Erdafitinib versus Chemotherapy in Fibroblast Growth Factor Receptor-Altered Advanced or Metastatic Urothelial Cancer After Progression on Anti-programmed Death-(Ligand) 1 Therapy: An Exploratory Analysis of the Asian Subpopulation in the THOR Phase 3 Study

Introduction: The randomized phase 3 THOR study showed significantly longer survival with erdafitinib (pan-fibroblast growth factor receptor [FGFR] inhibitor) over chemotherapy in adults with FGFR-altered locally advanced or metastatic urothelial cancer (la/mUC) who had progressed during or after anti-programmed death-(ligand) 1 (anti-PD-[L]1) therapy (Cohort 1). This exploratory post-hoc analysis was conducted to evaluate the efficacy and safety of erdafitinib in the Asian subpopulation within THOR Cohort 1. Patients and methods: Eligible patients were randomized in a 1:1 ratio to receive erdafitinib (8 mg once daily with pharmacodynamically guided up-titration to 9 mg) or chemotherapy (vinflunine or docetaxel once every 3 weeks). The primary endpoint was overall survival (OS). Results: Seventy-six patients were included in the Asian subpopulation: 37 were randomized to erdafitinib and 39 to docetaxel. The median follow-up for survival was 15.7 months. The median OS was longer with erdafitinib than chemotherapy (23.3 months vs.11.3 months; hazard ratio [HR], 0.47; 95% confidence interval [CI], 0.23–0.96). One patient (2.7%) in the erdafitinib arm and 5 patients (15.2%) in the chemotherapy arm had grade 3 or 4 treatment-related serious adverse events (SAEs). One patient (2.7%) in the erdafitinib arm and 4 patients (12.1%) in the chemotherapy arm discontinued treatment due to treatment-related AEs. Conclusions: Erdafitinib showed improved survival compared with chemotherapy, with no new safety concerns in the Asian subpopulation. These findings were consistent with those for the overall study population in THOR Cohort 1 who received prior anti-PD-(L)1 therapy.