A Trial to Investigate Benralizumab in Children With Eosinophilic Diseases

This study is open-label, multicentre, basket study to evaluate the safety, PK, pharmacodynamic (PD), efficacy, and immunogenicity of repeat dosing of benralizumab subcutaneous (SC) every 4 weeks (Q4W) in male and female children with rare eosinophilic diseases. Paediatric participants with eosinophilic granulomatosis with polyangiitis (EGPA) will be enrolled in the first cohort. Additional cohorts in other eosinophilic diseases may be added in future protocol amendments. The study consists of 3 periods: 1. Screening period: 1 to 4 weeks 2. Open-label treatment period: 52 weeks 3. Open-label extension period: at least 52 weeks (plus safety follow-up [SFU] weeks after last investigational product [IP] administration) All eligible participants will receive benralizumab SC Q4W during the 52-week open-label treatment period. All participants who complete the 52-week open-label treatment period on IP will be offered the opportunity to continue into an extension period. The extension period is intended to allow each participant at least an additional one year of treatment with benralizumab.