We now report that quizartinib not only targets FLT3 wildtype and ITD mutant kinases [24] – but also potently inhibits cellular proliferation and induces apoptosis of cells expressing a broad range of other clinically relevant class III (mutant) RTK isoforms associated with various diseases, including pediatric and adult leukemia (FLT3 and KIT), GIST, seminoma and melanoma (KIT), as well as myeloproliferative neoplasms associated with eosinophilia (PDGFRA). This evidence concerns the gene PDGFRA and gastrointestinal stromal tumor.