Seres Therapeutics' SER-428 reduces gut pathogens up to 1,000-fold in preclinical studies
MCRB•Seres Therapeutics said SER-428 reduced gut Enterococcus faecium and Klebsiella pneumoniae abundance by up to 1,000-fold in preclinical models. The company is designing a Phase 1b trial, with further development dependent on grants or other funding.
1. Preclinical findings
Seres Therapeutics reported that its investigational liquid live biotherapeutic SER-428 reduced gastrointestinal Enterococcus faecium and Klebsiella pneumoniae abundance by up to 1,000-fold in preclinical models. The formulation remained stable after simulated feeding-tube delivery and is intended to target bloodstream infection risk in critically ill patients.
2. Trial plans
The company is designing an open-label Phase 1b trial in high-risk medical intensive care patients, with further development dependent 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 findings are due to be presented at IDWeek in Washington, D.C., on October 22, 2026.
