IO Biotech (IOBT) 10-K 5 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	Feb. 28, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2023
Current Fiscal Year End Date	--12-31
Entity Registrant Name	IO BIOTECH, INC.
Entity Central Index Key	0001865494
Entity File Number	001-41008
Entity Tax Identification Number	87-0909276
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	Ole Maaløes Vej 3
Entity Address, City or Town	Copenhagen N
Entity Address, Country	DK
Entity Address, Postal Zip Code	DK-2200
City Area Code	+45
Local Phone Number	7070 2980
Title of each class	Common stock, par value $0.001 per share
Trading Symbol(s)	IOBT
Name of each exchange on which registered	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Document Financial Statement Error Correction [Flag]	false
Entity Public Float			$ 31.1
Entity Common Stock, Shares Outstanding		65,880,914
Document Annual Report	true
Document Transition Report	false
Documents incorporated by reference	Portions of the registrant’s proxy statement relating to its 2024 Annual Meeting of Stockholders have been incorporated by reference herein in response to Part III, as specifically set forth in Part III.
Auditor Name	EY Godkendt Revisionspartnerselskab
Auditor Firm ID	1757
Auditor Location	Copenhagen, Denmark

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets
Cash and cash equivalents	$ 143,193	$ 142,590
Prepaid expenses and other current assets	4,062	5,629
Total current assets	147,255	148,219
Restricted cash	268	268
Property and equipment, net	847	741
Right of use lease asset	2,259	2,493
Other non-current assets	89	84
Total non-current assets	3,463	3,586
Total assets	150,718	151,805
Current liabilities
Accounts payable	3,878	4,004
Lease liability - current	655	515
Accrued expenses and other current liabilities	11,184	6,157
Total current liabilities	15,717	10,676
Lease liability - noncurrent	1,839	2,275
Total non-current liabilities	1,839	2,275
Total liabilities	17,556	12,951
Commitments and contingencies (Note 9)
Stockholders' equity
Preferred stock, par value of $0.001 per share; 5,000,000 shares authorized, no shares issued and outstanding as of December 31, 2023 and 2022
Common stock, par value of $0.001 per share; 300,000,000 shares authorized at December 31, 2023 and December 31, 2022; 65,880,914 and 28,815,267 shares issued and outstanding as of December 31, 2023 and December 31, 2022, respectively	66	29
Additional paid-in capital	406,587	326,705
Accumulated deficit	(263,822)	(177,739)
Accumulated other comprehensive loss	(9,669)	(10,141)
Total stockholders' equity	133,162	138,854
Total liabilities and stockholders' equity	$ 150,718	$ 151,805

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022	Nov. 09, 2021
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	300,000,000	300,000,000	300,000,000
Common stock, shares issued	65,880,914	28,815,267	28,815,267
Common stock, shares outstanding	65,880,914	28,815,267	28,815,267

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Operating expenses
Research and development	$ 67,829	$ 46,986
General and administrative	23,614	24,438
Total operating expenses	91,443	71,424
Loss from operations	(91,443)	(71,424)
Other income (expense)
Currency exchange gain, net	331	130
Interest income	5,881	1,411
Interest expense		(302)
Total other income, net	6,212	1,239
Loss before income tax expense	(85,231)	(70,185)
Income tax expense	852	1,273
Net loss	(86,083)	(71,458)
Net loss attributable to common shareholders	$ (86,083)	$ (71,458)
Net loss per common share, basic	$ (1.98)	$ (2.48)
Net loss per common share, diluted	$ (1.98)	$ (2.48)
Weighted-average number of shares used in computing net loss per common share, basic	43,539,976	28,815,267
Weighted-average number of shares used in computing net loss per common share, diluted	43,539,976	28,815,267
Other comprehensive loss
Net loss	$ (86,083)	$ (71,458)
Foreign currency translation	472	(8,652)
Total comprehensive loss	$ (85,611)	$ (80,110)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Other Comprehensive Loss	Accumulated Deficit
Balance at Dec. 31, 2021	$ 211,924	$ 29	$ 319,665	$ (1,489)	$ (106,281)
Balance, shares at Dec. 31, 2021		28,815,267
Equity-based compensation	7,040		7,040
Foreign currency translation	(8,652)			(8,652)
Net loss	(71,458)				(71,458)
Balance at Dec. 31, 2022	138,854	$ 29	326,705	(10,141)	(177,739)
Balance, shares at Dec. 31, 2022		28,815,267
Issuance of common shares and warrants in private placement, net of issuance costs, shares		37,065,647
Issuance of common shares and warrants in private placement, net of issuance costs	71,860	$ 37	71,823
Equity-based compensation	8,059		8,059
Foreign currency translation	472			472
Net loss	(86,083)				(86,083)
Balance at Dec. 31, 2023	$ 133,162	$ 66	$ 406,587	$ (9,669)	$ (263,822)
Balance, shares at Dec. 31, 2023		65,880,914

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Common shares and warrants issuance costs	$ 3,198

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities
Net loss	$ (86,083)	$ (71,458)
Adjustment to reconcile net loss to net cash used in operating activities
Depreciation	215	104
Equity-based compensation	8,059	7,040
Amortization of right of use lease asset	541	436
Foreign currency gain	(331)	(130)
Provision for deferred tax		87
Changes in operating assets and liabilities
Prepaid expenses and other current assets	1,568	4,578
Other non-current assets	(4)	(44)
Accounts payable	(126)	77
Lease liability	(604)	(139)
Accrued expenses and other current liabilities	5,028	(280)
Net cash used in operating activities	(71,737)	(59,729)
Cash flows from investing activities
Purchase of property and equipment	(323)	(690)
Net cash used in investing activities	(323)	(690)
Cash flows from financing activities
Proceeds from issuance of common shares and warrants	75,058
Common shares and warrants issuance costs	(3,198)
Net cash provided by financing activities	71,860
Net decrease in cash, cash equivalents and restricted cash	(200)	(60,419)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	803	(8,522)
Cash, cash equivalents and restricted cash, beginning of period	142,858	211,799
Cash, cash equivalents and restricted cash, end of period	143,461	142,858
Components of cash, cash equivalents, and restricted cash
Cash and cash equivalents	143,193	142,590
Restricted cash	268	268
Total cash, cash equivalents, and restricted cash	$ 143,461	$ 142,858

Description of Business, Organi

Description of Business, Organization and Liquidity	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business, Organization and Liquidity	1. Description of Business, Organization and Liquidity Business IO Biotech, Inc. is a clinical-stage biopharmaceutical company developing novel, immune-modulating therapeutic cancer vaccines based on our T-win® platform. As used in these financial statements, unless the context otherwise requires, references to the “Company,” “we,” “us,” and “our” refer to IO Biotech, Inc. and its subsidiaries. Corporate reorganization IO Biotech ApS was incorporated in Denmark in December 2014. In November 2021, we completed a corporate reorganization whereby IO Biotech ApS became a wholly-owned subsidiary of the Company. In connection with the corporate reorganization, each issued and outstanding Class A ordinary share ($ 0.16 par value) was exchanged on a one-for-one basis into shares of common stock of the Company ($ 0.001 par value). Each Class B and Class C preference share of IO Biotech ApS was exchanged on a one-for-one basis into shares of Class B and Class C preferred stock of the Company. IO Bio US, Inc., a wholly owned subsidiary of IO Biotech ApS, was incorporated in Delaware in May 2021. IO Biotech Limited, a wholly owned subsidiary of IO Biotech ApS, was incorporated in the UK in August 2021. In November 2021, the Company engaged in a series of transactions, referred to collectively as the Corporate Reorganization. As a result of the Corporate Reorganization, IO Biotech ApS became a wholly-owned subsidiary of IO Biotech, Inc. IO Biotech, Inc. is a holding company formed in October 2021, which, prior to our IPO, had nominal assets and no liabilities, contingencies, or commitments, and which has not conducted any operations prior to our IPO other than acquiring the entire issued and outstanding stock of IO Biotech ApS. The Company, IO Biotech ApS, and the holders of all of the issued and outstanding equity interests of IO Biotech ApS have entered into a Share Contribution and Exchange Agreement, dated as of October 29, 2021, pursuant to which the Corporate Reorganization was effected. Initial Public Offering (IPO) In November 2021, we completed our IPO, selling an aggregate of 8,222,500 shares of common stock at a price to the public of $ 14.00 per share, including 1,072,500 shares of common stock sold pursuant to the underwriters’ exercise of their option to purchase additional shares of common stock. We received net proceeds from the IPO, after deducting underwriting discounts and commissions and other offering costs, of $ 103.3 million. Immediately prior to the consummation of the IPO, all outstanding shares of our Class A ordinary shares and Class B and Class C convertible preference shares were converted into 20,592,413 shares of common stock. Upon the closing of the IPO on November 9, 2021, a total of 28,815,267 shares of common stock were issued and outstanding. Our common stock began trading on the Nasdaq Global Market on November 5, 2021 under the symbol “IOBT.” On November 9, 2021, we amended and restated the certificate of incorporation of IO Biotech, Inc. to authorize the issuance of 300,000,000 shares of common stock and 5,000,000 shares of preferred stock. The shares of preferred stock are currently undesignated. August 2023 Private Placement On August 9, 2023, the Company completed a private placement transaction (the Private Placement), pursuant to which we sold an aggregate of 37,065,647 shares of the Company’s common stock, par value $ 0.001 per share, and 37,065,647 warrants to purchase up to 37,065,647 shares of common stock (the Warrants) to certain institutional investors and existing shareholders (the Purchasers). Each Purchaser’s Warrant is exercisable for a number of shares of common stock equal to one hundred percent of the aggregate number of shares of common stock purchased by such Purchaser. The purchase price per share of common stock and Warrant was $ 2.025 (the Purchase Price). The Company received net proceeds from the Private Placement, after deducting $ 3.2 million in underwriting discounts and commissions and other offering costs, of $ 71.9 million. Refer to Note 2, “Summary of Significant Accounting Policies,” and Note 10, "Stockholders' Equity" in the accompanying notes to our consolidated financial statements for the years ended December 31, 2023 and 2022 for additional information on the Private Placement. At-The-Market Equity Program On February 15, 2023, we filed a new prospectus supplement with the U.S. Securities and Exchange Commission (the SEC) with respect to the offer and sale of shares of our common stock, with an aggregate offering price of up to $ 19,500,000 , establishing an at-the-market equity program. On February 15, 2023, we also entered into a common stock sales agreement, dated February 15, 2023 (the “Sales Agreement”) by and between the Company and Cowen and Company, LLC for shares with an aggregate offering price of up to $ 75,000,000 through which we may, from time to time, sell shares through Cowen and Company, LLC, acting as agent and/or principal. Any shares offered and sold through the at-the-market equity program will be issued pursuant to the Company’s Registration Statement on Form S-3 (File No. 333-269569), which was declared effective on February 10, 2023, the prospectus supplement related to the offering that forms a part of the registration statement, and any applicable prospectus supplements that may form a part of the registration statement in the future. The aggregate market value of shares eligible for sale under the prospectus supplement and under the Sales Agreement will be subject to the limitations of General Instruction I.B.6 of Form S-3, to the extent required under such instruction. We have no t issued any shares pursuant to our at-the-market equity program as of December 31, 2023. Risks and Uncertainties We are subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations and the need to obtain additional financing. Product candidates currently under development will require significant additional research and development efforts, including extensive pre-clinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance reporting capabilities. Our product candidates are in preclinical research and clinical development. There can be no assurance that our research and development will be successfully completed, that adequate protection for our intellectual property will be obtained, that any products developed will obtain necessary government regulatory approval or that any approved products will be commercially viable. Even if our product development efforts are successful, it is uncertain when, if ever, we will generate significant revenue from product sales. We operate in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. In addition, we are dependent upon the services of our employees and consultants. Liquidity Considerations and Going Concern Basis of Accounting Since inception, we have devoted substantially all of our efforts to business planning, conducting research and development, recruiting management and technical staff, and raising capital. We have financed our operations primarily through the issuance of convertible preference shares, convertible notes, our IPO and the Private Placement. Our continued discovery and development of product candidates will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if our product development efforts are successful, it is uncertain when, if ever, we will realize significant revenue from product sales. As of December 31, 2023, we had an accumulated deficit of $ 263.8 million. We have incurred losses and negative cash flows from operations since inception, including net losses of $ 86.1 million and $ 71.5 million for the years ended December 31, 2023 and 2022, respectively. We expect that our operating losses and negative cash flows will continue for the foreseeable future as we continue to develop our product candidates. We currently expect that our cash and cash equivalents of $ 143.2 million as of December 31, 2023 will be sufficient to fund our operating expenses and capital requirements for at least 12 months from the date the financial statements are issued. On this basis the financial statements are prepared on a going concern basis of accounting . However, additional funding will be necessary to fund future discovery research, pre-clinical and clinical activities. We will seek additional funding through public financings, debt financings, collaboration agreements, strategic alliances and licensing arrangements. Although we have been successful in raising capital in the past, there is no assurance that we will be successful in obtaining such additional financing on acceptable terms, or at all, and we may not be able to enter into collaborations or other arrangements. If we are unable to obtain funding, we could be forced to delay, reduce or eliminate our research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect our business prospects, even our ability to continue operations.

