Since 2002, the treatment of CML was revolutionized by the introduction of the ATP-competitive inhibitor imatinib mesylate (IM, Gleevec), a BCR-ABL tyrosine kinase inhibitor (TKI) with strong activity against the tyrosine kinases PDGFR, cKit and Abl. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.