Inhibition of BCR-ABL by imatinib induces durable responses in many patients with chronic myeloid leukemia (CML),but resistance attributable to kinase domain mutations can lead to relapse.Mutation of Bcr-Abl is an important mechanism by which chronic myelogenous leukemia (CML) cells become resistant to imatinib.The T3151 mutation is clinically significant since CML cells harboring this mutation are insensitive to imatinib and other Bcr-Abl-targeted drugs.