This is a multi-centre, randomised, double-blind, double-dummy, two way cross-over, 12 week non inferiority study to evaluate the efficacy, safety, and tolerability of FSC 250/50 mcg capsule-based inhaler and FSC 250/50 mcg multi-dose inhaler each administered BID in adults and adolescents with asthma. The primary objective of this study is to demonstrate that FSC 250/50 mcg administered BID by capsule-based inhaler is non-inferior compared to FSC 250/50 mcg administered BID by multi-dose inhaler . The study consists of six phases: Pre-screening, Screening/Run-in (3 weeks), Treatment Period 1 (12 weeks), Washout (minimum 3 weeks), Treatment Period 2 (12 weeks) and Follow-up (1 week). The total duration of the study for each subject will be at least 31 weeks.