Effect of UGT2B7 genotypes on plasma concentration of valproic acid: a meta-analysis

In vitro inhibitory effects of selumetinib on activity of human UDP-glucuronosyltransferases and prediction of in vivo drug-drug interactions

Selumetinib is an oral, effective, and selective tyrosine kinase inhibitor targeting mitogen-activated protein kinase 1 and 2 (MEK1/2), which is clinically active in multiple tumor types, such as neurofibromatosis type 1 (NF1), melanoma, gliomas and non-small cell lung cancer (NSCLC). The purpose of this article was to assess the effects of selumetinib on the activities of twelve human UDP-glucosyltransferases (UGTs) including UGT1A1, 1A3, 1A4, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, 2B15, and 2B17, and its potential for inducing clinical drug-drug interactions (DDIs). The results demonstrated that selumetinib potently inhibited the activity of UGT2B7 through the mechanism of mixed inhibition with the inhibition constant value of 5.79 ± 0.65 μM. Furthermore, the plasma concentration of UGT2B7 substrate as the co-administered drug was predicted to be increased by at least 84 % when patients took selumetinib 75 mg twice daily, suggesting a high potential to induce clinical DDIs. Selumetinib exhibited weak inhibitory effects on other human UGTs and was unlikely to trigger off UGTs-mediated DDIs except for UGT2B7. Therefore, the combination of selumetinib with the substrate drug of UGT2B7 requires additional attention to avoid adverse events in clinical treatment.

Hydrocodone, Oxycodone, and Morphine Metabolism and Drug-Drug Interactions

Awareness of drug interactions involving opioids is critical for patient treatment as they are common therapeutics used in numerous care settings, including both chronic and disease-related pain. Not only do opioids have narrow therapeutic indexes and are extensively used, but they have the potential to cause severe toxicity. Opioids are the classical pain treatment for patients who suffer from moderate to severe pain. More importantly, opioids are often prescribed in combination with multiple other drugs, especially in patient populations who typically are prescribed a large drug regimen. This review focuses on the current knowledge of common opioid drug-drug interactions (DDIs), focusing specifically on hydrocodone, oxycodone, and morphine DDIs. The DDIs covered in this review include pharmacokinetic DDI arising from enzyme inhibition or induction, primarily due to inhibition of cytochrome p450 enzymes (CYPs). However, opioids such as morphine are metabolized by uridine-5'-diphosphoglucuronosyltransferases (UGTs), principally UGT2B7, and glucuronidation is another important pathway for opioid-drug interactions. This review also covers several pharmacodynamic DDI studies as well as the basics of CYP and UGT metabolism, including detailed opioid metabolism and the potential involvement of metabolizing enzyme gene variation in DDI. Based upon the current literature, further studies are needed to fully investigate and describe the DDI potential with opioids in pain and related disease settings to improve clinical outcomes for patients. SIGNIFICANCE STATEMENT: A review of the literature focusing on drug-drug interactions involving opioids is important because they can be toxic and potentially lethal, occurring through pharmacodynamic interactions as well as pharmacokinetic interactions occurring through inhibition or induction of drug metabolism.

Assessment of clinically actionable pharmacogenetic markers to stratify anti-seizure medications

Epilepsy treatment is challenging due to heterogeneous syndromes, different seizure types and higher inter-individual variability. Identification of genetic variants predicting drug efficacy, tolerability and risk of adverse-effects for anti-seizure medications (ASMs) is essential. Here, we assessed the clinical actionability of known genetic variants, based on their functional and clinical significance and estimated their diagnostic predictability. We performed a systematic PubMed search to identify articles with pharmacogenomic (PGx) information for forty known ASMs. Functional annotation of the identified genetic variants was performed using different in silico tools, and their clinical significance was assessed using the American College of Medical Genetics (ACMG) guidelines for variant pathogenicity, level of evidence (LOE) from PharmGKB and the United States-Food and drug administration (US- FDA) drug labelling with PGx information. Diagnostic predictability of the replicated genetic variants was evaluated by calculating their accuracy. A total of 270 articles were retrieved with PGx evidence associated with 19 ASMs including 178 variants across 93 genes, classifying 26 genetic variants as benign/ likely benign, fourteen as drug response markers and three as risk factors for drug response. Only seventeen of these were replicated, with accuracy (up to 95%) in predicting PGx outcomes specific to six ASMs. Eight out of seventeen variants have FDA-approved PGx drug labelling for clinical implementation. Therefore, the remaining nine variants promise for potential clinical actionability and can be improvised with additional experimental evidence for clinical utility.

Population pharmacokinetics of oxcarbazepine active metabolite in Chinese children with epilepsy

Oxcarbazepine (OXC) is an antiepileptic drug whose efficacy is largely attributed to its monohydroxy derivative metabolite (MHD). Nevertheless, there exists significant inter-individual variability in both the pharmacokinetics and therapeutic response of this drug. The objective of this study is to explore the impact of patients' characteristics and genetic variants on MHD clearance in a population pharmacokinetic (PPK) model of Chinese pediatric patients with epilepsy. The PPK model was developed using a nonlinear mixed effects modeling method based on 231 MHD plasma concentrations obtained from 185 children with epilepsy. The one-compartment model and combined residual model were established to describe the pharmacokinetics of MHD. Forward addition and backward elimination were employed to evaluate the impact of covariates on the model parameters. The model was evaluated using goodness-of-fit, bootstrap, visual predictive checks, and normalized prediction distribution errors. In the two final PPK models, age, estimated glomerular filtration rate (eGFR), and a combined genotype of six variants (rs1045642, rs2032582, rs7668282, rs2396185, rs2304016, rs1128503) were found to significantly reduce inter-individual variability for MHD clearance. The inter-individual clearance equals to 1.38 × (Age/4.74)0.29 × (eGFR/128.66)0.25 × eθABCB-UGT-SCN-INSR for genetic variants included model and 1.30 × (Age/4.74)0.30 × (eGFR/128.66)0.23 for model without genetic variants. The precision of all parameters was deemed acceptable, and the model exhibited good predictability while remaining stable and effective.    Conclusion: Age, eGFR, and genotype may play a significant role in MHD clearance in children with epilepsy. The developed PPK models hold potential utility in facilitating oxcarbazepine dose adjustment in pediatric patients. What is Known: • The adjustment of the oxcarbazepine regimen remains difficult due to the considerable inter- and intra-individual variability of oxcarbazepine pharmacokinetics. • Body weight and co-administration with enzyme-inducing antiepileptic drugs emerge as the most influential factors contributing to the pharmacokinetics of MHD. What is New: • A positive correlation was observed between eGFR and the clearance of MHD in pediatric patients with epilepsy. • We explored the influence of genetic polymorphisms on MHD clearance and identified a combined genotype (ABCB-UGT-SCN-INSR) that exhibited a significant association with MHD concentration.

