Efficacy and Safety of Aclidinium Bromide 400 µg BID (Twice a Day)Compared to Placebo in Patients With Stable Moderate to Severe Chronic Obstructive Pulmonary Disease (COPD)

Inclusion Criteria: * Adult male and female patients aged ≥ 40 with stable moderate to severe COPD (Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines). * Post-salbutamol Forced Expiratory Volume in one second(FEV1) \< 80% and ≥ 30% of predicted normal value and Post-salbutamol FEV1/Forced Vital Capacity (FVC) \< 70%. * Current or ex-smokers of ≥ 10 pack-years * Functional residual capacity (FRC) measured by body plethysmography at Screening Visit ≥ 120% of predicted value Exclusion Criteria: * History or current diagnosis of asthma * Signs of an exacerbation within 6 weeks ( or 3 months if results in hospitalisation) prior to the screening visit or during the run-in period. * Clinically significant respiratory and/or cardiovascular conditions or laboratory abnormalities. * Conditions where the use of anticholinergic drugs is contraindicated, such as known symptomatic prostatic hypertrophy, bladder neck obstruction or narrow-angle glaucoma. * Patients with an oxygen saturation \< 85% during cycle exercise on room air at Screening Visit, Run- in Visit and Visit 1. * Contra-indications of cardiopulmonary exercise testing. * Patient who in the investigator's opinion will need to start a pulmonary rehabilitation program during the study and/or patients who have just started/finished pulmonary rehabilitation at least 3 months prior to the Screening Visit.