Apparent IC50 3.2 pM, steady state IC50 < 0.5 pM
GSK256066 is an exceptionally high-affinity and selective inhibitor of PDE4 designed for inhaled delivery.
Oral phosphodiesterase (PDE) 4 inhibitors have demonstrated clinical efficacy in chronic obstructive pulmonary disease and asthma.
In vitro: GSK256066 is a slow- and tight-binding inhibitor of PDE4B, more potent than any previously documented compound, for example roflumilast, tofimilast and cilomilast [1].
In vivo: When administered by the intratracheal route to rats, GSK256066 inhibited LPS-induced pulmonary neutrophilia with ED50s of 1.1 μg/kg (aqueous suspension) and 2.9 μg/kg (dry powder formulation) and was more potent than an aqueous suspension of the corticosteroid fluticasone propionate (ED50 9.3 μg/kg) [1].
Clinical trial: Administration of inhaled GSK256066 was well-tolerated in patients with moderate COPD. Further studies would be required to confirm the favorable safety profile and to demonstrate clinical efficacy of this compound [2].
References:
[1] Tralau-Stewart CJ, Williamson RA, Nials AT, Gascoigne M, Dawson J, Hart GJ, Angell AD, Solanke YE, Lucas FS, Wiseman J, Ward P, Ranshaw LE, Knowles RG. GSK256066, an exceptionally high-affinity and selective inhibitor of phosphodiesterase 4 suitable for administration by inhalation: in vitro, kinetic, and in vivo characterization. J Pharmacol Exp Ther. 2011;337(1):145-54.
[2] Watz H, Mistry SJ, Lazaar AL; IPC101939 investigators. Safety and tolerability of the inhaled phosphodiesterase 4 inhibitor GSK256066 in moderate COPD. Pulm Pharmacol Ther. 2013;26(5):588-95.