Investigational Therapy SER-109 Prevents Recurrent C Difficile Infection

At the Digestive Disease Week (DDW) Annual Meeting, Seres Therapeutics, Inc. presented findings that suggest their investigational microbiome-based therapeutic, SER-109, helped prevent recurrent Clostridioides difficile (C diff) infection.

The results are from the completed phase 3 trial, ECOSPOR III, that showed SER-109 rapidly established a long-lasting colony of beneficial gut microbes, which produce fatty acids that disrupt C diff’s lifecycle.

With these positive data, Seres plans to submit a biologics License Application (BLA) for SER-109 with the US Food and Drug Administration by mid-2022. SER-109 previously received Breakthrough Therapy and Orphan Drug designations for recurrent CDI by the FDA.

“These results suggest that our investigational microbiome therapeutic, SER-109, is a potentially fast-acting intervention that can provide durable relief from recurrent C difficile infections when administered to vulnerable patients,” said Matthew Henn, PhD, Chief Scientific Officer at Seres.

ECOSPOR III (NCT03183128), was a multicenter, randomized, placebo-controlled, clinical trial that tested the safety and efficacy of SER-109 in preventing recurrent C diff infection (rCDI). The phase 3 study enrolled 182 adults with rCDI. and demonstrated that SER-109 prevented rCDI in 88% of recipients, compared with the 60% of placebo recipients who were recurrence-free.

Approximately 2/3 of rCDI occurred in the first 2 weeks after CDI antibiotic treatment, when the diverse gut microbiome was stripped, making way for the highly resistant C diff bacteria to flourish. SER-109 introduces diverse bacteria spores into the guy, which rapidly germinate and are engrafted into the microbiome and the stool.

After a week of treatment with SER-109, the new bacteria species increased and remained at significantly higher levels than in the placebo group. In the placebo group, bacterial diversity rebounded more slowly and less robustly. These results lasted for the entirety of the 24-week study period.

SER-109 is an oral microbiome therapeutic candidate. It contains highly purified Firmicutes spores, which normally live in a healthy microbiome. SER-109 prevents rCDI by helping restore the gut microbiome and inhibit C diff colonization and growth.

“Confirming the multiple mechanisms that bacteria in SER-109 utilize to prevent this notoriously challenging infection on the cellular and molecular level not only increases our confidence in this particular therapeutic, but it has the potential to help guide the design of the next generation of microbiome-based therapeutics,” Henn said.