Study to Compare the Addition of Umeclidinium Bromide (UMEC) to Fluticasone Furoate (FF)/Vilanterol (VI), With Placebo Plus FF/VI in Subjects With Chronic Obstructive Pulmonary Disease (COPD) -Study 2

After screening, subjects will enter a 4 week open-label run-in period with fluticasone furoate (FF)/vilanterol (VI) 100/25 mcg administered once daily via dry powder inhaler (DPI). Subjects will then be randomized to receive any one of the 3 treatments (umeclidinium bromide \[UMEC\] \[62.5 mcg\] administered once daily via a DPI; OR UMEC \[125 mcg\] administered once daily via a DPI; OR matching placebo administered once daily via a DPI), while continuing treatment with open label FF/VI 100/25 mcg during a 12-week treatment period. There will be a total of eight scheduled clinic visits at Pre-Screening (Visit0), Screening (Visit 1), blinded treatment Day 1(Visit2), 2(Visit3), 28 (Visit4), 56 (Visit5), 84 (Visit6) and 85 (Visit7). A follow-up phone contact will be conducted approximately 7 days after the last clinic visit. The total duration of subject participation in the study from Screening to Follow-up will be approximately 17 weeks.