Seres Therapeutics Inc. (NASDAQ:MCRB) on Wednesday reported topline results from an investigator-sponsored trial evaluating SER-155 in patients with immune-related enterocolitis (irEC), with most participants achieving a steroid-free clinical response after treatment.
irEC is an inflammatory complication of immune checkpoint inhibitors.
The findings also showed favorable safety and biomarker data, supporting the continued development of the live biotherapeutic candidate.
SER-155 Meets Primary Endpoint
The 15-patient trial evaluated whether SER-155 could reduce gastrointestinal inflammation and diarrhea without the use of systemic immunosuppressive therapies, which are currently recommended under clinical guidelines but can increase infection risk, cause metabolic complications, and potentially interfere with ongoing cancer treatment.
By Day 15, 12 of 15 participants, or 80%, achieved the study’s primary endpoint of an immunosuppressive-free clinical response, defined as at least a one-grade improvement in diarrhea symptoms without corticosteroids or biologic immunomodulators.
Of those responders, eight patients experienced at least a two-grade improvement.
Additionally, five participants, representing 33% of the study population, achieved complete clinical remission, with diarrhea symptoms resolving to Grade 0 without systemic immunosuppressive therapy.
Response Durability And Safety Profile
At Day 43, five participants maintained an immunosuppressive-free clinical response, while two remained in complete clinical remission without systemic immunosuppressive treatment.
All 12 patients who responded by Day 15 maintained the same or better diarrhea grade through Day 43. Seven participants later received non-systemically acting gastrointestinal-targeted immunosuppressive therapies after the Day 15 assessment.
SER-155 was generally well tolerated through Day 43, with no serious adverse events considered related to the treatment and no bloodstream infections reported.
Two participants experienced four moderate, non-serious adverse events that investigators considered possibly related to vancomycin and SER-155. All events were resolved.
Biomarker Data Support Continued Development
The study also demonstrated robust bacterial strain engraftment consistent with previous SER-155 studies.
Researchers observed statistically significant reductions by Day 43 in fecal calprotectin, a marker of gastrointestinal inflammation, and fecal albumin, a marker of mucosal epithelial barrier integrity.
According to the company, these findings suggest SER-155 may improve intestinal barrier function and support further evaluation of the therapy for immune-related enterocolitis and potentially other inflammatory and immune-mediated diseases.
MCRB Price Action: Seres Therapeutics shares were down 10.87% at $8.00 at the time of publication on Wednesday, according to Benzinga Pro data.
Photo by PeopleImages.com – Yuri A via Shutterstock
Login to comment