Adrián LLerena

Pharmacogenomics education: International Society of Pharmacogenomics recommendations for medical, pharmaceutical, and health schools deans of education.

Pharmacogenomics would be instrumental for the realization of personalized medicine in coming decades. Efforts are evident to clarify the potential bioethical, societal, and legal implications of key pharmacogenomics-based technologies projected to be soon introduced into the core practice of medicine. In sharp contrast, a lack of sufficient attention to educational aspects of pharmacogenomics, both for professionals and for society at large, is evident. In order to contribute to this discussion, a ‘Pharmacogenomics Education Forum’ was held on October 2, 2004 during the 3rd Annual Meeting of the International Society of Pharmacogenomics (ISP) at Santorini, Greece. The participants, members of the ISP Pharmacogenomics Education Forum, after deliberate discussions, proposed a document of ‘Background Statement’ and ‘Recommendations and Call for Action’ addressed to Deans of Education at Medical, Pharmaceutical, and Health Schools globally. This document has been considered by the education committee of the International Society of Pharmacogenomics and the result is presented here. We hope that this call would be listened to, and soon followed by beneficial action, ultimately leading to enhanced implementation of personalized medicine into core medical education and practice.

QTc Interval, CYP2D6 and CYP2C9 Genotypes and Risperidone Plasma Concentrations

The role of certain drug metabolizing enzymes in cardiotoxicity, such as CYP2D6 for thioridazine, has been suggested. Risperidone has been shown to inhibit the delayed rectifier leading to lengthening of cardiac repolarization. The heart-rate corrected QT (QTc) interval lengthening has been reported in psychiatric patients receiving risperidone under steady-state conditions. CYP2D6 is involved in the metabolism of risperidone to 9-hydroxy (OH)-risperidone. CYP2C9 enzyme is also involved in the metabolism of several psychotropic drugs, although there are no data about its implication in risperidone metabolism. The present study aimed to evaluate the influence of CYP2D6 and CYP2C9 genotypes, and plasma concentrations of risperidone and 9-OH-risperidone on the QTc interval in patients under steady-state conditions. The relevance of CYP2D6 and CYP2C9 genotypes on risperidone metabolism was also analysed. Thirty-five White European psychiatric patients receiving risperidone monotherapy were studied. QTc interval was longer (p < 0.05) in subjects with one active CYP2D6 gene compared to those with two. The number of CYP2D6 active genes was related to the dose-corrected plasma concentration of risperidone (p < 0.05), the active moiety (risperidone plus 9-OH-risperidone) (p < 0.05) and the risperidone/9-OH-risperidone ratio (p < 0.05). CYP2C9genotypes were not related to plasma concentrations of risperidone or 9-OH-risperidone, nor QTc interval. The results suggest that CYP2D6, but not CYP2C9, may be related to QTc lengthening during treatment with risperidone. The effect of the CYP2D6 genotype in risperidone metabolism is also shown.

Low frequency of CYP2D6 poor metabolizers among schizophrenia patients

CYP2D6 has been suggested to be functionally similar to the dopamine transporter. The present study was aimed at analysing the frequency of CYP2D6 alleles and genotype among schizophrenic patients compared to healthy volunteers. CYP2D6 *3, *4, *5, *6, *10 and duplicated alleles were analysed in 128 unselected schizophrenia inpatients (SP) and 142 unrelated white European Spanish healthy volunteers (HV). SP and HV with >2, 2, 1 or 0 CYP2D6 active genes were 4.7, 64.8, 28.1 and 2.3%, and 6.3, 52.1, 33.1 and 8.5%, respectively. The frequency of homozygous for CYP2D6 inactive alleles or poor metabolizers (PMs) was lower (P<0.05) in SP than in HV. Furthermore, the frequency of CYP2D6 inactive alleles was also lower in SP than in HV (16.8 vs 25.7; P<0.05), specifically the CYP2D6*6 allele was not found among patients. The present study shows a lower frequency of PMs in schizophrenic patients than in healthy volunteers supporting the hypothesis of a potential role of CYP2D6 in the vulnerability to schizophrenia.

Neurological toxicity after phenytoin infusion in a pediatric patient with epilepsy: influence of CYP2C9, CYP2C19 and ABCB1 genetic polymorphisms

Pharmacogenetic studies have shown that genetic defects in drug-metabolizing enzymes encoded by CYP2C9, CYP2C19 genes and by the transporter ABCB1 gene can influence phenytoin (PTH) plasma levels and toxicity. The patient reported here is a 2-year-old girl with a medical history of cryptogenic (probably symptomatic) epilepsy, who had her first focal seizure with secondary generalization at 13 months of age. She initially received oral valproate treatment and three months later, she was prescribed an oral oxcarbazepine treatment. At 20 months of age, she was admitted to the Emergency Department because of generalized convulsive Status Epilepticus needing to be immediately treated with rectal diazepam (0.5 mg kg−1), intravenous diazepam (0.3 mg kg−1), and intravenous phenytoin with an initial-loading dose of 15 mg kg−1. However, two hours after the initial-loading dose of PTH, the patient developed dizziness, nystagmus, ataxia and excessive sedation. Other potential causes of PTH toxicity were excluded such as drug interactions, decreased albumin or lab error. Therefore, to explain the neurological toxicity, PTH plasma levels and CYP2C9, CYP2C19 and ABCB1 genetic polymorphisms were analyzed. Initial plasma PTH levels were higher than expected (69 mg l−1; normal range: 10–20 mg l−1), and the patient was homozygous for the CYP2C9*2 allele, heterozygous for the CYP2C19*4 allele and homozygous for the 3435C and 1236C ABCB1 alleles. Present findings support the previously established relationship between CYP2C9 and CYP2C19 genetic polymorphisms and the increased risk to develop PTH toxicity owing to high plasma concentrations. Nevertheless, although the association of these genes with PTH-induced adverse effects has been well-documented in adult populations, this is the first report examining the influence of these genetic polymorphisms on PTH plasma levels and toxicity in a pediatric patient.

