0001628280-23-037360 | 10-Q | XBRL Viewer

License, Collaboration, and Success Payment Agreements

9 Months Ended

Sep. 30, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

License, Collaboration, and Success Payment Agreements

License, Collaboration and Success Payment Agreements

Fred Hutch

License Agreement - In 2018, the Company entered into a license agreement with Fred Hutchinson Cancer Center (“Fred Hutch”) that grants the Company a worldwide, sublicensable license under certain patent rights (exclusive) and certain technology (non-exclusive) to research, develop and commercialize products and processes for all fields of use utilizing chimeric antigen receptors (“CARs”) and/or T-cell receptors (“TCRs”), subject to certain exceptions.

The Company is 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, with the research conducted in accordance with a research plan and budget approved by the parties. The Fred Hutch Collaboration Agreement has a six-year term. The Company incurred $0.3 million and $0.4 million in expense in connection with the Fred Hutch Collaboration Agreement for the three months ended September 30, 2023 and 2022, respectively, and $0.7 million and $1.4 million for the nine months ended September 30, 2023 and 2022, 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 per share fair market value of the Company’s common stock relative to the original $1.83 per share issuance price of the Company’s Series A convertible preferred stock, which converted into an equal number of shares of the Company’s common stock in connection with the Company’s initial public offering (“IPO”). The aggregate success payments to Fred Hutch are not to exceed $200.0 million, which would only occur upon a 50x 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. As of September 30, 2023, no success payments have been incurred as the per share fair value of the Company’s common stock was below the price required for payment.

The success payment liability was estimated at fair value at inception and at each subsequent reporting period and the associated expense was accreted over the service period of the success payment obligations as research and development expense through 2022. As of December 31, 2022, the Company’s associated success payment liability was fully accreted to fair value as Fred Hutch had provided the requisite service obligation to earn the potential success payment consideration under the continued collaboration. For the three and nine months ended September 30, 2023 and future periods, the change in the Fred Hutch success payment liability fair value is recognized in other income (expense), net, as the requisite service obligation had been met. The success payment liability was $0.4 million and $2.5 million as of September 30, 2023 and December 31, 2022, respectively. With respect to the Fred Hutch Collaboration Agreement success payment obligations, the Company recognized a gain of $1.5 million and expense of $1.4 million for the three months ended September 30, 2023 and 2022, respectively, and a gain of $2.1 million and expense of $0.8 million for the nine months ended September 30, 2023 and 2022, respectively.

Stanford

License Agreement - In 2019, the Company entered into a license agreement with The Board of Trustees of the Leland Stanford Junior University (“Stanford”) to license specified patent rights. The Company is 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 $0.8 million in expense in connection with the Stanford Collaboration Agreement for both the three months ended September 30, 2023 and 2022, respectively, and $2.3 million for both the nine months ended September 30, 2023 and 2022, 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 Collaboration Agreement success payments are based on multiples of increased value ranging from 10x to 50x based on a comparison of the per share fair market value of the Company’s common stock relative to the original $1.83 issuance price of the Company’s Series A convertible preferred stock, which converted into an equal number of shares of the Company’s common stock in connection with the Company’s IPO. The aggregate success payments to Stanford are not to exceed $200.0 million, which would only occur upon a 50x 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 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. As of September 30, 2023, no success payments have been incurred as the per share fair value of the Company’s common stock was below the price required for payment.

The estimated fair values of the success payments to Stanford as of September 30, 2023 and December 31, 2022 were $0.8 million and $3.3 million, respectively. The success payment liability is estimated at the fair value at inception and at each subsequent reporting period and the expense is accreted over the service period of the Stanford Collaboration Agreement as research and development expense. The success payment liability was $0.6 million and $1.9 million as of September 30, 2023 and December 31, 2022, respectively. With respect to the Stanford Collaboration Agreement success payment obligations, the Company recognized a gain of $1.2 million and expense of $1.0 million for the three months ended September 30, 2023 and 2022, respectively, and a gain of $1.2 million and expense of $1.4 million for the nine months ended September 30, 2023 and 2022, respectively.

GSK

In 2019, the Company entered into the GSK Agreement with GSK for potential T‑cell therapies that apply the Company’s platform technologies and cell therapy innovations with TCRs or CARs under distinct collaboration programs. The GSK Agreement defined two initial collaboration targets, LYL331 and LYL132, and allowed GSK to nominate seven additional targets through July 2024, though no additional targets were nominated over the life of the GSK Agreement. The Company was expected to perform research and development services for each selected target up until a defined point (the “GSK Option Point”), at which time GSK would 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. In April 2021, GSK exercised the License Option on LYL331 (NY-ESO-1 TCR with c-Jun) and assumed sole responsibility for future development and commercialization of the program at its own cost and expense. The investigational new drug (“IND”) application for LYL132 was cleared in January 2022, though no patients were treated, and the IND for LYL331 was not submitted to the U.S. Food and Drug Administration. GSK terminated the GSK Agreement effective December 24, 2022, and Lyell has also discontinued any further work on these programs. There are no future performance obligations associated with the GSK Agreement.

The Company received a non-refundable upfront payment of $45.0 million under the GSK Agreement. In connection with the GSK Agreement, in May 2019, the Company also entered into a stock purchase agreement with GSK, 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 consideration of the GSK Agreement to $103.6 million.

The GSK Agreement was deemed to be within the scope of Accounting Standards Codification (“ASC”) 606, Revenue from Contracts with Customers, because GSK engaged the Company to initially provide research and development services, which were outputs of its ongoing activities, in exchange for consideration. In June 2022, the Company recorded an adjustment to revenue related to a change in estimate in connection with the GSK Agreement due to GSK and the Company mutually agreeing to conclude research activities on an undisclosed target for hematological cancers. The change in estimate decreased the related estimated project costs, which resulted in an increase in the measure of proportional cumulative performance. This adjustment increased revenue by $35.3 million, decreased net loss by $35.3 million and resulted in a $0.14 reduction in the Company’s basic and diluted net loss per common share for the nine months ended September 30, 2022.

The Company recognized no revenue related to the research and development services related to the two initial targets for both the three months ended September 30, 2023 and 2022, and zero and $36.3 million for the nine months ended September 30, 2023 and 2022, respectively. As of September 30, 2023 and December 31, 2022, there were no contract assets or contract liabilities related to the license contract.

PACT

In June 2020, the Company entered into a commitment agreement (“PACT Commitment Agreement”) with PACT Pharma, Inc. (“PACT”) to jointly develop and test an anti-cancer T-cell therapy against solid tumors, in connection with which it also purchased PACT Series C-1 convertible preferred stock, which was recorded in other investments at $36.4 million in the Company’s Condensed Consolidated Balance Sheet. In December 2021, the Company recorded a $36.4 million impairment expense for its investment in PACT.

In February 2021, the Company filed a demand for arbitration seeking, among other things, rescission of the PACT Commitment Agreement. On October 1, 2022, the Company entered into a settlement agreement to resolve its

outstanding legal dispute with PACT, pursuant to which PACT issued shares of PACT’s Series D convertible preferred stock to the Company in exchange for the Company’s tender of its PACT Series C-1 convertible preferred stock. The settlement agreement also included the termination of the commitment agreement with PACT. The Company recorded a gain of $2.9 million in October 2022 for the estimated fair value of the PACT Series D convertible preferred stock, which was included in other investments in the Company’s Condensed Consolidated Balance Sheet as of December 31, 2022. In connection with the preparation of the financial statements for the nine months ended September 30, 2023, the Company performed a qualitative assessment of potential indicators of impairment of the PACT Series D convertible preferred stock investment, resulting in $2.9 million impairment expense for the nine months ended September 30, 2023. See Note 5, Other Investments, for additional details regarding the PACT investment impairment.

