The purpose of this study is to investigate the efficacy, safety and tolerability of AD 237 in patients with chronic obstructive pulmonary disease (COPD).

Inclusion Criteria:

• Diagnosed with COPD, with symptoms of cough and chronic sputum production and/or dyspnea.
• Post-bronchodilator FEV1 at no more than 65% and at least 30% of the predicted normal value.
• Pre-bronchodilator FEV1/FVC ratio of less than 70%.
• Current or ex-smokers with a smoking history of at least 10 pack years.

Exclusion Criteria:

• History of asthma, atopy or allergic rhinitis.
• Other serious respiratory or other medical conditions which may interfere with the outcome of the study.