Targeting FGFR inhibition in cholangiocarcinoma

Cholangiocarcinomas (CCAs) are rare but aggressive tumours of the bile ducts, which are often diagnosed at an advanced stage and have poor outcomes on systemic therapy. Somatic alterations with therapeutic implications have been identified in almost half of CCAs, in particular in intrahepatic CCA (iCCA), the subtype arising from bile ducts within the liver. Among patients with CCA, fibroblast growth factor receptor 2 (FGFR2) fusions or rearrangements occur almost exclusively in iCCA, where they are estimated to be found in up to 10?15% of patients. Clinical trials for selective FGFR kinase inhibitors have shown consistent activity of these agents in previously treated patients with iCCA harbouring FGFR alterations. Current FGFR kinase inhibitors show differences in their structure, mechanisms of target engagement, and specificities for FGFR1, 2, 3 and 4 and other related kinases. These agents offer the potential to improve outcomes in FGFR-driven CCA, and the impact of variations in the molecular profiles of the FGFR inhibitors on efficacy, safety, acquired resistance mechanisms, and patients? health-related quality of life remains to be fully characterized. The most common adverse event associated with FGFR inhibitors is hyperphosphatemia, an on-target off-tumour effect of FGFR1 inhibition, and strategies to manage this include dose adjustment, chelators, and the use of a low phosphate diet. As FGFR inhibitors and other targeted agents enter the clinic for use in FGFR-driven CCA, molecular testing for actionable mutations and monitoring for the emergence of acquired resistance will be essential.

Automated summary

CCAs, particularly iCCAs, often have therapeutic implications from somatic alterations such as FGFR2 fusions or rearrangements. Clinical trials for FGFR kinase inhibitors have shown consistent activity in previously treated iCCA patients with FGFR alterations, although differences in structure, mechanisms, and specificities remain to be fully characterized. Managing adverse events such as hyperphosphatemia and monitoring for acquired resistance are essential as FGFR inhibitors and other targeted agents are used in the clinic for FGFR-driven CCA.