Prime Medicine (PRME) 10-Q 10 May 24 2024 Q1 Quarterly report Financial data

Cover

Cover - shares	3 Months Ended
	Mar. 31, 2024	May 01, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
Document Transition Report	false
Entity File Number	001-41536
Entity Registrant Name	Prime Medicine, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	84-3097762
Entity Address, Address Line One	21 Erie Street
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	564-0013
Title of 12(b) Security	Common stock, par value $0.00001 per share
Trading Symbol	PRME
Security Exchange Name	NASDAQ
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
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		120,030,813
Entity Central Index Key	0001894562
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands		Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents		$ 94,162	$ 41,574
Prepaid expenses		4,203	19,057
Other current assets		2,728	2,254
Total current assets		217,654	142,976
Property and equipment, net		23,926	22,659
Operating lease right-of-use assets		55,528	13,941
Restricted cash		13,496	13,496
Other assets		779	779
Total assets		311,383	193,851
Current liabilities:
Accounts payable		10,078	19,537
Accrued expenses and other current liabilities	[1]	7,612	14,110
Accrued settlement payment — related party		0	13,500
Operating lease liability		6,751	9,276
Total current liabilities		24,441	56,423
Operating lease liability, net of current		37,042	4,357
Non current deferred tax liability		134	0
Research and development funding liability		6,000	0
Total liabilities		67,617	60,780
Commitments and contingencies
Stockholders’ equity
Common stock, par value of $0.00001 per share; 775,000,000 shares authorized; 120,021,274 and 97,377,121 shares issued and outstanding as of March 31, 2024 and December 31, 2023, respectively		2	2
Additional paid-in capital		780,950	624,414
Accumulated other comprehensive loss		(95)	(15)
Accumulated deficit		(537,091)	(491,330)
Total stockholders’ equity		243,766	133,071
Total liabilities and stockholders’ equity		311,383	193,851
Nonrelated Party
Current assets:
Short-term investments		109,943	74,639
Current liabilities:
Accrued expenses and other current liabilities		7,612	14,110
Related Party
Current assets:
Short-term investments		$ 6,618	5,452
Current liabilities:
Accrued expenses and other current liabilities			$ 300
[1](1) Includes related party amount of $0.3 million as of December 31, 2023

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands		Mar. 31, 2024	Dec. 31, 2023
Common stock, par or stated value (in dollars per share)		$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)		775,000,000	775,000,000
Common stock, shares issued (in shares)		120,021,274	97,377,121
Common stock, shares outstanding (in shares)		120,021,274	97,377,121
Accrued expenses and other current liabilities	[1]	$ 7,612	$ 14,110
Related Party
Accrued expenses and other current liabilities			$ 300
[1](1) Includes related party amount of $0.3 million as of December 31, 2023

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Collaboration revenue		$ 591	$ 0
Operating expenses:
Research and development	[1]	37,774	30,880
General and administrative		11,158	9,153
Total operating expenses		48,932	40,033
Loss from operations		(48,341)	(40,033)
Other income:
Change in fair value of short-term investment — related party		1,166	(1,701)
Other income, net		1,548	2,135
Total other income, net		2,714	434
Net loss before income taxes		(45,627)	(39,599)
(Provision for) benefit from income taxes		(134)	202
Net loss attributable to common stockholders, basic		(45,761)	(39,397)
Net loss attributable to common stockholders, diluted		$ (45,761)	$ (39,397)
Net loss per share attributable to common stockholders, basic (in dollars per share)		$ (0.44)	$ (0.44)
Net loss per share attributable to common stockholders, diluted (in dollars per share)		$ (0.44)	$ (0.44)
Weighted-average common shares outstanding, basic (in shares)		104,466,178	89,064,895
Weighted-average common shares outstanding, diluted (in shares)		104,466,178	89,064,895
Comprehensive loss:
Net loss		$ (45,761)	$ (39,397)
Change in unrealized loss on investments, net of tax		(80)	179
Comprehensive loss		$ (45,841)	$ (39,218)
[1] (1) Includes related party amount of $0.3 million for the three months ended March 31, 2023.

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($)
Research and development	$ 30,880	[1]
Related Party | General and administrative
Research and development	$ 300
[1] (1) Includes related party amount of $0.3 million for the three months ended March 31, 2023.

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Losses	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2022		97,209,213
Beginning balance at Dec. 31, 2022	$ 316,270	$ 2	$ 609,849	$ (384)	$ (293,197)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		18,596
Issuance of common stock upon exercise of stock options	68		68
Stock-based compensation expense	1,681		1,681
Change in unrealized loss on investments, net of tax	179			179
Net loss	(39,397)				(39,397)
Ending balance (in shares) at Mar. 31, 2023		97,227,809
Ending balance at Mar. 31, 2023	$ 278,801	$ 2	611,598	(205)	(332,594)
Beginning balance (in shares) at Dec. 31, 2023	97,377,121	97,377,121
Beginning balance at Dec. 31, 2023	$ 133,071	$ 2	624,414	(15)	(491,330)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from public offering, net of issuance costs of $8.9 million (in shares)		22,560,001
Issuance of common stock from public offering, net of issuance costs of $8.9 million	132,055	$ 0	132,055
Issuance of pre-funded warrants, net of issuance costs of $1.2 million	18,800		18,800
Issuances of common under ESPP (in shares)		74,488
Issuances of common under ESPP	$ 436		436
Issuance of common stock upon exercise of stock options (in shares)	9,664	9,664
Issuance of common stock upon exercise of stock options	$ 36		36
Stock-based compensation expense	5,209		5,209
Change in unrealized loss on investments, net of tax	(80)			(80)
Net loss	$ (45,761)				(45,761)
Ending balance (in shares) at Mar. 31, 2024	120,021,274	120,021,274
Ending balance at Mar. 31, 2024	$ 243,766	$ 2	$ 780,950	$ (95)	$ (537,091)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows used in operating activities:
Net loss	$ (45,761)	$ (39,397)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	5,209	1,681
Non cash lease expense	3,348	2,831
Depreciation expense	1,315	1,052
Change in fair value of short-term investment — related party	(1,166)	1,701
Amortization of premiums and discount on short-term investments	(675)	(611)
Deferred income taxes	134	(202)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,794)	(1,285)
Accounts payable	(5,880)	(504)
Accrued expenses and other current liabilities	(4,475)	(4,046)
Accrued settlement payment — related party	(13,500)	0
Lease liabilities	(3,462)	(2,781)
Net cash used in operating activities	(67,707)	(41,561)
Cash flows used in investing activities:
Maturities of investments	72,500	35,000
Purchases of investments	(107,208)	(45,666)
Purchases of property and equipment	(2,324)	(1,999)
Net cash used in investing activities	(37,032)	(12,665)
Cash flows provided by financing activities:
Proceeds from follow-on offering, net of issuance costs	132,055	0
Proceeds from issuance of pre-funded warrants, net of issuance costs	18,800	0
Proceeds from research and development funding liability	6,000	0
Proceeds from ESPP offerings	436	0
Net proceeds from stock option exercises	36	68
Net cash provided by financing activities	157,327	68
Net change in cash, cash equivalents, and restricted cash	52,588	(54,158)
Cash, cash equivalents, and restricted cash at beginning of period	55,070	201,116
Cash, cash equivalents, and restricted cash at end of period	107,658	146,958
Reconciliation of cash, cash equivalents and restricted cash:
Cash, cash equivalents, and restricted cash at end of period	107,658	146,958
Less: restricted cash	13,496	13,496
Total cash, and cash equivalents	94,162	133,462
Supplemental cash flow information:
Right-of-use assets obtained in exchange for new operating lease liabilities	44,935	0
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued expenses	$ 833	$ 2,603

