Transporters In Drug-drug Interactions Research Articles

Innovative Approaches to Optimize Clinical Transporter Drug-Drug Interaction Studies.

Of the 450 cell membrane transporters responsible for shuttling substrates, nutrients, hormones, neurotransmitters, antioxidants, and signaling molecules, approximately nine are associated with clinically relevant drug-drug interactions (DDIs) due to their role in drug and metabolite transport. Therefore, a clinical study evaluating potential transporter DDIs is recommended if an investigational product is intestinally absorbed, undergoes renal or hepatic elimination, or is suspected to either be a transporter substrate or perpetrator. However, many of the transporter substrates and inhibitors administered during a DDI study also affect cytochrome P450 (CYP) activity, which can complicate data interpretation. To overcome these challenges, the assessment of endogenous biomarkers can help elucidate the mechanism of complex DDIs when multiple transporters or CYPs may be involved. This perspective article will highlight how creative study designs are currently being utilized to address complex transporter DDIs and the role of physiology-based -pharmacokinetic (PBPK) models can play.

Involvement of Transporters in Intestinal Drug-Drug Interactions of Oral Targeted Anticancer Drugs Assessed by Changes in Drug Absorption Time.

(1) Background: Oral targeted anticancer drugs are victims of presystemic pharmacokinetic drug-drug interactions (DDI). Identification of the nature of these DDIs, i.e., enzyme-based or/and transporter-based, is challenging, since most of these drugs are substrates of intestinal and/or hepatic cytochrome P-450 enzymes and of intestinal membrane transporters. (2) Methods: Variations in mean absorption time (MAT) between DDIs and control period (MAT ratios < 0.77 or >1.30) have been proposed to implicate transporters in DDIs at the intestinal level. This methodology has been applied to a large set of oral targeted anticancer drugs (n = 54, involved in 77 DDI studies), from DDI studies available either in the international literature and/or in publicly accessible FDA files. (3) Results: Significant variations in MAT were evidenced in 33 DDI studies, 12 of which could be explained by modulation of an efflux transporter. In 21 DDI studies, modulation of efflux transporters could not explain the MAT variation, suggesting a possible relevant role of influx transporters in the intestinal absorption. (4) Conclusions: This methodology allows one to suggest the involvement of intestinal transporters in DDIs, and should be used in conjunction with in vitro methodologies to help understanding the origin of DDIs.

Development of best practices in physiologically based pharmacokinetic modeling to support clinical pharmacology regulatory decision-making-A workshop summary.

Development of best practices in physiologically based pharmacokinetic modeling to support clinical pharmacology regulatory decision-making-A workshop summary.

Contribution of Uptake and Efflux Transporters to Oral Pharmacokinetics of Furosemide.

Furosemide is a widely used diuretic for treating excessive fluid accumulation caused by disease conditions like heart failure and liver cirrhosis. Furosemide tablet formulation exhibits variable pharmacokinetics (PK) with bioavailability ranging from 10 to almost 100%. To explain the variable absorption, we integrated the physicochemical, in vitro dissolution, permeability, distribution, and the elimination parameters of furosemide in a physiologically-based pharmacokinetic (PBPK) model. Although the intravenous PBPK model reasonably described the observed in vivo PK data, the reported low passive permeability failed to capture the observed data after oral administration. To mechanistically justify this discrepancy, we hypothesized that transporter-mediated uptake contributes to the oral absorption of furosemide in conjunction with passive permeability. Our in vitro results confirmed that furosemide is a substrate of intestinal breast cancer resistance protein (BCRP), multidrug resistance-associated protein 4 (MRP4), and organic anion transporting polypeptide 2B1 (OATP2B1), but it is not a substrate of P-glycoprotein (P-gp) and MRP2. We then estimated the net transporter-mediated intestinal uptake and integrated it into the PBPK model under both fasting and fed conditions. Our in vitro data and PBPK model suggest that the absorption of furosemide is permeability-limited, and OATP2B1 and MRP4 are important for its permeability across intestinal membrane. Further, as furosemide has been proposed as a probe substrate of renal organic anion transporters (OATs) for assessing clinical drug–drug interactions (DDIs) during drug development, the confounding effects of intestinal transporters identified in this study on furosemide PK should be considered in the clinical transporter DDI studies.

