Glucuronidation converts clopidogrel to a strong time-dependent inhibitor of CYP2C8: a phase II metabolite as a perpetrator of drug-drug interactions

Screening of 16 major drug glucuronides for time-dependent inhibition of nine drug-metabolizing CYP enzymes - detailed studies on CYP3A inhibitors

Time-dependent inhibition of cytochrome P450 (CYP) enzymes has been observed for a few glucuronide metabolites of clinically used drugs. Here, we investigated the inhibitory potential of 16 glucuronide metabolites towards nine major CYP enzymes in vitro. Automated substrate cocktail methods were used to screen time-dependent inhibition of CYP1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2J2 and 3A in human liver microsomes. Seven glucuronides (carvedilol β-D-glucuronide, diclofenac acyl-β-D-glucuronide, 4-hydroxyduloxetine β-D-glucuronide, ezetimibe phenoxy-β-D-glucuronide, raloxifene 4'-glucuronide, repaglinide acyl-β-D-glucuronide and valproic acid β-D-glucuronide) caused NADPH- and time-dependent inhibition of at least one of the CYPs investigated, including CYP2A6, CYP2C19 and CYP3A. In more detailed experiments, we focused on the glucuronides of carvedilol and diclofenac, which inhibited CYP3A. Carvedilol β-D-glucuronide showed weak time-dependent inhibition of CYP3A, but the parent drug carvedilol was found to be a more potent inhibitor of CYP3A, with the half-maximal inhibitor concentration (IC50) decreasing from 7.0 to 1.1 µM after a 30-min preincubation with NADPH. The maximal inactivation constant (kinact) and the inhibitor concentration causing half of kinact (KI) for CYP3A inactivation by carvedilol were 0.051 1/min and 1.8 µM, respectively. Diclofenac acyl-β-D-glucuronide caused time-dependent inactivation of CYP3A at high concentrations, with a 4-fold IC50 shift (from 400 to 98 µM after a 30-min preincubation with NADPH) and KI and kinact values of >2,000 µM and >0.16 1/min. In static predictions, carvedilol caused significant (>1.25-fold) increase in the exposure of the CYP3A substrates midazolam and simvastatin. In conclusion, we identified several glucuronide metabolites with CYP inhibitory properties. Based on detailed experiments, the inactivation of CYP3A by carvedilol may cause clinically significant drug-drug interactions.

A genetic algorithm-based approach for the prediction of metabolic drug-drug interactions involving CYP2C8 or CYP2B6

BACKGROUND AND OBJECTIVES

A genetic algorithm (GA) approach was developed to predict drug-drug interactions (DDIs) caused by cytochrome P450 2C8 (CYP2C8) inhibition or cytochrome P450 2B6 (CYP2B6) inhibition or induction. Nighty-eight DDIs, obtained from published in vivo studies in healthy volunteers, have been considered using the area under the plasma drug concentration-time curve (AUC) ratios (i.e., ratios of AUC of the drug substrate administered in combination with a DDI perpetrator to AUC of the drug substrate administered alone) to describe the extent of DDI.

METHODS

The following parameters were estimated in this approach: the contribution ratios (CRCYP2B6 and CRCYP2C8, i.e., the fraction of the dose metabolized via CYP2B6 or CYP2C8, respectively) and the inhibitory or inducing potency of the perpetrator drug (IRCYP2B6, IRCYP2C8 and ICCYP2B6, for inhibition of CYP2B6 and CYP2C8, and induction of CYP2B6, respectively). The workflow consisted of three main phases. First, the initial estimates of the parameters were estimated through GA. Then, the model was validated using an external validation. Finally, the parameter values were refined via a Bayesian orthogonal regression using all data.

RESULTS

The AUC ratios of 5 substrates, 11 inhibitors and 19 inducers of CYP2B6, and the AUC ratios of 19 substrates and 23 inhibitors of CYP2C8 were successfully predicted by the developed methodology within 50-200% of observed values.

CONCLUSIONS

The approach proposed in this work may represent a useful tool for evaluating the suitable doses of a CYP2C8 or CYP2B6 substrates co-administered with perpetrators.

Small molecule drug metabolite synthesis and identification: why, when and how?

The drug discovery and development process encompasses the interrogation of metabolites arising from the biotransformation of drugs. Here we look at why, when and how metabolites of small-molecule drugs are synthesised from the perspective of a specialist contract research organisation, with particular attention paid to projects for which regulatory oversight is relevant during this journey. To illustrate important aspects, we look at recent case studies, trends and learnings from our experience of making and identifying metabolites over the past ten years, along with with selected examples from the literature.

Construction of a fused grid-based CYP2C8-Template system and the application

A ligand-accessible space in the CYP2C8 active site was reconstituted as a fused grid-based Template∗ with the use of structural data of the ligands. An evaluation system of CYP2C8-mediated metabolism has been developed on Template with the introduction of the idea of Trigger-residue initiated ligand-movement and fastening. Reciprocal comparison of the data of simulation on Template with experimental results suggested a unified way of the interaction of CYP2C8 and its ligands through the simultaneous plural-contact with Rear-wall of Template. CYP2C8 was expected to have a room for ligands between vertically standing parallel walls termed Facial-wall and Rear-wall. Both the walls were separated by a distance corresponding to 1.5-Ring (grid) diameter size, which was termed Width-gauge. The ligand sittings were stabilized through contacts with Facial-wall and the left-side borders of Template including specific Position 29, left-side border of Rings I/J, or Left-end, after Trigger-residue initiated ligand-movement. Trigger-residue movement is suggested to force ligands to stay firmly in the active site and then to initiate CYP2C8 reactions. Simulation experiments for over 350 reactions of CYP2C8 ligands supported the system established.

Creation of Novel Sensitive Probe Substrate and Moderate Inhibitor Models for a Comprehensive Prediction of CYP2C8 Interactions for Tucatinib

A physiologically-based pharmacokinetic (PBPK) model was developed to simulate plasma concentrations of tucatinib (TUKYSA®) after single-dose or multiple-dose administration of 300 mg b.i.d. orally. This PBPK model was subsequently applied to support evaluation of drug-drug interaction (DDI) risk as a perpetrator resulting from tucatinib inhibition of CYP3A4, CYP2C8, CYP2C9, P-gp, or MATE1/2-K. The PBPK model was also applied to support evaluation of DDI risk as a victim resulting from co-administration with CYP3A4 or CYP2C8 inhibitors, or a CYP3A4 inducer. After refinement with clinical DDI data, the final PBPK model was able to recover the clinically observed single and multiple-dose plasma concentrations for tucatinib when tucatinib was administered as a single agent in healthy subjects. In addition, the final model was able to recover clinically observed plasma concentrations of tucatinib when administered in combination with itraconazole, rifampin, or gemfibrozil as well as clinically observed plasma concentrations of probe substrates of CYP3A4, CYP2C8, CYP2C9, P-gp, or MATE1/2-K. The PBPK model was then applied to prospectively predict the potential perpetrator or victim DDIs with other substrates, inducers, or inhibitors. To simulate a potential interaction with a moderate CYP2C8 inhibitor, two novel PBPK models representing a moderate CYP2C8 inhibitor and a sensitive CYP2C8 substrate were developed based on the existing PBPK models for gemfibrozil and rosiglitazone, respectively. The simulated population geometric mean area under the curve ratio of tucatinib with a moderate CYP2C8 inhibitor ranged from 1.98- to 3.08-fold, and based on these results, no dose modifications were proposed for moderate CYP2C8 inhibitors for the tucatinib label.

Interplay of UDP-Glucuronosyltransferase and CYP2C8 for CYP2C8 Mediated Drug Oxidation and Its Impact on Drug-Drug Interaction Produced by Standardized CYP2C8 Inhibitors, Clopidogrel and Gemfibrozil

BACKGROUND AND OBJECTIVE

Early investigations into drug-drug interactions (DDIs) involving cytochrome P450 2C8 (CYP2C8) have highlighted the complexity of interactions between CYP2C8 substrate drugs, including montelukast, desloratadine, pioglitazone, repaglinide, and cerivastatin (the latter two being OATP1B1 substrates), and standardized CYP2C8 inhibitors such as clopidogrel (Clop) and gemfibrozil (Gem). These interactions have proven challenging to predict based solely on simple CYP inhibition. A hypothesis has emerged suggesting that these substrate drugs first distribute to UDP-glucuronosyltransferase (UGT) before undergoing oxidation by CYP2C8, resulting in bidirectional elimination. The process of drug distribution to UGT is believed to significantly impact these DDIs. This study aims to explore the intricate interplay between UGT and CYP2C8 in the context of DDIs involving CYP2C8 substrates affected by Clop and Gem.

METHODS

Plasma-level data for the unchanged drug and its metabolite, drawn from the respective literature, formed the basis of our analysis. We evaluated the enzymatic inhibitory activities of DDIs and utilized simulations to estimate plasma levels of the unchanged victim drug and its metabolite in each DDI. This was accomplished by employing a functional relationship that considered the fractional contributions of CYP2C8 and UGT to clearance, perpetrator-specific inhibitory activities against CYP2C8, and drug distribution to UGT.

