Sana Biotechnology (SANA) 10-Q 8 May 24 2024 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2024	May 03, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Entity Registrant Name	Sana Biotechnology, Inc.
Entity Central Index Key	0001770121
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		221,502,908
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity File Number	001-39941
Entity Tax Identification Number	83-1381173
Entity Address Address Line1	188 East Blaine Street
Entity Address, Address Line Two	Suite 400
Entity Address City Or Town	Seattle
Entity Address State Or Province	WA
Entity Address Postal Zip Code	98102
City Area Code	206
Local Phone Number	701-7914
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation State Country Code	DE
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	SANA
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 177,054	$ 133,517
Marketable securities	134,028	71,678
Restricted cash	3,832	3,832
Prepaid expenses and other current assets	6,349	4,488
Total current assets	321,263	213,515
Property and equipment, net	81,649	70,689
Operating lease right-of-use assets	71,565	74,903
Intangible asset	59,195	59,195
Goodwill	140,627	140,627
Other non-current assets	7,078	6,370
TOTAL ASSETS	681,377	565,299
Current liabilities:
Accounts payable	6,095	4,108
Accrued compensation	13,965	23,722
Accrued expenses and other current liabilities	19,674	23,462
Operating lease liabilities	13,167	13,195
Total current liabilities	52,901	64,487
Operating lease liabilities, net of current portion	92,922	90,901
Contingent consideration, net of current portion	114,990	109,606
Success payment liabilities	45,422	12,799
Total liabilities	306,235	277,793
Commitments and contingencies (Note 9)
Stockholders' equity:
Preferred stock, $0.0001 par value; 50,000 shares authorized; zero shares issued and outstanding as of March 31, 2024 and December 31, 2023
Common stock, $0.0001 par value; 750,000 shares authorized; 221,286 and 197,857 shares issued and outstanding as of March 31, 2024 and December 31, 2023, respectively	22	20
Additional paid-in capital	1,820,701	1,625,637
Accumulated other comprehensive loss	(15)	(60)
Accumulated deficit	(1,445,566)	(1,338,091)
Total stockholders' equity	375,142	287,506
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 681,377	$ 565,299

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	750,000,000	750,000,000
Common stock, shares issued	221,286,000	197,857,000
Common stock, shares outstanding	221,286,000	197,857,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating expenses:
Research and development	$ 56,448	$ 67,166
Research and development related success payments and contingent consideration	38,007	120
General and administrative	16,269	16,766
Total operating expenses	110,724	84,052
Loss from operations	(110,724)	(84,052)
Interest income, net	3,034	1,976
Other income (expense), net	215	(47)
Net loss	$ (107,475)	$ (82,123)
Net loss per common share - basic	$ (0.49)	$ (0.43)
Net loss per common share - diluted	$ (0.49)	$ (0.43)
Weighted-average number of common shares - basic	217,290	191,228
Weighted-average number of common shares - diluted	217,290	191,228

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ (107,475)	$ (82,123)
Other comprehensive income, net of tax:
Unrealized gain on marketable securities, net	45	2,188
Total comprehensive loss	$ (107,430)	$ (79,935)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	At The Market Offering	Common Stock	Common Stock At The Market Offering	Additional Paid-in Capital	Additional Paid-in Capital At The Market Offering	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance at Dec. 31, 2022	$ 499,315		$ 19		$ 1,558,459		$ (4,327)	$ (1,054,836)
Beginning balance (in shares) at Dec. 31, 2022			191,022
Fees incurred related to issuance of common stock from at the market offering	(200)				(200)
Vesting of restricted stock (in shares)			154
Exercise of stock options	331				331
Exercise of stock options (in shares)			233
Stock-based compensation expense	8,751				8,751
Unrealized gain (loss) on marketable securities, net	2,188						2,188
Net income (loss)	(82,123)							(82,123)
Ending balance at Mar. 31, 2023	428,262		$ 19		1,567,341		(2,139)	(1,136,959)
Ending balance (in shares) at Mar. 31, 2023			191,409
Beginning balance at Dec. 31, 2023	$ 287,506		$ 20		1,625,637		(60)	(1,338,091)
Beginning balance (in shares) at Dec. 31, 2023	197,857		197,857
Issuance of common stock, net of offering costs (in shares)			21,773	150
Issuance of common stock, net of offering costs	$ 180,008	$ 1,037	$ 2		180,006	$ 1,037
Fees incurred related to issuance of common stock from at the market offering		$ (113)
Vesting of restricted stock (in shares)			386
Exercise of stock options	$ 4,929				4,929
Exercise of stock options (in shares)	1,120		1,120
Stock-based compensation expense	$ 9,092				9,092
Unrealized gain (loss) on marketable securities, net	45						45
Net income (loss)	(107,475)							(107,475)
Ending balance at Mar. 31, 2024	$ 375,142		$ 22		$ 1,820,701		$ (15)	$ (1,445,566)
Ending balance (in shares) at Mar. 31, 2024	221,286		221,286

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
At The Market Offering
Issuance of common stock, net of offering costs	$ 113
Pre Funded Warrants
Issuance of common stock, net of offering costs	$ 9,741

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
OPERATING ACTIVITIES:
Net loss	$ (107,475)	$ (82,123)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and impairment of long-lived assets	3,746	4,346
Stock-based compensation expense	9,092	8,751
Change in the estimated fair value of contingent consideration	5,384	5,460
Change in the estimated fair value of success payment liabilities	32,623	(5,340)
Non-cash expense for operating lease right-of-use assets	3,338	3,354
Other non-cash items, net	(4,879)	(2,913)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(2,380)	(106)
Operating lease right-of-use assets and liabilities	5,804	(8)
Accounts payable	(1,064)	(354)
Accrued expenses and other liabilities	(9,821)	(10,339)
Net cash used in operating activities	(65,632)	(79,272)
INVESTING ACTIVITIES:
Purchases of marketable securities	(114,393)	(20,431)
Proceeds from maturities of marketable securities	53,010	85,334
Purchases of property and equipment	(15,845)	(2,176)
Net cash provided by (used in) investing activities	(77,228)	62,727
FINANCING ACTIVITIES:
Proceeds from employee stock purchase plan and exercise of stock options	4,929	236
Proceeds from issuance of common stock from equity financings, net	181,468
Net cash provided by financing activities	186,397	236
Net increase (decrease) in cash, cash equivalents, and restricted cash	43,537	(16,309)
Cash, cash equivalents, and restricted cash at beginning of period	137,349	187,273
Cash, cash equivalents, and restricted cash at end of period	180,886	170,964
SUPPLEMENTAL CASH FLOW INFORMATION:
Operating lease right-of-use assets obtained in exchange for lease obligations		8,984
Purchases of property and equipment included in accounts payable and accrued liabilities	8,375	$ 968
Cash received for tenant improvement allowances	$ 6,121

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (107,475)	$ (82,123)

Insider Trading Arrangements

Insider Trading Arrangements - shares		3 Months Ended
	Mar. 05, 2024	Mar. 31, 2024
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		During our last fiscal quarter, the following officer, as defined in Rule 16a-1(f), adopted a “Rule 10b5-1 trading arrangement” as defined in Regulation S-K Item 408, as follows: On March 5, 2024 , Nathan Hardy , our Chief Financial Officer , adopted a Rule 10b5-1 trading arrangement providing for the sale from time to time of an aggregate of up to 76,125 shares of our common stock and aggregate of up to 23,813 shares of common stock issuable upon the exercise of options. The trading arrangement is intended to satisfy the affirmative defense in Rule 10b5-1(c). The duration of the trading arrangement is until March 15, 2026, or earlier if all transactions under the trading arrangement are completed. On March 13, 2024 , Mr. Hardy terminated a separate Rule 10b5-1 trading arrangement providing for the sale from time to time of an aggregate of up to 140,236 shares of our common stock and an aggregate of up to 76,692 shares of common stock issuable upon the exercise of options. The trading arrangement was intended to satisfy the affirmative defense in Rule 10b5-1(c). The duration of the trading arrangement was until April 20, 2024, or earlier if all transactions under the trading arrangement were completed. No other officers or directors, as defined in Rule 16a-1(f), adopted and/or terminated a “Rule 10b5-1 trading arrangement” or a “non-Rule 10b5-1 trading arrangement,” as defined in Regulation S-K Item 408, during the last fiscal quarter.
Rule 10b5-1 Arrangement Adopted		true
Non-Rule 10b5-1 Arrangement Adopted		false
Rule 10b5-1 Arrangement Terminated		true
Non-Rule 10b5-1 Arrangement Terminated		false
Nathan Hardy [Member]
Trading Arrangements, by Individual
Name	Nathan Hardy
Title	Chief Financial Officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	March 5, 2024
Aggregate Available	76,125
Mr. Hardy [Member]
Trading Arrangements, by Individual
Name	Mr. Hardy
Rule 10b5-1 Arrangement Terminated	true
Termination Date	March 13, 2024
Aggregate Available	140,236
Rule 10B51Trading Plan One [Member] | Nathan Hardy [Member]
Trading Arrangements, by Individual
Aggregate Available	23,813
Rule 10B51Trading Plan Two [Member] | Mr. Hardy [Member]
Trading Arrangements, by Individual
Aggregate Available	76,692

