Futibatinib after non-covalent FGFR inhibitors in FGFR2-rearranged intrahepatic cholangiocarcinoma: clinical activity and resistance patterns.

PURPOSE: The optimal sequencing of non-covalent and covalent FGFR inhibitors in FGFR2-rearranged intrahepatic cholangiocarcinoma (iCCA) remains undefined. Futibatinib, an irreversible FGFR1-4 inhibitor, may retain activity in the setting of acquired resistance to non-covalent FGFR inhibitors, but data on the patterns of acquired alterations are limited. METHODS: We conducted a retrospective multicenter study across three European centers including patients with advanced FGFR2-rearranged iCCA treated with futibatinib after progression on non-covalent FGFR inhibitors. Clinical outcomes and safety were evaluated. Available genomic profiling at progression was analyzed to characterize resistance mechanisms and their association with outcomes. RESULTS: Sixteen patients were included. Median progression-free survival (mPFS) with prior non-covalent FGFR inhibitors was 10.2 months (95% CI 7.0-15.5), with an objective response rate (ORR) of 60.0%. Among patients with post-progression genomic profiling (n = 11), all harbored FGFR2 resistance mutations, with polyclonal alterations (≥2) in 45.5%. A higher burden of FGFR2 mutations and the presence of co-alterations were associated with shorter mPFS on non-covalent inhibitors. Futibatinib was administered at a median of fourth-line therapy. ORR was 31.3% and disease control rate was 50.0%. Median PFS and overall survival were 4.5 months (95% CI 2.0-9.1) and 9.9 months (95% CI 5.7-not reached), respectively. Notably, outcomes with futibatinib were independent of the number of acquired FGFR2 resistance mutations, and the adverse impact of co-alterations appeared attenuated. Safety was consistent with the known profile. CONCLUSIONS: Futibatinib demonstrates clinically meaningful activity after progression on non-covalent FGFR inhibitors, supporting its use in FGFR2-rearranged iCCA, including in the post-non-covalent inhibitor setting. The distinct resistance patterns provide a biological rationale for the continued efficacy of covalent FGFR inhibition. Prospective studies incorporating longitudinal molecular profiling are needed to optimize treatment sequencing.