This study was a 24-week , Phase III , multicenter , randomized , blinded , double-dummy , parallel-group study of the once-daily , inhaled , fixed-dose combination of the long-acting muscarinic antagonist umeclidinium bromide and the long-acting 2-agonist vilanterol ( UMEC/VI 62.5 / 25 mcg ) versus tiotropium ( TIO , 18 mcg ) .