Cynomolgus monkey as a potential model to assess drug interactions involving hepatic organic anion transporting polypeptides: in vitro, in vivo, and in vitro-to-in vivo extrapolation

Mechanistic Determinants of Daprodustat Drug-Drug Interactions and Pharmacokinetics in Hepatic Dysfunction and Chronic Kidney Disease: Significance of OATP1B-CYP2C8 Interplay

Daprodustat is the first oral hypoxia-inducible factor prolyl hydroxylase inhibitor approved recently for the treatment of anemia caused by chronic kidney disease (CKD) in adults receiving dialysis. We evaluated the role of organic anion transporting polypeptide (OATP)1B-mediated hepatic uptake transport in the pharmacokinetics (PKs) of daprodustat using in vitro and in vivo studies, and physiologically-based PK (PBPK) modeling of its drug-drug interactions (DDIs) with inhibitor drugs. In vitro, daprodustat showed specific transport by OATP1B1/1B3 in the transfected cell systems and primary human and monkey hepatocytes. A single-dose oral rifampin (OATP1B inhibitor) reduced daprodustat intravenous clearance by a notable 9.9 ± 1.2-fold (P < 0.05) in cynomolgus monkeys. Correspondingly, volume of distribution at steady-state was also reduced by 5.0 ± 1.1-fold, whereas the half-life change was minimal (1.5-fold), corroborating daprodustat hepatic uptake inhibition by rifampin. A PBPK model accounting for OATP1B-CYP2C8 interplay was developed, which well described daprodustat PK and DDIs with gemfibrozil (CYP2C8 and OATP1B inhibitor) and trimethoprim (weak CYP2C8 inhibitor) within 25% error of the observed data in healthy subjects. About 18-fold increase in daprodustat area under the curve (AUC) following gemfibrozil treatment was found to be associated with strong CYP2C8 inhibition and moderate OATP1B inhibition. Moreover, PK modulation in hepatic dysfunction and subjects with CKD, in comparison to healthy control, was well-captured by the model. CYP2C8 and/or OATP1B inhibitor drugs (e.g., gemfibrozil, clopidogrel, rifampin, and cyclosporine) were predicted to perpetrate moderate-to-strong DDIs in healthy subjects, as well as, in target CKD population. Daprodustat can be used as a sensitive CYP2C8 index substrate in the absence of OATP1B modulation.

Building a Predictive PBPK Model for Human OATP Substrates: a Strategic Framework for Early Evaluation of Clinical Pharmacokinetic Variations Using Pitavastatin as an Example

To select a drug candidate for clinical development, accurately and promptly predicting human pharmacokinetic (PK) profiles, assessing drug-drug interactions (DDIs), and anticipating potential PK variations in disease populations are crucial steps in drug discovery. The complexity of predicting human PK significantly increases when hepatic transporters are involved in drug clearance (CL) and volume of distribution (Vss). A strategic framework is developed here, utilizing pitavastatin as an example. The framework includes the construction of a monkey physiologically-based PK (PBPK) model, model calibration to obtain scaling factors (SF) of in vitro-in vivo extrapolation (IVIVE) for various clearance parameters, human model development and validation, and assessment of DDIs and PK variations in disease populations. Through incorporating in vitro human parameters and calibrated SFs from the monkey model of 3.45, 0.14, and 1.17 for CLint,active, CLint,passive, and CLint,bile, respectively, and together with the relative fraction transported by individual transporters obtained from in vitro studies and the optimized Ki values for OATP inhibition, the model reasonably captured observed pitavastatin PK profiles, DDIs and PK variations in human subjects carrying genetic polymorphisms, i.e., AUC within 20%. Lastly, when applying the functional reduction based on measured OATP1B biomarkers, the model adequately predicted PK changes in the hepatic impairment population. The present study presents a strategic framework for early-stage drug development, enabling the prediction of PK profiles and assessment of PK variations in scenarios like DDIs, genetic polymorphism, and hepatic impairment-related disease states, specifically focusing on OATP substrates.

The fluorescence-based competitive counterflow assay developed for organic anion transporting polypeptides 1A2, 1B1, 1B3 and 2B1 identifies pentamidine as a selective OATP1A2 substrate

Organic anion transporting polypeptides OATP1A2, OATP1B1, OATP1B3 and OATP2B1 are Na+ - and ATP-independent exchangers of large, organic compounds, encompassing structurally diverse xenobiotics, including various drugs. These OATPs influence intestinal absorption (OATP2B1), hepatic clearance (OATP1B1/3) and blood to brain penetration (OATP1A2, OATP2B1) of their drug substrates. Consequently, OATP-mediated drug or food interactions may lead to altered pharmacokinetics and toxicity. During drug development, investigation of hepatic OATP1B1 and OATP1B3 is recommended by international regulatory agencies. Most frequently, OATP-drug interactions are investigated in an indirect assay, i.e., by examining uptake inhibition of a radioactive or fluorescent probe. However, indirect assays do not distinguish between transported substrates and non-transported OATP inhibitors. To fill this hiatus, a novel assay, termed competitive counterflow (CCF) has been developed and has since been applied for several OATPs to differentiate between substrates and non-transported inhibitors. However, previous OATP CCF assays, with the exception of that for OATP1B1, used radioactive probes. In the current study, we demonstrate that sulforhodamine 101 or pyranine can be used as fluorescent probes in a CCF assay to identify transported substrates of OATP1A2, or OATPs 1B1, 1B3 and 2B1, respectively. With the help of the newly developed fluorescence-based CCF method, we identify the FDA-approved anti-protozoal drug, pentamidine as a unique substrate of OATP1A2. Furthermore, we confirm the selective, OATP1A2-mediated uptake of pentamidine in a cytotoxicity assay. Based on our results, OATP1A2 may be an important determinant of pentamidine transport through the blood-brain barrier.

Elucidation of clearance mechanism of TP0463518, a novel hypoxia-inducible factor prolyl hydroxylase inhibitor: does a species difference in excretion routes exist between humans and animals?

