Foghorn Therapeutics (FHTX) 10-K 7 Mar 24 2023 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Feb. 29, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Current Fiscal Year End Date	--12-31
Document Period End Date	Dec. 31, 2023
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	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
Trading Symbol(s)	FHTX
Name of each exchange on which registered	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 199.7
Entity Common Stock, Shares Outstanding		42,565,904
Amendment Flag	false
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Central Index Key	0001822462

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2023
Audit Information [Abstract]
Auditor Name	Deloitte & Touche LLP
Auditor Firm ID	34
Auditor Location	Boston, Massachusetts

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 80,336	$ 52,214
Marketable securities	153,721	293,584
Prepaid expenses and other current assets	6,124	5,601
Total current assets	240,181	351,399
Property and equipment, net	12,956	15,311
Restricted cash	1,708	1,708
Other assets	1,115	2,379
Operating lease right-of-use assets	29,956	34,086
Total assets	285,916	404,883
Current liabilities:
Accounts payable	6,260	5,414
Accrued expenses and other current liabilities	9,108	11,001
Operating lease liabilities	8,518	5,970
Deferred revenue	34,550	32,820
Total current liabilities	58,436	55,205
Operating lease liabilities, net of current portion	36,555	45,537
Deferred revenue, net of current portion	268,115	304,000
Other liabilities	0	29
Total liabilities	363,106	404,771
Commitments and contingencies (Note 11)
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value; 25,000,000 shares authorized as of December 31, 2023 and 2022; no shares issued and outstanding as of December 31, 2023 and 2022	0	0
Common stock, $0.0001 par value; 175,000,000 shares authorized at December 31, 2023 and 2022; 42,282,040 shares issued and outstanding at December 31, 2023 and 41,803,436 shares issued and outstanding at December 31, 2022	4	4
Additional paid-in capital	395,196	377,232
Accumulated other comprehensive loss	(826)	(3,986)
Accumulated deficit	(471,564)	(373,138)
Total stockholders’ equity (deficit)	(77,190)	112
Total liabilities and stockholders’ equity (deficit)	$ 285,916	$ 404,883

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock 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)	42,282,040	41,803,436
Common stock, shares, outstanding (in shares)	42,282,040	41,803,436

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Statement [Abstract]
Collaboration revenue	$ 34,155	$ 19,228
Operating expenses:
Research and development	109,689	105,618
General and administrative	32,372	30,747
Total operating expenses	142,061	136,365
Loss from operations	(107,906)	(117,137)
Other income (expense):
Interest income	10,875	5,675
Other income, net	2,831	2,580
Total other income, net	13,706	8,255
Loss before income taxes	(94,200)	(108,882)
Provision for income taxes	(4,226)	0
Net loss	$ (98,426)	$ (108,882)
Net loss per share attributable to common stockholders—basic (in dollars per share)	$ (2.34)	$ (2.62)
Net loss per share attributable to common stockholders—diluted (in dollars per share)	$ (2.34)	$ (2.62)
Weighted average common shares outstanding—basic (in shares)	41,974,484	41,591,433
Weighted average common shares outstanding—diluted (in shares)	41,974,484	41,591,433
Comprehensive loss:
Net loss	$ (98,426)	$ (108,882)
Other comprehensive loss:
Unrealized gains (losses) on marketable securities	3,160	(3,976)
Total other comprehensive gain (loss)	3,160	(3,976)
Total comprehensive loss	$ (95,266)	$ (112,858)
Revenue from Contract with Customer, Product and Service [Extensible Enumeration]	Collaboration Revenue [Member]	Collaboration Revenue [Member]

Consolidated Statements of Stoc

Consolidated Statements of Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning balance at Dec. 31, 2021	$ 96,871	$ 4	$ 361,133	$ (10)	$ (264,256)
Beginning balance (in shares) at Dec. 31, 2021		41,299,720
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options and employee stock purchase plan	1,763		1,763
Issuance of common stock upon exercise of stock options (in shares)		503,716
Stock-based compensation expense	14,336		14,336
Unrealized losses on marketable securities	(3,976)			(3,976)
Net loss	(108,882)				(108,882)
Ending balance at Dec. 31, 2022	$ 112	$ 4	377,232	(3,986)	(373,138)
Ending balance (in shares) at Dec. 31, 2022	41,803,436	41,803,436
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of stock options and employee stock purchase plan	$ 1,778		1,778
Issuance of common stock upon exercise of stock options (in shares)	437,407	478,604
Stock-based compensation expense	$ 16,186		16,186
Unrealized losses on marketable securities	3,160			3,160
Net loss	(98,426)				(98,426)
Ending balance at Dec. 31, 2023	$ (77,190)	$ 4	$ 395,196	$ (826)	$ (471,564)
Ending balance (in shares) at Dec. 31, 2023	42,282,040	42,282,040

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net loss	$ (98,426)	$ (108,882)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Stock-based compensation expense	16,186	14,336
Depreciation and amortization expense	3,451	3,321
Loss on disposal of property and equipment	3	6
Noncash lease expense	5,210	4,580
Accretion of discount on marketable securities	(2,651)	(1,295)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	741	(307)
Collaboration receivable	0	300,000
Accounts payable	846	1,614
Accrued expenses and other liabilities	(1,797)	1,441
Operating lease liabilities	(7,514)	(6,975)
Deferred revenue	(34,155)	(14,227)
Net cash provided by (used in) operating activities	(118,106)	193,612
Cash flows from investing activities:
Purchases of property and equipment	(1,224)	(1,210)
Purchases of marketable securities	(73,901)	(409,345)
Proceeds from maturities of marketable securities	219,575	166,233
Net cash provided by (used in) investing activities	144,450	(244,322)
Cash flows from financing activities:
Proceeds from issuance of common stock upon exercise of stock options and employee stock purchase plan	1,778	1,763
Net cash provided by financing activities	1,778	1,763
Net increase (decrease) in cash, cash equivalents and restricted cash	28,122	(48,947)
Cash, cash equivalents and restricted cash at beginning of period	53,922	102,869
Cash, cash equivalents and restricted cash at end of period	82,044	53,922
Supplemental cash flow information:
Cash paid for taxes	3,551	0
Supplemental disclosure of noncash investing and financing information:
Purchases of property and equipment included in accounts payable and accrued expenses	35	160
Reconciliation of cash, cash equivalents and restricted cash:
Cash and cash equivalents	80,336	52,214
Restricted cash (non-current)	1,708	1,708
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 82,044	$ 53,922

