Imatinib mesylate, a small molecule tyrosine kinase inhibitor (TKI) that competitively binds to the ATP-binding site of BCR/ABL, is currently considered a first-line agent for the treatment of patients with newly diagnosed chronic-phase (CP) CML [2, 4]. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.