Disclosure Devil

<html xmlns="http://www.w3.org/1999/xhtml" xmlns:xs="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xbrldi="http://xbrl.org/2006/xbrldi" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:iso4217="http://www.xbrl.org/2003/iso4217" xmlns:ix="http://www.xbrl.org/2013/inlineXBRL" xmlns:ixt="http://www.xbrl.org/inlineXBRL/transformation/2015-02-26" xmlns:ixt-sec="http://www.sec.gov/inlineXBRL/transformation/2015-08-31" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:dei="http://xbrl.sec.gov/dei/2025" xmlns:us-gaap="http://fasb.org/us-gaap/2025" xmlns:us-roles="http://fasb.org/us-roles/2025" xmlns:country="http://xbrl.sec.gov/country/2025" xmlns:srt="http://fasb.org/srt/2025" xmlns:GTBP="http://gtbiopharma.com/20251120"> <head> <title></title> <meta http-equiv="Content-Type" content="text/html"/> </head>         <body style="font: 10pt Times New Roman, Times, Serif"> <div style="display: none"> <ix:header> <ix:hidden> <ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000003" name="dei:AmendmentFlag">false</ix:nonNumeric> <ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000004" name="dei:EntityCentralIndexKey">0000109657</ix:nonNumeric> </ix:hidden> <ix:references> <link:schemaRef xlink:href="gtbp-20251120.xsd" xlink:type="simple"/> </ix:references> <ix:resources> <xbrli:context id="AsOf2025-11-20"> <xbrli:entity> <xbrli:identifier scheme="http://www.sec.gov/CIK">0000109657</xbrli:identifier> </xbrli:entity> <xbrli:period> <xbrli:startDate>2025-11-20</xbrli:startDate> <xbrli:endDate>2025-11-20</xbrli:endDate> </xbrli:period> </xbrli:context> <xbrli:unit id="USD"> <xbrli:measure>iso4217:USD</xbrli:measure> </xbrli:unit> <xbrli:unit id="Shares"> <xbrli:measure>xbrli:shares</xbrli:measure> </xbrli:unit> <xbrli:unit id="USDPShares"> <xbrli:divide> <xbrli:unitNumerator> <xbrli:measure>iso4217:USD</xbrli:measure> </xbrli:unitNumerator> <xbrli:unitDenominator> <xbrli:measure>xbrli:shares</xbrli:measure> </xbrli:unitDenominator> </xbrli:divide> </xbrli:unit> </ix:resources> </ix:header> </div>   <div style="width: 100%"><div style="border-top: Black 4pt solid; border-bottom: Black 1pt solid; font-size: 1pt"> </div></div>   UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549   <div style="margin-left: auto; margin-right: auto; width: 100%"><div style="border-top: Black 1pt solid; font-size: 1pt"> </div></div>   FORM <ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000009" name="dei:DocumentType">8-K</ix:nonNumeric>   CURRENT REPORT Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934   Date of Report: <ix:nonNumeric contextRef="AsOf2025-11-20" format="ixt:datemonthdayyearen" id="Fact000010" name="dei:DocumentPeriodEndDate">November 20, 2025</ix:nonNumeric> (Date of earliest event reported)   <div style="margin-left: auto; margin-right: auto; width: 100%"><div style="border-top: Black 1pt solid; font-size: 1pt"> </div></div>   <ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000011" name="dei:EntityRegistrantName">GT Biopharma, Inc.</ix:nonNumeric> (Exact name of registrant as specified in its charter)   <ix:nonNumeric contextRef="AsOf2025-11-20" format="ixt-sec:stateprovnameen" id="Fact000012" name="dei:EntityIncorporationStateCountryCode">Delaware</ix:nonNumeric> (State or other Jurisdiction of Incorporation)   <table cellspacing="0" cellpadding="0" style="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse"> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif; width: 49%; text-align: center"><ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000013" name="dei:EntityFileNumber">1-40023</ix:nonNumeric></td> <td style="font: 10pt Times New Roman, Times, Serif; width: 2%; text-align: center"> </td> <td style="font: 10pt Times New Roman, Times, Serif; width: 49%; text-align: center"><ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000014" name="dei:EntityTaxIdentificationNumber">94-1620407</ix:nonNumeric></td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif">(Commission File Number)</td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: center"> </td> <td style="font: 10pt Times New Roman, Times, Serif">(IRS Employer Identification No.)