NKGen Biotech, Inc. Common Stock (NKGN) 10-K 16 Apr 24 2023 FY Annual report Financial data

Cover

Cover - USD ($)	12 Months Ended
	Dec. 31, 2023	Apr. 16, 2024	Jun. 30, 2023
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	001-40427
Entity Registrant Name	NKGen Biotech, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	86-2191918
Entity Address, Address Line One	3001 Daimler Street
Entity Address, City or Town	Santa Ana
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92705
City Area Code	(949)
Local Phone Number	396-6830
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
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		22,805,643
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Part III of this report incorporates information by reference from the Company's definitive proxy statement, which proxy statement is due to be filed with the Securities and Exchange Commission not later than 120 days after December 31, 2023.
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001845459
Amendment Flag	false
Entity Public Float			$ 0
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	NKGN
Security Exchange Name	NASDAQ
Warrant
Document Information [Line Items]
Title of 12(b) Security	Warrants, each whole warrant exercisable for one share of Common Stock at an exercise price of $11.50 per share
Trading Symbol	NKGNW
Security Exchange Name	NASDAQ

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2023
Auditor Information [Abstract]
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	Irvine, California

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 26	$ 117
Accounts receivable	0	29
Restricted cash	250	0
Prepaid expenses and other current assets	1,654	204
Total current assets	1,930	350
Property and equipment, net	14,459	15,521
Operating lease right-of-use assets, net	0	362
Capitalized software, net	92	97
Total assets	16,481	16,330
Current liabilities:
Accounts payable and accrued expenses (including related party amounts of $688 and $81 as of the year ended December 31, 2023 and 2022, respectively)	13,395	2,652
Convertible promissory notes, current	0	11,392
Convertible promissory notes, due to related parties	0	263
Revolving line of credit	4,991	0
Related party loans	5,000	0
Operating lease liability	0	379
Other current liabilities (including related party amounts of $202 and zero as of the year ended December 31, 2023 and 2022, respectively)	262	55
Forward purchase derivative liability	15,804	0
Total current liabilities	39,452	14,741
Deferred tax liability	33	26
Derivative warrant liabilities	25,759	0
Senior convertible promissory notes, noncurrent, due to related parties	9,930	0
Total liabilities	75,174	14,767
Commitments and contingencies (Note 14)
Stockholders’ equity (deficit):
Common stock, $0.0001 par value; 500,000,000 authorized shares as of December 31, 2023 and 2022; 21,888,976 and 13,303,795 shares issued and outstanding as of December 31, 2023 and 2022, respectively	2	1
Additional paid-in capital	121,727	80,738
Subscription receivable	(17,792)	0
Receivable from shareholder	(500)	0
Accumulated deficit	(162,130)	(79,176)
Total stockholders’ equity (deficit)	(58,693)	1,563
Total liabilities and stockholders’ equity (deficit)	$ 16,481	$ 16,330

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Statement [Abstract]
Revenues	$ 0	$ 77
Costs and expenses:
Cost of revenues	0	18
Research and development (including related party amounts of $620 and $439 for the year ended December 31, 2023 and 2022, respectively)	15,668	16,746
General and administrative	14,078	7,659
Total expenses	29,746	24,423
Loss from operations	(29,746)	(24,346)
Other income (expense):
Interest expense (including related party amounts of $431 and $2,271 for the year ended December 31, 2023 and 2022, respectively)	(745)	(2,306)
Change in fair value of convertible promissory notes and convertible promissory notes due to related parties (including related party amounts of $12 and $4 for the years ended December 31, 2023 and 2022, respectively)	(1,043)	(177)
Loss on issuance of forward purchase contract	(24,475)	0
Loss on amendment of forward purchase contract	(442)	0
Change in fair value of forward purchase derivative liability	(9,784)	0
Change in fair value of derivative warrant liabilities	(13,503)	0
Transaction costs expensed	(3,329)	0
Other income, net	120	82
Net loss before provision for income taxes	(82,947)	(26,747)
Provision for income taxes	(7)	(7)
Net loss	(82,954)	(26,754)
Comprehensive loss	$ (82,954)	$ (26,754)
Earnings Per Share [Abstract]
Weighted-average common shares outstanding, basic (in shares)	15,426,908	6,356,348
Weighted-average common shares outstanding, diluted (in shares)	15,426,908	6,356,348
Net loss per share, basic (in usd per share)	$ (5.38)	$ (4.21)
Net loss per share, diluted (in usd per share)	$ (5.38)	$ (4.21)

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Subscription Receivable	Receivable from Shareholder	Accumulated Deficit	Previously Reported	Previously Reported Common Stock	Previously Reported Additional Paid-In Capital	Previously Reported Subscription Receivable	Previously Reported Receivable from Shareholder	Previously Reported Accumulated Deficit	Revision of Prior Period, Adjustment	Revision of Prior Period, Adjustment Common Stock	Revision of Prior Period, Adjustment Additional Paid-In Capital	Revision of Prior Period, Adjustment Subscription Receivable	Revision of Prior Period, Adjustment Receivable from Shareholder	Revision of Prior Period, Adjustment Accumulated Deficit
Balance as of beginning of period (in shares) at Dec. 31, 2021	0						14,382,093						(14,382,093)
Balance as of beginning of period at Dec. 31, 2021	$ 0						$ 14						$ (14)
Balance as of end of period (in shares) at Dec. 31, 2022	0
Balance as of end of period at Dec. 31, 2022	$ 0
Balance as of beginning of period (in shares) at Dec. 31, 2021		5,873,711						0						5,873,711
Beginning balance at Dec. 31, 2021	(38,052)	$ 1	$ 14,369	$ 0	$ 0	$ (52,422)	$ (38,052)	$ 0	$ 14,356	$ 0	$ 0	$ (52,422)	$ 0	$ 1	$ 13	$ 0	$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	69		69
Exercise of common stock options (in shares)		486,295
Exercise of common stock options	161		161
Issuance of common stock upon conversion of related party loans (in shares)		6,943,789
Issuance of common stock upon conversion of related party loans	66,139		66,139
Net loss	(26,754)					(26,754)
Balance as of ending of period (in shares) at Dec. 31, 2022		13,303,795
Ending balance at Dec. 31, 2022	$ 1,563	$ 1	80,738	0	0	(79,176)
Balance as of end of period (in shares) at Dec. 31, 2023	0
Balance as of end of period at Dec. 31, 2023	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	$ 4,135		4,135
Exercise of common stock options (in shares)	12,866	12,867
Exercise of common stock options	$ 12		12
Reverse recapitalization transactions, net (in shares)		8,572,314
Reverse recapitalization transactions, net	3,928	$ 1	36,842	(32,915)
Loss on amendment of forward purchase contract	14,623			15,123	(500)
Net loss	(82,954)					(82,954)
Balance as of ending of period (in shares) at Dec. 31, 2023		21,888,976
Ending balance at Dec. 31, 2023	$ (58,693)	$ 2	$ 121,727	$ (17,792)	$ (500)	$ (162,130)

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Operating Activities
Net loss	$ (82,954)	$ (26,754)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,203	1,210
Stock-based compensation	4,135	69
Noncash lease expense	362	440
Change in fair value of convertible promissory notes and convertible promissory notes due to related parties	1,043	177
Noncash interest expense (including related party amounts of $431 and $2,271 for the years ended December 31, 2023 and 2022, respectively)	504	2,271
Transaction costs expensed	3,329	0
Loss on issuance of forward purchase contract	24,475	0
Loss on amendment of forward purchase contract	442	0
Change in fair value of forward purchase derivative liability	9,784	0
Change in fair value of derivative warrant liabilities	13,503	0
Changes in operating assets and liabilities:
Accounts receivable	29	(29)
Prepaid expenses and other current assets	(1,403)	57
Accounts payable and accrued expenses	3,993	443
Operating lease liabilities	(379)	(437)
Other, net	(14)	(4)
Net cash used in operating activities	(21,948)	(22,557)
Investing activities
Purchases of property and equipment	0	(101)
Purchases of capitalized software	(48)	(62)
Net cash used in investing activities	(48)	(163)
Financing activities
Proceeds from exercise of common stock options	12	161
Proceeds from related party loans	5,300	23,000
Repayments of related party loans	(300)	0
Proceeds from draws on revolving line of credit	4,991	0
Proceeds from issuance of common stock	1,668	0
Proceeds from issuance of PIPE warrants	10,210	0
Payment of debt issuance costs on revolving line of credit	(100)	0
Repayments on paycheck protection loan	0	(675)
Payment of deferred underwriting fee	(1,250)	0
Payment of transaction costs	(14,591)	0
Net cash provided by financing activities	22,155	22,486
Net increase (decrease) in cash, cash equivalents, and restricted cash	159	(234)
Cash, cash equivalents, and restricted cash at the beginning of period	117	351
Cash, cash equivalents, and restricted cash at the end of period	276	117
Cash and cash equivalents	26	117
Restricted cash	250	0
Total cash, cash equivalents, and restricted cash	276	117
Supplemental cash flow information
Cash paid for interest expense	241	35
Supplemental disclosure of noncash investing and financing activities
Related party loans and interest payable converted into common stock	0	66,139
Issuance of subscription receivable	32,915	0
Conversion of legacy convertible promissory notes (including accrued interest)	18,913	0
Unpaid transaction costs included in accounts payable and accrued expenses	5,802	0
Assumption of derivative warrant liabilities	2,046	0
Receivable from shareholders in connection with amendment of forward purchase contracts	500	0
Receivable from shareholder	500	0
Property and equipment included in accounts payable and accrued expenses	73	8
Capitalized software costs included in accounts payable and accrued expenses	15	0
Convertible Promissory Notes and Convertible Promissory Notes
Financing activities
Proceeds from Convertible Debt	6,215	0
Senior Convertible Promissory Notes with Warrants
Financing activities
Proceeds from Convertible Debt	$ 10,000	$ 0

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accounts payable and accrued expenses (including related party amounts of $688 and $81 as of the year ended December 31, 2023 and 2022, respectively)	$ 13,395	$ 2,652
Other current liabilities (including related party amounts of $202 and zero as of the year ended December 31, 2023 and 2022, respectively)	$ 262	$ 55
Common stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	21,888,976	13,303,795
Common stock outstanding (in shares)	21,888,976	13,303,795
Related Party
Accounts payable and accrued expenses (including related party amounts of $688 and $81 as of the year ended December 31, 2023 and 2022, respectively)	$ 688	$ 81
Other current liabilities (including related party amounts of $202 and zero as of the year ended December 31, 2023 and 2022, respectively)	$ 202	$ 0

CONSOLIDATED STATEMENTS OF OP_2

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Research and development (including related party amounts of $620 and $439 for the year ended December 31, 2023 and 2022, respectively)	$ 15,668	$ 16,746
Interest expense (including related party amounts of $431 and $2,271 for the year ended December 31, 2023 and 2022, respectively)	745	2,306
Change in fair value of convertible promissory notes and convertible promissory notes due to related parties (including related party amounts of $12 and $4 for the years ended December 31, 2023 and 2022, respectively)	(1,043)	(177)
Related Party
Research and development (including related party amounts of $620 and $439 for the year ended December 31, 2023 and 2022, respectively)	620	439
Interest expense (including related party amounts of $431 and $2,271 for the year ended December 31, 2023 and 2022, respectively)	431	2,271
Change in fair value of convertible promissory notes and convertible promissory notes due to related parties (including related party amounts of $12 and $4 for the years ended December 31, 2023 and 2022, respectively)	$ 12	$ 4

CONSOLIDATED STATEMENTS OF CA_2

CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Paid-in-kind interest	$ 504	$ 2,271
Related Party
Paid-in-kind interest	$ 431	$ 2,271

Company Information

Company Information	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company Information	Company Information NKGen Biotech, Inc. (“ Company ” or “ NKGen ”), a Delaware corporation headquartered in Santa Ana, California, is a clinical-stage biotechnology company focused on the development and commercialization of innovative autologous, allogeneic and CAR-NK natural killer cell therapies utilizing their proprietary SNK (Super-Natural-Killer) platform. The Company is majority owned and controlled by NKMAX Co., Ltd. (“ NKMAX ”), a company formed under the laws of the Republic of Korea. The Company was originally Incorporated in Delaware on January 28, 2021 under the name Graf Acquisition Corp. IV (“ Graf ”), as a special-purpose acquisition company for the purpose of effecting a merger, capital stock exchange, asset acquisition, stock purchase, reorganization or engaging in any other similar business combination with one or more businesses or entities. On April 14, 2023, the Company entered into the Agreement and Plan of Merger by and among Graf, Austria Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of Graf (“ Merger Sub ”), and NKGen Biotech, Inc. (“ Merger Agreement ”). Upon consummation of the transactions under the Merger Agreement on September 29, 2023 (the “ Business Combination ”), Merger Sub merged with and into NKGen Biotech, Inc. (“ Legacy NKGen ”) with Legacy NKGen surviving the merger as a wholly owned subsidiary of Graf (the “ Merger ”). In connection with the consummation of the Business Combination (the “ Closing ”), Graf was renamed to “ NKGen Biotech, Inc. ” and Legacy NKGen changed its name to “ NKGen Operating Biotech, Inc. ” The Common Stock and warrants of the combined company began trading on The Nasdaq Stock Market LLC under the symbols “ NKGN ” and “ NKGNW ”, respectively, on October 2, 2023. Throughout the notes to the consolidated financial statements, unless otherwise noted or otherwise suggested by context, the “ Company ” refers to Legacy NKGen prior to the consummation of the Business Combination, and the Company after the consummation of the Business Combination. Liquidity The Company follows Financial Accounting Standards Board (“ FASB ”) Accounting Standards Codification (“ ASC ”) Topic 205-40, Presentation of Financial Statements — Going Concern , which requires that management evaluate whether there are relevant conditions and events that in aggregate raise substantial doubt about the entity’s ability to continue as a going concern and to meet its obligations as they become due within one year after the date that the consolidated financial statements are issued. Under the guidance, the Company must first evaluate whether there are conditions and events that raise substantial doubt about the entity’s ability to continue as a going concern (step 1). If the Company concludes substantial doubt is raised, management also is required to consider whether its plans alleviate that doubt (step 2). The Company has a limited operating history, has incurred significant operating losses since its inception, and the revenue and income potential of the Company’s business and market are unproven. The Company’s consolidated financial statements are prepared using the generally accepted accounting principles applicable to a going concern, which contemplates the realization of assets and liquidation of liabilities in the normal course of business. As of December 31, 2023 , the Company had an accumulated deficit of $162.1 million and cash and cash equivalents of less than $0.1 million . To date, the Company has funded its operations primarily with the net proceeds from the issuance of senior convertible promissory notes, the issuance of related party loans, draws upon a revolving line of credit, the issuance and sale of equity securities, PIPE warrants, private placements and proceeds from the Business Combination. The Company expects to incur substantial operating losses for the next several years and will need to obtain additional near-term financing in order to continue its research and development activities, initiate and complete clinical trials and launch and commercialize any product candidates for which it receives regulatory approval. Management has prepared cash flow forecasts which indicate that based on the Company’s expected operating losses and negative cash flows, there is substantial doubt about the Company’s ability to continue as a going concern for twelve months from the issuance of these consolidated financial statements. The Company plans to continue to fund its losses from operations and capital funding needs through additional debt or equity financings to be received from related parties, private equity, or other sources. If the Company is not able to secure adequate additional funding, the Company may be forced to make reductions in spending, extend payment terms with suppliers, liquidate assets where possible, suspend or curtail planned programs, or may be forced to cease operations or file for bankruptcy protection. Any of these actions could materially harm the Company’s business, results of operations and future prospects. There can be no