RESULTS

Our findings emphasize the pivotal role of UGT-mediated distribution in the context of CYP2C8 substrate metabolism, particularly in the complex DDIs induced by Clop and Gem. In these DDIs, Gem exerts inhibitory effects on both UGT and CYP2C8, whereas Clop (specifically its metabolite, Clop-COOH) solely targets CYP2C8. Importantly, the inhibition of CYP2C8 by both Clop and Gem is achieved through a non-competitive mechanism, driven by the actions of their acyl-glucuronides. Clop and Gem exhibit inhibition activities accounting for 85% (pAi,CYP2C8 = 7) and 93% (pAi,CYP2C8 = 15), respectively. In contrast, Gem's inhibition of UGT is relatively modest (50%, pAi,UGT(d) = 2), and it operates through a non-specific, competitive process in drug distribution to UGT. Within this context, our UGT-CYP2C8 interplay model offers an accurate means of predicting the alterations resulting from DDIs, encompassing changes in plasma levels of the unchanged drug and its metabolites, as well as shifts in metabolite formation rates. Our analysis highlights the critical importance of considering the fractional contributions of CYP2C8 and UGT to the victim drug's clearance (fm,CYP2C8; fm,UGT) in DDI prediction. Furthermore, our examination of DDIs involving OATP1B1 substrate drugs underscores that accounting for the hepatic uptake transporters' role in the liver is superfluous in DDI prediction.

CONCLUSION

These findings substantially enhance our comprehension of CYP2C8-mediated oxidation and DDIs, holding crucial implications for drug development and the planning of clinical trials involving these inhibitors.

Rottlerin renders a selective and highly potent CYP2C8 inhibition to impede EET formation for implication in cancer therapy

CYP2C8 is a crucial CYP isoform responsible for the metabolism of xenobiotics and endogenous molecules. CYP2C8 converts arachidonic acid to epoxyeicosatrienoic acids (EETs) that cause cancer progression. Rottlerin possess significant anticancer actions. However, information on its CYP inhibitory action is lacking in the literature and therefore, we aimed to explore the same using in silico, in vitro, and in vivo approaches. Rottlerin showed highly potent and selective CYP2C8 inhibition (IC₅₀ < 0.1 μM) compared to negligible inhibition (IC₅₀ > 10 μM) for seven other experimental CYPs in human liver microsomes (HLM) (in vitro) using USFDA recommended index reactions. Mechanistic studies reveal that rottlerin could reversibly (mixed-type) block CYP2C8. Molecular docking (in silico) results indicate a strong interaction could occur between rottlerin and the active site of human CYP2C8. Rottlerin boosted the plasma exposure of repaglinide and paclitaxel (CYP2C8 substrates) by delaying their metabolism using the rat model (in vivo). Multiple-dose treatment of rottlerin with CYP2C8 substrates lowered the CYP2C8 protein expression and up-regulated & down-regulated the mRNA for CYP2C12 and CYP2C11 (rat homologs), respectively, in rat liver tissue. Rottlerin substantially hindered the EET formation in HLM. Overall results of rottlerin on CYP2C8 inhibition and EET formation insinuate further exploration for targeted cancer therapy.

Pharmacotherapy of type 2 diabetes: An update and future directions

Type 2 diabetes (T2D) is a widely prevalent disease with substantial economic and social impact for which multiple conventional and novel pharmacotherapies are currently available; however, the landscape of T2D treatment is constantly changing as new therapies emerge and the understanding of currently available agents deepens. This review aims to provide an updated summary of the pharmacotherapeutic approach to T2D. Each class of agents is presented by mechanism of action, details of administration, side effect profile, cost, and use in certain populations including heart failure, non-alcoholic fatty liver disease, obesity, chronic kidney disease, and older individuals. We also review targets of novel therapeutic T2D agent development. Finally, we outline an up-to-date treatment approach that starts with identification of an individualized goal for glycemic control then selection, initiation, and further intensification of a personalized therapeutic plan for T2D.

Drug metabolism and drug transport of the 100 most prescribed oral drugs

Safe and effective use of drugs requires an understanding of metabolism and transport. We identified the 100 most prescribed drugs in six countries and conducted a literature search on in vitro data to assess contribution of Phase I and II enzymes and drug transporters to metabolism and transport. Eighty-nine of the 100 drugs undergo drug metabolism or are known substrates for drug transporters. Phase I enzymes are involved in metabolism of 67 drugs, while Phase II enzymes mediate metabolism of 18 drugs. CYP3A4/5 is the most important Phase I enzyme involved in metabolism of 43 drugs followed by CYP2D6 (23 drugs), CYP2C9 (23 drugs), CYP2C19 (22 drugs), CYP1A2 (14 drugs) and CYP2C8 (11 drugs). More than half of the drugs (54 drugs) are known substrates for drug transporters. P-glycoprotein (P-gp) is known to be involved in transport of 30 drugs, while breast cancer resistance protein (BCRP) facilitates transport of 11 drugs. A considerable proportion of drugs are subject to a combination of Phase I metabolism, Phase II metabolism and/or drug transport. We conclude that the majority of the most frequently prescribed drugs depend on drug metabolism or drug transport. Thus, understanding variability of drug metabolism and transport remains a priority.

Inhibition of CYP2C8 by Acyl Glucuronides of Gemfibrozil and Clopidogrel: Pharmacological Significance, Progress and Challenges

The lipid-regulating drug gemfibrozil is a useful medication for reducing high cholesterol and triglycerides in the blood. In addition to oxidation, it undergoes extensive glucuronidation to produce gemfibrozil acyl glucuronide, which is a known mechanism-based inactivator of cytochrome P450 (CYP) 2C8. Such selective and time-dependent inhibition results in clinically important drug–drug interactions (DDI) with the drugs metabolized by CYP2C8. Similarly, the acyl glucuronide of clopidogrel, a widely used antiplatelet agent, is a potent time-dependent inhibitor of CYP2C8 that demonstrated significant DDI with the substrates of CYP2C8. Current progress in atomic-level understanding mostly involves studying how different drugs bind and undergo oxidation in the active site of CYPs. It is not clear how an acyl glucuronide metabolite of the drug gemfibrozil or clopidogrel interacts in the active site of CYP2C8 and selectively inhibit the enzyme. This mini-review summarizes the current knowledge on some of the important clinical DDI caused by gemfibrozil and clopidogrel due to the inhibition of CYP2C8 by acyl glucuronide metabolites of these drugs. Importantly, it examines recent developments and potential applications of structural biology tools to elucidate the binding and orientation of gemfibrozil acyl glucuronide and clopidogrel acyl glucuronide in the active site near heme that contributes to the inhibition and inactivation of CYP2C8.

Physiologically Based Pharmacokinetic (PBPK) Modeling of Clopidogrel and Its Four Relevant Metabolites for CYP2B6, CYP2C8, CYP2C19, and CYP3A4 Drug–Drug–Gene Interaction Predictions

The antiplatelet agent clopidogrel is listed by the FDA as a strong clinical index inhibitor of cytochrome P450 (CYP) 2C8 and weak clinical inhibitor of CYP2B6. Moreover, clopidogrel is a substrate of—among others—CYP2C19 and CYP3A4. This work presents the development of a whole-body physiologically based pharmacokinetic (PBPK) model of clopidogrel including the relevant metabolites, clopidogrel carboxylic acid, clopidogrel acyl glucuronide, 2-oxo-clopidogrel, and the active thiol metabolite, with subsequent application for drug–gene interaction (DGI) and drug–drug interaction (DDI) predictions. Model building was performed in PK-Sim^® using 66 plasma concentration-time profiles of clopidogrel and its metabolites. The comprehensive parent-metabolite model covers biotransformation via carboxylesterase (CES) 1, CES2, CYP2C19, CYP3A4, and uridine 5′-diphospho-glucuronosyltransferase 2B7. Moreover, CYP2C19 was incorporated for normal, intermediate, and poor metabolizer phenotypes. Good predictive performance of the model was demonstrated for the DGI involving CYP2C19, with 17/19 predicted DGI AUC_last and 19/19 predicted DGI C_max ratios within 2-fold of their observed values. Furthermore, DDIs involving bupropion, omeprazole, montelukast, pioglitazone, repaglinide, and rifampicin showed 13/13 predicted DDI AUC_last and 13/13 predicted DDI C_max ratios within 2-fold of their observed ratios. After publication, the model will be made publicly accessible in the Open Systems Pharmacology repository.

