Theriva Biologics Reports Fourth Quarter and Full-Year 2022 Operational Highlights and Financial Results - Dosed the first patient in VIRAGE, a Phase 2b clinical trial of systemically administered VCN-01 in combination w

Theriva Biologics Reports Fourth Quarter and

Full-Year 2022 Operational Highlights and Financial Results

- Dosed the first patient in VIRAGE,

a Phase 2b clinical trial of systemically administered VCN-01 in combination with chemotherapy for Pancreatic Ductal Adenocarcinoma -

-Dosed the first patient in the investigator

sponsored Phase 1 clinical trial of VCN-01 for patients with brain tumors-

- Presented positive safety and pharmacokinetic

data from the ongoing Phase 1b/2a clinical trial of SYN-004 (ribaxamase) in allogeneic hematopoietic cell transplant recipients at 2023

Tandem Meetings Transplantation & Cellular Therapy Meetings ; Dosed the first patient in Cohort 2-

-As of December 31, 2022, Theriva Biologics

reports $41.8 million in cash, which is expected to provide runway into the third quarter of 2024-

-Conference call and webcast to be held on Thursday,

March 30th at 8:30 a.m. ET-

MD, March 30, 2023 - 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 fourth quarter and full-year ended December 31, 2022, and provided a corporate update.

2022, we delivered on key milestones that further validate the value of Theriva's oncology-focused platform, advanced our systemically

administered lead oncolytic adenovirus, VCN-01, and with cash runway into the third quarter of 2024, we believe we are well positioned

to propel our clinical development program forward," said Steven A. Shallcross, Chief Executive Officer of Theriva Biologics. "The

dosing of the first patient in VIRAGE, our Phase 2b trial of VCN-01 in patients with newly-diagnosed metastatic pancreatic ductal adenocarcinoma

(PDAC), as well as the Phase 1 trial of VCN-01 in patients with brain tumors, represent important steps in our pursuit to address unmet

needs for difficult-to-treat cancers. Now, a key priority is to build on our compelling Phase 1 outcomes and generate clinical data that

establish VCN-01's differentiated mechanism of action, and potential synergistic clinical benefit in combination with chemotherapy

and immunotherapy in a range of clinical indications. We will also leverage our discovery platform to identify the next generation of

potent OV products."

Recent Program Highlights and Anticipated

SYN-004 (ribaxamase):

Fourth Quarter and Full-Year Ended December

31, 2022 Financial Results

General and administrative expenses increased

to $9.9 million for the year ended December 31, 2022, from $6.5 million for the year ended December 31, 2021. This increase of 50.8%

is primarily comprised of increased expense related to the fair value of the contingent consideration, higher insurance costs, additional

salary and benefits related to new headcount, public relations expenses, and VCN administrative expenses not included in the prior year,

offset by a decrease in consulting and legal costs related to the VCN acquisition. The charge relating to stock-based compensation

expense was $0.4 million for the year ended December 31, 2022, compared to $0.3 million for the year ended December 31, 2021. In addition,

we expect general and administrative expenses to increase as we increase headcount and related overhead due to the VCN acquisition.

Research and development expenses increased to

$11.7 million for the year ended December 31, 2022, from $7.8 million for the year ended December 31, 2021. This increase of 50% is primarily

the result of increased clinical trial expenses related to VCN-01 not incurred in the prior year, offset by lower clinical and manufacturing

expenses related to our Phase 1a clinical trial of SYN-020 and expenses related to our Phase 1b/2a clinical trial of SYN-004 (ribaxamase)

in allogeneic HCT recipients. 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 $112,000 for the year ended December 31, 2022, compared to $76,000 for

the year ended December 31, 2021. 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 $471,000 for the year ended December

31, 2022, compared to other income of $6,000 for the year ended December 31, 2021. Other income for the year ended December 31, 2022 and

is primarily comprised of interest income of $512,000 offset by an exchange loss of $41,000. Other income for the year ended December

2021 was primarily comprised of interest income.

Cash and cash equivalents totaled $41.8 million

as of December 31, 2022, compared to $67.3 million as of December 31, 2021.

Theriva Biologics will host a conference call on Thursday, March 30,

2022, at 8:30 a.m. ET to review the full-year 2022 operational highlights and financial results. 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: 13736047. 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 "Investors" section of the company's website, https://www.therivabio.com, under "Events"

or by clicking here, for 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 and include statements regarding cash being expected to provide runway into the first quarter of 2024,

being well positioned to propel our clinical development program forward, generating clinical data that establish VCN-01's differentiated

mechanism of action and potential synergistic clinical benefit in combination with chemotherapy and immunotherapy in a range of clinical

indications, leveraging our discovery platform to identify the next generation of potent OV products, the trial being conducted at St.

James's University Hospital, United Kingdom, in collaboration with the University of Leeds being transformative for patients and

providing a potential systemic line of treatment that may minimize or eliminate complicated brain surgery if the results show that intravenous

VCN-01 gains entry to brain tumors that are otherwise only accessible through surgery, holding a pre-IND meeting with the FDA (H2 2023)

to discuss the clinical development and potential registration pathway for VCN-01 as an adjunct to chemotherapy in pediatric patients

with advanced retinoblastoma, presenting additional data from the study of VCN-01 in combination with durvalumab in patients with recurrent/metastatic

squamous cell carcinoma of the head and neck (H2 2023), completing the second cohort of our Phase 1b/2a clinical study of SYN-004 for

the prevention of acute graft-versus-host-disease in bone marrow transplant patients (Q1 2024) and research and development expenses increasing

as we incur higher clinical program costs for our VCN product candidates.. These forward-looking statements are based on management's

expectations and assumptions as of the date of this press release and are subject to a number of risks and uncertainties, many of which

are difficult to predict that could cause actual results to differ materially from current expectations and assumptions from those set

forth or implied by any forward-looking statements. 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 Company's and VCN's ability to reach clinical milestones when anticipated, including generating clinical data that establishes

VCN-01's differentiated mechanism of action and potential synergistic clinical benefit in combination with chemotherapy and immunotherapy

in a range of clinical indications, the ability to leverage our discovery platform to identify the next generation of potent OV products,

the ability of VCN-01 to gain entry to brain tumors that are otherwise only accessible through surgery, the ability to schedule a pre-IND

meeting with the FDA (H2 2023) to discuss the clinical development and potential registration pathway for VCN-01 as an adjunct to chemotherapy

in pediatric patients with advanced retinoblastoma, the ability to present additional data from the study of VCN-01 in combination with

durvalumab in patients with recurrent/metastatic squamous cell carcinoma of the head and neck (H2 2023), the ability to complete the second

cohort of our Phase 1b/2a clinical study of SYN-004 for the prevention of acute graft-versus-host-disease in bone marrow transplant patients

(Q1 2024), the ability of VCN-01 as a potential means of enabling the use of immunotherapeutic agents in patients who are unresponsive