Background: The phase 3 JAVELIN Bladder 100 trial showed significantly prolonged overall survival (OS) with avelumab as first-line (1L) maintenance therapy + best supportive care (BSC) vs BSC alone in patients with advanced urothelial carcinoma (UC) that had not progressed with 1L platinum-containing chemotherapy. Efficacy and safety were assessed in patients enrolled in Japan. Methods: Patients with locally advanced or metastatic UC that had not progressed with 4–6 cycles of 1L platinum-containing chemotherapy were randomized to avelumab (10 mg/kg intravenously every 2 weeks) + BSC or BSC alone. The primary endpoint was OS, and secondary endpoints included progression-free survival (PFS) and safety. Results: In Japanese patients (n = 73) randomized to avelumab + BSC (n = 36) or BSC alone (n = 37), median OS was 24.7 months (95% CI, 18.2-not estimable) vs 18.7 months (95% CI, 12.8–33.0), respectively (HR, 0.81 [95% CI, 0.41–1.58]), and median PFS was 5.6 months (95% CI, 1.9–9.4) vs 1.9 months (95% CI, 1.9–3.8), respectively (HR, 0.63 [95% CI, 0.36–1.11]). In the avelumab + BSC and BSC-alone arms, grade ≥ 3 treatment-emergent adverse events (AEs) occurred in 50.0% vs 8.1%, including grade ≥ 3 treatment-related AEs in 13.9% vs 0%, respectively. Efficacy and safety results in Japanese patients were generally consistent with findings in the overall trial population. Conclusion: Avelumab 1L maintenance treatment showed a favorable benefit-risk balance in Japanese patients, supporting avelumab 1L maintenance as a new standard of care in Japanese patients with advanced UC that has not progressed with 1L platinum-containing chemotherapy. Trial registration: Clinicaltrials.gov NCT02603432.
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