Background:  Vilanterol (GW642444M) (VI) is a novel, inhaled, long-acting β2 agonist with inherent 24-h activity under development as a once-daily combination therapy with an inhaled corticosteroid for COPD and asthma. This study assessed the dose response, efficacy, and safety of VI at doses of 3 to 50 μg in patients with moderate to severe COPD.

Methods:  Six hundred two patients (intent-to-treat) were randomized (double-blind) to VI 3, 6.25, 12.5, 25, or 50 μg or placebo once daily for 28 days. The primary end point was change from baseline in trough FEV1 at the end of the 28-day treatment period. Secondary end points included 0- to 24-h weighted mean FEV1 on days 1 and 28 and time to i