ABCB1 and chronic myelogenous leukemia, BCR-ABL1 positive: A unique feature of BK124.1 is its high cytotoxicity to CML cells resistant to chemotherapy due to BCR-ABL1-independent mechanisms, such as K562-MDR1 cells with elevated PgP efflux pump or CD34+ progenitor and CD34+/CD38− stem cells from CML patients.