ABCB1 and chronic myelogenous leukemia, BCR-ABL1 positive: Here, we show BK124.1 efficacy against the human CML cells in a xenotransplantation mouse model and in the two groups of particularly resistant cells: K562 cells expressing MDR1 (K562-MDR1) and in CD34+/CD38- leukemia stem cells from peripheral blood of CML chronic phase patients.