P-CrKL in CD34⁺ and CD34⁺CD38^– CML cells treated with IM. CD34⁺ and CD34⁺CD38^– CML cells (n = 8) were cultured with or without IM (5 μM) for 72 hours. Intracellular FACS was used to measure P-CrKL status at 16 and 72 hours. After 16 hours, CD34⁺ cells treated with IM (5 μM) showed an 86% decrease in P-CrKL, as compared to no-drug control (100%). After re-exposure to IM at 60 hours, the surviving CD34⁺ cells showed minimal reduction in P-CrKL at 72 hours (–1.3%) (P = .01). CD34⁺CD38^– CML cells treated with IM (5 μM) showed little dephosphorylation or even hyperphosphorylation of CrKL at either 16-(–4%) or 72-hour (+11%) time points, respectively (P = .40), as compared to no-drug control (100%).