Microsomal prostaglandin E2 synthase-1 (mPGES-1) is the terminal enzyme in the biosynthesis of PGE2. MF63 is a potent, selective, and orally active inhibitor of human mPGES-1 (IC50 = 1.3 nM). It displays greater than 1,000-fold selectivity over other prostanoid synthases. MF63 also potently inhibits guinea pig mPGES-1 (IC50 = 0.9 nM) but not mouse or rat mPGES-1. In guinea pigs or in mice expressing human mPGES-1, MF63 prevents LPS-induced pyresis, hyperalgesia, and iodoacetate-induced osteoarthritic pain. It does not produce the gastrointestinal toxicity that is caused by non-selective COX inhibitors, although it markedly suppresses PGE2 synthesis in the stomach.
