Imatinib (Gleevec®) was the first tyrosine kinase inhibitor (TKI) designed to selectively inhibit the BCR-ABL fusion protein, which results from the oncogenic Philadelphia chromosome translocation occurring in chronic myeloid leukemia (CML) and some cases of acute lymphoblastic leukemia (ALL) [5]. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.