Transporters and drug-drug interactions: important determinants of drug disposition and effects

Drug-nutrient interactions: discovering prescription drug inhibitors of the thiamine transporter ThTR-2 (SLC19A3)

BACKGROUND

Transporter-mediated drug-nutrient interactions have the potential to cause serious adverse events. However, unlike drug-drug interactions, these drug-nutrient interactions receive little attention during drug development. The clinical importance of drug-nutrient interactions was highlighted when a phase III clinical trial was terminated due to severe adverse events resulting from potent inhibition of thiamine transporter 2 (ThTR-2; SLC19A3).

OBJECTIVE

In this study, we tested the hypothesis that therapeutic drugs inhibit the intestinal thiamine transporter ThTR-2, which may lead to thiamine deficiency.

METHODS

For this exploration, we took a multifaceted approach, starting with a high-throughput in vitro primary screen to identify inhibitors, building in silico models to characterize inhibitors, and leveraging real-world data from electronic health records to begin to understand the clinical relevance of these inhibitors.

RESULTS

Our high-throughput screen of 1360 compounds, including many clinically used drugs, identified 146 potential inhibitors at 200 μM. Inhibition kinetics were determined for 28 drugs with half-maximal inhibitory concentration (IC50) values ranging from 1.03 μM to >1 mM. Several oral drugs, including metformin, were predicted to have intestinal concentrations that may result in ThTR-2-mediated drug-nutrient interactions. Complementary analysis using electronic health records suggested that thiamine laboratory values are reduced in individuals receiving prescription drugs found to significantly inhibit ThTR-2, particularly in vulnerable populations (e.g., individuals with alcoholism).

CONCLUSIONS

Our comprehensive analysis of prescription drugs suggests that several marketed drugs inhibit ThTR-2, which may contribute to thiamine deficiency, especially in at-risk populations.

In silico modelling, identification of crucial molecular fingerprints, and prediction of new possible substrates of human organic cationic transporters 1 and 2

The cation membrane transporters are crucial to regulate movement of foreign molecules within the body. The present study found out structural fingerprints within molecules to be recognized as substrate/non-substrate against these transporters.

Pharmacokinetic parameters of ifosfamide in mouse pre-administered with grapefruit juice or naringin

Grapefruit juice (GFJ) and naringin when consumed previously or together with medications may alter their bioavailavility and consequently the clinical effect. Ifosfamide (IF) is an antitumoral agent prescribed against various types of cancer. Nevertheless, there is no information regarding its interaction with the ingestion of GFJ or naringin. The aims of the present report were validating a method for the quantitation of IF in the plasma of mouse, and determine if mice pretreated with GFJ or naringin may modify the IF pharmacokinetics. Our HPLC results to quantify IF showed adequate intra and inter-day precision (RSD < 15%) and accuracy (RE < 15%) indicating reliability. Also, the administration of GFJ or naringin increased C_max of IF 22.9% and 17.8%, respectively, and decreased T_max of IF 19.2 and 53.8%, respectively. The concentration of IF was higher when GFJ (71.35 ± 3.5 µg/mL) was administered with respect to that obtained in the combination naringin with IF (64.12 ± µg/mL); however, the time required to reach such concentration was significantly lower when naringin was administered (p < 0.5). We concluded that pre-administering GFJ and naringin to mice increased the T_max and decreased the C_max of IF.

Transporter-Mediated Drug-Drug Interactions and Their Significance

Drug transporters are considered to be determinants of drug disposition and effects/toxicities by affecting the absorption, distribution, and excretion of drugs. Drug transporters are generally divided into solute carrier (SLC) family and ATP binding cassette (ABC) family. Widely studied ABC family transporters include P-glycoprotein (P-GP), breast cancer resistance protein (BCRP), and multidrug resistance proteins (MRPs). SLC family transporters related to drug transport mainly include organic anion-transporting polypeptides (OATPs), organic anion transporters (OATs), organic cation transporters (OCTs), organic cation/carnitine transporters (OCTNs), peptide transporters (PEPTs), and multidrug/toxin extrusions (MATEs). These transporters are often expressed in tissues related to drug disposition, such as the small intestine, liver, and kidney, implicating intestinal absorption of drugs, uptake of drugs into hepatocytes, and renal/bile excretion of drugs. Most of therapeutic drugs are their substrates or inhibitors. When they are comedicated, serious drug-drug interactions (DDIs) may occur due to alterations in intestinal absorption, hepatic uptake, or renal/bile secretion of drugs, leading to enhancement of their activities or toxicities or therapeutic failure. This chapter will illustrate transporter-mediated DDIs (including food drug interaction) in human and their clinical significances.

Organic Anion-Transporting Polypeptide Genes Are Not Induced by the Pregnane X Receptor Activator Rifampin: Studies in Hepatocytes In Vitro and in Monkeys In Vivo

Induction potentials of the pregnane X receptor (PXR) activator rifampin (RIF) on transporter genes [e.g., organic anion-transporting polypeptides (OATPs)] are still in its infancy or remain controversial in the field. The present investigations characterized changes in transporter gene expression by RIF in sandwich-cultured hepatocytes from multiple donors of human and cynomolgus monkey using real-time quantitative reverse transcription polymerase chain reaction method. Three-day treatment of RIF significantly induced CYP3A4 (∼60-fold induction), but not CYP1A2 and CYP2D6 genes. SLC51B was the most highly induced uptake transporter gene (>10-fold) in both human and monkey hepatocytes. A greater induction of CYP2C9 was observed in monkey hepatocytes than that in humans. ATP-binding cassette (ABC)B1 and ABCC2 were induced slightly above 2-fold in human and monkey hepatocytes and appeared to be dose-dependent. The induction of OATP and other transporter genes was generally less than 2-fold and considered not clinically relevant. SLCO2B1 was not detectable in monkey hepatocytes. To investigate in vivo OATP induction, RIF (18 mg/kg per day) was orally dosed to cynomolgus monkeys for 7 days. Pitavastatin and antipyrine were intravenously dosed before and after RIF treatment as exogenous probes of OATP and CYP activities, respectively. Plasma coproporphyrin-I (CP-I) and coproporphyrin-III (CP-III) were measured as OATP endogenous biomarkers. Although a significant increase of antipyrine clearance (CL) was observed after RIF treatment, the plasma exposures of pitavastatin, CP-I, and CP-III remained unchanged, suggesting that OATP function was not significantly altered. The results suggested that OATP transporters were not significantly induced by PXR ligand RIF. The data are consistent with current regulatory guidances that the in vitro characterization of transporter induction during drug development is not required. SIGNIFICANCE STATEMENT: Organic anion-transporting polypeptide (OATP) genes were not induced by rifampin in sandwich-cultured human and monkey hepatocytes OATP functions measured by OATP probe pitavastatin and endogenous marker coproporphyrins were not altered in monkeys in vivo by 7-day rifampin treatment. The data suggested that OATP transporters are unlikely induced by the pregnane X receptor ligand rifampin, which are consistent with current regulatory guidances that the in vitro characterization of OATP1B induction during drug development is not required.