Organization

Organization	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Organization	1. Organization Sana Biotechnology, Inc. (the Company or Sana) is a biotechnology company focusing on utilizing engineered cells as medicines. The Company’s operations to date have included identifying and developing potential product candidates, executing preclinical studies, establishing manufacturing capabilities, preparing for and executing clinical trials of its product candidates and supporting clinical trials of product candidates developed using its technologies, acquiring technology, organizing and staffing the Company, business planning, establishing and maintaining the Company’s intellectual property portfolio, raising capital, and providing general and administrative support for these operations. Liquidity and capital resources The Company is subject to a number of risks and uncertainties similar to other biotechnology companies in the development stage, including, but not limited to, those related to the need to obtain adequate additional funding, possible failure of preclinical testing or clinical trials, the need to obtain marketing approval for its product candidates, building out internal and external manufacturing capabilities, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of the Company’s products, the need to protect the Company’s intellectual property and proprietary technologies, and the need to attract and retain key scientific and management personnel. If the Company does not successfully commercialize or partner any of its product candidates, it will be unable to generate product revenue or achieve profitability. Until such time as the Company can generate significant revenue from product sales, if ever, it expects to finance its operations with the proceeds from additional equity or debt financings or capital obtained in connection with strategic collaborations or licensing or other arrangements. In the event that additional financing is required, the Company may not be able to raise it on terms acceptable to it or at all. In February 2024, the Company completed an underwritten public offering pursuant to which it sold 21.8 million shares of its common stock, including 4.5 million shares pursuant to the full exercise of the underwriters' option to purchase additional shares, and pre-funded warrants to purchase 12.7 million shares of its common stock for net proceeds of approximately $ 180.0 million, after deducting underwriting discounts and commissions and offering expenses. In August 2022, the Company entered into a sales agreement with Cowen and Company, LLC (Cowen), acting as sales agent, pursuant to which it may offer and sell through Cowen up to $ 150.0 million in shares of the Company’s common stock from time to time in a series of one or more at the market equity offerings (collectively, the ATM facility). As of March 31, 2024, the Company has sold an aggregate of 4.9 million shares of the Company's common stock under the ATM facility for net proceeds of $ 28.7 million, after deducting commissions and expenses. The Company has incurred operating losses each year since inception and expects such losses to continue for the foreseeable future. As of March 31, 2024, the Company had cash, cash equivalents, and marketable securities of $ 311.1 million, and an accumulated deficit of $ 1.4 billion, which includes cumulative non-cash charges related to the revaluation of the success payment liabilities and contingent consideration of $ 43.0 million and $ 63.7 million, respectively.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of significant accounting policies Basis of presentation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, and have been prepared in accordance with generally accepted accounting principles in the United States (GAAP). Certain prior period amounts have been reclassified to conform to current period presentation. The condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023 filed with the Securities and Exchange Commission (SEC) on February 29, 2024 (2023 Annual Report). Significant accounting policies The significant accounting policies used in the preparation of these condensed consolidated financial statements as of March 31, 2024 and for the three months ended March 31, 2024 and 2023 are consistent with those discussed in Note 2 in the 2023 Annual Report. Use of estimates The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates. The most significant estimates in the Company’s condensed consolidated financial statements relate to success payment liabilities, contingent consideration, business combinations, accrued expenses, and operating lease right-of-use assets and liabilities. Recent accounting pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard-setting bodies that the Company adopts as of the specified effective date. Unless otherwise discussed, the Company does not believe that the adoption of any recently issued standards has had or may have a material impact on its condensed consolidated financial statements or disclosures. In December 2023, the FASB issued ASU 2023-09 Income Taxes (Topic 740) Improvements to Income Tax Disclosures that requires disclosure of disaggregated income taxes paid, prescribes standard categories for the components of the effective tax rate reconciliation, and modifies other income tax-related disclosures. This ASU is effective for the Company's fiscal year 2025. Early adoption is permitted. The Company is currently evaluating income tax disclosures related to its annual report for fiscal year 2025. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280). The amendments in this update expand segment disclosure requirements, including new segment disclosure requirements for entities with a single reportable segment among other disclosure requirements. This update is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. The adoption of this standard is not expected to have a material impact on the Company’s consolidated financial statements.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2024
Business Combinations [Abstract]
Acquisitions	3. Acquisitions Cobalt Biomedicine, Inc. In February 2019, the Company acquired 100 % of the outstanding equity of Cobalt Biomedicine, Inc. (Cobalt), a privately held early-stage biotechnology company developing a platform technology using its fusogen technology to specifically and consistently deliver various biological payloads to cells (the Cobalt acquisition). As part of the Cobalt acquisition, the Company recorded an intangible asset of $ 59.2 million, which consists of in-process research and development that is classified as indefinite-lived until the successful completion of the associated research and development technology, at which point it becomes a finite-lived asset and will be amortized over its estimated useful life. If the research and development technology is abandoned, an impairment charge will be recorded. The Company is actively developing the fusogen technology and, accordingly, the intangible asset is not complete. Amortization will begin when regulatory approval of a product candidate developed using the fusogen technology is obtained in a major market, typically either the United States or the European Union. The Company recognized $ 140.6 million of goodwill as a result of the Cobalt acquisition, which is primarily attributable to the value the acquisition provides the Company by complementing the Company’s ex vivo portfolio with in vivo fusogen cell engineering technology and furthering the Company’s research in using engineered cells as medicines. The goodwill is not deductible for income tax purposes. There were no impairments of the intangible asset or goodwill since the acquisition. Pursuant to the terms and conditions in the Cobalt acquisition agreement, the Company has an obligation to pay to certain former Cobalt stockholders contingent consideration (Cobalt Contingent Consideration) of up to an aggregate of $ 500.0 million upon the achievement of certain specified development milestones and a success payment (Cobalt Success Payment) of up to $ 500.0 million, each of which is payable in cash or stock. The Cobalt Success Payment is payable if, at pre-determined valuation measurement dates, the Company’s market capitalization equals or exceeds $ 8.1 billion, and the Company is advancing a program based on the fusogen technology in a clinical trial pursuant to an investigational new drug (IND) application, or has filed, or received approval for, a biologics license application or new drug application for a product developed using the fusogen technology. The Cobalt Success Payment can be achieved over a maximum of 20 years from the date of the acquisition, but this period could be shorter upon the occurrence of certain events. A valuation measurement date would also be triggered upon a change of control of the Company if at least one of the Company’s programs based on the fusogen technology is an active research program at the time of such change of control. If the Company’s market capitalization is below $ 8.1 billion as of the date of a change of control, the amount of the potential Cobalt Success Payment will decrease, and the amount of potential Cobalt Contingent Consideration will increase. As of March 31, 2024, a Cobalt Success Payment had not been triggered. The following table sets forth various thresholds for the Company’s market capitalizations as of the date of a change of control and the resulting potential Cobalt Success Payment and additional potential Cobalt Contingent Consideration: Sana market capitalization upon a change of control and resulting impact to Cobalt Success Cobalt Success Additional (in millions) Equal to or exceeds $ 8.1 billion $ 500 $ - Equal to or exceeds $ 7.4 billion, but less than $8.1 billion 150 350 Equal to or exceeds $ 6.8 billion, but less than $7.4 billion 100 400 Less than $ 6.8 billion - 500 The Cobalt Success Payment and Cobalt Contingent Consideration liabilities are carried at fair value, with changes in fair value recognized in research and development related success payments and contingent consideration. As of March 31, 2024 and December 31, 2023, the estimated fair value of the Cobalt Success Payment liability was $ 39.1 million and $ 11.2 million, respectively, and was recorded in long-term liabilities. In connection with the change in the estimated fair value of the Cobalt Success Payment, the Company recognized an expense of $ 27.9 million and a gain of $ 4.8 million for the three months ended March 31, 2024 and 2023, respectively. As of March 31, 2024 and December 31, 2023, the estimated fair value of the Cobalt Contingent Consideration was $ 115.0 million and $ 109.6 million, respectively, and was recorded in long-term liabilities. In connection with the change in the estimated fair value of the Cobalt Contingent Consideration, the Company recognized expenses of $ 5.4 million and $ 5.5 million for the three months ended March 31, 2024 and 2023, respectively.

