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Stockholder’s Equity	9 Months Ended
Stockholder’s Equity	Sep. 30, 2024
Equity [Abstract]
Stockholder’s Equity	Stockholder’s Equity Common Stock Under the Company’s Third Amended and Restated of Certificate of Incorporation, as amended, 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. In September 2024, the Company entered into the BMS Purchase Agreement pursuant to which the Company issued, and BMS purchased, in an unregistered offering (the “Offering”), 11,006,163 shares (the “Shares”) of the Company’s common stock for an aggregate purchase price of $55.0 million pursuant to the terms and conditions thereof. The BMS Purchase Agreement includes lock-up restrictions with respect to the Shares. Pursuant to the terms of the BMS Purchase Agreement, BMS has agreed not to, directly or indirectly, sell or transfer any of the Shares until September 30, 2027 subject to specified conditions and exceptions. In addition, the Company agreed, among other things, to file with the Securities and Exchange Commission a registration statement covering the resale of the Shares and to use commercially reasonable efforts to cause such registration statement to become effective on or prior to ninety (90) calendar days after closing. Please refer to Note 9, Significant Agreements, for additional discussion of the BMS Collaboration Agreement. 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 any time. As of September 30, 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 AgreementSM (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 September 30, 2024, there have been no sales of common stock pursuant to the Sales Agreement.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Leases (Tables)

9 Months Ended

Sep. 30, 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 September 30, 2024:


(in thousands)	Undiscounted Amounts
Undiscounted lease payments:
Remaining in 2024	$	1,591
2025	19,773
2026	23,387
2027	22,921
2028	22,294
Thereafter	118,079
Total undiscounted lease payments	208,045
Less: payments related to leases not commenced	(136,637)
Less: imputed interest	(30,160)
Total operating lease liability	$	41,248

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, 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]
Change in unrealized loss on investments, net of tax	235
Net loss	(132,490)
Ending balance (in shares) at Sep. 30, 2023		97,324,301
Ending balance at Sep. 30, 2023	193,957	$ 2	619,791	(149)	(425,687)
Beginning balance (in shares) at Mar. 31, 2023		97,227,809
Beginning balance at Mar. 31, 2023	278,801	$ 2	611,598	(205)	(332,594)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		42,106
Issuance of common stock upon exercise of stock options	166		166
Stock-based compensation expense	3,583		3,583
Change in unrealized loss on investments, net of tax	(63)			(63)
Net loss	(42,385)				(42,385)
Ending balance (in shares) at Jun. 30, 2023		97,269,915
Ending balance at Jun. 30, 2023	240,102	$ 2	615,347	(268)	(374,979)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		54,386
Issuance of common stock upon exercise of stock options	227		227
Stock-based compensation expense	4,217		4,217
Change in unrealized loss on investments, net of tax	119			119
Net loss	(50,708)				(50,708)
Ending balance (in shares) at Sep. 30, 2023		97,324,301
Ending balance at Sep. 30, 2023	$ 193,957	$ 2	619,791	(149)	(425,687)
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 (in shares)		22,560,001
Issuance of common stock	132,055		132,055
Issuance of pre-funded warrants, net of issuance costs of $1.2 million	18,800		18,800
Issuances of common stock under the employee stock purchase plan (in shares)		74,488
Issuances of common stock under the employee stock purchase plan	436		436
Issuance of common stock upon exercise of stock options (in shares)		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
Ending balance at Mar. 31, 2024	$ 243,766	$ 2	780,950	(95)	(537,091)
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 upon exercise of stock options (in shares)	28,048
Change in unrealized loss on investments, net of tax	$ 36
Net loss	$ (153,606)
Ending balance (in shares) at Sep. 30, 2024	131,160,842	131,160,842
Ending balance at Sep. 30, 2024	$ 189,504	$ 2	834,417	21	(644,936)
Beginning balance (in shares) at Mar. 31, 2024		120,021,274
Beginning balance at Mar. 31, 2024	243,766	$ 2	780,950	(95)	(537,091)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		9,539
Issuance of common stock upon exercise of stock options	35		35
Stock-based compensation expense	8,091		8,091
Change in unrealized loss on investments, net of tax	24			24
Net loss	(55,327)				(55,327)
Ending balance (in shares) at Jun. 30, 2024		120,030,813
Ending balance at Jun. 30, 2024	196,589	$ 2	789,076	(71)	(592,418)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock (in shares)		11,006,163
Issuance of common stock	38,081		38,081
Issuances of common stock under the employee stock purchase plan (in shares)		115,021
Issuances of common stock under the employee stock purchase plan	401		401
Issuance of common stock upon exercise of stock options (in shares)		8,845
Issuance of common stock upon exercise of stock options	32		32
Stock-based compensation expense	6,827		6,827
Change in unrealized loss on investments, net of tax	92			92
Net loss	$ (52,518)				(52,518)
Ending balance (in shares) at Sep. 30, 2024	131,160,842	131,160,842
Ending balance at Sep. 30, 2024	$ 189,504	$ 2	$ 834,417	$ 21	$ (644,936)

Fair Value Measurements and Investments (Tables)

9 Months Ended

Sep. 30, 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 September 30, 2024:
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	59,329	$	—	$	59,329

Corporate debt securities	—		995		—		995
Short-term investments:
U.S. Treasury and government securities	—		40,603		—		40,603
Corporate debt securities	—		12,039		—		12,039
Related party short-term investment:
Beam equity securities	4,908		—		—		4,908
Total cash equivalents and investments	$	4,908	$	112,966	$	—	$	117,874


	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 September 30, 2024:
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Short-term investments in debt securities:
U.S. Treasury and government securities	$	40,585	$	18	$	—	$	40,603
Corporate debt securities	12,035		4		—		12,039


Total short-term investments in debt securities	$	52,620	$	22	$	—	$	52,642


	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 September 30, 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:

Corporate debt securities	2	$	3,995	$	—

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)	September 30, 2024		December 31, 2023
Due within one year	$	52,642	$	74,639

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
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-URI https://asc.fasb.org/1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 35,166	$ 30,143
Less: Accumulated depreciation	(11,879)	(7,484)
Total property and equipment, net	23,287	22,659
Laboratory equipment
Property, Plant and Equipment [Line Items]
Total property and equipment	26,024	23,873
Leasehold improvement
Property, Plant and Equipment [Line Items]
Total property and equipment	5,463	579
Furniture and Fixture
Property, Plant and Equipment [Line Items]
Total property and equipment	1,059	278
Computer hardware and software
Property, Plant and Equipment [Line Items]
Total property and equipment	869	11
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 1,751	$ 5,402

Net Loss per Share

9 Months Ended

Sep. 30, 2024

Earnings Per Share [Abstract]

Net Loss per Share

Basic and diluted net loss per common share attributable to common stockholders was calculated as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands, except share and per share amounts)	2024		2023		2024		2023
Numerator:



Net loss attributable to common stockholders	$	(52,518)	$	(50,708)	$	(153,606)	$	(132,490)
Denominator:
Weighted-average common shares outstanding, basic and diluted	119,764,270		91,846,835		114,492,416		90,469,866
Net loss per share attributable to common stockholders, basic and diluted	$	(0.44)	$	(0.55)	$	(1.34)	$	(1.46)

The weighted-average number of common shares outstanding used in the basic and diluted net loss per share calculations includes the weighted-average effect of pre-funded warrants sold by the Company to purchase 3,200,005 shares of the Company's common stock. The shares of common stock underlying the pre-funded warrants are considered outstanding for the purposes of computing earnings per share, because the shares may be issued for little or no consideration, they are fully vested, and the pre-funded warrants are immediately exercisable upon their issuance date.

