Omega Therapeutics (OMGA) 10-K 28 Mar 24 2023 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Mar. 21, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Entity Registrant Name	Omega Therapeutics, Inc.
Entity Central Index Key	0001850838
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		55,154,985
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Title of 12(b) Security	Common stock, par value $0.001 per share
Trading Symbol	OMGA
Security Exchange Name	NASDAQ
Entity File Number	001-40657
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-3247585
Entity Address, Address Line One	140 First StreetSuite 501
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02141
City Area Code	617
Local Phone Number	949-4360
Document Transition Report	false
ICFR Auditor Attestation Flag	false
Entity Public Float			$ 140.2
Document Financial Statement Error Correction [Flag]	false
Documents Incorporated by Reference [Text Block]	Portions of the Registrant’s definitive proxy statement relating to its 2024 Annual Meeting of Stockholders, to be filed with the Securities and Exchange Commission within 120 days after the end of the fiscal year ended December 31, 2023, are incorporated herein by reference in Part III.
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	$ 68,443	$ 70,615
Marketable securities	4,986	54,063
Accounts receivable, due from related party	1,006	618
Accounts receivable	5,125
Prepaid expenses and other current assets	10,324	12,294
Total current assets	89,884	137,590
Property and equipment, net	5,311	4,195
Operating lease right-of-use assets, net	108,736	3,668
Restricted cash	341	341
Other assets	94	204
Total assets	204,366	145,998
Current liabilities:
Accounts payable	1,620	3,107
Accrued expenses	7,914	13,841
Other current liabilities	1,972	159
Lease liabilities, current	11,300	1,524
Long-term debt, current portion	4,000	3,333
Total current liabilities	26,806	21,964
Lease liabilities, non-current	98,243	1,120
Long-term debt, net	14,885	16,603
Other liabilities	6,416	340
Total liabilities	146,350	40,027
Commitments and contingencies (Note 9)
Stockholders' equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized as of December 31, 2023 and December 31, 2022; no shares issued and outstanding as of December 31, 2023 and December 31, 2022	0	0
Common stock, $0.001 par value; 200,000,000 shares authorized as of December 31, 2023 and December 31, 2022; 55,144,982 and 48,072,517 issued and outstanding as of December 31, 2023 and December 31, 2022, respectively	55	48
Additional paid-in capital	392,609	343,608
Accumulated other comprehensive loss	(14)	(479)
Accumulated deficit	(334,634)	(237,206)
Total stockholders' equity	58,016	105,971
Total liabilities and stockholders' equity	$ 204,366	$ 145,998

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	55,144,982	48,072,517
Common stock, shares outstanding	55,144,982	48,072,517

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 from related party	$ 3,094	$ 2,073
Operating expenses:
Research and development	77,169	81,167
General and administrative	26,186	23,672
Total operating expenses	103,355	104,839
Loss from operations	(100,261)	(102,766)
Other Income (expense), net:
Interest income, net	2,810	222
Other income (expense), net	23	(157)
Total other income, net	2,833	65
Net loss	$ (97,428)	$ (102,701)
Net loss per common stock attributable to common stockholders, basic	$ (1.8)	$ (2.14)
Net loss per common stock attributable to common stockholders, diluted	$ (1.8)	$ (2.14)
Weighted-average common stock used in net loss per share attributable to common stockholders, basic	54,010,996	47,880,819
Weighted-average common stock used in net loss per share attributable to common stockholders, diluted	54,010,996	47,880,819
Comprehensive loss:
Net Income (Loss)	$ (97,428)	$ (102,701)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	465	(417)
Comprehensive loss	$ (96,963)	$ (103,118)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Balance at Dec. 31, 2021	$ 200,628	$ 48	$ 335,147	$ (62)	$ (134,505)
Balance (in shares) at Dec. 31, 2021		47,793,469
Issuance of common stock for options exercised	708		708
Issuance of common stock for options exercised, shares		279,048
Other comprehensive gain (loss)	(417)			(417)
Stock-based compensation	7,753		7,753
Net Income (Loss)	(102,701)				(102,701)
Balance at Dec. 31, 2022	105,971	$ 48	343,608	(479)	(237,206)
Balance (in shares) at Dec. 31, 2022		48,072,517
Issuance of common stock for registered direct offering, net of issuance costs, shares		6,920,415
Issuance of common stock for registered direct offering, net of issuance costs	39,727	$ 7	39,720
Issuance of common stock for options exercised	488		488
Issuance of common stock for options exercised, shares		152,050
Other comprehensive gain (loss)	465			465
Stock-based compensation	8,793		8,793
Net Income (Loss)	(97,428)				(97,428)
Balance at Dec. 31, 2023	$ 58,016	$ 55	$ 392,609	$ (14)	$ (334,634)
Balance (in shares) at Dec. 31, 2023		55,144,982

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating activities
Net loss	$ (97,428)	$ (102,701)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,568	1,564
Amortization of debt issuance costs and debt discount	53	67
Amortization of operating lease right-of-use assets	5,203	3,626
Accretion of discounts on marketable securities	(192)	1,045
Change in fair value of success fee obligation	92	13
Gain on disposal of fixed assets	(233)
Stock-based compensation expense	8,793	7,753
Changes in operating assets and liabilities:
Accounts receivable due from related party	(388)	(362)
Accounts receivable	(5,125)
Prepaid expenses and other current assets	1,418	(8,592)
Other assets	111	(3,763)
Accounts payable	(1,487)	985
Accrued expenses and other current liabilities	(5,558)	3,233
Other liabilities	1,663	(1,383)
Net cash used in operating activities	(91,510)	(98,515)
Investing activities
Purchases of property and equipment	(2,869)	(1,380)
Proceeds from sale of property and equipment	650
Purchases of marketable securities	(19,768)	(57,415)
Proceeds from maturities of marketable securities	69,502	40,735
Net cash provided by (used in) investing activities	47,515	(18,060)
Financing activities
Proceeds from equity offering	40,000
Payments of equity offering costs	(273)
Proceeds from lease financing	2,623
Repayment of debt	(1,000)
Payments of financing fees	(15)
Proceeds from issuance of common stock under equity incentive plans	488	708
Net cash provided by financing activities	41,823	708
Net change in cash, cash equivalents and restricted cash	(2,172)	(115,867)
Cash, cash equivalents and restricted cash—beginning of period	70,956	186,823
Cash, cash equivalents and restricted cash—end of period	68,784	70,956
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents	68,443	70,615
Restricted cash	341	341
Cash, cash equivalents and restricted cash—end of period	68,784	70,956
Supplemental disclosures of cash flow information
Cash paid for interest	1,723	1,263
Supplemental disclosure of noncash investing and financing activities
Purchases of property and equipment included in accounts payable and accrued expenses	$ 438	$ 13

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Pay vs Performance Disclosure
Net Income (Loss)	$ (97,428)	$ (102,701)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Dec. 31, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Nature of the Business and Basi