Interaction between Fexofenadine and CYP Phenotyping Probe Drugs in Geneva Cocktail

Drug metabolic enzymes and transporters are responsible for an important variability in drug disposition. The cocktail approach is a sound strategy for the simultaneous evaluation of several enzyme and transporter activities for a personalized dosage of medications. Recently, we have demonstrated the reliability of the Geneva cocktail, combining the use of dried blood spots (DBS) and reduced dose of phenotyping drugs for the evaluation of the activity of six cytochromes and P-glycoprotein (P-gp). As part of a study evaluating potential drug–drug interactions between probe drugs of the Geneva cocktail, the present paper focuses on the impact of cytochromes (CYP) probe drugs on the disposition of fexofenadine, a P-gp test drug. In a randomized four-way Latin-square crossover study, 30 healthy volunteers (15 men and 15 women) received caffeine 50 mg, bupropion 20 mg, flurbiprofen 10 mg, omeprazole 10 mg, dextromethorphan 10 mg, midazolam 1 mg, and fexofenadine 25 mg alone (or as part of a previously validated combination) and all together (Geneva cocktail). The determination of drug concentrations was performed in DBS samples and pharmacokinetic parameters were calculated. Fexofenadine AUC_{0–8 h} and C_max decreased by 43% (geometric mean ratio: 0.57; CI 90: 0.50–0.65; p < 0.001) and 49% (geometric mean ratio: 0.51; CI 90: 0.44–0.59; p < 0.001), respectively, when fexofenadine was administered as part of the Geneva cocktail in comparison to fexofenadine alone. Consequently, the apparent oral clearance (Cl/F) increased 1.7-fold (CI 90: 1.49–1.93; p < 0.001). There was no interaction between the remaining probes. In conclusion, an unexpected interaction occurred between fexofenadine and one or several of the following substances: caffeine, bupropion, flurbiprofen, omeprazole, dextromethorphan, and midazolam. Further studies are necessary to elucidate the mechanism of this interaction.

The pharmacokinetic properties of HIV-1 protease inhibitors: A computational perspective on herbal phytochemicals

Acquired Immune Deficiency Syndrome is the most severe phase of Human Immunodeficiency Virus (HIV) infection. Recent studies have seen an effort to isolate phytochemicals from plants to repress HIV, but less studies have focused on the effects of these phytochemicals on the activities of enzymes/transporters involved in the metabolism of these drugs, which is one of the aims of this study and, to examine the antiviral activity of these compounds against HIV-1 protease enzyme using computational tools. Centre of Awareness-Food Supplement (COA®-FS) herbal medicine, has been said to have potential anti-HIV features. SWISSTARGETPREDICTION and SWISSADME servers were used for determination of the enzymes/transporters involved in the metabolism of these protease inhibitor drugs, (PIs) (Atazanavir, Lopinavir, Darunavir, Saquinavir) and the effects of the selected phytochemicals on the enzymes/transporters involved in the metabolism of these PIs. Using Computational tools, potential structural inhibitory activities of these phytochemicals were explored. Two sub-families of Cytochrome P450 enzymes (CYP3A4 and CYP2C19) and Permeability glycoprotein (P-gp) were predicted to be involved in metabolism of the PIs. Six phytochemicals (Geranin, Apigenin, Fisetin, Luteolin, Phthalic acid and Gallic acid) were predicted to be inhibitors of CYP3A4 and, may slowdown elimination of PIs thereby maintain optimal PIs concentrations. Free binding energy analysis for antiviral activities identified four phytochemicals with favourable binding landscapes with HIV-1 protease enzyme. Epigallocatechin gallate and Kaempferol-7-glucoside exhibited pronounced structural evidence as potential HIV-1 protease enzyme inhibitors. This study acts as a steppingstone toward the use of natural products against diseases that are plagued with adverse drug-interactions.

Sorafenib Activity and Disposition in Liver Cancer Does Not Depend on Organic Cation Transporter 1

Systemic therapy of advanced hepatocellular carcinoma (HCC) with the small-molecule multikinase inhibitor sorafenib is associated with large interindividual pharmacokinetic variability and unpredictable side effects potentially requiring dose reduction or treatment termination. Organic cation transporter (OCT1; gene SLC22A1) has been proposed as a clinical biomarker of HCC response. Because proof is lacking that OCT1 transports sorafenib, we used a combinatorial approach to define how OCT1 contributes to sorafenib transport. Overexpression of functional OCT1 protein in Xenopus laevis oocytes and mammalian cell lines did not facilitate sorafenib transport. Otherwise, sorafenib considerably accumulated in liver cancer cell lines despite negligible OCT1 mRNA and protein levels. Sorafenib pharmacokinetics was independent of OCT1 genotype in mice. Finally, SLC22A1 mRNA expression was significantly reduced by DNA methylation in The Cancer Genome Atlas HCC cohort. These results clearly demonstrate OCT1-independent cellular sorafenib uptake indicating that OCT1 is apparently not a valid biomarker of sorafenib response in HCC.

High degree of pharmacokinetic compatibility exists between the five-herb medicine XueBiJing and antibiotics comedicated in sepsis care

Managing the dysregulated host response to infection remains a major challenge in sepsis care. Chinese treatment guideline recommends adding XueBiJing, a five-herb medicine, to antibiotic-based sepsis care. Although adding XueBiJing further reduced 28-day mortality via modulating the host response, pharmacokinetic herb–drug interaction is a widely recognized issue that needs to be studied. Building on our earlier systematic chemical and human pharmacokinetic investigations of XueBiJing, we evaluated the degree of pharmacokinetic compatibility for XueBiJing/antibiotic combination based on mechanistic evidence of interaction risk. Considering both XueBiJing‒antibiotic and antibiotic‒XueBiJing interaction potential, we integrated informatics-based approach with experimental approach and developed a compound pair-based method for data processing. To reflect clinical reality, we selected for study XueBiJing compounds bioavailable for drug interactions and 45 antibiotics commonly used in sepsis care in China. Based on the data of interacting with drug metabolizing enzymes and transporters, no XueBiJing compound could pair, as perpetrator, with the antibiotics. Although some antibiotics could, due to their inhibition of uridine 5′-diphosphoglucuronosyltransferase 2B15, organic anion transporters 1/2 and/or organic anion-transporting polypeptide 1B3, pair with senkyunolide I, tanshinol and salvianolic acid B, the potential interactions (resulting in increased exposure) are likely desirable due to these XueBiJing compounds' low baseline exposure levels. Inhibition of aldehyde dehydrogenase by 7 antibiotics probably results in undesirable reduction of exposure to protocatechuic acid from XueBiJing. Collectively, XueBiJing/antibiotic combination exhibited a high degree of pharmacokinetic compatibility at clinically relevant doses. The methodology developed can be applied to investigate other drug combinations.

Pharmacokinetic and Pharmacodynamic Effects of Oral CXA-10, a Nitro Fatty Acid, After Single and Multiple Ascending Doses in Healthy and Obese Subjects

10‐nitro‐9(E)‐octadec‐9‐enoic acid (CXA‐10), a novel nitro fatty acid compound, demonstrates potential as a therapeutic agent in multiple disease indications in which oxidative stress, inflammation, fibrosis, and/or direct tissue toxicity play significant roles. Phase I studies were conducted in healthy and obese subjects to evaluate the pharmacokinetics (PK), pharmacodynamics (PD), safety, and tolerability of oral CXA‐10 after single and multiple doses in the fed and fasted states that would confirm the mechanisms of action of CXA‐10. After single and multiple ascending doses, CXA‐10 demonstrated dose‐proportional increases in plasma exposure. CXA‐10 decreased levels of biomarkers associated with altered inflammation and metabolic stress observed from nonclinical studies. In CXA‐10‐202, a consistent decrease from baseline was observed with CXA‐10 150 mg dose, but not 25 or 450 mg doses, for biomarkers of altered inflammation and metabolic dysfunction, including leptin, triglycerides, cholesterol, MCP‐1, and IL‐6. In CXA‐10‐203, after coadministration with CXA‐10, geometric mean peak plasma concentration (C_max) and area under the plasma concentration‐time curve from time point 0 to the end of the dosing interval (AUC_0−t) decreased 20% and 25% for pravastatin, increased 10% and 25% for simvastatin, and decreased 20% and 5% for ezetimibe. These findings are consistent with the pharmacological effects of CXA‐10. Adverse events (AEs) were dose‐related, and the most frequently reported AEs (>10% of subjects) were diarrhea, abdominal pain, and nausea. CXA‐10 was safe and well‐tolerated with no clinically significant abnormalities reported on physical examination, vital signs, clinical laboratory evaluations, or electrocardiographic evaluation. Phase II studies are underway in patients with focal segmental glomerulosclerosis and pulmonary arterial hypertension to investigate the efficacy and tolerability of CXA‐10 75–300 mg once daily.