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2024 USD ($)
Proceeds from issuance of warrants	$ 18,800
Warrant
Proceeds from issuance of warrants	1,200
Public Offering
Issuance costs	$ 8,900

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the Business and Basis of Presentation	Nature of the Business and Basis of Presentation Prime Medicine, Inc., together with its consolidated subsidiary (the “Company”) is a biotechnology company committed to delivering a new class of differentiated one-time curative genetic therapies to address the widest spectrum of diseases. The Company is deploying Prime Editing technology, which it believe is a versatile, precise, and efficient gene editing technology. The Company was incorporated in the State of Delaware in September 2019. Its principal offices are in Cambridge, Massachusetts. Liquidity and Capital Resources Since its inception, the Company has devoted substantially all of its resources to building its Prime editing platform and advancing development of its portfolio of programs, establishing and protecting its intellectual property, conducting research and development activities, organizing and staffing the company, business planning, raising capital and providing general and administrative support for these operations. To date, the Company has funded its operations primarily with proceeds from sales of preferred stock and from public offerings of its common stock. In February 2024, the Company issued and sold 22,560,001 shares of its common stock, including 3,360,000 shares pursuant to the exercise of the underwriters’ option to purchase additional shares, at a price to the public of $6.25 per share. Further, in lieu of common stock to certain investors, the Company sold pre-funded warrants to purchase 3,200,005 shares of common stock at a public offering price of $6.24999 per pre-funded warrant, which represents the per share public offering price of each share of common stock less the $0.00001 per share exercise price for each pre-funded warrant. As a result of the offering, the Company received approximately $150.9 million in net proceeds, after deducting underwriting discounts, commissions and estimated offering costs of $10.1 million. Risks and Uncertainties The Company is subject to risks and uncertainties common to early stage companies in the biotechnology industry, including, but not limited to, completing preclinical studies and clinical trials, obtaining regulatory approval for product candidates, market acceptance of products, development by competitors of new technological innovations, dependence on key personnel, the ability to attract and retain qualified employees, reliance on third-party organizations, protection of proprietary technology, compliance with government regulations, and the ability to raise additional capital to fund operations. The Company’s product candidates currently under development will require significant additional 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. Since its inception, the Company has incurred substantial losses and, as of March 31, 2024, the Company had an accumulated deficit of $537.1 million. 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 investments as of March 31, 2024 of $210.7 million 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 to raise additional capital to support its continuing operations and to 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 capital or enter into such other agreements when needed on favorable terms or at all. The inability to raise capital as and when needed would 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. Basis of Presentation The accompanying condensed consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiary. Intercompany balances and transactions have been eliminated in consolidation. The accompanying condensed consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“U.S. 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 Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). The accompanying condensed consolidated financial statements of Prime Medicine, Inc. are unaudited. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of March 31, 2024, the results of its operations for the three months ended March 31, 2024 and 2023, the condensed consolidated statements of stockholders’ equity for the three months ended March 31, 2024 and 2023, and its cash flows for the three months ended March 31, 2024 and 2023. The financial data and other information disclosed in these notes related to the three months ended March 31, 2024 and 2023 are also unaudited. The results for the three months ended March 31, 2024 are not necessarily indicative of results to be expected for the year ending December 31, 2024, any other interim periods, or any future year or period. The condensed consolidated balance sheet data as of December 31, 2023 was derived from our audited financial statements, but does not include all disclosures required by U.S. GAAP. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2023, and notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the Securities and Exchange Commission (the “SEC”) on March 1, 2024.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The Company’s significant accounting policies are disclosed in Note 2, Summary of significant accounting policies , in the audited consolidated financial statements for the year ended December 31, 2023, and notes thereto, included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 1, 2024. Since the date of those financial statements, there have been no material changes to its significant accounting policies, except as noted below. Use of Estimates The preparation of the Company’s condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and assumptions reflected within these condensed consolidated financial statements include, but are not limited to the valuation of the Company’s common stock and stock-based awards, and the valuation of the related party forward contract liability. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates, as there are changes in circumstances, facts and experience. Actual results may differ materially from those estimates or assumptions. Warrants Management assesses warrants under ASC 480, Distinguishing Liabilities from Equity to determine whether they should be classified as equity or liability. If the classification is determined to be equity, proceeds received for the warrants are recorded as an increase to additional paid-in capital in the condensed consolidated balance sheets. If classified as a liability, the Company records the warrant as a liability on its consolidated balance sheet and remeasures this liability to fair value at each reporting date and recognizes changes in the fair value of the warrant liability as a component of other expense in the condensed consolidated statements of operations and comprehensive loss. Recently Issued Accounting Pronouncements Not Yet Adopted Accounting standards that have been issued by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on our financial statements upon adoption.

