A 6-month Study to Evaluate the Efficacy and Safety of Fluticasone Furoate (FF)/GW642444 Inhalation Powder in Subjects With Chronic Obstructive Pulmonary Disease (COPD)

Inclusion Criteria: * Type of subject: outpatient * Informed consent: Subjects must give their signed and dated written informed consent to participate. * Gender: Male or female subjects A female is eligible to enter and participate in the study if she is of: * Non-child bearing potential OR * Child bearing potential, has a negative pregnancy test at screening, and agrees to one of the acceptable contraceptive methods defined in the protocol * Age: ≥40 years of age at Screening (Visit 1) * COPD diagnosis: Subjects with a clinical history of COPD in accordance with the definition by the American Thoracic Society/European Respiratory Society \[Celli, 2004\] * Tobacco use: Subjects with a current or prior history of ≥10 pack-years of cigarette smoking at Screening (Visit 1). * Severity of Disease: Subjects with a Screening (Visit 1) measured post-albuterol/salbutamol: * FEV1/FVC ratio of ≤0.70 and * FEV1 ≤70% of predicted normal values * Dyspnea: Achieved a score of ≥2 on the Modified Medical Research Council Dyspnea Scale (mMRC) at Screening (Visit 1). Exclusion Criteria: Subjects meeting any of the following criteria must not be enrolled in the study: * Pregnancy: Women who are pregnant or lactating or are planning on becoming pregnant during the study. * Asthma: Subjects with a current diagnosis of asthma * α1-antitrypsin deficiency: Subjects with α1-antitrypsin deficiency as the underlying cause of COPD * Other respiratory disorders: Subjects with active tuberculosis, lung cancer, bronchiectasis, sarcoidosis, lung fibrosis, pulmonary hypertension, interstitial lung diseases, or other active pulmonary diseases * Lung resection: Subjects with lung volume reduction surgery within the 12 months prior to Screening (Visit 1) * Chest X-ray (or CT scan): Subjects with a chest X-ray (or CT scan) that reveals evidence of clinically significant abnormalities not believed to be due to the presence of COPD. * Hospitalization: Subjects who are hospitalized due to poorly controlled COPD within 12 weeks of Visit 1. * Poorly controlled COPD: Subjects with poorly controlled COPD, defined as the occurrence of the following in the 6 weeks prior to Visit 1: Acute worsening of COPD that is managed by subject with corticosteroids or antibiotics or that requires treatment prescribed by a physician. * Lower respiratory tract infection: Subjects with lower respiratory tract infection that required the use of antibiotics within 6 weeks prior to Visit 1. * Other diseases/abnormalities: Subjects with historical or current evidence of clinically significant cardiovascular (i.e., pacemaker), neurological, psychiatric, renal, hepatic, immunological, endocrine (including uncontrolled diabetes or thyroid disease) or haematological abnormalities that are uncontrolled. * Peptic Ulcer disease: Subjects with clinically significant peptic ulcer disease that is uncontrolled. * Hypertension: Subjects with clinically significant hypertension that is uncontrolled. * Cancer: Subjects with carcinoma that has not been in complete remission for at least 5 years. Carcinoma in situ of the cervix, squamous cell carcinoma and basal cell carcinoma of the skin would not be excluded if the subject has been considered cured within 5 years since diagnosis. * Drug/food allergy: Subjects with a history of hypersensitivity to any of the study medication or components of the inhalation powder * Drug/alcohol abuse: Subjects with a known or suspected history of alcohol or drug abuse within the last 2 years * Medication prior to spirometry: Subjects who are medically unable to withhold their albuterol/salbutamol and/or their ipratropium 4 hours prior to spirometry testing at each study visit * Additional medication: Use of certain medications such as bronchodilators and corticosteroids for the protocol-specified times prior to Visit 1 (the Investigator will discuss the specific medications) * Oxygen therapy: Subjects receiving treatment with long-term oxygen therapy (LTOT) or nocturnal oxygen therapy required for greater than 12 hours a day. Oxygen prn use (i.e., ≤12 hours per day) is not exclusionary. * Sleep apnea: Subjects with clinically significant sleep apnea who require use of continuous positive airway pressure (CPAP) device or non-invasive positive pressure ventilation (NIPPV) device. * Pulmonary rehabilitation: Subjects who have participated in the acute phase of a Pulmonary Rehabilitation Program within 4 weeks prior to Screening (Visit 1) or who will enter the acute phase of a Pulmonary Rehabilitation Program during the study. * Non-compliance: Subjects at risk of non-compliance, or unable to comply with the study procedures. Any infirmity, disability, or geographic location that would limit compliance for scheduled visits. * Questionable validity of consent: Subjects with a history of psychiatric disease, intellectual deficiency, poor motivation or other conditions that will limit the validity of informed consent to participate in the study. * Prior use of study medication/other investigational drugs * Affiliation with investigator site: Study investigators, sub-investigators, study coordinators, employees of a participating investigator or immediate family members of the aforementioned are excluded from participating in this study.