Imatinib is used to treat chronic myeloid leukemia , gastrointestinal stromal tumors , and other diseases. In chronic myeloid leukemia, ABL, a tyrosine kinase , is always activated. Imatinib attaches to the active site of tyrosine kinase and blocks its activity. Imatinib is the first new substance that inhibits only specific enzymes in specific cancers without killing all rapidly dividing cells in an unspecific manner, and has become an example for other targeted therapies that inhibit tyrosine phosphatase. Imatinib price plays major role in CLL patients life.