Genetic polymorphism in cytochrome P450 2D6 (CYP2D6): Population distribution of CYP2D6 activity

Pharmacogenetic Approach to Tramadol Use in the Arab Population

Tramdol is one of most popular opioids used for postoperative analgesia worldwide. Among Arabic countries, there are reports that its dosage is not appropriate due to cultural background. To provide theoretical background of the proper usage of tramadol, this study analyzed the association between several genetic polymorphisms (CYP2D6/OPRM1) and the effect of tramadol. A total of 39 patients who took tramadol for postoperative analgesia were recruited, samples were obtained, and their DNA was extracted for polymerase chain reaction products analysis followed by allelic variations of CYP2D6 and OPRM A118G determination. Numerical pain scales were measured before and 1 h after taking tramadol. The effect of tramadol was defined by the difference between these scales. We concluded that CYP2D6 and OPRM1 A118G single nucleotide polymorphisms may serve as crucial determinants in predicting tramadol efficacy and susceptibility to post-surgical pain. Further validation of personalized prescription practices based on these genetic polymorphisms could provide valuable insights for the development of clinical guidelines tailored to post-surgical tramadol use in the Arabic population.

Exploring the impact of CYP2D6 and UGT2B7 gene-drug interactions, and CYP-mediated DDI on oxycodone and oxymorphone pharmacokinetics using physiologically-based pharmacokinetic modeling and simulation

Oxycodone is one of the most commonly used opioids to treat moderate to severe pain. It is metabolized mainly by CYP3A4 and CYP2D6, while only a small fraction of the dose is excreted unchanged into the urine. Oxymorphone, the metabolite primarily formed by CYP2D6, has a 40- to 60-fold higher mu-opioid receptor affinity than the parent compound. While CYP2D6-mediated gene-drug-interactions (GDIs) and drug-drug interactions (DDIs) are well-studied, they only account for a portion of the variability in oxycodone and oxymorphone exposure. The combined impact of CYP2D6-mediated GDIs and DDIs, CYP3A4-mediated DDIs, and UGT2B7 GDIs is not fully understood yet and hard to study in head-to-head clinical trials given the relatively large number of scenarios. Instead, we propose the use of a physiologically-based pharmacokinetic model that integrates available information on oxycodone's metabolism to characterize and predict the impact of DDIs and GDIs on the exposure of oxycodone and its major, pharmacologically-active metabolite oxymorphone. To this end, we first developed and verified a PBPK model for oxycodone and its metabolites using published clinical data. The verified model was then applied to determine the dose-exposure relationship of oxycodone and oxymorphone stratified by CYP2D6 and UGT2B7 phenotypes respectively, and administered perpetrators of CYP-based drug interactions. Our simulations demonstrate that the combination of CYP2D6 UM and a UGT2B7Y (268) mutation may lead to a 2.3-fold increase in oxymorphone exposure compared to individuals who are phenotyped as CYP2D6 NM / UGT2B7 NM. The extent of oxymorphone exposure increases up to 3.2-fold in individuals concurrently taking CYP3A4 inhibitors, such as ketoconazole. Inhibition of the CYP3A4 pathway results in a relative increase in the partial metabolic clearance of oxycodone to oxymorphone. Oxymorphone is impacted to a higher extent by GDIs and DDIs than oxycodone. We predict oxymorphone exposure to be highest in CYP2D6 UMs/UGT2B7 PMs in the presence of ketoconazole (strong CYP3A4 index inhibitor) and lowest in CYP2D6 PMs/UGT2B7 NMs in the presence of rifampicin (strong CYP3A4 index inducer) covering a 55-fold exposure range.

The potential impact of CYP and UGT drug-metabolizing enzymes on brain target site drug exposure

Drug metabolism is one of the critical determinants of drug disposition throughout the body. While traditionally associated with the liver, recent research has unveiled the presence and functional significance of drug-metabolizing enzymes (DMEs) within the brain. Specifically, cytochrome P-450 enzymes (CYPs) and UDP-glucuronosyltransferases (UGTs) enzymes have emerged as key players in drug biotransformation within the central nervous system (CNS). This comprehensive review explores the cellular and subcellular distribution of CYPs and UGTs within the CNS, emphasizing regional expression and contrasting profiles between the liver and brain, humans and rats. Moreover, we discuss the impact of species and sex differences on CYPs and UGTs within the CNS. This review also provides an overview of methodologies for identifying and quantifying enzyme activities in the brain. Additionally, we present factors influencing CYPs and UGTs activities in the brain, including genetic polymorphisms, physiological variables, pathophysiological conditions, and environmental factors. Examples of CYP- and UGT-mediated drug metabolism within the brain are presented at the end, illustrating the pivotal role of these enzymes in drug therapy and potential toxicity. In conclusion, this review enhances our understanding of drug metabolism's significance in the brain, with a specific focus on CYPs and UGTs. Insights into the expression, activity, and influential factors of these enzymes within the CNS have crucial implications for drug development, the design of safe drug treatment strategies, and the comprehension of drug actions within the CNS. To that end, CNS pharmacokinetic (PK) models can be improved to further advance drug development and personalized therapy.

Population Pharmacokinetic-Pharmacodynamic Modeling of Carvedilol to Evaluate the Effect of Cytochrome P450 2D6 Genotype on the Heart Rate Reduction

BACKGROUND

Carvedilol is a beta-adrenergic receptor antagonist primarily metabolized by cytochromes P450 (CYP) 2D6. This study established a carvedilol population pharmacokinetic (PK)-pharmacodynamic (PD) model to describe the effects of CYP2D6 genetic polymorphisms on the inter-individual variability of PK and PD.

METHODS

The PK-PD model was developed from a clinical study conducted on 21 healthy subjects divided into three CYP2D6 phenotype groups, with six subjects in the extensive metabolizer (EM, *1/*1, *1/*2), seven in the intermediate metabolizer-1 (IM-1, *1/*10, *2/*10), and eight in the intermediate metabolizer-2 (IM-2, *10/*10) groups. The PK-PD model was sequentially developed, and the isoproterenol-induced heart rate changes were used to establish the PD model. A direct effect response and inhibitory E_max model were used to develop a carvedilol PK-PD model.

RESULTS

The carvedilol PK was well described by a two-compartment model with zero-order absorption, lag time, and first-order elimination. The carvedilol clearance in the CYP2D6*10/*10 group decreased by 32.8% compared with the other groups. The inhibitory concentration of carvedilol estimated from the final PK-PD model was 16.5 ng/mL regardless of the CYP2D6 phenotype.

CONCLUSION

The PK-PD model revealed that the CYP2D6 genetic polymorphisms were contributed to the inter-individual variability of carvedilol PK, but not PD.

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.

Genetic variants affecting chemical mediated skin immunotoxicity

The skin is an immune-competent organ and this function may be impaired by exposure to chemicals, which may ultimately result in immune-mediated dermal disorders. Interindividual variability to chemical-induced skin immune reactions is associated with intrinsic individual characteristics and their genomes. In the last 30-40 years, several genes influencing susceptibility to skin immune reactions were identified. The aim of this review is to provide information regarding common genetic variations affecting skin immunotoxicity. The polymorphisms selected for this review are related to xenobiotic-metabolizing enzymes (CYPA1 and CYPB1 genes), antioxidant defense (GSTM1, GSTT1, and GSTP1 genes), aryl hydrocarbon receptor signaling pathway (AHR and ARNT genes), skin barrier function transepidermal water loss (FLG, CASP14, and SPINK5 genes), inflammation (TNF, IL10, IL6, IL18, IL31, and TSLP genes), major histocompatibility complex (MHC) and neuroendocrine system peptides (CALCA, TRPV1, ACE genes). These genes present variants associated with skin immune responses and diseases, as well as variants associated with protecting skin immune homeostasis following chemical exposure. The molecular and association studies focusing on these genetic variants may elucidate their functional consequences and contribution in the susceptibility to skin immunotoxicity. Providing information on how genetic variations affect the skin immune system may reduce uncertainties in estimating chemical hazards/risks for human health in the future.

Pharmacogenomics in Children

Historically genetics has not been considered when prescribing drugs for children. However, it is clear that genetics are not only an important determinant of disease in children but also of drug response for many important drugs that are core agents used in the therapy of common problems in children. Advances in therapy and in the ethical construct of children's research have made pharmacogenomic assessment for children much easier to pursue. It is likely that pharmacogenomics will become part of the therapeutic decision-making process for children, notably in areas such as childhood cancer where weighing benefits and risks of therapy is crucial.