Stock-based Compensation - Schedule of Assumptions Used in Black-Scholes Option-Pricing Model for Estimating Fair Value of Stock Options Granted (Details)	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Share-Based Payment Arrangement [Abstract]
Risk-free interest rate	4.13%	2.32%
Expected volatility	88.20%	85.60%
Expected term (in years)	6 years 21 days	5 years 11 months 23 days
Expected dividend yield	0.00%	0.00%

Fair Value Measurements - Schedule of Estimated Fair Value of Success Payment Liability Assumptions (Details)	Sep. 30, 2023 $ / shares	Dec. 31, 2022 $ / shares
Fred Hutch
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of common stock (in dollars per share)	$ 1.47	$ 3.47
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)	4.26	3.58
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)	5.42	4.65
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)	0.800	0.800
Fred Hutch \| Expected term (in years) \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.71	0.46
Fred Hutch \| Expected term (in years) \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	4.22	4.97
Stanford
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of common stock (in dollars per share)	$ 1.47	$ 3.47
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)	4.21	3.58
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)	5.42	4.65
Stanford \| Expected volatility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.800	0.800
Stanford \| Expected term (in years) \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.71	0.46
Stanford \| Expected term (in years) \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	6.00	6.75

Other Investments	9 Months Ended
Other Investments	Sep. 30, 2023
Investments, All Other Investments [Abstract]
Other Investments	Other Investments From time to time, the Company makes minority ownership strategic investments. As of September 30, 2023 and December 31, 2022, the aggregate carrying amounts of the Company’s strategic investments in non-publicly traded companies were $32.0 million and $44.9 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. Cumulative impairments of strategic investments in equity investments without readily determinable fair values still held as of September 30, 2023 and December 31, 2022 were $17.9 million and $5.0 million, respectively. As a part of the acquisition of each of the Company’s other investments, the Company determines whether an investment or other interest is considered a variable interest. As of September 30, 2023 and December 31, 2022, the Company held an interest in two entities that were concluded to be variable interests for which the Company was not the primary beneficiary. As of September 30, 2023 and December 31, 2022, the carrying value and maximum exposure to loss of the Company’s variable interests were $13.0 million and $15.9 million, respectively, which is recorded in other investments in the Company’s Condensed Consolidated Balance Sheets. In October 2022, the Company received shares of PACT’s Series D non-voting convertible preferred stock (See Note 3, License, Collaboration and Success Payment Agreements). The Company recognized its investment in PACT preferred stock at its estimated fair value of $2.9 million on October 1, 2022, which was included in the Company’s Condensed Consolidated Balance Sheet within other investments as of December 31, 2022. For the nine months ended September 30, 2023 and the three and nine months ended September 30, 2022, the Company performed qualitative assessments of potential indicators of impairment and determined that indicators existed for certain of its other investments. The Company did not identify any impairments for the three months ended September 30, 2023. The Company did identify impairments for the nine months ended September 30, 2023 and for the three and nine months ended September 30, 2022. While there was no single event or factor in each instance, the Company considered the underlying companies’ operating cash flow requirements over the next year, liquid asset balances to fund those requirements and the underlying companies’ inability to raise funds as indicators of impairment. Due to these indicators, the Company assessed the valuation of these investments and determined the fair values to be negligible and the impairments to be other-than-temporary in nature. As a result, the Company recorded a $2.9 million impairment expense for the PACT Series D convertible preferred stock investment and a $10.0 million impairment expense for one investment for the nine months ended September 30, 2023 and $5.0 million impairment expense for one investment for the three and nine months ended September 30, 2022, which were recorded within impairment of other investments on the Condensed Consolidated Statements of Operations and Comprehensive Loss and as reductions to the investment balances within other investments on the Condensed Consolidated Balance Sheets.

Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The unaudited Condensed Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiary. All significant intercompany transactions and balances have been eliminated in consolidation. The Condensed Consolidated Balance Sheet as of December 31, 2022 included herein was derived from the audited consolidated financial statements as of that date. Certain information and footnote disclosures typically included in the Company’s audited consolidated financial statements have been condensed or omitted. The accompanying unaudited Condensed Consolidated Financial Statements have been prepared on the same basis as the annual consolidated financial statements and reflect, in the opinion of management, all adjustments of a normal and recurring nature that are necessary for the fair presentation of the Company’s financial position, results of operations and cash flows for the periods presented, but are not necessarily indicative of results to be expected for any future annual or interim period. These unaudited Condensed Consolidated Financial Statements should be read in conjunction with the Company’s audited financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2022. Liquidity and Management’s Plan The Company discovers and develops product candidates that involve experimental technologies. The product candidates 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 September 30, 2023 will be adequate to fund its operations at least through the next 12 months from the date these unaudited Condensed Consolidated Financial Statements are issued. Use of Estimates The preparation of the Company’s Condensed 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, valuation of other investments, 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. In June 2022, the Company recorded an adjustment to revenue related to a change in estimate in connection with the Collaboration and License Agreement, entered into in 2019 and amended in June 2020 and December 2021 (“GSK Agreement”) with GlaxoSmithKline Intellectual Property (No. 5) Limited and Glaxo Group Limited (together, “GSK”). The Company and GSK mutually agreed to conclude research activities on an undisclosed target for hematological cancers in June 2022. As a result, the Company decreased the related estimated project costs, which resulted in an increase in the measure of proportional cumulative performance. This adjustment increased revenue by $35.3 million, decreased net loss by $35.3 million and resulted in a $0.14 reduction in the Company’s basic and diluted net loss per common share for the nine months ended September 30, 2022. 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. Restricted cash is cash held in a bank account and is used as collateral associated with the Company’s corporate credit card program. Cash, cash equivalents and restricted cash 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. Significant Accounting Policies There have been no material changes to the significant accounting policies from the Annual Report on Form 10-K for the year ended December 31, 2022. Recently Adopted Accounting Pronouncements None.

Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Oct. 01, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of other investments	$ 0	$ 5,000	$ 12,923	$ 5,000
PACT
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock at fair value					$ 2,900
Other Investment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment of other investments		$ 5,000	10,000	$ 5,000
Other Investment \| PACT
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock at fair value					$ 2,900
Impairment of other investments			$ 2,900

Condensed Consolidated Statements of Stockholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2021		242,738,000
Beginning balance at Dec. 31, 2021	$ 929,787	$ 24	$ 1,515,748	$ (1,623)	$ (584,362)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		3,513,000
Issuance of common stock upon exercise of stock options	9,252	$ 1	9,251
Issuance of common stock under employee stock purchase plan (in shares)		284,000
Issuance of common stock under employee stock purchase plan	887		887
Issuance of common stock in connection with restricted stock units, net of tax (in shares)		105,000
Issuance of common stock in connection with restricted stock units, net of tax	(367)		(367)
Stock-based compensation (in shares)		2,600,000
Stock-based compensation	63,561		63,561
Other comprehensive income (loss)	(8,373)			(8,373)
Net loss	(174,721)				(174,721)
Ending balance (in shares) at Sep. 30, 2022		249,240,000
Ending balance at Sep. 30, 2022	820,026	$ 25	1,589,080	(9,996)	(759,083)
Beginning balance (in shares) at Jun. 30, 2022		247,110,000
Beginning balance at Jun. 30, 2022	868,042	$ 25	1,565,197	(8,351)	(688,829)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		1,375,000
Issuance of common stock upon exercise of stock options	5,127		5,127
Issuance of common stock in connection with restricted stock units, net of tax (in shares)		105,000
Issuance of common stock in connection with restricted stock units, net of tax	(367)		(367)
Stock-based compensation (in shares)		650,000
Stock-based compensation	19,123		19,123
Other comprehensive income (loss)	(1,645)			(1,645)
Net loss	(70,254)				(70,254)
Ending balance (in shares) at Sep. 30, 2022		249,240,000
Ending balance at Sep. 30, 2022	$ 820,026	$ 25	1,589,080	(9,996)	(759,083)
Beginning balance (in shares) at Dec. 31, 2022	249,567,343	249,567,000
Beginning balance at Dec. 31, 2022	$ 833,252	$ 25	1,608,306	(7,599)	(767,480)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)	1,478,537	1,479,000
Issuance of common stock upon exercise of stock options	$ 155		155
Issuance of common stock under employee stock purchase plan (in shares)		543,000
Issuance of common stock under employee stock purchase plan	1,163		1,163
Issuance of common stock in connection with restricted stock units, net of tax (in shares)		280,000
Issuance of common stock in connection with restricted stock units, net of tax	(334)		(334)
Stock-based compensation	38,621		38,621
Other comprehensive income (loss)	6,418			6,418
Net loss	$ (181,702)				(181,702)
Ending balance (in shares) at Sep. 30, 2023	251,868,968	251,869,000
Ending balance at Sep. 30, 2023	$ 697,573	$ 25	1,647,911	(1,181)	(949,182)
Beginning balance (in shares) at Jun. 30, 2023		251,027,000
Beginning balance at Jun. 30, 2023	736,855	$ 25	1,637,538	(2,379)	(898,329)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		646,000
Issuance of common stock upon exercise of stock options	72		72
Issuance of common stock in connection with restricted stock units, net of tax (in shares)		196,000
Issuance of common stock in connection with restricted stock units, net of tax	(215)		(215)
Stock-based compensation	10,516		10,516
Other comprehensive income (loss)	1,198			1,198
Net loss	$ (50,853)				(50,853)
Ending balance (in shares) at Sep. 30, 2023	251,868,968	251,869,000
Ending balance at Sep. 30, 2023	$ 697,573	$ 25	$ 1,647,911	$ (1,181)	$ (949,182)

