Sana Biotechnology (SANA) 10-Q 5 May 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	May 04, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
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	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		187,675,648
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
Trading Symbol	SANA
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 750,687	$ 124,806
Marketable securities	209,550	253,458
Prepaid expenses and other current assets	7,237	6,203
Total current assets	967,474	384,467
Property and equipment, net	50,986	46,775
Operating lease right-of-use assets	61,770	63,168
Restricted cash	2,143	2,143
Long-term marketable securities	21,627	33,731
Intangible asset	59,195	59,195
Goodwill	140,627	140,627
Other non-current assets	644	190
TOTAL ASSETS	1,304,466	730,296
Current liabilities:
Accounts payable	4,258	2,253
Accrued compensation	10,811	16,020
Accrued expenses and other current liabilities	11,171	9,466
Operating lease liabilities	3,910	3,712
Success payment liabilities	5,000
Total current liabilities	35,150	31,451
Operating lease liabilities, net of current portion	66,349	68,197
Contingent consideration	133,294	121,901
Success payment liabilities, net of current portion	187,151	76,494
Other non-current liabilities	539	540
Total liabilities	422,483	298,583
Commitments and contingencies (Note 10)
Convertible preferred stock, $0.0001 par value; zero and 537,786 shares authorized as of March 31, 2021 and December 31, 2020, respectively; zero and 134,113 shares issued and outstanding as of March 31, 2021 and December 31, 2020, respectively; aggregate liquidation preference of zero and $926,666 as of March 31, 2021 and December 31, 2020, respectively		852,897
Stockholders' equity (deficit):
Preferred stock, $0.0001 par value; 50,000 and zero shares authorized as of March 31, 2021 and December 31, 2020, respectively; zero shares issued and outstanding as of March 31, 2021 and December 31, 2020, respectively
Common stock, $0.0001 par value; 750,000 and 707,000 shares authorized as of March 31, 2021 and December 31, 2020, respectively; 178,941 and 16,170 shares issued and outstanding as of March 31, 2021 and December 31, 2020, respectively	18	2
Additional paid-in capital	1,491,958	8,216
Accumulated other comprehensive income	56	30
Accumulated deficit	(610,049)	(429,432)
Total stockholders' equity (deficit)	881,983	(421,184)
TOTAL LIABILITIES, CONVERTIBLE PREFERRED STOCK, AND STOCKHOLDERS' EQUITY (DEFICIT)	$ 1,304,466	$ 730,296

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	0	537,786,000
Convertible preferred stock, shares issued	0	134,113,000
Convertible preferred stock, shares outstanding	0	134,113,000
Convertible preferred stock, aggregate liquidation preference	$ 0	$ 926,666
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	50,000,000	0
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	707,000,000
Common stock, shares issued	178,941,000	16,170,000
Common stock, shares outstanding	178,941,000	16,170,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating expenses:
Research and development	$ 168,930	$ 27,320
General and administrative	11,821	5,955
Total operating expenses	180,751	33,275
Loss from operations	(180,751)	(33,275)
Interest income, net	121	395
Other income, net	13	5
Net loss	$ (180,617)	$ (32,875)
Net loss per share, basic and diluted	$ (1.52)	$ (3.04)
Weighted-average shares outstanding, basic and diluted	119,131	10,820

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (180,617)	$ (32,875)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on marketable securities, net	26	(10)
Total comprehensive loss	$ (180,591)	$ (32,885)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	IPO	Convertible Preferred Stock	Common Stock	Common StockIPO	Additional Paid-in Capital	Additional Paid-in CapitalIPO	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance at Dec. 31, 2019	$ (142,542)			$ 1		$ 1,558		$ 26	$ (144,127)
Beginning balance (in shares) at Dec. 31, 2019			106,890,000
Beginning balance at Dec. 31, 2019			$ 417,359
Beginning balance (in shares) at Dec. 31, 2019				10,003,000
Vesting of restricted stock (in shares)				1,427,000
Exercise of stock options	2					2
Exercise of stock options (in shares)				2,000
Stock-based compensation expense	755					755
Unrealized gain (loss) on marketable securities, net	(10)							(10)
Net loss	(32,875)								(32,875)
Ending balance at Mar. 31, 2020	(174,670)			$ 1		2,315		16	(177,002)
Ending balance (in shares) at Mar. 31, 2020			106,890,000
Ending balance at Mar. 31, 2020			$ 417,359
Ending balance (in shares) at Mar. 31, 2020				11,432,000
Beginning balance at Dec. 31, 2020	$ (421,184)			$ 2		8,216		30	(429,432)
Beginning balance (in shares) at Dec. 31, 2020	134,113,000		134,113,000
Beginning balance at Dec. 31, 2020	$ 852,897		$ 852,897
Beginning balance (in shares) at Dec. 31, 2020	16,170,000			16,170,000
Conversion of convertible preferred stock into common stock, upon initial public offering	$ 852,897			$ 13		852,884
Conversion of convertible preferred stock into common stock, upon initial public offering (in shares)			(134,113,000)
Conversion of convertible preferred stock into common stock, upon initial public offering			$ (852,897)
Conversion of convertible preferred stock into common stock, upon initial public offering (in shares)				134,113,000
Issuance of common stock in initial public offering, net of offering costs		$ 626,405			$ 3		$ 626,402
Issuance of common stock in initial public offering, net of offering costs (in shares)					27,025,000
Vesting of restricted stock (in shares)				1,428,000
Exercise of stock options	$ 298					298
Exercise of stock options (in shares)	205,000			205,000
Stock-based compensation expense	$ 4,158					4,158
Unrealized gain (loss) on marketable securities, net	26							26
Net loss	(180,617)								(180,617)
Ending balance at Mar. 31, 2021	$ 881,983			$ 18		$ 1,491,958		$ 56	$ (610,049)
Ending balance (in shares) at Mar. 31, 2021	0		0
Ending balance (in shares) at Mar. 31, 2021	178,941,000			178,941,000

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) (Unaudited) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
IPO
Issuance of common stock in initial public offering, net of offering costs	$ 49,220

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
OPERATING ACTIVITIES:
Net loss	$ (180,617)	$ (32,875)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	2,247	1,265
Stock-based compensation expense	4,158	755
Change in fair value of contingent consideration	11,393	362
Change in fair value of success payment liabilities	115,657	552
Non-cash expense in connection with license agreement		373
Non-cash expense for operating lease right-of-use assets	1,398	784
Other non-cash items, net	(1,013)	350
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,614)	(501)
Accounts payable	1,599	2,370
Accrued expenses and other liabilities	(3,121)	(2,982)
Net cash used in operating activities	(49,913)	(29,547)
INVESTING ACTIVITIES:
Purchases of marketable securities	(44,811)
Proceeds from sales and maturities of marketable securities	100,342	44,781
Purchases of property and equipment	(6,440)	(5,600)
Net cash provided by investing activities	49,091	39,181
FINANCING ACTIVITIES:
Proceeds from initial public offering of common stock, net of offering costs	626,405
Proceeds from exercise of stock options	298	2
Net cash provided by financing activities	626,703	2
Net increase in cash, cash equivalents, and restricted cash	625,881	9,636
Cash, cash equivalents, and restricted cash at beginning of period	126,949	81,807
Cash, cash equivalents, and restricted cash at end of period	752,830	91,443
SUPPLEMENTAL CASH FLOW DISCLOSURES:
Tenant improvement allowance included in operating lease liabilities	8,515	3,837
Purchases of property and equipment included in accounts payable and accrued liabilities	$ 3,157	644
Right-of-use assets obtained in exchange for operating lease liabilities		$ 14,271

