Efavirenz reduces renal excretion of lamivudine in rats by inhibiting organic cation transporters (OCT, Oct) and multidrug and toxin extrusion proteins (MATE, Mate).

Efavirenz (EFV) is a non-nucleoside reverse transcriptase inhibitor used in first-line combination antiretroviral therapy (cART). It is usually administered with nucleoside reverse transcriptase inhibitors (NRTI), many of which are substrates of OCT uptake solute carriers (SLC22A) and MATE (SLC47A), P-gp (MDR1, ABCB1), BCRP (ABCG2), or MRP2 (ABCC2) efflux transporters. The aim of this study was to evaluate the inhibitory potential of efavirenz towards these transporters and investigate its effects on the pharmacokinetics and tissue distribution of a known Oct/Mate substrate, lamivudine, in rats. Accumulation and transport assays showed that efavirenz inhibits the uptake of metformin by OCT1-, OCT2- and MATE1-expressing MDCK cells and reduces transcellular transport of lamivudine across OCT1/OCT2- and MATE1-expressing MDCK monolayers. Only negligible inhibition of MATE2-K was observed in HEK-MATE2-K cells. Efavirenz also reduced the efflux of calcein from MDCK-MRP2 cells, but had a rather weak inhibitory effect on Hoechst 33342 accumulation in MDCK-MDR1 and MDCK-BCRP cells. An in vivo pharmacokinetic interaction study in male Wistar rats revealed that intravenous injection of efavirenz or the control Oct/Mate inhibitor cimetidine significantly reduced the recovery of lamivudine in urine and greatly increased lamivudine retention in the renal tissue. Co-administration with efavirenz or cimetidine also increased the AUC0-∞ value and reduced total body clearance of lamivudine. These data suggest that efavirenz is a potent inhibitor of OCT/Oct and MATE/Mate transporters. Consequently, it can engage in drug-drug interactions that reduce renal excretion of co-administered substrates and enhance their retention in the kidneys, potentially compromising therapeutic safety.

MDR1 and BCRP Transporter-Mediated Drug-Drug Interaction between Rilpivirine and Abacavir and Effect on Intestinal Absorption.

Rilpivirine (TMC278) is a highly potent nonnucleoside reverse transcriptase inhibitor (NNRTI) representing an effective component of combination antiretroviral therapy (cART) in the treatment of HIV-positive patients. Many antiretroviral drugs commonly used in cART are substrates of ATP-binding cassette (ABC) and/or solute carrier (SLC) drug transporters and, therefore, are prone to pharmacokinetic drug-drug interactions (DDIs). The aim of our study was to evaluate rilpivirine interactions with abacavir and lamivudine on selected ABC and SLC transporters in vitro and assess its importance for pharmacokinetics in vivo Using accumulation assays in MDCK cells overexpressing selected ABC or SLC drug transporters, we revealed rilpivirine as a potent inhibitor of MDR1 and BCRP, but not MRP2, OCT1, OCT2, or MATE1. Subsequent transport experiments across monolayers of MDCKII-MDR1, MDCKII-BCRP, and Caco-2 cells demonstrated that rilpivirine inhibits MDR1- and BCRP-mediated efflux of abacavir and increases its transmembrane transport. In vivo experiments in male Wistar rats confirmed inhibition of MDR1/BCRP in the small intestine, leading to a significant increase in oral bioavailability of abacavir. In conclusion, rilpivirine inhibits MDR1 and BCRP transporters and may affect pharmacokinetic behavior of concomitantly administered substrates of these transporters, such as abacavir.

Universal efavirenz determination in transport study, rat placenta perfusion and placenta lysate by HPLC-UV.

Efavirenz is an antiretroviral drug used in the treatment of HIV-positive patients. A simple, fast and sensitive high-performance liquid chromatography (HPLC) method was developed in order to determine efavirenz in three types of samples provided from pharmacokinetic studies. The analysis took 5min and was performed using a C18 analytical column (Discovery HS C18, 150×4.6mm, particle size of 5µm) in isocratic mode with a mobile phase containing acetonitrile and water (65:35, v/v), a flow rate of 1.6mLmin-1, a sample volume of 10µL and UV detection at 245nm. Three different sample matrices (Opti-MEM medium, Krebs perfusion liquid and tissue lysate) and their treatment (dilution, SPE) were considered. The validated method was applied for the analysis of 805 real samples arising from in vitro transcellular transport assays and in vivo organ perfusion experiments in order to evaluate the interaction of efavirenz with ATP-dependent drug efflux transporters. The lack of interaction of efavirenz with ABCB1, ABCG2 and ABCC2 transporters as well as technical aspects of this analysis, including the adhesion of efavirenz to the plastic materials and the stability of the drug during different tissue lysis approaches are discussed.

Emtricitabine is a substrate of MATE1 but not of OCT1, OCT2, P-gp, BCRP or MRP2 transporters.