Cash Equivalents and Marketable Securities

9 Months Ended

Sep. 30, 2023

Cash and Cash Equivalents [Abstract]

Cash Equivalents and Marketable Securities

The fair value and amortized cost of cash equivalents and marketable securities by major security type are as follows (in thousands):


	September 30, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	168,800	$	—	$	—	$	168,800
U.S. Treasury securities	249,643		6		(492)		249,157
U.S. government agency securities	69,497		—		(544)		68,953
Corporate debt securities	89,714		—		(151)		89,563
Total cash equivalents and marketable securities	$	577,654	$	6	$	(1,187)	$	576,473


Classified as:	Fair Value
Cash equivalents	$	264,527
Marketable securities	289,217
Marketable securities, non-current	22,729
Total cash equivalents and marketable securities	$	576,473


	December 31, 2022
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	67,970	$	—	$	—	$	67,970
U.S. Treasury securities	277,056		—		(5,257)		271,799
U.S. government agency securities	135,460		1		(1,416)		134,045
Corporate debt securities	221,608		3		(930)		220,681
Total cash equivalents and marketable securities	$	702,094	$	4	$	(7,603)	$	694,495


Classified as:	Fair Value
Cash equivalents	$	107,780
Marketable securities	516,598
Marketable securities, non-current	70,117
Total cash equivalents and marketable securities	$	694,495

The fair values of securities held by the Company in an unrealized loss position for less than 12 months were $247.6 million and $287.8 million as of September 30, 2023 and December 31, 2022, respectively. The fair values of securities held by the Company in an unrealized loss position for greater than 12 months were $104.9 million and $278.7 million as of September 30, 2023 and December 31, 2022, respectively. As of September 30, 2023 and December 31, 2022, 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. 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. The Company determined that there was no material change in the credit risk of the above investments as of both September 30, 2023 and

December 31, 2022. As such, an allowance for credit losses has not been recognized. Gross realized gains and losses were de minimis for the three and nine months ended September 30, 2023 and 2022 and as a result, amounts reclassified out of accumulated other comprehensive loss for the three and nine months ended September 30, 2023 and 2022 were also de minimis. See Note 6, Fair Value Measurements, for additional information regarding cash equivalents and marketable securities.

Fair Value Measurements

9 Months Ended

Sep. 30, 2023

Fair Value Disclosures [Abstract]

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):


	September 30, 2023
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds	$	168,800	$	—	$	—	$	168,800
U.S. Treasury securities	—		249,157		—		249,157
U.S. government agency securities	—		68,953		—		68,953
Corporate debt securities	—		89,563		—		89,563

Total financial assets	$	168,800	$	407,673	$	—	$	576,473
Financial liabilities:
Success payment liabilities	$	—	$	—	$	1,047	$	1,047
Total financial liabilities	$	—	$	—	$	1,047	$	1,047


	December 31, 2022
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds	$	67,970	$	—	$	—	$	67,970
U.S. Treasury securities	—		271,799		—		271,799
U.S. government agency securities	—		134,045		—		134,045
Corporate debt securities	—		220,681		—		220,681
Total financial assets	$	67,970	$	626,525	$	—	$	694,495
Financial liabilities:
Success payment liabilities	$	—	$	—	$	4,356	$	4,356
Total financial liabilities	$	—	$	—	$	4,356	$	4,356

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, U.S. government agency securities and corporate debt securities, which are valued using third-party pricing sources. The pricing services applied 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 Company’s Level 3 financial instruments fair values are estimated using valuation models, including Monte Carlo simulations for the Company’s success payment liabilities. Monte Carlo simulations model 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, expected volatility, the 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:


	September 30, 2023			December 31, 2022
Fair value of common stock	$	1.47		$	3.47
Risk-free interest rate	4.26% - 5.42%			3.58% - 4.65%
Expected volatility	80.0		%	80.0		%
Expected term (in years)	0.71 - 4.22			0.46 - 4.97

The following assumptions were incorporated into the calculation of the estimated fair value of the Stanford success payment liability:


	September 30, 2023			December 31, 2022
Fair value of common stock	$	1.47		$	3.47
Risk-free interest rate	4.21% - 5.42%			3.58% - 4.65%
Expected volatility	80.0		%	80.0		%
Expected term (in years)	0.71 - 6.00			0.46 - 6.75

The Company utilizes estimates and assumptions in determining the estimated success payment liabilities and associated changes in fair value. 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 changes in fair value.

The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 liabilities (in thousands):


	Success Payment Liabilities
Balance at December 31, 2022	$	4,356
Change in fair value (1)	(3,309)
Balance at September 30, 2023	$	1,047

(1)The change in the fair value associated with the Fred Hutch success payment liabilities of approximately $(2.1) million is recorded in other income (expense), net. The change in the fair value of approximately $(1.2) million associated with the Stanford success payment liabilities is recorded as research and development expenses. (See Note 3, License, Collaboration and Success Payment Agreements).

In October 2022, the Company received non-voting PACT Series D convertible preferred stock with a fair value of $2.9 million (See Note 3, License, Collaboration and Success Payment Agreements). In connection with the preparation of the financial statements for the nine months ended September 30, 2023, the Company performed a qualitative assessment of potential indicators of impairment of the PACT Series D convertible preferred stock investment, resulting in $2.9 million impairment expense for the nine months ended September 30, 2023. See Note 5, Other Investments, for additional details regarding the PACT investment impairment.

- Definition

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

+ References + Details

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock authorized (in shares)	10,000,000	10,000,000
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	500,000,000
Common stock issued (in shares)	251,869,000	249,567,000
Common stock outstanding (in shares)	251,868,968	249,567,343

Summary of Significant Accounting Policies (Details) - USD ($)
$ / shares in Units, $ in Thousands

3 Months Ended

9 Months Ended

Sep. 30, 2023

Sep. 30, 2022

Sep. 30, 2023

Sep. 30, 2022

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Revenue

^[1]

$ 25

$ 3

$ 117

$ 36,297

Net loss

$ (50,853)

$ (70,254)

$ (181,702)

$ (174,721)

Net loss per common share, basic (in dollars per share)

$ (0.20)

$ (0.28)

$ (0.73)

$ (0.71)

Net loss per common share, diluted (in dollars per share)

$ (0.20)

$ (0.28)

$ (0.73)

$ (0.71)

GSK | GSK Agreement | Change in Collaboration and License Agreement estimate

Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]

Revenue

$ 35,300

Net loss

$ 35,300

Net loss per common share, basic (in dollars per share)

$ 0.14

Net loss per common share, diluted (in dollars per share)

$ 0.14

[1]	(1) Including related-party revenue of zero for both the three months ended September 30, 2023 and 2022, and zero and $36,299 for the nine months ended September 30, 2023 and 2022, respectively.

- Definition

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

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+ Details

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

+ Details

Cash Equivalents and Marketable Securities - Schedule of Fair Value and Amortized Cost of Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Marketable Securities [Line Items]
Amortized Cost	$ 286,214	$ 123,554	$ 116,311
Amortized Cost	577,654	702,094
Gross Unrealized Gains	6	4
Gross Unrealized Losses	(1,187)	(7,603)
Fair Value	576,473	694,495
Classified as:
Cash equivalents	264,527	107,780
Marketable securities	289,217	516,598
Marketable securities, non-current	22,729	70,117
Total cash equivalents and marketable securities	576,473	694,495
U.S. Treasury securities
Marketable Securities [Line Items]
Amortized Cost	249,643	277,056
Gross Unrealized Gains	6	0
Gross Unrealized Losses	(492)	(5,257)
Fair Value	249,157	271,799
U.S. government agency securities
Marketable Securities [Line Items]
Amortized Cost	69,497	135,460
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(544)	(1,416)
Fair Value	68,953	134,045
Corporate debt securities
Marketable Securities [Line Items]
Amortized Cost	89,714	221,608
Gross Unrealized Gains	0	3
Gross Unrealized Losses	(151)	(930)
Fair Value	89,563	220,681
Money market funds
Marketable Securities [Line Items]
Amortized Cost	168,800	67,970
Fair Value	$ 168,800	$ 67,970