Rhinacanthin-C Mediated Herb-Drug Interactions with Drug Transporters and Phase I Drug-Metabolizing Enzymes

Rhinacanthin-C is a major active constituent in Rhinacanthus nasutus (L.) Kurz, a plant widely used in herbal remedies. Its potential for pharmacokinetic herb-drug interaction may exist with drug transporters and drug metabolizing enzymes. This study assessed the possibility for rhinacanthin-C-mediated drug interaction by determining its inhibitory effects against major human efflux and influx drug transporters as well as various human cytochrome P450(CYP) isoforms. Rhinacanthin-C demonstrated a moderate permeability through the Caco-2 monolayers [P_{app (AP-to-BL)} = 1.26 × 10^-6 cm/s]. It significantly inhibited transport mediated by both P-glycoprotein (P-gp) (IC₅₀ = 5.20 µM) and breast cancer resistance protein (BCRP) (IC₅₀ = 0.83 µM) across Caco-2 and BCRP-overexpressing Madin-Darby canine kidney II cells (MDCKII) cells. This compound also strongly inhibited uptake mediated by organic anion-transporting polypeptide 1B1 (OATP1B1) (IC₅₀ = 0.70 µM) and OATP1B3 (IC₅₀ = 3.95 µM) in OATP1B-overexpressing HEK cells. In addition to its inhibitory effect on these drug transporters, rhinacanthin-C significantly inhibited multiple human CYP isoforms including CYP2C8 (IC₅₀ = 4.56 µM), 2C9 (IC₅₀ = 1.52 µM), 2C19 (IC₅₀ = 28.40 µM), and 3A4/5 (IC₅₀ = 53 µM for midazolam and IC₅₀ = 81.20 µM for testosterone), but not CYP1A2, 2A6, 2B6, 2D6, and 2E1. These results strongly support a high propensity for rhinacanthin-C as a perpetrator of clinical herb-drug interaction via inhibiting various influx and efflux drug transporters (i.e., P-gp, BCRP, OATP1B1, and OATP1B3) and CYP isoforms (i.e., CYP2C8, CYP2C9, and CYP2C19). Thus, the potential for significant pharmacokinetic herb-drug interaction should be addressed when herbal products containing rhinacanthin-C are to be used in conjunction with other prescription drugs.

Protein-protein interactions of drug uptake transporters that are important for liver and kidney

Drug uptake transporters are membrane proteins responsible for the trans-membrane transport of endo- and xenobiotics, including numerous drugs. They are important for the uptake of drugs into target tissues or into organs for metabolism and excretion. Many drug uptake transporters have a broad spectrum of structural-independent substrates, which make them vulnerable to drug-drug interactions. Recent studies have shown more and more complex pharmacokinetics involving transporters, and regulatory agencies now require studies to be performed to measure the involvement of transporters in drug development. A better understanding of the factors affecting the expression of transporters is needed. Despite many efforts devoted to the functional characterization of different drug uptake transporters, transporter in vitro to in vivo extrapolations are far from predicting the behavior under physiological conditions. There is an increasing number of uptake transporters demonstrated to form protein-protein interactions or to oligomerize. This raises the possibility that these interactions between or among transporters could help explaining the gap between in vitro and in vivo measurement of drug transporters. In this review, we summarized protein-protein interactions of drug uptake transporters that are important for pharmacokinetics, especially those in the liver and the kidneys.

Tackling drug resistance with efflux pump inhibitors: from bacteria to cancerous cells

Drug resistance is a serious concern in a clinical setting jeopardizing treatment for both infectious agents and cancers alike. The wide-spread emergence of multi-drug resistant (MDR) phenotypes from bacteria to cancerous cells necessitates the need to target resistance mechanisms and prevent the emergence of resistant mutants. Drug efflux seems to be one of the preferred approaches embraced by both microbial and mammalian cells alike, to thwart the action of chemotherapeutic agents thereby leading to a drug resistant phenotype. Relative to microbes, which predominantly employs proton motive force (PMF) powered, Major Facilitator Superfamily (MFS)/Resistance Nodulation and Division (RND) classes of efflux pumps to efflux drugs, cancerous cells preferentially use ATP fuelled ATP binding cassette (ABC) transporters to extrude chemotherapeutic agents. The prevalence, evolutionary characteristics and overlapping functions of ABC transporters have been highlighted in this review. Additionally, we outline the role of ABC pumps in conferring MDR phenotype to both bacteria and cancerous cells and underscore the importance of efflux pump inhibitors (EPI) to mitigate drug resistance. Based on the literature reports and analysis, we reason out feasibility of employing bacteria as a tool to screen for EPI's targeting ABC pumps of cancerous cells.

A comprehensive evaluation of anti-diabetic drugs on nuclear receptor PXR platform

Pregnane & Xenobiotic Receptor (PXR), one of the members of nuclear receptor superfamily, acts as a 'master-regulator' of drug metabolism and disposition machinery (DMD). Activation of PXR enables detoxification and elimination of toxic xenobiotics/endobiotics, and defends our body against chemical insults. On the contrary, PXR activation also imposes a serious concern for drug-drug interactions (DDIs). Such DDIs could either decrease the efficacy or lead to accumulation of co-administered drugs at toxic level. Therefore, it is desirable that during drug development process the small drug molecules are screened on PXR-platform prior to their clinical trial and prevent late stage failures. In view of this, we have selected a group of anti-diabetic drug molecules to examine if the success and potential failure of small molecule modulators can be pre-assessed and judiciously correlated on PXR platform. For this purpose, we have examined the PXR activation potential of the selected anti-diabetic drugs. Subsequent to screening of these anti-diabetic drugs, we elaborated the study further with rosiglitazone and pioglitazone (thiazolidinediones, TZDs) which are oral anti-diabetic formulations and have been in controversy owing to their association with cardiotoxicity and bladder cancer respectively. Our study revealed that some of the selected anti-diabetic drugs possess PXR activation potential, implying that these can up-regulate the expression of CYP3A4, UGT1A1, MDR1 and thereby can be predicted to inflict undesirable consequences.

Physicochemical and pathohistological changes in experimental fibrosarcoma tumors of hamsters treated with metformin and itraconazole

The anticancer effects of metformin (an antihyperglycaemic agent) and itraconazole (an antifungal agent), which are established non-oncologic drugs, were investigated in the present study. The weight, diameter, volume, density, surface, surface to volume ratio and immunohistochemistry of experimental fibrosarcoma tumors were investigated in hamsters treated with metformin and itraconazole. Briefly, the hamsters were injected with BHK-21/C13 cells in order to induce fibrosarcoma, and the animals were treated daily with metformin, itraconazole or a combination of the two drugs. Subsequently, blood samples were obtained for biochemical analyses and the tumors were excised, weighed and measured. The tumor samples were pathohistologically and immunohistochemically assessed for proliferation marker protein Ki-67, hematopoietic progenitor cell antigen CD34, cytochrome c oxidase subunit 4 (COX4), glucose transporter 1 (GLUT1) and inducible nitric oxide synthase (iNOS), and vital organs were toxicologically tested. Ki-67-positivity and cytoplasmic marker (CD34, COX4, GLUT1, iNOS) immunoexpression in the tumor samples were quantified. The results revealed that the combination of metformin and itraconazole significantly altered the physicochemical and pathohistological characteristics of the hamster fibrosarcoma tumors, including absolute and relative weight, volume, density, length, surface area, surface to volume ratio, Ki-67-positivity and the immunoexpression of cytoplasmic markers, without indications of toxicity. Furthermore, metformin with itraconazole demonstrated antiproliferative functions in cervical carcinoma HeLa, colon carcinoma HT-29, lung carcinoma A549 and fibrosarcoma BHK-21/C13 cells, with markedly lower cytotoxicity in the normal fetal lung MRC-5 cells. In conclusion, the administration of metformin in combination with itraconazole may inhibit the growth of fibrosarcoma tumors in vivo and the proliferation of various malignant cell lines in vitro, suggesting that this may be an effective and safe approach as a nontoxic anticancer adjuvant and relapse prevention therapy.

