Exhibit 5.1

APRIL 26, 2022

VIA ELECTRONIC TRANSMISSION

Securities and Exchange Commission

100 F Street, N.E.

Washington, DC 20549

Ladies and Gentlemen:

We refer to the above-captioned amended registration statement on Form S-1 POSAM (the “Registration Statement”) under the Securities Act of 1933, as amended (the “Act”), filed by Oncotelic Therapeutics, Inc., a Delaware corporation (the “Company”), with the Securities and Exchange Commission on the date hereof.

We have examined the originals, photocopies, certified copies or other evidence of such records of the Company, certificates of officers of the Company and public officials, and other documents as we have deemed relevant and necessary as a basis for the opinion hereinafter expressed. In such examination, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as certified copies or photocopies and the authenticity of the originals of such latter documents.

Based on our examination mentioned above, we are of the opinion that the shares of common stock being offered pursuant to the Registration Statement are duly authorized, and will be, when issued in the manner described in the Registration Statement, legally and validly issued, fully paid and non-assessable.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement and to the reference to our firm under “Legal Matters” in the related Prospectus. In giving the foregoing consent, we do not hereby admit that we are in the category of persons whose consent is required under Section 7 of the Act, or the rules and regulations of the Securities and Exchange Commission.

Exhibit 23.1

Consent of Independent Registered Public Accounting Firm

We consent to the incorporation by reference in this Registration Statement on Form S-1 (No. 333-256448) of Oncotelic Therapeutics, Inc. (formerly Mateon Therapeutics, Inc.) of our report dated April 15, 2022, relating to the consolidated financial statements of Oncotelic Therapeutics, Inc. (formerly Mateon Therapeutics, Inc.) and Subsidiaries, appearing in the Annual Report on Form 10-K of Oncotelic Therapeutics, Inc. (formerly Mateon Therapeutics, Inc.) for the year ended December 31, 2021. Our report relating to the consolidated financial statements contains an explanatory paragraph regarding the Company’s ability to continue as a going concern.

We also consent to the reference of our Firm under the caption “Experts” in the Registration Statement.

Exhibit 107

CALCULATION OF REGISTRATION FEE

(1)Represents shares offered by the Selling Stockholder. Includes an indeterminable number of additional shares of Common Stock, pursuant to Rule 416 under the Securities Act that may be issued to prevent dilution from stock splits, stock dividends or similar transaction that could affect the shares to be offered by Selling Stockholder.

(2)Consists of 33,613,445 shares of Common Stock of which 3,735,000 shares have been sold as of the date of this filing and remaining 29,878,445 shares are open for sale now, that we may issue to the Peak One Opportunity Fund, LP (“Peak One”) pursuant to put notices under the May 3, 2021 Equity Purchase Agreement with Peak One and also consists of 250,000 shares of Common Stock issuable pursuant to a Commitment Fee of 250,000 Common Stock Shares, 125,000 of which were issued to each of Peak One and Peak One Investments, LLC (“Peak One Investments”) on May 3, 2021.

(3)Estimated solely for the purpose of calculating the registration fee pursuant to Rule 457(c) under the Securities Act of 1933, as amended, and is based upon the closing price of $0.2975 per share of the Registrant’s Common Stock on the OTCQB on May 20, 2021.