High affinity and selective EP4 antagonist (Ki = 3 nM). Exhibits >2500-fold selectivity for EP4 over EP2 and EP3. Also selective over a range of other prostanoid receptors, ion channels, transporters and enzymes. Inhibits PGE2-induced vasodilation of middle cerebral and meningeal arteries in vitro, and carotid blood flow in vivo. Orally bioavailable. Purity 98%. MW (observed): 529