The major effective components in Shengmai Formula interact with sodium taurocholate co-transporting polypeptide

BACKGROUND

Shengmai Formula (SMF) is widely used to treat cardiovascular disease such as chronic heart disease, coronary atherosclerotic heart disease, viral myocarditis, and others. Our previous studies have shown that OATP1B1/1B3 mediates the interactions between ophiopogon D and ginsenoside Rb1/Rd, which are the major active components in SMF. The herb-drug interactions that involve sodium taurocholate co-transporting polypeptide (NTCP) have been drawing increasing amounts of attention.

PURPOSE

The aim of the present study was to investigate the interactions of the major effective components in SMF mediated by NTCP.

METHODS

By using NTCP-overexpressing HEK293T cells and liquid chromatograph-mass spectrometer (LC-MS) analytical methods, we investigated the impact of the four main effective fractions and the 12 main effective components in SMF on NTCP-mediated sodium taurocholate (TCNa) uptake. The interactions of these effective components in SMF mediated by NTCP were further studied.

RESULTS

The main effective fractions, ginseng total saponins (GTS), ophiopogon total saponins (OTS), ophiopogon total flavonoids (OTF), and fructus schisandrae total lignans (STL), all exhibited a certain inhibitory effect on the uptake of TCNa. Among the 12 main effective components, only ginsenoside Rg1, ophiopogon D', and schizandrin A showed inhibition of TCNa uptake, with IC₅₀ values of 50.49 ± 4.24 μM, 6.71 ± 0.70 μM, and 45.80 ± 3.10 μM, respectively. Additionally, we found that ginsenoside Re and schizandrin B could be transported by NTCP-overexpressing HEK293T cells, and that the uptake of ginsenoside Re was significantly inhibited by OTS, OTF, STL, ginsenoside Rg1, ophiopogon D', and schizandrin A. The uptake of schizandrin B was significantly inhibited by GTS, OTS, OTF, and ophiopogon D'.

CONCLUSION

Ginsenoside Rg1, ophiopogon D', and schizandrin A are potential inhibitors of NTCP and may interact with clinical drugs mediated by NTCP. Ginsenoside Re and schizandrin B are also potential substrates of NTCP, and their uptake mediated by NTCP was inhibited by the other components in SMF. The interaction of complex components based on NTCP may be one of the important compatibility mechanisms in SMF.

Xenobiotic Metabolising Enzymes: Impact on Pathologic Conditions, Drug Interactions and Drug Design

Background:

The biotransformation of xenobiotics is a homeostatic defensive response of the body against bioactive invaders. Xenobiotic metabolizing enzymes, important for the metabolism, elimination and detoxification of exogenous agents, are found in most tissues and organs and are distinguished into phase I and phase II enzymes, as well as phase III transporters. The cytochrome P450 superfamily of enzymes plays a major role in the biotransformation of most xenobiotics as well as in the metabolism of important endogenous substrates such as steroids and fatty acids. The activity and the potential toxicity of numerous drugs are strongly influenced by their biotransformation, mainly accomplished by the cytochrome P450 enzymes, one of the most versatile enzyme systems.

Objective:

In this review, considering the importance of drug metabolising enzymes in health and disease, some of our previous research results are presented, which, combined with newer findings, may assist in the elucidation of xenobiotic metabolism and in the development of more efficient drugs.

Conclusion:

Study of drug metabolism is of major importance for the development of drugs and provides insight into the control of human health. This review is an effort towards this direction and may find useful applications in related medical interventions or help in the development of more efficient drugs.

Quantitative Contribution of Six Major Transporters to the Hepatic Uptake of Drugs: "SLC-Phenotyping" Using Primary Human Hepatocytes

Hepatic uptake transporters [solute carriers (SLCs)], including organic anion transporting polypeptide (OATP) 1B1, OATP1B3, OATP2B1, sodium-dependent taurocholate cotransporting polypeptide (NTCP), and organic anion (OAT2) and organic cation (OCT1) transporters, play a key role in determining the systemic and liver exposure of chemically diverse drugs. Here, we established a phenotyping approach to quantify the contribution of the six SLCs, and passive diffusion, to the overall uptake using plated human hepatocytes (PHHs). First, selective inhibitor conditions were identified by screening about 20 inhibitors across the six SLCs using single-transfected human embryonic kidney 293 cells. Data implied rifamycin SV (20 µM) inhibits three OATPs, while rifampicin (5 µM) inhibits OATP1B1/1B3 only. Further, hepatitis B virus myristoylated-preS1 peptide (0.1 µM), quinidine (100 µM), and ketoprofen (100-300 µM) are relatively selective against NTCP, OCT1, and OAT2, respectively. Second, using these inhibitory conditions, the fraction transported (f_t ) by the individual SLCs was characterized for 20 substrates with PHH. Generally, extended clearance classification system class 1A/3A (e.g., warfarin) and 1B/3B compounds (e.g., statins) showed predominant OAT2 and OATP1B1/1B3 contribution, respectively. OCT1-mediated uptake was prominent for class 2/4 compounds (e.g., metformin). Third, in vitro f_t values were corrected using quantitative proteomics data to obtain "scaled f_t " Fourth, in vitro-in vivo extrapolation of the scaled OATP1B1/1B3 f_t was assessed, leveraging statin clinical drug-drug interaction data with rifampicin as the perpetrator. Finally, we outlined a novel stepwise strategy to implement phenotypic characterization of SLC-mediated hepatic uptake for new molecular entities and drugs in a drug discovery and development setting.

Induction of multidrug resistance-associated protein 3 expression by diesel exhaust particle extract in human bronchial epithelial BEAS-2B cells

Diesel exhaust particles (DEPs) are common environmental air pollutants known to impair expression and activity of drug detoxifying proteins, including hepatic ATP-binding cassette (ABC) drug transporters. The present study was designed to determine whether organic DEP extract (DEPe) may also target ABC drug transporters in bronchial cells. DEPe (10 μg/mL) was demonstrated to induce mRNA and protein expression of the multidrug resistance-associated protein (MRP) 3 in cultured bronchial epithelial BEAS-2B cells, whereas mRNA levels of other MRPs, multidrug resistance gene 1 or breast cancer resistance protein were unchanged, reduced or not detected. DEPe also increased MRP3 mRNA expression in normal human bronchial epithelial cells. Inhibition of the aryl hydrocarbon receptor (AhR) pathway by AhR antagonist or AhR silencing, as well as the silencing of nuclear-factor-E2-related factor 2 (Nrf2) repressed DEPe-mediated MRP3 induction. This underlines the implication of the AhR and Nrf2 signaling cascades in DEPe-mediated MRP3 regulation. DEPe was additionally demonstrated to directly inhibit MRP activity in BEAS-2B cells, in a concentration-dependent manner. Taken together, these data indicate that DEPs may impair expression and activity of MRPs, notably MRP3, in human bronchial cells, which may have consequences in terms of lung barrier and toxicity for humans exposed to diesel pollution.

