Verve Therapeutics (VERV) 10-K 14 Mar 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 09, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Registrant Name	VERVE THERAPEUTICS, INC.
Entity Central Index Key	0001840574
Trading Symbol	VERV
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 2,185
Entity Common Stock, Shares Outstanding		48,576,595
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common stock, par value $0.001 per share
Entity File Number	001-40489
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-4800132
Entity Address, Address Line One	500 Technology Square, Suite 901
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	617
Local Phone Number	603-0070
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Portions of the registrant’s definitive proxy statement that will be filed for the 2022 Annual Meeting of Stockholders which the registrant intends to file with the Securities and Exchange Commission not later than 120 days after the registrant’s fiscal year ended December 31, 2021, are incorporated by reference in Part III of this Annual Report on Form 10-K.
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	Boston, Massachusetts

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 64,330	$ 8,993
Marketable securities	296,112	63,119
Prepaid expenses and other current assets	6,686	1,854
Total current assets	367,128	73,966
Property and equipment, net	7,224	3,984
Restricted cash	5,237	463
Operating lease right-of-use assets	1,839	0
Other long term assets	2,696	0
Total assets	384,124	78,413
Current liabilities:
Accounts payable	7,077	36
Accrued expenses	12,992	7,189
Operating lease obligations, current portion	1,955	0
Deferred rent, current portion	0	90
Total current liabilities	22,024	7,315
Deferred rent, net of current portion	0	125
Success payment liability (See Notes 5, 8 and 15)	4,371	2,806
Antidilution rights liability (See Notes 5, 8 and 15)	0	6,916
Other long term liabilities	377	0
Total liabilities	26,772	17,162
Commitments and contingencies (See Note 7 and 8)
Convertible preferred stock (See Note 10)
Stockholders’ equtiy (deficit):
Preferred stock, $0.001 par value; 5,000,000 shares authorized, no shares issued and oustanding
Common stock, $0.001 par value; 200,000,000 and 255,000,000 shares authorized, 48,511,735 and 3,123,424 shares issued at December 31, 2021 and 2020, respectively; 48,511,735 and 2,585,789 shares outstanding at December 31, 2021 and 2020, respectively	49	3
Additional paid-in capital	544,381	2,616
Accumulated other comprehensive (loss) income	(228)	8
Accumulated deficit	(186,850)	(66,536)
Total stockholders’ equity (deficit)	357,352	(63,909)
Total liabilities, convertible preferred stock, and stockholders’ equity (deficit)	384,124	78,413
Convertible Preferred Stock
Current liabilities:
Convertible preferred stock (See Note 10)	0	125,160
Stockholders’ equtiy (deficit):
Preferred stock, $0.001 par value; 5,000,000 shares authorized, no shares issued and oustanding	$ 0	$ 125,160

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, value per share	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	255,000,000
Common stock, shares issued	48,511,735	3,123,424
Common stock, shares outstanding	48,511,735	2,585,789

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating expenses:
Research and development	$ 68,202	$ 35,371	$ 11,144
General and administrative	18,865	5,256	2,498
Total operating expenses	87,067	40,627	13,642
Loss from operations	(87,067)	(40,627)	(13,642)
Other income (expense):
Change in fair value of preferred stock tranche liability	0	2,507	(4,883)
Change in fair value of antidilution rights liability	(25,574)	(5,359)	(982)
Change in fair value of success payment liability	(7,815)	(2,387)	(68)
Interest and other income, net	142	162	278
Total other expense, net	(33,247)	(5,077)	(5,655)
Net loss	$ (120,314)	$ (45,704)	$ (19,297)
Net loss per common share attributable to common stockholders, basic and diluted	$ (4.48)	$ (20.31)	$ (15.11)
Weighted-average common shares used in net loss per share attributable to common stockholders, basic and diluted	26,872,036	2,250,093	1,277,156
Comprehensive Loss:
Net loss	$ (120,314)	$ (45,704)	$ (19,297)
Other comprehensive (loss) income:
Unrealized (loss) gain on marketable securities	(236)	(1)	9
Comprehensive loss	$ (120,550)	$ (45,705)	$ (19,288)

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Preferred Stock
Beginning balance at Dec. 31, 2018	$ (1,484)	$ 0	$ 51	$ 0	$ (1,535)	$ 6,905
Beginning balance (in shares) at Dec. 31, 2018		537,635				19,565,217
Issuance of Series A convertible preferred stock and settlement of tranche right liability, net of issuance costs						$ 17,956
Issuance of Series A convertible preferred stock and settlement of tranche right liability, net of issuance costs (in shares)						30,183,947
Issuance of Series A Preferred Stock in payment of licensing fee						$ 619
Issuance of Series A Preferred Stock in payment of licensing fee (shares)						1,672,240
Issuances of common stock to licensor institutions	748	$ 1	747
Issuances of common stock to licensor institutions (in shares)		673,562
Vesting of restricted common stock	$ 1	$ 1
Vesting of restricted common stock (in shares)	537,635	643,241
Repayment of shareholder loan	$ 24		24
Unrealized gain (loss) on available-for-sale securities	9			9
Stock-based compensation	446		446
Net loss	(19,297)				(19,297)
Ending balance at Dec. 31, 2019	(19,553)	$ 2	1,268	9	(20,832)	$ 25,480
Ending balance (in shares) at Dec. 31, 2019		1,854,438				51,421,404
Issuance of Series A convertible preferred stock and settlement of tranche right liability, net of issuance costs						$ 36,792
Issuance of Series A convertible preferred stock and settlement of tranche right liability, net of issuance costs (in shares)						49,749,167
Issuance of Series A-2 convertible preferred stock, net of issuance costs of $112						$ 62,888
Issuance of Series A-2 convertible preferred stock, net of issuance costs (in shares)						78,348,461
Additional issuances of common stock to licensor institutions	487		487
Additional issuances of common stock to licensor institutions (in shares)		187,867
Vesting of restricted common stock	$ 1	$ 1
Vesting of restricted common stock (in shares)	537,635	537,635
Exercise of stock options	$ 11		11
Exercise of stock options (in shares)		5,849
Unrealized gain (loss) on available-for-sale securities	(1)			(1)
Stock-based compensation	850		850
Net loss	(45,704)				(45,704)
Ending balance at Dec. 31, 2020	$ (63,909)	$ 3	2,616	8	(66,536)	$ 125,160
Ending balance (in shares) at Dec. 31, 2020	2,585,789	2,585,789				179,519,032
Issuance of Series B convertible preferred stock, net of issuance costs of $241						$ 93,759
Issuance of Series B convertible preferred stock, net of issuance costs (in shares)						77,163,022
Conversion of convertible preferred stock to common stock upon closing of initial public offering	$ 218,919	$ 28	218,891			$ (218,919)
Conversion of convertible preferred stock to common stock upon closing of initial public offering (in shares)		27,720,923				(256,682,054)
Issuance of common stock from initial public offering, net of issuance costs of $25,098	281,584	$ 16	281,568
Issuance of common stock from initial public offering, net of issuance costs of (in shares)		16,141,157
Issuances of common stock to licensor institutions	$ 32,490	$ 1	32,489
Issuances of common stock to licensor institutions (in shares)		878,098
Vesting of restricted common stock (in shares)	537,633	537,633
Exercise of stock options	$ 966	$ 1	965
Exercise of stock options (in shares)	599,838	599,838
Purchase of common stock under ESPP	$ 780		780
Purchase of common stock under ESPP(shares)		48,297
Unrealized gain (loss) on available-for-sale securities	(236)			(236)
Stock-based compensation	7,072		7,072
Net loss	(120,314)				(120,314)
Ending balance at Dec. 31, 2021	$ 357,352	$ 49	$ 544,381	$ (228)	$ (186,850)
Ending balance (in shares) at Dec. 31, 2021	48,511,735	48,511,735

Consolidated Statements of Co_2

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement Of Stockholders Equity [Abstract]
Issuance of Series A convertible preferred stock and settlement of tranche right liability		$ 7,000	$ 84
Issuance costs of series A convertible preferred stock		22	$ 10
Issuance costs of series A2 convertible preferred stock		$ 112
Issuance costs of series B convertible preferred stock	$ 241
Issuance costs of common stock from initial public offering	$ 25,098

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (120,314)	$ (45,704)	$ (19,297)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,535	1,328	106
Non-cash research and development license expense in operating activity in cash flow	0	0	2,781
Non-cash lease expense	1,842		0
Amortization of premium on marketable securities	1,508	380	(72)
Stock-based compensation	7,072	850	446
Change in fair value of preferred stock tranche liabilities	0	(2,507)	4,883
Change in fair value of antidilution rights	25,574	5,359	982
Change in fair value of success payments liabilities	7,815	2,387	68
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(7,528)	(1,582)	(182)
Accounts payable	6,829	(1,898)	1,735
Accrued expenses and other liabilities	5,977	6,071	945
Success of payment liability	(6,250)	0	0
Operating lease liabilities	(1,940)		0
Deferred rent liability	0	51	163
Net cash used in operating activities	(77,880)	(35,265)	(7,442)
Cash flows from investing activities:
Purchases of property and equipment	(4,359)	(3,424)	(1,857)
Purchases of marketable securities	(371,494)	(98,484)	(22,001)
Maturities of marketable securities	136,755	50,781	11,100
Net cash used in investing activities	(239,098)	(51,127)	(12,758)
Cash flows from financing activities
Proceeds from issuance of Preferred Stock, net	93,759	92,616	18,040
Proceeds from initial public offering, net of underwriting discount	285,214		0
Shareholder loan given	0		(110)
Payment of initial public offering costs	(3,630)
Proceeds from exercise of stock options	966	11
Payments received on shareholder loan	0		24
Proceeds from purchase of shares through employee stock purchase plan	780
Net cash provided by financing activities	377,089	92,627	17,954
Increase (decrease) in cash, cash equivalents and restricted cash	60,111	6,235	(2,246)
Cash, cash equivalents and restricted cash—beginning of period	9,456	3,221	5,467
Cash, cash equivalents and restricted cash—end of period	69,567	9,456	3,221
Supplemental disclosure of noncash investing and finnacing activities:
Property and equipment additions included in accounts payable and accrued expenses	503	86	556
Issuance of preferred stock tranche liability			84
Settlement of tranche right liability	0	7,064
Conversion of convertible preferred stock to common stock upon closing of initial public offering	218,919
Settlement of derivative liability by issuing common stock	32,490	487	135
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 809

