The objective of this study is to evaluate the efficacy and safety of SC administrations of Benralizumab or Placebo in the subjects with Eosinophilic Chronic Rhinosinusitis in a multicenter, randomized, double-blind, placebo-controlled study. The pharmacokinetics and immunogenicity will be assessed secondarily.

Screening Period (maximum 4 weeks) , Randomized Treatment Period (24 weeks)

Inclusion Criteria:

• Patients 20 years to 75 years of age
• Eosinophilic chronic rhinosinusitis with a total score of ≥ 11 according to the diagnosis of eosinophilic chronic rhinosinusitis at enrollment
• A minimum bilateral nasal polyp score of 3 out of the maximum score of 8 (with a score of at least 1 out of the maximum score of 4 for each nostril) at screening and at enrollment
• Weight of ≥ 40 kg at screening

Exclusion Criteria:

• A Sino-Nasal Outcome Test-22 (SNOT-22) score of < 7 at enrollment
• Any nasal surgery (including polypectomy) within 1 year prior to the date of consent
• Hospitalization for ≥ 24 hours for treatment of asthma exacerbation, within 12 weeks prior to the date of consent
• Exposure to any commercially available (e.g., omalizumab) or investigational biologic agent within 16 weeks or 5 half-lives prior to enrollment, whichever is longer
• Use of systemic corticosteroids (including oral corticosteroids) or corticosteroid nasal solution (except spraying) within 4 weeks prior to enrollment or planned use of such medications during the double-blind period
• Prior treatment with benralizumab