Fair Value Measurements and Inv

Fair Value Measurements and Investments	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements and Investments	Fair Value Measurements and Investments The following tables present the Company’s fair value hierarchy for its assets that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair value: As of March 31, 2024: (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 47,915 $ — $ 47,915 U.S. Treasury and government securities — 35,854 — 35,854 Corporate debt securities — 9,932 — 9,932 Short-term investments: U.S. Treasury and government securities — 74,656 — 74,656 Corporate debt securities — 35,287 — 35,287 Related party short-term investment: Beam equity securities 6,618 — — 6,618 Total cash equivalents and investments $ 6,618 $ 203,644 $ — $ 210,262 As of December 31, 2023: (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 24,209 $ — $ 24,209 Short-term investment: U.S. Treasury and government securities — 74,639 — 74,639 Related party short-term investment: Beam equity securities 5,452 — — 5,452 Total cash equivalents and investments $ 5,452 $ 98,848 $ — $ 104,300 The Company classifies its U.S. Treasury securities as short-term based on each instrument’s underlying contractual maturity date. The fair value of the Company’s U.S. Treasury securities and money market funds are classified as Level 2 because they are valued using observable inputs to quoted market prices, benchmark yields, reported trades, broker/dealer quotes or alternative pricing sources with reasonable levels of price transparency and U.S. Treasury securities. Investments in Debt Securities Unrealized gains and losses of investments in debt securities consisted of the following: As of March 31, 2024: (in thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Short-term investments in debt securities: U.S. Treasury and government securities $ 74,697 $ — $ (41) $ 74,656 Corporate debt securities 35,329 — (42) 35,287 Total short-term investments in debt securities $ 110,026 $ — $ (83) $ 109,943 As of December 31, 2023: (in thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Short-term investments: U.S. Treasury and government securities $ 74,654 $ 7 $ (22) $ 74,639 Total short-term investments in debt securities $ 74,654 $ 7 $ (22) $ 74,639 The contractual maturities of the Company’s investments in debt securities held were as follows: (in thousands) March 31, December 31, Due within one year $ 109,943 $ 74,639 Marketable securities in unrealized loss positions consisted of the following: As of March 31, 2024: (in thousands, except number of securities) Number of Securities Fair Value Gross Unrealized Losses Investments in continuous loss position for less than 12 months: U.S. Treasury and government securities 15 $ 72,156 $ (41) Corporate debt securities 19 $ 35,287 $ (42) Based on factors such as historical experience, market data, issuer-specific factors, and current economic conditions, the Company did not record an allowance for credit losses as of March 31, 2024 related to these investments. Further, given the lack of significant change in the credit risk, the Company does not consider these investments to be impaired.

Property and Equipment, Net

Property and Equipment, Net	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net consisted of the following: (in thousands) March 31, December 31, Property and equipment: Laboratory equipment $ 24,672 $ 23,873 Leasehold improvement 579 579 Furniture and Fixture 1,042 278 Computer hardware and software 724 11 Construction in progress 5,708 5,402 Total property and equipment 32,725 30,143 Less: Accumulated depreciation (8,799) (7,484) Total property and equipment, net $ 23,926 $ 22,659 Depreciation expense related to property and equipment is as follows: Three Months Ended March 31, (in thousands) 2024 2023 Depreciation Expense $ 1,315 $ 1,052

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2024
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following: (in thousands) March 31, December 31, Accrued expenses and other current liabilities Accrued employee compensation and benefits $ 3,062 $ 8,270 Lab-related supplies and services 2,441 1,962 Accrued professional fees 1,138 2,273 Other 971 1,605 Total accrued expenses and other current liabilities $ 7,612 $ 14,110

Leases

Leases	3 Months Ended
	Mar. 31, 2024
Leases [Abstract]
Leases	Leases The Company leases office and laboratory space under various non-cancelable operating leases. The Company’s significant lease agreements are disclosed in Note 9, Leases , in the audited consolidated financial statements for the year ended December 31, 2023, and notes thereto, included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 1, 2024. Since the date of those financial statements, there have been no changes to the Company’s significant agreements except as described below. 60 First Street, Cambridge, Massachusetts Lease In November 2021, the Company entered into a lease for three floors of office and laboratory space in Cambridge, Massachusetts, with rent commencing in March 2024, subject to any credits pursuant to the terms of the lease. Also subject to any credits pursuant to the terms of the lease, the Company expects to pay up to approximately $208.7 million over the initial non-cancelable term of the lease of ten years, and the Company has an option to extend the lease for an additional period of ten years with the rent during the extension term being the then fair market rent. The Company secured the lease with a $13.1 million security deposit, which was recorded as restricted cash on the condensed consolidated balance sheets as of March 31, 2024 and December 31, 2023. Accounting Considerations The Company determined that the lease contained three separate lease components each of which represents a right of use that the Company can benefit from on its own and none which are neither highly dependent nor highly related to each other. The Company allocated the consideration among the three lease components based on their relative fair market value. In accordance with ASC 842, Leases, the lease commenced for one of the lease components in March 2024 and the Company recorded a right-of-use asset of $44.9 million, and a corresponding lease liability of $33.6 million on the lease commencement date; this includes a reclass of $11.3 million from prepaid expenses to right-of-use asset related to build out costs which were determined to be owned by the lessor. As the exercise of the option to extend the lease term was not reasonably certain, the Company will recognize lease expense for this lease component through February 2034. The lease commencement for the other two lease components is expected to occur in 2025. Any consideration paid to lease components for which the lease has not commenced are recorded as prepaid expense on the condensed consolidated balance sheets. The table below reconciles the undiscounted future annual lease payments to the total operating lease liabilities recorded in the condensed consolidated balance sheet as of March 31, 2024 : (in thousands) Undiscounted Undiscounted lease payments: Remaining in 2024 $ 5,868 2025 18,584 2026 21,339 2027 20,812 2028 20,853 Thereafter 118,079 Total undiscounted lease payments 205,535 Less: payments related to leases not commenced (129,866) Less: imputed interest (31,876) Total operating lease liability $ 43,793

