of the estimated fair value of the Stanford success payment liability: December 31, 2021 2020 Fair value of common stock (Series A convertible preferred stock) $ 7.74 $ 9.07 Risk-free interest rate 0.19% - 1.88% 0.10% - 1.53% Expected volatility 75 % 80 % Expected term (in years) 0.46 - 7.75 1.00 - 8.75
Changes in the Estimated Fair Value of Level 3 Financial Assets	The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial assets and liabilities (in thousands): Equity Warrant Success Payment Balance at December 31, 2019 $ — $ 436 Additions 1,380 — Change in fair value (1) (57) 5,337 Balance at December 31, 2020 1,323 5,773 Change in fair value (1) (256) 3,713 Balance at December 31, 2021 $ 1,067 $ 9,486 __________ (1) The change in fair value associated with the equity warrant investment held is recorded in other (expense) income, net and the change in fair value associated with success payments liabilities is recorded in research and development expense.
Changes in the Estimated Fair Value of Level 3 Financial Liabilities	The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial assets and liabilities (in thousands): Equity Warrant Success Payment Balance at December 31, 2019 $ — $ 436 Additions 1,380 — Change in fair value (1) (57) 5,337 Balance at December 31, 2020 1,323 5,773 Change in fair value (1) (256) 3,713 Balance at December 31, 2021 $ 1,067 $ 9,486 __________ (1) The change in fair value associated with the equity warrant investment held is recorded in other (expense) income, net and the change in fair value associated with success payments liabilities is recorded in research and development expense.

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net, consisted of the following (in thousands): December 31, 2021 2020 Leasehold improvements $ 95,001 $ 8,452 Laboratory equipment 27,039 17,083 Computer equipment and software 1,610 724 Furniture and fixtures 384 178 Construction in progress 10,577 55,712 Property and equipment, at cost 134,611 82,149 Less: Accumulated depreciation and amortization (14,513) (5,104) Total property and equipment, net $ 120,098 $ 77,045

Accrued Liabilities and Other_2

Accrued Liabilities and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2021
Accrued Liabilities and Other Liabilities [Abstract]
Schedule of Accrued Liabilities and Other Current Liabilities	Accrued liabilities and other current liabilities consisted of the following (in thousands): December 31, 2021 2020 Accrued compensation and related benefits $ 17,296 $ 14,850 Accrued property and equipment 4,055 5,910 Accrued legal 2,619 412 Accrued research and development expenses 2,449 2,575 Current lease liabilities 1,169 3,617 Other 1,469 657 Total accrued liabilities and other current liabilities $ 29,057 $ 28,021

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Schedule of Future Minimum Operating Lease Commitments, Including Expected Lease Incentives to be Received	The following table summarizes the Company’s future minimum operating lease commitments, including expected lease incentives to be received, as of December 31, 2021 (in thousands): Year Ending December 31: 2022 $ 9,807 2023 11,018 2024 11,347 2025 11,859 2026 12,209 Thereafter 48,094 Total undiscounted lease payments 104,334 Less: imputed interest (31,754) Less: tenant improvement allowances (4,761) Total operating lease liabilities $ 67,819 Reported as of December 31, 2021: Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities) $ 1,169 Operating lease liabilities, non-current 66,650 Total $ 67,819
Schedule of Lease Assets and Liabilities	The following table summarizes the Company’s future minimum operating lease commitments, including expected lease incentives to be received, as of December 31, 2021 (in thousands): Year Ending December 31: 2022 $ 9,807 2023 11,018 2024 11,347 2025 11,859 2026 12,209 Thereafter 48,094 Total undiscounted lease payments 104,334 Less: imputed interest (31,754) Less: tenant improvement allowances (4,761) Total operating lease liabilities $ 67,819 Reported as of December 31, 2021: Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities) $ 1,169 Operating lease liabilities, non-current 66,650 Total $ 67,819