1. TP0463518, a novel hypoxia-inducible factor prolyl hydroxylase inhibitor, is reportedly excreted predominantly through urinary excretion in an unchanged form in humans, with partial biliary excretion also possible. However, the clearance mechanisms remain unclear. The aim of this study was to investigate the clearance mechanisms in humans and to assess species differences in the excretion routes.2. TP0463518 was not metabolised in rat, dog, or human hepatocytes. TP0463518 is a substrate for human BCRP, OATP1B1, OATP1B3, and OAT3, suggesting that renal uptake by OAT3 is probably the predominant clearance route, with hepatic uptake by OATP1B1 and OATP1B3 contributing partially to clearance in humans.3. A species difference in excretion routes was observed. The unchanged urinary excretion rates in humans, male rats, female rats, dogs, and monkeys were 80.7%, 0.1%, 40.9%, 15.2%, and 72.6%, respectively. Urinary excretion was predominant in humans and monkeys, while only biliary excretion was observed in male rats. Uptake studies using hepatocytes showed that the hepatic uptake clearance in rats was 13.6-fold higher than that in humans. Therefore, not only reabsorption via renal tubules, but also hepatic uptake seems to be involved in the species differences in excretion routes between rats and humans.

Simultaneous measurement of mouse and human albumin in chimeric mice with humanized livers

Background: The degree of human hepatocyte replacement in chimeric mice with humanized liver has previously been shown to correlate with human plasma albumin measurements. However, there are no reports that directly compare the remaining endogenous mouse albumin with the newly expressed human albumin following engraftment. To better understand the disposition of serum albumin in PXB-mice, we developed a liquid chromatography tandem mass spectrometry (LC-MS/MS) method to simultaneously quantitate both human and mouse albumin from plasma. Results: A robust correlation was observed between the serum human albumin levels measured by LC-MS/MS and the estimated replacement index of PXB-mice. Conclusion: All data were shown to be specific and suitable to accurately quantify both human and mouse albumin from plasma of chimeric mice with humanized livers.

Dual kinetics of OATP2B1: Inhibitory potency and pH-dependence of OATP2B1 inhibitors

Organic anion transporting polypeptide (OATP) 2B1 is expressed in the intestine and liver, and OATP2B1-mediated transport of estrone 3-sulfate is pH-dependent and consists of: the high-affinity component (Hc) and low-affinity component (Lc). This study aimed to evaluate the influence of pH on the transport kinetics of each component, along with the inhibitory nature of ten OATP2B1 inhibitors. The Michaelis constants (K_m) were 4-fold and 1.5-fold lower at pH 6.3 than at pH 7.4, for Hc and Lc respectively. The inhibitory potencies of diclofenac, indomethacin, and ibuprofen towards Hc were 1.5-4.3 fold lower at pH 6.3 than at pH 7.4. Contrastingly, inhibitory potencies towards Lc were 9.0-52 fold lower at pH 7.4. Similarly, the inhibitory effect of naproxen was stronger towards Hc at pH 6.3 and towards Lc at pH 7.4. On the other hand, celecoxib selectively inhibited Lc transport at pH 7.4. Rifampicin inhibited both components at pH 6.3 and 7.4 to a similar extent, while bromosulphophthalein, naringin, and gefitinib selectively inhibited Hc irrespective of pH. Fexofenadine inhibited neither component. In conclusion, the transport affinities of both Hc and Lc were enhanced under acidic conditions. The influence of pH on the inhibitory potency towards each component varied among the inhibitors.

Transporter-mediated drug-drug interactions: advancement in models, analytical tools, and regulatory perspective

Drug-drug interactions mediated by transporters are a serious clinical concern hence a tremendous amount of work has been done on the characterization of the transporter-mediated proteins in humans and animals. The underlying mechanism for the transporter-mediated drug-drug interaction is the induction or inhibition of the transporter which is involved in the cellular uptake and efflux of drugs. Transporter of the brain, liver, kidney, and intestine are major determinants that alter the absorption, distribution, metabolism, excretion profile of drugs, and considerably influence the pharmacokinetic profile of drugs. As a consequence, transporter proteins may affect the therapeutic activity and safety of drugs. However, mounting evidence suggests that many drugs change the activity and/or expression of the transporter protein. Accordingly, evaluation of drug interaction during the drug development process is an integral part of risk assessment and regulatory requirements. Therefore, this review will highlight the clinical significance of the transporter, their role in disease, possible cause underlying the drug-drug interactions using analytical tools, and update on the regulatory requirement. The recent in-silico approaches which emphasize the advancement in the discovery of drug-drug interactions are also highlighted in this review. Besides, we discuss several endogenous biomarkers that have shown to act as substrates for many transporters, which could be potent determinants to find the drug-drug interactions mediated by transporters. Transporter-mediated drug-drug interactions are taken into consideration in the drug approval process therefore we also provided the extrapolated decision trees from in-vitro to in-vivo, which may trigger the follow-up to clinical studies.

Application of a PBPK model to elucidate the changes of systemic and liver exposures for rosuvastatin, carotegrast, and bromfenac followed by OATP inhibition in monkeys

The impact of organic anion‐transporting polypeptide (OATP) inhibition on systemic and liver exposures of three OATP substrates was investigated in cynomolgus monkeys. A monkey physiologically‐based pharmacokinetic (PBPK) model was constructed to describe the exposure changes followed by OATP functional attenuation. Rosuvastatin, bromfenac, and carotegrast were administered as a single intravenous cassette dose (0.5 mg/kg each) in monkeys with and without predosing with rifampin (RIF; 20 mg/kg) orally. The plasma exposure of rosuvastatin, bromfenac, carotegrast, and OATP biomarkers, coproporphyrin I (CP‐I) and CP‐III were increased 2.3, 2.1, 9.1, 5.4, and 8.8‐fold, respectively, when compared to the vehicle group. The liver to plasma ratios of rosuvastatin and bromfenac were reduced but the liver concentration of the drugs remained unchanged by RIF treatment. The liver concentrations of carotegrast, CP‐I, and CP‐III were unchanged at 1 h but increased at 6 h in the RIF‐treated group. The passive permeability, active uptake, and biliary excretion were characterized in suspended and sandwich‐cultured monkey hepatocytes and then incorporated into the monkey PBPK model. As demonstrated by the PBPK model, the plasma exposure is increased through OATP inhibition while liver exposure is maintained by passive permeability driven from an elevated plasma level. Liver exposure is sensitive to the changes of metabolism and biliary clearances. The model further suggested the involvement of additional mechanisms for hepatic uptakes of rosuvastatin and bromfenac, and of the inhibition of biliary excretion for carotegrast, CP‐I, and CP‐III by RIF. Collectively, impaired OATP function would not reduce the liver exposure of its substrates in monkeys.

