SER 109 rolling submission completed at FDA for the prevention of recurrent C. difficile infection

SER 109 has FDA Breakthrough Therapy designation, which provides the potential for priority review of the BLA. If granted, Seres anticipates the potential approval and launch of SER 109 in the first half of 2023, with SER 109 potentially becoming the first ever FDA-approved oral microbiome therapeutic.

The submission is supported by the results of two Phase III studies: ECOSPOR III (NCT03183128) and ECOSPOR IV (NCT03183141). The ECOSPOR III study was a multicenter, randomized, placebo-controlled study, results of which were published in the New England Journal of Medicine. ECOSPOR III achieved its primary endpoint demonstrating that SER-109 was superior to placebo in reducing CDI recurrence at eight weeks, with a sustained clinical response rate of approximately 88% at eight weeks post-treatment, compared to 60% in the placebo arm. In June 2022, Seres shared confirmatory results from the ECOSPOR IV open-label extension study, where the overall safety profile observed through 24 weeks indicated that SER 109 was well tolerated, consistent with the safety profile observed in the placebo-controlled ECOSPOR III study. Further, ECOSPOR IV subjects treated with SER-109 demonstrated a recurrence rate of 8.7% at eight weeks, which indicates a 91.3% sustained clinical response.