Stockholder_s Equity

Stockholder’s Equity	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Stockholder’s Equity	Stockholder’s Equity Common Stock Under the Company’s Third Amended and Restated of Certificate of Incorporation, the Company’s common stock had a par value of $0.0001 and each share of common stock entitles the holder to one vote on all matters submitted to the stockholders for a vote. The holders of common stock are entitled to receive dividends, if any, as declared by the Company’s Board of Directors (the “Board of Directors”). As previously discussed, in February 2024, the Company issued and sold 22,560,001 shares of its common stock, including 3,360,000 shares pursuant to the exercise of the underwriters’ option to purchase additional shares, at a price to the public of $6.25 per share. Pre-funded Warrants As discussed in Note 1, Nature of the Business and Basis of Presentation , in February 2024, the Company sold pre-funded warrants to purchase 3,200,005 shares of common stock at a public offering price of $6.24999 per pre-funded warrant, which represents the per share public offering price of each share of common stock less the $0.00001 per share exercise price for each pre-funded warrant. Subject to certain requirements, the pre-funded warrants can be exercised by the holder at anytime. As of March 31, 2024, there have not been any exercises of the pre-funded warrants. The pre-funded warrants meet the definition of an equity instrument under ASC 815-40, Derivatives and Hedging — Contracts in Entity’s Own Equity , and funds received were recorded as an increase in additional paid-in capital in the condensed consolidated balance sheets. Funds received upon exercise of warrants will be recorded as common stock in the condensed consolidated balance sheets as the exercise price represents the par value of the underlying common stock. At-The-Market Equity Program In November 2023, the Company entered into Open Market Sale Agreement SM (the “Sales Agreement”) with Jefferies LLC, acting as the Company’s agent and/or principal (the “Sales Agent”), with respect to an “at the market offering” program under which the Company may, from time to time, at its sole discretion, issue and sell shares of its common stock having an aggregate offering price of up to $300.0 million through the Sales Agent. As of March 31, 2024, there have been no sales of common stock pursuant to the Sales Agreement.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation 2019 Equity Incentive Plan The Company’s 2019 Stock Option and Grant Plan (the “2019 Plan”) provides for the Company to grant incentive stock options (“ISO”), non-qualified stock options, unrestricted stock awards, restricted stock awards (“RSA”) and other stock-based awards (collectively, the “Awards”) to the officers, employees, consultants and other key persons of the Company. The 2019 Plan was administered by the Board of Directors, or at the discretion of the Board of Directors, by a committee of the Board of Directors. The exercise prices, vesting and other restrictions are determined at the discretion of the Board of Directors, or its committee if so delegated. In October 2022, in connection with the closing of the Company’s initial public offering (“IPO”), the Board of Directors determined that no further awards would be granted under the 2019 Plan. 2022 Stock Option and Incentive Plan On February 9, 2022, the Board of Directors adopted, and on October 10, 2022, the Company’s stockholders approved, the 2022 Stock Option and Incentive Plan (the “2022 Plan”), which became effective on October 18, 2022. The 2022 Plan allows the Company to make equity-based and cash-based incentive awards to its officers, employees, directors, and consultants. The 2022 Plan provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. The shares of common stock underlying any awards under the 2022 Plan and the 2019 Plan that are forfeited, cancelled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without the issuance of stock, expire, or are otherwise terminated (other than by exercise) will be added back to the shares of common stock available for issuance under the 2022 Plan. The number of shares reserved and available for issuance under the 2022 Plan increased on January 1, 2023 and will increase on each January 1 hereafter, by five percent of the outstanding number of shares of common stock on the immediately preceding December 31 or such lesser number of shares as determined by the Compensation Committee. On January 1, 2023, the annual increase resulted in an additional 4,868,856 shares authorized being added to the 2022 Plan. As of March 31, 2024, the Company had 21,290,494 shares reserved under the 2022 Plan and the 2019 Plan, and 9,088,040 shares available for issuance under the 2022 ESPP. 2022 Employee Stock Purchase Plan On February 9, 2022, the Board of Directors adopted, and on October 10, 2022, the Company’s stockholders approved, the 2022 Employee Stock Purchase Plan (the “2022 ESPP”), which became effective on October 18, 2022. The number of shares of common stock that may be issued under the 2022 ESPP cumulatively increased beginning on January 1, 2023 and shall increase on each January 1 hereafter through January 1, 2032, by the least of (i) 971,350 shares of common stock, (ii) one percent of the outstanding number of shares of common stock on the immediately preceding December 31, or (iii) such number of shares of common stock as determined by the administrator of the 2022 ESPP. There was no annual increase for the 2022 ESPP on January 1, 2024. As of March 31, 2024, the Company had 1,868,212 shares available for issuance under the 2022 Plan. During the three months ended March 31, 2024, the Company issued 74,488 shares of the Company’s common stock under the 2022 ESPP. Stock Options The following table summarizes the Company’s stock option activity for the three months ended March 31, 2024: Number of Shares Weighted-Average Exercise Price Outstanding at December 31, 2023 7,641,863 $ 9.79 Granted 3,898,410 8.23 Exercised (9,664) 3.73 Cancelled or forfeited (139,885) 11.59 Outstanding at March 31, 2024 11,390,724 $ 9.24 Options vested and exercisable at March 31, 2024 2,838,246 $ 7.64 Options vested and expected to vest at March 31, 2024 11,390,724 $ 9.24 As of March 31, 2024, there was $57.5 million of total unrecognized compensation cost related to time-based unvested stock options the Company expects to recognize such amount over a remaining weighted-average period of 2.8 years. Performance-Based Stock Options The following table summarizes the Company’s performance-based stock option activity for the three months ended March 31, 2024: Number of Shares Weighted-Average Outstanding at December 31, 2023 411,730 $ 6.65 Granted 400,000 8.32 Exercised — — Cancelled or forfeited — — Outstanding at March 31, 2024 811,730 $ 7.47 Vested and exercisable at March 31, 2024 131,882 $ 5.34 As of March 31, 2024, there was $4.7 million of total unrecognized compensation cost related to performance-based stock options. Restricted Common Stock Awards The Company awarded restricted common stock to employees and non-employees under its 2019 Plan. The vesting of these restricted stock awards are time-based or performance-based. Time-Based Restricted Common Stock The following table summarizes the Company’s time-based restricted common stock activity for the three months ended March 31, 2024 : Number of Shares Weighted-Average Grant-Date Fair Value Outstanding at December 31, 2023 903,227 $ 0.17 Issued — — Vested (329,833) 0.14 Repurchased — — Outstanding at March 31, 2024 573,394 $ 0.19 As of March 31, 2024, there was $0.1 million of total unrecognized compensation cost related to unvested ti me-based restricted common stock which the Company expects to recognize over a weighted-average period of 0.5 years. Performance-Based Restricted Common Stock The following table summarizes the Company’s performance-based restricted common stock activity for the three months ended March 31, 2024 : Number of Shares Weighted-Average Grant-Date Fair Value Outstanding at December 31, 2023 3,832,769 $ 0.07 Issued — — Vested — — Repurchased — — Outstanding at March 31, 2024 3,832,769 $ 0.07 As of March 31, 2024, there was $0.3 million of total unrecognized compensation cost related to unvested performance-based restricted common stock. Stock-Based Compensation The following table below summarizes the classification of the Company’s stock-based compensation expense related to stock options and restricted common stock awards in the condensed consolidated statements of operations and comprehensive loss: Three Months Ended (in thousands) 2024 2023 Stock-based compensation expense: Research and development $ 2,725 $ 1,170 General and administrative 2,484 511 Total stock-based compensation expense $ 5,209 $ 1,681

Significant Agreements

Significant Agreements	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Significant Agreements	Significant Agreements The Company’s significant agreements are disclosed in Note 11, License and Collaboration Agreements , in the audited consolidated financial statements for the year ended December 31, 2023, and notes thereto, included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 1, 2024. Since the date of those financial statements, there have been no changes to the Company’s significant agreements.

