This study was designed to establish the MTD and tolerability profile of quizartinib, and to gain preliminary evidence of antitumor activity in solid malignancies, in a patient population enriched for diseases whose pathophysiology is related to aberrant signaling through KIT or PDGFRA such as GIST, other sarcomas or mucosal melanomas. This evidence concerns the gene PDGFRA and gastrointestinal stromal tumor.