Efficacy and Safety of Depemokimab Compared With Mepolizumab in Adults With Relapsing or Refractory Eosinophilic Granulomatosis With Polyangiitis (EGPA)

This study aims to investigate the efficacy and safety of depemokimab compared with mepolizumab in adults with relapsing or refractory EGPA receiving SoC therapy.

Inclusion Criteria: * Participant (male or female) must be 18 years of age or older at the time of signing the informed consent. * Participants who are \>=40 kilogram at Screening Visit 1. * Participants with a documented diagnosis of EGPA for at least 6 months based on the history or presence of: asthma plus eosinophilia defined as \>1.0\*10\^9/Liter (L) and/or \>10 percentage (%) of leucocytes plus at least 2 of the following additional features of EGPA: a biopsy showing histopathological evidence of eosinophilic vasculitis, or perivascular eosinophilic infiltration, or eosinophil-rich granulomatous inflammation, neuropathy, mono or poly (motor deficit or nerve conduction abnormality), pulmonary infiltrates, non-fixed, sino-nasal abnormality, cardiomyopathy (established by echocardiography or magnetic resonance imaging), glomerulonephritis (hematuria, red cell casts, proteinuria), alveolar hemorrhage (by bronchoalveolar lavage), palpable purpura, anti-neutrophil cytoplasmic antibodies positive Myeloperoxidase or Proteinase 3. * History of relapsing OR refractory disease. * Participants must be on a stable dose of oral prednisolone or prednisone of \>=7.5 mg/day (but not \>50 mg/day) or equivalent for at least 4 weeks prior to Baseline (Visit 2). * If participants receiving immunosuppressive therapy (excluding cyclophosphamide) the dosage must be stable for the 4 weeks prior to Baseline (Visit 2) and during the study. * A female participant is eligible to participate if she is not pregnant or breastfeeding, and one of the following conditions applies: Is a woman of non-childbearing potential (WONCBP) OR Is a woman of childbearing potential (WOCBP) and using a contraceptive method that is highly effective, with a failure rate of \50 mg/day prednisolone/prednisone in the 4-week period prior to Baseline (Visit 2), Intravenous (IV), intramuscular or subcutaneous (SC) corticosteroids in the 4-week period prior to Baseline (Visit 2), Omalizumab within 130 days prior to Screening (Visit 1), Cyclophosphamide (CYC): oral CYC within 4 weeks prior to Baseline (Visit 2) and IV CYC within 3 weeks prior to Baseline (Visit 2), if their total white blood cells is \>=4\*10\^9/L (measured using the local laboratory if necessary), Rituximab within 12 months prior to Screening (Visit 1); in addition, the Participant must have shown recovery of peripheral B-cell count to within the normal range, Tezepelumab and Dupilumab with a washout period of 5 half-lives prior to Screening Visit 1, IV or SC immunoglobulin within 6 months prior to Screening (Visit 1); For China and Japan only within 12 weeks prior to Screening (Visit 1), Interferon-alpha within 6 months prior to Screening Visit 1, Anti-tumor necrosis factor therapy within 12 weeks prior to Screening Visit 1, Anti-CD52 (alemtuzumab) within 6 months prior to Screening Visit 1. * Participants with QT interval corrected for heart rate according to Fridericia's formula (QTcF) \>=450 milliseconds (msec) or QTcF \>=480 msec for participants with Bundle Branch Block in the 12-lead ECG central over-read from at Screening Visit 1.