Pharmacogenetics: an opportunity for a safer and more efficient pharmacotherapy

Genetic diversity of variants involved in drug response among Tunisian and Italian populations toward personalized medicine

Adverse drug reactions (ADR) represent a significant contributor to morbidity and mortality, imposing a substantial financial burden. Genetic ancestry plays a crucial role in drug response. The aim of this study is to characterize the genetic variability of selected pharmacogenes involved with ADR in Tunisians and Italians, with a comparative analysis against global populations. A cohort of 135 healthy Tunisians and 737 Italians were genotyped using a SNP array. Variants located in 25 Very Important Pharmacogenes implicated in ADR were extracted from the genotyping data. Distribution analysis of common variants in Tunisian and Italian populations in comparison to 24 publicly available worldwide populations was performed using PLINK and R software. Results from Principle Component and ADMIXTURE analyses showed a high genetic similarity among Mediterranean populations, distinguishing them from Sub-Saharan African and Asian populations. The Fst comparative analysis identified 27 variants exhibiting significant differentiation between the studied populations. Among these variants, four SNPs rs622342, rs3846662, rs7294, rs5215 located in SLC22A1, HMGCR, VKORC1 and KCNJ11 genes respectively, are reported to be associated with ethnic variability in drug responses. In conclusion, correlating the frequencies of genotype risk variants with their associated ADRs would enhance drug outcomes and the implementation of personalized medicine in the studied populations.

Effect of Nifedipine Used in the Treatment of the Threat of Preterm Labor on Total Uterine Artery Blood Volume Flow Rate

PURPOSE

Evaluation of the effect of maternal nifedipine treatment on total uterine artery blood volume flow rate (TVFR).

METHODS

In this prospective study, 43 women who were admitted to the Perinatology Department of the University of Health Sciences Etlik Zübeyde Hanım Gynecology Training and Research Hospital, with the diagnosis of the threat of preterm labor, and 40 healthy pregnant women, who were randomly selected as the control group, were evaluated between July 1, 2018, and September 1, 2018. A transabdominal ultrasound examination of uterine arteries was performed both before and 48 hours after administration of oral nifedipine for TVFR measurement. For the final analysis, the TVFR levels of the group diagnosed with the threat of preterm labor and the control group were compared.

RESULTS

There was no significant difference in either uterine artery pulsatility index or resistance index values as well as the diameters of the uterine arteries after nifedipine treatment (p>0.05 for all). Total uterine artery blood volume flow rate (TVFR) was 424.66±236.74 mL/min before and 543.39±309.68 mL/min after treatment with nifedipine and was statistically significantly higher (p < 0.05).

CONCLUSIONS

Our study showed a statistically significant increase in total uterine artery blood volume flow rate 48 hours after oral nifedipine treatment.

An Analysis of Pharmacogenomic-Guided Pathways and Their Effect on Medication Changes and Hospital Admissions: A Systematic Review and Meta-Analysis

Ninety-five percent of the population are estimated to carry at least one genetic variant that is discordant with at least one medication. Pharmacogenomic (PGx) testing has the potential to identify patients with genetic variants that puts them at risk of adverse drug reactions and sub-optimal therapy. Predicting a patient's response to medications could support the safe management of medications and reduce hospitalization. These benefits can only be realized if prescribing clinicians make the medication changes prompted by PGx test results. This review examines the current evidence on the impact PGx testing has on hospital admissions and whether it prompts medication changes. A systematic search was performed in three databases (Medline, CINAHL and EMBASE) to search all the relevant studies published up to the year 2020, comparing hospitalization rates and medication changes amongst PGx tested patients with patients receiving treatment-as-usual (TAU). Data extracted from full texts were narratively synthesized using a process model developed from the included studies, to derive themes associated to a suggested workflow for PGx-guided care and its expected benefit for medications optimization and hospitalization. A meta-analysis was undertaken on all the studies that report the number of PGx tested patients that had medication change(s) and the number of PGx tested patients that were hospitalized, compared to participants that received TAU. The search strategy identified 5 hospitalization themed studies and 5 medication change themed studies for analysis. The meta-analysis showed that medication changes occurred significantly more frequently in the PGx tested arm across 4 of 5 studies. Meta-analysis showed that all-cause hospitalization occurred significantly less frequently in the PGx tested arm than the TAU. The results show proof of concept for the use of PGx in prescribing that produces patient benefit. However, the review also highlights the opportunities and evidence gaps that are important when considering the introduction of PGx into health systems; namely patient involvement in PGx prescribing decisions, thus a better understanding of the perspective of patients and prescribers. We highlight the opportunities and evidence gaps that are important when considering the introduction of PGx into health systems.

Variability of Pharmacogenomics Information in Drug Labels Approved by Different Agencies and Its Ethical Implications

AIMS

The aim of this study was to determine if there are discrepancies among various agency-approved labels for the same active ingredient and where the labels approved by the Turkish Medicines and Medical Devices Agency (TMMDA) stand regarding the inclusion of PGx and discuss these ethical implications.

BACKGROUND

The efficacy and safety of drugs can be improved by rational prescription and personalization of medicine for each patient. Pharmacogenomics information (PGx) in drug labels (DL) is one of the important tools for the personalization of medications because genetic differences may affect both drug efficacy and safety. Providing adequate PGx to patients has ethical implications.

OBJECTIVE

To evaluate PGx in the DLs approved by TMMDA and other national agencies provided by the Pharmacogenomics Knowledgebase.

METHODS

DL annotations from the Pharmacogenomics Knowledgebase and DLs approved by the TMMDA were analyzed according to information and action levels, which are "testing required", "testing recommended", "actionable", and "informative".

RESULTS

There are 381 drugs listed in PharmGKB drug label annotations with pharmacogenomics information and 278 of these have biomarkers. A total of 242 (63.5%) drugs are approved and available in Turkey. Of these, 207 (85.5%) contain the same information as in or similar to that in the labels approved by the other agencies. The presence and level of information varied among the DLs approved by different agencies. The inconsistencies may have an important effect on the efficacy and the safety of drugs.

CONCLUSION

These findings suggest a need for the standardization of PGx information globally because it may not only affect the efficacy and safety of medications but also essential ethical rules regarding patient rights by violating not sufficiently sharing all available information.