Influence of Plasma Concentration of Hsa-Mir-370-3p and Cyp2d6*4 On Equilibrium Concentration of Phenazepam in Patients with Recurrent Depressive Disorder

INTRODUCTION

Phenazepam is commonly administered to patients diagnosed with major depressive disorder. Some proportion of such patients do not show adequate response to treatment regimen containing phenazepam, whereas many of them experience type A adverse drug reactions. Previous studies showed that CYP2D6 IS involved in the biotransformation of phenazepam, the activity of which is highly dependent on the polymorphism of the gene encoding it. Objective. The objective of the study was to evaluate the impact of 1846G>A polymorphism of the CYP2D6 gene on the concentration/dose indicator of phenazepam, using findings on enzymatic activity of CYP2D6 (as evaluated by the 6M-THBC/pinoline ratio measurement) and on CYP2D6 expression level obtained by measuring the hsa-miR-370-3p plasma concentration levels in patients suffering from major depressive disorder.

MATERIAL AND METHODS

The study enrolled 191 patients with recurrent depressive disorder (age -40.0 ± 16.3 years). Treatment regimen included phenazepam in an average daily dose of 6.0 ± 2.3 mg per day. Treatment efficacy was assessed using the validated psychometric scales. Therapy safety was assessed using the UKU Side-Effect Rating Scale. For genotyping and estimation of the microRNA (miRNA) plasma levels we performed the real-time polymerase chain reaction (PCR Real-time). The activity of CYP2D6 was evaluated using the HPLC-MS/MS method by the content of the endogenous substrate of given isoenzyme and its metabolite in urine (6M-THBC/pinoline). Therapeutic drug monitoring has been performed using HPLC-MS/MS.

RESULTS

Our findings didn't reveal the statistically significant results in terms of the treatment efficacy evaluation (HAMA scores at the end of the treatment course): (GG) 6.0 [4.0; 8.0] and (GA) 6.0 [5.0; 7.8], p > 0.999; the statistical significance in the safety profile was not obtained (the UKU scores): (GG) 3.0 [2.0; 4.0] and (GA) 3.0 [3.0; 3.0], p > 0.999. We didn't reveal a statistical significance for concentration/dose indicator of phenazepam in patients with different genotypes: (GG) 0.812 [0.558; 1.348] and (GA) 0.931 [0.630; 1.271], p = 0.645). Analysis of the results of the pharmacotranscriptomic part of the study didn't show the statistically significant difference in the hsa-miR-370-3p plasma levels in patients with different genotypes: (GG) 22.5 [16.9; 29.8], (GA) 22.7 [15.7; 31.5], p = 0.695. At the same time, correlation analysis didn't reveal a statistically significant relationship between the phenazepam efficacy profile evaluated by changes in HAMA scale scores and the hsa-miR-370-3p plasma concentration: rs = -0.01, p = 0.866. Also, we didn't reveal the correlation between the miRNA concentration and safety profile: rs = 0.07, p = 0.348. Also we did not reveal the relationship between the CYP2D6 enzymatic activity (as evaluated by 6M-THBC/pinoline ratio measurement) and the hsa-miR-370-3p plasma concentration: rs = -0.14, p = 0.056. At the same time, correlation analysis did not reveal a statistically significant relationship between the phenazepam concentration and the hsa-miR-370-3p plasma concentration: rs = -0.05, p = 0.468.

CONCLUSION

The effect of genetic polymorphism of the CYP2D6 gene on the efficacy and safety profiles of phenazepam was not demonstrated in a group of 191 patients with recurrent depressive disorder. At the same time, hsa-miR-370-3p does not remain a promising biomarker for assessing the level of CYP2D6 expression, because it does not correlate with encoded isoenzyme activity.

Modulating effect of DL-kavain on the mutagenicity and carcinogenicity induced by doxorubicin in Drosophila melanogaster

Kavain, kavalactone, present in Piper methysticum exhibits anticonvulsive, analgesic, anxiolytic, antiepileptic, antithrombotic, anti-inflammatory and antioxidant properties. Given its importance, the aim of the present study was to assess (1) the mutagenic and carcinogenicity of kavain administered alone and (2) the antimutagenic and anticarcinogenic potential when administered simultaneously with the chemotherapeutic drug doxorubicin (DXR) using the Somatic Mutation and Recombination Test (SMART) and Epithelial Tumor Test (ETT) using Drosophila melanogaster as a model system. Third-stage larvae from a standard (ST) and high metabolic bioactivation (HB) crosses were treated with different kavain concentrations (32, 64 or 128 μg/ml), alone or in conjunction with DXR (0.125 mg/ml). In ST descendants, kavain produced no significant mutagenic or recombinogenic effects. In the HB cross, mutagenic activity was observed at kavain concentrations of 64 and 128 μg/ml. In the DXR and kavain co-treatment, a modulating effect of the DXR-mediated mutagenic response dependent upon the concentration was detected in both crosses. In ETT, no marked carcinogenic or anticarcinogenic activity was noted for kavain. However, when kavain was combined with DXR synergistic induction of tumors by the chemotherapeutic drug occurred indicating that kavain enhanced the carcinogenic action of DXR.

Cytochrome P450-2D6: A novel biomarker in liver cancer health disparity

Liver cancer morbidity and mortality rates differ among ethnic groups. In the United States, the burden of liver cancer in Asian Americans (AS) is higher compared to Caucasian Americans (CA). Research on liver cancer health disparities has mainly focused on environmental and socioeconomic factors yet has ignored the genotypic differences among various racial/ethnic groups. This lack of molecular level understanding has hindered the development of personalized medical approaches for liver cancer treatment. To understand the genetic heterogeneity of liver cancer between AS and CA, we performed a systematic analysis of RNA-seq data of AS and CA patients from The Cancer Genome Atlas (TCGA). We used four differential gene expression analysis packages; DESeq2, limma, edgeR, and Superdelta2, to identify the differentially expressed genes. Our analysis identified cytochrome P450-2D6 enzyme (CYP2D6) as the gene with the greatest differential expression with higher levels in AS compared to CA. To scrutinize the underlying mechanism of CYP2D6, Ingenuity Pathway Analysis (IPA) and Cytoscape were conducted and found hepatocyte nuclear factor-4α (HNF4A) and interleukin-6 (IL6) in direct association with CYP2D6. IL6 is downregulated in AS compared to CA, while HNF4A is not significantly different. Herein, we report that CYP2D6 may serve as a putative biomarker in liver cancer health disparities. Its negative association with IL6 proclaims an intricate relationship between CYP2D6 and inflammation in the ethnic differences seen in AS and CA liver cancer patients. The goal of the present study was to understand how genetic factors may contribute to the interethnic variability of liver cancer prevalence and outcomes in AS and CA patients. Identifying ethnic-specific genes may help ameliorate detection, diagnosis, surveillance, and treatments of liver cancer, as well as reduce disease-related incidence and mortality rates in the vulnerable population.

Impact of CYP2D6 Polymorphism on Equilibrium Concentration of Fluoxetine in Patients Diagnosed With Major Depressive Disorder and Comorbid Alcohol Use Disorders

INTRODUCTION

Fluoxetine is used in the treatment of patients with recurrent depressive disorder. Some of these patients do not achieve an adequate response to a treatment regimen containing fluoxetine, and many of these patients experience dose-dependent adverse drug reactions. The cytochrome P450 enzyme CYP2D6 is involved in the biotransformation of fluoxetine, the activity of which is quite dependent on the polymorphism of the gene encoding this enzyme.

OBJECTIVE

The objective of the study was to investigate the influence of the 1846G>A polymorphism of the CYP2D6 gene on the concentration/dose indicator of fluoxetine in patients diagnosed with major depressive disorder and comorbid alcohol use disorder.

METHODS

Our study included 101 patients with major depressive disorder and alcohol use disorder (average age: 41.3±14.5 y) who were treated with fluoxetine at an average dose of 26.1±8.7 mg/d. Treatment efficacy was assessed using validated psychometric scales, and the safety/tolerability of the therapy was assessed using the Udvalg for Kliniske Undersogelser Side-Effect Rating Scale. Genotyping was done using a real-time polymerase chain reaction. Therapeutic drug monitoring was performed using high-performance liquid chromatography-mass spectrometry.

RESULTS

CYP2D6 genotyping by polymorphic marker 1846G>A (rs3892097) in the 101 patients found that there were 81 patients (80.2%) with the GG genotype ("wild-type," normal metabolism), 20 (19.8%) with the GA genotype (intermediate metabolism), and no subjects with the AA genotype (poor metabolism). Statistically significant results in treatment efficacy as evaluated by Hamilton Rating Scale for Depression scores at the end of the treatment course were found: GG 9.0 [confidence interval (CI): 6.0; 12.0] and GA 12.0 (CI: 9.5; 14.0), P=0.005. Statistically significant results were also obtained for the safety profile as measured by scores on the Udvalg for Kliniske Undersogelser Side-Effect Rating Scale: GG 3.0 (CI 2.0; 4.0) and GA 5.0 (CI: 4.0; 5.0), P<0.001. Finally, a statistically significant difference was found in concentration/dose indicators of fluoxetine in patients with the different genotypes: GG 4.831 (CI: 3.654; 6.204) and GA 7.011 (CI: 5.431; 8.252), P<0.001.

