SDH-deficient GIST is characterized by epigenetic changes, in particular global DNA methylation, which leads to upregulation of fibroblast growth factor receptor (FGFR).112-114 This overexpression of FGFR has been implicated in the pathogenesis of SDH-deficient GIST, and FGFR inhibition in patient-derived, SDH-deficient xenograft mice models led to significant tumor reduction.102 Rogaratinib (BAY 1163877: Bayer), an oral pan-FGFR inhibitor (FRFR 1-4) is currently undergoing phase II testing in patients with FGFR1-4 altered sarcomas or SDH-deficient GIST (NCT04595747).115. The gene discussed is FGFR1; the disease is gastrointestinal stromal tumor.