Series L preferred waiver disclosed by GT Biopharma (GTBP)

Rhea-AI Filing Summary

GT Biopharma, Inc. reports that certain holders of its Series L 10% Convertible Preferred Stock have agreed to waive their contractual redemption rights. On September 17, 18 and 23, 2025, these Series L preferred stockholders delivered a waiver to the company’s Certificate of Designation for the Series L 10% Convertible Preferred Stock.

Under this waiver, the participating Series L holders give up the right to require redemption described in Section 10 of the Certificate of Designations. This change reduces the possibility that the company could be required by these holders to redeem their preferred shares for cash or other consideration under that section. The company has filed the form of waiver as an exhibit so investors can review the detailed terms.

Insights

Capital structure and securities lawyer

Series L holders waive redemption rights, easing potential obligations.

The company describes a waiver by certain holders of its Series L 10% Convertible Preferred Stock that removes their redemption rights under Section 10 of the Series L Certificate of Designations. Redemption rights typically allow preferred holders to force the issuer to buy back their shares, which can create future cash or financing obligations.

By waiving these rights, the participating Series L holders limit their ability to demand redemption on the terms previously set out. This can lessen pressure on the company’s balance sheet and liquidity compared with the original structure, though the filing does not quantify the affected amount of preferred stock. The detailed form of waiver is attached as an exhibit for further review of specific conditions and scope.

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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: September 17, 2025

(Date of earliest event reported)

GT Biopharma, Inc.

(Exact name of registrant as specified in its charter)

Delaware

(State or other Jurisdiction

of Incorporation)

1-40023		94-1620407
(Commission File Number)		(IRS Employer Identification No.)

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:

☐	Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
☐	Soliciting material pursuant to Rule 14a-12(b) under the Exchange Act (17 CFR 240.14a-12(b))
☐	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, $0.001 par value		GTBP		The Nasdaq Stock Market LLC

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. ☐

¹ Effective 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 3.03 Material Modification to Rights of Security Holders.

On each of September 17, 2025, September 18, 2025 and September 23, 2025, certain of the holders of GT Biopharma, Inc.’s Series L 10% Convertible Preferred Stock (the “Series L Preferred Stock”) provided a waiver (the “Waiver”) to the Certificate of Designation of Preferences, Rights and Limitations of Series L 10% Convertible Preferred Stock (the “Certificate of Designations”). Pursuant to the Waiver, such Series L Preferred Stockholders agreed to waive the rights to redemption set forth in Section 10 of the Certificate of Designations.

The foregoing description of the Waiver does not purport to be complete and is qualified in its entirety by reference to the full text of the Waiver, which is attached hereto as Exhibit 10.1 and is incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit Number		Description
10.1		Form of Waiver
104		Cover Page Interactive Data File, formatted in Inline XBRL

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.

	GT BIOPHARMA, INC.
Date: September 23, 2025	By:	/s/ Alan Urban
		Alan Urban
		Chief Financial Officer

FAQ

What did GTBP change about its Series L preferred stock rights?

GT Biopharma reports that certain holders of its Series L 10% Convertible Preferred Stock agreed to waive their redemption rights under Section 10 of the Series L Certificate of Designations. This removes those holders’ ability to require redemption on those terms.

When did GTBP’s Series L preferred stockholders provide the waiver?

The company states that the waiver from certain Series L preferred stockholders was provided on September 17, 2025, September 18, 2025 and September 23, 2025.

Which security is affected by this GTBP 8-K filing?

The change applies to GT Biopharma’s Series L 10% Convertible Preferred Stock, as defined in the Certificate of Designation of Preferences, Rights and Limitations of Series L 10% Convertible Preferred Stock.

What specific right did the Series L preferred holders waive for GTBP?

The filing explains that the participating Series L preferred stockholders waived their rights to redemption set forth in Section 10 of the Series L Certificate of Designations.

Where can investors find the full terms of GTBP’s Series L waiver?

GT Biopharma attached the form of Waiver as Exhibit 10.1 to this report, and states that the summary in the text is qualified in its entirety by reference to that exhibit.

Does the GTBP filing include any financial statements or earnings data?

No financial statements or earnings data are described in this report. The focus is on a material modification to the rights of Series L security holders through the waiver of redemption rights.