The gut microbiome as a target in cancer immunotherapy: opportunities and challenges for drug development

The gut microbiome has a critical role in shaping the patient's immune response and influencing the efficacy of anticancer immunotherapy. Emerging evidence suggests that modulating the gut microbiome through interventions such as faecal microbiota transplantation, probiotics, prebiotics and lifestyle modifications may enhance therapeutic outcomes. Consequently, drug development efforts in immuno-oncology have expanded to explore microbiome-based therapeutic strategies. In this Review, we examine the rationale for targeting the microbiome in cancer treatment, highlighting key advances in clinical microbiome characterization and their implications for immunotherapy. We discuss findings from recent clinical trials evaluating microbiome-based interventions and address the challenges associated with translating these approaches into clinical practice. Finally, we outline future directions for the development and integration of microbiome-targeted therapies in oncology, with a focus on optimizing efficacy, safety and patient stratification strategies.