PDGFRB and chronic myelogenous leukemia, BCR-ABL1 positive: Imatinib is a well-tolerated cancer drug that inhibits tyrosine kinase activity of c-Abl, c-Kit, and platelet derived growth factor receptor [PDGFR], and is the frontline therapy for chronic myelogenous leukemia [CML] and gastrointestinal stromal tumors [GISTs].