Seres Therapeutics, Inc.

Seres Therapeutics, Inc. is a clinical-stage biotechnology company headquartered in Cambridge, Massachusetts, dedicated to transforming patient lives through revolutionary microbiome therapeutics. Its mission is to develop novel live biotherapeutics that modulate the human microbiome to address serious diseases.

The company's pipeline focuses on developing treatments for medically vulnerable patient populations. Its lead program, VOWST™ (formerly SER-109), was the first FDA-approved oral live biotherapeutic for preventing recurrent C. difficile infection (CDI), which Seres sold to Nestlé Health Science in September 2024. Other key pipeline candidates include SER-155, an investigational oral live biotherapeutic for preventing bacterial bloodstream infections in patients undergoing allogeneic hematopoietic stem cell transplantation, which has received FDA Breakthrough Therapy and Fast Track designations. Seres is also developing SER-603 for GI microbiome disruptions and SER-147 for infections in chronic liver disease, alongside other early-stage programs for inflammatory and immune diseases.

In recent developments, Richard N. Kender was appointed Executive Chair and Interim CEO in March 2026. The company announced in February 2026 a strategic shift, including a 30% workforce reduction and pausing further investment in the SER-155 program while seeking external funding, to prioritize earlier-stage programs in inflammatory and immune diseases. Despite these challenges, Seres presented positive Phase 1b data for SER-155 in April 2026, demonstrating a significant reduction in bacterial bloodstream infections. The company is actively pursuing funding and strategic partnerships to extend its cash runway, which is currently projected through the third quarter of 2026.