This study is a randomized, active- and placebo-controlled, single-dose, seven-arm, crossover and dose-ranging design. This study aims to evaluate the efficacy and initial safety profiles, and to identify the optimum dose of A006, from a select dose-range for future clinical PK/PD and Phase III studies. This study is to be conducted in generally healthy, adult subjects who have mild-to-moderate persistent asthma for at least 6 months prior to Screening.

Inclusion Criteria:

• With mild-to-moderate persistent asthma for at least 6 months and having used inhaled beta-agonist for asthma control;
• Must demonstrate response to beta 2 agonist by Reversing;
• Must demonstrate ability to use DPI;
• Females of child-bearing potential must be non-pregnant, non-lactating, and practicing a clinically acceptable form of birth control;
• Additional Criteria

Exclusion Criteria:

• Smoking history of ≥ 10 pack-years, or having smoked within 6 months;
• Upper respiratory tract infections
• Asthma exacerbations;
• Known intolerance or hypersensitivity to any of the ingredients of the study drug or Proventil®;
• Use of prohibited drugs or failure to observe the drug washout restrictions;
• Having been on other clinical drug/device studies in the last 30 days;
• Other Criteria