Stock-based Compensation (Table

Stock-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Schedule of Stock-based Compensation Expense by Classification	Stock-based compensation expense by classification included within the consolidated statements of operations and comprehensive loss was as follows (in thousands): Year Ended December 31, 2021 2020 2019 Research and development $ 15,328 $ 14,977 $ 4,926 General and administrative 46,873 18,284 10,806 Total stock-based compensation expense $ 62,201 $ 33,261 $ 15,732
Summary of Incremental Stock-Based Compensation Expense from Modifications	The following is a summary of the incremental stock-based compensation expense recognized during the years ended December 31, 2021 and 2020, as well as expense to be recognized in future periods as a result of the modifications (in thousands): Year Ended December 31, Future Total 2021 2020 Expense 2021 Equity Modifications: Former CEO - Options $ 21,948 $ 4,105 $ — $ 17,843 Other - Options 1,019 1,019 — — Former CEO - RSA 10,908 3,237 — 7,671 2020 Equity Modifications: Former CEO - Options 15,052 6,044 2,755 6,253 Other - Options 4,717 1,153 2,954 610 Former CEO - RSA 20,799 10,168 4,701 5,930 Other - RSA 9,029 1,975 7,054 — Total $ 83,472 $ 27,701 $ 17,464 $ 38,307
Summary of RSA Activity	A summary of the Company’s RSAs activity were as follows: Number of Shares Weighted-Average Unvested shares as of December 31, 2020 7,562,503 $ 0.0001 Vested (4,943,751) $ 0.0001 Forfeited (18,750) $ 0.0001 Unvested shares as of December 31, 2021 2,600,002 $ 0.0001
Summary of Stock Option Activity	A summary of the Company’s stock option activity were as follows: Number of Weighted- Average Exercise Price Per Share Weighted- Aggregate Options outstanding as of December 31, 2020 34,413,889 $ 3.33 8.67 $ 100,223 Granted 12,947,501 $ 9.09 Exercised (2,750,380) $ 3.43 Canceled or forfeited (2,835,831) $ 4.19 Options outstanding as of December 31, 2021 41,775,179 $ 5.05 7.84 $ 142,076 Options exercisable as of December 31, 2021 23,716,000 $ 3.39 7.08 $ 110,520
Schedule of Assumptions Used in Black-Scholes Option-Pricing Model for Estimating Fair Value of Stock Options Granted	The fair value of stock options granted to employees, directors and consultants was estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions: Year Ended December 31, 2021 2020 2019 Risk-free interest rate 0.80 % 0.79 % 1.91 % Expected volatility 79 % 75 % 75 % Expected term (in years) 6.10 6.11 6.08 Expected dividend yield 0 % 0 % 0 %

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of Reconciliation of Federal Statutory Income Tax Rate	A reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations follows: Year Ended December 31, 2021 2020 2019 Federal statutory tax 21.00 % 21.00 % 21.00 % State tax, net of federal benefit 6.39 4.71 0.52 Valuation allowance (22.43) (24.60) (15.27) Convertible preferred stock tranche liabilities — — (5.75) Stock-based compensation (5.92) (1.77) (1.69) Tax credits 0.99 0.95 1.24 Other (0.03) (0.29) (0.05) Effective income tax rate 0.00 % 0.00 % 0.00 %
Schedule of Deferred Tax Assets	The principal components of the Company’s net deferred tax assets were as follows (in thousands): Year Ended December 31, 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 70,855 $ 28,692 Tax credit carryforwards 8,338 4,980 Accrued liabilities & allowances 3,879 3,518 Deferred revenue 8,224 8,997 Amortization 15,961 14,375 Investment basis difference 13,587 3,334 Lease liability 18,429 13,421 Stock-based compensation 2,872 5,175 Other 2,613 1,454 Gross deferred tax assets 144,758 83,946 Valuation allowance (127,226) (71,093) Deferred tax assets, net of valuation allowance 17,532 12,853 Deferred tax liabilities: Operating lease right-of-use assets (12,647) (11,221) Property and equipment (4,885) (1,632) Deferred tax liabilities (17,532) (12,853) Net deferred tax assets $ — $ —
Summary of Changes to Company’s Unrecognized Tax Benefits	The following tab le summarized changes to the Company’s unrecognized tax benefits (in thousands): Year Ended December 31, 2021 2020 Beginning balance $ — $ — Additions based on tax position related to the current year 396 — Additions based on prior year tax positions 400 — Ending balance $ 796 $ —

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Schedule of Diluted Net Loss Per Share	The amounts in the table below were excluded from the calculation of diluted net loss per share attributed to common stockholders for the periods indicated due to their anti-dilutive effect: Year Ended December 31, 2021 2020 2019 Convertible preferred stock — 194,474,431 152,116,195 Unvested RSAs 2,600,002 7,562,503 13,663,338 Options to purchase common stock 41,775,179 34,413,889 27,028,217 Total 44,375,181 236,450,823 192,807,750

Asset Acquisition (Tables)

Asset Acquisition (Tables)	12 Months Ended
	Dec. 31, 2021
Business Combination and Asset Acquisition [Abstract]
Summary of Fair Value of Assets Acquired	The following table summarizes the fair value of assets acquired (in thousands): Other assets $ 487 In-process research and development (IPR&D) 7,528 Total assets acquired $ 8,015

Organization (Details)

Organization (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2021
Description of Organization [Line Items]
Offering expenses		$ 33,198
Convertible preferred stock
Description of Organization [Line Items]
Conversion of convertible preferred stock to common stock (in shares)	194,474,431
Common Stock
Description of Organization [Line Items]
Issuance of common stock, shares		25,000,000
Conversion of convertible preferred stock to common stock (in shares)		194,474,000
IPO | Common Stock
Description of Organization [Line Items]
Issuance of common stock, shares	25,000,000
Sale of stock, price per share (in dollars per share)	$ 17
Net proceeds from sale of stock, after underwriting discounts and commissions	$ 391,800
Payments of underwriting discounts and commissions	29,800
Offering expenses	3,400
IPO | Common Stock Including Additional Paid in Capital
Description of Organization [Line Items]
Converted preferred stock	$ 1,000,000