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 Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States (U.S. GAAP). Any reference in these notes to applicable guidance is meant to refer to U.S. GAAP, as found in the Accounting Standards Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB). Principles of Consolidation The Company’s consolidated financial statements include the accounts of its subsidiaries IO Biotech ApS, IO Bio US, Inc. and IO Biotech Limited. IO Bio US, Inc. is a wholly owned subsidiary of IO Biotech ApS. IO Biotech Limited is a wholly owned subsidiary of IO Biotech ApS. All intercompany transactions and balances have been eliminated. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect certain reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of expenses during the reporting periods. Significant items subject to such estimates and assumptions include contract research organization accruals, the fair value of stock-based compensation awards, the fair value of Warrants issued as part of the Private Placement and valuation of the Company’s deferred tax assets. We base our estimates on historical experience and various other assumptions that we believe to be reasonable under the circumstances. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates. Currency and Currency Translation The financial statements are presented in U.S. Dollars, our reporting currency. The functional currency of IO Biotech ApS and IO Biotech Limited is the Euro and the British Pound, respectively. The functional currency of IO Bio US, Inc. and IO Biotech, Inc. is the U.S. Dollar. Adjustments that arise from exchange rate changes on transactions denominated in a currency other than the functional currency are included in other income and expense in the consolidated statements of operations. Assets and liabilities recorded in our Euro and British Pound functional currencies are translated into the U.S. dollar reporting currency at the exchange rate on the balance sheet date. Our expenses in the Euro and the British Pound functional currencies are translated into the U.S. Dollar reporting currency at the average exchange rate prevailing each month. Resulting translation adjustments are recorded to other comprehensive income (loss) (OCI). Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. Cash equivalents, which consist of money market accounts, are stated at fair value. As of December 31, 2023 and 2022 we had money market funds of $ 131.6 million and $ 88.0 million , respectively, which are included in cash and cash equivalents and reported at fair value (Note 3). Concentrations of Credit Risk and Off-Balance Sheet Risk We maintain our cash in bank deposit and checking accounts that at times exceed insured limits. We have not experienced any losses in such accounts and believe we are not exposed to any significant credit risk, however, we are exposed to the potential loss of uninsured deposits should a financial institution we maintain our cash deposits with fail. Fair Value of Financial Instruments Fair value is defined as the price we would receive to sell an investment in a timely transaction or pay to transfer a liability in a timely transaction with an independent buyer in the principal market, or in the absence of a principal market, the most advantageous market for the investment or liability. A framework is used for measuring fair value utilizing a three-tier hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). The three levels of the fair value hierarchy are as follows: Level 1 —Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2 —Quoted prices in markets that are not considered to be active or financial instrument valuations for which all significant inputs are observable, either directly or indirectly; and Level 3 —Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable. Financial instruments are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement. The assessment of the significance of a particular input to the fair value measurement requires judgment and considers factors specific to the investment. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by us in determining fair value is greatest for instruments categorized in Level 3. We monitor the availability of inputs that are significant to the measurement of fair value to assess the appropriate categorization of financial instruments within the fair value hierarchy. Changes in economic conditions or model-based valuation techniques may require the transfer of financial instruments from one fair value level to another. In such instances, our policy is to recognize significant transfers between levels at the end of the reporting period. The significance of transfers between levels is evaluated based upon the nature of the financial instrument and size of the transfer relative to total net assets. As of December 31, 2023 and 2022, the Company only held Level 1 financial instruments, respectively. Property and Equipment, net Property and equipment consists of laboratory equipment, computer hardware and office furniture and are recorded at cost. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed as incurred. Property and equipment are depreciated on a straight-line basis over their estimated useful lives. The Company estimates useful life on an asset by asset basis, which generally consists of three years for computer hardware, five years for office furniture and five years for laboratory equipment. The Company reviews long-lived assets, such as property and equipment, for impairment when events or changes in circumstances indicate the carrying amount of the assets may not be recoverable. If circumstances require a long-lived asset to be tested for possible impairment, recoverability is measured by comparison of the carrying amount of the assets to estimated future undiscounted cash flows that the assets are expected to generate. If the carrying amount of an asset exceeds its estimated future cash flows, then impairment expense is recognized for the amount by which the carrying amount of the asset exceeds the fair value of the asset. For the years ended December 31, 2023 and 2022 , no impairment expenses were recognized. Research and Development Expenses Research and development costs are expensed as incurred. The Company’s research and development expenses consist primarily of costs incurred for the development of its product candidates and include expenses incurred under agreements with contract manufacturing organizations, or CMOs, contract research organizations, or CROs, investigative sites and consultants to conduct clinical trials and preclinical and non-clinical studies, costs to acquire, develop and manufacture supplies for clinical trials and other studies, salaries and related costs, including equity-based compensation, depreciation and other allocated facility-related and overhead expenses and licensing fees and milestone payments incurred under product license agreements where no alternative future use exists. We may obtain grants from public and private funds for our research and development projects. The grant income for a given period is recognized as a cost reimbursement and is typically based on the time and the costs that we have spent on the specific project during that period. During the years ended December 31, 2023 and 2022, we had active cost reimbursement grants with Innovation Fund Denmark. The grants provided partial reimbursement of employment-related costs related to two employees pursuant to Business Ph.D. and Business post-doctoral programs. For the years ended December 31, 2023 and 2022 , research and development expenses in the statements of operations include $ 0.02 million and $ 0.03 million, respectively, of grant income cost reimbursement. We have historically met the requirements to receive a tax credit in Denmark of up to 5.5 million Danish Kroner per year for tax losses resulting from research and development costs of up to 25.0 million Danish Kroner per year. The tax credit is reported as a reduction to research and development expense in the statements of operations. For the years ended December 31, 2023 and 2022 , research and development expenses include refundable tax credits of $ 0.8 million, respectively. Accrued Research and Development Costs Substantial portions of our pre-clinical and clinical trials are performed by third-party laboratories, medical centers, CMOs, CROs and other vendors. These vendors generally bill monthly for services performed, or bill based upon milestone achievement. For preclinical studies, we accrue expenses based upon estimated percentage of work completed and the contract milestones remaining. For clinical studies, expenses are accrued based upon the number of patients enrolled, the duration of the study and other investigative costs. We monitor patient enrollment, the progress of clinical studies and related activities to the extent possible through internal reviews of data reported to us by the CROs, correspondence with the CROs and clinical site visits. Our estimates depend on the timeliness and accuracy of the data provided by the CROs regarding the status of each program and total program spending. We periodically evaluate the estimates to determine if adjustments are necessary or appropriate based on information we receive. Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASC 842”) to enhance the transparency and comparability of financial reporting related to leasing arrangements. Under this lease standard, most leases are required to be recognized on the balance sheet as right-of-use (ROU) assets and lease liabilities. The right-of-use model requires a lessee to recognize a ROU asset and corresponding lease liability on the balance sheet for all leases with a term longer than 12 months. Leases are classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the income statement as well as the reduction of the right of use asset. In 2022, the Company adopted the standard effective January 1, 2022 and chose to use the effective date as date of initial application. The standard provides a number of optional practical expedients in transition. Upon adoption, the Company elected to apply the ‘package of practical expedients’ which allowed the Company to not reassess (1) whether existing or expired arrangements contain a lease; (2) the lease classification of existing or expired leases; or (3) whether previous initial direct costs would qualify for capitalization under the new lease standard. The Company also elected to apply (1) the practical expedient which allows us to not separate lease and non-lease components, for new leases entered into after adoption and (2) the short-term lease exemption for all leases with an original term of less than 12 months, for purposes of applying the recognition and measurements requirements in the new standard. At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on specific facts and circumstances, the existence of an identified asset(s), if any, and the Company’s control over the use of the identified asset(s), if applicable. Operating lease liabilities and their corresponding ROU assets are recorded based on the present value of future lease payments over the expected lease term. The interest rate implicit in lease contracts is typically not readily determinable. As such, the Company will utilize the incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. As of January 1, 2022, the ASC 842 effective date, the Company’s incremental borrowing rate was approximately 6.5 % based on the remaining lease term of the applicable leases. The Company has elected to combine lease and non-lease components as a single component. Operating leases are recognized on the balance sheet as ROU lease assets, lease liabilities current and lease liabilities non-current. Fixed rents are included in the calculation of the lease balances while variable costs paid for certain operating and pass-through costs are excluded. Lease expense is recognized over the expected term on a straight-line basis. Equity-Based Compensation We account for stock options granted in accordance with ASC 718, Compensation-Stock Compensation . In accordance with ASC 718, compensation expense is measured at the estimated fair value of the stock options at grant date and is included as compensation expense over the vesting period during which an employee provides service in exchange for the award on a straight-line basis. Vesting of the awards depend solely on service conditions required of the employee. All share-based awards granted are measured based on the fair value on the date of the grant and compensation expense is recognized with respect to those awards over the requisite service period, which is generally the vesting period of the respective award. The Company reverses any previously recognized compensation cost associated with forfeited awards in the period the forfeiture occurs. Equity-based compensation expense is classified in the Company’s consolidated statements of operations in the same manner in which the award recipients’ payroll costs are classified or in which the award recipients’ service payments are classified. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes model. The following summarizes the inputs used: Expected volatility : The Company estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies because we lack company-specific historical and implied volatility information due in part to the limited time in which we have operated as a publicly traded company. We expect to continue to do so until such time as we have adequate historical data regarding the volatility of our traded stock price. Expected term : The expected term of the Company’s stock options has been determined based on the expected time to liquidity. The Company uses the simplified method prescribed by the SEC’s Staff Accounting Bulletin No. 107, Share-Based Payment, to calculate the expected term of options granted because we lack company-specific historical and implied expected term information due in part to the limited time in which we have operated as a publicly traded company. Risk-free interest rate : The risk-free interest rate is based on the implied yield on a U.S. Treasury security at a constant maturity with a remaining term equal to the expected term of the option granted. Dividends : Expected dividend yield is zero because the Company does not pay cash dividends on common shares and does not expect to pay any cash dividends in the foreseeable future. Share Price : The Company's common stock trades on the Nasdaq Global Market under the symbol “IOBT" and is utilized to determine the fair value of the Company's share price. Income Taxes Deferred income tax assets and liabilities arise from temporary differences associated with differences between the financial statements and tax basis of assets and liabilities, as measured by the enacted tax rates, which are expected to be in effect when these differences reverse. Deferred tax assets and liabilities are classified as current or non-current, depending upon the classification of the asset or liabilities to which they relate. Deferred tax assets and liabilities not related to an asset or liability are classified as current or non-current depending on the periods in which the temporary differences are expected to reverse. Valuation allowances are established when necessary, to reduce deferred tax assets to the amount expected to be realized. We follow the provisions of ASC 740-10, Uncertainty in Income Taxes. We have not recognized a liability as a result of ASC 740-10. A reconciliation of the beginning and ending amount of unrecognized tax benefits has not been provided since there is no unrecognized benefit since the date of adoption and we have not recognized interest expense or penalties as a result of ASC 740-10. If there were an unrecognized tax benefit, we would recognize interest accrued related to unrecognized tax benefits as income tax expense within our consolidated statements of operations. We have identified Denmark and the U.S. as our major tax jurisdictions. Warrants Issued in Connection with Sale of Common Stock The Company accounts for warrants issued as a separable unit in connection with sale of common stock as either liability or equity in accordance with ASC 480-10, Accounting for Certain Financial Instruments with Characteristics of both Liabilities and Equity (“ASC 480-10”) or ASC 815-40, Accounting for Derivative Financial Instruments Indexed to, and Potentially Settled in, a Company’s Own Stock (“ASC 815-40”). Under ASC 480-10, warrants are considered liabilities if they are mandatorily redeemable and they require settlement in cash or other assets, or a variable number of shares. If warrants do not meet liability classification under ASC 480-10, the Company considers the requirements of ASC 815-40 to determine whether the warrants should be classified as liability or equity. If warrants do not require liability classification under ASC 815-40 or other applicable U.S. GAAP the warrants should be classified as equity. The proceeds received from the sale of equity classified warrants and sh ares of common stock in a bundled transaction are allocated based on the relative fair values of warrants and shares of common stock with no changes in fair value of warrants recognized after the issuance date. Based on our analysis of the foregoing, the Company's warrants issued in the Private Placement are classified as equity in our consolidated financial statements. Net Loss Per Share Basic net loss per share is computed by dividing the net loss attributable to common shareholders by the weighted-average number of shares of common stock outstanding for the period. Diluted net loss per share is computed by dividing the net loss attributable to common shareholders by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for the period, determined using the treasury-stock method and the as if-converted method, for convertible securities, if inclusion of these instruments is dilutive. Potentially dilutive securities include stock options and warrants to purchase common stock of the Company. In all periods presented, the Company’s outstanding stock options and warrants were excluded from the calculation of diluted net loss per share because their effects were anti-dilutive. For the years ended December 31, 2023 and 2022, both basic and diluted net loss per share are equivalent. Segments Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the chief operating decision maker (CODM), in deciding how to allocate resources to an individual segment and in assessing performance. Our CODM is our chief executive officer. The Company has concluded it has a single reporting segment for purposes of reporting financial condition and results of operations. Other Comprehensive Income (Loss) OCI is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Our OCI includes currency translation from the Euro and the British Pound, the functional currency of IO Biotech ApS and IO Biotech Limited, respectively, to the U.S. Dollar, our reporting currency. Emerging Growth Company Status We are an emerging growth company, as defined in the Jumpstart Our Business Startups Act (JOBS Act). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act, until such time as those standards apply to private companies. We have elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that we (1) are no longer an emerging growth company or (2) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates. Recently adopted accounting standards In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments. ASU 2016-13 requires measurement and recognition of expected credit losses for financial assets. In April 2019, the 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, or ASU 2016-13. The guidance is effective for fiscal years beginning after December 15, 2022. The Company has adopted the standard effective January 1, 2023 . The adoption of the standard has no t had a material impact on our financial statements or financial statement disclosures. Recently Issued Accounting Standards In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging Contracts in Entity s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity . ASU 2020-06 will simplify the accounting for convertible instruments by reducing the number of accounting models for convertible debt instruments and convertible preferred stock. Limiting the accounting models results in fewer embedded conversion features being separately recognized from the host contract as compared with current U.S. GAAP. Convertible instruments that continue to be subject to separation models are (1) those with embedded conversion features that are not clearly and closely related to the host contract, that meet the definition of a derivative, and that do not qualify for a scope exception from derivative accounting and (2) convertible debt instruments issued with substantial premiums for which the premiums are recorded as paid-in capital. ASU 2020-06 also amends the guidance for the derivatives scope exception for contracts in an entity’s own equity to reduce form-over-substance-based accounting conclusions. ASU 2020-06 will be effective for us in the interim periods in the fiscal year beginning after December 15, 2023. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. We are currently assessing the impact adoption of ASU 2020-06 will have on our financial statements and disclosures, but do not expect a material impact on the financial statements or disclosures. In October 2023, the FASB issued ASU 2023-06, Accounting Standards Update 2023-06—Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative. ASU 2023-06 will eliminate disclosure requirements that are redundant, duplicative, overlapping, outdated, or superseded as a result of subsequent changes to SEC disclosure requirements, U.S GAAP or technology. ASU 2023-06 is intended to better align U.S. GAAP requirements with those of the SEC and to facilitate the application of U.S. GAAP. The disclosure requirements would apply prospectively in the financial statements. ASU 2023-06 will be effective for us on the date on which the SEC’s removal of that related disclosure requirement from Regulation S-X or Regulation S-K becomes effective, if we are already subject to the SEC’s current disclosure requirements. For those current disclosure requirements we are not subject to, ASU 2023-06 will become effective two years after the date of such removal by the SEC. We are currently assessing the impact adoption of ASU 2023-06 will have on our financial statements and disclosures. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. ASU 2023-07 will improve reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. ASU 2023-07 will also enhance interim disclosure requirements, clarify circumstances in which an entity can disclose multiple segment measures of profit or loss, provide new segment disclosure requirements for entities with a single reportable segment and contain other disclosure requirements. The enhanced segment disclosure requirements apply retrospectively to all prior periods presented in the financial statements. ASU 2023-07 will be effective for us in the annual periods beginning after December 15, 2023. We are currently assessing the impact adoption of ASU 2023-07 will have on our financial statements and disclosures, but do not expect a material impact on the financial statements or disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. ASU 2023-09 will require disclosure of additional information in specified categories with respect to the reconciliation of the effective tax rate to the statutory rate (the rate reconciliation) for federal, state and foreign income taxes. ASU 2023-09 will also require information pertaining to taxes paid (net of refunds received) to be disaggregated for federal, state and foreign taxes and further disaggregated for specific jurisdictions to the extent the related amounts exceed a quantitative threshold. ASU 2023-09 will be effective for us in the annual periods beginning after December 15, 2025. Early adoption is permitted for annual financial statements that have not yet been issued or made available for issuance. We are currently assessing the impact adoption of ASU 2020-06 will have on our financial statements and disclosures. Other than the items noted above, there have been no new accounting pronouncements not yet effective or adopted in the current year that we believe have a significant impact, or potential significant impact, to our consolidated financial statements .

