PT001 MDI Versus Atrovent Study in Moderate to Severe Chronic Obstructive Pulmonary Disease (COPD)

Key Inclusion Criteria: * Signed written informed consent * 40 - 80 years of age * Clinical history of COPD with airflow limitation that is not fully reversible * Females of non-child bearing potential or females of child bearing potential with negative pregnancy test; and acceptable contraceptive methods * Current/former smokers with at least a 10 pack-year history of cigarette smoking * A measured post- bronchodilator FEV1/FVC ratio of \< or = 0.70 * A measured post- bronchodilator FEV1 \> or = 750ml or 30% predicted and \< or = 80% of predicted normal values * Able to change COPD treatment as required by protocol Key Exclusion Criteria: * Women who are pregnant or lactating * Primary diagnosis of asthma * Alpha-1 antitrypsin deficiency as the cause of COPD * Active pulmonary diseases * Prior lung volume reduction surgery * Abnormal chest X-ray (or CT scan) not due to the presence of COPD * Hospitalized due to poorly controlled COPD within 3 months of Screening * Clinically significant medical conditions that preclude participation in the study (e.g. clinically significant abnormal ECG, uncontrolled hypertension, glaucoma, symptomatic prostatic hypertrophy) * Cancer that has not been in complete remission for at least 5 years * Treatment with investigational study drug or participation in another clinical trial or study within the last 30 days or 5 half lives Other inclusion/exclusion criteria as defined in the protocol