VILANTEROL α-PHENYL CINNAMATE (GW642444H), originally developed by GlaxoSmithKline, is a long-acting β2 adrenoceptor agonist for once daily treatment of COPD and asthma. Phase III clinical trials are ongoing. GW642444H is Vilanterol a-phenylcinnimate salt. In clinical studies the study drug may been given as a dry powder in the form of either the ‘H’ salt (with the excipient lactose), or in the form of the ‘M’ salt (with the excipients lactose and cellobiose octaacetate). Its pharmacological effect is attributable to stimulation of intracellular adenylyl cyclase which catalyzes the conversion of adenosine triphosphate (ATP) to cyclic-3',5'-adenosine monophosphate (cAMP). Increases in cyclic AMP are associated with relaxation of bronchial smooth muscle and inhibition of release of hypersensitivity mediators from mast cells in the lungs.