Purity >94%. Prostaglandin E2 (PGE2) exerts its effects through four separate G coupled-protein receptors (EP1-4). L-161,982 is a potent and selective EP4 receptor antagonist. It demonstrates selective binding to human EP4 receptors with a Ki value of 0.024 μM compared to other receptors of the prostanoid family, EP1, EP2, EP3, DP, FP, and IP, with Ki values of 17, 23, 1.9, 5.1, 5.6, and 6.7 μM, respectively. L-161,982 at 10 mg/kg/day suppresses PGE2-stimulated bone formation in young rats and at 100 nM reverses the anti-inflammatory action of PGE2 in LPS-activated human macrophages. At 10 μM L-161982 blocks PGE2-induced cell proliferation in HCA-7 colon cancer cells.