Diluted net loss per share available to common stockholders is 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 September 30,
	2024	2023
Anti-dilutive common stock equivalents:
Options to purchase common stock	12,061,612	7,634,966
Unvested restricted common stock	3,565,262	5,094,769
Total anti-dilutive common stock equivalents:	15,626,874	12,729,735

Stock-Based Compensation - Schedule of Stock Option Activity (Details) - $ / shares	9 Months Ended
	Sep. 30, 2024
Number of Shares
Beginning of period (in shares)	7,641,863
Granted (in shares)	4,434,710
Exercised (in shares)	(28,048)
Cancelled or forfeited (in shares)	(372,121)
End of period (in shares)	11,676,404
Options vested and exercisable, end of period (in shares)	4,335,142
Options vested and expected to vest, end of period (in shares)	11,676,404
Weighted-Average Exercise Price
Beginning of period (in dollars per share)	$ 9.79
Granted (in dollars per share)	8.03
Exercised (in dollars per share)	3.69
Cancelled or forfeited (in dollars per share)	11.02
End of period (in dollars per share)	9.10
Options vested and exercisable, end of period (in dollars per share)	8.63
Options vested and expected to vest, end of period (in dollars per share)	$ 9.10
Performance-Based Stock Options
Number of Shares
Beginning of period (in shares)	411,730
Granted (in shares)	650,000
Exercised (in shares)	0
Cancelled or forfeited (in shares)	0
End of period (in shares)	1,061,730
Options vested and exercisable, end of period (in shares)	385,208
Weighted-Average Grant Date Fair Value
Beginning of period (in dollars per share)	$ 6.65
Granted (in dollars per share)	7.74
Exercised (in dollars per share)	0
Cancelled or forfeited (in dollars per share)	0
End of period (in dollars per share)	7.31
Vested and exercisable, end of period (in dollars per share)	$ 6.72

Leases

9 Months Ended

Sep. 30, 2024

Leases [Abstract]

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. Subsequent to the initial non-cancelable term of the lease of ten years, 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 September 30, 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 neither of which are highly dependent nor highly related to each other. The Company allocated the consideration among the three lease components based on their relative fair market values.

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 is 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.

Arsenal Street, Watertown, Massachusetts Leases

In August 2024, the Company entered into the third amendment to its existing lease for approximately 16,000 square feet of combined laboratory and office space at 480 Arsenal Street (the “480 Arsenal Amendment”). In September 2024, the Company entered into a new lease for approximately 48,500 square feet of combined laboratory and office

space at 500 Arsenal Street (the “500 Arsenal Lease”). The landlords of the spaces at 480 Arsenal Street and 500 Arsenal Street are affiliates.

The 480 Arsenal Amendment provides the Company with an additional 9,400 square feet of combined laboratory and office space (the “Expansion Space”) at no additional cost and also provides an early termination date for the existing space and the Expansion Space as the later of: 1) the date occurring 150 days after the lease commencement of 500 Arsenal Lease, or 2) 30 days after substantial completion, as defined in the 500 Arsenal Lease, of tenant improvements at 500 Arsenal Street. If the 500 Arsenal Lease is terminated prior to its lease commencement such that the lease commencement never occurs, the Company will begin paying lease payments on the Expansion Space at the current rate for its existing space at 480 Arsenal Street and the early termination provisions of the 480 Arsenal Amendment become null and void.

The 500 Arsenal Lease term is expected to commence in December 2024 with a base term of 11 months. Subsequent to the base term, the Company has an option to extend the lease through August 2028. The Company secured the lease with a $0.6 million security deposit, which was recorded as restricted cash on the condensed consolidated balance sheets as of September 30, 2024. The 500 Arsenal Lease also provides a tenant improvement allowance of $2.4 million and an additional tenant improvement allowance of $1.2 million, which the Company would be obligated to repay to the landlord.

Accounting Considerations

As the 480 Arsenal Amendment and the 500 Arsenal Lease meet the criteria for combining contracts under ASC 842, the Company determined that both 480 Arsenal Amendment and the 500 Arsenal Lease are modifications to its existing lease at 480 Arsenal Street. Within the combined contract the Company identified two 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 the other. The Company allocated the consideration under the combined contract among the two lease components based on their relative fair market value. In calculating the allocable consideration and the fair market value of each lease component, the Company determined it is probable that it will exercise the option to extend the lease term provided under the 500 Arsenal Lease.

In accordance with ASC 842, the Company possessed the ability to control and derive the economic benefit for its leased space at 480 Arsenal on the effective date of the modification. Therefore, on the effective date, the Company recorded a right-of-use asset and a corresponding lease liability, neither of which were materially different from the existing right-of-use asset and lease liability as of the modification date.

For accounting purposes, the lease commencement for 500 Arsenal is expected to occur in the first quarter of 2025. Consideration paid for this lease component is recorded as prepaid expense on the condensed consolidated balance sheets and is not recognized until lease commences.

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 September 30, 2024:


(in thousands)	Undiscounted Amounts
Undiscounted lease payments:
Remaining in 2024	$	1,591
2025	19,773
2026	23,387
2027	22,921
2028	22,294
Thereafter	118,079
Total undiscounted lease payments	208,045
Less: payments related to leases not commenced	(136,637)
Less: imputed interest	(30,160)
Total operating lease liability	$	41,248

Fair Value Measurements and Investments - Schedule of Hierarchy For Assets and Liabilities Measured At Fair Value On A Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 52,642	$ 74,639
Total assets	117,874	104,300
Related Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Related party short-term investment	4,908	5,452
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	59,329	24,209
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	995
Short-term investments	12,039
Corporate debt securities \| Nonrelated Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	12,039
U.S. Treasury and government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	40,603	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	40,603	74,639
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	4,908	5,452
Level 1 \| Related Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Related party short-term investment	4,908	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 \| 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 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 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	112,966	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	59,329	24,209
Level 2 \| Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	995
Level 2 \| Corporate debt securities \| Nonrelated Party
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	12,039
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	40,603	74,639
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 \| 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
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

Net Loss per Share (Tables)

9 Months Ended

Sep. 30, 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 September 30,				Nine Months Ended September 30,
(in thousands, except share and per share amounts)	2024		2023		2024		2023
Numerator:



Net loss attributable to common stockholders	$	(52,518)	$	(50,708)	$	(153,606)	$	(132,490)
Denominator:
Weighted-average common shares outstanding, basic and diluted	119,764,270		91,846,835		114,492,416		90,469,866
Net loss per share attributable to common stockholders, basic and diluted	$	(0.44)	$	(0.55)	$	(1.34)	$	(1.46)

Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share


	As of September 30,
	2024	2023
Anti-dilutive common stock equivalents:
Options to purchase common stock	12,061,612	7,634,966
Unvested restricted common stock	3,565,262	5,094,769
Total anti-dilutive common stock equivalents:	15,626,874	12,729,735

Nature of the Business and Basis of Presentation	9 Months Ended
Nature of the Business and Basis of Presentation	Sep. 30, 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. The Company is deploying Prime Editing technology, which it believes 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. On September 28, 2024 (the “Effective Date”), the Company entered into a Research Collaboration and License Agreement (the “BMS Collaboration Agreement”) with Juno Therapeutics, Inc., a wholly-owned subsidiary of the Bristol-Myers Squibb Company (“BMS”). Additionally, on the Effective Date, the Company entered into a Securities Purchase Agreement (the “BMS Purchase Agreement”) with BMS, pursuant which the Company agreed to sell and issue shares of its common stock to BMS. The BMS Collaboration Agreement and the BMS Purchase Agreement are discussed in greater detail in Note 9, Significant Agreements. Under the BMS Collaboration Agreement, the Company received the $55.0 million equity investment in September 2024 and the $55.0 million upfront payment in October 2024. Since its inception, the Company has incurred substantial losses and, as of September 30, 2024, the Company had an accumulated deficit of $644.9 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 of $175.5 million as of September 30, 2024, along with the $55.0 million upfront payment received from BMS in October 2024 discussed above, will be sufficient to fund its operations for at least the next twelve months from the date of issuance of these financial statements. 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. 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 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 September 30, 2024, the results of its operations for the three and nine months ended September 30, 2024 and 2023, the condensed consolidated statements of stockholders’ equity for the three and nine months ended September 30, 2024 and 2023, and its cash flows for the nine months ended September 30, 2024 and 2023. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2024 and 2023 are also unaudited. The results for the three and nine months ended September 30, 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. Change in Presentation For the three and nine months ended September 30, 2024, “Other income, net” as presented on the condensed consolidated statements of operations and comprehensive loss was disaggregated into “Accretion (amortization) of investments,” “Interest income,” and “Other income, net”. This presentation has been conformed for all previous periods presented and had no impact on previously reported results.

Significant Agreements - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions			1 Months Ended
	Sep. 30, 2024	Sep. 28, 2024	Sep. 30, 2024	Dec. 31, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock, par or stated value (in dollars per share)	$ 0.00001		$ 0.00001	$ 0.00001
Juno Therapeutics, Inc. \| Collaborative Arrangement, Research Collaboration and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment		$ 55.0
Milestone payments		3,500.0
Preclinical milestones		185.0
Developmental milestones		1,200.0
Commercialization milestones		2,100.0
Juno Therapeutics, Inc. \| Collaborative Arrangement, Research Collaboration and License Agreement \| Common Stock
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued to collaborating party (in shares)	$ 55.0		$ 55.0
Juno Therapeutics, Inc. \| Collaborative Arrangement, Stock Purchase Agreement \| Common Stock
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Stock issued to collaborating party (in shares)	$ 55.0
Fair value of common stock	11,006,163
Juno Therapeutics, Inc. \| Collaborative Arrangement, BMS Collaboration Agreement Accounting
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment		$ 72.0

Property and Equipment, Net - Schedule of Depreciation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Property, Plant and Equipment [Abstract]
Depreciation Expense	$ 1,558	$ 1,236	$ 4,411	$ 3,406

Stock-Based Compensation -Schedule of Restricted Stock Activity (Details)	9 Months Ended
	Sep. 30, 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	(806,085)
Repurchased (in shares) \| shares	(4,423)
End of period (in shares) \| shares	92,719
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	0.15
Repurchased (in dollars per share) \| $ / shares	0.34
End of period (in dollars per share) \| $ / shares	$ 0.32
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	(360,226)
Repurchased (in shares) \| shares	0
End of period (in shares) \| shares	3,472,543
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	0.18
Repurchased (in dollars per share) \| $ / shares	0
End of period (in dollars per share) \| $ / shares	$ 0.06

Related Party Transactions (Tables)

9 Months Ended

Sep. 30, 2024

Supplemental Information related to the BMS Collaboration Agreement

Supplemental information related to the BMS Collaboration Agreement consisted of the following as of September 30, 2024 (in thousands):


Collaboration receivable — related party	$	55,000
Deferred revenue — related party	9,280
Deferred revenue, net of current — related party	62,639

he Company and BMS, a related party, entered into the BMS Collaboration Agreement and the BMS Purchase Agreement. BMS is a related party due to its share of ownership of the Company.

The Company recognized the following amounts related to BMS (in thousands):


Collaboration receivable — related party	$	55,000
Deferred revenue — related party	9,280
Deferred revenue, net of current — related party	62,639

Property and Equipment, Net

9 Months Ended

Sep. 30, 2024

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

Property and equipment, net consisted of the following:


(in thousands)	September 30, 2024		December 31, 2023
Property and equipment:
Laboratory equipment	$	26,024	$	23,873
Leasehold improvement	5,463		579
Furniture and Fixture	1,059		278
Computer hardware and software	869		11
Construction in progress	1,751		5,402
Total property and equipment	35,166		30,143
Less: Accumulated depreciation	(11,879)		(7,484)
Total property and equipment, net	$	23,287	$	22,659

Depreciation expense related to property and equipment is as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2024		2023		2024		2023
Depreciation Expense	$	1,558	$	1,236	$	4,411	$	3,406

Fair Value Measurements and Investments - Schedule of Short-Term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	$ 52,620	$ 74,654
Unrealized Gains	22	7
Unrealized Losses	0	(22)
Fair Value	52,642	74,639
U.S. Treasury and government securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	40,585	74,654
Unrealized Gains	18	7
Unrealized Losses	0	(22)
Fair Value	40,603	$ 74,639
Corporate debt securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	12,035
Unrealized Gains	4
Unrealized Losses	0
Fair Value	$ 12,039

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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- Definition

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

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-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Section 50
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-Subparagraph (b)
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-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Section 50
-Paragraph 3
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-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

Net Loss per Share - Schedule of Antidilutive Securities (Details) - shares	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities (in shares)	15,626,874	12,729,735
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities (in shares)	12,061,612	7,634,966
Unvested restricted common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities (in shares)	3,565,262	5,094,769

Property and Equipment, Net (Tables)

9 Months Ended

Sep. 30, 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)	September 30, 2024		December 31, 2023
Property and equipment:
Laboratory equipment	$	26,024	$	23,873
Leasehold improvement	5,463		579
Furniture and Fixture	1,059		278
Computer hardware and software	869		11
Construction in progress	1,751		5,402
Total property and equipment	35,166		30,143
Less: Accumulated depreciation	(11,879)		(7,484)
Total property and equipment, net	$	23,287	$	22,659

Depreciation expense related to property and equipment is as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2024		2023		2024		2023
Depreciation Expense	$	1,558	$	1,236	$	4,411	$	3,406

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($)
$ in Thousands

Sep. 30, 2024

Dec. 31, 2023

Common stock, par or stated value (in dollars per share)