</td></tr> </table>   N/A1 (Address of Principal Executive Offices and zip code)   <ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000015" name="dei:CityAreaCode">(415)</ix:nonNumeric> <ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000016" name="dei:LocalPhoneNumber">919-4040</ix:nonNumeric> (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:   <table cellspacing="0" cellpadding="0" style="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse"> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif; width: 0.25in"><ix:nonNumeric contextRef="AsOf2025-11-20" format="ixt:booleanfalse" id="Fact000017" name="dei:WrittenCommunications">☐</ix:nonNumeric></td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: justify">Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)</td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: justify"> </td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif"><ix:nonNumeric contextRef="AsOf2025-11-20" format="ixt:booleanfalse" id="Fact000018" name="dei:SolicitingMaterial">☐</ix:nonNumeric></td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: justify">Soliciting material pursuant to Rule 14a-12(b) under the Exchange Act (17 CFR 240.14a-12(b))</td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: justify"> </td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif"><ix:nonNumeric contextRef="AsOf2025-11-20" format="ixt:booleanfalse" id="Fact000019" name="dei:PreCommencementTenderOffer">☐</ix:nonNumeric></td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: justify">Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))</td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: justify"> </td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif"><ix:nonNumeric contextRef="AsOf2025-11-20" format="ixt:booleanfalse" id="Fact000020" name="dei:PreCommencementIssuerTenderOffer">☐</ix:nonNumeric></td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: justify">Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))</td></tr> </table>   Securities registered pursuant to Section 12(b) of the Act:   <table cellspacing="0" cellpadding="0" style="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse"> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="border-bottom: Black 1pt solid; font: 10pt Times New Roman, Times, Serif; width: 32%; text-align: center">Title of each Class</td> <td style="font: 10pt Times New Roman, Times, Serif; padding-bottom: 1pt; width: 2%; text-align: center"> </td> <td style="border-bottom: Black 1pt solid; font: 10pt Times New Roman, Times, Serif; width: 19%; text-align: center">Trading Symbol(s)</td> <td style="font: 10pt Times New Roman, Times, Serif; padding-bottom: 1pt; width: 2%; text-align: center"> </td> <td style="border-bottom: Black 1pt solid; font: 10pt Times New Roman, Times, Serif; width: 45%; text-align: center">Name of each Exchange on which registered</td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif; text-align: center"><ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000021" name="dei:Security12bTitle">Common stock, $0.001 par value</ix:nonNumeric></td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: center"> </td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: center"><ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000022" name="dei:TradingSymbol">GTBP</ix:nonNumeric></td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: center"> </td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: center"><ix:nonNumeric contextRef="AsOf2025-11-20" format="ixt-sec:exchnameen" id="Fact000023" name="dei:SecurityExchangeName">The Nasdaq Stock Market LLC</ix:nonNumeric></td></tr> </table>   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 <ix:nonNumeric contextRef="AsOf2025-11-20" format="ixt:booleanfalse" id="Fact000024" name="dei:EntityEmergingGrowthCompany">☐</ix:nonNumeric>   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. ☐   <div style="width: 100%"><div style="border-top: Black 1pt solid; font-size: 1pt"> </div></div> 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 <ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000025" name="dei:EntityAddressAddressLine1">505 Montgomery Street</ix:nonNumeric>, <ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000026" name="dei:EntityAddressAddressLine2">10th Floor</ix:nonNumeric>, <ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000027" name="dei:EntityAddressCityOrTown">San Francisco</ix:nonNumeric>, <ix:nonNumeric contextRef="AsOf2025-11-20" format="ixt-sec:stateprovnameen" id="Fact000028" name="dei:EntityAddressStateOrProvince">California</ix:nonNumeric> <ix:nonNumeric contextRef="AsOf2025-11-20" id="Fact000029" name="dei:EntityAddressPostalZipCode">94111</ix:nonNumeric>, or by email to auditcommittee@gtbiopharma.com.   <div style="width: 100%"><div style="border-top: Black 1pt solid; border-bottom: Black 4pt solid; font-size: 1pt"> </div></div>    <div style="border-bottom: Black 1pt solid; margin-bottom: 6pt"><table cellpadding="0" cellspacing="0" style="border-collapse: collapse; width: 100%; font-size: 10pt"><tr style="vertical-align: top; text-align: left"><td style="width: 100%"> </td></tr></table></div> <div style="break-before: page; margin-top: 6pt"> </div>    Item 3.01 Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing.   On November 20, 2025, GT Biopharma, Inc. (the “Company”) received a letter (the “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 per share for 30 consecutive business days and, as a result, the Company was not in compliance with the $1 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”). This Letter has no immediate effect on the listing of the Company’s Common Stock which will continue to trade on The Nasdaq Capital Market under the symbol “GTBP,” subject to the Company’s compliance with the other Nasdaq listing requirements.   