The U.S. Food and Drug Administration approved Ayvakit (avapritinib) for the treatment of adults with unresectable (unable to be removed with surgery) or metastatic (when cancer cells spread to other parts of the body) gastrointestinal stromal tumor (GIST) – a type of tumor that occurs in the gastrointestinal tract, most commonly in the stomach or small intestine – harboring a platelet-derived growth factor receptor alpha (PDGFRA) exon 18 mutation. This approval includes GIST that harbors a PDGFRA D842V mutation, which is the most common exon 18 mutation. Ayvakit is a kinase inhibitor, meaning it blocks a type of enzyme called a kinase and helps keeps the cancer cells from growing.