Beyond CYP2C19: The Lysosome–CMA–SORT1–CES1 Axis as a Potential Regulator of Clopidogrel Response

Interindividual variability in clopidogrel response remains a significant limitation of antiplatelet therapy, particularly in patients with acute coronary syndrome undergoing percutaneous coronary intervention. Cytochrome P450 2C19 is a major determinant of clopidogrel bioactivation but accounts for only part of the variability in platelet inhibition, suggesting additional hepatic regulatory mechanisms. The main competing hydrolytic pathway is mediated by carboxylesterase 1 (CES1), which converts most absorbed clopidogrel into inactive metabolites. However, CES1 activity cannot be inferred from protein abundance alone, as active-metabolite formation also depends on catalytic function, intracellular localisation, isoform composition, substrate accessibility and residual CYP capacity.Recent evidence indicates that intracellular trafficking and lysosomal degradation can regulate hepatic CES1 abundance. Sortilin 1 (SORT1) may facilitate CES1 lysosomal targeting, while a cytosolic pool of SORT1 has been reported to undergo chaperone-mediated autophagy (CMA)-associated turnover involving HSPA8 and LAMP2A. These relationships were observed in hepatic cell systems and mouse models of lipid metabolism, but not in humans treated with clopidogrel, and thus they support a mechanistic hypothesis rather than an established pharmacological pathway.This review synthesises recent evidence on clopidogrel metabolism, CES1 regulation, lysosomal trafficking, CMA, and platelet P2Y12 signalling. We suggest that the lysosome-CMA-SORT1-CES1 axis may contribute to the heterogeneity of clopidogrel response by shifting the balance between hydrolytic inactivation and oxidative bioactivation. Although the individual molecular relationships are supported across different experimental models, their integration as a determinant of human clopidogrel response remains untested. Before the proposed axis can be considered clinically or pharmacologically established, direct causal validation is required.