Enitociclib has effective on-target activity in KMT2A-r leukemia cells. (A) MV4-11 (KMT2A-r) cells were treated with varying concentrations of enitociclib and respective DMSO control for 6 hours. Western blot was performed to measure changes in Ser 2 phosphorylation of Rpb1, as well as changes in protein levels of MCL-1 and c-MYC after enitociclib treatment. Western blots are representative images of 3 independent biological repeats. (B) Densitometry analysis shows changes in protein levels of MCL-1 and c-MYC as well as changes in phosphorylation levels at Ser 2 of Rpb1 from 3 independent biological experiments. For group comparisons, 1-way analysis of variance test was used. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001. NTD, Amino-Terminal Domain; P-Rpb1, Phospho-RNAP II subunit B1.