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. 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 are performed in a manner to maximize the use of observable inputs and minimize the use of unobservable inputs. The Company classified its money market funds within Level 1 as the fair value of the funds are based on their quoted market prices in an active market. The following tables present information about our financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values as of December 31, 2023 and 2022 (in thousands): December 31, 2023 Total Level 1 Level 2 Level 3 Assets Money market funds(1) $ 131,613 $ 131,613 $ — $ — Total assets measured at fair value $ 131,613 $ 131,613 $ — $ — December 31, 2022 Total Level 1 Level 2 Level 3 Assets Money market funds(1) $ 87,971 $ 87,971 $ — $ — Total assets measured at fair value $ 87,971 $ 87,971 $ — $ — (1) Money market funds with maturities of 90 days or less at the date of purchase are included within cash and cash equivalents in the accompanying consolidated balance sheets and are recognized at fair value. As of December 31, 2023 and 2022, the Company only held Level 1 financial instruments. There were no transfers among Level 1, Level 2 or Level 3 categories in the years ended December 31, 2 0 23 and 2 0 22 .

License and Collaboration Agree

License and Collaboration Agreements	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License and Collaboration Agreements	4. License and Collaboration Agreements Clinical Trial Collaboration and Supply Agreements with MSD International GmbH In February 2018, we entered into a clinical collaboration with MSD International GmbH (MSDIG) to evaluate IO102 in combination with KEYTRUDA® (pembrolizumab) in first-line treatment of patients with metastatic non-small cell lung cancer. Under the terms of the collaboration with MSDIG, we will conduct an international Phase 1/2 study to evaluate a combination therapy of IO102 and KEYTRUDA®. We will sponsor the clinical trials and MSDIG will provide KEYTRUDA® to be used in the clinical trials free of charge. We and MSDIG will be responsible for our own internal costs and expenses to support the study and we shall bear all other costs associated with conducting the study, including costs of providing IO102 for use in the study. The rights to the data from the clinical trials will be shared by us and MSDIG and we will maintain global commercial rights to IO102. In September 2021, we entered into a clinical collaboration with MSDIG and MSD International Business GmbH (MSDIB), another affiliate of Merck (collectively, “MSD”) to evaluate IO102-IO103 in combination with KEYTRUDA® versus KEYTRUDA® alone in treatment of patients with metastatic (advanced) melanoma. Under the terms of the collaboration with MSD, we are conducting an international Phase 3 study to evaluate a combination therapy of IO102-IO103 and KEYTRUDA®. We are the sponsor of the clinical trials and MSD will provide KEYTRUDA® to be used in the clinical trials free of charge. We and MSD are responsible for our own internal costs and expenses to support the study and we will bear all other costs associated with conducting the study, including costs of providing IO102-IO103 for use in the study. The rights to the data from the clinical trials will be shared by us and MSD and we will maintain global commercial rights to IO102-IO103. In December 2021, we entered into a clinical collaboration with MSD to evaluate IO102-IO103 in combination with KEYTRUDA® in previously untreated patients with three different tumor types— metastatic non-small cell lung cancer (NSCLC), squamous cell carcinoma of the head and neck (SCCHN), and urothelial bladder cancer (UBC). Under the terms of the collaboration with MSD, we are conducting an international Phase 2 study to evaluate a combination therapy of IO102-IO103 and KEYTRUDA®. We are the sponsor of the clinical trials and MSD will provide KEYTRUDA® to be used in the clinical trials free of charge. We and MSD are responsible for our own internal costs and expenses to support the study and we will bear all other costs associated with conducting the study, including costs of providing IO102-IO103 for use in the study. The rights to the data from the clinical trials will be shared by us and MSD and we will maintain global commercial rights to IO102-IO103. In November 2022, we entered into a clinical collaboration with MSD to evaluate IO102-IO103 in combination with KEYTRUDA® as a neo-adjuvant/adjuvant therapy for patients with metastatic melanoma and SCCHN. Under the terms of the collaboration with MSD, we will conduct an international Phase 2 study to evaluate a combination therapy of IO102-IO103 and KEYTRUDA®. We will sponsor the clinical trials and MSD will provide KEYTRUDA® to be used in the clinical trials free of charge. We and MSD will be responsible for our own internal costs and expenses to support the study and we shall bear all other costs associated with conducting the study, including costs of providing IO102-IO103 for use in the study. The rights to the data from the clinical trials will be shared by us and MSD and we will maintain global commercial rights to IO102-IO103.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2023
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	5. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): December 31, 2023 2022 Insurance $ 1,352 $ 1,716 Research and development tax credit receivable 814 792 Prepaid income taxes 829 124 Value-added tax refund receivable 313 741 Prepaid contract research and development costs — 1,695 Other 754 561 Total prepaid expenses and other current assets $ 4,062 $ 5,629

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	6. Property and Equipment, Net Property and equipment, net consist of the following (in thousands): December 31, 2023 2022 Laboratory equipment $ 836 $ 544 Office furniture 238 233 Computer hardware 103 79 Less: accumulated depreciation ( 330 ) ( 115 ) Total property and equipment, net $ 847 $ 741 For the years ended December 31, 2023 and 2022, the Company recognized $ 0.2 million and $ 0.1 million , respectively, of depreciation expense in the consolidated statements of operations.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	7. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consist of the following (in thousands): December 31, 2023 2022 Accrued contract research and development costs $ 6,153 $ 1,936 Employee compensation costs 4,225 1,863 Professional fees 243 407 Other liabilities 563 1,951 Total accrued expenses and other current liabilities $ 11,184 $ 6,157

