Abstract
In vitro evaluation of P-glycoprotein (P-gp) inhibitory potential is now a regulatory issue during drug development, in order to predict clinical inhibition of P-gp and subsequent drug–drug interactions. Assays for this purpose, commonly based on P-gp-expressing cell lines and digoxin as a reference P-gp substrate probe, unfortunately exhibit high variability, raising thus the question of developing alternative or complementary tests for measuring inhibition of P-gp activity. In this context, the present study was designed to investigate the use of the fluorescent dye rhodamine 123 as a reference P-gp substrate probe for characterizing P-gp inhibitory potential of 16 structurally-unrelated drugs known to interact with P-gp. 14/16 of these P-gp inhibitors were found to increase rhodamine 123 accumulation in P-gp-overexpressing MCF7R cells, thus allowing the determination of their P-gp inhibitory potential, i.e., their half maximal inhibitor concentration (IC50) value towards P-gp-mediated transport of the dye. These IC50 values were in the range of variability of previously reported IC50 for P-gp and can be used for the prediction of clinical P-gp inhibition according to Food and Drug Administration (FDA) criteria, with notable sensitivity (80%). Therefore, the data demonstrated the feasibility of the use of rhodamine 123 for evaluating the P-gp inhibitory potential of drugs.
Highlights
P-glycoprotein (P-gp), encoded by the multidrug resistance (MDR) 1 gene, is an ATP-binding cassette (ABC) membrane transporter acting as a drug efflux pump [1,2].This membrane protein was initially characterized as overexpressed in tumoral cells exhibiting multiple resistance to a wide variety of structurally-unrelated anticancer drugs [3]
P-gp activity can be inhibited by a wide range of drugs, which can lead to drug–drug interactions (DDIs) due to impairment of pharmacokinetics of a drug substrate for P-gp by the Pharmaceutics 2016, 8, 12; doi:10.3390/pharmaceutics8020012
Digoxin has a narrow therapeutic index and even slight changes in plasma exposure due to alteration of P-gp activity can alter its efficacy and/or safety. Owing to this implication of P-gp in DDIs, the determination of P-gp inhibitory potential is required by drug regulatory agencies such as the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for new drugs developed by pharmaceutical companies [6]
Summary
P-glycoprotein (P-gp), encoded by the multidrug resistance (MDR) 1 gene ( known as ABCB1), is an ATP-binding cassette (ABC) membrane transporter acting as a drug efflux pump [1,2]. Digoxin has a narrow therapeutic index and even slight changes in plasma exposure due to alteration of P-gp activity can alter its efficacy and/or safety Owing to this implication of P-gp in DDIs, the determination of P-gp inhibitory potential is required by drug regulatory agencies such as the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for new drugs developed by pharmaceutical companies [6]. The use of digoxin as a specific P-gp probe in transepithelial efflux assays has been recently challenged because digoxin is handled by (an) as yet unidentified basolateral uptake process(es) in intestinal cells [12] It required rather elaborated and specific bioanalytical methods and equipment, i.e., a scintillation counter when using radiolabeled digoxin or a liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) for quantifying unlabeled digoxin. 123 accumulation assay and to investigate their potential usefulness for the prediction of P-gp-related clinical relevant DDIs, notably in comparison with IC50 data from digoxin transport assays available in the literature
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