Engineered human CYP2C9 and its main polymorphic variants for bioelectrochemical measurements of catalytic response

Polymorphism is an important aspect in drug metabolism responsible for different individual response to drug dosage, often leading to adverse drug reactions. Here human CYP2C9 as well as its polymorphic variants CYP2C9*2 and CYP2C9*3 present in approximately 35% of the Caucasian population have been engineered by linking their gene to the one of D. vulgaris flavodoxin (FLD) that acts as regulator of the electron flow from the electrode surface to the haem. The redox properties of the immobilised proteins were investigated by cyclic voltammetry and electrocatalysis was measured in presence of the largely used anticoagulant drug S-warfarin, marker substrate for CYP2C9. Immobilisation of the CYP2C9-FLD, CYP2C9*2-FLD and CYP2C9*3-FLD on DDAB modified glassy carbon electrodes showed well defined redox couples on the oxygen-free cyclic voltammograms and mid-point potentials of all enzymes were calculated. Electrocatalysis in presence of substrate and quantification of the product formed showed lower catalytic activities for the CYP2C9*3-FLD (2.73 ± 1.07 min^-1) and CYP2C9*2-FLD (12.42 ± 2.17 min^-1) compared to the wild type CYP2C9-FLD (18.23 ± 1.29 min^-1). These differences in activity among the CYP2C9 variants are in line with the reported literature data, and this set the basis for the use of the bio-electrode for the measurement of the different catalytic responses towards drugs very relevant in therapy.

Molecular pathway analysis associates alterations in obesity-related genes and antipsychotic-induced weight gain

OBJECTIVE

Antipsychotics often induce excessive weight gain. We hypothesised that individuals with genetic variations related to known obesity-risk genes have an increased risk of excessive antipsychotic-induced weight gain (AIWG). This hypothesis was tested in a subset of the Clinical Antipsychotic Trials of Intervention Effectiveness (CATIE) trial data set.

METHODS

The CATIE trial compared effects and side effects of five different antipsychotics through an 18-month period. Based on the maximum weight gain recorded, excessive weight gain was defined as >7% weight gain. Cytoscape and GeneMANIA were instrumental in composing a molecular pathway from eight selected genes linked to obesity. Genetic information on a total of 495.172 single-nucleotide polymorphisms (SNPs) were available from 765 (556 males) individuals. Enrichment test was conducted through ReactomePA and Bioconductor. A permutation test was performed, testing the generated pathway against 105 permutated pathways (p ≤ 0.05). In addition, a standard genome-wide association study (GWAS) analysis was performed.

RESULT

GWAS analysis did not detect significant differences related to excessive weight gain. The pathway generated contained 28 genes. A total of 2067 SNPs were significantly expressed (p < 0.01) within this pathway when comparing excessive weight gainers to the rest of the sample. Affected genes including PPARG and PCSK1 were not previously related to treatment-induced weight gain.

CONCLUSIONS

The molecular pathway composed from high-risk obesity genes was shown to overlap with genetics of patients who gained >7% weight gain during the CATIE trial. This suggests that genes related to obesity compose a pathway of increased risk of excessive AIWG. Further independent analyses are warranted that may confirm or clarify the possible reasoning behind.

The effects of fasting on drug metabolism

Introduction: There is considerable variability in the rates and extent of drug metabolism between patients due to physiological, genetic, pharmacologic, environmental and nutritional factors such as fasting. This variability in drug metabolism may result in treatment failure or, conversely, in increased side effects or toxicity. Preclinical studies have shown that fasting alters drug metabolism by modulating the activity of drug metabolizing enzymes involved. However, until recently little was known about the effects of fasting on drug metabolism in humans.Areas covered: This review describes the effects of fasting on drug metabolism based on both preclinical studies and studies performed in humans.Expert opinion: A better understanding of the effects of fasting may improve the efficacy and safety of pharmacotherapy for individual patients. Fasting contributes to variability in human drug metabolism by differentially affecting drug metabolizing enzymes. Although the effects of fasting on drug metabolism appear to be small (between 10-20%), fasting may be relevant for drugs with a small therapeutic range and/or in combination with other factors that contribute to variability in drug metabolism such as physiological, genetic or pharmacological factors. Therefore, additional research on this topic is warranted.

Implications of genetic variation of common Drug Metabolizing Enzymes and ABC Transporters among the Pakistani Population

Genetic polymorphism of drug metabolizing enzymes and transporters may influence drug response. The frequency varies substantially between ethnicities thus having implications on appropriate selection and dosage of various drugs in different populations. The distribution of genetic polymorphisms in healthy Pakistanis has so far not been described. In this study, 155 healthy adults (98 females) were included from all districts of Karachi. DNA was extracted from saliva and genotyped for relevant SNVs in CYP1A1, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A4 and CYP3A5 as well as ALDH3A1, GSTA1, ABCB1 and ABCC2. About 64% of the participants were born to parents who were unrelated to each other. There was generally a higher prevalence (p < 0.05) of variant alleles of CYP450 1A2, 2B6, 2C19, 3A5, ALDH3A1, GSTM1 as well as ABCB1 and ABCC2 in this study cohort than in other ethnicities reported in the HapMap database. In contrast, the prevalence of variant alleles was lower in GSTA1. Therefore, in the Pakistani population sample from Karachi a significantly different prevalence of variant drug metabolizing enzymes and ABC transporters was observed as compared to other ethnicities, which could have putative clinical consequences on drug efficacy and safety.

Nutritional Status Differentially Alters Cytochrome P450 3A4 (CYP3A4) and Uridine 5'-Diphospho-Glucuronosyltransferase (UGT) Mediated Drug Metabolism: Effect of Short-Term Fasting and High Fat Diet on Midazolam Metabolism

BACKGROUND AND OBJECTIVES

Previous studies have shown that nutritional status can alter drug metabolism which may result in treatment failure or untoward side effects. This study assesses the effect of two nutritional conditions, short-term fasting, and a short-term high fat diet (HFD) on cytochrome P450 3A4 (CYP3A4) and uridine 5'-diphospho-glucuronosyltransferase (UGT) mediated drug metabolism by studying the pharmacokinetics of midazolam and its main metabolites.

METHODS

In a randomized-controlled cross-over trial, nine healthy subjects received a single intravenous administration of 0.015 mg/kg midazolam after: (1) an overnight fast (control); (2) 36 h of fasting; and (3) an overnight fast after 3 days of a HFD consisting of 500 ml of cream supplemented to their regular diet. Pharmacokinetic parameters were analyzed simultaneously using non-linear mixed-effects modeling.

RESULTS

Short-term fasting increased CYP3A4-mediated midazolam clearance by 12% (p < 0.01) and decreased UGT-mediated metabolism apparent 1-OH-midazolam clearance by 13% (p < 0.01) by decreasing the ratio of clearance and the fraction metabolite formed (ΔCL_1-OH-MDZ/f_1-OH-MDZ). Furthermore, short-term fasting decreased apparent clearance of 1-OH-midazolam-O-glucuronide (CL_{1-OH-MDZ-glucuronide}/(f_{1-OH-MDZ-glucuronide} × f_1-OH-MDZ)) by 20% (p < 0.01). The HFD did not affect systemic clearance of midazolam or metabolites.