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation 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. Business Combination 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. Principles of Consolidation The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All significant intercompany balances and transactions have been eliminated in consolidation. 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, 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 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. The Company’s Chief Executive Officer is the Company’s CODM. The CODM reviews financial information presented on an enterprise-wide basis for purposes of making operating decisions, allocating resources, and evaluating financial performance. As such, the Company has determined that it operates in one reportable segment. Additionally, the Company generates all of its revenues, and maintains all of its long-lived assets within the United States. 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 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 March 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, 2023 , $0.3 million in restricted cash was recorded on the consolidated balance sheet. No restricted cash balances were recorded as of December 31, 2022. 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, 2023 and 2022 . 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. For each of the years ended December 31, 2023 and 2022 , no customer accounted for over 10% of total revenue and the Company had no trade accounts receivables outstanding. For each of the years ended December 31, 2023 and 2022 , the Company had zero and less than $0.1 million in other receivables, respectively. 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 and comprehensive loss. 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 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, 2022 . 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 and comprehensive loss. Deferred Debt Issuance Costs Costs incurred through the issuance of the revolving line of credit to parties who are providing short-term financing availability are reflected as deferred debt issuance costs. These costs are generally amortized to interest expense over the life of the financing instrument using the effective interest rate method or other methods approximating the effective interest method. As of December 31, 2023 , less than $0.1 million in deferred debt issuance costs were recorded to prepaid expenses and other current assets on the consolidated balance sheets. No deferred debt issuance costs were recorded as of December 31, 2022. Hybrid Instruments The Company follows Financial Accounting Standards Board (“ FASB ”) Accounting Standard Codification (“ ASC ”) 480, Distinguishing Liabilities from Equity , 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 FASB ASC 815, Derivatives and Hedging Activities , 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 and comprehensive loss each period. Bifurcated embedded derivatives are classified with the related host contract in the Company’s consolidated balance sheet. 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. Debt For convertible debt instruments that are not considered liabilities under ASC 480 or ASC 815, the Company applies ASC 470, Debt , 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. 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 sheet. When subscription receivables or shareholder receivables are not received prior to the balance sheet date in satisfaction of the requirements under ASC 505, Equity , the subscription or shareholder receivable is reclassified as a contra account to stockholder’s equity (deficit) on the balance sheet. Shareholder receivables represent amounts due from shareholders. If the shareholder does not fund the receivable prior to the balance sheet date, the Company records a receivable that is reclassified as a contra account to stockholder’s equity (deficit) on the balance sheet. 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. The Company has not recognized any impairment losses for the years ended December 31, 2023 and 2022 . 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 ASC 825, Financial Instruments . The Company elected the fair value option for its legacy convertible promissory notes, which met the required criteria under ASC 825, Financial Instruments . Interest expense associated with the legacy convertible promissory notes is included in the change in fair value of such instruments. Fair Value of Financial Instruments The Company follows ASC 820-10, Fair Value Measurements and Disclosures , issued by the FASB with respect to fair value reporting for financial assets and liabilities. The guidance defines fair value, provides guidance for measuring fair value and requires certain disclosures. The guidance does not apply to measurements related to share-based payments. The guidance discusses valuation techniques such as the market approach (comparable market prices), the income approach (present value of future income or cash flow), and the cost approach (cost to replace the service capacity of an asset or replacement cost). The guidance establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three broad levels. The Company’s financial instruments include cash and cash equivalents, prepaid expenses and other current assets, capitalized software, accounts payable, accrued expenses, convertible promissory notes issued from 2019 through 2022 to investors (“2019 Convertible Notes”), convertible promissory notes due to related parties (“Related Party Convertible Notes”, together with the 2019 Convertible Notes, “Convertible Notes”), debt due to a related party (“Related Party Loans”), and other current liabilities. The carrying amount of cash and cash equivalents, prepaid expenses and other current assets, capitalized software, accounts payable, accrued expenses, revolving line of credit, and related party loans, and other current liabilities are generally considered to be representative of their respective values because of the short-term nature of those instruments. The Company elects to account for its 2019 Convertible Notes and Related Party Convertible Notes, which meet the required criteria, at fair value at inception and at each subsequent reporting date. Subsequent changes in fair value of the Convertible Notes are recorded within other expenses, net on the accompanying consolidated statements of operations and comprehensive loss. Interest expense associated with the Convertible Notes is included in the change in fair value for the Convertible Notes. These estimates may be subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. 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. ASC 820, Fair Value Measurement , 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. 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 one year from December 31, 2023 . Employee Benefit Plan Effective January 1, 2019, the Company adopted and maintains a defined contribution plan, which qualifies under Section 401(k) of the Internal Revenue Code, on behalf of its eligible employees. Upon consummation of the Business Combination, the Company adopted the 2023 equity incentive plan (“2023 Plan”), at which date NKGen determined it will no longer grant any additional awards under the 2019 Plan. Employee contributions are voluntary and are determined on an individual basis, limited to the maximum amount allowable under federal tax regulations. During the years ended December 31, 2023 and 2022 , the Company did not contribute to either plan. Revenue Recognition Historically, the Company recognized revenue in connection with Coronavirus Disease of 2019 (“ COVID-19 ”) testing services. During the first quarter of the year ended December 31, 2023 , the Company ceased providing COVID-19 testing services. The Company recognizes revenue in accordance with ASC 606, Revenue from Contracts with Customers , which applies to all contracts with customers, except for contracts within the scope of other standards, such as leases, insurance, collaboration arrangements, and financial instrument. Under ASC 606, revenue is recognized in a manner that depicts the transfer of control of a product or a service to a customer and reflects the amount of the consideration the Company is entitled to receive in exchange for such product or service. In doing so, the Company follows a five-step approach: (i) identify the contract with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations, and (v) recognize revenue when (or as) the customer obtains control of the product or service. The Company considers the terms of a contract and all relevant facts and circumstances when applying the revenue recognition standard. The Company applies the revenue recognition standard, including the use of any practical expedients, consistently to contracts with similar characteristics and in similar circumstances. The transaction price is the amount of consideration the Company is entitled to receive in exchange for the transfer of control of a product or a service to a customer. To determine the transaction price, the Company considers the existence of any significant financing component, the effects of any variable elements, noncash considerations and consideration payable to the customer. If a significant financing component exists, the transaction price is adjusted for the time value of money. If an element of variability exists, the Company must estimate the consideration it expects to receive and uses that amount as the basis for recognizing revenue as the product or the service is transferred to the customer. If a contract has multiple performance obligations, the Company allocates the transaction price to each distinct performance obligation in an amount that reflects the consideration the Company is entitled to receive in exchange for satisfying each distinct performance obligation. For each distinct performance obligation, revenue is recognized when (or as) the Company transfers control of the product or the service applicable to such performance obligation. In those instances where the Company first receives consideration in advance of satisfying its performance obligation, the Company classifies such consideration as contract liability until (or as) the Company satisfies such performance obligation. In those instances where the Company first satisfies its performance obligation prior to its receipt of consideration, the consideration is recorded as accounts receivable. The Company expenses incremental costs of obtaining and fulfilling a contract as and when incurred if the expected amortization period of the asset that would be recognized is one year or less, or if the amount of the asset is immaterial. Otherwise, such costs are capitalized as contract assets if they are incremental to the contract and amortized to expense proportionate to revenue recognition of the underlying contract. Collaboration Agreement The Company has entered into a research agreement that falls under the scope of 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 and comprehensive loss. Similarly, amounts that are owed to a collaboration partner are recognized as research and development expense in the consolidated statements of operations and comprehensive loss. 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 The Company accounts for its leases under 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 sheet. 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 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 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 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 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 and comprehensive 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. Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share for the year ended December 31, 2023 include the following: Private warrants 4,721,533 Working capital warrants 523,140 Public warrants 3,432,286 PIPE warrants 10,209,994 Stock options 2,078,986 SPA warrants 1,000,000 Senior convertible notes’ shares 1,000,000 Deferred founder shares (1) 1,173,631 Total 24,139,570 (1) As described in Note 8, Related Party Transactions , deferred founder shares do not have voting rights, do not participate in dividends and are not transferrable absent the Company’s consent. Therefore, while deferred founder shares are considered outstanding for legal purposes and are included in the total quantity of outstanding shares on the consolidated statements of stockholders’ equity (deficit), they are not considered outstanding for accounting purposes, including basic and diluted net loss per share purposes. Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share for the year ended December 31, 2022 includes stock options of 185,231 (after giving effect to the Exchange Ratio), in addition to the shares underlying the Legacy Convertible Notes. The Company is unable to quantify the number of shares underlying the legacy convertible notes for the year ended December 31, 2022 as the quantity of shares issuable upon conversion was not determinable for the period. Emerging Growth Company The Company is an “emerging growth company,” as defined in Section 2(a) of the Securities Act, as modified by the Jumpstart our Business Startups Act of 2012, (the “ JOBS Act ”), and it may take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies including, but not limited to, not being required to comply with the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act, reduced disclosure obligations regarding executive compensation in its periodic reports and proxy statements, and exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and shareholder approval of any golden parachute payments not previously approved. Further, Section 102(b)(1) of the JOBS Act exempts emerging growth companies from being required to comply with new or revised financial accounting standards until private companies (that is, those that have not had a Securities Act registration statement declared effective or do not have a class of securities registered under the Exchange Act) are required to comply with the new or revised financial accounting standards. The JOBS Act provides that a company can elect to opt out of the extended transition period and comply with the requirements that apply to non-emerging growth companies but any such election to opt out is irrevocable. The Company has elected not to opt out of such extended transition period which means that when a standard is issued or revised and it has

Reverse Recapitalization

Reverse Recapitalization	12 Months Ended
	Dec. 31, 2023
Reverse Recapitalization [Abstract]
Reverse Recapitalization	Reverse Recapitalization As discussed in Note 1, Company Information , the Closing of the Business Combination occurred on September 29, 2023. In connection with the Business Combination: • All of Legacy NKGen’s legacy convertible notes were converted into shares of Legacy NKGen common stock immediately prior to Closing and pursuant to their terms, totaling 5,579,266 shares, which were then cancelled and converted into 2,278,598 shares of the Company’s common stock after giving effect to the Exchange Ratio; • All of Legacy NKGen’s 38,185,814 issued and outstanding shares were cancelled and converted into 15,595,262 shares of the Company’s common stock after giving effect to the Exchange Ratio (inclusive of shares attributable to the Legacy NKGen convertible notes); • All of Legacy NKGen’s 5,146,354 issued and outstanding stock options were cancelled and converted into 2,101,760 outstanding stock options of the Company; • The Company’s amended and restated certificate of incorporation and amended and restated bylaws were adopted; • The Company adopted an employee stock purchase plan; and • The Company adopted the 2023 equity incentive plan. The other related events that occurred in connection with the Closing include the following: • The execution of the private placement agreements, as described in Note 4, Private Placement ; • The assumption of the public and private warrants, as described in Note 5, Warrants ; • The execution of the warrant subscription agreements, as described in Note 5, Warrants ; • The conversion of Legacy NKGen’s legacy convertible promissory notes, as described in Note 6, Convertible Notes ; • The execution of the securities purchase agreement, as described in Note 6, Convertible Notes ; and • The execution of the amended and restated sponsor support and lockup agreement, as described in Note 8, Related Party Transactions . Refer to Note 9, Fair Value of Financial Instruments , for the Company’s measurements with respect to the financial instruments issued in connection with the foregoing agreements. Legacy NKGen incurred $7.5 million of transaction costs in connection with the Business Combination, which was determined to be a capital-raising transaction for Legacy NKGen. Of the $7.5 million in transaction costs, $4.2 million and $3.3 million was allocated on a relative fair value basis to equity-classified instruments and liability-classified instruments, respectively. The following tables reconcile elements of the Business Combination to the Company’s consolidated financial statements, and should be read in conjunction with the footnotes referenced above (in thousands, except share amounts): Shares Graf public shares, net of redemptions 93,962 Private placement investors’ shares 3,683,010 Graf founder shares 2,516,744 Total Graf shares outstanding immediately prior to the Business Combination 6,293,716 Conversion of Legacy NKGen convertible promissory notes (after the application of the Exchange Ratio) 2,278,598 Legacy NKGen rollover shares (after the application of the Exchange Ratio) 13,316,662 Total Legacy NKGen shares 15,595,260 Total Company common stock outstanding immediately following the Business Combination 21,888,976 (In thousands) Recapitalization Closing proceeds Proceeds from issuance of common stock $ 1,667 Proceeds from issuance of PIPE warrants 10,210 Proceeds from issuance of senior convertible promissory notes with warrants 10,000 Closing disbursements Less: Payment of Graf deferred underwriter fees (1,250) Less: Payment of Graf transaction costs at Closing (1) (7,456) Less: Payment of Legacy NKGen transaction costs at Closing (3,510) Net cash proceeds from the Business Combination at Closing $ 9,661 Less: Payment of Legacy NKGen transaction costs prior to Closing (2,089) Net cash proceeds from the Business Combination $ 7,572 Noncash activity Conversion of legacy NKGen convertible promissory notes 18,913 Less: Operating liabilities assumed from Graf (860) Less: Unpaid transaction costs – assumed from Graf (1) (5,400) Less: Unpaid transaction costs – Legacy NKGen (1,938) Liability-classified instruments Less: Fair value of PIPE warrants (10,210) Less: Fair value of forward purchase derivative liability (20,201) Less: Fair value of senior convertible promissory notes (2) (9,707) Less: Fair value of private warrants (1,841) Less: Fair value of working capital warrants (204) Net equity impact of the Business Combination $ (23,876) (1) The Graf transaction costs includes a $4.0 million accrual related to a certain vendor to be paid in cash and common stock of $2.0 million each. At Closing, a cash payment of $1.3 million was disbursed to this vendor. The remaining $2.7 million amount was recognized as a component of the unpaid transaction costs assumed from Graf, of which $0.7 million represents a cash settlement obligation, and the remaining $2.0 million represents an obligation to issue a variable number of shares for a fixed monetary amount which was accounted for as a liability under ASC 480, Distinguishing Liabilities from Equity (“ASC 480”). Under ASC 480, the obligation to issue shares is not subsequently measured at fair value with changes recorded in earnings because the monetary amount is fixed. (2) Represents allocated fair value. As presented in the consolidated statements of stockholders’ equity (deficit) (in thousands): Net equity impact of the Business Combination $ (23,876) Loss on issuance of forward purchase contract 24,475 Transaction costs expensed 3,329 Total Impact of Business Combination on total stockholders’ deficit (1) $ 3,928 Issuance of subscription receivable 32,915 Par value of common stock issued (1) Total Impact of Business Combination on additional paid-in capital $ 36,842 (1) Excludes impact of the Business Combination on net loss, which is presented separately in the consolidated statements of stockholders’ equity (deficit).

Private Placement

Private Placement	12 Months Ended
	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Private Placement	Private Placement Initial Recognition Background Prior to the Closing, the Company entered into private agreements (“ Private Placement Agreements ”) with investors (“ FPA Investors ”) consisting of forward purchase agreements (“ Forward Purchase Agreements ”), subscription agreements, a side letter, and escrow agreements. The Private Placement Agreements closed on September 29, 2023. Pursuant to the Private Placement Agreements, the FPA Investors purchased 3,168,121 shares of common stock (“ FPA Shares ”) for $32.9 million (“ Prepayment Amount ”). Pursuant to the Private Placement Agreements the FPA Investors may subscribe for and purchase an additional 767,990 shares of common stock. The Prepayment Amount was deposited into escrow accounts. The terms of the Private Placement Agreements provide that following a one Measurement Period ”), funds in the escrow accounts may be released to the FPA Investors, the Company or a combination of both based on a combination of factors, including the volume weighted average price of the Company’s common stock (“ VWAP ”) over a specified valuation period during the Measurement Period (“ Reset Price ”), the number of shares sold by the FPA Investors during the Measurement Period, and the application of antidilution provisions. The Private Placement Agreements expire at the end of the Measurement Period. All funds in escrow will be released to the Company, the FPA Investors, or a combination of both, at or before the one year anniversary of the Closing. The maximum and minimum that could be released from escrow is the Prepayment Amount and zero, respectively, for both the FPA Investors and the Company. In addition, all interest earned on the funds in the escrow accounts will be released to the FPA Investors. During the Measurement Period, to the extent the Company’s share price approaches or exceeds $10.44 per share, the likelihood and amount of escrow funds to be released to the Company increases and the likelihood and amount of escrow funds to be released to the FPA Investors decreases. Conversely, during the Measurement Period, to the extent the Company’s share price decreases below $10.44 per share, the likelihood and amount of escrow funds to be released to the Company decreases and the likelihood and amount of escrow funds to be released to the FPA Investors increases. Other drivers of settlement outcomes include the number of shares sold by FPA Investors to third parties during the Measurement Period, whereby the selling of shares may decrease portions of escrow funds to be released to the FPA Investors by up to $2.00 per share sold, the application of antidilution provisions, the timing of sales and settlements, among other factors. Additionally, a prepayment shortfall of $0.1 million was established in connection with the Private Placement Agreements (“ Prepayment Shortfall ”). Pursuant to the terms and conditions of the Private Placement Agreements, sales of FPA Shares to third-parties are required to first be applied towards the Prepayment Shortfall prior to the subscription receivable (described further below). In addition to the FPA Shares, the FPA Investors received 514,889 shares of common stock for no incremental consideration (“ Bonus Shares ”). The Bonus Shares are not subject to an escrow arrangement. Accounting All FPA Shares and Bonus Shares are outstanding shares of the Company that are not held in escrow, are transferrable without restrictions, and have the same voting as well as dividend and liquidation participation rights as other shares of the Company. Accordingly, such shares are equity classified and presented together with other shares of common stock in the consolidated financial statements. The escrow agreements provide that funds placed into escrow are held in escrow for the benefit of the FPA Investors until they are released to the Company pursuant to the terms of the Private Placement Agreements and the Company’s creditors do not have access to the funds held in escrow in the event of bankruptcy of the Company. Accordingly, the Company accounted for the original Prepayment Amount of $32.9 million as a contra-equity subscription receivable because the funds held in escrow represent receivables from shareholders. The features of the Private Placement Agreements met the derivatives criteria under ASC 815 because they contained an underlying, notional amount, payment provision, and net settlement. Accordingly, a derivative liability was recognized based on the estimated measurement of the portion of the funds in escrow that could be released to the FPA Investors, based on circumstances existing as of Closing. The net balance of the Prepayment Amount presented as a subscription receivable and the derivative liability when considered together represents the estimated amount of escrow funds the Company expects to receive from the escrow accounts. Subsequent changes in fair value of the derivative liability associated with the Private Placement Agreements will be recognized through earnings on a quarterly basis. Upon the Closing, in addition to the $32.9 million subscription receivable, a loss on issuance of forward purchase contract totaling $24.5 million was recorded, which consisted of the fair value of the derivative liability of $20.2 million plus the fair value of the Bonus Shares of $4.3 million. The forward purchase derivative liability is treated as a current liability because the Private Placement Agreements mature or otherwise are subject to early termination at or prior to the one year at or before the one year anniversary of the Closing. December 2023 Amendment On December 26, 2023, the Company and an FPA Investor entered into an amendment to their Forward Purchase Agreement (" FPA Amendment ") for total proceeds of $0.5 million. No other Private Placement agreements were amended during the year ended December 31, 2023. The FPA Amendment provided that, (i) 200,000 FPA Shares were re-designated to Bonus Shares, (ii) the definition of Reset Price was changed (“ Amended Reset Price ”), (iii) the definition of the prepayment shortfall was amended (“ Amended Prepayment Shortfall ”), and (iv) the funds in the escrow account were transferred to a separate account held by the FPA Investor. The funds from the FPA Investor in connection with the amendment were not received by the Company until January 2024. The terms of the Amended Reset Price provide for (i) a rolling ceiling effective as of the FPA Amendment execution date based on a weekly trailing VWAP such that the Company does not benefit from increases in share price during the Measurement Period, and (ii) discounts of generally 10% to the VWAP measurement that benefit the FPA Investor. Proceeds from the sale of FPA Shares by FPA Investors to third parties are required to be treated as a reduction to the prepayment shortfall until no balance remains in the prepayment shortfall (“ Shortfall Sales ”), at which point proceeds from such sales of stock may be treated as reductions to the subscription receivable that may result in cash proceeds to the Company. If all FPA Shares are sold without full satisfaction of the prepayment shortfall, the Company is required, at their election, to either pay a cash amount equal to the remaining prepayment shortfall balance or issue additional shares at 90% of the VWAP for the trailing 20 trading days. The terms of the Amended Prepayment Shortfall provide for a $0.5 million increase to the FPA Investor’s pre-existing prepayment shortfall of $0.1 million. Upon execution of the FPA Amendment, the Company recognized a loss on amendment to forward purchase contract as set forth below (in thousands): Loss on Amendment Reduction of subscription receivable $ 15,123 Reduction in forward purchase derivative liability (14,181) Shareholder receivable (500) Loss on amendment to forward purchase contract $ 442 The $0.4 million loss recognized in connection with the FPA Amendment represents the reduction in cash proceeds the Company may receive under the forward purchase contract, partially offset by the reduction in the forward purchase derivative liability and the shareholder receivable. As a result of the FPA Amendment, the maximum cash proceeds the Company could receive under the forward purchase contract, reflected in the subscription receivable balance, was lowered. The reduction in the subscription receivable of $15.1 million was caused by (i) the Amended Reset Price, which reduced the maximum price per FPA Share the Company could receive (initially, $10.44 per share), (ii) the re-designation of 200,000 FPA Shares to Bonus Shares, reducing the total quantity of FPA Shares, and (iii) the Amended Prepayment Shortfall, which increased the prepayment shortfall amount. The Company does not receive any consideration for sales or settlements of Bonus Shares or Shortfall Sales, described further below. In addition to the reduction in the subscription receivable, the Company recognized a corresponding reduction in the fair value of the forward purchase derivative liability of $14.2 million . Sales of FPA Shares Pursuant to the terms and conditions of the Private Placement Agreements, any sales of the Company’s common stock associated with the Private Placement Agreements may not be treated as sales of Bonus Shares until all FPA Shares are sold, at which point such sales of stock may be considered sales of Bonus Shares. Following the FPA Amendment, the FPA Investor sold 139,793 shares of the Company’s common stock to third parties, which were treated as Shortfall Sales of FPA Shares. Accordingly, the balance of the subscription receivable was not impacted. No other sales of FPA Shares occurred during the year ended December 31, 2023. Change in fair value As set forth above in this Note 4, the forward purchase derivative liability represents the portion of the reduced subscription receivable, that may be released to the FPA Investors rather than the Company. G ains and losses resulting from the remeasurement of changes in the fair value of the forward purchase derivative liability are recognized in earnings on a quarterly basis. Refer to Note 9, Fair Value of Financial Instruments , for further discussion.