Nature of the Business and Basis of Presentation	12 Months Ended
	Dec. 31, 2023
Nature Of Business And Basis Of Presentation [Abstract]
Nature of the Business and Basis of Presentation	1. Nature of the Business and Ba sis of Presentation Organization Omega Therapeutics, Inc. (the “Company” or “Omega”) is a clinical-stage biotechnology company pioneering the development of a new class of programmable epigenomic mRNA medicines by leveraging its OMEGA platform. The OMEGA platform harnesses the power of epigenetics, the mechanism that controls gene expression and every aspect of an organism’s life from cell genesis, growth and differentiation to cell death. The OMEGA platform enables control of fundamental epigenetic processes to correct the root cause of disease by restoring aberrant gene expression to a normal range without altering native nucleic acid sequences. The Company was incorporated in July 2016 (“inception”) as a Delaware corporation and its offices are in Cambridge, Massachusetts. Liquidity and Going Concern Since its inception, the Company has devoted substantially all of its resources to building its platform and advancing development of its portfolio of programs, establishing and protecting its intellectual property, conducting research and development activities, organizing and staffing the Company, business planning, raising capital and providing general and administrative support for these operations. The Company is subject to risks and uncertainties common to early clinical-stage companies in the biotechnology industry including, but not limited to, technical risks associated with the successful research, development and manufacturing of product candidates, risks related to clinical development of product candidates, developments by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Current and future programs will require significant research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. In August 2021, the Company completed its initial public offering (“IPO”) pursuant to which it issued and sold 8,300,976 shares of its common stock, including 900,976 shares pursuant to the partial exercise of the underwriters’ option to purchase additional shares, at a public offering price of $ 17.00 per share, for aggregate gross proceeds of $ 141.1 million. The Company received approximately $ 128.1 million in net proceeds after deducting underwriting discounts and commissions and other offering expenses payable by the Company. In February 2023, the Company completed a registered direct offering of common stock pursuant to which it issued and sold 6,920,415 shares of its common stock at a purchase price of $ 5.78 per share and secured approximately $ 39.7 million in net proceeds after deducting offering expenses. The Company expects that its cash, cash equivalents and marketable securities of $ 73.4 million at December 31, 2023, will enable it to fund its operating expenses and capital expenditure requirements into the first quarter of 2025. The Company has had recurring losses since inception and incurred a loss of $ 97.4 million during the year ended December 31, 2023. Net cash used in operations for the year ended December 31, 2023 was $ 91.5 million. The Company expects to continue to generate operating losses and use cash in operations for the foreseeable future. Additional funding will be necessary to fund future preclinical and clinical activities and to develop new product candidates. The Company expects to finance its future cash needs through a combination of equity offerings, debt financings, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements, or other sources. Volatility in the capital markets and general economic conditions in the United States may be a significant obstacle to raising the required funds and, as a result, the Company may be unable to secure the necessary funding on acceptable terms. This raises substantial doubt about the Company's ability to continue as a going concern. The accompanying consolidated financial statements do not include any adjustments that might result from the outcome of these uncertainties. Accordingly, the consolidated financial statements have been prepared on a basis that assumes the Company will continue as a going concern which contemplates the realization of assets and satisfaction of liabilities and commitments in the ordinary course of business. Significant Risks and Uncertainties Related to Macroeconomic Conditions The global economy, including credit and financial markets, has recently experienced extreme volatility and disruptions, including, for example, severely diminished liquidity and credit availability, rising interest and inflation rates, crises involving banking and financial institutions, declines in consumer confidence, declines in economic growth, and uncertainty about economic stability. In addition, unstable market and economic conditions and further disruption created by pandemics or international political unrest, war and terrorism may have serious adverse consequences on our business, financial condition and results of operations. Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”), and Accounting Standards Update (“ASU”), of the Financial Accounting Standards Board (“FASB”). All amounts herein are expressed in U.S. dollars (“USD”) unless otherwise noted.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of significant accounting policies Principles of consolidation The accompanying consolidated financial statements include the accounts of Omega Therapeutics, Inc. and its wholly owned subsidiary, Omega Therapeutics Security Corporation, which is a Massachusetts subsidiary. All intercompany transactions and balances have been eliminated in consolidation. Reclassification The Company reclassified the related party expenses in the prior year to research and development and general and administrative expenses in the consolidated statements of operations and comprehensive loss to conform to the current year's presentation. Use of estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the selection of useful lives of property and equipment, the fair value of the success fee obligation, the incremental borrowing rate used in the calculation of lease liabilities, research and development expenses, certain judgments regarding revenue recognition and stock-based compensation. Actual results could differ from these estimates. Changes in estimates are reflected in reported results in the period in which they become known. Cash and cash equivalents Cash includes cash in readily available checking accounts, and cash equivalents include money market accounts and all highly liquid investments with an original maturity of three months or less from the date of purchase. Cash and cash equivalents are recorded at cost, which approximates fair value. Marketable securities The Company’s marketable securities as of December 31, 2023 consisted of corporate debt securities and are classified as available-for-sale and are reported at fair value. Unrealized gains and losses on available-for-sale debt securities are reported as a component of accumulated other comprehensive loss in stockholders’ equity until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the instrument. Realized gains and losses are determined using the specific identification method and are included as a component in other expense, net. The Company evaluates its marketable securities with unrealized losses for other-than-temporary impairment. When assessing marketable securities for other-than-temporary declines in value, the Company considers such factors as, among other things, how significant the decline in value is as a percentage of the original cost, how long the market value of the investment has been less than its original cost, the Company’s ability and intent to retain the investment for a period of time sufficient to allow for any anticipated recovery in fair value and market conditions in general. If any adjustment to fair value reflects a decline in the value of the investment that the Company considers to be “other than temporary,” the Company reduces the investment to fair value through a charge to the consolidated statements of operations and comprehensive loss. Restricted cash Restricted cash represents collateral provided for letters of credit issued as a security deposit in connection with the Company’s office lease. Concentrations of credit risk Financial instruments that are potentially subject to significant concentration of credit risk consist primarily of cash, cash equivalents, and marketable securities. The Company attempts to minimize the risk related to marketable securities by working with highly rated financial institutions that invest in a broad and diverse range of financial instruments as defined the Company. The Company has established guidelines relative to credit ratings and maturities intended to safeguard principal balances and maintain liquidity. The Company maintains its funds in accordance with its investment policy, which defines allowable investments, specifies credit quality standards and is designed to limit credit exposure to any single issuer. Guarantees and indemnifications As permitted under Delaware law, the Company indemnifies its officers, directors, consultants, and employees for certain events or occurrences that happen by reason of the relationship with, or position held at, the Company. Through December 31, 2023 and 2022, the Company had no t experienced any losses related to these indemnification obligations, and no claims were outstanding. The Company does not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related liabilities were established. Property and equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset category as follows: Asset category Estimated useful life Computer equipment and software 3 years Laboratory equipment and office furniture 5 years Leasehold improvements Shorter of useful life or remaining lease term Upon retirement or sale, the cost of assets disposed of, and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred. Accrued research and development expenses The Company estimates accrued research and development expenses based on its estimates of the services received and efforts expended pursuant to quotes and contracts with third-party service providers, including contract research organizations (“CROs”) and contract development and manufacturing organizations (“CDMOs”) that supply, conduct and manage preclinical and clinical studies on the Company’s behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. There may be instances in which payments made to its vendors will exceed the level of services provided and result in a prepayment of the expense, in which it will be evaluated for current or long-term classification based on when it is expected to be realized. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company adjusts the accrual or the amount of prepaid expenses accordingly. Debt issuance costs Costs incurred in connection with the issuance of the Company’s long-term debt have been recorded as a direct reduction against the debt and amortized over the life of the associated debt as a component of interest expense using the effective interest method. Success fee obligation The Loan Agreement, as amended, with PWB, requires the Company to pay a success fee (“success fee obligation”) upon the occurrence of a specified liquidity event as described in the Loan Agreement, as amended. The Company determined that this obligation represented a freestanding derivative instrument. Accordingly, the success fee obligation was classified as a liability on the Company’s consolidated balance sheets and initially recorded at fair value, with changes in fair value for each reporting period recognized in other expense, net in the consolidated statements of operations and comprehensive loss. The fair value of such obligation is remeasured at the end of each reporting period until the liability is settled. Equity issuance costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ equity as a reduction of proceeds generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the consolidated statement of operations. There were no deferred offering costs as of December 31, 2023 and 2022. 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. There were no impairment losses recognized during the years ended December 31, 2023 and 2022. Leases The Company has real estate leases for its corporate offices and lab space located in Cambridge, Massachusetts. It determines if an arrangement contains a lease at contract inception. Operating lease assets and liabilities are recognized at the commencement date of the lease based upon the present value of lease payments over the lease term. Lease payments are typically fixed and escalate over time. Variable payments relate to the Company’s usage or share of the lessor’s operating costs associated with the underlying asset and are recognized as incurred. When determining the lease term, the Company includes options to extend or terminate the lease when it is reasonably certain that it will exercise that option. The Company uses its incremental borrowing rate to calculate the lease liability when the implicit rate is not readily determinable. Lease expense is recognized on a straight-line basis over the lease term. Fair value measurements 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. Revenue recognition Revenue recognized through December 31, 2023 is solely generated from the collaboration agreement with PM (CF) Explorations, Inc., or PMCo. The Company recognizes revenue in accordance with ASU 2014-09, Revenue from Contracts with Customers (Topic 606) and its related amendments, or, collectively, ASC 606. At inception, the Company determines whether contracts are within the scope of ASC 606 or other topics. For contracts that are determined to be within the scope of ASC 606, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which the Company expects to be entitled to receive in exchange for these goods and services. To achieve this core principle, the Company applies the following five steps (i) identify the contract with the customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when performance obligation is satisfied. The Company only applies the five-step model to contracts when it determines that collection of substantially all consideration for goods and services that are transferred is probable based on the customer’s intent and ability to pay the promised consideration. Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct and are distinct in the context of the contract. To the extent a contract includes multiple promised goods and services, the Company applies judgment to determine whether promised goods and services are both capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation. The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method, depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in management’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. Determining the transaction price requires significant judgment. If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation. The consideration to be received is allocated among the separate performance obligations based on relative standalone selling prices. The Company satisfies performance obligations either over time or at a point in time. Revenue is recognized over time if either (i) the customer simultaneously receives and consumes the benefits provided by the entity’s performance, (ii) the entity’s performance creates or enhances an asset that the customer controls as the asset is created or enhanced, or (iii) the entity’s performance does not create an asset with an alternative use to the entity and the entity has an enforceable right to payment for performance completed to date. If the entity does not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring the control of a promised good or service to a customer. If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from consideration allocated to the license when the license is transferred to the customer and the customer can use and benefit from the license. For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. At the inception of each arrangement that includes milestone payments, the Company evaluates the probability of reaching the milestones 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 in the future, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control or the licensee’s are not considered probable of being achieved and therefore revenue recognized is constrained as management is unable to assert that a reversal of revenue would not be possible. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such milestones 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, which would affect revenues and earnings in the period of adjustment. To date, the Company has not recognized any milestone revenue. Deferred revenue arises from amounts received in advance of the culmination of the earnings process and is recognized as revenue in future periods as performance obligations are satisfied. Deferred revenue expected to be recognized within the next twelve months is classified as a current liability. Research and development expenses Research and development expenses are charged to expense as incurred. 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, consulting fees, cost of licensing technology, milestone payment, and external contract research and development and manufacturing expenses. Costs for certain research and development activities are recognized based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid or accrued research and development costs. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses and expensed as the related goods are delivered or the services are performed. Stock-based compensation The Company’s stock-based compensation program allows for grants of incentive stock options, non-qualified stock options, stock appreciation rights, and restricted stock awards, restricted stock units and other stock-based awards to employees, directors and consultants. The Company recognizes all stock-based compensation awards to employees and non-employees as expense in the consolidated statements of operations and comprehensive loss based on their fair values. For stock option awards, the Company estimates the fair value using the Black-Scholes option pricing model. The fair value of the Company’s common stock is used to determine the fair value of restricted stock awards. Stock-based compensation awards are subject to service vesting conditions, and forfeitures are recorded as they occur. Compensation expense related to awards to employees with service-based vesting conditions is recognized on a straight-line basis based on the grant date fair value over the associated service period of the award, which is generally the vesting term. The Company applies ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting (“ASU No. 2018-07”), in which the measurement date for non-employee awards is determined as the date of grant, and stock-based compensation costs for non-employees are recognized as expense over the vesting period on a straight-line basis. The Black-Scholes option pricing model requires inputs based on certain subjective assumptions, including (i) the expected stock price volatility, (ii) the expected term of the award, (iii) the risk-free interest rate, and (iv) expected dividends. Due to the lack of a public market for the Company’s common stock prior to the IPO and lack of sufficient company-specific historical and implied volatility data, the Company has based its computation of expected volatility on the historical volatility of a representative group of public companies with similar characteristics to the Company, including stage of product development and life science industry focus. The historical volatility is calculated based on a period of time commensurate with the expected term assumption. The Company uses the simplified method as prescribed by the Securities and Exchange Commission Staff Accounting Bulletin No. 107, Share-Based Payment , to calculate the expected term for options granted to employees and non-employees, whereby, the expected term equals the arithmetic average of the vesting term and the original contractual term of the options due to its lack of sufficient historical data. The risk-free interest rate is based on U.S. Treasury securities with a maturity date commensurate with the expected term of the associated award. The expected dividend yield is assumed to be zero as the Company has never paid dividends and has no current plans to pay any dividends on its common stock. Patent costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred as patents have no future alternative use. Income taxes The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s consolidated financial statements and tax returns. Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities and for loss and credit carryforwards, using enacted tax rates expected to be in effect in the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that these assets may not be realized. As of December 31, 2023 and 2022, the Company has recorded a full valuation allowance against its deferred tax assets. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. If it is not more likely than not that a position will be sustained, none of the benefit attributable to the position is recognized. The tax benefit to be recognized for any tax position that meets the more-likely-than-not recognition threshold is calculated as the largest amount that is more than 50% likely of being realized upon resolution of the contingency. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes. Comprehensive loss Comprehensive loss is defined as the change in stockholders’ equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive loss includes net loss as well as other changes in stockholders’ equity which includes certain changes in equity that are excluded from net loss. The Company’s only element of other comprehensive loss is unrealized gains and losses on its marketable securities. Net loss per share Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of common stock outstanding for the period. Diluted net loss attributable to common stockholders is computed by adjusting net loss attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net loss per share attributable to common stockholders is computed by dividing the diluted net loss attributable to common stockholders by the weighted average number of common stock outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common stock equivalents. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the years ended December 31, 2023 and 2022. Segment and geographic information Operating segments are defined as components of an entity about which discrete information is available for evaluation by the chief operating decision maker, or CODM, or decision-making group, in deciding how to allocate resources and in assessing performance. The CODM is the Company’s Chief Executive Officer. The CODM views its operations as and manages its business in one operating segment operating exclusively in the United States. Recent accounting pronouncements adopted On January 1, 2023, the Company adopted Accounting Standards Update No. 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). ASU 2016-13 requires measurement and recognition of expected credit losses for financial assets. In April 2019, the Financial Accounting Standards Board ("FASB") issued clarification to ASU 2016-13 within ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments . The guidance is effective for fiscal years beginning after December 15, 2022. The adoption of the standard was immaterial to the accompanying consolidated financial statements. Recent accounting pronouncements not yet adopted In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280) , Improvements to Reportable Segment Disclosures . The new standard requires enhanced disclosures about segment information and significant segment expenses. It does not change how a public entity identifies its operating segments. ASU 2023-07 is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. The new standard should be applied retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact on its consolidated financial statements. In December 2023, the FASB issued 2023-09, Income Taxes (Topic 740), Improvements to Income Tax Disclosures . The new standard requires public business entities to disclose information about income taxes paid, specific categories in the rate reconciliation, and additional information for reconciling items that meet a quantitative threshold. The guidance should be applied on a prospective basis. For public business entities, ASU 2023-08 is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. For all other entities, the standard is effective for annual periods beginning after December 15, 2025. The Company is currently evaluating the impact on its consolidated financial statements.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	3. Marketable Securities The following table summarizes the Company’s marketable securities (in thousands): December 31, 2023 Amortized cost Gross unrealized losses Fair value Corporate debt securities $ 5,000 $ ( 14 ) $ 4,986 December 31, 2022 Amortized cost Gross unrealized losses Fair value Corporate debt securities $ 54,542 $ ( 479 ) $ 54,063 The amortized cost of marketable securities is adjusted for amortization of premiums and accretion of discounts to maturity. At December 31, 2023 , the balance in accumulated other comprehensive loss was comprised solely of activity related to marketable securities. There were no realized gains or losses recognized on the sale or maturity of marketable securities for the year ended December 31, 2023 and, as a result, the Company did no t reclassify any amounts out of accumulated other comprehensive loss during the year. As of December 31, 2023 , the Company did not intend to sell, and was more than likely not required to sell, the debt securities in a loss position before recovery of their amortized cost bases. As a result, the Company determined it did no t hold any investments with any other-than-temporary impairment at December 31, 2023 .

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2023
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid Expenses and Other Current Assets	4. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following (in thousands): December 31, 2023 2022 Clinical development $ 5,168 $ 5,232 Research and development 1,609 2,072 Facilities 1,242 1,857 Other receivables 855 1,180 Insurance 716 1,020 Software 303 157 Other 431 776 Prepaid expenses and other current assets $ 10,324 $ 12,294

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	5. Property and Equipment, Net Property and equipment, net consists of the following (in thousands): December 31, 2023 2022 Lab equipment $ 6,633 $ 6,121 Furniture and fixtures 1,636 1,093 Leasehold improvements 1,290 1,378 Computer equipment 1,226 190 Construction in process 588 827 Total property and equipment 11,373 9,609 Less accumulated depreciation ( 6,062 ) ( 5,414 ) Property and equipment, net $ 5,311 $ 4,195 Depreciation expense for each of the years ended December 31, 2023 and 2022 w as $ 1.6 mi llion, respectively.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2023
Accrued Liabilities, Current [Abstract]
Accrued Expenses	6. Accrued Expenses Accrued expenses consist of the following (in thousands): December 31, 2023 2022 Employee related expenses $ 4,482 $ 4,368 Research costs 1,395 3,876 Professional and consulting fees 716 743 Manufacturing costs 547 4,303 Interest 147 122 Other 627 429 Total $ 7,914 $ 13,841

Term Loan

Term Loan	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Term Loan	7. Term Loan On March 9, 2018, the Company entered into the Loan Agreement with Pacific Western Bank (“PWB”) to initially borrow $ 8.0 million, which was further amended on September 30, 2019 (the "First Amendment"), January 22, 2020 (the "Second Amendment"), December 30, 2020 (the “Third Amendment”), and December 20, 2021 (the "Fourth Amendment"). On September 22, 2023, the Company entered into another amendment to the Loan Agreement (the "Fifth Amendment"), in which PWB extended the maturity date of the loan to September 30, 2027 , subject to further extension to September 30, 2028 upon receipt by the Company on or before December 31, 2024 of at least $ 50.0 million of cash proceeds from the sale of its equity securities and/or non-refundable upfront strategic partnership proceeds. Repayment of the loan began on September 30, 2023 , with monthly principal payments of $ 0.3 million plus interest, along with a closing payment of $ 4.0 million on September 30, 2027 if the maturity date is not extended to September 30, 2028. Interest will continue to be determined at a floating annual rate equal to the greater of (i) 0.50 % above the prime rate then in effect and (ii) 5.50 %. The Company incurred $ 15 thousand of debt issuance costs, which was recorded as a direct reduction against the additional term loan and will be amortized over the life of the associated term loan as a component of interest expense using the effective interest method. Under the terms of the Fifth Amendment, the Company is required to pay a success fee of $ 0.1 million pursuant to the Fifth Amendment, in addition to the $ 0.2 million success fee obligation pursuant to the Fourth Amendment. The success fees are contingent on achieving specified liquidity events. The Company determined that the success fee obligation represented a freestanding financial instrument, and it was classified as a liability on the Company’s consolidated balance sheet and initially recorded at fair value, with changes in fair value for each reporting period recognized in other expense, net in the consolidated statements of operations and comprehensive loss. The fair value of such obligation is remeasured at the end of each reporting period until the liability is settled. In addition, pursuant to the Fifth Amendment, the Company agreed to maintain with PWB, at all times, a balance of at least $ 5.0 million of unrestricted cash, subject to termination upon the Company’s prepayment of outstanding loans in an aggregate amount of at least $ 5.0 million or if the principal balance of the loans is less than $ 10.0 million. Borrowings under the Loan Agreement, as amended, are collateralized by substantially all of the Company’s personal property, other than its intellectual property. There are no financial covenants associated with the Loan Agreement, as amended; however, the Company is subject to certain affirmative and negative covenants to which the Company will remain subject until maturity. As of December 31, 2023, $ 4.0 m illion of the net carrying amount of the term loan was classified as short-term and $ 14.9 million was classified as long-term based on the repayment start date. The Company’s outstanding term loan balance was comprised of the following (in thousands): December 31, 2023 2022 Principal $ 19,000 $ 20,000 Unamortized debt discount ( 115 ) ( 64 ) Net carrying amount $ 18,885 $ 19,936 The Company determined that the expected life of the debt was equal to the term on the term loan. The effective interest rate on the liability component ranged fro m 5.53 % to 9.26 % for the period from the date of issuance through December 31, 2023 . The following table sets forth total interest expense recognized related to the term loan (in thousands): Year Ended December 31, 2023 2022 Contractual interest expense $ 1,748 $ 1,229 Amortization of debt issuance costs and debt discount 53 67 Total interest expense $ 1,801 $ 1,296 At December 31, 2023 and December 31, 2022, accrued interest on the term loan was $ 147 t housand and $ 121 thousand, respectively. The Company is required to repay the following principal amounts in connection with its term loan (in thousands): 2024 $ 4,000 2025 4,000 2026 4,000 2027 7,000 Total $ 19,000

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	8. Fair Value of Financial Instruments The fair value of the Company’s cash and cash equivalents and restricted cash are measured through quoted market prices; the fair value of the Company's marketable securities is determined based on the pricing inputs other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date. Other current assets, accounts payable and accrued liabilities approximate their fair values as of December 31, 2023 and 2022, due to their short-term nature. The carrying value of the Company’s debt approximates its fair value due to its variable interest rate, which approximates a market interest rate. The success fee obligation associated with the Loan Agreement, as amended, contains unobservable inputs that reflect the Company’s own assumptions in which there is little, if any, market activity at the measurement date, thus the Company’s success fee obligation is measured at its fair value on a recurring basis using unobservable inputs. The fair value of the Company’s financial instruments is summarized in the table below (in thousands): December 31, 2023 Level 1 Level 2 Level 3 Total Financial Assets Money market funds $ 10,402 $ — $ — $ 10,402 Corporate Debt Securities — 4,986 — 4,986 Total $ 10,402 $ 4,986 $ — $ 15,388 Financial Liabilities Success fee obligations $ — $ — $ 300 $ 300 December 31, 2022 Level 1 Level 2 Level 3 Total Financial Assets Money market funds $ 25,776 $ — $ — $ 25,776 Corporate Debt Securities — 54,063 — 54,063 Total $ 25,776 $ 54,063 $ — $ 79,839 Financial Liabilities Success fee obligation $ — $ — $ 118 $ 118