Basis of Presentation and Sig_3

Basis of Presentation and Significant Accounting Policies - Narrative (Details)	1 Months Ended	12 Months Ended
	Mar. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2021USD ($)segment	Dec. 31, 2020USD ($)shares	Dec. 31, 2019USD ($)
Class of Stock [Line Items]
Impairment of long-lived assets		$ 0	$ 0	$ 0
Repurchase of convertible preferred stock (in shares) | shares			547,000
Reduction in convertible preferred stock from deemed dividends			$ 662,000
Reduction in additional paid-in-capital from deemed dividends of convertible preferred stock			3,582,000
Number of operating segments | segment		1
Number of reportable segments | segment		1
Minimum
Class of Stock [Line Items]
Estimated life		3 years
Maximum
Class of Stock [Line Items]
Estimated life		5 years
Additional Paid-in Capital
Class of Stock [Line Items]
Reduction in additional paid-in-capital from deemed dividends of convertible preferred stock			3,582,000
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Repurchase of convertible preferred stock (in shares) | shares	546,806
Fair value of convertible preferred stock per share (in dollars per share) | $ / shares	$ 7.76
Deemed dividends on convertible preferred stock			3,600,000
Reduction in convertible preferred stock from deemed dividends	$ 4,200,000		700,000
Increase in net loss attributed to common stockholders from deemed dividends of convertible preferred stock			$ 3,600,000

Collaboration, License and Su_3

Collaboration, License and Success Payment Agreements - Narrative (Details)	1 Months Ended				3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2021USD ($)	Dec. 31, 2020USD ($)	Jun. 30, 2020USD ($)$ / sharesshares	May 31, 2019$ / sharesshares	Dec. 31, 2021USD ($)performance_obligation	Jun. 30, 2020USD ($)$ / shares	Dec. 31, 2021USD ($)performance_obligation	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)collaboration_targetpaymentrepresentative	Apr. 30, 2021USD ($)	Oct. 31, 2020USD ($)$ / shares	Dec. 31, 2018USD ($)$ / shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development expense							$ 138,693,000	$ 182,243,000	$ 63,595,000
Impairment of other investments							36,447,000	0	0
PACT
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Impairment of other investments					$ 36,400,000
Series A Convertible Preferred Stock
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Convertible preferred stock, par value (in dollars per share) | $ / shares											$ 1.83	$ 1.83
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Fred Hutch
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Annual license maintenance payments												$ 50,000
Aggregate research payments due												$ 12,000,000
Term of collaborative arrangement for research												6 years
Research and development expense							4,200,000	4,100,000	3,700,000
Term of success payment agreement												9 years
Trigger period from IPO date												1 year
Trigger period thereafter												2 years
Fair value of potential success payments due		$ 8,000,000			8,500,000		8,500,000	8,000,000
Success payment liability		5,200,000			6,400,000		6,400,000	5,200,000
Success payment expenses							1,200,000	4,800,000	400,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Fred Hutch | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance												10
Potential aggregate success payments												$ 10,000,000
Per share common stock price required for payment (in dollars per share) | $ / shares												$ 18.29
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Fred Hutch | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance												50
Potential aggregate success payments												$ 200,000,000
Per share common stock price required for payment (in dollars per share) | $ / shares												$ 91.44
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Stanford
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Annual license maintenance payments									50,000
Aggregate research payments due											$ 12,000,000
Term of collaborative arrangement for research											4 years
Research and development expense							3,000,000	800,000
Term of success payment agreement											9 years
Trigger period from IPO date											1 year
Trigger period thereafter											2 years
Fair value of potential success payments due		8,900,000			9,900,000		9,900,000	8,900,000
Success payment liability		600,000			3,100,000		3,100,000	600,000
Success payment expenses							2,500,000	600,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Stanford | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Commercial milestone payments due									2,500,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Stanford | Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance											10
Potential aggregate success payments											$ 10,000,000
Per share common stock price required for payment (in dollars per share) | $ / shares											$ 18.29
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Stanford | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance											50
Potential aggregate success payments											$ 200,000,000
Per share common stock price required for payment (in dollars per share) | $ / shares											$ 91.44
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | Stanford | Maximum | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments due									3,700,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | GSK
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities		95,161,000			84,653,000		84,653,000	95,161,000
Revenue							10,500,000	7,800,000	$ 700,000
Revenue recognized during the period previously recorded in deferred revenue							10,508,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | GSK | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of initial collaboration targets | collaboration_target									2
Number of additional collaboration targets | collaboration_target									7
Number of representatives of JSC appointed by company | representative									3
Contract liabilities		45,000,000			$ 0		$ 0	45,000,000	$ 45,000,000
Revenue, Remaining Performance Obligation, Variable Consideration Amount, Number Of One-Time Payments | payment									2
Stock Purchase Agreement portion of transaction price		58,600,000						58,600,000
Transaction price		103,600,000						103,600,000
Number of performance obligations | performance_obligation					2		2
Revenue							$ 0
Contract assets					$ 0		0
Capitalized contract costs					$ 0		0
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | GSK | Series AA Convertible Preferred Stock | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock sold under Stock Purchase Program (in shares) | shares				30,253,189
Price per share of stock sold under Stock Purchase Program (in dollars per share) | $ / shares				$ 6.78
Fair value per share of stock sold under Stock Purchase Program (in dollars per share) | $ / shares				$ 4.84
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | GSK | Maximum | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments, within pipeline									$ 400,000,000
Potential milestone payments, not within pipeline									900,000,000
Potential milestone payments, technology validation									$ 200,000,000
Variable consideration amount										$ 400,000,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | PACT
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment			$ 50,000,000
Stock purchase agreement, stock purchased (in shares) | shares			17,806,901
Stock purchase agreement, purchase price per share (in dollars per share) | $ / shares			$ 2.81
Stock purchase agreement, fair value per share (in dollars per share) | $ / shares						$ 2.05
Additional purchase price consideration			$ 13,600,000			$ 13,600,000
Total upfront payment paid			63,600,000			63,600,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | PACT | Other Investment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Strategic equity investment			$ 36,400,000			$ 36,400,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement | NCI
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development expense		100,000
Upfront payment	$ 25,000
Maintenance fees							$ 75,000	3,100
Maximum aggregate development milestone payments	$ 75,000	3,100,000						3,100,000
Maximum aggregate commercial milestone payments		$ 12,000,000						$ 12,000,000

