Synthetic Biologics Announces Agreement with Cedars-Sinai Medical Center for an Investigator- Sponsored Clinical Study of SYN-010, for the Treatment of IBS-C -- Co-funded Research to be Led by Dr. Mark Pimentel's Lab to

Synthetic Biologics Announces Agreement

with Cedars-Sinai Medical Center for an Investigator-

Sponsored Clinical Study of SYN-010, for the Treatment of IBS-C

-- Co-funded Research to

be Led by Dr. Mark Pimentel's Lab to Further Evaluate the Efficacy and

Safety of SYN-010 in a 12-Week, Placebo-Controlled,

Phase 2 Clinical Study --

Rockville, MD, September 06, 2018 -

Synthetic Biologics, Inc. (NYSE American: SYN), a late-stage clinical company developing therapeutics designed to preserve

the microbiome to protect and restore the health of patients, today announced it has entered into an agreement with Cedars-Sinai

Medical Center for an investigator-sponsored Phase 2 clinical study of SYN-010. The study will provide further evaluation of the

efficacy and safety of SYN-010, the Company's modified-release reformulation of lovastatin lactone, which is exclusively

licensed to the Company by Cedars-Sinai Medical Center. SYN-010 is designed to reduce methane production by certain microorganisms

(M. smithii) in the gut to treat an underlying cause of irritable bowel syndrome with constipation (IBS-C).

The Phase 2 study will be conducted out

of the Pimentel Laboratory at Cedars-Sinai Medical Center and is expected to be comprised of a 12-week, placebo-controlled, double-blind,

randomized clinical trial to evaluate two dose strengths of oral SYN-010 (21 mg and 42 mg) in approximately 150 patients diagnosed

with IBS-C. The investigator-sponsored Phase 2 clinical study will be led by the gastrointestinal microbiota researcher

Ruchi Mathur, M.D., director of Metabolism, Clinical Research and Administrative Operations at the Medically Associated Science

and Technology (MAST) Program at Cedars-Sinai. The Phase 2 study, which will be co-funded by Synthetic Biologics and Cedars-Sinai

Medical Center, is expected to begin enrollment during the fourth quarter of 2018, contingent upon approval of the clinical study

protocol by the Cedars-Sinai Medical Center Institutional Review Board. Both Cedars-Sinai and Dr. Pimentel have a financial interest

in Synthetic Biologics.

"This research collaboration is a

further demonstration of Cedars-Sinai's support for the advancement of promising therapies that harness the power of the

microbiome to treat GI disorders such as IBS-C," said Mark Pimentel, M.D., head of the Pimentel Laboratory and executive

director of the MAST Program. "By targeting a major cause of IBS-C, SYN-010 has the potential to provide long-term, chronic

relief to millions of patients who, to date, are forced to settle for therapies designed to treat the symptoms of IBS-C, but do

little to treat the underlying problem."

"We are delighted that Dr. Pimentel

and Cedars-Sinai share our view on the potential of SYN-010 as a new and efficacious treatment option for IBS-C," said Steven

A. Shallcross, Interim Chief Executive Officer of Synthetic Biologics. "In addition to expanding and fortifying our well-established

clinical dataset for SYN-010, the study is also intended to help determine the optimal dose strength of SYN-010 for potential future

registration studies."

The primary objective for the

study will be to determine the efficacy of SYN-010, measured as an improvement from baseline in the weekly average number

of complete spontaneous bowel movements (CSBMs) during the 12-week treatment period for SYN-010 21 mg and 42 mg daily

doses relative to placebo. Secondary efficacy endpoints for both dose strengths of SYN-010 are expected to measure changes

from baseline in abdominal pain, bloating, stool frequency as well as the use of rescue medication relative to placebo.

Exploratory outcomes include Adequate Relief and quality of life measures using the well-validated EQ-5D-5L and PAC-SYM

patient questionnaires.