Net Loss per Share

Net Loss per Share	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic and diluted net loss per common share attributable to common stockholders was calculated as follows: Three Months Ended (in thousands, except share and per share amounts) 2024 2023 Numerator: Net loss attributable to common stockholders $ (45,761) $ (39,397) Denominator: Weighted-average common shares outstanding, basic and diluted 104,466,178 89,064,895 Net loss per share attributable to common stockholders, basic and diluted $ (0.44) $ (0.44) Diluted net loss per share available to common stockholders was computed by giving effect to all potentially dilutive common stock equivalents outstanding for the period. For purposes of this calculation, preferred stock, unvested restricted stock and stock options to purchase common stock were considered common stock equivalents but had been excluded from the calculation of diluted net loss per share available to common stockholders as their effect was anti-dilutive. In periods in which the Company reports a net loss available to common stockholders, diluted net loss per share available to common stockholders is the same as basic net loss per share available to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The following common stock equivalents were excluded from the calculation of diluted net loss per share applicable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: As of March 31, 2024 2023 Anti-dilutive common stock equivalents: Options to purchase common stock 11,522,606 6,945,214 Unvested restricted common stock 4,406,163 7,530,495 Total anti-dilutive common stock equivalents: 15,928,769 14,475,709

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2024
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Consulting Agreement with David Liu Pursuant to a consulting agreement with David Liu, for the three months ended March 31, 2024 and 2023, the Company made payments of $37,500 in each period for scientific consulting and other expenses. As of March 31, 2024 and December 31, 2023, there were no amounts included within accounts payable or accrued expenses. Myeloid Therapeutics In December 2021, the Company and Myeloid entered into the Myeloid Collaboration Agreement and Myeloid Subscription Agreement during which time the Company and Myeloid had one common board member, who is also an affiliate of Newpath, one of the Company’s holders of common stock. In 2023, the Company terminated the Myeloid Collaboration Agreement. In January 2024, the Company and Myeloid entered into a settlement agreement resolving two arbitration proceedings, which are described in Note 10, Licenses and Collaboration Agreements. Under the terms of the settlement agreement, the parties agreed to resolve and settle all disputes between the parties and release all claims between them relating to the License Agreement and the arbitrations in exchange for the Company's payment to Myeloid of $13.5 million, certain mutual covenants, and other consideration. The settlement was accrued on the Company’s consolidated balance sheet as of December 31, 2023 and paid during the three months ended March 31, 2024. As of March 31, 2024, there were no amounts included within accounts payable or accrued expenses. Advisory Services Agreement with Jeffrey Marrazzo In February 2024, the Company entered into an advisory services agreement (“Marrazzo Agreement”) with Jeffrey Marrazzo, a member of the Board of Directors. Under the Marrazzo Agreement, Mr. Marrazzo agreed to provide certain professional services to the Company separate from and in addition to his service as a Board member. For his services, the Company agreed to pay Mr. Marrazzo an annual fee of $50,000 per year in addition to the grant of an option to purchase 250,000 shares of the Company's common stock, which has a grant date fair value of $1.5 million. The term of the Marrazzo Agreement runs through February 2025 and may be terminated or extended by mutual written agreement. If the Company terminates the Marrazzo Agreement without "Cause," the administrator of the 2022 Plan will accelerate the vesting of the option such that the pro rata portion of the option will vest and be immediately exercisable.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiary. Intercompany balances and transactions have been eliminated in consolidation. The accompanying condensed consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States of America (“U.S. 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 Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). The accompanying condensed consolidated financial statements of Prime Medicine, Inc. are unaudited. The unaudited interim condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of March 31, 2024, the results of its operations for the three months ended March 31, 2024 and 2023, the condensed consolidated statements of stockholders’ equity for the three months ended March 31, 2024 and 2023, and its cash flows for the three months ended March 31, 2024 and 2023. The financial data and other information disclosed in these notes related to the three months ended March 31, 2024 and 2023 are also unaudited. The results for the three months ended March 31, 2024 are not necessarily indicative of results to be expected for the year ending December 31, 2024, any other interim periods, or any future year or period. The condensed consolidated balance sheet data as of December 31, 2023 was derived from our audited financial statements, but does not include all disclosures required by U.S. GAAP. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2023, and notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the Securities and Exchange Commission (the “SEC”) on March 1, 2024.
Use of Estimates	Use of Estimates The preparation of the Company’s condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and assumptions reflected within these condensed consolidated financial statements include, but are not limited to the valuation of the Company’s common stock and stock-based awards, and the valuation of the related party forward contract liability. The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances. On an ongoing basis, management evaluates its estimates, as there are changes in circumstances, facts and experience. Actual results may differ materially from those estimates or assumptions.
Warrants	Warrants Management assesses warrants under ASC 480, Distinguishing Liabilities from Equity to determine whether they should be classified as equity or liability. If the classification is determined to be equity, proceeds received for the warrants are recorded as an increase to additional paid-in capital in the condensed consolidated balance sheets. If classified as a liability, the Company records the warrant as a liability on its consolidated balance sheet and remeasures this liability to fair value at each reporting date and recognizes changes in the fair value of the warrant liability as a component of other expense in the condensed consolidated statements of operations and comprehensive loss.
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently Issued Accounting Pronouncements Not Yet Adopted