CONCLUSIONS

Short-term fasting differentially alters midazolam metabolism by increasing CYP3A4-mediated metabolism but by decreasing UGT-mediated metabolism. In contrast, a short-term HFD did not affect systemic clearance of midazolam.

Human cytochrome P450 expression in bacteria: Whole-cell high-throughput activity assay for CYP1A2, 2A6 and 3A4

Cytochrome P450s (CYPs) are key enzymes involved in drug and xenobiotic metabolism. A wide array of in vitro methodologies, including recombinant sources, are currently been used to assess CYP catalysis, to identify the metabolic profile of compounds, potential drug-drug interactions, protein-protein interactions in the CYP enzyme complex and the role of polymorphic enzymes. We report here on a bacterial whole-cells high-throughput method for the activity evaluation of human CYP1A2, 2A6, and 3A4, when sustained by NADPH cytochrome P450 oxidoreductase (CPR), in the absence or presence of cytochrome b₅ (CYB5). This new assay consists of a microplate real-time fluorometric method, with direct measurement of metabolite formation, in a suspension of Escherichia coli BTC-CYP bacteria, a human CYP competent tester strain when incubated with specific fluorogenic substrates. Overall, the maximum turnover (k_cat) velocities of the three human CYPs resulting from the whole-BTC cells assays were similar to those obtained when applying the corresponding standard reference membrane fractions assays. CYP activity screening with co-expression of CYB5 suggests an enhancing effect of CYB5 on the k_cat of specific isoforms, when using the whole-BTC cells assay. Our results demonstrate that this new approach can offer an efficient high-throughput method for screening of CYP1A2, 2A6 and 3A4 activity and can be potentially applicable for other human CYPs. This can be of particular use for timely and efficient screening of chemical libraries or mutant libraries of CYP enzyme complex proteins, without the necessity for labor intensive isolation of subcellular fractions.

Genetic Testing in Clinical Settings

Genetic testing is used for screening, diagnosis, and prognosis of diseases consistent with a genetic cause and to guide drug therapy to improve drug efficacy and avoid adverse effects (pharmacogenomics). This In Practice review aims to inform about DNA-related genetic test availability, interpretation, and recommended clinical actions based on results using evidence from clinical guidelines, when available. We discuss challenges that limit the widespread use of genetic information in the clinical care setting, including a small number of actionable genetic variants with strong evidence of clinical validity and utility, and the need for improving the health literacy of health care providers and the public, including for direct-to-consumer tests. Ethical, legal, and social issues and incidental findings also need to be addressed. Because our understanding of genetic factors associated with disease and drug response is rapidly increasing and new genetic tests are being developed that could be adopted by clinicians in the short term, we also provide extensive resources for information and education on genetic testing.

Effect of Short-Term Fasting on Systemic Cytochrome P450-Mediated Drug Metabolism in Healthy Subjects: A Randomized, Controlled, Crossover Study Using a Cocktail Approach

Background and Objective

Short-term fasting can alter drug exposure but it is unknown whether this is an effect of altered oral bioavailability and/or systemic clearance. Therefore, the aim of our study was to assess the effect of short-term fasting on oral bioavailability and systemic clearance of different drugs.

Methods

In a randomized, controlled, crossover trial, 12 healthy subjects received a single administration of a cytochrome P450 (CYP) probe cocktail, consisting of caffeine (CYP1A2), metoprolol (CYP2D6), midazolam (CYP3A4), omeprazole (CYP2C19) and warfarin (CYP2C9), on four occasions: an oral (1) and intravenous (2) administration after an overnight fast (control) and an oral (3) and intravenous (4) administration after 36 h of fasting. Pharmacokinetic parameters of the probe drugs were analyzed using the nonlinear mixed-effects modeling software NONMEM.

Results

Short-term fasting increased systemic caffeine clearance by 17% (p = 0.04) and metoprolol clearance by 13% (p < 0.01), whereas S-warfarin clearance decreased by 19% (p < 0.01). Fasting did not affect bioavailability.

Conclusion

The study demonstrates that short-term fasting alters CYP-mediated drug metabolism in a non-uniform pattern without affecting oral bioavailability.

Awareness and attitude of the public toward personalized medicine in Korea

OBJECTIVES

As personalized medicine (PM) is expected to greatly improve health outcomes, efforts have recently been made for its clinical implementation in Korea. We aimed to evaluate public awareness and attitude regarding PM.

METHODS

We performed a self-administered questionnaire survey to 703 adults, who participated in the survey on a voluntary basis. The primary outcome measures included public knowledge, attitude, and acceptance of PM. We conducted multinomial multivariate logistic analysis for outcome variables with three response categories and performed multivariate logistic regression analyses for dichotomous outcome variables.

RESULTS

Only 28% of participants had knowledge that genetic factors can contribute to inter-individual variations in drug response and the definition of PM (199 out of 702). Higher family income was correlated with greater knowledge concerning PM (OR = 3.76, p = 0.034). A majority of respondents preferred integrated pharmacogenomic testing over drug-specific testing and agreed to inclusion of pharmacogenomic testing in the national health examination (64% and 77%, respectively), but only 51% were willing to pay for it.

DISCUSSION

Our results identify the urgent need for public education as well as the potential health disparities in access to PM. This study helps to frame policies for implementing PM in clinical practice.

Quantitative Method for Simultaneous Analysis of a 5-Probe Cocktail for Cytochrome P450 Enzymes

BACKGROUND

The metabolic activity of P450 enzymes in vivo can be determined using selective probe drugs. The simultaneous administration of multiple CYP-specific probe drugs is commonly known as the "cocktail approach." Disadvantages of a cocktail are large volumes of samples required for analysis and time-consuming analyses. The aim of this study was to develop and validate a simplified but sensitive method for the simultaneous quantification of 5 probe drugs [caffeine (CYP1A2), metoprolol (CYP2D6), midazolam (CYP3A4), omeprazole (CYP2C19), and S-warfarin (CYP2C9)] in a previously validated cocktail using a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method.

METHODS

The method entailed a single method for sample preparation that enables quick processing of the samples containing all 5 probe drugs in a small volume of blood (≥10 μL) followed by a chiral and nonchiral LC-MS/MS method. The method was validated for selectivity, specificity, resolution of racemic warfarin, linearity, accuracy, imprecision, recovery, process efficiency, ionization efficiency, and carryover effect.