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the business and basis of presentation Organization Verve Therapeutics, Inc. (the “Company” or “Verve”) is a genetic medicines company pioneering a new approach to the care of cardiovascular disease, transforming treatment from chronic management to single-course gene editing medicines. The Company was incorporated on March 9, 2018 as Endcadia, Inc., a Delaware corporation, and began operations shortly thereafter. In January 2019, the Company amended its certificate of incorporation to change its name to Verve Therapeutics, Inc. The Company’s principal offices are located in Cambridge, Massachusetts. Liquidity and capital resources Since its inception, the Company has devoted its efforts principally to research and development and raising capital. The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry including, but not limited to, technical risks associated with the successful research, development and manufacturing of product candidates, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Current and future programs will require significant research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. On June 21, 2021, the Company completed its initial public offering, or IPO, in which the Company issued and sold 16,141,157 shares of its common stock, including 2,105,368 shares pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $ 19.00 per share, for aggregate gross proceeds of $ 306.7 million. The Company received approximately $ 281.6 million in net proceeds after deducting underwriting discounts and offering expenses payable by the Company. In connection with the IPO, all outstanding shares of convertible preferred stock converted into 27,720,923 shares of the Company’s common stock. In connection with the Company's IPO, the Company effected a one-for-9.2595 reverse stock split of the Company’s issued and outstanding common stock. Accordingly, all shares of common stock and per share amounts, as well as the conversion ratio of the Company’s outstanding convertible preferred stock, for all periods presented in the accompanying consolidated financial statements and notes thereto have been retroactively adjusted, where applicable, to reflect the reverse stock split, including reclassification of par and additional paid-in capital amounts as a result of the reverse stock split. Basis of presentation and liquidity The accompanying consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). The accompanying consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. The Company has incurred losses since its inception, including losses of $ 120.3 million , $ 45.7 million and $ 19.3 million for the years ended December 31, 2021, 2020 and 2019, respectively. As of December 31, 2021, the Company had an accumulated deficit of $ 186.9 million . To date, the Company has funded its operations primarily through equity offerings. Through December 31, 2021, the Company had raised an aggregate $ 523.2 million in gross proceeds from the sales of its preferred stock in private placements and common stock in its IPO. The Company expects to generate operating losses and negative operating cash flows for the foreseeable future. The Company expects that its cash, cash equivalents and marketable securities as of December 31, 2021 will be sufficient to fund its operations for at least the next twelve months from the date of issuance of these financial statements. The Company will need additional financing to support its continuing operations and pursue its growth strategy. Until such time as the Company can generate significant revenue from product sales, if ever, it expects to finance its operations through a combination of equity offerings, debt financings, collaborations, strategic alliances and licensing arrangements. The Company may be unable to raise additional funds or enter into such other agreements when needed on favorable terms or at all. The inability to raise capital as and when needed could have a negative impact on the Company’s financial condition and its ability to pursue its business strategy. The Company will need to generate significant revenue to achieve profitability, and it may never do so.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. S ummary of significant accounting policies Principles of consolidation The accompanying consolidated financial statements include the accounts of Verve and its wholly owned subsidiary, Verve Securities Corporation. All intercompany transactions and balances have been eliminated in consolidation. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the fair values of common stock (prior to completion of the IPO), convertible preferred stock, preferred stock tranche liability, stock-based compensation, and the liabilities for antidilution rights and success payments. Actual results could differ from these estimates. Cash and cash equivalents Cash and cash equivalents consist of standard checking accounts and money market account funds that invest primarily in U.S. government-backed securities and treasuries. The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. Cash equivalents are stated at cost, which is substantially equivalent to fair value. Restricted cash Restricted cash represents collateral provided for a letter of credit issued as a security deposit in connection with the Company’s leases of its corporate facilities. A reconciliation of the cash, cash equivalents, and restricted cash reported within the balance sheet that sum to the total of the same amounts shown in the statement of cash flows is as follows: December 31, (in thousands) 2021 2020 Cash and cash equivalents $ 64,330 $ 8,993 Restricted cash 5,237 463 Total cash, cash equivalents and restricted cash $ 69,567 $ 9,456 Marketable securities The Company classifies marketable securities with a remaining maturity when purchased of greater than three months as available-for-sale. Available-for-sale securities are maintained by the Company’s investment managers and consist of U.S. treasury bills and U.S agency securities. Available-for-sale securities are carried at fair value with the unrealized gains and losses included in accumulated other comprehensive income (loss) as a component of stockholders’ equity until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the instrument. Realized gains and losses are determined using the specific identification method and are included in other income (expense). The Company reviews marketable securities for other-than-temporary impairment whenever the fair value of a marketable security is less than the amortized cost and evidence indicates that a marketable security’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the consolidated statements of operations if the Company has experienced a credit loss, has the intent to sell the marketable security, or if it is more likely than not that the Company will be required to sell the marketable security before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period. The Company evaluated its securities for other-than-temporary impairment and considered the decline in market value for the securities to be primarily attributable to current economic and market conditions. It is not more likely than not that the Company will be required to sell the securities, and the Company does not intend to do so prior to the recovery of the amortized cost basis. Based on this analysis, these marketable securities were not considered to be other-than-temporarily impaired as of December 31, 2021 and 2020 . Concentrations of credit risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents and restricted cash. Periodically, the Company may maintain deposits in financial institutions in excess of government insured limits. Management believes that the Company is not exposed to significant credit risk as the Company’s deposits are held at financial institutions that management believes to be of high credit quality, and the Company has not experienced any losses on these deposits. Deferred offering costs The Company capitalized incremental legal, professional accounting and other third-party fees that were directly associated with the IPO as other non-current assets until the IPO was consummated. After consummation of the IPO, these costs were recorded in stockholders’ equity (deficit) as a reduction of additional paid-in-capital generated as a result of the offering. Indemnification agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, contract research organizations, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The Company has not incurred any material costs as a result of such indemnifications and is not currently aware of any indemnification claims. Fair value of financial instruments ASC Topic 820, Fair Value Measurement (“ASC 820”), establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the assets or liability and are developed based on the best information available in the circumstances. ASC 820 identifies fair value as the price that would be received to sell an asset or paid to transfer a liability, in an orderly transaction between market participants at the measurement date. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tiered value hierarchy that distinguishes between the following: Level 1—Quoted market prices in active markets for identical assets or liabilities. Level 2—Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted market prices, interest rates and yield curves. Level 3—Unobservable inputs for the asset or liability (i.e. supported by little or no market activity). Level 3 inputs include management’s own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk). To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair values requires more judgement. Accordingly, the degree of judgement exercised by the Company in determining fair value is greatest for instruments categorized as Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. There have been no changes to the valuation methods utilized by the Company during the years ended December 31, 2021, 2020 and 2019. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of financial instruments between levels during the years ended December 31, 2021 and 2020 . Property and equipment, net Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows: Asset category Estimated useful life Computer equipment and software 3 years Office furniture 4 years Laboratory equipment 5 years Leasehold improvements Shorter of useful life or remaining lease term Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred. Impairment of long-lived assets The Company evaluates its long-lived assets, which consist primarily of property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset exceeds the fair value of the asset. There were no impairment losses recognized during the years ended December 31, 2021, 2020 and 2019 . Freestanding financial instruments and derivatives The Company has identified the following financial instruments, which are recorded as liabilities in the balance sheet and separately accounted for at fair value. Preferred Stock Tranche Liabilities —The Company has determined that its obligation to issue, and the Company’s investors’ right to purchase, additional shares of convertible Series A Preferred Stock (“Series A Preferred”) pursuant to subsequent closings represent a freestanding financial instrument. The freestanding preferred stock tranche liability (the “tranche liability”) was initially recorded at fair value, with gains and losses arising from changes in fair value recognized in other income (expense) in the statement of operations and comprehensive loss. The tranche liabilities were remeasured at each reporting period and upon the exercise or expiration of the obligation. As of December 31, 2020, all Series A Preferred closings occurred, and all preferred stock tranche liabilities have been settled. Refer to Note 9, Preferred Stock tranche liability, for additional discussion. Pursuant to license agreements with (i) the President and Fellows of Harvard College (“Harvard”) and The Broad Institute, Inc. (“Broad”) (“Harvard/Broad License Agreement”) and (ii) Broad (“Broad License Agreement”) (see Note 8, License agreements), the following financial instruments were issued by the Company. Antidilution Rights —The antidilution rights represent the obligation to issue additional shares of common stock to Harvard and Broad following the completion of additional financings, including the Company’s initial public offering. These antidilution rights were accounted for under ASC 815, Derivatives and Hedging ("ASC 815"), and were initially recorded at fair value with a corresponding charge to research and development expense. The liability was remeasured at each reporting period, with changes in fair value recognized in other income (expense) in the statement of operations and comprehensive loss while this instrument was outstanding. The obligation was satisfied in full upon the issuance of an aggregate of an additional 878,098 shares of common stock upon the closing of the Company's IPO in June 2021. Refer to Note 5, Fair value of financial instruments, for additional discussion. Success Payments —The Company is obligated to pay to Harvard and Broad tiered success payments in the event the Company’s average market capitalization exceeds specified thresholds ascending from a high nine digit dollar amount to $ 10.0 billion, or sale of the Company for consideration in excess of those thresholds. In the event of a change of control of the Company or a sale of the Company, the Company is required to pay in cash within a specified period following such event. Otherwise, the payments may be settled at the Company’s option in either cash or shares of the Company’s common stock. The success payments are accounted for under ASC 815 and were initially recorded at fair value with a corresponding charge to research and development expense. The liability is remeasured at each reporting period with all changes in value recognized in other income (expense) in the statement of operations and other comprehensive loss. During the year ended December 31, 2021, certain success payment obligations were triggered, and amounts paid to Harvard and Broad totaled $ 6.3 million. These amounts were settled in cash in November 2021. The Company will continue to adjust the liability for changes in fair value until the earlier of the achievement or expiration of the remaining success payment obligation. Refer to Note 5, Fair value of financial instruments, for additional discussion . Research and development costs Research and development costs are charged to expense as incurred. Research and development costs consist of costs incurred in performing research and development activities, including salaries and bonuses, stock-based compensation, employee benefits, facilities costs, third-party license fees related to technology with no alternative future use, laboratory supplies, depreciation, manufacturing expenses, preclinical expenses, consulting and other contracted services. Costs for certain research and development activities are recognized based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the financial statements as prepaid or accrued research and development. Stock-based compensation The Company’s stock-based compensation program allows for grants of stock options and restricted stock awards. Grants are awarded to employees and non-employees, including directors. The Company accounts for its stock-based compensation in accordance with ASC Topic 718, Compensation-Stock Compensation (‘‘ASC 718’’). ASC 718 requires all stock-based payments to employees, non-employees and directors, to be recognized as expense in the consolidated statements of operations and comprehensive loss based on their grant date fair values. The Company estimates the fair value of options granted using the Black-Scholes option pricing model (‘‘Black-Scholes’’) for stock option grants to both employees and non-employees. The fair value of the Company’s common stock is used to determine the fair value of restricted stock awards. The Company’s stock-based compensation awards are subject to either service or performance-based vesting conditions. Compensation expense related to awards to employees, directors and non-employees with service-based vesting conditions is recognized on a straight-line basis based on the grant date fair value over the associated service period of the award, which is generally the vesting term. Compensation expense related to awards to employees with performance-based vesting conditions is recognized over the implied service period when achievement of the performance-based milestones is deemed probable. The Company uses judgement to determine whether and, if so, how many awards are deemed probable of vesting at each reporting period. The estimation of fair value for stock-based compensation requires management to make estimates and judgments about, among other things, the estimated life of options and volatility of the Company’s common stock. The judgments directly affect the amount of compensation expense that will be recognized. Prior to the Company's IPO in June 2021, there was no public market for its common stock. As a result, prior to the IPO, the estimated fair value of the Company's common stock was determined by its board of directors as of the date of each option grant, with input from management, considering the Company's most recently available third-party valuations of common stock and its board of directors' assessment of additional objective and subjective factors that it believed were relevant and which may have changed from the date of the most recent valuation through the date of grant. Following the Company's IPO, the fair value of its common stock is determined based on the closing price of the Company's common stock as reported on the Nasdaq Global Select Market . Rent expense The Company’s real estate operating leases provide for scheduled annual rent increases throughout the lease term. The Company recognizes the effects of the scheduled rent increases on a straight-line basis over the full term of the lease. Prior to the adoption of ASU 2016-02, Leases , or ASC 842, tenant improvement allowances, if any, provided by the landlord are recorded as deferred rent and amortized as reduction to rent expense over the lease term. Subsequent to the adoption of ASC 842, tenant improvement allowances, if any, provided by a landlord are recorded as a reduction of the right-of-use, or ROU, asset related to that lease. Income taxes The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s financial statements and tax returns. Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities and for loss and credit carryforwards, using enacted tax rates expected to be in effect in the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that these assets may not be realized. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. If it is not more likely than not that a position will be sustained, none of the benefit attributable to the position is recognized. The tax benefit to be recognized for any tax position that meets the more-likely-than-not recognition threshold is calculated as the largest amount that is more than 50 % likely of being realized upon resolution of the contingency. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes. Comprehensive loss Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. For the years ended December 31, 2021, 2020 and 2019 , the Company’s only element of other comprehensive income (loss) was unrealized gains (losses) on marketable securities. Net loss per share The Company follows the two-class method when computing net loss per share, as the Company has issued shares that meet the definition of participating securities. The two-class method determines net loss per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net loss attributable to common stockholders is computed by adjusting net loss attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net loss per share attributable to common stockholders is computed by dividing the diluted net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common stock equivalents. The Company’s convertible preferred stock contractually entitled the holders of such shares to participate in dividends but did not contractually require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reports a net loss, such losses are not allocated to such participating securities. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the years ended December 31, 2021, 2020 and 2019 . Segment and geographic information Operating segments are defined as components of an entity about which separate discrete information is available for evaluation by the chief operating decision maker (“CODM”), or decision-making group, in deciding how to allocate resources and in assessing performance. The CODM is the Company’s Chief Executive Officer. The Company views its operations as and manages its business in one operating segment operating exclusively in the United States. Subsequent events The Company performs an evaluation of all subsequent events after the balance sheet date through the date of issuance of the consolidated financial statements to ensure appropriate disclosure of events both recognized in the consolidated financial statements and events which occurred subsequently but were not recognized in the consolidated financial statements. Recently adopted accounting pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), as subsequently amended, which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors), and replaces the existing guidance in ASC 840. The FASB has issued several updates to the standard which: (i) clarify how to apply certain aspects of the new standard; (ii) provide an additional transition method for adoption of the new standard; (iii) provide a practical expedient for certain lessor accounting; and (iv) amend certain narrow aspects of the guidance. The new standard requires the identification and classification of arrangements that are or contain a lease and requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine the recognition pattern of lease expense over the term of the lease. In addition, a lessee is required to record (i) a right-of-use asset and a lease liability on its balance sheet for all leases with accounting lease terms of more than 12 months regardless of whether it is an operating or finance lease and (ii) lease expense in its consolidated statement of operations for operating leases and amortization and interest expense in its consolidated statement of operations for financing leases. Leases with a term of 12 months or less may be accounted for similar to existing guidance for operating leases under ASC 840. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842), which added an optional transition method that allows companies to adopt the standard as of the beginning of the year of adoption as opposed to the earliest comparative period presented. Prior to January 1, 2021, the Company accounted for leases pursuant to ASC 840, Leases. At lease inception, the Company determined if an arrangement was an operating or capital lease. For operating leases, the Company recognized rent expense, inclusive of rent escalations, holidays and lease incentives, on a straight-line basis over the lease term. The difference between rent expense recorded and the amount paid was recorded as deferred rent. The Company presented lease incentives as deferred rent and amortized the incentives as a reduction to rent expense on a straight-line basis over the lease term. The Company classified deferred rent as current and noncurrent liabilities based on the portion of the deferred rent that was scheduled to mature within the next twelve months. The Company adopted Topic 842 during the quarter ended September 30, 2021, with an effective adoption date of January 1, 2021 , using the modified retrospective transition approach which uses the effective date, or January 1, 2021, as the date of initial application. As a result, prior periods are presented in accordance with the previous guidance in ASC 840. At contract inception, the Company determines if an arrangement is or contains a lease. A lease conveys the right to control the use of an identified asset for a period of time in exchange for consideration. If an arrangement is determined to be or contain a lease, the lease is assessed for classification as either an operating or finance lease at the lease commencement date, defined as the date on which the leased asset is made available for use by the Company, based on the economic characteristics of the lease. The Company has elected to apply the package of practical expedients requiring no reassessment of whether any expired or existing contracts are or contain leases, the lease classification of any expired or existing leases, or the capitalization of initial direct costs for any existing leases. As a result of the adoption of ASC 842, the Company recorded (i) an operating lease liability of $ 2.6 million determined using an incremental borrowing rate as of the effective adoption date and (ii) an operating lease right-of-use asset of $ 2.4 million, net of the unamortized balance of prepaid/accrued rent as of the transition date. There was no impact to the Company’s results of operations and cash flows from operations. The Company has elected the short-term lease exemption, which allows the Company to not recognize lease liabilities and right-of-use assets arising from lease arrangements with lease terms of twelve months or less. For each lease with a term greater than twelve months, the Company records a right-of-use asset and lease liability. A right-of-use asset represents the economic benefit conveyed to the Company by the right to use the underlying asset over the lease term. A lease liability represents the Company’s obligation to make lease payments under the arrangement. The Company measures its lease liabilities at lease commencement as the present value of the future lease payments in the contract using the rate implicit in the contract, when available. As an implicit rate has not historically been readily determinable, the Company uses an incremental borrowing rate measured as the rate at which the Company could borrow, on a fully collateralized basis, a commensurate loan in the same currency over a period consistent with the lease term at the commencement date. The incremental borrowing rate is determined based on the Company's synthetic secured rating using the ordered logit model as of the measurement date. The Company measures its right-of-use assets as the lease liability plus initial direct costs and prepaid lease payments, less lease incentives granted by the lessor. Components of a lease are split into three categories: lease components, non-lease components, and non-components. The fixed and in-substance fixed contract consideration (including any consideration related to non-components) are allocated, based on the respective relative fair values, to the lease components and non-lease components. The Company has elected to account for lease and associated non-lease components together as a single lease component for all underlying assets and allocate all of the contract consideration to the lease component only. The Company remeasures right-of-use assets and lease liabilities when a lease is modified, and the modification is not accounted for as a separate contract. A modification is accounted for as a separate contract if the modification grants the Company an additional right of use not included in the original lease arrangement and the increase in lease payments is commensurate with the additional right of use. The Company assesses its right-of-use assets for impairment in a manner consistent with its assessment for long-lived assets held and used in operations. The Company’s operating leases are presented in the consolidated balance sheet as operating lease right-of-use assets, classified as noncurrent assets, and operating lease liabilities, classified as current and noncurrent liabilities. Operating lease expense is recognized on a straight-line basis over the lease term. Variable costs associated with a lease, such as maintenance and utilities, are not included in the measurement of the lease liabilities and right-of-use assets but rather are expensed when the events determining the amount of variable consideration to be paid have occurred. Recently issued accounting pronouncements The Jumpstart Our Business Startups Act of 2012 permits an emerging growth company ("EGC") to take advantage of an extended transition period to comply with new or revised accounting standards applicable to public companies until those standards would otherwise apply to private companies. As an EGC, the Company has elected to take advantage of this extended transition period for certain new accounting standards. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The standard requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and establishes additional disclosures related to credit risks. For available-for-sale debt securities with unrealized losses, this standard requires allowances to be recorded instead of reducing the amortized cost of the investment. The new standard will be effective for the Company on January 1, 2023. The Company is currently evaluating the potential impact that this standard may have on its consolidated financial position and results of operations.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2021
Investments Debt And Equity Securities [Abstract]
Marketable Securities	3. Marketable securities Marketable securities by security type consisted of the following: December 31, 2021 (in thousands) Amortized Gross Gross Fair U.S. treasury bills and notes $ 277,559 $ — $ ( 218 ) $ 277,341 U.S. agency securities 18,781 — ( 10 ) 18,771 Total $ 296,340 $ — $ ( 228 ) $ 296,112 December 31, 2020 (in thousands) Amortized Gross Gross Fair U.S. treasury bills and notes $ 32,221 $ 3 $ — $ 32,224 U.S. agency securities 30,890 5 — 30,895 Total $ 63,111 $ 8 $ — $ 63,119 The remaining contractual maturities of all marketable securities were less than one year as of December 31, 2021 and 2020 .

Property and equipment, net

Property and equipment, net	12 Months Ended
	Dec. 31, 2021
Property Plant And Equipment [Abstract]
Property and Equipment	4. P roperty and equipment, net Property and equipment, net, consist of the following: December 31, (in thousands) 2021 2020 Lab equipment 8,567 $ 3,937 Leasehold improvements 266 259 Furniture and fixtures 566 481 Computer equipment 158 105 Total property and equipment 9,557 4,782 Less accumulated depreciation ( 2,333 ) ( 798 ) Property and equipment, net $ 7,224 $ 3,984 Depreciation expense for the years ended December 31, 2021, 2020 and 2019 w as $ 1.5 million, $ 1.3 million and $ 0.1 million, respectively.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Disclosure - Fair Value of Financial Instruments	5. f air value of financial instruments The Company’s financial instruments consist of money market funds, marketable securities, the preferred stock tranche liability, the antidilution right liability, and success payment liability pursuant to the Harvard/ Broad License Agreement and the Broad License Agreement. The preferred stock tranche liability was fully settled in the year ended December 31, 2020, and the antidilution right liability was fully settled in the year ended December 31, 2021. The liabilities are carried at fair value. The following tables set forth the fair value of the Company’s financial instruments by level within the fair value hierarchy: As of December 31, 2021 (in thousands) Fair Level 1 Level 2 Level 3 Assets Money market funds $ 58,127 $ 58,127 $ — $ — Marketable securities: U.S. treasury bills and notes 277,341 — 277,341 — U.S. agency securities 18,771 — 18,771 — Total assets $ 354,239 $ 58,127 $ 296,112 $ — Liabilities Success payment liability 4,371 — — 4,371 Total liabilities $ 4,371 $ — $ — $ 4,371 As of December 31, 2020 (in thousands) Fair Level 1 Level 2 Level 3 Assets Money market funds $ 6,724 $ 6,724 $ — $ — Marketable securities: U.S. treasury bills and notes 32,224 — 32,224 — U.S. agency securities 30,895 — 30,895 — Total assets $ 69,843 $ 6,724 $ 63,119 $ — Liabilities Success payment liability $ 2,806 $ — $ — $ 2,806 Antidilution rights liability 6,916 — — 6,916 Total liabilities $ 9,722 $ — $ — $ 9,722 Cash Equivalents —Cash equivalents of $ 58.1 million and $ 6.7 million as of December 31, 2021 and 2020, respectively, consisted of money market funds and are classified within Level 1 of the fair value hierarchy because they are valued using quoted market prices in active markets. Marketable Securities— The Company measures its marketable securities at fair value on a recurring basis and classifies those instruments within Level 2 of the fair value hierarchy. Marketable securities are classified within Level 2 of the fair value hierarchy because pricing inputs are other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date, and fair value is determined through the use of models or other valuation methodologies. Preferred Stock Tranche Liability —The preferred stock tranche liability is stated at fair value and is considered Level 3 within the fair value hierarchy because its fair value measurement is based, in part, on significant inputs not observed in the market. The tranche liability was valued using a probability-adjusted scenario-based method that considered the probability of triggering the tranche rights through achievement of certain non-scientific and scientific milestones as well as the pu rchase price of Series A preferred stock. Subsequent Series A Preferred Stock closings occurred in both 2019 and 2020 and the preferred stock tranche liability was fully settled as of December 31, 2020 (refer to Note 9, Preferred stock tranche liability). Prior to settlement, the Company remeasured the liability with a corresponding increase of $ 2.5 million to other expense for the year ended December 31, 2020. Antidilution Rights Liability — The antidilution rights liability represents the obligation to issue additional shares of common stock to Harvard and Broad following the completion of (1) a defined aggregate level of preferred stock financing and (2) either a sale of the Company’s preferred stock, an initial public offering, or a company sale meeting a certain value threshold. The antidilution rights liability was stated at fair value and was considered Level 3 in the fair value hierarchy because its fair value measurement was based, in part, on significant inputs not observed in the market. The antidilution rights liability related to meeting a defined aggregate level of preferred stock financing was valued using a probability-weighted present value model that considered the probability of meeting the defined aggregate level of preferred stock financing, as well as the fair value of the Company’s common stock. The antidilution rights liability related to the achievement of a specified valuation through either a sale of the Company’s preferred stock, an initial public offering, or a company sale was valued using a Monte Carlo simulation model, which models the value of the liability based on several key variables, including probability of event occurrence, timing of event occurrence, as well as the fair value of the Company’s common stock. At issuance in 2019, the estimated fair value of the antidilution rights liability was $ 1.2 million, which was recorded as research and development expense. The Company remeasured the liability at fair value with corresponding charges of $ 5.4 million and $ 1.0 million recorded to other expense for the years ended December 31, 2020 and 2019, respectively. The antidilution rights associated with the Company achieving a defined aggregate level of preferred stock financing were partially satisfied in 2019 and fully satisfied in 2020, which settlement amounts totaled $ 0.1 million and $ 0.5 million, respectively, and which amounts were settled through issuances of 121,411 and 187,867 shares of the Company common stock, respectively. In June 2021, upon completion of its IPO, the Company settled the antidilution rights liability in full through the issuance of 878,098 shares of the Company's common stock for a settlement amount of $ 32.5 million. Prior to settlement, the Company remeasured the liability with a corresponding increase of $ 25.6 million to other expense for the year ended December 31, 2021. Success Payment Liability — The Company is obligated to pay to Harvard and Broad tiered success payments in the event its average market capitalization exceeds specified thresholds for a specified period of time ascending from a high nine-digit dollar amount to $ 10.0 billion, or sale of the Company for consideration in excess of those thresholds. In the event of a change of control or a sale of the Company, the Company is required to pay success payments in cash within a specified period following such event. Otherwise, the success payments may be settled at the Company’s option in either cash or shares of its common stock, or a combination of cash and shares of its common stock. The maximum aggregate success payments that could be payable by the Company is $ 31.3 million (after termination of the Broad License Agreement). The success payments liability is stated at fair value and is considered Level 3 because its fair value measurement is based, in part, on significant inputs not observed in the market. The Company used a Monte Carlo simulation model, which models the value of the liability based on several key variables, including probability of event occurrence, timing of event occurrence, as well as the value of the Company’s common stock. The Company also estimated the likelihood that it would maintain both the Harvard/Broad License Agreement and the Broad License Agreement based on its on-going research efforts. The Company remeasured the liability at fair value with incre ases of $ 7.8 million , $ 2.4 million and $ 0.1 million recorded to other expense for the years ended December 31, 2021, 2020 and 2019, respectively. In September 2021, multiple success payments were triggered and amounts due to Harvard and Broad totaled $ 6.3 million. These amounts were settled in cash in November 2021. The Company will continue to adjust the remaining success payment liability for changes in fair value until the earlier of the achievement or expiration of the obligation. The primary inputs used in valuing (i) the success payments liability and (ii) the antidilution rights liability associated with the Company’s realization of a certain valuation threshold through either a sale of the Company’s preferred stock, an initial public offering, or a company sale at December 31, 2021 (only applicable to success payments liability), 2020 and 2019, were as follows: At At At Fair value of common stock (per share) $ 36.87 $ 8.24 $ 2.59 Equity volatility 77 % 105 % 100 % Cumulative probability of triggering event n/a 70 % 11 % Expected term (in years) n/a 0.50 2.89 At December 31, 2020 and 2019, the fair value of the Company's common stock was determined by management with the assistance of an independent third-party valuation specialist using methods consistent with the AICPA Valuation Guide. The computation of equity volatility was estimated using available information about the historical volatility of stocks of similar publicly traded companies for a period matching the expected term assumption. In addition, the Company incorporated the timing and probability of future events in the calculation of liabilities. The Company also estimated the likelihood that it would maintain both the Harvard/Broad License Agreement and the Broad License Agreement based on its on-going research efforts. The Company applied a 90 % probability of termination of the Broad License Agreement at December 31, 2020. In February 2021, the Company provided written notice to Broad of its election to terminate the Broad License Agreement, which termination became effective in June 2021. The reconciliation of changes in the fair value of financial instruments based on Level 3 inputs were as follows: (in thousands) Preferred Antidilution Success Total Balance at December 31, 2019 $ 9,571 $ 2,044 $ 419 $ 12,034 Issuance of Series A Preferred ( 7,064 ) — — ( 7,064 ) Issuance of common stock — ( 487 ) — ( 487 ) Changes in fair value ( 2,507 ) 5,359 2,387 5,239 Balance at December 31, 2020 — 6,916 2,806 9,722 Issuance of common stock — ( 32,490 ) — ( 32,490 ) Success payment liability earned and paid — — ( 6,250 ) ( 6,250 ) Change in fair value — 25,574 7,815 33,389 Balance at December 31, 2021 $ — $ — $ 4,371 $ 4,371