Fair Value Measurements and I_2

Fair Value Measurements and Investments (Tables)	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following tables present the Company’s fair value hierarchy for its assets that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair value: As of March 31, 2024: (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 47,915 $ — $ 47,915 U.S. Treasury and government securities — 35,854 — 35,854 Corporate debt securities — 9,932 — 9,932 Short-term investments: U.S. Treasury and government securities — 74,656 — 74,656 Corporate debt securities — 35,287 — 35,287 Related party short-term investment: Beam equity securities 6,618 — — 6,618 Total cash equivalents and investments $ 6,618 $ 203,644 $ — $ 210,262 As of December 31, 2023: (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents: Money market funds $ — $ 24,209 $ — $ 24,209 Short-term investment: U.S. Treasury and government securities — 74,639 — 74,639 Related party short-term investment: Beam equity securities 5,452 — — 5,452 Total cash equivalents and investments $ 5,452 $ 98,848 $ — $ 104,300
Schedule of Debt Securities, Available-for-Sale	Unrealized gains and losses of investments in debt securities consisted of the following: As of March 31, 2024: (in thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Short-term investments in debt securities: U.S. Treasury and government securities $ 74,697 $ — $ (41) $ 74,656 Corporate debt securities 35,329 — (42) 35,287 Total short-term investments in debt securities $ 110,026 $ — $ (83) $ 109,943 As of December 31, 2023: (in thousands) Amortized Cost Unrealized Gains Unrealized Losses Fair Value Short-term investments: U.S. Treasury and government securities $ 74,654 $ 7 $ (22) $ 74,639 Total short-term investments in debt securities $ 74,654 $ 7 $ (22) $ 74,639 Marketable securities in unrealized loss positions consisted of the following: As of March 31, 2024: (in thousands, except number of securities) Number of Securities Fair Value Gross Unrealized Losses Investments in continuous loss position for less than 12 months: U.S. Treasury and government securities 15 $ 72,156 $ (41) Corporate debt securities 19 $ 35,287 $ (42)
Schedule of Investments Classified by Contractual Maturity Date	The contractual maturities of the Company’s investments in debt securities held were as follows: (in thousands) March 31, December 31, Due within one year $ 109,943 $ 74,639

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net and Depreciation Expense	Property and equipment, net consisted of the following: (in thousands) March 31, December 31, Property and equipment: Laboratory equipment $ 24,672 $ 23,873 Leasehold improvement 579 579 Furniture and Fixture 1,042 278 Computer hardware and software 724 11 Construction in progress 5,708 5,402 Total property and equipment 32,725 30,143 Less: Accumulated depreciation (8,799) (7,484) Total property and equipment, net $ 23,926 $ 22,659 Depreciation expense related to property and equipment is as follows: Three Months Ended March 31, (in thousands) 2024 2023 Depreciation Expense $ 1,315 $ 1,052

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2024
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued expenses and other current liabilities consisted of the following: (in thousands) March 31, December 31, Accrued expenses and other current liabilities Accrued employee compensation and benefits $ 3,062 $ 8,270 Lab-related supplies and services 2,441 1,962 Accrued professional fees 1,138 2,273 Other 971 1,605 Total accrued expenses and other current liabilities $ 7,612 $ 14,110

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2024
Leases [Abstract]
Schedule of Operating Lease Liability	The table below reconciles the undiscounted future annual lease payments to the total operating lease liabilities recorded in the condensed consolidated balance sheet as of March 31, 2024 : (in thousands) Undiscounted Undiscounted lease payments: Remaining in 2024 $ 5,868 2025 18,584 2026 21,339 2027 20,812 2028 20,853 Thereafter 118,079 Total undiscounted lease payments 205,535 Less: payments related to leases not commenced (129,866) Less: imputed interest (31,876) Total operating lease liability $ 43,793

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Schedule of Share-Based Payment Arrangement, Option, Activity	The following table summarizes the Company’s stock option activity for the three months ended March 31, 2024: Number of Shares Weighted-Average Exercise Price Outstanding at December 31, 2023 7,641,863 $ 9.79 Granted 3,898,410 8.23 Exercised (9,664) 3.73 Cancelled or forfeited (139,885) 11.59 Outstanding at March 31, 2024 11,390,724 $ 9.24 Options vested and exercisable at March 31, 2024 2,838,246 $ 7.64 Options vested and expected to vest at March 31, 2024 11,390,724 $ 9.24 The following table summarizes the Company’s performance-based stock option activity for the three months ended March 31, 2024: Number of Shares Weighted-Average Outstanding at December 31, 2023 411,730 $ 6.65 Granted 400,000 8.32 Exercised — — Cancelled or forfeited — — Outstanding at March 31, 2024 811,730 $ 7.47 Vested and exercisable at March 31, 2024 131,882 $ 5.34
Schedule of Share-Based Payment Arrangement, Outstanding Award, Activity, Excluding Option	The following table summarizes the Company’s time-based restricted common stock activity for the three months ended March 31, 2024 : Number of Shares Weighted-Average Grant-Date Fair Value Outstanding at December 31, 2023 903,227 $ 0.17 Issued — — Vested (329,833) 0.14 Repurchased — — Outstanding at March 31, 2024 573,394 $ 0.19 The following table summarizes the Company’s performance-based restricted common stock activity for the three months ended March 31, 2024 : Number of Shares Weighted-Average Grant-Date Fair Value Outstanding at December 31, 2023 3,832,769 $ 0.07 Issued — — Vested — — Repurchased — — Outstanding at March 31, 2024 3,832,769 $ 0.07
Schedule of Share-Based Payment Arrangement, Expensed and Capitalized, Amount	The following table below summarizes the classification of the Company’s stock-based compensation expense related to stock options and restricted common stock awards in the condensed consolidated statements of operations and comprehensive loss: Three Months Ended (in thousands) 2024 2023 Stock-based compensation expense: Research and development $ 2,725 $ 1,170 General and administrative 2,484 511 Total stock-based compensation expense $ 5,209 $ 1,681

Net Loss per Share (Tables)

Net Loss per Share (Tables)	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Schedule of Net Loss Per Share, Basic and Diluted	Basic and diluted net loss per common share attributable to common stockholders was calculated as follows: Three Months Ended (in thousands, except share and per share amounts) 2024 2023 Numerator: Net loss attributable to common stockholders $ (45,761) $ (39,397) Denominator: Weighted-average common shares outstanding, basic and diluted 104,466,178 89,064,895 Net loss per share attributable to common stockholders, basic and diluted $ (0.44) $ (0.44)
Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share	The following common stock equivalents were excluded from the calculation of diluted net loss per share applicable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect: As of March 31, 2024 2023 Anti-dilutive common stock equivalents: Options to purchase common stock 11,522,606 6,945,214 Unvested restricted common stock 4,406,163 7,530,495 Total anti-dilutive common stock equivalents: 15,928,769 14,475,709