Clinical Aspects of Transporter-Mediated Drug-Drug Interactions

Drug transporters play an essential role in disposition and effects of multiple drugs. Plasma concentrations of the victim drug can be modified by drug-drug interactions occurring in enterocytes (e.g., P-glycoprotein), hepatocytes (e.g., organic anion-transporting polypeptide 1B1 (OATP1B1)), and/or renal proximal tubular cells (e.g., organic cation transporter 2 (OCT2)/multidrug and toxin extrusion 1 and 2-K (MATE1/MATE2-K)). In addition, transporter-mediated drug-drug interactions can cause altered local tissue concentrations and possibly altered effects/toxicity (e.g., in liver and kidneys). During drug development, there is now an intensive in vitro screening of new molecular entities as transporter substrates and inhibitors, followed if necessary by drug-drug interaction studies in healthy volunteers. Nevertheless, there are still unresolved issues, which will also be discussed in this review article (e.g., the clinical significance of transporter-mediated drug-drug interactions of particular relevance to the elderly who are prescribed multiple drugs, with additional impaired liver or kidney function, and the extent to which medication safety in real life could be improved by a reduction of those interactions).

Modulation of Fexofenadine Pharmacokinetics by Osimertinib in Patients With Advanced EGFR-Mutated Non-Small Cell Lung Cancer

Osimertinib is a potent, third-generation, irreversible, central nervous system active epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) that selectively inhibits EGFR-TKI sensitizing and EGFR T790M resistance mutations. It is approved for first-line treatment of patients with advanced non-small cell lung cancer (NSCLC) whose tumors have EGFR exon 19 deletions or exon 21 L858R mutations, and for patients with T790M-positive advanced NSCLC whose disease has progressed on or after EGFR-TKI therapy. This study investigated the pharmacokinetics (PK) of fexofenadine (P-glycoprotein substrate) following single- and multiple-dose osimertinib in patients with advanced NSCLC who have progressed on prior EGFR-TKI therapy. This open-label, phase 1 study (NCT02908750) comprised the PK phase and continued access phase. The former comprised 2 distinct periods with a 3- to 7-day washout: treatment period 1 (n = 24, fexofenadine 120 mg, day 1) and treatment period 2 (fexofenadine 120 mg + osimertinib 80 mg single dose on days 1 and 39 and osimertinib 80 mg once daily from days 4 to 41). Patients could continue osimertinib 80 mg once daily based on investigator's discretion in the continued access phase. Fexofenadine area under the plasma concentration-time curve and maximum concentration increased by 56% (90% confidence interval [CI], 35.4-78.6) and 76% (90%CI, 49.3-108.3) following coadministration with osimertinib single dose, and by 27% (90%CI, 11.2-45.8) and 25% (90%CI, 5.6-48.1) when given with osimertinib at steady state, respectively. Following osimertinib coadministration, median fexofenadine time to maximum concentration increased by approximately 30 minutes compared with time to maximum concentration following fexofenadine alone. No new osimertinib safety findings were observed. The increase in fexofenadine exposure following osimertinib coadministration shows osimertinib as a weak P-glycoprotein inhibitor.

Physiologically-Based Pharmacokinetic Modeling for Drug-Drug Interactions of Procainamide and N-Acetylprocainamide with Cimetidine, an Inhibitor of rOCT2 and rMATE1, in Rats

Previous observations demonstrated that cimetidine decreased the clearance of procainamide (PA) and/or N-acetylprocainamide (NAPA; the primary metabolite of PA) resulting in the increased systemic exposure and the decrease of urinary excretion. Despite an abundance of in vitro and in vivo data regarding pharmacokinetic interactions between PA/NAPA and cimetidine, however, a mechanistic approach to elucidate these interactions has not been reported yet. The primary objective of this study was to construct a physiological model that describes pharmacokinetic interactions between PA/NAPA and cimetidine, an inhibitor of rat organic cation transporter 2 (rOCT2) and rat multidrug and toxin extrusion proteins (rMATE1), by performing extensive in vivo and in vitro pharmacokinetic studies for PA and NAPA performed in the absence or presence of cimetidine in rats. When a single intravenous injection of PA HCl (10 mg/kg) was administered to rats, co-administration of cimetidine (100 mg/kg) significantly increased systemic exposure and decreased the systemic (CL) and renal (CL_R) clearance of PA, and reduced its tissue distribution. Similarly, cimetidine significantly decreased the CL_R of NAPA formed by the metabolism of PA and increased the AUC of NAPA. Considering that these drugs could share similar renal secretory pathways (e.g., via rOCT2 and rMATE1), a physiologically-based pharmacokinetic (PBPK) model incorporating semi-mechanistic kidney compartments was devised to predict drug-drug interactions (DDIs). Using our proposed PBPK model, DDIs between PA/NAPA and cimetidine were successfully predicted for the plasma concentrations and urinary excretion profiles of PA and NAPA observed in rats. Moreover, sensitivity analyses of the pharmacokinetics of PA and NAPA showed the inhibitory effects of cimetidine via rMATE1 were probably important for the renal elimination of PA and NAPA in rats. The proposed PBPK model may be useful for understanding the mechanisms of interactions between PA/NAPA and cimetidine in vivo.

Organic Anion Transporting Polypeptides: Emerging Roles in Cancer Pharmacology

The organic anion transporting polypeptides (OATPs) are a superfamily of drug transporters involved in the uptake and disposition of a wide array of structurally divergent endogenous and exogenous substrates, including steroid hormones, bile acids, and commonly used drugs, such as anti-infectives, antihypertensives, and cholesterol lowering agents. In the past decade, OATPs, primarily OATP1A2, OATP1B1, and OATP1B3, have emerged as potential mediators of chemotherapy disposition, including drugs such as methotrexate, doxorubicin, paclitaxel, docetaxel, irinotecan and its important metabolite 7-ethyl-10-hydroxycamptothecin, and certain tyrosine kinase inhibitors. Furthermore, OATP family members are polymorphic and numerous studies have shown OATP variants to have differential uptake, disposition, and/or pharmacokinetics of numerous drug substrates with important implications for interindividual differences in efficacy and toxicity. Additionally, certain OATPs have been found to be overexpressed in a variety of human solid tumors, including breast, liver, colon, pancreatic, and ovarian cancers, suggesting potential roles for OATPs in tumor development and progression and as novel targets for cancer therapy. This review focuses on the emerging roles for selected OATPs in cancer pharmacology, including preclinical and clinical studies suggesting roles in chemotherapy disposition, the pharmacogenetics of OATPs in cancer therapy, and OATP overexpression in various tumor tissues with implications for OATPs as therapeutic targets.

Interplay of the Organic Cation Transporters OCT1 and OCT2 with the Apically Localized Export Protein MATE1 for the Polarized Transport of Trospium

The anticholinergic drug trospium is secreted into urine and, to a smaller extent, into bile. Chemically, it is an organic cation, and it is a substrate of the uptake transporters OCT1 and OCT2 as well as for the export proteins MATE1 and MATE2-K as determined in uptake studies using HEK293 cells. So far, neither MATE-mediated export nor the interplay of OCT-mediated uptake and MATE-mediated export have been investigated. Therefore, we used polarized monolayers of single- and double-transfected MDCKII cells (MDCK-OCT1, MDCK-OCT2, MDCK-MATE1, MDCK-OCT1-MATE1, and MDCK-OCT2-MATE1) and the respective control cells (MDCK-Co) for transcellular transport assays. We demonstrate that the transcellular, basal-to-apical transport of trospium is significantly higher in all cell lines compared to control cells over nearly the complete concentration range tested. The transcellular transport mediated by double-transfected MDCK-OCT1-MATE1 and MDCK-OCT2-MATE1 exceeded that in the single-transfected cells (MDCK-OCT1-MATE1 vs MDCK-OCT1: 2.2-fold; MDCK-OCT1-MATE1 vs MDCK-MATE1: 1.7-fold; MDCK-OCT2-MATE1 vs MDCK-OCT2: 6.1-fold; MDCK-OCT2-MATE1 vs MDCK-MATE1: 1.8-fold at a trospium concentration of 1.0 μM; p < 0.001 each). Thus, we show that MATE1 does not only mediate the uptake of trospium into HEK293 cells but also the efflux of trospium out of polarized MDCKII-cells. Furthermore, our results indicate that OCT1 or OCT2 as uptake transporters and MATE1 as an export protein contribute to the transcellular transport of trospium at concentrations normally reached during trospium therapy. These data suggest that both, OCT-mediated uptake as well as MATE1-mediated efflux may contribute to trospium renal and biliary elimination.

