Imatinib is a type of cancer growth blocker and an example of a tyrosine kinase inhibitor. It was originally designed as a selective inhibitor against the BCR-Abl fusion protein, but was subsequently shown to inhibit the nononcogenic C-Abl kinase in normal cells. This additional activity was reported to be relevant for the drug's efficacy against chronic myeloid leukemia, with the drug's polypharmacological profile potentially forming the basis for its therapeutic activity. 12