Collaboration, License and Su_4

Collaboration, License and Success Payment Agreements - Aggregate Potential Success Payments (Details) - Collaborative Arrangement, Transaction with Party to Collaborative Arrangement $ / shares in Units, $ in Millions	Oct. 31, 2020USD ($)$ / shares	Dec. 31, 2018USD ($)$ / shares
Fred Hutch | Ten Times
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance		10
Per share common stock price required for payment (in dollars per share) | $ / shares		$ 18.29
Aggregate success payment(s) (in millions) | $		$ 10
Fred Hutch | Twenty Times
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance		20
Per share common stock price required for payment (in dollars per share) | $ / shares		$ 36.58
Aggregate success payment(s) (in millions) | $		$ 40
Fred Hutch | Thirty Times
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance		30
Per share common stock price required for payment (in dollars per share) | $ / shares		$ 54.86
Aggregate success payment(s) (in millions) | $		$ 90
Fred Hutch | Forty Times
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance		40
Per share common stock price required for payment (in dollars per share) | $ / shares		$ 73.15
Aggregate success payment(s) (in millions) | $		$ 140
Fred Hutch | Fifty Times
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance		50
Per share common stock price required for payment (in dollars per share) | $ / shares		$ 91.44
Aggregate success payment(s) (in millions) | $		$ 200
Stanford | Ten Times
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance		10
Per share common stock price required for payment (in dollars per share) | $ / shares	$ 18.29
Aggregate success payment(s) (in millions) | $	$ 10
Stanford | Twenty Times
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance		20
Per share common stock price required for payment (in dollars per share) | $ / shares	$ 36.58
Aggregate success payment(s) (in millions) | $	$ 40
Stanford | Thirty Times
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance		30
Per share common stock price required for payment (in dollars per share) | $ / shares	$ 54.86
Aggregate success payment(s) (in millions) | $	$ 90
Stanford | Forty Times
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance		40
Per share common stock price required for payment (in dollars per share) | $ / shares	$ 73.15
Aggregate success payment(s) (in millions) | $	$ 140
Stanford | Fifty Times
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance		50
Per share common stock price required for payment (in dollars per share) | $ / shares	$ 91.44
Aggregate success payment(s) (in millions) | $	$ 200

Collaboration, License and Su_5

Collaboration, License and Success Payment Agreements - Changes in Deferred Revenue (Details) - Collaborative Arrangement, Transaction with Party to Collaborative Arrangement - GSK $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Contract With Customer, Liability [Roll Forward]
Deferred revenue balance at December 31, 2020	$ 95,161
Revenue recognized during the period previously recorded in deferred revenue	(10,508)
Deferred revenue balance at December 31, 2021	$ 84,653

Cash Equivalents and Marketab_3

Cash Equivalents and Marketable Securities - Schedule of Fair Value and Amortized Cost of Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Marketable Securities [Line Items]
Amortized Cost	$ 293,828	$ 140,406	$ 96,674
Amortized Cost	876,356	669,831
Gross Unrealized Gains	4	268
Gross Unrealized Losses	(1,627)	(12)
Fair Value	874,733	670,087
Classified as:
Cash equivalents	270,236	117,879
Marketable securities	320,966	472,213
Marketable securities, non-current	283,531	79,995
Total cash equivalents and marketable securities	874,733	670,087
U.S. Treasury securities
Marketable Securities [Line Items]
Amortized Cost	290,909	202,674
Gross Unrealized Gains	2	27
Gross Unrealized Losses	(1,205)	0
Fair Value	289,706	202,701
U.S. government agency securities
Marketable Securities [Line Items]
Amortized Cost	93,864	205,558
Gross Unrealized Gains	2	207
Gross Unrealized Losses	(240)	(1)
Fair Value	93,626	205,764
Corporate debt securities
Marketable Securities [Line Items]
Amortized Cost	285,338	211,086
Gross Unrealized Gains	0	34
Gross Unrealized Losses	(182)	(11)
Fair Value	285,156	211,109
Money market funds
Marketable Securities [Line Items]
Amortized Cost	206,245	50,513
Fair Value	$ 206,245	$ 50,513

