Purity >98%. Prostaglandin E2 (PGE2 ) initiates its cellular effects by activating one of four E prostanoid (EP) receptors, EP1-4 . ONO-8711 is a potent and selective competitive antagonist of the EP1 receptor (Ki = 0.6 and 1.7 nM for human and mouse EP1, respectively, versus 67 and 76 nM for mouse EP3 and human thromboxane receptor, respectively, and >1,000 nM for other receptors). ONO-8711 effectively reduces tumor incidence and multiplicity in mouse models of colon, breast, and oral cancer. It also suppresses pain and acid-induced HCO3- secretion in the stomach.