A small phase 1 study (NCT02879695) is evaluating the safety and tolerability of blinatumomab combined with nivolumab targeting PD-1 and/or ipilimumab targeting cytotoxic T-lymphocyte antigen 4 (CTLA-4) in patients with r/r B-ALL. This evidence concerns the gene CTLA4 and acute lymphoblastic leukemia.