Seres Therapeutics reported early phase findings for SER-155, a live biotherapeutic designed to address immune checkpoint inhibitor-related enterocolitis (irEC). The approach targets a clinical problem that can limit patients’ ability to stay on potentially effective checkpoint regimens due to gastrointestinal inflammation. The company’s reported phase 1 data suggest SER-155 may help manage the condition while supporting a pathway toward broader tolerability of ICI therapy. For clinicians, irEC remains a major driver of treatment interruptions and discontinuations. As checkpoint inhibitor use expands, interventions that can safely mitigate toxicity are increasingly viewed as strategic complements to oncology drug portfolios. The update keeps attention on microbiome-derived or microbiome-modulating therapies as a mechanism class for immunotherapy side-effect control—not just as independent anticancer modalities.