BCR and chronic myelogenous leukemia, BCR-ABL1 positive: Abl is of clinical significance due to its causalrole in chronic myelogenous leukemia (CML); in about 90% of casesof CML, a chromosomal translocation forms a “Philadelphia chromosome”,which creates a fusion between the Abl and break-point cluster (Bcr)genes to produce a protein with constitutive kinase activity.63,64 Inhibitors of Abl kinase activity are in clinical use as treatmentsfor CML and other cancers since the US approval of the targeted inhibitorimatinib in 2001 and have significantly improved clinical outcomes.64