NKGen Biotech (NKGN) signs $25.84M secured promissory note with AlpineBrook

Rhea-AI Filing Summary

NKGen Biotech, Inc. entered into a new secured promissory note with AlpineBrook Capital GP I Limited on January 5, 2026. The note has an original principal amount of $25,840,106, bears interest at 12% per year, and initially matures two months after issuance, with any extension at the lender’s discretion. It formalizes earlier undocumented cash advances totaling $25,540,106 and adds a new $300,000 advance.

The note cannot be prepaid before maturity without lender consent and includes a “most favored nation” clause requiring NKGen to match more favorable terms granted in future debt or equity financings. A Change of Control triggers cash repayment of principal and interest plus a cash premium equal to 20% of outstanding principal, while events of default increase the interest rate to 24% per year. The lender receives security interests over substantially all U.S. personal property of the borrowers, certain U.S. real property, and Korean collateral related to NKGen Biotech Korea, alongside restrictive covenants limiting additional debt, liens, and equity issuances.

Positive

• None.

Negative

• High-cost, short-term secured debt: NKGen enters a $25.84M secured note at 12% interest with an initial two‑month maturity and 24% default rate, increasing financial pressure if repayment or extension is difficult.
• Extensive covenants and collateral: The note adds broad liens over U.S. and Korean assets, a 20% Change of Control premium, and restrictions on new debt, liens, and equity, which can limit financing flexibility.

Insights

Credit & capital structure analyst

NKGen documents costly short-term secured debt with tight covenants and broad collateral.

NKGen Biotech and its subsidiary entered a secured note with AlpineBrook for $25,840,106 at a 12% annual rate, initially maturing two months after issuance. Most of this amount ($25,540,106) represents prior advances tied to acquiring a majority stake in NKGen Biotech Korea, with only $300,000 of new cash funded at signing. Prepayment is blocked without lender consent, concentrating refinancing or repayment flexibility in the lender’s hands.

The agreement adds a “most favored nation” provision for future debt or equity financings, requiring NKGen to extend any more favorable economic or governance terms to this lender. That can influence the structure of future capital raises, since better terms elsewhere must be mirrored here. A Change of Control compels cash repayment plus a 20% principal premium, and default pushes interest to 24% annually, increasing the cost of adverse scenarios.

Security interests extend to substantially all U.S. personal property, certain U.S. real estate via a deed of trust, and Korean collateral tied to NKGen Korea shares and assets, subject to consents and existing liens. Covenants restrict additional indebtedness, liens, and equity issuances, and include a negative pledge in favor of the lender. This combination of high-cost, short-tenor debt, broad collateral, and restrictive covenants is likely to be viewed as a meaningful constraint on NKGen’s balance sheet strategy.

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15 (d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): January 5, 2026

NKGen Biotech, Inc.

(Exact name of registrant as specified in its charter)

Delaware		001-40427		86-2191918
(State or other jurisdiction of incorporation)		(Commission File Number)		(IRS Employer Identification No.)

3001 Daimler Street

Santa Ana, CA, 92705

(Address of principal executive offices and zip code)

Registrant’s telephone number, including area code: (949) 396-6830

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2 below):

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, $0.0001 par value per share		NKGN		OTC Expert Market
Warrants, each whole warrant exercisable for one share of Common Stock at an exercise price of $11.50 per share		NKGNW		OTC Expert Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 1.01. Entry into a Material Definitive Agreement.

On January 5, 2026, NKGen Biotech, Inc., a Delaware corporation (the “Company”), and NKGen Operating Biotech, Inc., a Delaware corporation (the “Company Sub,” and together with the Company, the “Borrowers”), entered into a secured promissory note (the “Note”) with AlpineBrook Capital GP I Limited (the “Lender”), in the original principal amount of $25,840,106, bearing interest at 12% per annum and maturing initially on the date falling two months after issuance, subject to extension at the Lender’s discretion. The Note documents and evidences certain undocumented cash advances made by the Lender to the Borrowers since late 2024, primarily in connection with the Company’s acquisition of a majority stake in NKGen Biotech Korea Co., Ltd. (f/k/a NKMax Co., Ltd.) (“NKGen Korea”) through the Korean bankruptcy process, together with accrued interest, fees and expenses associated with such advances, which totaled $25,540,106 immediately prior to issuance. In addition, the Note reflects an incremental $300,000 advanced by the Lender contemporaneously with execution, which is the only new capital funded in connection with the Note. The Note prohibits prepayment before the applicable maturity date without lender consent.

The Note includes a “most favored nation” provision applicable to future debt or equity financings of the Borrowers or any of their subsidiaries (including NKGen Korea). During the term of the Note, if either Borrower or any of its subsidiaries undertakes any subsequent debt or equity financing containing terms more favorable than those in the Note, the Borrowers must notify the Lender and provide the benefit of such more favorable terms to the Lender. The provision expressly covers, without limitation, economic terms (including interest rate), collateral, conversion price and related economics, warrant coverage, governance rights, information rights, director appointment rights, preemptive rights, and rights of first refusal.