The Necessity of Using Changes in Absorption Time to Implicate Intestinal Transporter Involvement in Oral Drug-Drug Interactions.

In drug discovery and development, it is of high interest to characterize the potential for intestinal drug-drug interactions to alter bioavailability of a victim drug. For drugs that are substrates of both intestinal transporters and enzymes, estimating the relative contribution of each process has proved challenging, especially since the susceptibility of drug to uptake or efflux transporters in vitro does not always translate to clinically significant in vivo involvement. Here we introduce a powerful methodology to implicate intestinal transporters in drug-drug interactions based on the theory that clinically relevant intestinal transporter interactions will result in altered rate of absorption of victim drugs. We present exemplary clinical drug-drug interaction studies that utilize well-characterized clinical substrates and perpetrators to demonstrate how mean absorption time (MAT) and time to maximum concentration (tmax) are expected to change (or remain unchanged) when either intestinal transporters or metabolic enzymes were/are altered. Apixaban was also selected to demonstrate the utility of the methodology, as the purported involvement of both intestinal enzymes and transporters has been suggested in its FDA package insert. Acute inhibition of gut efflux transporters resulted in decreased MAT and tmaxvalues, induction increased these values, while inhibition of intestinal metabolic enzymes did not result in altered MAT or tmax. Involvement of intestinal efflux transporters in apixaban disposition is unlikely. Utilization of this simple but powerful methodology to implicate intestinal transporter involvement will have significant impact on how drug-drug interactions are interpreted.

Physiologically-Based Pharmacokinetic Model-Informed Drug Development for Fenebrutinib: Understanding Complex Drug-Drug Interactions.

Fenebrutinib is a CYP3A substrate and time‐dependent inhibitor, as well as a BCRP and OATP1B transporter inhibitor in vitro. Physiologically‐based pharmacokinetic (PBPK) modeling strategies with the ultimate goal of understanding complex drug‐drug interactions (DDIs) and proposing doses for untested scenarios were developed. The consistency in the results of two independent approaches, PBPK simulation and endogenous biomarker measurement, supported that the observed transporter DDI is primarily due to fenebrutinib inhibition of intestinal BCRP, rather than hepatic OATP1B. A mechanistic‐absorption model accounting for the effects of excipient complexation with fenebrutinib was used to rationalize the unexpected observation of itraconazole‐fenebrutinib DDI (maximum plasma concentration (Cmax) decreased, and area under the curve (AUC) increased). The totality of the evidence from sensitivity analysis and clinical and nonclinical data suggested that fenebrutinib is likely a sensitive CYP3A substrate. This advanced PBPK application allowed the use of model‐informed approach to facilitate the development of concomitant medication recommendations for fenebrutinib without requiring additional clinical DDI studies.

Critical Assessment of Pharmacokinetic Drug-Drug Interaction Potential of Tofacitinib, Baricitinib and Upadacitinib, the Three Approved Janus Kinase Inhibitors for Rheumatoid Arthritis Treatment.

The introduction of novel, small-molecule Janus kinase inhibitors namely tofacitinib, baricitinib and upadacitinib has provided an alternative treatment option for patients with rheumatoid arthritis outside of traditional drugs and expensive biologics. This review aimed to critically assess the drug-drug interaction potential of tofacitinib, baricitinib and upadacitinib and provide a balanced perspective for choosing the most appropriate Janus kinase inhibitor based on the needs of patients with rheumatoid arthritis including co-medications and renal/hepatic impairment status. Based on the critical assessment, all three approved Janus kinase inhibitors generally provide a favourable opportunity for co-prescription with a plethora of drugs. While cytochrome P450 3A4-related inhibition or induction altered the exposures (area under the curve) of tofacitinib and upadacitinib, it did not impact the exposure of baricitinib. Transporter drug-drug interaction studies revealed that the disposition of baricitinib was altered with certain transporter inhibitors as compared with either tofacitinib or upadacitinib. Adjustment of tofacitinib or baricitinib dosages but not that of upadacitinib is required with the progression of renal impairment from a mild to a severe condition. While the dosage of tofacitinib needs to be adjusted for patients with moderate hepatic impairment status, it is not the case for either baricitinib or upadacitinib. Assessment of the drug-drug interaction potential suggests that tofacitinib, baricitinib and upadacitinib generally show a favourable disposition with no perpetrator activity; however, as victim drugs, they show subtle pharmacokinetic differences that may be considered during polypharmacy. Moreover, careful choice of the three drugs could be made in patients with rheumatoid arthritis with varying degrees of renal/hepatic impairments.