Organization

Organization	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Organization	1. Organization Sana Biotechnology, Inc. (the Company or Sana) was incorporated in Delaware on July 13, 2018 (inception) as FD Therapeutics, Inc., and changed its name to Sana Biotechnology, Inc. on September 17, 2018. 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, acquiring technology, organizing and staffing the Company, business planning, establishing the Company’s intellectual property portfolio, raising capital, and providing general and administrative support for these operations. Reverse stock split In January 2021, the Company’s board of directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a 1-for-4 Initial public offering In February 2021, the Company successfully completed its initial public offering (IPO) of its common stock. In connection with its IPO, the Company issued 27.0 million shares of its common stock, including 3.5 million shares pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a price of $25.00 per share, and received $626.4 million in net proceeds, after deducting underwriting discounts and commissions of $45.2 million and offering expenses of $4.0 million. At the closing of the IPO, 134.1 million shares of convertible preferred stock then outstanding were automatically converted into shares of common stock. The related carrying value of the converted preferred stock of $852.9 million was reclassified to common stock and additional paid in-capital. Need for additional capital 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, 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, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of the Company’s products, protect the Company’s intellectual property and proprietary technology, 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 from the sale of additional equity or debt financings, or other capital which come in the form of strategic collaborations, 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. The Company has incurred operating losses each year since inception and expects such losses to continue for the foreseeable future. As of March 31, 2021, the Company had cash, cash equivalents, and marketable securities of $981.9 million, and an accumulated deficit of $610.0 million, which includes non-cash charges of $189.7 million and $82.0 million related to the revaluation of the success payment liabilities and contingent consideration, respectively.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of significant accounting policies The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 filed with the SEC on March 24, 2021 (2020 Form 10-K). The significant accounting policies used in preparation of these condensed consolidated financial statements as of March 31, 2021 and for the three months ended March 31, 2021 and 2020 are consistent with those discussed in Note 2 in the 2020 Form 10-K. Basis of presentation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. The Company’s condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (GAAP). 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 the valuation of stock options. Recent accounting pronouncements Recently adopted Accounting Standards Updates (ASU) No. 2016-13, Financial Instruments—Credit Losses (Topic 362): Measurement of Credit Losses on Financial Statements, ASU No. 2019-05 Financial Instruments—Credit Losses (Topic 326): Targeted Transition Relief, ASU No. 2019-11, Codification Improvements to Topic 326, Financial Instruments—Credit Losses In June 2016, the Financial Accounting Standards Board (FASB) issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 362): Measurement of Credit Losses on Financial Statements (ASU 2016-13). The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which the carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The targeted transition relief standard allows companies an option to irrevocably elect the fair value option of ASC 825-10, Financial Instruments-Overall, applied on an instrument-by-instrument basis for eligible instruments. The Company adopted ASU 2016-13 effective January 1, 2021. The adoption of the guidance did not have a material impact on the condensed consolidated financial statements and related disclosures, and there was no allowance for losses on available-for-sale debt securities attributable to credit risk for the three months ended March 31, 2021. Not yet adopted ASU No. 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment In January 2017, the FASB issued ASU 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04). To address concerns over the cost and complexity of the two-step goodwill impairment test, the amendments in this ASU remove the second step of the test. An entity will instead apply a one-step quantitative test and record the amount of goodwill impairment as the excess of a reporting unit’s carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The new guidance does not amend the optional qualitative assessment of goodwill impairment. The new standard will be effective beginning January 1, 2023. The adoption of ASU 2017-04 is not expected to have a material impact on the Company’s consolidated financial statements.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2021
Business Combinations [Abstract]
Acquisitions	3. Acquisitions Oscine Corp. In September 2020, the Company entered into a stock purchase agreement to acquire 100% of the outstanding equity in Oscine for a purchase price of $8.5 million, of which $7.6 million was an upfront cash payment, and $0.9 million was set aside to satisfy certain general representations and warranties as set forth in the stock purchase agreement (Oscine Holdback Amount). The primary asset acquired in the acquisition was IPR&D technology related to Oscine’s glial progenitor ex vivo Business Combinations The Oscine Holdback Amount will be held for 15 months, until December 2021, at which time the remainder of the balance, after payment of any claims, will be released. In addition, the Company is required to make up to an aggregate of $225.8 million in future milestone payments upon the achievement of certain development and commercial milestones. Cobalt Biomedicine, Inc. In February 2019, the Company acquired 100% of the outstanding equity in 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. Pursuant to the terms and conditions in the Cobalt acquisition agreement, the Company agreed to pay contingent consideration of up to an aggregate of $500.0 million upon the achievement of certain pre-specified development milestones (Cobalt Contingent Consideration), and a Cobalt Success Payment of up to $500.0 million, payable in cash or stock, at the Company’s discretion. The Cobalt Success Payment is payable if, at pre-determined valuation measurement dates, which are an IPO and periodically thereafter, the Company’s market capitalization equals or exceeds $8.1 billion, and the Company has an active program based on the fusogen technology in a clinical trial pursuant to an investigational new drug application (IND), or has filed for, or received approval for, a biologics license application (BLA) or new drug application (NDA). The Cobalt Success Payment can be achieved over a maximum of 20 years but could be shorter upon the occurrence of certain events. The IPO in February 2021 did not trigger a success payment to Cobalt. In addition to an IPO, a valuation measurement date is triggered upon a change of control when at least one company product utilizing technology acquired from Cobalt is the subject of an active research program. If there is a change of control and Company’s market capitalization falls below certain thresholds on the change of control date, the amount of the potential Cobalt Success Payment will decrease, and the amount of potential Cobalt Contingent Consideration will increase. The following table sets forth the different market capitalizations and resulting potential Cobalt Success Payment and additional potential Cobalt Contingent Consideration if there is a change of control subsequent to the IPO: Sana market capitalization upon a change of control and resulting impact to Cobalt Success Payment and additional potential Cobalt Contingent Consideration Cobalt Success Payment Additional potential Cobalt Contingent Consideration (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 expense. As of March 31, 2021 and December 31, 2020, the estimated fair value of the Cobalt Success Payment liability was $156.5 million and $64.7 million, respectively, and the estimated fair value of the Cobalt Contingent Consideration was $133.3 million and $121.9 million, respectively. For the three months ended March 31, 2021 and 2020, the Company recognized $91.8 million and $0.3 million in research and development expense in connection with the change in fair value of the Cobalt Success Payment, respectively, and $11.4 million and $0.4 million in research and development expense in connection with the change in fair value of the Cobalt Contingent Consideration, respectively.

Intangible Asset and Goodwill

Intangible Asset and Goodwill	3 Months Ended
	Mar. 31, 2021
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible asset and goodwill	4. Intangible asset and goodwill As of March 31, 2021, the Company had an intangible asset of $59.2 million, which consists of in-process research and development (IPR&D) acquired in 2019 from the Cobalt acquisition. The IPR&D 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 that will be amortized over its estimated useful life. As of March 31, 2021, there was no amortization of the intangible asset. As of March 31, 2021, the Company had goodwill of $140.6 million. The goodwill represents the excess of the purchase price over the estimated fair value of the net assets acquired from the Cobalt acquisition in 2019. There were no impairments of the intangible asset or goodwill since the acquisition.

