Foghorn Therapeutics (FHTX) 10-Q 4 Nov 24 2024 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2024	Oct. 28, 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	001-39634
Entity Registrant Name	Foghorn Therapeutics Inc.
Entity Incorporation, State	DE
Entity Tax Identification Number	47-5271393
Entity Address, Street Name	500 Technology Square, Ste 700
Entity Address, City	Cambridge
Entity Address, State	MA
Entity Address, Postal Zip Code	02139
City Area Code	617
Local Phone Number	586-3100
Title of each class	Common Stock, $0.0001 par value per share
Trading Symbol(s)	FHTX
Name of each exchange on which registered	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		55,593,131
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001822462
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 57,678	$ 80,336
Marketable securities	209,719	153,721
Prepaid expenses and other current assets	3,837	6,124
Total current assets	271,234	240,181
Property and equipment, net	10,513	12,956
Restricted cash	1,708	1,708
Other assets	848	1,115
Operating lease right-of-use assets	24,069	29,956
Total assets	308,372	285,916
Current liabilities:
Accounts payable	3,451	6,260
Accrued expenses and other current liabilities	11,219	9,108
Operating lease liabilities	8,770	8,518
Deferred revenue	33,384	34,550
Total current liabilities	56,824	58,436
Operating lease liabilities, net of current portion	30,300	36,555
Deferred revenue, net of current portion	249,535	268,115
Total liabilities	336,659	363,106
Commitments and contingencies (Note 9)
Stockholders’ deficit:
Preferred stock, $0.0001 par value; 25,000,000 shares authorized at September 30, 2024 and December 31, 2023; no shares issued and outstanding at September 30, 2024 and December 31, 2023	0	0
Common stock, $0.0001 par value; 175,000,000 shares authorized at September 30, 2024 and December 31, 2023; 55,593,131 shares issued and outstanding at September 30, 2024 and 42,282,040 shares issued and outstanding at December 31, 2023	6	4
Additional paid-in capital	510,028	395,196
Accumulated other comprehensive gain/(loss)	360	(826)
Accumulated deficit	(538,681)	(471,564)
Total stockholders’ deficit	(28,287)	(77,190)
Total liabilities and stockholders’ deficit	$ 308,372	$ 285,916

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	25,000,000	25,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	175,000,000	175,000,000
Common stock, shares issued (in shares)	55,593,131	42,282,040
Common stock, shares outstanding (in shares)	55,593,131	42,282,040

Condensed Consolidated Statemen

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	$ 7,808	$ 17,478	$ 19,746	$ 28,386
Operating expenses:
Research and development	24,689	26,251	74,020	85,484
General and administrative	6,971	8,308	22,006	25,350
Impairment of long-lived assets	0	0	2,398	0
Total operating expenses	31,660	34,559	98,424	110,834
Loss from operations	(23,852)	(17,081)	(78,678)	(82,448)
Other income, net:
Interest income	3,495	2,753	8,804	8,215
Other income, net	1,235	721	2,757	2,153
Total other income, net	4,730	3,474	11,561	10,368
Loss before income taxes	(19,122)	(13,607)	(67,117)	(72,080)
Provision for income taxes	0	(738)	0	(2,240)
Net loss	$ (19,122)	$ (14,345)	$ (67,117)	$ (74,320)
Net loss per share attributable to common stockholders—basic (in dollars per share)	$ (0.31)	$ (0.34)	$ (1.28)	$ (1.77)
Net loss per share attributable to common stockholders—diluted (in dollars per share)	$ (0.31)	$ (0.34)	$ (1.28)	$ (1.77)
Weighted average common shares outstanding—basic (in shares)	62,602,848	42,025,938	52,241,942	41,888,314
Weighted average common shares outstanding—diluted (in shares)	62,602,848	42,025,938	52,241,942	41,888,314
Comprehensive loss:
Net loss	$ (19,122)	$ (14,345)	$ (67,117)	$ (74,320)
Other comprehensive gain:
Unrealized gains on marketable securities	698	826	1,186	2,093
Total other comprehensive gain	698	826	1,186	2,093
Total comprehensive loss	$ (18,424)	$ (13,519)	$ (65,931)	$ (72,227)
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	Collaboration Revenue [Member]	Collaboration Revenue [Member]	Collaboration Revenue [Member]	Collaboration Revenue [Member]

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2022	$ 112	$ 4	$ 377,232	$ (3,986)	$ (373,138)
Beginning balance (in shares) at Dec. 31, 2022		41,803,436
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options and employee stock purchase plan	102		102
Issuance of common stock upon exercise of stock options and employee stock purchase plan (in shares)		21,322
Stock-based compensation expense	4,572		4,572
Unrealized gains on marketable securities	1,116			1,116
Net loss	(30,488)				(30,488)
Ending balance at Mar. 31, 2023	(24,586)	$ 4	381,906	(2,870)	(403,626)
Ending balance (in shares) at Mar. 31, 2023		41,824,758
Beginning balance at Dec. 31, 2022	112	$ 4	377,232	(3,986)	(373,138)
Beginning balance (in shares) at Dec. 31, 2022		41,803,436
Increase (Decrease) in Stockholders' Equity
Net loss	(74,320)
Ending balance at Sep. 30, 2023	(57,388)	$ 4	391,959	(1,893)	(447,458)
Ending balance (in shares) at Sep. 30, 2023		42,217,126
Beginning balance at Mar. 31, 2023	(24,586)	$ 4	381,906	(2,870)	(403,626)
Beginning balance (in shares) at Mar. 31, 2023		41,824,758
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options and employee stock purchase plan	102		102
Issuance of common stock upon exercise of stock options and employee stock purchase plan (in shares)		27,680
Stock-based compensation expense	4,470		4,470
Unrealized gains on marketable securities	151			151
Net loss	(29,487)				(29,487)
Ending balance at Jun. 30, 2023	(49,350)	$ 4	386,478	(2,719)	(433,113)
Ending balance (in shares) at Jun. 30, 2023		41,852,438
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options and employee stock purchase plan	1,387		1,387
Issuance of common stock upon exercise of stock options and employee stock purchase plan (in shares)		364,688
Stock-based compensation expense	4,094		4,094
Unrealized gains on marketable securities	826			826
Net loss	(14,345)				(14,345)
Ending balance at Sep. 30, 2023	(57,388)	$ 4	391,959	(1,893)	(447,458)
Ending balance (in shares) at Sep. 30, 2023		42,217,126
Beginning balance at Dec. 31, 2023	$ (77,190)	$ 4	395,196	(826)	(471,564)
Beginning balance (in shares) at Dec. 31, 2023	42,282,040	42,282,040
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options and employee stock purchase plan	$ 1,167		1,167
Issuance of common stock upon exercise of stock options and employee stock purchase plan (in shares)		303,576
Stock-based compensation expense	3,224		3,224
Unrealized gains on marketable securities	329			329
Net loss	(25,016)				(25,016)
Ending balance at Mar. 31, 2024	(97,486)	$ 4	399,587	(497)	(496,580)
Ending balance (in shares) at Mar. 31, 2024		42,585,616
Beginning balance at Dec. 31, 2023	$ (77,190)	$ 4	395,196	(826)	(471,564)
Beginning balance (in shares) at Dec. 31, 2023	42,282,040	42,282,040
Increase (Decrease) in Stockholders' Equity
Net loss	$ (67,117)
Ending balance at Sep. 30, 2024	$ (28,287)	$ 6	510,028	360	(538,681)
Ending balance (in shares) at Sep. 30, 2024	55,593,131	55,593,131
Beginning balance at Mar. 31, 2024	$ (97,486)	$ 4	399,587	(497)	(496,580)
Beginning balance (in shares) at Mar. 31, 2024		42,585,616
Increase (Decrease) in Stockholders' Equity
Issuance of common stock and pre-funded warrants, net of underwriting discounts, commissions and offering costs	102,816	$ 2	102,814
Issuance of common stock and pre-funded warrants, net of underwriting discounts, commissions and offering costs (in shares)		12,743,039
Stock-based compensation expense	3,168		3,168
Unrealized gains on marketable securities	159			159
Net loss	(22,979)				(22,979)
Ending balance at Jun. 30, 2024	(14,322)	$ 6	505,569	(338)	(519,559)
Ending balance (in shares) at Jun. 30, 2024		55,328,655
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options and employee stock purchase plan	1,441		1,441
Issuance of common stock upon exercise of stock options and employee stock purchase plan (in shares)		264,476
Stock-based compensation expense	3,018		3,018
Unrealized gains on marketable securities	698			698
Net loss	(19,122)				(19,122)
Ending balance at Sep. 30, 2024	$ (28,287)	$ 6	$ 510,028	$ 360	$ (538,681)
Ending balance (in shares) at Sep. 30, 2024	55,593,131	55,593,131