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and contingencies Leases The Company has the following operating leases for its corporate offices and lab space located in Cambridge, Massachusetts . 325 Vassar Street In 2017, the Company entered a noncancelable operating lease agreement to lease its office space at 325 Vassar Street, Cambridge, Massachusetts, which will expire in September 2024 . The Company is required to pay property taxes, insurance, and normal maintenance costs. The operating lease contains predetermined fixed escalations of minimum rentals during the lease term. In 2019 and 2020, the Company entered into sublease agreements with two related parties to sublease this office and laboratory space. Refer to Note 16, Related party transactions , for further details. 20 Acorn Park Drive On July 13, 2020, the Company entered into a Shared Space Arrangement (the Arrangement) with Sail Biomedicines, Inc., (“Sail Bio”, also formerly known as Senda Biosciences, Inc. and Kintai Therapeutics, Inc. prior to its merger with LARONDE, Inc.) to share one-third of Sail Bio's 69,867 square feet of leased space at 20 Acorn Park Drive, Cambridge, Massachusetts . Sail Bio is a related party as it is an affiliate of Flagship Pioneering (“Flagship”). The Arrangement commenced on August 1, 2020, and was set to expire on July 31, 2022 with two options to extend the term of the Arrangement for a period of 24 months each. The operating lease contains predetermined fixed escalations of minimum rentals during the lease term, and the Company is required to pay property taxes, insurance, and normal maintenance costs. In January 2022, the Company entered into an amendment to the Arrangement with Sail Bio to exercise the option to renew the lease through July 2023 . The Company also modified certain provisions related to the extension term. Refer to Note 16, Related party transactions , for further details. 140 First Street (formerly known as One Charles Park) On November 4, 2021, the Company entered into a lease with ARE-MA Region No. 94, LLC to lease an aggregate of approximately 89,246 rentable square feet of office and laboratory space located at 140 First Street, Cambridge, Massachusetts, 02142. The lease includes two phases. Phase 1 includes approximately 78,380 rentable square feet. Phase 2 includes 10,866 rentable square feet in a separate suite. In accordance with the lease agreement, the Company paid $ 0.8 million upon the execution of the lease, which has offset the first month's rent. Phase 1 of the lease commenced in May 2023, and Phase 2 commenced in August 2023. On May 3, 2023, the Company entered into a first amendment to the lease to, among other things, delay the delivery date of part of the premises, increase the initial base rent by $ 1.00 per rentable square foot per year, and change the address. The operating lease commenced on May 1, 2023 for the fifth floor premises and August 1, 2023 for the first floor premises for accounting purposes. The lease term for each of the floor premises is fifteen years from the respective commenc ement date, subject to certain extension rights. The base rent for the leased space is $ 116.00 per square foot, subject to an annual upward adjustment of 3 % of the then current rental rate, starting on the first anniversary of the first full payment of rent under the lease. The operating lease includes a tenant improvement allowance of $ 300 per rentable square foot that is incorporated into the base rent payments, as well as an additional improvement allowance that is required to be repaid to the landlord as additional monthly rent over the lease term at an interest rate of 8 %. On July 11, 2023, the Company entered into a Shared Space Arrangement with Apriori Bio, Inc. (“Apriori”), and on July 12, 2023, the Company entered into two Shared Space Arrangements with Metaphore Biotechnologies, Inc. (“Metaphore”) and Flagship Labs 89, Inc. (“FL Labs” and, together with Metaphore and Apriori, the “Subtenants”), pursuant to which the Company agreed to sublease an aggregate of approximately 22,500 rentable square feet of office and laboratory space located at 140 First Street, Cambridge, Massachusetts, 02141 (the “Premises”). The Company leases an aggregate of approximately 89,246 rentable square feet of office and laboratory space located at the Premises pursuant to its lease with ARE-MA Region No. 94, LLC. Metaphore, Apriori and FL Labs are affiliates of Flagship Pioneering, a significant stockholder of the Company. The term of the Sublease with Metaphore and FL Labs has commenced in August, 2023 and will end in August, 2025, and the term of the Sublease with Apriori began in September, 2023 and will end in September, 2025. The Subleases provide that the Subtenants will pay to the Company a monthly license fee that is a proportionate share of the actual base rent, operating expenses and other costs for the use and occupancy of the subleased portion of the Premises charged by the Landlord under the Lease and paid by the Company. Such proportionate share will be 12.0 %, 8.4 % and 8.4 % for Metaphore, Apriori and Labs, respectively. The total commitment for the Subtenants' share of the base rent over the term of the Subleases is $ 5.2 million. The Company may terminate each Sublease and require the applicable Subtenant to immediately vacate the Premises if such Subtenant causes a default under the Lease, is in default of any provision in the applicable Sublease or acts in a manner deemed by the Company, in its sole discretion, as dangerous or threatening. The Subleases contain customary covenants, obligations and indemnities in favor of either party. For the year ended December 31, 2023, the Company received rental income o f $ 1.4 million, which was recorded as a reduction of research and development expense and general and administrative expense in the accompanying consolidated statements of operations and comprehensive loss. As of December 31, 2023, operating lease right-of-use assets, net were $ 108.7 million, which were recorded separately on the Company’s consolidated balance sheet. The corresponding operating lease liabilities were $ 109.5 million as of December 31, 2023, of which $ 11.3 million were recorded in current liabilities and $ 98.2 million were recorded in long-term liabilities on the Company’s consolidated balance sheet. The right-of-use assets represent the Company’s right to use an underlying asset during the lease term and the related lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Both the right-of-use assets and the corresponding liabilities are recognized at the commencement date of the lease based upon the present value of lease payments over the lease term. As the Company’s leases do not provide an implicit rate, the Company estimated the incremental borrowing rate based on the interest rate from the amended Term Loan, which was fully collateralized, as well as a term matched secured market rate. The following table summarizes the components of lease expense for the years ended December 31, 2023 and 2022 (in thousands). Year Ended December 31, 2023 December 31, 2022 Operating lease expense $ 11,624 $ 3,820 Variable lease expense 2,819 1,357 Total lease expense $ 14,443 $ 5,177 Variable lease expense generally includes common area maintenance, utilities and property taxes. For the year ended December 31, 2023, $ 11.3 million of lease expense was recorded within research and development expenses an d $ 3.1 millio n was recorded within general and administrative expenses in the consolidated statement of operations and comprehensive loss. For the year ended December 31, 2022, $ 3.9 million of lease expense was recorded within research and development expenses and $ 1.2 million was recorded within general and administrative expenses in the consolidated statement of operations and comprehensive loss. The weighted average remaining lease term and discount rate related to the Company's leases were as follows: As of December 31, 2023 December 31, 2022 Weighted average remaining lease term (years) 14.5 1.8 Weighted average discount rate 8.9 % 5.5 % Supplemental cash flow information relating to the Company's leases for the years ended December 31, 2023 and December 31, 2022 were as follows (in thousands): Year Ended December 31, 2023 December 31, 2022 Cash paid for amounts included in the measurement of lease liabilities $ 8,542 $ 2,637 Operating lease assets obtained in exchange for lease liabilities $ 110,424 $ 4,393 As of December 31, 2023, the estimated minimum lease payments for 140 First Street and 325 Vassar for each of the years ending December 31 were as follows (in thousands): 2024 $ 11,781 2025 11,887 2026 12,213 2027 12,549 2028 12,895 Thereafter 139,504 Total minimum lease payments 200,829 Less: Imputed interest ( 91,286 ) Present value of operating lease liabilities $ 109,543 Thermo Furniture Sale-Leaseback In December 2023 , the Company entered into a sale-leaseback arrangement with Thermo Fisher Financial Services, Inc. to provide $ 2.6 million in cash proceeds for previously acquired furniture and equipment. The term of the leaseback is 5 years, with an option to purchase the assets for $1 at the end of the term. The Company concluded the leaseback would be classified as a financing lease. Therefore, the transaction was deemed a failed sale-leaseback and was accounted for as a financing arrangement. T he Company will make monthly payments of $ 53 thousand over the term of the lease. As of December 31, 2023, $ 0.4 million of the financing obligation is included in current liabilities and $ 2.2 million is included in long-term liabilities on the Company’s consolidated balance sheet. The assets continue to be depreciated over their useful lives, and payments are allocated between interest expense and repayment of the financing liability.

License Agreements

License Agreements	12 Months Ended
	Dec. 31, 2023
License Agreements [Abstract]
License Agreements	10. License Agreements Flagship Pioneering Innovations V, Inc. In March 2019, the Company entered into an exclusive license agreement with Flagship Pioneering Innovations V, Inc., an affiliate of Flagship, under which the Company was granted an exclusive, worldwide, royalty-bearing, sublicensable, transferable license under specified patent rights to develop, manufacture and commercialize licensed products (the “Flagship License”). Under the terms of the Flagship License, the Company is obligated to pay low single digit percentage royalties on net sales of licensed products by the Company. Royalties shall be paid by the Company on a country-by-country basis until expiration or abandonment of the last valid patent claim covering such licensed product in such country. The Company is also obligated to reimburse Flagship for patent prosecution costs. The royalty payment is contingent upon sales of licensed products under the Flagship License. As such, when such expense is considered probable and estimable at the commencement of sales, the Company will account for the royalty expense as cost of sales for the amount it is obligated. Whitehead Institute for Biomedical Research In May 2019, the Company entered into an exclusive license agreement with the Whitehead Institute for Biomedical Research (“WIBR”), an affiliate of one of the Company’s board members, under which the Company was granted an exclusive, worldwide, royalty-bearing, sublicensable license under specified patent rights to research, make, have made, use, sell, offer to sell, lease and import products and to perform and have performed licensed processes (the “WIBR Exclusive License”). Under the terms of the WIBR Exclusive License, the Company paid a nonrefundable upfront fee of less than $ 0.1 million upon the commencement of the exclusive license agreement. The Company is obligated to pay WIBR annual license maintenance fees of less than $ 0.1 million and low single digit percentage royalties on net sales of licensed products by the Company and its affiliates and sublicensees. Additionally, the Company is required to make milestone payments of up to $ 1.7 million in the aggregate for each of the first three licensed products (excluding backup products) upon the achievement of specified clinical and regulatory milestones. In addition, the Company is required to pay to WIBR a percentage of the non-royalty payments that it receives from sublicensees of the WIBR Exclusive License. This percentage ranges from zero to low double-digits and will be based upon the stage of development of the licensed product at the time such sublicense is executed. In May 2019, the Company also entered into a co-exclusive license agreement with WIBR under which the Company was granted a co-exclusive, worldwide, royalty-bearing, sublicensable license under specified patent rights to research, make, have made, use, sell, offer to sell, lease and import products and to perform and have performed licensed processes (the “WIBR Co-Exclusive License”). Under the terms of the WIBR Co-Exclusive License, the Company paid a nonrefundable upfront fee of less than $ 0.1 million upon the commencement of the co-exclusive license agreement. The Company is obligated to pay WIBR annual license maintenance fees of less than $ 0.1 million and sub single digit percentage royalties on net sales of licensed products by the Company and its affiliates and sublicensees as well as low single digit percentage royalties on licensed service income received by the Company and its affiliates. Additionally, the Company is required to make milestone payments of up to $ 1.9 million in the aggregate for each of the first three licensed products (excluding backup products) upon the achievement of specified clinical and regulatory milestones. In addition, the Company is required to pay to WIBR annual fees of less than $ 0.1 million for each sublicense agreement. For the years ended December 31, 2023 and 2022 , the Company recognized expenses of $ 0.2 million a nd less than $ 0.2 million , respectively, for license maintenance fees and milestone payments. There was no outstanding payment due to WIBR as of December 31, 2023 and December 31, 2022. The annual maintenance fees will be recorded as an expense on an annual basis based on the stated amount for the applicable year. Upon determination that a milestone payment is probable to occur, the amount due will be recorded as research and development expense. Lastly, the royalty payments and the sublicense non-royalty payments are contingent upon sales of licensed products or execution of a sublicense agreement under the WIBR Exclusive and Co-Exclusive Licenses. As such, when such expenses are considered probable and estimable at the commencement of sales or execution of a sublicense agreement, the Company will accrue royalty expense and sublicense non-royalty payments, as applicable, for the amount the Company is obligated. Acuitas Therapeutics, Inc. In October 2020, the Company entered into a development and option agreement (the “Development and Option Agreement”) with Acuitas Therapeutics, Inc. (“Acuitas”). Under the terms of the Development and Option Agreement, the parties agreed to jointly develop certain products combining the Company’s gene modulating therapeutics with Acuitas' lipid nanoparticles. Additionally, in accordance with the Development and Option Agreement, the Company has options to obtain non-exclusive, worldwide, sublicensable licenses under Acuitas’ patents and know-how related to lipid nanoparticle technology (“Acuitas LNP Technology”) with respect to two specified targets (e.g., EC constructs) (“Reserved Targets”) to develop and commercialize one or more therapeutic products relating to such targets. For each option and Reserved Target, the Company is obligated to pay an annual technology access fee and target reservation and maintenance fees collectively in the low-mid six figures until such Reserved Target is removed from the Reserved Target list or until the Company exercises an option with respect to such Reserved Target. In the event that the Company exercises the options, the Company will pay $ 1.5 million for the first non-exclusive license and $ 1.75 million for the second non-exclusive license. Under the terms of the Development and Option Agreement, the Company is also responsible for the full-time equivalent ("FTE") funding obligations, which is expected to be approximately $ 0.4 million per year, and reimbursements to Acuitas for certain development and material costs incurred by them. In March 2021, the Company exercised the first option under the Development and Option Agreement and entered into a non-exclusive license agreement with Acuitas (the “Acuitas License Agreement”) under which the Company was granted a non-exclusive, worldwide, sublicensable license under the Acuitas LNP Technology to research, develop, manufacture, and commercially exploit products consisting of the Company’s gene modulating therapeutics and Acuitas’ lipid nanoparticles. In connection with the option exercise, the Company incurred an expense for the option exercise fee of $ 1.5 million. Under the Acuitas License Agreement, the Company is required to pay Acuitas an annual license maintenance fee in the high six figures until the Company achieves a certain development milestone. Acuitas is entitled to receive potential clinical and regulatory milestone payments of up to $ 18.0 million in the aggregate. With respect to the sale of each licensed products, the Company is also obligated to pay Acuitas low single digit percentage royalties on net sales of the licensed products by the Company and its affiliates and sublicensees in a given country until the last to occur, in such country, of (i) the expiration or abandonment of all licensed patent rights covering the licensed product, (ii) expiration of any regulatory exclusivity for the licensed product, or (iii) ten years from the first commercial sale of the licensed product. During the years ended December 31, 2023 and 2022, the Company recorded an aggregate of $ 0.4 million a nd $ 1.9 million of research and development expenses, respectively, consisting of technology access fees, target reservation and maintenance fees, the costs of services performed by Acuitas, material costs and reimbursable costs. The option exercise fee under the Development and Option Agreement was recorded as research and development expense upon the Company’s exercise of the first option in March 2021. Additionally, the technology access fees, target reservation and maintenance fees, expenses associated with the FTE funding obligations and reimbursements for development and material costs incurred by Acuitas are recorded as research and development expense when incurred. The annual maintenance fee will be recorded as an expense on an annual basis based on the stated amount for the applicable year. Upon determination that a milestone payment is probable to occur, the amount due will be recorded as research and development expense. For the year ended December 31, 2022, an annual maintenance fee of $ 0.8 million has been recorded as research and development expense. There were no milestones triggered, and no expense was recorded related to them for the years ended December 31, 2023. La stly, the royalty payment is contingent upon sales of licensed products under the Acuitas License Agreement. As such, when such expenses are considered probable and estimable at the commencement of sales, the Company will accrue royalty expense for the amount the Company is obligated. Nitto Denko Corporation On October 12, 2022, the Company entered into a Collaboration and License Agreement (the "Nitto Agreement”) with Nitto Denko Corporation (“Nitto”), pursuant to which, among other things, Nitto granted the Company an exclusive, worldwide, royalty-bearing, fully transferable and fully sublicensable license under all intellectual property owned or controlled by Nitto relating to its lipid nanoparticle delivery technology. Under the terms of the Nitto Agreement, the Company has made an upfront cash payment of $ 1.0 million, and developmental milestone payments of $ 1.0 million to Nitto in 2022. Both payments have been recorded as research and development expenses. The Company is also required to make up to $ 83.0 million in future payments to Nitto based upon the achievement of specified development, regulatory and sales milestones. The Company is also obligated to pay to Nitto tiered, single-digit percentage royalties on a country-by-country basis based on net sales of the licensed product, subject to reduction in specified circumstances. As such, when these expenses are considered probable and estimable, the Company will accrue expense for the amount the Company is obligated. During the year ended December 31, 2023, the Company recorded an aggregate of $ 0.9 millio n of research and development expenses consisting of material costs, costs of services performed by Nitto, and reimbursable costs.

