Effects of AF3442 [N-(9-ethyl-9H-carbazol-3-yl)-2-(trifluoromethyl)benzamide], a novel inhibitor of human microsomal prostaglandin E synthase-1, on prostanoid biosynthesis in human monocytes in vitro

Inhibitors of microsomal prostaglandin (PG) E synthase-1 (mPGES-1) are being developed for the relief of pain. Redirection of the PGH(2) substrate to other PG synthases, found both in vitro and in vivo, in mPGES-1 knockout mice, may influence their efficacy and safety. We characterized the contribution of mPGES-1 to PGH(2) metabolism in lipopolysaccharide (LPS)-stimulated isolated human monocytes and whole blood by studying the synthesis of prostanoids [PGE(2), thromboxane (TX)B-2, PGF(2 alpha) and 6-keto-PGF(1 alpha)] and expression of cyclooxygenase (COX)-isozymes and down-stream synthases in the presence of pharmacological inhibition by the novel mPGES-1 inhibitor AF3442 [N-(9-ethyl-9H-carbazol-3-yl)-2-(trifluorometllyl)benzamide]. AF3442 caused a concentration-dependent inhibition of PGE(2) in human recombinant rnPGES-1 with an IC50 of 0.06 mu M. In LPS-stimulated monocytes, AF3442 caused a concentration-dependent reduction of PGE(2) biosynthesis with an IC50 of 0.41 mu M. At 1 mu M, AF3442 caused maximal selective inhibitory effect of PGE(2) biosynthesis by 61 +/- 3.3% (mean +/- SEM, P < 0.01 versus DMSO vehicle) without significantly affecting other prostanoids (i.e. TXB2, PGF(2 alpha) and 6-keto-PGF(1 alpha)). In LPS-stimulated whole blood, AF3442 inhibited in a concentration-dependent fashion inducible PGE(2) biosynthesis with an IC50 of 29 mu M. A statistically significant inhibition of mPGES-1 activity was detected at 10 and 100 mu M (38 +/- 14%, P < 0.05, and 69 +/- 5%, P < 0.01, respectively). Up to 100 mu M, the other prostanoids were not significantly affected. In conclusion, AF3442 is a selective mPGES-1 inhibitor which reduced monocyte PGE(2) generation also in the presence of plasma proteins. Pharmacological inhibition of mPGES-1 did not translate into redirection of PGH(2) metabolism towards other terminal PG synthases in monocytes. The functional relevance of this observation deserves to be investigated in vivo. (C) 2009 Elsevier Inc. All rights reserved.