Seres Therapeutics, Inc. announced late-breaking data from its Phase 3 ECOSPOR III study evaluating SER-109, an investigational oral microbiome therapeutic for recurrent C. difficile infection (rCDI). New data from an exploratory analysis demonstrate SER-109 reduced the risk of rCDI compared to placebo in patients with risk factors for recurrence, including those taking acid-reducing medications such as proton pump inhibitors (PPIs) and H2 blockers (40.7% of patients). These data, presented by Louis Korman, M.D. on October 26 from 3:25-3:35 PM PT at the American College of Gastroenterology 2021 Annual Scientific Meeting in Las Vegas, may assist healthcare providers in their clinical decision-making on the use of PPIs and H2 blockers in patients at risk for recurrent CDI. The SER-109 ECOSPOR III Phase 3 study (ClinicalTrials.gov identifier: NCT03183128) was a multicenter, randomized, placebo-controlled study. Previously reported topline data demonstrated that the study achieved its primary endpoint where SER-109 was superior to placebo in reducing CDI recurrence at eight weeks reflecting a sustained clinical response rate of approximately 88% at eight weeks post-treatment. SER-109 resulted in a 27% absolute reduction of recurrence of CDI compared to placebo at eight weeks post-treatment, which is a relative risk reduction of 68%. In May 2021, Seres presented 24-week clinical data from the study that demonstrated significantly reduced recurrence rates compared to placebo over 24 weeks (21% vs. 47%, respectively). SER-109 was observed to be well tolerated in the study, with no treatment-related serious adverse events observed in the active arm and an adverse event profile comparable to placebo. Seres expects both the completed Phase 3 study results and the pending open-label study database to enable a Biologics License Application (BLA) filing in mid-2022.