Detecting and characterizing reactive metabolites by liquid chromatography/tandem mass spectrometry

Metabolic activation of a drug leading to reactive metabolite(s) that can covalently modify proteins is considered an initial step that may lead to drug-induced organ toxicities. Characterization of reactive metabolites is critical to designing new drug candidates with an improved toxicological profile. High performance liquid chromatography (HPLC) coupled with mass spectrometry (MS) predominates over all analytical tools used for screening and characterization of reactive metabolites. In this review, a brief description of experimental approaches employed for assessing reactive metabolites is followed by a discussion on the reactivity of acyl glucuronides and acyl coenzyme A thioesters. Techniques for high-throughput screening and quantitation of reactive metabolite formation are also described, along with proteomic approaches used to identify protein targets and modification sites by reactive metabolites. Strategies for dealing with reactive metabolites are reviewed. In conclusion, we discuss the challenges and future needs in this field of research.