CONCLUSION

The effect of the genetic polymorphism of the CYP2D6 gene on the efficacy and safety profiles of fluoxetine was demonstrated in a group of 101 patients with major depressive disorder and alcohol use disorder.

Use of proteomics to identify mechanisms of hepatocellular carcinoma with the CYP2D6*10 polymorphism and identification of ANGPTL6 as a new diagnostic and prognostic biomarker

BACKGROUND

Although an association between the cytochrome P4502D6 (CYP2D6) *10 (100C>T) polymorphism and hepatocellular carcinoma (HCC) is known, the mechanism remains unclear. Here we aimed to explore mechanisms of CYP2D6*10 (100C>T) polymorphism conferring to HCC, and screen markers for HCC.

METHODS

Label-free global proteome profiling with 34 normal livers and peritumor tissue from 61 HCC patients was performed, and angiopoietin-like protein-6 (ANGPTL6) was evaluated in 2 liver samples validation cohorts and 2 blood specimens validation cohorts.

RESULTS

We found a significantly decreased frequency of TT in HCC patients which reduced HCC susceptibility by 69.2% and was accompanied by lowered enzymatic activity for CYP2D6. Proteomic analysis revealed 1342 differentially expressed proteins (DEPs) that were associated with HCC and 88 DEPs were identified as 100 TT-related proteins, likely underlying the susceptibility to HCC. Twenty-two upregulated DEPs and 66 downregulated DEPs were mainly related to lipid metabolism and the extracellular matrix, respectively. High ANGPTL6 was associated with a higher risk to HCC and worse prognosis. ANGPTL6 was both an independent risk factor and an independent prognostic factor for HCC and exhibited strong potential for predicting HCC occurrence, with comparable AUC values and higher sensitivity compared with alpha-fetoprotein.

CONCLUSIONS

The TT genotype-associated decreased risk of HCC appears to be related to lowered CYP2D6 activity and altered protein expression in the tumor microenvironment, and ANGPTL6 is a promising new diagnostic and prognostic biomarker for HCC. Our findings reveal new mechanistic insights for polymorphisms related to HCC risk and provide avenues for screening for HCC.

Determinants of primaquine and carboxyprimaquine exposures in children and adults with Plasmodium vivax malaria

Background Primaquine is the only widely available drug for radical cure of Plasmodium vivax malaria. There is uncertainty whether the pharmacokinetic properties of primaquine are altered significantly in childhood or not. Methods Glucose-6-phosphate dehydrogenase normal patients with uncomplicated P. vivax malaria were randomized to receive either chloroquine (25mg base/kg) or dihydroartemisinin-piperaquine (dihydroartemisinin 7mg/kg and piperaquine 55mg/kg) plus primaquine; given either as 0.5 mg base/kg/day for 14 days or 1 mg/kg/day for 7 days. Pre-dose day 7 venous plasma concentrations of chloroquine, desethylchloroquine, piperaquine, primaquine and carboxyprimaquine were measured. Methemoglobin levels were measured on day 7. Results Day 7 primaquine and carboxyprimaquine concentrations were available for 641 patients. After adjustment for the primaquine mg/kg daily dose, day of sampling, partner drug, and fever clearance, there was a significant non-linear relationship between age and trough primaquine and carboxyprimaquine concentrations, and day methemoglobin levels. Compared to adults 30 years of age, children 5 years of age had trough primaquine concentrations 0.53 (95% CI: 0.39- 0.73) fold lower, trough carboxyprimaquine concentrations 0.45 (95% CI: 0.35- 0.55) fold lower, and day 7 methemoglobin levels 0.87 (95% CI: 0.58-1.27) fold lower. Increasing concentrations of piperaquine and chloroquine and poor metabolizer CYP 2D6 alleles were associated with higher day 7 primaquine and carboxyprimaquine concentrations. Higher blood methemoglobin concentrations were associated with a lower risk of recurrence. Conclusion Young children have lower primaquine and carboxyprimaquine exposures, and lower levels of methemoglobinemia, than adults. Young children may need higher weight adjusted primaquine doses than adults.

Effect of Genetic Polymorphism of the CYP2D6 Gene on the Efficacy and Safety of Fluvoxamine in Major Depressive Disorder

BACKGROUND

Previous studies have shown that cytochrome P450 2D6 (CYP2D6) is involved in the metabolism of fluvoxamine, the activity of which is highly dependent, inter alia, on the polymorphism of the gene encoding it. The objective of our study was to investigate the effect of 1846G>A polymorphism of the CYP2D6 gene on the efficacy and safety of fluvoxamine, using findings on CYP2D6 enzymatic activity and on CYP2D6 expression level in patients with depressive disorders comorbid with alcohol use disorder.

STUDY QUESTION

Efficacy and safety of fluvoxamine depend on the polymorphism of CYP2D6 gene in patients with major depressive disorder.

STUDY DESIGN

Our study enrolled 96 male patients with depressive disorders comorbid with alcohol use disorder. Patients were examined on days 1, 9, and 16 of fluvoxamine therapy.

MEASURES AND OUTCOMES

Treatment efficacy was evaluated using the validated psychometric scales. Therapy safety was assessed using the UKU Side-Effect Rating Scale. For genotyping and estimation of the microRNA (miRNA) plasma levels, we performed the real-time polymerase chain reaction. The activity of CYP2D6 was evaluated using the HPLC-MS/MS method by the content of the endogenous substrate of given isoenzyme and its metabolite in urine (6-hydroxy-1,2,3,4-tetrahydro-β-carboline/pinoline ratio).

RESULTS

Our study revealed the statistically significant results for the treatment efficacy evaluation [the Hamilton Depression Rating Scale scores at the end of the treatment course: (GG) 2.0 (1.0-4.0) and (GA) 5.0 (4.0-7.0), P < 0.001]. Analysis of the results of the pharmacotranscriptomic part of the study did not show the statistically significant difference in the hsa-miR-370-3p plasma levels in patients with different genotypes: (GG) 26.9 (15.0-32.2), (GA) 31.8 (22.7-33.7), P = 0.247. In addition, we evaluated the relationship between the CYP2D6 enzymatic activity (as evaluated by 6-hydroxy-1,2,3,4-tetrahydro-β-carboline/pinoline ratio measurement) and the hsa-miR-370-3p plasma concentration: rs = -0.243, P = 0.017.

CONCLUSIONS

The effect of genetic polymorphism of the CYP2D6 gene on the efficacy and safety profiles of fluvoxamine was demonstrated in a group of 96 patients with depressive disorders comorbid with alcohol use disorder.

Han Chinese specific cytochrome P450 polymorphisms and their impact on the metabolism of anti-hypertensive drugs with adrenoreceptor blocking properties

Introduction: Cytochrome P450 (CYP) is a monooxygenase superfamily mediating the elimination of anti-hypertensive drugs. Polymorphisms of CYP would lead to differential drug efficacy. Building relationships between genotype and phenotype will benefit individual medical treatment of hypertension.Areas covered: The review systematically summarizes the polymorphisms of four CYPs (CYP2C9, CYP2C19, CYP2D6, and CYP3A4) concentrated distributed in the Han Chinese population. Moreover, the activity of variants on metabolizing anti-hypertensive drugs are reviewed, especially drugs with adrenoceptor blocking properties, as well as their clinical relevancies.Expert opinion: The polymorphisms of CYP can cause stratification in drug exposure of antihypertensive drugs. Although the clinical relevance has been built partially, the translational medicine still lacks reliable data support. Furthermore, the studies have demonstrated that even the same CYP variant will exhibit different catalytic capability for different drugs, which is another obstacle to hinder its application. With the deepening of multiomics research and structural biology, nucleotide polymorphisms can be combined with transcriptome, proteome, metabolome and molecular structure analyses to study the susceptibility to hypertension and drug efficacy. A complete data chain would be further estabolished by combining studies of pharmacokinetics-pharmacodynamics, which can effectively promote the precise application of anti-hypertensive drugs.

Impact of the Omics-Based Biomarkers on the Mirtazapine's Steady-State Concentration, Efficacy and Safety in Patients with Affective Disorders Comorbid with Alcohol Use Disorder

Introduction

Mirtazapine is commonly administered to patients with recurrent depressive disorder. Some of these patients do not show adequate response to the therapy with mirtazapine, whereas many of them experience dose-dependent adverse drug reactions. Previous research revealed that CYP2D6 is involved in the metabolism of mirtazapine, the activity of which is highly dependent on the polymorphism of the gene encoding it.

Objective

The objective of this study was to investigate the effect of polymorphisms of the CYP3A4, CYP2C9, CYP3A5, ABCB1, CYP2C19, SCL6A4, and 5-HTR2A genes on the concentration/dose indicator of mirtazapine and on the CYP3A expression level obtained by measuring the miR-27b plasma concentration levels in patients suffering from a recurrent depressive disorder.