Overcoming the shortcomings of the extended-clearance concept: a framework for developing a physiologically-based pharmacokinetic (PBPK) model to select drug candidates involving transporter-mediated clearance

Introduction:Human pharmacokinetic (PK) prediction can be a significant challenge to drug candidates undergoing transporter-mediated clearance, when only animal data and in vitro human parameters are available in the drug discovery stage.Areas covered:The extended clearance concept (ECC) that incorporates the processes of hepatic uptake, passive diffusion, metabolism and biliary secretion has been adapted to determine the rate-determining process of hepatic clearance and drug-drug interactions (DDIs). However, since the ECC is derived from the well-stirred model and does not consider the liver as a drug distribution organ to reflect the time-dependent variation of drug concentrations between the liver and plasma, it can be misused for compound selection in drug discovery.Expert opinion:The PBPK model consists of a set of differential equations of drug mass balance, and can overcome the shortcomings of the ECC in predicting human PK. The predictability, relevance and reliability of the model and the scaling factors for IVIVE must be validated using either the measured liver concentrations or DDI data with known transporter inhibitors, or both, in monkeys. A human PBPK model that incorporates in vitro human data and SFs obtained from the validated monkey PBPK model can be used for compound selection in the drug discovery phase.

Organic Anion-Transporting Polypeptide 1B1/1B3-Mediated Hepatic Uptake Determines the Pharmacokinetics of Large Lipophilic Acids: In Vitro-In Vivo Evaluation in Cynomolgus Monkey

It is generally presumed that uptake transport mechanisms are of limited significance in hepatic clearance for lipophilic or high passive-permeability drugs. In this study, we evaluated the mechanistic role of the hepato-selective organic anion-transporting polypeptides (OATPs) 1B1/1B3 in the pharmacokinetics of compounds representing large lipophilic acid space. Intravenous pharmacokinetics of 16 compounds with molecular mass ∼400-730 Da, logP ∼3.5-8, and acid pKa <6 were obtained in cynomolgus monkey after dosing without and with a single-dose rifampicin-OATP1B1/1B3 probe inhibitor. Rifampicin (30 mg/kg oral) significantly (P < 0.05) reduced monkey clearance and/or steady-state volume of distribution (VDss) for 15 of 16 acids evaluated. Additionally, clearance of danoprevir was reduced by about 35%, although statistical significance was not reached. A significant linear relationship was noted between the clearance ratio (i.e., ratio of control to treatment groups) and VDss ratio, suggesting hepatic uptake contributes to the systemic clearance and distribution simultaneously. In vitro transport studies using primary monkey and human hepatocytes showed uptake inhibition by rifampicin (100 µM) for compounds with logP ≤6.5 but not for the very lipophilic acids (logP > 6.5), which generally showed high nonspecific binding in hepatocyte incubations. In vitro uptake clearance and fraction transported by OATP1B1/1B3 (f_t,OATP1B) were found to be similar in monkey and human hepatocytes. Finally, for compounds with logP ≤6.5, good agreement was noted between in vitro f_t,OATP1B and clearance ratio (as well as VDss ratio) in cynomolgus monkey. In conclusion, this study provides mechanistic evidence for the pivotal role of OATP1B-mediated hepatic uptake in the pharmacokinetics across a wide, large lipophilic acid space. SIGNIFICANCE STATEMENT: This study provides mechanistic insight into the pharmacokinetics of a broad range of large lipophilic acids. Organic anion-transporting polypeptides 1B1/1B3-mediated hepatic uptake is of key importance in the pharmacokinetics and drug-drug interactions of almost all drugs and new molecular entities in this space. Diligent in vitro and in vivo transport characterization is needed to avoid the false negatives often noted because of general limitations in the in vitro assays while handling compounds with such physicochemical attributes.

Hepatic transporter-mediated pharmacokinetic drug-drug interactions: Recent studies and regulatory recommendations

Transporter-mediated drug-drug interactions are one of the major mechanisms in pharmacokinetic-based drug interactions and correspondingly affecting drugs' safety and efficacy. Regulatory bodies underlined the importance of the evaluation of transporter-mediated interactions as a part of the drug development process. The liver is responsible for the elimination of a wide range of endogenous and exogenous compounds via metabolism and biliary excretion. Therefore, hepatic uptake transporters, expressed on the sinusoidal membranes of hepatocytes, and efflux transporters mediating the transport from hepatocytes to the bile are determinant factors for pharmacokinetics of drugs, and hence, drug-drug interactions. In parallel with the growing research interest in this area, regulatory guidances have been updated with detailed assay models and criteria. According to well-established preclinical results, observed or expected hepatic transporter-mediated drug-drug interactions can be taken into account for clinical studies. In this paper, various methods including in vitro, in situ, in vivo, in silico approaches, and combinational concepts and several clinical studies on the assessment of transporter-mediated drug-drug interactions were reviewed. Informative and effective evaluation by preclinical tools together with the integration of pharmacokinetic modeling and simulation can reduce unexpected clinical outcomes and enhance the success rate in drug development.

Prediction of Drug Clearance from Enzyme and Transporter Kinetics

Accurate estimation of in vivo clearance in human is pivotal to determine the dose and dosing regimen for drug development. In vitro-in vivo extrapolation (IVIVE) has been performed to predict drug clearance using empirical and physiological scalars. Multiple in vitro systems and mathematical modeling techniques have been employed to estimate in vivo clearance. The models for predicting clearance have significantly improved and have evolved to become more complex by integrating multiple processes such as drug metabolism and transport as well as passive diffusion. This chapter covers the use of conventional as well as recently developed methods to predict metabolic and transporter-mediated clearance along with the advantages and disadvantages of using these methods and the associated experimental considerations. The general approaches to improve IVIVE by use of appropriate scalars, incorporation of extrahepatic metabolism and transport and application of physiologically based pharmacokinetic (PBPK) models with proteomics data are also discussed. The chapter also provides an overview of the advantages of using such dynamic mechanistic models over static models for clearance predictions to improve IVIVE.

