- Evidence of a severe exacerbation, defined as deterioration of asthma requiring the use of systemic corticosteroids (tablets, suspension, or injection) for at least 3 days or an in-patient hospitalisation or emergency department visit due to asthma that required systemic corticosteroids between Visit 1 (Screening and Run-in Visit) and Visit 2 (randomization and Treatment Period 1 Baseline Visit)