 1 Age 12-75 2 Documented physician-diagnosed asthma. 3 Documented treatment with ICS at a total daily dose corresponding to 500μg fluticasone propionate dry powder formulation and a LABA. 4 Subjects must have received OCS for the treatment of asthma for 6 months prior to Visit 1 and on a stable OCS dose between 7.5 to 30mg daily or daily equivalent for at least one month prior to enrolment Visit 1 . 5 Pre-BD FEV1 value 80 90 for patients 12-17 yrs of age of their PNV. 6 Post-BD reversibility of 12 in FEV1. 