A 12-month, Open Label, Randomised, Effectiveness Study to Evaluate Fluticasone Furoate (FF, GW685698)/Vilanterol (VI, GW642444) Inhalation Powder Delivered Once Daily Via a Novel Dry Powder Inhaler Compared With Usual Maintenance Therapy in Subjects With Asthma

This study is designed to compare the effectiveness and safety of Fluticasone Furoate/Vilanterol Inhalation Powder (100mcg Fluticasone Furoate ((FF), GW685698)/25mcg Vilanterol ((VI), GW642444) or 200mcg Fluticasone Furoate ((FF), GW685698)/25mcg Vilanterol ((VI), GW642444) ) delivered once daily via a Novel Dry Powder Inhaler (NDPI) compared with the existing asthma maintenance therapy over twelve months in subjects diagnosed with asthma. This is a Phase III multi-centre, randomised open label study. Subjects who meet the eligibility criteria are randomised and will enter a 12 month treatment period.