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (181,702)	$ (174,721)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	38,621	63,561
Depreciation and amortization expense	15,193	12,979
Impairment of other investments	12,923	5,000
Net amortization and accretion on marketable securities	(6,212)	278
Change in fair value of success payment liabilities	(3,309)	2,177
Non-cash lease income	(1,344)	(1,104)
Loss on property and equipment disposals, net	1,072	97
Change in fair value of equity warrant	0	1,067
Changes in operating assets and liabilities:
Prepaid expenses, other current assets and other assets	(23)	(672)
Accounts payable	1,039	1,193
Accrued liabilities and other current liabilities	1,020	(5,836)
Deferred revenue	0	(36,299)
Operating lease liabilities, non-current	0	3,331
Other non-current liabilities	(337)	(339)
Net cash used in operating activities	(123,059)	(129,288)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(2,661)	(19,694)
Purchases of marketable securities	(220,095)	(346,647)
Sales and maturities of marketable securities	507,494	308,153
Net cash provided by (used in) investing activities	284,738	(58,188)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from exercise of stock options	155	9,252
Proceeds from employee stock purchase plan	1,163	887
Taxes paid related to net share settlement of equity awards	(334)	(367)
Net cash provided by financing activities	984	9,772
Net increase (decrease) in cash, cash equivalents and restricted cash	162,663	(177,704)
Cash, cash equivalents and restricted cash at beginning of period	123,834	294,294
Cash, cash equivalents and restricted cash at end of period	286,497	116,590
Represented by:
Cash and cash equivalents	286,214	116,311
Restricted cash	283	279
Total	286,497	116,590
SUPPLEMENTAL CASH FLOW INFORMATION
Cash paid for amounts included in the measurement of lease liabilities	8,030	8,136
Cash received for amounts related to tenant improvement allowances	0	3,238
Non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued liabilities	$ 2	$ 3,563

Stock-based Compensation

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

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 automatically increases 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. On January 1, 2023, the Company reserved an additional 12,478,367 shares of common stock for issuance under the 2021 Plan representing 5% of the total common shares outstanding as of December 31, 2022. Under the 2021 Plan, the Company may grant incentive stock options, non-statutory stock options, restricted stock awards (“RSAs”), restricted stock units (“RSUs”), 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 September 30, 2023, 22,478,430 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 automatically increases 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’s board of directors elected to reserve no additional shares under the 2021 ESPP for the year beginning January 1, 2023. The Company may specify offerings with durations not more than 27 months and may specify shorter purchase periods within each offering. Under the 2021 ESPP, no shares were issued for both the three months ended September 30, 2023 and 2022, and 542,921 and 283,574 shares were issued for the nine months ended September 30, 2023 and 2022, respectively.

As of September 30, 2023, 3,905,099 shares were available for future issuance pursuant to the 2021 ESPP.

2018 Equity Incentive Plan

In 2018, the Company established the 2018 Plan that provided for the grant of incentive stock options, non‑statutory stock options, RSAs, RSUs, stock appreciation rights and other stock-based awards. Terms of stock awards,

including vesting requirements, were 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 could have been 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 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 Condensed Consolidated Statements of Operations and Comprehensive Loss was as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development	$	4,548	$	4,442	$	14,439	$	12,401
General and administrative	5,968		14,681		24,182		51,160
Total stock-based compensation expense	$	10,516	$	19,123	$	38,621	$	63,561

At September 30, 2023, total stock-based compensation cost related to unvested awards not yet recognized was $76.5 million, which is expected to be recognized over a remaining weighted-average period of 2.79 years.

Restricted Stock Units

A summary of the Company’s RSU activity was as follows:


	Restricted Stock Units Outstanding	Weighted-Average Value at Grant Date Per Share
Unvested RSUs as of December 31, 2022	872,077	$	5.98
RSUs granted	2,559,677	$	2.24
RSUs vested	(414,018)	$	3.89
RSUs forfeited or canceled	(240,673)	$	3.66
Unvested RSUs as of September 30, 2023	2,777,063	$	3.04

Stock Options

A summary of the Company’s stock option activity was as follows:


	Number of Stock Options	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Options outstanding as of December 31, 2022	53,849,045	$	5.09	7.84	$	24,887
Granted	12,276,063	$	2.30
Exercised	(1,478,537)	$	0.10
Canceled or forfeited	(4,196,756)	$	5.26
Options outstanding as of September 30, 2023	60,449,815	$	4.63	7.58	$	7,517
Options exercisable as of September 30, 2023	32,422,027	$	4.90	6.47	$	7,517

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 weighted-average assumptions:


	Nine Months Ended September 30,
	2023		2022
Risk-free interest rate	4.13	%	2.32	%
Expected volatility	88.2	%	85.6	%
Expected term (in years)	6.06		5.98
Expected dividend yield	0	%	0	%

The weighted-average grant date fair value of options granted for the nine months ended September 30, 2023 and 2022 were $1.69 per share and $4.33 per share, respectively.

License, Collaboration, and Success Payment Agreements - Narrative (Details)		1 Months Ended	3 Months Ended			9 Months Ended
	Oct. 01, 2022 USD ($)	May 31, 2019 USD ($) $ / shares shares	Sep. 30, 2023 USD ($) $ / shares	Sep. 30, 2022 USD ($) $ / shares	Dec. 31, 2021 USD ($)	Sep. 30, 2023 USD ($) $ / shares	Sep. 30, 2022 USD ($) $ / shares	Dec. 31, 2022 USD ($)	Oct. 31, 2020 USD ($) $ / shares	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) $ / shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development expense			$ 43,849,000	$ 41,607,000		$ 135,950,000	$ 121,156,000
Net loss			$ (50,853,000)	$ (70,254,000)		$ (181,702,000)	$ (174,721,000)
Net loss per common share, basic (in dollars per share) \| $ / shares			$ (0.20)	$ (0.28)		$ (0.73)	$ (0.71)
Net loss per common share, diluted (in dollars per share) \| $ / shares			$ (0.20)	$ (0.28)		$ (0.73)	$ (0.71)
Impairment of other investments			$ 0	$ 5,000,000		$ 12,923,000	$ 5,000,000
PACT
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Impairment of other investments					$ 36,400,000
Other Investment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Impairment of other investments				5,000,000		10,000,000	5,000,000
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
Fred Hutch \| GSK Agreement
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			300,000	400,000		700,000	1,400,000
Aggregate success payment(s) (in millions)			0			0
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			400,000			400,000		$ 2,500,000
Success payment expense (gain)			(1,500,000)	1,400,000		(2,100,000)	800,000
Fred Hutch \| GSK Agreement \| Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance												10
Aggregate success payment(s) (in millions)												$ 10,000,000
Per share common stock price required for payment (in dollars per share) \| $ / shares												$ 18.29
Fred Hutch \| GSK Agreement \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance												50
Aggregate success payment(s) (in millions)												$ 200,000,000
Per share common stock price required for payment (in dollars per share) \| $ / shares												$ 91.44
Stanford \| GSK Agreement
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			800,000	800,000		2,300,000	2,300,000
Aggregate success payment(s) (in millions)			0			0
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			800,000			800,000		3,300,000
Success payment expense (gain)			(1,200,000)	1,000,000		(1,200,000)	1,400,000
Success payment liability			600,000			600,000		1,900,000
Stanford \| GSK Agreement \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments due											2,500,000
Stanford \| GSK Agreement \| Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance									10
Aggregate success payment(s) (in millions)									$ 10,000,000
Per share common stock price required for payment (in dollars per share) \| $ / shares									$ 18.29
Stanford \| GSK Agreement \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance									50
Aggregate success payment(s) (in millions)									$ 200,000,000
Per share common stock price required for payment (in dollars per share) \| $ / shares									$ 91.44
Stanford \| GSK Agreement \| Maximum \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments due											$ 3,700,000
GSK \| GSK Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized			0	$ 0		0	36,300,000
GSK \| GSK Agreement \| Change in Collaboration and License Agreement estimate
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized							35,300,000
Net loss							$ 35,300,000
Net loss per common share, basic (in dollars per share) \| $ / shares							$ 0.14
Net loss per common share, diluted (in dollars per share) \| $ / shares							$ 0.14
GSK \| GSK Agreement \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract liabilities		$ 45,000,000	0			0		0
Stock purchase agreement portion of transaction price		58,600,000
Transaction price		$ 103,600,000
Contract assets			$ 0			0		$ 0
GSK \| GSK Agreement \| License \| Series AA Convertible Preferred Stock
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
PACT
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Gain on other investments	$ 2,900,000
PACT \| Other Investment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Impairment of other investments						$ 2,900,000
PACT \| GSK Agreement \| Other Investment
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Strategic equity investment										$ 36,400,000

