PURPOSE: We aimed to compare the effects of P-glycoprotein (ABCB1) on the intestinal uptake of tenofovir disoproxil fumarate (TDF), tenofovir alafenamide fumarate (TAF), and metabolites, tenofovir isoproxil monoester (TEM) and tenofovir (TFV), and to study the molecular mechanism of drug-drug interaction (DDI) between sofosbuvir (SOF) and TDF/TAF. METHODS: Bidirectional transport experiments in Caco-2 cells and accumulation studies in precision-cut intestinal slices prepared from the ileal segment of rodent (rPCIS) and human (hPCIS) intestines were performed. RESULTS: TDF and TAF were extensively metabolised but TAF exhibited greater stability. ABCB1 significantly reduced the intestinal transepithelial transfer and uptake of the TFV(TDF) and TFV(TAF)-equivalents. However, TDF and TAF were absorbed more efficiently than TFV and TEM. SOF did not inhibit intestinal efflux of TDF and TAF or affect intestinal accumulation of TFV(TDF) and TFV(TAF)-equivalents but did significantly increase the proportion of absorbed TDF. CONCLUSIONS: TDF and TAF likely produce comparable concentrations of TFV-equivalents in the portal vein and the extent of permeation is reduced by the activity of ABCB1. DDI on ABCB1 can thus potentially affect TDF and TAF absorption. SOF does not inhibit ABCB1-mediated transport of TDF and TAF but does stabilise TDF, albeit without affecting the quantity of TFV(TDF)-equivalents crossing the intestinal barrier. Our data thus suggest that reported increases in the TFV plasma concentrations in patients treated with SOF and TDF result either from a DDI between SOF and TDF that does not involve ABCB1 or from a DDI involving another drug used in combination therapy.

• Keywords
• P-glycoprotein, intestinal permeability, sofosbuvir, tenofovir alafenamide fumarate, tenofovir disoproxil fumarate,
• MeSH
• Adenine metabolism   MeSH
• Alanine MeSH
• Caco-2 Cells MeSH
• Fumarates MeSH
• HIV Infections * drug therapy   MeSH
• Anti-HIV Agents * MeSH
• Humans MeSH
• ATP Binding Cassette Transporter, Subfamily B, Member 1 MeSH
• ATP Binding Cassette Transporter, Subfamily B MeSH
• Sofosbuvir therapeutic use   MeSH
• Tenofovir MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Adenine MeSH
• Alanine MeSH
• Fumarates MeSH
• Anti-HIV Agents * MeSH
• ATP Binding Cassette Transporter, Subfamily B, Member 1 MeSH
• ATP Binding Cassette Transporter, Subfamily B MeSH
• Sofosbuvir MeSH
• Tenofovir MeSH

The inhibition of P-glycoprotein (ABCB1) could lead to increased drug plasma concentrations and hence increase drug toxicity. The evaluation of a drug's ability to inhibit ABCB1 is complicated by the presence of several transport-competent sites within the ABCB1 binding pocket, making it difficult to select appropriate substrates. Here, we investigate the capacity of antiretrovirals and direct-acting antivirals to inhibit the ABCB1-mediated intestinal efflux of [3H]-digoxin and compare it with our previous rhodamine123 study. At concentrations of up to 100 µM, asunaprevir, atazanavir, daclatasvir, darunavir, elbasvir, etravirine, grazoprevir, ledipasvir, lopinavir, rilpivirine, ritonavir, saquinavir, and velpatasvir inhibited [3H]-digoxin transport in Caco-2 cells and/or in precision-cut intestinal slices prepared from the human jejunum (hPCIS). However, abacavir, dolutegravir, maraviroc, sofosbuvir, tenofovir disoproxil fumarate, and zidovudine had no inhibitory effect. We thus found that most of the tested antivirals have a high potential to cause drug-drug interactions on intestinal ABCB1. Comparing the Caco-2 and hPCIS experimental models, we conclude that the Caco-2 transport assay is more sensitive, but the results obtained using hPCIS agree better with reported in vivo observations. More inhibitors were identified when using digoxin as the ABCB1 probe substrate than when using rhodamine123. However, both approaches had limitations, indicating that inhibitory potency should be tested with at least these two ABCB1 probes.