License and collaboration agree

License and collaboration agreements	3 Months Ended
	Mar. 31, 2024
License And Collaboration Agreements [Abstract]
License and Collaboration Agreements	4. License and collaboration agreements Beam Therapeutics Inc. In October 2021, the Company entered into an option and license agreement with Beam Therapeutics Inc. (Beam), pursuant to which the Company was granted a non-exclusive license to use Beam’s proprietary CRISPR Cas12b nuclease editing technology to research, develop, and commercialize engineered cell therapy products that (i) are directed to certain antigen targets, with respect to the Company’s allogeneic T cell programs, or (ii) comprise certain human cell types, with respect to the Company’s stem cell-derived programs. The Company made an upfront payment of $ 50.0 million to Beam, which was recorded in research and development expense for the year ended December 31, 2021. Additionally, under the terms of the agreement, the Company may be obligated to pay up to $ 65.0 million in specified developmental and commercial milestone payments and royalties on licensed products for each licensed product. At the time of the entry into the option and license agreement, a member of the Company’s board of directors was a beneficial owner of greater than 10 % of the outstanding shares of Beam. This director is also affiliated with a member of the board of directors of Beam. President and Fellows of Harvard College In March 2019, the Company entered into an exclusive license agreement with the President and Fellows of Harvard College (Harvard) to access certain intellectual property for the development of hypoimmune-modified cells. Under the terms of the agreement, the Company paid to Harvard aggregate consideration of $ 12.0 million, comprising $ 9.0 million in common stock and $ 3.0 million in cash. Additionally, the Company may be required to pay to Harvard up to an aggregate of $ 175.0 million in success payments, payable in cash, based on increases in the fair value of the Company’s common stock (Harvard Success Payments). The potential Harvard Success Payments are based on multiples of increased value ranging from 5x to 40x, based on a comparison of the fair market value of the Company’s common stock relative to the original issuance price of $ 4.00 per share at ongoing pre-determined valuation measurement dates. The Harvard Success Payments can be achieved over a maximum of 12 years from the effective date of the agreement. If a higher success payment tier is first met at the same time a lower tier is first met, both tiers will be owed. Any previous success payments made to Harvard would be credited against the success payment owed as of any valuation measurement date so that Harvard does not receive multiple success payments in connection with the same threshold. As of March 31, 2024, a Harvard Success Payment had not been triggered. The following table summarizes the potential success payments and common stock price required for payment: Multiple of Equity Value at Issuance 5x 10x 20x 30x 40x Per share common stock price required for payment $ 20.00 $ 40.00 $ 80.00 $ 120.00 $ 160.00 Success payment(s) (in millions) $ 5.0 $ 15.0 $ 30.0 $ 50.0 $ 75.0 The Harvard Success Payment liabilities are carried at fair value, with the initial value and changes in fair value recognized in research and development related success payments and contingent consideration. As of March 31, 2024 and December 31, 2023, the estimated fair value of the Harvard Success Payment liability was $ 6.3 million and $ 1.6 million, respectively, and was recorded in long-term liabilities. In connection with the change in the estimated fair value of the Harvard Success Payment liability, the Company recognized an expense of $ 4.7 million and a gain of $ 0.6 million for the three months ended March 31, 2024 and 2023 respectively.

Restricted Cash

Restricted Cash	3 Months Ended
	Mar. 31, 2024
Restricted Cash and Cash Equivalents [Abstract]
Restricted Cash	5. Restricted cash The Company maintains standby letters of credit that are collateralized with a bank account at a financial institution in accordance with certain lease agreements. The aggregate amount of such standby letters of credit was $ 3.8 million as of each of March 31, 2024 and December 31, 2023.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	6. Fair value measurements The following tables summarize the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy: March 31, 2024 Valuation Amortized Cost Gross Gross Estimated (in thousands) Financial assets: Cash equivalents: Money market funds Level 1 $ 85,137 $ - $ - $ 85,137 U.S. government and agency securities Level 2 79,179 1 ( 1 ) 79,179 Corporate debt securities Level 2 514 - - 514 Total cash equivalents 164,830 1 ( 1 ) 164,830 Short-term marketable securities: U.S. government and agency securities Level 2 122,671 8 ( 22 ) 122,657 Corporate debt securities Level 2 11,372 1 ( 2 ) 11,371 Total short-term marketable securities 134,043 9 ( 24 ) 134,028 Other assets Level 3 381 - - 381 Total financial assets $ 299,254 $ 10 $ ( 25 ) $ 299,239 Financial liabilities: Long-term financial liabilities: Contingent consideration Level 3 114,990 - - 114,990 Success payment liabilities Level 3 45,422 - - 45,422 Total long-term financial liabilities 160,412 - - 160,412 Total financial liabilities $ 160,412 $ - $ - $ 160,412 December 31, 2023 Valuation Amortized Cost Gross Gross Estimated (in thousands) Financial assets: Cash equivalents: Money market funds Level 1 $ 70,315 $ - $ - $ 70,315 U.S. government and agency securities Level 2 33,091 3 - 33,094 Corporate debt securities Level 2 1,062 - - 1,062 Total cash equivalents 104,468 3 - 104,471 Short-term marketable securities: U.S. government and agency securities Level 2 57,924 7 ( 78 ) 57,853 Corporate debt securities Level 2 13,817 9 ( 1 ) 13,825 Total short-term marketable securities 71,741 16 ( 79 ) 71,678 Other assets Level 3 359 - - 359 Total financial assets $ 176,568 $ 19 $ ( 79 ) $ 176,508 Financial liabilities: Long-term financial liabilities: Contingent consideration Level 3 109,606 - - 109,606 Success payment liabilities Level 3 12,799 - - 12,799 Total long-term financial liabilities 122,405 - - 122,405 Total financial liabilities $ 122,405 $ - $ - $ 122,405 The Company measures the fair value of money market funds based on quoted prices in active markets for identical assets or liabilities. The Level 2 marketable securities include U.S. government and agency securities and corporate debt securities and are valued based on either recent trades of securities in inactive markets or quoted market prices of similar instruments and other significant inputs derived from or corroborated by observable market data. The following table summarizes available-for-sale debt securities in a continuous unrealized loss position for less than and greater than twelve months for the periods presented: Less than 12 months 12 months or greater Total Fair value Unrealized losses Fair value Unrealized losses Fair value Unrealized losses (in thousands) March 31, 2024 U.S. government and agency securities $ 111,511 $ ( 9 ) $ 5,984 $ ( 14 ) $ 117,495 $ ( 23 ) Corporate debt securities 7,858 ( 2 ) - - 7,858 ( 2 ) Total $ 119,369 $ ( 11 ) $ 5,984 $ ( 14 ) $ 125,353 $ ( 25 ) December 31, 2023 U.S. government and agency securities $ 9,186 $ ( 3 ) $ 10,386 $ ( 75 ) $ 19,572 $ ( 78 ) Corporate debt securities 1,396 ( 1 ) - - 1,396 ( 1 ) Total $ 10,582 $ ( 4 ) $ 10,386 $ ( 75 ) $ 20,968 $ ( 79 ) The Company determined that there was no material change in the credit risk of the above investments during the three months ended March 31, 2024. As such, an allowance for credit losses has not been recognized. As of March 31, 2024, the Company does not intend to sell such securities, and it is not more-likely-than-not that the Company will be required to sell the securities prior to the recovery of the amortized cost basis. As of March 31, 2024, all marketable securities had an effective maturity date of two years or less. Investments in securities with maturities of less than one year , or those for which management intends to use to fund current operations, are included in current assets and classified as available-for-sale. As of March 31, 2024, the balance in accumulated other comprehensive loss included net unrealized gains related to the Company’s available-for-sale debt securities. The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities: Contingent Cobalt Harvard (in thousands) Balance as of December 31, 2023 $ 109,606 $ 11,160 $ 1,639 Changes in fair value – expense 5,384 27,920 4,703 Balance as of March 31, 2024 $ 114,990 $ 39,080 $ 6,342 Contingent consideration The Company utilizes significant estimates and assumptions it believes would be made by a market participant in determining the estimated fair value of the Cobalt Contingent Consideration at each balance sheet date. The fair value of the Cobalt Contingent Consideration was determined by calculating the probability-weighted estimated value of the pre-specified development milestone payments based on the assessment of the likelihood and estimated timing that the milestones would be achieved and the applicable discount rates. The discount rate captures the credit risk associated with the payment of the contingent consideration when earned and due. The Company assesses these estimates on an ongoing basis as additional data impacting the assumptions are obtained. The fair value of the Cobalt Contingent Consideration was calculated using the following unobservable inputs: March 31, 2024 December 31, 2023 Unobservable Input Range Weighted-Average Range Weighted-Average Discount rates 10.9 % – 11.3 % 11.0 % 11.7 % – 12.4 % 11.9 % Probability of milestone achievement 5.0 % – 55.0 % 25.7 % 5.0 % – 55.0 % 25.7 % The weighted-average unobservable inputs were calculated based on the relative value of the pre-specified development milestones. The estimated fair value of the Cobalt Contingent Consideration may change significantly as development progresses and additional data are obtained, impacting the assumptions regarding probabilities of successful achievement of the milestones used to estimate the fair value of the liability and the timing in which they are expected to be achieved. In evaluating the fair value assumptions, judgment is required to interpret the market data used to develop the estimates. The estimates of fair value may not be indicative of the amounts that could be realized in a current market exchange. Accordingly, the use of different market assumptions, inputs and/or different valuation techniques could result in materially different fair value estimates. Success payments The Company utilizes significant estimates and assumptions in determining the estimated fair value of the success payment liabilities and the associated expense or gain at each balance sheet date. The estimated fair value of the Cobalt Success Payment and Harvard Success Payment liabilities was determined using a Monte Carlo simulation methodology, which models the estimated fair value of the liability based on several key assumptions, including the expected volatility, remaining term, risk-free interest rate, estimated number and timing of valuation measurement dates on the basis of which payment may be triggered, and, for the Cobalt Success Payment, the Company’s market capitalization, and, for the Harvard Success Payments, the per share fair value of the Company’s common stock. The fair values of the Cobalt Success Payments and Harvard Success Payments were calculated using the following unobservable inputs: March 31, 2024 December 31, 2023 Unobservable Input Cobalt Harvard Cobalt Harvard Expected stock price volatility 72.5 % 72.5 % 72.5 % 72.5 % Expected term (years) 14.9 7.0 15.1 7.2

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	7. Property and equipment, net Property and equipment, net consists of the following: March 31, 2024 December 31, 2023 (in thousands) Laboratory equipment $ 53,447 $ 51,643 Leasehold improvements 33,848 31,361 Construction in progress 35,028 26,332 Computer equipment, software, and other 4,843 3,124 Total property and equipment, at cost 127,166 112,460 Less: Accumulated depreciation ( 45,517 ) ( 41,771 ) Property and equipment, net $ 81,649 $ 70,689 Depreciation expense was $ 3.7 million and $ 4.3 million for the three months ended March 31, 2024 and 2023, respectively.