Accrued expenses

Accrued expenses	12 Months Ended
	Dec. 31, 2021
Payables And Accruals [Abstract]
Accrued Expenses	6. Accrued expenses Accrued expenses consist of the following: December 31, (in thousands) 2021 2020 Employee compensation and related benefits $ 6,050 $ 1,636 Accrued external research and development expenses 5,041 4,827 Professional fees 1,109 303 Other 792 423 Total $ 12,992 $ 7,189

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Leases	7. Leases The Company’s operating lease activity is comprised of non-cancelable facility leases for office and laboratory space in Cambridge, Massachusetts. In March 2020, the Company entered into an operating lease agreement for 16,843 square feet of space located at 500 Technology Square, Cambridge, Massachusetts (the “Cambridge Lease”), with the Company acting as subtenant. The term of the Cambridge Lease commenced in August 2020 and is scheduled to expire two years from the commencement date. The lease provides for annual rent escalations. The Company pays for its proportionate share of building operating costs such as maintenance, utilities, and insurance. In June 2020, the Company entered into the First Amendment to the Cambridge Lease adding 2,980 square feet of additional space. In January 2021, the Company entered into the Second Amendment to the Cambridge Lease adding 2,980 square feet of additional space at a commensurate rent increase which was treated as a new contract. In July, 2021, the Company entered into an amendment for its office space at 500 Technology Square and corresponding parking lot to extend the lease term through November 30, 2022 . The renewal operates under the same terms and conditions as the original lease. As a result of the renewal, the right-of-use asset and lease liability were remeasured at the present value of the lease payments not yet paid, discounted by the incremental borrowing rate (IBR) at the remeasurement date. This resulted in a net increase to the lease liability and right-of-use asset of $ 0.8 million. There was no impact on the consolidated statement of operations and comprehensive loss or the consolidated statement of cash flows as a result of the lease renewal. The Company has also entered into multiple contract research and contract manufacturing service agreements with third parties which contain embedded leases within the scope of ASC 842. The embedded leases are considered short term leases, as the contractual terms are twelve months or less. Accordingly, no lease liability or right of use asset has been recorded, and the Company has recognized $ 2.3 million of short term lease costs associated with the embedded leases during the year ended December 31, 2021. The components of operating lease cost were as follows: (in thousands) December 31, 2021 Operating lease costs $ 1,923 Variable lease costs 747 Short term lease costs 2,278 Total $ 4,948 Supplemental cash flow information related to operating leases was as follows: (in thousands) December 31, 2021 Cash paid for amounts included in the measurements of lease liabilities: Operating cash flows related to operating leases $ 2,021 As of December 31, 2021, the Company’s operating leases were measured using a weighted-average incremental borrowing rate of 1.57 % over a weighted-average remaining lease ter m of 0 .9 years. On August 19, 2021, the Company entered into a lease agreement with ARE-MA Region No. 87 Tenant, LLC, a Delaware limited liability company (the “Landlord”), pursuant to which the Company will lease approximately 104,933 square feet of office and laboratory space located at 201 Brookline Avenue, Boston, Massachusetts (the “Boston Lease”), further amended in January 2022 to include an additional 211 square feet, for a total of 105,144 square feet. The Boston Lease premises have not been made available to the Company as of December 31, 2021 and is therefore excluded from the table below, as the Lease has not commenced. The term of the Lease will commence on the earlier of (1) the date the Landlord delivers the premises under the Boston Lease to the Company, which the parties expect to be on or prior to August 1, 2022, or (2) the date the Landlord could have delivered the premises but for any delays attributable to the Company (the “Commencement Date”). The Company’s obligation for the payment of base rent for the Boston Lease begins 90 days after the Commencement Date (the “Rent Commencement Date”) and will initially be $0.8 million per month, which will increase by approximately 3% per annum. The Boston Lease has a term of 10 years, measured from the Rent Commencement Date. The Company has the option to extend the term of the Lease for a period of an additional five years . Under the terms of the Lease, the Landlord has agreed to make up to $ 21.0 million in certain tenant improvements to the premises to suit the Company’s use (the “Tenant Improvement Allowance”), which amount is included in the base rent set forth in the Boston Lease. In addition to the Tenant Improvement Allowance, the Company may receive up to $ 5.2 million for additional improvements to the premises, which amount is subject to an 8 % annual interest charge and may be paid in equal monthly installments. In connection with its entry into the Boston Lease and as a security deposit, the Company has provided the Landlord a letter of credit in the amount of approximately $ 4.8 million, which may be reduced to approximately $ 3.5 million on the expiration of the 36-month anniversary of the Rent Commencement Date so long as there are, and have been, no defaults by the Company under the terms of the Boston Lease. The Company also paid a deposit in the amount of $ 0.8 million, which is equal to the first month of base rent. The Landlord has the right to terminate the Boston Lease upon customary events of default. The Company may also termina te the Boston Lease if the premises are not ready for occupancy within a specified time period after August 1, 2022. The Boston Lease requires the Landlord to perform a scope of work to build-out the base building prior to the construction of the premises. The Company concluded the accounting commencement date will occur when the Landlord completes the build-out of the base building and control passes to the Company. The Company will assess the classification of the Boston Lease at the accounting commencement date, measure the right-of-use asset and lease liability. Payments made by the Company prior to commencement will be treated as prepaid rent which will increase the right-of-use asset. As of December 31, 2021, the Company has incurr ed $ 1.5 million re lated to the build out of the lease space prior to the Commencement Date. In October 2021, the Company entered into a sublease for 11,931 square feet of office and laboratory space in Cambridge, Massachusetts. The sublease commenced in December 2021 and has an initial noncancelable term of twelve months . The Company has the option to extend the sublease for one extension term of three months by written notice not less than six months prior to the expiration of the sublease term, which the Company is not reasonably certain of exercising. Therefore, this sublease is treated as a short term lease. The total fixed lease payments over the sublease term is approximately $ 1.4 million and the Company is also required to pay its proportional share of operating expenses. Future minimum commitments under non-cancellable leases as of December 31, 2021 were as follows: Years ending December 31, Amount (in thousands) 2022 $ 12,951 2023 9,958 2024 10,257 2025 10,565 2026 10,882 Thereafter 54,158 Total lease payments $ 108,771 Less: interest ( 13 ) Present value of operating lease liabilities $ 108,758 Accounting under ASC 840 Prior to the adoption of ASC 842, the Company recorded rent expense on a straight-line basis over the term of the lease, including any rent-free periods. In addition, the Company recorded deferred rent for certain lease incentives received, which were amortized as a reduction of rent expense over the life of the lease. Rent expense was presented as part of continuing operations in the consolidated statement of operations and comprehensive loss; deferred rent was recorded on the consolidated balance sheet. Rent expense for the years ended December 31, 2020 and 2019 was $ 1.3 million and $ 0.2 million, respectively.

License Agreements

License Agreements	12 Months Ended
	Dec. 31, 2021
License Agreement [Abstract]
License Agreement	8. License agreements Harvard/Broad license agreement and Broad license agreement In March 2019, the Company simultaneously entered into the Harvard/Broad License Agreement and Broad License Agreement (the “license agreements”) for certain base editing technologies pursuant to which the Company received exclusive, worldwide, sublicensable, royalty-bearing licenses under specified patent rights to develop and commercialize licensed products and nonexclusive, worldwide, sublicensable, royalty-bearing licenses under certain patent rights to research and develop licensed products. The Company agreed to use commercially reasonable efforts to develop licensed products in accordance with the development plans, to introduce any licensed products that gain regulatory approval into the commercial market, to market licensed products that have gained regulatory approval following such introduction into the market, and to make licensed products that have gained regulatory approval reasonably available to the public. The term of the agreements will continue until the expiration of the last to expire valid claim. The Company may terminate either of the license agreements without cause upon four months’ prior written notice to Harvard and Broad, unless terminated earlier. In February 2021, the Company provided written notice to Broad of its intent to terminate the Broad License Agreement, which termination was effective in June 2021. As partial consideration for the rights granted under the Harvard/ Broad License Agreement and Broad License Agreement, the Company paid $ 0.3 million in non-refundable upfront license fees and also issued 276,075 shares of its common stock with a fair value of $ 0.3 million. Additional consideration under the license agreements is as follows: Antidilution Rights —The initial shares of common stock issued to Harvard and Broad are subject to antidilution provisions as further described in Note 5, Fair value of financial instruments. The antidilution rights associated with the Company achieving a defined aggregate level of preferred stock financing were partially satisfied in 2019 and fully satisfied in 2020, which settlement amounts totaled $ 0.1 million and $ 0.5 million, respectively, and which amounts were settled through issuances of 121,411 and 187,867 shares of common stock, respectively. The remaining antidilution rights obligation was fully satisfied in June 2021 upon the Company’s IPO. The settlement amount totaled $ 32.5 million and was settled through issuance of 878,098 shares of the Company's common stock. Success Payments —The Company is required to make success payments under the license agreements as further described in Note 5, Fair value of financial instruments. For the years ended December 31, 2020 and 2019, no success payments were paid or due. In September 2021, certain success payments were triggered and amounts due to Harvard and Broad totaled $ 6.3 million. These amounts were settled in cash in November 2021. Other Payments —The Company agreed to pay an annual license maintenance fee ranging from low-to-mid five figures to low six figures, depending on the particular calendar year, for each of the license agreements. The Company is responsible for the payment of certain patent prosecution and maintenance costs incurred by Harvard and Broad related to licensed patents. To the extent achieved, the Company is obligated to pay up to an aggregate of $ 46.2 million and $ 108 million in development and sales-based milestones, respectively. If the Company undergoes a change of control during the term of the license agreements, then certain of the milestone payments would be increased by a mid-double-digit percentage. The milestones have not been achieved and no expense has been recorded for these milestones as of December 31, 2021. To the extent there are sales of a licensed product, the Company is required to pay low single digit royalties on net sales, for each of the license agreements. The Company is entitled to certain reductions and offsets on these royalties with respect to a licensed product in a given country. The Company concluded that the assets acquired from Harvard and Broad did not meet the accounting definition of a business as inputs, but no processes or outputs were acquired with the licenses. As the inputs that were acquired along with the licenses do not constitute a “business,” the transaction has been accounted for as an asset acquisition. As of the date of the license agreements, the assets acquired had no alternative future use and the assets had not reached a stage of technological feasibility. As a result, all share-based and cash payment obligations have been recorded as research and development expense in the statement of operations and comprehensive loss. At the inception of the license agreements in March 2019, the Company recognized $ 2.1 million as research and development expense, which includes the non-refundable upfront license fees payable in cash and the fair value of the common stock issued, along with the initial fair values of the antidilution rights liability and success payment liability. As further disclosed in Note 5, the antidilution rights liability and success payment liability are remeasured at fair value each reporting period with subsequent changes recognized in other income (expense). Verily agreement In March 2019, the Company and Verily Life Sciences LLC (“Verily”) entered into a collaboration agreement. Pursuant to the agreement, the Company and Verily intend to collaborate to utilize Verily’s nanoparticle platform to screen, develop and characterize improved nanoparticles for the delivery of the Company’s gene editing tools to enable development and commercialization of nanoparticle-based drug products. As part of the agreement, Verily granted the Company an exclusive, perpetual, worldwide, sublicensable, fully paid right and license to Verily’s solely owned and developed intellectual property to research, develop, make, offer for sale, sell and import products targeting the Company’s gene targets for the treatment or prevention of atherosclerotic cardiovascular disease. The term of the agreement continues until the earlier of (i) completion of all activities related to the collaboration or (ii) the three-year anniversary of the agreement date, unless terminated earlier. At any time during the term, the Company has the right to terminate the agreement in its entirety for any reason by delivering a 90-day termination notice to Verily. As partial consideration for the license rights granted by Verily, at inception of the arrangement, the Company paid a one-time, nonrefundable fee through the issuance of 1,672,240 shares of Series A Preferred with a fair value of $ 0.6 million. To the extent achieved, the Company was obligated to make one-time payments to Verily of up to $ 5.5 million in development-based milestones. The Company paid a milestone payment of $ 1.0 million in 2020 related to a study in wild type mice that demonstrated a certain gene editing percentage level. In addition, as consideration for Verily’s activities under the agreement, the Company was obligated to pay a $ 0.3 million quarterly development payment for a period of ten quarters. The Company concluded the assets acquired from Verily did not meet the accounting definition of a business as inputs, but no processes or outputs were acquired with the licenses. As the inputs that were acquired along with the licenses do not constitute a “business,” the transaction has been accounted for as an asset acquisition. As of the date of the collaboration agreement, the assets acquired had no alternative future use and the assets had not reached a stage of technological feasibility. As a result, at the inception of the agreement in 2019, the Company recognized $ 0.6 million as research and development expense, which includes the one-time, nonrefundable license fee settled through issuing 1,672,240 shares of Series A Preferred. In addition, the Company recognized $ 0.8 million in quarterly development payments to Verily as research and development expense in 2019. In 2020, the Company recognized the milestone payment of $ 1.0 million described above as research and development expense upon achievement of the related development-based milestone. Further, the Company recognized $ 0.5 million in quarterly development payments to Verily as research and development expense in 2020. The Company elected to terminate the agreement with Verily effective June 26, 2020 and has no outstanding amounts due or payable to Verily as of December 31, 2021 and 2020. Beam license agreement In April 2019, the Company and Beam Therapeutics, Inc. (“Beam”) entered into a collaboration and license agreement. Pursuant to the agreement, the Company received an exclusive, worldwide, sublicensable license under certain of Beam’s base editing technology, gene editing, and delivery technologies to develop, make, use, offer for sale, sell and import base editing products and nuclease products using Beam’s CRISPR associated protein 12b, or Cas12b technology, in each case, directed to any of four gene targets, including the PCSK9 and ANGPTL3 genes, that are associated with an increased risk of coronary diseases. In addition, the Company granted Beam an exclusive, worldwide, sublicensable license under certain of its delivery technology to develop, manufacture, sell and import product candidates and products, except for base editor products licensed to Verve. Both parties may conduct certain activities in accordance with an agreed-upon research and/or development plan. Following the final dosing of a patient in a Phase 1 clinical trial of a given licensed product, Beam has the right to opt in to share 33 % of worldwide expenses of the development of such licensed product, as well as jointly commercialize and share profits and expenses of commercializing such licensed product in the United States on a 50/50 basis. If Beam exercises its opt-in right for a given licensed product, which we refer to following such opt-in as a collaboration product, it will be obligated to pay for a specified percentage of the development and commercialization costs of such collaboration product and will have the right to receive a specified percentage of the profits from any sales of such collaboration product. The term of the agreement continues until the last to expire of any royalty term for any product. The Company has the right to terminate the agreement as to any licensed product, but not for any collaboration product, by delivering a 90-day termination notice to Beam, provided that Beam has elected not to exercise its opt-in right or the period to exercise such opt-in right has expired. The Company is responsible for all costs and expenses incurred in the conduct of activities under the research plan, any development plan and any costs and expenses for the development of a licensed product for which Beam has not elected to opt-in. As partial consideration for the license rights granted by Beam, the Company paid a one-time, nonrefundable fee through issuing 276,075 shares of its common stock with a fair value of $ 0.3 million. To the extent achieved, for each licensed product, the Company is also obligated to pay up to $ 11.3 million in development and regulatory-based milestones and $ 15.0 million in sales-based milestones. To the extent there are sales of a licensed product, the Company is required to pay low-to-mid single digit royalties on net sales. To the extent achieved, for each collaboration product outside of the United States, the Company is obligated to pay up to $ 5.6 million in development and regulatory-based milestones and $ 7.5 million in sales-based milestones. To the extent there are ex-U.S. sales of a collaboration product, the Company is required to pay low-to-mid single digit royalties on net sales. The milestones have not been achieved and no expense has been recorded for these milestones as of December 31, 2021. The parties have also promised that in further consideration for the licenses granted under the parties’ respective delivery technologies, each party will pay to the other party development-based milestone payments up to $ 6.0 million for each delivery technology product of such paying party to achieve the corresponding milestone event. The triggering of these milestone payments was not considered probable as of the transaction date, and no expense has been recorded for these milestones as of December 31, 2021. To the extent there are sales of a delivery technology product, each party will pay the other party low-to-mid single digit royalties based on the annual aggregate worldwide net sales resulting from the sale of each delivery technology product of such paying party; provided, however, that such royalty payments will not apply to net sales of the collaboration products or licensed products. The Company concluded the receipt of any milestone or royalty payments under the agreement was not probable as of December 31, 2021. The Company further concluded the assets acquired from Beam did not meet the accounting definition of a business as inputs, but no processes or outputs were acquired with the licenses. As the inputs that were acquired along with the licenses do not constitute a “business,” the transaction has been accounted for as an asset acquisition. As of the date of the license agreement, the assets acquired had no alternative future use and the assets had not reached a stage of technological feasibility. As a result, at the inception of the agreement in 2019, the Company recognized $ 0.3 million as research and development expense, which includes the one-time, nonrefundable license fee settled through the issuance of 276,075 shares of common stock. Beam materials exchange letter agreement In October 2020, the Company and Beam entered into a materials exchange agreement wherein the parties agreed that Beam would provide certain mRNA, gRNA, and protein to the Company and that the Company would provide certain gRNAs to Beam at an agreed upon price per each material provided. For the year ended December 31, 2021, the Company did no t purchase any materials from Beam. For the year ended December 31, 2020, the Company purchased $ 0.2 million as a charge to research and development expense related to materials purchased from Beam. For the year ended December 31, 2021, the Company recognized $ 0.2 million as a reduction to research and development expense related to reimbursements received for materials sold to Beam. During the year ended December 31, 2020, the Company recognized $ 0.3 million as a reduction to research and development expense related to reimbursements received for materials sold to Beam. Acuitas agreements Development and option agreement In December 2019, the Company and Acuitas Therapeutics, Inc. ("Acuitas") entered into a development and collaboration agreement, which agreement was amended and restated in October 2020. The Company agreed to reimburse Acuitas on a quarterly basis for its services performed related to the program activities based on an agreed upon number of fulltime employees committed to work on the program at an annual rate per employee, including reimbursement of reasonable external costs. These services commenced during 2020 and the Company recognized research and development expense of $ 1.0 million and $ 2.0 million for the years ended December 31, 2021 and 2020, respectively, related to the reimbursement of research and development services provided by Acuitas and technology maintenance fees. In 2020 upon the one-year anniversary of the agreement the Company had exercised one of its options to enter into a non-exclusive license agreement, as further described below. License agreement In October 2020, the Company paid Acuitas a non-refundable, upfront license fee of $ 2.0 million (less a previously paid target reservation fee) to exercise an option with respect to a licensed product and a licensed genome target and entered into a non-exclusive, worldwide license with Acuitas, with a right to sub-license through multiple tiers, under the licensed LNP technology to research, develop and commercialize the licensed products using the LNP technology in connection with the PCSK9 gene target for all human therapeutic or prophylactic uses. To the extent achieved, the Company is also obligated to pay up to an aggregate of $ 9.8 million in clinical and regulatory milestones and $ 9.5 million in sales-based milestones. The milestones have not been achieved and no expense has been recorded for these milestones as of December 31, 2021. Third-party license agreements In October 2021, the Company entered into a license agreement with a third party to obtain a non-exclusive license to certain technology the Company is using for research and development. As consideration for the license and rights granted under the agreement, the Company made a one-time, non-refundable, upfront payment of $ 0.8 million during the three months ended December 31, 2021. The license agreement provides for specified development milestones relating to the licensed technology and requires the Company to make payments upon achievement of each milestone up to an aggregate amount of $ 10.0 million.