Material and Methods

Our study included 108 patients with recurrent depressive disorder (average age - 35.2 ± 15.1 years). The treatment regimen included mirtazapine in an average daily dose of 45.0 [30.0; 60.0] mg per week. Therapy efficacy was assessed using the international psychometric scales. Therapy safety was assessed using the UKU Side-Effect Rating Scale. For genotyping and estimation of the microRNA (miRNA) plasma levels, we performed the real-time polymerase chain reaction. The activity of CYP3A was evaluated using the HPLC-MS/MS method by the content of the endogenous substrate of the given isoenzyme and its metabolite in urine (6b-HC/cortisol). Therapeutic drug monitoring has been performed using HPLC-MS/MS.

Results

Our study didn't reveal any statistically significant results in terms of the treatment efficacy and safety of the therapy. We also didn't reveal a statistical significance for the concentration/dose indicator of mirtazapine in patients with different genotypes. Analysis of the results of the pharmacotranscriptomic part of the study didn't demonstrate the statistically significant difference in the miR-27b plasma levels in patients with different genotypes. At the same time, correlation analysis didn't reveal a statistically significant relationship between the mirtazapine efficacy profile evaluated by changes in HAMD scale scores and the miR-27b plasma concentration: rs = -0.2, p = 0.46. Also, we didn't reveal the correlation between the miRNA concentration and safety profile: rs = 0.029, p = 0.93. In addition, we didn't reveal the relationship between the CYP3A enzymatic activity and the miR-27b plasma concentration: rs = -0,188, p = 0.85. However, the difference in the CYP3A enzymatic activity in carriers of AG and GG genotypes of the 6986A > G polymorphism of CYP3A5 gene has been revealed: (AG) 4.75 [1.28; 7.34] vs (GG) 8.83 [4.73; 13.62], p-value = 0.023.

Conclusion

Thus, the effect of genetic polymorphism of the CYP3A4, CYP2C9, CYP2C9, CYP3A5, ABCB1, CYP2C19, CYP2C19, CYP2C19, SCL6A4, 5-HTR2A gene on the efficacy and safety profiles of mirtazapine was not demonstrated in a group of 108 patients with depressive disorder and alcohol use disorder.

Functional phenotyping of the CYP2D6 probe drug codeine in the horse

BACKGROUND

In humans, the drug metabolizing enzyme CYP2D6 is highly polymorphic resulting in substantial differences in the metabolism of drugs including anti-arrhythmics, neuroleptics, and opioids. The objective of this study was to phenotype a population of 100 horses from five different breeds and assess differences in the metabolic activity of the equine CYP2D6 homolog using codeine as a probe drug. Administration of a probe drug is a common method used for patient phenotyping in human medicine, whereby the ratio of parent drug to metabolite (metabolic ratio, MR) can be used to compare relative enzyme function between individuals. A single oral dose of codeine (0.6 mg/kg) was administered and plasma concentrations of codeine and its metabolites were determined using liquid chromatography mass spectrometry. The MR of codeine O-demethylation [(codeine)/(morphine + morphine-3-glucuronide + morphine-6-glucuronide)] was determined using the area under the plasma concentration-time curve extrapolated from time zero to infinity (AUC0-∞) for each analyte and used to group horses into predicted phenotypes (high-, moderate-, and low-MR).

RESULTS

The MR of codeine O-demethylation ranged from 0.002 to 0.147 (median 0.018) among all horses. No significant difference in MR was observed between breeds, age, or sex. Of the 100 horses, 11 were classified as high-MR, 72 moderate-MR, and 17 low-MR. Codeine AUC0-∞ and O-demethylation MR were significantly different (p < 0.05) between all three groups. The mean ± SD MR was 0.089 ± 0.027, 0.022 ± 0.011, and 0.0095 ± 0.001 for high-, moderate-, and low-MR groups, respectively. The AUC for the morphine metabolites morphine-3-glucuronide and morphine-6-glucuronide were significantly different between high-and low-MR groups (p < 0.004 and p < 0.006).

CONCLUSIONS

The MR calculated from plasma following codeine administration allowed for classification of horses into metabolic phenotypes within a large population. The range of codeine metabolism observed among horses suggests the presence of genetic polymorphisms in CYP2D82 of which codeine is a known substrate. Additional studies including CYP2D82 genotyping of high- and low-MR individuals are necessary to determine the presence of CYP2D polymorphisms and their functional implications with respect to the metabolism of therapeutics.

Opioids and Sickle Cell Disease: From Opium to the Opioid Epidemic

Sickle cell disease (SCD) is an inherited disorder of hemoglobin structure. The clinical effects of the sickle gene are pleiotropic in nature causing multiple phenotypic expressions associated with the various complications of the disease. The hallmark of the disease is pain that could be acute, chronic, nociceptive, or neuropathic that could occur singly or in various combinations. The acute vaso-occlusive painful crisis (VOC) is the most common cause of admissions to the Emergency Department and/or the hospital. Although progress has been made in understanding the pathophysiology of SCD as well as in developing preventive and curative therapies, effective pain management continues to lag behind and depend mostly on the use of opioids. This review describes the history of opioids from the ancient times of opium to the current use of the many controversial opioids. In addition, the major cause of death of patients with SCD is the complications of the disease itself and not the use of opioids. The use of opioids by patients with SCD has been stable over the years. Judicious use of opioids to treat sickle cell pain according to available guidelines could minimize the unnecessary suffering experienced by patients with SCD.

Racial Disparity in Drug Disposition in the Digestive Tract

The major determinants of drug or, al bioavailability are absorption and metabolism in the digestive tract. Genetic variations can cause significant differences in transporter and enzyme protein expression and function. The racial distribution of selected efflux transporter (i.e., Pgp, BCRP, MRP2) and metabolism enzyme (i.e., UGT1A1, UGT1A8) single nucleotide polymorphisms (SNPs) that are highly expressed in the digestive tract are reviewed in this paper with emphasis on the allele frequency and the impact on drug absorption, metabolism, and in vivo drug exposure. Additionally, preclinical and clinical models used to study the impact of transporter/enzyme SNPs on protein expression and function are also reviewed. The results showed that allele frequency of the major drug efflux transporters and the major intestinal metabolic enzymes are highly different in different races, leading to different drug disposition and exposure. The conclusion is that genetic polymorphism is frequently observed in different races and the related protein expression and drug absorption/metabolism function and drug in vivo exposure can be significantly affected, resulting in variations in drug response. Basic research on race-dependent drug absorption/metabolism is expected, and FDA regulations of drug dosing adjustment based on racial disparity are suggested.

Impact of the Omics-Based Biomarkers on the Fluvoxamine's Steady-State Concentration, Efficacy and Safety in Patients with Affective Disorders Comorbid with Alcohol Use Disorder

Introduction

Fluvoxamine is commonly administered to patients with recurrent depressive disorder. Some of these patients do not show adequate response to the therapy with fluvoxamine, whereas many of them experience dose-dependent adverse drug reactions. Previous research revealed that CYP2D6 is involved in the metabolism of fluvoxamine, the activity of which is highly dependent on the polymorphism of the gene encoding it.

Objective

The objective of this study was to investigate the effect of polymorphisms of the CYP3A4, CYP2C9, CYP3A5, ABCB1, CYP2C19, SCL6A4, and 5-HTR2A genes on the concentration/dose indicator of fluvoxamine and on the CYP3A expression level obtained by measuring the miR-27b plasma concentration levels in patients suffering from a recurrent depressive disorder.

Material and Methods

Our study included 105 patients with recurrent depressive disorder (average age - 37.5 ± 13.2 years). The treatment regimen included fluvoxamine in an average daily dose of 117.6 ± 44.3 mg per week. Therapy efficacy was assessed using the international psychometric scales. Therapy safety was assessed using the UKU Side-Effect Rating Scale. For genotyping and estimation of the microRNA (miRNA) plasma levels, we performed the real-time polymerase chain reaction. The activity of CYP3A was evaluated using the HPLC-MS/MS method by the content of the endogenous substrate of the given isoenzyme and its metabolite in urine (6b-HC/cortisol). Therapeutic drug monitoring has been performed using HPLC-MS/MS.

Results

Our study didn't reveal any statistically significant results in terms of the treatment efficacy and safety of the therapy. We also didn't reveal a statistical significance for the concentration/dose indicator of fluvoxamine in patients with different genotypes. Analysis of the results of the pharmacotranscriptomic part of the study didn't demonstrate the statistically significant difference in the miR-27b plasma levels in patients with different genotypes. At the same time, correlation analysis didn't reveal a statistically significant relationship between the fluvoxamine efficacy profile evaluated by changes in HAMD scale scores and the miR-27b plasma concentration: rs = -0.012, p = 0.63. Also, we didn't reveal the correlation between the miRNA concentration and safety profile: rs = -0.175, p = 0.30. In addition, we didn't reveal the relationship between the CYP3A enzymatic activity and the miR-27b plasma concentration: rs = -0.197, p < 0.32. However, the difference in the CYP3A enzymatic activity in carriers of AG and GG genotypes of the 6986A > G polymorphism of CYP3A5 gene has been revealed: (AG) 4.72 [1.18; 8.45] vs (GG) 9.23 [5.12; 15.53], p-value = 0.23.

