PDCD1 and neoplasm: Pharmacologic differences between these inhibitors as well as variations of immune cells in the tumor microenvironment could potentially offer an explanation for the response to pembrolizumab therapy.[21] The side-by-side binding mode comparison of PD-1 with PD-L1 and the two clinically relevant blockers pembrolizumab and nivolumab shed light into some important differences of protein–protein interaction at the molecular level.