title: Analytical challenges for conducting rapid metabolism characterization for QIVIVE.
abstract: For quantitative in vitro-in vivo extrapolation (QIVIVE) of metabolism for the purposes of toxicokinetics prediction, a precise and robust analytical technique for identifying and measuring a chemical and its metabolites is an absolute prerequisite. Currently, high-resolution mass spectrometry (HR-MS) is a tool of choice for a majority of organic relatively lipophilic molecules, linked with a LC separation tool and simultaneous UV-detection. However, additional techniques such as gas chromatography, radiometric measurements and NMR, are required to cover the whole spectrum of chemical structures. To accumulate enough reliable and robust data for the validation of QIVIVE, there are some partially opposing needs: Detailed delineation of the in vitro test system to produce a reliable toxicokinetic measure for a studied chemical, and a throughput capacity of the in vitro set-up and the analytical tool as high as possible. We discuss current analytical challenges for the identification and quantification of chemicals and their metabolites, both stable and reactive, focusing especially on LC-MS techniques, but simultaneously attempting to pinpoint factors associated with sample preparation, testing conditions and strengths and weaknesses of a particular technique available for a particular task.
authors.affiliation: Admescope Ltd, Typpitie 1, FIN-90620 Oulu, Finland. Electronic address: ari.tolonen@admescope.com.
authors.forename: Ari
authors.initials: A
authors.lastname: Tolonen
authors.affiliation: University of Oulu, Department of Pharmacology and Toxicology, Aapistie 5 B (POB 5000), FIN-90014 Oulu, Finland. Electronic address: olavi.pelkonen@oulu.fi.
authors.forename: Olavi
authors.initials: O
authors.lastname: Pelkonen
mesh_terms: D000826:Animal Testing Alternatives; D000818:Animals; D001711:Biotransformation; D002853:Chromatography, Liquid; D003198:Computer Simulation; D057166:High-Throughput Screening Assays / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D013058:Mass Spectrometry; D008954:Models, Biological; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D013045:Species Specificity; D049490:Systems Biology; D018675:Toxicity Tests / Q000379:methods*; D014116:Toxicology / Q000379:methods*
keywords: Drug metabolism; Drug metabolites; High resolution mass spectrometry (HR-MS); High throughput screening (HTS); Liquid chromatography–mass spectrometry (LC–MS)