Cash Equivalents and Marketab_4

Cash Equivalents and Marketable Securities - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Fair value of securities held in an unrealized loss position	$ 602.9	$ 132.6
Fair value of securities held in a continuous unrealized loss position for less than twelve months	$ 602.9	$ 132.6
Maximum
Marketable Securities [Line Items]
Maturity of marketable securities	2 years	2 years

Other Investments (Details)

Other Investments (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2021	Nov. 30, 2020
Schedule of Investments [Line Items]
Other investments	$ 47,001	$ 47,001	$ 83,448
Impairment of other investments		36,447	0	$ 0
PACT
Schedule of Investments [Line Items]
Other investments					$ 36,400
Impairment of other investments	36,400
Outpace Bio Inc | Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments [Line Items]
Noncontrolling interest in variable interest entity	$ 13,000	$ 13,000	$ 13,000			$ 13,000

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Financial assets:
Equity warrant investment	$ 1,067	$ 1,323
Total financial assets	875,800	671,410
Financial liabilities:
Success payment liabilities	9,486	5,773
Total financial liabilities	9,486	5,773
U.S. Treasury securities
Financial assets:
Marketable securities	289,706	202,701
U.S. government agency securities
Financial assets:
Marketable securities	93,626	205,764
Corporate debt securities
Financial assets:
Marketable securities	285,156	211,109
Money market funds
Financial assets:
Cash and cash equivalents	206,245	50,513
Level 1
Financial assets:
Equity warrant investment	0	0
Total financial assets	206,245	50,513
Financial liabilities:
Success payment liabilities	0	0
Total financial liabilities	0	0
Level 1 | U.S. Treasury securities
Financial assets:
Marketable securities	0	0
Level 1 | U.S. government agency securities
Financial assets:
Marketable securities	0	0
Level 1 | Corporate debt securities
Financial assets:
Marketable securities	0	0
Level 1 | Money market funds
Financial assets:
Cash and cash equivalents	206,245	50,513
Level 2
Financial assets:
Equity warrant investment	0	0
Total financial assets	668,488	619,574
Financial liabilities:
Success payment liabilities	0	0
Total financial liabilities	0	0
Level 2 | U.S. Treasury securities
Financial assets:
Marketable securities	289,706	202,701
Level 2 | U.S. government agency securities
Financial assets:
Marketable securities	93,626	205,764
Level 2 | Corporate debt securities
Financial assets:
Marketable securities	285,156	211,109
Level 2 | Money market funds
Financial assets:
Cash and cash equivalents	0	0
Level 3
Financial assets:
Equity warrant investment	1,067	1,323
Total financial assets	1,067	1,323
Financial liabilities:
Success payment liabilities	9,486	5,773
Total financial liabilities	9,486	5,773
Level 3 | U.S. Treasury securities
Financial assets:
Marketable securities	0	0
Level 3 | U.S. government agency securities
Financial assets:
Marketable securities	0	0
Level 3 | Corporate debt securities
Financial assets:
Marketable securities	0	0
Level 3 | Money market funds
Financial assets:
Cash and cash equivalents	$ 0	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Estimated Fair Value of Success Payment Liability Assumptions (Details)	Dec. 31, 2021$ / shares	Dec. 31, 2020$ / shares
Fred Hutch
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of common stock Series A convertible preferred stock	$ 7.74	$ 9.07
Fred Hutch | Risk-free interest rate | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.0019	0.0010
Fred Hutch | Risk-free interest rate | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.0188	0.0152
Fred Hutch | Expected volatility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.75	0.80
Fred Hutch | Expected term | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.46	1
Fred Hutch | Expected term | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	5.97	6.97
Stanford
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of common stock Series A convertible preferred stock	$ 7.74	$ 9.07
Stanford | Risk-free interest rate | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.0019	0.0010
Stanford | Risk-free interest rate | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.0188	0.0153
Stanford | Expected volatility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.75	0.80
Stanford | Expected term | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.46	1
Stanford | Expected term | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	7.75	8.75

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Changes in Estimated Fair Value of Financial Liabilities (Details) - Level 3 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Equity Warrant Investment
Equity Warrant Investment
Beginning Balance	$ 1,323	$ 0
Additions		1,380
Changes in fair value	(256)	(57)
Ending Balance	1,067	1,323
Success Payment Liabilities
Success Payment Liabilities
Beginning Balance	5,773	436
Additions		0
Change in fair value	3,713	5,337
Ending Balance	$ 9,486	$ 5,773

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 134,611	$ 82,149
Less: Accumulated depreciation and amortization	(14,513)	(5,104)
Total property and equipment, net	120,098	77,045
Depreciation and amortization expense	13,500	4,200	$ 1,300
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	95,001	8,452
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	27,039	17,083
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	1,610	724
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	384	178
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 10,577	$ 55,712

Accrued Liabilities and Other_3

Accrued Liabilities and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accrued Liabilities and Other Liabilities [Abstract]
Accrued compensation and related benefits	$ 17,296	$ 14,850
Accrued property and equipment	4,055	5,910
Accrued legal	2,619	412
Accrued research and development expenses	2,449	2,575
Current lease liabilities	1,169	3,617
Other	1,469	657
Total accrued liabilities and other current liabilities	$ 29,057	$ 28,021
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Total accrued liabilities and other current liabilities	Total accrued liabilities and other current liabilities

