Imatinib mesylate (STI571, Gleevec) is a selective inhibitor of the tyrosine kinases BCR-ABL, c-KIT and PDGF-R and has been shown to be highly active in chronic myeloid leukemia (CML) and has significant antitumor efficacy against gastrointestinal stroma tumors (GIST). Here, KIT is linked to chronic myelogenous leukemia, BCR-ABL1 positive.