Theriva Biologics Inc美股招股说明书(2025-10-29版)

We have entered into an Amended and Restated At Market Issuance Sales Agreement, dated February9, 2021, as amended by Amendment No.1 thereto, datedMay3, 2021, as further amended by Amendment No.2 thereto, dated May2, 2024 (the “Sales Agreement”), with A.G.P./Alliance Global Partners (“AGP” orthe “Sales Agent”), relating to the sale of shares of our common stock, par value $0.001 per share (the “common stock”), offered by this prospectussupplement and the accompanying base prospectus. During the year ended December31, 2024 through the date hereof, we sold through the Sales Agreementapproximately 16,618,692 shares of our common stock and received net proceeds of approximately $10.1 million. On October27, 2025, the last reported sale price of our common stock on the NYSE American LLC was $0.3276 per share. Sales of our common stock, if any, under this prospectus supplement will be made by any method permitted that is deemed an “at the market offering” asdefined in Rule415 under the Securities Act of 1933, as amended (the “Securities Act”). The Sales Agent is not required to sell any specific amount but willact as our Sales Agent using commercially reasonable efforts consistent with its normal trading and sales practices, on mutually agreed terms between theSales Agent and us. There is no arrangement for funds to be received in any escrow, trust or similar arrangement. The Sales Agent will be entitled to compensation at a commission rate equal to up to 3.0% of the gross sales price per share sold. In connection with the sale ofthe common stock on our behalf, the Sales Agent will be deemed to be an “underwriter” within the meaning of the Securities Act and the compensation of theSales Agent will be deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution to the Sales Agentwith respect to certain liabilities, including liabilities under the Securities Act. As of the date of this prospectus, the aggregate market value of our outstanding common stock held by non-affiliates is approximately $28,332,900, which iscalculated based on 33,729,643 shares of our outstanding common stock held by non-affiliates and a price of $0.84 per share, the closing price of our commonstock on October15, 2025, which is the highest closing sale price of our common stock on the NYSE American LLC within the prior 60 days of thisprospectus. During the prior twelve calendar month period that ends on and includes the date hereof, we have offered and sold approximately $6,550,075 ofshares of our common stock pursuant to General Instruction I.B.6 to FormS-3. As a result, pursuant to General Instruction I.B.6 to FormS-3 and inaccordance with the terms of the Sales Agreement, we may offer and sell throughthis prospectus supplement and the accompanying base prospectusadditionalshares of our common stock having an aggregate offering price of up to $2,894,225 from time to time through or to the Sales Agent. If our public float increases such that we may sell additional amounts under the Sales Agreement and the registration statement of which this prospectussupplement is a part, we will file a prospectus supplement prior to making additional sales. In no event will we sell securities in public primary offerings onFormS-3 with a value exceeding more than one-third of our public float (as defined by General Instruction I.B.6 to FormS-3) in any 12 calendar month periodso long as our public float remains below $75 million. Investing in our common stock involves a high degree of risk. Before making an investment decision, please read the information under the heading“Risk Factors” beginning on pageS-4 of this prospectus supplement and in the documents incorporated by reference into this prospectus supplement,and the accompanying base prospectus. Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed uponthe adequacy or accuracy of this prospectus supplement or the accompanying base prospectus. Any representation to the contrary is a criminaloffense. A.G.P. The date of this prospectus supplement isOctober29, 2025 ABOUT THIS PROSPECTUS SUPPLEMENTS-iiINDUSTRY AND MARKET DATAS-ivPROSPECTUS SUPPLEMENT SUMMARYS-1THE OFFERINGS-3RISK FACTORSS-4SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTSS-7USE OF PROCEEDSS-8DIVIDEND POLICYS-9DILUTIONS-10PLAN OF DISTRIBUTIONS-11LEGAL MATTERSS-13EXPERTSS-13WHERE YOU CAN FIND MORE INFORMATIONS-13INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCES-13 Page ABOUT THIS PROSPECTUSiiPROSPECTUS SUMMARY1RISK FACTORS6FORWARD-LOOKING STATEMENTS7USE OF PROCEEDS8DESCRIPTION OF CAPITAL STOCK9DESCRIPTION OF DEBT SECURITIES14DESCRIPTION OF WARRANTS20DESCRIPTION OF UNITS22LEGAL OWNERSHIP OF SECURITIES23PLAN OF DISTRIBUTION26LEGAL MATTERS28EXPERTS28WHERE YOU CAN FIND MORE INFORMATION28INCORPORATION OF CERTAIN INFORMATION BY REFERENCE28 ABOUT THIS PROSPECTUS SUPPLEMENT This prospectus supplem