License and collaboration agree

License and collaboration agreements	3 Months Ended
	Mar. 31, 2021
License And Collaboration Agreements [Abstract]
License and Collaboration Agreements	5. License and collaboration agreements 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 hypo-immune cells. Under the terms of the agreement, the Company may be required to make Harvard Success Payments up to an aggregate of $175.0 million, payable in cash, based on increases in the fair value of the Company’s common stock. The potential 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 pre-determined valuation measurement dates which include: the one year anniversary of the IPO and periodically thereafter, a merger, an asset sale, the sale of the majority of the shares held by the Company’s Series A convertible preferred stockholders, and the last day of the term of the success payments. The first Harvard valuation measurement date is expected to occur in February 2022, one year from the IPO. The aggregate amount of the Harvard Success Payments does not exceed an aggregate of $175.0 million, which would only occur upon a 40x increase in value. 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 are 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. The Harvard Success Payments can be achieved over a maximum of 12 years from the effective date of the agreement. 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 As of March 31, 2021 and December 31, 2020, the estimated fair value of the Harvard Success Payment liability was $35.7 million and $11.8 million, respectively. As of March 31, 2021 and December 31, 2020, $5.0 million and zero was recorded in short-term liabilities, and $30.7 million and $11.8 million were recorded in long-term liabilities in the condensed consolidated balance sheet, respectively. For the three months ended March 31, 2021 and 2020, the Company recognized $23.9 million and $0.2 million, respectively, in research and development expense of in connection with the change in the estimated fair value of the Harvard Success Payment liability. In connection with this agreement, the Company also paid Harvard a license payment of $6.0 million in June 2020 that was contingent upon the closing of the Company’s Series B convertible preferred stock financing.

Restricted Cash

Restricted Cash	3 Months Ended
	Mar. 31, 2021
Restricted Cash And Cash Equivalents [Abstract]
Restricted Cash	6. Restricted cash As of March 31, 2021 and December 31, 2020, the Company maintained standby letters of credit of $2.1 million, which are collateralized with a bank account at a financial institution in accordance with the lease agreements.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	7. 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, 2021 Valuation Hierarchy Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value (in thousands) Financial assets: Cash equivalents: Money market funds Level 1 $ 708,413 $ - $ - $ 708,413 U.S. government and agency securities Level 2 2,400 - - 2,400 Corporate debt securities Level 2 552 - - 552 Total cash equivalents 711,365 - - 711,365 Short-term marketable securities: U.S. government and agency securities Level 2 193,058 56 (1 ) 193,113 Corporate debt securities Level 2 16,444 - (7 ) 16,437 Total short-term marketable securities 209,502 56 (8 ) 209,550 Long-term marketable securities: U.S. government and agency securities Level 2 17,437 7 - 17,444 Corporate debt securities Level 2 4,182 1 - 4,183 Total long-term marketable securities 21,619 8 - 21,627 Total financial assets $ 942,486 $ 64 $ (8 ) $ 942,542 Financial liabilities: Short-term financial liabilities: Success payment liabilities Level 3 $ 5,000 $ - $ - $ 5,000 Long-term financial liabilities: Contingent consideration Level 3 133,294 - - $ 133,294 Success payment liabilities Level 3 187,151 - - 187,151 Total financial liabilities $ 325,445 $ - $ - $ 325,445 December 31, 2020 Valuation Hierarchy Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value (in thousands) Financial assets: Cash equivalents: Money market funds Level 1 $ 48,359 $ - $ - $ 48,359 U.S. government and agency securities Level 2 40,727 1 (1 ) 40,727 Corporate debt securities Level 2 1,138 - - 1,138 Total cash equivalents 90,224 1 (1 ) 90,224 Short-term marketable securities: U.S. government and agency securities Level 2 244,637 30 (5 ) 244,662 Corporate debt securities Level 2 8,798 - (2 ) 8,796 Total short-term marketable securities 253,435 30 (7 ) 253,458 Long-term marketable securities: U.S. government and agency securities Level 2 33,724 7 - 33,731 Total long-term marketable securities 33,724 7 - 33,731 Total financial assets $ 377,383 $ 38 $ (8 ) $ 377,413 Financial liabilities: Long-term financial liabilities: Contingent consideration Level 3 $ 121,901 $ - $ - $ 121,901 Success payment liabilities Level 3 76,494 - - 76,494 Total financial liabilities $ 198,395 $ - $ - $ 198,395 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, 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. Securities in an unrealized loss position have been in an unrealized loss position for less than one year. The Company determined that there was no material change in the credit risk of the above investments during the three months ended March 31, 2021. As such, an allowance for credit losses would not be recognized. As of March 31, 2021, 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, 2021, 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, 2021, the balance in accumulated other comprehensive income included the net unrealized gains related to the Company’s available-for-sale debt securities. There were no material realized gains or losses recognized on the sale or maturity of available-for-sale securities during the three months ended March 31, 2021 or 2020. The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities: Contingent Consideration Cobalt Success Payment Liability Harvard Success Payment Liability (in thousands) Balance as of December 31, 2020 $ 121,901 64,694 $ 11,800 Changes in fair value 11,393 91,757 23,900 Balance as of March 31, 2021 $ 133,294 $ 156,451 $ 35,700 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 on-going 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, 2021 December 31, 2020 Unobservable Input Range Weighted-Average Range Weighted-Average Discount rates 8.3% - 9.7% 8.8% 10.5% - 10.8% 10.6% Probability of milestone achievement 5.0% - 65.0% 27.9% 2.5% - 65.0% 27.6% 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 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 and Harvard success payment liabilities were calculated using the following unobservable inputs: March 31, 2021 December 31, 2020 Unobservable Input Cobalt Harvard Cobalt Harvard Expected stock price volatility 70.0% 70.0% 70.0% 70.0% Expected term (years) 17.9 10.0 18.1 10.2

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2021
Property Plant And Equipment [Abstract]
Property and Equipment, Net	8. Property and equipment, net Property and equipment, net consists of the following: March 31, 2021 December 31, 2020 (in thousands) Laboratory equipment $ 31,921 $ 26,958 Leasehold improvements 23,788 15,598 Construction in progress 4,367 11,180 Computer equipment, software and other 894 776 Total property and equipment, at cost 60,970 54,512 Less: Accumulated depreciation (9,984 ) (7,737 ) Property and equipment, net $ 50,986 $ 46,775 Depreciation expense was $2.2 million and $1.3 million for the three months ended March 31, 2021 and 2020, respectively.

