ABCB1 and chronic myelogenous leukemia, BCR-ABL1 positive: However, a significant percentage of the patients with CML failed to respond effectively to the current regimen of drug therapy including frontline tyrosine kinase inhibitors (TKIs) therapy and had to be considered for allogeneic stem cell transplantation, which has a high risk of morbidity and mortality.2, 3, 4 MDR1 encodes a 170 kDa transmembrane protein, P-glycoprotein (P-gp), which causes the efflux of antineoplastic agents from tumor cells via an adenosine triphosphate-dependent process.