The advent of imatinib has been a major breakthrough in chronic myeloid leukemia (CML) treatment. A few patients treated with imatinib are either refractory to imatinib or eventually relapse. Resistance is frequently associated with mutations in the kinase domain of BCR-ABL. Over 100 point mutations coding for single amino acid substitutions in the BCR-ABL kinase domain have been isolated from CML patients resistant to imatinib treatment. Most reported mutants are rare, whereas 7 mutated residues comprise two-thirds of all mutations detected. BCR-ABL mutations affect amino acids involved in imatinib binding or in regulatory regions of the BCR-ABL kinase domain, resulting in decreased sensitivity to imatinib while retaining aberrant kinase activity. The early detection of BCR-ABL mutants during therapy may aid in risk stratification as well as molecularly based treatment decisions.
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