Implications of polymorphic cytochrome P450-dependent drug metabolism for drug development

ABSTRACT: The main part of human cytochrome P450-dependent drug metabolism is carried out by polymorphic enzymes that can cause abolished, quantitatively or qualitatively altered, or enhanced drug metabolism. Ultrarapid metabolism is due to stable duplication, multiduplication, or amplification of active genes. Several examples exist where subjects carrying certain alleles suffer from a lack of drug efficacy due to ultrarapid metabolism or, alternatively, adverse effects from the drug treatment due to the presence of defective alleles. The polymorphic enzymes create a problem for the drug industry because of the extensive interindividual variability in the metabolism of candidate drugs that are substrates for such enzymes. The new area for lead generation has a more preclinical emphasis and involves combinatorial chemistry in conjunction with high-throughput-based analysis of thousands of substances with respect to their absorption, metabolism, and excretion characteristics. The outcome is that companies drop substrates for polymorphic enzymes at an early stage in development, which will of course create fewer problems with polymorphic enzymes in the future. The risk is that very valuable candidates, which cannot be replaced easily, never come out on the market. The alternative, however, of using the patient's genotype as a basis for individualized drug treatment constitutes, in light of rapid methodological developments, a very feasible approach to safer and more efficient drug therapies. Pharmacokinetics and drug metabolism have been shown to be of greater importance during drug development today. It is evident that drugs that are too rapidly metabolized by drug-metabolizing enzymes mainly localized in the liver and the intestine are nonoptimal therapeutic candidates. In published overviews, it has been concluded that as many as 30 to 40% of the drugs undergoing clinical trials were withdrawn from further development due to unfavorable pharmacokinetic propertie

CYP2E1 in Alcoholic and Non-Alcoholic Liver Injury. Roles of ROS, Reactive Intermediates and Lipid Overload

CYP2E1 is one of the fifty-seven cytochrome P450 genes in the human genome and is highly conserved. CYP2E1 is a unique P450 enzyme because its heme iron is constitutively in the high spin state, allowing direct reduction of, e.g., dioxygen, causing the formation of a variety of reactive oxygen species and reduction of xenobiotics to toxic products. The CYP2E1 enzyme has been the focus of scientific interest due to (i) its important endogenous function in liver homeostasis, (ii) its ability to activate procarcinogens and to convert certain drugs, e.g., paracetamol and anesthetics, to cytotoxic end products, (iii) its unique ability to effectively reduce dioxygen to radical species causing liver injury, (iv) its capability to reduce compounds, often generating radical intermediates of direct toxic or indirect immunotoxic properties and (v) its contribution to the development of alcoholic liver disease, steatosis and NASH. In this overview, we present the discovery of the enzyme and studies in humans, 3D liver systems and genetically modified mice to disclose its function and clinical relevance. Induction of the CYP2E1 enzyme either by alcohol or high-fat diet leads to increased severity of liver pathology and likelihood to develop ALD and NASH, with subsequent influence on the occurrence of hepatocellular cancer. Thus, fat-dependent induction of the enzyme might provide a link between steatosis and fibrosis in the liver. We conclude that CYP2E1 has many important physiological functions and is a key enzyme for hepatic carcinogenesis, drug toxicity and liver disease.Peer reviewe

Pharmacogenomics in treatment of depression and psychosis: an update

Genetic factors can, to a certain extent, successfully predict the therapeutic effects, metabolism, and adverse reactions of drugs. This research field, pharmacogenomics, is well developed in oncology and is currently expanding in psychiatry. Here, we summarize the latest development in pharmacogenomic psychiatry, where results of several recent large studies indicate a true benefit and cost-effectiveness of pre-emptive genotyping for more successful psychotherapy. However, it is apparent that we still lack knowledge of many additional heritable genetic factors of importance for explanation of the interindividual differences in response to psychiatric drugs. Thus, more effort to further develop pharmacogenomic psychiatry should be invested to achieve a broader clinical implementation

Current level of evidence for improvement of antidepressant efficacy and tolerability by pharmacogenomic-guided treatment: A Systematic review and meta-analysis of randomized controlled clinical trials

