Theriva Biologics Reports Full-Year 2023 Operational Highlights and Financial Results - The independent data monitoring committee (IDMC) recommended the continuation of VIRAGE , the Phase 2b clinical trial of VCN-01 in c

Theriva Biologics Reports Full-Year 2023

Operational Highlights and Financial Results

- The independent data monitoring committee

(IDMC) recommended the continuation of VIRAGE, the Phase 2b clinical trial of VCN-01 in combination with chemotherapy for metastatic

Pancreatic Ductal Adenocarcinoma (PDAC), with no safety concerns raised -

- VIRAGE remains on track to complete enrollment

in the first half of 2024-

- As of December 31, 2023, Theriva Biologics

reports $23.2 million in cash, which is expected to provide runway into the first quarter of 2025 -

- Conference call and webcast to be held on

Monday, March 25 at 8:30 a.m. ET -

Rockville, MD, March 25, 2024 - Theriva

Biologics (NYSE American: TOVX), a diversified clinical-stage company developing therapeutics designed to treat cancer and related diseases

in areas of high unmet need, today reported financial results for the full-year ended December 31, 2023, and provided a corporate update.

"With continued advancement of our clinical

programs, we have the opportunity to achieve several important milestones this year," said Steven A. Shallcross, Chief Executive

Officer of Theriva Biologics. "VIRAGE, our Phase 2b trial of VCN-01 in newly-diagnosed metastatic PDAC remains on track to complete

enrollment in the first half of 2024. We completed the first safety review with the IDMC, and with a positive recommendation, VIRAGE will

continue to enroll patients as planned with no modifications to the protocol. Our clinical data has demonstrated that repeated systemic

dosing of VCN-01 is feasible from a safety perspective, and will now focus on determining whether the repeated-dose regimen of VCN-01

may lead to improved clinical outcomes for patients with PDAC and other solid cancers. In addition to advancing the VIRAGE PDAC trial,

we continue to work closely with key opinion leaders, and regulatory agencies to refine our protocol and clinical strategy for VCN-01

as an adjunct to chemotherapy in pediatric patients with advanced retinoblastoma. In parallel, our investigator sponsored Phase 1 trial

evaluating the safety and activity of intravitreal VCN-01 in pediatric patients with refractory retinoblastoma continues to progress and

will further inform our clinical development pathway in this area of high unmet need."

Recent Program Highlights and Anticipated

SYN-004 (ribaxamase):

Full-Year Ended December 31, 2023 Financial Results

General and administrative expenses decreased to $7.1 million for the

year ended December 31, 2023, from $9.9 million for the year ended December 31, 2022. This decrease of 28% is primarily comprised of the

decrease in the fair value of the contingent consideration of $2.8 million, along with lower salary, investor relations, legal costs,

consulting fees related to the VCN acquisition, and director and officer insurance offset by higher audit fees, and other consulting fees.

The charge relating to stock based compensation expense was $0.4 million for the year ended December 31, 2023, compared to $0.4 million

for the year ended December 31, 2022.

Research and development expenses increased to $14.3 million for the

year ended December 31, 2023, from $11.7 million for the year ended December 31, 2022. This increase of 22% is primarily the result of

higher clinical trial expenses related to our VIRAGE Phase 2 clinical trial of VCN-01 in PDAC, offset by lower expenses related to our

Phase 1b/2a clinical trial of SYN-004 (ribaxamase) in allogeneic HCT recipients, the completed Phase 1a clinical trial of SYN-020, decreased

manufacturing expenses related to our Phase 1a clinical trial of SYN-020 and lower other indirect costs. We anticipate research and development

expense to increase as we continue enrollment in our VIRAGE Phase 2 clinical trial of VCN-01 in PDAC and our ongoing Phase 1 clinical

trial in retinoblastoma, expand GMP manufacturing activities for VCN-01, and continue supporting our VCN-11 and other preclinical and

discovery initiatives. Research and development expenses also include a charge relating to non-cash stock-based compensation expense of

$165,000 for the year ended December 31, 2023, compared to $112,000 for the year ended December 31, 2022. In addition, we expect research

and development expenses to increase as we incur higher clinical program costs for our VCN product candidates.

Other income was $1,442,000 for the year ended December 31, 2023, compared

to other income of $471,000 for the year ended December 31, 2022. Other income for the year ended December 31, 2023 is primarily comprised

of interest income of $1,439,000 and an exchange gain of $3,000. Other income for the year ended December 31, 2022 is primarily comprised

of interest income of $512,000 offset by an exchange loss of $41,000.

Cash and cash equivalents totaled $23.2 million

as of December 31, 2023, compared to $41.8 million as of December 31, 2022.