Accrued Liabilities

Accrued Liabilities	3 Months Ended
	Mar. 31, 2021
Payables And Accruals [Abstract]
Accrued liabilities	9. Accrued liabilities Accrued compensation and accrued expenses and other current liabilities consist of the following: March 31, 2021 December 31, 2020 (in thousands) Accrued compensation: Accrued paid time off $ 4,561 $ 2,441 Accrued bonuses 3,194 11,582 Other accrued compensation 3,056 1,997 Total accrued compensation $ 10,811 $ 16,020 Accrued expenses and other current liabilities: Accrued research and development $ 3,121 $ 1,197 Accrued property and equipment 2,594 2,892 Accrued professional fees 2,051 1,717 Other 3,405 3,660 Total accrued expenses and other current liabilities $ 11,171 $ 9,466

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. Commitments and contingencies Lease commitments The Company’s lease portfolio is primarily comprised of operating leases for office, laboratory, and non-GMP pilot plant manufacturing space located in Seattle, WA, Cambridge, MA, and South San Francisco, CA. Operating leases have contractual periods expiring between April 2024 and April 2030. 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. The Seattle and South San Francisco lease agreements provide the Company with the option to renew for an additional period of five years. The Company is not reasonably certain it will renew these leases, and therefore the renewal options are not considered in the remaining lease term. Certain leases provide the Company the right to make tenant improvements, including the addition of laboratory space, and include a lease incentive allowance. The following table contains additional information related to our operating leases: Location Approximate Square Footage Commencement Dates Expiration Dates Seattle, WA 48,086 March 2019 to September 2020 December 2026 to April 2028 Cambridge, MA 56,859 March 2019 to May 2020 November 2025 to February 2028 South San Francisco, CA 66,075 December 2019 to October 2020 April 2024 to April 2030 Throughout the term of the lease agreements, the Company is responsible for paying certain operating costs, in addition to rent, 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, 2021 2020 (in thousands) Operating lease cost $ 2,898 $ 2,444 Shot-term lease cost 512 470 Variable lease cost 1,087 621 Total lease cost $ 4,497 $ 3,535 As of March 31, 2021, the weighted-average remaining lease term was 7.3 years and the weighted-average incremental borrowing rate was 10.72%. 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, 2021 (in thousands): 2021 (remaining 9 months) $ 10,300 2022 15,535 2023 15,989 2024 15,663 2025 15,621 2026 and thereafter 42,616 Total undiscounted lease payments 115,724 Less: imputed interest (36,950 ) Less: tenant improvement allowances (8,515 ) Present value of operating lease liabilities $ 70,259

Convertible Preferred Stock

Convertible Preferred Stock	3 Months Ended
	Mar. 31, 2021
Stockholders Equity Note [Abstract]
Convertible preferred stock	11. Convertible preferred stock In 2018, the Company issued 11.5 million shares of its Series A-1 convertible preferred stock at $4.00 per share, for gross proceeds of $45.9 million. In 2019, the Company issued 56.0 million shares of its Series A-2 convertible preferred stock at $4.00 per share, for gross proceeds of $224.0 million. In 2020, the Company issued 27.2 million shares of Series B convertible preferred stock at $16.00 per share, for gross proceeds of $435.6 million. Immediately prior to the closing of the Company’s IPO in February 2021, all outstanding shares of convertible preferred stock converted into 134.1 million shares of common stock. There were no shares of convertible preferred stock outstanding as of March 31, 2021.

Common Stock

Common Stock	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Common Stock	12. Common stock The Company amended and restated its certificate of incorporation, effective February 2021, increasing the number of shares of all classes of stock the Company has authority to issue to 800.0 million shares, of which 750.0 million shares are common stock, and 50.0 million shares are preferred stock. As of March 31, 2021, there were 178.9 million shares of the Company’s common stock outstanding, excluding 8.6 million shares of restricted common stock outstanding that are subject to vesting requirements.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based compensation	13. Stock-based compensation 2021 Incentive Award Plan In February 2021, the Company adopted the 2021 Incentive Award Plan, which became effective on the completion of the Company’s IPO. The 2021 Incentive Award Plan provides for a variety of stock-based compensation awards, including stock options, restricted stock awards (RSAs), and restricted stock units (RSUs). In conjunction with adopting the 2021 Incentive Award Plan, the Company discontinued the 2018 Equity Plan and the restricted stock unit plan with respect to new equity awards. The number of shares of the Company’s common stock reserved for issuance is subject to automatically increase by 5% of all shares outstanding at the beginning of each calendar year. 2021 Employee Stock Purchase Plan In February 2021, the Company adopted the 2021 Employee Stock Purchase Plan (2021 ESPP), which became effective on the completion of the Company’s IPO. The 2021 ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their earnings, subject to plan limitations. Unless otherwise determined by the Company’s board of directors, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first date of an offering or on the purchase date. The number of shares of the Company’s common stock reserved for issuance under the 2021 ESPP is subject to automatically increase by 1% of all shares outstanding at the beginning of each calendar year. The Company may specify offerings with durations of not more than 27 months and may specify shorter purchase periods within each offering. 2018 Equity Incentive Plan In October 2018, the Company adopted the 2018 Equity Incentive Plan (2018 Plan) under which it may grant incentive stock options, non-statutory stock options, RSAs, RSUs, and other stock-based awards to any person, including officers, directors, and consultants. Terms of stock agreements, including vesting requirements, are determined by the Company’s board of directors, or by a committee appointed by the board of directors, subject to the provisions of the 2018 Plan. Stock-based compensation expense Stock-based compensation expense is recognized in the condensed consolidated statements of operations as follows: Three Months Ended March 31, 2021 2020 (in thousands) Research and development $ 2,668 $ 648 General and administrative 1,490 107 Total stock-based compensation expense $ 4,158 $ 755 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, 2021 are as follows: Stock Options RSAs RSUs Unrecognized stock-based compensation expense (in thousands) $ 49,600 $ 2,875 $ 214 Weighted-average period costs expected to be recognized (years) 3.3 1.6 1.9 Stock options A summary of the Company’s stock option activity is as follows: Stock Options (in thousands) Weighted- Average Exercise Price per Share Weighted-Average Remaining Contractual Life (years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2020 15,677 $ 4.52 Granted 526 27.14 Exercised (205 ) 1.35 Forfeited/Cancelled (217 ) 3.35 Outstanding as of March 31, 2021 15,781 $ 5.33 9.2 $ 444,040 Exercisable as of March 31, 2021 2,324 $ 1.46 8.5 $ 74,383 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 2021 2020 Risk free interest rate 0.64% - 1.11% 0.48%-1.51% Expected volatility 70 % 70 % Expected term (years) 5.50 - 6.25 6.25-6.25 Expected dividend 0 % 0 % The following table summarizes additional information related to stock option activity: Three Months Ended March 31, 2021 2020 Weighted average grant date fair value per share for options granted $ 16.75 $ 1.08 Aggregate intrinsic value of stock options exercised (in thousands) $ 3,764 $ - Restricted stock awards A summary of the Company’s RSA activity is as follows: RSAs (in thousands) Weighted-Average Grant Date Fair Value per Share Unvested shares as of December 31, 2020 10,079 $ 0.33 Vested (1,428 ) 0.25 Forfeited (14 ) 0.68 Unvested shares as of March 31, 2021 8,637 $ 0.34 The fair value of vested RSAs was $0.4 million and $0.2 million for the three months ended March 31, 2021 and 2020, respectively.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	14. 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.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	15. Net loss per share Basic and diluted net loss per common share is calculated by dividing net loss by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. The Company was in a loss position for all periods presented, therefore basic net loss per share and diluted net loss per share are the same for all periods as the inclusion of all potential common securities outstanding would have been anti-dilutive. The following table sets forth the computation of basic and diluted net loss per share of common stock: Three Months Ended March 31, 2021 2020 (in thousands, except per share amounts) Net loss $ (180,617 ) $ (32,875 ) Weighted-average shares outstanding, basic and diluted 119,131 10,820 Net loss per share, basic and diluted $ (1.52 ) $ (3.04 ) The amounts in the table below were excluded from the calculation of diluted net loss per share due to their anti-dilutive effect: Three Months Ended March 31, 2021 2020 (in thousands) Series A-1 convertible preferred stock - 11,463 Series A-2 convertible preferred stock - 95,427 Unvested restricted common stock 8,637 15,352 Options to purchase common stock 2,324 357 Unvested RSUs 325 345 Total 11,286 122,944