Collaboration Agreement

Collaboration Agreement	12 Months Ended
	Dec. 31, 2023
Collaboration Agreement [Abstract]
Collaboration Agreement	11. Collaboration Agreements PMCo In November 2021, the Company entered into a five-year collaboration agreement with PM (CF) Explorations, Inc. ("PMCo"), an affiliate of Flagship, under which PMCo was granted an exclusive license covering specified patent rights of the Company’s lipid nanoparticle technology to develop one or more therapeutic products to treat diseases related to the cystic fibrosis transmembrane conductance regulator gene, like cystic fibrosis. Under the terms of the agreement, the Company performs certain research activities in accordance with the research plan, and PMCo will be solely responsible for, at its sole cost and expense, and will have sole discretion with respect to, developing, manufacturing, seeking regulatory approval for and commercializing licensed products. The research plan funding may be adjusted upon mutual written agreement from both parties. Additionally, in the event PMCo is acquired or sold, the Company is entitled to receive a portion of the proceeds of such transaction, subject to various reductions and other amounts payable in accordance with the agreement . The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, PMCo, is a customer. The Company determined that the research activities and the exclusive license granted under the collaboration agreement is considered as a single performance obligation, and therefore, the transaction price was allocated entirely to the single performance obligation. The Company recognizes revenue related to the single performance obligation over time as the underlying services are performed and/or external costs are incurred. The total transaction price at December 31, 2023 was determined to be $ 7.9 million based on the current estimated required efforts to fulfill the performance obligation. This total includes an increase of $ 1.9 million in the fourth quarter of 2022, and an increase of $ 2.4 million in the third quarter of 2023, and an increase of $ 0.1 million in the fourth quarter of 2023, all of which were agreed upon with PMCo. As of December 31, 2023, the remaining transaction price was estimated to be $ 2.7 million, which is expected to be recognized as revenue through 2024. The Company recognized funded research and collaboration revenue of $ 3.1 million and $ 2.1 million in the consolidated statements of operations and comprehensive loss during the years ended December 31, 2023 and 2022, respectively. Costs incurred associated with this collaboration agreement were recorded as research and development expenses. Pursuant to the agreement, the Company is entitled to receive a portion of the sales proceeds in the event PMCo is acquired or sold. At the end of each reporting period, the Company evaluates the probability of occurrence of such transaction. As of December 31, 2023, the Company determined that the proceeds from such transaction was not probable of recognition. Nitto Denko Corporation On October 12, 2022, the Company entered into a Collaboration and License Agreement with Nitto, pursuant to which, among other things, Nitto granted the Company an exclusive, worldwide, royalty-bearing, fully transferable and fully sublicensable license under all intellectual property owned or controlled by Nitto relating to its lipid nanoparticle delivery technology. See further discussion in Note 10, License Agreements . Novo Nordisk On December 31, 2023, the Company entered into a Research Collaboration Agreement with Novo Nordisk A/S ("Novo Nordisk") and Pioneering Medicines 08, Inc., an affiliate of Flagship (and with respect to certain provisions set forth in the agreement, Pioneering Medicines (NN), LLC and PM (NN) Explorations, Inc.). Under the terms of the agreement, the Company granted to Novo Nordisk an exclusive, royalty-bearing, transferable license, with the right to grant sublicenses through multiple tiers, for certain of its intellectual property to conduct research and development activities under an agreed-upon research and development plan relating to a product candidate, or program target, for the prevention, treatment or control of a cardiometabolic disease, including diabetes. In January 2024, the Company received an upfront nonrefundable payment of $ 5.1 million from Novo Nordisk and expects to receive approximately $ 21.6 million in cost reimbursement through 2027 to fund the related research and development activities. The research plan funding may be adjusted upon mutual written agreement from all the parties. The Company is also eligible to receive development and commercial milestone payments, as well as tiered royalties on annual net sales of a licensed product. The term of the agreement expires at the end of the royalty term, which is the later of the 10 th anniversary of the first commercial sale, the expiration of the last-to-expire payment claim, or expiration of regulatory exclusivity. Upon the expiration of the royalty term for a given licensed product in a given country in the territory, the licenses granted to Novo Nordisk pursuant to the agreement under the Omega licensed intellectual property survive and become perpetual, irrevocable, fully paid-up and royalty free with respect to such licensed product in such country. The Company assessed this arrangement in accordance with ASC 606 and concluded that the contract counterparty, Novo Nordisk, is a customer. The Company determined that the research activities and the exclusive license granted under the collaboration agreement is considered as a single combined performance obligation as they are incapable of being distinct. The Company will recognize revenue related to the single performance obligation over time using the input method. Under the input method, the extent of progress towards completion is measured based on the ratio of costs incurred to date to the total estimated costs at completion of the performance obligation, which the Company believes best measures its progress towards satisfying the combined performance obligation. A cost-based input method of revenue recognition requires management to make estimates of costs to complete performance obligation. In making such estimates, judgment is required to evaluate assumptions related to cost estimates. As of December 31, 2023, the total transaction price was determined to b e $ 26.7 m il lion based on the upfront nonrefundable payment and estimated required research and development efforts. The total transaction price, including the $ 5.1 million nonrefundable upfront payment, is expected to be recognized as revenue beginning in 2024 through 2027. The Company will assess the probability of achieving the milestones and include them in the transaction price when they are deemed probable. Royalties will be recognized when the subsequent sales occur based on the sales or usage-based royalty exception. Costs incurred associated with this research collaboration agreement are recorded as research and development expenses.

Preferred and Common Stock

Preferred and Common Stock	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Preferred and Common Stock	12. Preferred and Common Stock In 2021, the Company’s board of directors and stockholders approved the Company’s Amended and Restated Certificate of Incorporation to, among other things, provide for 200,000,000 authorized shares of common stock with a par value of $ 0.001 per share and 10,000,000 authorized shares of preferred stock with a par value of $ 0.001 per share. In February 2023, the Company completed a registered direct offering of common stock pursuant to which it issued and sold 6,920,415 shares of its common stock at a purchase price of $ 5.78 per share and secured approximately $ 39.7 million in net proceeds after deducting estimated offering expenses of $ 0.3 million. The holders of common stock are entitled to one vote for each share of common stock. Subject to the payment in full of all preferential dividends to which the holders of the preferred stock are entitled, the holders of common stock shall be entitled to receive dividends out of funds legally available. In the event of any voluntary or involuntary liquidation, dissolution, or winding up of the Company, after the payment or provision for payment of all debts and liabilities of the Company and all preferential amounts to which the holders of preferred stock are entitled with respect to the distribution of assets in liquidation, the holders of common stock shall be entitled to share ratably in the remaining assets of the Company available for distribution. As of December 31, 2023 , the Company has reserved an aggregate of 8,780,737 shares of common stock for the potential exercise of outstanding stock options under its equity incentive plans. Upon the effectiveness of the 2021 Incentive Award Plan (“2021 Plan”), the Company ceased granting awards under the 2017 Equity Incentive Plan (“2017 Plan”), and the 3,902,063 shares of common stock subject to outstanding stock options issued under the 2017 Plan may become available for future issuance under the 2021 Plan to the extent such stock options are forfeited.

Equity Incentive Plans

Equity Incentive Plans	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Equity Incentive Plans	13. Equity Incentive Plans 2017 Equity Incentive Plan In June 2017, the Company’s board of directors adopted the 2017 Plan, which provided for the grant of qualified incentive stock options and nonqualified stock options, restricted stock or other awards to the Company’s employees and non-employees for the issuance or purchase of shares of the Company’s common stock. As of December 31, 2023 , there were no shares available for future grants under the 2017 Plan and a total o f 3,902,063 sha res of the Company’s common stock were subject to outstanding stock options issued under the 2017 Plan. The 2017 Plan is administered by the Company’s board of directors or a committee thereof to the extent the Company’s board of directors has delegated its power or authority under the 2017 Plan. The exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, except that the exercise price per share of stock options may not be less than 100 % of the fair market value of the common stock on the date of grant. Stock options awarded under the 2017 Plan expire 10 years after the grant date unless the board of directors sets a shorter term. Incentive stock options and nonqualified stock options granted to employees and non-employees typically vest over four years . Certain stock options provide for accelerated vesting if there is a change in control, as defined in the 2017 Plan. 2021 Incentive Award Plan The Company's board of directors adopted, and the Company’s stockholders approved, the 2021 Plan in July 2021. The 2021 Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock-based awards, and subsequent to the IPO, all equity-based awards are granted under the 2021 Plan. The Company initially reserved 2,960,000 shares of its common stock for future issuance under the 2021 Plan, and such number of shares of common stock is subject to an annual increase on the first day of each calendar year, beginning on January 1, 2022 and ending on and including January 1, 2031, equal to the lesser of (i) 4 % of the aggregate number of shares of common stock outstanding on the final day of the immediately preceding calendar year and (ii) such smaller number of shares of common stock as is determined by the board of directors. As of December 31, 2023 , there were 2,581,038 shares available for future grants under the 2021 Plan, and a total of 4,878,674 shares of the Company’s common stock were subject to outstanding stock options issued under the 2021 Plan. The Company recorded stock-based compensation expense as research and development and general and administrative expenses in the consolidated statements of operations and comprehensive loss as follows (in thousands): Year ended December 31, 2023 2022 Research and development $ 4,269 $ 4,026 General and administrative 4,524 3,727 Total stock-based compensation expense $ 8,793 $ 7,753 Stock Options The assumptions used in the Black-Scholes option-pricing model for stock options granted were as follows : Year ended December 31, 2023 2022 Expected volatility 74.65 % - 77.06 % 76.09 % - 77.62 % Weighted-average risk-free interest rate 4.16 % 2.69 % Expected dividend yield 0.00 % 0.00 % Weighted-average expected term (in years) 6.08 6.11 A summary of option activity under the Company’s equity incentive plans during the year ended December 31, 2023 was as follows: Weighted Weighted Aggregate Number average contractual value (1) (in thousands) Outstanding as of January 1, 2023 8,438,573 $ 6.00 8.40 $ 12,976 Granted 1,586,002 5.74 Exercised ( 152,050 ) 3.21 Forfeited ( 964,787 ) 7.96 Expired ( 127,001 ) 12.73 Outstanding as of December 31, 2023 8,780,737 5.69 7.52 5,033 Vested and expected to vest as of December 31, 2023 8,780,737 5.69 7.52 5,033 Exercisable as of December 31, 2023 4,837,051 $ 4.79 6.71 $ 4,599 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money as of December 31, 2023 . The weighted-average grant date fair value per share of stock options granted during the years ended December 31, 2023 and 2022 was $ 3.97 and $ 5.08 , respectively. The aggregate intrinsic value of stock options exercised during the years ended December 31, 2023 and 2022 wa s $ 0.7 million a nd $ 1.0 million, respectively. As of December 31, 2023, there was $ 16.5 million of unrecognized compensation cost related to unvested stock options, which is expected to be recognized over a weighted-average period of approximately 2.0 years. 2021 Employee Stock Purchase Plan The Company's board of directors adopted, and the Company’s stockholders approved, the Employee Stock Purchase Plan (the “2021 ESPP”) in July 2021. The purpose of the 2021 ESPP is to provide eligible employees with an opportunity to purchase shares of the Company's common stock through accumulated contributions. The 2021 ESPP permits participants to purchase shares of common stock through contributions (generally in the form of payroll deductions) of up to an amount of their eligible compensation determined by the administrator. Subject to certain other limitations or unless otherwise determined by the administrator, a participant may purchase a maximum of 100,000 shares of common stock during an offering period. The offering periods under the 2021 ESPP will begin on such date as determined by the administrator and not exceed 27 months. Amounts deducted and accumulated by the participant are used to purchase shares of common stock on each exercise date. The purchase price of the shares will be determined by the administrator but in no event will be less than 85 % of the lower of the fair market value of common stock on the enrollment date or on the exercise date. Participants may end their participation at any time during an offering period and will be paid their accrued contributions that have not yet been used to purchase shares of common stock, provided that they give notice of such withdrawal within the time period required by the administrator. Participation ends automatically upon termination of employment with the Company. The 2021 ESPP provides for an annual increase to the number of shares available for issuance thereunder on the first day of each calendar year beginning on January 1, 2022 and ending on and including January 1, 2031, by an amount equal to the lesser of (i) 1 % of the aggregate number of shares of common stock outstanding on the final day of the immediately preceding calendar year and (ii) such smaller number of shares of common stock as is determined by our board of directors, provided that no more than 6,450,000 shares of our common stock may be issued under the 2021 ESPP. As of December 31, 2023, the Company had not consummated an offering period under the 2021 ESPP. As of December 31, 2023, the Company had 1,438,649 shares of common stock available for issuance under the 2021 ESPP.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	14. Net Loss per Share Attributable to Common Stockholders For periods in which the Company reports a net loss attributable to common stockholders, potentially dilutive securities have been excluded from the computation of diluted net loss per share as their effects would be anti-dilutive. Therefore, the weighted average number of shares of common stock outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands except share and per share amounts): Year Ended December 31, 2023 2022 Numerator: Net loss attributable to common stockholders $ ( 97,428 ) $ ( 102,701 ) Denominator: Weighted average number of common stock, basic and diluted 54,010,996 47,880,819 Net loss per common stock attributable to common stockholders, basic and diluted $ ( 1.80 ) $ ( 2.14 ) The Company excluded the following potential common stock, presented based on amounts outstanding at period end, from the computation of diluted net loss per share attributable to common stockholders because including them would have had an anti-dilutive effect: As of December 31, 2023 2022 Outstanding options to purchase common stock 8,780,737 8,438,573

