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: September 22, 2026

(Date of earliest event reported)

GT Biopharma, Inc.

(Exact name of registrant as specified in its charter)

Delaware

(State or other Jurisdiction of Incorporation)

N/A¹

(Address of Principal Executive Offices and zip code)

(415)-919-4040

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of registrant under any of the following provisions:

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

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. ☐

¹Effective as of July 1, 2024, the Company became a fully remote company. We do not maintain a principal executive office. For purposes of compliance with applicable requirements of the Securities Act of 1933, as amended, and the Securities Exchange Act of 1934, as amended, any stockholder communication required to be sent to the Company’s principal executive offices may be directed to 505 Montgomery Street, 10th Floor, San Francisco, California 94111, or by email to auditcommittee@gtbiopharma.com.

Item 8.01 Other Events.

As previously disclosed, on November 20, 2025, GT Biopharma, Inc. (the “Company”) received a letter from the Nasdaq Listing Qualifications Staff (the “Staff”) of The Nasdaq Stock Market LLC (“Nasdaq”) notifying the Company that its common stock, $0.001 par value per share (the “Common Stock”) had closed below $1.00 per share for 30 consecutive business days and, as a result, the Company was not in compliance with the $1.00 minimum bid price requirement for continued listing on the Nasdaq Capital Market, as set forth in Nasdaq Listing Rule 5550(a)(2) (the “Minimum Bid Price Requirement”). On May 20, 2026, the Company received a letter from the Staff notifying the Company that the Staff granted the Company an additional compliance period of 180 calendar days, or until November 16, 2026, to regain compliance with the Minimum Bid Price Requirement.

On September 22, 2026, the Company received notice from Nasdaq that it has regained compliance with the Minimum Bid Price Requirement under the Nasdaq Listing Rules. The Company’s Common Stock maintained a closing bid price above $1.00 per share for at least ten consecutive business days, thereby meeting Nasdaq’s requirements for regaining compliance.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

SIGNATURES

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