Umeclidinium bromide (GSK573719A) is a novel mAChR antagonist.

M4 mAChR:0.05 nM（Ki）, M2 mAChR:0.15 nM（Ki）, M3 mAChR:0.06 nM（Ki）, M5 mAChR:0.13 nM（Ki）, M1 mAChR:0.16 nM（Ki）

在人类胚胎肾293细胞中，Umeclidinium bromide (GSK573719A) 以浓度依赖的方式抑制人类ether-a-go-go相关基因通道的尾电流（IC50=9.4 μM）。

当Umeclidinium bromide (GSK573719A) 以每日一次的剂量连续给予小鼠5天（0.025 μg，经鼻途径），第五天的抑制水平较单次给药后有所提高（分别为60%对35%）。连续给药五天后，小鼠休息5天，使支气管运动音调恢复至基线水平。在第六天，小鼠再次接受一剂拮抗剂，并再次面临Mch挑战。此时的抑制水平基本与测试的第一天相同，表明通过经鼻途径反复给予Umeclidinium bromide并未出现耐受性。相反，当以口服途径给予小鼠Umeclidinium bromide（2.0 mg/kg，剂量为ED50值的100倍），在Mch挑战中没有观察到任何保护作用。

Mice:Age-matched male BALB/c mice (23-25 gm) are pretreated intranasally (50 μL per mouse) with vehicle (0.9% saline) or Umeclidinium bromide at intervals (0.25-48 hours) prior to methacholine challenge, and placed into individual plethysmograph chambers. Fresh air is supplied by bias flow pumps to the chambers. After baseline respiratory [enhanced pause (Penh)] values are collected, the mice received methacholine (30 mg/mL or EC80) by aerosol delivery (flow=1.6 mL/min×2 minutes). An average Penh is then calculated for 5 minutes. Penh=[(expiratory time/relaxation time)?1]×(peak expiratory flow/peak inspiratory flow), and relaxation time is the amount of time required for 70% of the tidal volume to expire. In some cases, animals are treated on multiple, consecutive days as described in the figure legends. The data are expressed as the mean±S.E.M. percent inhibition of Penh or (mean Penh value of vehicle treated group-Penh for each drug-treated animal) divided by (mean Penh value of vehicle treated group)×100%. Data are analyzed using commercially available software.