New insights in predictive determinants of the tumor immune microenvironment for immune checkpoint inhibition: a never ending story?

Checkpoint inhibitors such as Pembrolizumab (Keytruda^®, MSD), Atezolizumab (Tecentriq^®, Roche), Durvalumab (Imfinzi^®, AstraZeneca) or Nivolumab (Opdivo^®, BMS) have significantly improved curative and palliative treatment of solid malignancies (1-4). However, clinical responses vary largely across different tumor entities. Since the currently used standard predictive tool—PD-L1 assessment by immunohistochemistry—shows largely varying predictive efficacy in different tumor types, e.g., in urothelial cancer (5-7), there is a heavy need for additional complementary biomarkers which can improve the current immunotherapy selection and prediction of therapy success.