Exhibit 5.1

October 27, 2025

Coya Therapeutics, Inc.

5850 San Felipe St., Suite 500

Houston, Texas 77057

Ladies and Gentlemen:

This opinion is being furnished to you in connection with (i) the Registration Statement on Form S-3 (Registration No. 333-289511) initially filed by Coya Therapeutics, Inc. (the “Company”), with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”) on August 12, 2025 (the “Registration Statement”), and the related base prospectus contained in the Registration Statement (the “Base Prospectus”) and (ii) the preparation and filing of the prospectus supplement, dated October 23, 2025 (the “Prospectus Supplement”) relating to the issuance and sale by the Company of up to 4,181,818 shares (the “Shares”) of common stock, par value $0.0001 per share (the “Common Stock”) of the Company (including 545,454 shares of Common Stock issuable by the Company upon exercise of an option to purchase additional shares of Common Stock granted by the Company to the Underwriter (as defined below)) pursuant to the Registration Statement.

The Shares are to be issued and sold by the Company pursuant to that certain underwriting agreement, dated as of October 23, 2025 (the “Underwriting Agreement”), by and between the Company and Lucid Capital Markets, LLC, as underwriter (the “Underwriter”), which is being filed with the Commission as Exhibit 1.1 to the Company’s Current Report on Form 8-K, filed on the date hereof.

We are acting as counsel for the Company in connection with the issuance and sale by the Company of the Shares. In connection with this opinion, we have (i) examined a signed copy of the Registration Statement as filed with the Commission, including the exhibits thereto, the Base Prospectus and the Prospectus Supplement as filed with the Commission, (ii) investigated such questions of law, (iii) examined originals or certified, conformed or reproduction copies of such agreements, instruments, documents of the Company, such certificates of public officials and such other documents, and (iv) received such information from officers and representatives of the Company as we have deemed necessary or appropriate for the purposes of this opinion.

In all such examinations, we have assumed the legal capacity of all natural persons, the genuineness of all signatures, the authenticity of original and certified documents and the conformity to original or certified documents of all copies submitted to us as conformed or reproduction copies. As to various questions of fact relevant to the opinion expressed herein, we have relied upon, and assume the accuracy of, the representations and warranties set forth in the Underwriting Agreement, and certificates and oral or written statements and other information of or from public officials and officers and representatives of the Company.

Based upon the foregoing and subject to the limitations, qualifications and assumptions set forth herein, we are of the opinion that the Shares have been duly authorized and, when issued and paid for in accordance with the terms of the Underwriting Agreement, will be validly issued, fully paid and non-assessable.

The opinion expressed herein is limited to the applicable provisions of the General Corporation Law of the State of Delaware (the “DGCL”), as currently in effect, and reported judicial decisions interpreting such provisions of the DGCL) and the applicable laws of the State of New York and we express no opinion as to the effect on the matters covered by this letter of the laws of any other jurisdiction.

The opinion expressed herein is limited to the matters stated herein and no opinion is implied or may be inferred beyond the matters expressly stated herein. We undertake no obligation to supplement this letter if any applicable laws change after the date hereof or if we become aware of any facts that might change the opinion expressed herein after that date or for any other reason.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Current Report on Form 8-K filed by the Company on the date hereof and which is incorporated by reference into the Registration Statement and to the references to this firm under the caption “Legal Matters” in the Prospectus Supplement. In giving these consents, we do not admit that we are “experts” within the meaning of Section 11 of the Securities Act or within the category of persons whose consent is required by Section 7 of the Securities Act.

 

		Very truly yours,
		/s/ Lowenstein Sandler LLP
		Lowenstein Sandler LLP