GT Biopharma Inc美股招股说明书(2026-05-13版)

This prospectus relates to the offering from time to time by the selling stockholders named in this prospectus (the “SellingStockholders”) of up to an aggregate 9,723,057 shares of common stock, par value $0.001 per share (the “Common Stock”), of GTBiopharma, Inc., a Delaware corporation (the “Company”), consisting of (i) 4,527,654 shares of Common Stock issuable upon theconversion of 2,055.5554 shares of Series L 10% Convertible Preferred Stock, par value $0.001 per share (the “Series L PreferredStock” or the “Preferred Shares,” and the shares of Common Stock issuable upon conversion of the Preferred Shares, the “ConversionShares”) issued upon the exercise of certain of the Greenshoe Rights (as defined below) issued in connection with our privateplacement in May 2025, (ii) 4,527,654 shares of Common Stock issuable upon the exercise of vested warrants (the “Vesting Warrants,”and the shares of Common Stock issuable upon the exercise of the Vesting Warrants, the “Vesting Warrant Shares”) issued inconnection with our private placement in May 2025, (iii) 267,749 shares of Common Stock issued to the holders of Series L PreferredStock of record as of March 19, 2026 as a dividend, which represents 10% of the outstanding stated value of the Series L PreferredStock, payable on April 1, 2026 (the “Dividend Shares”), and (iv) 400,000 shares of Common Stock issuable upon the exercise of thepre-funded warrants (the “PDPC Pre-Funded Warrants,” and the shares of Common Stock issuable upon exercise of the PDPC Pre-Funded Warrants, the “Advisory Shares”) issued to PDPC Advisors Inc., a Delaware limited liability company (“PDPC”), pursuant tothe First Amendment to Advisory Agreement, effective as of April 3, 2026, between PDPC and the Company (the “Amended PDPCAdvisory Agreement”). The Conversion Shares, the Vesting Warrant Shares, the Dividend Shares and the Advisory Shares arecollectively referred to as the “Shares.” We are registering the Shares on behalf of the Selling Stockholders, to be offered and sold bythem from time to time. We will not receive any proceeds from the sale of the Shares offered by this prospectus. We have agreed to bear all of the expenses incurred in connection with the registration of the Shares. The SellingStockholders will pay or assume discounts, commissions, fees of underwriters, selling brokers or dealer managers and similarexpenses, if any, incurred for the sale of the Shares of our Common Stock. The Selling Stockholders, or their respective donees, pledgees, transferees or other successors-in-interest, may sell orotherwise dispose of the Shares covered by this prospectus in a number of different ways. We provide more information about how theSelling Stockholders may sell or otherwise dispose of their Shares in the section entitled “Plan of Distribution.” For a list of theSelling Stockholders, see the section entitled “Selling Stockholders.” Our Common Stock is presently listed on the Nasdaq Capital Market (“Nasdaq”) under the trading symbol “GTBP.” On May12, 2026, the closing sale price for our Common Stock was $0.32 per share. Investing in our securities involves a high degree of risk. See the section entitled “Risk Factors” beginning on page 7 ofthis prospectus and in the documents incorporated by reference into this prospectus for a discussion of risks that should beconsidered in connection with an investment in our securities. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved ofthese securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminaloffense. The date of this prospectus is May 13, 2026. TABLE OF CONTENTS PageABOUT THIS PROSPECTUS1CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS2PROSPECTUS SUMMARY3THE OFFERING6RISK FACTORS7USE OF PROCEEDS11MARKET INFORMATION FOR SECURITIES AND DIVIDEND POLICY12DESCRIPTION OF CAPITAL STOCK13SELLING STOCKHOLDERS19MATERIAL TAX CONSIDERATIONS22PLAN OF DISTRIBUTION26INCORPORATION OF CERTAIN INFORMATION BY REFERENCE28WHERE YOU CAN FIND MORE INFORMATION29LEGAL MATTERS29EXPERTS29 ABOUT THIS PROSPECTUS This prospectus is part of a registration statement filed with the U.S. Securities and Exchange Commission (the “SEC”) usinga “shelf” registration process. By using a shelf registration statement, the Selling Stockholders may sell up to 9,723,057 shares ofCommon Stock from time to time in one or more offerings as described in this prospectus. We will not receive any proceeds from thesale by the Selling Stockholders of the shares of Common Stock offered pursuant to this prospectus. We may also file a prospectus supplement or post-effective amendment to the registration statement of which this prospectusforms a part that may contain material information relating to these offerings. The prospectus supplement or post-effective amendmentmay also add, update or change information contained in this prospectus with respect to that o