A 674 Toni Lassila IN VITRO METHODS IN THE STUDY OF REACTIVE DRUG METABOLITES WITH LIQUID CHROMATOGRAPHY / MASS SPECTROMETRY

Reactive metabolites are believed to be responsible for rare but serious idiosyncratic adverse drug reactions (IADRs) that have led to the withdrawal of numerous drugs from the market. This has resulted in major harm to patients, economic losses for the pharmaceutical companies and represents a serious problem in drug development. Reactive metabolites can be studied by trapping them with suitable nucleophiles, most commonly with glutathione. The glutathione conjugates formed in these reactions can be analyzed with liquid chromatography mass spectrometry (LC/ MS) techniques. In this study, new in vitro methods for the detection and analysis of reactive metabolites were developed. The suitability for reactive metabolite screening of different enzyme sources commonly used in vitro were compared. It was found that sub-cellular fractions yielded significantly larger amounts of glutathione-trapped reactive metabolites as compared to the amounts obtained from intact hepatocytes. Additionally, different metabolites were detected in some cases. Biomimetic metalloporphyrin catalysts were tested for their ability to produce larger amounts of glutathione-trapped metabolites relative to liver S9 fraction incubations. An increase in reactive metabolite production was observed with biomimetic models, but not all of the metabolites produced by liver S9 were observed. The glutathione conjugates of pulegone and of its metabolite menthofuran were analyzed with LC/MS/MS, and the fragmentation spectra of Nand S-/Ndi-linked glutathione conjugate were interpreted in detail for the first time. These results will enable more efficient screening of reactive metabolites of furan-containing compounds. Acyl glucuronides are metabolites produced from carboxylic acid-containing compounds and can be reactive. A good correlation was found between the acyl migration half-life and the tendency of a drug to cause IADRs. The carboxylic moiety can also be metabolized to yield acyl coenzyme A (CoA) conjugates that may be more reactive than their corresponding acyl glucuronides. The formation of CoA conjugates and additional conjugates formed from them was found to be more likely with drugs that cause IADRs.