0001628280-24-035617 | 10-Q | XBRL Viewer

License, Collaboration, and Success Payment Agreements

6 Months Ended

Jun. 30, 2024

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 $0.1 million in expense in connection with the Fred Hutch Collaboration Agreement for both the three months ended June 30, 2024 and 2023, and $0.2 million and $0.4 million for the six months ended June 30, 2024 and 2023, 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 10 times to 50 times 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 closing of 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 50 times increase in value. Each threshold is associated with a success payment, ascending from $10.0 million at $18.29 per share to $200.0 million at $91.44 per share, payable if such threshold is reached during the measurement period. Any previous success payments made are credited against the success payment owed as of any valuation date, such that Fred Hutch does not receive multiple success payments in connection with the same threshold. The term of the success payment agreement ends on the earlier to occur of (i) the nine-year anniversary of the date of the agreement and (ii) a change in control transaction.

The following table summarizes the aggregate potential success payments, which are payable to Fred Hutch in cash or cash equivalents, or at the Company’s discretion, publicly-tradeable shares of the Company’s common stock:


Multiple of initial equity value at issuance	10x		20x		30x		40x		50x
Per share common stock price required for payment	$	18.29	$	36.58	$	54.86	$	73.15	$	91.44
Aggregate success payment(s) (in millions)	$	10	$	40	$	90	$	140	$	200

The success payments will be owed if the per share fair value of the Company’s common stock on the contractually specified valuation measurement dates during the term of the success payment agreement equals or exceeds the above outlined multiples. The valuation measurement dates are triggered by the following events: the one-year anniversary of the Company’s IPO and each two-year anniversary of the Company’s IPO thereafter, the closing of a change in control transaction and the last day of the term of the success payment agreement, unless the term has ended due to the closing of a change of control transaction. As of June 30, 2024, 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 $0.3 million and $0.7 million as of June 30, 2024 and December 31, 2023, respectively. With respect to the Fred Hutch Collaboration Agreement success payment obligations, the Company recognized a success payment expense reversal of $0.7 million and an expense of $0.5 million for the three months ended June 30, 2024 and 2023, respectively, and expense reversals of $0.3 million and $0.6 million for the six months ended June 30, 2024 and 2023, respectively, which are recognized in other (expense) income, net.

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 $0.7 million in expense in connection with the Stanford Collaboration Agreement for both the three months ended June 30, 2024 and 2023, and $1.5 million for both the six months ended June 30, 2024 and 2023.

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 10 times to 50 times 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 closing of the Company’s IPO. The aggregate success payments to Stanford are not to exceed $200.0 million, which would only occur upon a 50 times increase in value. Each threshold is associated with a success payment, ascending from $10.0 million at $18.29 per share to $200.0 million at $91.44 per share, payable if such threshold is reached during the measurement period. Any previous success payments made are credited against the success payment owed as of any valuation date, so that Stanford does not receive multiple success payments in connection with the same threshold. The term of each success payment agreement ends on the earlier to occur of (i) the nine-year anniversary of the date of the agreement and (ii) a change in control transaction.

The following table summarizes the aggregate potential success payments, which are payable to Stanford in cash or cash equivalents, or at the Company’s discretion, publicly-tradeable shares of the Company’s common stock:


Multiple of initial equity value at issuance	10x		20x		30x		40x		50x
Per share common stock price required for payment	$	18.29	$	36.58	$	54.86	$	73.15	$	91.44
Aggregate success payment(s) (in millions)	$	10	$	40	$	90	$	140	$	200

The estimated fair values of the success payments to Stanford as of June 30, 2024 and December 31, 2023 were $0.7 million and $1.1 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 $0.7 million and $0.9 million as of June 30, 2024 and December 31, 2023, respectively. With respect to the Stanford Collaboration Agreement success payment obligations, the Company recognized a success payment expense reversal of $0.8 million and an expense of $0.6 million for the three months ended June 30, 2024 and 2023, respectively, and an expense reversal of $0.3 million and an expense of approximately zero for the six months ended June 30, 2024 and 2023, respectively.

Related-party Transactions

6 Months Ended

Jun. 30, 2024

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 Sonoma’s board of directors. 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 June 30, 2024 and December 31, 2023, there were accrued liabilities and other current liabilities of $0.5 million and as of June 30, 2024 and December 31, 2023, other non-current liabilities of $2.8 million and $3.0 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 June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Sonoma other operating income, net	$	677	$	648	$	1,484	$	1,317
Sonoma sublease income	$	465	$	464	$	930	$	930

- 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.

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+ Details

Stock-based Compensation - Schedule of Stock-Based Compensation Expense by Classification (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 8,284	$ 14,223	$ 17,439	$ 28,105
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	3,865	5,279	7,657	9,891
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,419	$ 8,944	$ 9,782	$ 18,214

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 133,424	$ 145,647
Marketable securities	357,695	400,576
Prepaid expenses and other current assets	8,705	8,463
Total current assets	499,824	554,686
Restricted cash	287	284
Marketable securities, non-current	0	16,506
Other investments	19,000	32,001
Property and equipment, net	93,096	102,654
Operating lease right-of-use assets	37,696	39,663
Other non-current assets	4,239	4,235
Total assets	654,142	750,029
Current liabilities:
Accounts payable	4,199	4,817
Accrued liabilities and other current liabilities	25,670	28,126
Success payment liabilities	1,010	1,576
Total current liabilities	30,879	34,519
Operating lease liabilities, non-current	53,323	56,894
Other non-current liabilities	3,439	3,664
Total liabilities	87,641	95,077
Commitments and contingencies (Note 11)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 10,000 shares authorized at June 30, 2024 and December 31, 2023; no shares issued and outstanding at June 30, 2024 and December 31, 2023	0	0
Common stock, $0.0001 par value; 500,000 shares authorized at June 30, 2024 and December 31, 2023; 255,948 and 253,958 shares issued and outstanding at June 30, 2024 and December 31, 2023, respectively	26	25
Additional paid-in capital	1,675,460	1,657,133
Accumulated other comprehensive loss	(397)	(94)
Accumulated deficit	(1,108,588)	(1,002,112)
Total stockholders’ equity	566,501	654,952
Total liabilities and stockholders’ equity	$ 654,142	$ 750,029

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Jun. 30, 2024
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

Cash Equivalents and Marketable Securities

6 Months Ended

Jun. 30, 2024

Cash and Cash Equivalents [Abstract]

Cash Equivalents and Marketable Securities

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


	June 30, 2024
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	66,942	$	—	$	—	$	66,942
U.S. Treasury securities	291,040		4		(251)		290,793
U.S. government agency securities	38,651		1		(77)		38,575
Corporate debt securities	81,010		—		(74)		80,936
Total cash equivalents and fixed income marketable securities	$	477,643	$	5	$	(402)	$	477,246


Classified as:	Fair Value
Cash equivalents	$	119,701
Marketable securities	357,545
Marketable securities, non-current	—
Total cash equivalents and fixed income marketable securities	$	477,246


	December 31, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	62,075	$	—	$	—	$	62,075
U.S. Treasury securities	374,214		237		(95)		374,356
U.S. government agency securities	48,924		3		(177)		48,750
Corporate debt securities	59,668		—		(62)		59,606
Total cash equivalents and fixed income marketable securities	$	544,881	$	240	$	(334)	$	544,787


Classified as:	Fair Value
Cash equivalents	$	127,705
Marketable securities	400,576
Marketable securities, non-current	16,506
Total cash equivalents and fixed income marketable securities	$	544,787

The fair values of money market and fixed income marketable securities held by the Company in an unrealized loss position for less than 12 months were $338.2 million and $117.8 million as of June 30, 2024 and December 31, 2023, respectively. The fair values of money market and fixed income marketable securities held by the Company in an unrealized loss position for greater than 12 months were $31.1 million and $43.6 million as of June 30, 2024 and December 31, 2023, respectively. As of June 30, 2024 and December 31, 2023, all of the Company’s money market and fixed income 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 June 30, 2024 and December 31, 2023. As such, an allowance for credit losses has not been recognized. Gross realized gains and losses were de minimis for the three and six months ended June 30, 2024 and 2023 and as a result, amounts reclassified out of accumulated other comprehensive loss for the three and six months ended June 30, 2024 and 2023 were also de minimis. See Note 6, Fair Value Measurements, for additional information regarding cash equivalents and fixed income marketable securities.