Nature of Business, Going Conce

Nature of Business, Going Concern and Basis of Presentation	12 Months Ended
	Dec. 31, 2023
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 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 early-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. Going concern The accompanying 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, an upfront payment from a collaboration agreement, a public offering and a stock purchase agreement all prior to 2022. In January 2022, the Company received an upfront payment of $300.0 million pursuant to a collaboration agreement (the “Lilly Collaboration Agreement”) completed with Loxo Oncology at Eli Lilly and Company (“Lilly”) (see Note 8). In the third quarter of 2022, the Company achieved a research milestone related to a collaboration agreement (the “Merck Collaboration Agreement”) with Merck Sharp & Dohme Corp. (“Merck”) and received a $5.0 million milestone payment. The Company has incurred recurring losses, including net losses of $98.4 million and $108.9 million for the years ended December 31, 2023 and 2022, respectively. As of December 31, 2023, the Company had an accumulated deficit of $471.6 million. The Company expects to continue to generate operating losses in the foreseeable future. As of the issuance date of these 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 consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying 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	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, revenue recognition and the accrual of research and development expenses. 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 from those estimates or assumptions. Concentrations of credit risk and of significant suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company relies, and expects to continue to rely, on a small number of vendors to provide services, supplies and materials for certain activities related to its programs. These programs could be adversely affected by a significant interruption in these services or the availability of materials. Cash equivalents The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents. Marketable Securities The Company’s marketable securities are classified as available-for-sale and are carried at fair value with the unrealized gains and losses reported as a component of accumulated other comprehensive loss in stockholders’ equity. The Company classifies its marketable securities with maturities beyond one year as short-term, based on their highly liquid nature and because such marketable securities are available for current operations. The Company reviews marketable securities whenever the fair value of an investment is less than the amortized cost and evidence indicates that an investment’s carrying value is not recoverable. For available-for-sale debt securities, the credit allowance is limited to the amount that fair value is less than amortized cost. Unrealized gains (losses) are evaluated for impairment under ASC 326, Financial Instruments - Credit Losses , to determine if the impairment is credit-related or noncredit-related. Credit-related impairment is recognized as an allowance on the consolidated balance sheets with a corresponding adjustment to earnings, and noncredit-related impairment is recognized in other comprehensive loss. Evidence considered in this assessment includes reasons for the impairment, compliance with our investment policy, the severity of the impairment, collectability of the security, and any adverse conditions specifically related to the security, an industry, or geographic area. Unrealized gains and losses are included as a component of accumulated other comprehensive loss in the consolidated balance sheets and consolidated statements of stockholders’ equity (deficit) and a component of total comprehensive loss. Realized gains and losses are included as a component of other income (expense), net based on the specific identification method. Restricted cash Amounts included in restricted cash represent amounts pledged as collateral for letters of credit required for security deposits on the Company’s leased facilities. These amounts are classified as restricted cash in the Company’s consolidated balance sheets. Property and equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset as follows: Estimated Useful Life Laboratory equipment 5 years Furniture and fixtures 5 years Computer equipment and software 3 years Leasehold improvements Shorter of useful life or remaining term of lease Costs for capital assets not yet placed into service are depreciated once placed into service. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation and amortization are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred. Impairment of long-lived assets The Company evaluates its long-lived assets, which consist primarily of property and equipment and operating lease right-of-use assets, for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset exceeds the fair value of the asset. The Company recorded no impairment losses on long-lived assets for the years ended December 31, 2023 or 2022. Fair value measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The Company’s cash equivalents and marketable securities are carried at fair value, determined according to the fair value hierarchy described above (see Note 3). The carrying values of the Company’s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities. Collaboration Agreements The Company analyzes its collaboration arrangements to assess whether they are within the scope of ASC 808, Collaborative Arrangements (“ASC 808”) to determine whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities. This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. When the Company has concluded that it has a customer relationship with one of its collaborators, the Company follows the guidance in ASC Topic 606, Revenue From Contracts With Customers (“ASC 606”). Revenue recognition The Company accounts for its collaboration arrangements under ASC 606, as the Company concluded that it has a customer relationship with each of its collaborators. For additional information on the Company’s collaboration agreements, see Note 8, Collaboration Agreements, to these consolidated financial statements. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. The Company assesses the goods or services promised within each contract and determines those that are performance obligations. The promised goods or services in the Company’s arrangements would likely consist of licenses, rights to the Company’s intellectual property, research and development services and related supporting activities. Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations. The Company assesses whether each promised good or service is distinct for the purpose of identifying the performance obligations in the contract. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services and whether such are separable from the other aspects of the contractual relationship. Promised goods and services are considered distinct provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer (that is, the good or service is capable of being distinct) and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract (that is, the promise to transfer the good or service is distinct within the context of the contract). In assessing whether a promised good or service is distinct, the Company considers factors such as the research, development, manufacturing and commercialization capabilities of the customer and the availability of the associated expertise in the general marketplace. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, an entity is required to combine that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct. The transaction price is then determined and allocated to the identified performance obligations in proportion to their standalone selling prices (“SSP”) on a relative SSP basis. SSP is determined at contract inception and is not updated to reflect changes between contract inception and when the performance obligations are satisfied. Determining the SSP for performance obligations requires significant judgment. In developing the SSP for a performance obligation, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. The Company validates the SSP for performance obligations by evaluating whether changes in the key assumptions used to determine the SSP will have a significant effect on the allocation of arrangement consideration between multiple performance obligations. If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment. If an arrangement includes development and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached 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 Company’s control such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied. The Company records amounts as accounts receivable when the right to consideration is deemed unconditional. When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer under the terms of a contract, a contract liability is recorded for deferred revenue. In determining the transaction price, the Company adjusts consideration for the effects of the time value of money if the timing of payments provides the Company with a significant benefit of financing. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between the transfer of the promised goods or services to the customer and the payment by the customer will be one year or less. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied, either at a point in time or over time, and if over time, recognition is based on the use of an output or input method. Research and development costs Research and development expenses consist of costs incurred in performing research and development activities, including salaries and bonuses, stock-based compensation, employee benefits, facilities costs, laboratory supplies, depreciation, and external costs of vendors engaged to conduct research, preclinical and clinical development activities as well as the cost of licensing technology. Upfront payments and milestone payments made for the licensing of technology are expensed as research and development over the period to which they relate. Costs for research and development activities are expensed in the period in which they are incurred. Payments for such activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid expense or accrued research and development expense. Determining the prepaid and accrued balances at the end of any reporting period incorporate certain judgments and estimates by management that are based on information available to the Company including information provided by vendors regarding the progress to completion of specific tasks or costs incurred. Patent costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses. Leases The Company accounts for a contract as a lease when it has the right to control the asset for a period of time while obtaining substantially all of the asset’s economic benefits. The Company determines if an arrangement is a lease or contains an embedded lease at inception. For arrangements that meet the definition of a lease, the Company determines the initial classification and measurement of its right-of-use asset and lease liability at the lease commencement date and thereafter if modified. The lease term includes any renewal options that the Company is reasonably assured to exercise. The present value of lease payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its estimated secured incremental borrowing rate for that lease term. The Company’s policy is to not record leases with an original term of twelve months or less on its consolidated balance sheets and recognizes those lease payments in the consolidated statements of operations and comprehensive loss as incurred over the lease term. The Company’s existing leases are for office and laboratory space and an equipment lease. In addition to rent, the leases may require the Company to pay additional costs, such as utilities, maintenance and other operating costs, which are generally referred to as non-lease components. The Company has elected to not separate lease and non-lease components. Only the fixed costs for lease components and their associated non-lease components are accounted for as a single lease component and recognized as part of a right-of-use asset and liability. Rent expense for operating leases is recognized on a straight-line basis over the reasonably assured lease term based on the total lease payments and is included in operating expense in the consolidated statements of operations and comprehensive loss. The Company receives payments and income from a sublease on a portion of the Company’s primary office lease (see Note 10). The Company recognizes sublease income on a straight-line basis over the lease term in other income (expense), net on the consolidated statements of operations and comprehensive loss, net of any revenue share due to the Company’s lessor. Stock-based compensation The Company measures stock options with service-based vesting or performance-based vesting granted to employees, non-employees and directors based on the fair value on the date of grant using the Black-Scholes option-pricing model. Compensation expense for the awards is recognized over the requisite service period for employees and directors and as services are delivered for non-employees, both of which are generally the vesting period of the respective award. The Company uses the straight-line method to record the expense of awards with only service-based vesting conditions. The Company uses the graded-vesting method to record the expense of awards with both service-based and performance-based vesting conditions, commencing once achievement of the performance condition becomes probable. The Company accounts for forfeitures of share-based awards as they occur. The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified. Net loss per share Basic net income (loss) per share attributable to common stockholders is computed by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net income (loss) per share attributable to common stockholders is computed by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period, adjusted for potential dilutive common shares. In periods in which the Company reported a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the years ended December 31, 2023 and 2022. The following common stock equivalents presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive impact: December 31, 2023 2022 Stock options to purchase common stock 8,951,588 7,911,211 Warrants to purchase common stock 18,445 18,445 8,970,033 7,929,656 Segments Operating segments are defined as components of an entity for which separate discrete financial information is made available and that is regularly evaluated by the chief operating decision maker (“CODM”) in making decisions regarding resource allocation and assessing performance. The Company’s CODM is its chief executive officer and the Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company is focused on pioneering the discovery and development of a new class of medicines targeting genetically determined dependencies within the chromatin regulatory system. Comprehensive loss Comprehensive loss includes net loss as well as other changes in stockholders’ equity that result from transactions and economic events other than those with stockholders. For the years ended December 31, 2023 and 2022, the Company’s only element of other comprehensive loss was unrealized gains (losses) on available for sale debt securities. Income taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to the provision for income taxes. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. Any resulting unrecognized tax benefits are recorded within the provision for income taxes. 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 June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) . The new standard adjusts the accounting for assets held at amortized costs basis by eliminating the probable initial recognition threshold and requires an entity to reflect its current estimate of all expected credit losses as an allowance for credit losses. The Company adopted this as of January 1, 2023 and the adoption had no material impact to the Company’s consolidated financial position, results of operation, or cash flows.

Marketable Securities and Fair

Marketable Securities and Fair Value Measurements	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Marketable Securities and Fair Value Measurements	Marketable Securities and Fair Value Measurements As of December 31, 2023, available for sale marketable securities by security type consisted of (in thousands): Amortized Gross Gross Estimated 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 years) 5,890 — (32) 5,858 Total $ 154,547 $ 18 $ (844) $ 153,721 As of December 31, 2022, available for sale marketable securities by security type consisted of (in thousands): Amortized Gross Gross Estimated U.S. treasury notes (due within one year) $ 7,987 $ — $ (115) $ 7,872 Commercial paper (due within one year) 56,697 2 (301) 56,398 Corporate notes and bonds (due within one year) 139,764 — (1,342) 138,422 Corporate notes and bonds (due after one year through three years) 93,122 4 (2,234) 90,892 Total $ 297,570 $ 6 $ (3,992) $ 293,584 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 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 Fair Value Measurements at Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 28,077 $ — $ — $ 28,077 U.S. treasury notes — 1,998 — 1,998 Commercial paper — 22,139 — 22,139 Marketable securities: U.S. treasury notes — 7,872 — 7,872 Commercial paper — 56,398 — 56,398 Corporate notes and bonds — 229,314 — 229,314 Total $ 28,077 $ 317,721 $ — $ 345,798

