This study is a phase 2/3 clinical trial to evaluate the efficacy and safety of SHR-1703 in patients with EGPA.

Inclusion Criteria:

1. Male or female subjects age 18 years or older;
2. Diagnosed with EGPA for at least 6 months;
3. History of relapsing or refractory EGPA；
4. Stable dose of oral prednisone of ≥7.5 mg/day (but not >50 mg/day) for at least 4 weeks prior to randomization;
5. If receiving immunosuppressive therapy (excluding cyclophosphamide), the dosage must be stable within 4 weeks prior to randomization and during the study.

Exclusion Criteria:

1. Subjects with other eosinophilic-related diseases;
2. Diagnosed with granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA).
3. Life-threatening EGPA within 3 months prior to randomization;
4. Malignancy history within 5 years prior to randomization;
5. Immunodeficiency;
6. Uncontrolled hypertension；
7. Uncontrolled cerebrovascular and cardiovascular disease;
8. parasitic infection within 6 months prior to randomization;
9. Active infectious disease requiring clinical treatment within 4 weeks prior to randomization;
10. Subjects with a dose of oral prednisone of >50 mg/day within 4 weeks prior to randomization;
11. Oral or intravenous cyclophosphamide therapy within 4 weeks prior to randomization;
12. Intravenous or subcutaneous immunoglobulin within 12 weeks prior to randomization;
13. Biological agents or TH2 cytokine inhibitors used within 12 weeks prior to randomization or within 5 half-lives of the drug;
14. Rituximab used within 6 months prior to randomization；
15. Surgical plans that might affect the evaluation;
16. Significant laboratory abnormalities；
17. Prolonged QTc interval or other electrocardiogram abnormalities with significant safety risk at screening;
18. History of drug or substance abuse or alcohol abuse within 1 year prior to screening;
19. Subjects participated another clinical study and received active drug within 30 days or 5 half-lives of the drug prior to screening;
20. Subjects is pregnant, lactating, or planning to be pregnant;
21. Subjects have a known history of hypersensitivity or intolerance to anti-IL-5 mabs or other biological agents or previous failure of IL-5/IL-5R therapy;
22. Other conditions unsuitable for participation in the study per investigator judgement.