Preferred Stock Tranche Liabili

Preferred Stock Tranche Liability	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Preferred Stock Tranche Liability	9. Preferred stock tranche liability Included in the terms of the Series A Preferred Stock purchase agreement were certain tranche rights whereupon the Company was obligated to issue, and the Series A Preferred investors had the obligation to purchase, additional shares of Series A Preferred Stock, as follows: • 29,347,825 shares of Series A Preferred Stock at $ 0.598 per share upon the Company achieving certain scientific and non-scientific milestones ("second tranche"); and • 49,749,167 shares of Series A Preferred Stock at $ 0.598 per share upon the Company achieving additional scientific and non-scientific milestones ("third tranche"). The second tranche and third tranche represent freestanding financial instruments accounted for as liabilities under ASC 480, Distinguishing Liabilities From Equity, because these tranche rights (i) embody an obligation to repurchase the Company's equity shares and (ii) may require the Company to settle the obligation by transferring assets. As a result, upon issuance, the respective tranche rights were initially recorded at fair value and subsequently re-measured at fair value in each reporting period (and at settlement, as applicable). Changes in fair value were recognized as a component of other income (expense) in the consolidated statements of operations and comprehensive loss. The second tranche and third tranche were settled in 2019 and 2020, respectively. Second tranche In April 2019, the board of directors agreed to amend certain scientific milestones and subsequently determined the second tranche milestones, as modified, were achieved and the Company settled the second tranche by issuing 29,347,825 shares of Series A Preferred Stock at a price of $ 0.598 per share for gross proceeds of $ 17.5 million. Third tranche In March 2020, the board of directors agreed to waive the final remaining milestones and determined the third tranche milestones, as modified, were achieved. In March 2020, the Company settled the third tranche by issuing 49,749,167 shares of Series A Preferred Stock at a price of $ 0.598 per share for gross proceeds of $ 29.8 million.

Preferred and Common Stock

Preferred and Common Stock	12 Months Ended
	Dec. 31, 2021
Preferred Stock [Abstract]
Preferred and Common Stock	10. Preferred and common stock The Company has issued and sold Series A Preferred, Series A-2 Preferred, Series B Preferred and common stock, as follows: During 2018, the Company issued and sold 19,565,217 shares of Series A Preferred at a price of $ 0.598 per share for gross proceeds of $ 11.7 million. The Company incurred issuance costs in connection with these transactions of $ 0.2 million. These issuances included the tranche rights for the second tranche and third tranche, as previously described in Note 9, Preferred Stock tranche liability. In March 2019, the Company issued 1,672,240 shares of Series A Preferred in exchange for in-licensing certain technologies from Verily. See Note 8, License agreements. In August 2019, the Company issued 29,347,825 shares of Series A Preferred at a price of $ 0.598 per share for gross proceeds of $ 17.5 million. This issuance represented the settlement of the second tranche. See Note 9, Preferred Stock tranche liability. In October 2019, the Company issued 836,122 shares of Series A Preferred at a price of $ 0.598 per share for gross proceeds of $ 0.5 million. This issuance included tranche rights for the third tranche. In March 2020, the Company issued 49,749,167 shares of Series A Preferred at a price of $ 0.598 per share for gross proceeds of $ 29.8 million. This issuance represented the settlement of the third tranche. Between April and June 2020, the Company issued 78,348,461 shares of Series A-2 Preferred at a price of $ 0.8041 per share for gross proceeds of $ 63.0 million. The Company incurred issuance costs in connection with this transaction of $ 0.1 million. In January 2021, the Company issued 77,163,022 shares of Series B Preferred Stock at a price of $ 1.2182 per share for gross proceeds of $ 94.0 million. The Company incurred issuance costs in connection with this transaction of $ 0.2 million. In June 2021, the Company amended and restated its certificate of incorporation to authorize 5,000,000 shares of preferred stock, which shares of preferred stock are currently undesignated, and 200,000,000 shares of common stock, $ 0.001 par value per share. In June 2021, the Company completed its IPO, pursuant to which the Company issued and sold 16,141,157 shares of its common stock, including 2,105,368 shares pursuant to the full exercise of the underwriters' option to purchase additional shares, at a public offering price of $ 19.00 per share, for aggregate gross proceeds of $ 306.7 million. The Company received approximately $ 281.6 million in net proceeds, after deducting underwriting discounts and offering expenses payable by the Company. Upon the closing of the IPO, all outstanding shares of the Company's preferred stock automatically converted into 27,720,923 shares of the Company's common stock. In June 2021, the Company issued 878,098 shares of its common stock to Harvard and Broad as final settlement of its antidilution rights obligation. The holders of common stock are entitled to one vote for each share of common stock. The following is a summary of the rights and preferences of the Series A Preferred, Series A-2 Preferred and Series B Preferred, prior to the completion of the Company's IPO: Conversion — Each share of Series A Preferred, Series A-2 Preferred and Series B Preferred may be converted at any time, at the option of the holder, into shares of common stock, subject to the applicable conversion rate as determined by dividing the original issue price by the conversion price. The initial conversion price for each of the Series A Preferred, Series A-2 Preferred and Series B Preferred (each as may be adjusted for certain dilutive events) was $ 0.598 , $ 0.8041 and $ 1.2182 per share, respectively. Each series of Series A Preferred, Series A-2 Preferred and Series B Preferred automatically converted into shares of common stock on a 1:1 conversion ratio (as may be adjusted for certain dilutive events) at the earlier of the closing of an initial public offering of the Company’s common stock with gross proceeds to the Company of at least $ 50.0 million and a purchase price of $ 22.34 per share, or at the election of the holders of at least two-thirds of the then-outstanding shares of Preferred Stock. Dividends —Holders were entitled to non-cumulative dividends of $ 0.05 per share with respect to Series A Preferred and $ 0.06 per share with respect to the Series A-2 Preferred, and $ 0.10 per share with respect to Series B Preferred when, as, and if declared by the board of directors. No dividends have been declared through December 31, 2021. Voting Rights —Series A Preferred, Series A-2 Preferred, Series B Preferred and common stock generally voting together as one class on an as-converted basis; however, common stock voting rights on certain matters were subject to the powers, preferences, and rights of the Series A Preferred, Series A-2 Preferred and Series B Preferred. The holders of Series A Preferred, Series A-2 Preferred and Series B Preferred, voting together as a single class, were entitled to elect three directors to the Company’s board of directors and the holders of common stock, voting as a single class, were entitled to elect two directors to the Company’s board of directors. Certain actions, such as mergers, consolidation, sale of substantially all assets, liquidation, dissolution, wind up of business, or any other deemed liquidation events, must be approved by the holders of at least two-thirds of the then-outstanding shares of Series A Preferred, Series A-2 Preferred and Series B Preferred. Liquidation Preference —Upon liquidation, dissolution, or winding up of business, the holders of the Series A Preferred, Series A-2 Preferred and Series B Preferred were entitled to receive a liquidation preference in priority over the holders of common stock, at an amount per share equal to the greater of i) the original Series A Preferred, Series A-2 Preferred and Series B Preferred issue price plus any declared but unpaid dividends, or ii) the amount per share payable had all shares of Series A Preferred, Series A-2 Preferred and Series B Preferred been converted to common stock immediately prior to such liquidation. If assets available for distribution are insufficient to satisfy the liquidation payment to holders in full, assets available for distribution would have been allocated among holders based on their pro rata shareholdings. When holders are satisfied in full, any excess assets available for distribution would have been allocated ratably among the holders of common stock based on their pro rata holdings. Upon a deemed liquidation event, as defined, holders had the option to redeem their outstanding shares at a price equal to the liquidation payment amounts summarized above. Redemption —Aside from upon the occurrence of a deemed liquidation event, the Series A Preferred, Series A-2 Preferred and Series B Preferred were not redeemable.

