Investigational Microbiome Therapeutic SER-109 Reduces C Difficile Recurrence

Today, Seres Therapeutics announced confirmatory results from ECOSPOR IV, the open-label clinical study of their treatment for recurrent Clostridioides difficile (C diff) infection.

The investigational oral microbiome therapeutic, SER-109, was well-tolerated and had a sustained clinical response rate of 91.3% after 8 weeks in a trial population with a history of recurrent C diff infection (rCDI).

“The 91.3% sustained clinical response rate observed at 8 weeks in the overall study population with recurrent CDI, including those with first recurrence, reaffirms the superior efficacy and favorable safety profile previously observed in the pivotal placebo-controlled ECOSPOR III trial,” said Paul Feuerstadt, MD, FACG, AGAF, the lead author of the New England Journal of Medicine-published study. “As a treating physician, I look forward to the potential approval of this meaningful therapeutic option for patients living with this challenging and debilitating disease.”

The US Food and Drug Administration (FDA) previously designated SER-109 as a Breakthrough Therapy and Orphan Drug for the prevention of rCDI. With positive data from the ECOSPOR IV and prior ECOSPOR III trials, Seres has begun a rolling submission of a Biologics License Application (BLA) to the FDA for SER-109.

The FDA requested safety data from at least 300 subjects treated with a commercial dose of SER-109 to confirm its safety. Seres expects the BLA submission to be completed by mid-2022, and if granted priority review of the application, anticipated launching SER-109 in the first half of 2023.

CDI commonly occurs when antibiotics wipe out the healthy bacteria in the gut, allowing the harmful C diff bacteria to flourish. SER-109 contains a consortium of highly purified Firmicutes spores, which normally live in a healthy gut microbiome. The investigational therapeutic is designed to prevent further CDI recurrence by removing unwanted microbes and restoring the disrupted microbiome to a state that resists C diff colonization and growth.

The ECOSPOR IV (NCT03183141) multicenter, randomized, placebo-controlled, open-label study included 2 cohorts of adults with rCDI. Enrolled patients had a clinical profile consistent with those frequently evaluated and treated in clinical practice.

The participants treated with SER-109 had a recurrence rate of 8.7% at 8 weeks, indicating a 91.3% sustained clinical response. At 24 weeks, 13.7% of all subjects treated with SER-109 had a CDI recurrence.

SER-109 was well-tolerated through 24 weeks. The safety profile observed in ECOSPOR IV was consistent with that of its preceding placebo-controlled study, ECOSPOR III. Together, these 2 trials complete the SER-109 phase 3 development program.

“The ECOSPOR IV data confirm the well-tolerated safety profile and clinical benefit observed in the prior ECOSPOR III study,” said Eric Shaff, president and CEO of Seres. “We believe that SER-109 has the potential to fundamentally transform the management of rCDI across all 170000 annual cases in the US and are working closely with Aimmune Therapeutics, a Nestlé Health Science Company, to bring this therapeutic candidate to patients as quickly as possible.”

Seres hopes SER-109 will become a first-in-class, FDA-approved microbiome therapeutic. SER-109 previously achieved the first-ever positive pivotal clinical trial results for a targeted microbiome drug candidate. Seres is also currently developing microbiome therapeutics for ulcerative colitis.