Seres' Gut Microbiome Therapy Shows Transformative Results

Seres Therapeutics has announced that its investigational therapy, SER-155, has been granted FDA Breakthrough Therapy designation. This decision is based on promising Phase 1b trial results demonstrating that SER-155 significantly reduces bloodstream infections (BSIs) in patients undergoing allogeneic hematopoietic stem cell transplants (allo-HSCT). The therapy also reduced the need for systemic antibiotics and the incidence of febrile neutropenia.

SER-155 is designed to address critical complications in allo-HSCT patients by modulating the gut microbiome. Unlike traditional antibiotic prophylaxis, SER-155 targets the root causes of BSIs. In clinical trials, it showed a 77% reduction in BSIs and shorter durations of antibiotic use, while being well-tolerated with no serious adverse events.

Seres plans to meet with the FDA in 2025 to discuss the next clinical study, potentially a single registrational trial for efficacy. The company also intends to explore the use of SER-155 in other vulnerable populations, including cancer and organ transplant patients, as well as ICU cases, signaling a significant commercial opportunity.