• 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 \<1%.

• Capable of giving signed informed consent