BCR and acute lymphoblastic leukemia: [1]–[3] The BCR-ABL translocation is characterized by a constitutively active fusion tyrosine kinase and plays a causal role in CML. It is therefore an attractive target for drug therapy. [4], [5] Imatinib mesylate (Gleevec/Glivec), a selective Abl kinase inhibitor, has been shown to have marked efficacy as a single agent and is used as a first-line therapy for the treatment of CML and Ph+ ALL patients. [6]