Several biomarkers, such as BRCA1/2 mutations in pancreatic cancer, IDH1 and FGFR2 alterations in cholangiocarcinoma, Claudin 18.2 expression in gastric cancer, the hotspot KRAS p.G12C in CRC and pancreatic cancers, and NRG1 fusions across multiple GI tumor types, have emerged as promising therapeutic targets. The gene discussed is IDH1; the disease is cholangiocarcinoma.