Material Agreement, Financial Obligation (Form 8-K)

Item 1.01. Entry into a Material Definitive Agreement.

On April 28, 2026, NKGen Biotech, Inc., a Delaware corporation (the "Company"), and NKGen Operating Biotech, Inc., a Delaware corporation and wholly owned subsidiary of the Company ("NKGen OpCo," and together with the Company, the "Borrowers"), entered into an Omnibus Amendment to Secured Convertible Loan Agreement and Other Loan Documents (the "Amendment") with AlpineBrook Capital GP I Limited (the "Lender"). The Amendment amends that certain Secured Convertible Loan Agreement, dated as of April 15, 2026, by and among the Borrowers and the Lender (as amended, the "Loan Agreement"), and certain other related loan documents executed in connection with the Loan Agreement (as described on the Company's Current Report on Form 8-K filed with the Securities and Exchange Commission (the "SEC") on April 21, 2026).

Pursuant to the Amendment, the Lender agreed to extend an additional loan to the Borrowers in the principal amount of $607,200 (the "Additional Loan"), which includes a facilitation fee of $55,200 that is fully earned by and owed to the Lender on the effective date and is included in the principal of the Additional Loan. The net proceeds to the Borrowers from the Additional Loan are $552,000. The Additional Loan is documented by a new Secured Convertible Promissory Note (Additional Note #1) (the "Additional Note") issued by the Borrowers in favor of the Lender in the principal amount of $607,200. The Additional Note bears interest at the Applicable Rate (as defined in the Loan Agreement) and is convertible into shares of the Company's common stock, par value $0.0001 per share (the "Common Stock"), at a conversion price of $0.08 per share, subject to adjustment.

In addition, the Amendment provides that the number of consideration shares of Common Stock to be issued by the Company to the Lender pursuant to the Loan Agreement (the "Consideration Shares") was increased to 12,009,780 shares, to be delivered in five installments over 25 months following the closing date of the Loan Agreement.

In connection with the Amendment and the Additional Loan, the Company also issued to the Lender a Common Stock Purchase Warrant (the "Additional Warrant"), dated April 28, 2026. The Additional Warrant entitles the Lender to purchase a number of shares of Common Stock equal to three times the quotient of the principal amount outstanding under the Additional Note as of the date of issuance divided by the conversion price as of the date of issuance, at an exercise price of $0.08 per share, subject to adjustment. The Additional Warrant is exercisable at any time during the ten-year period commencing on the date of issuance and includes provisions for cashless exercise. The Additional Warrant contains a beneficial ownership limitation of 9.99% and customary anti-dilution protections.

In connection with the Amendment, the Company, the Lender, Graf Acquisition Partners IV LLC, NKGen Biotech Korea Co., Ltd., and Paul Song entered into a Voting Agreement, dated April 28, 2026 (the "Voting Agreement"), pursuant to which such stockholders agreed to vote their shares of Common Stock in favor of an increase in the number

of authorized shares of Common Stock sufficient to provide for the issuance of the Consideration Shares and five (5) times the shares of Common Stock issuable in connection with the conversion of the 2026 Secured Convertible Note (as defined in the Loan Agreement) and the Additional Note, and the exercise of the Warrant (as defined in the Loan Agreement) and the Additional Warrant. Pursuant to the Loan Agreement, the Company is required to obtain stockholder approval for such increase no later than the earlier of (a) two months after the closing date of the Loan Agreement and (b) immediately prior to the closing of the Company's next financing (whether equity or debt).

The foregoing descriptions of the Amendment, the Additional Note, the Additional Warrant, and the Voting Agreement do not purport to be complete and are qualified in their entirety by reference to the full text of such documents, copies of which are filed as exhibits to this Current Report on Form 8-K and are incorporated herein by reference.

Item 2.03. Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.

The disclosures set forth in Item 1.01 are incorporated into this Item 2.03 by reference.