Accordingly, the TK inhibitor imatinib mesylate (STI571; Gleevec; Novartis) has become first-line therapy for patients with chronic myeloid leukaemia (CML) harbouring BCR/ABL translocation [6] or for those with advanced gastrointestinal stromal tumor (GIST) showing specific mutations in c-KIT or PDGFRα genes, which activate these TKs [7]. This evidence concerns the gene TKT and chronic myelogenous leukemia, BCR-ABL1 positive.