PDGFRA and gastrointestinal stromal tumor: Imatinib mesylate (aka Gleevec or STI571) [28], is a small molecule inhibitor that targets the ATP-binding site in c-Abl kinase domain and is successful in treating CML patients [29], [30], as well as gastrointestinal stromal tumors (GIST) expressing mutant c-KIT, or overexpressing α- or β platelet-derived growth factor receptors (PDGFRα or β) [31].