Prior to any study specific treatment or evaluation being performed a subject must have signed an IRB/EC/REB approved consent form. Once the subject has received the initial treatment regimen the subject will be assessed for response to the treatment including spirometry.If the subject meets all entry criteria the subject will be randomized to receive MN-221 or placebo. Throughout the screening process the subject will continue to receive standardized treatment consistent with the appropriate guidelines for the treatment of acute exacerbations of asthma.