Warrants

Warrants	12 Months Ended
	Dec. 31, 2023
Warrants [Abstract]
Warrants	Warrants As of December 31, 2023, all warrants described below remained outstanding and unexercised. Public Warrants In connection with Graf’s initial public offering (“ IPO ”), 3,432,286 warrants were issued to Graf’s investors (“ Public Warrants” ). The Public Warrants, which entitle th e registered holder to purchase one share of the Company’s common stock, have an exercise price of $11.50 per warrant, became exercisable 30 days after the completion of the Business Combination, and are set to expire five years from the completion of the Business Combination, or earlier upon redemption. The Public Warrants may be called for redemption at the sole discretion of the Company if the Company’s stock price equals or exceeds $18.00 per share and other certain conditions are met. The Public Warrants are equity classified due to terms indexed to the Company’s own stock and the satisfaction of other equity classification criteria. Private Warrants Concurrently with Graf’s IPO, Graf issued 4,721,533 warrants to Graf Acquisition Partners IV LLC (“ Private Warrants ”). The terms of the Private Warrants are identical to the Public Warrants with an exercise price of $11.50 per warrant, except that they are subject to certain transfer and sale restrictions and are not optionally redeemable so long as they are held by the initial purchasers or their permitted transferees. Additionally, the Private Warrants are exercisable on a cashless basis. If the Private Warrants are held by a party other than the initial purchasers or their permitted transferees, the Private Warrants will be redeemable by the Company and exercisable by such holders on the same basis as the Public Warrants. The Private Warrants are liability classified due to terms not indexed to the Company’s own stock. As described in Note 8, Related Party Transactions, the Private Warrants are a related party financial instrument. Private Warrants are classified to non-current liabilities because their term ends beyond one year from the latest consolidated balance sheet date. SPA Warrants Together with the issuance of the Senior Convertible Notes described in Note 6, Convertible Notes , 1,000,000 warrants were issued to NKMAX at an exercise price of $11.50 per warrant (“ SPA Warrants ”). The terms of the SPA Warrants are identical to the terms of the Public Warrants with redemption at the sole discretion of the Company if the Company’s stock price equals or exceeds $18.00 per share and other certain conditions are met. The SPA Warrants are equity classified due to terms indexed to the Company’s own stock and the satisfaction of other equity classification criteria, including redemption in the Company’s control if the Company’s stock price equals or exceeds $18.00 per share. As described in Note 8, Related Party Transactions, the SPA Warrants are a related party financial instrument. Working Capital Warrants Prior to the Closing, Graf executed drawdowns upon a working capital loan facility. Upon Closing, the $0.8 million balance of the working capital loan facility was settled through the issuance of 523,140 warrants (“ Working Capital Warrants” ). The terms of the Working Capital Warrants are identical to the terms of the Private Warrants with an exercise price of $11.50 per warrant. The Working Capital Warrants are liability classified due to terms not indexed to the Company’s own stock. As described in Note 8, Related Party Transactions, the Working Capital Warrants are a related party financial instrument. Working Capital Warrants are classified to non-current liabilities because their term ends beyond one year from the latest consolidated balance sheet date. PIPE Warrants Prior to the Closing, the Company entered into warrant subscription agreements (the “ Warrant Subscription Agreements ”) with certain investors (“ Warrant Investors ”), which closed on September 29, 2023. Pursuant to the Warrant Subscription Agreements, the Warrant Investors purchased an aggregate of 10,209,994 warrants, at a purchase price of $1.00 per warrant (“ PIPE Warrants ”) for total proceeds of $10.2 million. The PIPE Warrants are exercisable for cash (or by “cashless” exercise under certain circumstances) during the five-year period beginning on the Closing. One-third of the PIPE Warrants are exercisable initially at $10.00 per warrant, one-third of the PIPE Warrants are exercisable initially at $12.50 per warrant, and one-third of the PIPE Warrants are exercisable initially at $15.00 per warrant. The initial exercise prices of each tranche are subject to adjustment every 180 days after the Closing based upon declines in trading prices of the Company’s common stock, as well as antidilution adjustments for stock splits, stock dividends, and the like. In addition, the PIPE Warrants contain a downside protection provision, pursuant to which the Warrant Investors may demand a cashless exchange of certain PIPE Warrants and, to the extent the relevant reference price is less than $1.50 per share, a cash payment calculated as the difference between $1.50 per share and the then-current exercise price multiplied by the applicable number of warrant shares shall be paid to the Warrant Investors. The PIPE Warrants are liability classified due to terms not indexed to the Company’s own stock and their cash settlement provisions. PIPE Warrants are classified to non-current liabilities because their term ends beyond one year from the latest consolidated balance sheet date.

Convertible Notes

Convertible Notes	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Convertible Notes	Convertible Notes Legacy Convertible Notes From November to December 2019, the Company issued convertible promissory notes to investors (“ 2019 Convertible Notes ”) and related parties (“ 2019 Related Party Convertible Notes ”). From March to September 2023, the Company issued additional convertible promissory notes issued to investors (“ 2023 Convertible Notes ”) and to related parties (“ 2023 Related Party Convertible Notes ”), collectively referred to as “ Legacy Convertible Notes ”. Total proceeds raised from the 2019 Convertible Notes and 2019 Related Party Convertible Notes were $10.8 million and $0.3 million, respectively, which each bore interest at 1.7% per year and had a maturity date of December 31, 2023. Total proceeds raised from the 2023 Convertible Notes and 2023 Related Party Convertible Notes were $6.1 million and $0.1 million, respectively, which each bore interest at 4.6% per year and had maturity dates of three years from their respective issuance dates. The terms of the Legacy Convertible Notes provided for conversion into common stock upon the occurrence of a qualified financing transaction, including upon the Closing of the Business Combination. Pursuant to their terms, immediately prior to Closing, all of the Legacy Convertible Notes were converted into 5,579,266 shares of Legacy NKGen common stock, which then converted into 2,278,598 shares of the Company’s Common Stock at Closing based on the Exchange Ratio. Senior Convertible Notes Prior to the Closing, the Company entered into convertible note subscription agreements (“ Securities Purchase Agreement ”) with NKMAX for total proceeds of $10.0 million , with a four -year term and an interest rate of 5.0% paid in cash semi-annually or 8.0% paid in kind (“ Senior Convertible Notes ”), which closed on September 29, 2023. Interest began accruing at Closing and is payable semi-annually in arrears, with interest that is paid in kind (if applicable) increasing the principal amount outstanding on each interest payment date. The Company currently expects to make their interest payments in-kind in lieu of periodic cash payments. The Senior Convertible Notes are convertible at any time, in whole or in part, at NKMAX’s option at a conversion price of $10.00 per share of common stock (subject to anti-dilution adjustments in the event of stock splits and the like). The Senior Convertible Notes have a put option which may be exercised by NKMAX 2.5 years after the issuance of the Senior Convertible Notes. No less than six months after exercise of the put option, the Company will be required to repay all principal and accrued interest of the Senior Convertible Notes. Should the put option remain unexercised, the outstanding principal and accrued interest will be due and payable on September 29, 2027. Additionally, as described in Note 5, Warrants , together with the Securities Purchase Agreement, the SPA Warrants were issued to NKMAX, and accordingly, a relative fair value allocation was applied and discount was recognized on the Senior Convertible Notes as set forth in Note 9, Fair Value of Financial Instruments . There are no financial or non-financial covenants associated with the Senior Convertible Notes. During the year ended December 31, 2023, the Company recorded $0.2 million of interest expense and discount amortization related to the Senior Convertible Notes. As described in Note 8, Related Party Transactions, the Senior Convertible Notes are a related party financial instrument. The following table presents a reconciliation of the Senior Convertible Notes (in thousands): Senior Convertible Balance as of December 31, 2022 $ — Issuance 9,707 Amortization of discount 17 Paid-in-kind interest 206 Balance as of December 31, 2023 $ 9,930 Debt Revolving Line of Credit In June 2023, the Company entered into a $5.0 million revolving line of credit agreement (as amended on September 19, 2023, January 30, 2024 and April 5, 2024) with a commercial bank with a one-year term and an interest rate based on the higher of (i) the one month secured overnight financing rate plus 2.9% or (ii) 7.5%. Issuance fees of $0.1 million were incurred in connection with this revolving line of credit. All outstanding balances under the revolving line of credit were due and payable on June 20, 2024. In April 2024, the agreement was amended to extended the maturity date of the revolving line of credit to September 18, 2024. The revolving line of credit is secured by all of the Company’s assets, including a deed of trust over the Company’s owned real property located in Santa Ana, California. The Company was required to maintain deposits with the lender in an amount of at least $15.0 million from a certain period of time as long as there was a debt balance outstanding. The Company was in compliance with our debt covenants as of December 31, 2023. 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. Additionally, the Company is required to maintain a restricted cash balance of $0.3 million following the issuance. As of December 31, 2023, the interest rate for the revolving line of credit was 8.2%. Through December 31, 2023, the Company drew down $4.9 million upon the revolving line of credit and no repayments of drawdowns occurred. Interest expense of $0.2 million was incurred upon the revolving line of credit, which was paid in cash during the year ended December 31, 2023. No interest expense was incurred for the revolving line of credit during the year ended December 31, 2022. Related Party Loans Between August 2019 and April 2023, the Company entered into related party loans with NKMAX (“Related Party Loans”). In December 2022, the then-outstanding aggregate Related Party Loans’ principal and interest of $66.1 million was converted into 6,943,789 shares of common stock (after the application of the Exchange Ratio) which was recognized as a capital contribution for the year ended December 31, 2022. From January through April 2023, the Company entered into additional Related Party Loans with NKMAX for aggregate gross proceeds of $5.0 million. These additional Related Party Loans bear an interest rate of 4.6% and mature on December 31, 2024. There are no financial or non-financial covenants associated with the Related Party Loans. The additional Related Party Loans are not convertible into equity. In connection with the Related Party Loans, interest expenses incurred were $0.2 million and $2.3 million for the year ended December 31, 2023 and 2022, respectively. Related party interest payable amounts recorded to other current liabilities on the consolidated balance sheets were $0.2 million and zero as of December 31, 2023 and December 31, 2022, respectively. Short Term Related Party Loan In September 2023 , NKGen raised $0.3 million in proceeds in connection with a related party loan with a 30 -day term and an interest rate of 5.1% (“ Short Term Related Party Loan ”). This related party loan was not convertible into equity and was repaid in cash on October 5, 2023. Related party interest expense was less than $0.1 million for the year ended December 31, 2023 , and zero for the year ended December 31, 2022 . Paycheck Protection Program Loan In May 2020, the Company received loan proceeds of $1.1 million pursuant to the Paycheck Protection Program (“PPP”). The PPP, established as part of the CARES Act, provides loans for small businesses to cover qualified payroll costs, rent, utilities, and interest on mortgage and other debt obligations. The loan has an interest rate of 1.0%. The loan was paid off in May 2022. The Company recorded interest expense of $0.1 million related to the PPP loan to interest expense in the consolidated statements of operations and comprehensive loss for the year ended December 31, 2022. No amounts related to the Paycheck Protection Program Loan were recorded as of December 31, 2023 .

Debt

Debt	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Debt	Convertible Notes Legacy Convertible Notes From November to December 2019, the Company issued convertible promissory notes to investors (“ 2019 Convertible Notes ”) and related parties (“ 2019 Related Party Convertible Notes ”). From March to September 2023, the Company issued additional convertible promissory notes issued to investors (“ 2023 Convertible Notes ”) and to related parties (“ 2023 Related Party Convertible Notes ”), collectively referred to as “ Legacy Convertible Notes ”. Total proceeds raised from the 2019 Convertible Notes and 2019 Related Party Convertible Notes were $10.8 million and $0.3 million, respectively, which each bore interest at 1.7% per year and had a maturity date of December 31, 2023. Total proceeds raised from the 2023 Convertible Notes and 2023 Related Party Convertible Notes were $6.1 million and $0.1 million, respectively, which each bore interest at 4.6% per year and had maturity dates of three years from their respective issuance dates. The terms of the Legacy Convertible Notes provided for conversion into common stock upon the occurrence of a qualified financing transaction, including upon the Closing of the Business Combination. Pursuant to their terms, immediately prior to Closing, all of the Legacy Convertible Notes were converted into 5,579,266 shares of Legacy NKGen common stock, which then converted into 2,278,598 shares of the Company’s Common Stock at Closing based on the Exchange Ratio. Senior Convertible Notes Prior to the Closing, the Company entered into convertible note subscription agreements (“ Securities Purchase Agreement ”) with NKMAX for total proceeds of $10.0 million , with a four -year term and an interest rate of 5.0% paid in cash semi-annually or 8.0% paid in kind (“ Senior Convertible Notes ”), which closed on September 29, 2023. Interest began accruing at Closing and is payable semi-annually in arrears, with interest that is paid in kind (if applicable) increasing the principal amount outstanding on each interest payment date. The Company currently expects to make their interest payments in-kind in lieu of periodic cash payments. The Senior Convertible Notes are convertible at any time, in whole or in part, at NKMAX’s option at a conversion price of $10.00 per share of common stock (subject to anti-dilution adjustments in the event of stock splits and the like). The Senior Convertible Notes have a put option which may be exercised by NKMAX 2.5 years after the issuance of the Senior Convertible Notes. No less than six months after exercise of the put option, the Company will be required to repay all principal and accrued interest of the Senior Convertible Notes. Should the put option remain unexercised, the outstanding principal and accrued interest will be due and payable on September 29, 2027. Additionally, as described in Note 5, Warrants , together with the Securities Purchase Agreement, the SPA Warrants were issued to NKMAX, and accordingly, a relative fair value allocation was applied and discount was recognized on the Senior Convertible Notes as set forth in Note 9, Fair Value of Financial Instruments . There are no financial or non-financial covenants associated with the Senior Convertible Notes. During the year ended December 31, 2023, the Company recorded $0.2 million of interest expense and discount amortization related to the Senior Convertible Notes. As described in Note 8, Related Party Transactions, the Senior Convertible Notes are a related party financial instrument. The following table presents a reconciliation of the Senior Convertible Notes (in thousands): Senior Convertible Balance as of December 31, 2022 $ — Issuance 9,707 Amortization of discount 17 Paid-in-kind interest 206 Balance as of December 31, 2023 $ 9,930 Debt Revolving Line of Credit In June 2023, the Company entered into a $5.0 million revolving line of credit agreement (as amended on September 19, 2023, January 30, 2024 and April 5, 2024) with a commercial bank with a one-year term and an interest rate based on the higher of (i) the one month secured overnight financing rate plus 2.9% or (ii) 7.5%. Issuance fees of $0.1 million were incurred in connection with this revolving line of credit. All outstanding balances under the revolving line of credit were due and payable on June 20, 2024. In April 2024, the agreement was amended to extended the maturity date of the revolving line of credit to September 18, 2024. The revolving line of credit is secured by all of the Company’s assets, including a deed of trust over the Company’s owned real property located in Santa Ana, California. The Company was required to maintain deposits with the lender in an amount of at least $15.0 million from a certain period of time as long as there was a debt balance outstanding. The Company was in compliance with our debt covenants as of December 31, 2023. 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. Additionally, the Company is required to maintain a restricted cash balance of $0.3 million following the issuance. As of December 31, 2023, the interest rate for the revolving line of credit was 8.2%. Through December 31, 2023, the Company drew down $4.9 million upon the revolving line of credit and no repayments of drawdowns occurred. Interest expense of $0.2 million was incurred upon the revolving line of credit, which was paid in cash during the year ended December 31, 2023. No interest expense was incurred for the revolving line of credit during the year ended December 31, 2022. Related Party Loans Between August 2019 and April 2023, the Company entered into related party loans with NKMAX (“Related Party Loans”). In December 2022, the then-outstanding aggregate Related Party Loans’ principal and interest of $66.1 million was converted into 6,943,789 shares of common stock (after the application of the Exchange Ratio) which was recognized as a capital contribution for the year ended December 31, 2022. From January through April 2023, the Company entered into additional Related Party Loans with NKMAX for aggregate gross proceeds of $5.0 million. These additional Related Party Loans bear an interest rate of 4.6% and mature on December 31, 2024. There are no financial or non-financial covenants associated with the Related Party Loans. The additional Related Party Loans are not convertible into equity. In connection with the Related Party Loans, interest expenses incurred were $0.2 million and $2.3 million for the year ended December 31, 2023 and 2022, respectively. Related party interest payable amounts recorded to other current liabilities on the consolidated balance sheets were $0.2 million and zero as of December 31, 2023 and December 31, 2022, respectively. Short Term Related Party Loan In September 2023 , NKGen raised $0.3 million in proceeds in connection with a related party loan with a 30 -day term and an interest rate of 5.1% (“ Short Term Related Party Loan ”). This related party loan was not convertible into equity and was repaid in cash on October 5, 2023. Related party interest expense was less than $0.1 million for the year ended December 31, 2023 , and zero for the year ended December 31, 2022 . Paycheck Protection Program Loan In May 2020, the Company received loan proceeds of $1.1 million pursuant to the Paycheck Protection Program (“PPP”). The PPP, established as part of the CARES Act, provides loans for small businesses to cover qualified payroll costs, rent, utilities, and interest on mortgage and other debt obligations. The loan has an interest rate of 1.0%. The loan was paid off in May 2022. The Company recorded interest expense of $0.1 million related to the PPP loan to interest expense in the consolidated statements of operations and comprehensive loss for the year ended December 31, 2022. No amounts related to the Paycheck Protection Program Loan were recorded as of December 31, 2023 .

