AH 6809 is an EP and DP receptor antagonist with nearly equal affinity for the cloned human EP1, EP2, EP3-III, and DP1 receptors.{8322} AH 6809 blocks the PGE2-induced accumulation of cAMP in COS cells transfected with the human EP2 receptor.{3391} It also blocks the accumulation of Ca2+ in Xenopus oocytes expressing the human EP1 receptor.{3176} In the human and guinea pig, the activity profile of AH 6809 is similar to that of SC-19220, but it is somewhat more potent.{3409} In the mouse, AH 6809 has the highest affinity for the EP2 receptor, but also acts as a weak ligand at the murine EP1 and DP1 receptors.{6640} In whole human platelets, AH 6809 is an effective antagonist of the antiaggregatory actions of PGD2, but not PGI2, with an EC50 of about 5 x 10−5 M.{3319}