Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation NKMAX Co., Ltd. (“NKMAX”) held a majority of the voting power of Legacy NKGen before the Business Combination and continued to hold a majority of the voting power of the Company after the Business Combination. Therefore, as there was no change in control, the Business Combination was accounted for as a common control transaction with respect to Legacy NKGen along with a reverse recapitalization of the Company. Accordingly, for accounting purposes, the financial statements of the Company represent a continuation of the financial statements of Legacy NKGen with the Business Combination being treated as the equivalent of Legacy NKGen issuing shares for the net assets of Graf, accompanied by a recapitalization. The net assets of Graf were recognized as of the Closing at historical cost, with no goodwill or other intangible assets recorded. Operations prior to the Business Combination are presented as those of Legacy NKGen, and the accumulated deficit of Legacy NKGen has been carried forward after Closing. Upon the consummation of the Business Combination, all of Legacy NKGen’s equity was converted into equity of the Company based upon an exchange ratio (“Exchange Ratio”). In addition, all stock options of Legacy NKGen were converted using the Exchange Ratio into options exercisable for shares of the Company with the same terms and vesting conditions. The Exchange Ratio as of September 29, 2023, the date of Closing, was approximately 0.408. All periods prior to the Business Combination have been retrospectively adjusted using the Exchange Ratio to reflect the reverse recapitalization. In connection with the reverse recapitalization treatment of the Business Combination, all issued and outstanding securities of Graf upon Closing were treated as issuances of the Company upon the consummation of the Business Combination. The accompanying financial statements have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission (“SEC”) and generally accepted accounting principles in the United States of America (“US GAAP”). The Company maintains its accounting records under the accrual method of accounting in conformity with US GAAP.
Principles of Consolidation	Principles of Consolidation The accompanying consolidated financial statements include the accounts of the Company. All significant intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in accordance with US GAAP requires management to make estimates and assumptions that impact the reported amounts of certain assets and liabilities, certain disclosures at the date of the consolidated financial statements, as well as the reported amounts of revenues and expenses during the reporting period. The most significant estimates in the Company’s consolidated financial statements include, but are not limited to, accrued clinical and research and development expenses, legacy convertible promissory notes, senior convertible promissory notes due to related parties, forward purchase derivative liabilities, derivative warrant liabilities, derivative warrant assets, common stock, and equity awards. These estimates and assumptions are based upon historical experience, knowledge of current events, and various other factors believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and the recording of expenses that are not readily apparent from other sources. Actual results could differ materially from those estimates.
Segments	Segments The Company applies the provisions of ASC 280 – Segment Reporting, as amended by ASU 2023-07, to determine its reportable segments. Based on management’s evaluation, the Company operates as a single reportable segment, consistent with the manner in which the Chief Operating Decision Maker (“CODM”) assesses financial performance and allocates resources. The CODM, identified as the Company’s Chief Executive Officer, reviews financial information on a consolidated basis consistent with the Company’s consolidated US GAAP financial statements and uses net loss, as reported in the consolidated statements of operations, to evaluate performance and make resource allocation decisions. This approach reflects the integrated nature of the Company’s operations and cost management practices. As such, all required segment disclosures are included within the consolidated financial statements. For additional information, refer to Note 17 – Segment Information.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less when purchased to be cash equivalents. The carrying amounts reported in the balance sheets for cash and cash equivalents are valued at cost, which approximate their fair value. The Company has not experienced any losses in such accounts and management believes the Company has no highly liquid investments exposed to credit risk.
Restricted Cash	Restricted Cash Restricted cash consists of funds that are contractually restricted due to a revolving line of credit, which was entered into during June 2023. In accordance with the terms of the revolving line of credit, the Company was required to maintain $15.0 million in cash balances with the lender from December 31, 2024 until repayment of all principals and other payables to the lender under the revolving line of credit was made as additional collateral for the borrowings. In April 2024, the lender subsequently waived the minimum cash deposit requirement in exchange for the Company's agreement to use the lender as their primary banking relationship. As of December 31, 2024 and 2023, $0.1 million and $0.3 million in restricted cash was recorded on the consolidated balance sheets, respectively. The Company includes its restricted bank deposits in cash, cash equivalents and restricted cash when reconciling beginning-of-period and end-of-period total amounts shown on the consolidated statements of cash flows for the years ended December 31, 2024 and 2023.