Cannabis Pharmacogenomics: A Path to Personalized Medicine

Cannabis and related compounds have created significant research interest as a promising therapy in many disorders. However, the individual therapeutic effects of cannabinoids and the incidence of side effects are still difficult to determine. Pharmacogenomics may provide the answers to many questions and concerns regarding the cannabis/cannabinoid treatment and help us to understand the variability in individual responses and associated risks. Pharmacogenomics research has made meaningful progress in identifying genetic variations that play a critical role in interpatient variability in response to cannabis. This review classifies the current knowledge of pharmacogenomics associated with medical marijuana and related compounds and can assist in improving the outcomes of cannabinoid therapy and to minimize the adverse effects of cannabis use. Specific examples of pharmacogenomics informing pharmacotherapy as a path to personalized medicine are discussed.

Effect of ANKK1 Polymorphisms on Serum Valproic Acid Concentration in Chinese Han Adult Patients in the Early Postoperative Period

INTRODUCTION

This study aimed to investigate the relationship between gene polymorphisms and clinical factors with the concentrations of valproic acid (VPA) in adult patients who underwent neurosurgery in China.

METHODS

A total of 531 serum concentration samples at steady state were collected from 313 patients to develop a population pharmacokinetic (PPK) model. Data analysis was performed using nonlinear mixed effects modeling. Covariates included demographic parameters, biological characteristics, and genetic polymorphism. Bootstrap evaluation showed that the final model was stable. Sensitive analysis was performed to verify the relationship between gene polymorphisms and concentrations of VPA. Linear regression was used to analyze the relationship between VPA concentration, ANKK1, and daily dosage.

RESULTS

In the recruited patients, 17 of 25 single-nucleotide polymorphism distributions were consistent with the Hardy-Weinberg equilibrium. A one-compartment model with first-order absorption and elimination was developed for VPA injections. VPA clearance was significantly influenced by three variables: sex (17.41% higher in male than female patients), body weight, and the ANKK1 gene. Typical values for the elimination clearance and the volume of central compartment were 0.614 L/min and 23.5 L, respectively. The model evaluation indicated the stable and precise performance of the final model. After sensitive analysis using Kruskal-Wallis and Mann-Whitney U tests, we found that patients with AA alleles had higher VPA concentrations than those with GG and AG alleles. Linear regression models showed that gene polymorphisms of ANKK1 had little effects on VPA concentration.

CONCLUSION

A PPK model of VPA in Chinese Han patients was successfully established; this can be helpful for model-informed precision-dosing approaches in clinical patient care, and for exploring the mechanism of VPA-induced weight gain.

UGT2B7 c.-161C>T polymorphism frequency in Croatian population

Uridine diphosphate glucuronosyltransferase-2B7 (UGT2B7), enzyme responsible for the elimination of a number of xenobiotics through glucuronidation, is expressed in the gut, kidneys, intestines, and brain. However, data on the frequency of UGT2B7 polymorphisms in the Croatian population are limited. The aim of this study was to assess the frequency of the UGT2B7 c.-161C>T (rs7668258) polymorphism in the Croatian population and to compare it with reported frequencies in other populations. This polymorphism is in complete linkage disequilibrium with the UGT2B7 c.802C>T (UGT2B7*2, rs7439366) variant, which is important in clinical medicine. The study reports data of 501 participants from University Hospital Centre Zagreb. All data were collected and analysed retrospectively. Genotyping was performed by real-time polymerase chain reaction (PCR) using the TaqMan® Drug Metabolism Genotyping Assay for UGT2B7 c.-161C>T (rs7668258). We found that 120 (23.95 %) participants were carriers of the UGT2B7 c.-161CC genotype and 255 (50.9 %) were heterozygous carriers (UGT2B7 c.-161CT), while 126 (25.15 %) were homozygous carriers of the variant allele (UGT2B7 c.-161TT). The frequency of the variant UGT2B7 c.-161C>T allele in this study was T=0.506. The frequency of the UGT2B7 c.-161C>T allelic variants and genotypes in the Croatian population is similar to other European populations.

Published population pharmacokinetic models of valproic acid in adult patients: a systematic review and external validation in a Chinese sample of inpatients with bipolar disorder

BACKGROUND

This study reviewed all published valproic acid (VPA) population pharmacokinetic (PPK) models in adult patients and assessed them using external validation methods to determine predictive performance.

METHODS

Thirteen published PPK models (labeled with letters A to M) not restricted to children were identified in PubMed, Embase, and Web of Science databases. They were evaluated in a sample totaling 411 serum concentrations from 146 adult inpatients diagnosed with bipolar disorder in a Chinese hospital. Serum concentrations of VPA were analyzed by validated ultra-performance liquid chromatography-tandem mass spectrometry. Performance was assessed by 4 tests (prediction-based diagnostics, visual predictive checks, normalized prediction distribution error, and Bayesian forecasting).

