Additionally, BK124.1 evoked massive apoptosis in multidrug resistant K562-MDR1 cells (IC50 = 2.16 μM), in CD34+ cells from CML patients (IC50 = 1.5 μM), and in the CD34+/CD38− subpopulation consisting of rare, drug-resistant cancer initiating stem cells. The gene discussed is ABCB1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.