Overcoming clopidogrel resistance: discovery of vicagrel as a highly potent and orally bioavailable antiplatelet agent.

A series of optically active 2-hydroxytetrahydrothienopyridine derivatives were designed and synthesized as prodrugs of clopidogrel thiolactone in order to overcome clopidogrel resistance. The final compounds were evaluated for their inhibitory effect on ADP-induced platelet aggregation in rats. Compound 9a was selected for further in vitro and in vivo metabolism studies, since its potency was comparable to that of prasugrel and was much higher than that of clopidogrel. Preliminary pharmacokinetic study results showed that the bioavailability of clopidogrel thiolactone generated from 9a was 6-fold higher than that generated from clopidogrel, implying a much lower clinically effective dose for 9a in comparison with clopidogrel. In summary, 9a (vicagrel) holds great promise as a more potent and a safer antiplatelet agent that might have the following advantages over clopidogrel: (1) no drug resistance for CYP2C19 poor metabolizers; (2) lower dose-related toxicity due to a much lower effective dose; (3) faster onset of action.