MCL1 and acute myeloid leukemia: AZD4573 is a selective CDK9 inhibitor that has been shown to be successful in treating AML (as well as other hematologic malignancies) both in vitro and in vivo, as demonstrated in cell line-derived and patient-derived xenograft models.108 AML cell death was dependent on downregulation of Mcl-1 by inhibition of CDK9 and showed significant synergy when combined with venetoclax.108 There is a phase I clinical trial ongoing to test the safety and tolerability of AZD4573 in a variety of hematologic malignancies, including AML (NCT03263637).