Leases - Narrative (Details)

Leases - Narrative (Details) ft² in Thousands, $ in Thousands	Oct. 31, 2021USD ($)	Jan. 31, 2021USD ($)	Sep. 30, 2021USD ($)ft²	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)ft²contractrenewal_option	May 31, 2020ft²	Jan. 01, 2019ft²	Dec. 31, 2018ft²renewal_option
Lessee, Lease, Description [Line Items]
Gain on net operating lease liability disposal				$ 308	$ 0	$ 0
Increase to lease liability				13,202	2,966	2,194
Operating lease cost				9,400	11,200	4,600
Variable lease cost				$ 4,100	$ 2,100	$ 1,000
Weighted average remaining lease term of operating leases				8 years 9 months 18 days	9 years
Operating lease, weighted average discount rate (as a percent)				8.40%	9.60%
Rentable area (in square feet) | ft²							11
Monthly fixed rental payment due				$ 100
Sonoma
Lessee, Lease, Description [Line Items]
Rentable area (in square feet) | ft²			18
Monthly fixed rental payment due			$ 100
Tenant improvements			$ 4,600
Building | Expires in December 2028
Lessee, Lease, Description [Line Items]
Area of space (in square feet) | ft²									34
Number of renewal options | renewal_option									2
Renewal term									5 years
Building | Expires in August 2029
Lessee, Lease, Description [Line Items]
Area of space (in square feet) | ft²								34
Gain on net operating lease liability disposal	$ 300			$ 600	$ 2,900
Building | Expires in May 2030
Lessee, Lease, Description [Line Items]
Area of space (in square feet) | ft²						73
Number of renewal options | renewal_option						2
Renewal term						90 months
Number of operating lease agreements | contract						2
Building | Expires in January 2031
Lessee, Lease, Description [Line Items]
Area of space (in square feet) | ft²						108
Renewal term						10 years
Increase to right of use asset		$ 4,200
Increase to lease liability		$ 4,200

Leases - Summary of Operating L

Leases - Summary of Operating Lease Commitments Including Expected Lease Incentives to be Received (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
2022	$ 9,807
2023	11,018
2024	11,347
2025	11,859
2026	12,209
Thereafter	48,094
Total undiscounted lease payments	104,334
Less: imputed interest	(31,754)
Less: tenant improvement allowances	(4,761)
Total operating lease liabilities	67,819
Operating Lease Liability
Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities)	1,169	$ 3,617
Operating lease liabilities, non-current	66,650	$ 50,957
Total	$ 67,819

Convertible Preferred Stock (De

Convertible Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 17, 2021	Dec. 31, 2018
Class of Stock [Line Items]
Stock issuance costs		$ 33,198
Repurchase of convertible preferred stock (in shares)			547,000
Repurchase of convertible preferred stock			$ 662
Outstanding shares of convertible preferred stock converted into shares of common stock (in shares)					194,474,431
Convertible preferred stock outstanding (in shares)		0	194,474,000	152,116,000		74,406,000
Series C Convertible Preferred Stock
Class of Stock [Line Items]
Number of shares sold (in shares)	42,905,042
Sale of stock, price per share (in dollars per share)	$ 11.49
Proceeds from sale of stock, net of issuance costs	$ 492,500
Stock issuance costs	$ 500		$ 533
Series A Convertible Preferred Stock
Class of Stock [Line Items]
Stock issuance costs				$ 29
Repurchase of convertible preferred stock (in shares)	546,806
Repurchase of convertible preferred stock	$ 4,200		$ 700

Stockholders_ Equity (Deficit)

Stockholders’ Equity (Deficit) (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jun. 30, 2021
Class of Stock [Line Items]
Preferred stock and common stock authorized (in shares)					510,000,000
Common stock authorized (in shares)		500,000,000	264,905,000		500,000,000
Preferred stock authorized (in shares)		10,000,000	0		10,000,000
Preferred stock, par value (in dollars per share)		$ 0.0001	$ 0.0001		$ 0.0001
Preferred stock outstanding (in shares)		0	0
Common stock outstanding (in shares)		242,738,350	15,569,788
Payments for repurchase of common stock		$ 0	$ 11,806	$ 185
Affiliated Entity | Stock Repurchase from Related Party
Class of Stock [Line Items]
Repurchase of common stock (in shares)	2,032,166
Payments for repurchase of common stock	$ 11,800
RSAs
Class of Stock [Line Items]
Awards outstanding (in shares)		2,600,002	7,562,503

