In vitro pharmacological characterization of CJ-042794, a novel, potent, and selective prostaglandin EP4 receptor antagonist

Activation of the prostaglandin E-2 (PGE(2)) EP4 receptor, a G-protein-coupled receptor (GPCR), results in increases in intracellular cyclic AMP (cAMP) levels via stimulation of adenylate cyclase. Here we describe the in vitro pharmacological characterization of a novel EP4 receptor antagonist, CJ-042794 (4-{(1S)-1-[({5-chloro-2-[(4-fluorophenyl)oxy]phenyl}carbonyl)amino]ethyl}benzoic acid). CJ-042794 inhibited [H-3]-PGE(2) binding to the human EP4 receptor with a mean pK(i) of 8.5, a binding affinity that was at least 200-fold more selective for the human EP4 receptor than other human EP receptor subtypes (EP1, EP2, and EP3). CJ-042794 did not exhibit any remarkable binding to 65 additional proteins, including GPCRs, enzymes, and ion channels, suggesting that CJ-042794 is highly selective for the EP4 receptor. CJ-042794 competitively inhibited PGE(2)-evoked elevations of intracellular cAMP levels in HEK293 cells overexpressing human EP4 receptor with a mean pA(2) value of 8.6. PGE(2) inhibited the lipopolysaccharide (LPS)-induced production of tumor necrosis factor alpha (TNF alpha) in human whole blood (HWB); CJ-042794 reversed the inhibitory effects of PGE(2) on LPS-induced TNFa production in a concentration-dependent mariner. These results suggest that CJ-042794, a novel, potent, and selective EP4 receptor antagonist, has excellent pharmacological properties that make it a useful tool for exploring the physiological role of EP4 receptors. (c) 2007 Elsevier Inc. All rights reserved.