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): December 31, 2023 2022 Laboratory equipment $ 6,804 $ 5,884 Furniture and fixtures 815 815 Computer equipment and software 115 100 Leasehold improvements 17,239 17,123 24,973 23,922 Less: Accumulated depreciation and amortization (12,017) (8,611) $ 12,956 $ 15,311

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	Accrued Expenses and Other Current Liabilities Accrued expenses consisted of the following (in thousands): December 31, 2023 2022 Accrued employee compensation and benefits $ 4,347 $ 4,743 Accrued external research and development expenses 3,610 5,262 Accrued income taxes 674 — Accrued professional fees 441 678 Other 36 318 $ 9,108 $ 11,001

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Common Stock	Common StockEach 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.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2023
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 December 31, 2023, 1,638,199 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 1,691,282 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). As of December 31, 2023, 1,143,300 shares remained available for future grant under the ESPP. The number of shares reserved for issuance under the ESPP was increased by 422,820 shares effective January 1, 2024. 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 first offering period commenced under the ESPP on September 1, 2021. For the years ended December 31, 2023 and 2022, the Company recognized $0.1 million of expense related to the ESPP. Stock option valuation The fair value of stock option grants is estimated using the Black-Scholes option-pricing model. The Company currently lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future. The following table presents, on a weighted average basis, the assumptions used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted for the years ended December 31, 2023 and 2022 which was as follows: Year Ended December 31, 2023 2022 Risk-free interest rate 3.7 % 2.1 % Expected volatility 87.9 % 83.8 % Expected dividend yield — — Expected term (in years) 6.0 6.1 The following table summarizes the Company’s option activity for the year ended December 31, 2023 which was as follows: Number of Weighted Weighted Aggregate (in years) (in thousands) Outstanding as of December 31, 2022 7,911,211 $ 10.36 7.8 $ 8,648 Granted 2,481,884 8.17 Exercised (437,407) 3.61 Forfeited (1,004,100) 11.28 Outstanding as of December 31, 2023 8,951,588 $ 9.97 7.4 $ 7,598 Vested and expected to vest as of December 31, 2023 8,951,588 $ 9.97 7.4 $ 7,598 Options exercisable as of December 31, 2023 4,879,493 $ 9.16 6.4 $ 7,530 The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock. The aggregate intrinsic value of stock options exercised for the years ended December 31, 2023 and 2022 was $1.8 million and $4.3 million, respectively. The weighted average grant-date fair value of stock options granted for the years ended December 31, 2023 and 2022 was $6.12 per share and $10.08 per share, respectively. Stock-based compensation The Company recorded stock-based compensation expense related to common stock options in the following expense categories of its consolidated statements of operations and comprehensive loss for the years ended December 31, 2023 and 2022 which was as follows (in thousands): Year Ended December 31, 2023 2022 Research and development expenses $ 6,856 $ 6,452 General and administrative expenses 9,330 7,884 $ 16,186 $ 14,336 As of December 31, 2023, total unrecognized compensation cost related to unvested options was $26.2 million, which is expected to be recognized over a weighted average period of 2.2 years.

Collaboration Agreements

Collaboration Agreements	12 Months Ended
	Dec. 31, 2023
Collaboration Agreement [Abstract]
Collaboration Agreements	Collaboration Agreements Lilly Collaboration Agreement and Stock Purchase Agreement In December 2021, the Company entered into the Lilly Collaboration Agreement with 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 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 t he 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 c ompletion 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. Under the terms of the Lilly Collaboration Agreement, Lilly agreed to make a nonrefundable upfront payment of $300.0 million to the Company within thirty (30) business days following the effective date of the agreement. Simultaneously with the execution of the Lilly Collaboration Agreement, the Company and Lilly entered into a stock purchase agreement with Lilly (the “Lilly SPA”), pursuant to which Lilly purchased 4,000,000 shares of the Company’s common stock at $20.00 per share, for an aggregate purchase price of $80.0 million. The Company determined that the Lilly Collaboration Agreement and the Lilly SPA should be evaluated as a combined contract in accordance with ASC 606. The Company determined the fair value of the shares sold under the Lilly SPA to be $37.8 million less than the contractual purchase price stipulated in the Lilly SPA. In accordance with the applicable accounting guidance in ASC 815-40, Contracts in Entity’s Own Equity , the Company determined that the sale of stock should be recorded at fair value and therefore allocated the excess consideration received under the Lilly SPA to the Lilly Collaboration Agreement, which along with the non-refundable payment of $300.0 million will be recognized as revenue over the total estimated period of performance. The Company accounted for the arrangement under ASC 606 as the Company concluded it has a customer relationship with Lilly. 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 BRM Selective inhibitor program into development activities for which Lilly will lead and the Company will participate and share in 50% of the costs until registrational trials. Costs incurred will continue to be included in research and development expenses on the consolidated statements of operations and comprehensive loss. The transaction price of $337.8 million was initially recorded as deferred revenue and is being recognized as revenue as the performance obligation is satisfied. The Company recognizes revenue using the cost-to-cost method, which it believes best depicts the transfer of control to the customer over time. Under the cost-to-cost method, the extent of progress towards completion is measured based on the ratio of actual costs incurred to the total estimated costs expected upon satisfying the identified performance obligation. Under this method, revenue is recorded as a percentage of the estimated transaction price based on the extent of progress towards completion. As of December 31, 2023, the potential research, development and regulatory milestone payments that the Company is eligible to receive were excluded from the transaction price as they were fully constrained by uncertain events. The Company will reevaluate the transaction price at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur, and if necessary, the Company will adjust its estimate of the transaction price. Any additions to the transaction price would be reflected in the period as a cumulative revenue catch-up based on the ratio of costs incurred to the total estimated costs expected applied to the revised transaction price. Sales-based royalties and milestone payments, which predominantly relate to the license, will be recognized if and when the related sales occur. As of December 31, 2023 , the aggregate amount of the transaction price related to the unsatisfied portion of the performance obligation was $302.7 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 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. During the year ended December 31, 2023, the Company re-evaluated its estimates related to the Lilly Collaboration Agreement. As a result of this re-evaluation, expected future costs over the course of the Lilly Collaboration Agreement increased, resulting in an adjustment that decreased revenue by $3.2 million for the year ended December 31, 2023. At inception, the Company assessed the Lilly Collaboration Agreement to determine whether a significant financing component exists and concluded that a significant financing component does not exist. For the years ended December 31, 2023 and 2022 , the Company had recorded $17.1 million and $17.4 million, respectively, of revenue under the Lilly Collaboration Agreement, which was included in deferred revenue at the beginning of the respective periods. As of December 31, 2023, the Company had a payable to Lilly of $1.5 million recorded in accrued expenses and other current liabilities on the Company’s consolidated balance sheets. As of December 31, 2022, the Company did not have a receivable or payable with Lilly. 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 Merck Collaboration Agreement, the Company granted Merck exclusive global rights to develop, manufacture and commercialize drugs that target dysregulation of a single transcription factor. The Company recognizes revenue using the cost-to-cost method. Under this method, revenue is recorded as a percentage of the estimated transaction price based on the extent of progress towards completion. In the third quarter of 2022, the Company achieved a research milestone related to the Merck Collaboration Agreement and received a $5.0 million milestone payment from Merck. On August 9, 2023 the Company received notice from Merck that it is terminating the Merck Collaboration Agreement effective November 7, 2023. At the time of notice, no material obligations remained under the Merck Collaboration Agreement. As such, the Company recognized the remaining $16.1 million of deferred revenue, related to the original $15.0 million upfront payment and the $5.0 million milestone payment received from Merck, in the year ended December 31, 2023 as collaboration revenue. As of December 31, 2023, there was no remaining performance obligation under the Merck Collaboration Agreement. For the year ended December 31, 2023 and 2022, the Company had recorded $17.0 million and $1.8 million of revenue under the Merck Collaboration Agreement. For the years ended December 31, 2023 and 2022, the Company had recorded $17.0 million and $1.1 million, respectively, of revenue under the Merck Collaboration Agreement, which was included in deferred revenue at the beginning of the respective periods and the classification of deferred revenue between short-term and long-term .

