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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): October 20, 2025

THERIVA BIOLOGICS, INC.

(Exact name of registrant as specified in its charter)

Nevada |  | 001-12584 |  | 13-3808303
(State or other jurisdiction of incorporation) |  | (Commission File No.) |  | (IRS Employer Identification No.)

9605 Medical Center Drive, Suite 270

Rockville, Maryland 20850

(Address of principal executive offices and zip code)

(301) 417-4364

Registrant’s telephone number, including area code

N/A

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

¨ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
¨ | Soliciting material pursuant to Rule 14a-12(b) under the Exchange Act (17 CFR 240.14a-12)
¨ | Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
¨ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class | Trading Symbol(s) | Name of each exchange on which registered
Common stock, par value $0.001 per share | TOVX | NYSE American

Indicate by check mark whether the registrant is an emerging growth company as defined in in Rule 405 of the Securities Act of 1933 (17 CFR §230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2 of this chapter).

Emerging growth company ¨

If an emerging growth company, indicate by checkmark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ¨

Item 8.01. Other Events.

On October 20, 2025, expanded metastatic pancreatic ductal adenocarcinoma (mPDAC) data from Theriva Biologics, Inc.’s VIRAGE Phase 2b trial (NCT05673811) was presented at a mini oral session at the European Society for Medical Oncology (ESMO 2025) Annual Congress

The ESMO presentation is atatched as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference

Item 9.01. Financial Statements and Exhibits.

(d) | Exhibits.

Exhibit Number |  | Description
99.1 |  | ESMO presentation
104 |  | Cover Page Interactive Data File (embedded within the XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Dated: October 20, 2025 | THERIVA BIOLOGICS, INC.
| By: | /s/ Steven A. Shallcross
|  | Name: | Steven A. Shallcross
|  | Title: | Chief Executive Officer and Chief Financial Officer