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	15. Income taxes A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows: Year ended December 31, 2023 2022 U.S. federal statutory income tax rate 21.0 % 21.0 % State income taxes, net of federal benefit 6.6 7.1 Research and development tax credits 4.7 4.3 Nondeductible/ nontaxable permanent items ( 0.9 ) ( 0.5 ) Change in valuation allowance ( 31.4 ) ( 32.0 ) Other 0.0 0.1 Effective income tax rate 0.0 % 0.0 % The components of the Company’s deferred taxes are as follows (in thousands): Year ended December 31, 2023 2022 Deferred tax assets: Net operating loss carryforwards $ 50,762 $ 40,157 Research and development credit carryforwards 16,309 11,013 Accrued expenses 1,154 1,098 Stock-based compensation 3,329 1,726 Intangibles 120 136 IRC 174 R&D capitalization 32,505 20,024 ASC 842 lease liability 30,198 722 Unrealized gain/loss — 325 Total deferred tax assets 134,377 75,201 Less: valuation allowance ( 104,630 ) ( 74,005 ) Deferred tax assets, net 29,747 1,196 Deferred tax liabilities: Depreciation ( 12 ) ( 194 ) Right of use asset ( 29,706 ) ( 1,002 ) Unrealized gain/loss ( 29 ) — Total deferred tax liabilities ( 29,747 ) ( 1,196 ) Net deferred taxes $ — $ — The Company had no income tax expense due to the operating loss incurred for the years ended December 31, 2023 and 2022. Management has evaluated the positive and negative evidence bearing upon the realizability of the Company’s net deferred tax assets and has determined that it is more likely than not that the Company will not recognize the benefits of the net deferred tax assets. As a result, the Company has recorded a full valuation allowance as of December 31, 2023 and 2022. The valuation allowance increased by $ 30.6 million in 2023, due to the increase in deferred tax assets, primarily resulting from the net operating loss carryforwards, research and development tax credits, IRC 174 R&D capitalization, stock-based compensation expense and deductible accrued expenses. Realization of the future tax benefits is dependent on many factors, including the Company’s ability to generate taxable income within the net operating loss carryforward period. Under the provisions of the Internal Revenue Code, certain substantial changes in the Company’s ownership, including a sale of the Company or significant changes in ownership due to sales of equity, may have limited, or may limit in the future, the amount of net operating loss carryforwards, which could be used annually to offset future taxable income. The Company has not completed a study to assess whether a change of control has occurred or whether there have been multiple changes of control since the Company’s formation due to the significant complexity and cost associated with such study and because there could be additional changes in control in the future. As a result, the Company is not able to estimate the effect of the change in control, if any, on the Company’s ability to utilize net operating loss and research and development credit carryforwards in the future. As of December 31, 2023, the Company had $ 187.4 million of federal and $ 180.4 million of state net operating loss carryforwards. If not utilized, both the federal and state net operating loss carryforwards have components that begin to expire starting in 2036 . Of the $ 187.4 million federal net operating loss carryforwards, $ 181.9 million of net operating loss generated from 2018 to 2023 will not expire. Additionally, as of December 31, 2023, the Company had $ 12.4 million of federal and $ 4.9 million of Massachusetts tax credits that expire starting in 2036 and 2031, respectively. As of December 31, 2023 and 2022, the Company had no uncertain tax positions. The Company will recognize both interest and penalties associated with unrecognized tax benefits as a component of income tax expense. The Company has not recorded any interest or penalties for unrecognized tax benefits since its inception. The Company filed income tax returns in the United States and the Commonwealth of Massachusetts in all tax years since inception. All tax years remain open to examination by these jurisdictions, as carryforward attributes generated in past years may be adjusted in a future period. The Company is not currently under examination by the Internal Revenue Service or any other taxing authority for these ye ars.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Transactions	16. Related Party Transactions For the year ended December 31, 2023, related party transactions consisted primarily of rent payments and reimbursable expenses, offset by sublease income received from related parties. The majority ownership of the Company is held by Flagship, in which it holds shares representing approximately 53 % of the Company’s outstanding voting stock as of December 31, 2023. Flagship historically provided management services to the Company, and the Company reimburses Flagship for certain expenses, including insurance and benefits, and related fees, and software licenses incurred on the Company’s behalf. For the years ended December 31, 2023 and 2022, the Company incurred $ 0.2 million and $ 1.7 million, respectively, primarily for reimbursable expenses. These expenses are recorded as general and administrative expense in the accompanying consolidated statements of operations and comprehensive loss. As of December 31, 2023 and 2022, there was an immaterial amount of outstanding payments due to Flagship. In July 2023 the Company entered into three Shared Space Agreements with related parties Metaphore Biotechnologies, Inc., Apriori Bio, Inc., and Flagship Labs 89, Inc. These companies are affiliates of Flagship Pioneering, a significant stockholder of the Company. Pursuant to the agreements, the Company agreed to sublease an aggregate of approximately 22,500 rentable square feet of office and laboratory space at 140 First Street. Under the agreements, the Company has received rental income of $ 1.4 million for the year ended December 31, 2023 . Such rental income was reflected as a reduction of research and development expense and general and administrative expense in the accompanying consolidated statements of operations and comprehensive loss. There were no outstanding receivables due from the subtenants as of December 31, 2023. In September 2020, the Company sublet the entire space of its 325 Vassar Street facility, approximately 19,404 square feet, to Sail Bio (formerly known as LARONDE, Inc. and VL50, Inc.), which is an affiliate of Flagship. The sublease term will expire at the end of the Company’s lease agreement with the landlord in September 2024. The rental rate for the sublease arrangement is equal to the Company’s rental obligation per the agreement with BMR-325 Vassar Street LLC, reduced by the sublease income received from Cygnal Therapeutics, Inc. (“Cygnal”), approximating $ 1.6 million per year. The sublessee is obligated to pay all real estate taxes and costs related to the subleased premises, including cost of operations, maintenance, repair, replacement and property management. Under the sublease agreement, the Company received rental income of $ 2.5 million and $ 2.3 million during the years ended December 31, 2023 and 2022, respectively, which was recorded within research and development expense and general and administrative expense in the consolidated statements of operations and comprehensive loss. There was no outstanding receivable due from Sail Bio as of December 31, 2023 and December 31, 2022. In July 2020, the Company entered into a Shared Space Arrangement (the Arrangement) with Sail Bio to share one-third of Sail Bio's 69,867 square feet of leased space at 20 Acorn Park Drive, Cambridge, Massachusetts . In January 2022, the Company entered into an amendment to the Arrangement with Sail Bio to exercise the option to renew the lease through July 2023 . In connection with the amendment, the Company made an upfront payment of $ 2.9 million in January 2022, to cover the rent payments for the extended lease term. Additionally, upon the expiration of the extended lease term, the Company received $ 0.65 million from Sail Bio for all furniture, fixtures and equipment owned by the Company that will remain at the lease property. The net book value of these assets was determined to be $ 0.4 million, and the Company recognized a gain on this disposal of $ 0.2 million in June 2023 since the assets are no longer in service, which was recorded in other income (expense), net in the consolidated statements of operations and comprehensive loss. In September 2019, the Company sublet approximately 1,445 square feet of its 325 Vassar Street facility to Cygnal, which is an affiliate of Flagship, for two years . The lease term was to continue on a month-to-month basis until advanced notice is provided to the Company. Cygnal gave notice, terminated the agreement and vacated the property in May 2022. The rental rate for the sublease arrangement was equal to the Company’s rental obligation per the agreement with BMR-325 Vassar Street LLC, approximating $ 0.1 million per year. The sublessee was obligated to pay all real estate taxes and costs related to the subleased premises, including cost of operations, maintenance, repair, replacement and property management. Under the sublease agreement, the Company received rental income of less th an $ 0.1 mil lion for the year ended December 31, 2022, which was recorded as a reduction of rental expenses. Such rental income was reflected as a reduction of research and development expense and general and administrative expense in th e accompanying consolidated statements of operations and comprehensive loss. There was no outstanding receivable due from Cygnal as of December 31, 2022. Refer to other related party transactions as described in Note 9, Commitments and contingencies , Note 10, License agreements and Note 11, Collaboration agreements .