$ 0.00001

Common stock, shares authorized (in shares)

775,000,000

Common stock, shares issued (in shares)

131,160,842

97,377,121

Common stock, shares outstanding (in shares)

131,160,842

97,377,121

Accrued expenses and other current liabilities

^[1]

$ 18,684

$ 14,110

$ 100

[1]	(1) Includes related party amount of $0.1 million as of December 31, 2023

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($)
$ in Thousands

3 Months Ended

9 Months Ended

Sep. 30, 2024

Sep. 30, 2023

Sep. 30, 2024

Sep. 30, 2023

Income Statement [Abstract]

Collaboration revenue

$ 209

$ 0

$ 800

$ 0

Operating expenses:

Research and development

^[1]

40,340

40,967

121,185

106,446

General and administrative

14,101

10,492

37,860

30,303

Total operating expenses

54,441

51,459

159,045

136,749

Loss from operations

(54,232)

(51,459)

(158,245)

(136,749)

Other income:

Amortization of premiums and discount on short-term investments

885

1,769

3,201

4,551

Interest income

697

410

1,984

2,320

Change in fair value of short-term investment — related party

215

(1,579)

(544)

(3,017)

Other income, net

(83)

(2)

126

Total other income, net

1,714

643

4,639

3,980

Net loss before income taxes

(52,518)

(50,816)

(153,606)

(132,769)

Benefit from income taxes

108

279

Net loss attributable to common stockholders, basic

(52,518)

(50,708)

(153,606)

(132,490)

Net loss attributable to common stockholders, diluted

$ (52,518)

$ (50,708)

$ (153,606)

$ (132,490)

Net loss per share attributable to common stockholders, basic (in dollars per share)

$ (0.44)

$ (0.55)

$ (1.34)

$ (1.46)

Net loss per share attributable to common stockholders, diluted (in dollars per share)

$ (0.44)

$ (0.55)

$ (1.34)

$ (1.46)

Weighted-average common shares outstanding, basic (in shares)

119,764,270

91,846,835

114,492,416

90,469,866

Weighted-average common shares outstanding, diluted (in shares)

119,764,270

91,846,835

114,492,416

90,469,866

Comprehensive loss:

Net loss

$ (52,518)

$ (50,708)

$ (153,606)

$ (132,490)

Change in unrealized loss on investments, net of tax

119

235

Comprehensive loss

$ (52,426)

$ (50,589)

$ (153,570)

$ (132,255)

[1]	(1) Includes related party amount of $0.1 million and $0.8 million for the three and nine months ended September 30, 2023.

Net Loss per Share - Narrative (Details)	9 Months Ended
Net Loss per Share - Narrative (Details)	Sep. 30, 2024 shares
Earnings Per Share [Abstract]
Weighted-average effect of pre-funded warrants (in shares)	3,200,005

Fair Value Measurements and Investments - Schedule of Contractual Maturities of Short-Term Investments in Available-For-Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Due within one year	$ 52,642	$ 74,639

Leases - Narrative (Details) $ in Thousands	1 Months Ended
Leases - Narrative (Details) $ in Thousands	Aug. 31, 2024 ft²	Sep. 30, 2024 USD ($) ft²	Dec. 31, 2023 USD ($)	Nov. 30, 2021
Lessee, Lease, Description [Line Items]
Restricted cash		$ 14,062	$ 13,496
Operating lease right-of-use assets		49,364	13,941
Total operating lease liability		41,248
Prepaid expenses		(6,006)	(19,057)
60 First Street, Cambridge, Massachusetts Lease
Lessee, Lease, Description [Line Items]
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
480 Arsenal Amendment
Lessee, Lease, Description [Line Items]
Area of operating lease \| ft²	16,000
500 Arsenal Lease
Lessee, Lease, Description [Line Items]
Term of contract, lease not yet commenced (in years)		11 months
Restricted cash		$ 600
Area of operating lease \| ft²		48,500
Tenant Improvements		$ 2,400
500 Arsenal Lease, Additional Tenant Improvement Allowance
Lessee, Lease, Description [Line Items]
Tenant Improvements		$ 1,200
Expansion Space
Lessee, Lease, Description [Line Items]
Area of operating lease \| ft²	9,400
Expansion Space, Termination Period One
Lessee, Lease, Description [Line Items]
Termination period	150 days
Expansion Space, Termination Period Two
Lessee, Lease, Description [Line Items]
Termination period	30 days

Related Party Transactions - Supplemental Information related to the BMS Collaboration Agreement (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Collaboration receivable — related party	$ 55,000	$ 0
Deferred revenue — related party	9,280	0
Deferred revenue, net of current — related party	62,639	$ 0
Juno Therapeutics, Inc. \| Collaborative Arrangement, Research Collaboration and License Agreement
Related Party Transaction [Line Items]
Collaboration receivable — related party	55,000
Deferred revenue — related party	9,280
Deferred revenue, net of current — related party	$ 62,639

Cover - shares	9 Months Ended
Cover - shares	Sep. 30, 2024	Oct. 31, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 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	60 First Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02141
City Area Code	(617)
Local Phone Number	465-0013
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		131,160,842
Entity Central Index Key	0001894562
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 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 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 September 30, 2024, the results of its operations for the three and nine months ended September 30, 2024 and 2023, the condensed consolidated statements of stockholders’ equity for the three and nine months ended September 30, 2024 and 2023, and its cash flows for the nine months ended September 30, 2024 and 2023. The financial data and other information disclosed in these notes related to the three and nine months ended September 30, 2024 and 2023 are also unaudited. The results for the three and nine months ended September 30, 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. 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.
Revenue recognition and Milestone payments	Revenue recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers, (“ASC 606”). This standard applies to all contracts with customers, except for contracts that are within the scope of other standards. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. The Company enters into collaboration and licensing agreements with partners, which are within the scope of ASC 606, under which it may exclusively license rights to research, develop, manufacture, and commercialize product candidates to third parties. The terms of these arrangements typically include payment to the Company of one or more of the following: (1) non-refundable, upfront fees; (2) equity investment; (3) reimbursement of certain costs; (4) customer option fees for additional goods or services; (5) development milestone payments; (6) regulatory milestone payments; (7) commercial milestone payments; and (8) royalties on net sales of licensed products. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. As part of the accounting for these arrangements, the Company must use its judgment to determine: (a) the number of performance obligations based on the determination under step (ii) above; (b) the transaction price under step (iii) above; (c) the stand-alone selling price for each performance obligation identified in the contract for the allocation of transaction price in step (iv) above; and (d) the contract term and pattern of satisfaction of the performance obligations under step (v) above. The Company uses judgment to determine whether milestones or other variable consideration, except for royalties, should be included in the transaction price as described further below. The transaction price is allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Amounts due to the Company for satisfying the revenue recognition criteria or that are contractually due based upon the terms of the collaboration agreements are recorded as collaboration receivable in the Company’s condensed consolidated balance sheet. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s condensed consolidated balance sheets. Deferred revenue expected to be recognized as revenue within 12 months following the balance sheet date are classified as current deferred revenue. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current. Milestone payments At the inception of each arrangement that includes development milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether it is probable that a significant revenue reversal would not occur. At the end of each subsequent reporting period, the Company reevaluates the probability of achievement of all milestones subject to constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment.
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 In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires all public entities, including public entities with a single reportable segment, to provide in interim and annual periods one or more measures of segment profit or loss used by the chief operating decision maker to allocate resources and assess performance. In addition, this guidance requires disclosures of significant segment expenses and other segment items as well as incremental qualitative disclosures. This guidance is effective for fiscal years beginning after December 15, 2023, and interim periods after December 15, 2024, with retrospective application required, and early adoption permitted. The Company is currently in the process of evaluating the effects of this guidance on its related disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which requires enhanced income tax disclosures, including specific categories and disaggregation of information in the effective tax rate reconciliation, disaggregated information related to income taxes paid, income or loss from continuing operations before income tax expense or benefit, and income tax expense or benefit from continuing operations. This guidance is effective for annual periods beginning after December 15, 2024, with early adoption permitted. The Company is currently in the process of evaluating the impact of this pronouncement on its related disclosures. In November 2024, the FASB issued ASU 2024-03, Disaggregation of Income Statement Expenses, which requires more detailed information about specified categories of expenses included in certain expense captions presented on the face of the income statement. This ASU is effective for fiscal years beginning after December 15, 2026, and for interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. The amendments may be applied either (1) prospectively to financial statements issued for reporting periods after the effective date of this ASU or (2) retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact this ASU will have on its disclosures. Other 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 the Company’s financial statements upon adoption