RESULTS

The method showed good selectivity without matrix interferences and differentiated S- and R-warfarin enantiomers with adequate resolution (Rs = 1.55). For all analytes, the mean process efficiency was >95%, and the mean ionization efficiency was >97%. Furthermore, the accuracy was between 94.9% and 108% for all analytes, and the within- and between-run imprecision were <11.7% for the lower limit of quantification and <12.6% for the middle level and upper limit of quantification.

CONCLUSIONS

The method presented here enables the simultaneous quantification of the 5 probes in a very small blood volume (≥10 μL). Furthermore, it is less time consuming than previously reported methods because it requires only 1 simple method for sample preparation followed by a nonchiral and chiral LC-MS/MS method that can be performed sequentially.

Distribution of polymorphic variants of CYP2A6 and their involvement in nicotine addiction

Tobacco consumption has become a major public health issue, which has motivated studies to identify and understand the biological processes involved in the smoking behavior for prevention and smoking cessation treatments. CYP2A6 has been identified as the main gene that codifies the enzyme that metabolizes nicotine. Many alleles have been identified after the discovery of CYP2A6, suggesting a wide interethnic variability and a diverse smoking behavior of the allele carrying individuals. The main purpose of this review is to update and highlight the effects of the CYP2A6 gene variability related to tobacco consumption reported from diverse human populations. The review further aims to consider CYP2A6 in future studies as a possible genetic marker for the prevention and treatment of nicotine addiction. Therefore, we analyzed several population studies and their importance at addressing and characterizing a population using specific parameters. Our efforts may contribute to a personalized system for detecting, preventing and treating populations at a higher risk of smoking to avoid diseases related to tobacco consumption.

Oral Adverse Drug Reactions to Cardiovascular Drugs

A great many cardiovascular drugs (CVDs) have the potential to induce adverse reactions in the mouth. The prevalence of such reactions is not known, however, since many are asymptomatic and therefore are believed to go unreported. As more drugs are marketed and the population includes an increasing number of elderly, the number of drug prescriptions is also expected to increase. Accordingly, it can be predicted that the occurrence of adverse drug reactions (ADRs), including the oral ones (ODRs), will continue to increase. ODRs affect the oral mucous membrane, saliva production, and taste. The pathogenesis of these reactions, especially the mucosal ones, is largely unknown and appears to involve complex interactions among the drug in question, other medications, the patient’s underlying disease, genetics, and life-style factors. Along this line, there is a growing interest in the association between pharmacogenetic polymorphism and ADRs. Research focusing on polymorphism of the cytochrome P450 system (CYPs) has become increasingly important and has highlighted the intra- and inter-individual responses to drug exposure. This system has recently been suggested to be an underlying candidate regarding the pathogenesis of ADRs in the oral mucous membrane. This review focuses on those CVDs reported to induce ODRs. In addition, it will provide data on specific drugs or drug classes, and outline and discuss recent research on possible mechanisms linking ADRs to drug metabolism patterns. Abbreviations used will be as follows: ACEI, ACE inhibitor; ADR, adverse drug reaction; ANA, antinuclear antigen; ARB, angiotensin II receptor blocker; BAB, beta-adrenergic blocker; CCB, calcium-channel blocker; CDR, cutaneous drug reaction; CVD, cardiovascular drug; CYP, cytochrome P450 enzyme; EM, erythema multiforme; FDE, fixed drug eruption; I, inhibitor of CYP isoform activity; HMG-CoA, hydroxymethyl-glutaryl coenzyme A; NAT, N-acetyltransferase; ODR, oral drug reaction; RDM, reactive drug metabolite; S, substrate for CYP isoform; SJS, Stevens-Johnson syndrome; SLE, systemic lupus erythematosus; and TEN, toxic epidermal necrolysis.

Pharmacogenetics: Policy needs for personal prescribing

Pharmacogenetics involves genetic testing of individual patients to guide drug treatment. Proponents argue that pharmacogenetics will achieve major gains in drug safety and efficacy, and revolutionise marketing. Pharmacogenetics also raises several policy concerns, including the need for sound information for clinical decision-making on drug-genetic test combinations. Currently, the pharmacogenetics science base and the rate of emergence of clinical applications are uncertain. Most commentary on pharmacogenetics focuses on new compounds, yet older drugs cause most adverse events. Test regulation in the USA appears fundamentally different from Europe, where evidence of safety or efficacy may not be required. Genetics research is needed as part of postmarketing surveillance systems. In routine clinical practice, computer-based health records with relevant decision support systems will also be needed. Without health policy action, pharmacogenetics could produce a new generation of poorly evaluated tests and drugs, with medicine becoming significantly less evidence-based, leading to rising costs, patient hazard and exclusions of drug-related ‘genetic minorities’ from evaluated treatments.

DL-ADR: a novel deep learning model for classifying genomic variants into adverse drug reactions

Background

Genomic variations are associated with the metabolism and the occurrence of adverse reactions of many therapeutic agents. The polymorphisms on over 2000 locations of cytochrome P450 enzymes (CYP) due to many factors such as ethnicity, mutations, and inheritance attribute to the diversity of response and side effects of various drugs. The associations of the single nucleotide polymorphisms (SNPs), the internal pharmacokinetic patterns and the vulnerability of specific adverse reactions become one of the research interests of pharmacogenomics. The conventional genomewide association studies (GWAS) mainly focuses on the relation of single or multiple SNPs to a specific risk factors which are a one-to-many relation. However, there are no robust methods to establish a many-to-many network which can combine the direct and indirect associations between multiple SNPs and a serial of events (e.g. adverse reactions, metabolic patterns, prognostic factors etc.). In this paper, we present a novel deep learning model based on generative stochastic networks and hidden Markov chain to classify the observed samples with SNPs on five loci of two genes (CYP2D6 and CYP1A2) respectively to the vulnerable population of 14 types of adverse reactions.

Methods

A supervised deep learning model is proposed in this study. The revised generative stochastic networks (GSN) model with transited by the hidden Markov chain is used. The data of the training set are collected from clinical observation. The training set is composed of 83 observations of blood samples with the genotypes respectively on CYP2D6*2, *10, *14 and CYP1A2*1C, *1 F. The samples are genotyped by the polymerase chain reaction (PCR) method. A hidden Markov chain is used as the transition operator to simulate the probabilistic distribution. The model can perform learning at lower cost compared to the conventional maximal likelihood method because the transition distribution is conditional on the previous state of the hidden Markov chain. A least square loss (LASSO) algorithm and a k-Nearest Neighbors (kNN) algorithm are used as the baselines for comparison and to evaluate the performance of our proposed deep learning model.