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the year ended December 31, 2023 the Company recorded a provision for income taxes of $4.2 million, representing an effective tax rate of 4.6%. The income tax provision and the effective tax rate is primarily driven by the current federal and state taxes related to the $300.0 million upfront payment for Lilly Collaboration Agreement, which will be recognized as taxable income in the current year, and the required capitalization of research and development costs pursuant to Internal Revenue Code Section 174. As a result, the Company expects to have taxable income in the current year, which will be reduced by utilizing available net operating loss carryforwards and research and development tax credit carryforwards. The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products that would generate revenue from product sales and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the net deferred tax assets. For the year ended December 31, 2023, the Company recorded income tax expense on pre-tax losses of $94.2 million. Historically, no income tax benefits for the net deferred tax assets comprised primarily of net operating losses incurred and research and development tax credits generated in each year, due to its uncertainty of realizing a benefit from these items. All of the Company’s operating losses since inception have been generated in the United States. A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate was as follows: Year Ended December 31, 2023 2022 Federal statutory income tax rate (21.0) % (21.0) % State taxes, net of federal benefit (6.3) (6.0) Federal and state research and development tax credits (5.5) (4.3) Other 4.4 1.3 Change in deferred tax asset valuation allowance 33.0 30.0 Effective income tax rate 4.6 % 0.0 % Net deferred tax assets consisted of the following (in thousands): December 31, 2023 2022 Deferred tax assets: Net operating loss carryforwards $ 631 $ 59,398 Capitalized research expenditures 46,627 22,212 Research and development tax credit carryforwards 5,777 14,071 Capitalized start-up costs 125 141 Deferred revenue 82,731 10,017 Accrued expenses 468 1,288 Stock-based compensation 5,044 3,090 Operating lease liabilities 12,328 14,052 Total deferred tax assets 153,731 124,269 Deferred tax liabilities: Depreciation (2,567) (3,048) Operating lease right-of-use assets (8,197) (9,317) Total deferred tax liabilities (10,764) (12,365) Valuation allowance (142,967) (111,904) Net deferred tax assets $ — $ — As of December 31, 2023, the Company had U.S. federal net operating loss carryforwards of $3.0 million which can be carried forward indefinitely but limited to offset 80% of annual taxable income. As of December 31, 2023, the Company also had U.S. federal and state research and development tax credit carryforwards of $3.7 million and $2.6 million, respectively, which may be available to offset future tax liabilities and expire at various dates beginning in 2041 and 2037, respectively. Beginning in 2022, the Tax Cuts and Jobs Act of 2017 eliminated the option to deduct research and development expenditures currently and requires taxpayers to amortize them, over five years for domestically incurred expenditures and over fifteen years for foreign incurred expenditures, pursuant to Internal Revenue Code Section 174. As of December 31, 2023, the Company has recorded a gross deferred tax asset of $170.6 million related to the Capitalized IRC Section 174 expenditures. The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products that would generate revenue from product sales and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the net deferred tax assets as of December 31, 2023 and 2022. Management reevaluates the positive and negative evidence at each reporting period. The valuation allowance increased by $31.1 million and $32.8 million for the years ended December 31, 2023 and 2022, respectively, primarily as a result of the increase in total deferred tax assets. As of December 31, 2023 and 2022, the Company had not recorded any amounts for unrecognized tax benefits. The Company files income tax returns in the U.S. Massachusetts, Florida and Tennessee as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending tax examinations. Since the Company is in a loss carryforward position, it is generally subject to examination by the U.S. federal, state, and local income tax authorities for all tax years in which a loss carryforward is available.

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Leases	Leases In October 2019, the Company entered into a lease for 81,441 square feet of office and laboratory space in Cambridge, Massachusetts, commencing in January 2020 (the “Office Lease”). The initial term of the Office Lease was eight years with a five-year option to extend at fair-market rent at the time of the extension. In June 2020, the Company amended the Office Lease to defer payment of a portion of the base rent and operating expenses and to extend the lease term by nine months to September 2028. The base rent payments escalate annually over the eight-year lease term and totaled approximately $60.3 million. In connection with the Office Lease, the landlord agreed to fund up to $3.0 million in tenant improvements to the leased facility as well as up to an additional $16.3 million, which resulted in additional rent payments to the landlord over the lease term. For the years ended December 31, 2023 and 2022, $0.1 million and $0.1 million, respectively, of leasehold improvements were reimbursed by the landlord, which resulted in an increase to operating lease liabilities. The Company is obligated to pay its portion of real estate taxes and costs related to the premises, including costs of operations and management of the leased premises. The Company is required to maintain a cash balance of $1.7 million to secure a letter of credit associated with the lease. This amount was classified as restricted cash (non-current) on the consolidated balance sheets as of December 31, 2023 and 2022. The components of lease expense were as follows for the years ended December 31, 2023 and 2022 (in thousands): Year Ended December 31, 2023 2022 Operating lease cost $ 7,708 $ 7,532 Variable lease cost 2,755 3,323 $ 10,463 $ 10,855 Supplemental disclosure of cash flow information related to leases was as follows (in thousands): Year Ended December 31, 2023 2022 Cash paid for amounts included in the measurement of operating lease liabilities $ 10,147 $ 9,986 Operating lease liabilities arising from obtaining right-of-use assets $ 1,080 $ 150 The weighted average remaining lease term and discount rate was as follows: 2023 2022 Weighted-average remaining lease term—operating leases (in years) 4.6 5.7 Weighted-average discount rate—operating leases 5.24 % 5.35 % Future annual minimum lease payments under operating leases as of December 31, 2023 was as follows (in thousands): 2024 $ 10,688 2025 10,655 2026 10,594 2027 10,857 2028 8,346 Total future minimum lease payments 51,140 Less: imputed interest (6,067) Total operating lease liabilities $ 45,073 Year Ended December 31, Included in the consolidated balance sheets (in thousands): 2023 2022 Current operating lease liabilities $ 8,518 $ 5,970 Operating lease liabilities, net of current portion 36,555 45,537 Total operating lease liabilities $ 45,073 $ 51,507 Sublease agreement During the year 2022, the Company was given notice by its sublessee (the “Former Sublessee”) that it would terminate the sublease in accordance with its terms and vacate the subleased premises, prior to the original expiration date. At the time, the Company was subletting 19,823 square feet of office space under the Office Lease, as amended, to the Former Sublessee. On August 2, 2022, the Company entered into a sublease with another party (the “New Sublease”) to sublease the same premises. The New Sublease became effective during the fourth quarter of 2022 and has an initial term of 18 months. During the year ended December 31, 2023, the sublessee notified the Company that they will exercise the 12-month renewal option, extending the New Sublease through April 28, 2025. As of December 31, 2023, the remaining rent payments due to the Company under the New Sublease were $3.4 million. For the years ended December 31, 2023 and 2022, the Company recorded other income of $2.9 million and $2.6 million, respectively, related to its subleases.
Leases	Leases In October 2019, the Company entered into a lease for 81,441 square feet of office and laboratory space in Cambridge, Massachusetts, commencing in January 2020 (the “Office Lease”). The initial term of the Office Lease was eight years with a five-year option to extend at fair-market rent at the time of the extension. In June 2020, the Company amended the Office Lease to defer payment of a portion of the base rent and operating expenses and to extend the lease term by nine months to September 2028. The base rent payments escalate annually over the eight-year lease term and totaled approximately $60.3 million. In connection with the Office Lease, the landlord agreed to fund up to $3.0 million in tenant improvements to the leased facility as well as up to an additional $16.3 million, which resulted in additional rent payments to the landlord over the lease term. For the years ended December 31, 2023 and 2022, $0.1 million and $0.1 million, respectively, of leasehold improvements were reimbursed by the landlord, which resulted in an increase to operating lease liabilities. The Company is obligated to pay its portion of real estate taxes and costs related to the premises, including costs of operations and management of the leased premises. The Company is required to maintain a cash balance of $1.7 million to secure a letter of credit associated with the lease. This amount was classified as restricted cash (non-current) on the consolidated balance sheets as of December 31, 2023 and 2022. The components of lease expense were as follows for the years ended December 31, 2023 and 2022 (in thousands): Year Ended December 31, 2023 2022 Operating lease cost $ 7,708 $ 7,532 Variable lease cost 2,755 3,323 $ 10,463 $ 10,855 Supplemental disclosure of cash flow information related to leases was as follows (in thousands): Year Ended December 31, 2023 2022 Cash paid for amounts included in the measurement of operating lease liabilities $ 10,147 $ 9,986 Operating lease liabilities arising from obtaining right-of-use assets $ 1,080 $ 150 The weighted average remaining lease term and discount rate was as follows: 2023 2022 Weighted-average remaining lease term—operating leases (in years) 4.6 5.7 Weighted-average discount rate—operating leases 5.24 % 5.35 % Future annual minimum lease payments under operating leases as of December 31, 2023 was as follows (in thousands): 2024 $ 10,688 2025 10,655 2026 10,594 2027 10,857 2028 8,346 Total future minimum lease payments 51,140 Less: imputed interest (6,067) Total operating lease liabilities $ 45,073 Year Ended December 31, Included in the consolidated balance sheets (in thousands): 2023 2022 Current operating lease liabilities $ 8,518 $ 5,970 Operating lease liabilities, net of current portion 36,555 45,537 Total operating lease liabilities $ 45,073 $ 51,507 Sublease agreement During the year 2022, the Company was given notice by its sublessee (the “Former Sublessee”) that it would terminate the sublease in accordance with its terms and vacate the subleased premises, prior to the original expiration date. At the time, the Company was subletting 19,823 square feet of office space under the Office Lease, as amended, to the Former Sublessee. On August 2, 2022, the Company entered into a sublease with another party (the “New Sublease”) to sublease the same premises. The New Sublease became effective during the fourth quarter of 2022 and has an initial term of 18 months. During the year ended December 31, 2023, the sublessee notified the Company that they will exercise the 12-month renewal option, extending the New Sublease through April 28, 2025. As of December 31, 2023, the remaining rent payments due to the Company under the New Sublease were $3.4 million. For the years ended December 31, 2023 and 2022, the Company recorded other income of $2.9 million and $2.6 million, respectively, related to its subleases.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases The Company’s commitments under its leases are described in Note 10. 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 current 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.