License, Collaboration, and Success Payment Agreements (Tables)

6 Months Ended

Jun. 30, 2024

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

Organization	6 Months Ended
Organization	Jun. 30, 2024
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 enhanced with proprietary anti-exhaustion T-cell reprogramming technologies for patients with solid tumors or hematologic malignancies. The Company’s primary activities since incorporation have been to develop T‑cell therapies, conduct 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.

Fair Value Measurements

6 Months Ended

Jun. 30, 2024

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):


	June 30, 2024
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds	$	66,942	$	—	$	—	$	66,942
U.S. Treasury securities	—		290,793		—		290,793
U.S. government agency securities	—		38,575		—		38,575
Corporate debt securities	—		80,936		—		80,936
Marketable equity security	149		—		—		149
Total financial assets	$	67,091	$	410,304	$	—	$	477,395
Financial liabilities:
Success payment liabilities	$	—	$	—	$	1,010	$	1,010
Total financial liabilities	$	—	$	—	$	1,010	$	1,010


	December 31, 2023
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds	$	62,075	$	—	$	—	$	62,075
U.S. Treasury securities	—		374,356		—		374,356
U.S. government agency securities	—		48,750		—		48,750
Corporate debt securities	—		59,606		—		59,606
Total financial assets	$	62,075	$	482,712	$	—	$	544,787
Financial liabilities:
Success payment liabilities	$	—	$	—	$	1,576	$	1,576
Total financial liabilities	$	—	$	—	$	1,576	$	1,576

The Company measures the fair value of money market funds based on quoted prices in active markets for identical assets or liabilities. The Company measures the fair value of marketable equity securities traded in active markets based on quoted prices of identical assets. 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 marketable equity security relates to a company that began being publicly traded on the Nasdaq Global Market in February 2024 and had a fair value of $0.1 million as of June 30, 2024. The Company recorded unrealized losses of $1.4 million and zero for the three months ended June 30, 2024 and 2023, respectively, and unrealized gains of $0.1 million and zero for the six months ended June 30, 2024 and 2023, respectively, within other (expense) income, net in the Company’s Condensed Consolidated Statement of Operations and Comprehensive Loss. Prior to being publicly traded, as of December 31, 2023, the investment was fully impaired and classified in the Company’s Condensed Consolidated Balance Sheet as other investments.

The Company’s success payment liabilities are Level 3 financial instruments, which were estimated using Monte Carlo simulations through December 31, 2023. 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 Monte Carlo simulation to determine 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. As of June 30, 2024, success payment liabilities were estimated by management using its historical experience of the correlation of success payment fair values relative to the Company’s stock price.

The following assumptions were incorporated into the calculation of the estimated fair value of the Fred Hutch and Stanford success payment liabilities as of December 31, 2023:


	Fred Hutch			Stanford
Fair value of common stock	$	1.94		$	1.94
Risk-free interest rate	3.51% - 5.19%			3.51% - 5.19%
Expected volatility	80.0		%	80.0		%
Expected term (in years)	0.46 - 3.97			0.46 - 5.75

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 financial liabilities (in thousands):


	Success Payment Liabilities
Balance at December 31, 2023	$	1,576
Change in fair value (1)	(566)
Balance at June 30, 2024	$	1,010

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

- 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.

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-URI https://asc.fasb.org/1943274/2147478119/940-820-50-1

+ Details

Stockholders' Equity	6 Months Ended
Stockholders' Equity	Jun. 30, 2024
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 June 30, 2024 and December 31, 2023, 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 June 30, 2024 and December 31, 2023, there were 255,948,333 shares and 253,957,709 shares of the Company’s common stock outstanding, respectively. On February 28, 2024, the Company entered into a sales agreement with Cowen and Company, LLC (“Cowen”) acting as the Company’s sales agent (the “Sales Agreement”), pursuant to which the Company may offer and sell shares of common stock having an aggregate offering price of up to $150.0 million from time to time in a series of one or more at‑the‑market equity offerings. The Company will pay Cowen commissions of up to 3.0% of the gross proceeds of the sale, and reimbursement of certain expenses, under this agreement. Neither the Company nor Cowen is obligated to sell any shares and, to date, the Company has not made any sales under the Sales Agreement.

- Definition

The entire disclosure for equity.

+ References

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+ Details

Cover - shares	6 Months Ended
Cover - shares	Jun. 30, 2024	Aug. 02, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2024
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		256,003,113
Entity Central Index Key	0001806952
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Amendment Flag	false

Related-party Transactions - Narrative (Details) ft² in Thousands, $ in Thousands	Jun. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)	Sep. 30, 2021 USD ($) ft²
Related Party Transaction [Line Items]
Accrued liabilities and other current liabilities	$ 25,670	$ 28,126
Other non-current liabilities	3,439	3,664
Related Party
Related Party Transaction [Line Items]
Rentable area (in square feet) \| ft²			18
Related Party \| Sonoma
Related Party Transaction [Line Items]
Rentable area (in square feet) \| ft²			18
Tenant improvements			$ 4,600
Accrued liabilities and other current liabilities	500	500
Other non-current liabilities	$ 2,800	$ 3,000