Employee Benefit Plan

Employee Benefit Plan	3 Months Ended
	Mar. 31, 2021
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plan	16. 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 has not made a matching contribution since plan inception.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
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. The Company’s condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (GAAP).
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 the valuation of stock options.
Recent accounting pronouncements	Recent accounting pronouncements Recently adopted Accounting Standards Updates (ASU) No. 2016-13, Financial Instruments—Credit Losses (Topic 362): Measurement of Credit Losses on Financial Statements, ASU No. 2019-05 Financial Instruments—Credit Losses (Topic 326): Targeted Transition Relief, ASU No. 2019-11, Codification Improvements to Topic 326, Financial Instruments—Credit Losses In June 2016, the Financial Accounting Standards Board (FASB) issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 362): Measurement of Credit Losses on Financial Statements (ASU 2016-13). The new standard requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. It also limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which the carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. The targeted transition relief standard allows companies an option to irrevocably elect the fair value option of ASC 825-10, Financial Instruments-Overall, applied on an instrument-by-instrument basis for eligible instruments. The Company adopted ASU 2016-13 effective January 1, 2021. The adoption of the guidance did not have a material impact on the condensed consolidated financial statements and related disclosures, and there was no allowance for losses on available-for-sale debt securities attributable to credit risk for the three months ended March 31, 2021. Not yet adopted ASU No. 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment In January 2017, the FASB issued ASU 2017-04, Intangibles—Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment (ASU 2017-04). To address concerns over the cost and complexity of the two-step goodwill impairment test, the amendments in this ASU remove the second step of the test. An entity will instead apply a one-step quantitative test and record the amount of goodwill impairment as the excess of a reporting unit’s carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The new guidance does not amend the optional qualitative assessment of goodwill impairment. The new standard will be effective beginning January 1, 2023. The adoption of ASU 2017-04 is not expected to have a material impact on the Company’s consolidated financial statements.

Acquisitions - (Tables)

Acquisitions - (Tables)	3 Months Ended
	Mar. 31, 2021
Business Combinations [Abstract]
Schedule of Different Market Capitalizations Resulting Potential Success Payment and Additional Potential Contingent Consideration	The following table sets forth the different market capitalizations and resulting potential Cobalt Success Payment and additional potential Cobalt Contingent Consideration if there is a change of control subsequent to the IPO: Sana market capitalization upon a change of control and resulting impact to Cobalt Success Payment and additional potential Cobalt Contingent Consideration Cobalt Success Payment Additional potential Cobalt Contingent Consideration (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, 2021
License And Collaboration Agreements [Abstract]
Summary of Potential Success Payments and Common Stock Price Required for Payment	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, 2021
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, 2021 Valuation Hierarchy Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value (in thousands) Financial assets: Cash equivalents: Money market funds Level 1 $ 708,413 $ - $ - $ 708,413 U.S. government and agency securities Level 2 2,400 - - 2,400 Corporate debt securities Level 2 552 - - 552 Total cash equivalents 711,365 - - 711,365 Short-term marketable securities: U.S. government and agency securities Level 2 193,058 56 (1 ) 193,113 Corporate debt securities Level 2 16,444 - (7 ) 16,437 Total short-term marketable securities 209,502 56 (8 ) 209,550 Long-term marketable securities: U.S. government and agency securities Level 2 17,437 7 - 17,444 Corporate debt securities Level 2 4,182 1 - 4,183 Total long-term marketable securities 21,619 8 - 21,627 Total financial assets $ 942,486 $ 64 $ (8 ) $ 942,542 Financial liabilities: Short-term financial liabilities: Success payment liabilities Level 3 $ 5,000 $ - $ - $ 5,000 Long-term financial liabilities: Contingent consideration Level 3 133,294 - - $ 133,294 Success payment liabilities Level 3 187,151 - - 187,151 Total financial liabilities $ 325,445 $ - $ - $ 325,445 December 31, 2020 Valuation Hierarchy Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value (in thousands) Financial assets: Cash equivalents: Money market funds Level 1 $ 48,359 $ - $ - $ 48,359 U.S. government and agency securities Level 2 40,727 1 (1 ) 40,727 Corporate debt securities Level 2 1,138 - - 1,138 Total cash equivalents 90,224 1 (1 ) 90,224 Short-term marketable securities: U.S. government and agency securities Level 2 244,637 30 (5 ) 244,662 Corporate debt securities Level 2 8,798 - (2 ) 8,796 Total short-term marketable securities 253,435 30 (7 ) 253,458 Long-term marketable securities: U.S. government and agency securities Level 2 33,724 7 - 33,731 Total long-term marketable securities 33,724 7 - 33,731 Total financial assets $ 377,383 $ 38 $ (8 ) $ 377,413 Financial liabilities: Long-term financial liabilities: Contingent consideration Level 3 $ 121,901 $ - $ - $ 121,901 Success payment liabilities Level 3 76,494 - - 76,494 Total financial liabilities $ 198,395 $ - $ - $ 198,395
Summary of Changes in Estimated Fair Value of 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 Consideration Cobalt Success Payment Liability Harvard Success Payment Liability (in thousands) Balance as of December 31, 2020 $ 121,901 64,694 $ 11,800 Changes in fair value 11,393 91,757 23,900 Balance as of March 31, 2021 $ 133,294 $ 156,451 $ 35,700
Cobalt Contingent Consideration
Fair Value of Contingent Consideration and Success Payment Liabilities Calculated Using Unobservable Inputs	The fair value of the Cobalt Contingent Consideration was calculated using the following unobservable inputs: March 31, 2021 December 31, 2020 Unobservable Input Range Weighted-Average Range Weighted-Average Discount rates 8.3% - 9.7% 8.8% 10.5% - 10.8% 10.6% Probability of milestone achievement 5.0% - 65.0% 27.9% 2.5% - 65.0% 27.6%
Cobalt and Harvard Success Payment
Fair Value of Contingent Consideration and Success Payment Liabilities Calculated Using Unobservable Inputs	The fair values of the Cobalt and Harvard success payment liabilities were calculated using the following unobservable inputs: March 31, 2021 December 31, 2020 Unobservable Input Cobalt Harvard Cobalt Harvard Expected stock price volatility 70.0% 70.0% 70.0% 70.0% Expected term (years) 17.9 10.0 18.1 10.2

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2021
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consists of the following: March 31, 2021 December 31, 2020 (in thousands) Laboratory equipment $ 31,921 $ 26,958 Leasehold improvements 23,788 15,598 Construction in progress 4,367 11,180 Computer equipment, software and other 894 776 Total property and equipment, at cost 60,970 54,512 Less: Accumulated depreciation (9,984 ) (7,737 ) Property and equipment, net $ 50,986 $ 46,775

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	3 Months Ended
	Mar. 31, 2021
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, 2021 December 31, 2020 (in thousands) Accrued compensation: Accrued paid time off $ 4,561 $ 2,441 Accrued bonuses 3,194 11,582 Other accrued compensation 3,056 1,997 Total accrued compensation $ 10,811 $ 16,020 Accrued expenses and other current liabilities: Accrued research and development $ 3,121 $ 1,197 Accrued property and equipment 2,594 2,892 Accrued professional fees 2,051 1,717 Other 3,405 3,660 Total accrued expenses and other current liabilities $ 11,171 $ 9,466

