Synthetic Biologics Announces First Two Patients Enrolled in Phase 2b Investigator-Sponsored Clinical Study of SYN-010, for the Treatment of IBS-C Rockville, MD

Synthetic Biologics Announces First

Two Patients Enrolled in Phase 2b Investigator-Sponsored

Clinical Study of SYN-010, for the Treatment

Rockville, MD, January 03, 2019 -

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 that the first two patients have been enrolled in

SYN-010's Phase 2b investigator-sponsored clinical study. SYN-010 is a proprietary, modified-release reformulation of lovastatin

lactone 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). Cedars-Sinai Medical Center (CSMC) and Synthetic Biologics are co-funding

the study, which will further assess the efficacy and safety of SYN-010 in patients diagnosed with IBS-C.

"IBS with constipation can be debilitating

for millions of people worldwide, and this study will go a long way toward helping identify whether SYN-010 can become a valuable

tool in addressing the underlying causes and offering relief to those patients," said Mark Pimentel, M.D., head of the Pimentel

Laboratory and executive director of the Medically Associated Science and Technology (MAST) Program at CSMC.

The Phase 2b study is beng conducted by

the MAST Program at CSMC and comprises 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. A data readout from this investigator-sponsored

clinical study is expected during the second half of 2019.

"We are very excited to begin enrollment

of our SYN-010 Phase 2b investigator-sponsored clinical study," said Steven A. Shallcross, Chief Executive Officer of Synthetic

Biologics. "SYN-010 remains an integral component in our portfolio of microbiome-focused assets and represents a promising

and differentiated approach to treating the underlying cause of the symptoms commonly associated with IBS-C. This study will be

instrumental in our efforts to expand and fortify the already well-established dataset for SYN-010 and may 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.

The patent rights covering the use of SYN-010

are owned by Cedars-Sinai Medical Center and are exclusively licensed by Cedars-Sinai Medical Center to Synthetic Biologics. Both

Cedars-Sinai and Dr. Pimentel have a financial interest in Synthetic Biologics.

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 late-stage candidates 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 to prevent microbiome damage, 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. 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 SYN-010 representing a promising and differentiated approach to treating the underlying cause

of the symptoms commonly associated with IBS-C, potential future registration studies, the planned design of the Phase 2b study,

the expected data readout from this investigator-sponsored clinical study during the second half of 2019, the potential of SYN-010

to treat the cause of IBS-C not just the symptoms and 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 2b 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 in the marketplace and the successful

development, marketing or sale of Synthetic Biologics' products by competitors that render Synthetic Biologics' products obsolete

or non-competitive, the continued maintenance and growth of Synthetic Biologics' patent estate, Synthetic Biologics becoming and

remaining profitable, Synthetic Biologics' ability to obtain or maintain the capital or grants necessary to fund its research and

development activities, a loss of any of Synthetic Biologics' key scientists or management personnel and other factors described

in Synthetic Biologics' Form 10-K for the year ended December 31, 2017 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.

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