Stock-based Compensation - Narr

Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		11 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2019	Nov. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2021	Jun. 16, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense				$ 62,201	$ 33,261	$ 15,732
Weighted average grant date fair value (in dollars per share)				$ 6.59	$ 3.36	$ 2.24
Total stock-based compensation cost related to unvested awards not yet recognized	$ 136,800			$ 136,800
Expected weighted-average period compensation cost to be recognized				2 years 3 months 29 days
Intrinsic value of options exercised				$ 16,100	$ 300	$ 0
IPO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense				2,600
Stock option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incremental stock-based compensation expense of modifications				3,300
Incremental stock-based compensation expense of modifications recognized during period				300	700	600
Weighted average grant date fair value (in dollars per share)		$ 3.65	$ 4.78
RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incremental stock-based compensation expense of modifications						8,600
Fair value of awards vested during period				$ 57,100	$ 29,400	$ 33,500
2021 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares reserved for future issuance (in shares)									26,662,087
Period of increase in term of awards				10 years
Proportion of stock outstanding (as a percent)				5.00%
Vesting period				4 years
Future issuance of common shares (in shares)	24,700,000			24,700,000
2021 Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period				10 years
2021 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares reserved for future issuance (in shares)								2,470,000
Period of increase in term of awards							10 years
Proportion of stock outstanding (as a percent)					1.00%
Purchase of common stock at discount (as a percent)	15.00%			15.00%
Purchase price in relation to common stock price (as a percent)	85.00%
Maximum number of shares to be purchased under ESPP (in shares)				4,940,000
Maximum offering period	27 months
Awards issued during period (in shares)				0
2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiration period							10 years
Vesting period							4 years
Future issuance of common shares (in shares)							0

Stock-based Compensation - Sche

Stock-based Compensation - Schedule of Stock-Based Compensation Expense by Classification (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 62,201	$ 33,261	$ 15,732
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	15,328	14,977	4,926
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 46,873	$ 18,284	$ 10,806

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Incremental Stock-Based Compensation Expense from Modifications (Details) - USD ($) $ 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]
Future Expense	$ 136,800
Options and RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Incremental stock-based compensation expense of modifications and future expense	83,472
Incremental stock-based compensation expense of modifications	27,701	$ 17,464
Future Expense	38,307
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incremental stock-based compensation expense of modifications	3,300
Options | Former CEO | 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Incremental stock-based compensation expense of modifications and future expense	21,948
Incremental stock-based compensation expense of modifications	4,105
Future Expense	17,843
Options | Former CEO | 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Incremental stock-based compensation expense of modifications and future expense	15,052
Incremental stock-based compensation expense of modifications	6,044	2,755
Future Expense	6,253
Options | Other | 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Incremental stock-based compensation expense of modifications and future expense	1,019
Incremental stock-based compensation expense of modifications	1,019
Future Expense	0
Options | Other | 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Incremental stock-based compensation expense of modifications and future expense	4,717
Incremental stock-based compensation expense of modifications	1,153	2,954
Future Expense	610
RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incremental stock-based compensation expense of modifications			$ 8,600
RSAs | Former CEO | 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Incremental stock-based compensation expense of modifications and future expense	10,908
Incremental stock-based compensation expense of modifications	3,237
Future Expense	7,671
RSAs | Former CEO | 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Incremental stock-based compensation expense of modifications and future expense	20,799
Incremental stock-based compensation expense of modifications	10,168	4,701
Future Expense	5,930
RSAs | Other | 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Incremental stock-based compensation expense of modifications and future expense	9,029
Incremental stock-based compensation expense of modifications	1,975	$ 7,054
Future Expense	$ 0

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of RSA Activity (Details) - RSAs	12 Months Ended
	Dec. 31, 2021$ / sharesshares
Number of Shares
Unvested shares of beginning balance (in shares) | shares	7,562,503
Vested (in shares) | shares	(4,943,751)
Forfeited (in shares) | shares	(18,750)
Unvested shares of ending balance (in shares) | shares	2,600,002
Weighted-Average Grant Date Fair Value per Share
Unvested shares of beginning balance (in dollars per share) | $ / shares	$ 0.0001
Vested (in dollars per share) | $ / shares	0.0001
Forfeited (in dollars per share) | $ / shares	0.0001
Unvested shares of ending balance (in dollars per share) | $ / shares	$ 0.0001

Stock-based Compensation - Su_3

Stock-based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Number of Stock Options
Beginning Balance (in shares)	34,413,889
Granted (in shares)	12,947,501
Exercised (in shares)	(2,750,380)
Canceled or forfeited (in shares)	(2,835,831)
Ending Balance (in shares)	41,775,179	34,413,889
Options Exercisable (in shares)	23,716,000
Weighted-Average Exercise Price per Share
Beginning Balance (in dollars per share)	$ 3.33
Granted (in dollars per share)	9.09
Exercised (in dollars per share)	3.43
Cancelled or forfeited (in dollars per share)	4.19
Ending Balance (in dollars per share)	5.05	$ 3.33
Options Exercisable (in dollars per share)	$ 3.39
Weighted-Average Remaining Contractual Life (years)
Options Outstanding	7 years 10 months 2 days	8 years 8 months 1 day
Options Exercisable	7 years 29 days
Aggregate Intrinsic Value
Options Outstanding	$ 142,076	$ 100,223
Options Exercisable	$ 110,520

Stock-based Compensation - Sc_2

Stock-based Compensation - Schedule of Assumptions Used in Black-Scholes Option-Pricing Model for Estimating Fair Value of Stock Options Granted (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Risk-free interest rate (as a percent)	0.80%	0.79%	1.91%
Expected volatility (as a percent)	79.00%	75.00%	75.00%
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 9 days	6 years 29 days
Expected dividend yield (as a percent)	0.00%	0.00%	0.00%