• Keywords
• ABCB1, antiretrovirals, direct-acting antivirals, drug–drug interactions, human precision-cut intestinal slices,
• Publication type
• Journal Article MeSH

Depression is a prevalent condition affecting up to 20% of pregnant women. Hence, more than 10% are prescribed antidepressant drugs, mainly serotonin reuptake inhibitors (SSRIs) and selective serotonin and noradrenaline reuptake inhibitors (SNRIs). We hypothesize that antidepressants disturb serotonin homeostasis in the fetoplacental unit by inhibiting serotonin transporter (SERT) and organic cation transporter 3 (OCT3) in the maternal- and fetal-facing placental membranes, respectively. Paroxetine, citalopram, fluoxetine, fluvoxamine, sertraline, and venlafaxine were tested in situ (rat term placenta perfusion) and ex vivo (uptake studies in membrane vesicles isolated from healthy human term placenta). All tested antidepressants significantly inhibited SERT- and OCT3-mediated serotonin uptake in a dose-dependent manner. Calculated half-maximal inhibitory concentrations (IC50) were in the range of therapeutic plasma concentrations. Using in vitro and in situ models, we further showed that the placental efflux transporters did not compromise mother-to-fetus transport of antidepressants. Collectively, we suggest that antidepressants have the potential to affect serotonin levels in the placenta or fetus when administered at therapeutic doses. Interestingly, the effect of antidepressants on serotonin homeostasis in rat placenta was sex dependent. As accurate fetal programming requires optimal serotonin levels in the fetoplacental unit throughout gestation, inhibition of SERT-/OCT3-mediated serotonin uptake may help explain the poor outcomes of antidepressant use in pregnancy.

• Keywords
• antidepressants, fetal programming, placenta, pregnancy, serotonin, transport,
• Publication type
• Journal Article MeSH

PURPOSE: S-(4-Nitrobenzyl)-6-thioinosine (NBMPR) is routinely used at concentrations of 0.10 μM and 0.10 mM to specifically inhibit transport of nucleosides mediated by equilibrative nucleoside transporters 1 (ENT1) and 2 (ENT2), respectively. We recently showed that NBMPR (0.10 mM) might also inhibit placental active efflux of [3H]zidovudine and [3H]tenofovir disoproxil fumarate. Here we test the hypothesis that NBMPR abolishes the activity of P-glycoprotein (ABCB1) and/or breast cancer resistance protein (ABCG2). METHODS: We performed accumulation assays with Hoechst 33342 (a model dual substrate of ABCB1 and ABCG2) and bi-directional transport studies with the ABCG2 substrate [3H]glyburide in transduced MDCKII cells, accumulation studies in choriocarcinoma-derived BeWo cells, and in situ dual perfusions of rat term placenta with glyburide. RESULTS: NBMPR inhibited Hoechst 33342 accumulation in MDCKII-ABCG2 cells (IC50 = 53 μM) but not in MDCKII-ABCB1 and MDCKII-parental cells. NBMPR (0.10 mM) also inhibited bi-directional [3H]glyburide transport across monolayers of MDCKII-ABCG2 cells and blocked ABCG2-mediated [3H]glyburide efflux by rat term placenta in situ. CONCLUSION: NBMPR at a concentration of 0.10 mM abolishes ABCG2 activity. Researchers using NBMPR to evaluate the effect of ENTs on pharmacokinetics must therefore interpret their results carefully if studying compounds that are substrates of both ENTs and ABCG2.

• Keywords
• NBMPR, breast cancer resistance protein, equilibrative nucleoside transporters, inhibition, selectivity,
• MeSH
• ATP Binding Cassette Transporter, Subfamily G, Member 2 antagonists & inhibitors   metabolism   MeSH
• Antiviral Agents metabolism   pharmacokinetics   MeSH
• Biological Transport drug effects   MeSH
• Cell Line MeSH
• Madin Darby Canine Kidney Cells MeSH
• Rats MeSH
• Humans MeSH
• Neoplasm Proteins antagonists & inhibitors   metabolism   MeSH
• ATP Binding Cassette Transporter, Subfamily B antagonists & inhibitors   metabolism   MeSH
• Placenta drug effects   metabolism   MeSH
• Rats, Wistar MeSH
• Dogs MeSH
• Pregnancy MeSH
• Thioinosine analogs & derivatives   pharmacology   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Dogs MeSH
• Pregnancy MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• 4-nitrobenzylthioinosine MeSH Browser
• ATP Binding Cassette Transporter, Subfamily G, Member 2 MeSH
• ABCB1 protein, human MeSH Browser
• ABCG2 protein, human MeSH Browser
• Antiviral Agents MeSH
• Neoplasm Proteins MeSH
• ATP Binding Cassette Transporter, Subfamily B MeSH
• Thioinosine MeSH