Leases

Leases	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Leases	8. Leases On January 1, 2022, the Company adopted ASC 842 using the modified retrospective transition approach allowed under ASU 2018-11 which releases companies from presenting comparative periods and related disclosures under ASC 842 and requires a cumulative-effect adjustment to the opening balance of accumulated deficit in the period of adoption (Note 2). The Company had an immaterial cumulative-effect adjustment to the opening balance of accumulated deficit as of January 1, 2022. The Company is party to five operating leases for laboratory and office space. The Company’s finance leases are immaterial both individually and in the aggregate. The Company has elected to apply the short-term lease exception to all leases of one year or less. Further, the Company has applied the guidance in ASC 842 to our corporate office and laboratory leases and has determined that these should be classified as operating leases. Consequently, as a result of the adoption of ASC 842 on January 1, 2022, we recognized an ROU lease asset of approximately $ 2.3 million with a corresponding lease liability of approximately $ 2.4 million based on the present value of the minimum rental payments of such leases. In accordance with ASC 842, the beginning balance of the ROU lease asset was reduced by the existing deferred rent liability at inception of approximately $ 0.1 million. In the consolidated balance sheet as of December 31, 2023, the Company has an ROU asset balance of $ 2.3 million and a current and non-current lease liability of $ 0.7 million and $ 1.8 million , respectively, relating to the ROU lease asset. The balance of both the ROU lease asset and the lease liabilities primarily consists of future payments under the Company’s office leased in New York, New York, Rockville, Maryland and Copenhagen, Denmark. The Company is party to an operating lease in Copenhagen, Denmark for office space that commenced in March 2021 with an initial term that expired in January 2025. Base rent for this initial lease was $ 0.1 million annually. The Company amended its operating lease in Copenhagen, Denmark on September 1, 2022 with a new term set to expire in December 2027. The base rent for the amended lease is $ 0.2 million annually. The Company is also party to an operating lease in Copenhagen, Denmark for laboratory space that commenced in January 2023 with the term set to expire in December 2027. The base rent for the lease is $ 0.04 million annually. The Company is party to an operating lease in New York, New York for office space that commenced in October 2021 with the initial term set to expire in January 2027. Base rent for this lease is $ 0.2 million annually. The Company is party to an operating lease in Rockville, Maryland for office and laboratory space that commenced in December 2021 with the initial term set to expire in May 2027. Base rent for this lease is $ 0.3 million annually. The Company is party to an immaterial operating lease in Newport, United Kingdom that commenced in June 2023. Rent expense for the years ended December 31, 2023 and 2022 was $ 0.7 million and $ 0.8 million , respectively. Quantitative information regarding the Company’s leases for the year ended December 31, 2023 is as follows (in thousands): Year Ended December 31, Lease Cost 2023 2022 Operating lease cost $ 730 $ 755 Operating cash flows paid for amounts included in the measurement of lease liabilities $ 723 $ 419 Operating lease liabilities arising from obtaining right‑of‑use assets $ 235 $ 2,600 Remaining lease term (years) 3.5 4.5 Weighted average discount rate 6.3 % 6.5 % Future lease payments (undiscounted) under noncancelable leases are as follows as of December 31, 2023 (in thousands): Future Lease Payments Amount 2024 $ 793 2025 792 2026 798 2027 403 2028 — Thereafter — Total $ 2,786 The Company’s leases do not provide an implicit rate, therefore the Company used its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The Company used the incremental borrowing rate on January 1, 2022 for operating leases that commenced prior to that date, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies From time to time, we may be party to litigation arising in the ordinary course of its business. We were not subject to any material legal proceedings during the years ended December 31, 2023 and 2022, and, to our knowledge, no material legal proceedings are currently pending or threatened. Contractual Obligations and Commitments We enter into contracts in the ordinary course of business with third-party service providers for clinical trials, preclinical research studies and testing, manufacturing and other services and products for operating purposes. These contracts generally provide for termination upon notice of 30 to 90 days, and therefore, we believe that our noncancelable obligations under these agreements are not material and we cannot reasonably estimate whether they will occur. However, in the event of a termination of any contracts with CROs or other institutions and with respect to active patients enrolled in our clinical trials, we may be financially obligated for a period beyond the contractual termination notice periods. We may also enter into additional research, manufacturing, supplier, lease and other agreements in the future, which may require up-front payments and even long-term commitments of cash. Indemnification Agreements We enter into certain types of contracts that contingently requires us to indemnify various parties against claims from third parties. These contracts primarily relate to procurement, service, consultancy or license agreements under which we may be required to indemnify vendors, service providers or licensees for certain claims, including claims that may be brought against them arising from our acts or omissions with respect to our products, technology, intellectual property or services. The Company, as permitted under Delaware law and in accordance with its amended and restated certificate of incorporation and amended and restated bylaws and pursuant to indemnification agreements with certain of its officers and directors, indemnifies its officers and directors for certain events or occurrences, subject to certain limits, which the officer or director is or was serving at the Company’s request in such capacity. At the 2023 Annual Meeting of Stockholders, the Company’s stockholders approved an amendment to, and the Company subsequently amended, its amended and restated certificate of incorporation to extend the indemnification of officers pursuant to recent amendments to the General Corporation Law of the State of Delaware. From time to time, we may receive indemnification claims under existing contracts in the normal course of business. In the event that one or more of these matters were to result in a claim against us, an adverse outcome, including a judgment or settlement, may cause a material adverse effect on our future business, operating results or financial condition. It is not possible to estimate the maximum amount potentially payable under these contracts since we have no history of prior indemnification claims and the unique facts and circumstances involved in each particular claim will be determinative.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2023
Class of Stock Disclosures [Abstract]
Stockholders' Equity	10. Stockholders' Equity Common and Preferred Stock Upon the closing of our IPO in November 2021, we filed an amended and restated certificate of incorporation, which authorized us to issue 300,000,000 shares of common stock and 5,000,000 shares of preferred stock. The shares of preferred stock are currently undesignated. Common stockholders are entitled to one vote for each share of common stock held at all meetings of stockholders and written actions in lieu of meetings. Common stockholders are entitled to receive dividends, if and when declared by the Company's board of directors (Board). No dividends have been declared or paid by us through December 31, 2023. The Private Placement On August 7, 2023, the Company entered into the Purchase Agreement, pursuant to which the Company agreed to sell and issue (i) 37,065,647 shares of the Company’s common stock, and (ii) 37,065,647 Warrants in the Private Placement. Each Purchaser’s Warrant is exercisable for a number of shares of common stock equal to one hundred percent of the aggregate number of shares of common stock purchased by such Purchaser. The Purchase Price for each common stock and Warrant was $ 2.025 per share. The Warrants are exercisable at an exercise price of $ 2.47 per share, subject to adjustment as set forth therein. The Warrants are exercisable until the earlier of (i) February 9, 2027, and (ii) one day prior to the closing of an acquisition, as defined in the Warrants. The Warrants may be exercised on a cashless basis if there is no effective registration statement registering the shares underlying the Warrants. The Private Placement closed on August 9, 2023. The Company received $ 75.1 million in gross proceeds from the Private Placement, before deducting offering expenses of $ 3.2 million. Of the total proceeds, legal entities of certain related parties contributed $33 .4 million, and members of management contributed $ 0.2 million. The Company intends to use the net proceeds of $ 71.9 from the Private Placement for general corporate purposes. The Warrants were classified as a component of permanent stockholders’ equity within additional paid-in-capital and were recorded at the issuance date using a relative fair value allocation method. The Warrants are equity classified because they are freestanding financial instruments that are legally detachable and separately exercisable from the equity instruments, are immediately exercisable, do not embody an obligation for the Company to repurchase its shares, permit the holders to receive a fixed number of common shares upon exercise, are indexed to the Company’s common stock and meet the equity classification criteria. In addition, such Warrants do not provide any guarantee of value or return. The Company valued the Warrants at issuance using the Black-Scholes valuation model and allocated proceeds from the sale proportionately to the common stock and Warrants, of which $ 29.6 million was allocated to the Warrants and recorded as a component of additional paid-in-capital. As of December 31, 2023 , the Company had 37,065,647 warrants issued and outstanding at an exercise price of $ 2.47 per share to purchase shares of the Company's common stock. In connection with the execution of the Purchase Agreement, the Company also entered into a registration rights agreement (the Registration Rights Agreement) with the Purchasers. Under the terms of the Registration Rights Agreement, the Company has filed the Registration Statement with the SEC to register for resale the common stock issued under the Purchase Agreement and the shares of common stock issuable upon conversion of the Warrants issued pursuant to the Purchase Agreement (the Registrable Securities), which Registration Statement was declared effective on September 8, 2023. The Company may be required to pay certain liquidated damages under the terms of the Registration Rights Agreement in the event sales cannot be made pursuant to the Registration Statement. As of December 31, 2023 and 2022, the Company had 65,880,914 and 28,815,267 common shares outstanding, respectively.

Equity-Based Compensation

Equity-Based Compensation	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Equity-Based Compensation	11. Equity-Based Compensation 2021 Equity Incentive Plan In November 2021, our Board adopted, and our stockholders approved, the 2021 Equity Incentive Plan (2021 Equity Plan), which became effective on November 4, 2021. The 2021 Equity Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, awards of restricted stock, restricted stock units and other stock-based awards. The number of shares of our common stock reserved for issuance under the 2021 Equity Plan is equal to 2,496,934 , subject to an annual increase, to be added on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2022 and continuing until, and including, the fiscal year ending December 31, 2031, equal to the lesser of (i) 4 % of the number of shares of common stock outstanding on the first day of such fiscal year or (ii) such other amount determined by our Board. As of December 31, 2023, we had 593,468 options available for future grant under the 2021 Equity Plan. 2021 Employee Stock Purchase Plan In November 2021, our Board adopted and our stockholders approved the 2021 IO Biotech, Inc. Employee Stock Purchase Plan (2021 ESPP), which became effective on November 4, 2021. The number of shares of our common stock reserved for issuance under the 2021 ESPP is equal to 257,272 , subject to an annual increase, to be added on the first day of each fiscal year, beginning January 1, 2023, equal to the lesser of (1) 1 % of the number of shares of common stock outstanding on the first day of such fiscal year; (2) 257,272 shares of our common stock; or (3) such other amount as determined by our Board. As of December 31, 2023, the Board had not yet approved any offering under the 2021 ESPP. 2023 Inducement Award Plan In September 2023, our Board adopted the 2023 Inducement Award Plan (2023 Inducement Plan), which became effective on September 28, 2023. The 2023 Inducement Plan provides for the grant of non-statutory stock options, stock appreciation rights, awards of restricted stock, restricted stock units and other stock-based awards to eligible employees who satisfy the standards for inducement grants under Nasdaq Global Market rules. The number of shares of our common stock reserved for issuance under the 2023 Inducement Plan is equal to 1,976,427 . As of December 31, 2023 , there were 1,976,427 shares available for future grant under the 2023 Inducement Plan. The following table summarizes our stock options activity for the years ended December 31, 2023 and 2022: Number of Weighted- Weighted- Aggregate Outstanding December 31, 2021 3,071,613 $ 13.12 8.5 $ — Granted 1,211,155 $ 5.34 — $ — Cancelled or forfeited ( 362,596 ) $ 12.51 — $ — Outstanding December 31, 2022 3,920,172 $ 10.77 8.1 $ — Granted 2,519,994 $ 1.99 — $ — Cancelled or forfeited ( 588,243 ) $ 8.74 — $ — Outstanding, December 31, 2023 5,851,923 $ 7.20 8.4 $ 102 Exercisable at December 31, 2023 1,902,547 $ 11.26 7.7 $ 2 Equity-Based Compensation All share-based awards granted are measured based on the fair value on the date of the grant and compensation expense is recognized with respect to those awards over the requisite service period, which is generally the vesting period of the respective award. Forfeitures related to equity-based compensation awards are recognized as they occur, and we reverse any previously recognized compensation cost associated with forfeited awards in the period the forfeiture occurs. For the years ended December 31, 2023 and 2022, we recorded equity-based compensation expense of $ 8.1 million and $ 7.0 million , respectively, related to the issuance of stock options and warrants. As of December 31, 2023, there was $ 11.2 million of unrecognized compensation cost related to unvested stock-based compensation arrangements that is expected to be recognized over a weighted average period of 2.5 years. The fair values of the options granted were estimated based on the Black-Scholes model, using the following assumptions: Year Ended December 31, 2023 2022 Expected volatility 86.4 % - 102.2 % 74.0 % - 77.3 % Risk-free interest rate 3.5 % - 4.5 % 1.62 % - 4.2 % Expected term (in years) 5.5 - 6.1 5.5 - 6.0 Expected dividend yield 0 % 0 % Equity-based compensation expense recorded as research and development and general and administrative expenses is as follows (in thousands): December 31, 2023 2022 Research and development $ 4,204 $ 2,859 General and administrative 3,855 4,181 Total equity-based compensation $ 8,059 $ 7,040 We did no t recognize any tax benefits for stock-based compensation during the years ended December 31, 2023 and 2022 .