S8.2 - Mechanistic models for coproporphyrin I and creatinine as endogenous biomarkers for transporter drug-drug interactions

S8.2 - Mechanistic models for coproporphyrin I and creatinine as endogenous biomarkers for transporter drug-drug interactions

Modeling Gadoxetate Liver Uptake and Efflux Using Dynamic Contrast-Enhanced Magnetic Resonance Imaging Enables Preclinical Quantification of Transporter Drug-Drug Interactions.

The aim of this study was to model the in vivo transporter-mediated uptake and efflux of the hepatobiliary contrast agent gadoxetate in the liver. The efficacy of the proposed technique was assessed for its ability to provide quantitative insights into drug-drug interactions (DDIs), using rifampicin as inhibitor. Three groups of C57 mice were scanned twice with a dynamic gadoxetate-enhanced magnetic resonance imaging protocol, using a 3-dimensional spoiled gradient-echo sequence for approximately 72 minutes. Before the second magnetic resonance imaging session, 2 of the groups received a rifampicin dose of 20 (n = 7) or 40 (n = 7) mg/kg, respectively. Data from regions of interest in the liver were analyzed using 2 simplifications of a 2-compartment uptake and efflux model to provide estimates for the gadoxetate uptake rate (ki) into the hepatocytes and its efflux rate (kef) into the bile. Both models were assessed for goodness-of-fit in the group without rifampicin (n = 9), and the appropriate model was selected for assessing the ability to monitor DDIs in vivo. Seven of 9 mice from the group without rifampicin were assessed for model implementation and reproducibility. A simple 3 parameter model (ki, kef, and extracellular space, vecs) adequately described the observed liver concentration time series with mean ki = 0.47 ± 0.11 min and mean kef = 0.039 ± 0.016 min. Visually, the area under the liver concentration time profile was reduced for the groups receiving rifampicin. Furthermore, tracer kinetic modeling demonstrated a significant dose-dependent decrease in the uptake (5.9- and 17.3-fold decrease for 20 mg/kg and 40 mg/kg, respectively) and efflux rates (2.2- and 7.9-fold decrease) compared with the first scan for each group. This study presents the first in vivo implementation of a 2-compartment uptake and efflux model to monitor DDIs at the transporter-protein level, using the clinically relevant organic anion transporting polypeptide inhibitor rifampicin. The technique has the potential to be a novel alternative to other methods, allowing real-time changes in transporter DDIs to be measured directly in vivo.

When Does the Rate-Determining Step in the Hepatic Clearance of a Drug Switch from Sinusoidal Uptake to All Hepatobiliary Clearances? Implications for Predicting Drug-Drug Interactions.

For dual transporter-enzyme substrate drugs, the extended clearance model can be used to predict the rate-determining step(s) (RDS) of a drug and hence predict its drug-drug interaction (DDI) liabilities (i.e., transport, metabolism, or both). If the RDS of the hepatic clearance of the drug is sinusoidal uptake clearance (CLs in), even if the drug is eliminated mainly by hepatic metabolism, its DDI liability (as viewed from changes to systemic drug concentrations) is expected to be inhibition or induction of uptake transporters but not hepatic enzymes; however, this is true only if the condition required to maintain CLs in as the RDS is maintained. Here, we illustrate through theoretical simulations that the RDS condition may be violated in the presence of a DDI. That is, the RDS of a drug can switch from CLs in to all hepatobiliary clearances [i.e., metabolic/biliary clearance (CLmet + bile) and CLs in], leading to unexpected systemic DDIs, such as metabolic DDIs, when only transporter DDIs were anticipated. As expected, these analyses revealed that the RDS switch depends on the ratio of CLmet + bile to sinusoidal efflux clearance (CLs ef). Additional analyses revealed that for intravenously administered drugs, the RDS switch also depends on the magnitude of CLs in We analyzed published in vitro quantified hepatobiliary clearances and observed that most drugs have a CLmet + bile/CLs ef ratio < 4; hence, in practice, the magnitude of CLs in must be considered when establishing the RDS. These analyses provide insights previously not appreciated and a theoretical framework to predict DDI liabilities for drugs that are dual transporter-enzyme substrates.