Accrued Liabilities

Accrued Liabilities	3 Months Ended
	Mar. 31, 2024
Payables and Accruals [Abstract]
Accrued liabilities	8. Accrued liabilities Accrued compensation and accrued expenses and other current liabilities consist of the following: March 31, 2024 December 31, 2023 (in thousands) Accrued compensation: Accrued bonuses $ 3,957 $ 14,379 Accrued paid time off 5,398 4,731 Accrued payroll 4,065 3,936 Other accrued compensation 545 676 Total accrued compensation $ 13,965 $ 23,722 Accrued expenses and other current liabilities: Accrued research and development services $ 9,749 $ 10,110 Accrued professional fees 3,509 1,470 Accrued property and equipment 5,053 9,200 Other accrued current liabilities 1,363 2,682 Total accrued expenses and other current liabilities $ 19,674 $ 23,462

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and contingencies Lease commitments The Company’s lease portfolio primarily comprises operating leases for office, laboratory, and manufacturing space. These leases contain various rent abatement periods, after which they require monthly lease payments that may be subject to annual increases throughout the lease term. Certain leases include options to extend the term. The renewal option is considered in the remaining lease term for the lease only when the Company is reasonably certain it will renew the lease. Certain leases provide the Company with the right to make tenant improvements, including the addition of laboratory space or build-out of manufacturing capabilities, and include a lease incentive allowance. In June 2022, the Company entered into a lease agreement for 79,565 square feet of office, laboratory, and manufacturing space located in Bothell, Washington (the Bothell facility). The initial term of the lease expires in February 2039, with the option to extend the lease for up to three additional five-year terms. The lease agreement also provides for up to $ 19.9 million for reimbursement of tenant improvements, as well as an additional $ 8.0 million for tenant improvements, available at the Company’s election, which the Company would be obligated to repay to the landlord monthly over the initial term of the lease with interest at a rate of 6.5 % per year. The Company is obligated to pay base rent of approximately $ 68.8 million over the initial term of the lease. In accordance with the lease agreement, the Company has obtained a letter of credit in the amount of $ 1.6 million. The Company recognized the right-of-use asset and lease liability in the three months ended March 31, 2023, when the lease commenced. The following table contains additional information related to the Company’s operating leases: Location Use Approximate Commencement Dates Expiration Dates Seattle, WA Office/Laboratory 48,000 March 2019 to September 2020 December 2026 to April 2028 Cambridge, MA Office/Laboratory 60,000 March 2019 to January 2022 November 2025 to February 2028 South San Francisco, CA Office/Laboratory 100,000 December 2019 to April 2022 April 2024 to April 2030 Rochester, NY Office/Laboratory 3,000 January 2022 January 2025 Bothell, WA Office/Laboratory/Manufacturing 80,000 January 2023 January 2039 Throughout the term of the lease agreements, the Company is responsible for paying, in addition to base rent, certain operating costs, such as common area maintenance, taxes, utilities, and insurance. 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 lease costs: Three Months Ended March 31, 2024 2023 (in thousands) Operating lease cost $ 5,981 $ 7,061 Variable lease cost 2,014 1,982 Total lease cost $ 7,995 $ 9,043 As of March 31, 2024, the weighted-average remaining lease term was 9.3 years, and the weighted-average incremental borrowing rate was 11.2 %. The following table reconciles the Company’s undiscounted operating lease cash flows by fiscal year to the present value of the operating lease liabilities as of March 31, 2024 (in thousands): 2024 (remaining 9 months) $ 16,971 2025 25,394 2026 22,472 2027 19,899 2028 15,226 2029 and thereafter 93,495 Total undiscounted lease payments 193,457 Less: imputed interest ( 85,980 ) Less: tenant improvement allowances ( 1,388 ) Present value of operating lease liabilities 106,089 Less: current portion of operating lease liabilities $ ( 13,167 ) Operating lease liabilities, net of current portion $ 92,922

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Stockholders' Equity	10. Stockholders’ equity In February 2024, the Company completed an underwritten public offering pursuant to which it sold 21.8 million shares of its common stock, including 4.5 million shares pursuant to the full exercise of the underwriters' option to purchase additional shares, and pre-funded warrants to purchase 12.7 million shares of its common stock, for net proceeds of approximately $ 180.0 million, after deducting underwriting discounts and commissions and offering expenses. The pre-funded warrants have an exercise price of $ 0.0001 per share of common stock. As the pre-funded warrants are indexed to the Company’s common stock and otherwise meet the requirements to be classified in equity, the Company recorded the consideration received from the issuance of the pre-funded warrants as additional paid-in capital on the Company’s consolidated balance sheet. The pre-funded warrants are exercisable at any time; however, the holders of pre-funded warrants may not exercise the warrant if the holder, together with its affiliates, would beneficially own more than 4.99 % of the number of shares of the Common Stock outstanding immediately after giving effect to such exercise. The holders of pre-funded warrants may increase or decrease such percentages not in excess of 19.99 % by providing at least 61 days’ prior notice to the Company. The pre-funded warrants do not expire. During the three months ended March 31, 2024, no pre-funded warrants were exercised. In August 2022, the Company entered into a sales agreement with Cowen, acting as sales agent, pursuant to which it may offer and sell through Cowen up to $ 150.0 million in shares of the Company’s common stock from time to time in a series of one or more at the market equity offerings. As of March 31, 2024, the Company has sold an aggregate of 4.9 million shares of the Company's common stock under the ATM facility for net proceeds of $ 28.7 million, after deducting commissions and expenses.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Stock-based compensation	11. Stock-based compensation Equity incentive plans In February 2021, the Company adopted the 2021 Incentive Award Plan (2021 Plan) and the 2021 Employee Stock Purchase Plan (2021 ESPP), both of which became effective on the completion of the Company’s initial public offering. The 2021 Plan provides for a variety of stock-based compensation awards, including stock options, restricted stock awards (RSAs), and restricted stock units (RSUs). 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 may 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 period or on the purchase date. As of March 31, 2024, 20.9 million shares and 6.5 million shares were available for future issuance under the 2021 Plan and the 2021 ESPP, respectively. Stock-based compensation expense Stock-based compensation expense is recognized in the condensed consolidated statements of operations as follows: Three Months Ended March 31, 2024 2023 (in thousands) Research and development $ 5,848 $ 5,972 General and administrative 3,244 2,779 Total stock-based compensation expense $ 9,092 $ 8,751 Unrecognized stock-based compensation costs related to unvested awards and the weighted-average period over which the costs are expected to be recognized as of March 31, 2024 are as follows: Stock Options RSUs Unrecognized stock-based compensation expense (in thousands) $ 75,911 $ 27,876 Weighted-average period costs expected to be recognized (in years) 2.8 3.5 Stock options A summary of the Company’s stock option activity is as follows: Stock Options Weighted-Average Weighted-Average Aggregate Intrinsic Outstanding as of December 31, 2023 26,849 $ 6.60 8.0 $ 11,235 Granted 5,551 9.49 Exercised ( 1,120 ) 4.40 Forfeited/Cancelled ( 1,048 ) 9.12 Outstanding as of March 31, 2024 30,232 $ 7.12 8.1 $ 113,377 Exercisable as of March 31, 2024 13,187 $ 7.01 7.1 $ 57,144 The fair value of stock options granted to employees, directors, and consultants was estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions: Three Months Ended March 31, Assumptions 2024 2023 Risk free interest rate 3.82 % – 4.34 % 3.47 % – 4.28 % Expected volatility 72.5 % 70.0 % Expected term (years) 6.25 6.25 – 6.50 Expected dividend 0 % 0 % The following table summarizes additional information related to stock option activity: Three Months Ended March 31, 2024 2023 Weighted average grant date fair value per share for options granted $ 6.46 $ 2.48 Aggregate intrinsic value of stock options exercised (in thousands) $ 3,586 $ 561 Restricted stock A summary of the Company’s RSU activity is as follows: RSUs RSUs Unvested shares as of December 31, 2023 2,341 $ 3.88 Granted 2,461 9.49 Vested ( 388 ) 4.21 Forfeited ( 188 ) 5.21 Unvested shares as of March 31, 2024 4,226 $ 7.05 The fair value of RSUs that vested during the three months ended March 31, 2024 and 2023 was $ 4.1 million and $ 0.6 million, respectively.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2024
Income Tax Disclosure [Abstract]
Income Taxes	12. Income taxes The Company’s income tax provision for interim periods is determined using an estimate of the Company’s annual effective tax rate, adjusted for discrete items arising in the quarter. The Company’s effective tax rate differs from the U.S. statutory tax rate primarily due to a valuation allowance on the deferred tax assets. Deferred tax assets and deferred tax liabilities are recognized based on temporary differences between the financial reporting and tax basis of assets and liabilities using statutory rates. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some or all of the deferred tax assets will not be realized. Due to the uncertainty surrounding the realization of the favorable tax attributes in future tax returns, the Company has recorded a full valuation allowance against the Company’s otherwise recognizable net deferred tax assets. The Company applies judgment in its determination of the financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. As of March 31, 2024 and December 31, 2023, the Company’s uncertain tax positions were immaterial.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Net Loss Per Share	13. Net loss per share Basic and diluted net loss per common share are calculated by dividing net loss by the weighted-average number of common shares outstanding during the relevant period, including the pre-funded warrants given their nominal exercise price. The Company was in a loss position for all periods presented, and basic net loss per share and diluted net loss per share are therefore the same for all periods, as the inclusion of all potential common securities outstanding would have been anti-dilutive. The following securities were excluded from the computation of net loss per diluted share of common stock for periods presented as their effect would have been anti-dilutive: Three Months Ended March 31, 2024 2023 (in thousands) Options to purchase common stock 30,232 29,202 Unvested restricted common stock - 5 Unvested RSUs 4,226 1,891 Total 34,458 31,098