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes We are subject to U.S. federal, state and foreign corporate income taxes. Our loss before provision for income taxes for the years ended December 31, 2023 and 2022 consisted of the following (in thousands): Year Ended December 31, 2023 2022 Domestic $ 2,365 $ ( 1,885 ) Foreign ( 87,596 ) ( 68,300 ) Total $ ( 85,231 ) $ ( 70,185 ) Our provision for income taxes consists of the following (in thousands): Year Ended December 31, 2023 2022 Current: Federal $ 439 $ 1,059 State 374 86 Foreign 39 52 852 1,197 Deferred: Federal — 76 State — — Foreign — — — 76 Total provision for income taxes $ 852 $ 1,273 Reconciliation of Effective Tax Rate Our effective tax rate for the years ended December 31, 2023 and 2022 is different from the statutory rate in the U.S. primarily due to the valuation allowance against deferred tax assets as a result of insufficient sources of income. The reconciliation of the statutory income tax rate to our effective income tax rate is as follows: Year Ended December 31, 2023 2022 Income tax benefit at the statutory rate 21.0 % 21.0 % Permanent differences 1.0 0.7 Difference in tax rate 1.0 1.0 R&D Deduction 1.1 4.0 Change in valuation allowance ( 24.7 ) ( 27.4 ) Prior period adjustments ( 0.2 ) ( 1.0 ) Other ( 0.2 ) ( 0.1 ) Total ( 1.0 )% ( 1.8 )% Deferred Taxes Deferred tax assets and liabilities represent future tax consequences of temporary differences between the financial statement carrying amounts and the tax basis of assets and liabilities and for loss carryforwards using enacted tax rates expected to be in effect in the years in which the differences reverse. A valuation allowance is recorded when it is more likely than not that some or all of the deferred tax assets will not be realized. The principal components of the Company’s deferred tax assets consisted of the following (in thousands): December 31, 2023 2022 Deferred tax assets: Net operating loss carryforwards $ 50,343 $ 31,338 Equity-based compensation expense 3,602 1,828 Accrued compensation 33 21 ROU Lease Liability 526 618 Capitalized R&D 3,348 1,231 Other 529 529 Total deferred tax assets $ 58,381 $ 35,565 Valuation allowance ( 57,902 ) ( 34,984 ) Net deferred tax assets $ 479 $ 581 ROU Lease Asset 441 567 Fixed Assets 26 13 Other Liabilities 12 1 Total deferred tax liabilities 479 581 Net deferred tax asset (liability) $ — $ — In 2017, the U.S. enacted the Tax Cuts and Jobs Act (the 2017 Tax Act), which contained a provision that requires capitalization and amortization of research and development expenses for tax purposes starting in 2022. Previously, these expenses could be deducted in the year incurred. The implementation of this provision increased our deferred tax asset and valuation allowance by approximately $ 2.1 million and $ 1.2 million for the years ended December 31, 2023 and 2022 . When realization of a deferred tax asset is more likely than not to occur, the benefit related to the deductible temporary differences attributable to operations is recognized as a reduction of income tax expense. Valuation allowances are provided against deferred tax assets when, based on all available evidence, it is considered more likely than not that some portion or all of the recorded deferred tax assets will not be realized in future periods. We cannot be certain that future income in Denmark will be sufficient to realize the Company’s deferred tax assets. Accordingly, a full valuation allowance has been provided against our net deferred tax assets in Denmark. We have also provided a full valuation allowance against our net deferred tax assets in the U.S. for IO Bio US, Inc. The Company's valuation allowance increased by $ 22.9 million and $ 19.9 million for the years ended December 31, 2023 and 2022, respectively. The increase for the years ended December 31, 2023 and 2022 is primarily the result of an increase in net operating loss carryforwards (NOL carryforwards) in Denmark. Available Carryforward Tax Losses As of December 31, 2023, we had NOL carryforwards of approximately $ 228.5 million that can be carried forward indefinitely according to Danish Tax Authority regulations. Uncertain Tax Positions We determine our uncertain tax positions based on whether and how much of a tax benefit taken by us in our tax filings is more likely than not to be sustained upon examination by the relevant income tax authorities. We determine 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%. We have reviewed the tax positions taken, or to be taken, in our tax returns for all tax years currently open to examination by the Danish Tax Authority. As of December 31, 2023 and 2022 , we have no t recorded an uncertain tax position liability. Tax filings in Denmark remain subject to examination by the Danish Tax Authority. As of December 31, 2023 , tax years 2020 and forward were generally open to examination by the Danish Tax Authority. Tax Credits As of September 30, 2023, we have elected to claim a research and development tax credit on the federal income tax return filed for the year ended December 31, 2022. We plan to continue to make this election on the federal income tax return filed for the year ended December 31, 2023 based on law currently enacted, and will continue to monitor impacts of proposed or enacted law changes on the cost to benefit of making this election. The Company included $ 1.0 million in research and development tax credits in the U.S. provision for income taxes for the year ended December 31, 2023. Other Tax Matters The Company recognizes accrued interest related to unrecognized tax benefits and penalties as income tax expense in the statements of operations. The Company does not have any material unrecognized tax benefits which would affect the effective tax rate, if recognized. The Company does not have any unrecognized tax benefits which would reverse within the next twelve months. The Company is eligible for the Danish enhanced research and development tax allowance, providing for an increase in the deductible value of the amount of certain R&D expenditur es. For 2019, the deduction is set at 101.5 %. Furthermore, the deduction for R&D expenditures is set at 130 % for 2020 through 2022, 108 % for 2023 through 2025, and 110 % for 2026. The tax allowance is reported as a reduction to research and development expense in the statements of operations. For the years ended December 31, 2023 and 2022, we applied for refundable tax credit of 25.0 million DKK for the years ended December 31, 2023 and 2022 and a receivable was recorded for $ 0.8 million in each year, respectively.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Net Loss Per Share	13. Net Loss Per Share Basic and diluted net loss per common share is calculated as follows (in thousands except share and per share amounts): Year Ended December 31, 2023 2022 Net loss $ ( 86,083 ) $ ( 71,458 ) Net loss attributable to common shareholders $ ( 86,083 ) $ ( 71,458 ) Net loss per common share, basic and diluted $ ( 1.98 ) $ ( 2.48 ) Weighted-average number of shares used in computing net loss per common share, basic and diluted 43,539,976 28,815,267 The following outstanding potentially dilutive securities have been excluded from the calculation of diluted net loss per common share, as their effect is anti-dilutive: December 31, 2023 2022 Stock options to purchase common stock 5,851,923 3,920,172 Warrants issued in Private Placement 37,065,647 —

