Pre-screening Visit will allow subjects who had recent asthma medication changes to be stabilized prior to Screening. During the run-in and wash-out periods, all the subjects will receive budesonide dry powder inhaler (DPI) 400 mcg twice daily (BID) (NEUMOTEX™ 400) and salbutamol 100mcg pressurized metered dose inhaler (pMDI) on demand, as rescue medication. The dose of NEUMOTEROL 400 (400/12 mcg) and SYMBICORT Forte (320/9 mcg) will be one inhalation BID, and each treatment will be given to all subjects for 4 weeks (with a 4-week Washout Period between treatments).