Results

There are 53 adverse reactions reported during the observation. They are assigned to 14 categories. In the comparison of classification accuracy, the deep learning model shows superiority over the LASSO and kNN model with a rate over 80 %. In the comparison of reliability, the deep learning model shows the best stability among the three models.

Conclusions

Machine learning provides a new method to explore the complex associations among genomic variations and multiple events in pharmacogenomics studies. The new deep learning algorithm is capable of classifying various SNPs to the corresponding adverse reactions. We expect that as more genomic variations are added as features and more observations are made, the deep learning model can improve its performance and can act as a black-box but reliable verifier for other GWAS studies.

Within and beyond the communal turn to informed consent in industry-sponsored pharmacogenetics research: merits and challenges of community advisory boards

The one-size-fits-all paradigm of drug development fails to address inter-individual variability in drug response. Pharmacogenetics research aims at studying the role of genotypic differences in drug response. Recently, the pharmaceutical industry has shown interest to embed pharmacogenetics studies in the process of drug development. Nevertheless, population-based and commercial aspects of such future-oriented studies pose challenges for individually based informed consent (IC). As an exemplar of the communal turn to IC procedures, community advisory boards (CABs) have been integrated into different types of medical research. CABs hold the promise of organizing the relationship between participants and researchers in a more reciprocal and participatory way, offering possible means of overcoming the lapses of individualistic IC. However, the involvement of CABs with pharmacogenetics research might be rife with difficulties, uncertainties, and challenges. The current study first reviews the existing literature to discuss added values and challenges of relying on CABs as a supplement to individually based IC. Then, the particular moral and regulatory landscape of pharmacogenetics research will be delineated to argue that community engagement is both necessary and promising beyond the communal turn to IC processes. Three main features of the landscape include (1) new supportive stances that some regulatory bodies have adopted toward pharmacogenetics research, (2) the motivation of the industry to draw reception and trust from the subpopulations, and (3) the important role of the society in generating and embedding pharmacogenetics knowledge. Finally, some points to consider will be discussed to contextualize relying on CABs within this landscape.

A Multi-scale Computational Platform to Mechanistically Assess the Effect of Genetic Variation on Drug Responses in Human Erythrocyte Metabolism

Progress in systems medicine brings promise to addressing patient heterogeneity and individualized therapies. Recently, genome-scale models of metabolism have been shown to provide insight into the mechanistic link between drug therapies and systems-level off-target effects while being expanded to explicitly include the three-dimensional structure of proteins. The integration of these molecular-level details, such as the physical, structural, and dynamical properties of proteins, notably expands the computational description of biochemical network-level properties and the possibility of understanding and predicting whole cell phenotypes. In this study, we present a multi-scale modeling framework that describes biological processes which range in scale from atomistic details to an entire metabolic network. Using this approach, we can understand how genetic variation, which impacts the structure and reactivity of a protein, influences both native and drug-induced metabolic states. As a proof-of-concept, we study three enzymes (catechol-O-methyltransferase, glucose-6-phosphate dehydrogenase, and glyceraldehyde-3-phosphate dehydrogenase) and their respective genetic variants which have clinically relevant associations. Using all-atom molecular dynamic simulations enables the sampling of long timescale conformational dynamics of the proteins (and their mutant variants) in complex with their respective native metabolites or drug molecules. We find that changes in a protein's structure due to a mutation influences protein binding affinity to metabolites and/or drug molecules, and inflicts large-scale changes in metabolism.

A short-term high fat diet increases exposure to midazolam and omeprazole in healthy subjects

OBJECTIVES

Knowledge of factors contributing to variation in drug metabolism is of vital importance to optimize drug treatment. This study assesses the effects of a short-term hypercaloric high fat diet on metabolism of five oral drugs, which are each specific for a single P450 isoform: midazolam (CYP3A4), omeprazole (CYP2C19), metoprolol (CYP2D6), S-warfarin (CYP2C9) and caffeine (CYP1A2).

METHODS

In 9 healthy volunteers, pharmacokinetics of the five drugs were assessed after an overnight fast at two separate occasions: after a regular diet and after 3 days of a hypercaloric high fat diet (i.e. regular diet supplemented with 500 mL cream [1715 kcal, 35% fat]). Pharmacokinetic parameters (mean [SEM]) were estimated by non-compartmental analysis.

RESULTS

The high fat diet increased exposure to midazolam by 19% from 24.7 (2.6) to 29.5 (3.6) ng ml-1h-1 (p=0.04) and exposure to omeprazole by 31% from 726 (104) to 951 (168) ng ml-1h-1 (p=0.05). Exposure to metoprolol, caffeine and S-warfarin was not affected by the high fat diet.

CONCLUSION

A short-term hypercaloric high fat diet increases exposure to midazolam and omeprazole, possibly reflecting modulation of CYP3A4 and CYP2C19.

Phenoconversion of CYP2C9 in epilepsy limits the predictive value of CYP2C9 genotype in optimizing valproate therapy

Aim: Since prominent role in valproate metabolism is assigned to CYP2C9 in pediatric patients, the association between children's CYP2C9-status and serum valproate concentrations or dose-requirements was evaluated. Materials & Methods: The contribution of CYP2C9 genotype and CYP2C9 expression in children (n = 50, Caucasian) with epilepsy to valproate pharmacokinetics was analyzed. Results: Valproate concentrations were significantly lower in normal expressers with CYP2C9*1/*1 than in low expressers or in patients carrying polymorphic CYP2C9 alleles. Consistently, the dose-requirement was substantially higher in normal expressers carrying CYP2C9*1/*1 (33.3 mg/kg vs 13.8–17.8 mg/kg, p < 0.0001). Low CYP2C9 expression significantly increased the ratio of poor metabolizers predictable from CYP2C9 genotype (by 46%). Conclusion: Due to the substantial downregulation of CYP2C9 expression in epilepsy, inferring patients’ valproate metabolizing phenotype merely from CYP2C9 genotype results in false prediction.

Personalized medicine and the clinical laboratory

Personalized medicine is the use of biomarkers, most of them molecular markers, for detection of specific genetic traits to guide various approaches for preventing and treating different conditions. The identification of several genes related to heredity, oncology and infectious diseases lead to the detection of genetic polymorphisms that are involved not only in different clinical progression of these diseases but also in variations in treatment response. Currently, it is possible to detect these polymorphisms using several methodologies: detection of single nucleotide polymorphisms using polymerase chain reaction methods; nucleic acid microarray detection; and nucleic acid sequencing with automatized DNA sequencers using Sanger-derived methods and new generation sequencing. Personalized medicine assays are directed towards detecting genetic variations that alter interactions of drugs with targets or the metabolic pathways of drugs (upstream and downstream) and can be utilized for the selection of drug formulations and detect different immunogenicities of the drug. Personalized medicine applications have already been described in different areas of Medicine and allow specific treatment approaches to be applied to each patient and pathology according to the results of these assays. The application of such a protocol demands an increasing interaction between the clinical laboratory and the clinical staff. For its implementation, a coordinated team composed of basic researchers and physicians highly specialized in their areas supported by a highly specialized team of clinical analysts particularly trained in molecular biology assays is necessary.

