Pharmacokinetic/Pharmacodynamic Assessment of the Structural Refinement of Clopidogrel Focusing on the Balance between Bioactivation and Deactivation

The delicate balance between ischemic and bleeding risks is a significant consideration in the administration of antiplatelet therapy. Clopidogrel and prasugrel, both members of the thienopyridine class of antiplatelet drugs, are well established for their variability in individual responsiveness and for a high number of bleeding events, respectively. The current study focuses on evaluating the pharmacokinetics and pharmacodynamics of a series of deuterated clopidogrel derivatives, leveraging insights gained from the structure-pharmacokinetic relationships in the development of thienopyridine drugs. Our approaches were based on the molecular skeleton of clopidogrel and adopted the C₂-pharmacophore design from prasugrel. The selected C₂-pharmacophore distinguishes itself from the acetyloxy substituent of prasugrel by exhibiting a moderated hydrolysis rate, resulting in a gentler formation of the active metabolite. An excessive and burst release of the active metabolite are therefore to be avoided, as it is believed to be associated with an increased risk of bleeding. Our proposed structural modification maintains the hydrolysis-sensitive methyl ester of clopidogrel but replaces it with a deuterated methyl group, which has been shown to effectively reduce metabolic deactivation. The evaluation of the clopidogrel derivatives has been primarily based on the criteria related to the exposure to active metabolites. Three promising compounds demonstrate higher biotransformation efficiency, similar C_max, delayed T_max, enhanced antiplatelet activity, and a lower risk of bleeding compared to clopidogrel, when administered at a dosage resulting in a similar exposure to the active metabolites. Significance Statement The pharmacokinetics and pharmacodynamics of a series of newly designed clopidogrel derivatives were assessed to validate the rationale for their structural modifications. Three promising compounds displayed balanced pharmacokinetics, characterized by slower deactivation compared to clopidogrel and a more gradual bioactivation than prasugrel. Under similar exposure to active metabolites, these compounds have demonstrated enhanced antiplatelet activity and a diminished risk of bleeding compared to clopidogrel. The D3-clopidogrel-ozagrel conjugate was found to exert a synergistic therapeutic effect.