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Examination [Line Items]
Increase (decrease) in valuation allowance on deferred tax assets	$ 56,100,000	$ 50,400,000
Penalties or interest accrued on income taxes	0	0
Federal and State
Income Tax Examination [Line Items]
Tax credit carryforwards	9,800,000	5,700,000
Federal
Income Tax Examination [Line Items]
Operating loss carryforwards not subject to expiration	271,000,000	$ 116,100,000
State
Income Tax Examination [Line Items]
Operating loss carryforwards subject to expiration	$ 199,400,000

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Federal Statutory Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal statutory tax (as a percent)	21.00%	21.00%	21.00%
State tax, net of federal benefit (as a percent)	6.39%	4.71%	0.52%
Valuation allowance (as a percent)	(22.43%)	(24.60%)	(15.27%)
Convertible preferred stock tranche liabilities (as a percent)	0.00%	0.00%	(5.75%)
Stock-based compensation (as a percent)	(5.92%)	(1.77%)	(1.69%)
Tax credits (as a percent)	0.99%	0.95%	1.24%
Other (as a percent)	(0.03%)	(0.29%)	(0.05%)
Effective income tax rate (as a percent)	(0.00%)	(0.00%)	(0.00%)

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 70,855	$ 28,692
Tax credit carryforwards	8,338	4,980
Accrued liabilities & allowances	3,879	3,518
Deferred revenue	8,224	8,997
Amortization	15,961	14,375
Investment basis difference	13,587	3,334
Lease liability	18,429	13,421
Stock-based compensation	2,872	5,175
Other	2,613	1,454
Gross deferred tax assets	144,758	83,946
Valuation allowance	(127,226)	(71,093)
Deferred tax assets, net of valuation allowance	17,532	12,853
Deferred tax liabilities:
Operating lease right-of-use assets	(12,647)	(11,221)
Property and equipment	(4,885)	(1,632)
Deferred tax liabilities	(17,532)	(12,853)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Summary of Chang

Income Taxes - Summary of Changes to Company’s Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 0	$ 0
Additions based on tax position related to the current year	396	0
Additions based on prior year tax positions	400	0
Ending balance	$ 796	$ 0

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share (in shares)	44,375,181	236,450,823	192,807,750
Convertible preferred stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share (in shares)	0	194,474,431	152,116,195
Unvested RSAs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share (in shares)	2,600,002	7,562,503	13,663,338
Options to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share (in shares)	41,775,179	34,413,889	27,028,217

Related-Party Transactions (Det

Related-Party Transactions (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Sep. 30, 2021	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Repurchase of convertible preferred stock (in shares)				547,000
Common Stock
Related Party Transaction [Line Items]
Repurchase of common stock (in shares)				2,032,000
Series A Convertible Preferred Stock
Related Party Transaction [Line Items]
Repurchase of convertible preferred stock (in shares)		546,806
Affiliated Entity | Sublease with Sonoma
Related Party Transaction [Line Items]
Amount of related party transaction	$ 4.6
Due to related parties, current			$ 0.5
Due to related parties, noncurrent			4
Revenue recognized from related parties			1.8
Affiliated Entity | Stock Repurchase from Related Party
Related Party Transaction [Line Items]
Repurchase of common stock (in shares)		2,032,166
Affiliated Entity | Stock Repurchase from Related Party | Common Stock
Related Party Transaction [Line Items]
Repurchase of common stock (in shares)		2,032,166
Affiliated Entity | Stock Repurchase from Related Party | Series A Convertible Preferred Stock
Related Party Transaction [Line Items]
Repurchase of convertible preferred stock (in shares)		546,806
Investor | GSK Agreement
Related Party Transaction [Line Items]
Due to related parties, current			5	$ 6.1
Due to related parties, noncurrent			79.7	89.1
Revenue recognized from related parties			$ 10.5	$ 7.8	$ 0.7
Investor | GSK Agreement | Lyell Immunopharma | Minimum | GSK
Related Party Transaction [Line Items]
Ownership interest (as a percent)			10.00%

Asset Acquisition - Narrative (

Asset Acquisition - Narrative (Details) - Immulus, Inc - USD ($)	1 Months Ended	12 Months Ended
	May 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Business Acquisition [Line Items]
Percentage of voting interests acquired (as a percent)	100.00%
Payments to acquire businesses, gross	$ 3,500,000
Stock issued during period, shares, acquisitions (in shares)	688,463
Stock issued during period value acquisitions	$ 4,000,000
Asset acquisition, transaction costs	500,000
Total consideration	8,000,000
Milestone Payments
Business Acquisition [Line Items]
Payments expense incurred		$ 0	$ 0
Maximum | Milestone Payments
Business Acquisition [Line Items]
Payments payable	$ 37,000,000

Asset Acquisition - Summary of

Asset Acquisition - Summary of Fair Value of Assets Acquired (Details) - Immulus, Inc $ in Thousands	May 31, 2020USD ($)
Business Acquisition [Line Items]
Other assets	$ 487
In-process research and development (IPR&D)	7,528
Total assets acquired	$ 8,015