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities:
Net loss	$ (19,122)	$ (14,345)	$ (67,117)	$ (74,320)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	3,018	4,094	9,410	13,135
Depreciation and amortization expense	700	900	2,359	2,599
Loss on disposal of property and equipment			0	3
Impairment of long-lived assets	0	0	2,398	0
Noncash lease expense			4,254	3,815
Accretion of discount on marketable securities			(3,044)	(2,156)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets			2,554	1,297
Accounts payable			(2,809)	1,082
Accrued expenses and other liabilities			1,857	(2,129)
Operating lease liabilities			(6,003)	(5,505)
Deferred revenue			(19,746)	(28,386)
Net cash used in operating activities			(75,887)	(90,565)
Cash flows from investing activities:
Purchases of property and equipment			(427)	(1,187)
Proceeds from sale of property and equipment			0	1
Purchases of marketable securities			(221,821)	(67,061)
Proceeds from maturities of marketable securities			170,053	175,312
Net cash provided by (used in) investing activities			(52,195)	107,065
Cash flows from financing activities:
Proceeds from offerings of common stock and pre-funded warrants, net of underwriting discounts and commissions			103,401	0
Payments of public offering costs			(585)	0
Proceeds from issuance of common stock upon exercise of stock options and employee stock purchase plan			2,608	1,592
Net cash provided by financing activities			105,424	1,592
Net increase (decrease) in cash, cash equivalents and restricted cash			(22,658)	18,092
Cash, cash equivalents and restricted cash at beginning of period			82,044	53,922
Cash, cash equivalents and restricted cash at end of period	59,386	72,014	59,386	72,014
Supplemental disclosure and noncash investing and financing information:
Cash paid for taxes			813	2,686
Purchases of property and equipment included in accounts payable and accrued expenses			289	58
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	57,678	70,306	57,678	70,306
Restricted cash	1,708	1,708	1,708	1,708
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 59,386	$ 72,014	$ 59,386	$ 72,014

Nature of Business, Going Conce

Nature of Business, Going Concern and Basis of Presentation	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Business, Going Concern and Basis of Presentation	Nature of Business, Going Concern and Basis of Presentation Nature of Business Foghorn Therapeutics Inc. (the “Company”) is a clinical-stage biopharmaceutical company discovering and developing a new class of medicines targeting genetically determined dependencies within the chromatin regulatory system. The Company uses its proprietary Gene Traffic Control platform to identify, validate and potentially drug targets within the system. The Company was founded in October 2015 as a Delaware corporation. The Company is headquartered in Cambridge, Massachusetts. The Company is subject to risks similar to those of other clinical-stage companies in the biopharmaceutical industry, including dependence on key individuals, the need to develop commercially viable products, competition from other companies, many of whom are larger and better capitalized, and the need to obtain adequate additional financing to fund the development of its products. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be maintained, that any products developed will obtain required regulatory approval or that any approved products will be commercially viable. Even if the Company’s development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from the sale of its products. In May 2024, the Company entered into an underwriting agreement with Jefferies LLC, TD Securities (USA) LLC and Evercore Group LLC relating to the issuance and sale of an aggregate of 12,743,039 shares of its common stock at a public offering price of $5.51 per share to certain investors. In addition, the Company issued and sold pre-funded warrants to purchase 7,220,794 shares of its common stock (the “Pre-funded Warrants”) at a public offering price of $5.5099 per pre-funded warrant, which equals the public offering price per share of the common stock less the $0.0001 exercise price per share of each pre-funded warrant. The offering closed on May 22, 2024, resulting in net proceeds of $102.8 million, after deducting underwriting discounts, commissions and other offering expenses. Going concern The accompanying unaudited condensed consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. Since inception, the Company has funded its operations primarily with proceeds from sales of preferred stock, upfront and milestone payments from collaboration agreements, public offerings and a stock purchase agreement. The Company has incurred recurring losses, including net losses of $67.1 million and $74.3 million for the nine months ended September 30, 2024 and 2023, respectively. As of September 30, 2024, the Company had an accumulated deficit of $538.7 million. The Company expects to continue to generate operating losses in the foreseeable future. As of the issuance date of these interim unaudited condensed consolidated financial statements the Company expects that its cash, cash equivalents and marketable securities will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months. The Company will need to obtain additional funding through public or private equity offerings, debt financings, collaborations, strategic alliances and/or licensing arrangements to continue to fund its operations. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into collaborative or strategic alliances or licensing arrangements. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. Arrangements with collaborators or others may require the Company to relinquish rights to certain of its technologies or programs. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its research and development programs, pipeline expansion or commercialization efforts, which could adversely affect its business prospects. Although management will continue to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding in the future on terms acceptable to the Company to fund continuing operations when needed or at all. Basis of presentation The Company’s unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and pursuant to the rules and regulations of the United States Securities and Exchange Commission for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary. All intercompany accounts and transactions have been eliminated in consolidation. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The accounting policies of the Company are set forth in Note 2 to the consolidated financial statements contained in the Company’s 2023 Annual Report on Form 10-K, and the accounting policies followed by the Company for interim financial reporting are consistent with the accounting policies therein . Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that the Company adopts as of the specified effective date. The Company qualifies as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 and has elected not to “opt out” of the extended transition related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different application dates for public and nonpublic companies, the Company can adopt the new or revised standard at the time nonpublic companies adopt the new or revised standard and can do so until such time that the Company either (i) irrevocably elects to opt out of such extended transition period or (ii) no longer qualifies as an emerging growth company. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which is intended to provide enhancements to segment disclosures, even for entities with only one reportable segment. In particular, the standard will require disclosures of significant segment expenses regularly provided to the chief operating decision maker and included within each reported measure of segment profit and loss. The standard will also require disclosure of all other segment items by reportable segment and a description of its composition. Finally, the standard will require disclosure of the title and position of the chief operating decision maker and an explanation of how the chief operating decision maker uses the reported measure(s) of segment profit or loss in assessing segment performance and deciding how to allocate resources. The standard is effective for annual periods beginning after December 15, 2023 and interim periods within annual periods beginning after December 15, 2024. Early adoption is permitted. The Company is currently evaluating the impact of the standard on the presentation of its condensed consolidated financial statements and footnotes.

