Expiratory airflow limitation is the most obvious physiological change associated with chronic obstructive pulmonary disease (COPD). A consequence of airflow limitation is gas trapping as expiration becomes flow limited. This may occur at rest with more severe airway obstruction and is most evident during exercise as lung emptying is reduced and increased ventilation does not allow full expiration. This increased gas trapping or hyperinflation is the cause of much of the increased work of breathing, dyspnea, and exercise intolerance in subjects with COPD (O'Donnell 1997; O'Donnell, 1993). Spirometric measurement of airflow limitation, particularly as assessed by forced expiratory volume in one second (FEV1), is commonly used for the diagnosis of and assessment of response to pharmacotherapeutic intervention in COPD. However, changes in FEV1 may not fully predict symptomatic responses and alternative measures of lung hyperinflation such as exercise tolerance and exertional dyspnea may be more sensitive to therapeutic intervention and/or more clinically relevant than FEV1 \[O'Donnell1999; Bauerle, 1998; O'Donnell, 1998; Officer, 1998\]. GSK573719/GW642444 Inhalation Powder, a combination of the long-acting muscarinic antagonist (LAMA) bronchodilator GSK573719 and the long-acting beta2-agonist (LABA) bronchodilator GW642444, is in development for the maintenance treatment of airflow obstruction associated with COPD. Development of this product is supported by studies showing improvement in lung function with similar safety when use of combinations of long-acting bronchodilators with different mechanisms of action are compared with single bronchodilator therapy \[van Noord 2005; van Noord van Noord 2006; Tashkin 2008\]. Previous studies have demonstrated that treatment with short- and long-acting bronchodilators including ipratropium, tiotropium, and salmeterol reduces resting lung hyperinflation as measured by functional residual capacity (FRC), residual volume (RV), and inspiratory capacity (IC), with associated improvements in exercise endurance time and exertional dyspnoea in subjects with COPD \[Ayers, 2001; O'Donnell 1998; O'Donnell 2004; Pepin 2005; Pepin 2007; Ramirez-Venegas 1997\]. However, the effect of combined LAMA/LABA therapy on these measures is not well characterized.

This is a phase III multicenter, randomized, double-blind, placebo-controlled, combination and component, two-period, incomplete block design cross-over study using GSK573719/GW642444. The primary objective is to evaluate lung function and exercise endurance time after 12 weeks of once-daily administration of GSK573719/GW642444 Inhalation Powder (125/25mcg and 62.5/25mcg), GSK573719 Inhalation Powder (125mcg and 62.5mcg), GW642444 Inhalation Powder 25 mcg and placebo delivered by a Novel dry powder inhaler (Novel DPI) Approximately 312 subjects with moderate/severe chronic obstructive pulmonary disease (COPD) will be randomised in order to achieve 208 subjects completing both treatment periods of 3 months.. There will be a total of 12 study clinic visits conducted on an outpatient basis. Subjects who meet the eligibility criteria at Screening (Visit 1) will complete a 12 to 21 day run-in period followed by two 12-week treatment periods that are separated by a 14 day wash-out. Clinic visits will be conducted at Screening (Visit 1), twice during the run-in period (Visits 2 and 3), at randomization (Visit 4) and three times during the first treatment period, on Treatment Day 2 (Visit 5) and at 6 and 12 weeks (Visits 6 and 7 respectively). During the washout period of 14 days there will be 2 clinic visits (Visits 8 and 9). During the second treatment period there will be 3 clinic visits, on Treatment Day 2 (Visit 10) and at 6 and 12 weeks (Visits 11 and 12 respectively). A Safety Follow-Up assessment (Visit 13) to record adverse events will be conducted by telephone 7 days after the end of the second treatment period or early withdrawal. Efficacy measurements will include pre and post dose FEV1, lung volume measurements and exercise endurance time measured using the endurance shuttle walking test (ESWT). Oxycon mobile measurements will be conducted in a subgroup of approximately 104 patients to investigate cardio respiratory measures during exercise. Safety and tolerability will be assessed by collection of adverse events (AEs), vital signs, 12-lead electrocardiograms (ECGs), clinical laboratory tests and incidence of COPD exacerbations. Dyspnea will be assessed using the Exercise Dyspnea Scale (EDS), a patient-reported outcome. Blood samples will also be collected for potential pharmacogenetics analysis