Conclusion

Thus, the effect of genetic polymorphism of the CYP3A4, CYP2C9, CYP2C9, CYP3A5, ABCB1, CYP2C19, CYP2C19, CYP2C19, SCL6A4, 5-HTR2A gene on the efficacy and safety profiles of fluvoxamine was not demonstrated in a group of 105 patients with depressive disorder and alcohol use disorder.

Pharmacogenetics of Obsessive-Compulsive Disorder: An Evidence-Update

Pharmacogenetics has become increasingly important in the treatment of psychiatric disorders because approximately 50% of individuals who take psychotropic medications do not typically respond to them. Obsessive-compulsive disorder (OCD) is one such chronic and often debilitating mental illness with significant non-response to even the first-line medication, serotonin reuptake inhibitors. Precision medicine utilizing genetic testing panels has received significant attention based on the evidence that the variability of antidepressant response and adverse effects is partly due to the variability in an individual's genome. Thus, extensive research has investigated the role of genetic factors on antidepressant response in major depressive disorder (MDD) and their utility for guiding antidepressant treatment to significantly improving outcomes in individuals with MDD. However, limited progress remains in the pharmacogenetics of OCD. This chapter will provide an overview of the recent findings in the pharmacogenetics of OCD. Promising results with limited replications have been reported for the cytochrome P450 liver metabolism genes in addition to several serotonergic and glutamatergic system genes, which may play an important role in antidepressant response in the treatment of OCD.

Mutagenic, Genotoxic and Immunomodulatory effects of Hydroxychloroquine and Chloroquine: a review to evaluate its potential to use as a prophylactic drug against COVID-19

Hydroxychloroquine (HCQ) and Chloroquine (CQ) are two anti-malarial drugs that are now being extensively used by front-line healthcare workers and other common people as a prophylactic drug against the Corona Virus Disease − 19 (COVID-19) in India and as well as in many parts of the world. While only a few in vitro studies have pointed to some efficacy of these drugs as a prophylactic against COVID-19, to date, there are no clinical studies that have established any clinical efficacy of these drugs as a prophylactic. These drugs are commonly used for the treatment of Rheumatoid Arthritis (RA) and Systemic Lupus Erythematosus (SLE) because of its immunomodulatory effects. Previously, we have evaluated the genetic toxicology of different drugs and chemicals including antimalarial drug CQ both in vitro and in vivo. Thus, we recognize the need to critically review the mutagenic, genotoxic, and immunomodulatory effects of these drugs, to find out whether it is safe to use as a prophylactic drug against COVID-19. Existing literature suggests that CQ can induce mutagenic and genotoxic effects in multiple test systems and both the drugs have immunomodulatory effects. There was no data available to evaluate the mutagenicity and genotoxicity for HCQ. However, during metabolism about 60% of both the drugs remain unchanged and about 40% of the drugs are metabolized into two metabolites, desethylchloroquine and bisdesethylchloroquine by the action of the cytochrome P450 (CYP) enzymes in the liver. Both HCQ and CQ are immunomodulatory drugs and have the potential to suppress normal immune system activation. In this review, we have elucidated the mechanism of immunomodulation by both HCQ and CQ and highlighted the mutagenic and genotoxic effects from the available literature. This article is written with the sole objective that the reader will be able to recognize the adverse effects of these drugs when consumed by healthy individuals as a prophylactic. Current literature indicates that healthy individuals should refrain from the use of these drugs until further investigation.

The Influence of Concentration of Micro-RNA hsa-miR-370-3p and CYP2D6*4 on Equilibrium Concentration of Mirtazapine in Patients With Major Depressive Disorder

INTRODUCTION

Mirtazapine is commonly prescribed to patients diagnosed with major depressive disorder.Some proportion of these patients do not show adequate response to treatment regimen containing mirtazapine, whereas many of them experience dose-dependent adverse drug reactions. Results of the previous studies showed that CYP2D6 is involved in the biotransformation of mirtazapine, the activity of which is highly dependent on the polymorphism of the gene encoding it.

OBJECTIVE

The objective of our study was to investigate the influence of 1846G>A polymorphism of the CYP2D6 gene on the concentration/dose indicator of mirtazapine, using findings on enzymatic activity of CYP2D6 (as evaluated by the 6M-THBC/pinoline ratio measurement) and on CYP2D6 expression level obtained by measuring the hsa-miR-370-3p plasma levelsin patients suffering from recurrent depressive disorder.

MATERIAL AND METHODS

Our study included 192 patients with major depressive disorder (age - 41.4 ± 15.6 years). Treatment regimen included mirtazapine in an average daily dose of 37.4 ± 13.5 mg per week. Treatment efficacy was evaluated using the international psychometric scales. Therapy safety was assessed using the UKU Side-Effect Rating Scale. For genotyping and estimation of the microRNA (miRNA) plasma levels we performed the real-time polymerase chain reaction. The activity of CYP2D6 was assessed with HPLC-MS/MS method by the content of the endogenous substrate of given isoenzyme and its metabolite in urine (6M-THBC/pinoline). Therapeutic drug monitoring (TDM) has been performed using HPLC-MS/MS.

RESULTS

Our study revealed the statistically significant results in terms of the treatment efficacy evaluation (HAMD scores at the end of the treatment course): (GG) 10.0 [9.0; 11.0] and (GA) 12.0 [11.0; 12.0], p < 0.001; at the same time, the statistical significance in the safety profile was obtained (the UKU scores): (GG) 3.0 [2.0; 4.0] and (GA) 4.0 [3.0; 5.0], p < 0.001. We didn't reveal a statistical significance for concentration/dose indicator of mirtazapine in patients with different genotypes: (GG) 0.229 [0.158; 0.468] and (GA) 0.290 [0.174; 0.526], p = 0.196. Analysis of the results of the pharmacotranscriptomic part of the study didn't demonstrate the statistically significant difference in the hsa-miR-370-3p plasma levels in patients with different genotypes: (GG) 23.6 [17.6; 28.0], (GA) 21.8 [17.2; 27.0], p = 0.663. At the same time, correlation analysis didn't reveal a statistically significant relationship between the mirtazapine efficacy profile evaluated by changes in HAMD scale scores and the hsa-miR-370-3p plasma concentration: rs = 0.05, p = 0.460. Also, we didn't reveal the correlation between the miRNA concentration and safety profile: rs = 0.11, p = 0.124. In addition, we revealed the relationship between the CYP2D6 enzymatic activity (as evaluated by 6M-THBC/pinoline ratio measurement) and the hsa-miR-370-3p plasma concentration: rs = -0.32, p < 0.001. At the same time, correlation analysis revealed a statistically significant relationship between the mirtazapine concentration and the hsa-miR-370-3p plasma concentration: rs = 0.31, p < 0.001.

CONCLUSION

Thus, the effect of genetic polymorphism of the CYP2D6 gene on the efficacy and safety profiles of mirtazapine was demonstrated in a group of 192 patients with recurrent depressive disorder. At the same time, hsa-miR-370-3p remains a promising biomarker for assessing the level of CYP2D6 expression, because it correlates with encoded isoenzyme activity.

Impact of Polymorphism of CYP2D6 on Equilibrium Concentration of Duloxetine in Patients Suffering from Major Depressive Disorder

INTRODUCTION

Duloxetine is commonly prescribed to patients with recurrent depressive disorder. Some part of patients in this group do not respond adequately to treatment regimen containing duloxetine, while many of them experience dose-dependent adverse drug reactions. Previous research investigated that CYP2D6 is involved in the biotransformation of duloxetine, the activity of which is highly dependent on the polymorphism of the gene encoding it.

OBJECTIVE

The objective of this study was to evaluate the influence of 1846G > A polymorphism of the CYP2D6 gene on the concentration/dose indicator of duloxetine, using findings on enzymatic activity of CYP2D6 (as evaluated by the 6M-THBC/pinoline ratio measurement) and on CYP2D6 expression level obtained by measuring the hsa-miR-370-3p plasma concentration levels in patients suffering from recurrent depressive disorder.

MATERIAL AND METHODS

This study enrolled 118 patients with recurrent depressive disorder (average age - 40.6±17.1 years). Therapy included duloxetine in an average daily dose of 103.7±37.1 mg per day. Treatment efficacy was assessed using the international psychometric scales. Therapy safety was assessed using the UKU Side-Effect Rating Scale. For genotyping we performed the real-time polymerase chain reaction (PCR Real-time). Therapeutic drug monitoring has been performed using HPLC-MS/MS.