Employee Benefit Plan

Employee Benefit Plan	3 Months Ended
	Mar. 31, 2024
Retirement Benefits [Abstract]
Employee Benefit Plan	14. Employee benefit plan In January 2019, the Company adopted a 401(k) retirement and savings plan (the 401(k) Plan) covering all employees. The 401(k) Plan allows employees to make pre- and post-tax contributions up to the maximum allowable amount set by the IRS. The Company matches each participant’s 401(k) contributions, up to $ 4,000 per year per participant.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, and have been prepared in accordance with generally accepted accounting principles in the United States (GAAP). Certain prior period amounts have been reclassified to conform to current period presentation. The condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023 filed with the Securities and Exchange Commission (SEC) on February 29, 2024 (2023 Annual Report).
Significant accounting policies	Significant accounting policies The significant accounting policies used in the preparation of these condensed consolidated financial statements as of March 31, 2024 and for the three months ended March 31, 2024 and 2023 are consistent with those discussed in Note 2 in the 2023 Annual Report.
Use of estimates	Use of estimates The preparation of the financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could materially differ from those estimates. The most significant estimates in the Company’s condensed consolidated financial statements relate to success payment liabilities, contingent consideration, business combinations, accrued expenses, and operating lease right-of-use assets and liabilities.
Recent accounting pronouncements	Recent accounting pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (FASB) or other standard-setting bodies that the Company adopts as of the specified effective date. Unless otherwise discussed, the Company does not believe that the adoption of any recently issued standards has had or may have a material impact on its condensed consolidated financial statements or disclosures. In December 2023, the FASB issued ASU 2023-09 Income Taxes (Topic 740) Improvements to Income Tax Disclosures that requires disclosure of disaggregated income taxes paid, prescribes standard categories for the components of the effective tax rate reconciliation, and modifies other income tax-related disclosures. This ASU is effective for the Company's fiscal year 2025. Early adoption is permitted. The Company is currently evaluating income tax disclosures related to its annual report for fiscal year 2025. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280). The amendments in this update expand segment disclosure requirements, including new segment disclosure requirements for entities with a single reportable segment among other disclosure requirements. This update is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024. The adoption of this standard is not expected to have a material impact on the Company’s consolidated financial statements.

Acquisitions - (Tables)

Acquisitions - (Tables)	3 Months Ended
	Mar. 31, 2024
Cobalt Biomedicine, Inc
Business Acquisition [Line Items]
Schedule of Various Thresholds for Market Capitalizations Resulting Potential Success Payment and Additional Potential Contingent Consideration	The following table sets forth various thresholds for the Company’s market capitalizations as of the date of a change of control and the resulting potential Cobalt Success Payment and additional potential Cobalt Contingent Consideration: Sana market capitalization upon a change of control and resulting impact to Cobalt Success Cobalt Success Additional (in millions) Equal to or exceeds $ 8.1 billion $ 500 $ - Equal to or exceeds $ 7.4 billion, but less than $8.1 billion 150 350 Equal to or exceeds $ 6.8 billion, but less than $7.4 billion 100 400 Less than $ 6.8 billion - 500

License and collaboration agr_2

License and collaboration agreements (Tables)	3 Months Ended
	Mar. 31, 2024
License And Collaboration Agreements [Abstract]
Summary of Potential Success Payments	The following table summarizes the potential success payments and common stock price required for payment: Multiple of Equity Value at Issuance 5x 10x 20x 30x 40x Per share common stock price required for payment $ 20.00 $ 40.00 $ 80.00 $ 120.00 $ 160.00 Success payment(s) (in millions) $ 5.0 $ 15.0 $ 30.0 $ 50.0 $ 75.0

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2024
Fair Value Assets and Liabilities Measured on Recurring Basis	The following tables summarize the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy: March 31, 2024 Valuation Amortized Cost Gross Gross Estimated (in thousands) Financial assets: Cash equivalents: Money market funds Level 1 $ 85,137 $ - $ - $ 85,137 U.S. government and agency securities Level 2 79,179 1 ( 1 ) 79,179 Corporate debt securities Level 2 514 - - 514 Total cash equivalents 164,830 1 ( 1 ) 164,830 Short-term marketable securities: U.S. government and agency securities Level 2 122,671 8 ( 22 ) 122,657 Corporate debt securities Level 2 11,372 1 ( 2 ) 11,371 Total short-term marketable securities 134,043 9 ( 24 ) 134,028 Other assets Level 3 381 - - 381 Total financial assets $ 299,254 $ 10 $ ( 25 ) $ 299,239 Financial liabilities: Long-term financial liabilities: Contingent consideration Level 3 114,990 - - 114,990 Success payment liabilities Level 3 45,422 - - 45,422 Total long-term financial liabilities 160,412 - - 160,412 Total financial liabilities $ 160,412 $ - $ - $ 160,412 December 31, 2023 Valuation Amortized Cost Gross Gross Estimated (in thousands) Financial assets: Cash equivalents: Money market funds Level 1 $ 70,315 $ - $ - $ 70,315 U.S. government and agency securities Level 2 33,091 3 - 33,094 Corporate debt securities Level 2 1,062 - - 1,062 Total cash equivalents 104,468 3 - 104,471 Short-term marketable securities: U.S. government and agency securities Level 2 57,924 7 ( 78 ) 57,853 Corporate debt securities Level 2 13,817 9 ( 1 ) 13,825 Total short-term marketable securities 71,741 16 ( 79 ) 71,678 Other assets Level 3 359 - - 359 Total financial assets $ 176,568 $ 19 $ ( 79 ) $ 176,508 Financial liabilities: Long-term financial liabilities: Contingent consideration Level 3 109,606 - - 109,606 Success payment liabilities Level 3 12,799 - - 12,799 Total long-term financial liabilities 122,405 - - 122,405 Total financial liabilities $ 122,405 $ - $ - $ 122,405
Summary of Estimated Fair Value Available For Sale Debt Securities Continuous Unrealized Loss Position	The following table summarizes available-for-sale debt securities in a continuous unrealized loss position for less than and greater than twelve months for the periods presented: Less than 12 months 12 months or greater Total Fair value Unrealized losses Fair value Unrealized losses Fair value Unrealized losses (in thousands) March 31, 2024 U.S. government and agency securities $ 111,511 $ ( 9 ) $ 5,984 $ ( 14 ) $ 117,495 $ ( 23 ) Corporate debt securities 7,858 ( 2 ) - - 7,858 ( 2 ) Total $ 119,369 $ ( 11 ) $ 5,984 $ ( 14 ) $ 125,353 $ ( 25 ) December 31, 2023 U.S. government and agency securities $ 9,186 $ ( 3 ) $ 10,386 $ ( 75 ) $ 19,572 $ ( 78 ) Corporate debt securities 1,396 ( 1 ) - - 1,396 ( 1 ) Total $ 10,582 $ ( 4 ) $ 10,386 $ ( 75 ) $ 20,968 $ ( 79 )
Changes in 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: Contingent Cobalt Harvard (in thousands) Balance as of December 31, 2023 $ 109,606 $ 11,160 $ 1,639 Changes in fair value – expense 5,384 27,920 4,703 Balance as of March 31, 2024 $ 114,990 $ 39,080 $ 6,342
Success Payment Liabilities
Summary of Estimated Fair Value of Liabilities using Unobservable Inputs	The fair values of the Cobalt Success Payments and Harvard Success Payments were calculated using the following unobservable inputs: March 31, 2024 December 31, 2023 Unobservable Input Cobalt Harvard Cobalt Harvard Expected stock price volatility 72.5 % 72.5 % 72.5 % 72.5 % Expected term (years) 14.9 7.0 15.1 7.2
Cobalt Contingent Consideration
Summary of Estimated Fair Value of Liabilities using Unobservable Inputs	The fair value of the Cobalt Contingent Consideration was calculated using the following unobservable inputs: March 31, 2024 December 31, 2023 Unobservable Input Range Weighted-Average Range Weighted-Average Discount rates 10.9 % – 11.3 % 11.0 % 11.7 % – 12.4 % 11.9 % Probability of milestone achievement 5.0 % – 55.0 % 25.7 % 5.0 % – 55.0 % 25.7 %

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consists of the following: March 31, 2024 December 31, 2023 (in thousands) Laboratory equipment $ 53,447 $ 51,643 Leasehold improvements 33,848 31,361 Construction in progress 35,028 26,332 Computer equipment, software, and other 4,843 3,124 Total property and equipment, at cost 127,166 112,460 Less: Accumulated depreciation ( 45,517 ) ( 41,771 ) Property and equipment, net $ 81,649 $ 70,689

