Exhibit 5.1

October 22, 2021

The Board of Directors

Synthetic Biologics, Inc.

9605 Medical Center Drive, Suite 270

Rockville, Maryland 20850

Re: Registration Statement on Form S-3

Ladies & Gentlemen:

We have acted as counsel to Synthetic Biologics, Inc., a Nevada corporation (the “Company”), in connection with its filing on the date hereof with the Securities and Exchange Commission (the “Commission”) of a Registration Statement on Form S-3 (the “Registration Statement”) under the Securities Act of 1933, as amended (the “Securities Act”), relating to an aggregate of 6,344,966 shares (the “Shares”) of the Company’s common stock, par value $0.0001 per share (the “Common Stock”), issuable upon exercise of 6,344,966 warrants previously issued on October 15, 2018 (the “Warrants”) in an underwritten public offering pursuant to the terms of that certain underwriting agreement, dated October 10, 2018, by and between the Company and A.G.P./Alliance Global Partners, as representative of the several underwriters listed on Schedule 1 thereto (the “Underwriting Agreement”), and the related warrant agency agreement by and between the Company and Corporate Stock Transfer, Inc., as Warrant Agent, dated October 15, 2018 (the “Warrant Agreement”).

This opinion letter is being delivered in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act.

As counsel to the Company, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter. With your consent, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters. We are opining herein as to the Nevada Revised Statutes (the “NRS”), and we express no opinion with respect to the applicability thereto, or the effect thereon, of the laws of any other jurisdiction or, in the case of Nevada, any other laws, or as to any matters of municipal law or the laws of any local agencies within any state.

We have made such examination as we have deemed necessary for the purpose of this opinion.

Based upon and subject to the foregoing, we are of the opinion that the Shares have been duly and validly authorized, and upon their issuance, delivery and payment therefor in the manner contemplated by the Registration Statement and the Warrant Agreement, if issued upon exercise of the Warrants against payment therefor in accordance with the terms of the Warrants and the Warrant Agreement, will be legally issued, fully paid and non-assessable.

In rendering the foregoing opinion, we have assumed that (i) the Company will comply with all applicable notice requirements regarding uncertificated shares provided in the NRS and (ii) upon the issuance of any of the Shares, the total number of shares of common stock issued and outstanding will not exceed the total number of shares of common stock that the Company is then authorized to issue under its articles of incorporation, as amended and restated as of the date hereof.

This opinion is given as of the date hereof and we assume no obligation to advise you of changes that may hereafter be brought to our attention. This opinion is delivered solely in connection with the consummation of the transactions described herein, and may not be relied upon by you for any other purpose nor by any other person for any purpose.

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We hereby consent to the reference to our firm under the caption “Legal Matters” in the Prospectus and to the filing of this opinion as Exhibit 5.1 to the Company’s Current Report on Form 8-K relating to the issuance and sale of the Shares pursuant to the Sales Agreement.  In giving our consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission thereunder.

Very truly yours,

/s/ PARSONS BEHLE & LATIMER

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