Characterization of the cellular transport mechanisms for the anti-cachexia candidate compound TCMCB07

BACKGROUND

Cachexia is a debilitating, life-threatening condition whose pathology includes reduced food intake accompanied by hypermetabolism, leading to a catabolic state. The hypothalamic melanocortin system is a critical regulator of metabolic rate with effects being mediated through the melanocortin-4 receptor (MC4R). MC4R activation is also critical to the initiation and maintenance of cachexia. A major problem in the design of anti-cachexia drugs has been the need to cross the blood-brain barrier to access the metabolic rate-controlling centres in the hypothalamus. The overwhelming majority of anti-cachexia drugs are only effective when administered intracerebroventricularly. TCMCB07 is a cyclic nonapeptide peptide MC4R antagonist with parenteral anti-cachexia activity in both small and large animal models. This suggests it can cross the blood-brain barrier. The aim of this study was to examine potential transport mechanisms of TCMCB07 furthering its preclinical development for subsequent studies in humans.

METHODS

In vitro studies were performed in transporter-transfected cells to study whether or not TCMCB07 was an inhibitor as well as substrate for OATP1A2, OATP1B1, OATP1B3, OATP2B1, OCT2, OAT1, OAT3, MATE1, MATE2-K, P-gp (MDR1), and BCRP. In vivo mass balance studies were also performed in mice to evaluate the absorption and disposition of TCMCB07 after oral and intravenous bolus administrations.

RESULTS

TCMCB07 inhibited the uptake of prototypical substrates in cells transfected with OATP1A2 (IC₅₀ 24.0 μM), OATP1B1 (IC₅₀ 6.8 μM), OATP1B3 (IC₅₀ 307 μM), OATP2B1 (IC₅₀ 524 μM), OCT2 (IC₅₀ 1,169 μM), MATE1 (IC₅₀ 8.7 μM), and MATE2-K (IC₅₀ 20.7 μM) but not in cells transfected with OAT1 and OAT3. TCMCB07 did not affect the P-gp (MDR1)-mediated and BCRP-mediated permeability of prototypical substrates in transfected cells. Importantly, direct evidence was shown for the uptake of TCMCB07 in OATP1A2-transfected cells (i.e. V_max 236 pmol/mg, K_m 58.4 μM, and K_d 0.39 μL/mg), demonstrating that the nonapeptide was a substrate for this transporter. Mass balance studies demonstrated that 24.2% of TCMCB07 was absorbed orally in vivo (P = 0.0033) and excreted primarily in the bile after both oral and intravenous administrations.

CONCLUSIONS

OATP1A2 is the transporter responsible for the oral absorption of TCMCB07 in the intestine and for its pharmacologic response in the brain.

Predicting the Human Hepatic Clearance of Acidic and Zwitterionic Drugs

Prospective predictions of human hepatic clearance for anionic/zwitterionic compounds, which are oftentimes subjected to transporter-mediated uptake, are challenging in drug discovery. We evaluated the utility of preclinical species, rats and cynomolgus monkeys [nonhuman primates (NHPs)], to predict the human hepatic clearance using a diverse set of acidic/zwitterionic drugs. Preclinical clearance data were generated following intravenous dosing in rats/NHPs and compared to the human clearance data (n = 18/27). Single-species scaling of NHP clearance with an allometric exponent of 0.50 allowed for good prediction of human clearance (fold error ∼2.1, bias ∼1.0), with ∼86% predictions within 3-fold. In comparison, rats underpredicted the clearance of lipophilic acids, while overprediction was noted for hydrophilic acids. Finally, an in vitro clearance assay based on human hepatocytes, which is routinely used in discovery setting, markedly underpredicted human clearance (bias ∼0.12). Collectively, this study provides insights into the usefulness of the preclinical models in enabling pharmacokinetic optimization for acid/zwitterionic drug candidates.

In Vitro Hepatic Uptake in Human and Monkey Hepatocytes in the Presence and Absence of Serum Protein and Its In Vitro to In Vivo Extrapolation

It is well documented that human hepatic clearance based on in vitro metabolism or transporter assays systematically resulted in underprediction; therefore, large empirical scalars are often needed in either static or physiologically based pharmacokinetic (PBPK) models to accurately predict human pharmacokinetics (PK). In our current investigation, we assessed hepatic uptake in hepatocyte suspension in Krebs-Henseleit buffer in the presence and absence of serum. The results showed that the unbound intrinsic active clearance (CL_u,int,active) values obtained by normalizing the unbound fraction in the buffer containing 10% serum were generally higher than the CL_u,int,active obtained directly from protein free buffer, suggesting "protein-facilitated" uptake. The differences of CL_u,int,active in the buffer with and without protein ranged from 1- to 925-fold and negatively correlated to the unbound serum binding of organic anion transporting polypeptide substrates. When using the uptake values obtained from buffer containing serum versus serum-free buffer, the median of scaling factors (SFs) for CL_u,int,active reduced from 24.2-4.6 to 22.7-7.1 for human and monkey, respectively, demonstrating the improvement of in vitro to in vivo extrapolation in a PBPK model. Furthermore, values of CL_u,int,active were significantly higher in monkey hepatocytes than that in human, and the species differences appeared to be compound dependent. Scaling up in vitro uptake values derived in assays containing species-specific serum can compensate for the species-specific variabilities when using cynomolgus monkey as a probe animal model. Incorporating SFs calibrated in monkey and together with scaled in vitro data can be a reliable approach for the prospective human PK prediction in early drug discovery. SIGNIFICANCE STATEMENT: We investigated the protein effect on hepatic uptake in human and monkey hepatocytes and improved the in vitro to in vivo extrapolation using parameters obtained from the incubation in the present of serum protein. In addition, significantly higher active uptake clearances were observed in monkey hepatocytes than in human, and the species differences appeared to be compound dependent. The physiologically based pharmacokinetic model that incorporates scaling factors calibrated in monkey and together with scaled in vitro human data can be a reliable approach for the prospective human pharmacokinetics prediction.