Short-term fasting alters cytochrome P450-mediated drug metabolism in humans

Experimental studies indicate that short-term fasting alters drug metabolism. However, the effects of short-term fasting on drug metabolism in humans need further investigation. Therefore, the aim of this study was to evaluate the effects of short-term fasting (36 h) on P450-mediated drug metabolism. In a randomized crossover study design, nine healthy subjects ingested a cocktail consisting of five P450-specific probe drugs [caffeine (CYP1A2), S-warfarin (CYP2C9), omeprazole (CYP2C19), metoprolol (CYP2D6), and midazolam (CYP3A4)] on two occasions (control study after an overnight fast and after 36 h of fasting). Blood samples were drawn for pharmacokinetic analysis using nonlinear mixed effects modeling. In addition, we studied in Wistar rats the effects of short-term fasting on hepatic mRNA expression of P450 isoforms corresponding with the five studied P450 enzymes in humans. In the healthy subjects, short-term fasting increased oral caffeine clearance by 20% (P = 0.03) and decreased oral S-warfarin clearance by 25% (P < 0.001). In rats, short-term fasting increased mRNA expression of the orthologs of human CYP1A2, CYP2C19, CYP2D6, and CYP3A4 (P < 0.05), and decreased the mRNA expression of the ortholog of CYP2C9 (P < 0.001) compared with the postabsorptive state. These results demonstrate that short-term fasting alters cytochrome P450-mediated drug metabolism in a nonuniform pattern. Therefore, short-term fasting is another factor affecting cytochrome P450-mediated drug metabolism in humans.

Therapeutic drug monitoring: perspectives of psychiatrists in Turkey

OBJECTIVES

Although the medical and economic implications of therapeutic drug monitoring have been intensely discussed over the past years, little is known about the experiences and attitudes of psychiatrists in their clinical practice. The aim of this study was to investigate psychiatrists' daily practice with therapeutic drug monitoring in Turkey.

METHODS

A nation-wide cross-sectional survey among adult and child psychiatry specialist psychiatrists in Turkey was conducted.

RESULTS

We found that 98.4% (n = 380) of the study participants used TDM in clinical practice and 1.6% (n = 6) did not. However, TDM use is limited to mood stabilizers (lithium 96.3%, valproate 97.6%) to a great extent. Only a small number of psychiatrists perform TDM for other psychotropic drugs, e.g., clozapine 2.4%, tricyclic antidepressants 1.3%, benzodiazepines 1.1%, and selective serotonin reuptake inhibitors 0,8%.

CONCLUSIONS

Most of the psychiatrists in Turkey have a positive attitude toward use of therapeutic drug monitoring although there is also a considerable difficulty to reach services for the therapeutic drug monitoring of psychotropics other than mood stabilizers.

Repression of multiple CYP2D genes in mouse primary hepatocytes with a single siRNA construct

The Cyp2d subfamily is the second most abun-dant subfamily of hepatic drug-metabolizing CYPs. In mice, there are nine Cyp2d members that are believed to have redundant catalytic activity. We are testing and optimizing the ability of one short interfering RNA (siRNA) construct to knockdown the expression of multiple mouse Cyp2ds in primary hepatocytes. Expression of Cyp2d10, Cyp2d11, Cyp2d22, and Cyp2d26 was observed in the primary male mouse hepatocytes. Cyp2d9, which is male-specific and growth hormone-dependent, was not expressed in male primary hepatocytes, potentially because of its dependence on pulsatile growth hormone release from the anterior pituitary. Several different siRNAs at different concentrations and with different reagents were used to knockdown Cyp2d expression. siRNA constructs designed to repress only one construct often mildly repressed several Cyp2d isoforms. A construct designed to knockdown every Cyp2d isoform provided the best results, especially when incubated with transfection reagents designed specifically for primary cell culture. Interestingly, a construct designed to knockdown all Cyp2d isoforms, except Cyp2d10, caused a 2.5× increase in Cyp2d10 expression, presumably because of a compensatory response. However, while RNA expression is repressed 24 h after siRNA treatment, associated changes in Cyp2d-mediated metabolism are tenuous. Overall, this study provides data on the expression of murine Cyp2ds in primary cell lines, valuable information on designing siRNAs for silencing multiple murine CYPs, and potential pros and cons of using siRNA as a tool for repressing Cyp2d and estimating Cyp2d's role in murine xenobiotic metabolism.

CYP2D6 P34S Polymorphism and Outcomes of Escitalopram Treatment in Koreans with Major Depression

OBJECTIVE

Cytochrome P450 (CYP) enzymatic activity, which is influenced by CYP genetic polymorphism, is known to affect the inter-individual variation in the efficacy and tolerability of antidepressants in major depressive disorder (MDD). Escitalopram is metabolized by CYP2D6, and recent studies have reported a correlation between clinical outcomes and CYP2D6 genetic polymorphism. The purpose of this study was to determine the relationship between the CYP2D6 P34S polymorphism (C188T, rs1065852) and the efficacy of escitalopram treatment in Korean patients with MDD.

METHODS

A total of 94 patients diagnosed with MDD were recruited for the study and their symptoms were evaluated using the 21-item Hamilton Depression Rating scale (HAMD-21). The association between the CYP2D6 P34S polymorphism and the clinical outcomes (remission and response) was investigated after 1, 2, 4, 8, and 12 weeks of escitalopram treatment using multiple logistic regression analysis and χ(2) test.

RESULTS

The proportion of P allele carriers (PP, PS) in remission status was greater than that of S allele homozygotes (SS) after 8 and 12 weeks of escitalopram treatment. Similarly, P allele carriers exhibited a greater treatment response after 8 and 12 weeks of escitalopram treatment than S allele homozygotes.

CONCLUSION

Our results suggest that the P allele of the CYP2D6 P34S polymorphism is a favorable factor in escitalopram treatment for MDD, and that the CYP2D6 P34S polymorphism may be a good genetic marker for predicting escitalopram treatment outcomes.

