A "healthy gut state" as the key determinant of immune checkpoint inhibitor efficacy

The gut ecosystem emerges as a key determinant of immune checkpoint inhibitor (ICI) efficacy. Rather than individual "beneficial" bacteria, a broader framework of gut health better explains inter-individual variability in ICI response: a non-inflamed gastrointestinal tract with preserved epithelial barrier and functionally eubiotic microbiome promotes responsiveness, whereas gut inflammation and barrier disruption predict poor outcomes. By integrating human and mechanistic mouse data, we propose shifting the research focus toward clinically actionable gut-health axes to optimize cancer immunotherapy.