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
Employee Benefits	17. Employee benefits In 2018, the Company established a defined-contribution plan under Section 401(k) of the Internal Revenue Code, or the 401(k) Plan. The 401(k) Plan covers all employees who meet defined minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. On May 1, 2022, the Company began matching 50 % of employee contributions of up to 6 % of eligible compensation contributed on a pre-tax and/or Roth after-tax basis to the 401(k) Plan. During the years ended December 31, 2023 and 2022, the Company made matching contributions totaling $ 0.6 million and $ 0.5 million, respectively.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Principles of consolidation	Principles of consolidation The accompanying consolidated financial statements include the accounts of Omega Therapeutics, Inc. and its wholly owned subsidiary, Omega Therapeutics Security Corporation, which is a Massachusetts subsidiary. All intercompany transactions and balances have been eliminated in consolidation.
Reclassification	Reclassification The Company reclassified the related party expenses in the prior year to research and development and general and administrative expenses in the consolidated statements of operations and comprehensive loss to conform to the current year's presentation.
Use of estimates	Use of estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases its estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the selection of useful lives of property and equipment, the fair value of the success fee obligation, the incremental borrowing rate used in the calculation of lease liabilities, research and development expenses, certain judgments regarding revenue recognition and stock-based compensation. Actual results could differ from these estimates. Changes in estimates are reflected in reported results in the period in which they become known.
Cash and cash equivalents	Cash and cash equivalents Cash includes cash in readily available checking accounts, and cash equivalents include money market accounts and all highly liquid investments with an original maturity of three months or less from the date of purchase. Cash and cash equivalents are recorded at cost, which approximates fair value.
Marketable securities	Marketable securities The Company’s marketable securities as of December 31, 2023 consisted of corporate debt securities and are classified as available-for-sale and are reported at fair value. Unrealized gains and losses on available-for-sale debt securities are reported as a component of accumulated other comprehensive loss in stockholders’ equity until realized. Any premium or discount arising at purchase is amortized and/or accreted to interest income and/or expense over the life of the instrument. Realized gains and losses are determined using the specific identification method and are included as a component in other expense, net. The Company evaluates its marketable securities with unrealized losses for other-than-temporary impairment. When assessing marketable securities for other-than-temporary declines in value, the Company considers such factors as, among other things, how significant the decline in value is as a percentage of the original cost, how long the market value of the investment has been less than its original cost, the Company’s ability and intent to retain the investment for a period of time sufficient to allow for any anticipated recovery in fair value and market conditions in general. If any adjustment to fair value reflects a decline in the value of the investment that the Company considers to be “other than temporary,” the Company reduces the investment to fair value through a charge to the consolidated statements of operations and comprehensive loss.
Restricted cash	Restricted cash Restricted cash represents collateral provided for letters of credit issued as a security deposit in connection with the Company’s office lease.
Concentrations of credit risk	Concentrations of credit risk Financial instruments that are potentially subject to significant concentration of credit risk consist primarily of cash, cash equivalents, and marketable securities. The Company attempts to minimize the risk related to marketable securities by working with highly rated financial institutions that invest in a broad and diverse range of financial instruments as defined the Company. The Company has established guidelines relative to credit ratings and maturities intended to safeguard principal balances and maintain liquidity. The Company maintains its funds in accordance with its investment policy, which defines allowable investments, specifies credit quality standards and is designed to limit credit exposure to any single issuer.
Guarantees and indemnifications	Guarantees and indemnifications As permitted under Delaware law, the Company indemnifies its officers, directors, consultants, and employees for certain events or occurrences that happen by reason of the relationship with, or position held at, the Company. Through December 31, 2023 and 2022, the Company had no t experienced any losses related to these indemnification obligations, and no claims were outstanding. The Company does not expect significant claims related to these indemnification obligations and, consequently, concluded that the fair value of these obligations is negligible, and no related liabilities were established.
Property and equipment	Property and equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset category as follows: Asset category Estimated useful life Computer equipment and software 3 years Laboratory equipment and office furniture 5 years Leasehold improvements Shorter of useful life or remaining lease term Upon retirement or sale, the cost of assets disposed of, and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance are charged to expense as incurred.
Accrued research and development expenses	Accrued research and development expenses The Company estimates accrued research and development expenses based on its estimates of the services received and efforts expended pursuant to quotes and contracts with third-party service providers, including contract research organizations (“CROs”) and contract development and manufacturing organizations (“CDMOs”) that supply, conduct and manage preclinical and clinical studies on the Company’s behalf. The financial terms of these agreements are subject to negotiation, vary from contract to contract and may result in uneven payment flows. There may be instances in which payments made to its vendors will exceed the level of services provided and result in a prepayment of the expense, in which it will be evaluated for current or long-term classification based on when it is expected to be realized. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company adjusts the accrual or the amount of prepaid expenses accordingly.
Debt issuance costs	Debt issuance costs Costs incurred in connection with the issuance of the Company’s long-term debt have been recorded as a direct reduction against the debt and amortized over the life of the associated debt as a component of interest expense using the effective interest method.
Success fee obligation	Success fee obligation The Loan Agreement, as amended, with PWB, requires the Company to pay a success fee (“success fee obligation”) upon the occurrence of a specified liquidity event as described in the Loan Agreement, as amended. The Company determined that this obligation represented a freestanding derivative instrument. Accordingly, the success fee obligation was classified as a liability on the Company’s consolidated balance sheets and initially recorded at fair value, with changes in fair value for each reporting period recognized in other expense, net in the consolidated statements of operations and comprehensive loss. The fair value of such obligation is remeasured at the end of each reporting period until the liability is settled.
Equity issuance costs	Equity issuance costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ equity as a reduction of proceeds generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the consolidated statement of operations. There were no deferred offering costs as of December 31, 2023 and 2022.
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. There were no impairment losses recognized during the years ended December 31, 2023 and 2022.
Leases	Leases The Company has real estate leases for its corporate offices and lab space located in Cambridge, Massachusetts. It determines if an arrangement contains a lease at contract inception. Operating lease assets and liabilities are recognized at the commencement date of the lease based upon the present value of lease payments over the lease term. Lease payments are typically fixed and escalate over time. Variable payments relate to the Company’s usage or share of the lessor’s operating costs associated with the underlying asset and are recognized as incurred. When determining the lease term, the Company includes options to extend or terminate the lease when it is reasonably certain that it will exercise that option. The Company uses its incremental borrowing rate to calculate the lease liability when the implicit rate is not readily determinable. Lease expense is recognized on a straight-line basis over the lease term.
Fair value measurements	Fair value measurements 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.
Revenue recognition	Revenue recognition Revenue recognized through December 31, 2023 is solely generated from the collaboration agreement with PM (CF) Explorations, Inc., or PMCo. The Company recognizes revenue in accordance with ASU 2014-09, Revenue from Contracts with Customers (Topic 606) and its related amendments, or, collectively, ASC 606. At inception, the Company determines whether contracts are within the scope of ASC 606 or other topics. For contracts that are determined to be within the scope of ASC 606, revenue is recognized when a customer obtains control of promised goods or services. The amount of revenue recognized reflects the consideration to which the Company expects to be entitled to receive in exchange for these goods and services. To achieve this core principle, the Company applies the following five steps (i) identify the contract with the customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when performance obligation is satisfied. The Company only applies the five-step model to contracts when it determines that collection of substantially all consideration for goods and services that are transferred is probable based on the customer’s intent and ability to pay the promised consideration. Performance obligations promised in a contract are identified based on the goods and services that will be transferred to the customer that are both capable of being distinct and are distinct in the context of the contract. To the extent a contract includes multiple promised goods and services, the Company applies judgment to determine whether promised goods and services are both capable of being distinct and distinct in the context of the contract. If these criteria are not met, the promised goods and services are accounted for as a combined performance obligation. The transaction price is determined based on the consideration to which the Company will be entitled in exchange for transferring goods and services to the customer. To the extent the transaction price includes variable consideration, the Company estimates the amount of variable consideration that should be included in the transaction price utilizing either the expected value method or the most likely amount method, depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in management’s judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur. Any estimates, including the effect of the constraint on variable consideration, are evaluated at each reporting period for any changes. Determining the transaction price requires significant judgment. If the contract contains a single performance obligation, the entire transaction price is allocated to the single performance obligation. Contracts that contain multiple performance obligations require an allocation of the transaction price to each performance obligation on a relative standalone selling price basis unless the transaction price is variable and meets the criteria to be allocated entirely to a performance obligation or to a distinct service that forms part of a single performance obligation. The consideration to be received is allocated among the separate performance obligations based on relative standalone selling prices. The Company satisfies performance obligations either over time or at a point in time. Revenue is recognized over time if either (i) the customer simultaneously receives and consumes the benefits provided by the entity’s performance, (ii) the entity’s performance creates or enhances an asset that the customer controls as the asset is created or enhanced, or (iii) the entity’s performance does not create an asset with an alternative use to the entity and the entity has an enforceable right to payment for performance completed to date. If the entity does not satisfy a performance obligation over time, the related performance obligation is satisfied at a point in time by transferring the control of a promised good or service to a customer. If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenues from consideration allocated to the license when the license is transferred to the customer and the customer can use and benefit from the license. For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. At the inception of each arrangement that includes milestone payments, the Company evaluates the probability of reaching the milestones 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 in the future, the associated milestone value is included in the transaction price. Milestone payments that are not within the Company’s control or the licensee’s are not considered probable of being achieved and therefore revenue recognized is constrained as management is unable to assert that a reversal of revenue would not be possible. The transaction price is then allocated to each performance obligation on a relative standalone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such milestones 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, which would affect revenues and earnings in the period of adjustment. To date, the Company has not recognized any milestone revenue. Deferred revenue arises from amounts received in advance of the culmination of the earnings process and is recognized as revenue in future periods as performance obligations are satisfied. Deferred revenue expected to be recognized within the next twelve months is classified as a current liability.
Research and development expenses	Research and development expenses Research and development expenses are charged to expense as incurred. 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, consulting fees, cost of licensing technology, milestone payment, and external contract research and development and manufacturing expenses. Costs for certain research and development activities are recognized based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated financial statements as prepaid or accrued research and development costs. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses and expensed as the related goods are delivered or the services are performed.
Stock-based compensation	Stock-based compensation The Company’s stock-based compensation program allows for grants of incentive stock options, non-qualified stock options, stock appreciation rights, and restricted stock awards, restricted stock units and other stock-based awards to employees, directors and consultants. The Company recognizes all stock-based compensation awards to employees and non-employees as expense in the consolidated statements of operations and comprehensive loss based on their fair values. For stock option awards, the Company estimates the fair value using the Black-Scholes option pricing model. The fair value of the Company’s common stock is used to determine the fair value of restricted stock awards. Stock-based compensation awards are subject to service vesting conditions, and forfeitures are recorded as they occur. Compensation expense related to awards to employees with service-based vesting conditions is recognized on a straight-line basis based on the grant date fair value over the associated service period of the award, which is generally the vesting term. The Company applies ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting (“ASU No. 2018-07”), in which the measurement date for non-employee awards is determined as the date of grant, and stock-based compensation costs for non-employees are recognized as expense over the vesting period on a straight-line basis. The Black-Scholes option pricing model requires inputs based on certain subjective assumptions, including (i) the expected stock price volatility, (ii) the expected term of the award, (iii) the risk-free interest rate, and (iv) expected dividends. Due to the lack of a public market for the Company’s common stock prior to the IPO and lack of sufficient company-specific historical and implied volatility data, the Company has based its computation of expected volatility on the historical volatility of a representative group of public companies with similar characteristics to the Company, including stage of product development and life science industry focus. The historical volatility is calculated based on a period of time commensurate with the expected term assumption. The Company uses the simplified method as prescribed by the Securities and Exchange Commission Staff Accounting Bulletin No. 107, Share-Based Payment , to calculate the expected term for options granted to employees and non-employees, whereby, the expected term equals the arithmetic average of the vesting term and the original contractual term of the options due to its lack of sufficient historical data. The risk-free interest rate is based on U.S. Treasury securities with a maturity date commensurate with the expected term of the associated award. The expected dividend yield is assumed to be zero as the Company has never paid dividends and has no current plans to pay any dividends on its common stock.
Patent costs	Patent costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred as patents have no future alternative use.
Income taxes	Income taxes The Company recognizes deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the Company’s consolidated financial statements and tax returns. Deferred tax assets and liabilities are determined based upon the differences between the financial statement carrying amounts and the tax bases of existing assets and liabilities and for loss and credit carryforwards, using enacted tax rates expected to be in effect in the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that these assets may not be realized. As of December 31, 2023 and 2022, the Company has recorded a full valuation allowance against its deferred tax assets. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. If it is not more likely than not that a position will be sustained, none of the benefit attributable to the position is recognized. The tax benefit to be recognized for any tax position that meets the more-likely-than-not recognition threshold is calculated as the largest amount that is more than 50% likely of being realized upon resolution of the contingency. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes.
Comprehensive loss	Comprehensive loss Comprehensive loss is defined as the change in stockholders’ equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive loss includes net loss as well as other changes in stockholders’ equity which includes certain changes in equity that are excluded from net loss. The Company’s only element of other comprehensive loss is unrealized gains and losses on its marketable securities.
Net loss per share	Net loss per share Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted average number of common stock outstanding for the period. Diluted net loss attributable to common stockholders is computed by adjusting net loss attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net loss per share attributable to common stockholders is computed by dividing the diluted net loss attributable to common stockholders by the weighted average number of common stock outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common stock equivalents. In periods in which the Company reports a net loss attributable to common stockholders, diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders, since dilutive common shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to common stockholders for the years ended December 31, 2023 and 2022.
Segment and geographic information	Segment and geographic information Operating segments are defined as components of an entity about which discrete information is available for evaluation by the chief operating decision maker, or CODM, or decision-making group, in deciding how to allocate resources and in assessing performance. The CODM is the Company’s Chief Executive Officer. The CODM views its operations as and manages its business in one operating segment operating exclusively in the United States.
Recently accounting pronouncements adopted/Recent accounting pronouncements not yet adopted	Recent accounting pronouncements adopted On January 1, 2023, the Company adopted Accounting Standards Update No. 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). ASU 2016-13 requires measurement and recognition of expected credit losses for financial assets. In April 2019, the Financial Accounting Standards Board ("FASB") issued clarification to ASU 2016-13 within ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments . The guidance is effective for fiscal years beginning after December 15, 2022. The adoption of the standard was immaterial to the accompanying consolidated financial statements. Recent accounting pronouncements not yet adopted In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280) , Improvements to Reportable Segment Disclosures . The new standard requires enhanced disclosures about segment information and significant segment expenses. It does not change how a public entity identifies its operating segments. ASU 2023-07 is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. The new standard should be applied retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating the impact on its consolidated financial statements. In December 2023, the FASB issued 2023-09, Income Taxes (Topic 740), Improvements to Income Tax Disclosures . The new standard requires public business entities to disclose information about income taxes paid, specific categories in the rate reconciliation, and additional information for reconciling items that meet a quantitative threshold. The guidance should be applied on a prospective basis. For public business entities, ASU 2023-08 is effective for fiscal years beginning after December 15, 2024, with early adoption permitted. For all other entities, the standard is effective for annual periods beginning after December 15, 2025. The Company is currently evaluating the impact on its consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Estimated Useful Life of Each Asset Category	Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the estimated useful life of each asset category as follows: Asset category Estimated useful life Computer equipment and software 3 years Laboratory equipment and office furniture 5 years Leasehold improvements Shorter of useful life or remaining lease term

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Summary of Marketable Securities	The following table summarizes the Company’s marketable securities (in thousands): December 31, 2023 Amortized cost Gross unrealized losses Fair value Corporate debt securities $ 5,000 $ ( 14 ) $ 4,986 December 31, 2022 Amortized cost Gross unrealized losses Fair value Corporate debt securities $ 54,542 $ ( 479 ) $ 54,063

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Prepaid Expense and Other Assets, Current [Abstract]
Summary of Prepaid Expenses and other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): December 31, 2023 2022 Clinical development $ 5,168 $ 5,232 Research and development 1,609 2,072 Facilities 1,242 1,857 Other receivables 855 1,180 Insurance 716 1,020 Software 303 157 Other 431 776 Prepaid expenses and other current assets $ 10,324 $ 12,294

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Summary of Property and Equipment, Net	Property and equipment, net consists of the following (in thousands): December 31, 2023 2022 Lab equipment $ 6,633 $ 6,121 Furniture and fixtures 1,636 1,093 Leasehold improvements 1,290 1,378 Computer equipment 1,226 190 Construction in process 588 827 Total property and equipment 11,373 9,609 Less accumulated depreciation ( 6,062 ) ( 5,414 ) Property and equipment, net $ 5,311 $ 4,195

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2023
Accrued Liabilities, Current [Abstract]
Summary of Accrued Expenses	Accrued expenses consist of the following (in thousands): December 31, 2023 2022 Employee related expenses $ 4,482 $ 4,368 Research costs 1,395 3,876 Professional and consulting fees 716 743 Manufacturing costs 547 4,303 Interest 147 122 Other 627 429 Total $ 7,914 $ 13,841

Term Loan (Tables)

Term Loan (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Summary of Outstanding Term Loan Balance	As of December 31, 2023, $ 4.0 m illion of the net carrying amount of the term loan was classified as short-term and $ 14.9 million was classified as long-term based on the repayment start date. The Company’s outstanding term loan balance was comprised of the following (in thousands): December 31, 2023 2022 Principal $ 19,000 $ 20,000 Unamortized debt discount ( 115 ) ( 64 ) Net carrying amount $ 18,885 $ 19,936
Summary of Interest Expense Recognized Related to Term loan	The following table sets forth total interest expense recognized related to the term loan (in thousands): Year Ended December 31, 2023 2022 Contractual interest expense $ 1,748 $ 1,229 Amortization of debt issuance costs and debt discount 53 67 Total interest expense $ 1,801 $ 1,296
Schedule of Principal Amount in Connection With Term Loan	The Company is required to repay the following principal amounts in connection with its term loan (in thousands): 2024 $ 4,000 2025 4,000 2026 4,000 2027 7,000 Total $ 19,000

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Summary of Fair Value of Financial Instruments	The fair value of the Company’s financial instruments is summarized in the table below (in thousands): December 31, 2023 Level 1 Level 2 Level 3 Total Financial Assets Money market funds $ 10,402 $ — $ — $ 10,402 Corporate Debt Securities — 4,986 — 4,986 Total $ 10,402 $ 4,986 $ — $ 15,388 Financial Liabilities Success fee obligations $ — $ — $ 300 $ 300 December 31, 2022 Level 1 Level 2 Level 3 Total Financial Assets Money market funds $ 25,776 $ — $ — $ 25,776 Corporate Debt Securities — 54,063 — 54,063 Total $ 25,776 $ 54,063 $ — $ 79,839 Financial Liabilities Success fee obligation $ — $ — $ 118 $ 118 In accordance with the Fourth and Fifth Amendments of the Loan Agreement with PWB, the Company will be required to pay success fees totaling $ 0.3 million upon the achievement of certain liquidity events; accordingly, the related obligation is recorded as current liabilities on the consolidated balance sheets as it is deemed more probable than not by the Company to be settled in less than one year. The fair value of the success fee obligation was determined using the probability-weighted expected return method. The key estimates and assumptions impacting the fair value included the probability of achieving a specified liquidity event, the expected timing of achieving a liquidity event and the discount rate. The fair value of the success fee obligation is remeasured at each reporting period, with changes in fair value recognized in the consolidated statements of operations and comprehensive loss, until such liability was settled. As of December 31, 2023, the Company determined it was 100 % probable of achieving the specified liquidity events and therefore accrued the full amount of the success fee obligations. The following reflects the significant quantitative inputs used to determine the valuation of the success fee obligation for the years ended December 31, 2023 and 2022: December 31, 2023 December 31, 2022 Discount rate 9.0 % 8.0 % Expected timing of achieving liquidity events (years) 1.0 0.3 - 1.3 Probability of achieving liquidity events 100 % 75 % - 25 % The following table provides a roll-forward of the fair values of the Company’s success fee obligation for which fair value is determined by Level 3 inputs (in thousands): Success fee Success fee Fair value at January 1, 2023 $ 118 $ — Initial fair value of success fee obligation — 90 Change in fair value 82 10 Fair value at December 31, 2023 $ 200 $ 100
Summary of Significant Quantitative Inputs Used to Determine Valuation of Success Fee Obligation	The following reflects the significant quantitative inputs used to determine the valuation of the success fee obligation for the years ended December 31, 2023 and 2022: December 31, 2023 December 31, 2022 Discount rate 9.0 % 8.0 % Expected timing of achieving liquidity events (years) 1.0 0.3 - 1.3 Probability of achieving liquidity events 100 % 75 % - 25 %
Summary of Fair Values of Success Fee Obligation	The following table provides a roll-forward of the fair values of the Company’s success fee obligation for which fair value is determined by Level 3 inputs (in thousands): Success fee Success fee Fair value at January 1, 2023 $ 118 $ — Initial fair value of success fee obligation — 90 Change in fair value 82 10 Fair value at December 31, 2023 $ 200 $ 100

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Summary of Components of Lease Expense	The following table summarizes the components of lease expense for the years ended December 31, 2023 and 2022 (in thousands). Year Ended December 31, 2023 December 31, 2022 Operating lease expense $ 11,624 $ 3,820 Variable lease expense 2,819 1,357 Total lease expense $ 14,443 $ 5,177
Summary of Weighted Average Remaining Lease Term And Discount Rate Related to Leases	The weighted average remaining lease term and discount rate related to the Company's leases were as follows: As of December 31, 2023 December 31, 2022 Weighted average remaining lease term (years) 14.5 1.8 Weighted average discount rate 8.9 % 5.5 %
Summary of Supplemental Cash Flow Information Relating to Leases	Supplemental cash flow information relating to the Company's leases for the years ended December 31, 2023 and December 31, 2022 were as follows (in thousands): Year Ended December 31, 2023 December 31, 2022 Cash paid for amounts included in the measurement of lease liabilities $ 8,542 $ 2,637 Operating lease assets obtained in exchange for lease liabilities $ 110,424 $ 4,393
Summary of Estimated Minimum Lease Payments	As of December 31, 2023, the estimated minimum lease payments for 140 First Street and 325 Vassar for each of the years ending December 31 were as follows (in thousands): 2024 $ 11,781 2025 11,887 2026 12,213 2027 12,549 2028 12,895 Thereafter 139,504 Total minimum lease payments 200,829 Less: Imputed interest ( 91,286 ) Present value of operating lease liabilities $ 109,543

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Summary of Stock-based Compensation Expense	The Company recorded stock-based compensation expense as research and development and general and administrative expenses in the consolidated statements of operations and comprehensive loss as follows (in thousands): Year ended December 31, 2023 2022 Research and development $ 4,269 $ 4,026 General and administrative 4,524 3,727 Total stock-based compensation expense $ 8,793 $ 7,753
Summary of Assumptions Used in Black-Scholes Option-pricing Model for Stock Options	The assumptions used in the Black-Scholes option-pricing model for stock options granted were as follows : Year ended December 31, 2023 2022 Expected volatility 74.65 % - 77.06 % 76.09 % - 77.62 % Weighted-average risk-free interest rate 4.16 % 2.69 % Expected dividend yield 0.00 % 0.00 % Weighted-average expected term (in years) 6.08 6.11
Summary of Option Activity	A summary of option activity under the Company’s equity incentive plans during the year ended December 31, 2023 was as follows: Weighted Weighted Aggregate Number average contractual value (1) (in thousands) Outstanding as of January 1, 2023 8,438,573 $ 6.00 8.40 $ 12,976 Granted 1,586,002 5.74 Exercised ( 152,050 ) 3.21 Forfeited ( 964,787 ) 7.96 Expired ( 127,001 ) 12.73 Outstanding as of December 31, 2023 8,780,737 5.69 7.52 5,033 Vested and expected to vest as of December 31, 2023 8,780,737 5.69 7.52 5,033 Exercisable as of December 31, 2023 4,837,051 $ 4.79 6.71 $ 4,599 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that were in the money as of December 31, 2023 .

