Imatinib (INN), marketed by Novartis as Gleevec (Canada, South Africa and the USA) or Glivec (Australia, Europe and Latin America), and sometimes referred to by its investigational name STI-571, is a tyrosine-kinase inhibitor used in the treatment of multiple cancers, most notably Philadelphia chromosome-positive (Ph+) chronic myelogenous leukemia (CML).Gleevec is actually the beta crystalline form of imatinib mesilate, the mesylate salt of imatinib.In order to survive, cells need signaling through proteins (signal cascade) to keep them alive.