Are there, or shall we discover, biomarkers to guide PD-1 inhibition?

Despite the recent success of PD-1/PD-L1-directed immunotherapy in a number of different malignancies, there are currently no effective biomarkers available to predict patient response to treatment. This question is particularly important because these immunotherapy agents are expensive and have significant toxicity profiles. Early data are emerging on biomarkers such as PD-L1 expression; however, it is clear that further studies are needed to identify alternative biomarkers and to improve understanding of the host immune system and tumor microenvironment. In a panel interview Paolo Ascierto and Ramon de Mello discuss this important clinical question