While anti-PD1 therapy has transformed melanoma outcomes, many patients develop resistance. Around one in three of these patients will benefit from the addition of ipilimumab (IPI) to PD1 therapy, but the mechanisms driving this response remain poorly understood. In this project, we are investigating how IPI+PD1 overcomes PD1 resistance by analysing tumours and blood samples from patients treated across multiple timepoints.Our aim is to uncover how combination immunotherapy unleashes antigen-specific T cell clones and to translate these insights into predictive biomarkers and novel therapeutic strategies for PD1-resistant melanoma.