Uptake of imatinib into CEM and VBL₁₀₀ cells in the presence of ABCB1 inhibitors. Cells were incubated for 60 minutes in transport media with ¹⁴C-labeled imatinib and (A) 20 μM verapamil or (B) 10 μM PSC-833. Data represent mean ± SEM from 4 experiments. ^*Significantly different from CEM control (P < .05). ^**Significantly different from VBL control (P < .001).