RESULTS

Models K and L, developed in large samples of Chinese and Thai patients, showed good performance in our Chinese dataset. Models H and J demonstrated good performance in Tests 2 and 3 of the 4 tests, respectively. Another 7 models exhibited intermediate performance. The models with the worst performance, F and M, could not be improved by Bayesian forecasting.

CONCLUSION

In our validation study the most important factors contributing to good performance were absence of children, Asian ethnicity, one-compartment models and inclusion of body weight and VPA dose in previously published models.

Effects of genetic polymorphism of drug-metabolizing enzymes on the plasma concentrations of antiepileptic drugs in Chinese population

As a chronic brain disease, epilepsy affects ~50 million people worldwide. The traditional antiepileptic drugs (AEDs) are widely applied but showing various problems. Although the new AEDs have partially solved the problems of traditional AEDs, the current clinical application of traditional AEDs are not completely replaced by new drugs, particularly due to the large individual differences in drug plasma concentrations and narrow therapeutic windows among patients. Therefore, it is still clinically important to continue to treat patients using traditional AEDs with individualized therapeutic plans. To date, our understanding of the molecular and genetic mechanisms regulating plasma concentrations of AEDs has advanced rapidly, expanding the knowledge on the effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of AEDs. It is increasingly imperative to summarize and conceptualize the clinical significance of recent studies on individualized therapeutic regimens. In this review, we extensively summarize the critical effects of genetic polymorphisms of genes encoding drug-metabolizing enzymes on the plasma concentrations of several commonly used AEDs as well as the clinical significance of testing genotypes related to drug metabolism on individualized drug dosage. Our review provides solid experimental evidence and clinical guidance for the therapeutic applications of these AEDs.

Population pharmacokinetics of valproic acid in adult Chinese patients with bipolar disorder

PURPOSE

To develop and validate a population pharmacokinetic (PPK) model of valproic acid (VPA) in adult Chinese patients with bipolar disorder, and provide guidance for individualized therapy in this population.

METHODS

A total of 1104 serum concentrations from 272 patients were collected in this study. The data analysis was performed using a nonlinear mixed-effects modeling approach. Covariates included demographic parameters, biological characteristics, and concomitant medications. Bootstrap validation (1000 runs), normalized prediction distribution error (NPDE), and external validation of 50 patients were employed to evaluate the final model.

RESULTS

A one-compartment model with first-order absorption and elimination was developed for VPA extended-release tablets. VPA clearance was significantly influenced by three variables: sex (12% higher in male patients), daily dose (increasing with the 0.13 exponent), and body weight (increasing with the 0.56 exponent). Typical values for the absorption rate constant (K_a), apparent clearance (CL/F), and apparent distribution volume (V/F) for a female patient weighing 70 kg administered VPA 1000 mg/day were 0.18 h^-1, 0.46 L/h, and 12.84 L, respectively. The results of model evaluation indicated a good stable and precise performance of the final model.

CONCLUSIONS

A qualified PPK model of VPA was developed in Chinese patients with bipolar disorder. This model could be used as a suitable tool for the personalization of VPA dosing for bipolar patients.

Valproic Acid After Neurosurgery Induces Elevated Risk of Liver Injury: A Prospective Nested Case-Control Study

BACKGROUND

Valproic acid (VPA) has been widely used to prevent epileptic seizures after neurosurgery in China. We have found that the incidence of liver injury (LI) in patients using VPA after neurosurgery is higher than that in other patients.

OBJECTIVE

The objective of this study was to investigate the risk factors of LI in patients using VPA after neurosurgery.

METHODS

A nested case-control study was conducted in patients using VPA after neurosurgery between September 2019 and March 2021. Cases of LI were matched to controls by age and body mass index (BMI). Conditional logistic regression was used to estimate matched odds ratios representing the odds of LI. A receiver operating characteristic curve was used to analyze the optimal cutoff condition.

RESULTS

A total of 248 people (62 LI and 186 control) were enrolled. Among patients with vs without LI, the matched odds ratio for trough concentration of VPA was significant (matched odds ratio [OR], 1.09; 95% confidence interval [CI]: 1.01-1.19). The course of treatment (OR: 1.17, 95% CI: 1.02-1.33), Glasgow score (OR: 0.26, 95% CI: 0.10-0.67), gene polymorphisms of CYP2C19 (OR: 2.09, 95% CI: 1.03-146.93), and UGT1A6 (OR: 34.61, 95% CI: 1.19-1003.23) were all related to the outcome. The optimal cutoff of the course of treatment was 10 days, while the trough concentration of VPA was determined to be 66.16 mg/L.

CONCLUSION

Length of treatment, VPA trough concentration, and Glasgow score were associated with LI in patients after neurosurgery. A gene test may be necessary for people who are prescribed VPA for a long time.

Genetics and antiepileptic mood stabilizer treatment response in bipolar disorder: what do we know?

Antiepileptic mood stabilizers (AED-MS) are often used to treat bipolar disorder (BD). Similar to other mood disorder medications, AED-MS treatment response varies between patients. Identification of biomarkers associated with treatment response may ultimately help with the delivery of individualized treatment and lead to improved treatment efficacy. Here, we conducted a narrative review of the current knowledge of the pharmacogenomics of AED-MS (valproic acid, lamotrigine and carbamazepine) treatment response in BD, including genetic contributions to AED-MS pharmacokinetics. Genes involved in neurotransmitter systems and drug transport have been shown to be associated with AED-MS treatment response. As more studies are conducted, and experimental and analytical methods advance, knowledge of AED-MS pharmacogenomics is expected to grow and contribute to precision medicine in BD.

