Purity >94%. Prostaglandin E2 exerts its effects through four separate G-protein coupled receptors (EP1, EP2, EP3, and EP4). L-798,106 is a highly selective EP3 receptor antagonist with Ki values of 0.3, 916, >5,000, and >5,000 nM at EP3, EP4, EP1, and EP2, respectively. At 0.2 μM, it blocks the EP3 agonist activity of sulprostone on guinea pig vas deferens and trachea.