Samuel Dawson

Background: Intrahepatic cholangiocarcinoma (iCCA) is a highly aggressive biliary tract malignancy with a 5-year survival rate below 5% in stage IV metastatic disease.¹⁻³ Despite advances in systemic chemotherapy and immune checkpoint inhibition, durable responses remain elusive. Fibroblast growth factor receptor 2 (FGFR2) fusions and rearrangements are identified in approximately 10–15% of iCCA cases and represent among the most clinically actionable oncogenic drivers in this disease.⁴ This review synthesizes current preclinical and clinical evidence surrounding FGFR2-targeted therapy, with a focus on molecular mechanisms of oncogenesis, adaptive and acquired resistance, and emerging combination strategies.

Objective: In this narrative review, we examined the preclinical and clinical mechanisms underlying FGFR2-driven oncogenesis in iCCA, the landscape of acquired and adaptive resistance to FGFR inhibition, and emerging combination strategies with the potential to improve outcomes in this disease.

Search Methods: An online search of PubMed and relevant clinical trial databases was conducted through the spring of 2026 using the following keywords: “cholangiocarcinoma,” “intrahepatic cholangiocarcinoma,” “FGFR2 fusion,” “FGFR inhibitor,” “futibatinib,” “lirafugratinib,” “EGFR bypass resistance,” and “HDAC inhibition.”

Results: Transposon-based in vivo screening and genomic analysis identified truncation of FGFR2 exon 18 (E18) as a powerful oncogenic event.⁵ Loss of the E18-encoded C-terminus produces constitutive kinase activation and ligand-independent engagement of the MAPK and PI3K-AKT-mTOR signaling pathways; notably, oncogenicity is not dependent on a specific fusion partner, broadening the treatable patient population across tumor types.⁵ Futibatinib, an irreversible covalent FGFR1–4 inhibitor, was established as a standard-of-care second-line therapy, achieving a roughly 40% response rate in pretreated patients with FGFR2 fusions or rearrangements across diverse molecular subgroups.⁴ The next-generation agent lirafugratinib demonstrated greater than 250-fold selectivity for FGFR2 over similar receptors, preserving activity against resistant mutations while significantly reducing off-target toxicities such as diarrhea and hyperphosphatemia.⁷ A meta-analysis of 82 patients across 12 studies identified secondary kinase domain mutations in 60% of resistance cases, most frequently at the N550 molecular brake and V565 gatekeeper residues, with polyclonal mutational heterogeneity complicating sequential treatment strategies.³⁶ Separately, adaptive resistance mediated by feedback activation of wild-type EGFR—driven by FGFR inhibitor-induced transcriptional downregulation of ERRFI1—was identified as a distinct, targetable bypass mechanism.² High-volume drug screening using patient-derived cell lines, organoids, and xenografts identified polyclonal HDAC inhibition with quisinostat as highly synergistic with pemigatinib, reducing Ki-67 proliferation indices by roughly 50% and dramatically enhancing late-stage apoptosis.¹ Mechanistically, HDAC inhibition appears to enforce FGFR2 dependency, sensitizing tumors to targeted inhibition therapy.¹ Dual FGFR and EGFR blockade similarly produced durable tumor regression in PDX models, outperforming monotherapy alone.²

Conclusions: FGFR2-targeted therapy represents a significant precision oncology advance in iCCA, yet is consistently limited by rapid acquired resistance and intrapatient molecular heterogeneity. Future strategies must integrate E18 truncation as a universal biomarker for patient selection, deploy combination regimens to preempt adaptive resistance, and leverage next-generation selective inhibitors to overcome on-target mutations.³⁶⁷ Earlier line integration with standard chemotherapy and co-mutation targeting—including IDH1, BRAF V600E, and MSI-H pathways—represents a critical novel frontier for improving outcomes in this overwhelmingly fatal disease.

Works Cited:

1. Lidsky ME, Wang Z, Lu M, et al. Leveraging patient derived models of FGFR2 fusion positive intrahepatic cholangiocarcinoma to identify synergistic therapies. npj Precis Oncol. 2022;6(1):75. doi:10.1038/s41698-022-00320-5
2. Wu Q, Zhen Y, Shi L, et al. EGFR inhibition potentiates FGFR inhibitor therapy and overcomes resistance in FGFR2 fusion-positive cholangiocarcinoma. Cancer Discov. 2022;12(5):1378-1395. doi:10.1158/2159-8290.CD-21-1168
3. Wu Q, Ellis H, Siravegna G, et al. Landscape of clinical resistance mechanisms to FGFR inhibitors in FGFR2-altered cholangiocarcinoma. Clin Cancer Res. 2024;30(1):198-208. doi:10.1158/1078-0432.CCR-23-1317
4. Goyal L, Meric-Bernstam F, Hollebecque A, et al. Futibatinib for FGFR2-rearranged intrahepatic cholangiocarcinoma. N Engl J Med. 2023;388(3):228-239. doi:10.1056/NEJMoa2206834
5. Zingg D, Bhin J, Yemelyanenko J, et al. Truncated FGFR2 is a clinically actionable oncogene in multiple cancers. Nature. 2022;608(7923):609-617. doi:10.1038/s41586-022-05066-5
6. Facchinetti F, Loriot Y, Brayé F, et al. Understanding and overcoming resistance to selective FGFR inhibitors across FGFR2-driven malignancies. Clin Cancer Res. 2024;30(21):4943-4956. doi:10.1158/1078-0432.CCR-24-1834
7. Subbiah V, Sahai V, Maglic D, et al. RLY-4008, the first highly selective FGFR2 inhibitor with activity across FGFR2 alterations and resistance mutations. Cancer Discov. 2023;13(9):2012-2031. doi:10.1158/2159-8290.CD-23-0475