Concentrations of Risk	Concentrations of Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents. The Company minimizes the amount of credit exposure by investing cash that is not required for immediate operating needs in money market funds, government obligations, and/or commercial paper with short maturities. To date, the Company has not experienced any losses associated with this credit risk and continues to believe this exposure is not significant. Cash deposits are insured by the Federal Deposit Insurance Corporations (“FDIC”) up to $250,000. From time to time, the Company may have cash deposits in excess of the FDIC insured limit.
Property and Equipment, net	Property and Equipment, net Property and equipment are recorded at cost and depreciated over their estimated useful lives using the straight-line method. Leasehold improvements are depreciated over the shorter of their estimated useful lives or the term of the lease by use of the straight-line method. Repairs and maintenance costs are charged to expense as incurred. When assets are retired or sold, the assets and accumulated depreciation are removed from the respective amounts and any gain or loss is recognized, as applicable, in the accompanying consolidated statements of operations.
Capitalized Software, net	Capitalized Software, net Expenditures related to internal use software are capitalized. Such expenditures are amortized over their period of benefit, which are generally three-year period, using the straight-line method.
Transaction Costs	Transaction Costs The Company capitalizes deferred transaction costs, which primarily consist of incremental legal fees, accounting fees and other costs directly attributable to anticipated capital-raising transactions. The deferred transaction costs are reclassified upon the occurrence of the associated capital-raising transactions. All deferred transaction costs during the year ended December 31, 2023 were reclassified upon Closing of the Business Combination. No deferred transaction costs were recorded as of December 31, 2024 and 2023. Transaction costs not specific to a single instrument are allocated on a relative fair value basis. Transaction costs allocated to equity-classified instruments are recorded to additional paid-in capital. Transaction costs allocated to liability-classified instruments with recurring fair value measurements are recorded as transaction costs expenses in the consolidated statements of operations.
Hybrid Instruments	Hybrid Instruments The Company follows FASB ASC 480, Distinguishing Liabilities from Equity ("ASC 480"), when evaluating the accounting for its hybrid instruments. A financial instrument that embodies an unconditional obligation, or a financial instrument other than an outstanding share that embodies a conditional obligation, that the issuer must or may settle by issuing a variable number of its equity shares shall be classified as a liability (or an asset in some circumstances) if, at inception, the monetary value of the obligation is based solely or predominantly on any one of the following: (a) a fixed monetary amount known at inception; (b) variations in something other than the fair value of the issuer’s equity shares; or (c) variations inversely related to changes in the fair value of the issuer’s equity shares. Hybrid instruments meeting these criteria are not further evaluated for any embedded derivatives and are carried as a liability at fair value at each balance sheet date.
Derivative Instruments	Derivative Instruments FASB ASC 815, Derivatives and Hedging Activities ("ASC 815"), requires companies to bifurcate certain features from their host instruments and account for them as free-standing derivative financial instruments should certain criteria be met. The Company does not use derivative instruments to hedge exposures to interest rate, market, or foreign currency risks. The Company evaluates its financial instruments to determine whether such instruments are derivatives or contain features that qualify as embedded derivatives. Embedded derivatives must be separately measured from the host contract if all the requirements for bifurcation are met. The assessment of the conditions surrounding the bifurcation of embedded derivatives depends on the nature of the host contract and the features of the derivatives. Bifurcated embedded derivatives are recognized at fair value, with changes in fair value recognized in the consolidated statements of operations each period. Bifurcated embedded derivatives are classified with the related host contract in the Company’s consolidated balance sheets. The classification of derivative instruments, including whether such instruments should be recorded as liabilities or as equity, is re-assessed at the end of each reporting period.
