Long-term safety and pharmacodynamics of mepolizumab in children with severe asthma with an eosinophilic phenotype

Background: Mepolizumab is approved for patients with severe asthma with an eosinophilic phenotype aged 12 or more (United States) or 6 or more (European Union) years, but its long-term use in children aged 6 to 11 years has not yet been assessed. Objective: We sought to assess the long-term safety, efficacy, and pharmacodynamics of mepolizumab in children aged 6 to 11 years with severe asthma with an eosinophilic phenotype. Methods: In this open-label, uncontrolled, repeat-dose extension study (NCT02377427), children aged 6 to 11 years with severe asthma with an eosinophilic phenotype (blood eosinophil counts >= 150 cells/mu L at screening or >= 300 cells/mu L in the previous year) received a body weight-dependent dose of subcutaneous mepolizumab of 40 mg (<40 kg) or 100 mg (>= 40 kg) over 52 weeks. End points included the incidence of adverse events (AEs) and immunogenicity (primary), absolute blood eosinophil counts (cells per microliter; secondary), and annualized exacerbation rates and asthma control questionnaire/childhood asthma control test scores (exploratory). Results: Over 52 weeks, 30 children received mepolizumab; 27 (90%) and 7 (23%) experienced on-treatment AEs and serious AEs, respectively. No serious AEs were treatment related. There were no fatal AEs. No specific patterns of AEs were evident, and no anti-drug antibody or neutralizing antibody responses were reported. Compared with baseline values, mepolizumab treatment reduced blood eosinophil counts and asthma exacerbations and improved asthma control across all treatment groups. Conclusion: Long-term safety, pharmacodynamic, and efficacy data from this study support a positive benefit-risk profile for mepolizumab in children with severe asthma with an eosinophilic phenotype and were similar to data in studies in adults and adolescents.