Role of Drug Metabolic Enzymes and Transporters in Drug-Drug Interactions Between Antiretroviral and Antituberculosis Drugs

Drug-drug interactions is one of the major determinant in drug development and clinical applications. Individual differences in pharmacokinetics may cause extensive variability in drug efficacy, toxicity and adverse drug reactions, and represent a major concern in drug development. According to world health organization, an estimated 1.2 million patients were diagnosed with HIV/TB coinfection in 2015, and approximately 400,000 coinfected individuals were died in 2016. During treatment of tuberculosis and human immunodeficiency virus (HIV) coinfections, a combination of multiple therapeutic drugs is used, which is potential for interactions between coadministered drugs. Drug metabolizing enzymes and transporters plays vital role in the disposition, pharmacokinetics as well as efficacy and toxicity of many antituberculosis (anti-TB) and antiretroviral (ARVs) drugs. The current understanding of drug-drug interactions involving the first-line antituberculosis and antiretroviral (ARVs) drugs are reviewed and summarized in this article emphasizing the role of drug transporters and metabolic enzymes. It is found that several clinical drug-interactions are caused by the phase I and II metabolic enzymes (cytochrome-P-450s, CYPs, UDP-glucuronosyltransferases, UGTs) and uptake/ efflux transporters, particularly permeability glycoprotein, brest cancer resistance protein, multidrug resistance protein and solute carrier transporters). Overall, this study will be helpful to understand the drug-interactions between the ARV or anti-TB drug regimen or with concomitantly used drugs at a glance. By understanding the unique functions and characteristics of enzymes and transporters, it may use in the management of drug interactions in the treatment of HIV and TB. Keywords: Drug-drug interactions, Metabolic Enzymes, Membrane Transporters, Antiretroviral and antituberculosis drugs

Causes and Consequences of Variability in Drug Transporter Activity in Pediatric Drug Therapy.

Drug transporters play a key role in mediating the uptake of endo- and exogenous substances into cells as well as their efflux. Therefore, variability in drug transporter activity can influence pharmaco- and toxicokinetics and be a determinant of drug safety and efficacy. In children, particularly in neonates and young infants, the contribution of tissue-specific drug transporters to drug absorption, distribution, and excretion may differ from that in adults. In this review 5 major factors and their interdependence that may influence drug transporter activity in children are discussed: developmental differences, genetic polymorphisms, pediatric comorbidities, interacting comedication, and environmental factors. Even if data are sparse, altered drug transporter activity due to those factors have been associated with clinically relevant differences in drug disposition, efficacy, and safety in pediatric patients. Single nucleotide polymorphisms in drug transporter-encoding genes were the most studied source of drug transporter variability in children. However, in the age group where drug transporter activity has been reported to differ from that in adults, namely neonates and young infants, hardly any studies have been performed. Longitudinal studies in this young population are required to investigate the age- and disease-dependent genotype-phenotype relationships and relevance of drug transporter drug-drug interactions. Physiologically based pharmacokinetic modeling approaches can integrate drug- and patient-specific parameters, including drug transporter ontogeny, and may further improve in silico predictions of pediatric-specific pharmacokinetics.

Preclinical Mouse Models To Study Human OATP1B1- and OATP1B3-Mediated Drug-Drug Interactions in Vivo.