About Irritable Bowel Syndrome

IBS affects an estimated 10 to 15 percent

of the population, or as many as 45 million people in North America. The illness affects both men and women; however, two-thirds

of diagnosed sufferers are women. It has been reported that up to 20 percent of all IBS patients have IBS-C and current FDA-approved

therapies for the treatment of IBS-C, which include prescription and over-the-counter laxatives, do little to treat the underlying

cause of the disease. These products provide patients with temporary relief from the symptoms of constipation by elevating the

amount of water which passes through the gastrointestinal tract, but tend to cause an IBS-C patient to swing from suffering from

constipation, to suffering from diarrhea.

SYN-010 is a proprietary, modified-release

formulation of lovastatin lactone that is intended to reduce methane production by certain microorganisms (M. smithii)

in the gut while minimizing disruption to the microbiome to treat an underlying cause of IBS-C. SYN-010 is intended to act primarily

in the intestinal lumen while avoiding systemic absorption, thereby targeting a major cause of IBS-C, not just the symptoms. To

learn more about SYN-010's unique mechanism of action, please click here.

About Cedars-Sinai Medical Center

Cedars-Sinai is a national leader in providing

high-quality, patient-centered healthcare encompassing primary care as well as specialized medicine and conducting research that

leads to lifesaving discoveries and innovations. Since its beginning in 1902, Cedars-Sinai has evolved to meet the healthcare needs

of one of the most diverse regions in the nation, continually setting new standards in quality and innovation in patient care,

research, teaching and community service.

Today, Cedars-Sinai is widely known for

its national leadership in transforming healthcare for the benefit of patients. Cedars-Sinai impacts the future of healthcare globally

by developing new approaches to treatment and educating tomorrow's physicians and other health professionals. At the same time,

Cedars-Sinai demonstrates a longstanding commitment to strengthening the Los Angeles community through wide-ranging programs that

improve the health of its most vulnerable residents.

About Synthetic Biologics, Inc.

Synthetic Biologics, Inc. (NYSE American:

SYN) is a late-stage clinical company developing therapeutics that preserve the microbiome to protect and restore the health of

patients. The Company's lead candidates poised for Phase 3 development are: (1) SYN-004 (ribaxamase) which is designed to protect

the gut microbiome from the effects of certain commonly used intravenous (IV) beta-lactam antibiotics for the prevention of C.

difficile infection (CDI), overgrowth of pathogenic organisms and the emergence of antimicrobial resistance (AMR), 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's preclinical pursuits include an oral formulation of

the enzyme intestinal alkaline phosphatase (IAP) to treat both local GI and systemic diseases as well as monoclonal antibody therapies

for the prevention and treatment of pertussis, and novel discovery stage biotherapeutics for the treatment of phenylketonuria

(PKU). 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 includes statements regarding the planned design of the Phase 2 study, the expected commencement of enrollment of the Phase

2 trial during the fourth quarter of 2018, the potential of SYN-010 as a new and efficacious treatment option for IBS-C, the potential

of SYN-010 to provide long-term, chronic relief to millions of patients who, to date, are forced to settle for therapies designed

to treat the symptoms of IBS-C, but do little to treat the underlying problem, the study helping to determine the optimal dose

strength of SYN-010 for potential future registration studies. 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 ability to received Institutional Board Approval of the Phase 2 trial protocol,

the ability to commence the trial when anticipated, the results of the SYN-010 trial demonstrating support for the use of SYN-010

to treat symptoms of IBS-C, Synthetic Biologics' ability to regain compliance with the continued listing standards of the NYSE

American by September 2, 2019, Synthetic Biologics' ability to comply with other continued listing requirements of the NYSE American,

the ability of its product candidates to demonstrate safety and effectiveness, as well as results that are consistent with prior

results, Synthetic Biologics' clinical trials continuing enrollment as expected, a failure to receive the necessary regulatory

approvals for commercialization of Synthetic Biologics' therapeutics, including approval of proposed trial designs, a failure of

Synthetic Biologics' clinical trials, and those conducted by investigators, for SYN-004 and SYN-010 to be commenced or completed

on time or to achieve desired results and benefits, 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, or a failure by Synthetic Biologics or its strategic

partners to successfully commercialize products, Synthetic Biologics' ability to achieve acceptance of its product candidates