Effectiveness Of Mepolizumab In Reducing Asthma Exacerbations In Japan

Background: Mepolizumab (MEPO) 100mg SC is indicated for severe eosinophilic asthma, which is characterized by persistent eosinophilic inflammation and recurrent exacerbations despite high-level therapy. This study evaluated MEPO effectiveness in reducing asthma exacerbation in standard clinical practice in Japan. Methods: Using nationwide JMDC health claims data, we ensembled a cohort of patients with asthma diagnosis, age≥12 yr, with first MEPO injection between 6/2016-3/2019, ≥12 months enrollment pre- and post-initiation, and no EGPA diagnosis. Asthma exacerbation rates were compared before and after MEPO initiation, defined as 1) outpatient asthma visit with short-term systemic corticosteroid (SCS) treatment or 2) inpatient asthma visit treated with adrenaline, IV steroids or aminophylline. For patients on maintenance SCS, at least double the existing maintenance dose was defined as an exacerbation. Results: Among 56 eligible patients (mean age=53 yr; 54% female), asthma exacerbation rate was reduced by 44% (figure). Rate of asthma exacerbations requiring hospitalizations was reduced by 57%, from 0.11 to 0.05 per person-year. Among patients with ≥2 asthma exacerbations in the pre-treatment period and ≥10 MEPO injections, we found a 55% reduction in exacerbation rate. Conclusion: MEPO effectiveness in reducing asthma-related exacerbations in clinical practice in Japan is consistent with efficacy data from multinational randomized trials.