The impact of OATP drug uptake transporters in drug-drug interactions (DDIs) is increasingly recognized. OATP1B1 and OATP1B3 are human hepatic uptake transporters that can mediate liver uptake of a wide variety of drugs. Recently, we generated transgenic mice with liver-specific expression of human OATP1B1 or OATP1B3 in a mouse Oatp1a/1b knockout background. Here, we investigated the applicability of these mice in OATP-mediated drug-drug interaction studies using the prototypic OATP inhibitor rifampicin and a good OATP substrate, the anticancer drug methotrexate (MTX). We next assessed the possibility of OATP-mediated interactions between telmisartan and MTX, a clinically relevant drug combination. Using HEK293 cells overexpressing OATP1B1 or OATP1B3, we estimated IC50 values for both rifampicin (0.9 or 0.3 μM) and telmisartan (6.7 or 7.9 μM) in inhibiting OATP-mediated MTX uptake in vitro. Using wild-type, Oatp1a/1b-/-, and OATP1B1- or OATP1B3-humanized transgenic mice, we found that rifampicin inhibits hepatic uptake of MTX mediated by the mouse Oatp1a/1b and human OATP1B1 and OATP1B3 transporters at clinically relevant concentrations. This highlights the applicability of these mouse models for DDI studies and may be exploited in the clinic to reduce the dose and thus methotrexate-mediated toxicity. On the other hand, telmisartan inhibited only human OATP1B1-mediated hepatic uptake of MTX at concentrations higher than those used in the clinic; therefore risks for OATP-mediated clinical DDIs for this drug combination are likely to be low. Overall, we show here that OATP1B1- and OATP1B3-humanized mice can be used as in vivo tools to assess and possibly predict clinically relevant DDIs.

Mobile apps for transporter drug-drug interaction prediction – a tool of the future, now

Mobile apps for transporter drug-drug interaction prediction – a tool of the future, now

PET Tracers To Study Clinically Relevant Hepatic Transporters.

Transporter proteins expressed on the cell membranes of hepatocytes are directly involved in the hepatic clearance, mediating the transport of drugs and metabolites through the hepatocyte, from the bloodstream into the bile. Reduction of hepatic transporter activity (due to chemical inhibition, genetic polymorphism, or low expression) can increase systemic or liver exposure to potentially toxic compounds, causing adverse effects. Many clinically used drugs have been associated with inhibition of hepatic transporters in vitro, suggesting the potential involvement of liver transporters in drug-drug interactions (DDIs). Recently, radiolabeled hepatic transporter substrates have been successfully employed in positron emission tomography (PET) imaging to demonstrate inhibition of clinically relevant hepatic transporters. The present article briefly describes the clinical relevance of hepatic transporters followed by a review of the application of PET imaging for the determination of pharmacokinetic parameters useful to describe the transporter activity and the design, accessibility, and preclinical and clinical applications of available radiotracers. Finally, based on the analysis of the strengths and limitations of the available tracers, some criteria for the development of novel PET probes for hepatic transporters and new potential applications are suggested.

Response to the Comment on the Article “Physiologically Based Modeling of Pravastatin Transporter-Mediated Hepatobiliary Disposition and Drug-Drug Interactions”

