Although not significant, lower CR rates (81%) were obtained in patients with positive ABCB1 AML compared to those with negative ABCB1 activity (91%) and ABCB1 activity was higher in non-responders vs. patients in CR (median V/E ratio: 2.2 vs. 1.5, p = 0.17, Figure 2A). This evidence concerns the gene ABCB1 and acute myeloid leukemia.