The aim of the study was to assess the clinical utility of currently available pharmacogenomic (PGx) tools compared with treatment as usual (TAU), using a meta-analysis of dichotomous and continuous antidepressant efficacy and tolerability data from previously published clinical trials. MEDLINE, clinicaltrial.gov, EU Clinical Trials Register, WHO ICTRP and CENTRAL were systematically searched; of the 962 results originally reviewed, 15 trials were included. Antidepressant efficacy was quantified by relative and absolute changes in symptom severity after eight weeks of treatment and by response and remission rates, while tolerability was estimated by the rate of study discontinuation for any reason. In the PGx-guided patients, symptom severity reduced by an average of 31.0% after eight weeks of treatment, compared to an average reduction of 26.8% in the TAU group. Accordingly, PGx-guided patients experienced a greater reduction in symptom severity of 3.4% (95%CI: 1.6-5.3%), which corresponded to a reduction in the Hamilton Depression score of 0.75 (0.30-1.21), a 37% (15-63%) higher remission rate, and an 18% (5-33%) higher response rate compared with TAU patients, while no difference was observed in discontinuation rate between groups. Notably, the majority of associations lost statistical significance when restricting the dataset to low risk of bias studies, while certain funnel plots suggested a potential publication bias favoring the reporting of statistically significant results. In summary, PGx tools marginally enhance antidepressant efficacy, but not antidepressant tolerability; thus, additional research and advancement of PGx tools are needed to improve integration of PGx in clinical pharmacotherapy of depression

The clinically relevant CYP2C8*3 and CYP2C9*2 haplotype is inherited from Neandertals

Genetic variation in genes encoding cytochrome P450 enzymes influences the metabolism of drugs and endogenous compounds. The locus containing the cytochrome genes CYP2C8 and CYP2C9 on chromosome 10 exhibits linkage disequilibrium between the CYP2C8*3 and CYP2C9*2 alleles, forming a haplotype of ~300 kilobases. This haplotype is associated with altered metabolism of several drugs, most notably reduced metabolism of warfarin and phenytoin, leading to toxicity at otherwise therapeutic doses. Here we show that this haplotype is inherited from Neandertals

Pharmacogenetic Variants and Plasma Concentrations of Antiseizure Drugs: A Systematic Review and Meta-Analysis

Importance: Precise estimation of a patient's drug metabolism capacity is important for antiseizure dose personalization. Objective: To quantify the differences in plasma concentrations for antiseizure drugs associated with variants of genes encoding drug metabolizing enzymes. Data Sources: PubMed, Clinicaltrialsregister.eu, ClinicalTrials.gov, International Clinical Trials Registry Platform, and CENTRAL databases were screened for studies from January 1, 1990, to September 30, 2023, without language restrictions. Study Selection: Two reviewers performed independent study screening and assessed the following inclusion criteria: appropriate genotyping was performed, genotype-based categorization into subgroups was possible, and each subgroup contained at least 3 participants. Data Extraction and Synthesis: The Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines were followed for data extraction and subsequent quality, validity, and risk-of-bias assessments. The results from the included studies were pooled with random-effect meta-analysis. Main Outcomes and Measures: Plasma concentrations of antiseizure drugs were quantified with the dose-normalized area under the concentration-time curve, the dose-normalized steady state concentration, or the concentrations after a single dose at standardized dose and sampling time. The ratio of the means was calculated by dividing the mean drug plasma concentrations of carriers and noncarriers of the pharmacogenetic variant. Results: Data from 98 studies involving 12 543 adult participants treated with phenytoin, valproate, lamotrigine, or carbamazepine were analyzed. Studies were mainly conducted within East Asian (69 studies) or White or European (15 studies) cohorts. Significant increases of plasma concentrations compared with the reference subgroup were observed for phenytoin, by 46% (95% CI, 33%-61%) in CYP2C9 intermediate metabolizers, 20% (95% CI, 17%-30%) in CYP2C19 intermediate metabolizers, and 39% (95% CI, 24%-56%) in CYP2C19 poor metabolizers; for valproate, by 12% (95% CI, 4%-20%) in CYP2C9 intermediate metabolizers, 12% (95% CI, 2%-24%) in CYP2C19 intermediate metabolizers, and 20% (95% CI, 2%-41%) in CYP2C19 poor metabolizers; and for carbamazepine, by 12% (95% CI, 3%-22%) in CYP3A5 poor metabolizers. Conclusions and Relevance: This systematic review and meta-analysis found that CYP2C9 and CYP2C19 genotypes encoding low enzymatic capacity were associated with a clinically relevant increase in phenytoin plasma concentrations, several pharmacogenetic variants were associated with statistically significant but only marginally clinically relevant changes in valproate and carbamazepine plasma concentrations, and numerous pharmacogenetic variants were not associated with statistically significant differences in plasma concentrations of antiseizure drugs. © This record is sourced from MEDLINE/PubMed, a database of the U.S. National Library of Medicine 1of1 Top of page Cited by 0 documents Inform me when this document is cited in Scopus: Related documents Find more related documents in Scopus based on: Authors Keyword