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, 2022		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)		833,000
Issuance of common stock upon exercise of stock options	83		83
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)		84,000
Issuance of common stock in connection with restricted stock units, net of tax	(119)		(119)
Stock-based compensation	28,105		28,105
Other comprehensive income (loss)	5,220			5,220
Net loss	(130,849)				(130,849)
Ending balance (in shares) at Jun. 30, 2023		251,027,000
Ending balance at Jun. 30, 2023	736,855	$ 25	1,637,538	(2,379)	(898,329)
Beginning balance (in shares) at Mar. 31, 2023		249,609,000
Beginning balance at Mar. 31, 2023	783,826	$ 25	1,622,119	(3,879)	(834,439)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		833,000
Issuance of common stock upon exercise of stock options	$ 83		83
Issuance of common stock under employee stock purchase plan (in shares)	543,000
Issuance of common stock under employee stock purchase plan	$ 1,163
Issuance of common stock in connection with restricted stock units, net of tax (in shares)		42,000
Issuance of common stock in connection with restricted stock units, net of tax	(50)		(50)
Stock-based compensation	14,223		14,223
Other comprehensive income (loss)	1,500			1,500
Net loss	(63,890)				(63,890)
Ending balance (in shares) at Jun. 30, 2023		251,027,000
Ending balance at Jun. 30, 2023	$ 736,855	$ 25	1,637,538	(2,379)	(898,329)
Beginning balance (in shares) at Dec. 31, 2023	253,957,709	253,958,000
Beginning balance at Dec. 31, 2023	$ 654,952	$ 25	1,657,133	(94)	(1,002,112)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)	1,245,836	1,246,000
Issuance of common stock upon exercise of stock options	$ 155	$ 1	154
Issuance of common stock under employee stock purchase plan (in shares)		491,000
Issuance of common stock under employee stock purchase plan	810		810
Issuance of common stock in connection with restricted stock units, net of tax (in shares)		253,000
Issuance of common stock in connection with restricted stock units, net of tax	(76)		(76)
Stock-based compensation	17,439		17,439
Other comprehensive income (loss)	(303)			(303)
Net loss	$ (106,476)				(106,476)
Ending balance (in shares) at Jun. 30, 2024	255,948,333	255,948,000
Ending balance at Jun. 30, 2024	$ 566,501	$ 26	1,675,460	(397)	(1,108,588)
Beginning balance (in shares) at Mar. 31, 2024		254,927,000
Beginning balance at Mar. 31, 2024	603,157	$ 25	1,666,315	(404)	(1,062,779)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		377,000
Issuance of common stock upon exercise of stock options	52	$ 1	51
Issuance of common stock under employee stock purchase plan (in shares)		491,000
Issuance of common stock under employee stock purchase plan	810		810
Issuance of common stock in connection with restricted stock units, net of tax (in shares)		153,000
Stock-based compensation	8,284		8,284
Other comprehensive income (loss)	7			7
Net loss	$ (45,809)				(45,809)
Ending balance (in shares) at Jun. 30, 2024	255,948,333	255,948,000
Ending balance at Jun. 30, 2024	$ 566,501	$ 26	$ 1,675,460	$ (397)	$ (1,108,588)

Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2024

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 June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development	$	3,865	$	5,279	$	7,657	$	9,891
General and administrative	4,419		8,944		9,782		18,214
Total stock-based compensation expense	$	8,284	$	14,223	$	17,439	$	28,105

Schedule of PSU Activity

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


	Performance-Based Restricted Stock Units Outstanding	Weighted-Average Value at Grant Date Per Share
Unvested PSUs as of December 31, 2023	—	$	—
PSUs granted(1)	2,703,400	$	1.88
PSUs vested	—	$	—
PSUs forfeited or canceled	—	$	—
Unvested PSUs as of June 30, 2024	2,703,400	$	1.88

(1) PSU grants reflect the target number of shares eligible to be earned at the time of grant.

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, 2023	2,072,855	$	2.96
RSUs granted	3,622,426	$	1.84
RSUs vested	(295,570)	$	3.41
RSUs forfeited or canceled	(225,914)	$	2.07
Unvested RSUs as of June 30, 2024	5,173,797	$	2.19

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, 2023	55,596,831	$	4.75	6.89	$	7,368
Granted	3,405,500	$	1.97
Exercised	(1,245,836)	$	0.12
Canceled or forfeited	(12,044,059)	$	6.74
Options outstanding as of June 30, 2024	45,712,436	$	4.14	7.33	$	3,696
Options exercisable as of June 30, 2024	26,720,167	$	4.71	6.42	$	3,696

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

The fair value of stock options granted to employees and directors was estimated on the date of grant using the Black-Scholes option pricing model using the following weighted-average assumptions:


	Six Months Ended June 30,
	2024		2023
Risk-free interest rate	4.17	%	4.09	%
Expected volatility	76.0	%	92.4	%
Expected term (in years)	5.90		5.99
Expected dividend yield	0	%	0	%

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Pay vs Performance Disclosure
Net loss	$ (45,809)	$ (63,890)	$ (106,476)	$ (130,849)

- Definition

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

+ References

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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Cash Equivalents and Marketable Securities - Schedule of Fair Value and Amortized Cost of Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Marketable Securities [Line Items]
Amortized Cost	$ 477,643	$ 544,881
Gross Unrealized Gains	5	240
Gross Unrealized Losses	(402)	(334)
Fair Value	477,246	544,787
Classified as:
Fair Value	477,246	544,787
Cash equivalents
Marketable Securities [Line Items]
Fair Value	119,701	127,705
Classified as:
Fair Value	119,701	127,705
Marketable securities
Marketable Securities [Line Items]
Fair Value	357,545	400,576
Classified as:
Fair Value	357,545	400,576
Marketable securities, non-current
Marketable Securities [Line Items]
Fair Value	0	16,506
Classified as:
Fair Value	0	16,506
Money market funds
Marketable Securities [Line Items]
Amortized Cost	66,942	62,075
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	66,942	62,075
Classified as:
Fair Value	66,942	62,075
U.S. Treasury securities
Marketable Securities [Line Items]
Amortized Cost	291,040	374,214
Gross Unrealized Gains	4	237
Gross Unrealized Losses	(251)	(95)
Fair Value	290,793	374,356
Classified as:
Fair Value	290,793	374,356
U.S. government agency securities
Marketable Securities [Line Items]
Amortized Cost	38,651	48,924
Gross Unrealized Gains	1	3
Gross Unrealized Losses	(77)	(177)
Fair Value	38,575	48,750
Classified as:
Fair Value	38,575	48,750
Corporate debt securities
Marketable Securities [Line Items]
Amortized Cost	81,010	59,668
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(74)	(62)
Fair Value	80,936	59,606
Classified as:
Fair Value	$ 80,936	$ 59,606

Related-party Transactions (Tables)

6 Months Ended

Jun. 30, 2024

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 June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Sonoma other operating income, net	$	677	$	648	$	1,484	$	1,317
Sonoma sublease income	$	465	$	464	$	930	$	930

Leases - Schedule of Operating Lease Commitments Including Expected Lease Incentives to be Received (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Leases [Abstract]
2024 (remaining six months)	$ 5,796
2025	11,859
2026	12,209
2027	12,569
2028	12,940
Thereafter	22,585
Total undiscounted lease payments	77,958
Less: imputed interest	(17,737)
Total operating lease liabilities	60,221
Operating Lease Liability
Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities)	6,898
Operating lease liabilities, non-current	53,323	$ 56,894
Total	$ 60,221

Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	Feb. 28, 2024	Jun. 30, 2024	Dec. 31, 2023
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)		255,948,333	253,957,709
Cowen and Company, LLC \| At The Market Offering
Class of Stock [Line Items]
Sale of stock, maximum aggregate offering amount	$ 150.0
Commissions payment, percentage of gross sale proceeds	3.00%

Other Investments (Details) $ in Thousands	3 Months Ended		6 Months Ended
Other Investments (Details) $ in Thousands	Jun. 30, 2024 USD ($) entity	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) entity	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($) entity
Schedule of Investments [Line Items]
Other investments	$ 19,000		$ 19,000		$ 32,001
Variable interest entity, number of entities company is not primary beneficiary \| entity	1		1		1
Variable interest entity maximum loss exposure, amount	$ 0		$ 0		$ 13,000
Impairment of other investments	0	$ 2,923	13,001	$ 12,923
Variable Interest Entity, Not Primary Beneficiary
Schedule of Investments [Line Items]
Other investments	0		0		13,000
Other Investment
Schedule of Investments [Line Items]
Cumulative impairments of strategic investments	23,000		23,000		$ 15,000
Impairment of other investments	$ 0	$ 2,900	$ 13,000	$ 12,900

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reference 49: http://www.xbrl.org/2003/role/disclosureRef
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Reference 58: http://www.xbrl.org/2003/role/disclosureRef
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Reference 65: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 19
-Subparagraph (3)
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-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-19

+ Details

Net Loss Per Share	6 Months Ended
Net Loss Per Share	Jun. 30, 2024
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 RSUs, unvested PSUs 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 RSUs and unvested PSUs were all excluded from consideration in the calculation of diluted net loss per share in all periods presented due to their anti-dilutive effects.

