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. The gene discussed is PDGFRA; the disease is sarcoma.