PDGFRB and Chronic Eosinophilic Leukemia, Not Otherwise Specified: PDGFR inhibitors are classified into two categories including specific and nonspecific inhibitors, based on their binding properties to the receptor, and many PDGFR inhibitors are currently used in the clinical treatment of different cancers.443 CP-673451, a specific ATP-competitive PDGFR inhibitor, effectively inhibits PDGFRβ activity.1110 CHMFL-PDGFR-159 is a highly selective inhibitor of PDGFRα, which significantly inhibits the proliferation of chronic eosinophilic leukemia cells.1111 In addition, there are a large number of nonspecific PDGFR inhibitors.