Cash Equivalents and Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2024

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 fixed income marketable securities by major security type are as follows (in thousands):


	June 30, 2024
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	66,942	$	—	$	—	$	66,942
U.S. Treasury securities	291,040		4		(251)		290,793
U.S. government agency securities	38,651		1		(77)		38,575
Corporate debt securities	81,010		—		(74)		80,936
Total cash equivalents and fixed income marketable securities	$	477,643	$	5	$	(402)	$	477,246


Classified as:	Fair Value
Cash equivalents	$	119,701
Marketable securities	357,545
Marketable securities, non-current	—
Total cash equivalents and fixed income marketable securities	$	477,246


	December 31, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	62,075	$	—	$	—	$	62,075
U.S. Treasury securities	374,214		237		(95)		374,356
U.S. government agency securities	48,924		3		(177)		48,750
Corporate debt securities	59,668		—		(62)		59,606
Total cash equivalents and fixed income marketable securities	$	544,881	$	240	$	(334)	$	544,787


Classified as:	Fair Value
Cash equivalents	$	127,705
Marketable securities	400,576
Marketable securities, non-current	16,506
Total cash equivalents and fixed income marketable securities	$	544,787

Schedule of Fair Value and Amortized Cost of Marketable Securities

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


	June 30, 2024
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	66,942	$	—	$	—	$	66,942
U.S. Treasury securities	291,040		4		(251)		290,793
U.S. government agency securities	38,651		1		(77)		38,575
Corporate debt securities	81,010		—		(74)		80,936
Total cash equivalents and fixed income marketable securities	$	477,643	$	5	$	(402)	$	477,246


Classified as:	Fair Value
Cash equivalents	$	119,701
Marketable securities	357,545
Marketable securities, non-current	—
Total cash equivalents and fixed income marketable securities	$	477,246


	December 31, 2023
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses		Fair Value
Money market funds	$	62,075	$	—	$	—	$	62,075
U.S. Treasury securities	374,214		237		(95)		374,356
U.S. government agency securities	48,924		3		(177)		48,750
Corporate debt securities	59,668		—		(62)		59,606
Total cash equivalents and fixed income marketable securities	$	544,881	$	240	$	(334)	$	544,787


Classified as:	Fair Value
Cash equivalents	$	127,705
Marketable securities	400,576
Marketable securities, non-current	16,506
Total cash equivalents and fixed income marketable securities	$	544,787

- 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
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-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
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-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
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

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

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-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
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

Stock-based Compensation - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Number of Stock Options
Beginning balance (in shares)	55,596,831	55,596,831
Granted (in shares)		3,405,500
Exercised (in shares)		(1,245,836)
Canceled or forfeited (in shares)		(12,044,059)
Ending balance (in shares)		45,712,436
Exercisable (in shares)		26,720,167
Weighted- Average Exercise Price Per Share
Beginning balance (in dollars per share)	$ 4.75	$ 4.75
Granted (in dollars per share)		1.97
Exercised (in dollars per share)		0.12
Cancelled or forfeited (in dollars per share)		6.74
Ending balance (in dollars per share)		4.14
Exercisable (in dollars per share)		$ 4.71
Weighted- Average Remaining Contractual Life (in years)
Options Outstanding	6 years 10 months 20 days	7 years 3 months 29 days
Options Exercisable		6 years 5 months 1 day
Aggregate Intrinsic Value (in thousands)
Options Outstanding		$ 3,696	$ 7,368
Options Exercisable		$ 3,696

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2024

Fair Value Disclosures [Abstract]

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


	June 30, 2024
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds	$	66,942	$	—	$	—	$	66,942
U.S. Treasury securities	—		290,793		—		290,793
U.S. government agency securities	—		38,575		—		38,575
Corporate debt securities	—		80,936		—		80,936
Marketable equity security	149		—		—		149
Total financial assets	$	67,091	$	410,304	$	—	$	477,395
Financial liabilities:
Success payment liabilities	$	—	$	—	$	1,010	$	1,010
Total financial liabilities	$	—	$	—	$	1,010	$	1,010


	December 31, 2023
	Level 1		Level 2		Level 3		Total
Financial assets:
Money market funds	$	62,075	$	—	$	—	$	62,075
U.S. Treasury securities	—		374,356		—		374,356
U.S. government agency securities	—		48,750		—		48,750
Corporate debt securities	—		59,606		—		59,606
Total financial assets	$	62,075	$	482,712	$	—	$	544,787
Financial liabilities:
Success payment liabilities	$	—	$	—	$	1,576	$	1,576
Total financial liabilities	$	—	$	—	$	1,576	$	1,576

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 and Stanford success payment liabilities as of December 31, 2023:


	Fred Hutch			Stanford
Fair value of common stock	$	1.94		$	1.94
Risk-free interest rate	3.51% - 5.19%			3.51% - 5.19%
Expected volatility	80.0		%	80.0		%
Expected term (in years)	0.46 - 3.97			0.46 - 5.75

Schedule of Changes in the Estimated Fair Value of Level 3 Financial Liabilities

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


	Success Payment Liabilities
Balance at December 31, 2023	$	1,576
Change in fair value (1)	(566)
Balance at June 30, 2024	$	1,010

Leases - Narrative (Details) ft² in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2023	Sep. 30, 2021 USD ($) ft²	May 31, 2021 ft²
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 2,300	$ 2,300	$ 4,600	$ 4,400
Variable lease cost	$ 1,600	1,400	$ 3,900	2,800
Weighted average remaining lease term of operating leases	6 years 3 months 18 days		6 years 3 months 18 days		6 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 (in square feet) \| ft²							11
Sublease income	$ 200	200	$ 400	400
Related Party
Lessee, Lease, Description [Line Items]
Rentable area (in square feet) \| ft²						18
Related Party \| Sonoma
Lessee, Lease, Description [Line Items]
Rentable area (in square feet) \| ft²						18
Sublease income	$ 465	$ 464	$ 930	$ 930
Tenant improvements						$ 4,600

Leases

6 Months Ended

Jun. 30, 2024

Leases [Abstract]

Leases

The Company’s lease portfolio is comprised of operating leases for laboratory, office and manufacturing facilities located in South San Francisco, California, and Seattle and Bothell, Washington with contractual periods expiring between December 2028 and March 2031. In addition to minimum rent, the leases require payment of real estate taxes, insurance, common area maintenance charges and other executory costs. These additional charges are considered variable 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 as of June 30, 2024 (in thousands):


Year Ending December 31:
2024 (remaining six months)	$	5,796
2025	11,859
2026	12,209
2027	12,569
2028	12,940
Thereafter	22,585
Total undiscounted lease payments	77,958
Less: imputed interest	(17,737)
Total operating lease liabilities	$	60,221

Reported as of June 30, 2024:
Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities)	$	6,898
Operating lease liabilities, non-current	53,323
Total	$	60,221

The operating lease costs for all operating leases were $2.3 million for both the three months ended June 30, 2024 and 2023, and $4.6 million and $4.4 million for the six months ended June 30, 2024 and 2023, respectively. The operating lease costs and total commitments for short-term leases were de minimis for the three and six months ended June 30, 2024 and 2023. Variable lease costs for operating leases were $1.6 million and $1.4 million for the three months ended June 30, 2024 and 2023, respectively, and $3.9 million and $2.8 million for the six months ended June 30, 2024 and 2023, respectively. The weighted-average remaining lease terms for operating leases were 6.3 and 6.8 years as of June 30, 2024 and December 31, 2023, respectively. The weighted‑average discount rate for operating leases was 8.5% as of both June 30, 2024 and December 31, 2023.