1. Emtricitabine is a nucleoside reverse transcriptase inhibitor used in combination antiretroviral therapy of HIV (cART). Although active transport mechanisms are believed to mediate tubular secretion of the drug into urine, the responsible transporter and its potential to cause pharmacokinetic drug--drug interactions (DDI) has not been identified so far. The aim of this study was to investigate whether drug transporters P-gp (ABCB1), BCRP (ABCG2), MRP2 (ABCC2), OCT1 (SLC22A1), OCT2 (SLC22A2) or MATE1 (SLC47A1) can mediate active transcellular transfer of emtricitabine. 2. We employed transport assays in polarized monolayers of MDCK cells stably expressing P-gp, BCRP, MRP2, OCT1, OCT2 and/or MATE1. Among the transporters studied only MATE1 accelerated basal-to-apical transport of emtricitabine over a wide range of concentrations (6 nM to 1 mM). The transport was enhanced by an oppositely directed pH gradient and significantly reduced (p < 0.001) at low temperature in MDCK-MATE1, MDCK-OCT1/MATE1 and MDCK-OCT2/MATE1 cells. Co-administration of cimetidine or ritonavir decreased MATE1-mediated transport of emtricitabine by up to 42 and 39%, respectively (p < 0.01) and augmented intracellular accumulation of emtricitabine (p < 0.05). 3. We demonstrate emtricitabine as a substrate of MATE1 and suggest that MATE1 might cause DDI between emtricitabine and other co-administrated drugs including antiretrovirals.

Etravirine inhibits ABCG2 drug transporter and affects transplacental passage of tenofovir disoproxil fumarate.

INTRODUCTION: All HIV positive pregnant women should receive combination antiretroviral therapy (cART) to prevent mother-to-child transmission (MTCT) of the virus. It has recently been shown that fetal exposure of nucleoside reverse transcriptase inhibitors (NRTIs) tenofovir disoproxil fumarate (TDF) and abacavir is decreased by placental ABC transporters p-glycoprotein (ABCB1) and BCRP (ABCG2). The aim of this study was to evaluate transporter-mediated drug-drug interactions (DDI) between etravirine (TMC125), a novel non-nucleoside reverse transcriptase inhibitor used in cART, and the NRTIs and to assess the relevance of such DDI for transplacental pharmacokinetics of TDF and abacavir. METHODS: In vitro accumulation assays and transport experiments on ABCB1 and ABCG2 overexpressing MDCKII monolayers were employed. Furthermore, the effect of etravirine on the transplacental passage of TDF and abacavir was assessed using in situ dually perfused rat placenta. RESULTS: We confirmed significant inhibition of ABCG2 but not ABCB1 by etravirine in hoechst accumulation assays. In transport studies on MDCKII-ABCG2 monolayers etravirine completely abolished the ABCG2-mediated transfer of [3H]-TDF. Similar effect was observed in [3H]-abacavir albeit at markedly lower etravirine concentration. Using dually perfused rat placenta, etravirine co-administration resulted in reduced fetal-to-maternal passage of TDF but not abacavir. DISCUSSION: Etravirine is able to affect transplacental passage of TDF but not that of abacavir through interactions on ABCG2. These results should be considered when introducing etravirine into TDF-containing cART in pregnancy.

Role of ABC and Solute Carrier Transporters in the Placental Transport of Lamivudine.

Lamivudine is one of the antiretroviral drugs of choice for the prevention of mother-to-child transmission (MTCT) in HIV-positive women. In this study, we investigated the relevance of drug efflux transporters P-glycoprotein (P-gp) (MDR1 [ABCB1]), BCRP (ABCG2), MRP2 (ABCC2), and MATE1 (SLC47A1) for the transmembrane transport and transplacental transfer of lamivudine. We employed in vitro accumulation and transport experiments on MDCK cells overexpressing drug efflux transporters, in situ-perfused rat term placenta, and vesicular uptake in microvillous plasma membrane (MVM) vesicles isolated from human term placenta. MATE1 significantly accelerated lamivudine transport in MATE1-expressing MDCK cells, whereas no transporter-driven efflux of lamivudine was observed in MDCK-MDR1, MDCK-MRP2, and MDCK-BCRP monolayers. MATE1-mediated efflux of lamivudine appeared to be a low-affinity process (apparent Km of 4.21 mM and Vmax of 5.18 nmol/mg protein/min in MDCK-MATE1 cells). Consistent with in vitro transport studies, the transplacental clearance of lamivudine was not affected by P-gp, BCRP, or MRP2. However, lamivudine transfer across dually perfused rat placenta and the uptake of lamivudine into human placental MVM vesicles revealed pH dependency, indicating possible involvement of MATE1 in the fetal-to-maternal efflux of the drug. To conclude, placental transport of lamivudine does not seem to be affected by P-gp, MRP2, or BCRP, but a pH-dependent mechanism mediates transport of lamivudine in the fetal-to-maternal direction. We suggest that MATE1 might be, at least partly, responsible for this transport.