Chronic myeloid leukemia (CML) is characterized by the Philadelphia chromosome (Ph) and fusion oncogene BCR-ABL1 and is currently very treatable with tyrosine kinase inhibitors (TKIs) that inhibit the tyrosine kinase activity of the chimeric BCR-ABL1 protein. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.