Absence of OATP1B (Organic Anion-Transporting Polypeptide) Induction by Rifampin in Cynomolgus Monkeys: Determination Using the Endogenous OATP1B Marker Coproporphyrin and Tissue Gene Expression

Organic anion-transporting polypeptide (OATP) 1B induction is an evolving mechanism of drug disposition and interaction. However, there are contradictory reports describing OATP1B expression in hepatocytes and liver biopsies after administration of an inducer. This study investigated the in vivo effects of the common inducer rifampin (RIF) on the activity and expression of cynomolgus monkey OATP1B1 and OATP1B3 transporters, which are structurally and functionally similar their human OATP1B counterparts. Multiple doses of oral RIF (15 mg/kg) resulted in a steady 3.9-fold increase of CYP3A biomarker, 4β-hydroxycholesterol (4βHC), in the plasma samples collected before each RIF dose during the treatment period (i.e., predose). In contrast, the predose plasma levels of OATP1B biomarkers coproporphyrin (CP) I and CPIII did not change when compared with RIF treatment. The trough concentration, area under plasma concentration-time curve (AUC), and half-life of RIF decreased markedly during RIF treatment, suggesting that RIF induced its own clearance. Consequently, RIF treatment increased CPI and CPIII AUCs substantially after a single administration and, to a lesser extent, after multiple administrations compared with preadministration AUCs. In addition, OATP1B1 and OATP1B3 mRNA expressions were not modulated by RIF treatment (0.85-1.3-fold), whereas CYP3A8 expression was increased 3.7-5.0-fold, which correlated well with the predose levels of CP and 4βHC. Rifampin treatment showed 2.0-3.3-fold increases in P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug resistance-associated protein 2 (MRP2) expression in the small intestine. Collectively, these findings indicate that monkey OATP1B and OATP1B3 are not induced by RIF, and further investigation of OATP1B induction by RIF and other nuclear receptor activators in humans is warranted. SIGNIFICANCE STATEMENT: In this study, combined endogenous biomarker and gene expression data suggested that RIF did not induce OATP1B in cynomolgus monkeys. For the first time, the study determines transporter gene expression in the nonhuman primate liver, gut, and kidney tissues after administration of RIF for 7 days, leading to a better understanding of the induction of OATP1B and other major drug transporters. Finally, it provides evidence to strengthen the claim that coproporphyrin is a suitable endogenous probe of OATP1B activity.

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.

Effect of Rifampicin on the Plasma Concentrations of Bile Acid-O-Sulfates in Monkeys and Human Liver-Transplanted Chimeric Mice With or Without Bile Flow Diversion

The present study examined the significance of enterohepatic circulation and the effect of rifampicin [an inhibitor of organic anion-transporting polypeptide 1B (OATP1B)] on the plasma concentrations of bile acid-O-sulfates (glycochenodeoxycholate-O-sulfate, lithocholate-O-sulfate, glycolithocholate-O-sulfate, and taurolithocholate-O-sulfate) in monkeys and human liver-transplanted chimeric mice (PXB mouse). Rifampicin significantly increased the area under the curve of bile acid-O-sulfates in monkeys (13-69 times) and PXB mice (13-25 times) without bile flow diversion. Bile flow diversion reduced the concentration of plasma bile acid-O-sulfates under control conditions in monkeys and the concentration of plasma glycochenodeoxycholate-O-sulfate in PXB mice. It also diminished diurnal variation of plasma lithocholate-O-sulfate, glycolithocholate-O-sulfate, and taurolithocholate-O-sulfate in PXB mice under control conditions. Bile flow diversion did not affect the plasma concentration of bile acid-O-sulfates in monkeys and PXB mice treated with rifampicin. Plasma coproporphyrin I and III levels were constant in monkeys throughout the study, even with bile flow diversion. This study demonstrated that bile acid-O-sulfates are endogenous OATP1B biomarkers in monkeys and PXB mice. Enterohepatic circulation can affect the baseline levels of plasma bile acid-O-sulfates and modify the effect of OATP1B inhibition.

Pharmacokinetics and metabolism of pemafibrate, a novel selective peroxisome proliferator-activated receptor-alpha modulator, in rats and monkeys

The metabolic profiles and pharmacokinetics of pemafibrate, a novel selective peroxisome proliferator activated receptor-alpha modulator currently launched as an antidyslipidemic drug, were investigated in vitro using hepatocytes from rats, monkeys and humans and in vivo in rats and monkeys. Hepatocytes from rats, monkeys and humans all biotransformed pemafibrate to its demethylated form (M1). The bioavailabilities of pemafibrate in Sprague-Dawley rats and cynomolgus monkeys were 15% and 87%, respectively, after a single oral administration of pemafibrate (1 mg/kg). In rat plasma, unmetabolized pemafibrate was the major form, accounting for 29% of the area under the curve (AUC) of total radioactivity. In monkey plasma, in contrast, the major circulating metabolites were M2/3 (dearylated/dicarboxylic acid forms, 15%), M4 (N-dealkylated form, 21%) and M5 (benzylic oxidative form, 9%), but pemafibrate was the notable minor form (3%). These results, in combination with the reported findings in humans, suggest that the metabolite profile of pemafibrate in plasma was different for rats and monkeys, and that monkeys could be a suitable animal model for further pharmacokinetic studies of pemafibrate in humans.

Hepatic Organic Anion Transporting Polypeptide-Mediated Clearance in the Beagle Dog: Assessing In Vitro-In Vivo Relationships and Applying Cross-Species Empirical Scaling Factors to Improve Prediction of Human Clearance

In the present study, the beagle dog was evaluated as a preclinical model to investigate organic anion transporting polypeptide (OATP)-mediated hepatic clearance. In vitro studies were performed with nine OATP substrates in three lots of plated male dog hepatocytes ± OATP inhibitor cocktail to determine total uptake clearance (CL_uptake) and total and unbound cell-to-medium concentration ratio (Kp_uu). In vivo intrinsic hepatic clearances (CL_int,H) were determined following intravenous drug administration (0.1 mg/kg) in male beagle dogs. The in vitro parameters were compared with those previously reported in plated human, monkey, and rat hepatocytes; the ability of cross-species scaling factors to improve prediction of human in vivo clearance was assessed. CL_uptake in dog hepatocytes ranged from 9.4 to 135 µl/min/10⁶ cells for fexofenadine and telmisartan, respectively. Active process contributed >75% to CL_uptake for 5/9 drugs. Rosuvastatin and valsartan showed Kp_uu > 10, whereas cerivastatin, pitavastatin, repaglinide, and telmisartan had Kp_uu < 5. The extent of hepatocellular binding in dog was consistent with other preclinical species and humans. The bias (2.73-fold) obtained from comparison of predicted versus in vivo dog CL_int,H was applied as an average empirical scaling factor (ESF_av) for in vitro-in vivo extrapolation of human CL_int,H The ESF_av based on dog reduced underprediction of human CL_int,H for the same data set (geometric mean fold error = 2.1), highlighting its utility as a preclinical model to investigate OATP-mediated uptake. The ESF_av from all preclinical species resulted in comparable improvement of human clearance prediction, in contrast to drug-specific empirical scalars, rationalized by species differences in expression and/or relative contribution of particular transporters to drug hepatic uptake.