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
Defined Contribution Plan	Defined Contribution PlanThe Company has a 401(k) defined contribution plan (the “401(k) Plan”) for its employees. Eligible employees may make pretax contributions to the 401(k) Plan up to statutory limits. For the year ended December 31, 2023, the Company recorded $0.4 million of expense related to 401(k) discretionary match. For the year ended December 31, 2022, there was no discretionary match made under the 401(k) Plan

Related Parties

Related Parties	12 Months Ended
	Dec. 31, 2023
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, 2024, and is subject to automatic one-year renewal terms until terminated. For the years ended December 31, 2023 and 2022, the Company paid the scientific founder $0.1 million. As of December 31, 2023 and 2022, the Company had less than $0.1 million in 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 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 years ended December 31, 2023 and 2022. For the years ended December 31, 2023 and 2022 , the Company had recorded $17.1 million and $17.4 million, respectively, of revenue under the Lilly Collaboration Agreement. As of December 31, 2023 and 2022, the Company had $302.7 million and $319.8 million , of deferred revenue related to the Lilly Collaboration Agreement. As of December 31, 2023, the Company had a payable of $1.5 million due to Lilly. As of December 31, 2022, the Company did not have a receivable or payable with Lilly.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The Company’s consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying 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”).
Use of estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, revenue recognition and the accrual of research and development expenses. 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 from those estimates or assumptions.
Concentrations of credit risk and of significant suppliers	Concentrations of credit risk and of significant suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company relies, and expects to continue to rely, on a small number of vendors to provide services, supplies and materials for certain activities related to its programs. These programs could be adversely affected by a significant interruption in these services or the availability of materials.
Cash equivalents	Cash equivalents The Company considers all highly liquid investments with original maturities of three months or less at the date of purchase to be cash equivalents.
Marketable Securities	Marketable Securities The Company’s marketable securities are classified as available-for-sale and are carried at fair value with the unrealized gains and losses reported as a component of accumulated other comprehensive loss in stockholders’ equity. The Company classifies its marketable securities with maturities beyond one year as short-term, based on their highly liquid nature and because such marketable securities are available for current operations. The Company reviews marketable securities whenever the fair value of an investment is less than the amortized cost and evidence indicates that an investment’s carrying value is not recoverable. For available-for-sale debt securities, the credit allowance is limited to the amount that fair value is less than amortized cost. Unrealized gains (losses) are evaluated for impairment under ASC 326, Financial Instruments - Credit Losses , to determine if the impairment is credit-related or noncredit-related. Credit-related impairment is recognized as an allowance on the consolidated balance sheets with a corresponding adjustment to earnings, and noncredit-related impairment is recognized in other comprehensive loss. Evidence considered in this assessment includes reasons for the impairment, compliance with our investment policy, the severity of the impairment, collectability of the security, and any adverse conditions specifically related to the security, an industry, or geographic area. Unrealized gains and losses are included as a component of accumulated other comprehensive loss in the consolidated balance sheets and consolidated statements of stockholders’ equity (deficit) and a component of total comprehensive loss. Realized gains and losses are included as a component of other income (expense), net based on the specific identification method.
Restricted cash	Restricted cash Amounts included in restricted cash represent amounts pledged as collateral for letters of credit required for security deposits on the Company’s leased facilities. These amounts are classified as restricted cash in the Company’s consolidated balance sheets.
Property and equipment	Property and equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset as follows: Estimated Useful Life Laboratory equipment 5 years Furniture and fixtures 5 years Computer equipment and software 3 years Leasehold improvements Shorter of useful life or remaining term of lease Costs for capital assets not yet placed into service are depreciated once placed into service. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation and amortization are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred.
Impairment of long-lived assets	Impairment of long-lived assets The Company evaluates its long-lived assets, which consist primarily of property and equipment and operating lease right-of-use assets, for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset exceeds the fair value of the asset. The Company recorded no impairment losses on long-lived assets for the years ended December 31, 2023 or 2022.
Fair value measurements	Fair value measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The Company’s cash equivalents and marketable securities are carried at fair value, determined according to the fair value hierarchy described above (see Note 3). The carrying values of the Company’s accounts payable and accrued expenses approximate their fair values due to the short-term nature of these liabilities.
Collaboration Agreements and Revenue recognition	Collaboration Agreements The Company analyzes its collaboration arrangements to assess whether they are within the scope of ASC 808, Collaborative Arrangements (“ASC 808”) to determine whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities. This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. When the Company has concluded that it has a customer relationship with one of its collaborators, the Company follows the guidance in ASC Topic 606, Revenue From Contracts With Customers (“ASC 606”). Revenue recognition The Company accounts for its collaboration arrangements under ASC 606, as the Company concluded that it has a customer relationship with each of its collaborators. For additional information on the Company’s collaboration agreements, see Note 8, Collaboration Agreements, to these consolidated financial statements. Under ASC 606, an entity recognizes revenue when its customer obtains control of promised goods or services in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements within the scope of ASC 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price, including variable consideration, if any; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer. The Company assesses the goods or services promised within each contract and determines those that are performance obligations. The promised goods or services in the Company’s arrangements would likely consist of licenses, rights to the Company’s intellectual property, research and development services and related supporting activities. Arrangements that include rights to additional goods or services that are exercisable at a customer’s discretion are generally considered options. The Company assesses if these options provide a material right to the customer and if so, they are considered performance obligations. The Company assesses whether each promised good or service is distinct for the purpose of identifying the performance obligations in the contract. This assessment involves subjective determinations and requires management to make judgments about the individual promised goods or services and whether such are separable from the other aspects of the contractual relationship. Promised goods and services are considered distinct provided that: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer (that is, the good or service is capable of being distinct) and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract (that is, the promise to transfer the good or service is distinct within the context of the contract). In assessing whether a promised good or service is distinct, the Company considers factors such as the research, development, manufacturing and commercialization capabilities of the customer and the availability of the associated expertise in the general marketplace. The Company also considers the intended benefit of the contract in assessing whether a promised good or service is separately identifiable from other promises in the contract. If a promised good or service is not distinct, an entity is required to combine that good or service with other promised goods or services until it identifies a bundle of goods or services that is distinct. The transaction price is then determined and allocated to the identified performance obligations in proportion to their standalone selling prices (“SSP”) on a relative SSP basis. SSP is determined at contract inception and is not updated to reflect changes between contract inception and when the performance obligations are satisfied. Determining the SSP for performance obligations requires significant judgment. In developing the SSP for a performance obligation, the Company considers applicable market conditions and relevant entity-specific factors, including factors that were contemplated in negotiating the agreement with the customer and estimated costs. The Company validates the SSP for performance obligations by evaluating whether changes in the key assumptions used to determine the SSP will have a significant effect on the allocation of arrangement consideration between multiple performance obligations. If the consideration promised in a contract includes a variable amount, the Company estimates the amount of consideration to which it will be entitled in exchange for transferring the promised goods or services to a customer. The Company determines the amount of variable consideration by using the expected value method or the most likely amount method. The Company includes the unconstrained amount of estimated variable consideration in the transaction price. The amount included in the transaction price is constrained to the amount for which it is probable that a significant reversal of cumulative revenue recognized will not occur. At the end of each subsequent reporting period, the Company re-evaluates the estimated variable consideration included in the transaction price and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis in the period of adjustment. If an arrangement includes development and regulatory milestone payments, the Company evaluates whether the milestones are considered probable of being reached 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 Company’s control such as regulatory approvals, are generally not considered probable of being achieved until those approvals are received. For arrangements with licenses of intellectual property that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes royalty revenue and sales-based milestones at the later of (i) when the related sales occur, or (ii) when the performance obligation to which the royalty has been allocated has been satisfied. The Company records amounts as accounts receivable when the right to consideration is deemed unconditional. When consideration is received, or such consideration is unconditionally due, from a customer prior to transferring goods or services to the customer under the terms of a contract, a contract liability is recorded for deferred revenue. In determining the transaction price, the Company adjusts consideration for the effects of the time value of money if the timing of payments provides the Company with a significant benefit of financing. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between the transfer of the promised goods or services to the customer and the payment by the customer will be one year or less. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) each performance obligation is satisfied, either at a point in time or over time, and if over time, recognition is based on the use of an output or input method.
Research and development costs	Research and development costs Research and development expenses consist of costs incurred in performing research and development activities, including salaries and bonuses, stock-based compensation, employee benefits, facilities costs, laboratory supplies, depreciation, and external costs of vendors engaged to conduct research, preclinical and clinical development activities as well as the cost of licensing technology. Upfront payments and milestone payments made for the licensing of technology are expensed as research and development over the period to which they relate. Costs for research and development activities are expensed in the period in which they are incurred. Payments for such activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid expense or accrued research and development expense. Determining the prepaid and accrued balances at the end of any reporting period incorporate certain judgments and estimates by management that are based on information available to the Company including information provided by vendors regarding the progress to completion of specific tasks or costs incurred.
Patent costs	Patent costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.
Leases	Leases The Company accounts for a contract as a lease when it has the right to control the asset for a period of time while obtaining substantially all of the asset’s economic benefits. The Company determines if an arrangement is a lease or contains an embedded lease at inception. For arrangements that meet the definition of a lease, the Company determines the initial classification and measurement of its right-of-use asset and lease liability at the lease commencement date and thereafter if modified. The lease term includes any renewal options that the Company is reasonably assured to exercise. The present value of lease payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its estimated secured incremental borrowing rate for that lease term. The Company’s policy is to not record leases with an original term of twelve months or less on its consolidated balance sheets and recognizes those lease payments in the consolidated statements of operations and comprehensive loss as incurred over the lease term. The Company’s existing leases are for office and laboratory space and an equipment lease. In addition to rent, the leases may require the Company to pay additional costs, such as utilities, maintenance and other operating costs, which are generally referred to as non-lease components. The Company has elected to not separate lease and non-lease components. Only the fixed costs for lease components and their associated non-lease components are accounted for as a single lease component and recognized as part of a right-of-use asset and liability. Rent expense for operating leases is recognized on a straight-line basis over the reasonably assured lease term based on the total lease payments and is included in operating expense in the consolidated statements of operations and comprehensive loss. The Company receives payments and income from a sublease on a portion of the Company’s primary office lease (see Note 10). The Company recognizes sublease income on a straight-line basis over the lease term in other income (expense), net on the consolidated statements of operations and comprehensive loss, net of any revenue share due to the Company’s lessor.
Stock-based compensation	Stock-based compensation The Company measures stock options with service-based vesting or performance-based vesting granted to employees, non-employees and directors based on the fair value on the date of grant using the Black-Scholes option-pricing model. Compensation expense for the awards is recognized over the requisite service period for employees and directors and as services are delivered for non-employees, both of which are generally the vesting period of the respective award. The Company uses the straight-line method to record the expense of awards with only service-based vesting conditions. The Company uses the graded-vesting method to record the expense of awards with both service-based and performance-based vesting conditions, commencing once achievement of the performance condition becomes probable. The Company accounts for forfeitures of share-based awards as they occur. The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.
Net loss per share	Net loss per share Basic net income (loss) per share attributable to common stockholders is computed by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period. Diluted net income (loss) per share attributable to common stockholders is computed by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding for the period, adjusted for potential dilutive common shares. In periods in which the Company reported a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive.
Segments	Segments Operating segments are defined as components of an entity for which separate discrete financial information is made available and that is regularly evaluated by the chief operating decision maker (“CODM”) in making decisions regarding resource allocation and assessing performance. The Company’s CODM is its chief executive officer and the Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company is focused on pioneering the discovery and development of a new class of medicines targeting genetically determined dependencies within the chromatin regulatory system.
Comprehensive loss	Comprehensive loss
Income taxes	Income taxes The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to the provision for income taxes. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies. The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. Any resulting unrecognized tax benefits are recorded within the provision for income taxes.
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 June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326) . The new standard adjusts the accounting for assets held at amortized costs basis by eliminating the probable initial recognition threshold and requires an entity to reflect its current estimate of all expected credit losses as an allowance for credit losses. The Company adopted this as of January 1, 2023 and the adoption had no material impact to the Company’s consolidated financial position, results of operation, or cash flows.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Property and Equipment are Stated at Cost Less Accumulated Depreciation and Amortization	Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset as follows: Estimated Useful Life Laboratory equipment 5 years Furniture and fixtures 5 years Computer equipment and software 3 years Leasehold improvements Shorter of useful life or remaining term of lease Property and equipment, net consisted of the following (in thousands): December 31, 2023 2022 Laboratory equipment $ 6,804 $ 5,884 Furniture and fixtures 815 815 Computer equipment and software 115 100 Leasehold improvements 17,239 17,123 24,973 23,922 Less: Accumulated depreciation and amortization (12,017) (8,611) $ 12,956 $ 15,311
Summary of Earnings Per Share Diluted Anti Dilutive Impact	The following common stock equivalents presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive impact: December 31, 2023 2022 Stock options to purchase common stock 8,951,588 7,911,211 Warrants to purchase common stock 18,445 18,445 8,970,033 7,929,656

