A new mechanism of action of thienopyridine antiplatelet drugs - A role for gastric nitrosothiol metabolism

Abstract

This article outlines a new hypothesis that illustrates the potential role of the stomach (and subsequent chemical reactions involving nitrite therein) in modifying thienopyridines, such as clopidogrel. Gastric modification of thienopyridines can occur before standard accepted biotransformation pathways ensue. We hypothesised that thienopyridines expose the free thiol group once acidified (by the stomach) before biotransformation into active metabolites, and in the presence of nitrite (from saliva and the stomach) to form nitrosothiol derivatives (Thienopyridine induced-SNO formation). We have performed in vitro studies with each of the thienopyridines tablets/compounds confirming direct Th-SNO formation from the parent (inactive) drug by the following mechanism. Thienopyridine-SH + H+ (Stomach) + View the MathML sourceNO2−(Salivaandstomach) ↔ Thienopyridine-SNO + H2O

Thienopyridine-SNO (an S-nitrosothiol molecule) would have the potential to participate in all the reactions expected of native nitric oxide (NO) with added benefit that the NO “moiety” is protected, transportable and largely preserved from further reactive metabolism. All these biochemical steps are present in humans and could occur prior to enzymatic biotransformation.