Valproic acid autoinduction: a case-based review

Although valproic acid (VPA) induces the metabolism of multiple other drugs, the clinical reports of VPA autoinduction are rare. A comprehensive literature search yielded only one published case series, which provided the rationale to conduct a review of the published cases along with a new case of VPA autoinduction. Although there may be myriad of reasons for lack of published cases of VPA autoinduction, potential underreporting may be one of the core reasons. Lack of understanding into the highly complex metabolism of VPA may also make it difficult to recognize and report VPA autoinduction. However, it is important to mention that in addition to autoinduction increased elimination of VPA may be mediated by several pharmacokinetic (PK) factors, such as drug interactions, genetic polymorphisms of metabolic enzymes, and protein displacement reactions. As VPA is metabolized by multiple metabolic pathways, the risk for drug interactions is relatively high. There is also a growing evidence for high genetic inducibility of some enzymes involved in VPA metabolism. Protein displacement reactions with VPA increase the biologically active and readily metabolizable free fraction and pose a diagnostic challenge as they are usually not requested by most clinicians. Thus, monitoring of free fraction with total VPA levels may prevent clinically serious outcomes and optimize VPA treatment in clinically challenging patients. This case-based review compares the clinical data from three published cases and a new case of VPA autoinduction to enhance clinicians' awareness of this relatively rare but clinically relevant phenomenon along with a discussion of potential underlying mechanisms.

The Functionality of UDP-Glucuronosyltransferase Genetic Variants and their Association with Drug Responses and Human Diseases

UDP-glucuronosyltransferases (UGTs) are phase II drug-metabolizing enzymes that metabolize endogenous fatty acids such as arachidonic acid metabolites, as well as many prescription drugs, such as opioids, antiepileptics, and antiviral drugs. The UGT1A and 2B genes are highly polymorphic, and their genetic variants may affect the pharmacokinetics and hence the responses of many drugs and fatty acids. This study collected data and updated the current view of the molecular functionality of genetic variants on UGT genes that impact drug responses and the susceptibility to human diseases. The functional information of UGT genetic variants with clinical associations are essential to understand the inter-individual variation in drug responses and susceptibility to toxicity.

Influence of UGT2B7 and UGT1A6 polymorphisms on plasma concentration to dose ratio of valproic acid in Chinese epileptic children

We explored the potential effects of genetic variations on the concentration to dose ratio (CDR) of valproic acid (VPA) in paediatric epilepsy patients.Two hundred and twenty-nine epileptic children on VPA monotherapy were included, and the VPA trough concentrations at steady-state of all subjects were determined.Nineteen single nucleotide polymorphisms (SNPs) of seven selected genes related to the metabolising enzymes and transporters of VPA were identified, and their influences on CDR_VPA (a logarithmic transformation was performed if abnormally distributed) were evaluated.UGT2B7 rs7668258 (C>T) TT genotype was associated with a decrease in lnCDR_VPA among epileptic children receiving VPA monotherapy (β=-0.191, p = 0.036). Significantly lower lnCDR_VPA was also observed in paediatric patients with UGT1A6 rs2070959 (A>G) GG genotype compared to those AA genotype (β=-0.270, p = 0.021).This research indicated that UGT2B7 rs7668258 (C>T) and UGT1A6 rs2070959 (A>G) polymorphisms may be correlated to the normalised plasma concentrations of VPA in Chinese epileptic children. The associations could be abolished after Bonferroni's correction and our findings need to be validated in further and larger investigations.

The association of adjusted plasma valproic acid concentration with CYP2C9 gene polymorphism in patients with epilepsy: a systematic review and meta-analysis

Background

Valproic acid (VPA) is a common antiepileptic drug used to treat both generalized and partial epilepsy. Although there is increasing evidence to suggest that CYP2C9 gene polymorphisms are associated with interindividual variability of VPA metabolism, the results are debatable. Therefore, in the present study, we conducted a meta-analysis to evaluate the correlation between CYP2C9 gene polymorphisms and adjusted plasma VPA concentration.

Methods

The EMBASE, MEDLINE, and Cochrane Library databases were searched to obtain relevant studies. Eligible articles were reviewed, and data extraction was performed. We calculated 95% confidence intervals (CIs) and mean differences (MDs) to assess the strength of the relationship of CYP2C9 gene polymorphisms with adjusted plasma VPA concentration.

Results

The meta-analysis included 6 studies involving 847 patients with epilepsy. The pooled analysis showed that the CYP2C9 A1075C (AA vs. AC) polymorphism was related to the adjusted plasma concentration of VPA (P=0.02, I²= 82%). Additionally, the AC phenotype statistically significantly increased the adjusted plasma VPA concentration in children compared with the mixed age subgroup (P=0.04, I²= 48%). A similar association was observed between the AC phenotype for Asians (P<0.00001, I²=0%) but not for Caucasians (P=0.34, I²=87%).

Discussion

Age might be a crucial covariate influencing the dosage-adjusted VPA concentration in patients with epilepsy. A reduced VPA dosage may be recommendable for children, particularly Asian children, who are CYP2C9 A1075C AC carriers. Further studies could provide high-quality evidence to confirm the correlation between VPA pharmacokinetics and CYP2C9 A1075C polymorphisms.

Developing a gene panel for pharmacoresistant epilepsy: a review of epilepsy pharmacogenetics

Evaluating genes involved in the pharmacodynamics and pharmacokinetics of epilepsy drugs is critical to better understand pharmacoresistant epilepsy. We reviewed the pharmacogenetics literature on six antiseizure medicines (carbamazepine, perampanel, lamotrigine, levetiracetam, sodium valproate and zonisamide) and compared the genes found with those present on epilepsy gene panels using a functional annotation pathway analysis. Little overlap was found between the two gene lists; pharmacogenetic genes are mainly involved in detoxification processes, while epilepsy panel genes are involved in cell signaling and gene expression. Our work provides support for a specific pharmacoresistant epilepsy gene panel to assist antiseizure medicine selection, enabling personalized approaches to treatment. Future efforts will seek to include this panel in genomic analyses of pharmacoresistant patients, to determine clinical utility and patient treatment responses.