Upon a Change of Control (as defined in the Note) of either Borrower, the Note requires repayment in cash of outstanding principal plus accrued but unpaid interest, together with a cash premium equal to 20% of the then-outstanding principal amount. Borrowers must provide notice at least 10 business days’ advance notice of any such transaction.

If an event of default occurs and is continuing, all outstanding obligations under the Note bear default interest at a rate of 24% per annum, calculated on a 360-day year and payable on demand.

The Note contains restrictive covenants that, among other things, limit additional indebtedness and the granting of liens, subject to limited customary baskets and existing liens in favor of East West Bank (“EWB”) and BDW Investments LLC (“BDW”). The covenant package also restricts equity issuances and changes to the capital structure, subject to ordinary-course exceptions (including plan-based equity awards, exercises, and ministerial adjustments), and includes a negative pledge whereby the Borrowers and their subsidiaries (including NKGen Korea) may not grant collateral or guarantees in favor of third parties without the Lender’s prior written consent.

Pursuant to the Note, the Borrowers granted the Lender security interests in certain collateral, subject to existing liens in favor of EWB and BDW, respectively. The security interests will not be perfected unless and until consents from said secured creditors are obtained, and all grants are subordinate to existing liens. The collateral package includes (1) a security interest in substantially all U.S. personal property of the Borrowers; (2) a deed of trust and an assignment of leases and rents with respect to U.S. real property owned or hereafter owned by the Company Sub, to be executed and delivered in agreed form following execution of the Note, subject to consents of EWB and BDW; and (3) security arrangements under Korean law relating to the Company’s shares of NKGen Korea, and related account collateral. Additionally, the Note requires the Company to use commercially reasonable best efforts to cause NKGen Korea to provide an unconditional guarantee of the Borrowers’ obligations and to grant a first-priority security interest over substantially all of NKGen Korea’s assets to secure that guarantee (subject to NKGen Korea board approval, certain waivers/consents, and compliance with applicable law).

Additionally, the Note grants the Lender a right of first refusal over any proposed transfer or other disposition by the Company of its shares of NKGen Korea, on terms generally consistent with the third-party offer.

The foregoing description of the Note does not purport to be complete and is qualified in its entirety by the terms and conditions of the Note which is filed as Exhibit 10.1 to this Current Report on Form 8-K and 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 by into this Item 2.03 by reference.

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Item 9.01. Financial Statements and Exhibits

(d) Exhibits.

Exhibit No.		Description
10.1		Secured Promissory Note issued to the AlpineBrook Capital GP I Limited, dated January 5, 2026.
104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

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SIGNATURES

Pursuant to the requirements of Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	NKGEN BIOTECH, INC.
Date: January 9, 2026	/s/ Paul Y. Song
	Name:	Paul Y. Song
	Title:	Chief Executive Officer
		(Principal Executive Officer)

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FAQ

What financing did NKGen Biotech (NKGN) enter into on January 5, 2026?

NKGen Biotech and its subsidiary entered into a secured promissory note with AlpineBrook Capital GP I Limited in the original principal amount of $25,840,106, bearing 12% annual interest and initially maturing two months after issuance.

How much new capital does the AlpineBrook note provide to NKGen Biotech (NKGN)?

The note documents prior undocumented cash advances of $25,540,106 and adds an incremental $300,000 advanced contemporaneously with execution, which is the only new capital funded in connection with the note.

What are the key interest and penalty terms of NKGen Biotech’s new note?

The note carries 12% interest per annum and prohibits prepayment without lender consent. If an event of default occurs and is continuing, all obligations bear default interest at 24% per annum, calculated on a 360‑day year and payable on demand.

What happens to NKGen Biotech’s note if there is a Change of Control?

Upon a Change of Control of either borrower, the note requires cash repayment of outstanding principal plus accrued but unpaid interest, together with a cash premium equal to 20% of the then‑outstanding principal amount. Borrowers must give at least 10 business days’ advance notice of such a transaction.

What collateral secures NKGen Biotech’s promissory note with AlpineBrook?

The collateral package includes security interests in substantially all U.S. personal property of the borrowers, a deed of trust and assignment of leases and rents over U.S. real property owned by the subsidiary, and Korean law security over NKGen Korea shares and related account collateral, all subject to existing liens and required consents.

How does the “most favored nation” clause in NKGen Biotech’s note work?

During the term of the note, if NKGen or its subsidiaries complete any debt or equity financing with more favorable terms, they must notify the lender and provide those more favorable terms to the lender, covering economic terms, collateral, conversion price, warrant coverage, and specified governance and rights provisions.

What restrictions does the new note place on NKGen Biotech’s future financing activities?

The note contains restrictive covenants limiting additional indebtedness and liens, restricting equity issuances and capital structure changes (with ordinary‑course exceptions), and includes a negative pledge preventing collateral or guarantees in favor of third parties without the lender’s prior written consent.