GT Biopharma, Inc. filed a current report on Form 8-K on September 21, 2026, disclosing a First Amendment to its Securities Purchase Agreement dated September 18, 2026, which added a new purchaser and increased the size of its previously announced private placement of Series M 10% Convertible Preferred Stock and accompanying warrants.

Key Highlights

  • Expanded offering size: The amended agreement increases shares of Preferred Stock issuable to 8,611.111 shares, with an aggregate stated value of $8,611,111.11 and an aggregate purchase price of $7,750,000.
  • Original offering terms: The original Securities Purchase Agreement, dated September 14, 2026, covered up to 8,277.778 shares of Series M 10% Convertible Preferred Stock at an aggregate purchase price of $7,450,000.
  • Greenshoe Rights: Each purchaser may elect to purchase additional shares of Preferred Stock with an aggregate stated value of up to $34,675,615, for an aggregate purchase price of $31,208,054, subject to adjustments.
  • Certificate of Increase filed: On September 18, 2026, the Company filed a Certificate of Increase with the Delaware Secretary of State, raising the authorized shares of Series M Preferred Stock from 41,778 to 43,287 shares.
  • Registration rights: The Company agreed to file a registration statement within 30 days after each closing, to become effective no later than 60 days after the applicable closing date, or 90 days in the event of a full SEC review.
  • Exempt offering: The securities were offered pursuant to Rule 506(b) of Regulation D under the Securities Act of 1933, as amended.

GT Biopharma Amends Private Placement to Add New Purchaser and Raise Offering Cap

According to the filing, GT Biopharma, Inc. (NASDAQ:GTBP) entered into a First Amendment to Securities Purchase Agreement on September 18, 2026, bringing in a new purchaser alongside the original purchasers identified in the initial agreement dated September 14, 2026. The amendment increased the total shares of Series M 10% Convertible Preferred Stock issuable under the agreement from 8,277.778 shares to 8,611.111 shares, and correspondingly increased the aggregate stated value from $8,277,778 to $8,611,111.11, with the aggregate purchase price rising from $7,450,000 to $7,750,000. The filing states that all terms and conditions otherwise remain the same as previously disclosed.

The filing also discloses that warrants accompany the Preferred Stock issuance. Common Warrants cover up to a number of shares of common stock equal to 100% of the shares issuable upon conversion of the Preferred Stock, and Vesting Warrants cover shares equal to the number of Greenshoe Conversion Shares issuable upon exercise of Greenshoe Rights. Each purchaser's Greenshoe Right is proportional to its original subscription amount relative to the total original aggregate subscription amount of all purchasers, according to the filing.

The new purchaser also executed a joinder to the Registration Rights Agreement on September 18, 2026, under which the Company agreed to file a registration statement covering the public resale of common stock issuable upon conversion of the Preferred Stock and upon exercise of the warrants. The filing also discloses that on September 18, 2026, the Company filed a Certificate of Increase with the Delaware Secretary of State, increasing the designated shares of Series M Preferred Stock from 41,778 to 43,287. The filing was signed by Alan Urban, Chief Financial Officer, on September 21, 2026.

What Was Disclosed

GT Biopharma disclosed the expansion of its Series M 10% Convertible Preferred Stock private placement through a First Amendment to its Securities Purchase Agreement, adding a new purchaser, increasing the offering size, filing a Certificate of Increase in Delaware, and securing a joinder to the Registration Rights Agreement.