Marketable Securities and Fai_2

Marketable Securities and Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Summary of Available for Sale Marketable Securities By Security Type	As of December 31, 2023, available for sale marketable securities by security type consisted of (in thousands): Amortized Gross Gross Estimated 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 years) 5,890 — (32) 5,858 Total $ 154,547 $ 18 $ (844) $ 153,721 As of December 31, 2022, available for sale marketable securities by security type consisted of (in thousands): Amortized Gross Gross Estimated U.S. treasury notes (due within one year) $ 7,987 $ — $ (115) $ 7,872 Commercial paper (due within one year) 56,697 2 (301) 56,398 Corporate notes and bonds (due within one year) 139,764 — (1,342) 138,422 Corporate notes and bonds (due after one year through three years) 93,122 4 (2,234) 90,892 Total $ 297,570 $ 6 $ (3,992) $ 293,584
Schedule of Fair Value, Assets and Liabilities Measured on 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 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 Fair Value Measurements at Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 28,077 $ — $ — $ 28,077 U.S. treasury notes — 1,998 — 1,998 Commercial paper — 22,139 — 22,139 Marketable securities: U.S. treasury notes — 7,872 — 7,872 Commercial paper — 56,398 — 56,398 Corporate notes and bonds — 229,314 — 229,314 Total $ 28,077 $ 317,721 $ — $ 345,798

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Sumary of Property and Equipment Net	Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset as follows: Estimated Useful Life Laboratory equipment 5 years Furniture and fixtures 5 years Computer equipment and software 3 years Leasehold improvements Shorter of useful life or remaining term of lease Property and equipment, net consisted of the following (in thousands): December 31, 2023 2022 Laboratory equipment $ 6,804 $ 5,884 Furniture and fixtures 815 815 Computer equipment and software 115 100 Leasehold improvements 17,239 17,123 24,973 23,922 Less: Accumulated depreciation and amortization (12,017) (8,611) $ 12,956 $ 15,311

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Table)	12 Months Ended
	Dec. 31, 2023
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following (in thousands): December 31, 2023 2022 Accrued employee compensation and benefits $ 4,347 $ 4,743 Accrued external research and development expenses 3,610 5,262 Accrued income taxes 674 — Accrued professional fees 441 678 Other 36 318 $ 9,108 $ 11,001

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Schedule of Weighted-Average Assumptions Used to Estimate Fair Value of Stock Options and Restricted Stock Awards using Black-Scholes Option Pricing Model	The following table presents, on a weighted average basis, the assumptions used in the Black-Scholes option-pricing model to determine the grant-date fair value of stock options granted for the years ended December 31, 2023 and 2022 which was as follows: Year Ended December 31, 2023 2022 Risk-free interest rate 3.7 % 2.1 % Expected volatility 87.9 % 83.8 % Expected dividend yield — — Expected term (in years) 6.0 6.1
Schedule of Share Option Activity	The following table summarizes the Company’s option activity for the year ended December 31, 2023 which was as follows: Number of Weighted Weighted Aggregate (in years) (in thousands) Outstanding as of December 31, 2022 7,911,211 $ 10.36 7.8 $ 8,648 Granted 2,481,884 8.17 Exercised (437,407) 3.61 Forfeited (1,004,100) 11.28 Outstanding as of December 31, 2023 8,951,588 $ 9.97 7.4 $ 7,598 Vested and expected to vest as of December 31, 2023 8,951,588 $ 9.97 7.4 $ 7,598 Options exercisable as of December 31, 2023 4,879,493 $ 9.16 6.4 $ 7,530
Summary of Stock-Based Compensation Expense	The Company recorded stock-based compensation expense related to common stock options in the following expense categories of its consolidated statements of operations and comprehensive loss for the years ended December 31, 2023 and 2022 which was as follows (in thousands): Year Ended December 31, 2023 2022 Research and development expenses $ 6,856 $ 6,452 General and administrative expenses 9,330 7,884 $ 16,186 $ 14,336

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Summary of Reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax rate	A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate was as follows: Year Ended December 31, 2023 2022 Federal statutory income tax rate (21.0) % (21.0) % State taxes, net of federal benefit (6.3) (6.0) Federal and state research and development tax credits (5.5) (4.3) Other 4.4 1.3 Change in deferred tax asset valuation allowance 33.0 30.0 Effective income tax rate 4.6 % 0.0 %
Summary of Net Deferred Tax Assets	Net deferred tax assets consisted of the following (in thousands): December 31, 2023 2022 Deferred tax assets: Net operating loss carryforwards $ 631 $ 59,398 Capitalized research expenditures 46,627 22,212 Research and development tax credit carryforwards 5,777 14,071 Capitalized start-up costs 125 141 Deferred revenue 82,731 10,017 Accrued expenses 468 1,288 Stock-based compensation 5,044 3,090 Operating lease liabilities 12,328 14,052 Total deferred tax assets 153,731 124,269 Deferred tax liabilities: Depreciation (2,567) (3,048) Operating lease right-of-use assets (8,197) (9,317) Total deferred tax liabilities (10,764) (12,365) Valuation allowance (142,967) (111,904) Net deferred tax assets $ — $ —