- Definition

Disclosure of accounting policy for revenue from contract with customer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 19
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-19

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-18

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
-Paragraph 20
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-20

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
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-Name Accounting Standards Codification
-Section 50
-Paragraph 20
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-20

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
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Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Name Accounting Standards Codification
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Topic 606
-Publisher FASB
-URI https://asc.fasb.org/606/tableOfContent

+ Details

Stock-Based Compensation

9 Months Ended

Sep. 30, 2024

Share-Based Payment Arrangement [Abstract]

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 September 30, 2024, the Company had 21,522,110 shares reserved under the 2022 Plan and the 2019 Plan, and 8,783,976 shares available for issuance under the 2022 Plan.

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 September 30, 2024, the Company had 1,753,191 shares available for issuance under the 2022 Plan.

During the nine months ended September 30, 2024, the Company issued 189,509 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 nine months ended September 30, 2024:


	Number of Shares	Weighted-Average Exercise Price
Outstanding at December 31, 2023	7,641,863	$	9.79
Granted	4,434,710	8.03
Exercised	(28,048)	3.69
Cancelled or forfeited	(372,121)	11.02
Outstanding at September 30, 2024	11,676,404	$	9.10
Options vested and exercisable at September 30, 2024	4,335,142	$	8.63
Options vested and expected to vest at September 30, 2024	11,676,404	$	9.10

As of September 30, 2024, there was $46.7 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 2.4 years.

Performance-Based Stock Options

The following table summarizes the Company’s performance-based stock option activity for the nine months ended September 30, 2024:


	Number of Shares	Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2023	411,730	$	6.65
Granted	650,000	7.74
Exercised	—	—
Cancelled or forfeited	—	—
Outstanding at September 30, 2024	1,061,730	$	7.31
Vested and exercisable at September 30, 2024	385,208	$	6.72

As of September 30, 2024, there was $3.2 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 nine months ended September 30, 2024:


	Number of Shares	Weighted-Average Grant-Date Fair Value
Outstanding at December 31, 2023	903,227	$	0.17
Issued	—	—
Vested	(806,085)	0.15
Repurchased	(4,423)	0.34
Outstanding at September 30, 2024	92,719	$	0.32

Performance-Based Restricted Common Stock

The following table summarizes the Company’s performance-based restricted common stock activity for the nine months ended September 30, 2024:


	Number of Shares	Weighted-Average Grant-Date Fair Value
Outstanding at December 31, 2023	3,832,769	$	0.07
Issued	—	—
Vested	(360,226)	0.18
Repurchased	—	—
Outstanding at September 30, 2024	3,472,543	$	0.06

As of September 30, 2024, there was $0.2 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 September 30,				Nine Months Ended September 30,
(in thousands)	2024		2023		2024		2023
Stock-based compensation expense:
Research and development	$	2,982	$	2,224	$	9,928	$	5,558
General and administrative	3,845		1,993		10,199		3,923
Total stock-based compensation expense	$	6,827	$	4,217	$	20,127	$	9,481

Accrued Expenses and Other Current Liabilities (Tables)

9 Months Ended

Sep. 30, 2024

Payables and Accruals [Abstract]

Schedule of Accrued Liabilities

Accrued expenses and other current liabilities consisted of the following:


(in thousands)	September 30, 2024		December 31, 2023
Accrued expenses and other current liabilities
Accrued employee compensation and benefits	$	7,510	$	8,270
Accrued professional fees	5,575		2,273
Accrued license fee	4,197		—
Lab-related supplies and services	296		1,962
Other	1,106		1,605
Total accrued expenses and other current liabilities	$	18,684	$	14,110

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows used in operating activities:
Net loss	$ (153,606)	$ (132,490)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	20,127	9,481
Non cash lease expense	10,147	9,440
Depreciation expense	4,411	3,406
Change in fair value of short-term investment — related party	544	3,017
Amortization of premiums and discount on short-term investments	(2,949)	(2,320)
Deferred income taxes	0	(279)
Changes in operating assets and liabilities:
Collaboration receivable — related party	(55,000)	0
Prepaid expenses and other current assets	(9,466)	(9,040)
Accounts payable	(7,717)	6,861
Accrued expenses and other current liabilities	1,987	(755)
Accrued settlement payment — related party	(13,500)	0
Deferred revenue — related party	71,919	0
Lease liabilities	(6,007)	(8,869)
Net cash used in operating activities	(139,110)	(121,548)
Cash flows provided by (used in) investing activities:
Maturities of investments	171,300	85,021
Purchases of investments	(146,317)	(100,541)
Purchases of property and equipment	(5,503)	(6,884)
Return (payments) of security deposits	724	(170)
Net cash provided by (used in) investing activities	20,204	(22,574)
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 issuance of common under the BMS Securities Purchase Agreement — related party	38,081	0
Proceeds from research and development funding liability	6,000	0
Proceeds from ESPP offerings	836	0
Net proceeds from stock option exercises	103	461
Net cash provided by financing activities	195,875	461
Net change in cash, cash equivalents, and restricted cash	76,969	(143,661)
Cash, cash equivalents, and restricted cash at beginning of period	55,070	201,116
Cash, cash equivalents, and restricted cash at end of period	132,039	57,455
Reconciliation of cash, cash equivalents and restricted cash:
Cash, cash equivalents, and restricted cash at end of period	132,039	57,455
Less: restricted cash	14,062	13,496
Total cash, and cash equivalents	117,977	43,959
Supplemental cash flow information:
Right-of-use assets obtained in exchange for new operating lease liabilities	44,935	3,265
Decrease in right-of-use assets due to lease termination	0	6,100
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued expenses	$ 111	$ 513

