Material Agreement (Form 8-K)

Item 1.01. Entry into a Material Definitive Agreement.

On April 15, 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 a Secured Convertible Loan Agreement (the "Loan Agreement") with AlpineBrook Capital GP I Limited (the "Lender").

Background

Pursuant to the Loan Agreement, the Lender agreed to extend a secured convertible loan in the aggregate principal amount of $39,922,134.22 (the "Convertible Loan") to the Borrowers. The Convertible Loan refinances and replaces the following existing indebtedness of the Borrowers to the Lender and East West Bank ("EWB"): (i) a promissory note issued by the Company to EWB on June 20, 2023 (the "EWB Note"), which was acquired by the Lender from EWB in connection with the closing of the transactions contemplated by the Loan Agreement, (ii) a convertible promissory note issued by the Borrowers to the Lender on December 31, 2024, (iii) a convertible promissory note issued by the Borrowers to the Lender on March 10, 2025, (iv) a secured promissory note issued by the Borrowers to the Lender on January 5, 2026 (as amended), (v) new cash funding in the amount of $350,000 to the Borrowers, which will be used to cover immediate operating expenses, and (vi) accrued interest, charges, fees and other obligations in respect of the refinancing, indebtedness and advances described in clauses (i) to (v) above.

As of the date of this Current Report on Form 8-K, the Company has a limited cash balance and intends to continue to seek additional funding for its operations.

Material Terms of the Loan Agreement and Note

In connection with the Convertible Loan, the Borrowers issued to the Lender a Secured Convertible Promissory Note dated April 15, 2026 (the "Note") in the principal amount of $39,922,134.22. The material terms of the Loan Agreement and the Note are summarized below:

Interest Rate. The Convertible Loan bears interest at a rate of 12% per annum (the "Applicable Rate"), payable monthly in arrears on the first calendar day of each calendar month. Interest is computed on the basis of a 360-day year for the actual number of days elapsed. Any unpaid amount (that is due and payable) bears interest at the Applicable Rate plus 12% per annum.

Maturity Date. The Convertible Loan matures on the one-year anniversary of the closing date of the transaction, subject to extension by the Lender in its sole discretion for any period it deems fit, or earlier upon acceleration following an event of default.

Conversion. The Lender has the right, at its sole discretion, to convert the outstanding principal, accrued and unpaid interest, fees and other obligations under the Convertible Loan, in whole or in part, at any time and from time to time, 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 (the "Conversion Price"), subject to adjustment as described below. No conversion may be effected, and no shares of Common Stock may be delivered to the Lender, until after sixty-one (61) full days following the date of the Lender's issuance of a conversion notice.

Prepayment. The Borrowers may not voluntarily prepay the Convertible Loan, in whole or in part, without the prior written consent of the Lender. Mandatory prepayment is required upon acceleration following an event of default and from proceeds of any sale of shares of NKGen Biotech Korea Co., Ltd. ("NKGen Korea") consented to by the Lender.

Beneficial Ownership Limitation. In no event shall the Company issue to the Lender shares of Common Stock which would result in the Lender and its affiliates together beneficially owning more than 9.99% of the then issued and outstanding Common Stock.