Nilotinib is a potent and selective inhibitor of the Abl tyrosine kinase activity of the Bcr-Abl oncoprotein, active in cell lines and primary Philadelphia chromosome-positive leukemia cells. The drug binds tightly to the ATP-binding site, thereby forming a potent inhibitor of wild-type Bcr-Abl, and retains activity against 32 of 33 imatinib-resistant Bcr-Abl mutants. As a result of this biochemical activity, nilotinib selectively inhibits proliferation and induces apoptosis in cell lines and primary Philadelphia chromosome-positive leukemia cells derived from patients with chronic myeloid leukemia (CML). In a mouse model of CML, oral administration of nilotinib alone has been shown to reduce tumor burden and prolong survival.