An Efficacy and Safety Study of Fluticasone Furoate/Vilanterol (FF/VI) 200/25 Microgram (mcg) , FF/VI 100/25 mcg, and FF 100 mcg in Adults and Adolescents With Persistent Asthma.

This is a Phase III, multicenter, randomized, double-blind, stratified, parallel-group study with three active comparators in subjects with moderate to severe persistent asthma. The study consists of a run-in period of 4 weeks, followed by a treatment period of 12 weeks, and a follow up contact period of one week. The total duration of the study is 17 weeks. 990 subjects will be randomized to one of three treatments (FF/VI Inhalation Powder 200/25 mcg once daily in the evening; FF/VI Inhalation Powder 100/25 mcg once daily in the evening; FF 100 Inhalation Powder once daily in the evening) for 12 weeks. In addition, all subjects will be supplied albuterol/salbutamol inhalation aerosol at Visit 1 to use as needed for acute asthma symptoms throughout the entire study. Subjects will attend four on-treatment visits at Weeks 2, 4, 8, and 12 (Visits 4 through 7).