Significantly lower CYP2D6 metabolism measured as the O/N-desmethylvenlafaxine metabolic ratio in carriers of CYP2D6*41 versus CYP2D6*9 or CYP2D6*10: a study on therapeutic drug monitoring data from 1003 genotyped Scandinavian patients

Aims CYP2D6*9, CYP2D6*10 and CYP2D6*41 are the most frequent reduced-function CYP2D6 alleles in Caucasians. Despite lacking in vivo evidence, they are collectively classified with an enzyme activity score of 0.5. Thus, the aim of this study was to compare the functional impact of CYP2D6*9, CYP2D6*10 and CYP2D6*41 on CYP2D6 metabolism in a large patient population. Methods A total of 1003 patients (mainly Caucasians) with data on CYP2D6 genotype and serum concentrations of venlafaxine and metabolites were included from a therapeutic drug monitoring service in Oslo, Norway. The O-desmethyl-to-N-desmethyl-venlafaxine metabolic ratio (MR) was applied as CYP2D6 biomarker and compared (Mann-Whitney) between carriers of CYP2D6*9-10 (merged) and CYP2D6*41, either combined with CYP2D6*1 or non-coding (null) alleles. MR subgroup estimates were obtained by multiple linear regression for calculations of CYP2D6*9-10 and CYP2D6*41 activity scores. Results MR was significantly lower in carriers of CYP2D6*41 than CYP2D6*9-10 (P lt 0.002). The majority of CYP2D6*41/null carriers (86.7%) had MR in the observed range of CYP2D6null/null carriers compared with the minority of CYP2D6*9-10/null carriers (17.4%). CYP2D6 genotype explained 60.7% of MR variability in the multivariate analysis providing subgroup estimates of 9.54 (95% CI; 7.45-12.20), 3.55 (2.06-6.10), 1.33 (0.87-2.05) and 0.47 (0.35-0.61) in carriers of CYP2D6*1/null (n = 269), CYP2D6*9-10/null (n = 17), CYP2D6*41/null (n = 30) and CYP2D6null/null (n = 95), respectively. Based on these estimates, the calculated activity score of CYP2D6*41 was 0.095 compared to 0.34 for CYP2D6*9-10. Conclusions CYP2D6 metabolism measured as the O/N-desmethylvenlafaxine ratio is significantly lower in Scandinavian carriers of CYP2D6*41 vs. CYP2D6*9-10. Thus, these alleles should be differentiated when classifying CYP2D6 phenotype from genotype

The Polymorphic Nuclear Factor NFIB Regulates Hepatic CYP2D6 Expression and Influences Risperidone Metabolism in Psychiatric Patients

The genetic background for interindividual variability of the polymorphic CYP2D6 enzyme activity remains incompletely understood and the role of NFIB genetic polymorphism for this variability was evaluated in this translational study. We investigated the effect of NFIB expression in vitro using 3D liver spheroids, Huh7 cells, and the influence of the NFIB polymorphism on metabolism of risperidone in patients in vivo. We found that NFIB regulates several important pharmacogenes, including CYP2D6. NFIB inhibited CYP2D6 gene expression in Huh7 cells and NFIB expression in livers was predominantly nuclear and reduced at the mRNA and protein level in carriers of the NFIB rs28379954 T>C allele. Based on 604 risperidone treated patients genotyped for CYP2D6 and NFIB, we found that the rate of risperidone hydroxylation was elevated in NFIB rs28379954 T>C carriers among CYP2D6 normal metabolizers, resulting in a similar rate of drug metabolism to what is observed in CYP2D6 ultrarapid metabolizers, with no such effect observed in CYP2D6 poor metabolizers lacking functional enzyme. The results indicate that NFIB constitutes a novel nuclear factor in the regulation of cytochrome P450 genes, and that its polymorphism is a predictor for the rate of CYP2D6 dependent drug metabolism in vivo