Table 1 Key inclusion and exclusion criteria

Key inclusion criteria

• Men or women, 18–80 years old, weight ≥ 40 kg at visit 1

• Documented physician-diagnosed asthma for ≥ 12 months before visit 1, and receiving medium- or high-dose ICS (as per GINA 2017 guidelines [1]) for 12 months before visit 1

• Documented physician-prescribed LABA and high-dose ICS (total daily dose corresponding to fluticasone propionate > 500 μg dry powder formulation equivalent) for ≥ 3 months before visit 1

• Additional maintenance asthma controller medications (e.g. LAMA, LTRA, theophylline, secondary ICS and cromones) are permitted if documented for ≥ 3 months before visit 1

• Received OCS for the treatment of asthma for ≥ 6 months before visit 1 and receiving a stable dose of prednisone or prednisolone 7.5–30 mg daily or daily equivalent for ≥ 1 month before visit 1

• Morning pre-bronchodilator FEV₁ < 80% predicted at either visit 1 or visit 2

• Documented historical FEV₁ reversibility of ≥ 12% and ≥ 200 mL (15–30 min after administration of four puffs of albuterol/salbutamol) in the 12 months before visit 1 or at visit 1 or visit 2

• History of ≥ 1 asthma exacerbation event ≤ 12 months before visit 1

• Received optimized OCS dose for ≥ 2 weeks before randomization

Key exclusion criteria

• Any clinically important pulmonary disease, other than asthma, associated with high peripheral eosinophil counts

• Any disorder that could, in the opinion of the investigator, affect the safety of the patient or influence study findings

• Any clinically significant infection requiring antibiotic or antiviral treatment in the 2 weeks before visit 1 or during the enrolment period

• Helminth or parasitic infection diagnosed in the 6 months before visit 1 that has not been treated with, or is unresponsive to, standard-of-care therapy

• History of cancer, HIV, or hepatitis B or C

• Current smokers or patients with a smoking history of ≥ 10 pack-years

• History of chronic alcohol or drug abuse ≤ 12 months before visit 1

• Tuberculosis requiring treatment ≤ 12 months before visit 1

• Use of any marked or investigational biologic agent in the 4 months or 5 half-lives before visit 1, or any investigational non-biologic agent in the 30 days or 5 half-lives before visit 1

• Use of any immunosuppressive medication in the 12 weeks before randomization

• History of anaphylaxis after biologic therapy

• Pregnant, breastfeeding or lactating

• If, during the optimization period, asthma control requires an OCS dose < 7.5 mg or > 30 mg and/or if asthma control is still maintained after three consecutive OCS dose reductions