Safety, Efficacy of Oral Microbiome Therapeutic Confirmed in Recurrent CDI Study

The investigational oral microbiome therapeutic SER-109 was found to be safe and effective for the prevention of recurrent CDI.

Confirmatory results were announced from a phase 3 study investigating the oral microbiome therapeutic SER-109 for the treatment of recurrent Clostridioides difficile infection (CDI).

SER-109 contains purified bacterial spores of multiple Firmicute species obtained from the stool of healthy human donors. The open-label ECOSPOR IV study ( Identifier: NCT03183141) included a total of 263 adults with recurrent CDI. Patients received 4 capsules of SER-109 orally once daily for 3 consecutive days.

Results showed a recurrence rate of 8.7% for patients treated with SER-109 at 8 weeks, indicating a 91.3% sustained clinical response; this was consistent with the 88% response seen in the ECOSPOR III study ( Identifier: NCT03183128).

The CDI recurrence rate was reported to be 6.5% for patients with a first recurrence of CDI and 9.7% for patients with at least 2 prior CDI episodes. At 24 weeks, the CDI recurrence rate was 13.7% for all patients treated with SER-109.

Findings also showed that SER-109 was well tolerated, with a safety profile consistent with that seen in ECOSPOR III.

“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 at Seres. “These results, along with the start of the rolling BLA submission, significantly advance our ability to deliver what may be the first FDA-approved microbiome therapeutic.”

The Company anticipates completion of the application by mid-2022.


Seres Therapeutics announces confirmatory results from investigational microbiome therapeutic SER-109 ECOSPOR IV open-label study in recurrent C. difficile infection. News release. Seres Therapeutics, Inc. June 7, 2022. Accessed June 9, 2022.

This article originally appeared on MPR