RNA sequencing of kidney and liver transcriptome obtained from wild cynomolgus macaque (Macaca fascicularis) originating from Peninsular Malaysia

Objective

Using high-throughput RNA sequencing technology, this study aimed to sequence the transcriptome of kidney and liver tissues harvested from Peninsular Malaysia cynomolgus macaque (Macaca fascicularis). M. fascicularis are significant nonhuman primate models in the biomedical field, owing to the macaque’s biological similarities with humans. The additional transcriptomic dataset will supplement the previously described Peninsular Malaysia M. fascicularis transcriptomes obtained in a past endeavour.

Results

A total of 75,350,240 sequence reads were obtained via Hi-seq 2500 sequencing technology. A total of 5473 significant differentially expressed genes were called. Gene ontology functional categorisation showed that cellular process, catalytic activity, and cell part categories had the highest number of expressed genes, while the metabolic pathways category possessed the highest number of expressed genes in the KEGG pathway analysis. The additional sequence dataset will further enrich existing M. fascicularis transcriptome assemblies, and provide a dataset for further downstream studies.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-4014-1) contains supplementary material, which is available to authorized users.

Drug Transporters in Xenobiotic Disposition and Pharmacokinetic Prediction

Drug transporters are widely expressed in organs and tissue barriers throughout human and animal bodies. Studies over the last two decades have identified various ATP-binding cassette and solute carrier transporters that play critical roles in the absorption, distribution, metabolism, and elimination of drugs and xenobiotics. This special section contains more than 20 original manuscripts and reviews that cover the most recent advances in the areas of drug transporter research, including the basic biology and function of transporters, expression of drug transporters in organ and tissue barriers, the mechanisms underlying regulation of transporter expression, transporter-mediated drug disposition in animal models, and the development and utilization of new technologies in drug transporter study, as well as pharmacokinetic modeling and simulation to assess transporter involvement in drug disposition and drug-drug interactions. We believe that the topics covered in this special section will advance our understanding of the roles of transporters in drug disposition, efficacy, and safety.

Comparison of uptake transporter functions in hepatocytes in different species to determine the optimal model for evaluating drug transporter activities in humans

A thorough understanding of species-dependent differences in hepatic uptake transporters is critical for predicting human pharmacokinetics (PKs) from preclinical data. In this study, the activities of organic anion transporting polypeptide (OATP/Oatp), organic cation transporter 1 (OCT1/Oct1), and sodium-taurocholate cotransporting polypeptide (NTCP/Ntcp) in cultured rat, dog, monkey and human hepatocytes were compared. The activities of hepatic uptake transporters were evaluated with respect to culture duration, substrate and species-dependent differences in hepatocytes. Longer culture duration reduced hepatic uptake transporter activities across species except for Oatp and Ntcp in rats. Comparable apparent Michaelis-Menten constant (K_m,app) values in hepatocytes were observed across species for atorvastatin, estradiol-17β-glucuronide and metformin. The K_m,app values for rosuvastatin and taurocholate were significantly different across species. Rat hepatocytes exhibited the highest Oatp percentage of uptake transporter-mediated permeation clearance (PS_inf,act) while no difference in %PS_inf,act of probe substrates were observed across species. The in vitro hepatocyte inhibition data in rats, monkeys and humans provided reasonable predictions of in vivo drug-drug interaction (DDIs) between atorvastatin/rosuvastatin and rifampin. These findings suggested that using human hepatocytes with a short culture time is the most robust preclinical model for predicting DDIs for compounds exhibiting active hepatic uptake in humans.

Simultaneous Assessment of Transporter-Mediated Drug-Drug Interactions Using a Probe Drug Cocktail in Cynomolgus Monkey

We aim to establish an in vivo preclinical model to enable simultaneous assessment of inhibition potential of an investigational drug on clinically relevant drug transporters, organic anion-transporting polypeptide (OATP)1B, breast cancer resistance protein (BCRP), P-glycoprotein (P-gp), and organic anion transporter (OAT)3. Pharmacokinetics of substrate cocktail consisting of pitavastatin (OATP1B substrate), rosuvastatin (OATP1B/BCRP/OAT3), sulfasalazine (BCRP), and talinolol (P-gp) were obtained in cynomolgus monkey-alone or in combination with transporter inhibitors. Single-dose rifampicin (30 mg/kg) significantly (P < 0.01) increased the plasma exposure of all four drugs, with a marked effect on pitavastatin and rosuvastatin [area under the plasma concentration-time curve (AUC) ratio ∼21-39]. Elacridar, BCRP/P-gp inhibitor, increased the AUC of sulfasalazine, talinolol, as well as rosuvastatin and pitavastatin. An OAT1/3 inhibitor (probenecid) significantly (P < 0.05) impacted the renal clearance of rosuvastatin (∼8-fold). In vitro, rifampicin (10 µM) inhibited uptake of pitavastatin, rosuvastatin, and sulfasalazine by monkey and human primary hepatocytes. Transport studies using membrane vesicles suggested that all probe substrates, except talinolol, are transported by cynoBCRP, whereas talinolol is a cynoP-gp substrate. Elacridar and rifampicin inhibited both cynoBCRP and cynoP-gp in vitro, indicating potential for in vivo intestinal efflux inhibition. In conclusion, a probe substrate cocktail was validated to simultaneously evaluate perpetrator impact on multiple clinically relevant transporters using the cynomolgus monkey. The results support the use of the cynomolgus monkey as a model that could enable drug-drug interaction risk assessment, before advancing a new molecular entity into clinical development, as well as providing mechanistic insights on transporter-mediated interactions.

