Dasatinib is effective in most chronic phase chronic myeloid leukemia patients both in first-line therapy and following imatinib failure. While imatinib uptake into CD34+ cells is low compared to mononuclear cells, few data evaluate how well dasatinib targets primitive CML cells. This study compares intracellular concentration of dasatinib and Bcr-Abl kinase inhibition in CML-CD34+ progenitors and mononuclear cells induced by dasatinib. The intracellular concentrations of dasatinib were similar between CML-CD34+ and mononuclear cells (P=0.8). Similarly, there was no significant difference in the degree of dasatinib-mediated Bcr-Abl kinase inhibition. ABCB1 (MDR1) and ABCG2 inhibitors neither increased dasatinib intracellular concentration nor enhanced dasatinib-mediated Bcr-Abl kinase inhibition. In contrast to nilotinib, we show that dasatinib is not an ABCB1 inhibitor. Thus, dasatinib targets CML-CD34+ progenitors as effectively as it targets mononuclear cells. ABCB1 and ABCG2 efflux pumps do not appear to influence the intracellular dasatinib concentration in CML-CD34+ progenitors.