Effect of Myricetin on CYP2C8 Inhibition to Assess the Likelihood of Drug Interaction Using In Silico, In Vitro, and In Vivo Approaches

Myricetin, a bioflavonoid, is widely used as functional food/complementary medicine and has promising multifaceted pharmacological actions against therapeutically validated anticancer targets. On the other hand, CYP2C8 is not only crucial for alteration in the pharmacokinetics of drugs to cause drug interaction but also unequivocally important for the metabolism of endogenous substances like the formation of epoxyeicosatrienoic acids (EETs), which are considered as signaling molecules against hallmarks of cancer. However, there is hardly any information known to date about the effect of myricetin on CYP2C8 inhibition and, subsequently, the CYP2C8-mediated drug interaction potential of myricetin at the preclinical/clinical level. We aimed here to explore the CYP2C8 inhibitory potential of myricetin using in silico, in vitro, and in vivo investigations. In the in vitro study, myricetin showed a substantial effect on CYP2C8 inhibition in human liver microsomes using CYP2C8-catalyzed amodiaquine-N-deethylation as an index reaction. Considering the Lineweaver-Burk plot, the Dixon plot, and the higher α-value, myricetin is found to be a mixed type of CYP2C8 inhibitor. Moreover, in vitro-in vivo extrapolation data suggest that myricetin is likely to cause drug interaction at the hepatic level. The molecular docking study depicted a strong interaction between myricetin and the active site of the human CYP2C8 enzyme. Moreover, myricetin caused considerable elevation in the oral exposure of amodiaquine as a CYP2C8 substrate via a slowdown of amodiaquine clearance in the rat model. Overall, the potent action of myricetin on CYP2C8 inhibition indicates that there is a need for further exploration to avoid drug interaction-mediated precipitation of obvious adverse effects as well as to optimize anticancer therapy.

A physiologically based pharmacokinetic model of clopidogrel in populations of European and Japanese ancestry: An evaluation of CYP2C19 activity

Treatment response to clopidogrel is associated with CYP2C19 activity through the formation of the active H4 metabolite. The aims of this study were to develop a physiologically based pharmacokinetic (PBPK) model of clopidogrel and its metabolites for populations of European ancestry, to predict the pharmacokinetics in the Japanese population by CYP2C19 phenotype, and to investigate the effect of clinical and demographic factors. A PBPK model was developed and verified to describe the two metabolic pathways of clopidogrel (H4 metabolite, acyl glucuronide metabolite) for a population of European ancestry using plasma data from published studies. Subsequently, model predictions in the Japanese population were evaluated. The effects of CYP2C19 activity, fluvoxamine coadministration (CYP2C19 inhibitor), and population-specific factors (age, sex, BMI, body weight, cancer, hepatic, and renal dysfunction) on the pharmacokinetics of clopidogrel and its metabolites were then characterized. The predicted/observed ratios for clopidogrel and metabolite exposure parameters were acceptable (twofold acceptance criteria). For all CYP2C19 phenotypes, steady-state AUC0-τ of the H4 metabolite was lower for the Japanese (e.g., EM, 7.69 [6.26-9.45] ng·h/ml; geometric mean [95% CI]) than European (EM, 24.8 [20.4-30.1] ng·h/ml, p < .001) population. In addition to CYP2C19-poor metabolizer phenotype, fluvoxamine coadministration, hepatic, and renal dysfunction were found to reduce H4 metabolite but not acyl glucuronide metabolite concentrations. This is the first PBPK model describing the two major metabolic pathways of clopidogrel, which can be applied to populations of European and Japanese ancestry by CYP2C19 phenotype. The differences between the two populations appear to be determined primarily by the effect of varying CYP2C19 liver activity.

Investigation of Human in vivo Metabolism of SEP-227900 Using the Samples from a Randomized First-in-Human Study by LC-UV/HRMS and NMR

OBJECTIVE

To explore the human in vivo metabolism of SEP-227900 (4H-furo[3, 2-b]pyrrole-carboxylic acid, m.w 151.03), a D-amino-acid oxidase (DAAO) inhibitor by using plasma and urine samples from first-in-human study.

METHODS

The human plasma and urine samples were from a single dose cohort that consisted of 9 healthy male volunteers each received 80-mg dose of SEP-227900 orally. The pooled pre-dose urine and the pooled 0-24 h urine sample were created across 9 subjects by equal volume. Plasma samples were pooled by equal volume across 9 subjects to obtain 0-12 h plasma for metabolite searching, and also pooled by timepoints across 9 subjects to obtain 0.5-, 5-, and 12-h plasma for semi-quantitation. The plasma was de-proteinized by acetonitrile (1:3 v/v plasma-acetonitrile) then the supernatant was dried down, reconstituted and injected for LC-HRMS/UV analysis. The urine sample was just simply centrifuged before analysis. LC-HRMS/UV was utilized to search predictable and unknown metabolites and estimate their relative abundances. Accurate mass measurement by Orbitrap-MS and MS/MS were used for metabolite identification. Chromatographic separation was achieved on a MACMOD AQ C8 column (250 × 4.6 mm, 5-µm) with a gradient mobile phase (A: 10 mM NH4Ac; B: acetonitrile; flowrate: 0.700 ml/min) for a total run-time of 65 min. The definite position in the molecule for the glucuronidation metabolism was characterized by detected migration phenomenon, methylation with diazomethane (CH2N2), and NMR.

RESULTS

Unchanged parent drug and four metabolite peaks were detected in humans: M1 was a mono-oxidative metabolite of SEP-227900; M2 was a glucuronide conjugate of SEP-227900; M3 was a glycine conjugate of SEP-227900; and M4 was a glycine conjugate of M1. The specific position of the oxidation in M1 solely based on the mass spectral (MS and MS/MS) data was not identified. However, for the major metabolite M2, the acyl glucuronidation was unambiguously determined through multiple pieces of experimental evidence such as the observation of a migration pattern, mono-methylation by diazomethane, and NMR measurement. This determination is of significance related to the safety evaluation of an investigational new drug development. The glycine conjugate of SEP-227900, i.e. M3 was found to be the most abundant metabolite in human urine (approximately 3-fold higher level as the glucuronide level). All together (mainly glycine-conjugate and glucuronide), it resulted in greater than 80% of the dosed amount in urine excretion (a separate measurement showed 23% of the dosed amount in urine excretion as the glucuronide).

CONCLUSION

Four metabolites were found in humans: SEP-227900-glycine conjugate, SEP227900-glucuronide, mono-oxidative metabolite and its consequent glycine conjugate. The glucuronide metabolite was identified as the acyl glucuronide. Greater than 80% of the dosed amount of SEP-227900 was excreted in urine mainly in the forms of glycine- and glucuronide- conjugates.

A pharmacovigilance study of pharmacokinetic drug interactions using a translational informatics discovery approach

BACKGROUND

While the pharmacokinetic (PK) mechanisms for many drug interactions (DDIs) have been established, pharmacovigilance studies related to these PK DDIs are limited. Using a large surveillance database, a translational informatics approach can systematically screen adverse drug events (ADEs) for many DDIs with known PK mechanisms.

METHODS

We collected a set of substrates and inhibitors related to the cytochrome P450 (CYP) isoforms, as recommended by the United States Food and Drug Administration (FDA) and Drug Interactions Flockhart table™. The FDA's Adverse Events Reporting System (FAERS) was used to obtain ADE reports from 2004 to 2018. The substrate and inhibitor information were used to form PK DDI pairs for each of the CYP isoforms and Medical Dictionary for Regulatory Activities (MedDRA) preferred terms used for ADEs in FAERS. A shrinkage observed-to-expected ratio (Ω) analysis was performed to screen for potential PK DDI and ADE associations.

RESULTS

We identified 149 CYP substrates and 62 CYP inhibitors from the FDA and Flockhart tables. Using FAERS data, only those DDI-ADE associations were considered that met the disproportionality threshold of Ω > 0 for a CYP substrate when paired with at least two inhibitors. In total, 590 ADEs were associated with 2085 PK DDI pairs and 38 individual substrates, with ADEs overlapping across different CYP substrates. More importantly, we were able to find clinical and experimental evidence for the paclitaxel-clopidogrel interaction associated with peripheral neuropathy in our study.

CONCLUSION

In this study, we utilized a translational informatics approach to discover potentially novel CYP-related substrate-inhibitor and ADE associations using FAERS. Future clinical, population-based and experimental studies are needed to confirm our findings.

The Role of Uptake and Efflux Transporters in the Disposition of Glucuronide and Sulfate Conjugates

Glucuronidation and sulfation are the most typical phase II metabolic reactions of drugs. The resulting glucuronide and sulfate conjugates are generally considered inactive and safe. They may, however, be the most prominent drug-related material in the circulation and excreta of humans. The glucuronide and sulfate metabolites of drugs typically have limited cell membrane permeability and subsequently, their distribution and excretion from the human body requires transport proteins. Uptake transporters, such as organic anion transporters (OATs and OATPs), mediate the uptake of conjugates into the liver and kidney, while efflux transporters, such as multidrug resistance proteins (MRPs) and breast cancer resistance protein (BCRP), mediate expulsion of conjugates into bile, urine and the intestinal lumen. Understanding the active transport of conjugated drug metabolites is important for predicting the fate of a drug in the body and its safety and efficacy. The aim of this review is to compile the understanding of transporter-mediated disposition of phase II conjugates. We review the literature on hepatic, intestinal and renal uptake transporters participating in the transport of glucuronide and sulfate metabolites of drugs, other xenobiotics and endobiotics. In addition, we provide an update on the involvement of efflux transporters in the disposition of glucuronide and sulfate metabolites. Finally, we discuss the interplay between uptake and efflux transport in the intestine, liver and kidneys as well as the role of transporters in glucuronide and sulfate conjugate toxicity, drug interactions, pharmacogenetics and species differences.

