However, a case study of a 71-year-old man with ET treated with the PD-1 checkpoint inhibitor, pembrolizumab, for a PD-L1-positive lung adenocarcinoma reported a decrease in elevated platelet counts and a dramatic decrease in the JAK2V617F allele burden after 17 months of pembrolizumab treatment (41). This evidence concerns the gene CD274 and essential thrombocythemia.