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	3 Months Ended
	Mar. 31, 2024
Payables and Accruals [Abstract]
Schedule of Accrued Compensation and Accrued Expenses and Other Current Liabilities	Accrued compensation and accrued expenses and other current liabilities consist of the following: March 31, 2024 December 31, 2023 (in thousands) Accrued compensation: Accrued bonuses $ 3,957 $ 14,379 Accrued paid time off 5,398 4,731 Accrued payroll 4,065 3,936 Other accrued compensation 545 676 Total accrued compensation $ 13,965 $ 23,722 Accrued expenses and other current liabilities: Accrued research and development services $ 9,749 $ 10,110 Accrued professional fees 3,509 1,470 Accrued property and equipment 5,053 9,200 Other accrued current liabilities 1,363 2,682 Total accrued expenses and other current liabilities $ 19,674 $ 23,462

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Schedule of Additional Information Related to Operating Leases	The following table contains additional information related to the Company’s operating leases: Location Use Approximate Commencement Dates Expiration Dates Seattle, WA Office/Laboratory 48,000 March 2019 to September 2020 December 2026 to April 2028 Cambridge, MA Office/Laboratory 60,000 March 2019 to January 2022 November 2025 to February 2028 South San Francisco, CA Office/Laboratory 100,000 December 2019 to April 2022 April 2024 to April 2030 Rochester, NY Office/Laboratory 3,000 January 2022 January 2025 Bothell, WA Office/Laboratory/Manufacturing 80,000 January 2023 January 2039
Summary of Lease Costs	The following table summarizes the Company’s lease costs: Three Months Ended March 31, 2024 2023 (in thousands) Operating lease cost $ 5,981 $ 7,061 Variable lease cost 2,014 1,982 Total lease cost $ 7,995 $ 9,043
Reconciliation of Undiscounted Operating Lease Cash Flows by Fiscal Year to Present Value of Operating Lease Liabilities	The following table reconciles the Company’s undiscounted operating lease cash flows by fiscal year to the present value of the operating lease liabilities as of March 31, 2024 (in thousands): 2024 (remaining 9 months) $ 16,971 2025 25,394 2026 22,472 2027 19,899 2028 15,226 2029 and thereafter 93,495 Total undiscounted lease payments 193,457 Less: imputed interest ( 85,980 ) Less: tenant improvement allowances ( 1,388 ) Present value of operating lease liabilities 106,089 Less: current portion of operating lease liabilities $ ( 13,167 ) Operating lease liabilities, net of current portion $ 92,922

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Schedule of Stock Based Compensation Expense Recognized	Stock-based compensation expense is recognized in the condensed consolidated statements of operations as follows: Three Months Ended March 31, 2024 2023 (in thousands) Research and development $ 5,848 $ 5,972 General and administrative 3,244 2,779 Total stock-based compensation expense $ 9,092 $ 8,751
Schedule of Unrecognized Stock-Based Compensation Costs Related to Unvested Awards and Weighted-Average Period Over Which Costs are Expected to be Recognized	Unrecognized stock-based compensation costs related to unvested awards and the weighted-average period over which the costs are expected to be recognized as of March 31, 2024 are as follows: Stock Options RSUs Unrecognized stock-based compensation expense (in thousands) $ 75,911 $ 27,876 Weighted-average period costs expected to be recognized (in years) 2.8 3.5
Summary of Stock Option Activity	A summary of the Company’s stock option activity is as follows: Stock Options Weighted-Average Weighted-Average Aggregate Intrinsic Outstanding as of December 31, 2023 26,849 $ 6.60 8.0 $ 11,235 Granted 5,551 9.49 Exercised ( 1,120 ) 4.40 Forfeited/Cancelled ( 1,048 ) 9.12 Outstanding as of March 31, 2024 30,232 $ 7.12 8.1 $ 113,377 Exercisable as of March 31, 2024 13,187 $ 7.01 7.1 $ 57,144
Schedule of Assumptions Used in Black-Scholes Option-Pricing Model for Estimating Fair Value of Stock Options Granted	The fair value of stock options granted to employees, directors, and consultants was estimated on the date of grant using the Black-Scholes option pricing model using the following assumptions: Three Months Ended March 31, Assumptions 2024 2023 Risk free interest rate 3.82 % – 4.34 % 3.47 % – 4.28 % Expected volatility 72.5 % 70.0 % Expected term (years) 6.25 6.25 – 6.50 Expected dividend 0 % 0 %
Summary of Additional Information Related to Stock Option Activity	The following table summarizes additional information related to stock option activity: Three Months Ended March 31, 2024 2023 Weighted average grant date fair value per share for options granted $ 6.46 $ 2.48 Aggregate intrinsic value of stock options exercised (in thousands) $ 3,586 $ 561
Summary of RSU Activity	A summary of the Company’s RSU activity is as follows: RSUs RSUs Unvested shares as of December 31, 2023 2,341 $ 3.88 Granted 2,461 9.49 Vested ( 388 ) 4.21 Forfeited ( 188 ) 5.21 Unvested shares as of March 31, 2024 4,226 $ 7.05

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Anti-dilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The following securities were excluded from the computation of net loss per diluted share of common stock for periods presented as their effect would have been anti-dilutive: Three Months Ended March 31, 2024 2023 (in thousands) Options to purchase common stock 30,232 29,202 Unvested restricted common stock - 5 Unvested RSUs 4,226 1,891 Total 34,458 31,098

Organization - Additional Infor

Organization - Additional Information (Details) - USD ($) shares in Thousands	1 Months Ended	3 Months Ended
	Feb. 29, 2024	Mar. 31, 2024	Dec. 31, 2023	Aug. 31, 2022
Description Of Organization [Line Items]
Accumulated deficit		$ 1,445,566,000	$ 1,338,091,000
Cash, cash equivalents and marketable securities		311,100,000
Success payment liabilities		43,000,000
Contingent consideration		63,700,000
Over Allotment Option
Description Of Organization [Line Items]
Number of warrants to purchase common stock	12,700
Net proceeds from issuance of common stock	$ 180,000,000	$ 180,000,000
Common Stock
Description Of Organization [Line Items]
Aggregate common stock sold		21,773
Common Stock | At The Market Offering
Description Of Organization [Line Items]
Aggregate common stock sold		150
Common Stock | Underwritten Public Offering
Description Of Organization [Line Items]
Aggregate common stock sold	21,800
Common Stock | Underwriters' Option To Purchase Additional Shares
Description Of Organization [Line Items]
Aggregate common stock sold	4,500
Pre Funded Warrants [Member] | Over Allotment Option
Description Of Organization [Line Items]
Number of warrants to purchase common stock	12,700
Cowen | At The Market Offering
Description Of Organization [Line Items]
Common stock maximum aggregate offering price				$ 150,000,000
Net proceeds from issuance of common stock		$ 28,700,000
Aggregate common stock sold		4,900

Acquisitions - Additional Infor

Acquisitions - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended
	Feb. 28, 2019	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Business Acquisition [Line Items]
Goodwill		$ 140,627,000		$ 140,627,000
Estimated fair value of contingent consideration, long-term liabilities		114,990,000		109,606,000
Change in the estimated fair value of contingent consideration		5,384,000	$ 5,460,000
Cobalt Biomedicine, Inc | Acquisition Agreement
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired	100%
Business acquisition, impairment of intangible assets or goodwill	$ 0
Goodwill	140,600,000
Maximum contingent consideration upon achievement of certain pre-specified development milestones	$ 500,000,000
Maximum term for success payment	20 years
Cobalt Biomedicine, Inc | Acquisition Agreement | Research and Development Expense
Business Acquisition [Line Items]
Estimated fair value of contingent consideration		115,000,000		109,600,000
Change in estimated fair value of success payment		27,900,000	4,800,000
Change in the estimated fair value of contingent consideration		5,400,000	$ 5,500,000
Cobalt Biomedicine, Inc | Acquisition Agreement | Long-term Liabilities | Research and Development Expense
Business Acquisition [Line Items]
Estimated fair value of success payment liability		$ 39,100,000		$ 11,200,000
Cobalt Biomedicine, Inc | Acquisition Agreement | Minimum
Business Acquisition [Line Items]
Threshold market capitalization	$ 8,100,000,000
Cobalt Biomedicine, Inc | Acquisition Agreement | Market Capitalization Equal to or Exceeds $8.1 billion
Business Acquisition [Line Items]
Cobalt success payment	500,000,000
Cobalt Biomedicine, Inc | Acquisition Agreement | IPR&D
Business Acquisition [Line Items]
Business combination, intangible assets	$ 59,200,000

Acquisitions - Schedule of Vari

Acquisitions - Schedule of Various Thresholds for Market Capitalizations Resulting Potential Success Payment and Additional Potential Contingent Consideration (Details) - Cobalt Biomedicine, Inc $ in Millions	1 Months Ended
	Feb. 28, 2019 USD ($)
Market Capitalization Equal to or Exceeds $8.1 billion
Business Acquisition [Line Items]
Cobalt Success Payment	$ 500
Market Capitalization Equal to or exceeds $7.4 billion, but less than $8.1 billion
Business Acquisition [Line Items]
Cobalt Success Payment	150
Additional potential Cobalt Contingent Consideration	350
Market Capitalization Equal to or exceeds $6.8 billion, but less than $7.4 billion
Business Acquisition [Line Items]
Cobalt Success Payment	100
Additional potential Cobalt Contingent Consideration	400
Market Capitalization Less than $6.8 billion
Business Acquisition [Line Items]
Additional potential Cobalt Contingent Consideration	$ 500

