Synthetic Biologics Reports First Quarter 2022 Operational Highlights and Financial Results -Encouraging data further supports the development of novel oncolytic adenovirus (OV) platform; Announced a peer-reviewed public

Synthetic Biologics Reports First Quarter 2022

Operational Highlights and Financial Results

-Encouraging data further supports the development

of novel oncolytic adenovirus (OV) platform; Announced a peer-reviewed publication highlighting positive clinical data on VCN-01 and

an upcoming oral presentation on VCN-11, a novel oncolytic adenovirus designed to evade neutralizing antibodies-

- Reported positive safety data on SYN-020

intestinal alkaline phosphatase from the Phase 1 Multiple Ascending Dose clinical trial-

-Formed Scientific Advisory Board and strengthened

the leadership team to support transformative clinical development strategy and extension into oncology -

-As of March 31, 2022, Synthetic Biologics

reports $56.7 million in cash, which is expected to provide runway through the end of 2023-

-Conference call and webcast to be held today

MD, May 16, 2022 - Synthetic Biologics, Inc. (NYSE American: SYN), a diversified clinical-stage company developing

therapeutics designed to treat diseases in areas of high unmet need, today reported financial results for the year ended March 31, 2022,

and provided a corporate update.

Recent Developments:

Anticipated Milestones:

"We are extremely pleased with the continued

momentum following the transformative VCN acquisition, and our significant corporate advancements that mark a new phase of strategic

growth," said Steven A. Shallcross, Chief Executive Officer of Synthetic Biologics. "This is an important phase of Synthetic

Biologics' evolution, and to support our extension into oncology, we strengthened our leadership team and recently formed a Scientific

Advisory Board of leading experts composed of key opinion leaders. These distinguished leaders have made groundbreaking scientific advances

in their respective fields of oncology, immunology and gene therapy, and we look forward to their counsel as we advance our oncolytic

adenovirus development program to address devastating cancers with high unmet need. We are well positioned to deliver on our sharpened

clinical development strategy and are poised for an exciting year ahead with the anticipation of multiple clinical studies and pivotal

milestones that should continue to drive shareholder value."

Quarter Ended March 31, 2022 Financial

General and administrative expenses increased

to $1.7 million for the for the three months ended March 31, 2022, from $1.4 million for the three months ended March 31, 2021. This

increase of 17% primarily composed of increased consulting and legal costs related to the VCN acquisition, higher insurance costs, audit

fees, and public relations expenses and VCN administrative expenses not included in prior year. The charge related to stock-based compensation

expense was $85,000 for the three months ended March 31, 2022, compared to $82,000 the three months ended March 31, 2021.

Research and development expenses increase to

$2.6 million for the three months ended March 31, 2022, from approximately $1.1 million for the three months ended March 31, 2021. This

increase of 132% is primarily the result of higher manufacturing expense for SYN-020, costs incurred related to our Phase 1a clinical

trial of SYN-020 and the Phase 1b/2a clinical trial of SYN-004 (ribaxamase) in allogeneic HCT recipients and VCN research expenses related

to VCN-01 not incurred in the prior year. We anticipate research and development expense to increase as we plan for and initiate enrollment

for our phase 2 clinical trial for VCN-01 in PDAC, phase 2/3 clinical trial in retinoblastoma, expand GMP manufacturing activities for

VCN-01 and SYN-020, and continue with supporting our VCN-11 and other preclinical and discovery initiatives. The charge related to stock-based

compensation expense was $28,000 for the three months ended March 31, 2022, compared to $19,000 related to stock-based compensation expense

for the three months ended March 31, 2021.

Other expense was $21,068 for the three months

ended March 31, 2022 compared to other income of $347 for the three months ended March 31, 2021. Other expense is primarily composed

of exchange loss of $22,607, offset by interest income of $1,539. Other income for the three months ended March 31, 2021 is primarily

comprised of interest income.

Cash and cash equivalents totaled $56.7 million

as of March 31, 2022, a decrease of $10.5 million from December 31, 2021.

