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J. Gerry Kenna, Claudia Green, Catherine D. G. Hines Iina Laitinen, Aleksandra Galetin, Paul D. Hockings,  Nicola Melillo, Mikael Montelius,  Daniel Scotcher, Steven Sourbron, John C. Watertone, Gunnar Schütz
 

Virtual 2021 Annual Meeting of the US Society of Toxicology and ToxExpo

Abstract

Inhibition of transporters that mediate hepatic drug uptake and/or biliary excretion may cause clinically relevant drug-drug interactions (DDIs) leading to potentiated or reduced efficacy, and/or increased or reduced toxicity to liver or other tissues. These DDIs are difficult to assess, since accurate prediction of changes in tissue exposure in vivo based on in vitro transport interaction data is challenging. Dynamic contract enhanced magnetic resonance imaging (DCE-MRI) enables in vivo visualisation of hepatic transporter mediated uptake and efflux of the contrast agent gadoxetate. When analysed using a compartmental kinetic model of gadoxetate disposition, gadoxetate DCE-MRI studies provide quantitative rate constants for hepatic gadoxetate uptake (khe) and biliary excretion (kbh). These processes are mediated primarily by Organic Anion Transport Polypeptides (OATPs) and Multidrug Resistance Protein Type 2 (MRP2), respectively. To evaluate drug effects on hepatic gadoxetate khe and kbh, DCE-MRI studies were undertaken in adult male Wistar rats (approx. 250g body weight) dosed intravenously (iv) with single doses of 
drugs (rifampicin, asunaprevir, bosentan, cyclosporin, ketoconazole, pioglitazone) that inhibited rat oatp, and human OATP, activities in vitro. Drug doses were selected, via pharmacokinetic modelling and simulation, to achieve rat peripheral blood plasma concentrations following iv administration that were equivalent to steady-state human blood plasma concentrations. Simulations predicted that the selected doses of rifampicin and cyclosporin reduced liver gadoxetate exposure in vivo, whereas the other tested drugs did not. Gadoxetate khe values were determined 20 min after iv administration of dose vehicle and then, in the same animals, after a minimum 48 hr washout interval and following drug administration (n=6 per group). Gadoxetate khe (min-1) was reduced (p < 0.01) following administration of rifampicin at 2 mg/kg (mean +SD, dose: 0.44+0.06; vehicle: 0.92+0.17) or cyclosporin at 5 mg/kg (mean+SD, dose: 0.08+0.02; vehicle: 1.00+0.24); but not after dosing of asunaprevir at 5 mg/kg, bosentan at 2 mg/kg, ketoconazole at 3 mg/kg or pioglitazone at 0.4 mg/kg. These results indicate that gadoxetate DCE-MRI may aid assessment of hepatic transporter-mediated DDI risk.