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Summary of the Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders	The following table summarizes the computation of basic and diluted net loss per share attributable to common stockholders of the Company (in thousands except share and per share amounts): Year Ended December 31, 2023 2022 Numerator: Net loss attributable to common stockholders $ ( 97,428 ) $ ( 102,701 ) Denominator: Weighted average number of common stock, basic and diluted 54,010,996 47,880,819 Net loss per common stock attributable to common stockholders, basic and diluted $ ( 1.80 ) $ ( 2.14 )
Schedule of Anti-Dilutive Securities Excluded from Computation of Earnings Per Share	The Company excluded the following potential common stock, presented based on amounts outstanding at period end, from the computation of diluted net loss per share attributable to common stockholders because including them would have had an anti-dilutive effect: As of December 31, 2023 2022 Outstanding options to purchase common stock 8,780,737 8,438,573

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Summary of Reconciliation of Federal Statutory Income Tax Rate to Effective Income Tax Rate	A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows: Year ended December 31, 2023 2022 U.S. federal statutory income tax rate 21.0 % 21.0 % State income taxes, net of federal benefit 6.6 7.1 Research and development tax credits 4.7 4.3 Nondeductible/ nontaxable permanent items ( 0.9 ) ( 0.5 ) Change in valuation allowance ( 31.4 ) ( 32.0 ) Other 0.0 0.1 Effective income tax rate 0.0 % 0.0 %
Summary of Components of Deferred Taxes	The components of the Company’s deferred taxes are as follows (in thousands): Year ended December 31, 2023 2022 Deferred tax assets: Net operating loss carryforwards $ 50,762 $ 40,157 Research and development credit carryforwards 16,309 11,013 Accrued expenses 1,154 1,098 Stock-based compensation 3,329 1,726 Intangibles 120 136 IRC 174 R&D capitalization 32,505 20,024 ASC 842 lease liability 30,198 722 Unrealized gain/loss — 325 Total deferred tax assets 134,377 75,201 Less: valuation allowance ( 104,630 ) ( 74,005 ) Deferred tax assets, net 29,747 1,196 Deferred tax liabilities: Depreciation ( 12 ) ( 194 ) Right of use asset ( 29,706 ) ( 1,002 ) Unrealized gain/loss ( 29 ) — Total deferred tax liabilities ( 29,747 ) ( 1,196 ) Net deferred taxes $ — $ —

Nature of the Business and Ba_2

Nature of the Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Feb. 28, 2023	Aug. 31, 2021	Dec. 31, 2023	Dec. 31, 2022
Nature Of Business And Basis Of Presentation [Line Items]
Common stock, shares issued			55,144,982	48,072,517
Recurring losses			$ 97,400
Cash, cash equivalents and marketable securities			73,400
Net cash used in operations			$ (91,510)	$ (98,515)
IPO
Nature Of Business And Basis Of Presentation [Line Items]
Common stock, shares issued		8,300,976
Offering price per share		$ 17
Gross proceeds from IPO		$ 141,100
Net proceeds		$ 128,100
Underwriters’ Option to Purchase Additional Shares
Nature Of Business And Basis Of Presentation [Line Items]
Common stock, shares issued		900,976
Registered Direct Offering
Nature Of Business And Basis Of Presentation [Line Items]
Offering price per share	$ 5.78
Common stock issued and sold	6,920,415
Net proceeds from direct offering	$ 39,700

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Indemnification obligations losses	$ 0	$ 0
Indemnification obligations claims outstanding	0	0
Deferred offering costs	0	0
Impairment losses recognized	0	0
Operating lease right-of-use assets	108,736,000	$ 3,668,000
Present value of operating lease liabilities	$ 109,543,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Estimated Useful Life of Each Asset Category (Details)	Dec. 31, 2023
Computer Equipment and Software
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Laboratory Equipment and Office Furniture
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property, Plant, and Equipment, Useful Life, Term, Description [Extensible Enumeration]	Property, Plant and Equipment, Net

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities (Details) - Marketable Securities - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale [Line Items]
Marketable Securities, Amortized cost	$ 5,000	$ 54,542
Marketable Securities, Gross unrealized losses	(14)	(479)
Marketable Securities, Fair value	$ 4,986	$ 54,063

Marketable Securities - Additio

Marketable Securities - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023 USD ($)
Investments, Debt and Equity Securities [Abstract]
Realized losses recognized on the sale or maturity of marketable securities	$ 0
Realized gains recognized on the sale or maturity of marketable securities	0
Investments with other-than-temporary impairment	0
Debt securities reclassified to accumulated other comprehensive loss	$ 0

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Summary of Prepaid Expenses and other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Prepaid Expense and Other Assets, Current [Abstract]
Clinical development	$ 5,168	$ 5,232
Research and development	1,609	2,072
Facilities	1,242	1,857
Other receivables	855	1,180
Insurance	716	1,020
Software	303	157
Other	431	776
Prepaid expenses and other current assets	$ 10,324	$ 12,294

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 [Line Items]
Total property and equipment	$ 11,373	$ 9,609
Less accumulated depreciation	(6,062)	(5,414)
Property and equipment, net	5,311	4,195
Lab Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	6,633	6,121
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	1,636	1,093
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	1,290	1,378
Computer Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	1,226	190
Construction in Process
Property Plant And Equipment [Line Items]
Total property and equipment	$ 588	$ 827

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	$ 1,568	$ 1,564

Accrued Expenses - Summary of A

Accrued Expenses - Summary of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accrued Liabilities, Current [Abstract]
Employee related expenses	$ 4,482	$ 4,368
Research costs	1,395	3,876
Professional and consulting fees	716	743
Manufacturing costs	547	4,303
Interest	147	122
Other	627	429
Total	$ 7,914	$ 13,841

Term Loan - Additional Informat

Term Loan - Additional Information (Details) - USD ($)			12 Months Ended
	Sep. 30, 2023	Sep. 22, 2023	Dec. 31, 2023	Dec. 31, 2022	Mar. 09, 2018
Debt [Line Items]
Aggregate principal amount			$ 19,000,000	$ 20,000,000
Unamortized debt discount			115,000	64,000
Accrued interest on term loan			147,000	121,000
Net carrying amount of term loan classified as short-term			4,000,000
Net carrying amount of term loan classified as long-term			$ 14,885,000	$ 16,603,000
Maximum
Debt [Line Items]
Effective interest rate on the liability component			9.26%
Minimum
Debt [Line Items]
Effective interest rate on the liability component			5.53%
Loan Agreement | Pacific Western Bank
Debt [Line Items]
Maximum borrowing capacity					$ 8,000,000
Fourth Amendment | Pacific Western Bank | Maximum
Debt [Line Items]
Success fee payable		$ 200,000
Fifth Amendment | Pacific Western Bank
Debt [Line Items]
Line of credit facility, Floating annual interest rate		0.50%
Line of credit facility, Interest rate during period		5.50%
Proceeds from bank		$ 50,000,000
Maturity date		Sep. 30, 2027	Sep. 30, 2028
Debt issuance costs		$ 15,000
Principal repayment start date			Sep. 30, 2023
Monthly principal payments plus interest	$ 300,000
Minimum unrestricted cash requirement		5,000,000
Minimum prepayment amount for termination of unrestricted cash		5,000,000
Minimum principal balance requirement		10,000
Fifth Amendment | Pacific Western Bank | Maximum
Debt [Line Items]
Monthly principal payments plus interest		4,000,000
Fifth Amendment | Pacific Western Bank | Minimum
Debt [Line Items]
Success fee payable		$ 100,000

Term Loan - Summary of Outstand

Term Loan - Summary of Outstanding Term Loan Balance (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Disclosure [Abstract]
Principal	$ 19,000	$ 20,000
Unamortized debt discount	(115)	(64)
Net carrying amount	$ 18,885	$ 19,936

Term Loan - Summary of Interest

Term Loan - Summary of Interest Expense Recognized Related to Term loan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Disclosure [Abstract]
Contractual interest expense	$ 1,748	$ 1,229
Amortization of debt issuance costs and debt discount	53	67
Total interest expense	$ 1,801	$ 1,296

Term Loan - Schedule of Princip

Term Loan - Schedule of Principal Amount in Connection With Term Loan (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Disclosure [Abstract]
2024	$ 4,000
2025	4,000
2026	4,000
2027	7,000
Total	$ 19,000	$ 20,000

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Summary of Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financial Assets
Total financial assets	$ 15,388	$ 79,839
Success Fee Obligation
Financial Liabilities
Total financial liabilities	300	118
Money Market Funds
Financial Assets
Total financial assets	10,402	25,776
Corporate Debt Securities
Financial Assets
Total financial assets	4,986	54,063
Level 1
Financial Assets
Total financial assets	10,402	25,776
Level 1 | Money Market Funds
Financial Assets
Total financial assets	10,402	25,776
Level 2
Financial Assets
Total financial assets	4,986	54,063
Level 2 | Corporate Debt Securities
Financial Assets
Total financial assets	4,986	54,063
Level 3 | Success Fee Obligation
Financial Liabilities
Total financial liabilities	$ 300	$ 118

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Additional Information (Details) $ in Millions	Dec. 31, 2023 USD ($)
Measurement Input Probability Of Achieving Liquidity Events [Member]
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input	1
Fourth And Fifth Amendments [Member] | Pacific Western Bank [Member]
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee payable	$ 0.3

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Summary of Significant Quantitative Inputs Used to Determine Valuation of Success Fee Obligation (Details)	Dec. 31, 2023 yr	Dec. 31, 2022 yr
Discount Rate
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input	0.09	0.08
Expected Timing of Achieving Liquidity Events (years)
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input	1
Expected Timing of Achieving Liquidity Events (years) | Minimum
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input		0.3
Expected Timing of Achieving Liquidity Events (years) | Maximum
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input		1.3
Probability of Achieving Liquidity Events
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input	1
Probability of Achieving Liquidity Events | Minimum
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input		0.75
Probability of Achieving Liquidity Events | Maximum
Fair Value Liabilities Measured On Recurring Basis [Line Items]
Success fee, measurement input		0.25

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Summary of Fair Values of Success Fee Obligation (Details) - Level 3 $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Success Fee Obligation from the Fourth Amendment
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 118
Change in fair value	82
Ending balance	200
Success Fee Obligation From The Fifth Amendment [Member]
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Initial fair value of success fee obligation	90
Change in fair value	10
Ending balance	$ 100

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Thousands

1 Months Ended

6 Months Ended

12 Months Ended

Jul. 12, 2023 Space

Jul. 11, 2023 Space

May 03, 2023 $ / ft²

Nov. 04, 2021 USD ($) ft² Phase

Dec. 31, 2023 USD ($)

Jul. 31, 2023 USD ($) ft² Space

Jan. 31, 2022 USD ($)

Jul. 31, 2020 ft²

Jun. 30, 2023 USD ($)

Dec. 31, 2023 USD ($) ft² Option

Dec. 31, 2022 USD ($)

Dec. 31, 2020 Sublease

Dec. 31, 2019 Sublease

Leases [Line Items]

Lease expiration date

Sep. 30, 2024

Lessee operating lease, description

share one-third of Sail Bio's 69,867 square feet of leased space at 20 Acorn Park Drive, Cambridge, Massachusetts

Net book value of assets

$ 400

Gain on disposal of assets

$ 200

Number of phases | Phase

2

Base rent per square foot | $ / ft²

1

Number of shared space arrangements | Space

3

Lease payment

$ 11,624

$ 3,820

Right-of-use assets

$ 108,736

108,736

3,668

Lease liabilities

109,543

109,543

Lease liabilities, current

11,300

11,300

1,524

Lease liabilities, non-current

$ 98,243

98,243

1,120

Lease expense

14,443

5,177

Thermo Fisher Financial Services, Inc.

Leases [Line Items]

Sale leaseback, date

December 2023

Sale leaseback term

5 years

Sale leaseback, terms

In December 2023, the Company entered into a sale-leaseback arrangement with Thermo Fisher Financial Services, Inc. to provide $2.6 million in cash proceeds for previously acquired furniture and equipment.

Cash proceeds from furniture and equipment

$ 2,600

Option to purchase the assets

option to purchase the assets for $1 at the end of the term.

Monthly payments

$ 53

53

Finance obligation current

$ 400

$ 400

Finance Obligation, Current, Statement of Financial Position

Liabilities, Current

Liabilities, Current

Finance obligation noncurrent

$ 2,200

$ 2,200

Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]

Liabilities

Liabilities

Research and Development Expenses

Leases [Line Items]

Lease expense

$ 11,300

3,900

General and Administrative Expenses

Leases [Line Items]

Lease expense

3,100

1,200

140 First Street Lease Agreement

Leases [Line Items]

Lessee operating lease, description

The operating lease commenced on May 1, 2023 for the fifth floor premises and August 1, 2023 for the first floor premises for accounting purposes. The lease term for each of the floor premises is fifteen years from the respective commencement date, subject to certain extension rights.

Rentable square feet of office and laboratory | ft²

89,246

Base rent per square foot | $ / ft²

116

Tenant improvement allowance per rentable square foot | $ / ft²

300

Lease term interest rate

8%

Base rent annual upward adjustment percentage

3%

Lease payment

$ 800

Shared Space Arrangement

Leases [Line Items]

Number of shared space arrangements | Space

2

1

Rentable area of office and laboratory space agreed to sublease | ft²

22,500

Commitment for subtenants

$ 5,200

Shared Space Arrangement | Research and Development Expense and General and Administrative Expense

Leases [Line Items]

Sublease rental income received

$ 1,400

Phase I

Leases [Line Items]

Rentable square feet of office and laboratory | ft²

78,380

Phase II

Leases [Line Items]

Rentable square feet of office and laboratory | ft²

10,866

Sail Biomedicines, Inc

Leases [Line Items]

Lease expiration date

Jul. 31, 2023

Lessee operating lease, description

share one-third of Sail Bio's 69,867 square feet of leased space at 20 Acorn Park Drive, Cambridge, Massachusetts

Number of options to extend terms | Option

2

Term of lease arrangement period

24 months

Lease arrangement description

The Arrangement commenced on August 1, 2020, and was set to expire on July 31, 2022 with two options to extend the term of the Arrangement for a period of 24 months each.

