Seres Therapeutics reported positive topline results from the pivotal Phase 3 ECOSPOR III study evaluating its investigational oral microbiome therapeutic SER-109 for recurrent C. difficile infection (CDI). The primary endpoint was reached, with SER-109 showing a highly statistically significant reduction in the rate of C. difficile infection recurrence compared to placebo.
ECOSPOR III was a multicenter, randomized, placebo-controlled study that enrolled 182 patients with multiply recurrent CDI. Patients were randomized 1:1 to receive either SER-109 or placebo, after standard of care antibiotic treatment. SER-109, or placebo, was administered orally for three consecutive days. All patients were required to have a positive C. difficile toxin diagnostic test both at study entry and suspected recurrence to ensure the selection of individuals with active disease and to confirm the accuracy of the primary endpoint.
The primary efficacy endpoint of ECOSPOR III was the proportion of patients with recurrent CDI at up to eight weeks following administration of SER-109 or placebo. SER-109 met the study’s primary endpoint with a significantly lower recurrence rate of 11.1% in SER-109 patients versus 41.3% in placebo patients at eight weeks. Patients administered SER-109 experienced a 30.2% lower rate of recurrence, on an absolute basis, compared to placebo. The ECOSPOR III recurrence rates translate into a sustained clinical response rate of 88.9% versus 58.7% with SER-109 and placebo.
SER-109 was well tolerated, with no treatment-related serious adverse events (SAEs) observed in the active arm, and an adverse event profile similar to placebo. The most frequently reported treatment-related AEs were flatulence, abdominal distention, and abdominal pain, which were generally mild to moderate in nature.
As a secondary endpoint, patients are evaluated for CDI recurrence through 24 weeks post-treatment the Company plans to present those results at a future date.
Seres Therapeutics plans to immediately request a Breakthrough Therapy designation meeting with the FDA to discuss the requirements to submit a BLA seeking regulatory approval of SER-109.
SER-019 is an oral, biologically-derived microbiome therapeutic designed to reduce the recurrence of C. difficile infection (CDI), enabling patients to achieve a sustained clinical response by breaking the vicious cycle of CDI recurrence and restoring the diversity of the gastrointestinal microbiome. SER-109 is a consortium of purified bacterial spores of multiple Firmicute species, manufactured by fractionating targeted bacteria from the stool of healthy human donors with further steps to inactivate potential pathogens.
C. difficile infection (CDI) is one of the top three most urgent antibiotic-resistant bacterial threats in the U.S., according to the Centers for Disease Control, and is a leading cause of hospital-acquired infection in the U.S. It is responsible for the deaths of approximately 20,000 Americans each year. CDI is associated with debilitating diarrhea, which significantly impacts the quality of life in every functional domain. The most common treatment is vancomycin but it only provides modest effects, which results in many patients having a recurrence of infections.