Marketable Securities and Fair

Marketable Securities and Fair Value Measurements	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Marketable Securities and Fair Value Measurements	Marketable Securities and Fair Value Measurements As of September 30, 2024, available for sale marketable securities by security type consisted of (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. treasury notes (due within one year) $ 47,369 $ 64 $ (1) $ 47,432 Commercial paper (due within one year) 63,082 108 — 63,190 Corporate notes and bonds (due within one year) 98,908 213 (24) 99,097 Total $ 209,359 $ 385 $ (25) $ 209,719 As of December 31, 2023, available for sale marketable securities by security type consisted of (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. government agencies (due within one year) 11,823 — (26) 11,797 Commercial paper (due within one year) 5,901 7 (2) 5,906 Corporate notes and bonds (due within one year) 130,933 11 (784) 130,160 Corporate notes and bonds (due after one year through two 5,890 — (32) 5,858 Total $ 154,547 $ 18 $ (844) $ 153,721 The following tables present the Company’s fair value hierarchy for its assets and liabilities, which are measured at fair value on a recurring basis (in thousands): Fair Value Measurements at September 30, 2024 Using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 38,974 $ — $ — $ 38,974 U.S. treasury notes — 8,667 — 8,667 Commercial paper — 10,037 — 10,037 Marketable securities: U.S. treasury notes — 47,432 — 47,432 Commercial paper — 63,190 — 63,190 Corporate notes and bonds — 99,097 — 99,097 Total $ 38,974 $ 228,423 $ — $ 267,397 Fair Value Measurements at December 31, 2023 Using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 53,336 $ — $ — $ 53,336 U.S. treasury notes — 27,000 — 27,000 Marketable securities: U.S. government agencies — 11,797 — 11,797 Commercial paper — 5,906 — 5,906 Corporate notes and bonds — 136,018 — 136,018 Total $ 53,336 $ 180,721 $ — $ 234,057 For the three and nine months ended September 30, 2024 and 2023, there were no transfers between Level 1, Level 2 and Level 3.

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2024
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): September 30, 2024 December 31, 2023 Laboratory equipment $ 6,870 $ 6,804 Furniture and fixtures 827 815 Computer equipment and software 61 115 Leasehold improvements 16,788 17,239 Assets not yet placed in service 289 — 24,835 24,973 Less: Accumulated depreciation and amortization (14,322) (12,017) $ 10,513 $ 12,956 Depreciation and amortization expense was $0.7 million and $0.9 million for the three months ended September 30, 2024 and 2023 and $2.4 million and $2.6 million for the nine months ended September 30, 2024 and 2023, respectively. The Company recognized a non-cash impairment of leasehold improvements of $0.8 million for the nine months ended September 30, 2024, see Note 9 Commitments and Contingencies for additional information.

Accrued Expenses and Other Curr

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 Accrued expenses consisted of the following (in thousands): September 30, 2024 December 31, 2023 Accrued external research and development expenses $ 6,602 $ 3,610 Accrued employee compensation and benefits 3,771 4,347 Accrued income taxes — 674 Accrued professional fees 633 441 Other 213 36 $ 11,219 $ 9,108

Common Stock and Net Loss Per S

Common Stock and Net Loss Per Share	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Common Stock and Net Loss Per Share	Common Stock and Net Loss Per Share Common Stock Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are not entitled to receive dividends, unless declared by the board of directors. In May 2024, the Company entered into an underwriting agreement with Jefferies LLC, TD Securities (USA) LLC and Evercore Group LLC relating to the issuance and sale of an aggregate of 12,743,039 shares of its common stock at a public offering price of $5.51 per share to certain investors. In addition, the Company issued and sold to certain investors in lieu of common stock the Pre-funded Warrants to purchase 7,220,794 shares of its common stock at a public offering price of $5.5099 per pre-funded warrant, which represents the public offering price per share of the common stock less the $0.0001 exercise price per share of each pre-funded warrant. The offering closed on May 22, 2024, resulting in net proceeds of $102.8 million after deducting underwriting discounts and commissions and other offering expenses. As the Pre-funded Warrants are indexed to the Company’s common stock (and otherwise meet the requirements to be classified in equity), the Company recorded the consideration received from the issuance of the pre-funded warrants as additional paid-in capital on the Company’s condensed consolidated balance sheets and statements of stockholders’ equity. The Pre-funded Warrants are exercisable at any time. A holder of Pre-Funded Warrants may not exercise any portion of any Pre-funded Warrant if the holder, together with its affiliates, would beneficially own more than 9.99% of the number of shares of the Company’s common stock outstanding immediately after giving effect to such exercise. A holder of Pre-Funded Warrants may increase or decrease this percentage to any other percentage not in excess of 19.99%, if exceeding such percentage would result in a change of control under Nasdaq Listing Rule 5636(b) or any successor rule, by providing at least 61 days’ prior notice to the Company subject to the terms of the Pre-funded Warrant. Net Loss Per Share The following pre-funded warrants outstanding at each period end were included in the basic and diluted net loss per share calculation: September 30, 2024 2023 Pre-funded warrants to purchase common stock 7,220,794 — During the three and nine months ended September 30, 2024, no pre-funded warrants were exercised. The following common stock equivalents presented based on amounts outstanding at each period end have been excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive impact: September 30, 2024 2023 Stock options to purchase common stock 9,016,562 9,532,730 Warrants to purchase common stock 18,445 18,445 9,035,007 9,551,175