To the Editor: We appreciated the letter by Neuhoff and Tucker, which corroborated the methodology adopted in our recent study, “Physiologically based modeling of pravastatin transportermediated hepatobiliary disposition and drug-drug interactions” (1), while providing further comments on the scope of ‘bottomup’ prediction of transporter-mediated drug-drug interactions (DDIs). We agree that there is a growing knowledge in the in vitro-in vivo extrapolation (IVIVE) of transporter data, which could facilitate a comprehensive “bottom-up” approach in the future. However, there are considerable knowledge gaps at this stage which made us adopt a ‘middle-out” approach, wherein, a whole-body physiologically based pharmacokinetic (PBPK) model was developed based majorly on preclinical data and later refined using clinical pharmacokinetic data. The apparent discrepancy in the active transport kinetics could be qualitatively justified by the differences in the protein expression levels. For example, sandwich cultured human hepatocyte (SCHH) system showed up-regulated MRP2, but down-regulated OATP transporters, based on the protein quantification generated in our laboratory (2, 3). Although a ~5-fold higher MRP2 expression in SCHH could justify the scaling factor estimated for canalicular efflux of pravastatin, such direct translation is not apparent for sinusoidal uptake transporters (OATPs relative expression factor ~2-7 (2) versus scaling factor ~31(1)). In fact, based on our previous studies (4), the scaling factors derived using similar approach seem to be compound-specific, which suggests the need to understand differences in both transporter expressions, as well as transporter functional activity of the in vitro experimental systems compared to that in vivo. Collectively, protein quantification data are undoubtedly essential for model building and provide confidence in the translation of in vitro parameters, however, the discrepancies in IVIVE cannot be explained by only considering transporter expression levels. While further understanding in this area is warranted, we strongly believe that refining the mechanistic model based on clinical pharmacokinetic data provides the confidence necessary to make quantitative DDI predictions. The estimated in vivo Ki values for cyclosporine and gemfibrozil are more potent compared to mean in vitro values. Interestingly, this trend is consistent with the CYPmediated DDIs, where relatively large differences were noted between the in vitro and in vivo Ki values for lipophilic inhibitors (5). Nevertheless, we note that the estimated in vivo Ki values also predicted DDIs for other OATP1B1 substrate drugs (6). We agree that the discrepancies between in vitro and in vivo Ki demand for careful considerations, with an emphasis on elucidating the mechanism of inhibition (competitive versus possible time-dependent inhibition). However, lack of data on interaction parameters such as Kdeg (degradation rate constant) for drug transporters precludes incorporation of time-dependent inhibition mechanism in transporter DDI predictions. Finally, the other major challenge in prospective predictions of the transporter-mediated DDIs is sparse availability of the clinical interaction data to validate the mechanistic models. As noted by Neuhoff and Tucker, the majority of interaction studies of various statins with cyclosporine were done in a organ-transplant patient population, who may not only have altered physiology but may also exhibit downregulation of drug transporters and metabolic enzymes. While the influence of elevated cytokines on transporter activity is not completely understood in vivo, decreasing the relative expression factor in the model for organ-transplant M. V. S. Varma (*) : Y. Lai : B. Feng : J. Litchfield : T. C. Goosen Pharmacokinetics, Dynamics and Metabolism, Pfizer Inc. Groton, Connecticut, USA e-mail: manthena.v.varma@pfizer.com

Drug Trafficking: Recent Advances in Therapeutics and Disease

Drug transporter proteins are of ever-increasing interest because of their role both in processes regulating pharmacokinetic properties of drugs (absorption, distribution, and elimination) and in the development of cellular drug resistance through decreased uptake or increased efflux of drugs in the target organ or tumor. Further understanding of the role of transporters in drug-drug interactions and identification of these proteins as possible therapeutic targets could contribute to improved treatment of a wide variety of diseases.

Herb-drug Interactions Involving Drug Metabolizing Enzymes and Transporters

Herbal medicines and their active ingredients are widely used worldwide, and they have become an important part of clinical medicine. The combined use of herbs and drugs has increased the possibility of pharmacokinetic and pharmacodynamic interactions. Clinical studies have demonstrated that the combined use of herbs and drugs can enhance or attenuate the drug efficacy and toxicity. The herb-drug combinations may reduce a drug efficacy and lead to treatment failure when long-term administration. Case reports detailing serious clinical adverse reactions have promoted studies on the interactions between herbs and drugs. This review highlights recent knowledge to discuss herb-drug interactions involving metabolizing enzymes and drug transporters. Drug transporters are widely present in body and play an important role in the absorption, distribution, excretion and metabolism, efficacy, and toxicity of drugs. Investigation of transporters has developed rapidly since 1990s, the effects of many transporters on the pharmacokinetics of drugs and herb-drug interactions have been reported. Some concepts on drug transporters issued experimentally and clinically drug-drug and herb-drug interactions have applied in many studies. Methodology studies are very important for understanding the mechanism, considerations and evaluation of experiments and clinical studies on drug metabolizing enzymes and transporters in drug-drug interactions.

Liver Transporters in Hepatic Drug Disposition: An Update

Drug transporters expressed on the hepatocyte membrane play an important role in hepatic drug disposition. In the last two decades, systematic research has resulted in a better understanding of the diversity, expression and substrate specificities of drug transporters in the liver. Here we review recent studies on the role of transporters in drug-drug interactions and disease states such as cirrhosis. We conclude the review by considering techniques and model systems used to study hepatic transporters, including the latest technological developments such as multiphoton microscopy.