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Direct Automated MALDI Mass Spectrometry Analysis of Cellular Transporter Function: Inhibition of OATP2B1 Uptake by 294 Drugs

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journal contribution
posted on 12.08.2020, 08:29 by Melissa S. Unger, Lena Schumacher, Thomas Enzlein, David Weigt, Maciej J. Zamek-Gliszczynski, Matthias Schwab, Anne T. Nies, Gerard Drewes, Sandra Schulz, Friedrich B. M. Reinhard, Carsten Hopf
OATP2B1, a member of the solute carrier (SLC) transporter family, is an important mechanism of substrate drug uptake in the intestine and liver and therefore a determinant of clinical pharmacokinetics and site of drug–drug interactions. Other SLC transporters have emerged as pharmacology targets. Studies of SLC transporter uptake to-date relied on radioisotope- or fluorescence-labeled reagents or low-throughput quantification of unlabeled compounds in cell lysate. In this study, we developed a cell-based MALDI MS workflow for investigation of OATP2B1 cellular uptake by optimizing the substrate, matrix, matrix–analyte ratio, and matrix application and normalization method. This workflow was automated and applied to characterize substrate transport kinetics and to test 294 top-marketed drugs for OATP2B1 inhibition and quantify inhibitory potencies necessary for extrapolation of clinical drug–drug interaction potential. Intra-assay reproducibility of this MALDI MS method was high (CV < 10%), and results agreed well (83% overlap) with previously published radioisotope assay data. Our results indicate that fast and robust MALDI MS cellular assays could emerge as a high-throughput label-free alternative for direct assessment of drug transporter function in DDIs and toxicities as well as enable drug discovery for transporters as pharmacology targets.