Inhibition of cytochrome P450 enzymes and uridine 5'-diphospho-glucuronosyltransferases by vicagrel in human liver microsomes: A prediction of potential drug-drug interactions

Vicagrel, an antiplatelet drug candidate targeting platelet P2Y₁₂ receptor and has finished its phase II clinical trial. The inhibition of six major cytochrome P450 enzymes (P450) (CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, and CYP3A4) and six UDP-glucuronosyltransferases (UGT) (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, and UGT2B7) by vicagrel was evaluated using pooled human liver microsomes and specific probe substrates. Physiology-based pharmacokinetic (PBPK) simulation was further applied to predict the in vivo drug-drug interaction (DDI) potential between vicagrel and bupropion as well as S-mephenytoin. The results suggested that vicagrel inhibited CYP2B6 and CYP2C19 potently with apparent IC₅₀ values of 1.6 and 2.0 μM, respectively. In terms of mode of reversible inhibition, vicagrel exhibited mixed-type inhibition of CYP2B6-catalyzed bupropion hydroxylation and noncompetitive inhibition of CYP2C19-mediated S-mephenytoin 4'-hydroxylation with K_i values of 0.19 μM and 1.2 μM, respectively. Vicagrel displayed profound time-dependent inhibition towards CYP2B6 with maximal rate constant of inactivation (k_inact) and half-maximal inactivator concentration (K_I) values of 0.062 min^-1 and 1.52 μM, respectively. No time-dependent inhibition by vicagrel was noted for CYP2C19. For UGT, negligible to moderate inhibition by vicagrel was observed with IC₅₀ values of >50.0, >50.0, 28.2, 8.7, >50.0 and 28.2 μM for UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9 and UGT2B7, respectively. In terms of mode of reversible inhibition, vicagrel exhibited mixed-type inhibition of UGT1A6-catalyzed N-Acetylserotonin β-D-glucuronidation with a K_i value of 5.6 μM. No time-dependent inhibition by vicagrel was noted for UGT1A6. PBPK simulation indicated that neither altered AUC nor C_max of bupropion and S-mephenytoin was observed in the presence of vicagrel. Our study provides inhibitory constants for future DDI prediction between vicagrel and drug substrates of CYP2B6, CYP2C19 and UGT1A6. In addition, our simulation suggests the lack of clinically important DDI between vicagrel and bupropion or S-mephenytoin.

Predictive In Vitro-In Vivo Extrapolation for Time Dependent Inhibition of CYP1A2, CYP2C8, CYP2C9, CYP2C19 and CYP2D6 Using Pooled Human Hepatocytes, Human Liver Microsomes, and a Simple Mechanistic Static Model

Inactivation of Cytochrome P450 (CYP450) enzymes can lead to significant increases in exposure of co-medicants. The majority of reported in vitro to in vivo extrapolation (IVIVE) data have historically focused on CYP3A4 leaving the assessment of other CYP isoforms insubstantial. To this end, the utility of human hepatocytes (HHEP) and microsome (HLM) to predict clinically relevant DDIs was investigated with a focus on CYP1A2, CYP2C8, CYP2C9, CYP2C19 and CYP2D6. Evaluation of IVIVE for CYP2B6 was limited to only weak inhibition. A search of the University of Washington Drug-Drug Interaction Database was conducted to identify a clinically relevant weak, moderate and strong inhibitor for selective substrates of CYP1A2, CYP2C8, CYP2C9, CYP2C19 and CYP2D6, resulting in 18 inhibitors for in vitro characterization against 119 clinical interaction studies. Pooled human hepatocytes and HLM were pre-incubated with increasing concentrations of inhibitors for designated timepoints. Time dependent inhibition (TDI) was detected in HLM for four moderate/strong inhibitors suggesting that some optimization of incubation conditions (i.e. lower protein concentrations) is needed to capture weak inhibition. Clinical risk assessment was conducted by incorporating the in vitro derived kinetic parameters k_inact and K_I into static equations recommended by regulatory authorities. Significant overprediction was observed when applying the basic models recommended by regulatory agencies. Mechanistic static models (MSM), which consider the fraction of metabolism through the impacted enzyme, using the unbound hepatic inlet concentration lead to the best overall prediction accuracy with 92% and 85% of data from HHEPs and HLM, respectively, within 2-fold of the observed value. Significance Statement Collectively, the data demonstrate that coupling time-dependent inactivation parameters derived from pooled human hepatocytes and HLM with a mechanistic static model provides an easy and quantitatively accurate means to determine clinical DDI risk from in vitro data. Weak and moderate inhibitors did not show TDI under standard incubation conditions using HLM and optimization of incubation conditions is warranted. Recommendations are made with respect to input parameters for IVIVE of TDI with non-CYP3A enzymes using available data from HLM and HHEPs.

Contributions of UDP-Glucuronosyltransferases to Human Hepatic and Intestinal Metabolism of Ticagrelor and Inhibition of UGTs and Cytochrome P450 Enzymes by Ticagrelor and its Glucuronidated Metabolite

Ticagrelor is the first reversibly binding, direct-acting, oral P2Y₁₂ receptor inhibitor. The contribution of UDP-glucuronosyltransferases (UGTs) enzymes to the metabolism of ticagrelor to its glucuronide conjugation, ticagrelor-O-glucuronide, in human liver microsomes (HLM) and human intestinal microsomes (HIM), was well characterized in the current study. The inhibition potential of human major UGTs by ticagrelor and ticagrelor-O-glucuronide was explored. The inhibitory effects of ticagrelor-O-glucuronide on cytochrome P450s (CYPs) enzymes were investigated as well. Ticagrelor glucuronidation exhibits substrate inhibition kinetics in both HLM and HIM with apparent K_m values of 5.65 and 2.52 μM, V_max values of 8.03 and 0.90 pmol min⁻¹·mg protein⁻¹, K_si values of 1,343.0 and 292.9 respectively. The in vitro intrinsic clearances (V_max/K_m) for ticagrelor glucuronidation by HLM and HIM were 1.42 and 0.36 μl min⁻¹·mg protein⁻¹, respectively. Study with recombinant human UGTs suggested that multiple UGT isoforms including UGT1A9, UGT1A7, UGT1A3, UGT1A4, UGT1A1, UGT2B7 and UGT1A8 are involved in the conversion of ticagrelor to ticagrelor-O-glucuronide with UGT1A9 showing highest catalytic activity. The results were further supported by the inhibition studies on ticagrelor glucuronidation with typical UGT inhibitors in pooled HLM and HIM. Little or no inhibition of UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9 and UGT2B7 by ticagrelor and ticagrelor-O-glucuronide was noted. Ticagrelor-O-glucuronide also exhibited limited inhibitory effects toward CYP2C8, CYP2D6 and CYP3A4. In contrast, ticagrelor-O-glucuronide weakly inhibited CYP2B6, CYP2C9 and CYP2C19 activity with apparent IC₅₀ values of 45.0, 20.0 and 18.8 μM, respectively. The potential of ticagrelor-O-glucuronide to cause drug-drug interactions warrant further study.

A Quantitative Approach to the Prediction of Drug-Drug Interactions Mediated by Cytochrome P450 2C8 Inhibition

BACKGROUND

Ohno and Colleagues proposed an approach for predicting drug-drug interactions (DDIs) mediated by cytochrome P450 (CYP) 3A4 based on the use of the ratio of the inhibited to non-inhibited area under the plasma concentration time curve (AUC) of substrates to estimate the fraction of the dose metabolized via CYP3A4 (contribution ratio, CR) and the in vivo inhibitory potency of a perpetrator (inhibition ratio, IR). This study evaluated the performance of this approach on DDIs mediated by CYP2C8 inhibitors.

RESEARCH DESIGN AND METHODS

Initial estimates of CR and IR of CYP2C8 substrates and inhibitors were calculated for 33 DDI in vivo studies. The approach was externally validated with 17 additional studies. Bayesian orthogonal regression was used to refine the estimates of the parameters. Assessment of prediction success was conducted by plotting observed versus predicted AUC ratios.

RESULTS

Final estimates of CRs and IRs were obtained for 19 CYP2C8 substrates and 23 inhibitors, respectively. The method demonstrated good predictive capacity, with only two values outside of the prespecified limits.

CONCLUSIONS

The approach may help to adapt dose regimens for CYP2C8 substrates when given in combination with CYP2C8 inhibitors and to map the potential DDIs of new molecular entities.

Evaluation of a Clinically Relevant Drug-Drug Interaction Between Rosuvastatin and Clopidogrel and the Risk of Hepatotoxicity

Purpose: The combination therapy of rosuvastatin (RSV) and the platelet inhibitor clopidogrel (CP) is widely accepted in the management of cardiovascular diseases. The objective of the present study was to identify the mechanism of RSV–CP DDI and evaluate the risk of hepatotoxicity associated with the concomitant use of CP.

Methods: We first studied the effect of CP and its major circulating metabolite, carboxylic acid metabolite (CPC), on RSV transport by overexpressing cells and membrane vesicles. Second, we investigated whether a rat model could replicate this DDI and then be used to conduct mechanistic studies and assess the risk of hepatotoxicity. Then, cytotoxicity assay in hepatocytes, biochemical examination, and histopathology were performed to measure the magnitude of liver injury in the presence and absence of DDI.