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	Stock-Based Compensation 2020 Equity Incentive Plan The Company’s 2020 Equity Incentive Plan (the “2020 Plan”) provides for the grant of incentive stock options, non-qualified options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. The number of shares initially reserved for issuance under the 2020 Plan was (i) 2,200,000 shares (the “share pool”), plus (ii) the number of shares of common stock available for issuance under the Company’s 2016 Stock Incentive Plan (the “2016 Plan”) as of the effective date of the 2020 Plan, plus the number of shares of common stock underlying awards under the 2016 Plan that on or after the date of adoption expire or become unexercisable without delivery of shares, are forfeited to, or repurchased for cash, are settled in cash, or otherwise become available again for grant under the 2016 Plan, in each case, in accordance with its terms (up to an aggregate of 5,078,295 shares). As of September 30, 2024, 2,718,499 shares remained available for future grant under the 2020 Plan. The share pool will automatically increase on January 1 of each year from 2021 to 2030 by the lesser of (i) four percent of the number of shares of our common stock outstanding as of the close of business on the immediately preceding December 31 and (ii) the number of shares determined by the board of directors on or prior to such date for such year. The number of shares reserved for issuance under the 2020 Plan was increased by 1,691,281 shares effective January 1, 2024. The 2020 Plan is 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. Stock options granted with service-based vesting conditions generally vest over four years and expire after ten years. The exercise price for stock options granted is not less than the fair value of common stock on the date of grant. The Company bases fair value of common stock on the quoted market price. 2020 Employee Stock Purchase Plan On October 21, 2020, the Company’s board of directors adopted and its stockholders approved the 2020 Employee Stock Purchase Plan (the “ESPP”), which became effective on October 21, 2020. The aggregate number of shares of common stock available for purchase pursuant to the exercise of options under the ESPP is 360,000 shares, plus an automatic annual increase, as of January 1 of each year from 2021 to 2030, equal to the lesser of one percent of the number of shares of common stock outstanding as of the close of business on the immediately preceding December 31 and (ii) the number of shares determined by the board of directors on or prior to such date for such year (up to a maximum of 3,220,520 shares). The number of shares reserved for issuance under the ESPP was increased by 422,820 shares to 1,566,120 shares effective January 1, 2024. As of September 30, 2024, 1,544,076 shares remained available for future grant under the ESPP. Eligible employees may authorize payroll deductions of up to 15% of their eligible compensation during an offering period. The purchase of shares is done at a 15% discount on the lesser of (i) the Fair Market Value of a share of Stock on the first day of the offering period and (ii) the Fair Market Value of a share of Stock on the last day of the offering period. The Company currently holds two offering periods, September 1 and March 1, respectively. The Company recognized less than $0.1 million of expense related to the ESPP for the three and nine months ended September 30, 2024 and 2023, respectively. Stock-Based Compensation Stock-based compensation expense was classified in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Research and development expenses $ 1,255 $ 1,776 $ 3,921 $ 5,800 General and administrative expenses 1,763 2,318 5,489 7,335 $ 3,018 $ 4,094 $ 9,410 $ 13,135 As of September 30, 2024, total unrecognized compensation cost related to unvested options was $18.5 million, which is expected to be recognized over a weighted average period of 2.2 years.