Related Party Transactions - Narrative (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Feb. 29, 2024	Jan. 31, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Co-Founder Shareholder \| Scientific Consulting \| Related Party
Related Party Transaction [Line Items]
Amounts of transaction			$ 25,000,000	$ 37,500	$ 100,000,000	$ 112,500
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

Significant Agreements - Supplemental Information related to the BMS Collaboration Agreement (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration receivable — related party	$ 55,000	$ 0
Deferred revenue — related party	9,280	0
Deferred revenue, net of current — related party	62,639	$ 0
Juno Therapeutics, Inc. \| Collaborative Arrangement, Research Collaboration and License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration receivable — related party	55,000
Deferred revenue — related party	9,280
Deferred revenue, net of current — related party	$ 62,639

Accrued Expenses - Schedule of Other Current Liabilities (Details) - USD ($)
$ in Thousands

Sep. 30, 2024

Dec. 31, 2023

Payables and Accruals [Abstract]

Accrued employee compensation and benefits

$ 7,510

$ 8,270

Accrued professional fees

5,575

2,273

Accrued license fee

4,197

Lab-related supplies and services

296

1,962

Other

1,106

1,605

Total accrued expenses and other current liabilities

^[1]

$ 18,684

$ 14,110

[1]	(1) Includes related party amount of $0.1 million as of December 31, 2023

Fair Value Measurements and Investments - Schedule of Marketable Securities In Unrealized Loss Position (Details) - Corporate debt securities $ in Thousands	Sep. 30, 2024 USD ($) security
Investments in continuous loss position for less than 12 months:
Number of Securities \| security	2
Fair Value	$ 3,995
Gross Unrealized Losses	$ 0

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($)
$ in Thousands

Sep. 30, 2024

Dec. 31, 2023

Current assets:

Cash and cash equivalents

$ 117,977

$ 41,574

Collaboration receivable — related party

55,000

Prepaid expenses

6,006

19,057

Other current assets

9,538

2,254

Total current assets

246,071

142,976

Property and equipment, net

23,287

22,659

Operating lease right-of-use assets

49,364

13,941

Restricted cash

14,062

13,496

Other assets

779

Total assets

332,784

193,851

Current liabilities:

Accounts payable

5,429

19,537

Accrued expenses and other current liabilities

^[1]

18,684

14,110

Accrued settlement payment — related party

13,500

Deferred revenue — related party

9,280

Operating lease liability

4,484

9,276

Total current liabilities

37,877

56,423

Deferred revenue, net of current — related party

62,639

Operating lease liability, net of current

36,764

4,357

Research and development funding liability

6,000

Total liabilities

143,280

60,780

Commitments and contingencies

Stockholders’ equity

Common stock, par value of $0.00001 per share; 775,000,000 shares authorized; 131,160,842 and 97,377,121 shares issued and outstanding as of September 30, 2024 and December 31, 2023, respectively

Additional paid-in capital

834,417

624,414

Accumulated other comprehensive loss

(15)

Accumulated deficit

(644,936)

(491,330)

Total stockholders’ equity

189,504

133,071

Total liabilities and stockholders’ equity

332,784

193,851

Nonrelated Party

Current assets:

Short-term investments

52,642

74,639

Related Party

Current assets:

Short-term investments

$ 4,908

5,452

Current liabilities:

Accrued expenses and other current liabilities

$ 100

[1]	(1) Includes related party amount of $0.1 million as of December 31, 2023

Stock-Based Compensation - Schedule of Stock-Based Compensation Classification (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense	$ 6,827	$ 4,217	$ 20,127	$ 9,481
Research and development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense	2,982	2,224	9,928	5,558
General and administrative
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation expense	$ 3,845	$ 1,993	$ 10,199	$ 3,923

Leases - Schedule of Maturity (Details) $ in Thousands	Sep. 30, 2024 USD ($)
Leases [Abstract]
Remaining in 2024	$ 1,591
2025	19,773
2026	23,387
2027	22,921
2028	22,294
Thereafter	118,079
Total undiscounted lease payments	208,045
Less: payments related to leases not commenced	(136,637)
Less: imputed interest	(30,160)
Total operating lease liability	$ 41,248

Net Loss per Share - Schedule of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Numerator:
Net loss attributable to common stockholders, basic	$ (52,518)	$ (50,708)	$ (153,606)	$ (132,490)
Net loss attributable to common stockholders, diluted	$ (52,518)	$ (50,708)	$ (153,606)	$ (132,490)
Denominator:
Weighted-average common shares outstanding, diluted (in shares)	119,764,270	91,846,835	114,492,416	90,469,866
Weighted-average common shares outstanding, basic (in shares)	119,764,270	91,846,835	114,492,416	90,469,866
Net loss per share attributable to common stockholders, basic (in dollars per share)	$ (0.44)	$ (0.55)	$ (1.34)	$ (1.46)
Net loss per share attributable to common stockholders, diluted (in dollars per share)	$ (0.44)	$ (0.55)	$ (1.34)	$ (1.46)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders.

+ References + Details

Accrued Expenses and Other Current Liabilities

9 Months Ended

Sep. 30, 2024

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:


(in thousands)	September 30, 2024		December 31, 2023
Accrued expenses and other current liabilities
Accrued employee compensation and benefits	$	7,510	$	8,270
Accrued professional fees	5,575		2,273
Accrued license fee	4,197		—
Lab-related supplies and services	296		1,962
Other	1,106		1,605
Total accrued expenses and other current liabilities	$	18,684	$	14,110

Significant Agreements (Tables)

9 Months Ended

Sep. 30, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Supplemental Information related to the BMS Collaboration Agreement

Supplemental information related to the BMS Collaboration Agreement consisted of the following as of September 30, 2024 (in thousands):


Collaboration receivable — related party	$	55,000
Deferred revenue — related party	9,280
Deferred revenue, net of current — related party	62,639

he Company and BMS, a related party, entered into the BMS Collaboration Agreement and the BMS Purchase Agreement. BMS is a related party due to its share of ownership of the Company.

The Company recognized the following amounts related to BMS (in thousands):


Collaboration receivable — related party	$	55,000
Deferred revenue — related party	9,280
Deferred revenue, net of current — related party	62,639

Stockholder’s Equity (Details) $ / shares in Units, $ in Thousands	1 Months Ended
	Sep. 30, 2024 USD ($) vote $ / shares shares	Feb. 29, 2024 $ / shares shares	Nov. 30, 2023 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock, par value under amendment (in dollars per share) \| $ / shares	$ 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) \| $ / shares		$ 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) \| $ / shares		$ 6.24999
Pre-funded warrants sold (in shares) \| shares		3,200,005
Exercise price of warrants (in dollars per share) \| $ / shares		$ 0.00001
Sales Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of stock, consideration received \| $			$ 300,000
Unregistered Offering
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of stock, number of shares issued (in shares) \| shares	11,006,163
Sale of stock, consideration received \| $	$ 55,000

