Imatinib mesylate (STI-571 or Gleevecs) is a relatively selective tyrosine inhibitor of BCR-ABL, PDGF-R, and c-kit, which is usually used in the treatment of chronic myelocytic leukemia (CML) and GIST. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.