Seres Therapeutics Initiates Phase 3 Study of SER-109

Seres Therapeutics announced the initiation of its Phase 3 SER-109 clinical study (ECOSPOR III) in patients with multiply recurrent C. difficile infection. Based on recent interactions with the U.S. Food and Drug Administration (FDA), ECOSPOR III will now be designated a Phase 3 trial and the company expects that this single pivotal study may support SER-109 registration and approval.

“We are extremely pleased to be able to initiate the SER-109 Phase 3 ECOSPOR III study. If ECOSPOR III is successful, we believe this study could serve as the basis for SER-109 approval. Our goal is to have SER-109 approved as the first microbiome drug in this new field of medicine, and the first for patients with multiply recurrent C. difficileinfection, an area of very high unmet need for patients in the U.S. and around the world,” said Roger J. Pomerantz, M.D., President, CEO and Chairman of Seres.

The ECOSPOR III Phase 3 study design incorporates direct learnings from prior SER-109 development efforts, as well as helpful feedback obtained from the FDA and study investigators. The study is expected to enroll approximately 320 patients with multiply recurrent C. difficile infection, randomized 1:1 to either SER-109 or placebo. The study is sized to contribute to an adequate safety database that may support product licensure. ECOSPOR III will utilize more than 100 clinical sites across the U.S. and Canada. The study’s primary endpoint will compare the reduction of C. difficile recurrence rates in subjects who receive SER-109 verses placebo at up to eight weeks after dosing.

The initiation of the SER-109 Phase 3 ECOSPOR III study triggers a $20 million milestone payment under the company’s previously announced development and commercialization collaboration agreement with Nestlé Health Science. In partnership with Nestlé Health Science, Seres plans to accelerate interactions with European regulatory agencies in the coming months to establish a path toward SER-109 product approval across Europe.

About SER-109 and C. difficile Infection

SER-109, an oral capsule, is Seres’ lead Ecobiotic® microbiome therapeutic for the treatment of multiply recurrent C. difficile infection. SER-109 is a biologically sourced consortium of bacterial spores designed to catalyze a shift in a dysbiotic gastrointestinal microbiome to a healthier state. The FDA has granted SER-109 both Breakthrough Therapy and Orphan Drug Designations.

C. difficile infection is one of the top three most urgent antibiotic-resistant bacterial threats in the United States according to the Centers for Disease Control. C. difficile is a leading cause of hospital acquired infection in the U.S. and is responsible for the death of approximately 29,000 Americans each year.