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended
	Feb. 29, 2024	Mar. 31, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Accumulated deficit		$ 537,091	$ 491,330
Cash, cash equivalents, and investments		$ 210,700
IPO
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Sale of stock, number of shares issued (in shares)	22,560,001
Sale of stock, price per share (in usd per share)	$ 6.25
Proceeds from IPO	$ 150,900
Stock issuance costs	$ 10,100
Over-Allotment Option
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Sale of stock, number of shares issued (in shares)	3,360,000
Public Offering | Warrant Purchase Agreement
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Sale of stock, price per share (in usd per share)	$ 6.24999
Pre-funded warrants sold (in shares)	3,200,005
Exercise price of warrants (in dollars per share)	$ 0.00001

Fair Value Measurements and I_3

Fair Value Measurements and Investments - Schedule of Hierarchy For Assets and Liabilities Measured At Fair Value On A Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 109,943	$ 74,639
Total assets	210,262	104,300
Related Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Related party short-term investment	6,618	5,452
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	47,915	24,209
U.S. Treasury and government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	35,854
Short-term investments	74,656	74,639
U.S. Treasury and government securities | Nonrelated Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	74,656	74,639
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	9,932
Short-term investments	35,287
Corporate debt securities | Nonrelated Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	35,287
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	6,618	5,452
Level 1 | Related Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Related party short-term investment	6,618	5,452
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 1 | U.S. Treasury and government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Level 1 | U.S. Treasury and government securities | Nonrelated Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 1 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Level 1 | Corporate debt securities | Nonrelated Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	203,644	98,848
Level 2 | Related Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Related party short-term investment	0	0
Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	47,915	24,209
Level 2 | U.S. Treasury and government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	35,854
Level 2 | U.S. Treasury and government securities | Nonrelated Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	74,656	74,639
Level 2 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	9,932
Level 2 | Corporate debt securities | Nonrelated Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	35,287
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Level 3 | Related Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Related party short-term investment	0	0
Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Level 3 | U.S. Treasury and government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Level 3 | U.S. Treasury and government securities | Nonrelated Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	$ 0
Level 3 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Level 3 | Corporate debt securities | Nonrelated Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 0

Fair Value Measurements and I_4

Fair Value Measurements and Investments - Schedule of Short-Term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	$ 110,026	$ 74,654
Unrealized Gains	0	7
Unrealized Losses	(83)	(22)
Fair Value	109,943	74,639
U.S. Treasury and government securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	74,697	74,654
Unrealized Gains	0	7
Unrealized Losses	(41)	(22)
Fair Value	74,656	$ 74,639
Corporate debt securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	35,329
Unrealized Gains	0
Unrealized Losses	(42)
Fair Value	$ 35,287

Fair Value Measurements and I_5

Fair Value Measurements and Investments - Schedule of Contractual Maturities of Short-Term Investments in Available-For-Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Due within one year	$ 109,943	$ 74,639

Fair Value Measurements and I_6

Fair Value Measurements and Investments - Schedule of Marketable Securities In Unrealized Loss Position (Details) $ in Thousands	Mar. 31, 2024 USD ($) security
U.S. Treasury and government securities
Investments in continuous loss position for less than 12 months:
Number of Securities | security	15
Fair Value	$ 72,156
Gross Unrealized Losses	$ (41)
Corporate debt securities
Investments in continuous loss position for less than 12 months:
Number of Securities | security	19
Fair Value	$ 35,287
Gross Unrealized Losses	$ (42)

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 32,725	$ 30,143
Less: Accumulated depreciation	(8,799)	(7,484)
Total property and equipment, net	23,926	22,659
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	24,672	23,873
Leasehold improvement
Property, Plant and Equipment [Line Items]
Total property and equipment	579	579
Furniture and Fixture
Property, Plant and Equipment [Line Items]
Total property and equipment	1,042	278
Computer hardware and software
Property, Plant and Equipment [Line Items]
Total property and equipment	724	11
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 5,708	$ 5,402

Property and Equipment, Net -_2

Property and Equipment, Net - Schedule of Depreciation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
Depreciation Expense	$ 1,315	$ 1,052

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Other Current Liabilities (Details) - USD ($) $ in Thousands		Mar. 31, 2024	Dec. 31, 2023
Payables and Accruals [Line Items]
Total accrued expenses and other current liabilities	[1]	$ 7,612	$ 14,110
Nonrelated Party
Payables and Accruals [Line Items]
Accrued employee compensation and benefits		3,062	8,270
Lab-related supplies and services		2,441	1,962
Accrued professional fees		1,138	2,273
Other		971	1,605
Total accrued expenses and other current liabilities		$ 7,612	$ 14,110
[1](1) Includes related party amount of $0.3 million as of December 31, 2023

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Nov. 30, 2021
Lessee, Lease, Description [Line Items]
Restricted cash	$ 13,496	$ 13,496
Operating lease right-of-use assets	55,528	13,941
Total operating lease liability	43,793
Prepaid expenses	(4,203)	(19,057)
60 First Street, Cambridge, Massachusetts Lease
Lessee, Lease, Description [Line Items]
Expected liability to be paid			$ 208,700
Term of contract, lease not yet commenced (in years)			10 years
Operating lease, extension (in years)			10 years
Restricted cash	13,100	$ 13,100
Operating lease right-of-use assets	44,900
Total operating lease liability	33,600
60 First Street, Cambridge, Massachusetts Lease | Revision of Prior Period, Reclassification, Adjustment
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets	11,300
Prepaid expenses	$ 11,300

Leases - Schedule of Maturity (

Leases - Schedule of Maturity (Details) $ in Thousands	Mar. 31, 2024 USD ($)
Leases [Abstract]
Remaining in 2024	$ 5,868
2025	18,584
2026	21,339
2027	20,812
2028	20,853
Thereafter	118,079
Total undiscounted lease payments	205,535
Less: payments related to leases not commenced	(129,866)
Less: imputed interest	(31,876)
Total operating lease liability	$ 43,793

Stockholder_s Equity (Details)