Related-Party Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2023
Related Party Transactions [Abstract]
Related-Party Transactions	Related Party Transactions Founder Shares Contemporaneously with the execution of the Merger Agreement, Graf and NKGen entered into an amended and restated sponsor support and lockup agreement (“ Amended and Restated Sponsor Support and Lockup Agreement ”). In connection with the Amended and Restated Sponsor Support and Lockup Agreement, of the 4,290,375 shares of Graf formerly held by Graf’s sponsor and insiders (“ Founder Shares ”): (i) 1,773,631 shares were forfeited, (ii) 1,173,631 shares became restricted shares subject to vesting conditions (“ Deferred Founder Shares ”), and (iii) the remaining 1,343,113 shares are subject to trading restrictions for up to two years and continued to be outstanding and fully vested shares. Deferred Founder Shares do not have voting rights, do not participate in dividends and are not transferable. During the vesting period of five years from Closing (“ Vesting Period ”), if the trading price or price per share consideration upon a change in control for Common Stock is greater than or equal to $14.00 at any 20 trading days in a 30 consecutive trading-day period, then 873,631 Deferred Founder Shares will immediately vest; and if greater than or equal to $20.00 at any 20 trading days in a 30 consecutive trading-day period, then an additional 300,000 Deferred Founder Shares will immediately vest. In the event there is a sale of the Company, then immediately prior to the consummation of such sale, the calculated Acquiror Sale Price, as defined in the agreement, will take into account the number of Deferred Founder Shares that will vest upon a change in control. Upon the expiration of the Vesting Period, unvested Founder Shares will be forfeited and cancelled for no consideration. All Founder Shares, including Deferred Founder Shares, are equity classified primarily due to terms indexed to the Company’s own stock, including upon a change in control. Related Party Financial Instruments The Company’s related party financial instruments include (i) the Founder Shares, including Deferred Founder Shares described above in this Note 8, (ii) the SPA Warrants described in Note 5, Warrants , (iii) the Working Capital Warrants described in Note 5, Warrants , (iv) the Senior Convertible Notes described in Note 6, Convertible Notes , (v) select Legacy Convertible Notes described in Note 6, Convertible Notes , (vi) the Related Party Loans described in Note 7, Debt , (vii) the Short Term Related Party Loan described in Note 7, Debt , and (viii) the Private Warrants described in Note 5, Warrants . Advisory and research services The Company was provided professional clinical program advisory services from Paul Song, prior to his hiring as Chief Executive Officer in December 2022 . No such services were provided to or incurred by the Company during the year ended December 31, 2023 . For the year ended December 31, 2022 , $0.4 million in research and development expenses related to these advisory services were recorded. As of December 31, 2022 , amounts payable of less than $0.1 million relating to advisory and research services from related parties remained outstanding, which were recorded to accounts payable and accrued expenses on the consolidated balance sheet. As of December 31, 2023 , no amounts payable remained outstanding relating to advisory and research services from related parties. Purchases of laboratory supplies For the year ended December 31, 2023 and December 31, 2022 , the Company recorded research and development expenses of $0.6 million and $0.1 million , respectively, associated with the purchase of laboratory supplies from NKMAX. As of December 31, 2023 and December 31, 2022 , $0.6 million and less than $0.1 million , respectively, remained outstanding relating to the purchase of laboratory supplies from NKMAX, which were recorded to accounts payable and accrued expenses on the consolidated balance sheet.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	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. The Company’s management used the following methods and assumptions to estimate the fair value of its financial instruments: 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. The carrying amounts of the Company’s financial assets and financial liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments. The Company does not measure assets at fair value on a recurring basis. Liabilities measured at fair value on a recurring basis as of December 31, 2023 are as follows (in thousands):  Fair Value Measurements at Reporting Date Using Balance as of Level 1 Level 2 Level 3 Private Warrants $ 378 $ — $ — $ 378 Working Capital Warrants 42 — — 42 Forward Purchase Derivative Liability 15,804 — — 15,804 PIPE Warrants 25,339 — — 25,339 Total $ 41,563 $ — $ — $ 41,563 In addition to items that are measured at fair value on a recurring basis, the Company also has liabilities that are measured at fair value on a nonrecurring basis. As these liabilities are not measured at fair value on a recurring basis, they are not included in the tables above. Liabilities that are measured at fair value on a nonrecurring basis as of December 31, 2023 include the Senior Convertible Notes. The valuation of the Senior Convertible Notes was $8.5 million as of December 31, 2023. The Senior Convertible Notes were determined to be in-scope of ASC 470, Debt . Accordingly, this instrument will not be measured at fair value on a recurring basis as the fair value measurement of this instrument was for purposes of the relative fair value allocation described below as the Senior Convertible Notes were issued together with the SPA Warrants. Legacy Convertible Notes The following table presents a reconciliation of the Legacy Convertible Notes (in thousands): 2019 2019 Related 2023 2023 Related Total Balance as of December 31, 2021 $ 11,219 $ 259 $ — $ — $ 11,478 Change in fair value 173 4 — — 177 Balance as of December 31, 2022 11,392 263 — — 11,655 Issuance — — 6,090 125 6,215 Change in fair value 1,083 13 (52) (1) 1,043 Conversion and settlement (12,475) (276) (6,038) (124) (18,913) Balance as of December 31, 2023 $ — $ — $ — $ — $ — The Company historically determined the carrying amount of the Legacy Convertible Notes using a scenario-based analysis that estimates the fair value of the Legacy Convertible Notes based on the probability-weighted present value of expected future investment returns by measuring the fair value of similar debt instruments that do not have the conversion feature. If no similar debt instrument existed, fair value was estimated by using assumptions that market participants would use in pricing a debt instrument, including market interest rates, credit standing, yield curves and volatilities. The following unobservable assumptions were used in determining the fair value of the Legacy Convertible Notes as of December 31, 2022: Probability of conversion — Probability of holding until maturity without conversion — Remaining term until potential conversion trigger date (years) 0 Discount yield (1) 20.0 % (1) Estimated using a comparable bond analysis and under S&P Global Inc.’s credit rating scale using a multinominal logical regression. The fair value of Legacy Convertible Notes immediately prior to their conversion at Closing was based upon the fair value of the 2,278,598 shares of the Company’s common stock issued upon their conversion totaling $18.9 million, at a per share value of $8.30 based upon the fair value of the Company’s common stock at Closing, which was the conversion date. Senior Convertible Notes The Senior Convertible Notes were recognized at Closing on September 29, 2023. Additionally, as described above in Note 6, Convertible Notes , the Senior Convertible Notes are not measured at fair value on a recurring basis. As such, a reconciliation of the Senior Convertible Notes is not presented. The Company determined the stand-alone fair value of the Senior Convertible Notes using a binomial lattice model, which generates a distribution of stock prices over the term of the note, calculates the associated payoff for the note, and discounts the probability-weighted values from the lattice back to the valuation date. The fair value was estimated by using assumptions that market participants would use in pricing a convertible debt instrument, including market interest rates, credit rating, yield curves, and volatilities. The following unobservable assumptions were used in determining the fair value of the Senior Convertible Notes at Closing: Credit spread (1) 12.1 % Equity volatility 45.0 % (1) Estimated using a comparable bond analysis and under S&P Global Inc.’s credit rating scale using a multinominal logical regression. As of December 31, 2023, the Company determined the fair value of the Senior Convertible Notes was $8.5 million. The following unobservable assumptions were used in determining the fair value of the Senior Convertible Notes at December 31, 2023: Credit spread (1) 12.7 % Equity volatility 45.0 % (1) Estimated using a comparable bond analysis and under S&P Global Inc.’s credit rating scale using a multinominal logical regression. Private Warrants and Working Capital Warrants The Private Warrants and Working Capital Warrants were recognized at Closing on September 29, 2023. The fair value as of Closing was $1.8 million and $0.2 million, respectively. As of December 31, 2023, the fair value was $0.4 million and less than $0.1 million respectively. The following table presents a reconciliation of the Private Warrants and Working Capital Warrants (in thousands): Private Working Total Balance as of December 31, 2022 $ — $ — $ — Recognition in connection with Business Combination 1,841 204 2,045 Change in fair value (1,464) (162) (1,626) Balance as of December 31, 2023 $ 377 $ 42 $ 419 The terms of the Private Warrants and Working Capital Warrants are identical. Accordingly, the methodology and assumptions used to value these instruments is identical. The fair value of the Private Warrants and Working Capital Warrants were measured using a Black-Scholes model. The estimated fair value of the Private Warrants and Working Capital Warrants was determined using Level 3 inputs. Inherent in a Black-Scholes model are assumptions related to expected stock-price volatility, expected life, risk-free interest rate and dividend yield. The Company estimates the volatility of its Private Warrants and Working Capital Warrants based on implied volatility from the Company’s traded Private Warrants and Working Capital Warrants and from historical volatility of select peer company’s common stock that matches the expected remaining life of the Private Warrants and Working Capital Warrants. The risk-free interest rate is based on the U.S. Treasury zero-coupon yield curve on the grant date for a maturity similar to the expected remaining life of the Private Warrants and Working Capital Warrants. The expected life of the Private Warrants and Working Capital Warrants is assumed to be equivalent to their remaining contractual term. The dividend rate is based on the historical rate, which the Company anticipates remaining at zero. The following unobservable assumptions were used in determining the fair value of the Private Warrants and Working Capital Warrants at Closing: Private Warrants’ volatility 9.6 % Dividend yield (per share) — The following unobservable assumptions were used in determining the fair value of the Private Warrants and Working Capital Warrants as of December 31, 2023: Private Warrants’ volatility 35.3 % Dividend yield (per share) — PIPE Warrants The PIPE Warrants were recognized at Closing on September 29, 2023. The fair value as of December 31, 2023 was $25.3 million. The following table presents a reconciliation of the PIPE Warrants (in thousands): PIPE Balance as of December 31, 2022 $ — Issuance 10,210 Change in fair value 15,129 Balance as of December 31, 2023 $ 25,339 The fair value of the PIPE Warrants was measured using its respective transaction price of $10.2 million for 10,209,994 PIPE Warrants at a purchase price of $1.00 per warrant at Closing. As of December 31, 2023 the fair value of the PIPE Warrants was $25.3 million. The fair value of the PIPE Warrants was valued using level three inputs and was estimated using a Monte Carlo simulation approach. The Company’s common share price was assumed to follow a Geometric Brownian Motion over a period from the Valuation Date to the Expiration Date. The breadth of all possible scenarios was captured in an estimate of volatility, based on comparable companies’ historical equity volatilities, considering differences in their capital structure. For each simulation path, the Test Price and Reset Price were calculated based on the daily stock price during the measurement period. On each Reset Date, the downside protection condition was assessed to see if it was met by comparing the Test Price with the downside protection threshold price. The value of each tranche of warrants was then computed, factoring in any downside protection shares and downside protection cash, if applicable. The average value across this range of possible scenarios, discounted to present using the risk-free rate, was used as the fair value of the PIPE Warrants. The change in fair value of the PIPE Warrants was primarily attributable to select features of the Warrant Subscription Agreements, including strike price resets and downside protection which results in increased value as the Company’s stock price declines and stock price volatility increases. The following unobservable assumptions were used in determining the fair value of the PIPE Warrants at December 31, 2023: Credit spread 12.7 % Equity volatility 100.0 %   Forward Purchase Derivative Liability The forward purchase derivative liability was recognized at Closing on September 29, 2023. The fair value as of December 31, 2023 was $15.8 million. The following table presents a reconciliation of the Forward Purchase Derivative Liability (in thousands): Forward Forward purchase derivative liability at Close $ 20,201 Change in fair value in connection with the loss on amendment of forward purchase contract (14,181) Change in fair value of forward purchase derivative liability 9,784 Balance as of December 31, 2023 $ 15,804 The fair value of the forward purchase derivative liability was estimated using a Monte Carlo simulation approach. The Company’s common share price was simulated with daily time steps for a range of various possible scenarios. The breadth of all possible scenarios was captured in an estimate of volatility, based on comparable companies’ historical equity volatilities, considering differences in their capital structure. The simulated prices were compared against the settlement adjustment features of the Forward Purchase Agreements. Under each simulated scenario of future stock price, the Company calculated the value of the forward purchase derivative liability arrangement. The average value across this range of possible scenarios, discounted to present using the risk-free rate, was used as the fair value of the forward purchase derivative liability. The following unobservable assumptions were used in determining the fair value of the forward purchase derivative liability at Closing: Dividend yield 0.0 % Equity volatility 105.0 % The following unobservable assumptions were used in determining the fair value of the forward purchase derivative liability immediately before and after modification at December 26, 2023: Dividend yield 0.0 % Equity volatility 125.0 % The following unobservable assumptions were used in determining the fair value of the forward purchase derivative liability at December 31, 2023: Dividend yield 0.0 % Equity volatility 115.0 %  Relative Fair Values The Senior Convertible Notes were issued together with the SPA Warrants. Each instrument was recorded at its fair value, limited to a relative fair value based upon the percentage of its fair value to the total fair value based on the transaction price of the Securities Purchase Agreement of $10.0 million at Closing on September 29, 2023. The relative fair value of the SPA Warrants was treated as a discount to the Senior Convertible Notes, which will be amortized to interest expense over the term of the Senior Convertible Notes. The stand-alone fair value at initial recognition for the Senior Convertible Notes and SPA Warrants was $12.9 million and $0.4 million, respectively. The stand-alone fair value of the Senior Convertible Notes and SPA Warrants was $8.5 million and $0.1 million as of December 31, 2023. The relative fair value at initial recognition and as of December 31, 2023 for the Senior Convertible Notes and SPA Warrants was $9.7 million and $0.3 million, respectively.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Stockholders' Equity	Stockholder’s Equity Reverse Recapitalization As described in Note 2, Summary of Significant Accounting Policies , all historical equity data, including stock option data, in these consolidated financial statements has been retrospectively adjusted by the Exchange Ratio to reflect the reverse recapitalization that occurred on September 29, 2023. Common Stock As of December 31, 2023, the Company had authorized 500,000,000 shares of common stock, par value $0.0001 per share. As of December 31, 2023, 21,888,976 shares of common stock were issued and outstanding, and 478,111,024 shares of common stock were reserved for future issuance. Preferred Stock As of December 31, 2023, the Company had authorized 10,000,000 shares of preferred stock, par value $0.0001. As of December 31, 2023, zero shares of preferred stock were issued or outstanding. Employee Stock Purchase Plan Upon consummation of the Business Combination, the Company adopted an employee stock purchase plan (“ ESPP ”). The maximum number of shares of the Company’s common stock that may be issued under the ESPP is 3.0% of the fully diluted common stock of the Company, determined as of immediately following Closing. Such maximum number of shares is subject to automatic annual increases. The Company’s employees and the employees of any designated affiliates may participate in the ESPP. The purchase price of the ESPP shares is 85% of the lesser of the fair market value of the Company’s common stock on the first day of an offering or on the applicable date of purchase. As of December 31, 2023, there were no transactions with respect to the ESPP.  2023 Plan Upon consummation of the Business Combination, the Company adopted the 2023 equity incentive plan (“ 2023 Plan ”). The maximum number of shares of common stock that may be issued under the 2023 Plan is 12.0% of the fully diluted common stock of the Company, determined as of immediately following Closing. Such maximum number of shares is subject to automatic annual increases. Under the 2023 Plan, restricted shares and stock options with service or performance based conditions may be granted to employees and nonemployees. Upon the effective date of the 2023 Plan, the Company may not grant any additional awards under the 2019 Plan. As of December 31, 2023, no awards were granted under the 2023 Plan. 2019 Plan The Company’s 2019 Plan (“2019 Plan”) became effective on October 23, 2019. The 2019 Plan provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock unit awards and performance share awards to employees, directors, and consultants of the Company. As of December 31, 2023, the Company has only issued stock options. Stock options granted under the 2019 Plan expire no later than ten years from the date of grant and generally vest over a four-year period, with vesting occurring at a rate of 25% at the end of the first and thereafter in 36 equal monthly installments, or in the case of awards granted to board members, on a monthly basis over three The fair value of each employee and non-employee stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. Due to the Company’s limited operating history and a lack of company-specific historical and implied volatility data, the Company estimated expected volatility based on the historical volatility of a group of similar companies that are publicly traded. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. Due to the lack of historical exercise history, the expected term of the Company’s stock options for employees has been determined utilizing the “simplified” method for awards. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. The expected dividend yield is zero since the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future. A summary of the Company’s stock option activity for the year ended December 31, 2023 is as follows: Stock Options Weighted Outstanding as of December 31, 2022 185,231 $ 1.37 Granted 2,173,693 6.67 Forfeited (267,072) 6.56 Exercised (12,866) 0.88 Outstanding as of December 31, 2023 2,078,986 $ 6.25 The weighted average assumptions used in the Black-Scholes option pricing model to determine the fair value of stock option grants for the year ended December 31, 2023 were as follows: Common stock fair value $ 9.18 Risk-free interest rate 3.5% Expected volatility 111.0% Expected term (in years) 6.1 Expected dividend yield 0.0% Stock options outstanding, vested and expected to vest and exercisable as of December 31, 2023 are as follows: Number of Weighted Weighted- Total Outstanding as of December 31, 2022 185,231 6.98 $ 1.37 $ 980 Outstanding as of December 31, 2023 2,078,986 8.86 $ 6.25 $ 317 Vested and expected to vest as of December 31, 2023 2,078,986 8.86 $ 6.25 $ 317 Exercisable as of December 31, 2023 302,760 7.46 $ 3.79 $ 317 Intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value of the common stock for the options that had exercise prices that were lower than the per share fair value of the common stock on the related measurement date. The aggregate intrinsic value of stock options exercised during the year ended December 31, 2023 was $0.1 million . The aggregate fair value of stock options vested during the year ended December 31, 2023 was $1.2 million . As of December 31, 2023 , the total unrecognized stock-based compensation related to unvested stock option awards granted was $14.1 million , which the Company expects to recognize over a remaining weighted- average period of approximately 3.0 years . Stock-based compensation expense, recognized in the Company’s consolidated statements of operations and comprehensive loss for the 2019 Plan was recorded as follows (in thousands): Years ended 2023 2022 Research and development $ 898 $ 45 General and administrative 3,237 24 Total stock-based compensation expense $ 4,135 $ 69

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment, net	Property and Equipment, net Property and equipment, net consist of the following (in thousands): Useful Life December 31, December 31, Land — $ 5,025 $ 5,025 Buildings 40 years 8,325 8,325 Furniture and fixtures 7 years 749 677 Lab equipment 5 years 4,004 4,003 Leasehold improvements Lesser of estimated useful life or 52 52 Office equipment 5 years 17 17 Vehicles 5 years 112 112 18,284 18,211 Less: Accumulated depreciation (3,825) (2,690) $ 14,459 $ 15,521 Depreciation expense related to property and equipment was $1.1 million and $1.2 million for the years ended December 31, 2023 and 2022 , respectively. No gains or losses on the disposal of property and equipment have been recorded for each of the years ended December 31, 2023 and 2022

Additional Balance Sheet Inform

Additional Balance Sheet Information	12 Months Ended
	Dec. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Additional Balance Sheet Information	Additional Balance Sheet Information Prepaid expenses and other current assets consist of the following (in thousands): December 31, December 31, Prepaid expenses $ 1,565 $ 133 Other receivables 26 67 Revolving line of credit issuance fees 47 — Other 16 4 Prepaid expenses and other current assets $ 1,654 $ 204 Accounts payable and accrued expenses consist of the following (in thousands): December 31, December 31, Accounts payable $ 11,040 $ 975 Accrued liabilities 1,360 1,359 Employee compensation 911 291 Other 84 27 Accounts payable and accrued expenses $ 13,395 $ 2,652

Collaboration Agreement

Collaboration Agreement	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration Agreement	Collaboration Agreement On September 17, 2020, the Company entered into a strategic collaboration with Affimed GmbH (“ Affimed ”) to initiate a Phase 1/2 trial of SNK01 in combination with AFM24, a tetravalent biologic created by Affimed designed to direct NK cell killing of epidermal growth factor receptor (“ EGFR ”) expressing tumors. Under the collaboration agreement, the Company and Affimed split the development costs of the combination product equally. The study associated with the strategic collaboration with Affimed was discontinued by mutual agreement in June 2023. Total reductions to research and development expenses for the years ended December 31, 2023 and 2022 were $0.2 million and $0.4 million , respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases In February 2018 , the Company entered into an operating lease agreement for office space located in 10 Pasteur, Irvine with a lease term of approximately five years . Rent payments commenced in February 2018. The lease expired on February 5, 2023. In October 2021 , the Company entered into an operating lease agreement for office space located in 19700 Fairchild with a lease term of approximately two years with an option to extend the term for one two -year term, which at the time was not reasonably assured of exercise and therefore, not included in the lease term. Rent payments commenced in December 2021 . The lease expired on December 31, 2023 . On November 9, 2023, the Company entered into a new operating lease agreement for office space located in Irvine, California with a lease term of approximately three years and rent payments commencing on January 1, 2024 (“ New Office Lease ”). The lease commencement date is January 1, 2024. Future minimum lease payments under the New Office Lease are as follows (in thousands): Minimum lease 2024 $ 235 2025 242 2026 249 Total operating lease liability $ 726 License Agreements The Company has entered into exclusive license agreements with NKMAX, as amended in October 2021, April 2023 and August 2023 (“Intercompany License”), pursuant to which the Company acquired certain intellectual property. Pursuant to each license agreement, as consideration for an exclusive license to the intellectual property, the Company paid an upfront fee of $1.0 million (“Licensed Technology”). As the license has no alternative future use, the Company recognized the upfront fee as research and development expense in the consolidated statements of operations and comprehensive loss during the year ended December 31, 2020 . Additionally, the Company is also required to pay one-time milestone payments for the first receipt of regulatory approval by the Company or any of its affiliates for a Licensed Technology in the following jurisdictions (and amounts): the United States ( $5.0 million ), the European Union (“EU”) ( $4.0 million ), and four other countries ( $1.0 million each). The Company is obligated to pay a mid-single digit royalty on net sales of Licensed Technology by it, its affiliates or its sublicensees, subject to customary reductions. The Company is also required to pay a percentage of its sublicensing revenue ranging from a low double-digit percentage to a mid-single digit percentage. As of December 31, 2023 , the Company has not paid any milestone payments and no sales of Licensed Technology have occurred. Litigation The Company is subject to legal proceedings and claims, which arise in the ordinary course of business. The Company is not subject to any currently pending legal matters or claims that would have a material adverse effect on its financial position, results of operations or cash flows. In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future but have not yet been made. The Company accrues a liability for such matters when it is probable that future expenditures will be made, and such expenditures can be reasonably estimated. No amounts were accrued as of December 31, 2023 and December 31, 2022 .

