The gut microbiome plays a critical role in shaping systemic immunity and influencing patient responses to immunotherapy. This project investigates how differences in the gut microbiome predict both treatment efficacy and immune-related toxicities in melanoma patients. By integrating microbiome sequencing with clinical and immunological data, we aim to identify microbial signatures associated with favourable outcomes. In parallel, using preclinical models we are exploring whether interventions that alter the gut microbiome, such as dietary modulation, probiotics, or faecal microbiota transplantation, can enhance responses to immunotherapy and reduce treatment-related toxicities. Our ultimate goal is to harness the gut microbiome as a predictive biomarker and therapeutic target to optimise cancer treatment.