Mechanisms of Resistance to ABL Kinase Inhibition in Chronic Myeloid Leukemia and the Development of Next Generation ABL Kinase Inhibitors

Chronic myeloid leukemia is increasingly viewed as a chronic illness; most patients have a life expectancy close to that of the general population. Despite progress made using BCR-ABL1 tyrosine kinase inhibitors (TKIs), drug resistance via BCR-ABL1 dependent and BCR-ABL1 independent mechanisms continues to be an issue. BCR-ABL1 dependent resistance is primarily mediated through oncoprotein kinase domain mutations and usually results in overt resistance to TKIs. However, BCR-ABL1 independent resistance in the setting of effective BCR-ABL1 inhibition is recognized as a major contributor to minimal residual disease. Efforts to eradicate persistent leukemic stem cells have focused on combination therapy.