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Schedule of Additional Information Related to Operating Leases	The following table contains additional information related to our operating leases: Location Approximate Square Footage Commencement Dates Expiration Dates Seattle, WA 48,086 March 2019 to September 2020 December 2026 to April 2028 Cambridge, MA 56,859 March 2019 to May 2020 November 2025 to February 2028 South San Francisco, CA 66,075 December 2019 to October 2020 April 2024 to April 2030
Summary of Lease Costs	The following table summarizes the Company’s lease costs: Three Months Ended March 31, 2021 2020 (in thousands) Operating lease cost $ 2,898 $ 2,444 Shot-term lease cost 512 470 Variable lease cost 1,087 621 Total lease cost $ 4,497 $ 3,535
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, 2021 (in thousands): 2021 (remaining 9 months) $ 10,300 2022 15,535 2023 15,989 2024 15,663 2025 15,621 2026 and thereafter 42,616 Total undiscounted lease payments 115,724 Less: imputed interest (36,950 ) Less: tenant improvement allowances (8,515 ) Present value of operating lease liabilities $ 70,259

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [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, 2021 2020 (in thousands) Research and development $ 2,668 $ 648 General and administrative 1,490 107 Total stock-based compensation expense $ 4,158 $ 755
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, 2021 are as follows: Stock Options RSAs RSUs Unrecognized stock-based compensation expense (in thousands) $ 49,600 $ 2,875 $ 214 Weighted-average period costs expected to be recognized (years) 3.3 1.6 1.9
Summary of Stock Option Activity	A summary of the Company’s stock option activity is as follows: Stock Options (in thousands) Weighted- Average Exercise Price per Share Weighted-Average Remaining Contractual Life (years) Aggregate Intrinsic Value (in thousands) Outstanding as of December 31, 2020 15,677 $ 4.52 Granted 526 27.14 Exercised (205 ) 1.35 Forfeited/Cancelled (217 ) 3.35 Outstanding as of March 31, 2021 15,781 $ 5.33 9.2 $ 444,040 Exercisable as of March 31, 2021 2,324 $ 1.46 8.5 $ 74,383
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 2021 2020 Risk free interest rate 0.64% - 1.11% 0.48%-1.51% Expected volatility 70 % 70 % Expected term (years) 5.50 - 6.25 6.25-6.25 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, 2021 2020 Weighted average grant date fair value per share for options granted $ 16.75 $ 1.08 Aggregate intrinsic value of stock options exercised (in thousands) $ 3,764 $ -
Summary of RSA Activity	A summary of the Company’s RSA activity is as follows: RSAs (in thousands) Weighted-Average Grant Date Fair Value per Share Unvested shares as of December 31, 2020 10,079 $ 0.33 Vested (1,428 ) 0.25 Forfeited (14 ) 0.68 Unvested shares as of March 31, 2021 8,637 $ 0.34

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss Per Share of Common Stock	The following table sets forth the computation of basic and diluted net loss per share of common stock: Three Months Ended March 31, 2021 2020 (in thousands, except per share amounts) Net loss $ (180,617 ) $ (32,875 ) Weighted-average shares outstanding, basic and diluted 119,131 10,820 Net loss per share, basic and diluted $ (1.52 ) $ (3.04 )
Anti-dilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The amounts in the table below were excluded from the calculation of diluted net loss per share due to their anti-dilutive effect: Three Months Ended March 31, 2021 2020 (in thousands) Series A-1 convertible preferred stock - 11,463 Series A-2 convertible preferred stock - 95,427 Unvested restricted common stock 8,637 15,352 Options to purchase common stock 2,324 357 Unvested RSUs 325 345 Total 11,286 122,944

Organization - Additional Infor

Organization - Additional Information (Details) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended
	Feb. 28, 2021USD ($)$ / sharesshares	Jan. 31, 2021	Mar. 31, 2021USD ($)shares	Dec. 31, 2020USD ($)shares	Mar. 31, 2020shares	Dec. 31, 2019shares
Description Of Organization [Line Items]
Entity incorporation, date of Incorporation			Jul. 13, 2018
Reverse stock split, conversion ratio		0.25
Reverse stock split, description			In January 2021, the Company’s board of directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a 1-for-4 reverse stock split of shares of the Company’s common and convertible preferred stock, which was effected on January 27, 2021.
Proceeds from public offering of common stock, net of offering costs			$ 626,405
Convertible preferred stock, shares outstanding | shares			0	134,113,000
Accumulated deficit			$ 610,049	$ 429,432
Cash, cash equivalents and marketable securities			981,900
Success payment liabilities			189,700
Contingent consideration			$ 82,000
Convertible Preferred Stock
Description Of Organization [Line Items]
Convertible preferred stock, shares outstanding | shares			0	134,113,000	106,890,000	106,890,000
Common Stock
Description Of Organization [Line Items]
Conversion of preferred stock into common stock (in shares) | shares			134,113,000
IPO
Description Of Organization [Line Items]
Convertible preferred stock, shares outstanding | shares	134,100,000
IPO | Convertible Preferred Stock
Description Of Organization [Line Items]
Conversion of preferred stock into common stock (in shares) | shares	134,100,000
Carrying value of converted preferred stock	$ 852,900
IPO | Common Stock
Description Of Organization [Line Items]
Issuance of common stock in initial public offering, net of offering costs (in shares) | shares	27,000,000		27,025,000
Common stock price per share | $ / shares	$ 25
Proceeds from public offering of common stock, net of offering costs	$ 626,400
Payments of underwriting discounts and commissions	45,200
Offering expenses	$ 4,000
Underwriters’ Option To Purchase Additional Shares | Common Stock
Description Of Organization [Line Items]
Issuance of common stock in initial public offering, net of offering costs (in shares) | shares	3,500,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details)	Mar. 31, 2021USD ($)
Summary Of Significant Accounting Policies [Line Items]
Allowance for losses on available-for-sale debt securities	$ 0
ASU 2016-13
Summary Of Significant Accounting Policies [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2021
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true

Acquisitions - Additional Infor

Acquisitions - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended
	Sep. 30, 2020	Feb. 28, 2019	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2020
Oscine
Business Acquisition [Line Items]
Business acquisition, consideration transferred	$ 8,500,000
Oscine | Stock Purchase Agreement
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired	100.00%			100.00%
Business acquisition, consideration transferred	$ 8,500,000			$ 8,500,000
Business acquisition, consideration transferred, cash	7,600,000
Business acquisition, consideration holdback amount	900,000
Oscine | Stock Purchase Agreement | Maximum
Business Acquisition [Line Items]
Future milestone payments upon achievement of certain development and commercial milestones	$ 225,800,000			$ 225,800,000
Cobalt Biomedicine Inc | Acquisition Agreement
Business Acquisition [Line Items]
Business acquisition, percentage of voting interests acquired		100.00%
Maximum success payment upon achievement of certain pre-specified development milestones		$ 500,000,000
Maximum period for success payment to achieve		20 years
Estimated fair value of success payment liability			$ 156,500,000			$ 64,700,000
Estimated fair value of contingent consideration			133,300,000			$ 121,900,000
Research and development expense in connection with change in fair value of success payment			91,800,000		$ 300,000
Research and development expense in connection with change in fair value of contingent consideration			$ 11,400,000		$ 400,000
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 | Minimum [Member]
Business Acquisition [Line Items]
Threshold market capitalization		$ 8,100,000,000

Acquisitions - Schedule of Diff

Acquisitions - Schedule of Different Market Capitalizations Resulting Potential Success Payment and Additional Potential Contingent Consideration (Details) - Cobalt Biomedicine Inc $ in Millions	1 Months Ended
	Feb. 28, 2019USD ($)
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 Di_2

