KIT and chronic myelogenous leukemia, BCR-ABL1 positive: The development of the pyridin-3-ylpyrimidine-based kinase inhibitor imatinib (inhibitor of ABL, PDGFR and c-KIT) was a milestone for the therapy of chronic myeloid leukemia (CML) with breakpoint cluster region protein (BCR)/ABL fusion proteins (generated by the Philadelphia chromosome, Ph+), and also became an important drug for the treatment of gastrointestinal stromal tumor based on its c-KIT inhibitory activity[125].