Genetic Polymorphism of Cytochrome p450 (2C19) Enzyme in Iranian Turkman Ethnic Group

OBJECTIVE

Different findings indicate that CYP2C plays a clinical role in determining interindividual and interethnic differences in drug effectiveness. The ethnic differences in the frequency of CYP2C19 mutant alleles continue to be a significant study topic. The aim of the present study was to assess the frequency of allelic variants of CYP2C19 in Turkman ethnic groups and compare them with the frequencies in other ethnic populations.

METHODS

The study group included 140 unrelated healthy ethnic Turkman subject referred to the Health Center. Genotyping of CYP2C19 alleles (CYP2C19*1, CYP2C19*2, and CYP2C19*3 alleles) was carried out by Polymerase Chain Reaction-Restriction Fragment Length Polymorphism technique.

RESULTS

The allele frequency of CYP2C19*1, CYP2C19*2 and CYP2C19*3 were 56.43%, 23.57% and 20%, respectively. The result also showed that 39.7% of subjects expressed the CYP2C19*1/*1 genotype. While 42.1%, 9.3%, 9.3% and 1.4% expressed CYP2C19*1/*2, CYP2C19*1/*3, CYP2C19*2/*2 and CYP2C19*3/*3 genotypes, respectively. The genotype CYP2C19*2/*3 was not expressed in this study population. The findings suggested that 10% of subjects were poor metabolizers by expressing CYP2C19*2/*2 and CYP2C19*3/*3 genotypes. Fifty one percent of subjects were intermediate metabolizers having CYP2C19*1/*2, CYP2C19*2/*3 and CYP2C19*1/*3 genotypes and 37.86% were found to be extensive metabolizers expressing CYP2C19*1/*1 genotype. The frequency of intermediate metabolizers genotype was high (51%) in Turkman ethnic groups.

CONCLUSION

This study showed that the determined allelic variants of CYP2C19 (CYP2C19*2 and CYP2C19*3 mutations) in Turkman ethnic group are comparable to other populations. These findings could be useful for the clinicians in different country to determine optimal dosage and effectiveness of drugs metabolized by this polymorphic enzyme.

Allele frequency distribution of CYP2C9 2 and CYP2C9 3 polymorphisms in six Mexican populations

Allele frequency differences of functional CYP2C9 polymorphisms are responsible for some of the variation in drug response observed in human populations. The most relevant CYP2C9 functional variants are CYP2C9*2 (rs1799853) and CYP2C9 3 (rs1057910). These polymorphisms show variation in allele frequencies among different population groups. The present study aimed to analyze these polymorphisms in 947 Mexican-Mestizo from Mexico City and 483 individuals from five indigenous Mexican populations: Nahua, Teenek, Tarahumara, Purepecha and Huichol. The CYP2C9*2 allele frequencies in the Mestizo, Nahua and Teenek populations were 0.051, 0.007 and 0.005, respectively. As for CYP2C9 3, the allelic frequencies in the Mestizo, Nahua and Teenek populations were 0.04, 0.005 and 0.005, respectively. The CYP2C9 2 and CYP2C9 3 alleles were not observed in the Tarahumara, Purepecha and Huichol populations. These findings are in agreement with previous studies reporting very low allele frequencies for these polymorphisms in American Indigenous populations.

The role of pharmacogenomics in metastatic renal cell carcinoma

Pharmacogenomics is the study of how variation in the genetic background affects an individual's response to a specific drug and/or its metabolism. Using knowledge about the genes which produce the enzymes that metabolize a specific drug, a physician may decide to raise or lower the dose, or even change to a different drug. Targeted therapy with tyrosine kinase inhibitors (TKIs) and mammalian target of rapamycin (mTOR) inhibitors has led to a substantial improvement in the standard of care for patients with advanced or metastatic renal cell carcinoma (RCC). Although few studies have identified biomarkers that predict the response of targeted drugs in the treatment of metastatic RCC, some associations have been found. Several studies have identified genetic polymorphisms with implications in the pharmacokinetics and/or pharmacodynamics of TKIs and mTOR inhibitors and which are associated with a prolonged progression-free survival and/or overall survival in patients with metastatic RCC. Among the genes of interest, we should consider IL8, FGFR2, VEGFA, FLT4, and NR1I2. In this review, we discuss single nucleotide polymorphisms (SNPs) associated with outcome and toxicity following targeted therapies and provide recommendations for future trials to facilitate the use of SNPs in personalized therapy for this disease.

Estimation of drug-metabolizing capacity by cytochrome P450 genotyping and expression

Many undesired side effects or therapeutic failures of drugs are the result of differences or changes in drug metabolism, primarily depending on the levels and activities of cytochrome P450 (P450) enzymes. To assess whether P450 expression profiles can reflect hepatic drug metabolism, we compared P450 mRNA levels in the liver or peripheral leukocytes with the corresponding hepatic P450 activities. A preliminary P450 genotyping for the most frequent polymorphisms in white populations (CYP2C9*2, CYP2C9*3, CYP2C19*2, CYP2C19*3, CYP2D6*3, CYP2D6*4, CYP2D6*6, and CYP3A5*3) was carried out before P450 phenotyping, excluding the donors with nonfunctional alleles of CYP2C9, CYP2C19, and CYP2D6 and those with a functional CYP3A5*1 allele from a correlation analysis. The hepatic mRNA levels of CYP1A2, CYP2B6, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 displayed a strong association with P450 activities in the liver, whereas the expression of CYP1A2, CYP2C9, CYP2C19, and CYP3A4 in leukocytes was proven to reflect the hepatic activities of these P450 species. The leukocytes were found to be inappropriate cells for the assessment of hepatic CYP2B6 and CYP2D6 activities. Combining the results of P450 genotyping and phenotyping analyses, patients' drug-metabolizing capacities can be estimated by the P450 expression in the liver and in leukocytes with some limitations. Patients' genetic and nongenetic variations in P450 status can guide the appropriate selection of drugs and the optimal dose, minimizing the risk of harmful side effects and ensuring a successful outcome of drug therapy.

Bridging the efficacy-effectiveness gap: a regulator's perspective on addressing variability of drug response

Drug regulatory agencies should ensure that the benefits of drugs outweigh their risks, but licensed medicines sometimes do not perform as expected in everyday clinical practice. Failure may relate to lower than anticipated efficacy or a higher than anticipated incidence or severity of adverse effects. Here we show that the problem of benefit-risk is to a considerable degree a problem of variability in drug response. We describe biological and behavioural sources of variability and how these contribute to the long-known efficacy-effectiveness gap. In this context, efficacy describes how a drug performs under conditions of clinical trials, whereas effectiveness describes how it performs under conditions of everyday clinical practice. We argue that a broad range of pre- and post-licensing technologies will need to be harnessed to bridge the efficacy-effectiveness gap. Successful approaches will not be limited to the current notion of pharmacogenomics-based personalized medicines, but will also entail the wider use of electronic health-care tools to improve drug prescribing and patient adherence.

