This study has 3 treatment periods: A 24-week double-blind treatment period, a 28-week open-label treatment period, and an open-label extension. Subjects that complete the 52-week treatment period, double blind and open label on investigational product will be eligible to continue into a 52-week open label extension period on benralizumab 30 mg every 4 weeks (Q4W). The open label extension period is intended to allow each patient 1 year of treatment with open label benralizumab after completion of the 52-week double blind and open label treatment periods. All eligible subjects will be invited to participate in the open label extension. Patients who do not enroll in the open label extension will have a follow-up visit 12 weeks after their last dose of IP.