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events We have evaluated subsequent events through the date on which the consolidated financial statements were issued. The Company has concluded that no subsequent events have occurred that require disclosure to the consolidated financial statements.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States (U.S. GAAP). Any reference in these notes to applicable guidance is meant to refer to U.S. GAAP, as found in the Accounting Standards Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB).
Principles of Consolidation	Principles of Consolidation The Company’s consolidated financial statements include the accounts of its subsidiaries IO Biotech ApS, IO Bio US, Inc. and IO Biotech Limited. IO Bio US, Inc. is a wholly owned subsidiary of IO Biotech ApS. IO Biotech Limited is a wholly owned subsidiary of IO Biotech ApS. All intercompany transactions and balances have been eliminated.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect certain reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of expenses during the reporting periods. Significant items subject to such estimates and assumptions include contract research organization accruals, the fair value of stock-based compensation awards, the fair value of Warrants issued as part of the Private Placement and valuation of the Company’s deferred tax assets. We base our estimates on historical experience and various other assumptions that we believe to be reasonable under the circumstances. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.
Currency and Currency Translation	Currency and Currency Translation The financial statements are presented in U.S. Dollars, our reporting currency. The functional currency of IO Biotech ApS and IO Biotech Limited is the Euro and the British Pound, respectively. The functional currency of IO Bio US, Inc. and IO Biotech, Inc. is the U.S. Dollar. Adjustments that arise from exchange rate changes on transactions denominated in a currency other than the functional currency are included in other income and expense in the consolidated statements of operations. Assets and liabilities recorded in our Euro and British Pound functional currencies are translated into the U.S. dollar reporting currency at the exchange rate on the balance sheet date. Our expenses in the Euro and the British Pound functional currencies are translated into the U.S. Dollar reporting currency at the average exchange rate prevailing each month. Resulting translation adjustments are recorded to other comprehensive income (loss) (OCI).
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity of three months or less at the date of purchase to be cash equivalents. Cash equivalents, which consist of money market accounts, are stated at fair value. As of December 31, 2023 and 2022 we had money market funds of $ 131.6 million and $ 88.0 million , respectively, which are included in cash and cash equivalents and reported at fair value (Note 3).
Concentrations of Credit Risk and Off-Balance Sheet Risk	Concentrations of Credit Risk and Off-Balance Sheet Risk We maintain our cash in bank deposit and checking accounts that at times exceed insured limits. We have not experienced any losses in such accounts and believe we are not exposed to any significant credit risk, however, we are exposed to the potential loss of uninsured deposits should a financial institution we maintain our cash deposits with fail.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair value is defined as the price we would receive to sell an investment in a timely transaction or pay to transfer a liability in a timely transaction with an independent buyer in the principal market, or in the absence of a principal market, the most advantageous market for the investment or liability. A framework is used for measuring fair value utilizing a three-tier hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1) and the lowest priority to unobservable inputs (Level 3). The three levels of the fair value hierarchy are as follows: Level 1 —Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2 —Quoted prices in markets that are not considered to be active or financial instrument valuations for which all significant inputs are observable, either directly or indirectly; and Level 3 —Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable. Financial instruments are categorized in their entirety based on the lowest level of input that is significant to the fair value measurement. The assessment of the significance of a particular input to the fair value measurement requires judgment and considers factors specific to the investment. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by us in determining fair value is greatest for instruments categorized in Level 3. We monitor the availability of inputs that are significant to the measurement of fair value to assess the appropriate categorization of financial instruments within the fair value hierarchy. Changes in economic conditions or model-based valuation techniques may require the transfer of financial instruments from one fair value level to another. In such instances, our policy is to recognize significant transfers between levels at the end of the reporting period. The significance of transfers between levels is evaluated based upon the nature of the financial instrument and size of the transfer relative to total net assets.
Property and Equipment, net	Property and Equipment, net Property and equipment consists of laboratory equipment, computer hardware and office furniture and are recorded at cost. Maintenance and repairs that do not improve or extend the lives of the respective assets are expensed as incurred. Property and equipment are depreciated on a straight-line basis over their estimated useful lives. The Company estimates useful life on an asset by asset basis, which generally consists of three years for computer hardware, five years for office furniture and five years for laboratory equipment. The Company reviews long-lived assets, such as property and equipment, for impairment when events or changes in circumstances indicate the carrying amount of the assets may not be recoverable. If circumstances require a long-lived asset to be tested for possible impairment, recoverability is measured by comparison of the carrying amount of the assets to estimated future undiscounted cash flows that the assets are expected to generate. If the carrying amount of an asset exceeds its estimated future cash flows, then impairment expense is recognized for the amount by which the carrying amount of the asset exceeds the fair value of the asset. For the years ended December 31, 2023 and 2022 , no impairment expenses were recognized.
Research and Development Expenses	Research and Development Expenses Research and development costs are expensed as incurred. The Company’s research and development expenses consist primarily of costs incurred for the development of its product candidates and include expenses incurred under agreements with contract manufacturing organizations, or CMOs, contract research organizations, or CROs, investigative sites and consultants to conduct clinical trials and preclinical and non-clinical studies, costs to acquire, develop and manufacture supplies for clinical trials and other studies, salaries and related costs, including equity-based compensation, depreciation and other allocated facility-related and overhead expenses and licensing fees and milestone payments incurred under product license agreements where no alternative future use exists. We may obtain grants from public and private funds for our research and development projects. The grant income for a given period is recognized as a cost reimbursement and is typically based on the time and the costs that we have spent on the specific project during that period. During the years ended December 31, 2023 and 2022, we had active cost reimbursement grants with Innovation Fund Denmark. The grants provided partial reimbursement of employment-related costs related to two employees pursuant to Business Ph.D. and Business post-doctoral programs. For the years ended December 31, 2023 and 2022 , research and development expenses in the statements of operations include $ 0.02 million and $ 0.03 million, respectively, of grant income cost reimbursement. We have historically met the requirements to receive a tax credit in Denmark of up to 5.5 million Danish Kroner per year for tax losses resulting from research and development costs of up to 25.0 million Danish Kroner per year. The tax credit is reported as a reduction to research and development expense in the statements of operations. For the years ended December 31, 2023 and 2022 , research and development expenses include refundable tax credits of $ 0.8 million, respectively.
Accrued Research and Development Costs	Accrued Research and Development Costs Substantial portions of our pre-clinical and clinical trials are performed by third-party laboratories, medical centers, CMOs, CROs and other vendors. These vendors generally bill monthly for services performed, or bill based upon milestone achievement. For preclinical studies, we accrue expenses based upon estimated percentage of work completed and the contract milestones remaining. For clinical studies, expenses are accrued based upon the number of patients enrolled, the duration of the study and other investigative costs. We monitor patient enrollment, the progress of clinical studies and related activities to the extent possible through internal reviews of data reported to us by the CROs, correspondence with the CROs and clinical site visits. Our estimates depend on the timeliness and accuracy of the data provided by the CROs regarding the status of each program and total program spending. We periodically evaluate the estimates to determine if adjustments are necessary or appropriate based on information we receive.
Leases	Leases In February 2016, the FASB issued ASU No. 2016-02, Leases (“ASC 842”) to enhance the transparency and comparability of financial reporting related to leasing arrangements. Under this lease standard, most leases are required to be recognized on the balance sheet as right-of-use (ROU) assets and lease liabilities. The right-of-use model requires a lessee to recognize a ROU asset and corresponding lease liability on the balance sheet for all leases with a term longer than 12 months. Leases are classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the income statement as well as the reduction of the right of use asset. In 2022, the Company adopted the standard effective January 1, 2022 and chose to use the effective date as date of initial application. The standard provides a number of optional practical expedients in transition. Upon adoption, the Company elected to apply the ‘package of practical expedients’ which allowed the Company to not reassess (1) whether existing or expired arrangements contain a lease; (2) the lease classification of existing or expired leases; or (3) whether previous initial direct costs would qualify for capitalization under the new lease standard. The Company also elected to apply (1) the practical expedient which allows us to not separate lease and non-lease components, for new leases entered into after adoption and (2) the short-term lease exemption for all leases with an original term of less than 12 months, for purposes of applying the recognition and measurements requirements in the new standard. At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on specific facts and circumstances, the existence of an identified asset(s), if any, and the Company’s control over the use of the identified asset(s), if applicable. Operating lease liabilities and their corresponding ROU assets are recorded based on the present value of future lease payments over the expected lease term. The interest rate implicit in lease contracts is typically not readily determinable. As such, the Company will utilize the incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment. As of January 1, 2022, the ASC 842 effective date, the Company’s incremental borrowing rate was approximately 6.5 % based on the remaining lease term of the applicable leases. The Company has elected to combine lease and non-lease components as a single component. Operating leases are recognized on the balance sheet as ROU lease assets, lease liabilities current and lease liabilities non-current. Fixed rents are included in the calculation of the lease balances while variable costs paid for certain operating and pass-through costs are excluded. Lease expense is recognized over the expected term on a straight-line basis.
Equity-Based Compensation	Equity-Based Compensation We account for stock options granted in accordance with ASC 718, Compensation-Stock Compensation . In accordance with ASC 718, compensation expense is measured at the estimated fair value of the stock options at grant date and is included as compensation expense over the vesting period during which an employee provides service in exchange for the award on a straight-line basis. Vesting of the awards depend solely on service conditions required of the employee. All share-based awards granted are measured based on the fair value on the date of the grant and compensation expense is recognized with respect to those awards over the requisite service period, which is generally the vesting period of the respective award. The Company reverses any previously recognized compensation cost associated with forfeited awards in the period the forfeiture occurs. Equity-based compensation expense is classified in the Company’s consolidated statements of operations in the same manner in which the award recipients’ payroll costs are classified or in which the award recipients’ service payments are classified. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes model. The following summarizes the inputs used: Expected volatility : The Company estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies because we lack company-specific historical and implied volatility information due in part to the limited time in which we have operated as a publicly traded company. We expect to continue to do so until such time as we have adequate historical data regarding the volatility of our traded stock price. Expected term : The expected term of the Company’s stock options has been determined based on the expected time to liquidity. The Company uses the simplified method prescribed by the SEC’s Staff Accounting Bulletin No. 107, Share-Based Payment, to calculate the expected term of options granted because we lack company-specific historical and implied expected term information due in part to the limited time in which we have operated as a publicly traded company. Risk-free interest rate : The risk-free interest rate is based on the implied yield on a U.S. Treasury security at a constant maturity with a remaining term equal to the expected term of the option granted. Dividends : Expected dividend yield is zero because the Company does not pay cash dividends on common shares and does not expect to pay any cash dividends in the foreseeable future. Share Price : The Company's common stock trades on the Nasdaq Global Market under the symbol “IOBT" and is utilized to determine the fair value of the Company's share price.
Income Taxes	Income Taxes Deferred income tax assets and liabilities arise from temporary differences associated with differences between the financial statements and tax basis of assets and liabilities, as measured by the enacted tax rates, which are expected to be in effect when these differences reverse. Deferred tax assets and liabilities are classified as current or non-current, depending upon the classification of the asset or liabilities to which they relate. Deferred tax assets and liabilities not related to an asset or liability are classified as current or non-current depending on the periods in which the temporary differences are expected to reverse. Valuation allowances are established when necessary, to reduce deferred tax assets to the amount expected to be realized. We follow the provisions of ASC 740-10, Uncertainty in Income Taxes. We have not recognized a liability as a result of ASC 740-10. A reconciliation of the beginning and ending amount of unrecognized tax benefits has not been provided since there is no unrecognized benefit since the date of adoption and we have not recognized interest expense or penalties as a result of ASC 740-10. If there were an unrecognized tax benefit, we would recognize interest accrued related to unrecognized tax benefits as income tax expense within our consolidated statements of operations. We have identified Denmark and the U.S. as our major tax jurisdictions.
Warrants Issued in Connection with Sale of Common Stock	Warrants Issued in Connection with Sale of Common Stock The Company accounts for warrants issued as a separable unit in connection with sale of common stock as either liability or equity in accordance with ASC 480-10, Accounting for Certain Financial Instruments with Characteristics of both Liabilities and Equity (“ASC 480-10”) or ASC 815-40, Accounting for Derivative Financial Instruments Indexed to, and Potentially Settled in, a Company’s Own Stock (“ASC 815-40”). Under ASC 480-10, warrants are considered liabilities if they are mandatorily redeemable and they require settlement in cash or other assets, or a variable number of shares. If warrants do not meet liability classification under ASC 480-10, the Company considers the requirements of ASC 815-40 to determine whether the warrants should be classified as liability or equity. If warrants do not require liability classification under ASC 815-40 or other applicable U.S. GAAP the warrants should be classified as equity. The proceeds received from the sale of equity classified warrants and sh ares of common stock in a bundled transaction are allocated based on the relative fair values of warrants and shares of common stock with no changes in fair value of warrants recognized after the issuance date. Based on our analysis of the foregoing, the Company's warrants issued in the Private Placement are classified as equity in our consolidated financial statements.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing the net loss attributable to common shareholders by the weighted-average number of shares of common stock outstanding for the period. Diluted net loss per share is computed by dividing the net loss attributable to common shareholders by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for the period, determined using the treasury-stock method and the as if-converted method, for convertible securities, if inclusion of these instruments is dilutive. Potentially dilutive securities include stock options and warrants to purchase common stock of the Company. In all periods presented, the Company’s outstanding stock options and warrants were excluded from the calculation of diluted net loss per share because their effects were anti-dilutive.
Segments	Segments Operating segments are defined as components of an entity for which separate financial information is available and that is regularly reviewed by the chief operating decision maker (CODM), in deciding how to allocate resources to an individual segment and in assessing performance. Our CODM is our chief executive officer. The Company has concluded it has a single reporting segment for purposes of reporting financial condition and results of operations.
Other Comprehensive Income (loss)	Other Comprehensive Income (Loss) OCI is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Our OCI includes currency translation from the Euro and the British Pound, the functional currency of IO Biotech ApS and IO Biotech Limited, respectively, to the U.S. Dollar, our reporting currency.
Emerging Growth Company Status	Emerging Growth Company Status We are an emerging growth company, as defined in the Jumpstart Our Business Startups Act (JOBS Act). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act, until such time as those standards apply to private companies. We have elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that we (1) are no longer an emerging growth company or (2) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates.
Recently Issued Accounting Standards	Recently adopted accounting standards In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses: Measurement of Credit Losses on Financial Instruments. ASU 2016-13 requires measurement and recognition of expected credit losses for financial assets. In April 2019, the 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, or ASU 2016-13. The guidance is effective for fiscal years beginning after December 15, 2022. The Company has adopted the standard effective January 1, 2023 . The adoption of the standard has no t had a material impact on our financial statements or financial statement disclosures. Recently Issued Accounting Standards In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging Contracts in Entity s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity . ASU 2020-06 will simplify the accounting for convertible instruments by reducing the number of accounting models for convertible debt instruments and convertible preferred stock. Limiting the accounting models results in fewer embedded conversion features being separately recognized from the host contract as compared with current U.S. GAAP. Convertible instruments that continue to be subject to separation models are (1) those with embedded conversion features that are not clearly and closely related to the host contract, that meet the definition of a derivative, and that do not qualify for a scope exception from derivative accounting and (2) convertible debt instruments issued with substantial premiums for which the premiums are recorded as paid-in capital. ASU 2020-06 also amends the guidance for the derivatives scope exception for contracts in an entity’s own equity to reduce form-over-substance-based accounting conclusions. ASU 2020-06 will be effective for us in the interim periods in the fiscal year beginning after December 15, 2023. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020, including interim periods within those fiscal years. We are currently assessing the impact adoption of ASU 2020-06 will have on our financial statements and disclosures, but do not expect a material impact on the financial statements or disclosures. In October 2023, the FASB issued ASU 2023-06, Accounting Standards Update 2023-06—Disclosure Improvements: Codification Amendments in Response to the SEC’s Disclosure Update and Simplification Initiative. ASU 2023-06 will eliminate disclosure requirements that are redundant, duplicative, overlapping, outdated, or superseded as a result of subsequent changes to SEC disclosure requirements, U.S GAAP or technology. ASU 2023-06 is intended to better align U.S. GAAP requirements with those of the SEC and to facilitate the application of U.S. GAAP. The disclosure requirements would apply prospectively in the financial statements. ASU 2023-06 will be effective for us on the date on which the SEC’s removal of that related disclosure requirement from Regulation S-X or Regulation S-K becomes effective, if we are already subject to the SEC’s current disclosure requirements. For those current disclosure requirements we are not subject to, ASU 2023-06 will become effective two years after the date of such removal by the SEC. We are currently assessing the impact adoption of ASU 2023-06 will have on our financial statements and disclosures. In November 2023, the FASB issued ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures. ASU 2023-07 will improve reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses. ASU 2023-07 will also enhance interim disclosure requirements, clarify circumstances in which an entity can disclose multiple segment measures of profit or loss, provide new segment disclosure requirements for entities with a single reportable segment and contain other disclosure requirements. The enhanced segment disclosure requirements apply retrospectively to all prior periods presented in the financial statements. ASU 2023-07 will be effective for us in the annual periods beginning after December 15, 2023. We are currently assessing the impact adoption of ASU 2023-07 will have on our financial statements and disclosures, but do not expect a material impact on the financial statements or disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures. ASU 2023-09 will require disclosure of additional information in specified categories with respect to the reconciliation of the effective tax rate to the statutory rate (the rate reconciliation) for federal, state and foreign income taxes. ASU 2023-09 will also require information pertaining to taxes paid (net of refunds received) to be disaggregated for federal, state and foreign taxes and further disaggregated for specific jurisdictions to the extent the related amounts exceed a quantitative threshold. ASU 2023-09 will be effective for us in the annual periods beginning after December 15, 2025. Early adoption is permitted for annual financial statements that have not yet been issued or made available for issuance. We are currently assessing the impact adoption of ASU 2020-06 will have on our financial statements and disclosures. Other than the items noted above, there have been no new accounting pronouncements not yet effective or adopted in the current year that we believe have a significant impact, or potential significant impact, to our consolidated financial statements

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Summary of Assets Measured at Fair Value	The following tables present information about our financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values as of December 31, 2023 and 2022 (in thousands): December 31, 2023 Total Level 1 Level 2 Level 3 Assets Money market funds(1) $ 131,613 $ 131,613 $ — $ — Total assets measured at fair value $ 131,613 $ 131,613 $ — $ — December 31, 2022 Total Level 1 Level 2 Level 3 Assets Money market funds(1) $ 87,971 $ 87,971 $ — $ — Total assets measured at fair value $ 87,971 $ 87,971 $ — $ — (1) Money market funds with maturities of 90 days or less at the date of purchase are included within cash and cash equivalents in the accompanying consolidated balance sheets and are recognized at fair value.