Results: CP inhibited OATP1B1-mediated transport of RSV with an IC₅₀ value of 27.39 μM. CP and CPC inhibited BCRP-mediated RSV transport with IC₅₀ values of <0.001 and 5.96 μM, respectively. The CP cocktail (0.001 μM CP plus 2 μM CPC) significantly inhibited BCRP-mediated transport of RSV by 26.28%. Multiple p.o. doses of CP significantly increased intravenous RSV plasma AUC_0-infinity by 76.29% and decreased intravenous RSV CL by 42.62%. Similarly, multiple p.o. doses of CP significantly increased p.o. RSV plasma AUC_0-infinity by 87.48% and decreased p.o. RSV CL by 43.27%. CP had no effect on cell viability, while RSV exhibited dose-dependent cytotoxicity after 96 h incubation. Co-incubation of 100 μM CP and RSV for 96 h significantly increased intracellular concentrations and cell-to-medium concentration ratios of RSV and reduced hepatocyte viability. Histological evaluation of liver specimens showed patterns of drug-induced liver injury. Cholestasis was found in rats in the presence of DDI.

Conclusion: CP is not a clinically relevant inhibitor for OATP1B1 and OATP1B3. The primary mechanism of RSV–CP DDI can be attributed to the inhibition of intestinal BCRP by CP combined with the inhibition of hepatic BCRP by CPC. The latter is likely to be more clinically relevant and be a contributing factor for increased hepatotoxicity in the presence of DDI.

Pharmacokinetics and Pharmacodynamics of Approved and Investigational P2Y12 Receptor Antagonists

Coronary artery disease remains the major cause of mortality worldwide. Antiplatelet drugs such as acetylsalicylic acid and P2Y12 receptor antagonists are cornerstone treatments for the prevention of thrombotic events in patients with coronary artery disease. Clopidogrel has long been the gold standard but has major pharmacological limitations such as a slow onset and long duration of effect, as well as weak platelet inhibition with high inter-individual pharmacokinetic and pharmacodynamic variability. There has been a strong need to develop potent P2Y12 receptor antagonists with more favorable pharmacological properties. Prasugrel and ticagrelor are more potent and have a faster onset of action; however, they have shown an increased bleeding risk compared with clopidogrel. Cangrelor is highly potent and has a very rapid onset and offset of effect; however, its indication is limited to P2Y12 antagonist-naïve patients undergoing percutaneous coronary intervention. Two novel P2Y12 receptor antagonists are currently in clinical development, namely vicagrel and selatogrel. Vicagrel is an analog of clopidogrel with enhanced and more efficient formation of its active metabolite. Selatogrel is characterized by a rapid onset of action following subcutaneous administration and developed for early treatment of a suspected acute myocardial infarction. This review article describes the clinical pharmacology profile of marketed P2Y12 receptor antagonists and those under development focusing on pharmacokinetic, pharmacodynamic, and drug-drug interaction liability.

Translational aspects of cytochrome P450-mediated drug-drug interactions: A case study with clopidogrel

Multimorbidity, polypharmacotherapy and drug interactions are increasingly common in the ageing population. Many drug-drug interactions (DDIs) are caused by perpetrator drugs inhibiting or inducing cytochrome P450 (CYP) enzymes, resulting in alterations of the plasma concentrations of a victim drug. DDIs can have a major negative health impact, and in the past, unrecognized DDIs have resulted in drug withdrawals from the market. Signals to investigate DDIs may emerge from a variety of sources. Nowadays, standard methods are widely available to identify and characterize the mechanisms of CYP-mediated DDIs in vitro. Clinical pharmacokinetic studies, in turn, provide experimental data on pharmacokinetic outcomes of DDIs. Physiologically based pharmacokinetic (PBPK) modelling utilizing both in vitro and in vivo data is a powerful tool to predict different DDI scenarios. Finally, epidemiological studies can provide estimates on the health outcomes of DDIs. Thus, to fully characterize the mechanisms, clinical effects and implications of CYP-mediated DDIs, translational research approaches are required. This minireview provides an overview of translational approaches to study CYP-mediated DDIs, going beyond regulatory DDI guidelines, and an illustrative case study of how the DDI potential of clopidogrel was unveiled by combining these different methods.

In Vitro Assessment of the Drug-Drug Interaction Potential of Verinurad and Its Metabolites as Substrates and Inhibitors of Metabolizing Enzymes and Drug Transporters

Verinurad is a selective uric acid transporter 1 (URAT1) inhibitor in development for the treatment of chronic kidney disease and heart failure. In humans, two major acyl glucuronide metabolites have been identified: direct glucuronide M1 and N-oxide glucuronide M8. Using in vitro systems recommended by regulatory agencies, we evaluated the interactions of verinurad, M1, and M8 with major drug-metabolizing enzymes and transporters and the potential for clinically relevant drug-drug interactions (DDIs). The IC50 for inhibition of CYP2C8, CYP2C9, and CYP3A4/5 for verinurad was ≥14.5 µM, and maximum free plasma concentration (Iu,max)/IC50 was <0.02 at the anticipated therapeutic Cmax and therefore not considered a DDI risk. Verinurad was not an inducer of CYP1A2, CYP2B6, or CYP3A4/5. Verinurad was identified as a substrate of the hepatic uptake transporter organic anion-transporting polypeptide (OATP) 1B3. Since verinurad hepatic uptake involved both active and passive transport, there is a low risk of clinically relevant DDIs with OATP, and further study is warranted. Verinurad was a substrate of the efflux transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), and renal transporter organic anion transporter 1 (OAT1), although it is not considered a DDI risk in vivo because of dose-proportional pharmacokinetics (P-gp and BCRP) and limited renal excretion of verinurad (OAT1). M1 and M8 were substrates of multidrug resistance-associated protein (MRP) 2 and MRP4 and inhibitors of MRP2. Apart from verinurad being a substrate of OATP1B3 in vitro, the potential for clinically relevant DDIs involving verinurad and its metabolites as victims or perpetrators of metabolizing enzymes or drug transporters is considered low. SIGNIFICANCE STATEMENT: Drug transporters and metabolizing enzymes have an important role in the absorption and disposition of a drug and its metabolites. Using in vitro systems recommended by regulatory agencies, we determined that, apart from verinurad being a substrate of organic anion-transporting polypeptide 1B3, the potential for clinically relevant drug-drug interactions involving verinurad and its metabolites M1 and M8 as victims or perpetrators of metabolizing enzymes or drug transporters is considered low.

An automated cocktail method for in vitro assessment of direct and time-dependent inhibition of nine major cytochrome P450 enzymes - application to establishing CYP2C8 inhibitor selectivity

We developed an in vitro high-throughput cocktail assay with nine major drug-metabolizing CYP enzymes, optimized for screening of time-dependent inhibition. The method was applied to determine the selectivity of the time-dependent CYP2C8 inhibitors gemfibrozil 1-O-β-glucuronide and clopidogrel acyl-β-D-glucuronide. In vitro incubations with CYP selective probe substrates and pooled human liver microsomes were conducted in 96-well plates with automated liquid handler techniques and metabolite concentrations were measured with quantitative UHPLC-MS/MS analysis. After determination of inter-substrate interactions and K_m values for each reaction, probe substrates were divided into cocktails I (tacrine/CYP1A2, bupropion/CYP2B6, amodiaquine/CYP2C8, tolbutamide/CYP2C9 and midazolam/CYP3A4/5) and II (coumarin/CYP2A6, S-mephenytoin/CYP2C19, dextromethorphan/CYP2D6 and astemizole/CYP2J2). Time-dependent inhibitors (furafylline/CYP1A2, selegiline/CYP2A6, clopidogrel/CYP2B6, gemfibrozil 1-O-β-glucuronide/CYP2C8, tienilic acid/CYP2C9, ticlopidine/CYP2C19, paroxetine/CYP2D6 and ritonavir/CYP3A) and direct inhibitor (terfenadine/CYP2J2) showed similar inhibition with single substrate and cocktail methods. Established time-dependent inhibitors caused IC₅₀ fold shifts ranging from 2.2 to 30 with the cocktail method. Under time-dependent inhibition conditions, gemfibrozil 1-O-β-glucuronide was a strong (>90% inhibition) and selective (<< 20% inhibition of other CYPs) inhibitor of CYP2C8 at concentrations ranging from 60 to 300 μM, while the selectivity of clopidogrel acyl-β-D-glucuronide was limited at concentrations above its IC₈₀ for CYP2C8. The time-dependent IC₅₀ values of these glucuronides for CYP2C8 were 8.1 and 38 µM, respectively. In conclusion, a reliable cocktail method including the nine most important drug-metabolizing CYP enzymes was developed, optimized and validated for detecting time-dependent inhibition. Moreover, gemfibrozil 1-O-β-glucuronide was established as a selective inhibitor of CYP2C8 for use as a diagnostic inhibitor in in vitro studies.