Cash Equivalents and Marketable Securities - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Marketable Securities [Line Items]
Fair value of securities held in a continuous unrealized loss position for less than twelve months	$ 247.6	$ 287.8
Fair value of securities held in a continuous unrealized loss position for greater than twelve months	$ 104.9	$ 278.7
Maximum
Marketable Securities [Line Items]
Maturity of marketable securities	2 years	2 years

Cover - shares	9 Months Ended
Cover - shares	Sep. 30, 2023	Nov. 02, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2023
Document Transition Report	false
Entity File Number	001-40502
Entity Registrant Name	Lyell Immunopharma, Inc.
Entity Incorporation State Country Code	DE
Entity Tax Identification Number	83-1300510
Entity Address Line	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
Security12b Title	Common Stock, $0.0001 par value per share
Trading Symbol	LYEL
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		251,868,968
Entity Central Index Key	0001806952
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3
Amendment Flag	false

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of PresentationThe accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The unaudited Condensed Consolidated Financial Statements include the accounts of the Company and its wholly-owned subsidiary.
Consolidations	All significant intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of the Company’s Condensed 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, valuation of other investments, 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. In June 2022, the Company recorded an adjustment to revenue related to a change in estimate in connection with the Collaboration and License Agreement, entered into in 2019 and amended in June 2020 and December 2021 (“GSK Agreement”) with GlaxoSmithKline Intellectual Property (No. 5) Limited and Glaxo Group Limited (together, “GSK”). The Company and GSK mutually agreed to conclude research activities on an undisclosed target for hematological cancers in June 2022. As a result, the Company decreased the related estimated project costs, which resulted in an increase in the measure of proportional cumulative performance.
Concentrations of Credit Risk	Concentrations of Credit Risk and Off-balance Sheet RiskThe Company maintains its cash, cash equivalents and restricted cash with high quality, accredited financial institutions. Restricted cash is cash held in a bank account and is used as collateral associated with the Company’s corporate credit card program. Cash, cash equivalents and restricted cash 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.
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.
Significant Accounting Policies	Significant Accounting Policies There have been no material changes to the significant accounting policies from the Annual Report on Form 10-K for the year ended December 31, 2022.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements None.

Fair Value Measurements - Schedule of Changes in Estimated Fair Value of Financial Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Fred Hutch \| GSK Agreement
Success Payment Liabilities
Success payment expense (gain)	$ (1,500)	$ 1,400	$ (2,100)	$ 800
Stanford \| GSK Agreement
Success Payment Liabilities
Success payment expense (gain)	(1,200)	$ 1,000	(1,200)	$ 1,400
Success Payment Liabilities \| Level 3
Success Payment Liabilities
Beginning Balance			4,356
Change in fair value			(3,309)
Ending Balance	$ 1,047		$ 1,047

Net Loss Per Share	9 Months Ended
Net Loss Per Share	Sep. 30, 2023
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per ShareBasic and diluted net loss per share is calculated by dividing net loss 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 unvested RSAs, unvested RSUs 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. Shares subject to options to purchase common stock, unvested RSAs and unvested RSUs were all excluded from consideration in the calculation of diluted net loss per share in all periods presented due to their anti-dilutive effects.

Related-party Transactions

9 Months Ended

Sep. 30, 2023

Related-party Transactions

In September 2021, the Company entered into a sublease with Sonoma (“Sonoma Sublease”), with whom the Company has common stockholders with board seats, whereby the Company agreed to sublease approximately 18,000 square feet of space in South San Francisco, California currently leased by the Company. Dr. Klausner, the Chair of the Company’s board of directors, also serves as Board Chair of the board of directors of Sonoma. As a part of the Sonoma Sublease, a $4.6 million tenant improvement contribution payment was made by Sonoma, which is recognized over the term of the Sonoma Sublease. As of both September 30, 2023 and December 31, 2022, there were accrued liabilities and other current liabilities of $0.5 million, and as of September 30, 2023 and December 31, 2022, other non-current liabilities of $3.1 million and $3.5 million, respectively, in connection with the Sonoma Sublease. Total operating income from Sonoma and income solely attributable to the Sonoma Sublease are shown in the table below (in thousands). Total operating income includes income attributable to the sublease, as well as additional operating fees recognized in “other operating income, net” such as common area maintenance charges. See Note 7, Leases, for more detail on the Sonoma Sublease.


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Sonoma other operating income, net	$	638	$	659	$	1,955	$	1,976
Sonoma sublease income	$	466	$	465	$	1,396	$	1,396

The Company was party to the GSK Agreement with GSK, which is a holder of more than 10% of the Company’s outstanding common stock. See Note 3, License, Collaboration and Success Payment Agreements. GSK terminated the

GSK Agreement effective December 24, 2022. The Company had no current or non-current deferred revenue in connection with the GSK Agreement as of both September 30, 2023 and December 31, 2022. Revenue recognized in connection with the GSK agreement was zero for both the three months ended September 30, 2023 and 2022, and zero and $36.3 million for the nine months ended September 30, 2023 and 2022, respectively.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-6

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 1
-Subparagraph (d)
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483575/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//850/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-6

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483326/850-10-50-1

+ Details

License, Collaboration, and Success Payment Agreements - Schedule of Aggregate Potential Success Payments (Details) - GSK Agreement	Sep. 30, 2023 USD ($)	Oct. 31, 2020 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares
Fred Hutch
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate success payment(s) (in millions)	$ 0
Stanford
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Aggregate success payment(s) (in millions)	$ 0
Ten Times \| Fred Hutch
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)			$ 10,000,000
Ten Times \| Stanford
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)		$ 10,000,000
Twenty Times \| Fred Hutch
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)			$ 40,000,000
Twenty Times \| Stanford
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)		$ 40,000,000
Thirty Times \| Fred Hutch
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)			$ 90,000,000
Thirty Times \| Stanford
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)		$ 90,000,000
Forty Times \| Fred Hutch
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)			$ 140,000,000
Forty Times \| Stanford
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)		$ 140,000,000
Fifty Times \| Fred Hutch
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)			$ 200,000,000
Fifty Times \| Stanford
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)		$ 200,000,000

Cash Equivalents and Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2023

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 are as follows (in thousands):


	September 30, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	168,800	$	—	$	—	$	168,800
U.S. Treasury securities	249,643		6		(492)		249,157
U.S. government agency securities	69,497		—		(544)		68,953
Corporate debt securities	89,714		—		(151)		89,563
Total cash equivalents and marketable securities	$	577,654	$	6	$	(1,187)	$	576,473


Classified as:	Fair Value
Cash equivalents	$	264,527
Marketable securities	289,217
Marketable securities, non-current	22,729
Total cash equivalents and marketable securities	$	576,473


	December 31, 2022
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	67,970	$	—	$	—	$	67,970
U.S. Treasury securities	277,056		—		(5,257)		271,799
U.S. government agency securities	135,460		1		(1,416)		134,045
Corporate debt securities	221,608		3		(930)		220,681
Total cash equivalents and marketable securities	$	702,094	$	4	$	(7,603)	$	694,495


Classified as:	Fair Value
Cash equivalents	$	107,780
Marketable securities	516,598
Marketable securities, non-current	70,117
Total cash equivalents and marketable securities	$	694,495

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 are as follows (in thousands):


	September 30, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	168,800	$	—	$	—	$	168,800
U.S. Treasury securities	249,643		6		(492)		249,157
U.S. government agency securities	69,497		—		(544)		68,953
Corporate debt securities	89,714		—		(151)		89,563
Total cash equivalents and marketable securities	$	577,654	$	6	$	(1,187)	$	576,473


Classified as:	Fair Value
Cash equivalents	$	264,527
Marketable securities	289,217
Marketable securities, non-current	22,729
Total cash equivalents and marketable securities	$	576,473


	December 31, 2022
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	67,970	$	—	$	—	$	67,970
U.S. Treasury securities	277,056		—		(5,257)		271,799
U.S. government agency securities	135,460		1		(1,416)		134,045
Corporate debt securities	221,608		3		(930)		220,681
Total cash equivalents and marketable securities	$	702,094	$	4	$	(7,603)	$	694,495


Classified as:	Fair Value
Cash equivalents	$	107,780
Marketable securities	516,598
Marketable securities, non-current	70,117
Total cash equivalents and marketable securities	$	694,495