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 June 30, 2024 and 2023, and $0.4 million for both the six months ended June 30, 2024 and 2023.

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 June 30, 2024 and 2023, and $0.9 million for both the six months ended June 30, 2024 and 2023.

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 as of June 30, 2024 (in thousands):


Year Ending December 31:
2024 (remaining six months)	$	5,796
2025	11,859
2026	12,209
2027	12,569
2028	12,940
Thereafter	22,585
Total undiscounted lease payments	77,958
Less: imputed interest	(17,737)
Total operating lease liabilities	$	60,221

Reported as of June 30, 2024:
Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities)	$	6,898
Operating lease liabilities, non-current	53,323
Total	$	60,221

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

Fair Value Measurements - Schedule of Changes in Estimated Fair Value of Financial Liabilities (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2024 USD ($)
Success Payment Liabilities
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other (expense) income, net, Research and development
Level 3 \| Success Payment Liabilities
Success Payment Liabilities
Beginning Balance	$ 1,576
Change in fair value	(566)
Ending Balance	$ 1,010

Fair Value Measurements - Schedule of Estimated Fair Value of Success Payment Liability Assumptions (Details)	Dec. 31, 2023 yr $ / shares
Fred Hutch
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of common stock (USD per share) \| $ / shares	$ 1.94
Fred Hutch \| Risk-free interest rate \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.0351
Fred Hutch \| Risk-free interest rate \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.0519
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
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)	0.46
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)	3.97
Stanford
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of common stock (USD per share) \| $ / shares	$ 1.94
Stanford \| Risk-free interest rate \| Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.0351
Stanford \| Risk-free interest rate \| Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success payment liability, measurement input (as a percent)	0.0519
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
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)	0.46
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)	5.75

Related-party Transactions - Schedule of Total Income Attributable to Sonoma Sublease (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Related Party Transaction [Line Items]
Sonoma other operating income, net	$ 976	$ 569	$ 2,066	$ 1,857
Related Party \| Sonoma
Related Party Transaction [Line Items]
Sonoma other operating income, net	677	648	1,484	1,317
Sonoma sublease income	$ 465	$ 464	$ 930	$ 930

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2024	Dec. 31, 2023
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)	255,948,000	253,958,000
Common stock outstanding (in shares)	255,948,333	253,957,709

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (106,476)	$ (130,849)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	17,439	28,105
Impairment of other investments	13,001	12,923
Depreciation and amortization expense	9,925	10,089
Net amortization and accretion on marketable securities	(8,129)	(3,925)
Gain on marketable equity security	(149)	0
Change in fair value of success payment liabilities	(566)	(603)
Non-cash lease income	(979)	(816)
Loss on property and equipment disposals, net	15	430
Changes in operating assets and liabilities:
Prepaid expenses, other current assets and other assets	(246)	641
Accounts payable	(630)	2,449
Accrued liabilities and other current liabilities	(3,090)	(3,592)
Other non-current liabilities	(225)	(225)
Net cash used in operating activities	(80,110)	(85,373)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchases of property and equipment	(361)	(2,466)
Purchases of marketable securities	(224,475)	(141,815)
Maturities of marketable securities	291,837	329,347
Net cash provided by investing activities	67,001	185,066
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from exercise of stock options	155	83
Proceeds from employee stock purchase plan	810	1,163
Taxes paid related to net share settlement of equity awards	(76)	(119)
Net cash provided by financing activities	889	1,127
Net (decrease) increase in cash, cash equivalents and restricted cash	(12,220)	100,820
Cash, cash equivalents and restricted cash at beginning of period	145,931	123,834
Cash, cash equivalents and restricted cash at end of period	133,711	224,654
Represented by:
Cash and cash equivalents	133,424	224,372
Restricted cash	287	282
Total	133,711	224,654
SUPPLEMENTAL CASH FLOW INFORMATION
Cash paid for amounts included in the measurement of lease liabilities	5,551	5,215
Non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued liabilities	$ 50	$ 33

Other Investments	6 Months Ended
Other Investments	Jun. 30, 2024
Investments, All Other Investments [Abstract]
Other Investments	Other Investments In prior years the Company made minority ownership strategic investments. As of June 30, 2024 and December 31, 2023, the aggregate carrying amount of the Company’s strategic investments in non-publicly traded companies was $19.0 million and $32.0 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 June 30, 2024 and December 31, 2023 were $23.0 million and $15.0 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 both June 30, 2024 and December 31, 2023, the Company held an interest in one entity that was concluded to be a variable interest for which the Company was not the primary beneficiary as the Company did not have the power to direct the activities that most significantly impact the economic performance of the variable interest entity. As of June 30, 2024 and December 31, 2023, the carrying value and maximum exposure to loss of the Company’s variable interests were zero and $13.0 million, respectively, which are recorded in other investments in the Company’s Condensed Consolidated Balance Sheets. In connection with the preparation of the financial statements for the three and six months ended June 30, 2024 and 2023, the Company performed a qualitative assessment of potential indicators of impairment and determined that indicators existed for certain of its other investments with carrying amounts of zero and $2.9 million for the three months ended June 30, 2024 and 2023, respectively, and $13.0 million and $12.9 million for the six months ended June 30, 2024 and 2023, respectively. During the six months ended June 30, 2024, the anticipated funding for one of its other investments was not secured within the expected timeframe. The Company considered all of 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 impairment expenses of zero and $2.9 million for one investment for the three months ended June 30, 2024 and 2023, respectively. Additionally, the Company recorded impairment expenses of $13.0 million for one investment and $12.9 million for two investments for the six months ended June 30, 2024 and 2023, respectively. The impairment expenses were recorded within impairment of other investments on the Condensed Consolidated Statements of Operations and Comprehensive Loss and as a reduction to the investment balances within other investments on the Condensed Consolidated Balance Sheets.