Prediction and Quantification of Hepatic Transporter-Mediated Uptake of Pitavastatin Utilizing a Combination of the Relative Activity Factor Approach and Mechanistic Modeling

Quantification of the fraction transported (f_t) by a particular transporter will facilitate more robust estimations of transporter interactions. Using pitavastatin as a model uptake transporter substrate, we investigated the utility of the relative activity factor (RAF) approach and mechanistic modeling to estimate f_t in hepatocytes. The transporters evaluated were organic anion-transporting polypeptides OATP1B1 and OATP1B3 and sodium-taurocholate cotransporting polypeptide. Transporter-expressing human embryonic kidney 293 cells and human hepatocytes were used for determining RAF values, which were then incorporated into the mechanistic model to simulate hepatocyte uptake of pitavastatin over time. There was excellent agreement between simulated and observed hepatocyte uptake of pitavastatin, indicating the suitability of this approach for translation of uptake from individual transporter-expressing cells to more holistic in vitro models. Subsequently, f_t values were determined. The largest contributor to hepatocyte uptake of pitavastatin was OATP1B1, which correlates with what is known about the in vivo disposition of pitavastatin. The f_t values were then used for evaluating in vitro-in vivo correlations of hepatic uptake inhibition with OATP inhibitors rifampicin and cyclosporine. Predictions were compared with previously reported plasma exposure changes of pitavastatin with these inhibitors. Although hepatic uptake inhibition of pitavastatin was 2-3-fold underpredicted, incorporation of scaling factors (SFs) into RAF values significantly improved the predictive ability. We propose that calibration of hepatocytes with standard transporter substrates and inhibitors would allow for determination of system-specific SFs, which could subsequently be used for refining predictions of clinical DDI potential for new chemical entities that undergo active hepatic uptake.

In Vitro-In Vivo Extrapolation of OATP1B-Mediated Drug-Drug Interactions in Cynomolgus Monkey

Hepatic organic anion-transporting polypeptides (OATP) 1B1 and 1B3 are clinically relevant transporters associated with significant drug-drug interactions (DDIs) and safety concerns. Given that OATP1Bs in cynomolgus monkey share >90% degree of gene and amino acid sequence homology with human orthologs, we evaluated the in vitro-in vivo translation of OATP1B-mediated DDI risk using this preclinical model. In vitro studies using plated cynomolgus monkey hepatocytes showed active uptake K_m values of 2.0 and 3.9 µM for OATP1B probe substrates, pitavastatin and rosuvastatin, respectively. Rifampicin inhibited pitavastatin and rosuvastatin active uptake in monkey hepatocytes with IC₅₀ values of 3.0 and 0.54 µM, respectively, following preincubation with the inhibitor. Intravenous pharmacokinetics of ²H₄-pitavastatin and ²H₆-rosuvastatin (0.2 mg/kg) and the oral pharmacokinetics of cold probes (2 mg/kg) were studied in cynomolgus monkeys (n = 4) without or with coadministration of single oral ascending doses of rifampicin (1, 3, 10, and 30 mg/kg). A rifampicin dose-dependent reduction in i.v. clearance of statins was observed. Additionally, oral pitavastatin and rosuvastatin plasma exposure increased up to 19- and 15-fold at the highest dose of rifampicin, respectively. Use of in vitro IC₅₀ obtained following 1 hour preincubation with rifampicin (0.54 µM) predicted correctly the change in mean i.v. clearance and oral exposure of statins as a function of mean unbound maximum plasma concentration of rifampicin. This study demonstrates quantitative translation of in vitro OATP1B IC₅₀ to predict DDIs using cynomolgus monkey as a preclinical model and provides further confidence in application of in vitro hepatocyte data for the prediction of clinical OATP1B-mediated DDIs.

Physiologically Based Pharmacokinetic Modeling of Transporter-Mediated Hepatic Clearance and Liver Partitioning of OATP and OCT Substrates in Cynomolgus Monkeys

In the present investigations, we evaluate in vitro hepatocyte uptake and partitioning for the prediction of in vivo clearance and liver partitioning. Monkeys were intravenously co-dosed with rosuvastatin and bosentan, substrates of the organic anion transporting polypeptides (OATPs), and metformin, a substrate of organic cation transporter 1 (OCT1). Serial plasma and liver samples were collected over time. Liver and plasma unbound fraction was determined using equilibrium dialysis. In vivo unbound partitioning (Kp_u,u) for rosuvastatin, bosentan, and metformin, calculated from total concentrations in the liver and plasma, were 243, 553, and 15, respectively. A physiologically based pharmacokinetic monkey model that incorporates active and passive hepatic uptake was developed to fit plasma and liver concentrations. In addition, a two-compartment model was used to fit in vitro hepatic uptake curves in suspended monkey hepatocyte to determine active uptake, passive diffusion, and intracellular unbound fraction parameters. At steady-state in the model, in vitro Kp_u,u was determined. The results demonstrated that in vitro values under-predicted in vivo active uptake for rosuvastatin, bosentan, and metformin by 6.7-, 28-, and 1.5-fold, respectively, while passive diffusion was over-predicted. In vivo Kp_u,u values were under-predicted from in vitro data by 30-, 79-, and 3-fold. In conclusion, active uptake and liver partitioning in monkeys for OATP substrates were greatly under-predicted from in vitro hepatocyte uptake, while OCT-mediated uptake and partitioning scaled reasonably well from in vitro, demonstrating substrate- and transporter-dependent scaling factors. The combination of in vitro experimental and modeling approaches proved useful for assessing prediction of in vivo intracellular partitioning.

