Immune checkpoint inhibitors have transformed the prognosis and treatment paradigm of many cancer types, through the potential for durable responses. However, the majority of patients still do not benefit. Response to checkpoint inhibition is determined by dynamic host, tumour and tumour microenvironment factors that display spatial and temporal variability, but our understanding of these interactions is incomplete. Through investigating biomarkers of resistance and response, opportunities arise to discover new therapeutic targets and shape personalised treatment strategies. Here we review approved and emerging biomarkers of response to immune checkpoint inhibitors, in particular the recent rapid progress in host and tumour genomics. It is unlikely that a single biomarker will precisely predict response, but multivariate multiomic markers may provide a balanced assessment of these factors and more accurately identify patients who will benefit. Further efforts are required to translate these groundbreaking discoveries into novel therapeutics and biomarker driven clinical trials, to provide durable treatment response to a greater population of patients.
Keywords: Immunotherapy; Microsatellite instability high (MSI-H); PD-L1; Predictive biomarkers; Tumour mutation burden (TMB).
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