RESULTS

Our findings revealed the statistically significant results in terms of the treatment efficacy evaluation (HAMD scores at the end of the treatment course): (GG) 9.0 [7.0; 10.0] and (GA) 11.0 [8.5; 14.0], p < 0.001; at the same time, the statistical significance in the safety profile was obtained (the UKU scores): (GG) 3.0 [3.0; 4.0] and (GA) 4.0 [3.0; 4.0], p = 0.007. We revealed a statistical significance for concentration/dose indicator of duloxetine in patients with different genotypes: (GG) 0.776 [0.529; 1.067] and (GA) 1.388 [0.942; 1.732], p < 0.001.

CONCLUSION

Thus, the effect of genetic polymorphism of the CYP2D6 gene on the efficacy and safety profiles of duloxetine was demonstrated in a group of 118 patients with recurrent depressive disorder.

Genetics and Opioids: Towards More Appropriate Prescription in Cancer Pain

Opioids are extensively used in patients with cancer pain; despite their efficacy, several patients can experience ineffective analgesia and/or side effects. Pharmacogenetics is a new approach to drug prescription based on the “personalized-medicine” concept, i.e., the ability of tailoring treatments to each individual’s genetic/genomic profile. Pharmacogenetics aims to identify specific genetic variants that influence pharmacokinetics and pharmacodynamics of drugs, better determining their effectiveness/safety profile. Opioid response is a complex scenario, but some gene variants have shown a correlation with pain sensitivity, as well as with opioid metabolism and clinical efficacy/adverse events. Although questions remain unanswered, some of these gene variants may already be used to identify specific patients’ phenotypes that are more prone to experience better clinical response (i.e., better analgesia and/or less adverse events). Once adopted, this approach to opioid prescription may improve a patient’s outcome. This review summarizes the available data on genetic variants and opioid response: we will focus on basic pharmacogenetic and its impact in the clinical scenario discussing how they may lead to more appropriate opioid prescription in cancer patients.

COVID-19 as an Acute Inflammatory Disease

The 2019 coronavirus disease (COVID-19) pandemic caused by the virus severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has created an unprecedented global crisis for the infrastructure sectors, including economic, political, healthcare, education, and research systems. Although over 90% of infected individuals are asymptomatic or manifest noncritical symptoms and will recover from the infection, those individuals presenting with critical symptoms are in urgent need of effective treatment options. Emerging data related to mechanism of severity and potential therapies for patients presenting with severe symptoms are scattered and therefore require a comprehensive analysis to focus research on developing effective therapeutics. A critical literature review suggests that the severity of SARS-CoV-2 infection is associated with dysregulation of inflammatory immune responses, which in turn inhibits the development of protective immunity to the infection. Therefore, the use of therapeutics that modulate inflammation without compromising the adaptive immune response could be the most effective therapeutic strategy.

Review of nutritional status, body composition, and effects of antineoplastic drug disposition

The overall survival for children with cancer in high income countries is excellent. However, there are many disparities that may negatively affect survival, which are particularly problematic in low income countries, such as nutritional status at diagnosis and throughout therapy. Nutritional status as well as concomitant foods, supplements, and medications may play a role in overall exposure and response to chemotherapy. Emerging science around the microbiome may also play a role and should be further explored as a contributor to disease progression and therapeutic response. This article highlights some of these issues and proposes additional areas of research relevant to nutritional status and pharmacology that are needed in pediatric oncology.

The effect of CYP2D6 variation on antipsychotic-induced hyperprolactinaemia: a systematic review and meta-analysis

Hyperprolactinemia is a known adverse drug reaction to antipsychotic treatment. Antipsychotic blood levels are influenced by cytochrome P450 enzymes, primarily CYP2D6. Variation in CYP450 genes may affect the risk of antipsychotic-induced hyperprolactinemia. We undertook a systematic review and meta-analysis to assess whether CYP2D6 functional genetic variants are associated with antipsychotic-induced hyperprolactinemia. The systematic review identified 16 relevant papers, seven of which were suitable for the meta-analysis (n = 303 participants including 134 extreme metabolisers). Participants were classified into four phenotype groups as poor, intermediate, extensive, and ultra-rapid metabolisers. A random effects meta-analysis was used and Cohen's d calculated as the effect size for each primary study. We found no significant differences in prolactin levels between CYP2D6 metabolic groups. Current evidence does not support using CYP2D6 genotyping to reduce risk of antipsychotic-induced hyperprolactinemia. However, statistical power is limited. Future studies with larger samples and including a range of prolactin-elevating drugs are needed.

Biotransformation, Using Recombinant CYP450-Expressing Baker's Yeast Cells, Identifies a Novel CYP2D6.10A122V Variant Which Is a Superior Metabolizer of Codeine to Morphine Than the Wild-Type Enzyme

CYP2D6, a cytochrome P450 (CYP) enzyme, metabolizes codeine to morphine. Within the human body, 0-15% of codeine undergoes O-demethylation by CYP2D6 to form morphine, a far stronger analgesic than codeine. Genetic polymorphisms in wild-type CYP2D6 (CYP2D6-wt) are known to cause poor-to-extensive metabolism of codeine and other CYP2D6 substrates. We have established a platform technology that allows stable expression of human CYP genes from chromosomal loci of baker's yeast cells. Four CYP2D6 alleles, (i) chemically synthesized CYP2D6.1, (ii) chemically synthesized CYP2D6-wt, (iii) chemically synthesized CYP2D6.10, and (iv) a novel CYP2D6.10 variant CYP2D6-C (i.e., CYP2D6.10^A122V) isolated from a liver cDNA library, were cloned for chromosomal integration in yeast cells. When expressed in yeast, CYP2D6.10 enzyme shows weak activity compared with CYP2D6-wt and CYP2D6.1 which have moderate activity, as reported earlier. Surprisingly, however, the CYP2D6-C enzyme is far more active than CYP2D6.10. More surprisingly, although CYP2D6.10 is a known low metabolizer of codeine, yeast cells expressing CYP2D6-C transform >70% of codeine to morphine, which is more than twice that of cells expressing the extensive metabolizers, CYP2D6.1, and CYP2D6-wt. The latter two enzymes predominantly catalyze formation of codeine's N-demethylation product, norcodeine, with >55% yield. Molecular modeling studies explain the specificity of CYP2D6-C for O-demethylation, validating observed experimental results. The yeast-based CYP2D6 expression systems, described here, could find generic use in CYP2D6-mediated drug metabolism and also in high-yield chemical reactions that allow the formation of regio-specific dealkylation products.

Analgesia and Opioids: A Pharmacogenetics Shortlist for Implementation in Clinical Practice

BACKGROUND

The use of opioids to alleviate pain is complicated by the risk of severe adverse events and the large variability in dose requirements. Pharmacogenetics (PGx) could possibly be used to tailor pain medication based on an individual's genetic background. Many potential genetic markers have been described, and the importance of genetic predisposition in opioid efficacy and toxicity has been demonstrated in knockout mouse models and human twin studies. Such predictors are especially of value for neonates and young children, in whom the assessment of efficacy or side effects is complicated by the inability of the patient to communicate this properly. The current problem is determining which of the many potential candidates to focus on for clinical implementation.

CONTENT

We systematically searched publications on PGx for opioids in 5 databases, aiming to identify PGx markers with sufficient robust data and high enough occurrence for potential clinical application. The initial search yielded 4257 unique citations, eventually resulting in 852 relevant articles covering 24 genes. From these genes, we evaluated the evidence and selected the most promising 10 markers: cytochrome P450 family 2 subfamily D member 6 (CYP2D6), cytochrome P450 family 3 subfamily A member 4 (CYP3A4), cytochrome P450 family 3 subfamily A member 5 (CYP3A5), UDP glucuronosyltransferase family 2 member B7 (UGT2B7), ATP binding cassette subfamily B member 1 (ABCB1), ATP binding cassette subfamily C member 3 (ABCC3), solute carrier family 22 member 1 (SLC22A1), opioid receptor kappa 1 (OPRM1), catechol-O-methyltransferase (COMT), and potassium voltage-gated channel subfamily J member 6 (KCNJ6). Treatment guidelines based on genotype are already available only for CYP2D6.

SUMMARY

The application of PGx in the management of pain with opioids has the potential to improve therapy. We provide a shortlist of 10 genes that are the most promising markers for clinical use in this context.

