This study will test an experimental drug called KQB198 in combination with imatinib. The goal is to determine if this combination is safe and tolerable and assess how effective the combination is at treating GIST. Imatinib has been approved by the FDA for the treatment of different types of cancer including GIST.
Unresectable or metastatic disease
Tissue confirmation of GIST
Valid results from local testing of blood or tumor tissue documenting the presence of a KIT mutation (must not have exon 9 mutation) or PDGFRA mutation (must not have PDGFRA D842V).
Measurable disease per RECIST v1.1.
Unable to swallow or GI condition that prevents absorption.
Other active malignancies within the last 2 years.
History of hypersensitivity to any component of KQB198 or imatinib.