CES1A -816C as a genetic marker to predict greater platelet clopidogrel response in patients with percutaneous coronary intervention

Regulation of carboxylesterases and its impact on pharmacokinetics and pharmacodynamics: an up-to-date review

INTRODUCTION

Carboxylesterase 1 (CES1) and carboxylesterase 2 (CES2) are among the most abundant hydrolases in humans, catalyzing the metabolism of numerous clinically important medications, such as methylphenidate and clopidogrel. The large interindividual variability in the expression and activity of CES1 and CES2 affects the pharmacokinetics (PK) and pharmacodynamics (PD) of substrate drugs.

AREAS COVERED

This review provides an up-to-date overview of CES expression and activity regulations and examines their impact on the PK and PD of CES substrate drugs. The literature search was conducted on PubMed from inception to January 2024.

EXPERT OPINION

Current research revealed modest associations of CES genetic polymorphisms with drug exposure and response. Beyond genomic polymorphisms, transcriptional and posttranslational regulations can also significantly affect CES expression and activity and consequently alter PK and PD. Recent advances in plasma biomarkers of drug-metabolizing enzymes encourage the research of plasma protein and metabolite biomarkers for CES1 and CES2, which could lead to the establishment of precision pharmacotherapy regimens for drugs metabolized by CESs. Moreover, our understanding of tissue-specific expression and substrate selectivity of CES1 and CES2 has shed light on improving the design of CES1- and CES2-activated prodrugs.

Identification of regulatory variants of carboxylesterase 1 (CES1): A proof-of-concept study for the application of the Allele-Specific Protein Expression (ASPE) assay in identifying cis-acting regulatory genetic polymorphisms

It is challenging to study regulatory genetic variants as gene expression is affected by both genetic polymorphisms and non-genetic regulators. The mRNA allele-specific expression (ASE) assay has been increasingly used for the study of cis-acting regulatory variants because cis-acting variants affect gene expression in an allele-specific manner. However, poor correlations between mRNA and protein expressions were observed for many genes, highlighting the importance of studying gene expression regulation at the protein level. In the present study, we conducted a proof-of-concept study to utilize a recently developed allele-specific protein expression (ASPE) assay to identify the cis-acting regulatory variants of CES1 using a large set of human liver samples. The CES1 gene encodes for carboxylesterase 1 (CES1), the most abundant hepatic hydrolase in humans. Two cis-acting regulatory variants were found to be significantly associated with CES1 ASPE, CES1 protein expression, and its catalytic activity on enalapril hydrolysis in human livers. Compared to conventional gene expression-based approaches, ASPE demonstrated an improved statistical power to detect regulatory variants with small effect sizes since allelic protein expression ratios are less prone to the influence of non-genetic regulators (e.g., diseases and inducers). This study suggests that the ASPE approach is a powerful tool for identifying cis-regulatory variants.

Emerging role of carboxylesterases in nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is increasingly recognized as a global public health problem. Carboxylesterases (CESs), as potential influencing factors of NAFLD, are very important to improve clinical outcomes. This review aims to deeply understand the role of CESs in the progression of NAFLD and proposes that CESs can be used as potential targets for NAFLD treatment. We first introduced CESs and analyzed the relationship between CESs and hepatic lipid metabolism and inflammation. Then, we further reviewed the regulation of nuclear receptors on CESs, including PXR, CAR, PPARα, HNF4α and FXR, which may influence the progression of NAFLD. Finally, we evaluated the advantages and disadvantages of existing NAFLD animal models and summarized the application of CES-related animal models in NAFLD research. In general, this review provides an overview of the relationship between CESs and NAFLD and discusses the role and potential value of CESs in the treatment and prevention of NAFLD.

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.