Deferred Debt Issuance Costs / Debt	Debt For convertible debt instruments that are not considered liabilities under ASC 480 or ASC 815, the Company applies FASB ASC 470, Debt ("ASC 470"), for the accounting of such instruments, including any premiums or discounts. The Company’s senior convertible promissory notes are accounted for under ASC 470. Accrued interest paid-in-kind is added to the carrying amount of the Company’s senior convertible promissory notes. The Company accretes the balance of the Convertible Bridge Loans on a straight-line basis to its repayment amount through interest expense.
Sequencing Sufficiency of Authorized and Unissued Shares	Sequencing Sufficiency of Authorized and Unissued Shares For purposes of assessment of the sufficiency of authorized and unissued shares relevant to classification of equity linked contracts, the Company applies a sequencing policy based upon issuance dates. Pursuant to the sequencing policy, as of the date an equity-linked contract is issued for which the underlying shares may exceed the Company’s pool of remaining authorized and unissued shares, taking into account outstanding pre-existing contracts that may be settled in shares, that equity-linked contract and all subsequent equity-linked contracts are deemed to meet the liability classification criteria due to insufficiency of authorized and unissued shares. This policy is applied on a dynamic basis such that upon termination of a given equity-linked contract, the sequencing policy is reapplied, which may result in qualification of equity classification criteria for certain previously issued equity-linked contracts that were previously liability classified solely due to insufficiency of authorized and unissued shares.
Subscription and Shareholder Receivables	Subscription and Shareholder Receivables The Company records stock issuances at the effective date. If the amounts are not funded upon issuance, the Company records a subscription receivable or shareholder receivable as an asset on the balance sheets. When subscription receivables or shareholder receivables are not received prior to the balance sheet date in satisfaction of the requirements under FASB ASC 505, Equity, the subscription or shareholder receivable is reclassified as a contra account to stockholder’s deficit on the balance sheets. Shareholder receivables represent amounts due from shareholders. If the shareholder does not fund the receivable prior to the balance sheets date, the Company records a receivable that is reclassified as a contra account to stockholder’s deficit on the balance sheet.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate the carrying amount of an asset, or asset group, may not be recoverable. Recoverability is measured by a comparison of the carrying amount of an asset or asset group to estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset or asset group exceeds its estimated future cash flows, an impairment charge is recognized by the amount by which the carrying amount of the asset or asset group exceeds the fair value of the asset or asset group.
Fair Value Option	Fair Value Option In lieu of bifurcation, on an instrument-by-instrument basis, the Company may elect the fair value option for certain financial instruments that meet the required criteria under FASB ASC 825, Financial Instruments ("ASC 825"). The Company elected the fair value option for both its legacy convertible notes and convertible promissory notes, which met the required criteria under ASC 825. Interest expense associated with both the legacy convertible and convertible promissory notes that is accrued and unpaid is included in the change in fair value of such instruments. Issuance and modification fees incurred on instruments for which the fair value option was elected are not deferred and are recognized as an expense when incurred.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company accounts for the fair value of its financial instruments under the framework established by US GAAP, which defines fair value and expands disclosures about fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The standard describes a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value. These estimates may be subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. Level 1 — Quoted prices in active markets for identical assets or liabilities the Company has the ability to access at the measurement date. Level 2 — Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of assets or liabilities. Level 3 — Pricing inputs that are unobservable, supported by little or no market activity and are significant to the fair value of the assets or liabilities. Transfers to/from Levels 1, 2, and 3 are recognized at the beginning of the reporting period. There were no transfers to/from Levels 1, 2, and 3 during the years ended December 31, 2024 and 2023. FASB ASC 820, Fair Value Measurement (“ASC 820”), states that in many cases, the transaction price will equal the fair value (for example, that might be the case when on the transaction date, the transaction to buy an asset takes place in the market in which the asset is sold). In determining whether a transaction price represents the fair value at initial recognition, the Company considers various factors such as whether the transaction was between related parties, is a forced transaction, or whether the unit of account for the transaction price does not represent the unit of account for the measured instrument. The Company does not measure assets at fair value on a recurring basis. The Company's liabilities that are measured at fair value on a recurring basis are its liability classified warrants, convertible promissory notes, forward purchase derivative liabilities, and obligation to issue common stock. Refer to Note 9, Fair Value of Financial Instruments, for further discussion regarding the Company’s fair value measurements. The carrying value of the Company’s related party loans approximates fair value as the stated interest rate approximates market rates for similar loans and due to the short-term nature of such loans, which are due within three years or less from issuance. The carrying value of the Company’s cash, restricted cash, accounts payable, accrued expenses, convertible bridge loans, other current liabilities, and revolving line of credit approximates fair value primarily due to the short-term nature of such accounts.