Stock-based compensation

Stock-based compensation	12 Months Ended
	Dec. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based compensation	11. Stock-based compensation The 2018 Equity Incentive Plan, or the 2018 Plan, adopted by the board of directors in August 2018 provided for the grant of qualified incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock and restricted stock units to the Company’s employees, officers, directors, advisors, and outside consultants for the issuance or purchase of shares of the Company’s common stock. The maximum number of shares of common stock that were authorized for issuance under the 2018 Plan was 6,885,653 . In June 2021, the Company's board of directors adopted, and the Company's stockholders approved, the 2021 Stock Incentive Plan, or the 2021 Plan, which became effective on June 16, 2021. The 2021 Plan provides for grant of qualified and nonqualified stock options, stock appreciation rights, restricted and unrestricted stock and stock units, performance awards, and other share-based awards to the Company's employees, directors, advisors and outside consultants. Under the 2021 Plan, the number of shares of common stock that was initially reserved for issuance under the 2021 Plan was the sum of: (1) 3,466,530 ; plus (2) the number of shares as is equal to the sum of (x) the number of shares of common stock reserved for issuance under the 2018 Plan that remained available for grant under the 2018 Plan on June 16, 2021 and (y) the number of shares of common stock subject to outstanding awards granted under the 2018 Plan that expire, terminate or are otherwise surrendered, cancelled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right; plus (3) an annual increase, to be added on the first day of each fiscal year, commencing on January 1, 2022 and continuing until, and including, January 1, 2031, equal to the lesser of (i) 5 % of the number of shares of common stock outstanding on such date and (ii) the number of shares of common stock determined by the Company's board of directors. As of December 31, 2021 the Company had reserved 4,632,042 shares of the Company's common stock for issuance of stock options and restricted stock, of which 3,489,589 remained outstanding for future grant under the 2021 Plan. On January 1, 2022, 2,425,587 shares of the Company's common stock were added to the amount reserved for issuance under the 2021 Plan in accordance with the 2021 Plan described above. Upon effectiveness of the 2021 Plan, the Company ceased granting additional awards under the 2018 Plan. Stock-based compensation expense recorded in the consolidated statements of operations and comprehensive loss is as follows: Year ended (in thousands) 2021 2020 2019 Research and development $ 3,830 $ 494 $ 336 General and administrative 3,242 356 110 Total stock-based compensation expense $ 7,072 $ 850 $ 446 Stock options The assumptions used in Black-Scholes for stock options granted were as follows: Year ended 2021 2020 2019 Expected volatility 77.7 % 84.8 % 76.1 % Weighted-average risk-free interest rate 0.9 % 0.4 % 2.2 % Expected dividend yield — — — Expected term (in years) 6.0 6.0 5.9 The following table provides a summary of stock option activity during the year ended December 31, 2021: Number of Weighted Weighted Aggregate (2) Outstanding at December 31, 2020 3,888,823 $ 2.13 Granted 2,869,946 $ 17.66 Exercised ( 599,838 ) $ 1.61 Forfeited ( 39,636 ) $ 2.56 Outstanding at December 31, 2021 6,119,295 $ 9.44 8.7 $ 171,636 Exercisable at December 31, 2021 1,373,507 $ 2.15 8.0 $ 47,691 Expected to vest after December 31, 2021 (1) 4,745,788 $ 11.56 8.9 $ 123,945 (1) This represents the number of unvested options outstanding as of December 31, 2021 that are expected to vest in the future. (2) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money as of December 31, 2021. During the year ended December 31, 2021 the weighted average grant-date fair value of the stock options granted was $ 14.27 per share. The aggregate intrinsic value of stock options exercised during the year ended December 31, 2021 was approximately $ 11.6 million while the Company received $ 1.0 million in proceeds for the exercise of these options. As of December 31, 2021 , there was $ 40.2 million of unrecognized compensation cost related to unvested stock options, which is expected to be recognized over a weighted-average period of approximately 2.9 years. Restricted stock and restricted stock units In 2018, the Company issued 2,150,537 shares of restricted common stock. The restricted shares vested in 48 equal monthly installments, commencing on January 1, 2018. The restricted shares were fully vested as of December 31, 2021. A summary of the status of and change in unvested restricted stock as of December 31, 2021 was as follows: Shares Weighted- Unvested restricted stock as of December 31, 2020 537,633 $ 0.0028 Restricted stock vested ( 537,633 ) $ 0.0028 Unvested restricted stock as of December 31, 2021 — $ — During the year ended December 31, 2021 , the Company granted 32,000 restricted stock units under the 2021 Plan. These restricted stock units vest in substantially equal installments over a four-year period. A summary of the status of and change in unvested restricted stock units as of December 31, 2021 was as follows: Shares Weighted- Unvested restricted stock units as of December 31, 2020 — $ — Restricted stock units granted 32,000 $ 36.58 Unvested restricted stock units as of December 31, 2021 32,000 $ 36.58 At December 31, 2021 , there was $ 1.1 million of unrecognized stock-based compensation expense related to restricted stock units that are expected to vest. These costs are expected to be recognized over a weighted-average remaining vesting period of 4.0 years. 2021 Amended and Restated Employee Stock Purchase Plan In June 2021, the board of directors adopted, and the Company's stockholders approved, the 2021 Employee Stock Purchase Plan, or the ESPP, as amended and restated, which became effective on June 16, 2021. The Company has initially reserved 433,316 shares of common stock for sale under the ESPP. The aggregate number of shares reserved for sale under the ESPP will increase automatically on the first day of each fiscal year commencing on January 1, 2022 through January 1, 2031, by the number of shares equal to the least of (a) 1,083,290 shares, (b) 1 % of the total outstanding shares of common stock on such date, and (c) a number of shares as may be determined by the board of directors in any particular year. The first offering period under the ESPP commenced on June 16, 2021 and ended on December 13, 2021. As of December 31, 2021 , 48,297 shares had been purchased by employees under the ESPP and 385,019 shares remained available for issuance under the ESPP. On January 1, 2022, 485,117 shares of common stock were added to the amount reserved for sale under the ESPP. The second offering period commenced on December 14, 2021 and will end on May 31, 2022.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	12. Net loss per share attributable to common stockholders The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company: Year ended December 31, (in thousands, except share and per share amounts) 2021 2020 2019 Numerator: Net loss attributable to common stockholders $ ( 120,314 ) $ ( 45,704 ) $ ( 19,297 ) Denominator: Weighted average number of common shares, basic and diluted 26,872,036 2,250,093 1,277,156 Net loss per common share attributable to common stockholders, basic and diluted $ ( 4.48 ) $ ( 20.31 ) $ ( 15.11 ) The Company’s potential dilutive securities, which include convertible preferred stock, unvested restricted stock and common stock options, have been excluded from the computation of diluted net loss per share as the effects would be anti-dilutive. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares, presented based on amounts outstanding at period end, from the computation of diluted net loss per share attributable to common stockholders for the period indicated because including them would have had an anti-dilutive effect: Year ended December 31, 2021 2020 2019 Convertible preferred stock — 19,387,544 5,553,367 Unvested restricted stock — 537,633 1,075,268 Unvested restricted stock units 32,000 — — Outstanding options to purchase common stock 6,119,295 3,888,823 1,933,507 Total 6,151,295 23,814,000 8,562,142 As part of the license agreements with Harvard and Broad, the Company is required to make success payments. The Company may elect to make these payments by issuing shares of the Company's common stock. As of December 31, 2021, an aggregate of $ 6.3 million was earned relating to these success payments, which the Company settled in cash in November 2021.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	13. Income taxes For the years ended December 31, 2021, 2020 and 2019, the Company did not record a current or deferred income tax expense or benefit due to current and historical losses incurred by the Company. The Company’s losses before income taxes consist solely of losses from domestic operations, which totaled $ 120.3 million , $ 45.7 million and $ 19.3 million for the years ended December 31, 2021, 2020 and 2019, respectively A reconciliation of the income tax expense computed using the federal statutory income tax rate to the Company’s effective income tax rate is as follows: Year ended December 31, (in thousands) 2021 2020 2019 Federal statutory rate 21.0 % 21.0 % 21.0 % Change in valuation allowance ( 31.3 )% ( 29.6 )% ( 17.9 )% Stock-based compensation 0.9 % ( 0.3 )% ( 0.1 )% Executive compensation ( 1.1 )% 0.0 % 0.0 % Other permanent items ( 0.1 )% 1.1 % ( 5.8 )% State income taxes, net of federal benefit 6.1 % 6.8 % 1.7 % Research and development tax credits 4.5 % 1.0 % 1.1 % Total — % — % — % Deferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statement and income tax purposes. The significant components of the Company’s deferred tax assets and liabilities as of December 31, 2021 and 2020 are comprised of the following : December 31, (in thousands) 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 33,409 $ 12,973 Capitalized costs—net of amortization 12,395 855 Research and development tax credits 6,098 682 Antidilution liability — 2,815 Stock-based compensation 1,117 149 Other 76 61 Lease liability 533 — Accrued expenses 2,852 905 Total deferred tax assets 56,480 18,440 Deferred tax liabilities: Property and equipment ( 899 ) ( 1,061 ) Right of use asset ( 501 ) — Total deferred tax liabilities ( 1,400 ) ( 1,061 ) Total deferred tax assets, net 55,080 17,379 Less: valuation allowance ( 55,080 ) ( 17,379 ) Deferred tax assets, net of valuation allowance $ — $ — The Company has incurred net operating losses in each year since inception. The Company had no income tax expense due to the operating loss incurred for all years since inception. Management has evaluated the positive and negative evidence bearing upon the realizability of the Company’s net deferred tax assets, which are comprised primarily of net operating loss carryforwards, tax credits, and costs capitalized for tax purposes. Management has considered the Company’s history of cumulative net losses in the United States and estimated future tax losses and has determined that it is more likely than not that the Company will not recognize the benefits of the net deferred tax assets. As a result, the Company has recorded a full valuation allowance at December 31, 2021 and 2020. The valuation allowance increased by $ 37.7 million in 2021 , due to the increase in deferred tax assets, primarily due to net operating loss carryforwards, tax credit carryforwards, and increase in deferred tax assets associated with current year temporary items. The valuation allowance increased by $ 13.6 million in 2020, primarily due to the increase in deferred tax assets, primarily due to net operating loss carryforwards. Realization of the future tax benefits is dependent on many factors, including the Company’s ability to generate taxable income within the net operating loss carryforward period. The Company’s ability to utilize these federal and state net operating loss and research and development credit carryforwards may be limited in the future if the Company experiences an ownership change pursuant to Internal Revenue Code 382. An ownership change occurs when the ownership percentages of 5% or greater shareholders change by more than 50% over a three-year period. As of December 31, 2021, the Company has not completed a study to assess whether a change of control has occurred and whether the net operating losses and credits are limited due to a change in ownership. To the extent that an assessment is completed in the future, the Company’s ability to utilize tax attributes could be restricted on a year-by-year basis and certain attributes could expire before they are utilized. As of December 31, 2021 , the Company had approximately $ 124.7 million of pre-tax federal and $ 114.4 million of pre-tax state net operating loss carryforwards. The federal net operating losses have an indefinite life and can be utilized to offset 80 % of future taxable income, while the state net operating losses will start to expire at various dates through 2041 . Additionally, as of December 31, 2021 , the Company had approximately $ 4.2 million of federal and $ 2.3 million of Massachusetts tax credits that expire starting in 2041 and 2036 , respectively. As of December 31, 2021 and 2020 , the Company had no uncertain tax positions. The Company recognizes both interest and penalties associated with unrecognized tax benefits as a component of income tax expense. The Company has no t recorded any interest or penalties for unrecognized tax benefits since its inception. The Company files income tax returns in the United States, California, Connecticut, the Commonwealth of Massachusetts, and Pennsylvania. The Company is not currently under examination by the Internal Revenue Service or any other jurisdiction for these years. All tax years remain open to tax examination. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may be adjusted upon examination by the Internal Revenue Service or state tax authorities to the extent utilized in a future period. No federal or state tax audits are currently in process.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2021
Related Party Transactions [Abstract]
Related Party Transactions	14. Related party transactions In the years ended December 31, 2021, 2020 and 2019, the Company made total payments o f $ 0.3 million, $ 0.4 million and $ 0.4 million, respectively, to the five founder shareholders for scientific consulting and other expenses. These same individuals also vested in 537,633 , 537,635 and 537,635 shares of restricted stock in the years ended December 31, 2021, 2020 and 2019, respectively. An executive officer of Beam is a board member of the Company. From February 2019 through December 2019, the Company leased office space from Beam in Cambridge, Massachusetts. Total rent payments under this sublease was less than $ 0.1 million. In April 2019, the Company and Beam entered into a collaboration and license agreement. As partial consideration for the license rights granted by Beam, the Company paid a one-time, nonrefundable fee through issuing 276,075 shares of its common stock with a fair value of $ 0.3 million. Refer to Note 8, License agreements. In July 2019, the Company agreed to be designated as Beam’s collaboration partner in an NHP study connected to Beam’s development and option agreement with Acuitas. As a result, Beam granted the Company a non-exclusive, royalty-free sublicense under Beam’s right, title and interest in and to certain Acuitas technology, solely to the extent necessary to enable the Company to perform the NHP study activities. The Company paid to Beam a one-time payment of $ 0.1 million upon execution of the agreement and is responsible for certain out-of-pocket costs incurred by Beam in connection with the performance of the NHP study activities. In October 2020, the Company and Beam entered into a materials exchange agreement wherein the parties agreed that Beam would provide certain mRNA, gRNA, and protein to the Company and that the Company would provide certain gRNAs to Beam at an agreed upon price per each material provided. For the year ended December 31, 2021, the Company recognized $ 0.2 million as a reduction to research and development expense related to reimbursements received for materials sold to Beam. For the year ended December 31, 2020, the Company recognized $ 0.2 million as research and development expense related to payments made for materials purchased from Beam and also recognized $ 0.3 million as a reduction to research and development expense related to reimbursements received for materials sold to Beam In December 2021, the Company entered into a sublease agreement with Beam for laboratory and office space in Cambridge, Massachusetts. Total rent payments under this sublease were less than $ 0.1 million for the year ended December 31, 2021. An officer of the Company was formerly affiliated with Massachusetts General Hospital (“MGH”) as a physician. As of August 2021, the officer is no longer a physician at MGH. In February 2019 and November of 2019, the Company entered into an Option License Agreement and Patent License Agreement, respectively, with MGH. Upon execution of the agreements in 2019, the Company incurred $ 0.2 million for option and license issue fees, which were recorded as research and development expense. For the years ended December 2021 and 2020, the Company incurred $ 0.1 million each year relating to the annual license fee, which was recorded as research and development expense. An executive of Broad was a board member of the Company. The board member resigned, effective May 2021. In March 2019, the Company simultaneously entered into the Harvard/Broad License Agreement and Broad License Agreement for certain base editing technologies pursuant to which the Company received exclusive, worldwide, sublicensable, royalty-bearing licenses under specified patent rights to develop and commercialize licensed products and nonexclusive, worldwide, sublicensable, royalty-bearing licenses under certain patent rights to research and develop licensed products. Additional consideration under the license agreements include antidilution rights and success payments. See Note 8, License agreements.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2021
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	15. Employee benefit plans The Company has a defined-contribution plan established under Section 401(k) of the Internal Revenue Code (the “401(k) Plan”), which covers substantially all employees. Employees are eligible to participate in the 401(k) Plan beginning on the first day of the month following commencement of their employment. The 401(k) Plan includes a salary deferral arrangement pursuant to which participants may elect to reduce their current compensation by up to the sta tutorily prescribed limit, equal to $ 19,500 in 2021 with a catch up contribution limit equal to $ 6,500 for those 50 years of age or older, and have the amount of the reduction contributed to the 401(k) Plan. Since January 1, 2020 the Company matches 100 % of each participant’s annual contribution to the 401(k) plan up to 3 % of the participant’s salary and then 50 % of each participant’s contribution up to 2 % of the participant’s salary. The match immediately vests 100 %. The matching c ontributions by the Company to the 401(k) plan were $ 0.4 million and $ 0.1 million for the years ended December 31, 2021 and 2020 , respectively.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	16. S ubsequent events The Company evaluated all subsequent events and determined there are no material recognized or unrecognized subsequent events requiring disclosure.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Principles of Consolidation	Principles of consolidation The accompanying consolidated financial statements include the accounts of Verve and its wholly owned subsidiary, Verve Securities Corporation. All intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the fair values of common stock (prior to completion of the IPO), convertible preferred stock, preferred stock tranche liability, stock-based compensation, and the liabilities for antidilution rights and success payments. Actual results could differ from these estimates.
Cash and Cash Equivalents	Cash and cash equivalents Cash and cash equivalents consist of standard checking accounts and money market account funds that invest primarily in U.S. government-backed securities and treasuries. The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. Cash equivalents are stated at cost, which is substantially equivalent to fair value.
Restricted cash	Restricted cash Restricted cash represents collateral provided for a letter of credit issued as a security deposit in connection with the Company’s leases of its corporate facilities. A reconciliation of the cash, cash equivalents, and restricted cash reported within the balance sheet that sum to the total of the same amounts shown in the statement of cash flows is as follows: December 31, (in thousands) 2021 2020 Cash and cash equivalents $ 64,330 $ 8,993 Restricted cash 5,237 463 Total cash, cash equivalents and restricted cash $ 69,567 $ 9,456
Marketable Securities	Marketable securities The Company classifies marketable securities with a remaining maturity when purchased of greater than three months as available-for-sale. Available-for-sale securities are maintained by the Company’s investment managers and consist of U.S. treasury bills and U.S agency securities. Available-for-sale securities are carried at fair value with the unrealized gains and losses included in accumulated other comprehensive income (loss) as a component of stockholders’ equity until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the instrument. Realized gains and losses are determined using the specific identification method and are included in other income (expense). The Company reviews marketable securities for other-than-temporary impairment whenever the fair value of a marketable security is less than the amortized cost and evidence indicates that a marketable security’s carrying amount is not recoverable within a reasonable period of time. Other-than-temporary impairments of investments are recognized in the consolidated statements of operations if the Company has experienced a credit loss, has the intent to sell the marketable security, or if it is more likely than not that the Company will be required to sell the marketable security before recovery of the amortized cost basis. Evidence considered in this assessment includes reasons for the impairment, compliance with the Company’s investment policy, the severity and the duration of the impairment and changes in value subsequent to the end of the period. The Company evaluated its securities for other-than-temporary impairment and considered the decline in market value for the securities to be primarily attributable to current economic and market conditions. It is not more likely than not that the Company will be required to sell the securities, and the Company does not intend to do so prior to the recovery of the amortized cost basis. Based on this analysis, these marketable securities were not considered to be other-than-temporarily impaired as of December 31, 2021 and 2020 .
Concentration of Credit Risk	Concentrations of credit risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents and restricted cash. Periodically, the Company may maintain deposits in financial institutions in excess of government insured limits. Management believes that the Company is not exposed to significant credit risk as the Company’s deposits are held at financial institutions that management believes to be of high credit quality, and the Company has not experienced any losses on these deposits.
Deferred Offering Costs	Deferred offering costs The Company capitalized incremental legal, professional accounting and other third-party fees that were directly associated with the IPO as other non-current assets until the IPO was consummated. After consummation of the IPO, these costs were recorded in stockholders’ equity (deficit) as a reduction of additional paid-in-capital generated as a result of the offering.
Indemnification Agreements	Indemnification agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, contract research organizations, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The Company has not incurred any material costs as a result of such indemnifications and is not currently aware of any indemnification claims.
Fair Value of Financial Instruments	Fair value of financial instruments ASC Topic 820, Fair Value Measurement (“ASC 820”), establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the assets or liability and are developed based on the best information available in the circumstances. ASC 820 identifies fair value as the price that would be received to sell an asset or paid to transfer a liability, in an orderly transaction between market participants at the measurement date. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tiered value hierarchy that distinguishes between the following: Level 1—Quoted market prices in active markets for identical assets or liabilities. Level 2—Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted market prices, interest rates and yield curves. Level 3—Unobservable inputs for the asset or liability (i.e. supported by little or no market activity). Level 3 inputs include management’s own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk). To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair values requires more judgement. Accordingly, the degree of judgement exercised by the Company in determining fair value is greatest for instruments categorized as Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. There have been no changes to the valuation methods utilized by the Company during the years ended December 31, 2021, 2020 and 2019. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of financial instruments between levels during the years ended December 31, 2021 and 2020 .
Property and Equipment, Net	Property and equipment, net Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows: Asset category Estimated useful life Computer equipment and software 3 years Office furniture 4 years Laboratory equipment 5 years Leasehold improvements Shorter of useful life or remaining lease term Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred.
Impairment of Long-Lived Assets	Impairment of long-lived assets The Company evaluates its long-lived assets, which consist primarily of property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset exceeds the fair value of the asset. There were no impairment losses recognized during the years ended December 31, 2021, 2020 and 2019 .
Freestanding Financial Instruments and Derivatives	Freestanding financial instruments and derivatives The Company has identified the following financial instruments, which are recorded as liabilities in the balance sheet and separately accounted for at fair value. Preferred Stock Tranche Liabilities —The Company has determined that its obligation to issue, and the Company’s investors’ right to purchase, additional shares of convertible Series A Preferred Stock (“Series A Preferred”) pursuant to subsequent closings represent a freestanding financial instrument. The freestanding preferred stock tranche liability (the “tranche liability”) was initially recorded at fair value, with gains and losses arising from changes in fair value recognized in other income (expense) in the statement of operations and comprehensive loss. The tranche liabilities were remeasured at each reporting period and upon the exercise or expiration of the obligation. As of December 31, 2020, all Series A Preferred closings occurred, and all preferred stock tranche liabilities have been settled. Refer to Note 9, Preferred Stock tranche liability, for additional discussion. Pursuant to license agreements with (i) the President and Fellows of Harvard College (“Harvard”) and The Broad Institute, Inc. (“Broad”) (“Harvard/Broad License Agreement”) and (ii) Broad (“Broad License Agreement”) (see Note 8, License agreements), the following financial instruments were issued by the Company. Antidilution Rights —The antidilution rights represent the obligation to issue additional shares of common stock to Harvard and Broad following the completion of additional financings, including the Company’s initial public offering. These antidilution rights were accounted for under ASC 815, Derivatives and Hedging ("ASC 815"), and were initially recorded at fair value with a corresponding charge to research and development expense. The liability was remeasured at each reporting period, with changes in fair value recognized in other income (expense) in the statement of operations and comprehensive loss while this instrument was outstanding. The obligation was satisfied in full upon the issuance of an aggregate of an additional 878,098 shares of common stock upon the closing of the Company's IPO in June 2021. Refer to Note 5, Fair value of financial instruments, for additional discussion. Success Payments —The Company is obligated to pay to Harvard and Broad tiered success payments in the event the Company’s average market capitalization exceeds specified thresholds ascending from a high nine digit dollar amount to $ 10.0 billion, or sale of the Company for consideration in excess of those thresholds. In the event of a change of control of the Company or a sale of the Company, the Company is required to pay in cash within a specified period following such event. Otherwise, the payments may be settled at the Company’s option in either cash or shares of the Company’s common stock. The success payments are accounted for under ASC 815 and were initially recorded at fair value with a corresponding charge to research and development expense. The liability is remeasured at each reporting period with all changes in value recognized in other income (expense) in the statement of operations and other comprehensive loss. During the year ended December 31, 2021, certain success payment obligations were triggered, and amounts paid to Harvard and Broad totaled $ 6.3 million. These amounts were settled in cash in November 2021. The Company will continue to adjust the liability for changes in fair value until the earlier of the achievement or expiration of the remaining success payment obligation. Refer to Note 5, Fair value of financial instruments, for additional discussion .
Research and Development Costs	Research and development costs Research and development costs are charged to expense as incurred. Research and development costs consist of costs incurred in performing research and development activities, including salaries and bonuses, stock-based compensation, employee benefits, facilities costs, third-party license fees related to technology with no alternative future use, laboratory supplies, depreciation, manufacturing expenses, preclinical expenses, consulting and other contracted services. Costs for certain research and development activities are recognized based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the financial statements as prepaid or accrued research and development.
Stock-Based Compensation	Stock-based compensation The Company’s stock-based compensation program allows for grants of stock options and restricted stock awards. Grants are awarded to employees and non-employees, including directors. The Company accounts for its stock-based compensation in accordance with ASC Topic 718, Compensation-Stock Compensation (‘‘ASC 718’’). ASC 718 requires all stock-based payments to employees, non-employees and directors, to be recognized as expense in the consolidated statements of operations and comprehensive loss based on their grant date fair values. The Company estimates the fair value of options granted using the Black-Scholes option pricing model (‘‘Black-Scholes’’) for stock option grants to both employees and non-employees. The fair value of the Company’s common stock is used to determine the fair value of restricted stock awards. The Company’s stock-based compensation awards are subject to either service or performance-based vesting conditions. Compensation expense related to awards to employees, directors and non-employees with service-based vesting conditions is recognized on a straight-line basis based on the grant date fair value over the associated service period of the award, which is generally the vesting term. Compensation expense related to awards to employees with performance-based vesting conditions is recognized over the implied service period when achievement of the performance-based milestones is deemed probable. The Company uses judgement to determine whether and, if so, how many awards are deemed probable of vesting at each reporting period. The estimation of fair value for stock-based compensation requires management to make estimates and judgments about, among other things, the estimated life of options and volatility of the Company’s common stock. The judgments directly affect the amount of compensation expense that will be recognized. Prior to the Company's IPO in June 2021, there was no public market for its common stock. As a result, prior to the IPO, the estimated fair value of the Company's common stock was determined by its board of directors as of the date of each option grant, with input from management, considering the Company's most recently available third-party valuations of common stock and its board of directors' assessment of additional objective and subjective factors that it believed were relevant and which may have changed from the date of the most recent valuation through the date of grant. Following the Company's IPO, the fair value of its common stock is determined based on the closing price of the Company's common stock as reported on the Nasdaq Global Select Market .
Rent Expense	Rent expense The Company’s real estate operating leases provide for scheduled annual rent increases throughout the lease term. The Company recognizes the effects of the scheduled rent increases on a straight-line basis over the full term of the lease. Prior to the adoption of ASU 2016-02, Leases , or ASC 842, tenant improvement allowances, if any, provided by the landlord are recorded as deferred rent and amortized as reduction to rent expense over the lease term. Subsequent to the adoption of ASC 842, tenant improvement allowances, if any, provided by a landlord are recorded as a reduction of the right-of-use, or ROU, asset related to that lease.
Income Taxes	Income taxes The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s financial statements and tax returns. Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities and for loss and credit carryforwards, using enacted tax rates expected to be in effect in the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that these assets may not be realized. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. If it is not more likely than not that a position will be sustained, none of the benefit attributable to the position is recognized. The tax benefit to be recognized for any tax position that meets the more-likely-than-not recognition threshold is calculated as the largest amount that is more than 50 % likely of being realized upon resolution of the contingency. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes.
Comprehensive Loss	Comprehensive loss Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. For the years ended December 31, 2021, 2020 and 2019 , the Company’s only element of other comprehensive income (loss) was unrealized gains (losses) on marketable securities.
Net Loss Per Share	Net loss per share The Company follows the two-class method when computing net loss per share, as the Company has issued shares that meet the definition of participating securities. The two-class method determines net loss per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net loss attributable to common stockholders is computed by adjusting net loss attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net loss per share attributable to common stockholders is computed by dividing the diluted net loss attributable to common stockholders by the weighted average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common stock equivalents. The Company’s convertible preferred stock contractually entitled the holders of such shares to participate in dividends but did not contractually require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reports a net loss, such losses are not allocated to such participating securities. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the years ended December 31, 2021, 2020 and 2019 .
Segment and Geographic Information	Segment and geographic information Operating segments are defined as components of an entity about which separate discrete information is available for evaluation by the chief operating decision maker (“CODM”), or decision-making group, in deciding how to allocate resources and in assessing performance. The CODM is the Company’s Chief Executive Officer. The Company views its operations as and manages its business in one operating segment operating exclusively in the United States.
Subsequent Events	Subsequent events The Company performs an evaluation of all subsequent events after the balance sheet date through the date of issuance of the consolidated financial statements to ensure appropriate disclosure of events both recognized in the consolidated financial statements and events which occurred subsequently but were not recognized in the consolidated financial statements.
Recently Adopted and Issued Accounting Pronouncements	Recently adopted accounting pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), as subsequently amended, which sets out the principles for the recognition, measurement, presentation and disclosure of leases for both parties to a contract (i.e., lessees and lessors), and replaces the existing guidance in ASC 840. The FASB has issued several updates to the standard which: (i) clarify how to apply certain aspects of the new standard; (ii) provide an additional transition method for adoption of the new standard; (iii) provide a practical expedient for certain lessor accounting; and (iv) amend certain narrow aspects of the guidance. The new standard requires the identification and classification of arrangements that are or contain a lease and requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine the recognition pattern of lease expense over the term of the lease. In addition, a lessee is required to record (i) a right-of-use asset and a lease liability on its balance sheet for all leases with accounting lease terms of more than 12 months regardless of whether it is an operating or finance lease and (ii) lease expense in its consolidated statement of operations for operating leases and amortization and interest expense in its consolidated statement of operations for financing leases. Leases with a term of 12 months or less may be accounted for similar to existing guidance for operating leases under ASC 840. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842), which added an optional transition method that allows companies to adopt the standard as of the beginning of the year of adoption as opposed to the earliest comparative period presented. Prior to January 1, 2021, the Company accounted for leases pursuant to ASC 840, Leases. At lease inception, the Company determined if an arrangement was an operating or capital lease. For operating leases, the Company recognized rent expense, inclusive of rent escalations, holidays and lease incentives, on a straight-line basis over the lease term. The difference between rent expense recorded and the amount paid was recorded as deferred rent. The Company presented lease incentives as deferred rent and amortized the incentives as a reduction to rent expense on a straight-line basis over the lease term. The Company classified deferred rent as current and noncurrent liabilities based on the portion of the deferred rent that was scheduled to mature within the next twelve months. The Company adopted Topic 842 during the quarter ended September 30, 2021, with an effective adoption date of January 1, 2021 , using the modified retrospective transition approach which uses the effective date, or January 1, 2021, as the date of initial application. As a result, prior periods are presented in accordance with the previous guidance in ASC 840. At contract inception, the Company determines if an arrangement is or contains a lease. A lease conveys the right to control the use of an identified asset for a period of time in exchange for consideration. If an arrangement is determined to be or contain a lease, the lease is assessed for classification as either an operating or finance lease at the lease commencement date, defined as the date on which the leased asset is made available for use by the Company, based on the economic characteristics of the lease. The Company has elected to apply the package of practical expedients requiring no reassessment of whether any expired or existing contracts are or contain leases, the lease classification of any expired or existing leases, or the capitalization of initial direct costs for any existing leases. As a result of the adoption of ASC 842, the Company recorded (i) an operating lease liability of $ 2.6 million determined using an incremental borrowing rate as of the effective adoption date and (ii) an operating lease right-of-use asset of $ 2.4 million, net of the unamortized balance of prepaid/accrued rent as of the transition date. There was no impact to the Company’s results of operations and cash flows from operations. The Company has elected the short-term lease exemption, which allows the Company to not recognize lease liabilities and right-of-use assets arising from lease arrangements with lease terms of twelve months or less. For each lease with a term greater than twelve months, the Company records a right-of-use asset and lease liability. A right-of-use asset represents the economic benefit conveyed to the Company by the right to use the underlying asset over the lease term. A lease liability represents the Company’s obligation to make lease payments under the arrangement. The Company measures its lease liabilities at lease commencement as the present value of the future lease payments in the contract using the rate implicit in the contract, when available. As an implicit rate has not historically been readily determinable, the Company uses an incremental borrowing rate measured as the rate at which the Company could borrow, on a fully collateralized basis, a commensurate loan in the same currency over a period consistent with the lease term at the commencement date. The incremental borrowing rate is determined based on the Company's synthetic secured rating using the ordered logit model as of the measurement date. The Company measures its right-of-use assets as the lease liability plus initial direct costs and prepaid lease payments, less lease incentives granted by the lessor. Components of a lease are split into three categories: lease components, non-lease components, and non-components. The fixed and in-substance fixed contract consideration (including any consideration related to non-components) are allocated, based on the respective relative fair values, to the lease components and non-lease components. The Company has elected to account for lease and associated non-lease components together as a single lease component for all underlying assets and allocate all of the contract consideration to the lease component only. The Company remeasures right-of-use assets and lease liabilities when a lease is modified, and the modification is not accounted for as a separate contract. A modification is accounted for as a separate contract if the modification grants the Company an additional right of use not included in the original lease arrangement and the increase in lease payments is commensurate with the additional right of use. The Company assesses its right-of-use assets for impairment in a manner consistent with its assessment for long-lived assets held and used in operations. The Company’s operating leases are presented in the consolidated balance sheet as operating lease right-of-use assets, classified as noncurrent assets, and operating lease liabilities, classified as current and noncurrent liabilities. Operating lease expense is recognized on a straight-line basis over the lease term. Variable costs associated with a lease, such as maintenance and utilities, are not included in the measurement of the lease liabilities and right-of-use assets but rather are expensed when the events determining the amount of variable consideration to be paid have occurred. Recently issued accounting pronouncements The Jumpstart Our Business Startups Act of 2012 permits an emerging growth company ("EGC") to take advantage of an extended transition period to comply with new or revised accounting standards applicable to public companies until those standards would otherwise apply to private companies. As an EGC, the Company has elected to take advantage of this extended transition period for certain new accounting standards. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The standard requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and establishes additional disclosures related to credit risks. For available-for-sale debt securities with unrealized losses, this standard requires allowances to be recorded instead of reducing the amortized cost of the investment. The new standard will be effective for the Company on January 1, 2023. The Company is currently evaluating the potential impact that this standard may have on its consolidated financial position and results of operations.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Reconciliation of Cash, Cash Equivalents and Restricted Cash	A reconciliation of the cash, cash equivalents, and restricted cash reported within the balance sheet that sum to the total of the same amounts shown in the statement of cash flows is as follows: December 31, (in thousands) 2021 2020 Cash and cash equivalents $ 64,330 $ 8,993 Restricted cash 5,237 463 Total cash, cash equivalents and restricted cash $ 69,567 $ 9,456
Schedule of Property and Equipment Estimated Useful Life	Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset as follows: Asset category Estimated useful life Computer equipment and software 3 years Office furniture 4 years Laboratory equipment 5 years Leasehold improvements Shorter of useful life or remaining lease term