The audited financial statements for the year

ended December 31, 2023 included in the Company's Annual Report on Form 10-K contain an unqualified audit opinion from the Company's

independent registered public accounting firm that includes an explanatory paragraph related to the Company's ability to continue as a

Theriva Biologics will host a conference call on Monday, March 25,

2024 at 8:30 a.m. ET to discuss its financial results for the full-year ended December 31, 2023 and provide a corporate update. Individuals

may participate in the live call via telephone by dialing 1-877-451-6152 (domestic) or 1-201-389-0879 (international) and using the conference

ID: 13744453. Participants are asked to dial in 15 minutes before the start of the call to register. Investors and the public can access

the live and archived webcast of this call via the "News & Media" section of the company's website, https://www.therivabio.com,

under "Events" or by clicking here, up to 90 days after the call.

About Theriva Biologics, Inc.

Theriva Biologics (NYSE American: TOVX),

is a diversified clinical-stage company developing therapeutics designed to treat cancer and related diseases in areas of high unmet need.

The Company is advancing a new oncolytic adenovirus platform designed for intravenous (IV), intravitreal and antitumoral delivery to trigger

tumor cell death, improve access of co-administered cancer therapies to the tumor, and promote a robust and sustained anti-tumor response

by the patient's immune system. The Company's lead candidates are: (1) VCN-01, an oncolytic adenovirus designed to replicate

selectively and aggressively within tumor cells, and to degrade the tumor stroma barrier that serves as a significant physical and immunosuppressive

barrier to cancer treatment; (2) SYN-004 (ribaxamase) which is designed to degrade certain commonly used IV beta-lactam antibiotics

within the gastrointestinal (GI) tract to prevent microbiome damage, thereby limiting overgrowth of pathogenic organisms such as VRE (vancomycin

resistant Enterococci) and reducing the incidence and severity of acute graft-versus-host-disease (aGVHD) in allogeneic hematopoietic

cell transplant (HCT) recipients; and (3) SYN-020, a recombinant oral formulation of the enzyme intestinal alkaline phosphatase (IAP)

produced under cGMP conditions and intended to treat both local GI and systemic diseases. For more information, please visit Theriva Biologics'

website at www.therivabio.com.

Forward-Looking Statement

This release contains forward-looking statements

within the meaning of the Private Securities Litigation Reform Act of 1995. In some cases forward-looking statements can be identified

by terminology such as "may," "should," "potential," "continue," "expects,"

"anticipates," "intends," "plans," "believes," "estimates," and similar expressions,

and include statements regarding VIRAGE remaining on track to complete enrollment in the first half of 2024, cash being expected to provide

runway into the first quarter of 2025, continued advancement of the Company's clinical programs providing the opportunity to

achieve several important milestones this year, VIRAGE remaining on track to complete enrollment in the first half of 2024, VIRAGE

continuing to enroll patients as planned with no modifications to the protocol, determining whether the repeated-dose regimen of VCN-01

may lead to improved clinical outcomes for patients with PDAC and other solid cancers, continuing to work closely with key opinion leaders,

and regulatory agencies to refine our protocol and clinical strategy for VCN-01 as an adjunct to chemotherapy in pediatric patients with

advanced retinoblastoma, the Company investigator sponsored Phase 1 trial evaluating the safety and activity of intravitreal VCN-01 in

pediatric patients with refractory retinoblastoma further informing the Company's clinical development pathway in this area of high

unmet need, the VIRAGE trial enrolling 92 evaluable patients, completing patient follow-up in Q1 2024 in the investigator sponsored Phase

1 trial evaluating VCN-01 in pediatric patients with refractory retinoblastoma, the SYN-004 trial being on track to complete enrollment

in the second cohort in Q2 2024 and expected increases in research and development expenses as the Company incurs higher clinical program

costs for its VCN product candidates. Important factors that could cause actual results to differ materially from current expectations

include, among others, the Company's and VCN's ability to reach clinical milestones when anticipated, including the ability

to continue to enroll patients as planned and the completion of enrollment in Virage in the first half of 2024, completion of patient

follow- up in Q1 2024 in the investigator sponsored Phase 1 trial patient evaluating VCN-01 in pediatric patients with refractory retinoblastoma,

and completing enrollment in the SYN-004 second cohort in Q2 of 2024, generating clinical data that establishes VCN-01 may lead to improved

clinical outcomes for patients with PDAC and other solid cancers; the Company's and VCN's product candidates demonstrating

safety and effectiveness, as well as results that are consistent with prior results; the ability to complete clinical trials on time and

achieve the desired results and benefits,; the ability to obtain regulatory approval for commercialization of product candidates or to

comply with ongoing regulatory requirements, regulatory limitations relating to the Company's and VCN's ability to promote

or commercialize their product candidates for the specific indications, acceptance of product candidates in the marketplace and the successful

development, marketing or sale of the Company's and VCN's products, developments by competitors that render such products

obsolete or non-competitive, the Company's and VCN's ability to maintain license agreements, the continued maintenance and