P-glycoprotein (ABCB1), an ATP-binding-cassette efflux transporter, limits intestinal absorption of its substrates and is a common site of drug-drug interactions (DDIs). ABCB1 has been suggested to interact with many antivirals used to treat HIV and/or chronic hepatitis C virus (HCV) infections. Using bidirectional transport experiments in Caco-2 cells and a recently established ex vivo model of accumulation in precision-cut intestinal slices (PCIS) prepared from rat ileum or human jejunum, we evaluated the potential of anti-HIV and anti-HCV antivirals to inhibit intestinal ABCB1. Lopinavir, ritonavir, saquinavir, atazanavir, maraviroc, ledipasvir, and daclatasvir inhibited the efflux of a model ABCB1 substrate, rhodamine 123 (RHD123), in Caco-2 cells and rat-derived PCIS. Lopinavir, ritonavir, saquinavir, and atazanavir also significantly inhibited RHD123 efflux in human-derived PCIS, while possible interindividual variability was observed in the inhibition of intestinal ABCB1 by maraviroc, ledipasvir, and daclatasvir. Abacavir, zidovudine, tenofovir disoproxil fumarate, etravirine, and rilpivirine did not inhibit intestinal ABCB1. In conclusion, using recently established ex vivo methods for measuring drug accumulation in rat- and human-derived PCIS, we have demonstrated that some antivirals have a high potential for DDIs on intestinal ABCB1. Our data help clarify the molecular mechanisms responsible for reported increases in the bioavailability of ABCB1 substrates, including antivirals and drugs prescribed to treat comorbidity. These results could help guide the selection of combination pharmacotherapies and/or suitable dosing schemes for patients infected with HIV and/or HCV.

• Keywords
• Caco-2 cells, P-glycoprotein, antiviral drugs, drug-drug interactions, intestinal absorption, precision-cut intestinal slices, rhodamine 123,
• MeSH
• Antiviral Agents pharmacology   MeSH
• Atazanavir Sulfate pharmacology   MeSH
• Benzimidazoles pharmacology   MeSH
• Caco-2 Cells drug effects   metabolism   MeSH
• Fluorenes pharmacology   MeSH
• Hepatitis C complications   drug therapy   virology   MeSH
• HIV Infections complications   drug therapy   virology   MeSH
• Imidazoles pharmacology   MeSH
• Carbamates MeSH
• Rats MeSH
• Anti-HIV Agents pharmacology   MeSH
• Drug Interactions MeSH
• Middle Aged MeSH
• Humans MeSH
• Lopinavir pharmacology   MeSH
• Maraviroc pharmacology   MeSH
• ATP Binding Cassette Transporter, Subfamily B, Member 1 antagonists & inhibitors   metabolism   MeSH
• Rats, Wistar MeSH
• Pyrrolidines MeSH
• Ritonavir pharmacology   MeSH
• Saquinavir pharmacology   MeSH
• Aged MeSH
• Intestines drug effects   MeSH
• Valine analogs & derivatives   MeSH
• Zidovudine pharmacology   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Antiviral Agents MeSH
• Atazanavir Sulfate MeSH
• Benzimidazoles MeSH
• daclatasvir MeSH Browser
• Fluorenes MeSH
• Imidazoles MeSH
• Carbamates MeSH
• Anti-HIV Agents MeSH
• ledipasvir MeSH Browser
• Lopinavir MeSH
• Maraviroc MeSH
• ATP Binding Cassette Transporter, Subfamily B, Member 1 MeSH
• Pyrrolidines MeSH
• Ritonavir MeSH
• Saquinavir MeSH
• Valine MeSH
• Zidovudine MeSH

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.

• MeSH
• ATP-Binding Cassette Transporters metabolism   MeSH
• Biological Transport physiology   MeSH
• Cell Line MeSH
• Madin Darby Canine Kidney Cells MeSH
• Rats MeSH
• Lamivudine metabolism   MeSH
• Humans MeSH
• ATP Binding Cassette Transporter, Subfamily B metabolism   MeSH
• Placenta metabolism   MeSH
• Rats, Wistar MeSH
• Multidrug Resistance-Associated Protein 2 MeSH
• Organic Cation Transport Proteins metabolism   MeSH
• Multidrug Resistance-Associated Proteins metabolism   MeSH
• Dogs MeSH
• Pregnancy MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Dogs MeSH
• Pregnancy MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• ATP-Binding Cassette Transporters MeSH
• ABCC2 protein, human MeSH Browser
• Lamivudine MeSH
• ATP Binding Cassette Transporter, Subfamily B MeSH
• Multidrug Resistance-Associated Protein 2 MeSH
• Organic Cation Transport Proteins MeSH
• Multidrug Resistance-Associated Proteins MeSH