Acquisitions - Schedule of Va_2

Acquisitions - Schedule of Various Thresholds for Market Capitalizations Resulting Potential Success Payment and Additional Potential Contingent Consideration (Parenthetical) (Details) - Sana $ in Billions	Feb. 28, 2019 USD ($)
Market Capitalization Equal to or Exceeds $8.1 billion
Business Acquisition [Line Items]
Threshold market capitalization	$ 8.1
Market Capitalization Equal to or exceeds $7.4 billion, but less than $8.1 billion
Business Acquisition [Line Items]
Threshold market capitalization	7.4
Market Capitalization Equal to or exceeds $6.8 billion, but less than $7.4 billion
Business Acquisition [Line Items]
Threshold market capitalization	6.8
Market Capitalization Less than $6.8 billion
Business Acquisition [Line Items]
Threshold market capitalization	$ 6.8

License and Collaboration Agr_3

License and Collaboration Agreements - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2021	Dec. 31, 2023	Oct. 31, 2021
Beam Therapeutics Inc. (Beam) | Research and Development Expense
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment to collaborators				$ 50,000,000
Beam Therapeutics Inc. (Beam) | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Developmental and commercial milestone payments and royalties on licensed products payable						$ 65,000,000
Beam Therapeutics Inc. (Beam) | Minimum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Beneficial ownership percentage held by a member of board of directors						10%
Harvard College
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Share issue price	$ 4
Aggregated consideration paid	$ 12,000,000
Common stock shares issued	9,000,000
Payment to collaborators	$ 3,000,000
Maximum period expected to achieve for success payments	12 years
Harvard College | Long-term Liabilities
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Estimated fair value of success payment liability		$ 6,300,000			$ 1,600,000
Harvard College | Research and Development Expense
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Expense in connection with change in estimated fair value of success payment liability		$ 4,700,000	$ 600,000
Harvard College | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cobalt success payment	$ 175,000,000

License and Collaboration Agr_4

License and Collaboration Agreements - Summary of Potential Success Payments (Details) - Harvard College $ / shares in Units, $ in Millions	1 Months Ended
	Mar. 31, 2019 USD ($) $ / shares
Multiple of Equity Value at Issuance, 5x
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Per share common stock price required for payment | $ / shares	$ 20
Success payment(s) | $	$ 5
Multiple of Equity Value at Issuance, 10x
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Per share common stock price required for payment | $ / shares	$ 40
Success payment(s) | $	$ 15
Multiple of Equity Value at Issuance, 20x
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Per share common stock price required for payment | $ / shares	$ 80
Success payment(s) | $	$ 30
Multiple of Equity Value at Issuance, 30x
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Per share common stock price required for payment | $ / shares	$ 120
Success payment(s) | $	$ 50
Multiple of Equity Value at Issuance, 40x
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Per share common stock price required for payment | $ / shares	$ 160
Success payment(s) | $	$ 75

Restricted Cash - Additional In

Restricted Cash - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Restricted Cash And Cash Equivalents Items [Line Items]
Standby letters of credit	$ 3.8	$ 3.8
Restricted cash and cash equivalents, noncurrent, nature of restriction, description	standby letters of credit that are collateralized with a bank account at a financial institution in accordance with certain lease agreements. The aggregate amount of such standby letters of credit was

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Cash Equivalents
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	$ 164,830	$ 104,468
Gross Unrealized Holding Gains	1	3
Gross Unrealized Holding Losses	(1)
Estimated Fair Value	164,830	104,471
Cash Equivalents | Money Market Funds | Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	85,137	70,315
Estimated Fair Value	85,137	70,315
Cash Equivalents | US Government Agencies Debt Securities | Fair Value, Inputs, Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	79,179	33,091
Gross Unrealized Holding Gains	1	3
Gross Unrealized Holding Losses	(1)
Estimated Fair Value	79,179	33,094
Cash Equivalents | Corporate Debt Securities | Fair Value, Inputs, Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	514	1,062
Estimated Fair Value	514	1,062
Short-term Marketable Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	134,043	71,741
Gross Unrealized Holding Gains	9	16
Gross Unrealized Holding Losses	(24)	(79)
Estimated Fair Value	134,028	71,678
Short-term Marketable Securities | US Government Agencies Debt Securities | Fair Value, Inputs, Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	122,671	57,924
Gross Unrealized Holding Gains	8	7
Gross Unrealized Holding Losses	(22)	(78)
Estimated Fair Value	122,657	57,853
Short-term Marketable Securities | Corporate Debt Securities | Fair Value, Inputs, Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	11,372	13,817
Gross Unrealized Holding Gains	1	9
Gross Unrealized Holding Losses	(2)	(1)
Estimated Fair Value	11,371	13,825
Financial Assets
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	299,254	176,568
Gross Unrealized Holding Gains	10	19
Gross Unrealized Holding Losses	(25)	(79)
Estimated Fair Value	299,239	176,508
Other Assets | Fair Value, Inputs, Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	381	359
Estimated Fair Value	381	359
Long-term Financial Liabilities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	160,412	122,405
Estimated Fair Value	160,412	122,405
Long-term Financial Liabilities | Contingent consideration | Fair Value, Inputs, Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	114,990	109,606
Estimated Fair Value	114,990	109,606
Long-term Financial Liabilities | Success Payment Liabilities | Fair Value, Inputs, Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	45,422	12,799
Estimated Fair Value	45,422	12,799
Financial Liabilities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	160,412	122,405
Estimated Fair Value	$ 160,412	$ 122,405

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Estimated Fair Value Available For Sale Debt Securities Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value less than 12 months	$ 119,369	$ 10,582
Unrealized losses less than 12 months	(11)	(4)
Fair value 12 months or greater	5,984	10,386
Unrealized losses 12 months or greater	(14)	(75)
Total fair value	125,353	20,968
Total unrealized losses	(25)	(79)
US Government Agencies Debt Securities
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value less than 12 months	111,511	9,186
Unrealized losses less than 12 months	(9)	(3)
Fair value 12 months or greater	5,984	10,386
Unrealized losses 12 months or greater	(14)	(75)
Total fair value	117,495	19,572
Total unrealized losses	(23)	(78)
Corporate Debt Securities
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value less than 12 months	7,858	1,396
Unrealized losses less than 12 months	(2)	(1)
Total fair value	7,858	1,396
Total unrealized losses	$ (2)	$ (1)

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - Maximum	3 Months Ended
	Mar. 31, 2024
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities maturity period	2 years
Investments in securities with maturities period	1 year

Fair Value Measurements - Chang

Fair Value Measurements - Changes in Estimated Fair Value of Level 3 Financial Liabilities (Details) - Fair Value, Inputs, Level 3 $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Contingent Consideration
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 109,606
Changes infair value - expense	5,384
Ending Balance	114,990
Cobalt Success Payment Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	11,160
Changes infair value - expense	27,920
Ending Balance	39,080
Harvard Success Payment Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,639
Changes infair value - expense	4,703
Ending Balance	$ 6,342

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Estimated Fair Value of Contingent Consideration Unobservable Inputs (Details) - Cobalt Contingent Consideration	Mar. 31, 2024	Dec. 31, 2023
Discount Rates | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.109	0.117
Discount Rates | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.113	0.124
Discount Rates | Weighted-Average
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.11	0.119
Probability of Milestone Achievement | Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.05	0.05
Probability of Milestone Achievement | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.55	0.55
Probability of Milestone Achievement | Weighted-Average
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.257	0.257

Fair Value Measurements - Sum_4

Fair Value Measurements - Summary of Estimated Fair Value of Success Payment Liabilities Unobservable Inputs (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Expected Stock Price Volatility | Cobalt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input	0.725	0.725
Expected Stock Price Volatility | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input	0.725	0.725
Expected Term (Years) | Cobalt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input expected term (years)	14 years 10 months 24 days	15 years 1 month 6 days
Expected Term (Years) | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement input expected term (years)	7 years	7 years 2 months 12 days

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property Plant And Equipment [Line Items]
Property and equipment, at cost	$ 127,166	$ 112,460
Less: Accumulated depreciation	(45,517)	(41,771)
Property and equipment, net	81,649	70,689
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, at cost	53,447	51,643
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, at cost	33,848	31,361
Construction In Progress
Property Plant And Equipment [Line Items]
Property and equipment, at cost	35,028	26,332
Computer Equipment, Software and Other
Property Plant And Equipment [Line Items]
Property and equipment, at cost	$ 4,843	$ 3,124

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 3.7	$ 4.3

Accrued Liabilities - Schedule

Accrued Liabilities - Schedule of Accrued Compensation and Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Accrued compensation:
Accrued bonuses	$ 3,957	$ 14,379
Accrued paid time off	5,398	4,731
Accrued payroll	4,065	3,936
Other accrued compensation	545	676
Total accrued compensation	13,965	23,722
Accrued expenses and other current liabilities:
Accrued research and development services	9,749	10,110
Accrued professional fees	3,509	1,470
Accrued property and equipment	5,053	9,200
Other accrued current liabilities	1,363	2,682
Total accrued expenses and other current liabilities	$ 19,674	$ 23,462

