Overcoming resistance in chronic myelogenous leukemia.

Resistance in chronic myelogenous leukemia is an issue that has developed in parallel to the availability of rationally designed small molecule tyrosine kinase inhibitors to treat the disease. A significant fraction of patients with clinical resistance are recognized to harbor point mutations/substitutions in the Abl kinase domain, which limit or preclude drug binding and activity. Recent data suggest that compound mutations may develop as well. Proper identification of clinical resistance and prudent screening for all causes of resistance, ranging from adherence to therapy to Abl kinase mutations, is crucial to success with kinase inhibitor therapy. There is currently an array of Abl kinase inhibitors with unique toxicity and activity profiles available, allowing for individualizing therapy beginning with initial choice at diagnosis and as well informed choice of subsequent therapy in the face of toxicity or resistance, with or without Abl kinase domain mutations. Recent studies continue to highlight the merits of increasingly aggressive initial therapy to subvert resistance and importance of early response to identify need for change in therapy. Proper knowledge and navigation amongst novel therapy options and consideration of drug toxicities, individual patient characteristics, disease response, and vigilance for development of resistance are necessary elements of optimized care for the patient with chronic myelogenous leukemia.