Collaboration Agreements

Collaboration Agreements	9 Months Ended
	Sep. 30, 2024
Collaboration Agreement [Abstract]
Collaboration Agreements	Collaboration Agreements Lilly Collaboration Agreement and Stock Purchase Agreement In December 2021, the Company entered into a collaboration agreement (the “Lilly Collaboration Agreement”) with Eli Lilly and Company (“Lilly”) to create novel oncology medicines by applying Foghorn’s proprietary Gene Traffic Control platform. The collaboration includes a co-development and co-commercialization agreement for the Company’s selective SMARCA2 (BRM) oncology target, consisting of two programs, and one additional undisclosed oncology target (collectively, the “Joint Programs”). The collaboration also includes three additional discovery targets or programs (collectively, the “Discovery Programs”) for a total of six programs directed at five targets. With respect to the Joint Programs, the Company will lead discovery and early research activities through the successful completion of dose finding toxicity studies for the identified compound, while Lilly will lead development and commercialization activities of the identified compound with participation from the Company in development activities and 50% cost sharing until registrational clinical trials. The Company and Lilly may jointly develop and commercialize the Joint Program compound though the Company may, in its sole discretion, opt-out on a program-by-program basis of further participation in the development and commercialization efforts prior to the first registrational clinical trial. If the Company does not opt-out, Lilly and the Company will continue to share in the costs to further develop and commercialize the Joint Program compound on a worldwide basis, equally share in the U.S. profits on product sales, subject to certain adjustments and receive royalties on sales outside of the United States (“Ex-U.S.”) at royalty rates ranging from low double digits to high twenties. If the Company opts-out of further development and commercialization efforts, it will have no further obligations to share in the development and commercialization costs, will receive royalties rather than profit share on U.S. sales and will receive royalties at a lower rate on Ex-U.S. sales. With respect to the Discovery Programs, the Company will lead discovery and early research activities through the successful completion of dose finding toxicity studies for the identified compounds. The Company may, in its sole discretion, opt-in on a program-by-program basis after the successful completion of dose finding toxicity to participate in the further development and commercialization efforts of the Discovery Program compounds. If the Company opts-in to the development and commercialization of the Discovery Program compounds, it will be eligible to receive milestone payments of up to $10.0 million per program upon specified research and development milestones and up to $180.0 million per program upon achievement of specified regulatory and commercial milestones and will also be eligible to share in the U.S. profits at pre-determined percentages on product sales. The Company would also be eligible to receive tiered Ex-U.S. royalty rates, calculated on a product-by-product and country-by-country basis, on net sales outside of the United States, if any, ranging from low single digits to low double digits, but less then teens. If the Company does not opt-in to further development and commercialization efforts for the Discovery Programs, it will be eligible to receive milestone payments of up to $70.0 million per program upon specified research and development milestones and up to $360.0 million per program upon achievement of specified regulatory and commercial milestones per approved product, if any. The Company would also be eligible to receive tiered royalties on net sales of products worldwide at royalty rates ranging from low single digits to low double digits, but less than teens. Lilly has the right to make substitutions for each of the five targets during the research term of each program, subject to certain limitations. Pursuant to the Lilly Collaboration Agreement, the Company will also participate in joint decision-making through the joint steering committee and subcommittees. Unless terminated earlier, the Lilly Collaboration Agreement will continue on a product-by-product basis until the expiration of all royalty obligations under the Lilly Collaboration Agreement and when neither the Company nor Lilly is developing, commercializing or manufacturing any product under the Lilly Collaboration Agreement. The Company or Lilly may terminate the Lilly Collaboration Agreement upon an uncured material breach by the other party. Lilly may also terminate the Lilly Collaboration Agreement in its entirety or on a target-by-target, program-by-program or product-by-product basis for any reason upon certain notice to the Company. The Company determined that (1) the research activities performed by the Company for both the Joint Programs and the Discovery Programs (2) the development activities and cost sharing for the Joint Program development efforts after dose finding toxicity until registrational clinical trials (3) the research, development, manufacture and commercialization licenses and (4) service on the joint steering committee and subcommittees represent a single performance obligation under the Lilly Collaboration Agreement. The Company determined that Lilly cannot benefit from the licenses separately from the research activities, the development activities until registrational clinical trials and participation on the joint steering committee and subcommittees because these services are specialized and rely on the Company’s expertise such that these activities are highly interrelated and therefore not distinct. Accordingly, the promised goods and services represent one combined performance obligation, and the entire transaction price was allocated to that single combined performance obligation. The performance obligation will be satisfied over time as the Company performs the research activities, participates and shares in the cost of the development activities for the Joint Programs and participates in a joint steering committee and subcommittees to oversee these activities. The Company’s options to share in further development and commercialization efforts via its opt-in/opt-out rights will be assessed and accounted for as separate units of accounting under the relevant guidance if, and when, such options are exercised by the Company. During the third quarter of 2023, the Company has transitioned the SMARCA2 (BRM) Selective inhibitor, FHD-909, into development activities for which Lilly will lead and the Company will participate and share in 50% of the costs until at least registrational trials. Costs incurred will continue to be included in research and development expenses on the condensed consolidated statements of operations and comprehensive loss. As of September 30, 2024, the aggregate amount of the transaction price related to the unsatisfied portion of the performance obligation was $282.9 million, which is expected to be recognized as revenue through 2029 or beyond depending on the timing of certain clinical development activities. The Company does not expect collaboration revenue to be recognized evenly over this period as it will be recognized on a percentage of completion basis (using a cost-to-cost method) as the Company performs the research and development activities and participates on the joint steering committee and subcommittees, which will likely vary from period to period. In estimating the total costs to satisfy its single performance obligation pursuant to the Lilly Collaboration Agreement, the Company is required to make significant estimates including an estimate of the number of target substitutions Lilly may elect to make and the expected time and expected costs to fulfill the performance obligation. The cumulative effect of revisions to the total estimated costs to complete the Company’s single performance obligation will be recorded in the period in which the changes are identified, and amounts can be reasonably estimated. While such revisions will have no impact on the Company’s cash flows, a significant change in these assumptions and estimates could have a material impact on the timing and amount of revenue recognized in future periods and the classification of deferred revenue between short-term and long-term. For the three months ended September 30, 2024 and 2023, the Company recorded $7.8 million and $1.4 million, respectively, of revenue under the Lilly Collaboration Agreement, which was included in deferred revenue at the beginning of the respective periods. For the nine months ended September 30, 2024 and 2023, the Company recorded $19.7 million and $11.3 million, respectively, of revenue under the Lilly Collaboration Agreement, which was included in deferred revenue at the beginning of the respective periods. As of September 30, 2024 and December 31, 2023, the Company had a payable to Lilly of $4.2 million and $1.5 million recorded in accrued expenses and other current liabilities on the Company’s condensed consolidated balance sheets. Merck Collaboration Agreement In July 2020, the Company entered into the Merck Collaboration Agreement with Merck, pursuant to which the Company and Merck applied Foghorn’s proprietary Gene Traffic Control platform to discover and develop novel therapeutics. Under the terms of the Merck Collaboration Agreement, the Company and Merck were each responsible to perform certain research activities in accordance with a mutually-agreed upon research plan. For the three and nine months ended September 30, 2023, the Company recorded $16.1 million and $17.0 million, respectively, of the revenue under the Merck Collaboration Agreement, which was included in deferred revenue at the beginning of the respective period and the classification of deferred revenue between short term and long term.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases The Company leases office space under a non-cancelable operating lease (the “Operating Lease”). There have been no material changes to the Company's Operating Lease during the three and nine months ended September 30, 2024. For additional information, see Note 10, Leases , to the consolidated financial statements in the Company's Annual Report on Form 10-K for the year ended December 31, 2023. Sublease agreement On May 10, 2024, the Company entered into a sublease with a new subtenant (the “Sublease”) to sublease 15,700 square feet at the Company’s main office in Cambridge, MA (the “Subleased Space”). The Sublease commenced during the third quarter of 2024 and has a term from July 1, 2024 through September 29, 2028. The Company expects to receive $6.6 million over the lease term. The Sublease qualified as a triggering event that could indicate that the carrying amount of the asset group related to the Subleased Space, which includes the Operating Lease right-of-use asset and related leasehold improvements, may not be recoverable. The Company tested for impairment by comparing the carrying amount of the asset group to the future undiscounted net cash flows expected to be generated by the asset group. The impairment test indicated that the asset group was impaired and the Company measured the impairment loss as the excess of the asset group’s carrying value over its fair value. The fair value of this asset group was calculated as the present value of the estimated future cash flows of the sublease income discounted at a rate of 9%. The fair value of this asset group was classified in level 3 of the fair value hierarchy and was nonrecurring. The Company recognized a non-cash impairment charge of $2.4 million on the condensed consolidated statements of operations and comprehensive loss of which $1.6 million was allocated to the Operating Lease right-of-use asset and $0.8 million was allocated to leasehold improvements. License agreements The Company has entered into various exclusive and non-exclusive license agreements for certain technologies. Under the terms of these license agreements, the Company could be required to reimburse the licensors for patent expenses and remit amounts in the low single-digit as sales-based royalties upon the occurrence of specific events as outlined in the corresponding license agreements. The Company is also required to make annual license maintenance fees of less than $0.3 million and pay up to $1.1 million in regulatory milestones on each licensed product upon the occurrence of specific events as outlined in one of the license agreements. None of our product candidates utilize technologies covered by these licenses. Indemnification agreements In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, contract research organizations, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and its executive officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. The Company has not incurred any material costs as a result of such indemnifications and is not currently aware of any indemnification claims. Legal Proceedings From time to time, the Company may become involved in litigation or other legal proceedings. The Company is not currently a party to any material litigation or legal proceedings.