Pharmacogenetics of Carbamazepine and Valproate: Focus on Polymorphisms of Drug Metabolizing Enzymes and Transporters

Pharmacogenomics can identify polymorphisms in genes involved in drug pharmacokinetics and pharmacodynamics determining differences in efficacy and safety and causing inter-individual variability in drug response. Therefore, pharmacogenomics can help clinicians in optimizing therapy based on patient's genotype, also in psychiatric and neurological settings. However, pharmacogenetic screenings for psychotropic drugs are not routinely employed in diagnosis and monitoring of patients treated with mood stabilizers, such as carbamazepine and valproate, because their benefit in clinical practice is still controversial. In this review, we summarize the current knowledge on pharmacogenetic biomarkers of these anticonvulsant drugs.

Association between sex hormones regulation-related SNP rs12233719 and lung cancer risk among never-smoking Chinese women

BACKGROUND

The mechanism of rapidly increased non-small cell lung cancer (NSCLC) among never-smoking Chinese women has not been elucidated. Ovarian sex steroid hormones have been suggested to counteract lung cancer development, and sex hormone-binding globulin (SHBG) is essential in sex hormones regulation. This study aims to exploring single nucleotide polymorphisms (SNPs) in genomic regions associated with SHBG concentrations that contributed to never-smoking female NSCLC.

METHODS

Candidate genes were selected by a genome-wide association (GWAS) meta-analysis and gene expression profiles of never-smoking NSCLC of Chinese women. The candidate SNPs limited to common minor allele frequency (MAF), missense variant, ethnic heterogeneous distribution, and SNPs were genotyped using the TaqMan method. A two-stage case-control design was adopted for exploration and validation of associations between candidate SNPs and risk of NSCLC. All participants were never-smoking Chinese women. Chi-square test and multivariate logistic regression were applied.

RESULTS

Beginning with 12 genomic regions associated with circulating SHBG concentrations and gene expression profiles from never-smoking NSCLC in Chinese women, candidate SNP rs12233719 and rs7439366 both located in candidate gene UGT₂ B_7, which may be related to circulating SHBG concentrations and cancer risk, were identified. A two-stage case-control study was conducted in Shenyang and Tianjin represented as the training stage and validation stage, respectively. Under the dominant model, compared to individuals with the wild G/G genotype, the adjusted OR of those with the T allele was 1.58 (95% CI: 1.15-2.16) in Chinese Shenyang training set, and was 1.49 (95% CI: 1.02-2.18) in Chinese Tianjin validation set, both accompanied with a significant trend relationship consistently. UGT2B7 was upregulated in female NSCLC patients' tumor tissues and was associated with a poor prognosis in NSCLC.

CONCLUSION

Our findings indicated that a sex hormones regulation-related SNP rs12233719 was associated with never-smoking female lung cancer risk, which might partially explain NSCLC-susceptibility in Chinese women.

An Investigation of the Metabolism and Excretion of KD101 and Its Interindividual Differences: A Microtracing Mass Balance Study in Humans

The absorption, metabolism, and excretion (AME) profiles of KD101, currently under clinical development to treat obesity, were assessed in humans using accelerator mass spectrometry (AMS) after a single oral administration of KD101 at 400 mg and a microdose of ¹⁴C‐KD101 at ~ 35.2 μg with a total radioactivity of 6.81 kBq. The mean total recovery of administered radioactivity was 85.2% with predominant excretion in the urine (78.0%). The radio‐chromatographic metabolite profiling showed that most of the total radioactivity in the plasma and the urine was ascribable to metabolites. The UDP‐glucuronosyltransferase (UGT), including UGT1A1, UGT1A3, and UGT2B7, might have contributed to the interindividual variability in the metabolism and excretion of KD101. The microtracing approach using AMS is a useful tool to evaluate the AME of a drug under development without risk for high radiation exposure to humans.

Personalized Medicine Using Cutting Edge Technologies for Genetic Epilepsies

Epilepsy is the most common chronic neurologic disorder in the world, affecting 1-2% of the population. Besides, 30% of epilepsy patients are drug-resistant. Genomic mutations seem to play a key role in its etiology and knowledge of strong effect mutations in protein structures might improve prediction and the development of efficacious drugs to treat epilepsy. Several genetic association studies have been undertaken to examine the effect of a range of candidate genes for resistance. Although, few studies have explored the effect of the mutations into protein structure and biophysics in the epilepsy field. Much work remains to be done, but the plans made for exciting developments will hold therapeutic potential for patients with drug-resistance. In summary, we provide a critical review of the perspectives for the development of individualized medicine for epilepsy based on genetic polymorphisms/mutations in light of core elements such as transcriptomics, structural biology, disease model, pharmacogenomics and pharmacokinetics in a manner to improve the success of trial designs of antiepileptic drugs.

Brazilian cohort and genes encoding for drug-metabolizing enzymes and drug transporters

Background & aim: Genetic variability in drug absorption, distribution, metabolism and excretion (ADME) genes contributes to the high heterogeneity of drug responses. The present study investigated polymorphisms of ADME genes frequencies and compared the findings with populations from other continents, available in the 1000 Genome Project (1 KGP) and the Exome Aggregation Consortium (ExAC) databases. Methodology & results: We conducted a study of 100 patients in Brazil and a total of 2003 SNPs were evaluated by targeted next-generation sequencing in 148 genes, including Phase I enzymes (n = 50), Phase II enzymes (n = 38) and drug transporters (n = 60). Overall, the distribution of minor allele frequency (MAF) suggests that the distribution of 2003 SNPs is similar between Brazilian cohort, 1 KGP and ExAC; however, we found moderate SNP allele-frequency divergence between Brazilian cohort and both 1000 KGP and ExAC. These differences were observed in several relevant genes including CYP3A4, NAT2 and SLCO1B1. Conclusion: We concluded that the Brazilian population needs clinical assessment of drug treatment based on individual genotype rather than ethnicity.

