A discriminative analytical method for detection of CES1A1 and CES1A2/CES1A3 genetic variants

Dosage optimization of clopidogrel via a precision medicine approach: the way forward

Clopidogrel is a prodrug chiefly metabolized by the hepatic isoenzyme CYP2C19 to its active metabolite that inhibits the platelet aggregation. It has been proven in many populations that the genetic polymorphism of CYP2C19 has influence on the pharmacokinetic and or pharmacodynamics of this drug and resulting in high inter-individual variability in the treatment outcomes. As CYP2C19 genetic polymorphism is highly prevalent among the Asian population, the influence of the same on the pharmacokinetics and; thereby, the pharmacodynamics of clopidogrel needs more attention. Using the pharmacogenetic information for drug therapy could help overcome these issues and to optimize the dosage regimen of clopidogrel, this review advocates the precision medicine approach for reducing the clopidogrel resistance and adverse cardiovascular events.

Potential Regulatory Role of Human-Carboxylesterase-1 Glycosylation in Liver Cancer Cell Growth

We previously reported that human carboxylesterase 1 (CES1), a serine esterase containing a unique N-linked glycosyl group at Asn79 (N79 CES1), is a candidate serological marker of hepatocellular carcinoma (HCC). CES1 is normally present at low-to-undetectable levels in normal human plasma, HCC tumors, and major liver cancer cell lines. To investigate the potential mechanism underlying the suppression of CES1 expression in liver cancer cells, we took advantage of the low detectability of this marker in tumors by overexpressing CES1 in multiple HCC cell lines, including stable Hep3B cells. We found that the population of CES1-overexpressing (OE) cells decreased and that their doubling time was longer compared with mock control liver cancer cells. Using interactive transcriptome, proteome, and subsequent Gene Ontology enrichment analysis of CES1-OE cells, we found substantial decreases in the expression levels of genes involved in cell cycle regulation and proliferation. This antiproliferative function of the N79 glycan of CES1 was further supported by quantitative real-time polymerase chain reaction, flow cytometry, and an apoptosis protein array assay. An analysis of the levels of key signaling target proteins via Western blotting suggested that CES1 overexpression exerted an antiproliferative effect via the PKD1/PKCμ signaling pathway. Similar results were also seen in another HCC cell line (PLC/RFP/5) after transient transfection with CES1 but not in similarly treated non-HCC cell lines (e.g., HeLa and Tera-1 cells), suggesting that CES1 likely exerts a liver cell-type-specific suppressive effect. Given that the N-linked glycosyl group at Asn79 (N79 glycan) of CES1 is known to influence CES1 enzyme activity, we hypothesized that the post-translational modification of CES1 at N79 may be linked to its antiproliferative activity. To investigate the regulatory effect of the N79 glycan on cellular growth, we mutated the single N-glycosylation site in CES1 from Asn to Gln (CES1-N79Q) via site-directed mutagenesis. Fluorescence 2-D difference gel electrophoresis protein expression analysis of cell lysates revealed an increase in cell growth and a decrease in doubling time in cells carrying the N79Q mutation. Thus our results suggest that CES1 exerts an antiproliferative effect in liver cancer cells and that the single N-linked glycosylation at Asn79 plays a potential regulatory role. These functions may underlie the undetectability of CES1 in human HCC tumors and liver cancer cell lines. Mass spectrometry data are available via ProteomeXchange under the identifier PXD021573.

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.

The discovery of IDX21437: Design, synthesis and antiviral evaluation of 2'-α-chloro-2'-β-C-methyl branched uridine pronucleotides as potent liver-targeted HCV polymerase inhibitors

Herein we describe the discovery of IDX21437 35b, a novel R_Pd-aminoacid-based phosphoramidate prodrug of 2'-α-chloro-2'-β-C-methyluridine monophosphate. Its corresponding triphosphate 6 is a potent inhibitor of the HCV NS5B RNA-dependent RNA polymerase (RdRp). Despite showing very weak activity in the in vitro Huh-7 cell based HCV replicon assay, 35b demonstrated high levels of active triphosphate 6 in mouse liver and human hepatocytes. A biochemical study revealed that the metabolism of 35b was mainly attributed to carboxyesterase 1 (CES1), an enzyme which is underexpressed in HCV Huh-7-derived replicon cells. Furthermore, due to its metabolic activation, 35b was efficiently processed in liver cells compared to other cell types, including human cardiomyocytes. The selected R_P diastereoisomeric configuration of 35b was assigned by X-ray structural determination. 35b is currently in Phase II clinical trials for the treatment of HCV infection.

