An antineoplastic agent that inhibits the Bcr-Abl fusion protein tyrosine kinase, an abnormal enzyme produced by chronic myeloid leukemia cells that contain the Philadelphia chromosome. Imatinib also inhibits the receptor tyrosine kinases for platelet-derived growth factor (PDGF) and stem cell factor (SCF)/c-kit; the SCF/c-kit receptor tyrosine kinase is activated in gastrointestinal stromal tumor (GIST). This agent inhibits proliferation and induces apoptosis in cells that overexpress these oncoproteins. It is also known as Gleevec. (NCI04)