Carboxylesterase 1 and Precision Pharmacotherapy: Pharmacogenetics and Nongenetic Regulators

Carboxylesterase (CES) 1 is the most abundant drug-metabolizing enzyme in human livers, comprising approximately 1% of the entire liver proteome. CES1 is responsible for 80%-95% of total hydrolytic activity in the liver and plays a crucial role in the metabolism of a wide range of drugs (especially ester-prodrugs), pesticides, environmental pollutants, and endogenous compounds. Expression and activity of CES1 vary markedly among individuals, which is a major contributing factor to interindividual variability in the pharmacokinetics (PK) and pharmacodynamics (PD) of drugs metabolized by CES1. Both genetic and nongenetic factors contribute to CES1 variability. Here, we discuss genetic polymorphisms, including single-nucleotide polymorphisms (SNPs), and copy number variants and nongenetic contributors, such as developmental status, genders, and drug-drug interactions, that could influence CES1 functionality and the PK and PD of CES1 substrates. Currently, the loss-of-function SNP G143E (rs71647871) is the only clinically significant CES1 variant identified to date, and alcohol is the only potent CES1 inhibitor that could alter the therapeutic outcomes of CES1 substrate medications. However, G143E and alcohol can only explain a small portion of the interindividual variability in the CES1 function. A better understanding of the regulation of CES1 expression and activity and identification of biomarkers for CES1 function in vivo could lead to the development of a precision pharmacotherapy strategy to improve the efficacy and safety of many CES1 substrate drugs. SIGNIFICANCE STATEMENT: The clinical relevance of CES1 has been well demonstrated in various clinical trials. Genetic and nongenetic regulators can affect CES1 expression and activity, resulting in the alteration of the metabolism and clinical outcome of CES1 substrate drugs, such as methylphenidate and clopidogrel. Predicting the hepatic CES1 function can provide clinical guidance to optimize pharmacotherapy of numerous medications metabolized by CES1.

Functional Study of Carboxylesterase 1 Protein Isoforms

Carboxylesterase 1 (CES1) is a primary human hepatic hydrolase involved in hydrolytic biotransformation of numerous medications. Considerable interindividual variability in CES1 expression and activity has been consistently reported. Four isoforms of the CES1 protein are produced by alternative splicing (AS). In the current study, the activity and expression of each CES1 isoform are examined using transfected cell lines, and CES1 isoform composition and its impact on CES1 activity in human livers are determined. In transfected cells, isoforms 3 and 4 show mRNA and protein expressions comparable to isoforms 1 and 2, but have significantly impaired activity when hydrolyzing enalapril and clopidogrel. In individual human liver samples, isoforms 1 and 2 are the major forms, contributing 73-90% of the total CES1 protein expression. In addition, the protein expression ratios of isoforms 1 and 2 to isoforms 3 and 4 are positively associated with CES1 activity in the liver, suggesting that CES1 isoform composition is a factor contributing to the variability in hepatic CES1 function. Further investigations of the regulation of CES1 AS would improve the understanding of CES1 variability and help develop a strategy to optimize the pharmacotherapy of many CES1 substrate medications.

Novel approach for CES1 genotyping: integrating single nucleotide variants and structural variation

Aim: Development of a specific procedure for genotyping of CES1A1 (CES1) and CES1A2, a hybrid of CES1A1  and the pseudogene CES1P1. Materials & methods: The number of CES1A1 and CES1A2  copies and that of CES1P1  were determined using real-time PCR. Long range PCRs followed by secondary PCRs allowed sequencing of single nucleotide variants in CES1A1 and CES1A2. Results & conclusion: A procedure consisting of two main steps was developed. Its first main step, the copy number determination, informed about presence of CES1A2 . This information enabled choice of PCR in the second main step, which selectively amplified CES1A1 and, if present, also CES1A2, for subsequent sequencing. Examination of 501 DNA samples suggested that our procedure is specific with potential for personalization of drug treatments.

