a. Subjects 18-75 years of age with severe asthma requiring medium to high-dose inhaled corticosteroids plus a second asthma controller in the previous 12 months
b. Two or more asthma exacerbations in the previous 12 months requiring treatment with systemic corticosteroids
c. Pre-screening FEV1 <80% of predicted
d. Current smokers and ex-smokers with >10 pack-year smoking history are not eligible