Area of leased space | ft²

69,867

69,867

Upfront payment

$ 2,900

Reimbursement for office furniture purchases

$ 650

Sail Biomedicines, Inc | Related Party Expense

Leases [Line Items]

Sublease rental income received

$ 2,500

$ 2,300

LARONDE, Inc.

Leases [Line Items]

Number of sublease agreements with related parties | Sublease

2

Cygnal

Leases [Line Items]

Number of sublease agreements with related parties | Sublease

2

Metaphore

Leases [Line Items]

Monthly license fee proportionate share, percentage

12%

Apriori

Leases [Line Items]

Monthly license fee proportionate share, percentage

8.40%

Labs

Leases [Line Items]

Monthly license fee proportionate share, percentage

8.40%

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Components of Lease Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Lessee Disclosure [Abstract]
Operating lease expense	$ 11,624	$ 3,820
Variable lease expense	2,819	1,357
Total lease expense	$ 14,443	$ 5,177

Commitments and Contingencies_3

Commitments and Contingencies - Summary of Weighted Average Remaining Lease Term And Discount Rate Related to Leases (Details)	Dec. 31, 2023	Dec. 31, 2022
Leases [Line Items]
Weighted average remaining lease term (years)	14 years 6 months	1 year 9 months 18 days
Weighted average discount rate	8.90%	5.50%

Commitments and Contingencies_4

Commitments and Contingencies - Summary of Supplemental Cash Flow Information Relating to Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Leases [Line Items]
Cash paid for amounts included in the measurement of lease liabilities	$ 8,542	$ 2,637
Operating lease assets obtained in exchange for lease liabilities	$ 110,424	$ 4,393

Commitments and Contingencies_5

Commitments and Contingencies - Summary of Estimated Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Leases [Abstract]
2024	$ 11,781
2025	11,887
2026	12,213
2027	12,549
2028	12,895
Thereafter	139,504
Total minimum lease payments	200,829
Less: Imputed interest	(91,286)
Present value of operating lease liabilities	$ 109,543

License Agreements - Additional

License Agreements - Additional Information (Details)		1 Months Ended			12 Months Ended
	Oct. 12, 2022 USD ($)	Mar. 31, 2021 USD ($)	Oct. 31, 2020 USD ($)	May 31, 2019 USD ($) Product	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
License Agreements [Line Items]
License maintenances fees					$ 200,000
Research and development					$ 77,169,000	$ 81,167,000
Maximum
License Agreements [Line Items]
License maintenances fees						200,000
WIBR Exclusive License Agreement
License Agreements [Line Items]
Number of licensed products | Product				3
Percentage of non-royalty payments description					This percentage ranges from zero to low double-digits and will be based upon the stage of development of the licensed product at the time such sublicense is executed.
WIBR Exclusive License Agreement | Maximum
License Agreements [Line Items]
Nonrefundable upfront fee paid.				$ 100,000
Annual license maintenance fees				100,000
Milestone payments				$ 1,700,000
WIBR Co-Exclusive License Agreement
License Agreements [Line Items]
Number of licensed products | Product				3
WIBR Co-Exclusive License Agreement | Maximum
License Agreements [Line Items]
Nonrefundable upfront fee paid.				$ 100,000
Annual license maintenance fees				100,000
Milestone payments				1,900,000
Annual fees for each sublicense agreement				$ 100,000
Development and Option Agreement
License Agreements [Line Items]
Reimbursements for development and material costs incurred by Acuitas			$ 400,000
Development and Option Agreement | First Non-exclusive License
License Agreements [Line Items]
Annual technology access fee			1,500,000
Development and Option Agreement | Second Non-exclusive License
License Agreements [Line Items]
Annual technology access fee			$ 1,750,000
Acuitas License Agreement
License Agreements [Line Items]
Milestone payments					$ 0
Annual maintenance fee						800,000
Option exercise fee		$ 1,500,000
Potential clinical and regulatory milestone payments aggregate amount entitled to receive Acuitas		$ 18,000,000
Research and development					400,000	1,900,000
Nitto
License Agreements [Line Items]
Research and development	$ 1,000,000				900,000
Upfront payment	1,000,000
Nitto | Maximum
License Agreements [Line Items]
Future payments based upon the achievement of specified development, regulatory and sales milestones	$ 83,000,000
Related Party
License Agreements [Line Items]
Other Liabilities					$ 0	$ 0

Collaboration Agreement - Addit

Collaboration Agreement - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended			12 Months Ended
	Jan. 31, 2024	Nov. 30, 2021	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Novo Nordisk
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction price						$ 26.7
Nonrefundable upfront payment						5.1
Novo Nordisk | Subsequent Event
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Amount of cost reimbursement receivable to fund research and development activities	$ 21.6
Nonrefundable upfront payment	$ 5.1
Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration agreement period		5 years
Transaction price						7.9
Increase in transaction price			$ 0.1	$ 2.4	$ 1.9
Remaining transaction price			$ 2.7			2.7
Research and collaboration revenue						$ 3.1	$ 2.1

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Class Of Stock [Line Items]
Gross proceeds	$ 488	$ 708

Preferred and Common Stock - Ad

Preferred and Common Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended
	Feb. 28, 2023	Aug. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Class of Stock [Line Items]
Common stock issued and sold			55,144,982	48,072,517
Shares of common stock authorized			200,000,000	200,000,000
Common stock, par value			$ 0.001	$ 0.001
Shares of preferred stock authorized			10,000,000	10,000,000
Preferred stock, par value			$ 0.001	$ 0.001
IPO
Class of Stock [Line Items]
Common stock issued and sold		8,300,976
Offering price per share		$ 17
Gross proceeds from IPO		$ 141.1
Net proceeds		$ 128.1
Underwriters’ Option to Purchase Additional Shares
Class of Stock [Line Items]
Common stock issued and sold		900,976
Registered Direct Offering
Class of Stock [Line Items]
Offering price per share	$ 5.78
Net proceeds from direct offering	$ 39.7
Estimated offering expenses	$ 0.3
Common stock issued and sold	6,920,415
2017 Plan
Class of Stock [Line Items]
Common stock subject to outstanding stock options issued		3,902,063
2017 and 2021 Plans
Class of Stock [Line Items]
Common stock subject to outstanding stock options issued			8,780,737
Amended and Restated Certificate of Incorporation
Class of Stock [Line Items]
Shares of common stock authorized					200,000,000
Common stock, par value					$ 0.001
Shares of preferred stock authorized					10,000,000
Preferred stock, par value					$ 0.001

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended		12 Months Ended
	Jul. 31, 2021	Jun. 30, 2017	Dec. 31, 2023	Dec. 31, 2022
2017 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant			0
Common stock subject to outstanding stock options issued			3,902,063
2017 Equity Incentive Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period		10 years
Vesting period		4 years
2017 Equity Incentive Plan | Stock Options | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase price of common stock percentage		100%
2021 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future grant			2,581,038
Common stock subject to outstanding stock options issued			4,878,674
Common stock reserved for future issuance	2,960,000
Common stock shares reserved for future issuance increased percentage			4%
2017 Equity Incentive Plan and 2021 Incentive Award Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value per share of stock options granted			$ 3.97	$ 5.08
Intrinsic value of stock options exercised			$ 0.7	$ 1
Unrecognized compensation cost related to unvested stock options			$ 16.5
Unrecognized compensation cost, weighted-average period of recognition			2 years
2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares reserved for future issuance increased percentage			1%
Total number of shares of common stock available for issuance			1,438,649
Maximum shares purchased under employee stock purchase plan during offering period	100,000
2021 Employee Stock Purchase Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase price of common stock percentage			85%
2021 Employee Stock Purchase Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock subject to outstanding stock options issued			6,450,000
Expiration period			27 months

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 8,793	$ 7,753
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	4,269	4,026
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 4,524	$ 3,727

Equity Incentive Plans - Summ_2

Equity Incentive Plans - Summary of Assumptions Used in Black-Scholes Option-pricing Model for Stock Options (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement, Disclosure [Abstract]
Expected volatility, minimum	74.65%	76.09%
Expected volatility, maximum	77.06%	77.62%
Weighted-average risk-free interest rate	4.16%	2.69%
Expected dividend yield	0%	0%
Weighted-average expected term (in years)	6 years 29 days	6 years 1 month 9 days

Equity Incentive Plans - Summ_3

Equity Incentive Plans - Summary of Option Activity (Details) - 2017 Equity Incentive Plan and 2021 Incentive Award Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options Outstanding, Beginning balance	8,438,573
Number of options, Granted	1,586,002
Number of options, Exercised	(152,050)
Number of options, Forfeited	(964,787)
Number of options, Expired	(127,001)
Number of options Outstanding, Ending balance	8,780,737	8,438,573
Number of options, Vested and expected to vest	8,780,737
Number of options, Exercisable	4,837,051
Weighted average exercise price Outstanding, Beginning balance	$ 6
Weighted average exercise price, Granted	5.74
Weighted average exercise price, Exercised	3.21
Weighted average exercise price, Forfeited	7.96
Weighted average exercise price, Expired	12.73
Weighted average exercise price Outstanding, Ending balance	5.69	$ 6
Weighted average exercise price, Vested and expected to vest	5.69
Weighted average exercise price, Exercisable	$ 4.79
Weighted average remaining contractual life (years), Outstanding	7 years 6 months 7 days	8 years 4 months 24 days
Weighted average remaining contractual life (years), Vested and expected to vest	7 years 6 months 7 days
Weighted average remaining contractual life (years), Exercisable	6 years 8 months 15 days
Aggregate intrinsic value, Outstanding	$ 5,033	$ 12,976
Aggregate intrinsic value, Vested and expected to vest	5,033
Aggregate intrinsic value, Exercisable	$ 4,599

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Summary of the Computation of Basic and Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Numerator:
Net loss attributable to common stockholders	$ (97,428)	$ (102,701)
Denominator:
Weighted-average common stock used in net loss per share attributable to common stockholders, basic	54,010,996	47,880,819
Weighted-average common stock used in net loss per share attributable to common stockholders, diluted	54,010,996	47,880,819
Net loss per common stock attributable to common stockholders, basic	$ (1.8)	$ (2.14)
Net loss per common stock attributable to common stockholders, diluted	$ (1.8)	$ (2.14)

Net Loss Per Share Attributab_4

Net Loss Per Share Attributable to Common Stockholders - Schedule of Anti-Dilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Outstanding Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	8,780,737	8,438,573

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Federal Statutory Income Tax Rate to Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
U.S. federal statutory income tax rate	21%	21%
State income taxes, net of federal benefit	6.60%	7.10%
Research and development tax credits	4.70%	4.30%
Nondeductible/ nontaxable permanent items	(0.90%)	(0.50%)
Change in valuation allowance	(31.40%)	(32.00%)
Other	0%	0.10%
Effective income tax rate%	0%	0%

Income Taxes - Summary of Compo

Income Taxes - Summary of Components of Deferred Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 50,762	$ 40,157
Research and development credit carryforwards	16,309	11,013
Accrued expenses	1,154	1,098
Stock-based compensation	3,329	1,726
Intangibles	120	136
IRC 174 R&D capitalization	32,505	20,024
ASC 842 lease liability	30,198	722
Unrealized gain/loss		325
Total deferred tax assets	134,377	75,201
Less: valuation allowance	(104,630)	(74,005)
Deferred tax assets, net	29,747	1,196
Deferred tax liabilities:
Depreciation	(12)	(194)
Right of use asset	(29,706)	(1,002)
Unrealized gain/loss	(29)
Total deferred tax liabilities	$ (29,747)	$ (1,196)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Contingency [Line Items]
Income tax expense	$ 0	$ 0
Increase in valuation allowance	30,600,000
Federal net operating loss carryforwards	187,400,000
State net operating loss carryforwards	$ 180,400,000
Federal and state net operating loss carryforwards will begin to expire	Jan. 01, 2036
Federal net operating loss carryforwards with no expiration date	$ 181,900,000
Federal
Income Tax Contingency [Line Items]
Tax credit	12,400,000
Massachusetts
Income Tax Contingency [Line Items]
Tax credit	$ 4,900,000

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details)	1 Months Ended				6 Months Ended	12 Months Ended
	Jul. 31, 2023 ft² Space	Jan. 31, 2022 USD ($)	Sep. 30, 2020 USD ($) ft²	Jul. 31, 2020 ft²	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($) ft²	Dec. 31, 2022 USD ($)	Sep. 30, 2019 ft²
Related Party Transaction [Line Items]
Number of shared space arrangements | Space	3
Lessee operating lease, description						share one-third of Sail Bio's 69,867 square feet of leased space at 20 Acorn Park Drive, Cambridge, Massachusetts
Net book value of assets					$ 400,000
Gain on disposal of assets					$ 200,000
Lease expiration date						Sep. 30, 2024
Shared Space Agreements
Related Party Transaction [Line Items]
Rentable area of office and laboratory space agreed to sublease | ft²	22,500
Cygnal
Related Party Transaction [Line Items]
Outstanding receivable							$ 0
Area of real estate property | ft²								1,445
Sublease income						$ 100,000
Sublease term						2 years
Sail Biomedicines, Inc
Related Party Transaction [Line Items]
Outstanding receivable						$ 0	0
Area of real estate property | ft²			19,404
Sublease income			$ 1,600,000
Area of leased space | ft²				69,867		69,867
Lessee operating lease, description						share one-third of Sail Bio's 69,867 square feet of leased space at 20 Acorn Park Drive, Cambridge, Massachusetts
Upfront payment		$ 2,900,000
Reimbursement for office furniture purchases		$ 650,000
Lease expiration date		Jul. 31, 2023
Subtenants
Related Party Transaction [Line Items]
Outstanding receivable						$ 0
Related Party Expense | Shared Space Agreements
Related Party Transaction [Line Items]
Sublease rental income received						1,400,000
Related Party Expense | Cygnal | Maximum
Related Party Transaction [Line Items]
Sublease rental income received							100,000
Related Party Expense | Sail Biomedicines, Inc
Related Party Transaction [Line Items]
Sublease rental income received						2,500,000	2,300,000
Flagship | Reimbursable Expenses | Related Party
Related Party Transaction [Line Items]
Related party expenses for management service						$ 200,000	$ 1,700,000
Omega Therapeutics, Inc. | Flagship
Related Party Transaction [Line Items]
Ownership percentage						53%

Employee Benefits - Additional

Employee Benefits - Additional Information (Details) - 401(k) Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Defined Contribution Plan Disclosure [Line Items]
Employee benefits description	the Company began matching 50% of employee contributions of up to 6% of eligible compensation contributed on a pre-tax and/or Roth after-tax basis to the 401(k) Plan.
Employer matching contribution, percentage of match	50%
Percentage of eligible compensation contributed	6%
Total contribution	$ 0.6	$ 0.5