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company is subject to taxation in the U.S. and various state jurisdictions. The Company is not subject to taxation in foreign countries. The provision for income taxes for the years ended December 31, 2023 and 2022 are as follows (in thousands): Years Ended December 31, 2023 2022 Current: Federal $ — $ — State — — Deferred: Federal 7 7 State — — Provision for income taxes $ 7 $ 7 A reconciliation of the income tax computed at federal statutory income tax rate to the reported provision for income taxes is as follows (in thousands): Years Ended December 31, 2023 2022 Tax benefit at statutory federal rate $ (17,419) $ (5,618) State tax, net of federal tax benefit (1,946) (1,694) Interest expense 47 477 Increase in valuation allowance 9,189 7,908 Permanent items 12 37 Stock compensation 359 (4) Unrealized loss FV of notes 219 — General business tax credit (1,278) (1,098) Loss on issuance of forward purchase contract 5,140 — Loss on amendment of the subscription receivable 93 — Loss on derivative valuation 4,890 — Other 701 (1) Provision for income taxes $ 7 $ 7 Significant components of the Company’s deferred income taxes are as follows (in thousands): Years Ended December 31, 2023 2022 Deferred tax assets: Net operating losses $ 22,843 $ 17,890 Tax credit carryforwards, net 4,523 3,285 Accrued expenses 395 347 Section 174 R&E capitalization 4,939 2,847 Intangibles 707 — Lease liability — 106 Stock-based compensation 699 20 Total deferred tax assets 34,106 24,495 Deferred tax liabilities: Operating lease right-of-use asset — (101) Property and equipment (406) (595) Total deferred tax liabilities (406) (696) Net deferred tax assets 33,700 23,799 Less: Valuation allowance (33,733) (23,825) Net deferred tax liability $ (33) $ (26) Realization of deferred tax assets is dependent upon future earnings, if any, the timing and amount of which are uncertain. Due to the lack of earnings history, the deferred tax assets have been offset by a valuation allowance net of reversing deferred tax liabilities that provided for a source of future taxable income. The valuation allowance increased by approximately $9.9 million and $7.9 million for the years ended December 31, 2023 and 2022 , respectively. The Company has net operating loss carryforwards for federal and state income tax purposes of approximately $76.3 million and $96.7 million , respectively, as of December 31, 2023 . Under the Tax Act and Jobs Act of 2017, the $76.3 million of federal net operating losses generated after December 31, 2017 will be carried forward indefinitely. The California net operating loss carryforwards will begin to expire in 2037 unless previously utilized. As of December 31, 2023 , the Company also had federal and California research and development tax credit carryforward of approximately $3.2 million and $2.3 million , respectively. The federal research and development credit carryforwards will begin to expire in 2038. The California research and development credit carryforwards are available indefinitely. Federal and California tax laws imposes significant restrictions on the utilization of net operating loss carryforwards in the event of a change in ownership of the Company, as defined by Internal Revenue Code Sections 382 and 383. The Company has not completed a formal study to determine the limitations on their tax attributes due to change in ownership and may have limitations on the utilization of net operating loss carryforwards, credit carryforwards, or other tax attributes due to ownership changes. The Inflation Reduction Act of 2022 (“IRA”) which incorporates a Corporate Alternative Minimum Tax (CAMT) was signed on August 16, 2022. The changes will be effective for the tax years beginning after December 31, 2022 . The new tax law will require companies to compute two separate calculations for federal income tax purposes and pay the greater of the new minimum tax or their regular tax liability. The IRA is not expected to have a material impact for the Company. Uncertain Tax Benefits No liability related to uncertain tax positions is recorded on the financial statements. The following table summarizes the activity related to the Company’s unrecognized tax benefits for the year ended December 31 (in thousands): Years Ended December 31, 2023 2022 Beginning balance $ 403 $ 269 Additions for tax positions related to the current year 129 131 Reductions for tax positions related to prior years 19 3 Ending balance $ 551 $ 403 The reversal of uncertain tax benefits would not affect the effective tax rate to the extent that the Company continues to maintain a valuation allowance against its deferred tax assets. The Company does not anticipate any significant changes to unrecognized tax benefits over the next 12 months . Income tax returns are filed in the United States and California. The Company is not currently under audit by the Internal Revenue Service and the State of California. The years 2019 and forward remain open to examination for federal income tax purposes and the years 2018 and forward for California income tax to which the Company is subject. Due to net operating loss carryforwards, all years effectively remain open to income tax examination by the domestic taxing jurisdictions in which the Company files tax returns. The Company’s practice is to recognize interest and penalties related to income tax matters in income tax expense. For the years ended December 31, 2023 and 2022 the Company has not recognized any interest or penalties related to income tax in the Company’s consolidated statements of operations and comprehensive loss.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Forward Purchase Contract Amendments On January 2, 2024 , the Company amended their Forward Purchase Agreement with an FPA Investor to increase the prepayment shortfall by $0.5 million in exchange for a $0.5 million payment to the Company. All other terms and conditions remained unchanged. On January 11, 2024 , the Company amended their Forward Purchase Agreement with an FPA Investor to increase the prepayment shortfall by $0.5 million in exchange for a $0.5 million payment to the Company. All other terms and conditions remained unchanged. On January 19, 2024 , the Company amended their Forward Purchase Agreement with an FPA Investor to increase the prepayment shortfall by $0.3 million plus 20% of the then-current prepayment shortfall balance in exchange for a $0.3 million payment to the Company. The agreement also amends the Reset Price such that the Reset Price (i) is adjusted on a rolling basis as based on the weekly trailing VWAP subject to a ceiling of $10.44 per share ("Initial Price"), and (ii) discounts of generally 10% to the VWAP measurement that benefit the FPA Investor. All other terms and conditions remained unchanged. On February 21, 2024 , the Company amended their Forward Purchase Agreement with an FPA Investor to increase the prepayment shortfall by $0.2 million and increase the Bonus Shares by 200,000 in exchange for a $0.2 million payment to the Company. All other terms and conditions remained unchanged. PIPE Warrants Amendment On February 9, 2024 , the Company amended their Warrant Subscription Agreement with a Warrant Investor to, among other things, (i) make all subscription warrants held by the Warrant Investor immediately eligible to accelerate the share conversion provisions of the Warrant Subscription Agreement in exchange for a cash payment of $0.3 million, (ii) a second cash payment of up to $0.3 million based on the trailing 5-day VWAP following the effective registration of the shares , (iii) to grant the Warrant Investor “Most Favored Nation” status with respect to warrant restructuring for so long as any subscription warrants remain outstanding and (iv) to grant certain registration rights to the Warrant Investor. All other terms and conditions remained unchanged. Convertible Bridge Loans On February 7, 2024 , the Company entered into a related party bridge loan agreement for $0.4 million with a 20% premium due at maturity. The related party bridge loan matures at the earlier of (i) 60 days from issuance or (ii) upon a financing event with third parties exceeding $5.0 million . In April 2024 the maturity of the bridge loan was amended to be the earliest of (i) 90 days from issuance, (ii) upon a financing event with third parties exceeding $5.0 million, or (iii) the occurrence of any event of default. The counterparty to this bridge loan agreement is also entitled to receive 400,000 warrants to purchase 400,000 shares of the Company’s common stock each at a strike price of $2.00 per share. On February 20, 2024, the Company entered into a bridge loan agreement for $0.1 million with a 20% premium due at maturity. The bridge loan matures at the earlier of (i) 60 days from issuance or (ii) upon a financing event with third parties exceeding $10.0 million . The counterparty to this bridge loan agreement also received 100,000 warrants to purchase 100,000 shares of the Company’s common stock at a $2.00 strike price per share. On February 27, 2024 , the Company entered into a bridge loan agreement for $0.1 million with a 20% premium due at maturity. The bridge loan matures at the earlier of (i) 60 days from issuance or (ii) upon a financing event with third parties exceeding $5.0 million . The counterparty to this bridge loan agreement is also entitled to receive 3,667 shares of common stock as well as 375,000 warrants to purchase 375,000 shares of the Company’s common stock at a $1.50 strike price per share. On March 7, 2024 , the Company entered into a bridge loan agreement for $0.1 million with a 20% premium due at maturity. The bridge loan matures at the earlier of (i) 60 days from issuance or (ii) upon a financing event with third parties exceeding $5.0 million . The counterparty to this bridge loan agreement is also entitled to receive 3,667 shares of common stock as well as 375,000 warrants to purchase 375,000 shares of the Company’s common stock at a strike price. Bridge Loans On March 7, 2024 , the Company entered into two bridge loan agreements for $0.1 million each that matured on March 22, 2024 with a 7.5% premium due at maturity. Both bridge loans were subsequently paid in full on April 10, 2024. Convertible Promissory Notes On March 21, 2024 , the Company entered into a 12% promissory note agreement for $0.3 million with a one year term , issued at a 10% discount. The lender retained the option to convert any or all outstanding and unpaid principal amount and interest into shares of the Company's common stock from the date of issuance until the maturity date. The promissory note was subsequently paid in full on April 8, 2024 . Concurrently with this agreement, the Company issued the lender warrants entitling the lender to acquire up to 330,000 shares of common stock at an initial exercise price of $2.00 per share, subject to adjustment. On March 26, 2024 , the Company entered into a 12% promissory note agreement with lender who is also a FPA Investor for $0.3 million with a one year term , issued at a 10% discount. The lender retains the option to convert any or all outstanding and unpaid principal amount and interest into shares of the Company's common stock from the date of issuance until the maturity date. Concurrently with this agreement, the Company issued the lender warrants entitling the lender to acquire up to 330,000 shares of common stock at an initial exercise price of $2.00 per share, subject to adjustment. On April 1, 2024 , the Company entered into a 12% promissory note agreement for $0.2 million with a one year term , issued at a 10% discount. The lender retains the option to convert any or all outstanding and unpaid principal amount and interest into shares of the Company's common stock from the date of issuance until the maturity date. Concurrently with this agreement, the Company issued the lender warrants entitling the lender to acquire up to 220,000 shares of common stock at an initial exercise price of $2.00 per share, subject to adjustment. On April 1, 2024 , the Company entered into a 12% promissory note agreement with lender who is also a FPA Investor for $0.3 million with a one year term , issued at a 10% discount. The lender retains the option to convert any or all outstanding and unpaid principal amount and interest into shares of the Company's common stock from the date of issuance until the maturity date. Concurrently with this agreement, the Company issued the lender warrants entitling the lender to acquire up to 330,000 shares of common stock at an initial exercise price of $2.00 per share, subject to adjustment. Convertible Secured Promissory Note On April 5, 2024, the Company entered into a convertible secured promissory note agreement for $5.0 million with an interest rate of the one month secured overnight financing rate plus 2.85% payable in cash in arrears on a monthly basis, with payments commencing one month from issuance which will mature on October 4, 2026. The convertible promissory note was issued in two tranches, the first of which was for $1.0 million and closed on April 8, 2024 and the second tranche was for $4.0 million which closed on April 9, 2024. The convertible secured promissory note is secured by a second lien on the Company’s owned real property located in Santa Ana, California. The convertible secured promissory note is subordinate to the $5.0 million revolving line of credit. The outstanding principal amount is convertible at any time until its maturity at the option of the lender, into common stock at a $2.00 conversion price (subject to customary anti-dilution adjustments for stock splits and the like). Concurrently with this agreement, the lender is entitled to receive 833,333 shares of common stock upon the first closing and an amount of shares equal to $2.5 million divided by a five days VWAP measurement upon the second closing as well as warrants entitling the lender to acquire up to 1,000,000 shares of common stock at an initial exercise price of $2.00 per share, subject to adjustment. Stock Option Grants On February 12, 2024 the Board of Directors approved the grant of 3,233,028 stock options. Sales of FPA Shares As of the date of issuance of these financial statements, an aggregate of 1,768,121 FPA Shares were sold, 1,000,000 FPA Shares from initial issuance remained outstanding, and up to an additional 1,167,990

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 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. Business Combination 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.
Principles of Consolidation	Principles of 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, 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 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. The Company’s Chief Executive Officer is the Company’s CODM. The CODM reviews financial information presented on an enterprise-wide basis for purposes of making operating decisions, allocating resources, and evaluating financial performance. As such, the Company has determined that it operates in one reportable segment. Additionally, the Company generates all of its revenues, and maintains all of its long-lived assets within the United States.
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 March 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, 2023 , $0.3 million in restricted cash was recorded on the consolidated balance sheet. No restricted cash balances were recorded as of December 31, 2022. 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, 2023 and 2022 .
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. For each of the years ended December 31, 2023 and 2022 , no customer accounted for over 10% of total revenue and the Company had no trade accounts receivables outstanding. For each of the years ended December 31, 2023 and 2022 , the Company had zero and less than $0.1 million in other receivables, respectively.
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 and comprehensive loss.
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, 2022 . 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 and comprehensive loss.
Deferred Debt Issuance Costs / Debt	Deferred Debt Issuance Costs Debt For convertible debt instruments that are not considered liabilities under ASC 480 or ASC 815, the Company applies ASC 470, Debt
Hybrid Instruments	Hybrid Instruments The Company follows Financial Accounting Standards Board (“ FASB ”) Accounting Standard Codification (“ ASC ”) 480, Distinguishing Liabilities from Equity
Derivative Instruments	Derivative Instruments FASB ASC 815, Derivatives and Hedging Activities
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. The Company has not recognized any impairment losses for the years ended December 31, 2023 and 2022 .
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 ASC 825, Financial Instruments . The Company elected the fair value option for its legacy convertible promissory notes, which met the required criteria under ASC 825, Financial Instruments . Interest expense associated with the legacy convertible promissory notes is included in the change in fair value of such instruments.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company follows ASC 820-10, Fair Value Measurements and Disclosures , issued by the FASB with respect to fair value reporting for financial assets and liabilities. The guidance defines fair value, provides guidance for measuring fair value and requires certain disclosures. The guidance does not apply to measurements related to share-based payments. The guidance discusses valuation techniques such as the market approach (comparable market prices), the income approach (present value of future income or cash flow), and the cost approach (cost to replace the service capacity of an asset or replacement cost). The guidance establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value into three broad levels. The Company’s financial instruments include cash and cash equivalents, prepaid expenses and other current assets, capitalized software, accounts payable, accrued expenses, convertible promissory notes issued from 2019 through 2022 to investors (“2019 Convertible Notes”), convertible promissory notes due to related parties (“Related Party Convertible Notes”, together with the 2019 Convertible Notes, “Convertible Notes”), debt due to a related party (“Related Party Loans”), and other current liabilities. The carrying amount of cash and cash equivalents, prepaid expenses and other current assets, capitalized software, accounts payable, accrued expenses, revolving line of credit, and related party loans, and other current liabilities are generally considered to be representative of their respective values because of the short-term nature of those instruments. The Company elects to account for its 2019 Convertible Notes and Related Party Convertible Notes, which meet the required criteria, at fair value at inception and at each subsequent reporting date. Subsequent changes in fair value of the Convertible Notes are recorded within other expenses, net on the accompanying consolidated statements of operations and comprehensive loss. Interest expense associated with the Convertible Notes is included in the change in fair value for the Convertible Notes. These estimates may be subjective in nature and involve uncertainties and matters of significant judgment and therefore cannot be determined with precision. 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. ASC 820, Fair Value Measurement , 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. 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 one year from December 31, 2023
Employee Benefit Plan	Employee Benefit Plan Effective January 1, 2019, the Company adopted and maintains a defined contribution plan, which qualifies under Section 401(k) of the Internal Revenue Code, on behalf of its eligible employees. Upon consummation of the Business Combination, the Company adopted the 2023 equity incentive plan (“2023 Plan”), at which date NKGen determined it will no longer grant any additional awards under the 2019 Plan. Employee contributions are voluntary and are determined on an individual basis, limited to the maximum amount allowable under federal tax regulations. During the years ended December 31, 2023 and 2022 , the Company did not contribute to either plan.
Revenue Recognition	Revenue Recognition Historically, the Company recognized revenue in connection with Coronavirus Disease of 2019 (“ COVID-19 ”) testing services. During the first quarter of the year ended December 31, 2023 , the Company ceased providing COVID-19 testing services. The Company recognizes revenue in accordance with ASC 606, Revenue from Contracts with Customers , which applies to all contracts with customers, except for contracts within the scope of other standards, such as leases, insurance, collaboration arrangements, and financial instrument. Under ASC 606, revenue is recognized in a manner that depicts the transfer of control of a product or a service to a customer and reflects the amount of the consideration the Company is entitled to receive in exchange for such product or service. In doing so, the Company follows a five-step approach: (i) identify the contract with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations, and (v) recognize revenue when (or as) the customer obtains control of the product or service. The Company considers the terms of a contract and all relevant facts and circumstances when applying the revenue recognition standard. The Company applies the revenue recognition standard, including the use of any practical expedients, consistently to contracts with similar characteristics and in similar circumstances. The transaction price is the amount of consideration the Company is entitled to receive in exchange for the transfer of control of a product or a service to a customer. To determine the transaction price, the Company considers the existence of any significant financing component, the effects of any variable elements, noncash considerations and consideration payable to the customer. If a significant financing component exists, the transaction price is adjusted for the time value of money. If an element of variability exists, the Company must estimate the consideration it expects to receive and uses that amount as the basis for recognizing revenue as the product or the service is transferred to the customer. If a contract has multiple performance obligations, the Company allocates the transaction price to each distinct performance obligation in an amount that reflects the consideration the Company is entitled to receive in exchange for satisfying each distinct performance obligation. For each distinct performance obligation, revenue is recognized when (or as) the Company transfers control of the product or the service applicable to such performance obligation. In those instances where the Company first receives consideration in advance of satisfying its performance obligation, the Company classifies such consideration as contract liability until (or as) the Company satisfies such performance obligation. In those instances where the Company first satisfies its performance obligation prior to its receipt of consideration, the consideration is recorded as accounts receivable. The Company expenses incremental costs of obtaining and fulfilling a contract as and when incurred if the expected amortization period of the asset that would be recognized is one year or less, or if the amount of the asset is immaterial. Otherwise, such costs are capitalized as contract assets if they are incremental to the contract and amortized to expense proportionate to revenue recognition of the underlying contract.
Collaboration Agreement	Collaboration Agreement The Company has entered into a research agreement that falls under the scope of 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 and comprehensive loss. Similarly, amounts that are owed to a collaboration partner are recognized as research and development expense in the consolidated statements of operations and comprehensive loss.
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 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 sheet. 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 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 and comprehensive 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. Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share for the year ended December 31, 2023 include the following: Private warrants 4,721,533 Working capital warrants 523,140 Public warrants 3,432,286 PIPE warrants 10,209,994 Stock options 2,078,986 SPA warrants 1,000,000 Senior convertible notes’ shares 1,000,000 Deferred founder shares (1) 1,173,631 Total 24,139,570 (1) As described in Note 8, Related Party Transactions , deferred founder shares do not have voting rights, do not participate in dividends and are not transferrable absent the Company’s consent. Therefore, while deferred founder shares are considered outstanding for legal purposes and are included in the total quantity of outstanding shares on the consolidated statements of stockholders’ equity (deficit), they are not considered outstanding for accounting purposes, including basic and diluted net loss per share purposes.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In June 2016, the Financial Accounting Standard Board (“ FASB ”) issued Accounting Standards Update (“ ASU ”) No. 2016-13, Measurement of Credit Losses on Financial Instruments . ASU 2016-13, together with a series of subsequently issued related ASUs, has been codified in Topic 326. Topic 326 establishes new requirements for companies to estimate expected credit losses when measuring certain financial assets, including accounts receivables. The new guidance is effective for fiscal years beginning after December 15, 2022. The Company adopted the new guidance with its fiscal year beginning January 1, 2023. The adoption of ASC 326 had no material impact on the Company’s financial statements. In August 2020, the FASB issued ASU 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 , which simplifies accounting for convertible instruments by removing major separation models required under current accounting principles and removes certain settlement conditions required for equity contracts to qualify for the derivative scope exception. ASU 2020-06 will be effective for the Company for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years, with early adoption permitted. The Company adopted the new guidance during the fiscal year ended December 31, 2023. The adoption of ASU 2020-06 had no material impact on the Company’s financial statements. 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.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Schedule of Potentially Antidilutive Shares Excluded from Computation of Diluted Net Loss Per Share	Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share for the year ended December 31, 2023 include the following: Private warrants 4,721,533 Working capital warrants 523,140 Public warrants 3,432,286 PIPE warrants 10,209,994 Stock options 2,078,986 SPA warrants 1,000,000 Senior convertible notes’ shares 1,000,000 Deferred founder shares (1) 1,173,631 Total 24,139,570 (1) As described in Note 8, Related Party Transactions , deferred founder shares do not have voting rights, do not participate in dividends and are not transferrable absent the Company’s consent. Therefore, while deferred founder shares are considered outstanding for legal purposes and are included in the total quantity of outstanding shares on the consolidated statements of stockholders’ equity (deficit), they are not considered outstanding for accounting purposes, including basic and diluted net loss per share purposes.

