Theriva Biologics, Inc.

**UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of

the Securities Exchange Act of 1934

Filed by the Registrant☒

Filed by a Party other than the Registrant☐

Check the appropriate box:

☐ Preliminary Proxy Statement

☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2))

☒ Definitive Proxy Statement

☐ Definitive Additional Materials

☐ Soliciting Material Pursuant to Section 240.14a-12

THERIVA BIOLOGICS, INC.

(Name of Registrant as Specified in Its Charter)

(Name of Person(s) Filing Proxy Statement, if Other Than the Registrant)

Payment of Filing Fee (check the appropriate box):

☒ No fee required.

☐ Fee paid previously with preliminary materials.

☐ Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a6(i)(1) and 0-11.

**9605 Medical Center Drive, Suite 270

Rockville, Maryland 20850

(301) 417-4364

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

To the Stockholders of Theriva Biologics, Inc.:

We hereby notify you that the 2026 Annual Meeting of Stockholders (the “Annual Meeting”) of Theriva Biologics, Inc., a Nevada corporation (the “Company”), will be held on August 3, 2026 at 3:30 p.m. (local time), at the Company’s principal place of business for research and clinical development, located at Carrer Torrent de Can Ninou, naus 5-6, 08150 - Parets del Vallès (Barcelona) Spain, for the following purposes:

(1) to elect the four (4) nominees for director named in the accompanying proxy statement to the Company’s Board of Directors (the “Board”) until such director’s successor is duly elected and qualified (the “Election of Directors”);

(2) to ratify the appointment of BDO USA, P.C. as the Company’s independent registered public accounting firm for the year ending December 31, 2026 (the “Auditor Ratification Proposal”);

(3) to approve an amendment to the Company’s 2020 Stock Incentive Plan (the “Plan”) to increase the number of shares of the Company’s common stock, par value $0.001 per share (“Common Stock”) that it will have authority to grant under the plan to 6,500,000 shares of Common Stock (the “Plan Increase Proposal”);

(4) to approve an amendment to the Company’s Articles of Incorporation, as amended (the “Articles of Incorporation”), to, at the discretion of the Board, effect an increase the number of authorized shares of Common Stock to 450,000,000 shares (the “Authorized Common Stock Increase Proposal”), such amendment to be effected after stockholder approval thereof only in the event the Board still deems it advisable;

(5) to approve, pursuant to Section 713(a) of the NYSE American Company Guide and the terms of an inducement agreement, the issuance of up to an aggregate of 16,184,560 shares of Common Stock upon the exercise of the Company’s common stock purchase warrants issued to institutional investors in the Company’s private placement offering, which closed on October 17, 2025 (the “Warrant Exercise Proposal”);

(6) to approve a proposal to adjourn the Annual Meeting to a later date, if necessary or appropriate, to permit further solicitation and vote of proxies in the event that there are insufficient votes for, or otherwise in connection with, the approval of the Plan Increase Proposal, the Authorized Common Stock Increase Proposal and/or the Warrant Exercise Proposal (the “Adjournment Proposal”); and

(7) to transact such other business as may properly come before the Annual Meeting or any adjournments or postponements of the Annual Meeting.

The matters listed in this notice of meeting are described in detail in the accompanying Proxy Statement. The Board has fixed the close of business on June 23, 2026 as the record date for determining those stockholders who are entitled to notice of and to vote at the meeting or any adjournment or postponement of the Annual Meeting. The list of the stockholders of record as of the close of business on June 23, 2026 will be made available for inspection at the meeting and during the ten days preceding the meeting at the Company’s offices for research and clinical development located at Carrer Torrent de Can Ninou, naus 5-6, 08150 - Parets del Vallès (Barcelona) Spain.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE ANNUAL MEETING TO BE HELD ON AUGUST 3, 2026:

THE NOTICE OF ANNUAL MEETING OF STOCKHOLDERS, THE PROXY STATEMENT AND THE COMPANY’S ANNUAL REPORT ON FORM 10-K FOR THE YEAR ENDED DECEMBER 31, 2025 ARE AVAILABLE ELECTRONICALLY ATWWW.THERIVABIO.COM.

Along with the attached Proxy Statement, the Company is sending to you its Annual Report on Form 10-K for the year ended December 31, 2025. Such annual report, which includes the Company’s audited financial statements, is not to be regarded as proxy solicitation material.

YOUR VOTE IS IMPORTANT

Even if you plan to attend the meeting, please submit a proxy to have your shares voted as promptly as possible by using the internet or kindly sign, date, and return the enclosed proxy card in the envelope provided so that your vote will be counted if you later decide not to attend the meeting. No postage is required if the proxy card is mailed in the United States.

By Order of the Board of Directors,

/s/ Steven A. Shallcross

Steven A. Shallcross Chief Executive Officer, Chief Financial Officer and Director Rockville, Maryland June 29, 2026

TABLE OF CONTENTS

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**9605 Medical Center Drive, Suite 270

Rockville, Maryland 20850

PROXY STATEMENT

For the 2026 Annual Meeting of Stockholders to be held on August 3, 2026