Related Parties

Related Parties	9 Months Ended
	Sep. 30, 2024
Related Party Transactions [Abstract]
Related Parties	Related Parties In October 2015, the Company entered into a five-year consulting agreement with a scientific founder of the Company who is also a shareholder. This agreement was amended and extended to January 1, 2025 and is subject to automatic one-year renewal terms until terminated if notice is provided more than 30 days before the current end of term date. During the three months ended September 30, 2024 and 2023, the Company paid the scientific founder a de minimis amount. During the nine months ended September 30, 2024 and 2023, the Company paid the scientific founder $0.2 million and $0.1 million, respectively. As of September 30, 2024 and December 31, 2023, the Company had none and less than $0.1 million, respectively, of accounts payable due to the scientific founder. On December 10, 2021, we entered into the Lilly Collaboration Agreement with Lilly. Concurrent with the Lilly Collaboration Agreement the Company also entered into a stock purchase agreement with Lilly (the “Lilly SPA”) where the Company issued and sold Lilly 4,000,000 shares of our common stock at a price of $20.00 per share, making them a 5% or greater shareholder in the Company for the nine months ended September 30, 2024 and 2023. We are obligated to make certain payments to Lilly pursuant to the Lilly Collaboration Agreement. During the three months ended September 30, 2024, the Company paid Lilly $1.3 million. The Company made no payments to Lilly during the three months ended September 30, 2023. During the nine months ended September 30, 2024, the Company paid Lilly $4.2 million. The Company made no payments to Lilly during the nine months ended September 30, 2023. As of September 30, 2024 and December 31, 2023, the Company had a payable of $4.2 million and $1.5 million, respectively, due to Lilly. On January 16, 2024, the Company appointed Stephen J. DiPalma, a managing director at Danforth Advisors, LLC (“Danforth”), as Treasurer and interim Chief Financial Officer, a position he held until April 16, 2024. The Company had previously entered into an agreement with Danforth to provide strategic and financial consulting services to the Company. During the three months ended September 30, 2024, the Company paid Danforth less than $0.1 million. During the nine months ended September 30, 2024, the Company paid Danforth $0.3 million. As of September 30, 2024 the Company had less than $0.1 million of accounts payable due to Danforth.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net loss	$ (19,122)	$ (22,979)	$ (25,016)	$ (14,345)	$ (29,487)	$ (30,488)	$ (67,117)	$ (74,320)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The Company’s unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and pursuant to the rules and regulations of the United States Securities and Exchange Commission for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary. All intercompany accounts and transactions have been eliminated in consolidation. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that the Company adopts as of the specified effective date. The Company qualifies as an “emerging growth company” as defined in the Jumpstart Our Business Startups Act of 2012 and has elected not to “opt out” of the extended transition related to complying with new or revised accounting standards, which means that when a standard is issued or revised and it has different application dates for public and nonpublic companies, the Company can adopt the new or revised standard at the time nonpublic companies adopt the new or revised standard and can do so until such time that the Company either (i) irrevocably elects to opt out of such extended transition period or (ii) no longer qualifies as an emerging growth company. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which is intended to provide enhancements to segment disclosures, even for entities with only one reportable segment. In particular, the standard will require disclosures of significant segment expenses regularly provided to the chief operating decision maker and included within each reported measure of segment profit and loss. The standard will also require disclosure of all other segment items by reportable segment and a description of its composition. Finally, the standard will require disclosure of the title and position of the chief operating decision maker and an explanation of how the chief operating decision maker uses the reported measure(s) of segment profit or loss in assessing segment performance and deciding how to allocate resources. The standard is effective for annual periods beginning after December 15, 2023 and interim periods within annual periods beginning after December 15, 2024. Early adoption is permitted. The Company is currently evaluating the impact of the standard on the presentation of its condensed consolidated financial statements and footnotes.

Marketable Securities and Fai_2

Marketable Securities and Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Summary of Available for Sale Marketable Securities by Security Type	As of September 30, 2024, available for sale marketable securities by security type consisted of (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. treasury notes (due within one year) $ 47,369 $ 64 $ (1) $ 47,432 Commercial paper (due within one year) 63,082 108 — 63,190 Corporate notes and bonds (due within one year) 98,908 213 (24) 99,097 Total $ 209,359 $ 385 $ (25) $ 209,719 As of December 31, 2023, available for sale marketable securities by security type consisted of (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value U.S. government agencies (due within one year) 11,823 — (26) 11,797 Commercial paper (due within one year) 5,901 7 (2) 5,906 Corporate notes and bonds (due within one year) 130,933 11 (784) 130,160 Corporate notes and bonds (due after one year through two 5,890 — (32) 5,858 Total $ 154,547 $ 18 $ (844) $ 153,721
Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables present the Company’s fair value hierarchy for its assets and liabilities, which are measured at fair value on a recurring basis (in thousands): Fair Value Measurements at September 30, 2024 Using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 38,974 $ — $ — $ 38,974 U.S. treasury notes — 8,667 — 8,667 Commercial paper — 10,037 — 10,037 Marketable securities: U.S. treasury notes — 47,432 — 47,432 Commercial paper — 63,190 — 63,190 Corporate notes and bonds — 99,097 — 99,097 Total $ 38,974 $ 228,423 $ — $ 267,397 Fair Value Measurements at December 31, 2023 Using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 53,336 $ — $ — $ 53,336 U.S. treasury notes — 27,000 — 27,000 Marketable securities: U.S. government agencies — 11,797 — 11,797 Commercial paper — 5,906 — 5,906 Corporate notes and bonds — 136,018 — 136,018 Total $ 53,336 $ 180,721 $ — $ 234,057

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2024
Property, Plant and Equipment [Abstract]
Summary of Property and Equipment Net	Property and equipment, net consisted of the following (in thousands): September 30, 2024 December 31, 2023 Laboratory equipment $ 6,870 $ 6,804 Furniture and fixtures 827 815 Computer equipment and software 61 115 Leasehold improvements 16,788 17,239 Assets not yet placed in service 289 — 24,835 24,973 Less: Accumulated depreciation and amortization (14,322) (12,017) $ 10,513 $ 12,956

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2024
Payables and Accruals [Abstract]
Summary of Accrued Expenses	Accrued expenses consisted of the following (in thousands): September 30, 2024 December 31, 2023 Accrued external research and development expenses $ 6,602 $ 3,610 Accrued employee compensation and benefits 3,771 4,347 Accrued income taxes — 674 Accrued professional fees 633 441 Other 213 36 $ 11,219 $ 9,108

