PDGFRA and gastrointestinal stromal tumor: Avapritinib was initially evaluated in NAVIGATOR, an open-label phase I trial of 250 patients with unresectable GIST, 56 of whom harbored a PDGFRA exon 18 D842V mutation.32,62 In the initial report, 49 D842V patients (88%) had an objective response with 5 patients (13%) achieving a CR.