Inclusion Criteria:

• Subjects must have a diagnosis of asthma for at least 12 months' duration.
• A subject must have been using a medium daily dose of inhaled glucocorticosteroids (alone or in combination with LABA) for at least 12 weeks and must have been on a stable regimen for at least 2 weeks prior to Screening.
• If there is no inherent harm in changing the subject's current asthma therapy, the subject must be willing to discontinue his/her prescribed ICS or ICS/LABA prior to initiating MF MDO run-in medication.
• The diagnosis of asthma must be documented by either demonstrating an increase in absolute forced expiratory volume in 1 second (FEV1) of at least 12% and a volume increase of at least 200 mL within approximately 15 to 20 minutes after administration of 4 inhalations of albuterol/salbutamol or of nebulized SABA OR PEF variability of more than 20% OR a diurnal variation PEF of more than 20% based on the difference between pre-bronchodilator (before taking albuterol/salbutamol) morning value and the post-bronchodilator value (after taking albuterol/salbutamol) from the evening before, expressed as a percentage of the mean daily PEF value on any day during the open-label Run-in Period.
• A subject must have a history of >= 2 asthma-related unscheduled visits to a physician or to an emergency room within the past year AND >= 3 asthma-related unscheduled visits within the past 2 years.
• Prior to randomization subjects must have used a total of 12 or more inhalations of SABA rescue medication during the last 10 days of run-in.
• Clinical laboratory tests (complete blood counts [CBC], blood chemistries, including serum pregnancy for females of child-bearing potential, and urinalysis) conducted at the Screening Visit must be within normal limits or clinically acceptable to the investigator/sponsor before the subject is instructed to start using open-label MF MDI run-in medication.
• An electrocardiogram (ECG) performed at the Screening Visit, using a centralized trans-telephonic technology, must be clinically acceptable to the investigator.
• A chest x-ray performed at the Screening Visit, or within 12 months prior to the Screening Visit, must be clinically acceptable to the investigator.
• A non-pregnant female subject of childbearing potential must be using a medically acceptable, adequate form of birth control. A female subject of childbearing potential must have a negative serum pregnancy test at Screening in order to be considered eligible for enrollment.

Exclusion Criteria:

• A subject who demonstrates a change in absolute FEV1 of > 20% at any time between the Screening and Baseline Visits on any 2 consecutive days between the Screening and Baseline visits.
• A subject who requires the use of greater than 8 inhalations per day of SABA MDI or 2 or more nebulized treatments per day of 2.5 mg SABA on any 2 consecutive days between the Screening and Baseline Visits.
• A subject who experiences a decrease in AM or PM PEF below the Run-in Period stability limit on any 2 consecutive days prior to randomization. The average AM and average PM PEF respective values from the preceding 7 days are added, divided by the number of non-missing values, and multiplied by 0.70 to determine the stability limit.
• A subject who experiences a clinical asthma exacerbation: defined as a clinical deterioration of asthma as judged by the clinical investigator between the Screening and Baseline Visits, that results in emergency treatment, hospitalization due to asthma, or treatment with additional, excluded asthma medication (including oral or other systemic corticosteroids, but allowing SABA).