This is a randomized, double-blind, parallel group, placebo-controlled study designed to evaluate efficacy and safety of tralokinumab administered subcutaneously in subjects with uncontrolled asthma on inhaled corticosteroid plus long-acting β2-agonist and having a history of asthma exacerbations. Approximately 770 subjects will be randomized globally. Subjects will receive tralokinumab, or placebo, administered via subcutaneous injection at the study site, over a 52-week treatment period.