Reappraisal of the genetic diversity and pharmacogenetic assessment of CES1

The CES1 gene encodes a hydrolase that metabolizes important drugs. Variants generated by exchange of segments with CES1P1 complicate genotyping of CES1. Using a highly specific procedure we examined DNA samples from 200 Caucasians and identified 46 single nucleotide variants (SNVs) in CES1 and 21 SNVs in CES1A2, a hybrid composed of CES1 and CES1P1. Several of these SNVs were novel. The frequencies of SNVs with a potential functional impact were below 0.02 suggesting limited pharmacogenetic potential for CES1 genotyping. In silico PCR revealed that the majority of the primer pairs for amplification of CES1 or CES1A2 in three previous studies lacked specificity, which partially explains a limited overlap with our findings.

Population Pharmacokinetics of Methylphenidate in Healthy Adults Emphasizing Novel and Known Effects of Several Carboxylesterase 1 (CES1) Variants

The aim of this study was to identify demographic and genetic factors that significantly affect methylphenidate (MPH) pharmacokinetics (PK), and may help explain interindividual variability and further increase the safety of MPH. d‐MPH plasma concentrations, demographic covariates, and carboxylesterase 1 (CES1) genotypes were gathered from 122 healthy adults and analyzed using nonlinear mixed effects modeling. The structural model that best described the data was a two‐compartment disposition model with absorption transit compartments. Novel effects of rs115629050 and CES1 diplotypes, as well as previously reported effects of rs71647871 and body weight, were included in the final model. Assessment of the independent and combined effect of CES1 covariates identified several specific risk factors that may result in severely increased d‐MPH plasma exposure.

Individualization of treatments with drugs metabolized by CES1: combining genetics and metabolomics

CES1 is involved in the hydrolysis of ester group-containing xenobiotic and endobiotic compounds including several essential and commonly used drugs. The individual variation in the efficacy and tolerability of many drugs metabolized by CES1 is considerable. Hence, there is a large interest in individualizing the treatment with these drugs. The present review addresses the issue of individualized treatment with drugs metabolized by CES1. It describes the composition of the gene encoding CES1, reports variants of this gene with focus upon those with a potential effect on drug metabolism and provides an overview of the protein structure of this enzyme bringing notice to mechanisms involved in the regulation of enzyme activity. Subsequently, the review highlights drugs metabolized by CES1 and argues that individual differences in the pharmacokinetics of these drugs play an important role in determining drug response and tolerability suggesting prospects for individualized drug therapies. Our review also discusses endogenous substrates of CES1 and assesses the potential of using metabolomic profiling of blood to identify proxies for the hepatic activity of CES1 that predict the rate of drug metabolism. Finally, the combination of genetics and metabolomics to obtain an accurate prediction of the individual response to CES1-dependent drugs is discussed.

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

This study was designed to determine whether CES1A -816A/C polymorphism could be associated with altered clopidogrel response. Recruited patients were pretreated with 300 mg clopidogrel loading dose before undergoing percutaneous coronary intervention for stenting and genotyped with CYP2C19 *2, *3, or *17, and CES1A -816A/C, respectively. Adenosine diphosphate-induced maximum platelet aggregation (MPA) was determined on day 3 after initiation of daily clopidogrel maintenance doses. The clinical primary end point was the 1-year incidence of definite stent thrombosis (ST). Multivariable linear regression revealed that the CES1A -816A/C polymorphism was independently associated with MPA measures with an absolute β value of 6.76. Of 617 patients, a subcohort of 249 patients not carrying CYP2C19 *2, *3, or *17 were categorized into 3 groups based on the -816A/C genotype. The median MPA value was lower in 125 carriers of the -816C variant than in 124 noncarriers (21.5% vs. 31.7%, P = 0.001). The 1-year definite ST occurred in 7 patients in that subcohort, and only 1 ST case was one of carriers of the -816 A/A that was associated with higher MPA values. The CES1A -816C would be used to predict greater platelet response to clopidogrel than the CES1A -816A in percutaneous coronary intervention-treated patients not carrying CYP2C19 variants.