Theriva Biologics Reports First Quarter 2024 Operational Highlights and Financial Results - Reported topline data from the investigator sponsored Phase 1 trial of intravitreal VCN-01 in pediatric patients with refractory

Theriva Biologics Reports First Quarter

2024 Operational Highlights and Financial Results

- Reported topline data from the investigator

sponsored Phase 1 trial of intravitreal VCN-01 in pediatric patients with refractory retinoblastoma; trial results were determined to

be positive by the study Monitoring Committee-

-Presented preclinical data demonstrating the

potential synergy between VCN-01 and liposomal irinotecan in a human pancreatic mouse xenograft at the ASGCT Annual Meeting; emphasizes

VCN-01's potential in diverse chemotherapy combinations for improved efficacy in pancreatic cancer-

- VIRAGE, the Phase 2b clinical trial of VCN-01

in combination with chemotherapy for metastatic Pancreatic Ductal Adenocarcinoma (PDAC), is expected to complete enrollment in the third

- As of March 31, 2024, Theriva Biologics reports

$18.3 million in cash, which is expected to provide runway into the first quarter of 2025-

Rockville, MD, May 7, 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 first quarter ended March 31, 2024, and provided a corporate update.

"In the first quarter we reported positive topline data from

the investigator sponsored Phase 1 trial in patients with refractory retinoblastoma, further validating VCN-01's unique mechanism

of action and therapeutic potential to improve treatment outcomes as an adjunct to chemotherapy in this area of high unmet need,"

said Steven A. Shallcross, Chief Executive Officer of Theriva Biologics. "In parallel, we continue to build a portfolio of potentially

improved therapeutic combinations for PDAC patients. VIRAGE, our Phase 2b trial evaluating VCN-01 in metastatic PDAC is progressing and

enrolling patients across sites in the U.S. and Spain. Further, the recently presented preclinical data at ASGCT support the potential

antitumor synergy of VCN-01 with topoisomerase 1 inhibitors, an important class of chemotherapeutic agents used in a number of different

cancers. We look forward to identifying opportunities to evaluate the combination of VCN-01 with additional first-line pancreatic cancer

chemotherapy regimens (FOLFIRINOX or NALIRIFOX) that incorporate the topoisomerase 1 inhibitor irinotecan. Building on this momentum,

we are well positioned to achieve several important milestones that will continue to drive forward our clinical development program."

Recent Program Highlights and Anticipated

Pancreatic Ductal Adenocarcinoma (PDAC):

SYN-004 (ribaxamase):

First Quarter Ended March 31, 2024 Financial Results

General and administrative expenses decreased

to $1.9 million for the three months ended March 31, 2024, from $2.2 million for the three months ended March 31, 2023. This decrease

of 12% is primarily comprised of the decrease in salary costs, consulting, legal fees, and lower director and officer insurance, offset

by an increase in fair value of the contingent consideration adjustment. The charge related to stock-based compensation expense was $101,000

for the three months ended March 31, 2024, compared to $87,000 for the three months ended March 31, 2023.

Research and development expenses increased to

$3.5 million for the three months ended March 31, 2024, from approximately $3.0 million for the three months ended March 31, 2023. This

increase of 16% is primarily the result of higher clinical trial expenses related to our VIRAGE Phase 2 clinical trial of VCN-01 in PDAC,

increased expenses related to the Phase 1 Trial of intravitreal VCN-01 in patients with retinoblastoma, and increased expenses related

to our Phase 1b/2a clinical trial of SYN-004 (ribaxamase) in allogeneic HCT recipients, offset by lower expenses related to our Phase

1a clinical trial of SYN-020. We anticipate research and development expense to increase as we continue enrollment in our VIRAGE Phase

2 clinical trial of VCN-01 in PDAC, advance our VCN-01 program in retinoblastoma, expand GMP manufacturing activities for VCN-01, and

continue supporting our VCN-11 and other preclinical and discovery initiatives. The charge related to stock-based compensation expense

was $58,000 for the three months ended March 31, 2024, compared to $39,000 related to stock-based compensation expense for the three months

ended March 31, 2023.

income for the three months ended March 31, 2024 is primarily comprised of interest income of $228,000 and an exchange loss of $1,000.

Other income for the three months ended March 31, 2023 is primarily comprised of interest income of $364,000 and exchange gain of $6,000.

Cash and cash equivalents totaled $18.3 million as of March 31, 2024,

compared to $23.2 million as of December 31, 2023.

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 the potential synergy between VCN-01 and liposomal irinotecan in a human pancreatic mouse xenograft,

VCN-01's potential in diverse chemotherapy combinations for improved efficacy in pancreatic cancer VIRAGE expecting to complete

enrollment in the the third quarter of 2024, enrolling 92 evaluable patients and continuing to enroll patients across seven sites in the

U.S. and ten sites in Spain, cash being expected to provide runway into the first quarter of 2025, the therapeutic potential of VCN-01

in retinoblastoma and VCN-01's potential for use in diverse cancer indications, the SYN-004 trial expecting to announce a data readout

in the third quarter of 2024, the potential synergy of VCN-01 and additional first-line pancreatic cancer chemotherapy, continuing to

build a portfolio of potentially improved therapeutic combinations for PDAC patients, identifying opportunities to evaluate the combination

of VCN-01 with additional first-line pancreatic cancer chemotherapy regimens, being well positioned to achieve several important milestones

that will continue to drive forward the clinical development program and anticipated research and development expense to increase . 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 third quarter of 2024, and announcing a data readout for the SYN-004 second cohort in the

third quarter 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 growth of the Company's and VCN's patent

estate, the ability to continue to remain well financed and the cash providing a runway into the first quarter of 2025, and other factors

described in the Company's Annual Report on Form 10-K for the year ended December 31, 2023 and its other filings with

the SEC, including subsequent periodic reports on Forms 10-Q and current reports on Form 8-K. The information in this release is

provided only as of the date of this release, and Theriva Biologics undertakes no obligation to update any forward-looking statements

contained in this release on account of new information, future events, or otherwise, except as required by law.

For further information, please contact:

LifeSci Advisors, LLC

Theriva Biologics, Inc. and Subsidiaries

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(In thousands except share and par value amounts)

Theriva Biologics, Inc. and Subsidiaries

Consolidated Statements of Operations and Comprehensive