Reverse Recapitalization (Table

Reverse Recapitalization (Tables)	12 Months Ended
	Dec. 31, 2023
Reverse Recapitalization [Abstract]
Schedule of Reverse Recapitalization	The following tables reconcile elements of the Business Combination to the Company’s consolidated financial statements, and should be read in conjunction with the footnotes referenced above (in thousands, except share amounts): Shares Graf public shares, net of redemptions 93,962 Private placement investors’ shares 3,683,010 Graf founder shares 2,516,744 Total Graf shares outstanding immediately prior to the Business Combination 6,293,716 Conversion of Legacy NKGen convertible promissory notes (after the application of the Exchange Ratio) 2,278,598 Legacy NKGen rollover shares (after the application of the Exchange Ratio) 13,316,662 Total Legacy NKGen shares 15,595,260 Total Company common stock outstanding immediately following the Business Combination 21,888,976 (In thousands) Recapitalization Closing proceeds Proceeds from issuance of common stock $ 1,667 Proceeds from issuance of PIPE warrants 10,210 Proceeds from issuance of senior convertible promissory notes with warrants 10,000 Closing disbursements Less: Payment of Graf deferred underwriter fees (1,250) Less: Payment of Graf transaction costs at Closing (1) (7,456) Less: Payment of Legacy NKGen transaction costs at Closing (3,510) Net cash proceeds from the Business Combination at Closing $ 9,661 Less: Payment of Legacy NKGen transaction costs prior to Closing (2,089) Net cash proceeds from the Business Combination $ 7,572 Noncash activity Conversion of legacy NKGen convertible promissory notes 18,913 Less: Operating liabilities assumed from Graf (860) Less: Unpaid transaction costs – assumed from Graf (1) (5,400) Less: Unpaid transaction costs – Legacy NKGen (1,938) Liability-classified instruments Less: Fair value of PIPE warrants (10,210) Less: Fair value of forward purchase derivative liability (20,201) Less: Fair value of senior convertible promissory notes (2) (9,707) Less: Fair value of private warrants (1,841) Less: Fair value of working capital warrants (204) Net equity impact of the Business Combination $ (23,876) (1) The Graf transaction costs includes a $4.0 million accrual related to a certain vendor to be paid in cash and common stock of $2.0 million each. At Closing, a cash payment of $1.3 million was disbursed to this vendor. The remaining $2.7 million amount was recognized as a component of the unpaid transaction costs assumed from Graf, of which $0.7 million represents a cash settlement obligation, and the remaining $2.0 million represents an obligation to issue a variable number of shares for a fixed monetary amount which was accounted for as a liability under ASC 480, Distinguishing Liabilities from Equity (“ASC 480”). Under ASC 480, the obligation to issue shares is not subsequently measured at fair value with changes recorded in earnings because the monetary amount is fixed. (2) Represents allocated fair value. As presented in the consolidated statements of stockholders’ equity (deficit) (in thousands): Net equity impact of the Business Combination $ (23,876) Loss on issuance of forward purchase contract 24,475 Transaction costs expensed 3,329 Total Impact of Business Combination on total stockholders’ deficit (1) $ 3,928 Issuance of subscription receivable 32,915 Par value of common stock issued (1) Total Impact of Business Combination on additional paid-in capital $ 36,842 (1) Excludes impact of the Business Combination on net loss, which is presented separately in the consolidated statements of stockholders’ equity (deficit).

Private Placement (Tables)

Private Placement (Tables)	12 Months Ended
	Dec. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments	Upon execution of the FPA Amendment, the Company recognized a loss on amendment to forward purchase contract as set forth below (in thousands): Loss on Amendment Reduction of subscription receivable $ 15,123 Reduction in forward purchase derivative liability (14,181) Shareholder receivable (500) Loss on amendment to forward purchase contract $ 442

Convertible Notes (Tables)

Convertible Notes (Tables)	12 Months Ended
	Dec. 31, 2023
Debt Disclosure [Abstract]
Convertible Debt	The following table presents a reconciliation of the Senior Convertible Notes (in thousands): Senior Convertible Balance as of December 31, 2022 $ — Issuance 9,707 Amortization of discount 17 Paid-in-kind interest 206 Balance as of December 31, 2023 $ 9,930

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Schedule of Fair Value Hierarchy	Liabilities measured at fair value on a recurring basis as of December 31, 2023 are as follows (in thousands):  Fair Value Measurements at Reporting Date Using Balance as of Level 1 Level 2 Level 3 Private Warrants $ 378 $ — $ — $ 378 Working Capital Warrants 42 — — 42 Forward Purchase Derivative Liability 15,804 — — 15,804 PIPE Warrants 25,339 — — 25,339 Total $ 41,563 $ — $ — $ 41,563
Schedule of Legacy Convertible Notes Reconciliation	The following table presents a reconciliation of the Legacy Convertible Notes (in thousands): 2019 2019 Related 2023 2023 Related Total Balance as of December 31, 2021 $ 11,219 $ 259 $ — $ — $ 11,478 Change in fair value 173 4 — — 177 Balance as of December 31, 2022 11,392 263 — — 11,655 Issuance — — 6,090 125 6,215 Change in fair value 1,083 13 (52) (1) 1,043 Conversion and settlement (12,475) (276) (6,038) (124) (18,913) Balance as of December 31, 2023 $ — $ — $ — $ — $ — The following table presents a reconciliation of the Private Warrants and Working Capital Warrants (in thousands): Private Working Total Balance as of December 31, 2022 $ — $ — $ — Recognition in connection with Business Combination 1,841 204 2,045 Change in fair value (1,464) (162) (1,626) Balance as of December 31, 2023 $ 377 $ 42 $ 419 The following table presents a reconciliation of the PIPE Warrants (in thousands): PIPE Balance as of December 31, 2022 $ — Issuance 10,210 Change in fair value 15,129 Balance as of December 31, 2023 $ 25,339 The following table presents a reconciliation of the Forward Purchase Derivative Liability (in thousands): Forward Forward purchase derivative liability at Close $ 20,201 Change in fair value in connection with the loss on amendment of forward purchase contract (14,181) Change in fair value of forward purchase derivative liability 9,784 Balance as of December 31, 2023 $ 15,804
Fair Value Unobservable Assumption Inputs	The following unobservable assumptions were used in determining the fair value of the Legacy Convertible Notes as of December 31, 2022: Probability of conversion — Probability of holding until maturity without conversion — Remaining term until potential conversion trigger date (years) 0 Discount yield (1) 20.0 % (1) Estimated using a comparable bond analysis and under S&P Global Inc.’s credit rating scale using a multinominal logical regression. The following unobservable assumptions were used in determining the fair value of the Senior Convertible Notes at Closing: Credit spread (1) 12.1 % Equity volatility 45.0 % (1) Estimated using a comparable bond analysis and under S&P Global Inc.’s credit rating scale using a multinominal logical regression. The following unobservable assumptions were used in determining the fair value of the Senior Convertible Notes at December 31, 2023: Credit spread (1) 12.7 % Equity volatility 45.0 % (1) Estimated using a comparable bond analysis and under S&P Global Inc.’s credit rating scale using a multinominal logical regression. The following unobservable assumptions were used in determining the fair value of the Private Warrants and Working Capital Warrants at Closing: Private Warrants’ volatility 9.6 % Dividend yield (per share) — The following unobservable assumptions were used in determining the fair value of the Private Warrants and Working Capital Warrants as of December 31, 2023: Private Warrants’ volatility 35.3 % Dividend yield (per share) — The following unobservable assumptions were used in determining the fair value of the PIPE Warrants at December 31, 2023: Credit spread 12.7 % Equity volatility 100.0 % The following unobservable assumptions were used in determining the fair value of the forward purchase derivative liability at Closing: Dividend yield 0.0 % Equity volatility 105.0 % The following unobservable assumptions were used in determining the fair value of the forward purchase derivative liability immediately before and after modification at December 26, 2023: Dividend yield 0.0 % Equity volatility 125.0 % The following unobservable assumptions were used in determining the fair value of the forward purchase derivative liability at December 31, 2023: Dividend yield 0.0 % Equity volatility 115.0 %

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Schedule of Stock Option Activity	A summary of the Company’s stock option activity for the year ended December 31, 2023 is as follows: Stock Options Weighted Outstanding as of December 31, 2022 185,231 $ 1.37 Granted 2,173,693 6.67 Forfeited (267,072) 6.56 Exercised (12,866) 0.88 Outstanding as of December 31, 2023 2,078,986 $ 6.25 Stock options outstanding, vested and expected to vest and exercisable as of December 31, 2023 are as follows: Number of Weighted Weighted- Total Outstanding as of December 31, 2022 185,231 6.98 $ 1.37 $ 980 Outstanding as of December 31, 2023 2,078,986 8.86 $ 6.25 $ 317 Vested and expected to vest as of December 31, 2023 2,078,986 8.86 $ 6.25 $ 317 Exercisable as of December 31, 2023 302,760 7.46 $ 3.79 $ 317
Schedule of Stock Option Valuation Assumptions	The weighted average assumptions used in the Black-Scholes option pricing model to determine the fair value of stock option grants for the year ended December 31, 2023 were as follows: Common stock fair value $ 9.18 Risk-free interest rate 3.5% Expected volatility 111.0% Expected term (in years) 6.1 Expected dividend yield 0.0%
Schedule of Stock-Based Compensation Expense	Stock-based compensation expense, recognized in the Company’s consolidated statements of operations and comprehensive loss for the 2019 Plan was recorded as follows (in thousands): Years ended 2023 2022 Research and development $ 898 $ 45 General and administrative 3,237 24 Total stock-based compensation expense $ 4,135 $ 69

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	Property and equipment, net consist of the following (in thousands): Useful Life December 31, December 31, Land — $ 5,025 $ 5,025 Buildings 40 years 8,325 8,325 Furniture and fixtures 7 years 749 677 Lab equipment 5 years 4,004 4,003 Leasehold improvements Lesser of estimated useful life or 52 52 Office equipment 5 years 17 17 Vehicles 5 years 112 112 18,284 18,211 Less: Accumulated depreciation (3,825) (2,690) $ 14,459 $ 15,521

Additional Balance Sheet Info_2

Additional Balance Sheet Information (Tables)	12 Months Ended
	Dec. 31, 2023
Balance Sheet Related Disclosures [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): December 31, December 31, Prepaid expenses $ 1,565 $ 133 Other receivables 26 67 Revolving line of credit issuance fees 47 — Other 16 4 Prepaid expenses and other current assets $ 1,654 $ 204
Schedule of Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses consist of the following (in thousands): December 31, December 31, Accounts payable $ 11,040 $ 975 Accrued liabilities 1,360 1,359 Employee compensation 911 291 Other 84 27 Accounts payable and accrued expenses $ 13,395 $ 2,652

Commitment and Contingencies (T

Commitment and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments Under the New Office Lease	Future minimum lease payments under the New Office Lease are as follows (in thousands): Minimum lease 2024 $ 235 2025 242 2026 249 Total operating lease liability $ 726

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	The provision for income taxes for the years ended December 31, 2023 and 2022 are as follows (in thousands): Years Ended December 31, 2023 2022 Current: Federal $ — $ — State — — Deferred: Federal 7 7 State — — Provision for income taxes $ 7 $ 7
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of the income tax computed at federal statutory income tax rate to the reported provision for income taxes is as follows (in thousands): Years Ended December 31, 2023 2022 Tax benefit at statutory federal rate $ (17,419) $ (5,618) State tax, net of federal tax benefit (1,946) (1,694) Interest expense 47 477 Increase in valuation allowance 9,189 7,908 Permanent items 12 37 Stock compensation 359 (4) Unrealized loss FV of notes 219 — General business tax credit (1,278) (1,098) Loss on issuance of forward purchase contract 5,140 — Loss on amendment of the subscription receivable 93 — Loss on derivative valuation 4,890 — Other 701 (1) Provision for income taxes $ 7 $ 7
Schedule of Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred income taxes are as follows (in thousands): Years Ended December 31, 2023 2022 Deferred tax assets: Net operating losses $ 22,843 $ 17,890 Tax credit carryforwards, net 4,523 3,285 Accrued expenses 395 347 Section 174 R&E capitalization 4,939 2,847 Intangibles 707 — Lease liability — 106 Stock-based compensation 699 20 Total deferred tax assets 34,106 24,495 Deferred tax liabilities: Operating lease right-of-use asset — (101) Property and equipment (406) (595) Total deferred tax liabilities (406) (696) Net deferred tax assets 33,700 23,799 Less: Valuation allowance (33,733) (23,825) Net deferred tax liability $ (33) $ (26)
Schedule of Unrecognized Tax Benefits Roll Forward	The following table summarizes the activity related to the Company’s unrecognized tax benefits for the year ended December 31 (in thousands): Years Ended December 31, 2023 2022 Beginning balance $ 403 $ 269 Additions for tax positions related to the current year 129 131 Reductions for tax positions related to prior years 19 3 Ending balance $ 551 $ 403

Company Information (Details)

Company Information (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ 162,130	$ 79,176
Cash and cash equivalents	$ 26	$ 117

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) stock segment shares	Dec. 31, 2022 USD ($) shares	Sep. 29, 2023	Jun. 30, 2023 USD ($)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Recapitalization exchange ratio			0.408
Number of reportable segments | segment	1
Trade accounts receivable	$ 0	$ 0
Business acquisition, transaction costs		0
Deferred debt issuance costs	100,000	0
Line of credit, minimum required cash balance				$ 15,000,000
Restricted cash	250,000	0
Unrecognized tax liability	$ 0
Number of class of shares | stock	1
Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share | shares	24,139,570
Computer Software, Intangible Asset
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Intangible asset, useful life	3 years
Maximum
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Other receivables	$ 0	$ 100,000
Related Party
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Borrowing term	1 year
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share | shares	2,078,986	185,231

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share	24,139,570
Private warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share	4,721,533
Working capital warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share	523,140
Public warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share	3,432,286
PIPE warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share	10,209,994
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share	2,078,986	185,231
SPA warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share	1,000,000
Senior convertible notes’ shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share	1,000,000
Deferred founder shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially anti-dilutive shares excluded from the calculation of diluted net loss per share	1,173,631

Reverse Recapitalization - Narr

Reverse Recapitalization - Narrative (Details) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended
	Sep. 29, 2023	Sep. 28, 2023	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Schedule Of Reverse Recapitalization [Line Items]
Converted shares (in shares)		5,579,266
Stock converted, reverse recapitalization (in shares)	2,278,598
Common stock outstanding (in shares)	21,888,976		21,888,976	21,888,976	13,303,795
Common stock, shares issued (in shares)			21,888,976	21,888,976	13,303,795
Stock options cancelled and converted (in shares)	2,101,760
Transaction costs expensed	$ 7,500		$ 3,329	$ 3,329	$ 0
Legacy NKGen
Schedule Of Reverse Recapitalization [Line Items]
Common stock outstanding (in shares)	38,185,814
Common stock, shares issued (in shares)	38,185,814
Options, issued and outstanding (in shares)	5,146,354
Equity Instruments
Schedule Of Reverse Recapitalization [Line Items]
Transaction costs expensed	$ 4,200
Liability Instruments
Schedule Of Reverse Recapitalization [Line Items]
Transaction costs expensed	$ 3,300
Common Stock, Including Convertible Debt Stock
Schedule Of Reverse Recapitalization [Line Items]
Stock converted, reverse recapitalization (in shares)	15,595,262

Reverse Recapitalization - Sche

Reverse Recapitalization - Schedule of Reverse Recapitalization Table 1 (Details)	Sep. 29, 2023 shares
Schedule Of Reverse Recapitalization [Line Items]
Total Legacy NKGen shares (in shares)	2,278,598
Legacy NKGen rollover shares (in shares)	13,316,662
Total Company common stock outstanding immediately following the Business Combination (in shares)	21,888,976
Graf public shares, net of redemptions | Graf Acquisition Partners IV LLC
Schedule Of Reverse Recapitalization [Line Items]
Total Graf shares outstanding immediately prior to the Business Combination (in shares)	93,962
Private placement investors’ shares | Graf Acquisition Partners IV LLC
Schedule Of Reverse Recapitalization [Line Items]
Total Graf shares outstanding immediately prior to the Business Combination (in shares)	3,683,010
Graf founder shares | Graf Acquisition Partners IV LLC
Schedule Of Reverse Recapitalization [Line Items]
Total Graf shares outstanding immediately prior to the Business Combination (in shares)	2,516,744
Common Shareholders | Graf Acquisition Partners IV LLC
Schedule Of Reverse Recapitalization [Line Items]
Total Graf shares outstanding immediately prior to the Business Combination (in shares)	6,293,716
Legacy NKGen
Schedule Of Reverse Recapitalization [Line Items]
Total Legacy NKGen shares (in shares)	15,595,260

