A cysteine trapping assay for risk assessment of reactive acyl CoA metabolites.

Some drugs with carboxylic acid moieties can potentially cause rare but severe hepatotoxicity. The reactive chemical species generated by drug metabolism are thought to be one reason for this event. Although the phase II conjugation metabolism of carboxylic acids generally renders a compound more polar and inactive, it is also responsible for the formation of reactive metabolites.This study aimed to provide a new approach towards the risk assessment of carboxylic acids in the aspect of reactive acyl CoA metabolites.Although acyl CoA metabolites have been concerned, it is difficult to detect them because of their instability. We investigated the trapping agents for acyl CoA metabolites. We found that cysteine is a good trapping agent and developed an assay method for the reactivity of acyl CoA metabolites. We evaluated 17 drugs with carboxylic acid moieties, all drugs concerned with hepatotoxicity displayed reactive potential. With consideration of the exposure of each parent drug, the correlation between drug labels and the calculated risk of carboxylic drugs was improved.These evaluations can be conducted without radiochemical reagents or the authentic standards of metabolites. We believe that the method will be beneficial for drug discovery.