Acquisitions - Schedule of Different Market Capitalizations Resulting Potential Success Payment and Additional Potential Contingent Consideration (Parenthetical) (Details) - Sana $ in Billions	Feb. 28, 2019USD ($)
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

Intangible Asset and Goodwill -

Intangible Asset and Goodwill - Additional Information (Details) - USD ($)	3 Months Ended	11 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2019	Dec. 31, 2020
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible asset	$ 59,195,000		$ 59,195,000
Amortization of intangible asset	0
Goodwill	140,627,000		140,627,000
Impairments of intangible asset or goodwill	$ 0	$ 0	$ 0

License and Collaboration Agr_3

License and Collaboration Agreements - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended
	Jun. 30, 2020	Mar. 31, 2019	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense			$ 168,930,000	$ 27,320,000
Series B Convertible Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Share issue price					$ 16
Harvard College
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Share issue price		$ 4
Maximum period expected to achieve for success payments		12 years
Estimated fair value of success payment liability			35,700,000		$ 11,800,000
Research and development expense			23,900,000	$ 200,000
Harvard College | Series B Convertible Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License payment upon closing of equity financing	$ 6,000,000
Harvard College | Short-term Liabilities
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Estimated fair value of success payment liability			5,000,000		0
Harvard College | Long-term Liabilities
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Estimated fair value of success payment liability			$ 30,700,000		$ 11,800,000
Harvard College | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential success payment		$ 175,000,000

License and Collaboration Agr_4

License and Collaboration Agreements - Summary of Potential Success Payments and Common Stock Price Required for Payment (Details) - Harvard College $ / shares in Units, $ in Millions	1 Months Ended
	Mar. 31, 2019USD ($)$ / 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 Thousands	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Restricted Cash And Cash Equivalents [Abstract]
Standby letters of credit	$ 2,143	$ 2,143
Restricted cash and cash equivalents, noncurrent, nature of restriction, description	standby letters of credit

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, 2021	Dec. 31, 2020
Cash Equivalents
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	$ 711,365	$ 90,224
Gross Unrealized Holding Gains	0	1
Gross Unrealized Holding Losses	0	(1)
Estimated Fair Value	711,365	90,224
Cash Equivalents | Money Market Funds | Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	708,413	48,359
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	708,413	48,359
Cash Equivalents | US Government and Agencies Securities | Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	2,400	40,727
Gross Unrealized Holding Gains	0	1
Gross Unrealized Holding Losses	0	(1)
Estimated Fair Value	2,400	40,727
Cash Equivalents | Corporate Debt Securities | Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	552	1,138
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	552	1,138
Short-term Marketable Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	209,502	253,435
Gross Unrealized Holding Gains	56	30
Gross Unrealized Holding Losses	(8)	(7)
Estimated Fair Value	209,550	253,458
Short-term Marketable Securities | US Government and Agencies Securities | Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	193,058	244,637
Gross Unrealized Holding Gains	56	30
Gross Unrealized Holding Losses	(1)	(5)
Estimated Fair Value	193,113	244,662
Short-term Marketable Securities | Corporate Debt Securities | Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	16,444	8,798
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	(7)	(2)
Estimated Fair Value	16,437	8,796
Long-term Marketable Securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	21,619	33,724
Gross Unrealized Holding Gains	8	7
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	21,627	33,731
Long-term Marketable Securities | US Government and Agencies Securities | Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	17,437	33,724
Gross Unrealized Holding Gains	7	7
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	17,444	33,731
Long-term Marketable Securities | Corporate Debt Securities | Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	4,182
Gross Unrealized Holding Gains	1
Gross Unrealized Holding Losses	0
Estimated Fair Value	4,183
Financial Assets
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	942,486	377,383
Gross Unrealized Holding Gains	64	38
Gross Unrealized Holding Losses	(8)	(8)
Estimated Fair Value	942,542	377,413
Short-term Financial Liabilities | Success Payment Liabilities | Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	5,000
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	0
Estimated Fair Value	5,000
Long-term Financial Liabilities | Contingent Consideration | Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	133,294	121,901
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	133,294	121,901
Long-term Financial Liabilities | Success Payment Liabilities | Level 3
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	187,151	76,494
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	187,151	76,494
Financial Liabilities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Amortized Cost	325,445	198,395
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	$ 325,445	$ 198,395

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Realized gains or losses recognized on sale or maturity of available-for-sale securities	$ 0	$ 0
Maximum
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 - Sum_2

Fair Value Measurements - Summary of Changes in Estimated Fair Value of Financial Liabilities (Details) - Level 3 $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Contingent Consideration
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance as of December 31, 2020	$ 121,901
Changes in fair value	11,393
Balance as of March 31, 2021	133,294
Cobalt Success Payment Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance as of December 31, 2020	64,694
Changes in fair value	91,757
Balance as of March 31, 2021	156,451
Harvard Success Payment Liabilitiy
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance as of December 31, 2020	11,800
Changes in fair value	23,900
Balance as of March 31, 2021	$ 35,700

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Contingent Consideration Calculated Using Unobservable Inputs (Details) - Cobalt Contingent Consideration	Mar. 31, 2021	Dec. 31, 2020
Discount Rates | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.083	0.105
Discount Rates | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.097	0.108
Discount Rates | Weighted-Average
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.088	0.106
Probability of Milestone Achievement | Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.050	0.025
Probability of Milestone Achievement | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.650	0.650
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	0.279	0.276

Fair Value Measurements - Fai_2

Fair Value Measurements - Fair Value of Success Payment Liabilities Calculated Using Unobservable Inputs (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Expected Stock Price Volatility | Cobalt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.700	0.700
Expected Stock Price Volatility | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input	0.700	0.700
Expected Term (Years) | Cobalt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input expected term (years)	17 years 10 months 24 days	18 years 1 month 6 days
Expected Term (Years) | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value contingent consideration measurement input expected term (years)	10 years	10 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, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, at cost	$ 60,970	$ 54,512
Less: Accumulated depreciation	(9,984)	(7,737)
Property and equipment, net	50,986	46,775
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment, at cost	31,921	26,958
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, at cost	23,788	15,598
Construction In Progress
Property Plant And Equipment [Line Items]
Property and equipment, at cost	4,367	11,180
Computer Equipment, Software and Other
Property Plant And Equipment [Line Items]
Property and equipment, at cost	$ 894	$ 776

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Property Plant And Equipment [Abstract]
Depreciation expense	$ 2,247	$ 1,265

Accrued Liabilities - Schedule

Accrued Liabilities - Schedule of Accrued Compensation and Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accrued compensation:
Accrued paid time off	$ 4,561	$ 2,441
Accrued bonuses	3,194	11,582
Other accrued compensation	3,056	1,997
Total accrued compensation	10,811	16,020
Accrued expenses and other current liabilities:
Accrued research and development	3,121	1,197
Accrued property and equipment	2,594	2,892
Accrued professional fees	2,051	1,717
Other	3,405	3,660
Total accrued expenses and other current liabilities	$ 11,171	$ 9,466

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	3 Months Ended
	Mar. 31, 2021
Lessee Lease Description [Line Items]
Lease arrangement, contractual expiration period, beginning year	2024-04
Lease arrangement, contractual expiration period, ending year	2030-04
Weighted-average remaining lease term	7 years 3 months 18 days
Weighted-average incremental borrowing rate	10.72%
Seattle Operating Lease Agreement
Lessee Lease Description [Line Items]
Operating lease, renew period	5 years
Lessee, operating lease, existence of option to extend [true false]	true
Lessee, operating lease, option to extend	The Seattle and South San Francisco lease agreements provide the Company with the option to renew for an additional period of five years.
South San Francisco Operating Lease Agreement
Lessee Lease Description [Line Items]
Operating lease, renew period	5 years
Lessee, operating lease, existence of option to extend [true false]	true
Lessee, operating lease, option to extend	The Seattle and South San Francisco lease agreements provide the Company with the option to renew for an additional period of five years.

