Nilotinib, a novel, selective BCR-ABL inhibitor, fits into the ATP-binding site of the BCR- ABL protein with higher affinity than imatinib. Nilotinib is not only more potent than imatinib against wild-type BCR-ABL (IC50 < 30 nM), but also significantly active against 32/33 imatinib-resistant BCR-ABL mutants.