Avapritinib is approved by FDA and EMA as monotherapy for the treatment of adult patients with inoperable or metastatic GIST harboring the PDGFRA exon 18 mutation, including PDGFRA D842V mutation, and for the treatment of adult patients with aggressive systemic mastocytosis, systemic mastocytosis with an associated haematological neoplasm, or mast cell leukaemia after at least one systemic therapy [203]. The gene discussed is PDGFRA; the disease is systemic mastocytosis.