Dextromethorphan and debrisoquine metabolism and polymorphism of the gene for cytochrome P450 isozyme 2D50 in Thoroughbreds

OBJECTIVE To characterize polymorphisms of the gene for cytochrome P450 isozyme 2D50 (CYP2D50) and the disposition of 2 CYP2D50 probe drugs, dextromethorphan and debrisoquine, in horses. ANIMALS 23 healthy horses (22 Thoroughbreds and 1 Standardbred). PROCEDURES Single-nucleotide polymorphisms (SNPs) in CYP2D50 were identified. Disposition of dextromethorphan (2 mg/kg) and debrisoquine (0.2 mg/kg) were determined after oral (dextromethorphan) or nasogastric (debrisoquine) administration to the horses. Metabolic ratios of plasma dextromethorphan and total dextrorphan (dextrorphan plus dextrorphan-O-β-glucuronide) and 4-hydroxydebrisoquine concentrations were calculated on the basis of the area under the plasma concentration-versus-time curve extrapolated to infinity for the parent drug divided by that for the corresponding metabolite. Pharmacokinetic data were used to categorize horses into the phenotypic drug-metabolism categories poor, extensive, and ultrarapid. Disposition patterns were compared among categories, and relationships between SNPs and metabolism categories were explored. RESULTS Gene sequencing identified 51 SNPs, including 27 nonsynonymous SNPs. Debrisoquine was minimally detected after oral administration. Disposition of dextromethorphan varied markedly among horses. Metabolic ratios for dextromethorphan ranged from 0.03 to 0.46 (mean, 0.12). On the basis of these data, 1 horse was characterized as a poor metabolizer, 18 were characterized as extensive metabolizers, and 3 were characterized as ultrarapid metabolizers. CONCLUSIONS AND CLINICAL RELEVANCE Findings suggested that CYP2D50 is polymorphic and that the disposition of the probe drug varies markedly in horses. The polymorphisms may be related to rates of drug metabolism. Additional research involving more horses of various breeds is needed to fully explore the functional implication of polymorphisms in CYP2D50.

A service improvement project to review prescribing information provided by general practitioners for new referrals to a UK National Health Service hospital pain clinic: potential implications of CYP2D6 enzyme inhibition

INTRODUCTION

Chronic pain is often managed using co-prescription of analgesics and adjuvants, with concomitant medication prescribed for comorbidities. Patients may have suboptimal response to some analgesics or be at risk of drug interactions or adverse drug reactions (ADRs) due to polypharmacy affecting CYP2D6 enzyme activity. The aim of the service improvement project was to determine the proportion of patients referred to a specialist pain service in the UK National Health Service (NHS) by general practitioners (GPs) who may be at risk of suboptimal analgesic response or ADRs due to CYP2D6 inhibition through polypharmacy. This was achieved by reviewing clinical prescribing information provided by GPs at time of referral. It was hoped that the findings could be used to aid clinical and prescribing decisions without conducting CYP2D6 genotyping or phenotyping.

METHODS

A review of letters from 250 patients referred to an NHS hospital pain service from GPs over a 3-month period was undertaken. Information about current and concomitant medications was analysed to identify the potential for CYP2D6 inhibition and adverse events.

RESULTS

Letters failed to provide information about current pain medication for 20 (8%) patients or non-pain concomitant medication for 54 (21.6%) patients. Of 176 patients, 52 (29.5%) patients with information about non-pain concomitant medication had been prescribed at least one known CYP2D6 inhibitor. A total of 35 (19.9%) patients were identified as being at risk of an adverse drug reaction and 33 (18.75%) patients at risk of suboptimal analgesic response due to co-administration of CYP2D6 inhibitors.

CONCLUSION

The review revealed the need for improved detail in GP referral letters used to transfer care to UK NHS hospital pain clinics. There is a need to consider an individual's CYP2D6 phenotype when prescribing analgesic prodrugs to manage persistent pain. Caution is needed when patients are co-prescribed codeine or tramadol with selective serotonin reuptake inhibitors (SSRIs).

Pharmacogenetics of CYP2D6 and tamoxifen therapy: Light at the end of the tunnel?

The clinical usefulness of assessing the enzymatic activity of CYPD6 in patients taking tamoxifen had been longly debated. In favour of preemptive evaluation of phenotypic profile of patients is the strong pharmacologic rationale, being that the formation of endoxifen, the major and clinically most important metabolite of tamoxifen, is largely dependent on the activity of CYP2D6. This enzyme is highly polymorphic for which the activity is largely depending on genetics, but that can also be inhibited by a number of drugs, i.e. antidepressants, which are frequently used in patients with cancer. Unfortunately, the clinical trials that have been published in the last years are contradicting each other on the association between CYP2D6 and significant clinical endpoints, and for this reason CYP2D6 genotyping is at present not generally recommended. Despite this, the CYP2D6 genotyping test for tamoxifen is available in many laboratories and it may still be an appropriate test to use it in specific cases.

From Individualized Treatment of Sickle Cell Pain to Precision Medicine: A 40-Year Journey

In the 1970s, sickle cell pain was treated with trial and error approach by increasing or decreasing the dose of an opioid or switching from one analgesic to another. This approach was controversial with criticism and doubt about its usefulness. Since then, advances in determining the structure of opioid receptors and the role of the CYP450 enzymes in metabolizing opioids revealed that these anatomic and metabolic findings are not the same in all persons, thus explaining the variability in response to opioids among patients. Thus, the “trial and error approach” has a scientific basis after all.

In vitro assessment of 24 CYP2D6 allelic isoforms on the metabolism of methadone

CYP2D6 is an important member of the cytochrome P450 (CYP450) enzyme super family, with at least 100 CYP2D6 alleles being previously identified. Genetic polymorphisms of CYP2D6 significantly influence the efficacy and safety of some drugs, which might cause adverse effects and therapeutic failure. The aim of this study was to clarify the catalytic activities of 24 CYP2D6 alleles on the oxidative in vitro metabolism of methadone. Reactions were incubated with 50-2000  µM methadone for 30 min at 37 °C and terminated by cooling to -80 °C immediately. Methadone and the major metabolite EDDP were analyzed by an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) system. Compared with wild-type CYP2D6*1, most variants showed significantly altered values in V_max and intrinsic clearance (V_max /K_m ). Only three variants (CYP2D6*88, *91 and E215K) exhibited markedly increased intrinsic clearance values, and one variant CYP2D6*94 showed no significant difference. On the other hand, the kinetic parameters of two CYP2D6 variants (CYP2D6*92 and *96) could not be determined because they had no detectable enzyme activity, whereas 18 variants exhibited significantly decreased values. To sum up, this study demonstrated that more attention should be paid in clinical administration of methadone to individuals carrying these CYP2D6 alleles. Copyright © 2016 John Wiley & Sons, Ltd.

Repeated tender point injections of granisetron alleviate chronic myofascial pain--a randomized, controlled, double-blinded trial

Background

Serotonin (5-HT) mediates pain by peripheral 5-HT₃-receptors. Results from a few studies indicate that intramuscular injections of 5-HT₃-antagonists may reduce musculoskeletal pain. The aim of this study was to investigate if repeated intramuscular tender-point injections of the 5-HT₃-antagonist granisetron alleviate pain in patients with myofascial temporomandibular disorders (M-TMD).

Methods

This prospective, randomized, controlled, double blind, parallel-arm trial (RCT) was carried out during at two centers in Stockholm, Sweden. The randomization was performed by a researcher who did not participate in data collection with an internet-based application (www.randomization.com). 40 patients with a diagnose of M-TMD according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) were randomized to receive repeated injections, one week apart, with either granisetron (GRA; 3 mg) or isotonic saline as control (CTR).

Results

The median weekly pain intensities decreased significantly at all follow-ups (1-, 2-, 6-months) in the GRA-group (Friedman test; P < 0.05), but not in the CTR-group (Friedman-test; P > 0.075). The numbers needed to treat (NNT) were 4 at the 1- and 6-month follow-ups, and 3.3 at the 2-month follow-up in favor of granisetron.

Conclusions

Repeated intramuscular tender-point injections with granisetron provide a new pharmacological treatment possibility for myofascial pain patients with repeated intramuscular tender-point injections with the serotonin type 3 antagonist granisetron. It showed a clinically relevant pain reducing effect in the temporomandibular region, both in a short- and long-term aspect.

Trial registration

European Clinical Trials Database 2005-006042-41 as well as at Clinical Trials NCT02230371.

Evidence for polymorphism in the cytochrome P450 2D50 gene in horses

Metabolism is an essential factor in the clearance of many drugs and as such plays a major role in the establishment of dosage regimens and withdrawal times. CYP2D6, the human orthologue to equine CYP2D50, is a drug-metabolizing enzyme that is highly polymorphic in humans leading to widely differing levels of metabolic activity. As CYP2D6 is highly polymorphic, in this study it was hypothesized that the gene coding for the equine orthologue, CYP2D50, may also be prone to polymorphism. Blood samples were collected from 150 horses, the CYP2D50 gene was cloned and sequenced; and full-length sequences were analyzed for single nucleotide polymorphisms (SNPs), deletions, or insertions. Pharmacokinetic data were collected from a subset of horses following the administration of a single oral dose of tramadol and probit analysis used to calculate metabolic ratios. Prior to drug administration, the ability of recombinant CYP2D50 to metabolize tramadol to O-desmethyltramadol was confirmed. Sequencing of CYP2D50 identified 126 exonic SNPs, with 31 of those appearing in multiple horses. Oral administration of tramadol to a subset of these horses revealed variable metabolic ratios (tramadol: O-desmethyltramadol) in individual horses and separation into three metabolic groups. While a limited number of horses of primarily a single breed were studied, the variability in tramadol metabolism to O-desmethyltramadol between horses and preliminary evidence of what appears to be poor, extensive, and ultra-rapid metabolizers supports further study of the potential for genetic polymorphisms in the CYP2D50 gene in horses.

