The mechanism of action of KBT-3022, a new antiplatelet agent.

1. The mechanism of action of a new antiplatelet agent, KBT-3022 (ethyl 2-[4,5-bis(4-methoxyphenyl)thiazol-2-yl]pyrrol-1-ylacetate) and its active main metabolite, desethyl KBT-3022, was investigated. 2. KBT-3022 and desethyl KBT-3022 inhibited cyclooxygenase from ovine seminal gland with IC50 values of 0.69 and 0.43 microM, respectively. 3. At concentrations higher than those required for cyclooxygenase inhibition, desethyl KBT-3022 inhibited cAMP-phosphodiesterase, specific binding of U46619, and release of phosphatidic acid from thrombin-stimulated platelets. 4. Oral administration of KBT-3022 inhibited the production of thromboxane B2 during blood coagulation more potently than the production of 6-keto-prostaglandin F1 alpha from aortic strips in guinea pigs. 5. These findings suggest that KBT-3022 may inhibit platelet activation principally via the inhibition of cyclooxygenase by desethyl KBT-3022.