The 40-week treatment period consisted of 3 phases: an induction phase (Week 0 to Week 12) where patients remained on their optimised OCS dose; an OCS reduction phase (Week 12 to Week 32) where OCS dose reduction could have started at Week 12 with the possibility of dose titration every 4 weeks to reach the lowest possible OCS dose; and a maintenance phase (Week 32 to Week 40) where patients remained on the OCS dose reached at Week 32 to demonstrate asthma control was maintained after achieving the lowest OCS dose. Criteria used to assess asthma control included lung function assessments (forced expiratory volume in 1 second and morning peak expiratory flow), night awakenings, and the use of rescue medication and systemic corticosteroids. The least squares (LS) mean percent change from baseline in average daily OCS dose is presented. The final daily percent change from baseline was defined as {(Final daily average dose - baseline daily average dose)/baseline daily average dose}\*100%.

The number of airway submucosal eosinophils per millimetre squared (mm\^2) was determined by microscopic evaluation of bronchoscopic biopsies. The ratio of post-randomisation value at Week 12 to baseline value was computed as (Week 12 value / baseline value). The change from baseline to Week 12 (ratio) in the number of airway submucosal eosinophils is presented as geometric mean ± standard deviation (SD) of log values.

Annualized AER was assessed based on AER data up to Week 53. An asthma exacerbation defined as a progressive increase of asthma symptoms that does not resolve after the initiation of rescue medications and remains troublesome for the participant resulting in either 1) use of systemic corticosteroids or increase of a stable systemic maintenance dose for a duration of at least 3 consecutive days as prescribed or administered by the investigator or healthcare provider; or 2) participant initiation of systemic corticosteroids for a duration of at least 3 consecutive days. An asthma exacerbation event was considered resolved 7 days after the last dose of oral corticosteroids (OCS) is administered (10 days after administration of an injectable corticosteroid). Courses of corticosteroids initiated after this time period were considered a separate new asthma exacerbation. Data were summarized together for 'Placebo, Q2W' and 'Placebo, Q2/4W' arms.

AUC (0 - infinity) = Area under the serum concentration versus time curve (AUC) from time zero to infinite time, obtained from AUC (0 - t) plus AUC (t - infinity). Units are day\*micrograms per millilitres = day\*mcg/mL.

The Cmax is the maximum observed serum concentration of tralokinumab.

Tmax is defined as actual sampling time to reach maximum observed tralokinumab concentration.

AUC \[0-t\] is defined as area under the serum concentration-time curve from zero to last observed tralokinumab concentration.

Terminal elimination half-life is the time measured for the serum concentration to decrease by one half. It is associated with the terminal slope of the semi logarithmic drug concentration-time curve, and is calculated as 0.693/lambda(z).

Clearance of a drug is a measure of the rate at which a drug is metabolized or eliminated by normal biological processes. Clearance obtained after subcutaneous dose (apparent systemic clearance) is influenced by the fraction of the dose absorbed (bioavailability).

Volume of distribution was defined as the theoretical volume in which the total amount of drug would need to be uniformly distributed to produce the desired serum concentration of a drug.

Terminal phase elimination half-life is the time measured for the serum concentration to decrease by one half.