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Jun. 30, 2022 USD ($) ft²	Mar. 31, 2024 USD ($)
Lessee Lease Description [Line Items]
Obligation to pay base rent		$ 193,457
Weighted-average remaining lease term		9 years 3 months 18 days
Weighted-average incremental borrowing rate		11.20%
Bothell, Washington
Lessee Lease Description [Line Items]
Square feet | ft²	79,565
Option to extend the lease term		with the option to extend the lease for up to three additional five-year terms.
Reimbursement of tenant improvements	$ 19,900
Optional additional tenant improvement allowance	$ 8,000
Optional additional tenant improvement allowance, interest rate	6.50%
Obligation to pay base rent	$ 68,800
Letter of credit	$ 1,600

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Additional Information Related to Operating Leases (Details) - ft²	1 Months Ended	3 Months Ended
	Jun. 30, 2022	Mar. 31, 2024
Seattle, WA | Office/Laboratory
Lessee Lease Description [Line Items]
Square feet		48,000
Commencement Dates, Beginning		2019-03
Commencement Dates, Ending		2020-09
Lease arrangement, contractual expiration period, beginning year		2026-12
Lease arrangement, contractual expiration period, ending year		2028-04
Cambridge, MA | Office/Laboratory
Lessee Lease Description [Line Items]
Square feet		60,000
Commencement Dates, Beginning		2019-03
Commencement Dates, Ending		2022-01
Lease arrangement, contractual expiration period, beginning year		2025-11
Lease arrangement, contractual expiration period, ending year		2028-02
South San Francisco, CA | Office/Laboratory
Lessee Lease Description [Line Items]
Square feet		100,000
Commencement Dates, Beginning		2019-12
Commencement Dates, Ending		2022-04
Lease arrangement, contractual expiration period, beginning year		2024-04
Lease arrangement, contractual expiration period, ending year		2030-04
Rochester, NY | Office/Laboratory
Lessee Lease Description [Line Items]
Square feet		3,000
Commencement Dates, Beginning		2022-01
Lease arrangement, contractual expiration period, ending year		2025-01
Bothell, WA
Lessee Lease Description [Line Items]
Square feet	79,565
Bothell, WA | Office/Laboratory/Manufacturing
Lessee Lease Description [Line Items]
Square feet		80,000
Commencement Dates, Beginning		2023-01
Lease arrangement, contractual expiration period, ending year		2039-01

Commitments and Contingencies_3

Commitments and Contingencies - Summary of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Lease, Cost [Abstract]
Operating lease cost	$ 5,981	$ 7,061
Variable lease cost	2,014	1,982
Total lease cost	$ 7,995	$ 9,043

Commitments and Contingencies_4

Commitments and Contingencies - Reconciliation of Undiscounted Operating Lease Cash Flows by Fiscal Year to Present Value of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
2024 (remaining 9 months)	$ 16,971
2025	25,394
2026	22,472
2027	19,899
2028	15,226
2029 and thereafter	93,495
Total undiscounted lease payments	193,457
Less: imputed interest	(85,980)
Less: tenant improvement allowances	(1,388)
Present value of operating lease liabilities	106,089
Less: current portion of operating lease liabilities	(13,167)	$ (13,195)
Operating lease liabilities, net of current portion	$ 92,922	$ 90,901

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended
	Feb. 29, 2024	Mar. 31, 2024	Aug. 31, 2022
Class Of Stock [Line Items]
Pre-funded warrants exercised		0
Description of pre-funded warrants exerciable		The pre-funded warrants are exercisable at any time; however, the holders of pre-funded warrants may not exercise the warrant if the holder, together with its affiliates, would beneficially own more than 4.99% of the number of shares of the Common Stock outstanding immediately after giving effect to such exercise. The holders of pre-funded warrants may increase or decrease such percentages not in excess of 19.99% by providing at least 61 days’ prior notice to the Company.
Maximum percentage of pre-funded warrants increase or decrease by providing atleast 61 days prior notice		19.99%
Pre-funded warrants not exercise if holder together owns maximum percentage of number of common stock outstanding		4.99%
Common Stock
Class Of Stock [Line Items]
Aggregate common stock sold		21,773,000
At The Market Offering | Common Stock
Class Of Stock [Line Items]
Aggregate common stock sold		150,000
Over Allotment Option
Class Of Stock [Line Items]
Number of warrants to purchase common stock	12,700,000
Net proceeds from issuance of common stock	$ 180,000,000	$ 180,000,000
Underwritten Public Offering | Common Stock
Class Of Stock [Line Items]
Aggregate common stock sold	21,800,000
Underwriters' Option To Purchase Additional Shares | Common Stock
Class Of Stock [Line Items]
Aggregate common stock sold	4,500,000
Pre Funded Warrants
Class Of Stock [Line Items]
Exercise price of common stock per share		$ 0.0001
Pre Funded Warrants | Over Allotment Option
Class Of Stock [Line Items]
Number of warrants to purchase common stock	12,700,000
Cowen | At The Market Offering
Class Of Stock [Line Items]
Common stock maximum aggregate offering price			$ 150,000,000
Aggregate common stock sold		4,900,000
Net proceeds from issuance of common stock		$ 28,700,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Feb. 28, 2021	Mar. 31, 2024	Mar. 31, 2023
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of vested		$ 4.1	$ 0.6
2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage related to employees able to purchase shares at lower of fair market value	85%
Number of shares available for future issuance		6,500,000
2021 Employee Stock Purchase Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage allowed for eligible employees to purchase shares of common stock	15%
2021 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance		20,900,000

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock Based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 9,092	$ 8,751
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	5,848	5,972
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 3,244	$ 2,779

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Unrecognized Stock-Based Compensation Costs Related to Unvested Awards and Weighted-Average Period Over Which Costs are Expected to be Recognized (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense (in thousands)	$ 75,911
Weighted-average period costs expected to be recognized (in years)	2 years 9 months 18 days
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense (in thousands)	$ 27,876
Weighted-average period costs expected to be recognized (in years)	3 years 6 months

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Stock Options
Stock Options Outstanding, Beginning Balance	26,849
Stock Options, Granted	5,551
Stock Options, Exercised	(1,120)
Stock Options, Forfeited/Cancelled	(1,048)
Stock Options Outstanding, Ending Balance	30,232	26,849
Stock Options Exercisable	13,187
Weighted-Average Exercise Price per Share
Weighted-Average Exercise Price per Share Outstanding, Beginning Balance	$ 6.6
Weighted-Average Exercise Price per Share, Granted	9.49
Weighted-Average Exercise Price per Share, Exercised	4.4
Weighted-Average Exercise Price per Share, Forfeited/Cancelled	9.12
Weighted-Average Exercise Price per Share Outstanding, Ending Balance	7.12	$ 6.6
Weighted-Average Exercise Price Per Share Exercisable	$ 7.01
Weighted-Average Remaining Contractual Life (years)
Weighted-Average Remaining Contractual Life (years), Outstanding	8 years 1 month 6 days	8 years
Weighted-Average Remaining Contractual Life (years), Exercisable	7 years 1 month 6 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding	$ 113,377	$ 11,235
Aggregate Intrinsic Value, Exercisable	$ 57,144

Stock-Based Compensation - Sc_3

Stock-Based Compensation - Schedule of Assumptions Used in Black-Scholes Option-Pricing Model for Estimating Fair Value of Stock Options Granted (Details)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk free interest rate, minimum	3.82%	3.47%
Risk free interest rate, maximum	4.34%	4.28%
Expected volatility	72.50%	70%
Expected term (years)	6 years 3 months
Expected dividend	0%	0%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)		6 years 3 months
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)		6 years 6 months

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Additional Information Related to Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-Based Payment Arrangement [Abstract]
Weighted average grant date fair value per share for options granted	$ 6.46	$ 2.48
Aggregate intrinsic value of stock options exercised (in thousands)	$ 3,586	$ 561

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of RSU Activity (Details) - Restricted Stock Units (RSUs) shares in Thousands	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested shares as of December 31, 2023 | shares	2,341
Granted | shares	2,461
Vested | shares	(388)
Forfeited | shares	(188)
Unvested shares as of March 31, 2024 | shares	4,226
Weighted-Average Grant Date Fair Value per Share
Unvested shares as of December 31, 2023 | $ / shares	$ 3.88
Granted | $ / shares	9.49
Vested | $ / shares	4.21
Forfeited | $ / shares	5.21
Unvested shares as of March 31, 2024 | $ / shares	$ 7.05

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Calculation of Basic and Diluted Net Loss Per Share of Common Stock (Details) - $ / shares shares in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Basic earnings per common share:
Weighted-average number of common shares - basic	217,290	191,228
Basic earnings (loss) per common share	$ (0.49)	$ (0.43)
Diluted earnings per common share:
Weighted-average number of common shares - basic	217,290	191,228
Effect of dilutive securities:
Weighted-average number of common shares - diluted	217,290	191,228
Diluted earnings (loss) per common share	$ (0.49)	$ (0.43)

Net Loss Per Share - Anti-dilut

Net Loss Per Share - Anti-dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share	34,458	31,098
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share	30,232	29,202
Unvested Restricted Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share	0	5
Unvested RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share	4,226	1,891

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Details)	3 Months Ended
	Mar. 31, 2024 USD ($)
Maximum
Defined Contribution Plan Disclosure [Line Items]
Matching contribution by employer under retirement and savings plan	$ 4,000