Protein Abundance of Clinically Relevant Drug Transporters in the Human Liver and Intestine: A Comparative Analysis in Paired Tissue Specimens

Bioavailability of orally administered drugs is partly determined by function of drug transporters in the liver and intestine. Therefore, we explored adenosine triphosphate-binding cassette (ABC) and solute carriers family transporters expression (quantitative polymerase chain reaction) and protein abundance (liquid chromatography tandem mass spectrometry (LC-MS/MS)) in human liver and duodenum, jejunum, ileum, and colon in paired tissue specimens from nine organ donors. The transporter proteins were detected in the liver (permeability-glycoprotein (P-gp), multidrug resistance protein (MRP)2, MRP3, breast cancer resistance protein (BCRP), organic anion-transporting polypeptide (OATP)1B1, OATP1B3, OATP2B1, organic cation transporter (OCT)1, OCT3, organic anion transporter 2, Na+-taurocholate cotransporting polypeptide, monocarboxylate transporter (MCT)1, and multidrug and toxin extrusion 1) and the intestine (P-gp, multidrug-resistance protein (MRP)2, MRP3, MRP4, BCRP, OATP2B1, OCT1, apical sodium-bile acid transporter (only ileum), MCT1, and peptide transporter (PEPT1)). Significantly higher hepatic gene expression and protein abundance of ABCC2/MRP2, SLC22A1/OCT1, and SLCO2B1/OATP2B1 were found, as compared to all intestinal segments. No correlations between hepatic and small intestinal protein levels were observed. These observations provide a description of drug transporters distribution without the impact of interindividual variability bias and may help in construction of superior physiologically based pharmacokinetic and humanized animal models.

Clinically relevant drug interactions with multikinase inhibitors: a review

Multikinase inhibitors (MKIs), including the tyrosine kinase inhibitors (TKIs), have rapidly become an established factor in daily (hemato)-oncology practice. Although the oral route of administration offers improved flexibility and convenience for the patient, challenges arise in the use of MKIs. As MKIs are prescribed extensively, patients are at increased risk for (severe) drug–drug interactions (DDIs). As a result of these DDIs, plasma pharmacokinetics of MKIs may vary significantly, thereby leading to high interpatient variability and subsequent risk for increased toxicity or a diminished therapeutic outcome. Most clinically relevant DDIs with MKIs concern altered absorption and metabolism. The absorption of MKIs may be decreased by concomitant use of gastric acid-suppressive agents (e.g. proton pump inhibitors) as many kinase inhibitors show pH-dependent solubility. In addition, DDIs concerning drug (uptake and efflux) transporters may be of significant clinical relevance during MKI therapy. Furthermore, since many MKIs are substrates for cytochrome P450 isoenzymes (CYPs), induction or inhibition with strong CYP inhibitors or inducers may lead to significant alterations in MKI exposure. In conclusion, DDIs are of major concern during MKI therapy and need to be monitored closely in clinical practice. Based on the current knowledge and available literature, practical recommendations for management of these DDIs in clinical practice are presented in this review.

Establishment of renal proximal tubule cell lines derived from the kidney of p53 knockout mice

The human cell line HK-2 is most commonly used as a model of renal proximal tubular epithelial cells (PTECs) for various studies despite the absence or low expression of transporters characteristic of parental PTECs. In an effort to develop reliable PTEC models, several human cell lines have been newly established over the last decade. In contrast, reliable mouse PTEC models are still unavailable. In this study, we established immortalized renal cortex tubule cell lines derived from p53 knockout mice and evaluated various PTEC characteristics toward the development of reliable mouse PTEC models. Here, we focus on MuRTE61, one of 13 newly established clonal cell lines. Albumin uptake in MuRTE61 cells was verified by incubation with fluorescent dye-labeled albumin. RT-PCR confirmed the expression of efflux transporter genes characteristic of PTECs in the MuRTE61 cells. MuRTE61 cells exhibited high sensitivity to treatment with cisplatin, a nephrotoxic agent, accompanied by upregulated expression of the uptake transporter Slc22a2 gene. Furthermore, MuRTE61 cells consistently formed spheroids with a lumen and apicobasal polarity in three-dimensional Matrigel cultures. Apical brush border microvilli were also observed in the spheroids by transmission electron microscopy. These data validate that MuRTE61 can be characterized as a reliable mouse PTEC line. In future, detailed analysis of reliable mouse and human PTEC lines will provide an accurate extrapolation of results of experiments using mice and humans, and may help resolve apparent inconsistencies between mouse and human nephrotoxicity.

No Effect of Plazomicin on the Pharmacokinetics of Metformin in Healthy Subjects

Plazomicin is an aminoglycoside that was engineered to overcome aminoglycoside-modifying enzymes, which are the most common aminoglycoside resistance mechanism in Enterobacteriaceae. Because plazomicin is predominantly eliminated via renal pathways, an in vitro study was conducted to determine whether plazomicin inhibits the organic cation transporter 2 (OCT2) and the multidrug and toxin extrusion (MATE1 and MATE2-K) transporters, using metformin as a probe substrate. Plazomicin inhibited OCT2, MATE1, and MATE2-K transporters with half-maximal inhibition of the transporter values of 5120, 1300, and 338 µg/mL, respectively. To determine whether this in vitro inhibition translates in vivo, an open-label, randomized, 2-period, 2-treatment crossover study (NCT03270553) was carried out in healthy subjects (N = 16), who received a single oral dose of metformin 850 mg alone and in combination with a single intravenous infusion of plazomicin 15 mg/kg. Geometric least-squares mean ratios of the test treatment (combination) vs the reference treatment (metformin alone) and 90% confidence intervals were within the equivalence interval of 80% to 125% (peak plasma concentration, 104.5 [95.1-114.9]; area under the plasma concentration-time curve from time zero to time of last quantifiable concentration, 103.7 [93.5-115.0]; area under the plasma concentration-time curve from time zero to infinity, 104.0 [94.2-114.8]). The results demonstrate that there is no clinically significant drug-drug interaction resulting from coadministration of single doses of intravenous plazomicin 15 mg/kg and oral metformin 850 mg in healthy subjects. Coadministration of plazomicin and metformin was well tolerated in healthy subjects.

Capturing the applicability of in vitro-in silico membrane transporter data in chemical risk assessment and biomedical research

Costs, scientific and ethical concerns related to animal tests for regulatory decision-making have stimulated the development of alternative methods. When applying alternative approaches, kinetics have been identified as a key element to consider. Membrane transporters affect the kinetic processes of absorption, distribution, metabolism and excretion (ADME) of various compounds, such as drugs or environmental chemicals. Therefore, pharmaceutical scientists have intensively studied transporters impacting drug efficacy and safety. Besides pharmacokinetics, transporters are considered as major determinant of toxicokinetics, potentially representing an essential piece of information in chemical risk assessment. To capture the applicability of transporter data for kinetic-based risk assessment in non-pharmaceutical sectors, the EU Reference Laboratory for Alternatives to Animal Testing (EURL ECVAM) created a survey with a view of identifying the improvements needed when using in vitro and in silico methods. Seventy-three participants, from different sectors and with various kinds of expertise, completed the survey. The results revealed that transporters are investigated mainly during drug development, but also for risk assessment purposes of food and feed contaminants, industrial chemicals, cosmetics, nanomaterials and in the context of environmental toxicology, by applying both in vitro and in silico tools. However, to rely only on alternative methods for chemical risk assessment, it is critical that the data generated by in vitro and in silico methods are scientific integer, reproducible and of high quality so that they are trusted by decision makers and used by industry. In line, the respondents identified various challenges related to the interpretation and use of transporter data from non-animal methods. Overall, it was determined that a combined mechanistically-anchored in vitro-in silico approach, validated against available human data, would gain confidence in using transporter data within an animal-free risk assessment paradigm. Finally, respondents involved primarily in fundamental research expressed lower confidence in non-animal studies to unravel complex transporter mechanisms.