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
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-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
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-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-2

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
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-Section 50
-Paragraph 3
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481800/320-10-50-3

+ Details

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2023

Fair Value Disclosures [Abstract]

Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis


	September 30, 2023
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds	$	168,800	$	—	$	—	$	168,800
U.S. Treasury securities	—		249,157		—		249,157
U.S. government agency securities	—		68,953		—		68,953
Corporate debt securities	—		89,563		—		89,563

Total financial assets	$	168,800	$	407,673	$	—	$	576,473
Financial liabilities:
Success payment liabilities	$	—	$	—	$	1,047	$	1,047
Total financial liabilities	$	—	$	—	$	1,047	$	1,047


	December 31, 2022
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds	$	67,970	$	—	$	—	$	67,970
U.S. Treasury securities	—		271,799		—		271,799
U.S. government agency securities	—		134,045		—		134,045
Corporate debt securities	—		220,681		—		220,681
Total financial assets	$	67,970	$	626,525	$	—	$	694,495
Financial liabilities:
Success payment liabilities	$	—	$	—	$	4,356	$	4,356
Total financial liabilities	$	—	$	—	$	4,356	$	4,356

Schedule 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:


	September 30, 2023			December 31, 2022
Fair value of common stock	$	1.47		$	3.47
Risk-free interest rate	4.26% - 5.42%			3.58% - 4.65%
Expected volatility	80.0		%	80.0		%
Expected term (in years)	0.71 - 4.22			0.46 - 4.97

The following assumptions were incorporated into the calculation of the estimated fair value of the Stanford success payment liability:


	September 30, 2023			December 31, 2022
Fair value of common stock	$	1.47		$	3.47
Risk-free interest rate	4.21% - 5.42%			3.58% - 4.65%
Expected volatility	80.0		%	80.0		%
Expected term (in years)	0.71 - 6.00			0.46 - 6.75

Schedule of 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 liabilities (in thousands):


	Success Payment Liabilities
Balance at December 31, 2022	$	4,356
Change in fair value (1)	(3,309)
Balance at September 30, 2023	$	1,047

Stockholders' Equity	9 Months Ended
Stockholders' Equity	Sep. 30, 2023
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Preferred Stock The Company is authorized to issue 10.0 million shares of preferred stock with a par value of $0.0001 per share. As of September 30, 2023 and December 31, 2022, no shares of preferred stock were outstanding. Common Stock The Company is authorized to issue 500.0 million shares of common stock with a par value of $0.0001 per share. As of September 30, 2023 and December 31, 2022, there were 251,868,968 shares and 249,567,343 shares of the Company’s common stock outstanding, respectively. On August 4, 2022, the Company entered into an Equity Distribution Agreement with Goldman Sachs & Co. LLC (“Goldman Sachs”) and BofA Securities, Inc. (“BofA”, and together with Goldman Sachs, the “Agents”) with respect to an at-the-market offering program (the “Equity Distribution Agreement”). In accordance with the terms of the Equity Distribution Agreement, the Company may offer and sell from time to time through the Agents shares of the Company’s common stock having an aggregate offering amount of up to $200.0 million (the “Placement Shares”). Sales of the Placement Shares, if any, will be made at prevailing market prices on Nasdaq at the time of sale, or as otherwise agreed with the Agents, by any method permitted by law deemed to be an “at-the-market offering” as defined in Rule 415 of the Securities Act of 1933, as amended. The Company will pay commissions to the Agents of up to 3.0% of the gross proceeds of the sale of the Placement Shares sold under the Equity Distribution Agreement and reimburse the Agents for certain expenses. Neither the Company nor the Agents are obligated to sell any shares and, to date, the Company has not made any sales under the Equity Distribution Agreement.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-16

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

+ Details

Organization	9 Months Ended
Organization	Sep. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	OrganizationLyell Immunopharma, Inc. (the “Company”) was incorporated in Delaware in June 2018. The Company is a clinical-stage cell therapy company advancing a pipeline of product candidates for patients with solid tumors utilizing its proprietary ex vivo genetic and epigenetic T‑cell reprogramming technologies. The Company’s primary activities since incorporation have been to develop T‑cell therapies, perform research and development, acquire technology, enter into strategic collaboration and license arrangements, enable and execute manufacturing activities in support of its product candidate development efforts, organize and staff the Company, conduct business planning, establish its intellectual property portfolio, submit regulatory submissions, execute clinical trials, raise capital and provide general and administrative support for these activities.

Stock-based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 01, 2023	Jun. 30, 2021	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation cost related to unvested awards not yet recognized			$ 76.5		$ 76.5
Expected weighted-average period compensation cost to be recognized					2 years 9 months 14 days
Weighted average grant date fair value (in dollars per share)					$ 1.69	$ 4.33
2021 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common shares reserved for future issuance (in shares)		26,662,087
Award expiration period		10 years
Proportion of stock outstanding (as a percent)		5.00%
Number of additional shares authorized for issuance (in shares)	12,478,367
Increase in proportion of common shares reserved for future issuance (as a percent)	5.00%
Vesting period		4 years
Future issuance of common shares (in shares)			22,478,430		22,478,430
Stock-based compensation (in shares)			0	0	542,921	283,574
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
Award expiration period		10 years
Proportion of stock outstanding (as a percent)		1.00%
Number of additional shares authorized for issuance (in shares)	0
Future issuance of common shares (in shares)			3,905,099		3,905,099
Purchase of common stock at discount (as a percent)		15.00%
Employee purchase of shares, proportion of fair value (as a percent)		85.00%
Maximum number of shares to be purchased under ESPP (in shares)		4,940,000
Maximum offering period		27 months
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

Leases - Schedule of Operating Lease Commitments Including Expected Lease Incentives to be Received (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Leases [Abstract]
2023 (remaining three months)	$ 2,815
2024	11,347
2025	11,859
2026	12,209
2027	12,569
Thereafter	35,525
Total undiscounted lease payments	86,324
Less: imputed interest	(21,687)
Total operating lease liabilities	64,637
Operating Lease Liability
Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities)	6,061
Operating lease liabilities, non-current	58,576	$ 63,168
Total	$ 64,637

Related-party Transactions - Narrative (Details) ft² in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)	Sep. 30, 2021 USD ($) ft²
Related Party Transaction [Line Items]
Accrued liabilities and other current liabilities	$ 29,652		$ 29,652		$ 28,755
Other non-current liabilities	3,776		3,776		4,113
Related Party
Related Party Transaction [Line Items]
Rentable area \| ft²						18
Related Party \| Sonoma
Related Party Transaction [Line Items]
Rentable area \| ft²						18
Tenant improvements						$ 4,600
Accrued liabilities and other current liabilities	500		500		500
Other non-current liabilities	3,100		3,100		3,500
Related Party \| GSK
Related Party Transaction [Line Items]
Contract liabilities	0		0		$ 0
Revenue recognized	$ 0	$ 0	$ 0	$ 36,300
Related Party \| Minimum \| Lyell Immunopharma \| GSK
Related Party Transaction [Line Items]
Ownership interest (as a percent)	10.00%		10.00%

Related-party Transactions - Schedule of Total Income Attributable to Sonoma Sublease (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Related Party Transaction [Line Items]
Sonoma other operating income, net	$ 292	$ 1,251	$ 2,149	$ 3,544
Related Party \| Sonoma
Related Party Transaction [Line Items]
Sonoma other operating income, net	638	659	1,955	1,976
Sonoma sublease income	$ 466	$ 465	$ 1,396	$ 1,396

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 286,214	$ 123,554
Marketable securities	289,217	516,598
Prepaid expenses and other current assets	11,423	11,143
Total current assets	586,854	651,295
Restricted cash	283	280
Marketable securities, non-current	22,729	70,117
Other investments	32,001	44,924
Property and equipment, net	108,096	123,023
Operating lease right-of-use assets	40,603	43,242
Other non-current assets	4,423	4,680
Total assets	794,989	937,561
Current liabilities:
Accounts payable	4,365	3,917
Accrued liabilities and other current liabilities	29,652	28,755
Success payment liabilities	1,047	4,356
Total current liabilities	35,064	37,028
Operating lease liabilities, non-current	58,576	63,168
Other non-current liabilities	3,776	4,113
Total liabilities	97,416	104,309
Commitments and contingencies (Note 11)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized at September 30, 2023 and December 31, 2022; no shares issued and outstanding at September 30, 2023 and December 31, 2022	0	0
Common stock, $0.0001 par value; 500,000 shares authorized at September 30, 2023 and December 31, 2022; 251,869 and 249,567 shares issued and outstanding at September 30, 2023 and December 31, 2022, respectively	25	25
Additional paid-in capital	1,647,911	1,608,306
Accumulated other comprehensive loss	(1,181)	(7,599)
Accumulated deficit	(949,182)	(767,480)
Total stockholders’ equity	697,573	833,252
Total liabilities and stockholders’ equity	$ 794,989	$ 937,561

