Seres Completes Rolling BLA for Microbiome Therapeutic

If approved, SER-109 to treat recurrent C. diff infections could be the first-ever FDA approved oral microbiome therapeutic.

Seres Therapeutics has completed the rolling submission process for its biologics license application (BLA) to the FDA for SER-109 for the prevention of recurrent C. difficile infection. C. difficile is a bacterium that causes diarrhea and colitis. The CDC estimates that there are about half a million infections a year, and one in six patients will have a second infection within two to eight weeks. In those over the age of 65, one in 11 patients with C. difficile will die within one month.

SER-109 is an oral microbiome therapeutic consisting of a purified Firmicutes spores, which normally live in a healthy microbiome. SER-109 is designed to modulate the disrupted microbiome so that it resists C. difficile growth. The SER-109 manufacturing purification process is designed to remove unwanted microbes, reducing the risk of pathogen transmission.

“Completing this BLA submission marks a key milestone for Seres and, more importantly, a potential turning point for the treatment of nearly 170,000 cases of recurrent C. difficile infection each year in the United States alone,” Lisa von Moltke, M.D., chief medical officer at Seres, said in a press release. “We look forward to continuing to work with the FDA on the review of this BLA so that, if approved, we can bring this therapeutic candidate to patients as quickly as possible with our collaborator, Aimmune Therapeutics, a Nestlé Health Science company.”

The submission is supported by the results of two phase 3 studies: ECOSPOR III and ECOSPOR IV. 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 about 88% at eight weeks post-treatment, compared with 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. 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.

Seres entered into an agreement with Nestlé Health Science in July 2021 to jointly commercialize SER-109 in the United States and Canada. Aimmune Therapeutics will assume the role of lead commercialization party.