Biomarkers for In Vivo Assessment of Transporter Function

Drug-drug interactions are a major concern not only during clinical practice, but also in drug development. Due to limitations of in vitro-in vivo predictions of transporter-mediated drug-drug interactions, multiple clinical Phase I drug-drug interaction studies may become necessary for a new molecular entity to assess potential drug interaction liabilities. This is a resource-intensive process and exposes study participants, who frequently are healthy volunteers without benefit from study treatment, to the potential risks of a new drug in development. Therefore, there is currently a major interest in new approaches for better prediction of transporter-mediated drug-drug interactions. In particular, researchers in the field attempt to identify endogenous compounds as biomarkers for transporter function, such as hexadecanedioate, tetradecanedioate, coproporphyrins I and III, or glycochenodeoxycholate sulfate for hepatic uptake via organic anion transporting polypeptide 1B or N¹-methylnicotinamide for multidrug and toxin extrusion protein-mediated renal secretion. We summarize in this review the currently proposed biomarkers and potential limitations of the substances identified to date. Moreover, we suggest criteria based on current experiences, which may be used to assess the suitability of a biomarker for transporter function. Finally, further alternatives and supplemental approaches to classic drug-drug interaction studies are discussed.

The regulation of drug-metabolizing enzymes and membrane transporters by inflammation: Evidences in inflammatory diseases and age-related disorders

Drug-metabolizing enzymes (DMEs) and membrane transporters play important roles in the absorption, distribution, metabolism, and excretion processes that determine the pharmacokinetics of drugs. Inflammation has been shown to regulate the expression and function of these drug-processing proteins. Given that inflammation is a common feature of many diseases, in this review, the general mechanisms for inflammation-mediated regulation of DMEs and transporters are described. Also, evidences regarding the aberrant expression of these drug-processing proteins in several inflammatory diseases and age-related disorders are provided.

Dose adjustment in orphan disease populations: the quest to fulfill the requirements of physiologically based pharmacokinetics

INTRODUCTION

While the media is engaged and fascinated by the idea of 'Precision Medicine', the nuances related to 'Precision Dosing' seem to be largely ignored. Assuming the 'right drug' is selected, clinicians still need to decide on the 'right dose' for individuals. Ideally, optimal dosing should be studied in clinical trials; however, many drugs on the market lack evidence-based dosing recommendations, and small groups of patients (orphan disease populations) are dependent on local guidance and clinician experience to determine drug dosage adjustments. Areas Covered: This report explores the current understanding of dosing adjustment in special populations and examines the requirements for developing 'in silico' models for pediatric, elderly and pregnant patients. The report also highlights current use of modeling to provide evidence-based recommendations for drug labeling in the absence of complete clinical trials in orphan disease populations. Expert Opinion: Physiologically based pharmacokinetics (PBPK) is an attractive prospect for determining the best drug dosage adjustments in special populations. However, it is not sufficient for individualized, or even stratified dosing, unless the systems (drug-independent) data required to build robust PBPK models are obtained. Such models are not a substitute for clinical trials, but they are an alternative to undocumented and inconsistent guesswork.

Bioengineering Organs for Blood Detoxification

For patients with severe kidney or liver failure the best solution is currently organ transplantation. However, not all patients are eligible for transplantation and due to limited organ availability, most patients are currently treated with therapies using artificial kidney and artificial liver devices. These therapies, despite their relative success in preserving the patients' life, have important limitations since they can only replace part of the natural kidney or liver functions. As blood detoxification (and other functions) in these highly perfused organs is achieved by specialized cells, it seems relevant to review the approaches leading to bioengineered organs fulfilling most of the native organ functions. There, the culture of cells of specific phenotypes on adapted scaffolds that can be perfused takes place. In this review paper, first the functions of kidney and liver organs are briefly described. Then artificial kidney/liver devices, bioartificial kidney devices, and bioartificial liver devices are focused on, as well as biohybrid constructs obtained by decellularization and recellularization of animal organs. For all organs, a thorough overview of the literature is given and the perspectives for their application in the clinic are discussed.

Baicalein Enhances the Oral Bioavailability and Hepatoprotective Effects of Silybin Through the Inhibition of Efflux Transporters BCRP and MRP2

Although hepatoprotective properties of silybin are well documented, the clinical therapeutic efficacy is limited by its low bioavailability due to absorption rates, extensive phase II metabolism, and biliary excretion. As our previous study indicated that metabolic enzymes may have limited effects on the pharmacokinetic (PK) behavior of silymarin, here, we intended to increase the oral bioavailability and bio-efficacy of silybin through the inhibition of active efflux. In Caco-2 and transfected MDCKII cell models, flavone baicalein significantly inhibited the efflux of silybin as a BCRP and MRP2 inhibitor. In addition, baicalein reduced the biliary excretion index (BEI) and biliary clearance of silybin conjugates in the sandwich-cultured rat hepatocyte (SCH) model, indicating the inhibition of baicalein in biliary excretion of conjugated silybin metabolites. PK study demonstrated that baicalein significantly increased the area under the curve (AUC) and C_max of silybin and its conjugates, suggesting enhanced absorption in vivo. Moreover, coadministration of silybin with baicalein boosted the liver protective, antioxidant, and anti-inflammatory effects of silybin in the carbon tetrachloride (CCl₄)-induced liver injury model in comparison with silybin given alone. In summary, efflux transporters play a critical role in the low bioavailability of silybin, while inhibition of breast cancer resistance protein (BCRP) and multi-drug resistance protein 2 (MRP2) by baicalein can significantly increase the absorption and bio-efficacy of silybin, which provides a new combination therapeutic approach for the treatment of chronic liver diseases.

Irinotecan Alters the Disposition of Morphine Via Inhibition of Organic Cation Transporter 1 (OCT1) and 2 (OCT2)

PURPOSE

The organic cation transporters (OCTs) and multidrug and toxin extrusions (MATEs) together are regarded as an organic cation transport system critical to the disposition and response of many organic cationic drugs. Patient response to the analgesic morphine, a characterized substrate for human OCT1, is highly variable. This study was aimed to examine whether there is any organic cation transporter-mediated drug and drug interaction (DDI) between morphine and commonly co-administrated drugs.

METHODS

The uptake of morphine and its inhibition by six drugs which are commonly co-administered with morphine in the clinic were assessed in human embryonic kidney 293 (HEK293) cells stably expressing OCT1, OCT2 and MATE1. The in vivo interaction between morphine and the select irinotecan was determined by comparing the disposition of morphine in the absence versus presence of irinotecan treatment in mice.

RESULTS

The uptake of morphine in the stable HEK293 cells expressing human OCT1 and OCT2 was significantly increased by 3.56 and 3.04 fold, respectively, than that in the control cells, with no significant uptake increase in the cells expressing human MATE1. All of the six drugs examined, including amitriptyline, fluoxetine, imipramine, irinotecan, ondansetron, and verapamil, were inhibitors of OCT1/2-mediated morphine uptake. The select irinotecan significantly increased the plasma concentrations and decreased hepatic and renal accumulation of morphine in mice.

CONCLUSIONS

Morphine is a substrate of OCT1 and OCT2. Clinician should be aware that the disposition of and thus the response to morphine may be altered by co-administration of an OCT1/2 inhibitor, such as irinotecan.

