In a clinical trial on relapsed and refractory AML, sensitivity to venetoclax increased with increased Bcl-2 expression; in contrast, sensitivity decreased with increased expression of myeloid cell leukemia-1 (Mcl-1)14, a critical anti-apoptotic member of the Bcl-2 family and target of various inhibitors now being used in clinical trials, such as S63845. The gene discussed is MCL1; the disease is acute myeloid leukemia.