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Additional Information Related to Operating Leases (Details)	3 Months Ended
	Mar. 31, 2021ft²
Lessee Lease Description [Line Items]
Expiration Dates, Beginning	2024-04
Expiration Dates, Ending	2030-04
Seattle, WA
Lessee Lease Description [Line Items]
Approximate Square Footage	48,086
Commencement Dates, Beginning	2019-03
Commencement Dates, Ending	2020-09
Expiration Dates, Beginning	2026-12
Expiration Dates, Ending	2028-04
Cambridge, MA
Lessee Lease Description [Line Items]
Approximate Square Footage	56,859
Commencement Dates, Beginning	2019-03
Commencement Dates, Ending	2020-05
Expiration Dates, Beginning	2025-11
Expiration Dates, Ending	2028-02
South San Francisco, CA
Lessee Lease Description [Line Items]
Approximate Square Footage	66,075
Commencement Dates, Beginning	2019-12
Commencement Dates, Ending	2020-10
Expiration Dates, Beginning	2024-04
Expiration Dates, Ending	2030-04

Commitments and Contingencies_3

Commitments and Contingencies - Summary of Lease Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Lease, Cost [Abstract]
Operating lease cost	$ 2,898	$ 2,444
Shot-term lease cost	512	470
Variable lease cost	1,087	621
Total lease cost	$ 4,497	$ 3,535

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) $ in Thousands	Mar. 31, 2021USD ($)
Commitments And Contingencies Disclosure [Abstract]
2021 (remaining 9 months)	$ 10,300
2022	15,535
2023	15,989
2024	15,663
2025	15,621
2026 and thereafter	42,616
Total undiscounted lease payments	115,724
Less: imputed interest	(36,950)
Less: tenant improvement allowances	(8,515)
Present value of operating lease liabilities	$ 70,259

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2021	Feb. 28, 2021	Mar. 31, 2020
Class Of Stock [Line Items]
Convertible preferred stock shares issued	134,113,000			0
Outstanding shares of convertible preferred stock converted into shares of common stock					134,100,000
Convertible preferred stock outstanding	134,113,000			0
Series A-1 Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock shares issued			11,500,000
Share price			$ 4
Gross proceeds from issuance of convertible preferred stock			$ 45.9
Series A-2 Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock shares issued		56,000,000
Share price		$ 4
Gross proceeds from issuance of convertible preferred stock		$ 224
Series B Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock shares issued	27,200,000
Share price	$ 16
Gross proceeds from issuance of convertible preferred stock	$ 435.6
Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock outstanding	134,113,000	106,890,000		0		106,890,000

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - shares	Mar. 31, 2021	Feb. 28, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Shares authorized		800,000,000
Common stock, shares authorized	750,000,000	750,000,000	707,000,000
Preferred stock, shares authorized	50,000,000	50,000,000	0
Common stock, shares outstanding	178,941,000		16,170,000
Restricted Stock
Class Of Stock [Line Items]
Common stock outstanding	8,637,000		10,079,000

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Feb. 28, 2021	Mar. 31, 2021	Mar. 31, 2020
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of vested RSAs		$ 0.4	$ 0.2
2021 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares of common stock reserved for issuance expressed as percentage of outstanding shares	5.00%
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	85.00%
Percentage of annual increase in shares available for issuance	1.00%
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	15.00%

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock Based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,158	$ 755
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	2,668	648
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 1,490	$ 107

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)	3 Months Ended
	Mar. 31, 2021USD ($)
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense (in thousands)	$ 49,600
Weighted-average period costs expected to be recognized (years)	3 years 3 months 18 days
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense (in thousands)	$ 2,875
Weighted-average period costs expected to be recognized (years)	1 year 7 months 6 days
RSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense (in thousands)	$ 214
Weighted-average period costs expected to be recognized (years)	1 year 10 months 24 days

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)$ / sharesshares
Stock Options
Stock Options Outstanding, Beginning Balance | shares	15,677
Stock Options, Granted | shares	526
Stock Options, Exercised | shares	(205)
Stock Options, Forfeited/Cancelled | shares	(217)
Stock Options Outstanding, Ending Balance | shares	15,781
Stock Options Exercisable | shares	2,324
Weighted-Average Exercise Price per Share
Weighted-Average Exercise Price per Share Outstanding, Beginning Balance | $ / shares	$ 4.52
Weighted-Average Exercise Price per Share, Granted | $ / shares	27.14
Weighted-Average Exercise Price per Share, Exercised | $ / shares	1.35
Weighted-Average Exercise Price per Share, Forfeited/Cancelled | $ / shares	3.35
Weighted-Average Exercise Price per Share Outstanding, Ending Balance | $ / shares	5.33
Weighted-Average Exercise Price Per Share Exercisable | $ / shares	$ 1.46
Weighted-Average Remaining Contractual Life (years)
Weighted-Average Remaining Contractual Life (years), Outstanding	9 years 2 months 12 days
Weighted-Average Remaining Contractual Life (years), Exercisable	8 years 6 months
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Outstanding | $	$ 444,040
Aggregate Intrinsic Value, Exercisable | $	$ 74,383

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, 2021	Mar. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk free interest rate, minimum	0.64%	0.48%
Risk free interest rate, maximum	1.11%	1.51%
Expected volatility	70.00%	70.00%
Expected dividend	0.00%	0.00%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	5 years 6 months	6 years 3 months
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 years 3 months	6 years 3 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, 2021	Mar. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Weighted average grant date fair value per share for options granted	$ 16.75	$ 1.08
Aggregate intrinsic value of stock options exercised (in thousands)	$ 3,764	$ 0

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of RSA Activity (Details) - Restricted Stock shares in Thousands	3 Months Ended
	Mar. 31, 2021$ / sharesshares
RSAs
Unvested shares as of December 31, 2020 | shares	10,079
Vested | shares	(1,428)
Forfeited | shares	(14)
Unvested shares as of March 31, 2021 | shares	8,637
Weighted-Average Grant Date Fair Value per Share
Unvested shares as of December 31, 2020 | $ / shares	$ 0.33
Vested | $ / shares	0.25
Forfeited | $ / shares	0.68
Unvested shares as of March 31, 2021 | $ / shares	$ 0.34

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share of Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net loss	$ (180,617)	$ (32,875)
Weighted-average shares outstanding, basic and diluted	119,131	10,820
Net loss per share, basic and diluted	$ (1.52)	$ (3.04)

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, 2021	Mar. 31, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share	11,286	122,944
Series A-1 Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share		11,463
Series A-2 Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share		95,427
Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share	8,637	15,352
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share	2,324	357
RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of dilutive net loss per share	325	345

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Details)	27 Months Ended
	Mar. 31, 2021USD ($)
Compensation And Retirement Disclosure [Abstract]
Defined Contribution Plan, Plan Name [Extensible List]	ck0001770121:RetirementAndSavingsPlanMember
Matching contribution by employer	$ 0