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Summary of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): December 31, 2023 2022 Insurance $ 1,352 $ 1,716 Research and development tax credit receivable 814 792 Prepaid income taxes 829 124 Value-added tax refund receivable 313 741 Prepaid contract research and development costs — 1,695 Other 754 561 Total prepaid expenses and other current assets $ 4,062 $ 5,629

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consist of the following (in thousands): December 31, 2023 2022 Laboratory equipment $ 836 $ 544 Office furniture 238 233 Computer hardware 103 79 Less: accumulated depreciation ( 330 ) ( 115 ) Total property and equipment, net $ 847 $ 741

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2023
Payables and Accruals [Abstract]
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): December 31, 2023 2022 Accrued contract research and development costs $ 6,153 $ 1,936 Employee compensation costs 4,225 1,863 Professional fees 243 407 Other liabilities 563 1,951 Total accrued expenses and other current liabilities $ 11,184 $ 6,157

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2023
Leases [Abstract]
Schedule of Quantitative Information Regarding Leases	Quantitative information regarding the Company’s leases for the year ended December 31, 2023 is as follows (in thousands): Year Ended December 31, Lease Cost 2023 2022 Operating lease cost $ 730 $ 755 Operating cash flows paid for amounts included in the measurement of lease liabilities $ 723 $ 419 Operating lease liabilities arising from obtaining right‑of‑use assets $ 235 $ 2,600 Remaining lease term (years) 3.5 4.5 Weighted average discount rate 6.3 % 6.5 %
Schedule of Future Lease Payments (Undiscounted) under Noncancelable Leases	Future lease payments (undiscounted) under noncancelable leases are as follows as of December 31, 2023 (in thousands): Future Lease Payments Amount 2024 $ 793 2025 792 2026 798 2027 403 2028 — Thereafter — Total $ 2,786

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Rental Payments Under Noncancellable Leases	Future lease payments (undiscounted) under noncancelable leases are as follows as of December 31, 2023 (in thousands): Future Lease Payments Amount 2024 $ 793 2025 792 2026 798 2027 403 2028 — Thereafter — Total $ 2,786

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Schedule of Stock Options Activity	The following table summarizes our stock options activity for the years ended December 31, 2023 and 2022: Number of Weighted- Weighted- Aggregate Outstanding December 31, 2021 3,071,613 $ 13.12 8.5 $ — Granted 1,211,155 $ 5.34 — $ — Cancelled or forfeited ( 362,596 ) $ 12.51 — $ — Outstanding December 31, 2022 3,920,172 $ 10.77 8.1 $ — Granted 2,519,994 $ 1.99 — $ — Cancelled or forfeited ( 588,243 ) $ 8.74 — $ — Outstanding, December 31, 2023 5,851,923 $ 7.20 8.4 $ 102 Exercisable at December 31, 2023 1,902,547 $ 11.26 7.7 $ 2
Summary of Assumptions for Estimated Fair Value of Options	The fair values of the options granted were estimated based on the Black-Scholes model, using the following assumptions: Year Ended December 31, 2023 2022 Expected volatility 86.4 % - 102.2 % 74.0 % - 77.3 % Risk-free interest rate 3.5 % - 4.5 % 1.62 % - 4.2 % Expected term (in years) 5.5 - 6.1 5.5 - 6.0 Expected dividend yield 0 % 0 %
Schedule of Equity-based Compensation Expense	Equity-based compensation expense recorded as research and development and general and administrative expenses is as follows (in thousands): December 31, 2023 2022 Research and development $ 4,204 $ 2,859 General and administrative 3,855 4,181 Total equity-based compensation $ 8,059 $ 7,040

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Loss Before Provision for Income Taxes	Our loss before provision for income taxes for the years ended December 31, 2023 and 2022 consisted of the following (in thousands): Year Ended December 31, 2023 2022 Domestic $ 2,365 $ ( 1,885 ) Foreign ( 87,596 ) ( 68,300 ) Total $ ( 85,231 ) $ ( 70,185 )
Schedule of Provision for Income Taxes	Our provision for income taxes consists of the following (in thousands): Year Ended December 31, 2023 2022 Current: Federal $ 439 $ 1,059 State 374 86 Foreign 39 52 852 1,197 Deferred: Federal — 76 State — — Foreign — — — 76 Total provision for income taxes $ 852 $ 1,273
Reconciliation of the Statutory Income Tax Rate to our Effective Income Tax Rate	The reconciliation of the statutory income tax rate to our effective income tax rate is as follows: Year Ended December 31, 2023 2022 Income tax benefit at the statutory rate 21.0 % 21.0 % Permanent differences 1.0 0.7 Difference in tax rate 1.0 1.0 R&D Deduction 1.1 4.0 Change in valuation allowance ( 24.7 ) ( 27.4 ) Prior period adjustments ( 0.2 ) ( 1.0 ) Other ( 0.2 ) ( 0.1 ) Total ( 1.0 )% ( 1.8 )%
Schedule of Principal Components of Deferred Tax Assets	The principal components of the Company’s deferred tax assets consisted of the following (in thousands): December 31, 2023 2022 Deferred tax assets: Net operating loss carryforwards $ 50,343 $ 31,338 Equity-based compensation expense 3,602 1,828 Accrued compensation 33 21 ROU Lease Liability 526 618 Capitalized R&D 3,348 1,231 Other 529 529 Total deferred tax assets $ 58,381 $ 35,565 Valuation allowance ( 57,902 ) ( 34,984 ) Net deferred tax assets $ 479 $ 581 ROU Lease Asset 441 567 Fixed Assets 26 13 Other Liabilities 12 1 Total deferred tax liabilities 479 581 Net deferred tax asset (liability) $ — $ — In 2017, the U.S. enacted the Tax Cuts and Jobs Act (the 2017 Tax Act), which contained a provision that requires capitalization and amortization of research and development expenses for tax purposes starting in 2022. Previously, these expenses could be deducted in the year incurred. The implementation of this provision increased our deferred tax asset and valuation allowance by approximately $ 2.1 million and $ 1.2 million for the years ended December 31, 2023 and 2022 .

Net Loss Per Share (Table)

Net Loss Per Share (Table)	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	Basic and diluted net loss per common share is calculated as follows (in thousands except share and per share amounts): Year Ended December 31, 2023 2022 Net loss $ ( 86,083 ) $ ( 71,458 ) Net loss attributable to common shareholders $ ( 86,083 ) $ ( 71,458 ) Net loss per common share, basic and diluted $ ( 1.98 ) $ ( 2.48 ) Weighted-average number of shares used in computing net loss per common share, basic and diluted 43,539,976 28,815,267
Schedule of Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss per Share	December 31, 2023 2022 Stock options to purchase common stock 5,851,923 3,920,172 Warrants issued in Private Placement 37,065,647 —

Description of Business, Orga_2

Description of Business, Organization and Liquidity - Additional Information (Details) - USD ($)		1 Months Ended	12 Months Ended
	Aug. 09, 2023	Nov. 30, 2021	Dec. 31, 2023	Dec. 31, 2022	Feb. 15, 2023	Nov. 09, 2021
Description Of Business Organization And Liquidity [Line Items]
Accumulated deficit			$ (263,822,000)	$ (177,739,000)
Proceeds from private placement	$ 71,900,000
Common stock shares issued			65,880,914	28,815,267		28,815,267
Net losses			$ (86,083,000)	$ (71,458,000)
Cash and cash equivalents			$ 143,193,000	$ 142,590,000
Common stock, par value			$ 0.001	$ 0.001
Net proceeds from IPO, after deducting underwriting discounts, commissions and offering costs		$ 103,300,000
Convertible preference share issued upon conversion						20,592,413
Common stock shares outstanding			65,880,914	28,815,267		28,815,267
Common stock shares authorized			300,000,000	300,000,000		300,000,000
Preferred stock shares authorized			5,000,000	5,000,000
Class A Ordinary Shares
Description Of Business Organization And Liquidity [Line Items]
Common stock, par value		$ 0.16
Common stock conversion basis		one-for-one
Class B Preference Shares
Description Of Business Organization And Liquidity [Line Items]
Common stock, par value		$ 0.001
Common stock conversion basis		one-for-one
Class C Preference Shares
Description Of Business Organization And Liquidity [Line Items]
Common stock, par value		$ 0.001
Common stock conversion basis		one-for-one
Undesignated Preferred Stock
Description Of Business Organization And Liquidity [Line Items]
Preferred stock shares authorized			5,000,000			5,000,000
Underwriters
Description Of Business Organization And Liquidity [Line Items]
Shares issued		1,072,500
IPO
Description Of Business Organization And Liquidity [Line Items]
Shares issued		8,222,500
Common stock shares sold, price per share		$ 14
Private Placement
Description Of Business Organization And Liquidity [Line Items]
Purchase price per share of common stock and warrant	$ 2.025
Offering expenses	$ 3,200,000
Warrants issued	37,065,647
Common stock, par value	$ 0.001
Shares issued	37,065,647
Private Placement | Maximum | Common Stock
Description Of Business Organization And Liquidity [Line Items]
Shares issued	37,065,647
At-The-Market Equity Program
Description Of Business Organization And Liquidity [Line Items]
Common stock, maximum aggregate offering price					$ 19,500,000
Shares issued			0
At-The-Market Equity Program | Sales Agreement
Description Of Business Organization And Liquidity [Line Items]
Common stock, maximum aggregate offering price					$ 75,000,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) $ / shares in Units, kr in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares	Dec. 31, 2023 DKK (kr)	Dec. 31, 2022 USD ($)	Dec. 31, 2022 DKK (kr)	Dec. 31, 2023 DKK (kr)
Property, Plant and Equipment [Line Items]
Money market funds	$ 131,600,000		$ 88,000,000
Impairment expenses	$ 0		$ 0
Operating lease incremental borrowing rate on remaining lease | $ / shares	$ 6.5
Expected dividend yield	0%	0%	0%	0%
Unrecognized tax benefits	$ 0		$ 0
Accounting standards update [extensible enumeration]	us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201613Member
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true				true
Change in accounting principle, accounting standards update, adoption date	Jan. 01, 2023				Jan. 01, 2023
Change in accounting principle, accounting standards update, immaterial effect [true false]	true				true
Computer hardware
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years				3 years
Office furniture
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years				5 years
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years				5 years
Research and Development Expense
Property, Plant and Equipment [Line Items]
Grant income cost reimbursement	$ 20,000		30,000
Research and Development Expense | Danish Tax Authority
Property, Plant and Equipment [Line Items]
Refundable tax credit | kr		kr 25		kr 25
Refundable tax credit receivable	$ 800,000		$ 800,000
Research and Development Expense | Maximum | Danish Tax Authority
Property, Plant and Equipment [Line Items]
Tax credit carryforward | kr					kr 5.5
Refundable tax credit | kr		kr 25

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets Measured at Fair Value (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Assets
Total assets measured at fair value	$ 131,613	$ 87,971
Money Market Funds
Assets
Total assets measured at fair value	131,613	87,971
Level 1
Assets
Total assets measured at fair value	131,613	87,971
Level 1 | Money Market Funds
Assets
Total assets measured at fair value	$ 131,613	$ 87,971