Progress in oral personalized medicine: contribution of 'omics'

BACKGROUND

Precision medicine (PM), representing clinically applicable personalized medicine, proactively integrates and interprets multidimensional personal health data, including clinical, 'omics', and environmental profiles, into clinical practice. Realization of PM remains in progress.

OBJECTIVE

The focus of this review is to provide a descriptive narrative overview of: 1) the current status of oral personalized medicine; and 2) recent advances in genomics and related 'omic' and emerging research domains contributing to advancing oral-systemic PM, with special emphasis on current understanding of oral microbiomes.

DESIGN

A scan of peer-reviewed literature describing oral PM or 'omic'-based research conducted on humans/data published in English within the last 5 years in journals indexed in the PubMed database was conducted using mesh search terms. An evidence-based approach was used to report on recent advances with potential to advance PM in the context of historical critical and systematic reviews to delineate current state-of-the-art technologies. Special focus was placed on oral microbiome research associated with health and disease states, emerging research domains, and technological advances, which are positioning realization of PM.

RESULTS

This review summarizes: 1) evolving conceptualization of personalized medicine; 2) emerging insight into roles of oral infectious and inflammatory processes as contributors to both oral and systemic diseases; 3) community shifts in microbiota that may contribute to disease; 4) evidence pointing to new uncharacterized potential oral pathogens; 5) advances in technological approaches to 'omics' research that will accelerate PM; 6) emerging research domains that expand insights into host-microbe interaction including inter-kingdom communication, systems and network analysis, and salivaomics; and 7) advances in informatics and big data analysis capabilities to facilitate interpretation of host and microbiome-associated datasets. Furthermore, progress in clinically applicable screening assays and biomarker definition to inform clinical care are briefly explored.

CONCLUSION

Advancement of oral PM currently remains in research and discovery phases. Although substantive progress has been made in advancing the understanding of the role of microbiome dynamics in health and disease and is being leveraged to advance early efforts at clinical translation, further research is required to discern interpretable constituency patterns in the complex interactions of these microbial communities in health and disease. Advances in biotechnology and bioinformatics facilitating novel approaches to rapid analysis and interpretation of large datasets are providing new insights into oral health and disease, potentiating clinical application and advancing realization of PM within the next decade.

Characterization of the CYP2D6 drug metabolizing phenotypes of the Chilean mestizo population through polymorphism analyses

We tested the influence of four polymorphisms and gene duplication in CYP2D6 on in vivo enzyme activity in a Chilean mestizo population in order to identify the most relevant genetic profiles that account for observed phenotypes in this ethnic group. CYP2D6*2 (2850C>T), *3 (2549A>del), *4 (1846G>A), *17 (1023C>T) and gene duplication were determined by PCR-RFLP or PCRL in a group of 321 healthy volunteers. Individuals with different variant alleles were phenotyped by determining debrisoquine 4-hydroxylase activity as a metabolic ratio (MR) using a validated HPLC assay. Minor allele frequencies were 0.41, 0.01, 0.12 and 0.00 for CYP2D6*2, *3, *4 and *17 variants, respectively, and the duplication frequency was 0.003. Genotype analysis correlated with phenotypes in 18 of 23 subjects (78.3%). 11 subjects were extensive metabolizers (EM), 8 were intermediate metabolizers (IM), 2 were poor metabolizers (PM) and 2 were ultra-rapid metabolizers (UM) which is fairly coincident with expected phenotypes metabolic ratios ranged from 0.11 to 126.41. The influence of CYP2D6*3 was particularly notable, although only heterozygote carriers were present in our population. Individuals homozygous for *4 were always PM. As expected, the only subject with gene duplication was UM. In conclusion, there was a clear effect of genotype on observed CYP2D6 activity. Classification of EM, PM and UM through genotyping was useful to characterize CYP2D6 phenotype in the Chilean mestizo population.

Concurrent use of amphetamine stimulants and antidepressants by undergraduate students

Undergraduate students were recruited to participate in an online survey to report their use of amphetamine stimulants and other drugs. Significant differences were found between students reporting (n=79; 4.0%) and not reporting (n=1,897; 96%) amphetamine-stimulant use in the past month - in terms of race/ethnicity, class standing, residence, health symptoms, self-health report - in addition to alcohol, tobacco, pain-reliever, and antidepressant use. Health symptoms reported more often by stimulant users included depression, diarrhea, difficulty sleeping, fatigue, dizziness, difficulty concentrating, and nicotine craving. Health care providers of college students should query these patients about symptoms that could be related to depression and amphetamine use. In particular, they should provide education at the point of care around the risks of amphetamine use in general and the specific risks in those students who have symptoms of depression and/or are taking antidepressant medication. Prevention programs should also target the risks of concurrent use of amphetamines, antidepressants, and other drugs among college students.

Pathophysiology and principles of management of the many faces of the acute vaso-occlusive crisis in patients with sickle cell disease

Effective management of sickle cell pain entails a thorough understanding of its pathophysiology and the pharmacogenomics of the opioids used to manage it. In recent years, there has been significant progress along these two lines. At the pathophysiologic level, there is evidence that the severity and frequency of painful stimuli modulate their transmission at the level of the dorsal horn of the spinal cord. This modulation is achieved via two channels: the α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and NMDA receptors. Initially, the AMPA channel controls the transmission of stimuli of mild-moderate severity. Once the AMPA channel reaches its limit of membrane depolarization, the NMDA channel is activated and facilitates the transmission of painful stimuli in a progressive fashion leading to central sensitization and glial activation. At the level of pharmacogenomics, the metabolism of each opioid is patient-specific. Glucuronidation is unique for the metabolism of morphine, hydromorphone, and oxymorphone. The metabolism of all other opioids requires specific Cytochrome P450 (CYP) isoenzymes. The activity of each isoenzyme and the activity of the metabolites of each opioid vary among patients depending on their genetic makeup and coexistent environmental factors such as the use of other medications that may enhance or inhibit the CYP isoenzyme activity.

Expression of P450 and nuclear receptors in normal and end-stage Chinese livers

AIM: To investigate the expression of P450 enzyme genes by using end-stage liver disease samples and trimmed normal Chinese donor livers.

METHODS: The end-stage liver disease samples [n = 93, including hepatocellular carcinoma (HCC), peri-HCC tissue, hepatitis B virus cirrhosis, alcoholic cirrhosis, and severe cirrhosis] and trimmed normal Chinese donor livers (n = 35) from The Institute of Organ Transplantation in Beijing, China. Total RNA was extracted, purified, and subjected to real-time RT-PCR analysis.

RESULTS: For cytochrome P450 enzymes 1 (CYP1) family, the expression of CYP1A2 was decreased 90% in HCC, 80% in alcoholic cirrhosis, and 65% in severe cirrhosis. For CYP2 family, the expression of CAR was decreased 50% in HCC, but increased 50% in peri-HCC tissues. Similar decreases (about 50%) of CYP2B6, CYP2C9, CYP2C19, CYP2D6 and CYP2E1 were observed in HCC, as compared to peri-HCC tissues and normal livers. CYP2C19 were decreased in all end-stage liver diseases and CYP2E1 also decreased in alcoholic cirrhosis and severe cirrhosis. For CYP3 family, the expression of PXR was decreased 60% in HCC, together with decreases in CYP3A4, CYP3A5, and CYP3A7. In contrast, the expression of CYP3A7 was slightly increased in HBV cirrhosis. The expression of CYP4A11 was decreased 85% in HCC, 7% in alcoholic cirrhosis and severe liver cirrhosis, along with decreases in PPARα. The 93 end-stage livers had much higher inter-individual variations in gene expression than 35 normal livers.

CONCLUSION: The expression of CYP enzyme genes and corresponding nuclear receptors was generally decreased in end-stage liver diseases, and significant differences in gene expression were evident between peri-HCC and HCC.

Pharmacogenetics of antidepressant treatment in obsessive–compulsive disorder: an update and implications for clinicians

Obsessive–compulsive disorder (OCD) is a chronic neuropsychiatric disorder with high genetic influence. Antidepressants such as serotonin reuptake inhibitors, are widely accepted as the first-line medications for OCD; however, approximately 50% of OCD patients show poor response. Personalized medicine utilizing genetic testing has recently received much attention because the variability of antidepressant response and tolerability are partly due to an individual’s genetic variations. This has led to researchers investigating the role of specific genetic factors on antidepressant response and utility of testing in the clinical realm. Genetic test panels are showing promise for guiding antidepressant treatment to improve outcomes in depression. This article will review the most recent findings in the pharmacogenetics of OCD and its related disorders. Promising results have been reported for several serotonergic and glutamatergic system genes and the cytochrome CYP450 liver enzyme genes, which appear to play an important role in OCD and antidepressant response.