D2.175 - Five-Year Real-World Outcomes of Mepolizumab Treatment in Severe Eosinophilic Asthma

Severe eosinophilic asthma remains uncontrolled despite treatment with high-dose inhaled corticosteroids plus a second controller and optimized care. While randomized trials have established the efficacy of anti–interleukin-5 therapy, long-term real-world evidence on sustained outcomes remains limited. We evaluated five-year clinical outcomes of mepolizumab in patients with severe refractory eosinophilic asthma treated in a university hospital setting.

This retrospective study included 27 patients who initiated mepolizumab between September 2018 and December 2023. Eligibility required ≥4 severe exacerbations/year and/or maintenance oral corticosteroids (OCS) for ≥6 months/year with blood eosinophils ≥300 cells/µL. Outcomes were annual exacerbation rate, FEV1 (forced expiratory volume in 1 second), peripheral eosinophil count, OCS exposure, 12-month responder rate and treatment persistence.

Of 27 patients, 92.6% were female and 74.1% had allergic eosinophilic phenotype; 55.6% required maintenance OCS at baseline. After 12 months of mepolizumab treatment, asthma exacerbations decreased by 87% (p < 0.001), with median annual exacerbations falling from 2.0 to 0 and remaining 0 through year 5. FEV1 improved from a median of 68% predicted at baseline to 88% at year 5 (p = 0.005). Peripheral eosinophils declined from 570 to 60 cells/µL within 2 years of treatment (p = 0.003). At one year, 85.2% of patients met responder criteria. Among baseline OCS users (n = 15), 66.7% discontinued OCS. At final follow-up (February 2025), 70.4% of patients remained on therapy, while 25.9% discontinued or switched, most often to benralizumab or dupilumab.

Five-year real-world data demonstrate sustained exacerbation reduction, lung function improvement, profound eosinophil suppression and meaningful corticosteroid sparing, confirming durable effectiveness in severe eosinophilic asthma.