Pharmacogenetics and the treatment of epilepsy: what do we know?

Seizure control with antiepileptic drugs (AEDs) as well as susceptibility to adverse drug reactions varies among individuals with epilepsy. This interindividual variability is partly determined by genetic factors. However, genetic testing to predict the efficacy and toxicity of AEDs is limited and genetic variability is, as yet, largely unexplainable. Accordingly, genetic testing can only be advised in a very limited number of cases in clinical routine. Currently, by applying different methodologies, many trials have been undertaken to evaluate cost benefits of preventive pharmacogenetic analysis for patients. There is significant progress in sequencing technologies, and focus is on next-generation sequencing-based methods, like exome and genome sequencing. In this review, an overview of the current scientific knowledge considering the pharmacogenetics of AEDs is given.

Human variability in isoform-specific UDP-glucuronosyltransferases: markers of acute and chronic exposure, polymorphisms and uncertainty factors

UDP-glucuronosyltransferases (UGTs) are involved in phase II conjugation reactions of xenobiotics and differences in their isoform activities result in interindividual kinetic differences of UGT probe substrates. Here, extensive literature searches were performed to identify probe substrates (14) for various UGT isoforms (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B7 and UGT2B15) and frequencies of human polymorphisms. Chemical-specific pharmacokinetic data were collected in a database to quantify interindividual differences in markers of acute (Cmax) and chronic (area under the curve, clearance) exposure. Using this database, UGT-related uncertainty factors were derived and compared to the default factor (i.e. 3.16) allowing for interindividual differences in kinetics. Overall, results show that pharmacokinetic data are predominantly available for Caucasian populations and scarce for other populations of different geographical ancestry. Furthermore, the relationships between UGT polymorphisms and pharmacokinetic parameters are rarely addressed in the included studies. The data show that UGT-related uncertainty factors were mostly below the default toxicokinetic uncertainty factor of 3.16, with the exception of five probe substrates (1-OH-midazolam, ezetimibe, raltegravir, SN38 and trifluoperazine), with three of these substrates being metabolised by the polymorphic isoform 1A1. Data gaps and future work to integrate UGT-related variability distributions with in vitro data to develop quantitative in vitro–in vivo extrapolations in chemical risk assessment are discussed.

Extensive literature search of human kinetic parameters for UGT probe substrates.

Bayesian meta-analysis quantifying human variability in acute and chronic kinetic parameters.

UGT isoform-related uncertainty factors were below the 3.16 kinetic default uncertainty factor for most probe substrates.

Quantifying human variability in UGT polymorphisms.

Pharmacogenomics of Cognitive Dysfunction and Neuropsychiatric Disorders in Dementia

Symptomatic interventions for patients with dementia involve anti-dementia drugs to improve cognition, psychotropic drugs for the treatment of behavioral disorders (BDs), and different categories of drugs for concomitant disorders. Demented patients may take >6–10 drugs/day with the consequent risk for drug–drug interactions and adverse drug reactions (ADRs >80%) which accelerate cognitive decline. The pharmacoepigenetic machinery is integrated by pathogenic, mechanistic, metabolic, transporter, and pleiotropic genes redundantly and promiscuously regulated by epigenetic mechanisms. CYP2D6, CYP2C9, CYP2C19, and CYP3A4/5 geno-phenotypes are involved in the metabolism of over 90% of drugs currently used in patients with dementia, and only 20% of the population is an extensive metabolizer for this tetragenic cluster. ADRs associated with anti-dementia drugs, antipsychotics, antidepressants, anxiolytics, hypnotics, sedatives, and antiepileptic drugs can be minimized by means of pharmacogenetic screening prior to treatment. These drugs are substrates, inhibitors, or inducers of 58, 37, and 42 enzyme/protein gene products, respectively, and are transported by 40 different protein transporters. APOE is the reference gene in most pharmacogenetic studies. APOE-3 carriers are the best responders and APOE-4 carriers are the worst responders; likewise, CYP2D6-normal metabolizers are the best responders and CYP2D6-poor metabolizers are the worst responders. The incorporation of pharmacogenomic strategies for a personalized treatment in dementia is an effective option to optimize limited therapeutic resources and to reduce unwanted side-effects.

Association of SCN1A, SCN2A, and UGT2B7 Polymorphisms with Responsiveness to Valproic Acid in the Treatment of Epilepsy

Purpose

The efficacy of valproic acid (VPA) varies widely in clinical treatment of epileptic patients. Our study is aimed at exploring a potential association between polymorphisms of SCN1A, SCN2A, and UGT2B7 genetic factors and VPA responses.

Methods

In this observational study, a total of 114 epileptic patients only treated with VPA for at least 1 year were included to explore the genetic polymorphisms of drug responses (mean follow-up time: 3.68 ± 1.78 years). Thirty-one single-nucleotide polymorphisms (SNPs) in three candidate genes that related with drug-metabolizing enzymes and receptors were genotyped.

Results

Of the 31 SNPs, eight were significantly associated with VPA responses, including rs1381105, rs2162600, rs10197716, rs2119068, rs2119067, rs353116, rs353112 and rs6740895. The interaction between rs10197716 and rs2119068 was the most significantly correlated with VPA responses compared with other combinations (the highest VPA-responsive rate 0.92 versus the lowest VPA-responsive rate 0.33, p = 0.007).

