Synthetic Biologics Reports 2020 Second Quarter Operational Highlights and Financial Results -- Announced FDA Clearance of IND Application for SYN-020 Intestinal Alkaline Phosphatase (IAP) -- -- Signed Option License Agr

Synthetic Biologics Reports 2020 Second

Quarter Operational Highlights and Financial Results

-- Announced FDA Clearance of IND

Application for SYN-020 Intestinal Alkaline Phosphatase (IAP) --

-- Signed Option License Agreement

with Massachusetts General Hospital to Develop SYN-020

to Treat and Prevent Metabolic and

Inflammatory Diseases Associated with Aging --

-- Enrollment in the Phase 2b Investigator-Sponsored

Clinical Trial of SYN-010 Has Recommenced

Following COVID-19-Related Postponement

-- Conference Call Today at 4:30 p.m.

MD, August 6, 2020 - Synthetic Biologics, Inc. (NYSE American: SYN),

a diversified clinical-stage company leveraging the microbiome to develop therapeutics designed to prevent and treat gastrointestinal

(GI) diseases in areas of high unmet need, today provided a clinical programs update and reported

financial results for the quarter ended June 30, 2020.

"During the second quarter, we remained

diligently focused on advancing our portfolio of GI and microbiome-focused clinical development programs while continuing to navigate

the unprecedented global health and economic crisis sparked by the COVID-19 global pandemic," said Steven A. Shallcross,

Chief Executive and Financial Officer of Synthetic Biologics. "We made significant progress positioning SYN-020, our orally

delivered recombinant version of bovine intestinal alkaline phosphatase (IAP), for its first clinical trial. We were pleased to

report the FDA responded to our Investigational New Drug application (IND) with a study-may-proceed letter to conduct a Phase

1 single ascending dose study of SYN-020 in healthy volunteers. Additionally, we expanded our collaboration with Massachusetts

General Hospital (MGH) in the form of an exclusive option agreement to license intellectual property and technology to commercially

develop SYN-020 for the treatment and prevention of metabolic and inflammatory diseases associated with aging. The Phase 1 clinical

trial is intended to support the clinical development of SYN-020 in multiple indications, including an initial indication for

the treatment of radiation enteropathy secondary to pelvic cancer therapy and indications that may be developed under the MGH

Mr. Shallcross continued, "Enrollment in the Phase 2b

investigator-sponsored clinical trial of SYN-010, intended to treat irritable bowel syndrome-constipation (IBS-C) and being conducted

out of Cedars-Sinai Medical Center (CSMC), has recommenced following a temporary postponement during the first and second quarter

due to the impact of the COVID-19 global pandemic. A data readout in the form of an interim futility analysis is expected during

the third quarter and topline data is anticipated during the first quarter of 2021, subject to potential COVID-19 complications."

Mr. Shallcross concluded, "We remain in close contact with Washington University as we continue to evaluate opportunities

to initiate the planned Phase 1b/2a clinical trial of SYN-004 (ribaxamase) in allogeneic hematopoietic cell transplant (HCT) recipients

in the face of the ongoing COVID-19 pandemic. We continue to closely monitor the crisis caused by the spread of the COVID-19 and

look forward to sharing important updates and progress for this and all our GI and microbiome-focused clinical programs."

Clinical Development and Operational

Quarter Ended June 30, 2020 Financial

General and administrative expenses increased

by 23% to $1.3 million for the three months ended June 30, 2020, from $1.0 million for the three months ended June 30, 2019. This

increase is primarily due to increased legal costs related to business development, patent execution and employee contract matters,

vacation expense, and insurance costs. The charge related to stock-based compensation expense was $67,000 for the three months

ended June 30, 2020, compared to $59,000 the three months ended June 30, 2019.

