Fibroblast Growth Factor Receptor (FGFR) Inhibitors for the Treatment of Cholangiocarcinoma: Key Therapeutic Developments and Knowledge Gaps.

Fibroblast growth factor receptor 2 (FGFR2) alterations have emerged as an important targetable oncogenic driver in a biologically distinct subset of biliary tract cancers (BTCs), particularly intrahepatic cholangiocarcinoma (iCCA), alongside other actionable genomic events such as IDH1 mutations, BRAF V600E, HER2 amplification and MSI-H. FGFR2 fusions and mutations define a distinct molecular subgroup whose prevalence varies across geographic regions and etiologic backgrounds such as liver fluke-associated disease. Clinical studies of both reversible and irreversible FGFR inhibitors have demonstrated meaningful activity in FGFR2-rearranged iCCA, while also highlighting a characteristic toxicity profile dominated by on-target hyperphosphataemia. Parallel translational work using cfDNA-based liquid biopsy has mapped a spectrum of secondary kinase-domain mutations that underlie acquired resistance, informing the development of next-generation FGFR2-selective inhibitors (eg, lirafugratinib) and combination strategies with EGFR/ERBB blockade. Collectively, these data underscore the need for comprehensive molecular profiling and innovative umbrella trial designs to optimise targeted therapy in this rare, biologically heterogeneous malignancy.