Conclusion

The study indicated that eight SNPs and SNP-SNP interaction may be associated with VPA responses in Chinese Han epileptic patients. The SNPs were rs1381105 (SCN1A), rs2162600 (SCN1A), rs10197716 (SCN2A), rs2119068 (SCN2A), rs2119067 (SCN2A), rs353116 (SCN2A), rs353112 (SCN2A) and rs6740895 (SCN2A), respectively. The interaction between the three pairs of rs10197716-rs2119068, rs10197716-rs11889342 and rs7598931-rs12233719 was the most significant for VPA. This implied that these SNPs may play an important role in the pharmacogenomics mechanism of valproic acid.

Genetic and Non-genetic Factors Contributing to the Significant Variation in the Plasma Trough Concentration-to-Dose Ratio of Valproic Acid in Children With Epilepsy

Objective: This study was conducted to evaluate the potential genetic and non-genetic factors contributing to plasma trough concentration-to-dose (C ₀/D) ratio of valproic acid (VPA) in pediatric patients with epilepsy. Study Design: A single-center, retrospective cohort study was performed by collecting data from 194 children aged 1-14 years between May 2018 and November 2018. The oral solution (n = 135) group and the sustained-release (SR) tablet group (n = 59) were defined, and the plasma VPA C ₀ was measured. Twenty-six single-nucleotide polymorphisms (SNPs) were chosen for genotyping with the MassARRAY system. A multiple logistic regression model was used for data analysis. Results: Body weight (BW) and age were positively correlated with the C ₀/D ratio in 194 patients, but the positive correlation disappeared after the patients were divided into oral solution and SR tablet subgroups. The average C ₀/D ratio was significantly increased by 2.11-fold (P = 0.000) in children who took VPA SR tablets compared with children who were administered VPA oral solutions. No significant association between genetic variants and the C ₀/D ratio was found, even for the five well-studied SNPs, namely UGT2B7 G211T, C802T, C161T, T125C, and CYP2C9 ^* 3 A1075C. However, a significant association between the C ₀/D ratio and UGT1A6/9 Del>A (rs144486213) was observed in the VPA oral solution group, but not in the VPA SR tablet group. Conclusions: The dosage forms of sodium valproate, rather than BW, age, or genetic polymorphisms, significantly affected the VPA C ₀/D ratios in pediatric patients with epilepsy. Based on our findings, switching the dosage form between solution and SR tablet should be performed cautiously. Total daily dose adjustment should be considered, and the plasma concentration, seizure-control effect, and adverse drug reaction should also be monitored very closely.

Pharmacogenomic Characterization in Bipolar Spectrum Disorders

The holistic approach of personalized medicine, merging clinical and molecular characteristics to tailor the diagnostic and therapeutic path to each individual, is steadily spreading in clinical practice. Psychiatric disorders represent one of the most difficult diagnostic challenges, given their frequent mixed nature and intrinsic variability, as in bipolar disorders and depression. Patients misdiagnosed as depressed are often initially prescribed serotonergic antidepressants, a treatment that can exacerbate a previously unrecognized bipolar condition. Thanks to the use of the patient's genomic profile, it is possible to recognize such risk and at the same time characterize specific genetic assets specifically associated with bipolar spectrum disorder, as well as with the individual response to the various therapeutic options. This provides the basis for molecular diagnosis and the definition of pharmacogenomic profiles, thus guiding therapeutic choices and allowing a safer and more effective use of psychotropic drugs. Here, we report the pharmacogenomics state of the art in bipolar disorders and suggest an algorithm for therapeutic regimen choice.

Association of UGT2B7 and CaMK4 with response of valproic acid in Chinese children with epilepsy

AIM OF THE STUDY

Valproic acid (VPA) is a widely used antiepileptic drug for epilepsy. However, approximately 30% of patients with epilepsy do not respond to this therapy even when it was appropriately used. In order to explore the potential genetic factors related to the VPA response, this pharmacogenetics study was conducted.

METHODS

A total of one hundred and fifty-seven Chinese children with epilepsy who were administered with by VPA for at least one year were enrolled. Thirteen single-nucleotide polymorphisms (SNPs) located in eight genes involving targets and metabolic enzymes of VPA were genotyped. The frequencies of these polymorphisms and the effect of genotypes on the efficacy of VPA were analyzed.

RESULTS

The frequencies of two SNPs, rs7668258 (uridine diphosphate glucuronosyltransferase-2B7, UGT2B7) and rs306104 (calmodulin-kinase 4, CaMK4) were associated with VPA responses. However, no association was found for the other SNPs. Furthermore, the polymorphism of UGT2B7 influenced the adjusted concentration (AC) in the responders rather than in the non-responders.

CONCLUSION

Two SNPs (UGT2B7 and CaMK4) were associated with VPA response, which may explain the pharmacological mechanism of VPA resistance to some extent.

Efficacy of antiepileptic drugs in the era of pharmacogenomics: A focus on childhood

BACKGROUND

In recent years advances in the field of pharmacogenomics have expanded the concept for more individualized treatments. Our aim is to provide literature data about the relationship between genetic polymorphisms and efficacy of antiepileptic drugs in children.

METHODS

Pubmed was used as the main medical database source. Only original research papers were considered. No year-of-publication restriction was placed. Quality of evidence was assessed according to American Academy of Neurology guidelines.

RESULTS

A total of 12 cross-sectional and case-control studies fulfilled our selection criteria. ABCB1 gene was associated with drug responsiveness in 2 out of 6 studies and ABCC2 gene in 1 out of 1 studies. SCN1A gene was also associated with seizure control in 4 out of 5 studies. Cytochrome P450 genes were found to significantly affect drug responsiveness in 2 out of 4 studies, while polymorphisms of uridinediphosphateglucuronosyltransferaseUGT2B7 gene predisposed to drug-resistance in 1 out of 2 studies.