Stock-Based Compensation - Narrative (Details) - USD ($) $ in Millions		9 Months Ended
	Feb. 09, 2022	Sep. 30, 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)	5.00%
Shares issuable under plan (in shares)			4,868,856
Shares available for grant (in shares)		8,783,976
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)		21,522,110
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)	1.00%
Shares available for grant (in shares)		1,753,191
Shares issued under ESPP (in shares)		189,509
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		$ 46.7
Unrecognized compensation costs, period of recognition (in years)		2 years 4 months 24 days
Performance-Based Stock Options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unrecognized compensation cost		$ 3.2
Restricted Stock, Performance-Based
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unrecognized compensation expense		$ 0.2

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

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 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 nine months ended September 30, 2024:


	Number of Shares	Weighted-Average Exercise Price
Outstanding at December 31, 2023	7,641,863	$	9.79
Granted	4,434,710	8.03
Exercised	(28,048)	3.69
Cancelled or forfeited	(372,121)	11.02
Outstanding at September 30, 2024	11,676,404	$	9.10
Options vested and exercisable at September 30, 2024	4,335,142	$	8.63
Options vested and expected to vest at September 30, 2024	11,676,404	$	9.10

The following table summarizes the Company’s performance-based stock option activity for the nine months ended September 30, 2024:


	Number of Shares	Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2023	411,730	$	6.65
Granted	650,000	7.74
Exercised	—	—
Cancelled or forfeited	—	—
Outstanding at September 30, 2024	1,061,730	$	7.31
Vested and exercisable at September 30, 2024	385,208	$	6.72

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 nine months ended September 30, 2024:


	Number of Shares	Weighted-Average Grant-Date Fair Value
Outstanding at December 31, 2023	903,227	$	0.17
Issued	—	—
Vested	(806,085)	0.15
Repurchased	(4,423)	0.34
Outstanding at September 30, 2024	92,719	$	0.32

The following table summarizes the Company’s performance-based restricted common stock activity for the nine months ended September 30, 2024:


	Number of Shares	Weighted-Average Grant-Date Fair Value
Outstanding at December 31, 2023	3,832,769	$	0.07
Issued	—	—
Vested	(360,226)	0.18
Repurchased	—	—
Outstanding at September 30, 2024	3,472,543	$	0.06

Schedule of Share-Based Payment Arrangement, Expensed and Capitalized, Amount


	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2024		2023		2024		2023
Stock-based compensation expense:
Research and development	$	2,982	$	2,224	$	9,928	$	5,558
General and administrative	3,845		1,993		10,199		3,923
Total stock-based compensation expense	$	6,827	$	4,217	$	20,127	$	9,481

Related Party Transactions	9 Months Ended
Related Party Transactions	Sep. 30, 2024
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Consulting Agreement with David Liu Pursuant to a Consulting Agreement dated September 13, 2019, as amended on October 22, 2021 and July 31, 2024 (as amended, the “Consulting Agreement”), between the Company and David Liu, for the three months ended September 30, 2024 and 2023, the Company made payments of $25,000 and $37,500, respectively, in each period, and for the nine months ended September 30, 2024 and 2023, the Company made payments of $100,000 and $112,500, respectively, in each period for scientific consulting and other expenses. As of September 30, 2024 and December 31, 2023, there were no amounts included within accounts payable or accrued expenses. The Consulting Agreement terminated on September 1, 2024. 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, in our Annual Report on Form 10-K for the year ended December 31, 2023, filed with the SEC on March 1, 2024. 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 nine months ended September 30, 2024. As of September 30, 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.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-5

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-6

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/850/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-6

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

+ Details

Nature of the Business and Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended			9 Months Ended
	Sep. 30, 2024	Sep. 28, 2024	Oct. 31, 2024	Sep. 30, 2024	Feb. 29, 2024	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Proceeds from issuance of common under the BMS Securities Purchase Agreement — related party						$ 38,081	$ 0
Accumulated deficit	$ 644,936			$ 644,936		644,936		$ 491,330
Cash, cash equivalents, and investments	175,500			175,500		$ 175,500
Juno Therapeutics, Inc. \| Collaborative Arrangement, Research Collaboration and License Agreement
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Upfront payment		$ 55,000
Juno Therapeutics, Inc. \| Common Stock \| Collaborative Arrangement, Research Collaboration and License Agreement
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Stock issued to collaborating party (in shares)	$ 55,000			$ 55,000
Subsequent Event \| Juno Therapeutics, Inc. \| Collaborative Arrangement, Research Collaboration and License Agreement
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Upfront payment			$ 55,000
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 issuance of common under the BMS Securities Purchase Agreement — related party					$ 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

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) - USD ($)
$ in Thousands

3 Months Ended

9 Months Ended

Sep. 30, 2023

Research and development

^[1]

$ 40,967

$ 106,446

Research and development

$ 100

$ 800

[1]	(1) Includes related party amount of $0.1 million and $0.8 million for the three and nine months ended September 30, 2023.

Summary of Significant Accounting Policies	9 Months Ended
Summary of Significant Accounting Policies	Sep. 30, 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. 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. Revenue recognition The Company recognizes revenue in accordance with ASC Topic 606, Revenue from Contracts with Customers, (“ASC 606”). This standard applies to all contracts with customers, except for contracts that are within the scope of other standards. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. The Company enters into collaboration and licensing agreements with partners, which are within the scope of ASC 606, under which it may exclusively license rights to research, develop, manufacture, and commercialize product candidates to third parties. The terms of these arrangements typically include payment to the Company of one or more of the following: (1) non-refundable, upfront fees; (2) equity investment; (3) reimbursement of certain costs; (4) customer option fees for additional goods or services; (5) development milestone payments; (6) regulatory milestone payments; (7) commercial milestone payments; and (8) royalties on net sales of licensed products. In determining the appropriate amount of revenue to be recognized as it fulfills its obligations under each of its agreements, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. As part of the accounting for these arrangements, the Company must use its judgment to determine: (a) the number of performance obligations based on the determination under step (ii) above; (b) the transaction price under step (iii) above; (c) the stand-alone selling price for each performance obligation identified in the contract for the allocation of transaction price in step (iv) above; and (d) the contract term and pattern of satisfaction of the performance obligations under step (v) above. The Company uses judgment to determine whether milestones or other variable consideration, except for royalties, should be included in the transaction price as described further below. The transaction price is allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Amounts due to the Company for satisfying the revenue recognition criteria or that are contractually due based upon the terms of the collaboration agreements are recorded as collaboration receivable in the Company’s condensed consolidated balance sheet. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s condensed consolidated balance sheets. Deferred revenue expected to be recognized as revenue within 12 months following the balance sheet date are classified as current deferred revenue. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, net of current. Milestone payments At the inception of each arrangement that includes development milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The Company evaluates factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether it is probable that a significant revenue reversal would not occur. At the end of each subsequent reporting period, the Company reevaluates the probability of achievement of all milestones subject to constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. 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 In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires all public entities, including public entities with a single reportable segment, to provide in interim and annual periods one or more measures of segment profit or loss used by the chief operating decision maker to allocate resources and assess performance. In addition, this guidance requires disclosures of significant segment expenses and other segment items as well as incremental qualitative disclosures. This guidance is effective for fiscal years beginning after December 15, 2023, and interim periods after December 15, 2024, with retrospective application required, and early adoption permitted. The Company is currently in the process of evaluating the effects of this guidance on its related disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which requires enhanced income tax disclosures, including specific categories and disaggregation of information in the effective tax rate reconciliation, disaggregated information related to income taxes paid, income or loss from continuing operations before income tax expense or benefit, and income tax expense or benefit from continuing operations. This guidance is effective for annual periods beginning after December 15, 2024, with early adoption permitted. The Company is currently in the process of evaluating the impact of this pronouncement on its related disclosures. In November 2024, the FASB issued ASU 2024-03, Disaggregation of Income Statement Expenses, which requires more detailed information about specified categories of expenses included in certain expense captions presented on the face of the income statement. This ASU is effective for fiscal years beginning after December 15, 2026, and for interim periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. The amendments may be applied either (1) prospectively to financial statements issued for reporting periods after the effective date of this ASU or (2) retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact this ASU will have on its disclosures. Other 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 the Company’s financial statements upon adoption.

