Seres Therapeutics Announces FDA Acceptance of Biologics License Application for Investigational Microbiome Therapeutic SER-109 for Recurrent C. Difficile Infection for Priority Review

On Oct 27, 2022

Seres Therapeutics, Inc. announced the U.S. Food and Drug Administration (FDA) has accepted for review a Biologics License Application (BLA) for investigational oral microbiome therapeutic SER-109 for the prevention of recurrent C. difficile infection (rCDI). The application has been granted Priority Review designation with a Prescription Drug User Fee Act (PDUFA) action date of April 26, 2023. The FDA advised that they are not currently planning to hold an Advisory Committee Meeting to discuss the SER-109 application.

“We are delighted by the FDA’s BLA acceptance for priority review, as we believe that SER-109 has the potential to fundamentally transform the management of rCDI,” said Lisa von Moltke, M.D., Chief Medical Officer at Seres. “We are working closely with the FDA to bring forth this entirely new treatment modality alongside our collaborator, Aimmune Therapeutics, Inc., a Nestlé Health Science Company.”

SER-109 is an investigational microbiome therapeutic composed of purified Firmicutes spores for the treatment of rCDI, which shows promise to improve the current standard of care for this debilitating disease. With nearly 170,000 cases of rCDI each year in the U.S., it is one of the top three most urgent bacterial threats in the country, according to the Centers for Disease Control and Prevention (CDC), and is a leading cause of hospital-acquired infection.

“We are working as quickly as possible to bring this first-ever oral microbiome therapeutic to patients most in need, if approved,” said Eric Shaff, President and Chief Executive Officer at Seres. “Today’s milestone is the result of tremendous hard work and perseverance by our team, and we look forward to collaborating with the FDA through the ongoing review process.”

The application is supported by the results of a completed Phase 3 development program including ECOSPOR III (NCT03183128) and ECOSPOR IV (NCT03183141):

ECOSPOR III (SERES-012): A multicenter, randomized, placebo-controlled study that enrolled 182 adults with rCDI. Results published in the New England Journal of Medicine in January showed that 88% of subjects in the SER-109 group were free from C. difficile recurrence at eight weeks post-treatment, compared to 60% in the placebo group. At 24 weeks post-treatment, 79% of the SER-109 group were still free from C. difficile recurrence, compared to 53% in the placebo group, reinforcing the durable relief. SER-109 was observed to be well tolerated with no drug-related serious adverse events.

ECOSPOR IV (SERES-013): An open-label extension study of ECOSPOR III and open-label program for evaluating SER-109 in 263 adult subjects with rCDI at the commercial dose to fulfill FDA requirements for the SER-109 safety database. The study duration for both cohorts was approximately 27 weeks, including a three-week screening period, an eight-week primary efficacy period, and a 16-week follow-up period. Topline results indicated that the safety profile was well-tolerated and there was a 91% sustained clinical response at eight weeks in the overall population. At 24 weeks post-treatment, 86% of subjects treated with SER-109 experienced sustained clinical response.

In July 2021, Seres entered into an agreement with Nestlé Health Science to jointly commercialize SER-109 in the U.S. and potentially Canada. Under the terms of the agreement, Nestlé Health Science will utilize its global pharmaceutical business, Aimmune Therapeutics, and will assume the role of lead commercialization party. Seres has received an upfront license payment of $175 million and will receive an additional $125 million upon FDA approval of SER-109. The agreement also includes sales target milestones which, if achieved, would total up to $225 million. Seres will be responsible for development and pre-commercialization costs in the U.S. Upon commercialization, Seres will be entitled to an amount equal to 50% of the commercial profits.

Seres plans to host a SER-109 investor event, including participation by Aimmune, focused on the rCDI market opportunity and launch preparations on December 8, 2022. Additional details will be provided at a later date.