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount	$ 0	$ 0
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	$ 0	$ 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
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Insurance	$ 1,352	$ 1,716
Research and development tax credit receivable	814	792
Prepaid income taxes	829	124
Value-added tax refund receivable	313	741
Prepaid contract research and development costs		1,695
Other	754	561
Total prepaid expenses and other current assets	$ 4,062	$ 5,629

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 0.2	$ 0.1

Property and Equipment, Net - S

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation	$ (330)	$ (115)
Total property and equipment, net	847	741
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	836	544
Office furniture
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	238	233
Computer hardware
Property, Plant and Equipment [Line Items]
Property and Equipment, gross	$ 103	$ 79

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Accrued contract research and development costs	$ 6,153	$ 1,936
Employee compensation costs	4,225	1,863
Professional fees	243	407
Other liabilities	563	1,951
Total accrued expenses and other current liabilities	$ 11,184	$ 6,157

Leases - Additional Information

Leases - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Lease	Dec. 31, 2022 USD ($)	Jan. 01, 2022 USD ($)
Lessee, Lease, Description [Line Items]
Rent expense	$ 700	$ 800
Number of operating leases | Lease	5
Right of use lease asset	$ 2,259	2,493	$ 2,300
Lease liability			2,400
Operating lease liability, current	655	515
Operating lease, liability, non-current	1,839	$ 2,275
Deferred rent			$ 100
Office and Laboratory | Denmark
Lessee, Lease, Description [Line Items]
Operating lease amended base rent	200
Office and Laboratory | New York, NY
Lessee, Lease, Description [Line Items]
Operating lease annual base rent	200
Office and Laboratory | Maryland
Lessee, Lease, Description [Line Items]
Operating lease annual base rent	300
Office | Denmark
Lessee, Lease, Description [Line Items]
Operating lease annual base rent	100
Laboratory | Denmark
Lessee, Lease, Description [Line Items]
Operating lease annual base rent	$ 40

Leases - Schedule of Quantitati

Leases - Schedule of Quantitative information Regarding Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Lessee, Lease, Description [Line Items]
Operating lease cost	$ 730	$ 755
Operating cash flows paid for amounts included in the measurement of lease liabilities	723	419
Operating lease liabilities arising from obtaining right-of-use assets	$ 235	$ 2,600
Remaining lease term (years)	3 years 6 months	4 years 6 months
Weighted average discount rate	6.30%	6.50%

Leases - Schedule of Future Lea

Leases - Schedule of Future Lease Payments (Undiscounted) under Noncancelable Leases (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Lessee, Operating Lease, Liability, to be Paid, Fiscal Year Maturity [Abstract]
2024	$ 793
2025	792
2026	798
2027	403
2028	0
Thereafter	0
Total	$ 2,786

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2023
Minimum
Other Commitments [Line Items]
Contractual obligations termination notice period	30 days
Maximum
Other Commitments [Line Items]
Contractual obligations termination notice period	90 days

Convertible Preference Shares -

Convertible Preference Shares - Additional information (Details)	Dec. 31, 2023 Vote $ / shares shares	Dec. 31, 2022 $ / shares shares	Nov. 09, 2021 shares
Class Of Stock [Line Items]
Preference shares authorized	5,000,000	5,000,000
Preference shares issued	0	0
Preference shares outstanding	0	0
Preference share per share | $ / shares	$ 0.001	$ 0.001
Convertible preference share issued upon conversion			20,592,413
Number of votes per share | Vote	1

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details)			1 Months Ended	12 Months Ended
	Aug. 09, 2023 USD ($) $ / shares shares	Aug. 07, 2023 $ / shares shares	Nov. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) Vote $ / shares shares	Dec. 31, 2022 shares	Nov. 09, 2021 shares
Subsidiary, Sale of Stock [Line Items]
Net proceeds from IPO, after deducting underwriting discounts, commissions and offering costs			$ 103,300,000
Common stock shares authorized | shares				300,000,000	300,000,000	300,000,000
Preferred stock shares authorized | shares				5,000,000	5,000,000
Number of votes per share | Vote				1
Common stock shares outstanding | shares				65,880,914	28,815,267	28,815,267
Proceeds from private placement	$ 71,900,000
Private Placement
Subsidiary, Sale of Stock [Line Items]
Shares issued | shares	37,065,647
Warrants issued | shares	37,065,647
Purchase price per share of common stock and warrant | $ / shares	$ 2.025
Offering expenses	$ 3,200,000
Private Placement | Securities Purchase Agreement
Subsidiary, Sale of Stock [Line Items]
Warrants issued | shares		37,065,647		37,065,647
Purchase price per share of common stock and warrant | $ / shares		$ 2.025
Purchase Price of Common Stock and Warrants | $ / shares		$ 2.47		$ 2.47
Proceeds from private placement	75,100,000
Offering expenses	3,200,000
Net Proceeds From Issuance Of Private Placement	71,900,000
Proceeds from Issuance of Warrants				$ 29,600,000
Private Placement | Securities Purchase Agreement | Management
Subsidiary, Sale of Stock [Line Items]
Proceeds from private placement	200,000
Private Placement | Securities Purchase Agreement | Related Party
Subsidiary, Sale of Stock [Line Items]
Proceeds from private placement	$ 400,000
Private Placement | Securities Purchase Agreement | Common Stock
Subsidiary, Sale of Stock [Line Items]
Shares issued | shares		37,065,647
IPO
Subsidiary, Sale of Stock [Line Items]
Shares issued | shares			8,222,500
Common stock shares sold, price per share | $ / shares			$ 14
Underwriters
Subsidiary, Sale of Stock [Line Items]
Shares issued | shares			1,072,500
Undesignated Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Preferred stock shares authorized | shares				5,000,000		5,000,000
Dividend Declared
Subsidiary, Sale of Stock [Line Items]
Dividends				$ 0
Dividend Paid
Subsidiary, Sale of Stock [Line Items]
Dividends				$ 0

Equity-Based Compensation - Add

Equity-Based Compensation - Additional Information (Details) - USD ($)		12 Months Ended
	Nov. 04, 2021	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Tax benefits for stock-based compensation		$ 0	$ 0
Equity-based compensation expense		8,059,000	$ 7,040,000
Unrecognized compensation cost		$ 11,200,000
Unrecognized compensation cost, recognition period		2 years 6 months
2021 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	2,496,934
Maximum percentage of shares that may be issued under the plan as a proportion of outstanding capital stock	4%
Number of warrants available for future grant		593,468
2021 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	257,272
2021 Employee Stock Purchase Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum percentage of shares that may be issued under the plan as a proportion of outstanding capital stock	1%
2023 Inducement Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance		1,976,427
Number of warrants available for future grant		1,976,427

Equity-Based Compensation - Sch

Equity-Based Compensation - Schedule of Stock Options Activity (Details) - Warrant - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Warrants, Beginning balance	3,920,172	3,071,613
Number of Warrants, Granted	2,519,994	1,211,155
Number of Warrants, Cancelled or forfeited	(588,243)	(362,596)
Number of Warrants, Ending balance	5,851,923	3,920,172	3,071,613
Number of Warrants, Exercisable	1,902,547
Weighted-average exercise price per share, Beginning balance	$ 10.77	$ 13.12
Weighted-average exercise price per share, Granted	1.99	5.34
Weighted-average exercise price per share, Cancelled or forfeited	8.74	12.51
Weighted-average exercise price per share, Ending balance	7.2	$ 10.77	$ 13.12
Weighted-average exercise price per share, Exercisable	$ 11.26
Weighted-average remaining contractual term (in years), Outstanding	8 years 4 months 24 days	8 years 1 month 6 days	8 years 6 months
Weighted-average remaining contractual term (in years), Exercisable	7 years 8 months 12 days
Aggregate intrinsic value, Outstanding	$ 102
Aggregate intrinsic value, Exercisable	$ 2

Equity-Based Compensation - Sum

Equity-Based Compensation - Summary of Assumptions for Estimated Fair Value of Options (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility minimum	86.40%	74%
Expected volatility maximum	102.20%	77.30%
Risk-free interest rate minimum	3.50%	1.62%
Risk-free interest rate maximum	4.50%	4.20%
Expected dividend yield	0%	0%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 6 months	5 years 6 months
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days	6 years

Equity-Based Compensation - S_2

Equity-Based Compensation - Schedule of Equity-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 equity-based compensation	$ 8,059	$ 7,040
Research and Development Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total equity-based compensation	4,204	2,859
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total equity-based compensation	$ 3,855	$ 4,181

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) kr in Millions	12 Months Ended
	Dec. 31, 2023 DKK (kr)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 DKK (kr)	Dec. 31, 2022 USD ($)	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Provision increase deferred tax assets and valuation allowance		$ 2,100,000		$ 1,200,000
Valuation allowance		22,900,000		19,900,000
Deferred tax assets, credit carryforwards		228,500,000
Unrecognized tax benefits		0		0
Research and development tax credits in U.S. provision for income taxes		$ 1,000,000
Danish Tax Authority
Operating Loss Carryforwards [Line Items]
Open tax year	2020	2020
Danish Tax Authority | Research and Development Expense
Operating Loss Carryforwards [Line Items]
Effective income tax rate					101.50%
Refundable tax credit | kr	kr 25		kr 25
Refundable tax credit receivable		$ 800,000		$ 800,000
Danish Tax Authority | Research and Development Expense | Maximum
Operating Loss Carryforwards [Line Items]
Refundable tax credit | kr	kr 25
Danish Tax Authority | 2020 through 2022 | Research and Development Expense
Operating Loss Carryforwards [Line Items]
Effective income tax rate	130%	130%
Danish Tax Authority | 2023 through 2025 | Research and Development Expense
Operating Loss Carryforwards [Line Items]
Effective income tax rate	108%	108%
Danish Tax Authority | Period 2026 | Research and Development Expense
Operating Loss Carryforwards [Line Items]
Effective income tax rate	110%	110%

Income Taxes - Schedule of Loss

Income Taxes - Schedule of Loss Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Domestic	$ 2,365	$ (1,885)
Foreign	(87,596)	(68,300)
Loss before income tax expense	$ (85,231)	$ (70,185)

Income Taxes - Schedule of Prov

Income Taxes - Schedule of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Current:
Federal	$ 439	$ 1,059
State	374	86
Foreign	39	52
Current	852	1,197
Deferred:
Federal		76
Deferred		76
Total provision for income taxes	$ 852	$ 1,273

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of the Statutory Income Tax Rate to our Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Income tax benefit at the statutory rate	21%	21%
Permanent differences	1%	0.70%
Difference in tax rate	1%	1%
R&D Deduction	1.10%	4%
Change in valuation allowance	(24.70%)	(27.40%)
Prior period adjustments	(0.20%)	(1.00%)
Other	(0.20%)	(0.10%)
Total	(1.00%)	(1.80%)

Income Taxes - Schedule of Prin

Income Taxes - Schedule of Principal Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 50,343	$ 31,338
Equity-based compensation expense	3,602	1,828
Accrued compensation	33	21
ROU Lease Liability	526	618
Capitalized R&D	3,348	1,231
Other	529	529
Total deferred tax assets	58,381	35,565
Valuation allowance	(57,902)	(34,984)
Net deferred tax assets	479	581
ROU Lease Asset	441	567
Fixed Assets	26	13
Other Liabilities	12	1
Total deferred tax liabilities	$ 479	$ 581

Net Loss Per Share - Basic and

Net Loss Per Share - Basic and Diluted Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Earnings Per Share [Abstract]
Net loss	$ (86,083)	$ (71,458)
Net loss attributable to common shareholders	$ (86,083)	$ (71,458)
Net loss per common share, basic	$ (1.98)	$ (2.48)
Net loss per common share, diluted	$ (1.98)	$ (2.48)
Weighted-average number of shares used in computing net loss per common share, basic	43,539,976	28,815,267
Weighted-average number of shares used in computing net loss per common share, diluted	43,539,976	28,815,267

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Stock Options to Purchase Common Stock
Earnings Per Share Basic [Line Items]
Outstanding potentially dilutive securities	5,851,923	3,920,172
Warrants issued in Private Placement
Earnings Per Share Basic [Line Items]
Outstanding potentially dilutive securities	37,065,647