To identify novel predictive biomarkers, we explored the characteristics of blood-circulating immune cell subsets within the population of the TITAN-RCC trial (NCT02917772)...in patients receiving nivo+ipi “boosts”, a higher proportion of PD-L1+ CD14+ monocytes (ORadj 1.22, 95% CI 1.06-1.58), PD-L1+ early-stage MDSC (ORadj 1.14, 95% CI 1.02-1.41) and PD-L1+ plasmacytoid DC (ORadj 1.08, 95% CI 1.01-1.17) was observed in responders compared to non-responders.