- For Part 1: Histologically- or cytologically-confirmed diagnosis of unresectable GIST or another advanced solid tumor. Patients with unresectable GIST must have disease that has progressed following imatinib and at least 1 of the following: sunitinib, regorafenib, sorafenib, dasatinib, pazopanib or an experimental kinase-inhibitor agent, or disease with a D842 mutation in the PDGFRα gene. Patients with an advanced solid tumor other than GIST must have relapsed or refractory disease without an available effective therapy.