Phase III ECOSPOR III study of SER 109 shows efficacy in C. difficile infection.

SER 109 was associated with significantly greater reduction of antimicrobial resistance genes (ARGs) compared to placebo, with the reduction observed both rapidly (by Week 1) and sustained through Week 8 of the study. Previously reported topline data indicated that the study achieved its primary endpoint at eight weeks and demonstrated 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 (21.3% vs. 47.3%, respectively). SER 109 was observed to be well tolerated, with no treatment-related serious adverse events observed in the active arm and an adverse event profile comparable to placebo. Seres expects to file a Biologics License Application (BLA) with the FDA in mid-2022.

These data, presented by Timothy Straub on October 2 at the IDWeek 2021 Virtual Conference, support a potential role for microbiome therapeutics in rapid decolonization of antibiotic resistant bacteria.