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Bangkok

Beijing

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Hanoi

Ho Chi Minh City

Hong Kong

Jakarta

Kuala Lumpur*

Manila*

Melbourne

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Shanghai

Singapore

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Taipei

Tokyo

Yangon

Europe, Middle East

& Africa

Abu Dhabi

Almaty

Amsterdam

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Bahrain

Baku

Barcelona

Berlin

Brussels

Budapest

Cairo

Casablanca

Doha

Dubai

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Frankfurt/Main

Geneva

Istanbul

Jeddah*

Johannesburg

Kyiv

London

Luxembourg

Madrid

Milan

Moscow

Munich

Paris

Prague

Riyadh*

Rome

St. Petersburg

Stockholm

Vienna

Warsaw

Zurich

The Americas

Bogota

Brasilia**

Buenos Aires

Caracas

Chicago

Dallas

Guadalajara

Houston

Juarez

Lima

Mexico City

Miami

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New York

Palo Alto

Porto Alegre**

Rio de Janeiro**

San Francisco

Santiago

Sao Paulo**

Tijuana

Toronto

Valencia

Washington, DC

* Associated Firm

** In cooperation with Trench, Rossi e Watanabe Advogados

May 21, 2024

GT Biopharma, Inc.

8000 Marina Blvd, Suite 100

Brisbane, CA 94005

Ladies and Gentlemen:

We have acted as counsel to GT Biopharma, Inc., a Delaware corporation (the “Company”), with respect to certain matters in connection with the sale by the Company of an aggregate of 740,000 shares of common stock, par value $0.001 per share (the “Shares”) in a public offering (the “Offering”), pursuant to the Company’s effective registration statement on Form S-3 (File No. 333-267870) (the “Registration Statement”), the prospectus therein (the “Prospectus”) and the prospectus supplement (the “Prospectus Supplement”) filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended (the “Securities Act”), relating to the registration under the Securities Act of the Shares and Warrants.

In connection therewith, we have examined originals or copies certified or otherwise identified to our satisfaction of (i) the Registration Statement, Prospectus and Prospectus Supplement, (ii) the Restated Certificate of Incorporation of the Company, as amended and supplemented to date, (iii) the restated Bylaws of the Company, as amended to date, (iv) the corporate proceedings with respect to the filing of the Prospectus Supplement and (v) such other corporate records, agreements, documents and instruments and certificates or comparable documents of public officials and officers and representatives of the Company as we have deemed necessary or appropriate for the expression of the opinions contained herein. As to any facts material to our opinion, we have made no independent investigation of such facts and have relied, to the extent that we deem such reliance proper, upon certificates of public officials and officers or other representatives of the Company.

In rendering the opinions contained herein, we have assumed (i) the truthfulness of all information contained in all of the documents reviewed by us, (ii) the genuineness of all signatures on all documents examined by us, (iii) the legal capacity of all natural persons signing such documents, (iv) the due authority of all parties signing such documents, (v) the authenticity of all documents submitted to us as originals, and (vi) the conformity to the originals of all documents submitted to us as copies.

Based upon and subject to the foregoing, we are of the opinion that the Shares have been duly and validly authorized and, when sold in accordance with the Registration Statement and the related Prospectus Supplement, will be validly issued, fully paid and non-assessable.

The opinions expressed above are limited to the General Corporation Law of the State of Delaware and the federal laws of the United States of America. We do not purport to cover herein the application of the securities or “Blue Sky” laws of the various states.

This opinion letter is limited to the matters stated herein, and no opinion is implied or may be inferred beyond the matters expressly stated. We hereby consent to the use of our opinion as herein set forth as an exhibit to the Registration Statement and to the use of our name under the caption “Legal Matters” in the prospectus forming a part of the Registration Statement. In giving this consent, we do not hereby admit that we come within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the SEC promulgated thereunder or Item 509 of Regulation S-K.

Very truly yours,

/s/ Baker & McKenzie LLP

BAKER & McKENZIE LLP