An inhibitor of the bcr-abl tyrosine kinase. It acts by binding to the ATP binding site of bcr-abl. Imatinib also stimulates the entry of the bcr-abl tyrosine kinase into the nucleus, where it cannot perform its anti-apoptopic functions. It inhibits EOL-1 cell viability (IC₅₀ = 0.5 nM), phosphorylation of a fusion protein (IC₅₀ = 30 nM), and viability of BaF3 cells expressing Rhe-PDGFRα in the absence of IL-3 (IC₅₀ = 0.17 nM).