Dabigatran etexilate activation is affected by the CES1 genetic polymorphism G143E (rs71647871) and gender

The oral anticoagulant prodrug dabigatran etexilate (DABE) is sequentially metabolized by intestinal carboxylesterase 2 (CES2) and hepatic carboxylesterase 1 (CES1) to form its active metabolite dabigatran (DAB). A recent genome-wide association study reported that the CES1 single nucleotide polymorphisms (SNPs) rs2244613 and rs8192935 were associated with lower DAB plasma concentrations in the Randomized Evaluation of Long-term Anticoagulation Therapy (RE-LY) study participants. In addition, gender differences in exposure to DAB were observed in clinical studies. The aim of this study was to examine the effect of CES1 genetic polymorphisms and gender on DABE activation using several in vitro approaches. The genotypes of the CES1 SNPs rs2244613, rs8192935, and the known loss-of-function CES1 variant rs71647871 (G143E), and the activation of DABE and its intermediate metabolites M1 and M2 were determined in 104 normal human liver samples. DABE, M1, and M2 activations were found to be impaired in human livers carrying the G143E variant. However, neither rs2244613 nor rs8192935 was associated with the activation in human livers. The incubation study of DABE with supernatant fractions (S9) prepared from the G143E-transfected cells showed that the G143E is a loss-of-function variant for DABE metabolism. Moreover, hepatic CES1 activity on M2 activation was significantly higher in female liver samples than male. Our data suggest that CES1 genetic variants and gender are important contributing factors to variability in DABE activation in humans. A personalized DABE treatment approach based on patient-specific CES1 genotypes and sex may have the potential to improve the efficacy and safety of DABE pharmacotherapy.

Association of Oseltamivir Activation with Gender and Carboxylesterase 1 Genetic Polymorphisms

Oseltamivir, an inactive anti-influenza virus prodrug, is activated (hydrolysed) in vivo by carboxylesterase 1 (CES1) to its active metabolite oseltamivir carboxylate. CES1 functions are significantly associated with certain CES1 genetic variants and some non-genetic factors. The purpose of this study was to investigate the effect of gender and several CES1 genetic polymorphisms on oseltamivir activation using a large set of individual human liver samples. CES1-mediated oseltamivir hydrolysis and CES1 genotypes, including the G143E (rs71647871), rs2244613, rs8192935, the -816A>C (rs3785161) and the CES1P1/CES1P1VAR, were determined in 104 individual human livers. The results showed that hepatic CES1 protein expression in females was 17.3% higher than that in males (p = 0.039), while oseltamivir activation rate in the livers from female donors was 27.8% higher than that from males (p = 0.076). As for CES1 genetic polymorphisms, neither CES1 protein expression nor CES1 activity on oseltamivir activation was significantly associated with the rs2244613, rs8192935, -816A>C or CES1P1/CES1P1VAR genotypes. However, oseltamivir hydrolysis in the livers with the genotype 143G/E was approximately 40% of that with the 143G/G genotype (0.7 ± 0.2 versus 1.8 ± 1.1 nmole/mg protein/min, p = 0.005). In summary, the results suggest that hepatic oseltamivir activation appears to be more efficient in females than that in males, and the activation can be impaired by functional CES1 variants, such as the G143E. However, clinical implication of CES1 gender differences and pharmacogenetics in oseltamivir pharmacotherapy warrants further investigations.

CES1 genetic variation affects the activation of angiotensin-converting enzyme inhibitors

The aim of the study was to determine the effect of carboxylesterase 1 (CES1) genetic variation on the activation of angiotensin-converting enzyme inhibitor (ACEI) prodrugs. In vitro incubation study of human liver, intestine and kidney s9 fractions demonstrated that the ACEI prodrugs enalapril, ramipril, perindopril, moexipril and fosinopril are selectively activated by CES1 in the liver. The impact of CES1/CES1VAR and CES1P1/CES1P1VAR genotypes and diplotypes on CES1 expression and activity on enalapril activation was investigated in 102 normal human liver samples. Neither the genotypes nor the diplotypes affected hepatic CES1 expression and activity. Moreover, among several CES1 nonsynonymous variants studied in transfected cell lines, the G143E (rs71647871) was a loss-of-function variant for the activation of all ACEIs tested. The CES1 activity on enalapril activation in human livers with the 143G/E genotype was approximately one-third of that carrying the 143G/G. Thus, some functional CES1 genetic variants (for example, G143E) may impair ACEI activation, and consequently affect therapeutic outcomes of ACEI prodrugs.