Leases (Tables)

6 Months Ended

Jun. 30, 2024

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 as of June 30, 2024 (in thousands):


Year Ending December 31:
2024 (remaining six months)	$	5,796
2025	11,859
2026	12,209
2027	12,569
2028	12,940
Thereafter	22,585
Total undiscounted lease payments	77,958
Less: imputed interest	(17,737)
Total operating lease liabilities	$	60,221

Reported as of June 30, 2024:
Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities)	$	6,898
Operating lease liabilities, non-current	53,323
Total	$	60,221

Schedule of Current and Non-current Lease Liabilities

The following table summarizes the Company’s future minimum operating lease commitments as of June 30, 2024 (in thousands):


Year Ending December 31:
2024 (remaining six months)	$	5,796
2025	11,859
2026	12,209
2027	12,569
2028	12,940
Thereafter	22,585
Total undiscounted lease payments	77,958
Less: imputed interest	(17,737)
Total operating lease liabilities	$	60,221

Reported as of June 30, 2024:
Short-term portion of lease liabilities (included in accrued liabilities and other current liabilities)	$	6,898
Operating lease liabilities, non-current	53,323
Total	$	60,221

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Financial assets:
Marketable securities	$ 477,246	$ 544,787
Marketable equity security	149
Total financial assets	477,395	544,787
Financial liabilities:
Success payment liabilities	1,010	1,576
Total financial liabilities	1,010	1,576
U.S. Treasury securities
Financial assets:
Marketable securities	290,793	374,356
U.S. government agency securities
Financial assets:
Marketable securities	38,575	48,750
Corporate debt securities
Financial assets:
Marketable securities	80,936	59,606
Money market funds
Financial assets:
Money market funds	66,942	62,075
Level 1
Financial assets:
Marketable equity security	149
Total financial assets	67,091	62,075
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	66,942	62,075
Level 2
Financial assets:
Marketable equity security	0
Total financial assets	410,304	482,712
Financial liabilities:
Success payment liabilities	0	0
Total financial liabilities	0	0
Level 2 \| U.S. Treasury securities
Financial assets:
Marketable securities	290,793	374,356
Level 2 \| U.S. government agency securities
Financial assets:
Marketable securities	38,575	48,750
Level 2 \| Corporate debt securities
Financial assets:
Marketable securities	80,936	59,606
Level 2 \| Money market funds
Financial assets:
Money market funds	0	0
Level 3
Financial assets:
Marketable equity security	0
Total financial assets	0	0
Financial liabilities:
Success payment liabilities	1,010	1,576
Total financial liabilities	1,010	1,576
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 Performance Shares Units (Details) - Performance Shares	6 Months Ended
	Jun. 30, 2024 $ / shares shares
Performance-Based Restricted Stock Units Outstanding
Balance at beginning of period (in shares) \| shares	0
PSUs granted (in shares) \| shares	2,703,400
PSUs vested (in shares) \| shares	0
PSUs forfeited or canceled (in shares) \| shares	0
Balance at end of period (in shares) \| shares	2,703,400
Weighted-Average Value at Grant Date Per Share
Balance at beginning of period (in dollars per share) \| $ / shares	$ 0
PSUs granted (in dollars per share) \| $ / shares	1.88
PSUs vested (in dollars per share) \| $ / shares	0
PSUs forfeited or canceled (in dollars per share) \| $ / shares	0
Balance at end of period (in dollars per share) \| $ / shares	$ 1.88

Stock-based Compensation

6 Months Ended

Jun. 30, 2024

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, 2024, the Company reserved an additional 12,697,885 shares of common stock for issuance under the 2021 Plan representing 5% of the total common shares outstanding as of December 31, 2023. Under the 2021 Plan, the Company may grant incentive stock options, non-statutory stock options, restricted stock awards (“RSAs”), restricted stock units (“RSUs”), PSUs, 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, option and RSU awards granted by the Company vest over four years but may be granted with different vesting terms. PSUs generally vest over three years, subject to the achievement of the associated performance conditions. In conjunction with adopting the 2021 Plan, the Company discontinued the 2018 Plan with respect to new equity awards.

As of June 30, 2024, 41,668,968 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. On January 1, 2024, the Company reserved an additional 2,539,577 shares of common stock for issuance under the 2021 ESPP representing 1% of the total common shares outstanding as of December 31, 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, 491,303 shares were issued for the three and six months ended June 30, 2024 and 542,921 shares for the three and six months ended June 30, 2023.

As of June 30, 2024, 5,509,903 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 June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development	$	3,865	$	5,279	$	7,657	$	9,891
General and administrative	4,419		8,944		9,782		18,214
Total stock-based compensation expense	$	8,284	$	14,223	$	17,439	$	28,105

At June 30, 2024, total stock-based compensation cost related to unvested awards not yet recognized was $59.0 million, which is expected to be recognized over a remaining weighted-average period of 2.6 years.

Stock Options Repricing

In November 2023, the Board of Directors of the Company approved, effective November 16, 2023, a one-time repricing of certain stock option awards that had been granted to date under the 2021 Plan and 2018 Plan. The repricing impacted stock options with exercise prices greater than $2.37 held by employees who remained employed as of November 16, 2023 and were not impacted by the Company’s November 2023 reduction in workforce. The original exercise prices of the repriced stock options ranged from $2.61 to $17.95 per share for 200 total grantees with 23,416,860 shares repriced. Each stock option was repriced to have a per share exercise price of $1.87, which was the closing price of the Company’s common stock on November 16, 2023. To receive the new exercise price, option holders must remain employed with the Company through November 15, 2024. Additionally, the vesting schedule for the unvested shares underlying repriced stock options held by executives at the level of senior vice president and above was extended for an additional year. There were no changes to the vesting schedules for employees below the level of senior vice president. No changes were made to the expiration dates of, or the number of shares underlying, the repriced stock options. Incremental stock-based compensation expense resulting from the repricing was $8.9 million in the aggregate. Expense for vested awards will be recognized through November 15, 2024 and expense for unvested awards will be recognized over the remaining service life of the option.

Performance-Based Restricted Stock Units

During the six months ended June 30, 2024, the Company granted PSU awards to certain key employees. PSUs awarded to employees have a three-year performance period and vest based upon the Company’s performance against a two and three-year relative total shareholder return (“rTSR”) metric, as well as upon the achievement of certain clinical development milestones. None of the clinical development milestones were probable of achievement as of June 30, 2024.

For the portion of PSUs subject to certain clinical development milestones (other than the bonus clinical development milestone), 50% vest upon the achievement of the applicable milestone, and the remaining 50% vest upon the earlier of (a) one year of service from the date of such achievement and (b) the end of the three-year performance period. The vesting of all PSU awards granted is also subject to the respective employee’s continued employment. The Company valued the portion of PSUs subject to the rTSR metric using a Monte Carlo simulation. The number of PSUs granted subject to the rTSR metrics represents the target number of units that are eligible to be earned based on the achievement of the metrics established at the beginning of the performance period, which ends on December 31st of the three year performance period. For the portion of PSUs subject to the rTSR metrics, employees may ultimately earn between zero and 200% of the target number of PSUs granted based on the degree of achievement of the applicable rTSR metric. Accordingly, additional PSUs may be issued or currently outstanding PSUs may be cancelled upon final determination of the number of units earned.

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


	Performance-Based Restricted Stock Units Outstanding	Weighted-Average Value at Grant Date Per Share
Unvested PSUs as of December 31, 2023	—	$	—
PSUs granted(1)	2,703,400	$	1.88
PSUs vested	—	$	—
PSUs forfeited or canceled	—	$	—
Unvested PSUs as of June 30, 2024	2,703,400	$	1.88

(1) PSU grants reflect the target number of shares eligible to be earned at the time of grant.

