There will be a total of 8 study clinic visits conducted on an outpatient basis. Subjects who meet the eligibility criteria at Screening (Visit 1) will complete a 5 to 9 days run-in period followed by a 12-week treatment period. Clinic visits will be at Screening, Randomization (Visit 2), Day 3 and Weeks 2, 4, 8, and 12, and 1 day after the Week 12 visit (Visits 1 to 8, respectively). A safety follow-up assessment will be conducted by telephone approximately 7 days after the end of the study treatment (FU Phone Contact). The total duration of subject participation, including the follow-up period will be approximately 14 weeks. All subjects will be provided with albuterol/salbutamol for use on an "as-needed" basis throughout the run-in and treatment periods.