Assessment of Metabolic Interaction between Repaglinide and Quercetin via Mixed Inhibition in the Liver: In Vitro and In Vivo

Repaglinide (RPG), a rapid-acting meglitinide analog, is an oral hypoglycemic agent for patients with type 2 diabetes mellitus. Quercetin (QCT) is a well-known antioxidant and antidiabetic flavonoid that has been used as an important ingredient in many functional foods and complementary medicines. This study aimed to comprehensively investigate the effects of QCT on the metabolism of RPG and its underlying mechanisms. The mean (range) IC₅₀ of QCT on the microsomal metabolism of RPG was estimated to be 16.7 (13.0–18.6) μM in the rat liver microsome (RLM) and 3.0 (1.53–5.44) μM in the human liver microsome (HLM). The type of inhibition exhibited by QCT on RPG metabolism was determined to be a mixed inhibition with a K_i of 72.0 μM in RLM and 24.2 μM in HLM as obtained through relevant graphical and enzyme inhibition model-based analyses. Furthermore, the area under the plasma concentration versus time curve (AUC) and peak plasma concentration (C_max) of RPG administered intravenously and orally in rats were significantly increased by 1.83- and 1.88-fold, respectively, after concurrent administration with QCT. As the protein binding and blood distribution of RPG were observed to be unaltered by QCT, it is plausible that the hepatic first-pass and systemic metabolism of RPG could have been inhibited by QCT, resulting in the increased systemic exposure (AUC and C_max) of RPG. These results suggest that there is a possibility that clinically significant pharmacokinetic interactions between QCT and RPG could occur, depending on the extent and duration of QCT intake from foods and dietary supplements.

Physiologically-Based Pharmacokinetic-Pharmacodynamics Model Characterizing CYP2C19 Polymorphisms to Predict Clopidogrel Pharmacokinetics and Its Anti-Platelet Aggregation Effect Following Oral Administration to Coronary Artery Disease Patients With or Without Diabetes

Background and Objective: Clopidogrel (CLOP) is commonly used in coronary artery disease (CAD) patients with or without diabetes (DM), but these patients often suffer CLOP resistance, especially those with diabetes. This study was aimed to develop a physiologically-based pharmacokinetic-pharmacodynamic (PBPK-PD) model to describe the pharmacokinetics and pharmacodynamics of clopidogrel active metabolite (CLOP-AM) in CAD patients with or without DM.

Methods: The PBPK-PD model was first established and validated in healthy subjects and then in CAD patients with or without DM. The influences of CYP2C19, CYP2C9, CYP3A4, carboxylesterase 1 (CES1), gastrointestinal transit rates (K_t,i) and platelets response to CLOP-AM (k_irre) on predicted pharmacokinetics and pharmacodynamics were investigated, followed with their individual and integrated effects on CLOP-AM pharmacokinetics due to changes in DM status.

Results: Most predictions fell within 0.5–2.0 folds of observations, indicating successful predictions. Sensitivity analysis showed that contributions of interested factors to pharmacodynamics were CES1> k_irre> K_t,i> CYP2C19 > CYP3A4> CYP2C9. Mimicked analysis showed that the decreased exposure of CLOP-AM by DM was mainly attributed to increased CES1 activity, followed by decreased CYP2C19 activity.

Conclusion: The pharmacokinetics and pharmacodynamics of CLOP-AM were successfully predicted using the developed PBPK-PD model. Clopidogrel resistance by DM was the integrated effects of altered K_t,i, CYP2C19, CYP3A4, CES1 and k_irre.

In Vitro Evidence of Potential Interactions between CYP2C8 and Candesartan Acyl-β-D-glucuronide in the Liver

Growing evidence suggests that certain glucuronides function as potent inhibitors of CYP2C8. We previously reported the possibility of drug-drug interactions between candesartan cilexetil and paclitaxel. In this study, we evaluated the effects of candesartan N2-glucuronide and candesartan acyl-β-D-glucuronide on pathways associated with the elimination of paclitaxel, including those involving organic anion-transporting polypeptide (OATP) 1B1, OATP1B3, CYP2C8, and CYP3A4. UDP-glucuronosyltransferase (UGT) 1A10 and UGT2B7 were found to increase candesartan N2-glucuronide and candesartan acyl-β-D-glucuronide formation in a candesartan concentration-dependent manner. Additionally, the uptake of candesartan N2-glucuronide and candesartan acyl-β-D-glucuronide by cells stably expressing OATPs is a saturable process with K _m of 5.11 and 12.1 μM for OATP1B1 and 28.8 and 15.7 μM for OATP1B3, respectively; both glucuronides exhibit moderate inhibition of OATP1B1/1B3. Moreover, the hydroxylation of paclitaxel was evaluated using recombinant CYP3A4 and CYP3A5. Results show that candesartan, candesartan N2-glucuronide, and candesartan acyl-β-D-glucuronide inhibit the CYP2C8-mediated metabolism of paclitaxel, with candesartan acyl-β-D-glucuronide exhibiting the strongest inhibition (IC₅₀ is 18.9 µM for candesartan acyl-β-D-glucuronide, 150 µM for candesartan, and 166 µM for candesartan N2-glucuronide). However, time-dependent inhibition of CYP2C8 by candesartan acyl-β-D-glucuronide was not observed. Conversely, the IC₅₀ values of all the compounds are comparable for CYP3A4. Taken together, these data suggest that candesartan acyl-β-D-glucuronide is actively transported by OATPs into hepatocytes, and drug-drug interactions may occur with coadministration of candesartan and CYP2C8 substrates, including paclitaxel, as a result of the inhibition of CYP2C8 function. SIGNIFICANCE STATEMENT: This study demonstrates that the acyl glucuronidation of candesartan to form candesartan acyl-β-D-glucuronide enhances CYP2C8 inhibition while exerting minimal effects on CYP3A4, organic anion-transporting polypeptide (OATP) 1B1, and OATP1B3. Thus, candesartan acyl-β-D-glucuronide might represent a potential mediator of drug-drug interactions between candesartan and CYP2C8 substrates, such as paclitaxel, in clinical settings. This work adds to the growing knowledge regarding the inhibitory effects of glucuronides on CYP2C8.

Predicting the Effects of CYP2C19 and Carboxylesterases on Vicagrel, a Novel P2Y12 Antagonist, by Physiologically Based Pharmacokinetic/Pharmacodynamic Modeling Approach

Vicagrel, a novel acetate derivative of clopidogrel, exhibits a favorable safety profile and excellent antiplatelet activity. Studies aim at identifying genetic and non-genetic factors affecting vicagrel metabolic enzymes Cytochrome P450 2C19 (CYP2C19), Carboxylesterase (CES) 1 and 2 (CES1 and CES2), which may potentially lead to altered pharmacokinetics and pharmacodynamics, are warranted. A physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model incorporating vicagrel and its metabolites was constructed, verified and validated in our study, which could simultaneously characterize its sequential two step metabolism and clinical response. Simulations were then performed to evaluate the effects of CYP2C19, CES1 and CES2 genetic polymorphisms as well as inhibitors of these enzymes on vicagrel pharmacokinetics and antiplatelet effects. Results suggested vicagrel was less influenced by CYP2C19 metabolic phenotypes and CES1 428 G > A variation, in comparison to clopidogrel. No pharmacokinetic difference in the active metabolite was also noted for volunteers carrying different CES2 genotypes. Omeprazole, a CYP2C19 inhibitor, and simvastatin, a CES1 and CES2 inhibitor, showed weak impact on the pharmacokinetics and pharmacodynamics of vicagrel. This is the first study proposing a dynamic PBPK/PD model of vicagrel able to capture its pharmacokinetic and pharmacodynamic profiles simultaneously. Simulations indicated that genetic polymorphisms and drug-drug interactions showed no clinical relevance for vicagrel, suggesting its potential advantages over clopidogrel for treatment of cardiovascular diseases. Our model can be utilized to support further clinical trial design aiming at exploring the effects of genetic polymorphisms and drug-drug interactions on PK and PD of this novel antiplatelet agent.

Effects of angiotensin II receptor blockers on serum levels of epoxyeicosatrienoic acids and dihydroxyeicosatrienoic acids in patients admitted to a cardiovascular center

Purpose

Several clinical studies have demonstrated that angiotensin-converting enzyme inhibitors, but not angiotensin II receptor blockers (ARBs), reduce the risk of non-fatal myocardial infarction and cardiovascular mortality. We found that ARBs inhibited the activity of various cytochrome enzymes in arachidonic acid metabolism, resulting in decreased in vitro production of epoxyeicosatrienoic acids (EETs), which exhibit vasodilation and anti-inflammatory effects, and their subsequent metabolites, dihydroxyeicosatrienoic acids (DHETs). The present study examined the effects of ARBs on serum levels of EETs and DHETs in patients admitted to a cardiovascular center.

Methods

A total of 223 patients were enrolled, of which 107 were exposed to ARBs in this study. ARB-free individuals were defined as the control group (n = 116). Serum levels of EETs and DHETs were measured by liquid chromatography–tandem mass spectrometry. Multiple linear regression analyses were carried out to identify covariates for total serum levels of EETs and DHETs.

Results

A significant negative association was observed between ARB use and serum EET and DHET levels (p = 0.034), whereas a significant positive association was observed between the estimated glomerular filtration rate (eGFR) and serum EET and DHET levels (p = 0.007). The median serum total EET and DHET level in the ARB group tended to become lower than that in the control group, although the difference was not significant.