Synthetic Biologics will host a conference call at 8:30 a.m. ET today

to review first quarter 2022 operational highlights and financial results. Individuals may participate in the live call via telephone

by dialing (877) 451-6152 (domestic) or (201) 389-0879 (international) and using the conference ID: 13729717. 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.syntheticbiologics.com, under

"Events" or by clicking here, for 90 days after the call.

About Synthetic Biologics, Inc.

Synthetic Biologics, Inc. (NYSE American: SYN) is a diversified clinical-stage

company developing therapeutics designed to treat diseases in areas of high unmet need. The Company recently consummated the acquisition

of VCN Biosciences, S.L. (VCN), which is developing a new oncolytic adenovirus (OV) 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 (a) microbiome damage, (b) Clostridioides

difficile infection (CDI), (c) overgrowth of pathogenic organisms, (d) the emergence of antimicrobial resistance (AMR), and (e) 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 Synthetic Biologics' website at www.syntheticbiologics.com.

Forward-Looking Statements

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 of VCN-11 to balance safety, the suggestion that treatment with VCN-01 is feasible has an acceptable safety profile,

the SAD and MAD studies supporting the development of SYN-020 in multiple clinical indications, initiation of VCN-01 dosing in

an investigator sponsored study of brain tumors at the University of Leeds (H1 2022) initiation of VCN-01 dosing in combination with

mesothelin-directed CAR-T cells for pancreatic and ovarian cancer in an investigator sponsored study at the University of Pennsylvania

(H1 2022), initiation of a Phase 2 study of VCN-01 in combination with standard-of-care chemotherapy (gemcitabine/nab-paclitaxel) as

a first line therapy in newly diagnosed metastatic PDAC patients (Q4 2022), initiation of a Phase 2/3 trial of VCN-01 as either an adjunct

to chemotherapy or a potential rescue therapy in pediatric patients with advanced retinoblastoma (early 2023), data read out from the

first cohort of the SYN-004 study in allo-HCT patients (H2 2022), planning for the initiation of a Phase 2a study of SYN-020 (H2 2022),

being well positioned to deliver on our sharpened clinical development strategy and being poised for an exciting year ahead with the

anticipation of multiple clinical studies and pivotal milestones that should continue to drive shareholder value and the potential for

each of our clinical programs. 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, whether

the combined business of Synthetic Biologics and VCN will be successful, Synthetic Biologics' and VCN's product candidates demonstrating

safety and effectiveness, as well as results that are consistent with prior results, the ability to initiate VCN-01 dosing in an investigator

sponsored study of brain tumors at the University of Leeds (H1 2022), initiate VCN-01 dosing in combination with mesothelin-directed

CAR-T cells for pancreatic and ovarian cancer in an investigator sponsored study at the University of Pennsylvania (H1 2022), initiate

a Phase 2 study of VCN-01 in combination with standard-of-care chemotherapy (gemcitabine/nab-paclitaxel) as a first line therapy in newly

diagnosed metastatic PDAC patients (Q4 2022), initiate a Phase 2/3 trial of VCN-01 as either an adjunct to chemotherapy or a potential

rescue therapy in pediatric patients with advanced retinoblastoma (early 2023), data read out from the first cohort of the SYN-004 study

in allo-HCT patients (H2 2022), the SAD and MAD studies supporting the development of SYN-020 in multiple clinical indications and planning

for the initiation of a Phase 2a study of SYN-020 (H2 2022) ; the ability to complete clinical trials on time and achieve the desired

results and benefits, continuing clinical trial enrollment as expected; the ability to obtain regulatory approval for commercialization

of product candidates or to comply with ongoing regulatory requirements, regulatory limitations relating to Synthetic Biologics' 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 Synthetic Biologics' and VCN's products, developments by competitors

that render such products obsolete or non-competitive, Synthetic Biologics' and VCN's ability to maintain license agreements, the continued

maintenance and growth of Synthetic Biologics' and VCN's patent estate, the ability to continue to remain well financed, and other factors