Synthetic Biologics Announces Positive Outcome of End-of-Phase 2 Meeting with FDA

Synthetic Biologics, Inc. recently announced it has successfully completed an End-of-Phase 2 meeting with the US FDA to discuss development of SYN-004 (ribaxamase) for the prevention of antibiotic-mediated Clostridium difficile infection (CDI). Pursuant to the meeting, the FDA has proposed criteria for Phase 3 clinical efficacy and safety which, if achieved, may support submission for marketing approval of ribaxamase on the basis of a single Phase 3 clinical trial. Final agreement on these criteria is contingent on FDA evaluation of a detailed Phase 3 clinical trial protocol.

“We are very pleased with the productive advice we have received from the FDA during our recent End-of-Phase 2 meeting,” said Steven A. Shallcross, Interim Chief Executive Officer and Chief Financial Officer. “Having a clear path forward in the form of a Phase 3 clinical program for ribaxamase is an exciting and important milestone for our company and should be highly beneficial in our ongoing strategic partnering discussions.”

Synthetic Biologics, in consultation with the FDA, has confirmed the key elements of the Phase 3 clinical program to support a marketing application for ribaxamase, the Company’s first-in-class oral enzyme designed to degrade certain intravenous (IV) beta-lactam antibiotics within the gastrointestinal (GI) tract to prevent microbiome damage, Clostridium difficile infection (CDI), overgrowth of pathogenic organisms and the emergence of antimicrobial resistance (AMR). The proposed ribaxamase Phase 3 clinical program will entail a single, global, event-driven clinical trial with a fixed maximum number of patients for total enrollment and will evaluate the potential efficacy and safety of ribaxamase in a broad patient population by enrolling patients with a variety of underlying infections treated with a range of IV beta-lactam antibiotics.

The primary efficacy endpoint of the Phase 3 clinical trial will be the reduction in the incidence of CDI at one month after the last drug dose in the ribaxamase treatment group versus placebo. The Company also confirmed that the FDA agreed to a primary safety endpoint of noninferiority in mortality between the ribaxamase treatment group versus placebo at 3 months post-randomization. The designation of efficacy and safety as separate and decoupled endpoints is critical for clinical studies of this nature, where the underlying population, regardless of treatment group, is projected to have a comparatively high incidence of safety events that may significantly dilute the smaller number of CDI events.

Synthetic Biologics anticipates initiating the Phase 3 clinical program after securing additional potential financing via a strategic partnership. In parallel, the Company is evaluating opportunities to advance ribaxamase through the pursuit of a more focused clinical indication in a specialty patient population with multiple potential disease endpoints associated with IV beta-lactam-induced gut microbiome damage. Such a dual approach is designed to advance ribaxamase in areas of clear unmet medical need while also expanding upon ribaxamase’s current data set and providing further validation for use in the broader indication for the prevention of CDI.

Clostridium difficile infection (CDI) is a leading hospital acquired infection in the US, with more than 453,000 patients diagnosed annually. CDI results in approximately 29,000 deaths, $5.4 billion in additional healthcare costs, as well as significant and sometimes prolonged illness. Approximately 1 in 5 CDI patients experience at least one CDI recurrence.

SYN-004 (ribaxamase) is a first-in-class oral enzyme prophylactic therapy designed to degrade certain IV beta-lactam antibiotics within the GI tract and maintain the natural balance of the gut microbiome for the prevention of Clostridium difficile infection (CDI), overgrowth of pathogenic organisms and the emergence of antimicrobial resistance (AMR). A previously completed randomized, double-blind, placebo-controlled Phase 2b proof-of-concept clinical trial of 412 patients met its primary endpoint of significantly reducing C. difficile infection (CDI). Preliminary analysis of the data indicated seven confirmed cases of CDI in the placebo group compared to two cases in the ribaxamase treatment group. Patients receiving ribaxamase achieved a 71.4% relative risk reduction (p-value=0.045) in CDI rates compared to patients receiving placebo.

Synthetic Biologics, Inc. 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 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, and novel discovery stage biotherapeutics for the treatment of phenylketonuria (PKU). For more information, visit www.syntheticbiologics.com.