Identification and Biological Activity of the Active Metabolite of Clopidogrel
P. Savi, J. M. Pereillo, M. F. Uzabiaga, J. Combalbert, C. Picard, J. P. Maffrand, M. Pascal, J. M. Herbert
From Sanofi-Synthélabo, Toulouse, Montpellier and Labège, France
Summary Like ticlopidine, the ADP receptor antagonist clopidogrel is inactivein vitro and must be administered i.v. or orally to exhibit antiaggrega-toryand antithrombotic activities. We have previously shown that he-paticmetabolism is necessary for activity. This study demonstrates thatan active metabolite can be generated from human liver microsomesincubated with clopidogrel. Using several analytical methodologies(LC/MS, NMR, chiral supercritical fluid chromatography), we haveidentified its structure. In vitro, this highly unstable compound, differentfrom that formed from ticlopidine, exhibited all the biological activitiesof clopidogrel observed ex vivo: Irreversible inhibition of the bindingof 33 P-2MeS-ADP to washed human platelets (IC 50 = 0.53 μM), selectiveinhibition of ADP-induced platelet aggregation (IC 50 = 1.8 μM)and ADP-induced adenylyl cyclase down-regulation. The irreversiblemodification of the ADP-receptor site which is responsible for thebiological activity could be explained by the formation of a disulfidebridge between the reactive thiol group of the active metabolite and acysteine residue of the platelet ADP receptor.