— First-in-Class Drug Candidate to Prevent C. difficile to Begin Phase 2 Testing in 1st Quarter 2015 —

ROCKVILLE, MD, USA I February 10, 2015 I Synthetic Biologics, Inc. (NYSE MKT: SYN), a developer of pathogen-specific therapies for serious infections and diseases, with a focus on protecting the microbiome, today announced positive topline safety and tolerability results from a Phase 1b clinical trial of SYN-004, the Company’s investigational oral beta-lactamase enzyme designed to protect the microbiome and prevent Clostridium difficile (C. difficile) infection, antibiotic-associated diarrhea and secondary antibiotic-resistant infections in patients receiving intravenous (IV) beta-lactam antibiotic therapy.

The U.S. Centers for Disease Control and Prevention (CDC) has identified C. difficile as an “urgent public health threat” that often occurs in people who have had recent medical care with IV antibiotics. These antibiotics can create a harmful imbalance in the gut microbiome by killing “good” bacteria, giving C. difficile a chance to multiply and cause diarrhea, which can lead to dehydration, fever, abdominal pain, cramping, nausea, colitis, and even death. In all, 24 million Americans receive IV antibiotics annuallyi.

“This study further validates the potential of investigational SYN-004 to become the first and only point-of-care therapy designed to preserve the microbiome and prevent C. difficile infection,” said Jeffrey Riley, Chief Executive Officer of Synthetic Biologics. “We plan to initiate Phase 2 studies of SYN-004 in the first quarter of this year to further evaluate our innovative prophylactic approach to preventing C. difficile infection by protecting the gut microbiome from the collateral damage caused by antibiotics. This revolutionary approach potentially holds the hope of treating a variety of GI, metabolic and CNS disorders.”

The randomized, double-blind, placebo-controlled Phase 1b study was designed to further evaluate the safety, tolerability and pharmacokinetics of escalating doses of oral SYN-004 in healthy adult volunteers. In all, the study enrolled 24 healthy adult volunteers in three cohorts, with six participants in each cohort receiving increasing doses of SYN-004 up to four times a day over a seven-day period and two participants in each cohort receiving placebo. No safety or tolerability issues were reported at dose levels and dose regimens both meeting and exceeding those expected post-licensure and registration. It is anticipated that topline pharmacokinetics data from the SYN-004 Phase 1b clinical trial will be reported during the first quarter of 2015.

SYN-004 is intended to block the unintended harmful effects of antibiotics within the gastrointestinal (GI) tract, maintaining the natural balance of the gut microbiome, potentially preventing the 1.1 million C. difficile infectionsii and 30,000 C. difficile-related deathsiii in the United States each year. Beta-lactam antibiotics are a mainstay in hospital infection management and include the commonly used penicillin and cephalosporin classes of antibiotics. During 2012, 14.4 million U.S. patients received approximately 117.6 million doses of IV beta-lactam antibioticsiv that could be inactivated in the GI tract by SYN-004.

About Synthetic Biologics, Inc.

Synthetic Biologics, Inc. (NYSE MKT: SYN) is a clinical-stage biotechnology company developing pathogen-specific therapies for serious infections and diseases, with a focus on protecting the microbiome. The Company is developing an oral biologic to protect the gut microbiome from  intravenous (IV) antibiotics for the prevention of C. difficile infection, an oral statin treatment to reduce the impact of methane producing organisms on constipation-predominant irritable bowel syndrome (C-IBS) and a monoclonal antibody combination for the treatment of Pertussis being developed in collaboration with Intrexon Corporation (NYSE: XON). In addition, the Company is developing a Phase 2 oral estriol drug for the treatment of relapsing-remitting multiple sclerosis (MS) and cognitive dysfunction in MS. For more information, please visit Synthetic Biologics’ website at www.syntheticbiologics.com.

SOURCE: Synthetic Biologics