CES1P1 variant -816A>C is not associated with hepatic carboxylesterase 1 expression and activity or antihypertensive effect of trandolapril

PURPOSE

The majority of angiotensin-converting enzyme inhibitors (ACEIs) are synthesized as ester prodrugs that must be converted to their active forms in vivo in order to exert therapeutic effects. Hepatic carboxylesterase 1 (CES1) is the primary enzyme responsible for the bioactivation of ACEI prodrugs in humans. The genetic variant -816A>C (rs3785161) is a common variant located in the promoter region of the CES1P1 gene. Previous studies report conflicting results with regard to the association of this variant and therapeutic outcomes of CES1 substrate drugs. The purpose of this study was to determine the effect of the variant -816A>C on the activation of the ACEI prodrug trandolapril in human livers and the blood pressure (BP)-lowering effect of trandolapril in hypertensive patients.

METHODS

The -816A>C genotypes and CES1 expression and activity on trandolapril activation were determined in 100 individual human liver samples. Furthermore, the association of the -816A>C variant and the BP lowering effect of trandolapril was evaluated in hypertensive patients who participated in the International Verapamil SR Trandolapril Study (INVEST).

RESULTS

Our in vitro study demonstrated that hepatic CES1 expression and activity did not differ among different -816A>C genotypes. Moreover, we were unable to identify a clinical association between the BP lowering effects of trandolapril and -816A>C genotypes.

CONCLUSIONS

We conclude that the -816A>C variant is not associated with interindividual variability in CES1 expression and activity or therapeutic response to ACEI prodrugs.

Development of a physiology-directed population pharmacokinetic and pharmacodynamic model for characterizing the impact of genetic and demographic factors on clopidogrel response in healthy adults

Clopidogrel (Plavix®), is a widely used antiplatelet agent, which shows high inter-individual variability in treatment response in patients following the standard dosing regimen. In this study, a physiology-directed population pharmacokinetic/pharmacodynamic (PK/PD) model was developed based on clopidogrel and clopidogrel active metabolite (clop-AM) data from the PAPI and the PGXB2B studies using a step-wise approach in NONMEM (version 7.2). The developed model characterized the in vivo disposition of clopidogrel, its bioactivation into clop-AM in the liver and subsequent platelet aggregation inhibition in the systemic circulation reasonably well. It further allowed the identification of covariates that significantly impact clopidogrel's dose-concentration-response relationship. In particular, CYP2C19 intermediate and poor metabolizers converted 26.2% and 39.5% less clopidogrel to clop-AM, respectively, compared to extensive metabolizers. In addition, CES1 G143E mutation carriers have a reduced CES1 activity (82.9%) compared to wild-type subjects, which results in a significant increase in clop-AM formation. An increase in BMI was found to significantly decrease clopidogrel's bioactivation, whereas increased age was associated with increased platelet reactivity. Our PK/PD model analysis suggests that, in order to optimize clopidogrel dosing on a patient-by-patient basis, all of these factors have to be considered simultaneously, e.g. by using quantitative clinical pharmacology tools.

Clinical pharmacokinetics and pharmacodynamics of clopidogrel

Acute coronary syndromes (ACS) remain life-threatening disorders, which are associated with high morbidity and mortality. Dual antiplatelet therapy with aspirin and clopidogrel has been shown to reduce cardiovascular events in patients with ACS. However, there is substantial inter-individual variability in the response to clopidogrel treatment, in addition to prolonged recovery of platelet reactivity as a result of irreversible binding to P2Y12 receptors. This high inter-individual variability in treatment response has primarily been associated with genetic polymorphisms in the genes encoding for cytochrome (CYP) 2C19, which affect the pharmacokinetics of clopidogrel. While the US Food and Drug Administration has issued a boxed warning for CYP2C19 poor metabolizers because of potentially reduced efficacy in these patients, results from multivariate analyses suggest that additional factors, including age, sex, obesity, concurrent diseases and drug-drug interactions, may all contribute to the overall between-subject variability in treatment response. However, the extent to which each of these factors contributes to the overall variability, and how they are interrelated, is currently unclear. The objective of this review article is to provide a comprehensive update on the different factors that influence the pharmacokinetics and pharmacodynamics of clopidogrel and how they mechanistically contribute to inter-individual differences in the response to clopidogrel treatment.