Seres Therapeutics is advancing a live biotherapeutic candidate designed to address one of the most serious infection risks in critical care: bloodstream infections in ICU patients who cannot tolerate standard oral dosage forms. Preclinical data for SER-428 are being presented at IDWeek 2026, the premier infectious disease conference, marking a notable step forward for the microbiome-modulation space in hospital settings.
Formulation Rationale
The investigational product is delivered as an oral liquid rather than a capsule — a deliberate engineering choice for a patient population that typically receives nutrition and medications through nasogastric or jejunal feeding tubes. Standard probiotic and live biotherapeutic products (LBPs) are almost universally formulated as capsules or powders designed for ambulatory, self-administering consumers. SER-428's liquid format reflects the clinical reality of the ICU, where swallowing solid dosage forms is often contraindicated. For formulators and contract manufacturers working in the finished formulation space, the development signals growing demand for LBP delivery innovation beyond the conventional capsule.
Mechanism and Market Context
Live biotherapeutics occupy a regulatory category distinct from conventional dietary supplements. The FDA classifies LBPs as biological drug products, meaning colony-forming unit (CFU) counts, strain identity, viability through shelf life, and clinical endpoints must meet pharmaceutical-grade evidentiary standards — a bar considerably higher than the structure-function claim framework governing most probiotic supplements. Seres, whose microbiome therapeutics work has previously produced the FDA-approved Clostridioides difficile treatment VOWST, brings established regulatory and manufacturing experience to SER-428's development.
Bloodstream infections (bacteremia and fungemia) in ICU patients are associated with high mortality and significant healthcare costs, creating a clear unmet clinical need. The gut microbiome is increasingly recognized as a reservoir for opportunistic pathogens in immunocompromised and critically ill populations, making microbiome-targeted intervention a scientifically plausible prevention strategy. While SER-428 remains at the preclinical stage, the IDWeek presentation positions the asset within the broader infectious disease and critical care communities, both of which represent high-value channels for LBP adoption if clinical trials confirm efficacy.
For the functional nutrition and nutraceutical ingredient industry, the SER-428 program is a bellwether. Gut health and microbiome science continue to migrate from consumer wellness into acute clinical care, and the probiotic and live biotherapeutic supply chain is being asked to meet pharmaceutical manufacturing standards — GMP compliance, documented CFU viability, and strain-specific safety dossiers — at scale. Ingredient suppliers and co-manufacturers that can bridge the consumer supplement and pharmaceutical LBP worlds are increasingly well-positioned as this category matures.
Written by Michael Politz, Author of Guide to Restaurant Success: The Proven Process for Starting Any Restaurant Business From Scratch to Success (ISBN: 978-1-119-66896-1), Founder of Food & Beverage Magazine, the leading online magazine and resource in the industry. Designer of the Bluetooth logo and recognized in Entrepreneur Magazine's "Top 40 Under 40" for founding American Wholesale Floral, Politz is also the Co-founder of the Proof Awards and the CPG Awards and a partner in numerous consumer brands across the food and beverage sector.