PDGFRA and chronic myelogenous leukemia, BCR-ABL1 positive: Imatinib mesylate is a tyrosine kinase inhibitor that was originally designed to inhibit the BCR-ABL tyrosine kinase in chronic myeloid leukemia, but was also found to inhibit other related receptors, such as PDGFRα (Buchdunger et al., 1996, 2000; Capdeville et al., 2002).