Theriva Biologics (NYSE: TOVX) unveils preclinical VCN-12 data vs. VCN-01

Rhea-AI Filing Summary

Theriva Biologics, Inc. reported new preclinical results for its next-generation oncolytic adenovirus VCN-12, developed within the VCN-X discovery program. The data were presented at the 32nd Annual Congress of the European Society of Gene & Cell Therapy and the full presentation is available as Exhibit 99.1.

VCN-12 uses the same capsid as the company’s lead clinical candidate VCN-01 but is engineered to increase stroma degradation by replacing human hyaluronidase PH20 with a more active bee hyaluronidase, and to boost tumor cell lysis by expressing the pore-forming protein parasporin-2. In vitro, VCN-12 showed increased cancer cell killing and higher hyaluronidase activity compared to VCN-01. In animal models, intravenous VCN-12 had a similar toxicity profile to VCN-01, while intratumoral dosing significantly reduced tumor growth versus VCN-01 in immunocompetent hamsters with HP-1 pancreatic tumors.

The antitumor effect was seen in both injected tumors and separate tumors implanted later but not injected. Complete regression of the first tumor occurred in two of nine hamsters, and the second implanted tumors did not grow in these animals. A persistent immune response appeared to prevent new tumor establishment when HP-1 cells were implanted again 43 days after VCN-12 treatment in these responders. The company plans further preclinical studies to expand on these findings.

Insights

Biotech pipeline analyst

Theriva highlights preclinical VCN-12 data showing stronger activity than VCN-01 in early models.

The company describes VCN-12 as a next-generation oncolytic adenovirus built on the same capsid as its lead candidate VCN-01, but with added features: a more active bee hyaluronidase to enhance stroma degradation and parasporin-2 to promote tumor cell lysis and immunogenic cell death. This positions VCN-12 as a potential follow-on or complementary asset in the same mechanistic space.

In vitro experiments showed increased cancer cell killing and higher hyaluronidase activity for VCN-12 versus VCN-01, while animal studies in immunodeficient mice indicated a similar toxicity profile on intravenous dosing. In immunocompetent hamsters bearing HP-1 pancreatic tumors, intratumoral VCN-12 reduced tumor growth more than VCN-01, with complete regression in two of nine animals and apparent protection against subsequent tumor implants, suggesting a durable immune component.

From an investment perspective, these results remain preclinical and VCN-12 is still in the discovery/preclinical stage. The main takeaway is an expanded oncolytic virus pipeline conceptually stronger than the current lead candidate, with further preclinical work planned to confirm and elaborate these early signals before any potential move toward clinical development.

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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 8, 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 8, 2025, preclinical data for VCN-12, a next generation oncolytic adenovirus developed as part of the VCN-X discovery program of Theriva Biologics, Inc. (the “Company”), was presented by Dr. Ramon Alemany at the 32^nd Annual Congress of the European Society of Gene & Cell Therapy. A copy of the presentation is filed as an exhibit to this Current Report on Form 8-K as Exhibit 99.1 and is incorporated herein by reference.

VCN-12 uses the same virus capsid as the Company’s lead clinical candidate VCN-01 (zabilugene almadenorepvec), but includes modifications intended to (i) increase stroma degradation by replacing human hyaluronidase PH20 with the more active bee hyaluronidase; and (ii) increase tumor cell lysis by expressing the pore forming protein parasporin-2 to enable both cytotoxic and immunogenic cell death. Parasporin-2 expression is expected to destroy both infected and surrounding uninfected tumor cells and stimulate a strong overall antitumor immune response and reduce viral immunodominance.

Data presented by Dr. Alemany support the proposed VCN-12 mechanisms of action. VCN-12 showed increased cell killing compared to VCN-01 in a variety of cancer cell models in vitro. VCN-12 also displayed higher levels of hyaluronidase activity. In animal studies, intravenous VCN-12 had a similar toxicity profile to VCN-01 in immunodeficient mice bearing human tumor xenografts. Intratumoral VCN-12 significantly reduced tumor growth compared to VCN-01 in immunocompetent hamsters bearing HP-1 pancreatic tumors. The antitumor effect of VCN-12 was observed in both the injected tumors and second tumors-implanted 4-days later but not injected. Complete tumor regression of the first tumor was observed in two of nine hamsters and the second implanted tumor did not grow in these animals. VCN-12 appeared to stimulate a persistent immune response that prevented the establishment of tumors in these two complete responders when they were implanted with HP-1 cells 43 days after VCN-12 treatment. Further preclinical studies are planned to elaborate these initial findings.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits.

Exhibit Number		Description
99.1		Preclinical Data presented at the 32nd Annual Congress of the European Society of Gene & Cell Therapy
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 8, 2025	THERIVA BIOLOGICS, INC.
	By:	/s/ Steven A. Shallcross
		Name:	Steven A. Shallcross
		Title:	Chief Executive Officer and Chief Financial Officer

FAQ

What did Theriva Biologics (TOVX) report about VCN-12 in this 8-K?

Theriva Biologics reported new preclinical data for its next-generation oncolytic adenovirus VCN-12, presented at the 32nd Annual Congress of the European Society of Gene & Cell Therapy. The data compare VCN-12 with the company’s lead clinical candidate VCN-01 in cell models and animal studies.

How is VCN-12 designed to differ from Theriva Biologics VCN-01?

VCN-12 uses the same virus capsid as VCN-01 but includes two main changes: it replaces human hyaluronidase PH20 with a more active bee hyaluronidase to increase stroma degradation, and it expresses the pore-forming protein parasporin-2 to enhance tumor cell lysis and promote both cytotoxic and immunogenic cell death.

What preclinical efficacy signals did VCN-12 show compared to VCN-01?

In vitro, VCN-12 showed increased cell killing versus VCN-01 across various cancer cell models and displayed higher hyaluronidase activity. In immunocompetent hamsters with HP-1 pancreatic tumors, intratumoral VCN-12 significantly reduced tumor growth compared to VCN-01 and produced complete tumor regression in two of nine animals.

Did VCN-12 show any signs of stimulating an immune response in preclinical models?

Yes. The antitumor effect of VCN-12 was seen not only in injected tumors but also in second tumors implanted four days later and not injected. In two complete responders, the second tumors did not grow, and when HP-1 cells were implanted again 43 days after VCN-12 treatment, tumors did not establish, suggesting a persistent immune response.

How did the safety profile of VCN-12 compare with VCN-01 in animal studies?

In immunodeficient mice bearing human tumor xenografts, intravenous VCN-12 had a similar toxicity profile to VCN-01 based on the reported preclinical observations, indicating no obvious new safety signal in that setting.

What are the next steps for VCN-12 according to Theriva Biologics?

The company states that further preclinical studies are planned to elaborate on the initial VCN-12 findings, indicating the program remains in the preclinical stage with additional nonclinical work ahead.