Stockholders' Equity (Details) - USD ($)	Aug. 04, 2022	Sep. 30, 2023	Dec. 31, 2022
Class of Stock [Line Items]
Preferred stock authorized (in shares)		10,000,000	10,000,000
Preferred stock, par value (in dollars per share)		$ 0.0001	$ 0.0001
Preferred stock outstanding (in shares)		0	0
Common stock authorized (in shares)		500,000,000	500,000,000
Common stock, par value (in dollars per share)		$ 0.0001	$ 0.0001
Common stock outstanding (in shares)		251,868,968	249,567,343
Goldman Sachs and BofA \| At The Market Offering \| Equity Distribution Agreement
Class of Stock [Line Items]
Aggregate offering amount	$ 200,000,000
Percentage of commission from each sale of shares	3.00%

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pay vs Performance Disclosure
Net loss	$ (50,853)	$ (70,254)	$ (181,702)	$ (174,721)

- Definition

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

+ References

+ Details

Condensed Consolidated Statements of Operations and Comprehensive Loss (Parenthetical) - USD ($)
$ in Thousands

3 Months Ended

9 Months Ended

Sep. 30, 2023

Sep. 30, 2022

Sep. 30, 2023

Sep. 30, 2022

Revenue

^[1]

$ 25

$ 3

$ 117

$ 36,297

Related Party

Revenue

$ 0

$ 36,299

[1]	(1) Including related-party revenue of zero for both the three months ended September 30, 2023 and 2022, and zero and $36,299 for the nine months ended September 30, 2023 and 2022, respectively.

- Definition

+ References

+ Details

Subsequent Events	9 Months Ended
Subsequent Events	Sep. 30, 2023
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsOn November 6, 2023, the Company committed to and commenced a reduction in its workforce of approximately 25% to reduce operating costs and improve operating efficiency. The reduction in workforce is expected to be completed in the fourth quarter of 2023. In connection with this reduction in workforce, the Company estimates that it will incur charges of approximately $6 million to $7 million for severance payments, employee benefits and related costs, primarily in the fourth quarter of 2023. Substantially all of the estimated charges are expected to result in future cash expenditures.

Subsequent Events (Details) - Subsequent Event - USD ($) $ in Millions	2 Months Ended
	Dec. 31, 2023	Nov. 06, 2023
Forecast
Subsequent Event [Line Items]
Reduction in workforce (as a percent)	25.00%
Minimum
Subsequent Event [Line Items]
Estimate of workforce reduction charges		$ 6
Maximum
Subsequent Event [Line Items]
Estimate of workforce reduction charges		$ 7

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Sep. 30, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Related-party Transactions (Tables)

9 Months Ended

Sep. 30, 2023

Schedule of Total Income Attributable to Sonoma Sublease

Total operating income from Sonoma and income solely attributable to the Sonoma Sublease are shown in the table below (in thousands). Total operating income includes income attributable to the sublease, as well as additional operating fees recognized in “other operating income, net” such as common area maintenance charges. See Note 7, Leases, for more detail on the Sonoma Sublease.


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Sonoma other operating income, net	$	638	$	659	$	1,955	$	1,976
Sonoma sublease income	$	466	$	465	$	1,396	$	1,396

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies License and Collaboration Agreements The Company has entered into certain license and collaboration agreements, including those identified in Note 3, License, Collaboration 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, including termination of such agreements. 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 both September 30, 2023 and December 31, 2022.

Leases (Tables)

9 Months Ended

Sep. 30, 2023

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 September 30, 2023 (in thousands):


Year Ending December 31:
2023 (remaining three months)	$	2,815
2024	11,347
2025	11,859
2026	12,209
2027	12,569
Thereafter	35,525
Total undiscounted lease payments	86,324
Less: imputed interest	(21,687)
Total operating lease liabilities	$	64,637

Reported as of September 30, 2023:
Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities)	$	6,061
Operating lease liabilities, non-current	58,576
Total	$	64,637

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 September 30, 2023 (in thousands):


Year Ending December 31:
2023 (remaining three months)	$	2,815
2024	11,347
2025	11,859
2026	12,209
2027	12,569
Thereafter	35,525
Total undiscounted lease payments	86,324
Less: imputed interest	(21,687)
Total operating lease liabilities	$	64,637

Reported as of September 30, 2023:
Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities)	$	6,061
Operating lease liabilities, non-current	58,576
Total	$	64,637

Stock-based Compensation - Schedule of Restricted Stock Units (Details) - RSUs	9 Months Ended
	Sep. 30, 2023 $ / shares shares
Restricted Stock Units Outstanding
Balance at beginning of period (in shares) \| shares	872,077
RSUs granted (in shares) \| shares	2,559,677
RSUs vested (in shares) \| shares	(414,018)
RSUs forfeited or canceled (in shares) \| shares	(240,673)
Balance at end of period (in shares) \| shares	2,777,063
Weighted-Average Value at Grant Date Per Share
Balance at beginning of period (in dollars per share) \| $ / shares	$ 5.98
RSUs granted (in dollars per share) \| $ / shares	2.24
RSUs vested (in dollars per share) \| $ / shares	3.89
RSUs forfeited or canceled (in dollars per share) \| $ / shares	3.66
Balance at end of period (in dollars per share) \| $ / shares	$ 3.04

Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Stock-based Compensation Expense by Classification

Stock-based compensation expense by classification included within the Condensed Consolidated Statements of Operations and Comprehensive Loss was as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development	$	4,548	$	4,442	$	14,439	$	12,401
General and administrative	5,968		14,681		24,182		51,160
Total stock-based compensation expense	$	10,516	$	19,123	$	38,621	$	63,561

Schedule of RSU Activity

A summary of the Company’s RSU activity was as follows:


	Restricted Stock Units Outstanding	Weighted-Average Value at Grant Date Per Share
Unvested RSUs as of December 31, 2022	872,077	$	5.98
RSUs granted	2,559,677	$	2.24
RSUs vested	(414,018)	$	3.89
RSUs forfeited or canceled	(240,673)	$	3.66
Unvested RSUs as of September 30, 2023	2,777,063	$	3.04

Schedule of Stock Option Activity

A summary of the Company’s stock option activity was as follows:


	Number of Stock Options	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Options outstanding as of December 31, 2022	53,849,045	$	5.09	7.84	$	24,887
Granted	12,276,063	$	2.30
Exercised	(1,478,537)	$	0.10
Canceled or forfeited	(4,196,756)	$	5.26
Options outstanding as of September 30, 2023	60,449,815	$	4.63	7.58	$	7,517
Options exercisable as of September 30, 2023	32,422,027	$	4.90	6.47	$	7,517

Schedule of Assumptions Used in Black-Scholes Option-Pricing Model for Estimating Fair Value of Stock Options Granted


	Nine Months Ended September 30,
	2023		2022
Risk-free interest rate	4.13	%	2.32	%
Expected volatility	88.2	%	85.6	%
Expected term (in years)	6.06		5.98
Expected dividend yield	0	%	0	%

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Financial assets:
Total financial assets	$ 576,473	$ 694,495
Financial liabilities:
Success payment liabilities	1,047	4,356
Total financial liabilities	1,047	4,356
U.S. Treasury securities
Financial assets:
Marketable securities	249,157	271,799
U.S. government agency securities
Financial assets:
Marketable securities	68,953	134,045
Corporate debt securities
Financial assets:
Marketable securities	89,563	220,681
Money market funds
Financial assets:
Money market funds	168,800	67,970
Level 1
Financial assets:
Total financial assets	168,800	67,970
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:
Money market funds	168,800	67,970
Level 2
Financial assets:
Total financial assets	407,673	626,525
Financial liabilities:
Success payment liabilities	0	0
Total financial liabilities	0	0
Level 2 \| U.S. Treasury securities
Financial assets:
Marketable securities	249,157	271,799
Level 2 \| U.S. government agency securities
Financial assets:
Marketable securities	68,953	134,045
Level 2 \| Corporate debt securities
Financial assets:
Marketable securities	89,563	220,681
Level 2 \| Money market funds
Financial assets:
Money market funds	0	0
Level 3
Financial assets:
Total financial assets	0	0
Financial liabilities:
Success payment liabilities	1,047	4,356
Total financial liabilities	1,047	4,356
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:
Money market funds	$ 0	$ 0