Common Stock and Net Loss Per_2

Common Stock and Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Summary of Earnings Per Share, Basic and Diluted	The following pre-funded warrants outstanding at each period end were included in the basic and diluted net loss per share calculation: September 30, 2024 2023 Pre-funded warrants to purchase common stock 7,220,794 —
Summary of Earnings Per Share Diluted Anti Dilutive Impact	The following common stock equivalents presented based on amounts outstanding at each period end have been excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive impact: September 30, 2024 2023 Stock options to purchase common stock 9,016,562 9,532,730 Warrants to purchase common stock 18,445 18,445 9,035,007 9,551,175

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Summary of Stock-Based Compensation Expense	Stock-based compensation expense was classified in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Research and development expenses $ 1,255 $ 1,776 $ 3,921 $ 5,800 General and administrative expenses 1,763 2,318 5,489 7,335 $ 3,018 $ 4,094 $ 9,410 $ 13,135

Nature of Business, Going Con_2

Nature of Business, Going Concern and Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended						9 Months Ended
	May 22, 2024	May 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements
Net loss			$ 19,122	$ 22,979	$ 25,016	$ 14,345	$ 29,487	$ 30,488	$ 67,117	$ 74,320
Accumulated deficit			$ 538,681						$ 538,681		$ 471,564
Private Placement
Organization, Consolidation and Presentation of Financial Statements
Sale of stock, number of shares issued in transaction (in shares)		12,743,039
Sale of stock issue price per share (in dollars per share)		$ 5.51
Pre-funded Warrants
Organization, Consolidation and Presentation of Financial Statements
Sale of stock, number of shares issued in transaction (in shares)		7,220,794
Sale of stock issue price per share (in dollars per share)		$ 5.5099
Exercise price of warrant (in dollars per share)		$ 0.0001
Proceed from issuance of stock	$ 102,800

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail)	1 Months Ended
	Nov. 30, 2023 segment
Accounting Policies [Abstract]
Number of reportable segments	1

Marketable Securities and Fai_3

Marketable Securities and Fair Value Measurements - Summary of Available for Sale Marketable Securities by Security Type (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Amortized Cost	$ 209,359	$ 154,547
Gross Unrealized Gains	385	18
Gross Unrealized Losses	(25)	(844)
Estimated Fair Value	209,719	153,721
U.S. treasury notes (due within one year)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Amortized Cost	47,369
Gross Unrealized Gains	64
Gross Unrealized Losses	(1)
Estimated Fair Value	47,432
U.S. government agencies (due within one year)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Amortized Cost		11,823
Gross Unrealized Gains		0
Gross Unrealized Losses		(26)
Estimated Fair Value		11,797
Commercial paper (due within one year)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Amortized Cost	63,082	5,901
Gross Unrealized Gains	108	7
Gross Unrealized Losses	0	(2)
Estimated Fair Value	63,190	5,906
Corporate notes and bonds (due within one year)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Amortized Cost	98,908	130,933
Gross Unrealized Gains	213	11
Gross Unrealized Losses	(24)	(784)
Estimated Fair Value	$ 99,097	130,160
Corporate notes and bonds (due after one year through two years)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Amortized Cost		5,890
Gross Unrealized Gains		0
Gross Unrealized Losses		(32)
Estimated Fair Value		$ 5,858

Marketable Securities and Fai_4

Marketable Securities and Fair Value Measurements - Summary of Financial 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
Marketable securities	$ 209,719	$ 153,721
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	63,190	5,906
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	267,397	234,057
Recurring | U.S. treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	47,432
Recurring | U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities		11,797
Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	63,190	5,906
Recurring | Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	99,097	136,018
Recurring | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	38,974	53,336
Recurring | U.S. treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	8,667	27,000
Recurring | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	10,037
Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	38,974	53,336
Recurring | Level 1 | U.S. treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0
Recurring | Level 1 | U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities		0
Recurring | Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0	0
Recurring | Level 1 | Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0	0
Recurring | Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	38,974	53,336
Recurring | Level 1 | U.S. treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	0	0
Recurring | Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	0
Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	228,423	180,721
Recurring | Level 2 | U.S. treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	47,432
Recurring | Level 2 | U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities		11,797
Recurring | Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	63,190	5,906
Recurring | Level 2 | Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	99,097	136,018
Recurring | Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	0	0
Recurring | Level 2 | U.S. treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	8,667	27,000
Recurring | Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	10,037
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Total	0	0
Recurring | Level 3 | U.S. treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0
Recurring | Level 3 | U.S. government agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities		0
Recurring | Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0	0
Recurring | Level 3 | Corporate notes and bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0	0
Recurring | Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	0	0
Recurring | Level 3 | U.S. treasury notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	0	$ 0
Recurring | Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	$ 0

Property and Equipment, Net - S

Property and Equipment, Net - Summary of Property and Equipment Net (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization
Property plant and equipment including finance right of use assets, gross	$ 24,835	$ 24,973
Less: Accumulated depreciation and amortization	(14,322)	(12,017)
Property and equipment, net	10,513	12,956
Laboratory equipment
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization
Property plant and equipment including finance right of use assets, gross	6,870	6,804
Furniture and fixtures
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization
Property plant and equipment including finance right of use assets, gross	827	815
Computer equipment and software
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization
Property plant and equipment including finance right of use assets, gross	61	115
Leasehold improvements
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization
Property plant and equipment including finance right of use assets, gross	16,788	17,239
Assets not yet placed in service
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization
Property plant and equipment including finance right of use assets, gross	$ 289	$ 0

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (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 and amortization expense	$ 700	$ 900	$ 2,359	$ 2,599
Impairment of leasehold improvements			$ 800

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued external research and development expenses	$ 6,602	$ 3,610
Accrued employee compensation and benefits	3,771	4,347
Accrued income taxes	0	674
Accrued professional fees	633	441
Other	213	36
Total	$ 11,219	$ 9,108

Common Stock and Net Loss Per_3

Common Stock and Net Loss Per Share - Narrative (Details) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended	9 Months Ended
	May 22, 2024 USD ($)	May 31, 2024 $ / shares shares	Sep. 30, 2024 vote shares	Sep. 30, 2024 vote shares
Antidilutive Securities Excluded from Computation of Earnings Per Share
Voting rights per share | vote			1	1
Pre-funded warrants were exercised (in shares) | shares			0	0
Private Placement
Antidilutive Securities Excluded from Computation of Earnings Per Share
Sale of stock, number of shares issued in transaction (in shares) | shares		12,743,039
Sale of stock issue price per share (in dollars per share) | $ / shares		$ 5.51
Pre-funded Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share
Sale of stock, number of shares issued in transaction (in shares) | shares		7,220,794
Sale of stock issue price per share (in dollars per share) | $ / shares		$ 5.5099
Exercise price of warrant (in dollars per share) | $ / shares		$ 0.0001
Proceed from issuance of stock | $	$ 102.8
Beneficial ownership threshold percentage		9.99%
Beneficial ownership maximum percentage		19.99%
Beneficial ownership notice period		61 days