Acetyl-coenzyme A carboxylase inhibition reduces de novo lipogenesis in overweight male subjects: A randomized, double-blind, crossover study

NDI-010976, an allosteric inhibitor of acetyl-coenzyme A carboxylases (ACC) ACC1 and ACC2, reduces hepatic de novo lipogenesis (DNL) and favorably affects steatosis, inflammation, and fibrosis in animal models of fatty liver disease. This study was a randomized, double-blind, placebo-controlled, crossover trial evaluating the pharmacodynamic effects of a single oral dose of NDI-010976 on hepatic DNL in overweight and/or obese but otherwise healthy adult male subjects. Subjects were randomized to receive either NDI-010976 (20, 50, or 200 mg) or matching placebo in period 1, followed by the alternate treatment in period 2; and hepatic lipogenesis was stimulated with oral fructose administration. Fractional DNL was quantified by infusing a stable isotope tracer, [1-¹³ C]acetate, and monitoring ¹³ C incorporation into palmitate of circulating very low-density lipoprotein triglyceride. Single-dose administration of NDI-010976 was well tolerated at doses up to and including 200 mg. Fructose administration over a 10-hour period stimulated hepatic fractional DNL an average of 30.9 ± 6.7% (mean ± standard deviation) above fasting DNL values in placebo-treated subjects. Subjects administered single doses of NDI-010976 at 20, 50, or 200 mg had significant inhibition of DNL compared to placebo (mean inhibition relative to placebo was 70%, 85%, and 104%, respectively). An inverse relationship between fractional DNL and NDI-010976 exposure was observed with >90% inhibition of fractional DNL associated with plasma concentrations of NDI-010976 >4 ng/mL.

CONCLUSION

ACC inhibition with a single dose of NDI-010976 is well tolerated and results in a profound dose-dependent inhibition of hepatic DNL in overweight adult male subjects. Therefore, NDI-010976 could contribute considerable value to the treatment algorithm of metabolic disorders characterized by dysregulated fatty acid metabolism, including nonalcoholic steatohepatitis. (Hepatology 2017;66:324-334).

Comparative Evaluation of Plasma Bile Acids, Dehydroepiandrosterone Sulfate, Hexadecanedioate, and Tetradecanedioate with Coproporphyrins I and III as Markers of OATP Inhibition in Healthy Subjects

Multiple endogenous compounds have been proposed as candidate biomarkers to monitor organic anion transporting polypeptide (OATP) function in preclinical species or humans. Previously, we demonstrated that coproporphyrins (CPs) I and III are appropriate clinical markers to evaluate OATP inhibition and recapitulate clinical drug-drug interactions (DDIs). In the present study, we investigated bile acids (BAs) dehydroepiandrosterone sulfate (DHEAS), hexadecanedioate (HDA), and tetradecanedioate (TDA) in plasma as endogenous probes for OATP inhibition and compared these candidate probes to CPs. All probes were determined in samples from a single study that examined their behavior and their association with rosuvastatin (RSV) pharmacokinetics after administration of an OATP inhibitor rifampin (RIF) in healthy subjects. Among endogenous probes examined, RIF significantly increased maximum plasma concentration (C_max) and area under the concentration-time curve (AUC)_(0-24h) of fatty acids HDA and TDA by 2.2- to 3.2-fold. For the 13 bile acids in plasma examined, no statistically significant changes were detected between treatments. Changes in plasma DHEAS did not correlate with OATP1B inhibition by RIF. On the basis of the magnitude of effects for the endogenous compounds that demonstrated significant changes from baseline over interindividual variations, the overall rank order for the AUC change was found to be CP I > CP III > HDA ≈ TDA ≈ RSV > > BAs. Collectively, these results reconfirmed that CPs are novel biomarkers suitable for clinical use. In addition, HDA and TDA are useful for OATP functional assessment. Since these endogenous markers can be monitored in conjunction with pharmacokinetics analysis, the CPs and fatty acid dicarboxylates, either alone or in combination, offer promise of earlier diagnosis and risk stratification for OATP-mediated DDIs.

Transporter-Mediated Hepatic Uptake Plays an Important Role in the Pharmacokinetics and Drug-Drug Interactions of Montelukast

Montelukast, a leukotriene receptor antagonist commonly prescribed for treatment of asthma, is primarily metabolized by cytochrome P450 (CYP)2C8, and has been suggested as a probe substrate for investigating CYP2C8 activity in vivo. We evaluated the quantitative role of hepatic uptake transport in its pharmacokinetics and drug-drug interactions (DDIs). Montelukast was characterized with significant active uptake in human hepatocytes, and showed affinity towards organic anion transporting polypeptides (OATPs) in transfected cell systems. Single-dose rifampicin, an OATP inhibitor, decreased montelukast clearance in rats and monkeys. Clinical DDIs of montelukast were evaluated using physiologically based pharmacokinetic modeling; and simulation of the interactions with gemfibrozil-CYP2C8 and OATP1B1/1B3 inhibitor, clarithromycin-CYP3A and OATP1B1/1B3 inhibitor, and itraconazole-CYP3A inhibitor, implicated OATPs-CYP2C8-CYP2C8 interplay as the primary determinant of montelukast pharmacokinetics. In conclusion, hepatic uptake plays a key role in the pharmacokinetics of montelukast, which should be taken into account when interpreting clinical interactions.

Role of gemfibrozil as an inhibitor of CYP2C8 and membrane transporters

INTRODUCTION

Cytochrome P450 (CYP) 2C8 is a drug metabolizing enzyme of major importance. The lipid-lowering drug gemfibrozil has been identified as a strong inhibitor of CYP2C8 in vivo. This effect is due to mechanism-based inhibition of CYP2C8 by gemfibrozil 1-O-β-glucuronide. In vivo, gemfibrozil is a fairly selective CYP2C8 inhibitor, which lacks significant inhibitory effect on other CYP enzymes. Gemfibrozil can, however, have a smaller but clinically meaningful inhibitory effect on membrane transporters, such as organic anion transporting polypeptide 1B1 and organic anion transporter 3. Areas covered: This review describes the inhibitory effects of gemfibrozil on CYP enzymes and membrane transporters. The clinical drug interactions caused by gemfibrozil and the different mechanisms contributing to the interactions are reviewed in detail. Expert opinion: Gemfibrozil is a useful probe inhibitor of CYP2C8 in vivo, but its effect on membrane transporters has to be taken into account in study design and interpretation. Moreover, gemfibrozil could be used to boost the pharmacokinetics of CYP2C8 substrate drugs. Identification of gemfibrozil 1-O-β-glucuronide as a potent mechanism-based inhibitor of CYP2C8 has led to recognition of glucuronide metabolites as perpetrators of drug-drug interactions. Recently, also acyl glucuronide metabolites of clopidogrel and deleobuvir have been shown to strongly inhibit CYP2C8.