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Summary of Lease Cost and Lease Details	The components of lease expense were as follows for the years ended December 31, 2023 and 2022 (in thousands): Year Ended December 31, 2023 2022 Operating lease cost $ 7,708 $ 7,532 Variable lease cost 2,755 3,323 $ 10,463 $ 10,855 Supplemental disclosure of cash flow information related to leases was as follows (in thousands): Year Ended December 31, 2023 2022 Cash paid for amounts included in the measurement of operating lease liabilities $ 10,147 $ 9,986 Operating lease liabilities arising from obtaining right-of-use assets $ 1,080 $ 150 The weighted average remaining lease term and discount rate was as follows: 2023 2022 Weighted-average remaining lease term—operating leases (in years) 4.6 5.7 Weighted-average discount rate—operating leases 5.24 % 5.35 %
Summary of Minimum Lease Payments	Future annual minimum lease payments under operating leases as of December 31, 2023 was as follows (in thousands): 2024 $ 10,688 2025 10,655 2026 10,594 2027 10,857 2028 8,346 Total future minimum lease payments 51,140 Less: imputed interest (6,067) Total operating lease liabilities $ 45,073
Schedule of Balance Sheet Location	Year Ended December 31, Included in the consolidated balance sheets (in thousands): 2023 2022 Current operating lease liabilities $ 8,518 $ 5,970 Operating lease liabilities, net of current portion 36,555 45,537 Total operating lease liabilities $ 45,073 $ 51,507

Nature of Business, Going Con_2

Nature of Business, Going Concern and Basis of Presentation (Details) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended
	Aug. 09, 2023	Dec. 10, 2021	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022
Organization Consolidation And Presentation Of Financial Statements
Net losses				$ (98,426)	$ (108,882)
Incurred recurring loss				(95,266)	(112,858)
Accumulated deficit				471,564	$ 373,138
Eli Lilly
Organization Consolidation And Presentation Of Financial Statements
Upfront payment received		$ 300,000		$ 300,000
Merck
Organization Consolidation And Presentation Of Financial Statements
Upfront payment received	$ 15,000
Merck | Merck Collaboration Agreement
Organization Consolidation And Presentation Of Financial Statements
Payment received for achievement of milestones			$ 5,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Impairment losses on long-lived assets	$ 0	$ 0

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Property and Equipment are Stated at Cost Less Accumulated Depreciation and Amortization (Details)	Dec. 31, 2023
Laboratory equipment
Property, Plant and Equipment
Property, plant and equipment, useful life	5 years
Furniture and fixtures
Property, Plant and Equipment
Property, plant and equipment, useful life	5 years
Computer equipment and software
Property, Plant and Equipment
Property, plant and equipment, useful life	3 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Earnings Per Share Diluted Anti Dilutive Impact (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	8,970,033	7,929,656
Stock options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	8,951,588	7,911,211
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	18,445	18,445

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	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Amortized Cost	$ 154,547	$ 297,570
Gross Unrealized Gains	18	6
Gross Unrealized Losses	(844)	(3,992)
Estimated Fair Value	153,721	293,584
U.S. treasury notes (due within one year)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Amortized Cost		7,987
Gross Unrealized Gains		0
Gross Unrealized Losses		(115)
Estimated Fair Value		7,872
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	5,901	56,697
Gross Unrealized Gains	7	2
Gross Unrealized Losses	(2)	(301)
Estimated Fair Value	5,906	56,398
Commercial paper (due within one year) | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Estimated Fair Value	5,906	56,398
Commercial paper (due within one year) | Level 1 | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Estimated Fair Value	0	0
Commercial paper (due within one year) | Level 2 | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Estimated Fair Value	5,906	56,398
Commercial paper (due within one year) | Level 3 | Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Estimated Fair Value	0	0
Corporate notes and bonds (due within one year)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Amortized Cost	130,933	139,764
Gross Unrealized Gains	11	0
Gross Unrealized Losses	(784)	(1,342)
Estimated Fair Value	130,160	138,422
Corporate notes and bonds (due after one year through two years)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Amortized Cost	5,890	93,122
Gross Unrealized Gains	0	4
Gross Unrealized Losses	(32)	(2,234)
Estimated Fair Value	$ 5,858	$ 90,892

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	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	$ 153,721	$ 293,584
Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	234,057	345,798
Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	53,336	28,077
Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	180,721	317,721
Level 3 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Assets, fair value	0	0
U.S. government agencies | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	11,797
U.S. government agencies | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0
U.S. government agencies | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	11,797
U.S. government agencies | Level 3 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0
U.S. treasury notes | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities		7,872
U.S. treasury notes | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities		0
U.S. treasury notes | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities		7,872
U.S. treasury notes | Level 3 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities		0
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	5,906	56,398
Commercial paper | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	5,906	56,398
Commercial paper | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0	0
Commercial paper | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	5,906	56,398
Commercial paper | Level 3 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0	0
Corporate notes and bonds | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	136,018	229,314
Corporate notes and bonds | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0	0
Corporate notes and bonds | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	136,018	229,314
Corporate notes and bonds | Level 3 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Marketable securities	0	0
Money market funds | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	53,336	28,077
Money market funds | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	53,336	28,077
Money market funds | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	0	0
Money market funds | Level 3 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	0	0
U.S. treasury notes | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	27,000	1,998
U.S. treasury notes | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	0	0
U.S. treasury notes | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	27,000	1,998
U.S. treasury notes | Level 3 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents	$ 0	0
Commercial paper | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents		22,139
Commercial paper | Level 1 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents		0
Commercial paper | Level 2 | Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Cash equivalents		22,139
Commercial paper | Level 3 | Recurring
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	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment
Property, plant and equipment, gross	$ 24,973	$ 23,922
Less: Accumulated depreciation and amortization	(12,017)	(8,611)
Property, plant and equipment, net	12,956	15,311
Laboratory equipment
Property, Plant and Equipment
Property, plant and equipment, gross	6,804	5,884
Furniture and fixtures
Property, Plant and Equipment
Property, plant and equipment, gross	815	815
Computer equipment and software
Property, Plant and Equipment
Property, plant and equipment, gross	115	100
Leasehold improvements
Property, Plant and Equipment
Property, plant and equipment, gross	$ 17,239	$ 17,123

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 3,451	$ 3,321

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Accrued employee compensation and benefits	$ 4,347	$ 4,743
Accrued external research and development expenses	3,610	5,262
Accrued income taxes	674	0
Accrued professional fees	441	678
Other	36	318
Total	$ 9,108	$ 11,001

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) $ / shares in Units, $ in Millions		1 Months Ended	12 Months Ended
	Jan. 01, 2024 shares	Oct. 21, 2020 shares	Dec. 31, 2023 USD ($) period $ / shares shares	Dec. 31, 2022 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate intrinsic value of stock options exercised | $			$ 1.8	$ 4.3
Weighted average grant-date fair value of stock options granted (in dollars per share) | $ / shares			$ 6.12	$ 10.08
Unrecognized compensation costs related to unvested options and unvested restricted stock | $			$ 26.2
Weighted average period of unrecognized compensation costs (years)			2 years 2 months 12 days
2020 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)			2,200,000
Number of remaining shares available for grant (in shares)			1,638,199
Percentage of automatic annual increase in number of shares			4%
Vesting period (years)			4 years
Stock option expiry period (years)			10 years
2020 Incentive Plan | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized (in shares)	1,691,282
2016 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)			5,078,295
2020 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)		360,000
Number of remaining shares available for grant (in shares)			1,143,300
Percentage of automatic annual increase in number of shares		1%
Maximum aggregate number of shares added to plan (in shares)			3,220,520
Percentage of payroll deductions			15%
Discount of shares rate, percent			15%
Number of offering periods (period) | period			2
Share-based payment arrangement, expense | $			$ 0.1	$ 0.1
2020 Employee Stock Purchase Plan | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized (in shares)	422,820

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Weighted Average Assumptions Used to Estimate Fair Value of Stock Options and Restricted Stock Awards using Black-Scholes Option Pricing Model (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement [Abstract]
Risk-free interest rate	3.70%	2.10%
Expected volatility	87.90%	83.80%
Expected dividend yield	0%	0%
Expected term (in years)	6 years	6 years 1 month 6 days