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, 2023	2,072,855	$	2.96
RSUs granted	3,622,426	$	1.84
RSUs vested	(295,570)	$	3.41
RSUs forfeited or canceled	(225,914)	$	2.07
Unvested RSUs as of June 30, 2024	5,173,797	$	2.19

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, 2023	55,596,831	$	4.75	6.89	$	7,368
Granted	3,405,500	$	1.97
Exercised	(1,245,836)	$	0.12
Canceled or forfeited	(12,044,059)	$	6.74
Options outstanding as of June 30, 2024	45,712,436	$	4.14	7.33	$	3,696
Options exercisable as of June 30, 2024	26,720,167	$	4.71	6.42	$	3,696

The fair value of stock options granted to employees and directors was estimated on the date of grant using the Black-Scholes option pricing model using the following weighted-average assumptions:


	Six Months Ended June 30,
	2024		2023
Risk-free interest rate	4.17	%	4.09	%
Expected volatility	76.0	%	92.4	%
Expected term (in years)	5.90		5.99
Expected dividend yield	0	%	0	%

The weighted-average grant date fair value of options granted for the six months ended June 30, 2024 and 2023 were $1.35 per share and $1.72 per share, respectively.

Summary of Significant Accounting Policies (Policies)	6 Months Ended
Summary of Significant Accounting Policies (Policies)	Jun. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation	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.
Consolidations	All significant intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of the unaudited 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 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.
Concentrations of Credit Risk	Concentrations of Credit Risk and Off-balance Sheet Risk The Company maintains its cash, cash equivalents and restricted cash with high quality, accredited financial institutions. 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. 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, 2023, except as set forth below regarding the Company’s stock-based compensation policy for performance-based restricted stock units (“PSUs”).
Stock-based Compensation	Stock-based Compensation Under ASC 718, the Company measures and recognizes expense for PSUs that settle in stock. The Company granted PSUs that vest upon the achievement of certain performance conditions to certain key employees. For awards with performance conditions that do not vest unless a performance condition is met, the Company recognizes expense if, and to the extent that, the Company estimates that the achievement of the performance condition is probable. At each reporting date, the Company is required to evaluate whether achievement of a performance condition is probable. Compensation expense is recorded over the appropriate service period based upon the Company’s assessment of accomplishing each performance condition. The fair values of the Company’s PSUs that have market-based metrics are estimated using Monte Carlo simulations. The Company applies an accelerated attribution method to recognize stock-based compensation expense over the applicable service period for these awards. The number of shares expected to be earned is considered in the grant date valuation; therefore, the expense is not subsequently adjusted to reflect the actual shares ultimately earned. The fair values of PSUs that do not have market-based metrics are based upon the grant date stock price. Compensation expense is recognized for the number of shares expected to be earned after assessing the probability that a certain performance condition will be met and the targeted payout level associated with the performance condition expected to be achieved. Cumulative adjustments are recorded each quarter to reflect the estimated outcome of the performance-related conditions until the date results are determined and settled. If performance conditions are not met or not expected to be met, any compensation expense previously recognized associated with the awards will be reversed.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted None. Not Yet Adopted Segment Reporting In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which expands required disclosures about a public entity’s reportable segments and requires more enhanced information about a reportable segment’s expenses, interim segment profit or loss, and how a public entity’s chief operating decision maker uses reported segment profit or loss information in assessing segment performance and allocating resources. Entities with a single reportable segment are required to provide all the updated and existing segment disclosures required by Topic 280. The amendments are effective for annual periods beginning after December 15, 2023 and interim periods within fiscal years beginning after December 15, 2024 on a retrospective basis. The Company is assessing the effect of the new disclosure requirements and does not anticipate the adoption will have a material impact to the Company’s financial statements. Income Taxes In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which includes amendments that further enhance income tax disclosures, primarily through standardization and disaggregation of rate reconciliation categories and income taxes paid by jurisdiction. The amendments are effective for annual periods beginning after December 15, 2024 and may be applied either prospectively or retrospectively. The Company is assessing the effect of the new disclosure requirements and does not anticipate the adoption will have a material impact to the Company’s financial statements.

- Definition

Disclosure of accounting policy for award under share-based payment arrangement. Includes, but is not limited to, methodology and assumption used in measuring cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.C.Q3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479830/718-10-S99-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.1.Q5)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479830/718-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.3.Q2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479830/718-10-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2.Q6)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479830/718-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/718/tableOfContent

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Cash Equivalents and Marketable Securities - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Marketable Securities [Line Items]
Fair value of securities held in a continuous unrealized loss position for less than twelve months	$ 338.2	$ 117.8
Fair value of securities held in a continuous unrealized loss position for greater than twelve months	$ 31.1	$ 43.6
Maximum
Marketable Securities [Line Items]
Maturity of marketable securities	2 years	2 years

Stock-based Compensation - Schedule of Restricted Stock Units (Details) - RSUs	6 Months Ended
	Jun. 30, 2024 $ / shares shares
Restricted Stock Units Outstanding
Balance at beginning of period (in shares) \| shares	2,072,855
RSUs granted (in shares) \| shares	3,622,426
RSUs vested (in shares) \| shares	(295,570)
RSUs forfeited or canceled (in shares) \| shares	(225,914)
Balance at end of period (in shares) \| shares	5,173,797
Weighted-Average Value at Grant Date Per Share
Balance at beginning of period (in dollars per share) \| $ / shares	$ 2.96
RSUs granted (in dollars per share) \| $ / shares	1.84
RSUs vested (in dollars per share) \| $ / shares	3.41
RSUs forfeited or canceled (in dollars per share) \| $ / shares	2.07
Balance at end of period (in dollars per share) \| $ / shares	$ 2.19

License, Collaboration, and Success Payment Agreements - Schedule of Aggregate Potential Success Payments (Details) - Collaborative Arrangement, Transaction with Party to Collaborative Arrangement	Jun. 30, 2024 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

Summary of Significant Accounting Policies	6 Months Ended
Summary of Significant Accounting Policies	Jun. 30, 2024
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, 2023 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, 2023. 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 June 30, 2024 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 unaudited 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 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. 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. 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, 2023, except as set forth below regarding the Company’s stock-based compensation policy for performance-based restricted stock units (“PSUs”). Stock-based Compensation Under ASC 718, the Company measures and recognizes expense for PSUs that settle in stock. The Company granted PSUs that vest upon the achievement of certain performance conditions to certain key employees. For awards with performance conditions that do not vest unless a performance condition is met, the Company recognizes expense if, and to the extent that, the Company estimates that the achievement of the performance condition is probable. At each reporting date, the Company is required to evaluate whether achievement of a performance condition is probable. Compensation expense is recorded over the appropriate service period based upon the Company’s assessment of accomplishing each performance condition. The fair values of the Company’s PSUs that have market-based metrics are estimated using Monte Carlo simulations. The Company applies an accelerated attribution method to recognize stock-based compensation expense over the applicable service period for these awards. The number of shares expected to be earned is considered in the grant date valuation; therefore, the expense is not subsequently adjusted to reflect the actual shares ultimately earned. The fair values of PSUs that do not have market-based metrics are based upon the grant date stock price. Compensation expense is recognized for the number of shares expected to be earned after assessing the probability that a certain performance condition will be met and the targeted payout level associated with the performance condition expected to be achieved. Cumulative adjustments are recorded each quarter to reflect the estimated outcome of the performance-related conditions until the date results are determined and settled. If performance conditions are not met or not expected to be met, any compensation expense previously recognized associated with the awards will be reversed. Recent Accounting Pronouncements Recently Adopted None. Not Yet Adopted Segment Reporting In November 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which expands required disclosures about a public entity’s reportable segments and requires more enhanced information about a reportable segment’s expenses, interim segment profit or loss, and how a public entity’s chief operating decision maker uses reported segment profit or loss information in assessing segment performance and allocating resources. Entities with a single reportable segment are required to provide all the updated and existing segment disclosures required by Topic 280. The amendments are effective for annual periods beginning after December 15, 2023 and interim periods within fiscal years beginning after December 15, 2024 on a retrospective basis. The Company is assessing the effect of the new disclosure requirements and does not anticipate the adoption will have a material impact to the Company’s financial statements. Income Taxes In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which includes amendments that further enhance income tax disclosures, primarily through standardization and disaggregation of rate reconciliation categories and income taxes paid by jurisdiction. The amendments are effective for annual periods beginning after December 15, 2024 and may be applied either prospectively or retrospectively. The Company is assessing the effect of the new disclosure requirements and does not anticipate the adoption will have a material impact to the Company’s financial statements.

Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable equity securities	$ 149		$ 149
Unrealized loss on marketable equity securities	0	$ 2,923	13,001	$ 12,923
Unrealized gain on marketable equity securities			149	0
Other (Expense) Income, Net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized loss on marketable equity securities	$ 1,400	$ 0
Unrealized gain on marketable equity securities			$ 100	$ 0

- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 80
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480078/944-80-55-14

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 80
-Name Accounting Standards Codification
-Section 55
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480078/944-80-55-9

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482736/825-10-45-1A

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

Commitments and Contingencies	6 Months Ended
Commitments and Contingencies	Jun. 30, 2024
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 June 30, 2024 and December 31, 2023.

Stock-based Compensation - Narrative (Details) $ / shares in Units, $ in Millions			1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 01, 2024 shares	Nov. 16, 2023 USD ($) grantee $ / shares shares	Jun. 30, 2021 shares	Jun. 30, 2024 USD ($) shares	Jun. 30, 2023 shares	Jun. 30, 2024 USD ($) $ / shares shares	Jun. 30, 2023 $ / shares shares	Dec. 31, 2018 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation cost related to unvested awards not yet recognized \| $				$ 59.0		$ 59.0
Expected weighted-average period compensation cost to be recognized						2 years 7 months 6 days
Weighted average grant date fair value (in dollars per share) \| $ / shares						$ 1.35	$ 1.72
Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award performance period						3 years
Service period from the milestone achievement date						1 year
Performance Shares \| Achievement of applicable milestone
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting rights, percentage						50.00%
Performance Shares \| Earlier of one year of service from achievement date and three-year performance period
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting rights, percentage						50.00%
2023 \| Stock option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Minimum exercise price of plan modifications (in dollars per share) \| $ / shares		$ 2.37
Original exercise price lower range (in dollars per share) \| $ / shares		2.61
Original exercise price upper range (in dollars per share) \| $ / shares		$ 17.95
Share-based payment arrangement, plan modification, number of grantees affected \| grantee		200
Shares repriced (in shares)		23,416,860
Plan modification, exercise price (in dollars per share) \| $ / shares		$ 1.87
Incremental stock-based compensation expense of modifications \| $		$ 8.9
Maximum \| Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance period relative to total shareholder return						3 years
Awards granted, percentage of target						200.00%
Minimum \| Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance period relative to total shareholder return						2 years
Awards granted, percentage of target						0.00%
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)	12,697,885
Increase in proportion of common shares reserved for future issuance (as a percent)	5.00%
Future issuance of common shares (in shares)				41,668,968		41,668,968
Stock-based compensation (in shares)				491,303	542,921	491,303	542,921
2021 Plan \| Stock option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			4 years
2021 Plan \| RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			4 years
2021 Plan \| Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			3 years
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)	2,539,577
Future issuance of common shares (in shares)				5,509,903		5,509,903
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

License, Collaboration, and Success Payment Agreements - Narrative (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Oct. 31, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) $ / shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development expense	$ 40,261,000	$ 47,471,000	$ 83,435,000	$ 92,101,000
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 \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
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	100,000	100,000	200,000	400,000
Aggregate success payments	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	300,000		300,000		$ 700,000
Success payment expense (reversal)	(700,000)	500,000	(300,000)	(600,000)
Fred Hutch \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement \| Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance								10
Aggregate success payments								$ 10,000,000
Per share common stock price required for payment (in dollars per share) \| $ / shares								$ 18.29
Fred Hutch \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance								50
Aggregate success payments								$ 200,000,000
Per share common stock price required for payment (in dollars per share) \| $ / shares								$ 91.44
Stanford \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
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	700,000	700,000	1,500,000	1,500,000
Aggregate success payments	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	700,000		700,000		1,100,000
Success payment expense (reversal)	(800,000)	$ 600,000	(300,000)	$ 0
Success payment liability	$ 700,000		$ 700,000		$ 900,000
Stanford \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments due							2,500,000
Stanford \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement \| Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance						10
Aggregate success payments						$ 10,000,000
Per share common stock price required for payment (in dollars per share) \| $ / shares						$ 18.29
Stanford \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Multiple of initial equity value at issuance						50
Aggregate success payments						$ 200,000,000
Per share common stock price required for payment (in dollars per share) \| $ / shares						$ 91.44
Stanford \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement \| Maximum \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone payments due							$ 3,700,000

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Comprehensive Income [Abstract]
Revenue	$ 13	$ 27	$ 16	$ 92
Operating expenses:
Research and development	40,261	47,471	83,435	92,101
General and administrative	12,256	19,030	25,750	38,309
Other operating income, net	(976)	(569)	(2,066)	(1,857)
Total operating expenses	51,541	65,932	107,119	128,553
Loss from operations	(51,528)	(65,905)	(107,103)	(128,461)
Interest income, net	6,364	5,264	13,183	9,761
Other (expense) income, net	(645)	(326)	445	774
Impairment of other investments	0	(2,923)	(13,001)	(12,923)
Total other income (loss), net	5,719	2,015	627	(2,388)
Net loss	(45,809)	(63,890)	(106,476)	(130,849)
Other comprehensive loss:
Net unrealized gain (loss) on marketable securities	7	1,500	(303)	5,220
Comprehensive loss	$ (45,802)	$ (62,390)	$ (106,779)	$ (125,629)
Net loss per common share, basic (in dollars per share)	$ (0.18)	$ (0.26)	$ (0.42)	$ (0.52)
Net loss per common share, diluted (in dollars per share)	$ (0.18)	$ (0.26)	$ (0.42)	$ (0.52)
Weighted-average shares used to compute net loss per common share, basic (in shares)	255,398	250,204	254,825	249,899
Weighted-average shares used to compute net loss per common share, diluted (in shares)	255,398	250,204	254,825	249,899

Stock-based Compensation - Schedule of Assumptions Used in Black-Scholes Option-Pricing Model for Estimating Fair Value of Stock Options Granted (Details)	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Share-Based Payment Arrangement [Abstract]
Risk-free interest rate	4.17%	4.09%
Expected volatility	76.00%	92.40%
Expected term (in years)	5 years 10 months 24 days	5 years 11 months 26 days
Expected dividend yield	0.00%	0.00%