The D842V mutation in the PDGFRA gene is detected in 5%-6% of GIST cases.9 Patients with unresectable or metastatic GIST harboring this mutation have a poor prognosis, with median progression-free survival (PFS) ranging from 2 to 10 months and median overall survival (OS) between 9 and 25 months for imatinib and other TKIs.10-13 This poor response is attributed to the primary resistance against all approved TKIs (all type II TKIs) prior to avapritinib, a type I kinase inhibitor.14 The gene discussed is PDGFRA; the disease is gastrointestinal stromal tumor.