In accordance with Nasdaq Listing Rule 5810(c)(3)(A), the Company was provided a compliance period of 180 calendar days from the date of the Letter, or until May 19, 2026 (the “Compliance Period”), to regain compliance with the Minimum Bid Price requirement. If at any time during the Compliance Period, the closing bid price of the Company’s Common Stock is at least $1.00 per share for a minimum of ten consecutive business days (unless the Nasdaq staff exercises its discretion to extend this ten business day period pursuant to Nasdaq Listing Rule 5810(c)(3)(H)), Nasdaq will provide the Company written confirmation of compliance with the Minimum Bid Price, and the matter will be closed.   If the Company does not regain compliance during the Compliance Period, the Company may be eligible for an additional 180-calendar day period to regain compliance with the Minimum Bid Price, provided that it meets the applicable market value of publicly held shares requirement for continued listing and all other applicable standards for initial listing on The Nasdaq Capital Market (except the Minimum Bid Price requirement), and notifies Nasdaq of its intent to cure the deficiency by effecting a reverse stock split of its Common Stock, if necessary. If Nasdaq determines that the Company is not eligible for an additional 180 calendar days compliance period or the Company will not be able to cure the deficiency with the Minimum Bid Price requirement within the allotted compliance period, the Company’s stock will be subject to delisting.   The Company intends to monitor the closing bid price of the Common Stock and assess its available options to regain compliance with the Minimum Bid Price requirement and continue listing on The Nasdaq Capital Market. There can be no assurance that the Company will be able to regain compliance with the Minimum Bid Price requirement or will otherwise be in compliance with other applicable Nasdaq listing rules.   Item 9.01 Financial Statements and Exhibits.   (d) Exhibits.   <table cellspacing="0" cellpadding="0" style="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse"> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="border-bottom: Black 1pt solid; font: 10pt Times New Roman, Times, Serif; width: 0.75in">Exhibit Number</td> <td style="font: 10pt Times New Roman, Times, Serif; padding-bottom: 1pt; width: 0.1in"> </td> <td style="border-bottom: Black 1pt solid; font: 10pt Times New Roman, Times, Serif; text-align: justify; vertical-align: bottom">Description</td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: justify"> </td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif">104</td> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td style="font: 10pt Times New Roman, Times, Serif; text-align: justify">Cover Page Interactive Data File, formatted in Inline XBRL</td></tr> </table>    <div style="border-bottom: Black 1pt solid; margin-bottom: 6pt"><table cellpadding="0" cellspacing="0" style="border-collapse: collapse; width: 100%; font-size: 10pt"><tr style="vertical-align: top; text-align: left"><td style="width: 100%"> </td></tr></table></div> <div style="break-before: page; margin-top: 6pt"> </div>    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.   <table cellspacing="0" cellpadding="0" style="font: 10pt Times New Roman, Times, Serif; width: 100%; border-collapse: collapse"> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td colspan="2" style="font: 10pt Times New Roman, Times, Serif">GT BIOPHARMA, INC.</td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td colspan="2" style="font: 10pt Times New Roman, Times, Serif"> </td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif; width: 50%">Date: November 26, 2025</td> <td style="font: 10pt Times New Roman, Times, Serif; width: 3%">By:</td> <td style="border-bottom: black 1pt solid; font: 10pt Times New Roman, Times, Serif; width: 47%">/s/ Alan Urban</td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td style="font: 10pt Times New Roman, Times, Serif">Alan Urban</td></tr> <tr style="font: 10pt Times New Roman, Times, Serif; vertical-align: top"> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td style="font: 10pt Times New Roman, Times, Serif"> </td> <td style="font: 10pt Times New Roman, Times, Serif">Chief Financial Officer</td></tr> </table>    <div style="border-bottom: Black 1pt solid; margin-bottom: 6pt"><table cellpadding="0" cellspacing="0" style="border-collapse: collapse; width: 100%; font-size: 10pt"><tr style="vertical-align: top; text-align: left"><td style="width: 100%"> </td></tr></table></div>      </body> </html>

Disclosure Devil - Summary