ABCB1 and leukemia: This study provides the first evidence from animal and cellular models that BK124.1 has several unique advantages as a novel potential anti-CML chemotherapeutic, including the ability to evoke massive apoptosis in multidrug resistant CML blasts (MDR1) and in the CD34+/CD38− cells from CML patients containing deleterious tumor-initiating leukemia stem cells.