ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: Imatinib mesylate (IM), a selective inhibitor of the BCR-ABL tyrosine kinase, has been established as the first-line treatment option for CML since the remarkable success of the IRIS (International Randomized Study of Interferon vs. STI571) trial [2], which demonstrated the dramatic superiority of IM over interferon plus cytarabine - at 18 months, the rate of complete cytogenetic response (CCyR) in patients treated with IM was a remarkable 76% versus 15% for patients treated with interferon plus cytarabine [2].