Common Stock and Net Loss Per_4

Common Stock and Net Loss Per Share - Summary of Earnings Per Share Pre-funded Warrants (Details) - shares	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Equity [Abstract]
Pre-funded warrants to purchase common stock (in shares)	7,220,794	0

Common Stock and Net Loss Per_5

Common Stock and Net Loss Per Share - Summary of Earnings Per Share Diluted Anti-Dilutive Impact (Details) - shares	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares excluded from the calculation of earnings per share (in shares)	9,035,007	9,551,175
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares excluded from the calculation of earnings per share (in shares)	9,016,562	9,532,730
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares excluded from the calculation of earnings per share (in shares)	18,445	18,445

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) $ in Millions			3 Months Ended		9 Months Ended
	Jan. 01, 2024 shares	Oct. 21, 2020 shares	Sep. 30, 2024 USD ($) period shares	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) period shares	Sep. 30, 2023 USD ($)
Share-based Payment Arrangement
Number of shares authorized (in shares)	1,566,120
Unrecognized compensation costs related to unvested options and unvested restricted stock | $			$ 18.5		$ 18.5
Weighted average period of unrecognized compensation costs					2 years 2 months 12 days
2020 Equity Incentive Plan
Share-based Payment Arrangement
Number of shares authorized (in shares)			2,200,000		2,200,000
Common stock shares available for grant (in shares)			2,718,499		2,718,499
Percentage of automatic annual increase in number of shares					4%
Number of additional shares authorized (in shares)	1,691,281
Vesting period (years)					4 years
Stock option expiry period (years)					10 years
2016 Stock Incentive Plan
Share-based Payment Arrangement
Number of shares authorized (in shares)			5,078,295		5,078,295
2020 Employee Stock Purchase Plan
Share-based Payment Arrangement
Number of shares authorized (in shares)		360,000
Common stock shares available for grant (in shares)			1,544,076		1,544,076
Percentage of automatic annual increase in number of shares		1%
Number of additional shares authorized (in shares)	422,820
Maximum aggregate number of shares added to plan (in shares)		3,220,520
Percentage of payroll deductions			15%		15%
Discount of shares rate, percent					15%
Number of offering periods (period) | period			2		2
Share-based payment arrangement, expense | $			$ 0.1	$ 0.1	$ 0.1	$ 0.1

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (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
Stock-based compensation expense	$ 3,018	$ 4,094	$ 9,410	$ 13,135
Research and development expenses
Share-based Payment Arrangement
Stock-based compensation expense	1,255	1,776	3,921	5,800
General and administrative expenses
Share-based Payment Arrangement
Stock-based compensation expense	$ 1,763	$ 2,318	$ 5,489	$ 7,335

Collaboration Agreements (Detai

Collaboration Agreements (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Dec. 31, 2021 USD ($) target program	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative
Collaboration revenue		$ 7,808	$ 17,478	$ 19,746	$ 28,386
Accrued expenses and other current liabilities		11,219		11,219		$ 9,108
Eli Lilly
Collaborative Arrangement and Arrangement Other than Collaborative
Number of programs | program	6
Number of targets | target	5
Cost sharing allocation	50%		50%		50%
Deferred revenue		282,900		282,900
Collaboration revenue		7,800	$ 1,400	19,700	$ 11,300
Accrued expenses and other current liabilities		$ 4,200		$ 4,200		1,500
Eli Lilly | Joint Programs
Collaborative Arrangement and Arrangement Other than Collaborative
Number of programs | program	2
Number of targets | target	1
Eli Lilly | Discovery Programs
Collaborative Arrangement and Arrangement Other than Collaborative
Number of additional targets | target	3
Eli Lilly | Sales Based Milestone
Collaborative Arrangement and Arrangement Other than Collaborative
Amount receivable for achievement of milestones	$ 180,000
Optout milestone receivable upon achievement	360,000
Eli Lilly | Maximum | Research Development and Regulatory
Collaborative Arrangement and Arrangement Other than Collaborative
Amount receivable for achievement of milestones	10,000
Optout milestone receivable upon achievement	$ 70,000
Merck
Collaborative Arrangement and Arrangement Other than Collaborative
Unsatisfied portion of the performance obligation						$ 0
Merck | Merck Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative
Collaboration revenue			$ 16,100		$ 17,000

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Thousands		3 Months Ended		9 Months Ended
	May 10, 2024 USD ($) ft²	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)
Commitments and Contingencies
Impairment of long-lived assets		$ 0	$ 0	$ 2,398	$ 0
Impairment of leasehold improvements				800
Stanford License Agreement | Maximum
Commitments and Contingencies
Annual license maintenance fees				300
Milestones payable upon event				$ 1,100
Office Space In Cambridge, Massachusetts
Commitments and Contingencies
Area of leased property | ft²	15,700
Impairment of long-lived assets	$ 2,400
Operating lease impairment	1,600
Impairment of leasehold improvements	800
Office Space In Cambridge, Massachusetts | Scenario, Plan
Commitments and Contingencies
Operating Lease, Lease Income	$ 6,600

Related Parties (Details)

Related Parties (Details) - USD ($)		1 Months Ended	3 Months Ended		9 Months Ended
	Dec. 10, 2021	Oct. 31, 2015	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Related Party Transaction
Accounts payable			$ 3,451,000		$ 3,451,000		$ 6,260,000
Revenue			7,808,000	$ 17,478,000	19,746,000	$ 28,386,000
Accrued expenses and other current liabilities			11,219,000		11,219,000		9,108,000
Eli Lilly
Related Party Transaction
Revenue			7,800,000	1,400,000	19,700,000	11,300,000
Accrued expenses and other current liabilities			4,200,000		4,200,000		1,500,000
Related Party | Eli Lilly
Related Party Transaction
Revenue			1,300,000	$ 0	4,200,000	$ 0
Accrued expenses and other current liabilities			$ 4,200,000		$ 4,200,000		1,500,000
Related Party | Eli Lilly | Share Purchase Agreement
Related Party Transaction
Sale of stock, number of shares issued in transaction (in shares)	4,000,000
Sale of stock issue price per share (in dollars per share)			$ 20	$ 20	$ 20	$ 20
Related Party | Danforth Advisors, LLC
Related Party Transaction
Accounts payable			$ 100,000		$ 100,000
Consulting fees			100,000		300,000
Related Party | Scientific Founder
Related Party Transaction
Service agreement term		5 years
Service agreement, renewal term		1 year
Payments made to related party under service agreement			0	$ 0	200,000	$ 100,000
Accounts payable			$ 0		$ 0		$ 100,000