Seres Therapeutics' SER — 428 reduces gut pathogens up to 1,000 — fold in preclinical studies

Seres Therapeutics reported SER-428 reduced gastrointestinal Enterococcus faecium and Klebsiella pneumoniae abundance by up to 1,000-fold in preclinical models. The investigational liquid live biotherapeutic targets bloodstream infection risk in critically ill patients; its formulation remained stable following simulated feeding-tube delivery. A Phase 1b open-label trial is being designed for high-risk medical intensive care patients; further development depends on grants or other funding. SER-428 shares key strains with SER-155, which demonstrated a 77% relative reduction in bloodstream infection risk in a Phase 1b transplant study. The preclinical findings will be presented at IDWeek in Washington, D.C., on October 22, 2026. Disclaimer: This news brief was created by Public Technologies (PUBT) using generative artificial intelligence. While PUBT strives to provide accurate and timely information, this AI-generated content is for informational purposes only and should not be interpreted as financial, investment, or legal advice. Seres Therapeutics Inc. published the original content used to generate this news brief via (Ref. ID: 202610150700PRIMZONEFULLFEED9846158) on October 15,