Significant Agreements

9 Months Ended

Sep. 30, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

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 except those discussed below.

Bristol-Myers Squibb — Related Party

On September 28, 2024 the Company entered into the BMS Collaboration Agreement with Juno Therapeutics, Inc., a wholly-owned subsidiary of BMS. Under the terms of the BMS Collaboration Agreement, the Company granted to BMS an exclusive worldwide license to certain Prime Editing technology for developing, manufacturing and commercializing ex vivo T-cell therapeutic products directed to select targets. Additionally, on the Effective Date, the Company entered into the BMS Purchase Agreement with BMS, pursuant which the Company agreed to sell and issue shares of its common stock to BMS.

Research Collaboration and License Agreement

Pursuant to the BMS Collaboration Agreement, the Company will design Prime Editing reagents to be used by BMS to develop, manufacture and commercialize ex vivo T-cell therapeutic products directed to specific targets selected by BMS.

Under the BMS Collaboration Agreement, the Company will receive a $55.0 million upfront payment, which is recorded as collaboration receivable — related party on the condensed consolidated balance sheets as of September 30, 2024, and received a $55.0 million equity investment from BMS (as described below). The Company is also eligible to receive more than $3.5 billion in milestones, including up to $185 million in preclinical milestones, up to $1.2 billion in development milestones, and up to $2.1 billion in commercialization milestones, along with royalties on net sales.

Unless earlier terminated, the term of the BMS Collaboration Agreement continues until expiration of the last royalty term for the applicable product in the applicable country. The BMS Collaboration Agreement is subject to customary termination provisions, including termination by a party for the other party’s uncured, material breach.

Stock Purchase Agreement

On the Effective Date, the Company entered into the BMS Purchase Agreement with BMS, pursuant to which the Company agreed to issue and sell, and BMS agreed to purchase, in the Offering, 11,006,163 Shares of the Company’s Common Stock for an aggregate purchase price of $55.0 million pursuant to the terms and conditions thereof. Pursuant to the terms of the BMS Purchase Agreement, BMS has agreed not to, directly or indirectly, sell or transfer any of the Shares until September 30, 2027 subject to specified conditions and exceptions. The BMS Collaboration Agreement and Stock Purchase Agreement were accounted for as a combined contract. The fair value of the Common Stock were recorded at their fair value as permanent equity as of September 30, 2024.

BMS Collaboration Agreement Accounting

The Company assessed the BMS Collaboration Agreement and concluded that BMS is a customer. The Company identified the following promises under the contract: (i) a license to develop, manufacture and commercialize the ex vivo T-cell therapeutic products to select targets, (ii) obligation to perform research services, (iii) participation in various committees, (iv) technology transfer services, and (v) regulatory support services. The Company assessed the promised goods and services to determine if they are distinct. Based on this assessment, the Company determined that BMS cannot benefit from the promised goods and services separately from the others as they are highly interrelated and interdependent and therefore not distinct. Accordingly, the promised goods and services represent one combined performance obligation and the entire transaction price will be allocated to that single combined performance obligation.

At contract inception, the transaction price was determined to be $72.0 million, which represents the aggregate of the upfront nonrefundable payment for the BMS Collaboration Agreement and the premium paid by BMS on its equity investment in the Company. Development milestones were fully constrained. The Company recognizes the portion of the transaction price as the single performance obligation is satisfied, using an input method, in proportion to costs incurred to date as compared to total costs incurred and expected to be incurred in the future to satisfy the underlying obligation. The transfer of control occurs over this period and, in management’s judgment, is the best measure of progress towards satisfying the performance obligation. Cost to perform the Company’s obligations

under the BMS Collaboration Agreement will be recognized as research and development expenses in the period incurred.

As of September 30, 2024, no revenue has been recognized under the BMS Collaboration Agreement and the full transaction price is recorded as deferred revenue and deferred revenue, net of current on the Company’s condensed consolidated balance sheets.

Supplemental information related to the BMS Collaboration Agreement consisted of the following as of September 30, 2024 (in thousands):


Collaboration receivable — related party	$	55,000
Deferred revenue — related party	9,280
Deferred revenue, net of current — related party	62,639

Amendment No. 4 to The Broad Institute License Agreement

In connection with the BMS Collaboration Agreement, the Company entered into a Letter Agreement (the “Amendment”) with The Broad Institute, Inc. (“Broad”) on September 27, 2024, which amends that certain license agreement by and between the Company and Broad, dated as of September 26, 2019 (as amended, the “Broad-Prime License Agreement”), to modify certain obligations of Company and rights of Broad in relation to the BMS Collaboration Agreement as a sublicense under the Broad-Prime License Agreement. The Amendment, among other things, modifies the royalty and certain commercial milestones that the Company is obligated to pay to Broad on net sales of products under the BMS Collaboration Agreement. Except as expressly stated in the Amendment, all other terms and provisions of the Broad-Prime License Agreement shall remain in full force and effect. Amounts due to Broad as a result of the BMS Collaboration Agreement are recorded as accrued expenses on the condensed consolidated balance sheet as of September 30, 2024.

Fair Value Measurements and Investments

9 Months Ended

Sep. 30, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements and Investments


	As of September 30, 2024:
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	—	$	59,329	$	—	$	59,329

Corporate debt securities	—		995		—		995
Short-term investments:
U.S. Treasury and government securities	—		40,603		—		40,603
Corporate debt securities	—		12,039		—		12,039
Related party short-term investment:
Beam equity securities	4,908		—		—		4,908
Total cash equivalents and investments	$	4,908	$	112,966	$	—	$	117,874


	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 investments as short-term based on each instrument’s underlying contractual maturity date. The fair value of the Company’s U.S. Treasury and government securities, corporate debt 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 September 30, 2024:
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Short-term investments in debt securities:
U.S. Treasury and government securities	$	40,585	$	18	$	—	$	40,603
Corporate debt securities	12,035		4		—		12,039


Total short-term investments in debt securities	$	52,620	$	22	$	—	$	52,642


	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)	September 30, 2024		December 31, 2023
Due within one year	$	52,642	$	74,639

Marketable securities in unrealized loss positions consisted of the following:


	As of September 30, 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:

Corporate debt securities	2	$	3,995	$	—

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 September 30, 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.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

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+ Details