We evaluate the therapeutic potential of a P-glycoprotein and BCRP inhibitor, elacridar, in sensitive (K562 and LAMA-84) and imatinib-resistant (K562-RC and K562-RD) CML cell lines as monotherapy and combined with imatinib. The gene discussed is ABCB1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.