Conclusion

ARB use and eGFR were significantly associated with total serum levels of EETs and DHETs. Our results suggest that ARBs could affect the concentration of EETs in vivo.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00228-020-03061-1.

Reversible Mechanisms of Enzyme Inhibition and Resulting Clinical Significance

Inhibition of a drug-metabolizing enzyme by the reversible interaction of a drug with the enzyme, thus decreasing the metabolism of another drug, is a major cause of clinically significant drug-drug interactions. This chapter defines the four reversible mechanisms of inhibition exhibited by drugs: competitive, noncompetitive, uncompetitive, and mixed competitive/noncompetitive. An in vitro procedure to determine the potential of a drug to be a reversible inhibitor is also provided. Finally, a number of examples of clinically significant drug-drug interactions resulting from reversible inhibition are described.

Hypoglycemia during the Concomitant Use of Repaglinide and Clopidogrel in an Elderly Patient with Type 2 Diabetes and Severe Renal Insufficiency

Hypoglycemia should be avoided when treating patients with diabetes. Repaglinide is an insulin secretagogue with a low hypoglycemic risk because of its rapid- and short-acting effects. However, its blood concentration has been reported to increase in combination with clopidogrel, an antiplatelet drug, and in patients with severe renal insufficiency. We herein report an elderly patient with type 2 diabetes mellitus and severe renal insufficiency who received repaglinide and hypoglycemia three days after starting clopidogrel. The concomitant use of repaglinide and clopidogrel can lead to hypoglycemia, especially in patients with severe renal insufficiency.

Clinical evaluation of drug-drug interactions between the cytochrome P450 substrates selexipag and clopidogrel in Japanese volunteers

AIMS

The strong cytochrome P450 (CYP) 2C8 inhibitor gemfibrozil has been demonstrated to increase the area under the plasma concentration-time curve from 0 to infinity (AUC_0-∞ ) of ACT-333679, an active metabolite of selexipag, by 11-fold. Similarly to gemfibrozil, the CYP2C8 inhibitor clopidogrel increased ACT-333679 concentration by 1.9-fold after a single loading dose (300 mg once daily) and 2.7-fold after repeated treatment with the maintenance dose (75 mg once daily) in Europeans. However, the effects of clopidogrel on the pharmacokinetics of selexipag and ACT-333679 have not been fully elucidated in the Japanese population.

METHODS

We investigated the effect of clopidogrel on the pharmacokinetics of selexipag and ACT-333679 in 14 healthy Japanese volunteers.

RESULTS

The concomitant administration of clopidogrel with selexipag did not influence the maximum concentration and AUC_0-∞ of selexipag, whereas it significantly increased AUC_0-∞ of ACT-333679 by approximately 1.90-fold (90% confidence interval 1.69-2.14) without changing the maximum concentration. When selexipag was administered 1 day after clopidogrel was discontinued, the increase in AUC_0-∞ of ACT-333679 was 1.37-fold (90% confidence interval 0.93-2.02), suggesting that, although the inhibitory effect of clopidogrel on CYP2C8 was reduced, it persisted for at least 1 day after withdrawal.

CONCLUSION

Our results demonstrated the impact of clopidogrel on the pharmacokinetics of selexipag and its active metabolite and suggested that selexipag should be carefully prescribed with clopidogrel with dose adjustment or reducing the dosing frequency in Japanese clinical settings.

Biotransformation: Impact and Application of Metabolism in Drug Discovery

Biotransformation has a huge impact on the efficacy and safety of drugs. Ultimately the effects of metabolism can be the lynchpin in the discovery and development cycle of a new drug. This article discusses the impact and application of biotransformation of drugs by mammalian systems, microorganisms, and recombinant enzymes, covering active and reactive metabolites, the impact of the gut microbiome on metabolism, and how insights gained from biotransformation studies can influence drug design from the combined perspectives of a CRO specializing in a range of biotransformation techniques and pharma biotransformation scientists. We include a commentary on how biology-driven approaches can complement medicinal chemistry strategies in drug optimization and the in vitro and surrogate systems available to explore and exploit biotransformation.

Inhibition and induction of CYP enzymes in humans: an update

The cytochrome P450 (CYP) enzyme family is the most important enzyme system catalyzing the phase 1 metabolism of pharmaceuticals and other xenobiotics such as herbal remedies and toxic compounds in the environment. The inhibition and induction of CYPs are major mechanisms causing pharmacokinetic drug–drug interactions. This review presents a comprehensive update on the inhibitors and inducers of the specific CYP enzymes in humans. The focus is on the more recent human in vitro and in vivo findings since the publication of our previous review on this topic in 2008. In addition to the general presentation of inhibitory drugs and inducers of human CYP enzymes by drugs, herbal remedies, and toxic compounds, an in-depth view on tyrosine-kinase inhibitors and antiretroviral HIV medications as victims and perpetrators of drug–drug interactions is provided as examples of the current trends in the field. Also, a concise overview of the mechanisms of CYP induction is presented to aid the understanding of the induction phenomena.

Evidence-based strategies for the characterisation of human drug and chemical glucuronidation in vitro and UDP-glucuronosyltransferase reaction phenotyping

Enzymes of the UDP-glucuronosyltransferase (UGT) superfamily contribute to the elimination of drugs from almost all therapeutic classes. Awareness of the importance of glucuronidation as a drug clearance mechanism along with increased knowledge of the enzymology of drug and chemical metabolism has stimulated interest in the development and application of approaches for the characterisation of human drug glucuronidation in vitro, in particular reaction phenotyping (the fractional contribution of the individual UGT enzymes responsible for the glucuronidation of a given drug), assessment of metabolic stability, and UGT enzyme inhibition by drugs and other xenobiotics. In turn, this has permitted the implementation of in vitro - in vivo extrapolation approaches for the prediction of drug metabolic clearance, intestinal availability, and drug-drug interaction liability, all of which are of considerable importance in pre-clinical drug development. Indeed, regulatory agencies (FDA and EMA) require UGT reaction phenotyping for new chemical entities if glucuronidation accounts for ≥25% of total metabolism. In vitro studies are most commonly performed with recombinant UGT enzymes and human liver microsomes (HLM) as the enzyme sources. Despite the widespread use of in vitro approaches for the characterisation of drug and chemical glucuronidation by HLM and recombinant enzymes, evidence-based guidelines relating to experimental approaches are lacking. Here we present evidence-based strategies for the characterisation of drug and chemical glucuronidation in vitro, and for UGT reaction phenotyping. We anticipate that the strategies will inform practice, encourage development of standardised experimental procedures where feasible, and guide ongoing research in the field.

Clopidogrel drug interactions: a review of the evidence and clinical implications

INTRODUCTION

Patients with cardiovascular disease are commonly affected by a number of comorbidities leading to a high prevalence of polypharmacy. Polypharmacy increases the probability of drug-drug interactions (DDIs). Amongst these, DDIs involving clopidogrel, the most commonly utilized platelet P2Y₁₂ inhibitor, is a topic of potential clinical concern.

AREAS COVERED

This article reviews DDIs between clopidogrel and drugs which are widely used in clinical practice. In particular, drugs shown to interfere with the pharmacodynamic and pharmacokinetic effects of clopidogrel and the clinical implications of these findings are reviewed. These drugs include inhibitors of gastric acid secretion, statins, calcium channel blockers, antidiabetic agents, and antimicrobial agents. For the references, we searched PubMed, EMBASE, or the Cochrane Library.

EXPERT OPINION

Clopidogrel-drug interactions are common. Most of these DDIs are limited to laboratory findings showing an impact on clopidogrel-induced antiplatelet effects. While variability in clopidogrel-induced antiplatelet effects is known to affect clinical outcomes, with high platelet reactivity being associated with thrombotic complications among patients undergoing coronary stenting, most studies assessing the clinical implications of clopidogrel-drug interactions have not shown to significantly affect outcomes. However, awareness of these DDIs remains important for optimizing the selection of concomitant therapies.

Clopidogrel, a CYP2C8 inhibitor, causes a clinically relevant increase in the systemic exposure to the active metabolite of selexipag in healthy subjects

Aims

Selexipag is a prostacyclin receptor agonist approved for the treatment of pulmonary arterial hypertension. Cytochrome P450 (CYP) 2C8 is involved in the metabolism of selexipag and its active metabolite, ACT‐333679. This study evaluated the interaction of selexipag and clopidogrel, a CYP2C8 inhibitor.

Methods

The study had a 2‐treatment, 1‐sequence, crossover design. Pharmacokinetics (PK) and CYP2C8 genotype were assessed in healthy male subjects administered selexipag (200 μg twice daily [b.i.d.]) alone or with clopidogrel (300 mg single dose or 75 mg once daily [o.d.]). PK modelling and simulation were conducted to support dosing recommendations.