CONCLUSION

Variability in genes coding for sodium channels, drug transporters and cytochrome P450 enzymes can have a significant impact on response to antiepileptic drugs. Larger prospective studies with better stratification of samples are needed to shed light on these associations.

Associations between UGT2B7 polymorphisms and cancer susceptibility: A meta-analysis

BACKGROUND

UGT2B7 was recently acknowledged as a new critical enzyme involved in biotransformation of a variety of carcinogens, whose function was reported to be significantly associated with its encoding gene (UGT2B7) polymorphisms. However, results regarding the associations between single nucleotide polymorphisms (SNPs) of UGT2B7 and cancer risk still remained controversial. Therefore, a meta-analysis was conducted to further elucidate the role of UGT2B7 SNPs on cancer susceptibilities.

METHODS

PubMed, EMBASE, Cochrane library, Chinese National Knowledge Infrastructure (CNKI), Technology of Chongqing (VIP) and Wan Fang Database were searched for eligible studies until March 2019. All analysis was carried out using the Review Manager 5.3 software. Subgroup analyses were performed by cancer types, ethnicity or source of controls.

RESULTS

13 studies with a total of 7688 cancer cases and 11,281 controls were included in this meta-analysis. The results showed that UGT2B7 rs7439366 increased the colorectal cancer risk in dominant model (OR = 0.76, 95% CI = 0.61-0.95, P = 0.02). However, as for the rs7435335 and rs12233719, we did not find their associations with cancer risk in all genetic models. In addition, the rs7441774 was found to be associated with breast cancer risk and significantly reduced papillary thyroid cancer risk in rs3924194 was also observed. Nevertheless, these findings remained to be further proven in future studies since these 2 SNPs were only respectively involved in 1 study.

CONCLUSION

This meta-analysis confirmed the association of UGT2B7 rs7439366 with colorectal cancer risk, which may be a potential promising biomarker for prediction of colorectal cancer risk.

Interaction between ABCG2 421C>A polymorphism and valproate in their effects on steady-state disposition of lamotrigine in adults with epilepsy

AIMS

To investigate the impact of glucuronidation enzyme (UGT1A4*3 142T>G, UGT1A4*2 70C>A, UGT2B7 -161C>T) and transporter (MDR1/ABCB1 1236C>T, ABCG2 421C>A) polymorphisms on steady-state disposition of lamotrigine and on the lamotrigine-valproate interaction.

METHODS

Adults with epilepsy on lamotrigine monotherapy (n = 131) or lamotrigine + valproate treatment (n = 74) were genotyped and steady-state lamotrigine and valproate morning troughs were determined as a part of routine therapeutic drug monitoring.

RESULTS

No effect of UGT and MDR1/ABCB1 polymorphisms was observed. In the entire cohort, ABCG2 421A allele had no effect however an interaction between the variant allele and valproate was observed: (i) in lamotrigine-only patients, variant allele (vs. wild type homozygosity) was independently (adjustments: age, sex, body mass index, lamotrigine dose, other polymorphisms) associated with mildly lower lamotrigine troughs [geometric means ratio (GMR) = 0.76, 95% confidence interval (CI) 0.59-0.98], whereas in lamotrigine + valproate patients it was associated with higher troughs (GMR = 1.72, 95%CI 1.14-2.62); (ii) valproate cotreatment was overall associated with markedly higher troughs vs. lamotrigine monotherapy (GMR = 3.49, 95%CI 2.73-4.44), but more so in variant allele carriers (GMR = 5.24, 95%CI 3.38-8.15) than in wild type homozygotes (GMR = 2.32, 95%CI 1.89-2.83); (iii) variant allele effects in two treatment subsets and valproate effects in two genotype subsets differed by 2.36-fold (95%CI 1.39-3.67); (iv) increase in lamotrigine troughs associated with increasing valproate troughs was greater in variant allele carriers than in wild type homozygotes, i.e. variant allele effect increased with increasing valproate troughs.

CONCLUSION

This study is first to indicate a potentially relevant interaction between ABCG2 421C>A polymorphism and valproate in their effects on lamotrigine disposition.

Population pharmacokinetics of valproic acid in epileptic children: Effects of clinical and genetic factors

Valproic acid (VPA) is a first-line anti-epileptic drug that is used in the treatment of generalized and partial seizures. Gene variants had been proved to influence the pharmacokinetics (PK) of VPA and contribute to its inter-individual variability (IIV). The aim of this study was to systematically investigate the effects of candidate gene variants (CYPs, UGTs, ABC transporters, and nuclear receptors) on VPA PK in Chinese children with epilepsy. A total of 1065 VPA serum trough concentrations at steady state were collected from 264 epileptic pediatric patients aged 3 months to 16 years. The population pharmacokinetic (PPK) model was developed using a nonlinear mixed effects modelling (NONMEM) approach. For the final PPK model, the oral clearance (CL/F) of VPA was estimated to be 0.259 L/h with IIV of 13.3%. The estimates generated by NONMEM indicated that the VPA CL/F was significantly influenced by patient body weight (increased by an exponent of 0.662), co-administration with carbamazepine (increased CL/F by 22%), and daily dose of VPA (increased by an exponent of 0.22). CL/F in patients with the LEPR rs1137101 variant (668 AG and GG genotypes) was much lower than in patients with the AA genotype (17.8% and 22.6% lower, respectively). However, none of the CYPs or UGTs gene variants was found to influence the PK of VPA in this study. Evaluation by bootstrap and normalized prediction distribution error (NPDE) showed that the final model was stable. The predictive performance was evaluated by goodness-of-fit (GOF) plots and visual predictive checks (VPC), and the results indicated satisfactory precision. Our model suggests a correlation between VPA CL/F and LEPR rs1137101 variants, which might be beneficial in the context of individual dose optimization.