MCL1 and acute myeloid leukemia: A phase I clinical trial showed a 19% complete response rate for ABT-199 monotherapy.9 However, all of the patients relapsed within a short period of time (median time to relapse was only 2.5 months), suggesting that ABT-199 would best be used in combination regimens.9,10 In this study, we demonstrated that inhibition of Mcl-1 enhanced ABT-199-induced apoptosis in both ABT-199-sensitive and ABT-199-resistant AML cells.