CTLA4 and acute lymphoblastic leukemia: Other antibodies approved for human use against different protein targets include rituximab, an anti-CD20 mAb for ALL [181]; ipilimumab, an anti-CTLA-4 antibody for pediatric patients with advanced melanoma [182]; and pembrolizumab, an anti-PD1 antibody approved for specific subsets of pediatric patients [183].