Stockholder’s Equity (Details) $ / shares in Units, $ in Millions	1 Months Ended
	Feb. 29, 2024 $ / shares shares	Nov. 30, 2023 USD ($)	Mar. 31, 2024 vote $ / shares
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock, par value under amendment (in dollars per share)			$ 0.0001
Number of votes per common share | vote			1
IPO
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of stock, number of shares issued (in shares) | shares	22,560,001
Sale of stock, price per share (in usd per share)	$ 6.25
Over-Allotment Option
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of stock, number of shares issued (in shares) | shares	3,360,000
Public Offering | Warrant Purchase Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of stock, price per share (in usd per share)	$ 6.24999
Pre-funded warrants sold (in shares) | shares	3,200,005
Exercise price of warrants (in dollars per share)	$ 0.00001
Sales Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of stock, consideration received | $		$ 300

Stock-Based Compensation - Narr

Stock-Based Compensation - Narrative (Details) - USD ($) $ in Millions		3 Months Ended
	Feb. 09, 2022	Mar. 31, 2024	Jan. 01, 2023
Options to purchase common stock | 2022 Stock Option and Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Percentage of annual increase in shares reserved for future issuance (as a percent)	5%
Shares issuable under plan (in shares)			4,868,856
Shares available for grant (in shares)		9,088,040
Options to purchase common stock | 2022 Stock Option and Incentive Plan and 2019 Equity Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Shares issuable under plan (in shares)		21,290,494
Employee Stock | 2022 Employee Stock Purchase Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Percentage of annual increase in shares reserved for future issuance (as a percent)	1%
Shares available for grant (in shares)		1,868,212
Shares issued under ESPP (in shares)		74,488
Additional shares allowable under plan (in shares)	971,350
Time-Based Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unrecognized compensation cost		$ 57.5
Unrecognized compensation costs, period of recognition (in years)		2 years 9 months 18 days
Performance-Based Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unrecognized compensation cost		$ 4.7
Restricted Stock, Time-Based
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unrecognized compensation costs, period of recognition (in years)		6 months
Unrecognized compensation expense		$ 0.1
Restricted Stock, Performance-Based
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unrecognized compensation expense		$ 0.3

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock Option Activity (Details)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Number of Shares
Beginning of period (in shares) | shares	7,641,863
Granted (in shares) | shares	3,898,410
Exercised (in shares) | shares	(9,664)
Cancelled or forfeited (in shares) | shares	(139,885)
End of period (in shares) | shares	11,390,724
Options vested and exercisable, end of period (in shares) | shares	2,838,246
Options vested and expected to vest, end of period (in shares) | shares	11,390,724
Weighted-Average Exercise Price
Beginning of period (in dollars per share) | $ / shares	$ 9.79
Granted (in dollars per share) | $ / shares	8.23
Exercised (in dollars per share) | $ / shares	3.73
Cancelled or forfeited (in dollars per share) | $ / shares	11.59
End of period (in dollars per share) | $ / shares	9.24
Options vested and exercisable, end of period (in dollars per share) | $ / shares	7.64
Options vested and expected to vest, end of period (in dollars per share) | $ / shares	$ 9.24
Performance-Based Stock Options
Number of Shares
Beginning of period (in shares) | shares	411,730
Granted (in shares) | shares	400,000
Exercised (in shares) | shares	0
Cancelled or forfeited (in shares) | shares	0
End of period (in shares) | shares	811,730
Options vested and exercisable, end of period (in shares) | shares	131,882
Weighted-Average Grant Date Fair Value
Beginning of period (in dollars per share) | $ / shares	$ 6.65
Granted (in dollars per share) | $ / shares	8.32
Exercised (in dollars per share) | $ / shares	0
Cancelled or forfeited (in dollars per share) | $ / shares	0
End of period (in dollars per share) | $ / shares	7.47
Vested and exercisable, end of period (in dollars per share) | $ / shares	$ 5.34

Stock-Based Compensation -Sched

Stock-Based Compensation -Schedule of Restricted Stock Activity (Details)	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Restricted Stock, Time-Based
Number of Shares
Beginning of period (in shares) | shares	903,227
Issued (in shares) | shares	0
Vested (in shares) | shares	(329,833)
Repurchased (in shares) | shares	0
End of period (in shares) | shares	573,394
Weighted-Average Grant-Date Fair Value
Beginning of period (in dollars per share) | $ / shares	$ 0.17
Issued (in dollars per share) | $ / shares	0
Vested (in dollars per share) | $ / shares	0.14
Repurchased (in dollars per share) | $ / shares	0
End of period (in dollars per share) | $ / shares	$ 0.19
Restricted Stock, Performance-Based
Number of Shares
Beginning of period (in shares) | shares	3,832,769
Issued (in shares) | shares	0
Vested (in shares) | shares	0
Repurchased (in shares) | shares	0
End of period (in shares) | shares	3,832,769
Weighted-Average Grant-Date Fair Value
Beginning of period (in dollars per share) | $ / shares	$ 0.07
Issued (in dollars per share) | $ / shares	0
Vested (in dollars per share) | $ / shares	0
Repurchased (in dollars per share) | $ / shares	0
End of period (in dollars per share) | $ / shares	$ 0.07

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Stock-Based Compensation Classification (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense	$ 5,209	$ 1,681
Research and development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense	2,725	1,170
General and administrative
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense	$ 2,484	$ 511

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Numerator:
Net loss attributable to common stockholders, basic	$ (45,761)	$ (39,397)
Net loss attributable to common stockholders, diluted	$ (45,761)	$ (39,397)
Denominator:
Weighted-average common shares outstanding, diluted (in shares)	104,466,178	89,064,895
Weighted-average common shares outstanding, basic (in shares)	104,466,178	89,064,895
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (0.44)	$ (0.44)
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (0.44)	$ (0.44)

Net Loss per Share - Schedule_2

Net Loss per Share - Schedule of Antidilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities (in shares)	15,928,769	14,475,709
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities (in shares)	11,522,606	6,945,214
Unvested restricted common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities (in shares)	4,406,163	7,530,495

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($)	1 Months Ended		3 Months Ended
	Feb. 29, 2024	Jan. 31, 2024	Mar. 31, 2024	Mar. 31, 2023
Co-Founder Shareholder | Scientific Consulting | Related Party
Related Party Transaction [Line Items]
Amounts of transaction			$ 37,500	$ 37,500
Myeloid Therapeutics
Related Party Transaction [Line Items]
Settlement payment — related party		$ 13,500,000
Jeffrey Marrazzo | Related Party
Related Party Transaction [Line Items]
Annual fee	$ 50,000
Jeffrey Marrazzo | Related Party | Advisory Services Agreement
Related Party Transaction [Line Items]
Sale of stock, number of shares issued (in shares)	250,000
Fair value as of grant date	$ 1,500,000