Loss on Issuances of Financial Instruments	Loss on Issuances of Financial Instruments Select financing transactions the Company enters into may include a combination of convertible promissory notes, convertible bridge loans, warrants, tranche right derivatives, forward purchase derivative liabilities, obligations to issue common stock, and issued common stock. Pursuant to ASC 815, upon initial recognition of these bundled transactions, the proceeds received are first allocated to instruments that are measured at fair value on a recurring basis, which are typically liability-classified instruments, and any residual proceeds are allocated on a relative fair value basis to securities that are not required to be measured at fair value on a recurring basis, which are typically equity-classified issued common stock. Upon initial recognition for each respective financing transaction, to the extent the total fair value of the liability-classified instruments exceeds proceeds received, a loss on issuance is recognized. When a loss on issuance is recognized and the bundled transaction includes issued common stock, such common stock is recorded at par as there are no remaining proceeds to be allocated. The fair value of tranche rights from a market participant perspective pursuant to the principles of ASC 820 may include value associated with common stock embedded in the tranche rights. When a tranche right is exercised and the value of the tranche right plus proceeds received upon exercise exceeds the fair value of liability-classified instruments issued upon exercise, a gain on issuance of financial instruments may be recognized for the value of the equity-classified shares, which were included in the then-extinguished tranche right derivative liability due to the application of ASC 820, but are not recognized at fair value upon issuance due to the absence of proceeds to allocate to the stock.
Collaboration Agreement	Collaboration Agreement The Company has entered into a research agreement that falls under the scope of FASB ASC 808, Collaborative Arrangements. Reimbursements from a collaboration partner are recorded as a reduction to research and development expense in the consolidated statements of operations. Similarly, amounts that are owed to a collaboration partner are recognized as research and development expense in the consolidated statements of operations.
Research and Development Expense	Research and Development Expenses All research and development costs are expensed in the period incurred. Research and development expenses primarily consist of services provided by contract organizations for clinical development, salaries and related expenses for personnel, including stock-based compensation expense, outside service providers, facilities costs, fees paid to consultants and other professional services, license fees, depreciation and supplies used in research and development. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the related goods or services are received. Costs are accrued for research performed over the service periods specified in the contracts and estimates are adjusted, if required, based upon an ongoing review of the level of effort and costs actually incurred.
Leases	Leases The Company accounts for its leases under FASB ASC 842, Leases. Operating lease right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset during the lease term, and operating lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating leases are included in ROU assets, current operating lease liabilities, and non-current operating lease liabilities in the accompanying balance sheets. Operating lease ROU assets and lease liabilities are initially recognized based on the present value of the future minimum lease payments over the lease term at commencement date calculated using the Company’s incremental borrowing rate applicable to the lease asset, unless the implicit rate is readily determinable. Operating lease ROU assets also include any lease payments made at or before lease commencement and exclude any lease incentives received. The Company determines the lease term as the noncancelable period of the lease and may include options to extend or terminate the lease when it is reasonably certain the Company will exercise that option. Leases with a term of 12 months or less are not recognized in the balance sheets. The Company’s leases do not contain any residual value guarantees. Lease expense for minimum lease payments is recognized as rent expense on a straight-line basis over the lease term. Variable lease payments include lease operating expenses.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense is comprised of stock options awarded to employees and consultants. The Company accounts for share-based awards under the fair value method prescribed by FASB ASC 718-10, Stock Compensation. The fair value of stock options is estimated using the Black-Scholes option pricing model on the date of grant. This option pricing model involves a number of estimates, including the per share value of the underlying common stock, exercise price, estimate of future volatility, expected term of the stock option award, risk-free interest rate and expected annual dividend yield. The fair value of the shares of common stock underlying the stock options has historically been determined by the Company’s board of directors as there was no public market for the underlying common stock prior to October 2, 2023. The Company’s board of directors determines the fair value of the Company’s common stock by considering a number of objective and subjective factors including contemporaneous third-party valuations of its common stock, the valuation of comparable companies, sales of the Company’s common stock to outside investors in arms-length transactions, the Company’s operating and financial performance, the lack of marketability, and general and industry specific economic outlook, and the implied fair values upon a merger transaction, amongst other factors. The Company recognizes the expense for options with graded-vesting schedules on a straight-line basis over the requisite service period, which is generally the vesting period. Forfeitures are recognized as they occur.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company recognizes net deferred tax assets to the extent the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions on the basis of a two-step process whereby (1) management determines whether it is more likely than not the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense. Any accrued interest and penalties are included within the related tax liability. No tax liability, interest and penalties have been recognized in the consolidated financial statements attributed to uncertain tax positions.
