Pharmacologic inhibition of BTK in primary AML blasts. (A) AML blasts and the AML cell line U937 were treated with increasing doses of ibrutinib for 1 hour and then assayed for occupancy of the BTK active site. (B) AML blasts and CD34⁺ control cells were treated with increasing doses of ibrutinib (0.1-10 µM) for 72 hours and then assessed by Cell TitreGlo. Data were normalized to dimethyl sulfoxide (DMSO)-treated cells and represent the mean ± SD of 3 experiments. (C) AML cell lines were treated with increasing doses of ibrutinib (0.1-10 µM) for 72 hours and then assessed by Cell TitreGlo. Data were normalized to DMSO-treated cells and represent the mean ± SD of 3 experiments. (D) Correlation analysis of 50% inhibitory concentration (IC₅₀) values of AML blasts treated with ibrutinib and percent of BTK phosphorylation.