Research and development expenses decreased

by 38% to $1.6 million for the three months ended June 30, 2020, from $2.6 million for the three months ended June 30, 2019. This

decrease is primarily the result of the response to the global COVID-19 pandemic by our clinical development partners which led

to the postponement of the Phase 1b/2a clinical trial of SYN-004 (ribaxamase) in allogeneic HCT recipients and a temporary halt

during the second quarter in new enrollment in the Phase 2b investigator sponsored clinical trial of SYN-010. The charge related

to stock-based compensation expense was $19,000 for the three months ended June 30, 2020, compared to $31,000 for the three months

ended June 30, 2019.

Other income was $6,000 for the three months

ended June 30, 2020, compared to other income of $80,000 for the three months ended June 30, 2019. Other income for the three months

ended June 30, 2020 and 2019 is primarily comprised of interest income.

Cash and cash equivalents as of June 30,

2020 totaled $8.1 million, a decrease of $7.0 million from December 31, 2019.

Synthetic Biologics will hold a conference call today, Thursday,

August 6, 2020, at 4:30 p.m. (EST). The dial-in

information for the call is as follows, U.S. toll free: 1-888-347-5280 or International: +1 412-902-4280. Participants are asked

to dial in 15 minutes before the start of the call to register. The call will also be webcast over the Internet at https://www.webcaster4.com/Webcast/Page/1096/35797.

An archive of the call will be available for replay at the same URL, https://www.webcaster4.com/Webcast/Page/1096/35797,

for 90 days after the call.

About Synthetic Biologics, Inc.

Synthetic Biologics, Inc. (NYSE American:

SYN) is a clinical-stage company leveraging the microbiome to develop therapeutics designed to prevent and treat gastrointestinal

(GI) diseases in areas of high unmet need. The Company's lead clinical candidates are: (1) SYN-004 (ribaxamase) which is designed

to degrade certain commonly used intravenous (IV) beta-lactam antibiotics within the gastrointestinal (GI) tract to prevent microbiome

damage, C. difficile infection (CDI), overgrowth of pathogenic organisms, the emergence of antimicrobial resistance (AMR)

and acute graft-versus-host-disease (aGVHD) in allogeneic hematopoietic cell transplant (HCT) recipients, and (2) SYN-010, which

is intended to reduce the impact of methane-producing organisms in the gut microbiome to treat an underlying cause of irritable

bowel syndrome with constipation (IBS-C). The Company is also advancing SYN-020, an oral formulation of the enzyme intestinal

alkaline phosphatase (IAP) to treat both local GI and systemic diseases. For more information, please visit Synthetic Biologics'

website at www.syntheticbiologics.com.

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 Phase 1 clinical trial of SYN-020 supporting the clinical development of SYN-020 in multiple

indications, a data readout in the investigator-sponsored Phase 2b clinical trial of SYN-010 in the form of an interim futility

analysis during the third quarter and topline data during the first quarter of 2021, subject to potential COVID-19 complications,

and use of the license with MGH in the advancement of an expanded clinical development program for SYN-020. 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, a failure to receive the

necessary regulatory approvals for commercialization of Synthetic Biologics' therapeutics, a failure of Synthetic Biologics'

clinical trials, and those conducted by investigators, for SYN-004, SYN-010 and SYN-020 to be commenced or completed on time or

to achieve desired results and benefits, especially in light of COVID-19, a failure of Synthetic Biologics' clinical trials

to continue enrollment as expected or receive anticipated funding, a failure of Synthetic Biologics to successfully develop, market

or sell its products, Synthetic Biologics' inability to maintain its material licensing agreements, a failure to maintain

our listing on the NYSE American, or a failure by Synthetic Biologics or its strategic partners to successfully commercialize

products and other factors described in Synthetic Biologics' Annual Report on Form 10-K for the year ended December 31,

2019 and its other filings with the SEC, including subsequent periodic reports on Forms 10-Q and 8-K. The information in this

release is provided only as of the date of this release, and Synthetic 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:

Synthetic Biologics, Inc. (Corporate and

Vincent I. Perrone, Director Corporate Communication, (240)

660-2000, info@syntheticbiologics.com

Gregory Kelley, Senior Vice President, (404) 836-2302, gregory.kelley@ogilvy.com