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2021
Investments Debt And Equity Securities [Abstract]
Schedule of Marketable Securities	Marketable securities by security type consisted of the following: December 31, 2021 (in thousands) Amortized Gross Gross Fair U.S. treasury bills and notes $ 277,559 $ — $ ( 218 ) $ 277,341 U.S. agency securities 18,781 — ( 10 ) 18,771 Total $ 296,340 $ — $ ( 228 ) $ 296,112 December 31, 2020 (in thousands) Amortized Gross Gross Fair U.S. treasury bills and notes $ 32,221 $ 3 $ — $ 32,224 U.S. agency securities 30,890 5 — 30,895 Total $ 63,111 $ 8 $ — $ 63,119

Property and equipment, net (Ta

Property and equipment, net (Table)	12 Months Ended
	Dec. 31, 2021
Property Plant And Equipment [Abstract]
Schedule of Property, Plant and Equipment	Property and equipment, net, consist of the following: December 31, (in thousands) 2021 2020 Lab equipment 8,567 $ 3,937 Leasehold improvements 266 259 Furniture and fixtures 566 481 Computer equipment 158 105 Total property and equipment 9,557 4,782 Less accumulated depreciation ( 2,333 ) ( 798 ) Property and equipment, net $ 7,224 $ 3,984

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Financial Instruments, Assets and Liabilities	The following tables set forth the fair value of the Company’s financial instruments by level within the fair value hierarchy: As of December 31, 2021 (in thousands) Fair Level 1 Level 2 Level 3 Assets Money market funds $ 58,127 $ 58,127 $ — $ — Marketable securities: U.S. treasury bills and notes 277,341 — 277,341 — U.S. agency securities 18,771 — 18,771 — Total assets $ 354,239 $ 58,127 $ 296,112 $ — Liabilities Success payment liability 4,371 — — 4,371 Total liabilities $ 4,371 $ — $ — $ 4,371 As of December 31, 2020 (in thousands) Fair Level 1 Level 2 Level 3 Assets Money market funds $ 6,724 $ 6,724 $ — $ — Marketable securities: U.S. treasury bills and notes 32,224 — 32,224 — U.S. agency securities 30,895 — 30,895 — Total assets $ 69,843 $ 6,724 $ 63,119 $ — Liabilities Success payment liability $ 2,806 $ — $ — $ 2,806 Antidilution rights liability 6,916 — — 6,916 Total liabilities $ 9,722 $ — $ — $ 9,722
Schedule of Fair Value Liabilities Measured on Recurring Basis	The primary inputs used in valuing (i) the success payments liability and (ii) the antidilution rights liability associated with the Company’s realization of a certain valuation threshold through either a sale of the Company’s preferred stock, an initial public offering, or a company sale at December 31, 2021 (only applicable to success payments liability), 2020 and 2019, were as follows: At At At Fair value of common stock (per share) $ 36.87 $ 8.24 $ 2.59 Equity volatility 77 % 105 % 100 % Cumulative probability of triggering event n/a 70 % 11 % Expected term (in years) n/a 0.50 2.89
Schedule of Reconciliation of Changes in Fair Value of Financial Instruments	The reconciliation of changes in the fair value of financial instruments based on Level 3 inputs were as follows: (in thousands) Preferred Antidilution Success Total Balance at December 31, 2019 $ 9,571 $ 2,044 $ 419 $ 12,034 Issuance of Series A Preferred ( 7,064 ) — — ( 7,064 ) Issuance of common stock — ( 487 ) — ( 487 ) Changes in fair value ( 2,507 ) 5,359 2,387 5,239 Balance at December 31, 2020 — 6,916 2,806 9,722 Issuance of common stock — ( 32,490 ) — ( 32,490 ) Success payment liability earned and paid — — ( 6,250 ) ( 6,250 ) Change in fair value — 25,574 7,815 33,389 Balance at December 31, 2021 $ — $ — $ 4,371 $ 4,371

Accrued expenses (Tables)

Accrued expenses (Tables)	12 Months Ended
	Dec. 31, 2021
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consist of the following: December 31, (in thousands) 2021 2020 Employee compensation and related benefits $ 6,050 $ 1,636 Accrued external research and development expenses 5,041 4,827 Professional fees 1,109 303 Other 792 423 Total $ 12,992 $ 7,189

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Components of Operating Lease Cost	The components of operating lease cost were as follows: (in thousands) December 31, 2021 Operating lease costs $ 1,923 Variable lease costs 747 Short term lease costs 2,278 Total $ 4,948
Supplemental Cash Flow Information Related to Operating Leases	Supplemental cash flow information related to operating leases was as follows: (in thousands) December 31, 2021 Cash paid for amounts included in the measurements of lease liabilities: Operating cash flows related to operating leases $ 2,021
Schedule of Future Minimum Lease Commitments under Non-Cancellable Leases	Future minimum commitments under non-cancellable leases as of December 31, 2021 were as follows: Years ending December 31, Amount (in thousands) 2022 $ 12,951 2023 9,958 2024 10,257 2025 10,565 2026 10,882 Thereafter 54,158 Total lease payments $ 108,771 Less: interest ( 13 ) Present value of operating lease liabilities $ 108,758