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Share Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Number of Shares
Beginning Balance (in shares)	7,911,211
Granted (in shares)	2,481,884
Exercised (in shares)	(437,407)
Forfeited (in shares)	(1,004,100)
Ending Balance (in shares)	8,951,588	7,911,211
Vested and expected to vest (in shares)	8,951,588
Options exercisable (in shares)	4,879,493
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 10.36
Granted (in dollars per share)	8.17
Exercised (in dollars per share)	3.61
Forfeited (in dollars per share)	11.28
Ending balance (in dollars per share)	9.97	$ 10.36
Vested and expected to vest (in dollars per share)	9.97
Options, exercisable (in dollars per share)	$ 9.16
Weighted Average Contractual Term
Outstanding weighted average contractual term	7 years 4 months 24 days	7 years 9 months 18 days
Vested and expected to vest	7 years 4 months 24 days
Options exercisable	6 years 4 months 24 days
Aggregate Intrinsic Value
Outstanding aggregate intrinsic value	$ 7,598	$ 8,648
Vested and expected to vest	7,598
Options exercisable	$ 7,530

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-based compensation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-based Payment Arrangement
Stock-based compensation expense	$ 16,186	$ 14,336
Research and development expenses
Share-based Payment Arrangement
Stock-based compensation expense	6,856	6,452
General and administrative expenses
Share-based Payment Arrangement
Stock-based compensation expense	$ 9,330	$ 7,884

Collaboration Agreement (Detail

Collaboration Agreement (Details) $ / shares in Units, $ in Thousands			1 Months Ended	3 Months Ended	12 Months Ended
	Aug. 09, 2023 USD ($)	Dec. 10, 2021 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) program target	Sep. 30, 2022 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Sep. 30, 2023
Collaborative Arrangement and Arrangement Other than Collaborative
Revenue					$ 34,155	$ 19,228
Accrued expenses and other current liabilities					9,108	11,001
Eli Lilly
Collaborative Arrangement and Arrangement Other than Collaborative
Number of additional targets | target			3
Number of programs | program			6
Number of targets | target			5
Cost sharing rate (percent)			50%
Upfront payment received		$ 300,000			300,000
Payment period (days)		30 days
Difference between fair value of shares and contract price			$ 37,800
Cost sharing allocation							50%
Deferred revenue			337,800		302,700
Revenue					17,100	17,400
Accrued expenses and other current liabilities					1,500
Eli Lilly | Share Purchase Agreement
Collaborative Arrangement and Arrangement Other than Collaborative
Sale of stock, number of shares issued in transaction (in shares) | shares		4,000,000
Sale of stock issue price per share (in dollars per share) | $ / shares		$ 20
Sale of stock consideration received on the transaction		$ 80,000
Merck
Collaborative Arrangement and Arrangement Other than Collaborative
Upfront payment received	$ 15,000
Revenue					17,000	1,100
Unsatisfied portion of the performance obligation					0
Research Development And Regulatory | Eli Lilly | Scenario, Adjustment
Collaborative Arrangement and Arrangement Other than Collaborative
Revenue					(3,200)
Research Development And Regulatory | Eli Lilly | Maximum
Collaborative Arrangement and Arrangement Other than Collaborative
Amount receivable for achievement of milestones			10,000
Amounts receivable for opt out milestones			70,000
Sales Based Milestone | Eli Lilly
Collaborative Arrangement and Arrangement Other than Collaborative
Amount receivable for achievement of milestones			180,000
Amounts receivable for opt out milestones			$ 360,000
Merck Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative
Revenue					$ 17,000	$ 1,800
Merck Collaboration Agreement | Merck
Collaborative Arrangement and Arrangement Other than Collaborative
Revenue	$ 16,100
Payment received for achievement of milestones				$ 5,000

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)		12 Months Ended
	Dec. 10, 2021	Dec. 31, 2023	Dec. 31, 2022
Income Tax Contingency
Provision for income taxes		$ 4,226,000	$ 0
Effective income tax rate		(4.60%)	(0.00%)
Pre-tax losses		$ 94,200,000	$ 108,882,000
Deferred tax assets		153,731,000	124,269,000
Increase in valuation allowance		31,100,000	32,800,000
Unrecognized tax benefits		0	$ 0
Research Tax Credit Carryforward
Income Tax Contingency
Deferred tax assets		170,600,000
Domestic Tax Authority
Income Tax Contingency
Operating loss carry forward		3,000,000
Tax credit carry forward		$ 3,700,000
Operating loss carryforward limit (percentage)		80%
State and Local Jurisdiction
Income Tax Contingency
Tax credit carry forward		$ 2,600,000
Eli Lilly
Income Tax Contingency
Upfront payment received	$ 300,000,000	$ 300,000,000

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of the U.S. federal statutory income tax rate to the Company's effective income tax rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	(21.00%)	(21.00%)
State taxes, net of federal benefit	(6.30%)	(6.00%)
Federal and state research and development tax credits	(5.50%)	(4.30%)
Other	4.40%	1.30%
Change in deferred tax asset valuation allowance	33%	30%
Effective income tax rate	4.60%	0%

Income Taxes - Summary of Net D

Income Taxes - Summary of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 631	$ 59,398
Capitalized research expenditures	46,627	22,212
Research and development tax credit carryforwards	5,777	14,071
Capitalized start-up costs	125	141
Deferred revenue	82,731	10,017
Accrued expenses	468	1,288
Stock-based compensation	5,044	3,090
Operating lease liabilities	12,328	14,052
Total deferred tax assets	153,731	124,269
Deferred tax liabilities:
Depreciation	(2,567)	(3,048)
Operating lease right-of-use assets	(8,197)	(9,317)
Total deferred tax liabilities	(10,764)	(12,365)
Valuation allowance	(142,967)	(111,904)
Net deferred tax assets	$ 0	$ 0

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands	12 Months Ended		108 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) ft²	Dec. 31, 2028 USD ($)	Oct. 31, 2019 USD ($) ft²
Lessee, Lease, Description
Restricted cash	$ 1,708	$ 1,708
Future sublease income outstanding	3,400
Sublease income recorded as other income	2,900	2,600
Office and Laboratory Space In Cambridge, Massachusetts
Lessee, Lease, Description
Area of leased property | ft²				81,441
Lessee, operating lease, term of contract				8 years
Operating lease term extension				5 years
Reimbursements from lessor	100	$ 100
Restricted cash	$ 1,700
Office and Laboratory Space In Cambridge, Massachusetts | Maximum
Lessee, Lease, Description
Leasehold improvements landlord allowance				$ 3,000
Leasehold improvements landlord allowance to be repaid				$ 16,300
Office and Laboratory Space In Cambridge, Massachusetts | Forecast
Lessee, Lease, Description
Operating lease rent payments			$ 60,300
Office Space In Cambridge, Massachusetts
Lessee, Lease, Description
Area of leased property | ft²		19,823
Lessor, operating lease, term of contract		18 months
Lessor, operating lease renewal term		12 months

Leases - Summary of Lease Cost

Leases - Summary of Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Operating lease cost	$ 7,708	$ 7,532
Variable lease cost	2,755	3,323
Total	$ 10,463	$ 10,855

Leases - Summary of Supplementa

Leases - Summary of Supplemental Cash Flow Information Related to Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities	$ 10,147	$ 9,986
Operating lease liabilities arising from obtaining right-of-use assets	$ 1,080	$ 150

Leases - Summary of Weighted-Av

Leases - Summary of Weighted-Average Remaining Lease Term and Discount Rate Leases (Details)	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Weighted-average remaining lease term—operating leases (in years)	4 years 7 months 6 days	5 years 8 months 12 days
Weighted-average discount rate—operating leases	5.24%	5.35%

Leases - Summary of Minimum Lea

Leases - Summary of Minimum Lease Payment (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Lessee, Operating Lease, Liability, Payment, Due
2024	$ 10,688
2025	10,655
2026	10,594
2027	10,857
2028	8,346
Total future minimum lease payments	51,140
Less: imputed interest	(6,067)
Total operating lease liabilities	$ 45,073	$ 51,507

Leases - Summary of Operating L

Leases - Summary of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Current operating lease liabilities	$ 8,518	$ 5,970
Operating lease liabilities, net of current portion	36,555	45,537
Total operating lease liabilities	$ 45,073	$ 51,507

Commitments and Contingencies (

Commitments and Contingencies (Details) - Stanford License Agreement - Maximum $ in Millions	Jul. 31, 2017 USD ($)
Contingencies
Annual license maintenance fees	$ 0.3
Milestones payable upon event	$ 1.1

Defined Contribution Plan (Deta

Defined Contribution Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Retirement Benefits [Abstract]
Discretionary contribution amount	$ 400,000	$ 0

Related Parties (Details)

Related Parties (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	12 Months Ended
	Jan. 01, 2022	Dec. 10, 2021	Oct. 31, 2015	Dec. 31, 2023	Dec. 31, 2022
Related Party Transaction
Accounts payable				$ 6,260	$ 5,414
Accrued expenses and other current liabilities				(9,108)	(11,001)
Eli Lilly
Related Party Transaction
Accrued expenses and other current liabilities				(1,500)
Deferred revenue				302,700
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
Related Party
Related Party Transaction
Service agreement renewal term	1 year
Related Party | Scientific Founder
Related Party Transaction
Service agreement term			5 years
Payments made to related party under service agreement				100	100
Accounts payable				$ 100	$ 100