Inclusion Criteria:

• Male or female subjects age 18 years or older.
• EGPA diagnosis based on history or presence asthma and eosinophilia (> 1.0x10^9/L and/or >10% of leucocytes) and at least 2 of; biopsy with eosinophilic vasculitis or perivascular/granulomatous inflammation; mono-or polyneuropathy, non-fixed pulmonary infiltrates, sino-nasal abnormality; cardiomyopathy; glomerulonephritis; alveolar haemorrhage; palpable purpura; anti neutrophil cytoplasmic anti-body (ANCA) positivity (Myeloperoxidase or proteinease 3).
• History of relapsing (at least 1 confirmed EGPA relapse within last 2 years and > 12 weeks prior to screening, or refractory (failure to attain remission, defined as BVAS=0 and oral corticosteroid (OCS) dose ≤ 7.5 mg/day of prednisolone or equivalent, following standard induction regimen for at least 3 months and within 6 months prior to screening, or recurrence of symptoms upon OCS tapering at any dose of ≥ 7.5 mg/day prednisolone or equivalent. If induction with glucocorticoidsalone, patient must have failed to attain remission after 3 months and the glucocorticoid dose must be ≥ 15 mg/day prednisolone or equivalent for the 4 weeks prior to randomization.
• Must be on a stable dose of oral prednisolone or prednisone of ≥ 7.5 mg/day (but not > 50mg/day) for at least 4 weeks prior to randomization.
• If receiving immunosuppressive therapy (excluding cyclophosphamide) the dose must be stable for the 4 weeks prior to randomization and during the study (dose reductions for safety reasons will be permitted).
• QTc(F)< 450 msec or QTc(F)< 480 msec for patients with bundle branch block.
• Females of childbearing potential must use an acceptable method of birth control from signing the informed consent until 4 months after the last study drug administration.

Exclusion Criteria:

• Diagnosed with granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA).
• Organ or life-threatening EGPA < 3 months prior to screening.
• Currently pregnant or breastfeeding, or planning to become pregnant during study participation.
• Current malignancy or history of malignancy, unless received curative therapy > 5 years ago, or > 1 year ago for basal cell carcinoma, localized squamous cell carcinoma of the skin or in situ carcinoma of the cervix.
• An untreated or refractory helminth parasitic infection < 24 weeks prior to screening.
• Unstable liver disease.
• Severe or clinically significant, uncontrolled cardiovascular disease.
• Other concurrent disease that may put the patient at risk, or may influence the results of the study, or the patients' ability to complete entire duration of the study.
• Chronic or ongoing infectious disease requiring systemic antiinfective treatment.
• Known immunodeficiency disorder or positive HIV test.
• Prior receipt of mepolizumab, reslizumab, dupilumab or benralizumab. Receipt of intravenous/intramuscular/subcutaneous corticosteroids within 4 weeks prior to randomization, receipt of omalizumab within 130 days prior to screenin, rituximab within 6 months prior to screening (or B-cells not recovered), interferon-α or alemtuzumab within 6 months prior to screening, receipt of anti-tumor necrosis factor therapy within 12 weeks prior to screening or an investigational drug within 30 days or 5 terminal phase drug half-lives, whichever is longer, prior to screening.