Stock-based compensation (Table

Stock-based compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Based Compensation Expense	Stock-based compensation expense recorded in the consolidated statements of operations and comprehensive loss is as follows: Year ended (in thousands) 2021 2020 2019 Research and development $ 3,830 $ 494 $ 336 General and administrative 3,242 356 110 Total stock-based compensation expense $ 7,072 $ 850 $ 446
Schedule of Assumptions Used for Options Granted	The assumptions used in Black-Scholes for stock options granted were as follows: Year ended 2021 2020 2019 Expected volatility 77.7 % 84.8 % 76.1 % Weighted-average risk-free interest rate 0.9 % 0.4 % 2.2 % Expected dividend yield — — — Expected term (in years) 6.0 6.0 5.9
Schedule of Stock Option Activity	The following table provides a summary of stock option activity during the year ended December 31, 2021: Number of Weighted Weighted Aggregate (2) Outstanding at December 31, 2020 3,888,823 $ 2.13 Granted 2,869,946 $ 17.66 Exercised ( 599,838 ) $ 1.61 Forfeited ( 39,636 ) $ 2.56 Outstanding at December 31, 2021 6,119,295 $ 9.44 8.7 $ 171,636 Exercisable at December 31, 2021 1,373,507 $ 2.15 8.0 $ 47,691 Expected to vest after December 31, 2021 (1) 4,745,788 $ 11.56 8.9 $ 123,945 (1) This represents the number of unvested options outstanding as of December 31, 2021 that are expected to vest in the future. (2) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money as of December 31, 2021.
Schedule of Status and Change in Unvested Restricted Stock and Restricted Stock Units	A summary of the status of and change in unvested restricted stock as of December 31, 2021 was as follows: Shares Weighted- Unvested restricted stock as of December 31, 2020 537,633 $ 0.0028 Restricted stock vested ( 537,633 ) $ 0.0028 Unvested restricted stock as of December 31, 2021 — $ — A summary of the status of and change in unvested restricted stock units as of December 31, 2021 was as follows: Shares Weighted- Unvested restricted stock units as of December 31, 2020 — $ — Restricted stock units granted 32,000 $ 36.58 Unvested restricted stock units as of December 31, 2021 32,000 $ 36.58

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted net Loss Per Share	The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company: Year ended December 31, (in thousands, except share and per share amounts) 2021 2020 2019 Numerator: Net loss attributable to common stockholders $ ( 120,314 ) $ ( 45,704 ) $ ( 19,297 ) Denominator: Weighted average number of common shares, basic and diluted 26,872,036 2,250,093 1,277,156 Net loss per common share attributable to common stockholders, basic and diluted $ ( 4.48 ) $ ( 20.31 ) $ ( 15.11 )
Potential Common Shares, Based on Amounts Outstanding at Period End were Excluded From the Computation of Diluted Net Loss Per Share Attributable to Common Stockholders	The Company excluded the following potential common shares, presented based on amounts outstanding at period end, from the computation of diluted net loss per share attributable to common stockholders for the period indicated because including them would have had an anti-dilutive effect: Year ended December 31, 2021 2020 2019 Convertible preferred stock — 19,387,544 5,553,367 Unvested restricted stock — 537,633 1,075,268 Unvested restricted stock units 32,000 — — Outstanding options to purchase common stock 6,119,295 3,888,823 1,933,507 Total 6,151,295 23,814,000 8,562,142

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of the income tax expense computed using the federal statutory income tax rate to the Company’s effective income tax rate is as follows: Year ended December 31, (in thousands) 2021 2020 2019 Federal statutory rate 21.0 % 21.0 % 21.0 % Change in valuation allowance ( 31.3 )% ( 29.6 )% ( 17.9 )% Stock-based compensation 0.9 % ( 0.3 )% ( 0.1 )% Executive compensation ( 1.1 )% 0.0 % 0.0 % Other permanent items ( 0.1 )% 1.1 % ( 5.8 )% State income taxes, net of federal benefit 6.1 % 6.8 % 1.7 % Research and development tax credits 4.5 % 1.0 % 1.1 % Total — % — % — %
Schedule of Deferred Taxes	: December 31, (in thousands) 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 33,409 $ 12,973 Capitalized costs—net of amortization 12,395 855 Research and development tax credits 6,098 682 Antidilution liability — 2,815 Stock-based compensation 1,117 149 Other 76 61 Lease liability 533 — Accrued expenses 2,852 905 Total deferred tax assets 56,480 18,440 Deferred tax liabilities: Property and equipment ( 899 ) ( 1,061 ) Right of use asset ( 501 ) — Total deferred tax liabilities ( 1,400 ) ( 1,061 ) Total deferred tax assets, net 55,080 17,379 Less: valuation allowance ( 55,080 ) ( 17,379 ) Deferred tax assets, net of valuation allowance $ — $ —

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Jun. 21, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net loss		$ (120,314)	$ (45,704)	$ (19,297)
Accumulated deficit		$ (186,850)	(66,536)
Sale of stock, price per share		$ 22.34
Proceeds from initial public offering, net of underwriting discount		$ 285,214		0
Proceeds From Issuance Of Preferred Stock And Preference Stock		$ 93,759	$ 92,616	$ 18,040
Over-Allotment Option [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of Stock, Number of Shares Issued in Transaction	2,105,368
IPO
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of Stock, Number of Shares Issued in Transaction	16,141,157
Sale of stock, price per share	$ 19
Proceeds from initial public offering, net of underwriting discount	$ 306,700
Sale of Stock, Consideration Received on Transaction	$ 281,600
Shares issued upon conversion of preferred stock	27,720,923	27,720,923
Stockholders' Equity, Reverse Stock Split		one-for-9.2595
Proceeds From Issuance Of Preferred Stock And Preference Stock		$ 523,200

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 64,330	$ 8,993
Restricted cash	5,237	463
Total cash, cash equivalents and restricted cash	$ 69,567	$ 9,456	$ 3,221	$ 5,467

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021USD ($)Segment	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Jun. 30, 2021shares
Summary Of Significant Accounting Policies [Line Items]
Impairment losses	$ 0	$ 0	$ 0
Percentage of tax benefit realized	50.00%
Success payment liability, payable	$ 6,250,000
Number of operating segment | Segment	1
Operating lease liability	$ 108,758,000
Operating lease right-of-use assets	$ 1,839,000	$ 0
ASC 842
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2021
Operating lease liability	$ 2,600,000
Operating lease right-of-use assets	$ 2,400,000
Change in accounting principle, accounting standards update, immaterial effect	true
Harvard and Board
Summary Of Significant Accounting Policies [Line Items]
Success payment liability, payable	$ 10,000,000,000
Issuance of Additional Common Stock | shares				878,098
Success Liability Payment	$ 6,300,000

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Property and Equipment Estimated Useful Life (Details)	12 Months Ended
	Dec. 31, 2021
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Property and equipment estimated useful life	3 years
Office Furniture
Property Plant And Equipment [Line Items]
Property and equipment estimated useful life	4 years
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment estimated useful life	5 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment estimated useful life	Shorter of useful life or remaining lease term

Marketable Securities - Schedul

Marketable Securities - Schedule of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Amortized cost	$ 296,340	$ 63,111
Gross unrealized gains		8
Gross unrealized losses	(228)
Fair value	296,112	63,119
U.S. Treasury Bills and Notes [Member]
Marketable Securities [Line Items]
Amortized cost	277,559	32,221
Gross unrealized gains		3
Gross unrealized losses	(218)
Fair value	277,341	32,224
U.S. Agency Securities [Member]
Marketable Securities [Line Items]
Amortized cost	18,781	30,890
Gross unrealized gains		5
Gross unrealized losses	(10)
Fair value	$ 18,771	$ 30,895

Marketable securities - Additio

Marketable securities - Additional Information (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Remaining contractual maturities of marketable securities term	1 year	1 year

Property and equipment, net - S

Property and equipment, net - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 9,557	$ 4,782
Less accumulated depreciation	(2,333)	(798)
Property and equipment, net	7,224	3,984
Lab equipment
Property Plant And Equipment [Line Items]
Total property and equipment	8,567	3,937
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	266	259
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	566	481
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	$ 158	$ 105

Property and equipment, net - A

Property and equipment, net - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Depreciation	$ 1.5	$ 1.3	$ 0.1

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Financial Instruments within Fair value hierarchy (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets
Total assets	$ 354,239	$ 69,843
Liabilities
Total liabilities	4,371	9,722
Money Market Funds
Assets
Total assets	58,127	6,724
U S Treasury Bills And Notes [Member]
Assets
Total assets	277,341	32,224
U S Agency Securities [Member]
Assets
Total assets	18,771	30,895
Success Payment Liability
Liabilities
Total liabilities	4,371	2,806
Antidilution Rights Liability
Liabilities
Total liabilities		6,916
Level 1
Assets
Total assets	58,127	6,724
Liabilities
Total liabilities	0	0
Level 1 | Money Market Funds
Assets
Total assets	58,127	6,724
Level 1 | U S Treasury Bills And Notes [Member]
Assets
Total assets	0	0
Level 1 | U S Agency Securities [Member]
Assets
Total assets	0	0
Level 1 | Success Payment Liability
Liabilities
Total liabilities	0	0
Level 1 | Antidilution Rights Liability
Liabilities
Total liabilities		0
Level 2
Assets
Total assets	296,112	63,119
Liabilities
Total liabilities	0	0
Level 2 | Money Market Funds
Assets
Total assets	0	0
Level 2 | U S Treasury Bills And Notes [Member]
Assets
Total assets	277,341	32,224
Level 2 | U S Agency Securities [Member]
Assets
Total assets	18,771	30,895
Level 2 | Success Payment Liability
Liabilities
Total liabilities	0	0
Level 2 | Antidilution Rights Liability
Liabilities
Total liabilities		0
Level 3
Assets
Total assets	0	0
Liabilities
Total liabilities	4,371	9,722
Level 3 | Money Market Funds
Assets
Total assets	0	0
Level 3 | U S Treasury Bills And Notes [Member]
Assets
Total assets	0	0
Level 3 | U S Agency Securities [Member]
Assets
Total assets	0	0
Level 3 | Success Payment Liability
Liabilities
Total liabilities	$ 4,371	2,806
Level 3 | Antidilution Rights Liability
Liabilities
Total liabilities		$ 6,916

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2021	Jun. 30, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 58,100	$ 6,700
Common Stock, Shares Issued	48,511,735	3,123,424
Issuance of common stock, value	$ 49	$ 3
Success payment liability, payable	6,250
Servicing Liability at Fair Value, Other Changes in Fair Value		$ 5,400	$ 1,000
Research and development expense of antidilution rights liability			1,200
Harvard and Board
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, payable	10,000,000
Success payment liability	$ 6,300			$ 6,300
Success payment, current portion				$ 6,300
Broad License Agreement
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common Stock, Shares Issued	276,075
Fair value inputs probability of termination		90.00%
Maximum | Harvard
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability, payable	$ 31,300
Other Expense
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Success payment liability	7,800	$ 2,400	$ 100
Antidilution Rights Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Common Stock, Shares Issued		187,867	121,411		878,098
Issuance of common stock, value		$ 100	$ 500		$ 32,500
Success payment liability, payable
Antidilution Rights Liability | Other Expense
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Increase in liabilities	25,600
Preferred Stock Tranche Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Increase in liabilities		$ 2,500
Success payment liability, payable

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Schedule of Fair Value Liabilities Measured on Recurring Basis (Details) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of common stock (per share)	$ 36.87	$ 8.24	$ 2.59
Cumulative probability of triggering event		70.00%	11.00%
Expected term (in years)			2 years 10 months 20 days
Equity Volatility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity volatility	77.00%	105.00%	100.00%
Expected Term
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Expected term (in years)		6 months

Fair Value of Financial Insrume

Fair Value of Financial Insruments - Schedule of Reconciliation of Changes in Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 9,722	$ 12,034
Issuance of Series A Preferred		(7,064)
Issuance of common stock	(32,490)	(487)
Success payment liability, payable	(6,250)
Changes in fair value	33,389	5,239
Ending balance	4,371	9,722
Preferred Stock Tranche Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	0	9,571
Issuance of Series A Preferred		(7,064)
Issuance of common stock	0	0
Success payment liability, payable
Changes in fair value	0	(2,507)
Ending balance	0	0
Antidilution Rights Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	6,916	2,044
Issuance of Series A Preferred		0
Issuance of common stock	(32,490)	(487)
Success payment liability, payable
Changes in fair value	25,574	5,359
Ending balance	0	6,916
Success Payment Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	2,806	419
Issuance of Series A Preferred		0
Issuance of common stock	0	0
Success payment liability, payable	(6,250)
Changes in fair value	7,815	2,387
Ending balance	$ 4,371	$ 2,806

Accrued expenses - Schedule of

Accrued expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Employee compensation and related benefits	$ 6,050	$ 1,636
Accrued external research and development expenses	5,041	4,827
Professional fees	1,109	303
Other	792	423
Total	$ 12,992	$ 7,189

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands	Aug. 19, 2021USD ($)ft²	Jul. 31, 2021USD ($)	Oct. 31, 2021USD ($)ft²	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Jan. 30, 2022ft²	Jan. 31, 2021ft²	Jun. 30, 2020ft²	Mar. 31, 2020ft²
Lessee Lease Description [Line Items]
Lease commencement date			2021-12
Lease noncancelable term			12 months
Lessee, operating lease, option to extend			The Company has the option to extend the sublease for one extension term of three months by written notice not less than six months prior to the expiration of the sublease term, which the Company is not reasonably certain of exercising.
Increase in operating lease liability				$ (1,940)		$ 0
Operating lease liability				108,758
Operating lease right-of-use assets				$ 1,839	0
Operating lease incremental borrowing rate				1.57%
Weighted average remaining lease term				10 months 24 days
Operating lease payments				$ 2,021
Operating lease, rent expense					$ 1,300	$ 200
Short term lease costs				2,278
New Amendment | Subsequent Event
Lessee Lease Description [Line Items]
Lease area | ft²							105,144
Additional Lease Area | ft²							211
ASC 842
Lessee Lease Description [Line Items]
Operating lease liability				2,600
Operating lease right-of-use assets				2,400
Short term lease costs				$ 2,300
Cambridge Lease
Lessee Lease Description [Line Items]
Lease area | ft²										16,843
Lease term										2 years
Lease expiration date				Nov. 30, 2022
Increase in Right-Of-Use assets		$ 800
Increase in operating lease liability		$ 800
Cambridge Lease | First Amendment
Lessee Lease Description [Line Items]
Lease area | ft²									2,980
Cambridge Lease | Second Amendment
Lessee Lease Description [Line Items]
Lease area | ft²								2,980
Premises
Lessee Lease Description [Line Items]
Lease area | ft²	104,933		11,931
Lease not yet commenced, lease term	10 years
Option to extend, lease not yet commenced	five years
Option to extend true/false, lease not yet commenced	true
Operating lease payment term, lease not yet commenced, terms and conditions				The Company’s obligation for the payment of base rent for the Boston Lease begins 90 days after the Commencement Date (the “Rent Commencement Date”) and will initially be $0.8 million per month, which will increase by approximately 3% per annum.
Option to terminate, lease not yet commenced	true
Tenant improvements allowance	$ 21,000
Additional tenant improvements allowance	$ 5,200
Improvement allowance interest rate	8.00%
Operating lease payments			$ 1,400
Prepaid rent				$ 800
Lease space build out cost prior to commencement				$ 1,500
Premises | Letter of Credit
Lessee Lease Description [Line Items]
Letter of credit issued	$ 4,800
Letter of credit reduced value	$ 3,500

Leases - Summary of Components

Leases - Summary of Components of Operating Lease Cost (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Lease Cost [Abstract]
Operating lease costs	$ 1,923
Variable lease costs	747
Short term lease costs	2,278
Total	$ 4,948

Leases - Summary of Supplementa

Leases - Summary of Supplemental Cash Flow Information Related to Operating Leases (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Cash Paid For Amounts Included In The Measurements Of Lease Liabilities [Abstract]
Operating cash flows related to operating leases	$ 2,021

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Commitments under Non-Cancellable Operating Leases (Details) $ in Thousands	Dec. 31, 2021USD ($)
Operating Lease Liabilities Payments Due [Abstract]
2022	$ 12,951
2023	9,958
2024	10,257
2025	10,565
2026	10,882
Thereafter	54,158
Total lease payments	108,771
Less: interest	(13)
Operating lease liability	$ 108,758