Effect of Rifampicin on the Distribution of [11C]Erlotinib to the Liver, a Translational PET Study in Humans and in Mice

Organic anion-transporting polypeptides (OATPs) mediate the uptake of various drugs from blood into the liver in the basolateral membrane of hepatocytes. Positron emission tomography (PET) is a potentially powerful tool to assess the activity of hepatic OATPs in vivo, but its utility critically depends on the availability of transporter-selective probe substrates. We have shown before that among the three OATPs expressed in hepatocytes (OATP1B1, OATP1B3, and OATP2B1), [¹¹C]erlotinib is selectively transported by OATP2B1. In contrast to OATP1B1 and OATP1B3, OATP2B1 has not been thoroughly explored yet, and no specific probe substrates are currently available. To assess if the prototypical OATP inhibitor rifampicin can inhibit liver uptake of [¹¹C]erlotinib in vivo, we performed [¹¹C]erlotinib PET scans in six healthy volunteers without and with intravenous pretreatment with rifampicin (600 mg). In addition, FVB mice underwent [¹¹C]erlotinib PET scans without and with concurrent intravenous infusion of high-dose rifampicin (100 mg/kg). Rifampicin caused a moderate reduction in the liver distribution of [¹¹C]erlotinib in humans, while a more pronounced effect of rifampicin was observed in mice, in which rifampicin plasma concentrations were higher than in humans. In vitro uptake experiments in an OATP2B1-overexpressing cell line indicated that rifampicin inhibited OATP2B1 transport of [¹¹C]erlotinib in a concentration-dependent manner with a half-maximum inhibitory concentration of 72.0 ± 1.4 μM. Our results suggest that rifampicin-inhibitable uptake transporter(s) contributed to the liver distribution of [¹¹C]erlotinib in humans and mice and that [¹¹C]erlotinib PET in combination with rifampicin may be used to measure the activity of this/these uptake transporter(s) in vivo. Furthermore, our data suggest that a standard clinical dose of rifampicin may exert in vivo a moderate inhibitory effect on hepatic OATP2B1.

Loop diuretics decrease the renal elimination rate and increase the plasma levels of trimethylamine-N-oxide

AIMS

Trimethylamine-N-oxide (TMAO) is a novel cardiovascular risk marker. We explored the association of commonly used cardiovascular medications with TMAO levels in patients and validated the identified associations in mice.

METHODS

Detailed history of drug treatment was recorded in 300 patients with cardiovascular disease without diabetes in an observational, cross-sectional study. Animal study was performed in CD1 mice.

RESULTS

Median plasma TMAO (interquartile range) level was 2.144 (1.570-3.104) μmol l^-1 . Among nine cardiovascular drug groups, the use of loop diuretics (0.510 ± 0.296 in users vs. 0.336 ± 0.272 in nonusers, P = 0.008) and mineralocorticoid receptor antagonists (0.482 ± 0.293 in users vs. 0.334 ± 0.272 in nonusers, P = 0.007) was associated with increased log-TMAO. Acute concomitant administration of furosemide or torasemide with TMAO in mice significantly influenced TMAO pharmacokinetic profile and almost doubled the plasma TMAO area under the curve. Furosemide decreased the TMAO excretion rate by 1.9-fold during the first 30 min after administration and increased TMAO concentrations in kidney, heart and liver, suggesting the interaction of furosemide and TMAO with efflux transporters. The concentrations of TMAO in blood plasma after the administration of the organic anion transporter inhibitor probenecid were not different from those of the control group, suggesting an effect not mediated by organic anion transporters.

CONCLUSIONS

Loop diuretics increased plasma TMAO concentration by decreasing its urinary excretion rate. Loop diuretic use should be considered a potential confounder in TMAO studies.

Impact of rifampicin-inhibitable transport on the liver distribution and tissue kinetics of erlotinib assessed with PET imaging in rats

Background

Erlotinib is an epidermal growth factor receptor (EGFR)-targeting tyrosine kinase inhibitor approved for treatment of non-small cell lung cancer. The wide inter-individual pharmacokinetic (PK) variability of erlotinib may impact treatment outcome and/or toxicity. Recent in vivo studies reported a nonlinear uptake transport of erlotinib into the liver, suggesting carrier-mediated system(s) to mediate its hepatobiliary clearance. Erlotinib has been identified in vitro as a substrate of organic anion-transporting polypeptide (OATP) transporters which expression does not restrict to hepatocytes and may impact the tissue uptake of erlotinib in vivo.

Results

The impact of rifampicin (40 mg/kg), a potent OATP inhibitor, on the liver uptake and exposure to tissues of ¹¹C-erlotinib was investigated in rats (4 animals per group) using positron emission tomography (PET) imaging. Tissue pharmacokinetics (PK) and corresponding exposure (area under the curve, AUC) were assessed in the liver, kidney cortex, abdominal aorta (blood pool) and the lungs. The plasma PK of parent ¹¹C-erlotinib was also measured using arterial blood sampling to estimate the transfer rate constant (k_uptake) of ¹¹C-erlotinib from plasma into different tissues.

PET images unveiled the predominant distribution of ¹¹C-erlotinib-associated radioactivity to the liver, which gradually moved to the intestine, thus highlighting hepatobiliary clearance. ¹¹C-erlotinib also accumulated in the kidney cortex. Rifampicin did not impact AUC_aorta but reduced k_{uptake, liver} (p < 0.001), causing a significant 27.3% decrease in liver exposure (p < 0.001). Moreover, a significant decrease in k_{uptake, kidney} with a concomitant decrease in AUC_kidney (− 30.4%, p < 0.001) were observed. Rifampicin neither affected k_{uptake, lung} nor AUC_lung.

Conclusions

Our results suggest that ¹¹C-erlotinib is an in vivo substrate of rOATP transporters expressed in the liver and possibly of rifampicin-inhibitable transporter(s) in the kidneys. Decreased ¹¹C-erlotinib uptake by elimination organs did not translate into changes in systemic exposure and exposure to the lungs, which are a target tissue for erlotinib therapy.

Effects of Metformin and Furosemide on Rosuvastatin Pharmacokinetics in Healthy Volunteers: Implications for Their Use as Probe Drugs in a Transporter Cocktail

Background

In a recently described probe drug cocktail for clinically relevant drug transporters containing digoxin, furosemide, metformin and rosuvastatin, mutual interactions were essentially absent except for increases in the systemic exposure of rosuvastatin. To optimize the cocktail, we further examined the dose dependence of the effects of metformin and furosemide on rosuvastatin pharmacokinetics.

Methods

This was a randomized, open label, single center, six-treatment, six-period, six-sequence crossover trial. Eighteen healthy male subjects received 10 mg rosuvastatin as reference treatment and, as test treatments, 10 mg rosuvastatin combined with 10, 50 or 500 mg metformin (T1, T2 and T3) or with 1 or 5 mg furosemide (T4 and T5). Primary pharmacokinetic endpoints were rosuvastatin C_max (maximum plasma concentration) and AUC_0–tz (area under the plasma concentration–time curve from time zero to the last quantifiable concentration).

Results

The relative bioavailability of rosuvastatin was essentially unchanged when administered with metformin in T1 and T2, but in T3 it increased to 152% for AUC_0–tz (90% CI 135–171%) and 154% for C_max (90% CI 132–180%). Coadministration with furosemide did not change rosuvastatin relative bioavailability in T4, but in T5 it increased slightly to 116% for AUC_0–tz (90% CI 102–132%) and 118% for C_max (90% CI 98–142%).

Conclusion

The increased systemic exposure of rosuvastatin when administered as part of the proposed transporter cocktail is most likely attributable to metformin and only to a minor degree to furosemide. Reduction of the doses of metformin and furosemide is expected to eliminate the previously described interaction.

EudraCT no. 2015-003052-46, ClinicalTrials.gov identifier NCT02574845.