Results

Clopidogrel had a comparatively small effect on selexipag (<1.5‐fold difference in any PK variable). For ACT‐333679, the major contributor to the drug effect, the area under the plasma concentration–time curve during a dose interval and the maximum plasma concentration increased 2.25‐fold (90% confidence interval [CI] 2.06, 2.46) and 1.69‐fold (90% CI 1.55, 1.84), respectively with clopidogrel 300 mg and 2.70‐fold (90% CI 2.45, 2.96) and 1.90‐fold (90% CI 1.72, 2.11), respectively with clopidogrel 75 mg. The effect of clopidogrel on selexipag and ACT‐333679 exposure was comparable for all identified CYP2C8 genotypes. PK simulations predicted comparable exposure to ACT‐333679 following selexipag 400 μg b.i.d., 400 μg o.d. in combination with clopidogrel 75 mg o.d and 200 μg b.i.d. with clopidogrel 75 mg o.d.

Conclusion

Results suggest that ACT‐333679 exposure can be maintained within the therapeutic range by reducing selexipag dosing frequency to o.d. or dose to half, when selexipag is coadministered with clopidogrel.

Risk of hypoglycemia associated with repaglinide combined with clopidogrel, a retrospective cohort study

Background

Repaglinide is widely prescribed to reduce postprandial hyperglycemia and elevated glycated hemoglobin (HbA1c) levels associated with type 2 diabetes, and clopidogrel is a thienopyridine antiplatelet agent and widely used in cardiovascular and cerebrovascular diseases. It has been suggested that the concomitant use of repaglinide with clopidogrel may inhibit repaglinide metabolism, because repaglinide is a substrate of cytochrome P450 2C8 (CYP2C8) and the main metabolite of clopidogrel acyl-β-D-glucuronide inhibits CYP2C8 activity. In this study, we retrospectively investigated the effect of clopidogrel with repaglinide on plasma glucose and the risk of hypoglycemia associated with the combination of both drugs.

Method

Patients were taking clopidogrel (75 mg/day) and started taking glinide (1.5 mg/day repaglinide or 30 mg/day mitiglinide) for the first time from April 2012 to March 2017. We targeted subjects who were hospitalized at the start of glinide and whose preprandial plasma glucose was measured by a nurse. The glucose levels were collected for up to 5 days before and after the glinide start date.

Results

Average fasting plasma glucose levels (before breakfast) in the repaglinide and clopidogrel group before and after starting repaglinide were 180.1±35.5 and 136.5 ± 44.1 mg/dL, with a mean decrease of 43.6 ± 33.6 mg/dL. In contrast, there was only a moderate decrease of 11.6 ± 30.0 mg/dL in the mitiglinide and clopidogrel group. Minimum plasma glucose levels in the repaglinide and clopidogrel group before and after starting repaglinide were 145.2 ± 42.9 and 93.3 ± 36.3 mg/dL, respectively. Decrease in minimum levels after starting glinide in the repaglinide and clopidogrel group (51.9 ± 47.5 mg/dL) was more significant than those in the mitiglinide and clopidogrel group (only 2.1 ± 29.1 mg/dL), and the repaglinide group (without clopidogrel, 15.5 ± 20.0 mg/dL). Hypoglycemia was observed in 6 of 15 patients in the repaglinide and clopidogrel group, but only 1 of 15 patients in the mitiglinide and clopidogrel group, and no patients in the repaglinide group.

Conclusion

These findings indicate that minimum plasma glucose levels were significantly decreased in patients taking repaglinide and clopidogrel. Considering the risk of hypoglycemia associated with taking repaglinide and clopidogrel, when a glinide is required in patients taking clopidogrel, mitiglinide may be a better choice.

The Role of CYP450 Drug Metabolism in Precision Cardio-Oncology

As many novel cancer therapies continue to emerge, the field of Cardio-Oncology (or onco-cardiology) has become crucial to prevent, monitor and treat cancer therapy-related cardiovascular toxicity. Furthermore, given the narrow therapeutic window of most cancer therapies, drug-drug interactions are prevalent in the cancer population. Consequently, there is an increased risk of affecting drug efficacy or predisposing individual patients to adverse side effects. Here we review the role of cytochrome P450 (CYP450) enzymes in the field of Cardio-Oncology. We highlight the importance of cardiac medications in preventive Cardio-Oncology for high-risk patients or in the management of cardiotoxicities during or following cancer treatment. Common interactions between Oncology and Cardiology drugs are catalogued, emphasizing the impact of differential metabolism of each substrate drug on unpredictable drug bioavailability and consequent inter-individual variability in treatment response or development of cardiovascular toxicity. This inter-individual variability in bioavailability and subsequent response can be further enhanced by genomic variants in CYP450, or by modifications of CYP450 gene, RNA or protein expression or function in various 'omics' related to precision medicine. Thus, we advocate for an individualized approach to each patient by a multidisciplinary team with clinical pharmacists evaluating a treatment plan tailored to a practice of precision Cardio-Oncology. This review may increase awareness of these key concepts in the rapidly evolving field of Cardio-Oncology.

CYP2B6 Genotype-Dependent Inhibition of CYP1A2 and Induction of CYP2A6 by the Antiretroviral Drug Efavirenz in Healthy Volunteers

We investigated the effect of efavirenz on the activities of cytochrome P450 (CYP)1A2, CYP2A6, xanthine oxidase (XO), and N-acetyltransferase 2 (NAT2), using caffeine as a probe. A single 150 mg oral dose of caffeine was administered to healthy volunteers (n = 58) on two separate occasions; with a single 600 mg oral dose of efavirenz and after treatment with 600 mg/day efavirenz for 17 days. Caffeine and its metabolites in plasma and urine were quantified using liquid chromatography/tandem-mass spectrometry. DNA was genotyped for CYP2B6*4 (785A>G), CYP2B6*9 (516G>T), and CYP2B6*18 (983T>C) alleles using TaqMan assays. Relative to single-dose efavirenz treatment, multiple doses of efavirenz decreased CYP1A2 (by 38%) and increased CYP2A6 (by 85%) activities (P < 0.05); XO and NAT2 activities were unaffected. CYP2B6*6*6 genotype was associated with lower CYP1A2 activity following both single and multiple doses of efavirenz. No similar association was noted for CYP2A6 activity. This is the first report showing that efavirenz reduces hepatic CYP1A2 and suggesting chronic efavirenz exposure likely enhances the elimination of CYP2A6 substrates. This is also the first to report the extent of efavirenz-CYP1A2 interaction may be efavirenz exposure-dependent and CYP2B6 genotype-dependent.

Clinical Studies on Drug-Drug Interactions Involving Metabolism and Transport: Methodology, Pitfalls, and Interpretation

Many drug-drug interactions (DDIs) are based on alterations of the plasma concentrations of a victim drug due to another drug causing inhibition and/or induction of the metabolism or transporter-mediated disposition of the victim drug. In the worst case, such interactions cause more than tenfold increases or decreases in victim drug exposure, with potentially life-threatening consequences. There has been tremendous progress in the predictability and modeling of DDIs. Accordingly, the combination of modeling approaches and clinical studies is the current mainstay in evaluation of the pharmacokinetic DDI risks of drugs. In this paper, we focus on the methodology of clinical studies on DDIs involving drug metabolism or transport. We specifically present considerations related to general DDI study designs, recommended enzyme and transporter index substrates and inhibitors, pharmacogenetic perspectives, index drug cocktails, endogenous substrates, limited sampling strategies, physiologically-based pharmacokinetic modeling, complex DDIs, methodological pitfalls, and interpretation of DDI information.

Critical Differences between Enzyme Sources in Sensitivity to Detect Time-Dependent Inactivation of CYP2C8

Clopidogrel acyl-β-d-glucuronide is a mechanism-based inhibitor of cytochrome P450 2C8 in human liver microsomes (HLMs). However, time-dependent inactivation (TDI) of CYP2C8 could not be detected in an earlier study in human recombinant CYP2C8 (Supersomes). Here, we investigate whether different enzyme sources exhibit differences in detection of CYP2C8 TDI under identical experimental conditions. Inactivation of CYP2C8 by amiodarone (100 μM), clopidogrel acyl-β-d-glucuronide (100 μM), gemfibrozil 1-O-β-glucuronide (100 μM), and phenelzine (100 μM) was investigated in HLMs and three recombinant human CYP2C8 preparations (Supersomes, Bactosomes, and EasyCYP Bactosomes) using amodiaquine N-deethylation as the marker reaction. Furthermore, the inactivation kinetics of CYP2C8 by clopidogrel glucuronide (5-250 μM) was determined in Supersomes and Bactosomes. Amiodarone caused weak TDI in all enzyme preparations tested, while the extent of inactivation by clopidogrel glucuronide, gemfibrozil glucuronide, and phenelzine varied markedly between preparations, and even different Supersome lots. Both glucuronides caused strong inactivation of CYP2C8 in HLMs, Bactosomes and in one Supersome lot (>50% inhibition), but significant inactivation could not be reliably detected in other Supersome lots or EasyCYP Bactosomes. In Bactosomes, the concentration producing half of kinact (KI) and maximal inactivation rate (kinact) of clopidogrel glucuronide (14 μM and 0.054 minute-1) were similar to those determined previously in HLMs. Phenelzine caused strong inactivation of CYP2C8 in one Supersome lot (91% inhibition) but not in HLMs or other recombinant CYP2C8 preparations. In conclusion, different enzyme sources and different lots of the same recombinant enzyme preparation are not equally sensitive to detect inactivation of CYP2C8, suggesting that recombinant CYPs should be avoided when identifying mechanism-based inhibitors.