The study is aimed at evaluating efficacy and safety of oglemilast in the treatment of stable mild to moderate persistent asthma. The study involves two weeks of run in period. This is a placebo controlled study. One of the four treatment arms is placebo. The duration of treatment is 12 weeks.

Eligibility Criteria:

• Adult patients with a physician-documented diagnosis of chronic, stable, persistent, mild to moderate asthma (clinical symptoms and documented reversibility of airway obstruction, with an FEV1 of 60% to 85% of the predicted value).

The following criteria must be met at the randomisation visit:

• At least 80% compliance during the single-blind placebo run-in period
• FEV1 between 60% and 85% of the predicted value
• Without asthma exacerbation during the run-in period
• Reversibility: patients are required to demonstrate a ≥ 12% increase in FEV1 (with an absolute improvement in FEV1 of at least 200mL) ≥ 10 min and up to 15 minutes after inhalation of 400 μg salbutamol via a spacer
• Any symptom score being ≥ 1 for at least 4 out of the last 7 days of the run-in
• Use of salbutamol for symptom relief on > 2 occasions on at least 4 out of the last 7 days of the run-in