Reverse Recapitalization - Sc_2

Reverse Recapitalization - Schedule of Reverse Recapitalization Table 2 (Details) - USD ($) $ in Thousands		12 Months Ended
	Sep. 29, 2023	Dec. 31, 2023	Dec. 31, 2022
Schedule Of Reverse Recapitalization [Line Items]
Proceeds from issuance of common stock	$ 1,667	$ 1,668	$ 0
Proceeds from issuance of PIPE warrants	10,210	10,210	0
Proceeds from issuance of senior convertible promissory notes with warrants	10,000
Less: Payment of Graf deferred underwriter fees	(1,250)	(1,250)	0
Less: Payment of transaction costs at Closing		(14,591)	0
Net cash proceeds from the Business Combination at Closing	9,661
Less: Payment of Legacy NKGen transaction costs prior to Closing	(2,089)
Net cash proceeds from the Business Combination	7,572
Conversion of legacy NKGen convertible promissory notes	18,913	18,913	0
Less: Operating liabilities assumed from Graf	(860)
Less: Unpaid transaction costs		$ (5,802)	$ 0
Less: Fair value of PIPE warrants	(10,210)
Less: Fair value of forward purchase derivative liability	(20,201)
Less: Fair value of senior convertible promissory notes	(9,707)
Less: Fair value of private warrants	(1,841)
Less: Fair value of working capital warrants	(204)
Net equity impact of the Business Combination	(23,876)
Reverse recapitalization obligation, cash settlement	700
Reverse recapitalization obligation, shares issuable	2,000
Graf Acquisition Partners IV LLC
Schedule Of Reverse Recapitalization [Line Items]
Less: Payment of transaction costs at Closing	(7,456)
Less: Unpaid transaction costs	(5,400)
Legacy NKGen
Schedule Of Reverse Recapitalization [Line Items]
Less: Payment of transaction costs at Closing	(3,510)
Less: Unpaid transaction costs	(1,938)
Vendor
Schedule Of Reverse Recapitalization [Line Items]
Less: Payment of transaction costs at Closing	(1,300)
Less: Unpaid transaction costs	(2,700)
Vendor | Graf Acquisition Partners IV LLC
Schedule Of Reverse Recapitalization [Line Items]
Less: Unpaid transaction costs	(4,000)
Vendor | Graf Acquisition Partners IV LLC | Common Stock
Schedule Of Reverse Recapitalization [Line Items]
Less: Unpaid transaction costs	(2,000)
Vendor | Graf Acquisition Partners IV LLC | Cash
Schedule Of Reverse Recapitalization [Line Items]
Less: Unpaid transaction costs	$ (2,000)

Reverse Recapitalization - Sc_3

Reverse Recapitalization - Schedule of Reverse Recapitalization Table 3 (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Sep. 29, 2023	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Schedule Of Reverse Recapitalization [Line Items]
Net equity impact of the Business Combination	$ (23,876)
Loss on issuance of forward purchase contract	24,500	$ 24,475	$ 24,475	$ 0
Transaction costs expensed	$ 7,500	3,329	$ 3,329	$ 0
Reverse recapitalization transactions, net		3,928
Subscription Receivable
Schedule Of Reverse Recapitalization [Line Items]
Reverse recapitalization transactions, net		32,915
Common Stock
Schedule Of Reverse Recapitalization [Line Items]
Reverse recapitalization transactions, net		(1)
Additional Paid-In Capital
Schedule Of Reverse Recapitalization [Line Items]
Reverse recapitalization transactions, net		$ 36,842

Private Placement - Additional

Private Placement - Additional Information (Details)					3 Months Ended		12 Months Ended
	Sep. 29, 2024 USD ($) $ / shares shares	Dec. 26, 2023 USD ($) d shares	Sep. 29, 2023 USD ($)	Sep. 28, 2023 USD ($) shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($)	Dec. 25, 2023 USD ($)
Derivative [Line Items]
Shares purchased (in shares) | shares				3,168,121
Repayment amount			$ 32,900,000	$ 32,900,000
Number of additional shares available (in shares) | shares					767,990
Anniversary of closing period				1 year
Minimum escrow releasement				$ 0
Loss on issuance of forward purchase contract			24,500,000			$ 24,475,000	$ 24,475,000	$ 0
Forward purchase derivative liability			20,200,000		$ 15,804,000	$ 15,804,000	15,804,000	0
Bonus stock			$ 4,300,000
Anniversary term			1 year
Proceeds from issuance of common stock			$ 1,667,000				1,668,000	0
Loss on amendment of forward purchase contract							$ 442,000	$ 0
Forecast
Derivative [Line Items]
Approaches or exceeds, threshold trigger (in USD per share) | $ / shares	$ 10.44
Decreases below, threshold trigger (in USD per share) | $ / shares	10.44
Change in share price | $ / shares	$ 2
Shortfall, consideration received on transaction	$ 100,000
FPA Investor
Derivative [Line Items]
Shares purchased (in shares) | shares							139,793
Bonus Shares | Forecast
Derivative [Line Items]
Shares purchased (in shares) | shares	514,889
Forward Purchase Agreement
Derivative [Line Items]
Repayment amount		$ 500,000
Number of additional shares available (in shares) | shares		200,000
Approaches or exceeds, threshold trigger (in USD per share) | $ / shares					$ 10.44	$ 10.44	$ 10.44
Number of shares re-designated (in shares) | shares		200,000
Sale of stock, common stock purchase agreement, prepayment shortfall increase available		$ 500,000
Pre-existing prepayment shortfall									$ 100,000
Loss on amendment of forward purchase contract		$ 442,000
Discount of VWAP measurement		0.10
Derivative liability, additional share issuance of VWAP		0.90
VWAP trading days | d		20
Reduction of subscription receivable		$ 15,123,000

Private Placement - Forward Pur

Private Placement - Forward Purchase Contract (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 26, 2023	Dec. 31, 2023	Dec. 31, 2022
Derivative [Line Items]
Reduction in forward purchase derivative liability	$ 14,200
Loss on amendment of forward purchase contract		$ 442	$ 0
Forward Purchase Agreement
Derivative [Line Items]
Reduction of subscription receivable	15,123
Reduction in forward purchase derivative liability	(14,181)
Shareholder receivable	(500)
Loss on amendment of forward purchase contract	$ 442

Warrants (Details)

Warrants (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	Sep. 29, 2023 USD ($) $ / shares shares	May 20, 2021 $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($)	Sep. 28, 2023 USD ($)
Class of Warrant or Right [Line Items]
Conversion ratio		1
Proceeds from issuance of PIPE warrants | $	$ 10,210		$ 10,210	$ 0
Redemption price of warrants (in usd per share)			$ 18
Working Capital Loan | Line of Credit
Class of Warrant or Right [Line Items]
Working capital loan | $					$ 800
Public warrants
Class of Warrant or Right [Line Items]
Warrant, exercise price (in dollars per share)		$ 11.50
Period before warrants become exercisable		30 days
Warrant term		5 years
Public warrants | Graf Acquisition Partners IV LLC
Class of Warrant or Right [Line Items]
Warrants issued (in shares) | shares		3,432,286
Public warrants | Common Stock
Class of Warrant or Right [Line Items]
Closing price required to redeem warrants (in dollars per share)		$ 18
Private warrants | Graf Acquisition Partners IV LLC
Class of Warrant or Right [Line Items]
Warrants issued (in shares) | shares		4,721,533
Warrant, exercise price (in dollars per share)		$ 11.50
SPA warrants
Class of Warrant or Right [Line Items]
Warrants issued (in shares) | shares			1,000,000
Warrant, exercise price (in dollars per share)			$ 11.50
Working capital warrants
Class of Warrant or Right [Line Items]
Warrants issued (in shares) | shares	523,140
Warrant, exercise price (in dollars per share)	$ 11.50
PIPE warrants
Class of Warrant or Right [Line Items]
Warrants issued (in shares) | shares	10,209,994
Warrant term	5 years
Proceeds from issuance of PIPE warrants | $	$ 10,200
Purchase price (usd per share)	$ 1
Period before warrant adjustment	180 days
PIPE warrants | First Tranche
Class of Warrant or Right [Line Items]
Warrant, exercise price (in dollars per share)	$ 10
PIPE warrants | Second Tranche
Class of Warrant or Right [Line Items]
Warrant, exercise price (in dollars per share)	12.50
PIPE warrants | Third Tranche
Class of Warrant or Right [Line Items]
Warrant, exercise price (in dollars per share)	15
PIPE warrants | Minimum
Class of Warrant or Right [Line Items]
Cashless exchange, stock price trigger (in USD per share)	$ 1.50

Convertible Notes (Details)

Convertible Notes (Details) - USD ($) $ / shares in Units, $ in Thousands			2 Months Ended	3 Months Ended	7 Months Ended	12 Months Ended
	Sep. 29, 2023	Sep. 28, 2023	Dec. 31, 2019	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Proceeds from issuance of senior convertible promissory notes with warrants	$ 10,000
Converted shares (in shares)		5,579,266
Stock converted, reverse recapitalization (in shares)	2,278,598
Interest expense (including related party amounts of $431 and $2,271 for the year ended December 31, 2023 and 2022, respectively)						$ 745	$ 2,306
Legacy NKGen Common Stock
Debt Instrument [Line Items]
Converted shares (in shares)	5,579,266
2019 Convertible Notes
Debt Instrument [Line Items]
Proceeds from issuance of senior convertible promissory notes with warrants			$ 10,800
2019 Related Party Convertible Notes
Debt Instrument [Line Items]
Proceeds from issuance of senior convertible promissory notes with warrants			$ 300
2023 Convertible Notes
Debt Instrument [Line Items]
Proceeds from issuance of senior convertible promissory notes with warrants					$ 6,100
Borrowing term						3 years
2023 Related Party Convertible Notes
Debt Instrument [Line Items]
Proceeds from issuance of senior convertible promissory notes with warrants					$ 100
Borrowing term						3 years
Convertible Debt | 2019 Convertible Notes
Debt Instrument [Line Items]
Interest rate			1.70%
Convertible Debt | 2019 Related Party Convertible Notes
Debt Instrument [Line Items]
Interest rate			1.70%
Convertible Debt | 2023 Convertible Notes
Debt Instrument [Line Items]
Interest rate					4.60%
Convertible Debt | 2023 Related Party Convertible Notes
Debt Instrument [Line Items]
Interest rate					4.60%
Convertible Debt | Senior Convertible Notes
Debt Instrument [Line Items]
Proceeds from issuance of senior convertible promissory notes with warrants		$ 10,000
Interest rate		5%
Borrowing term		4 years
Paid in kind interest rate		0.080
Conversion price (in dollars per share)		$ 10
Exercise term	2 years 6 months
Minimum holding period post exercise		6 months
Interest expense (including related party amounts of $431 and $2,271 for the year ended December 31, 2023 and 2022, respectively)				$ 200		$ 200

Convertible Notes - Reconciliat

Convertible Notes - Reconciliation of Senior Convertible Notes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Paid-in-kind interest	$ 504	$ 2,271
Senior Notes | Convertible Notes Payable
Debt Instrument [Line Items]
Beginning Balance	0
Issuance	9,707
Amortization of discount	17
Paid-in-kind interest	206
Ending Balance	$ 9,930	$ 0

Debt (Details)

Debt (Details) - USD ($) $ in Thousands		1 Months Ended				3 Months Ended			4 Months Ended	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	May 31, 2020	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022	May 01, 2023	Dec. 31, 2023	Dec. 31, 2022	Jun. 30, 2024	Apr. 30, 2023
Debt Instrument [Line Items]
Issuance fees				$ 0		$ 100		$ 0		$ 100	$ 0
Proceeds from draws on revolving line of credit										4,991	0
Interest expense (including related party amounts of $431 and $2,271 for the year ended December 31, 2023 and 2022, respectively)										745	2,306
Proceeds from related party loans		$ 300							$ 5,000	$ 5,300	23,000
Related Party
Debt Instrument [Line Items]
Line of credit borrowing term										1 year
Interest expense (including related party amounts of $431 and $2,271 for the year ended December 31, 2023 and 2022, respectively)						200		2,300		$ 431	2,271
Interest payable				0		100		0		100	0
Related Party | Loans Payable
Debt Instrument [Line Items]
Interest payable				0		$ 200		$ 0		$ 200	0
Related Party Loans | Convertible Debt
Debt Instrument [Line Items]
Principal and interest				$ 66,100
Related Party Loans | Loans Payable
Debt Instrument [Line Items]
Interest rate													4.60%
Related Party Loans | Common Stock
Debt Instrument [Line Items]
Converted shares (in shares)							6,943,789
Related Party Loans | Related Party | Loans Payable
Debt Instrument [Line Items]
Line of credit borrowing term	30 days
Interest rate	5.10%	5.10%
Paycheck Protection Program Loan | Loans Payable
Debt Instrument [Line Items]
Interest rate					1%
Interest expense (including related party amounts of $431 and $2,271 for the year ended December 31, 2023 and 2022, respectively)											100
Proceeds from Paycheck Protection Program Loan					$ 1,100
Revolving Credit Facility | Commercial Bank Credit Facility | Line of Credit
Debt Instrument [Line Items]
Revolving line of credit			$ 5,000
Line of credit borrowing term			1 year
Interest rate			7.50%
Issuance fees			$ 100
Restricted cash balance requirement			$ 300
Interest rate for the revolving line of credit						8.20%				8.20%
Proceeds from draws on revolving line of credit										$ 4,900
Interest expense (including related party amounts of $431 and $2,271 for the year ended December 31, 2023 and 2022, respectively)										$ 200	$ 0
Revolving Credit Facility | Commercial Bank Credit Facility | Forecast | Line of Credit
Debt Instrument [Line Items]
Minimum deposit balance												$ 15,000
Revolving Credit Facility | Commercial Bank Credit Facility | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Line of Credit
Debt Instrument [Line Items]
Basis spread interest rate on secured overnight financing rate			2.90%

Related-Party Transactions (Det

Related-Party Transactions (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Apr. 14, 2023 d $ / shares shares	Dec. 31, 2023 USD ($) shares	Dec. 31, 2022 USD ($) shares	Sep. 29, 2023 shares
Related Party Transaction [Line Items]
Common stock outstanding (in shares) | shares		21,888,976	13,303,795	21,888,976
Award trading restriction period	2 years
Research and development expense | $		$ 15,668	$ 16,746
Accounts payable | $		11,040	975
Related Party
Related Party Transaction [Line Items]
Research and development expense | $		620	439
Amended And Restated Sponsor Support Lockup Agreement | Related Party | Graf Acquisition Partners IV LLC
Related Party Transaction [Line Items]
Common stock outstanding (in shares) | shares	4,290,375
Shares forfeited (in shares) | shares	1,773,631
Restricted shares subject to vesting conditions (in shares) | shares	1,173,631
Shares were not forfeited, did not become restricted, nor subject to vesting conditions (in shares) | shares	1,343,113
Advisory and Research Services | Related Party
Related Party Transaction [Line Items]
Research and development expense | $		0	400
Accounts payable | $		0	100
Purchases of Laboratory Supplies | Related Party
Related Party Transaction [Line Items]
Research and development expense | $		600	100
Accounts payable | $		$ 600	$ 100
Deferred Founder Shares | Amended And Restated Sponsor Support Lockup Agreement | Related Party | Graf Acquisition Partners IV LLC
Related Party Transaction [Line Items]
Vesting period	5 years
Deferred Founder Shares | Trance One | Amended And Restated Sponsor Support Lockup Agreement | Related Party | Graf Acquisition Partners IV LLC
Related Party Transaction [Line Items]
Share price trigger (in USD per share) | $ / shares	$ 14
Threshold trading days | d	20
Threshold consecutive trading days | d	30
Shares vested (in shares) | shares	873,631
Deferred Founder Shares | Tranche Two | Amended And Restated Sponsor Support Lockup Agreement | Related Party | Graf Acquisition Partners IV LLC
Related Party Transaction [Line Items]
Share price trigger (in USD per share) | $ / shares	$ 20
Threshold trading days | d	20
Threshold consecutive trading days | d	30
Shares vested (in shares) | shares	300,000

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Schedule of Fair Value Hierarchy (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	$ 41,563
Private warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	378
Working capital warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	42
Forward Purchase Derivative Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	15,804
PIPE warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	25,339
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	0
Level 1 | Private warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Level 1 | Working capital warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Level 1 | Forward Purchase Derivative Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Level 1 | PIPE warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	0
Level 2 | Private warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Level 2 | Working capital warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Level 2 | Forward Purchase Derivative Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Level 2 | PIPE warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value	41,563
Level 3 | Private warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	378
Level 3 | Working capital warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	42
Level 3 | Forward Purchase Derivative Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	15,804
Level 3 | PIPE warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	$ 25,339

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Narrative (Details) $ / shares in Units, $ in Thousands		2 Months Ended	12 Months Ended
	Sep. 29, 2023 USD ($) $ / shares shares	Dec. 31, 2019 USD ($)	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Stock converted, reverse recapitalization (in shares) | shares	2,278,598
Conversion of legacy NKGen convertible promissory notes	$ 18,913		$ 18,913	$ 0
Stock converted, reverse recapitalization (in USD per share) | $ / shares	$ 8.30
Derivative warrant liabilities			25,759	0
Forward purchase derivative liability	$ 20,200		15,804	$ 0
Proceeds from issuance of senior convertible promissory notes with warrants	10,000
Fair Value, Recurring
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Senior Notes			$ 8,500
SPA warrants
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Warrants issued (in shares) | shares			1,000,000
Warrant, exercise price (in dollars per share) | $ / shares			$ 11.50
Senior convertible notes’ shares
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value of debt			$ 8,500
Private warrants
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative warrant liabilities	1,800		400
Working capital warrants
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative warrant liabilities	200		100
PIPE warrants
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative warrant liabilities	$ 10,200		25,300
Warrants issued (in shares) | shares	10,209,994
Warrant, exercise price (in dollars per share) | $ / shares	$ 1
Forward Purchase Derivative Liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Forward purchase derivative liability			$ 15,800
Dividend yield (per share)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Private warrants and working capital warrants unobservable input	0		0	0
2019 Convertible Notes
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Proceeds from issuance of senior convertible promissory notes with warrants		$ 10,800
Relative Fair Value At Initial Recognition | SPA warrants
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Warrants, stand-alone fair value disclosure	$ 400		$ 100
Warrants, relative fair value disclosure			300
Relative Fair Value At Initial Recognition | Senior convertible notes’ shares
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Convertible debt, stand-alone fair value disclosures	$ 12,900		8,500
Convertible debt, relative fair value disclosures			$ 9,700

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Legacy Convertible Notes Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities measured at fair value, beginning balance	$ 11,655	$ 11,478
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Change in fair value of convertible promissory notes and convertible promissory notes due to related parties (including related party amounts of $12 and $4 for the years ended December 31, 2023 and 2022, respectively)
Issuance	$ 6,215
Change in fair value	1,043	177
Conversion and settlement	(18,913)
Balance as of December 31, 2023	0	11,655
2019 Convertible Notes | Nonrelated Party
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities measured at fair value, beginning balance	11,392	11,219
Issuance	0
Change in fair value	1,083	173
Conversion and settlement	(12,475)
Balance as of December 31, 2023	0	11,392
2019 Convertible Notes | Related Party
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities measured at fair value, beginning balance	263	259
Issuance	0
Change in fair value	13	4
Conversion and settlement	(276)
Balance as of December 31, 2023	0	263
2023 Convertible Notes | Nonrelated Party
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities measured at fair value, beginning balance	0	0
Issuance	6,090
Change in fair value	(52)	0
Conversion and settlement	(6,038)
Balance as of December 31, 2023	0	0
2023 Convertible Notes | Related Party
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Liabilities measured at fair value, beginning balance	0	0
Issuance	125
Change in fair value	(1)	0
Conversion and settlement	(124)
Balance as of December 31, 2023	$ 0	$ 0

