Given that a significant proportion of CLL patients develop a Richter’s transformation, the objective response rate of 44% in this trial is promising and suggests that PD-1 blockade with pembrolizumab or the PD-1 antibody durvalumab[116] may represent a promising treatment strategy for patients with aggressive disease or disease transformation. This evidence concerns the gene PDCD1 and B-cell chronic lymphocytic leukemia.