Study to Assess Efficacy and Safety of Aclidinium Bromide and Aclidinium Bromide/Formoterol Fumarate in Stabile COPD Patients

Inclusion Criteria: * 1\. Adult male or non-pregnant, non-lactating female patients aged ≥40 * 2\. Patients with a diagnosis of COPD prior to Visit 1 (screening) * 3\. Patients with moderate to severe stable COPD (Stage II or Stage III) at Visit 1: post-bronchodilator FEV1 ≥30% and \< 80% and post-bronchodilator FEV1/Forced vital capacity (FVC) \< 70% * 4\. Current or former smokers with a smoking history of ≥ 10 pack-years * 5\. Patients able to perform repeatable pulmonary function testing for FEV1 according to the American Thoracic Society (ATS)/European Respiratory Society (ERS) 2005 criteria at Visit 1(screening) * 6\. Patients who understand the study procedures and are willing to participate in the study as indicated by signing the informed consent Exclusion Criteria: * 1\. Involvement in the planning and/or conduct of the study (applies to AstraZeneca staff and/or site staff) or patients employed by or relatives of the employees of the site or sponsor. * 2\. Previous enrolment or randomisation in the present study * 3\. History or current diagnosis of asthma * 4\. Any respiratory tract infection (including the upper respiratory tract) or COPD exacerbation (including the mild COPD exacerbation) within 6 weeks prior to screening or during the run-in period * 5\. Patients hospitalized for COPD exacerbation (an emergency room visit for longer than 24 hours will be considered a hospitalization) within 3 months prior to screening and during the run-in period * 6\. Clinic…