title: Loss of response to imatinib: mechanisms and management.
abstract: The treatment of chronic myeloid leukemia (CML) has been revolutionized by the small molecule BCR-ABL-selective kinase inhibitor imatinib. Although imatinib is highly effective initially and generally well-tolerated, relapse is increasingly encountered clinically. Until recently, for the majority of CML patients with disease no longer responsive to imatinib, as well as for patients with imatinib intolerance, few effective therapeutic options existed. Our understanding of the major mechanisms of imatinib resistance has led to the clinical development of two novel BCR-ABL inhibitors that harbor significant therapeutic promise in early clinical trial experience. These agents, dasatinib (BMS-354825) and AMN107, are more potent inhibitors of BCR-ABL than imatinib, and moreover, harbor activity against nearly all imatinib-resistant BCR-ABL kinase domain mutant forms tested in vitro. Notably, neither of these compounds is effective against the imatinib-resistant BCR-ABL/T315I mutation. The potential availability of highly effective medications for the treatment of imatinib-resistant and intolerant cases of CML is expected to further complicate the timing of other effective therapies, such as allogeneic stem cell transplantation. Additionally, periodic genotyping of the BCR-ABL kinase domain to screen for drug-resistant mutations may play an increasingly important role in the future management of CML cases.
authors.affiliation: University of California - Los Angeles, 11-934 Louis Factor Building, Box 951678, Los Angeles, CA 90095, USA. nshah@ucla.edu
authors.forename: Neil P
authors.initials: NP
authors.lastname: Shah
mesh_terms: D000970:Antineoplastic Agents / Q000009:adverse effects / Q000627:therapeutic use*; D001549:Benzamides; D000069439:Dasatinib; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation; D016044:Fusion Proteins, bcr-abl / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D005838:Genotype; D006801:Humans; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000235:genetics* / Q000601:surgery; D009154:Mutation; D010879:Piperazines / Q000009:adverse effects / Q000627:therapeutic use*; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011743:Pyrimidines / Q000009:adverse effects / Q000627:therapeutic use*; D033581:Stem Cell Transplantation / Q000379:methods*; D013844:Thiazoles / Q000627:therapeutic use; D014184:Transplantation, Homologous; D017211:Treatment Failure
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D013844:Thiazoles; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases; D016044:Fusion Proteins, bcr-abl; C498826:nilotinib; D000069439:Dasatinib