Basic and Diluted Net Loss Per Common Share	Basic and Diluted Net Loss Per Common Share Basic net loss per common share is computed by dividing net loss for the year by the weighted-average number of common shares outstanding during the year. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding and potentially dilutive securities outstanding for the period using the treasury stock or if-converted method if their inclusion is dilutive. Diluted net loss per common share is the same as basic net loss per common share because the inclusion of potentially dilutive shares would be anti-dilutive to the calculation of loss per common share. The Company has one class of shares issued and outstanding. Accordingly, basic and diluted net loss per share is not allocated among multiple classes of shares. Basic and diluted net loss per share for all periods prior to the Closing have been retrospectively adjusted by the Exchange Ratio to affect the reverse recapitalization.
Recently Adopted Accounting Pronouncements and Recently Issued Account Pronouncements Not Yet Adopted	Recently Adopted Accounting Pronouncements In November 2023, the FASB issued Accounting Standards Update ("ASU") No. 2023-07, Segment Reporting, Improvements to Reportable Segment Disclosures (Topic 280). The FASB issued this update to improve the disclosures about an entity’s reportable segments, including providing more detailed information about a reportable segment’s expenses, enhancing interim disclosure requirements and providing new segment disclosure requirements for entities with a single reportable segment. This standard is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. Entities should apply the amendments retrospectively to all prior periods presented in the financial statements. This ASU is applicable to the Company’s Annual Report on Form 10-K for the fiscal year ending December 31, 2024, and subsequent interim periods. The Company adopted the new guidance during the fiscal year ended December 31, 2024. The adoption of ASU No. 2023-07 only impacted the Company's disclosures, which were updated retrospectively, and had no material impact on the Company's results of operations, financial condition or cash flows. Recently Issued Accounting Pronouncements Not Yet Adopted In December 2023, the FASB issued ASU No. 2023-09, Improvements to Income Tax Disclosures (Topic 740). The ASU requires disaggregated information about a reporting entity’s effective tax rate reconciliation as well as additional information on income taxes paid. The ASU is effective on a prospective basis for annual periods beginning after December 15, 2024. Early adoption is also permitted for annual financial statements that have not yet been issued or made available for issuance. This ASU will result in the required additional disclosures being included in our consolidated financial statements, once adopted. The Company is currently evaluating the impact of this standard on its financial statements and related disclosures. In November 2024, the FASB issued ASU No. 2024-03, Income Statement -Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses ("ASU 2024-03"). ASU 2024-03 requires additional disclosures about the nature of expenses included in the income statement, such as purchases of inventory, employee compensation and depreciation. ASU 2024-03 is effective for public business entities for annual periods beginning after December 15, 2026 and interim reporting periods within fiscal years beginning after December 15, 2027. Early adoption is permitted. The Company is currently evaluating the impact of ASU 2024-03 on its financial statements and related disclosures.

NKGen Biotech, Inc. 10-K