Imatinib Resistance and Intolerance

Resistance and intolerance

Resistance can be defined as the failure to respond to therapy, known as primary resistance, or loss of response, known as acquired resistance. Thus defined, resistance is a problem with all therapies for chronic myeloid leukaemia (CML). For example, in a large comparative trial, only 56% of early chronic phase CML patients achieved a complete haematologic response when treated with interferon alpha, the treatment of choice prior to the development of BCR-ABL tyrosine kinase inhibitors. Also, the incidence of resistance increases over time and is more common in advanced phases of CML. ^4,5,6,7

Although imatinib—the first available tyrosine kinase inhibitor—has dramatically changed the treatment of CML in recent years, primary and acquired resistance to imatinib have both been reported.

Another factor that can limit the effectiveness of therapy for CML is drug intolerance. Intolerance to imatinib could be an issue for some patients. ^4,13,14 Agents used to treat CML can have toxicity that may require dose reduction or discontinuation and a switch to an alternative treatment. ^2,7,8