Long-term safety and effectiveness of mepolizumab for patients with bronchial asthma in routine clinical practice in Japan — final report of special drug use investigation

BACKGROUND: Mepolizumab is an anti-interleukin-5 (IL-5) monoclonal antibody that blocks IL-5-driven airway inflammation, including eosinophilia. Mepolizumab is well tolerated and effective in reducing exacerbations in patients with bronchial asthma. However, limited real-world data are available for treatment outcomes of mepolizumab in patients with bronchial asthma in Japan. Therefore, this large-scale study aimed to assess the long-term safety and effectiveness of mepolizumab in patients with bronchial asthma in Japan. METHODS: In this real-world observational study conducted between January 2017 and September 2023, patients with bronchial asthma who had available data in an electronic data capture system for at least 52 weeks prior to subcutaneous mepolizumab treatment were monitored for 52 weeks from their first dose of mepolizumab. Safety was evaluated based on patient-reported adverse drug reactions (ADRs), and effectiveness was evaluated by frequency of asthma exacerbations, changes in Asthma Control Test (ACT) scores, and peak expiratory flow (PEF). RESULTS: Overall, 1061 patients were enrolled. ADRs were reported by 4.1 % of patients in the safety population (n = 1027). No new safety concerns were identified. The overall effectiveness was evaluated in 959 patients in the effectiveness population. Post-mepolizumab initiation, asthma exacerbations were reduced from 3.8 to 1.0 per person-year; mean (standard deviation [SD]) ACT scores improved from 15.9 (4.6) to 21.4 (3.9); mean (SD) PEF improved from 304.4 L/min (146.8) to 349.5 L/min (134.7) compared with pre-mepolizumab initiation. CONCLUSIONS: This analysis of real-world data demonstrates that mepolizumab was well tolerated and effective in patients with bronchial asthma in Japan.