PDCD1 and acute lymphoblastic leukemia: The combination of blinatumomab with nivolumab (anti-PD-1; OPDIVO®, Bristol-Myers Squibb Company, Princeton, NJ) in patients with R/R ALL is being investigated in a phase 1 study, with later intensification to include ipilimumab (anti-CTLA-4; YERVOY®, Bristol-Myers Squibb Company, Princeton, NJ).