Pharmacogenetics in medico-legal context

Medico-legal autopsy is the primary method in determining the cause and manner of death when the death is suspected to be unnatural. In some of these autopsies, the death remains ambiguous, even after a complete autopsy including histological investigation and toxicological screenings. In cases where there are no morphological abnormalities, medico-legal genetics may offer additional means to provide knowledge of possible genetic mutations, which may have initiated the process or predisposed the individual to stress risk conditions leading to death. One class of ambiguous deaths consists of drug-related deaths where the interpretation of the toxicological results are not clear. In such situations post mortem genotyping and the analysis of metabolite rations may provide an insight to the findings. A few cases demonstrating the potential strength of pharmacogenetics in medico-legal context has been published. However, there is a paramount need for serious scientific studies before the field of post mortem pharmacogenetics can be utilized in routine medico-legal analyses casework and brought routinely into courtroom.

Resequencing, haplotype construction and identification of novel variants of CYP2D6 in Mexican Mestizos

AIM

The CYP2D6 enzyme participates in the metabolism of commonly prescribed drugs: antidepressants, antipsychotics and antihypertensives. The CYP2D6 gene shows a high degree of interindividual and interethnic variability that influences its expression and function. Mexican Mestizos are a recently admixed population resulting from the combination of Amerindian, European and, to a lesser extent, African populations. This study aimed to comprehensively characterize the CYP2D6 gene in Mexican Mestizos.

MATERIALS & METHODS

We performed linkage disequilibrium and network analyses in resequencing data of 96 individuals from two regions within Mexico with a different history of admixture and particular population dynamics, the Northwestern state of Sonora and the Central-Pacific state of Guerrero.

RESULTS & CONCLUSION

We identified 64 polymorphisms, including 14 novel variants: 13 SNPs and a CYP2D7 exon 2 conversion, that was assigned CYP2D6*82 by the Human Cytochrome P450 (CYP) Allele Nomenclature Committee. Three novel SNPs were predicted to have functional effects. For CYP2D6*82 we hypothesize an Amerindian origin that is supported by its identification in three Mexican Amerindian groups (Mayas, Tepehuanos and Mixtecos). Frequencies of CYP2D6*1, *2, *4, *5, *10, *29, *53, *82 and its duplications were 50.0, 25.5, 14.1, 2.0, 2.6, 1.0, 0.5, 2.1 and 3.6%, respectively. We found significant frequency differences in CYP2D6*1 and *2 between Mexican Mestizos and in CYP2D6*1, *2, *4, *5, *10 and *29 between Mexicans and at least one other population. We observed strong linkage disequilibrium and phylogenetic relationships between haplotypes. To our knowledge, this study is the first comprehensive resequencing analysis of CYP2D6 in Mexicans or any other Latin American population, providing information about genetic diversity relevant in the development of pharmacogenomics in this region.

Advances of molecular clinical pharmacology in gastroenterology and hepatology

During developmental age, differences in pharmacodynamic reactions to several drugs may reflect polymorphisms of genes encoding drug-transporting proteins, receptors, drug targets, and gene products, whose disturbed activity sometimes plays an important role in certain diseases. Administration of drugs with a narrow therapeutic index may quite easily be associated with changes in pharmacokinetics and development of adverse drug reactions, which occasionally may cause fatalities. In such cases, polypragmasy and resulting drug interactions may enhance effects of changes in drug-metabolizing enzymes' activities. Phenotyping and genotyping of patients slowly are finding their place in some therapeutic regimens used in clinical gastroenterology and hepatology. At present, some assays to measure, for example, thiopurine S-methyltransferase activity are already commercially available. Polymorphisms of CYP450 enzymes, interleukins, and altered gene expression play an important role in some patients' various gastrointestinal tract and liver diseases. Herbal drugs also affect proinflammatory and antiinflammatory cytokine and nitric oxide balance in the body. Therapeutic use of recombined proteins, such as infliximab, natalizumab, onercept, humanized antibody to integrin α-4 β-7, or IFN-β in some large-bowel diseases increased therapeutic efficacy. IFN-α used in the patients with chronic hepatitis C improved cellular immunity in these subjects and exerted antiviral activity. Practical application of progress in pharmacogenetics, pharmacokinetics, pharmacodynamics, and use of bioproducts in novel therapeutic regimens has opened therapeutic frontiers and increased clinical safety.

Personalized medicine in oncology: tailoring the right drug to the right patient

Despite advances in the management of many human cancers over the past few decades, improvements in survival are marginal, and the overall diagnosis and prognosis for cancer patients remain poor. Tailoring therapy to the individual patient has become a promising approach for maximizing efficacy and minimizing drug toxicity. Aided by major technological advances, the field of personalized medicine has become extremely active in the identification of predictive biomarkers that can guide treatment decisions and, ultimately, improve treatment outcomes. Genomics and proteomics have provided a means for molecular profiling that allows tailoring of therapy. Although implementing genomic and proteomic testing into clinical practice is still in its infancy, the rapid development of newer technologies and platforms provides hope for personalized medicine.

Stereoselective Inhibition of the hERG1 Potassium Channel

A growing number of drugs have been shown to prolong cardiac repolarization, predisposing individuals to life-threatening ventricular arrhythmias known as Torsades de Pointes. Most of these drugs are known to interfere with the human ether à-gogo related gene 1 (hERG1) channel, whose current is one of the main determinants of action potential duration. Prolonged repolarization is reflected by lengthening of the QT interval of the electrocardiogram, as seen in the suitably named drug-induced long QT syndrome. Chirality (presence of an asymmetric atom) is a common feature of marketed drugs, which can therefore exist in at least two enantiomers with distinct three-dimensional structures and possibly distinct biological fates. Both the pharmacokinetic and pharmacodynamic properties can differ between enantiomers, as well as also between individuals who take the drug due to metabolic polymorphisms. Despite the large number of reports about drugs reducing the hERG1 current, potential stereoselective contributions have only been scarcely investigated. In this review, we present a non-exhaustive list of clinically important molecules which display chiral toxicity that may be related to hERG1-blocking properties. We particularly focus on methadone cardiotoxicity, which illustrates the importance of the stereoselective effect of drug chirality as well as individual variations resulting from pharmacogenetics. Furthermore, it seems likely that, during drug development, consideration of chirality in lead optimization and systematic assessment of the hERG1 current block with all enantiomers could contribute to the reduction of the risk of drug-induced LQTS.