Approximately 250 patients will be randomized to receive benralizumab 30 mg SC or matching placebo. After enrolment, eligible patients will enter a 6-week screening/run in period. Patients who meet eligibility criteria will be randomised 1:1 at Week 0 (Day 0) to receive either placebo or benralizumab 30 mg SC every 4 weeks for the first 3 doses (Weeks 0, 4 and 8) and every 8 weeks thereafter (Weeks 16, 24, 32, 40 and 48). An end of treatment visit will be conducted at Week 56.All patients who complete the 56-week DB treatment period on investigational product (IP) may be eligible to continue into around one year OLE (Open Label Extension), during which all patients will receive 8 doses of benralizumab 30 mg. Patients in Benra arm during DB period will receive one dummy dose for the second dose during OLE (Open Label Extension). The last study visit will occur at 8 weeks after the last dose of IP (Week 112/FU). Patients who do not enter OLE (Open Label Extension), will have their last study visit at Week 56 (EoDB) for follow-up and without administration of IP.