Stock-based Compensation - Schedule of Stock-Based Compensation Expense by Classification (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 10,516	$ 19,123	$ 38,621	$ 63,561
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	4,548	4,442	14,439	12,401
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 5,968	$ 14,681	$ 24,182	$ 51,160

License, Collaboration, and Success Payment Agreements (Tables)

9 Months Ended

Sep. 30, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Aggregate Potential Success Payments


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


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

Stock-based Compensation - Schedule of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares
Number of Stock Options
Beginning balance (in shares) \| shares	53,849,045
Granted (in shares) \| shares	12,276,063
Exercised (in shares) \| shares	(1,478,537)
Canceled or forfeited (in shares) \| shares	(4,196,756)
Ending balance (in shares) \| shares	60,449,815	53,849,045
Exercisable (in shares) \| shares	32,422,027
Weighted- Average Exercise Price Per Share
Beginning balance (in dollars per share) \| $ / shares	$ 5.09
Granted (in dollars per share) \| $ / shares	2.30
Exercised (in dollars per share) \| $ / shares	0.10
Cancelled or forfeited (in dollars per share) \| $ / shares	5.26
Ending balance (in dollars per share) \| $ / shares	4.63	$ 5.09
Exercisable (in dollars per share) \| $ / shares	$ 4.90
Weighted- Average Remaining Contractual Life (in years)
Options Outstanding	7 years 6 months 29 days	7 years 10 months 2 days
Options Exercisable	6 years 5 months 19 days
Aggregate Intrinsic Value (in thousands)
Options Outstanding \| $	$ 7,517	$ 24,887
Options Exercisable \| $	$ 7,517

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($)
shares in Thousands, $ in Thousands

3 Months Ended

9 Months Ended

Sep. 30, 2023

Sep. 30, 2022

Sep. 30, 2023

Sep. 30, 2022

Statement of Comprehensive Income [Abstract]

Revenue

^[1]

$ 25

$ 3

$ 117

$ 36,297

Operating expenses:

Research and development

43,849

41,607

135,950

121,156

General and administrative

15,507

26,084

53,816

90,959

Other operating income, net

(292)

(1,251)

(2,149)

(3,544)

Total operating expenses

59,064

66,440

187,617

208,571

Loss from operations

(59,039)

(66,437)

(187,500)

(172,274)

Interest income, net

6,608

2,251

16,369

3,600

Other income (expense), net

1,578

(1,068)

2,352

(1,047)

Impairment of other investments

(5,000)

(12,923)

(5,000)

Total other income (loss), net

8,186

(3,817)

5,798

(2,447)

Net loss

(50,853)

(70,254)

(181,702)

(174,721)

Other comprehensive loss:

Net unrealized gain (loss) on marketable securities

1,198

(1,645)

6,418

(8,373)

Comprehensive loss

$ (49,655)

$ (71,899)

$ (175,284)

$ (183,094)

Net loss per common share, basic (in dollars per share)

$ (0.20)

$ (0.28)

$ (0.73)

$ (0.71)

Net loss per common share, diluted (in dollars per share)

$ (0.20)

$ (0.28)

$ (0.73)

$ (0.71)

Weighted-average shares used to compute net loss per common share, basic (in shares)

251,318

248,320

250,377

246,285

Weighted-average shares used to compute net loss per common share, diluted (in shares)

251,318

248,320

250,377

246,285

[1]	(1) Including related-party revenue of zero for both the three months ended September 30, 2023 and 2022, and zero and $36,299 for the nine months ended September 30, 2023 and 2022, respectively.

Leases - Narrative (Details) ft² in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2022	Sep. 30, 2021 USD ($) ft²	May 31, 2021 ft²
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 2,300	$ 2,300	$ 6,700	$ 7,000
Variable lease cost	$ 1,300	1,300	$ 4,100	3,800
Weighted average remaining lease term of operating leases	7 years		7 years		7 years 9 months 18 days
Operating lease, weighted average discount rate (as a percent)	8.50%		8.50%		8.50%
South San Francisco, California
Lessee, Lease, Description [Line Items]
Rentable area \| ft²							11
Sublease income	$ 200	200	$ 600	600
Related Party
Lessee, Lease, Description [Line Items]
Rentable area \| ft²						18
Related Party \| Sonoma
Lessee, Lease, Description [Line Items]
Rentable area \| ft²						18
Sublease income	$ 466	$ 465	$ 1,396	$ 1,396
Tenant improvements						$ 4,600

Leases

9 Months Ended

Sep. 30, 2023

Leases [Abstract]

Leases

LeasesThe 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 lease costs and are recognized in the period in which the costs are incurred.

The following table summarizes the Company’s future minimum operating lease commitments, including expected lease incentives to be received, as of September 30, 2023 (in thousands):


Year Ending December 31:
2023 (remaining three months)	$	2,815
2024	11,347
2025	11,859
2026	12,209
2027	12,569
Thereafter	35,525
Total undiscounted lease payments	86,324
Less: imputed interest	(21,687)
Total operating lease liabilities	$	64,637

Reported as of September 30, 2023:
Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities)	$	6,061
Operating lease liabilities, non-current	58,576
Total	$	64,637

The operating lease costs for all operating leases were $2.3 million for both the three months ended September 30, 2023 and 2022, and $6.7 million and $7.0 million for the nine months ended September 30, 2023 and 2022, respectively. The operating lease costs and total commitments for short-term leases were de minimis for the three and nine months ended September 30, 2023 and 2022. Variable lease costs for operating leases were $1.3 million for both the three months ended September 30, 2023 and 2022, and $4.1 million and $3.8 million for the nine months ended September 30, 2023 and 2022, respectively. The weighted-average remaining lease terms for operating leases were 7.0 and 7.8 years as of September 30, 2023 and December 31, 2022, respectively. The weighted‑average discount rates for operating leases were 8.5% as of both September 30, 2023 and December 31, 2022.

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 Company recognized sublease income for this sublease of $0.2 million for both the three months ended September 30, 2023 and 2022, and $0.6 million for both the nine months ended September 30, 2023 and 2022.

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 12, Related-Party Transactions. As a part of the sublease, in September 2021, the Company received a $4.6 million tenant improvement contribution payment, which is recognized over the term of the sublease. The sublease is classified as an operating lease and will expire in March 2031. The Company recognized Sonoma sublease income of $0.5 million for both the three months ended September 30, 2023 and 2022, and $1.4 million for both the nine months ended September 30, 2023 and 2022.

The Company's sublease income is recognized within other operating income, net in the Condensed Consolidated Statements of Operations and Comprehensive Loss.

Leases

The following table summarizes the Company’s future minimum operating lease commitments, including expected lease incentives to be received, as of September 30, 2023 (in thousands):


Year Ending December 31:
2023 (remaining three months)	$	2,815
2024	11,347
2025	11,859
2026	12,209
2027	12,569
Thereafter	35,525
Total undiscounted lease payments	86,324
Less: imputed interest	(21,687)
Total operating lease liabilities	$	64,637

Reported as of September 30, 2023:
Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities)	$	6,061
Operating lease liabilities, non-current	58,576
Total	$	64,637

The Company's sublease income is recognized within other operating income, net in the Condensed Consolidated Statements of Operations and Comprehensive Loss.

Other Investments (Details) $ in Thousands	3 Months Ended		9 Months Ended
Other Investments (Details) $ in Thousands	Sep. 30, 2023 USD ($) entity	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) entity	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) entity	Oct. 01, 2022 USD ($)
Schedule of Investments [Line Items]
Other investments	$ 32,001		$ 32,001		$ 44,924
Variable interest entity, number of entities company is not primary beneficiary \| entity	2		2		2
Variable interest entity maximum loss exposure, amount	$ 13,000		$ 13,000		$ 15,900
Impairment of other investments	0	$ 5,000	12,923	$ 5,000
PACT
Schedule of Investments [Line Items]
Preferred stock at fair value						$ 2,900
Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments [Line Items]
Other investments	13,000		13,000		15,900
Other Investment
Schedule of Investments [Line Items]
Cumulative impairments of strategic investments	$ 17,900		17,900		$ 5,000
Impairment of other investments		$ 5,000	10,000	$ 5,000
Other Investment \| PACT
Schedule of Investments [Line Items]
Preferred stock at fair value						$ 2,900
Impairment of other investments			$ 2,900