PTA2 is a stable analog of TXA2. It is a TP receptor antagonist and an inhibitor of TX synthase.{516,794} PTA2 inhibits U-46619-induced cat coronary artery constriction (ID50 = 0.1 μM), U-46619-induced aggregation of human platelets (IC50 = 2 μM), and rabbit platelet TX synthase (ID50 = 50 μM). PTA2 does not affect PGI synthase up to a concentration of 100 μM.{516}