License Agreements - Additional

License Agreements - Additional Information (Details) - USD ($)	1 Months Ended			9 Months Ended		10 Months Ended	12 Months Ended
	Oct. 31, 2021	Apr. 30, 2019	Mar. 31, 2019	Sep. 30, 2021	Sep. 30, 2020	Oct. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common stock, shares issued							48,511,735	3,123,424
Issuance of common stock							$ 281,584,000
Issuance of common stock, value							49,000	$ 3,000
Research and development expense							$ 68,202,000	$ 35,371,000	$ 11,144,000
Preferred stock, shares issued							0	0
Broad License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common stock, shares issued							276,075
Issuance of common stock							$ 300,000
Preferred stock financing partially satisfied									100,000
Preferred stock financing were fully satisfied								$ 500,000
Common stock issued for partly satisfying preferred stock financing									121,411
Common stock issued for fully satisfying preferred stock financing								187,867
Payment of milestone development							46,200,000
Payment of sales based milestone							108,000,000
Milestone related expenses							0
Harvard and Board
Research And Development Arrangement Contract To Perform For Others [Line Items]
Success payment liability				$ 6,300,000			6,300,000
Verily License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Non-refundable upfront license fees paid			$ 600,000
Research and development expense									600,000
Developed base milestone payments			5,500,000
Developed base milestone payments for quarterly period			300,000					$ 500,000	$ 800,000
Milestone payments			$ 1,000,000					1,000,000
Amount due as a result of termination							0	0
Verily License Agreement | Series A Preferred Stock
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common stock, shares issued			1,672,240						1,672,240
Beam License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common stock, shares issued		276,075
Issuance of common stock, value		$ 300,000
Payment of milestone development		11,300,000
Payment of sales based milestone		15,000,000
Research and development expense		$ 300,000					0	200,000
Percentage Shares of Development Expense		33.00%
Milestone related expenses							0
Reimbursement received related to reduction to research and development expense				$ 200,000	$ 300,000
Beam License Agreement | Delivery Technology Product
Research And Development Arrangement Contract To Perform For Others [Line Items]
Payment of milestone development		$ 6,000,000
Beam License Agreement | Non-US
Research And Development Arrangement Contract To Perform For Others [Line Items]
Payment of milestone development		5,600,000
Payment of sales based milestone		$ 7,500,000
Acuitas Agreements
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expense							1,000,000	$ 2,000,000
License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expense			$ 2,100,000
Milestone related expenses	$ 10,000,000						0
Non Refundable Upfront License Fee						$ 2,000,000
Clinical And Regulatory Milestone							9,800,000
Sales Based Milestone							9,500,000
Non Refundable Upfront Payment	$ 800,000
License Agreement | Broad License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Non-refundable upfront license fees paid							$ 300,000
Antidilution Rights | Broad License Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Common stock, shares issued							878,098
Issuance of common stock, value							$ 32,500,000

Preferred Stock Tranche Liabi_2

Preferred Stock Tranche Liability - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Mar. 31, 2020	Apr. 30, 2019	Dec. 31, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Preferred stock, shares authorized			5,000,000	5,000,000
Preferred stock, value per share			$ 0.001	$ 0.001
Preferred stock, shares issued			0	0
Series A Preferred Stock [Member] | Second Tranche [Member]
Class Of Stock [Line Items]
Preferred stock, shares authorized			29,347,825
Preferred stock, value per share		$ 0.598	$ 0.598
Preferred stock, shares issued		29,347,825
Proceeds from issuance or sale of preferred stock		$ 17.5
Series A Preferred Stock [Member] | Third Tranche [Member]
Class Of Stock [Line Items]
Preferred stock, shares authorized			49,749,167
Preferred stock, value per share	$ 0.598		$ 0.598
Preferred stock, shares issued	49,749,167
Proceeds from issuance or sale of preferred stock	$ 29.8

Preferred and Common Stock - Ad

Preferred and Common Stock - Additional Information (Details) $ / shares in Units, $ in Thousands	Jun. 21, 2021USD ($)$ / sharesshares	Jun. 30, 2021USD ($)$ / sharesshares	Jan. 31, 2021USD ($)$ / sharesshares	Mar. 31, 2020USD ($)$ / sharesshares	Oct. 31, 2019USD ($)$ / sharesshares	Aug. 31, 2019USD ($)$ / sharesshares	Jun. 30, 2020USD ($)$ / sharesshares	Dec. 31, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)$ / sharesshares	Mar. 31, 2019shares
Subsidiary Sale Of Stock [Line Items]
Preferred stock, shares issued | shares								0	0
Preferred stock, value per share | $ / shares								$ 0.001	$ 0.001
Proceeds from issuance of Preferred Stock, net | $								$ 93,759	$ 92,616	$ 18,040
Preferred stock, shares authorized | shares								5,000,000	5,000,000
Common stock, shares authorized | shares								200,000,000	255,000,000
Common Stock, Shares Issued | shares								48,511,735	3,123,424
Common stock, par value | $ / shares								$ 0.001	$ 0.001
Preferred stock, convertible, conversion ratio								100
Preferred stock, convertible terms								Each share of Series A Preferred, Series A-2 Preferred and Series B Preferred may be converted at any time, at the option of the holder, into shares of common stock, subject to the applicable conversion rate as determined by dividing the original issue price by the conversion price. The initial conversion price for each of the Series A Preferred, Series A-2 Preferred and Series B Preferred (each as may be adjusted for certain dilutive events) was $0.598, $0.8041 and $1.2182 per share, respectively. Each series of Series A Preferred, Series A-2 Preferred and Series B Preferred automatically converted into shares of common stock on a 1:1 conversion ratio (as may be adjusted for certain dilutive events) at the earlier of the closing of an initial public offering of the Company’s common stock with gross proceeds to the Company of at least $50.0 million and a purchase price of $22.34 per share, or at the election of the holders of at least two-thirds of the then-outstanding shares of Preferred Stock.
Proceeds from initial public offering, net of underwriting discount | $								$ 285,214		$ 0
Sale of stock, price per share | $ / shares								$ 22.34
IPO
Subsidiary Sale Of Stock [Line Items]
Proceeds from issuance of Preferred Stock, net | $								$ 523,200
Proceeds from issuance of Preferred Stock, net | $								$ 281,600
Additional shares of common stock | shares		2,105,368
Public Price | $ / shares		$ 19
Proceeds from common stock, gross | $		$ 306,700
Shares issued upon conversion of preferred stock | shares	27,720,923							27,720,923
Proceeds from initial public offering, net of underwriting discount | $	$ 306,700
Sale of stock, price per share | $ / shares	$ 19
Series A Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Preferred stock, convertible, conversion price | $ / shares								$ 0.598
Non-cumulative dividends payable per share | $ / shares								0.05
Series A Preferred Stock | Verily License Agreement
Subsidiary Sale Of Stock [Line Items]
Common Stock, Shares Issued | shares										1,672,240		1,672,240
Series A-2 Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Preferred stock, convertible, conversion price | $ / shares								0.8041
Non-cumulative dividends payable per share | $ / shares								0.06
Series B Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Preferred stock, convertible, conversion price | $ / shares								1.2182
Non-cumulative dividends payable per share | $ / shares								$ 0.10
Harvard And Board [Member]
Subsidiary Sale Of Stock [Line Items]
Common Stock, Shares Issued | shares		878,098
Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Preferred stock, shares authorized | shares		5,000,000
Preferred Stock | Series A Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Preferred stock, shares issued | shares				49,749,167	836,122	29,347,825					19,565,217
Preferred stock, value per share | $ / shares				$ 0.598	$ 0.598	$ 0.598					$ 0.598
Proceeds from issuance of Preferred Stock, net | $				$ 29,800	$ 500	$ 17,500					$ 11,700
Transaction costs on issuance | $											$ 200
Preferred Stock | Series A Preferred Stock | Verily License Agreement
Subsidiary Sale Of Stock [Line Items]
Preferred stock, shares issued | shares												1,672,240
Preferred Stock | Series A-2 Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Preferred stock, shares issued | shares							78,348,461
Preferred stock, value per share | $ / shares							$ 0.8041
Proceeds from issuance of Preferred Stock, net | $							$ 63,000
Transaction costs on issuance | $							$ 100
Preferred Stock | Series B Preferred Stock
Subsidiary Sale Of Stock [Line Items]
Preferred stock, shares issued | shares			77,163,022
Preferred stock, value per share | $ / shares			$ 1.2182
Proceeds from issuance of Preferred Stock, net | $			$ 94,000
Transaction costs on issuance | $			$ 200
Common Stock
Subsidiary Sale Of Stock [Line Items]
Common stock, shares authorized | shares		200,000,000
Common stock, par value | $ / shares		$ 0.001
Proceeds from initial public offering, net of underwriting discount | $								$ 50,000
Common Stock | IPO
Subsidiary Sale Of Stock [Line Items]
Common Stock, Shares Issued | shares		16,141,157

Stock-based compensation - Addi

Stock-based compensation - Additional Information (Details) $ / shares in Units, $ in Thousands	Jan. 01, 2022shares	Dec. 31, 2021USD ($)Instalment$ / sharesshares	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018shares	Jun. 16, 2021shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock reserved for future issuance		4,632,042
Proceeds from exercise of stock options | $		$ 966	$ 11
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value of stock options granted | $ / shares		$ 14.27
Aggregate intrinsic value of stock options exercised | $		$ 11,600
Proceeds from exercise of stock options | $		1,000
Unrecognized stock-based compensation cost | $		$ 40,200
Weighted average period over which unrecognized compensation is expected to be recognized		2 years 10 months 24 days
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average period over which unrecognized compensation is expected to be recognized		4 years
Unrecognized stock-based compensation cost | $		$ 1,100
Purchase of common stock under ESPP(shares)					2,150,537
Number of RSUs, Granted		32,000
Number of Installments for Restricted Shares Vested | Instalment		48
Twenty Eighteen | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock reserved for future issuance		6,885,653
2021 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock reserved for future issuance						3,466,530
Share-based Compensation Arrangement by Share-based Payment Award, Description		an annual increase, to be added on the first day of each fiscal year, commencing on January 1, 2022 and continuing until, and including, January 1, 2031, equal to the lesser of (i) 5% of the number of shares of common stock outstanding on such date
Shares available for future grant		3,489,589
2021 Stock Incentive Plan | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for future grant		32,000
Vesting period		4 years
2021 Stock Incentive Plan | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock reserved for future issuance	2,425,587
2021 Stock Incentive Plan | Common Stock | Forecast
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of outstanding stock, reserved for issuance	5.00%
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock reserved for future issuance		433,316
Purchase of common stock under ESPP(shares)		48,297
Stock available for issuance under ESPP		385,019
ESPP | Subsequent Event
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares of common stock reserved for future issuance	485,117
ESPP | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of outstanding stock, reserved for issuance		1.00%
Increase in common stock capital shares, reserved for future issuance		1,083,290

Stock-based compensation - Summ

Stock-based compensation - Summary of Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 7,072	$ 850	$ 446
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	3,830	494	336
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 3,242	$ 356	$ 110

Stock-based compensation - Sche

Stock-based compensation - Schedule of Assumptions Used for Options Granted (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected volatility	77.70%	84.80%	76.10%
Weighted-average risk-free interest rate	0.90%	0.40%	2.20%
Expected dividend yield	0.00%
Expected term (in years)	6 years	6 years	5 years 10 months 24 days

Stock-based compensation - Sc_2

Stock-based compensation - Schedule of Stock Option Activity (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of options, Outstanding, Beginning balance | shares	3,888,823
Number of options, Granted | shares	2,869,946
Number of options, Exercised | shares	(599,838)
Number of options, Forfeited | shares	(39,636)
Number of options, Outstanding, Ending balance | shares	6,119,295
Number of options, Exercisable | shares	1,373,507
Number of options, Expected to vest | shares	4,745,788	[1]
Weighted average exercise price, Beginning balance | $ / shares	$ 2.13
Weighted average exercise price, Granted | $ / shares	17.66
Weighted average exercise price, Exercised | $ / shares	1.61
Weighted average exercise price, Forfeited | $ / shares	2.56
Weighted average exercise price, Ending balance | $ / shares	9.44
Weighted average exercise price, Exercisable | $ / shares	2.15
Weighted average exercise price, Expected to vest | $ / shares	$ 11.56	[1]
Weighted average remaining contractual life (in years), Outstanding	8 years 8 months 12 days
Weighted average remaining contractual life (in years), Exercisable	8 years
Weighted average remaining contractual life (in years), Expected to vest	8 years 10 months 24 days
Aggregate intrinsic value, Outstanding | $	$ 171,636	[2]
Aggregate intrinsic value, Exercisable | $	47,691	[2]
Aggregate intrinsic value, Expected to vest | $	$ 123,945	[2]
[1]	This represents the number of unvested options outstanding as of December 31, 2021 that are expected to vest in the future.
[2]	The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money as of December 31, 2021.

Stock-based compensation - Sc_3

Stock-based compensation - Schedule of Status and Change in Unvested Restricted Stock and Restricted Stock Units (Details)	12 Months Ended
	Dec. 31, 2021$ / sharesshares
2021 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested RSUs, beginning balance, Unvested | shares	537,633
Unvested Restricted stock vested | shares	(537,633)
Unvested RSUs, ending balance, Unvested | shares	0
Weighted-Average Grant Date Fair Value Per Share, beginning balance, Unvested | $ / shares	$ 0.0028
Weighted-Average Grant Date Fair Value Per Share, Vested | $ / shares	0.0028
Weighted-Average Grant Date Fair Value Per Share, ending balance, Unvested | $ / shares	$ 0
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested RSUs, beginning balance, Unvested | shares	0
Number of RSUs, Granted | shares	32,000
Unvested RSUs, ending balance, Unvested | shares	32,000
Weighted-Average Grant Date Fair Value Per Share, beginning balance, Unvested | $ / shares	$ 0
Weighted-Average Grant-Date Fair Value, Granted | $ / shares	36.58
Weighted-Average Grant Date Fair Value Per Share, ending balance, Unvested | $ / shares	$ 36.58

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Schedule of Computation of Basic and Diluted net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator:
Net loss attributable to common stockholders	$ (120,314)	$ (45,704)	$ (19,297)
Denominator:
Weighted-average common shares used in net loss per share attributable to common stockholders, basic and diluted	26,872,036	2,250,093	1,277,156
Net loss per common share attributable to common stockholders, basic and diluted	$ (4.48)	$ (20.31)	$ (15.11)

Net Loss Per Share Attributab_4

Net Loss Per Share Attributable to Common Stockholders - Potential Common Shares, Based on Amounts Outstanding at Period End were Excluded From the Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	6,151,295	23,814,000	8,562,142
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	0	19,387,544	5,553,367
Unvested Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	0	537,633	1,075,268
Unvested Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	32,000	0	0
Outstanding Options To Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	6,119,295	3,888,823	1,933,507

Net Loss Per Share Attributab_5

Net Loss Per Share Attributable to Common Stockholders - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Earnings Per Share Basic [Line Items]
Success payment liability (See Notes 5, 8 and 15)	$ 4,371	$ 2,806
Harvard And Board | License
Earnings Per Share Basic [Line Items]
Success payment liability (See Notes 5, 8 and 15)	$ 6,300

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal statutory rate	21.00%	21.00%	21.00%
Change in valuation allowance	(31.30%)	(29.60%)	(17.90%)
Stock-based compensation	0.90%	(0.30%)	(0.10%)
Executive compensation	(1.10%)	0.00%	0.00%
Other permanent items	(0.10%)	1.10%	(5.80%)
State income taxes, net of federal benefit	6.10%	6.80%	1.70%
Research and development tax credits	4.50%	1.00%	1.10%
Total	0.00%	0.00%

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 33,409	$ 12,973
Capitalized costs—net of amortization	12,395	855
Research and development tax credits	6,098	682
Antidilultion liability		2,815
Stock-based compensation	1,117	149
Other	76	61
Lease liability	533
Accrued expenses	2,852	905
Total deferred tax assets	56,480	18,440
Deferred tax liabilities:
Property and equipment	(899)	(1,061)
Right of use asset	(501)
Total deferred tax liabilities	(1,400)	(1,061)
Total deferred tax assets, net	55,080	17,379
Less: valuation allowance	(55,080)	(17,379)
Deferred tax assets, net of valuation allowance	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Domestic	$ 120,300,000	$ 45,700,000	$ 19,300,000
Deferred tax assets valuation allowance increase (decrease)	$ 37,700,000	13,600,000
Change in ownership, description	An ownership change occurs when the ownership percentages of 5% or greater shareholders change by more than 50% over a three-year period.
Uncertain tax positions	$ 0	$ 0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	0
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	124,700,000
Tax credit amount	$ 4,200,000
Tax credit carryforward expiration year	2041
State
Operating Loss Carryforwards [Line Items]
Percentage of future taxable income utilized to offset	80.00%
Net operating loss carryforwards	$ 114,400,000
Net operating loss carryforwards expiration year	2041
Massachusetts
Operating Loss Carryforwards [Line Items]
Tax credit amount	$ 2,300,000
Tax credit carryforward expiration year	2036

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Apr. 30, 2019
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party		$ 300	$ 400	$ 400
Vesting of restricted common stock (in shares)		537,633	537,635	537,635
Common Stock Shares Issued		48,511,735	3,123,424
Common Stock Value		$ 49	$ 3
Issuance of common stock from initial public offering, net of issuance costs of $25,098		281,584
Research and development expense		68,202	35,371	$ 11,144
Option And License Issue Fees		200
Maximum
Related Party Transaction [Line Items]
Lease Rent Payment		100		$ 100
Beam | Research and Development
Related Party Transaction [Line Items]
Research and development expense			300
Beam | Collaboration And License Agreement
Related Party Transaction [Line Items]
Common Stock Shares Issued					276,075
Common Stock Value					$ 300
Out-of-pocket costs incurred	$ 100
Beam | Materials Exchange Agreement | Research and Development
Related Party Transaction [Line Items]
Research and development expense		200	200
Officer [Member] | Option License Agreement And Patent License Agreement | Research and Development
Related Party Transaction [Line Items]
Annual license fee		$ 100	$ 100

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Details) - USD ($)	Jan. 01, 2020	Dec. 31, 2021	Dec. 31, 2020
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, maximum annual contributions per employee, amount		$ 6,500
401(k) Plan
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan employer matching contribution percent of match upto two percent of employee salary		2.00%
Defined contribution plan, maximum annual contributions per employee, amount		$ 19,500
Defined contribution plan, employer matching contribution, percent of match upto 3% of employee's salary	100.00%	3.00%
Defined contribution plan, employer matching contribution, percent of match after 3% and before 5% of employee's salary	50.00%
Defined contribution plan, employers matching contribution, annual vesting percentage	100.00%
Defined contribution plan, description		The 401(k) Plan includes a salary deferral arrangement pursuant to which participants may elect to reduce their current compensation by up to the statutorily prescribed limit, equal to $19,500 in 2021 with a catch up contribution limit equal to $6,500 for those 50 years of age or older, and have the amount of the reduction contributed to the 401(k) Plan.
Defined contribution plan, employer Contribution amount		$ 400,000	$ 100,000