Fair Value of Financial Instr_6

Fair Value of Financial Instruments - Valuation Assumptions of Legacy Convertible Notes (Details) - Legacy Convertible Notes	Dec. 31, 2022
Probability of conversion
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0
Probability of holding until maturity without conversion
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0
Remaining term until potential conversion trigger date (years)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0
Discount Yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.200

Fair Value of Financial Instr_7

Fair Value of Financial Instruments - Valuation Assumptions of Senior Convertible Notes (Details) - Senior convertible notes’ shares	Dec. 31, 2023	Sep. 29, 2023
Credit spread
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.127	0.121
Equity volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.450	0.450

Fair Value of Financial Instr_8

Fair Value of Financial Instruments - Warrants and Working Capital Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Balance as of December 31, 2022	$ 0	$ 11,655	$ 11,478
Issuance	6,215
Change in fair value	1,043	177
Balance as of December 31, 2023	$ 0	11,655
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Change in fair value of convertible promissory notes and convertible promissory notes due to related parties (including related party amounts of $12 and $4 for the years ended December 31, 2023 and 2022, respectively)
Private Warrants
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Balance as of December 31, 2022	$ 377	0
Issuance	1,841
Change in fair value	(1,464)
Balance as of December 31, 2023	377	0
Working capital warrants
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Balance as of December 31, 2022	42	0
Issuance	204
Change in fair value	(162)
Balance as of December 31, 2023	42	0
Total
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Balance as of December 31, 2022	419	0
Issuance	2,045
Change in fair value	(1,626)
Balance as of December 31, 2023	$ 419	$ 0

Fair Value of Financial Instr_9

Fair Value of Financial Instruments - Private Warrants and Working Capital Warrants (Details)	Dec. 31, 2023	Sep. 29, 2023	Dec. 31, 2022
Equity volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Private warrants and working capital warrants unobservable input	0.353	0.096
Dividend yield (per share)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Private warrants and working capital warrants unobservable input	0	0	0

Fair Value of Financial Inst_10

Fair Value of Financial Instruments - PIPE Warrants Reconciliation (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance as of December 31, 2022		$ 0	$ 11,655	$ 11,478
Change in fair value		1,043	177
Issuance		$ 6,215
PIPE warrants
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance as of December 31, 2022	$ 25,339		$ 0
Change in fair value	15,129
Issuance	$ 10,210

Fair Value of Financial Inst_11

Fair Value of Financial Instruments - Valuation Assumptions of PIPE Warrants (Details) - PIPE warrants	Dec. 31, 2022
Credit spread
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.127
Equity volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	1

Fair Value of Financial Inst_12

Fair Value of Financial Instruments - Forward Purchase Derivative Liability Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Balance as of December 31, 2022	$ 0	$ 11,655	$ 11,478
Issuance	(6,215)
Change in fair value	1,043	177
Balance as of December 31, 2023	0	11,655
Forward Purchase Derivative Liability
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Balance as of December 31, 2022	15,804	20,201
Issuance	(14,181)
Change in fair value	9,784
Balance as of December 31, 2023	$ 15,804	$ 20,201

Fair Value of Financial Inst_13

Fair Value of Financial Instruments - Valuation Assumptions of Forward Purchase Derivative Liability (Details) - Forward Purchase Derivative Liability	Dec. 31, 2023	Dec. 26, 2023	Sep. 29, 2023
Dividend yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Forward purchase derivative liability unobservable input	0	0	0
Equity volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Forward purchase derivative liability unobservable input	1.150	1.250	1.050

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) installment $ / shares shares	Sep. 29, 2023 shares	Dec. 31, 2022 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock, shares authorized (shares)	500,000,000		500,000,000
Common stock, par value (in USD per share) | $ / shares	$ 0.0001		$ 0.0001
Common stock, shares issued (in shares)	21,888,976		13,303,795
Common stock outstanding (in shares)	21,888,976	21,888,976	13,303,795
Common stock, reserved for future issuance (in shares)	478,111,024
Preferred stock, shares authorized (in shares)	10,000,000
Preferred stock, par value (in USD per share) | $ / shares	$ 0.0001
Preferred stock, shares issued (in shares)	0
Preferred stock, shares outstanding (in shares)	0
Intrinsic value of stock options exercised | $	$ 0.1
Fair value of options vested | $	1.2
Unrecognized stock-based compensation | $	$ 14.1
Employee Stock
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Maximum shares allowed to be issued (as a percent)	3%
ESPP purchase price of common stock, percent of market price (as a percent)	85%
Weighted- average period of recognition	3 years
Stock Compensation | 2023 Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Maximum shares allowed to be issued (as a percent)	12%
Stock options
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected dividend yield	0%
Stock options | 2019 Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration period (in years)	10 years
Vesting period	4 years
Vested, expiration period	3 months
Vesting percentage (as a percent)	25%
Number of monthly installments | installment	36
Stock options | 2019 Plan | Minimum | Board Member
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period	3 years
Stock options | 2019 Plan | Maximum | Board Member
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period	4 years

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Stock Option Activity (Details)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Stock Options Outstanding
Outstanding at beginning of period (in shares) | shares	185,231
Granted (in shares) | shares	2,173,693
Forfeited (in shares) | shares	(267,072)
Exercised (in shares) | shares	(12,866)
Outstanding at end of period (in shares) | shares	2,078,986
Weighted Average Exercise Price
Outstanding at beginning of period (in USD per share) | $ / shares	$ 1.37
Granted (in USD per share) | $ / shares	6.67
Forfeited (in USD per share) | $ / shares	6.56
Exercised (in USD per share) | $ / shares	0.88
Outstanding at end of period (in USD per share) | $ / shares	$ 6.25

Stockholders' Equity - Stock Op

Stockholders' Equity - Stock Option Valuation Assumptions (Details) - Stock options	12 Months Ended
	Dec. 31, 2023 $ / shares
Equity [Abstract]
Common stock fair value (in usd per share)	$ 9.18
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock fair value (in usd per share)	$ 9.18
Risk-free interest rate	3.50%
Expected volatility	111%
Expected term (in years)	6 years 1 month 6 days
Expected dividend yield	0%

Stockholders' Equity - Schedu_2

Stockholders' Equity - Schedule of Stock Options Vested and Expected to Vest (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Number of Stock Options
Outstanding at beginning of period (in shares)	185,231
Outstanding at end of period (in shares)	2,078,986	185,231
Vested and expected to vest (in shares)	2,078,986
Exercisable (in shares)	302,760
Weighted Average Remaining Contractual Life (Years)
Outstanding as of December 31, 2022	8 years 10 months 9 days	6 years 11 months 23 days
Outstanding as of December 31, 2023	8 years 10 months 9 days	6 years 11 months 23 days
SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1	8 years 10 months 9 days
Exercisable (years)	7 years 5 months 15 days
Weighted- Average Exercise Price
Outstanding at beginning of period (in USD per share)	$ 1.37
Outstanding at end of period (in USD per share)	6.25	$ 1.37
Vested and expected to vest (in USD per share)	6.25
Exercisable (in USD per share)	$ 3.79
Total Aggregate Intrinsic Value (in thousands)
Outstanding at beginning of period	$ 980
Outstanding at end of period	317	$ 980
Vested and expected to vest	317
Exercisable	$ 317

Stockholders' Equity - Schedu_3

Stockholders' Equity - Schedule of Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 4,135	$ 69
Research and development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	898	45
General and administrative
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 3,237	$ 24

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]
Property and equipment, gross	$ 18,284	$ 18,211
Less: Accumulated depreciation	(3,825)	(2,690)
Property and equipment, net	14,459	15,521
Land
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 5,025	5,025
Buildings
Property, Plant and Equipment [Line Items]
Useful Life	40 years
Property and equipment, gross	$ 8,325	8,325
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Useful Life	7 years
Property and equipment, gross	$ 749	677
Lab equipment
Property, Plant and Equipment [Line Items]
Useful Life	5 years
Property and equipment, gross	$ 4,004	4,003
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 52	52
Office equipment
Property, Plant and Equipment [Line Items]
Useful Life	5 years
Property and equipment, gross	$ 17	17
Vehicles
Property, Plant and Equipment [Line Items]
Useful Life	5 years
Property and equipment, gross	$ 112	$ 112

Property and Equipment, net - N

Property and Equipment, net - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1.1	$ 1.2

Additional Balance Sheet Info_3

Additional Balance Sheet Information - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Prepaid expenses	$ 1,565	$ 133
Other receivables	26	67
Revolving line of credit issuance fees	47	0
Other	16	4
Prepaid expenses and other current assets	$ 1,654	$ 204

Additional Balance Sheet Info_4

Additional Balance Sheet Information - Schedule of Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Balance Sheet Related Disclosures [Abstract]
Accounts payable	$ 11,040	$ 975
Accrued liabilities	1,360	1,359
Employee compensation	911	291
Other	84	27
Accounts payable and accrued expenses	$ 13,395	$ 2,652

Collaboration Agreement (Detail

Collaboration Agreement (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Reductions to research and development expenses	$ 0.2	$ 0.4

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details)	3 Months Ended
	Mar. 31, 2021 USD ($)	Dec. 31, 2023 USD ($) country	Nov. 09, 2023	Dec. 31, 2022 USD ($)	Oct. 31, 2021	Feb. 28, 2018
Other Commitments [Line Items]
Term of lease			3 years		2 years	5 years
Renewal extension period					2 years
Payments for license agreement	$ 1,000,000
Accrued litigation liability		$ 0		$ 0
NKMAX
Other Commitments [Line Items]
Number of countries | country		4
NKMAX | UNITED STATES
Other Commitments [Line Items]
Milestone payment, after regulatory approval		$ 5,000,000
NKMAX | European Union
Other Commitments [Line Items]
Milestone payment, after regulatory approval		4,000,000
NKMAX | Country A
Other Commitments [Line Items]
Milestone payment, after regulatory approval		1,000,000
NKMAX | Country B
Other Commitments [Line Items]
Milestone payment, after regulatory approval		1,000,000
NKMAX | Country C
Other Commitments [Line Items]
Milestone payment, after regulatory approval		1,000,000
NKMAX | Country D
Other Commitments [Line Items]
Milestone payment, after regulatory approval		$ 1,000,000

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Rental Payments for Operating Leases (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2024	$ 235
2025	242
2026	249
Total operating lease liability	$ 726

Income Taxes - Provision For In

Income Taxes - Provision For Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Current:
Federal	$ 0	$ 0
State	0	0
Deferred:
Federal	7	7
State	0	0
Provision for income taxes	$ 7	$ 7

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Tax Provision (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Tax benefit at statutory federal rate	$ (17,419)	$ (5,618)
State tax, net of federal tax benefit	(1,946)	(1,694)
Interest expense	47	477
Increase in valuation allowance	9,189	7,908
Permanent items	12	37
Stock compensation	359	(4)
Unrealized loss FV of notes	219	0
General business tax credit	(1,278)	(1,098)
Loss on issuance of forward purchase contract	5,140	0
Loss on amendment of the subscription receivable	93	0
Loss on derivative valuation	4,890	0
Other	701	(1)
Provision for income taxes	$ 7	$ 7

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating losses	$ 22,843	$ 17,890
Tax credit carryforwards, net	4,523	3,285
Accrued expenses	395	347
Section 174 R&E capitalization	4,939	2,847
Intangibles	707	0
Lease liability	0	106
Stock-based compensation	699	20
Total deferred tax assets	34,106	24,495
Deferred tax liabilities:
Operating lease right-of-use asset	0	(101)
Property and equipment	(406)	(595)
Total deferred tax liabilities	(406)	(696)
Net deferred tax assets	33,700	23,799
Less: Valuation allowance	(33,733)	(23,825)
Net deferred tax liability	$ (33)	$ (26)

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Valuation Allowance [Line Items]
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	$ 9,900	$ 7,900
Operating Loss Carryforwards	76,300
Tax Credit Carryforward, Amount	3,200
Tax cut and Jobs Act, Net Operating Loss Generated	76,300
California Research And Development
Valuation Allowance [Line Items]
Tax Credit Carryforward, Amount	2,300
State and Local Jurisdiction
Valuation Allowance [Line Items]
Operating Loss Carryforwards	$ 96,700

Income Taxes- Unrecognized Tax

Income Taxes- Unrecognized Tax Benefits, Excluding Accrued Interest and Penalties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 403	$ 269
Additions for tax positions related to the current year	129	131
Reductions for tax positions related to prior years	19	3
Ending balance	$ 551	$ 403

Subsequent Events (Details)

Subsequent Events (Details) $ / shares in Units, $ in Thousands

1 Months Ended

3 Months Ended

Apr. 15, 2024 shares

Apr. 05, 2024 USD ($) tranche $ / shares shares

Apr. 01, 2024 USD ($) $ / shares shares

Mar. 26, 2024 USD ($) $ / shares shares

Mar. 21, 2024 USD ($) $ / shares shares

Mar. 07, 2024 USD ($) agreement shares

Feb. 27, 2024 USD ($) $ / shares shares

Feb. 21, 2024 USD ($) shares

Feb. 20, 2024 USD ($) $ / shares shares

Feb. 12, 2024 shares

Feb. 09, 2024 USD ($)

Feb. 07, 2024 USD ($) $ / shares shares

Feb. 02, 2024 USD ($)

Jan. 19, 2024 USD ($) $ / shares

Jan. 11, 2024 USD ($)

Jan. 02, 2024 USD ($)

Dec. 26, 2023 shares

Sep. 29, 2023 shares

Sep. 28, 2023 shares

Apr. 30, 2024

Dec. 31, 2023 shares

Subsequent Event [Line Items]

Shares purchased (in shares)

3,168,121

Stock options issued (in shares)

2,101,760

Number of additional shares available (in shares)

767,990

Forecast | Bridge Loan

Subsequent Event [Line Items]

Number of securities purchased (in shares)

375,000

100,000

400,000

Warrant, exercise price (in dollars per share) | $ / shares

$ 1.50

$ 2

$ 2

Forecast | Bridge Loan | Bridge Loan Agreement Due Either 60 Days or Financing Event

Subsequent Event [Line Items]

Number of securities purchased (in shares)

375,000

Forecast | Convertible Debt

Subsequent Event [Line Items]

Warrant, exercise price (in dollars per share) | $ / shares

$ 2

Forward Purchase Agreement

Subsequent Event [Line Items]

Discount of VWAP measurement

0.10

Number of additional shares available (in shares)

200,000

Subsequent Event

Subsequent Event [Line Items]

Sale of Stock, Common Stock Purchase Agreement, Increase To The Prepayment Shortfall | $

$ 200

$ 300

$ 500

$ 500

Sale Of Stock, Common Stock Purchase Agreement, Proceeds Received From Increase Of Prepayment Shortfall | $

$ 200

$ 500

$ 300

$ 500

Sale Of Stock, Common Stock Purchase Agreement, Percent Of Prepayment Shortfall, Proceeds Received

20%

Initial price ceiling (in usd per share) | $ / shares

$ 10.44

VWAP trailing period

5 days

Stock options issued (in shares)

3,233,028

Subsequent Event | Bridge Loan Agreement Maturing March 22, 2024

Subsequent Event [Line Items]

Number of bridge loan agreements | agreement

2

Subsequent Event | Convertible Debt

Subsequent Event [Line Items]

VWAP trailing period

5 days

Number of securities purchased (in shares)

1,000,000

Warrant, exercise price (in dollars per share) | $ / shares

$ 2

$ 2

Interest rate

2.85%

Promissory note agreement | $

$ 5,000

Number of trances | tranche

2

Conversion price (in dollars per share) | $ / shares

$ 2

Number of additional shares available (in shares)

2,500,000

Stock issued during period (in shares)

833,333

Subsequent Event | Convertible Debt | First Tranche

Subsequent Event [Line Items]

Promissory note agreement | $

$ 1,000

Subsequent Event | Convertible Debt | Second Tranche

Subsequent Event [Line Items]

Promissory note agreement | $

$ 4,000

Subsequent Event | First Tranche

Subsequent Event [Line Items]

Proceeds from warrant investors, warrant amendment option | $

$ 300

Subsequent Event | Second Tranche

Subsequent Event [Line Items]

Proceeds from warrant investors, warrant amendment option | $

$ 300

Subsequent Event | Bridge Loan

Subsequent Event [Line Items]

Bridge loan | $

$ 100

$ 100

$ 400

Premium, percentage

20%

20%

20%

Debt instrument, financing event threshold, debt maturity | $

$ 5,000

$ 10,000

$ 5,000

Number of additional shares available (in shares)

3,667

Subsequent Event | Bridge Loan | Bridge Loan Agreement Due Either 60 Days or Financing Event

Subsequent Event [Line Items]

Bridge loan | $

$ 100

Premium, percentage

20%

Debt instrument, financing event threshold, debt maturity | $

$ 5,000

Number of additional shares available (in shares)

3,667

Subsequent Event | Bridge Loan | Bridge Loan Agreement Maturing March 22, 2024

Subsequent Event [Line Items]

Bridge loan | $

$ 100

Premium, percentage

7.50%

Subsequent Event | Commercial Paper | FPA Investor

Subsequent Event [Line Items]

Borrowing term

1 year

Subsequent Event | Commercial Paper | Other Lender

Subsequent Event [Line Items]

Borrowing term

1 year

Subsequent Event | Convertible Debt

Subsequent Event [Line Items]

Borrowing term

1 year

1 year

Number of securities purchased (in shares)

330,000

330,000

Warrant, exercise price (in dollars per share) | $ / shares

$ 2

Interest rate

12%

12%

Promissory note agreement | $

$ 300

$ 300

Discount percentage, issued

0.10

0.10

Subsequent Event | Convertible Debt | FPA Investor

Subsequent Event [Line Items]

Number of securities purchased (in shares)

330,000

Interest rate

12%

Promissory note agreement | $

$ 300

Discount percentage, issued

0.10

Subsequent Event | Convertible Debt | Other Lender

Subsequent Event [Line Items]

Number of securities purchased (in shares)

220,000

Warrant, exercise price (in dollars per share) | $ / shares

$ 2

Interest rate

12%

Promissory note agreement | $

$ 200

Discount percentage, issued

0.10

Subsequent Event | Warrant | Bridge Loan

Subsequent Event [Line Items]

Warrants issued (in shares)

100,000

Number of additional warrants available (in warrants)

375,000

400,000

Subsequent Event | Warrant | Bridge Loan | Bridge Loan Agreement Due Either 60 Days or Financing Event

Subsequent Event [Line Items]

Number of additional warrants available (in warrants)

375,000

Subsequent Event | Minimum | Bridge Loan

Subsequent Event [Line Items]

Borrowing term

60 days

60 days

60 days

90 days

Subsequent Event | Minimum | Bridge Loan | Bridge Loan Agreement Due Either 60 Days or Financing Event

Subsequent Event [Line Items]

Borrowing term

60 days

Subsequent Event | Forward Purchase Agreement

Subsequent Event [Line Items]

Number of shares re-designated (in shares)

200,000

Shares purchased (in shares)

1,768,121

Discount of VWAP measurement

0.10

Subsequent Event | FPA Shares Subject To Sale

Subsequent Event [Line Items]

Number of additional shares available (in shares)

1,000,000

Subsequent Event | Private Placement Agreements

Subsequent Event [Line Items]

Number of additional shares available (in shares)

1,167,990