Vilanterol (GW642444) trifenatate is a long-acting β2 adrenergic receptor agonist. Vilanterol trifenatate has pEC50 values for β2-AR, β1-AR, and β3-AR of 9.4, 6.4, and 6.1, respectively. Vilanterol trifenatate selectively activates airway β2 adrenergic receptors, increases cAMP and thus relaxes bronchial smooth muscle. Vilanterol trifenatate can be used in asthma research[2][4].