CYP2C9 gene and susceptibility to major depressive disorder

ABSTRACTAlteration of monoaminergic neurotransmission has been implicated in the pathophysiology of mood disorders, and CYP2C9 enzyme activity has been shown to be modulated by serotonin in vitro. The present study was aimed at analysing the frequency of CYP2C9 alleles (*1, *2, *3) among patients suffering from major depressive disorder. In all, 70 such suffering psychiatric outpatients were studied. The CYP2C9 genotypes were determined by allele-specific PCR. The CYP2C9*3 allele frequency was higher (P<0.01) among the patients suffering from major depression than in a population of 89 schizophrenic patients (odds ratio=3.3) and 138 healthy volunteers (odds ratio=2.8). The results suggest that CYP2C9 genetic polymorphism may be related to a major depressive disorder due to an alteration in endogenous metabolism, although a linkage between CYP2C9 and some other gene related to depression cannot be ruled out.

Influence of admixture components on CYP2C9*2 allele frequency in eight indigenous populations from Northwest Mexico

We previously documented the lowest frequency of CYP2C9*2 in Mexican indigenous Tepehuanos followed by Mestizos and Mexican-Americans populations, suggesting a negative correlation between the CYP2C9*2 frequency and the degree of Asian ancestry in indigenous Americans. We determined the influence of ethnic admixture components on the CYP2C9 allele distribution in 505 Amerindian from eight indigenous populations through genotyping CYP2C9*2, *3 and *6 alleles by real-time PCR and molecular evaluation of ancestry. The frequencies for CYP2C9*2 were 0.026 in Seris and 0.057 in Mayos, being higher than in Asians (P<0.001). CYP2C9*3 was found in Tarahumaras (0.104), Mayos (0.091), Tepehuanos (0.075), Guarijíos (0.067), Huicholes (0.033) and Coras (0.037), with East Asians having lower frequencies than the former three groups (P<0.001). CYP2C9*6 was not found. The frequency of CYP2C9*2 was lower in Amerindians than in European populations, and higher than their Asian ancestors. The presence of this allele in ethnic groups in Mexico can be explained by European admixture.

Determination of debrisoquine and 4-hydroxydebrisoquine by high-performance liquid chromatography: application to the evaluation of CYP2D6 genotype and debrisoquine metabolic ratio relationship

Abstract The drug-metabolizing cytochrome P450 (CYP) enzyme CYP2D6 is involved in the metabolism of several clinically important drugs. So far more than 50 different CYP2D6 allelic variants have been described, and thus there is an increased need for routine high-performance liquid chromatography (HPLC) methods for the evaluation of the functional implication of CYP2D6 polymorphism. Debrisoquine is metabolized to 4-hydroxydebrisoquine by CYP2D6, and therefore it has been used widely to determine the hydroxylation capacity of the enzyme. The aim of the present study was to develop a simple, accurate HPLC method with ultraviolet detection for the measurement of debrisoquine and 4-hydroxydebrisoquine in urine for evaluation of the relationship between CYP2D6 enzyme activity and genotypes. For the HPLC determination, a C18 extraction column was used with a flow rate of 0.8mL/min and detection at 210nm. The compounds were eluted from the column in less than 10min. Coefficients of variation at all concentrations were less than 4% for both compounds. The debrisoquine/4-hydroxydebrisoquine ratio (debrisoquine metabolic ratio) was determined in a panel of 16 Caucasian healthy volunteers with zero (poor metabolizers), one, two or more than two (ultrarapid metabolizers) CYP2D6 active genes. Significant correlation (p<0.05) between the number of CYP2D6 active genes and the hydroxylation capacity of the enzyme was found. The present HPLC method was simple, fast and accurate, and thus will be useful for the evaluation of CYP2D6 hydroxylation capacity in pharmacogenetic studies.

Third Santorini conference pharmacogenomics workshop report: “Pharmacogenomics at the crossroads: what else than good science will be needed for the field to become part of Personalized Medicine?”

Abstract This workshop discussed the use of pharmacogenomics knowledge in clinical practice. It was organized in three sections: educational needs, definition of industry as a potential trigger, and regulatory aspects. Regarding pharmacogenomics education, it appears that this is truly lacking, except for patients, who are becoming increasingly educated thanks to the media. Regarding administrators, education is mainly a problem of cost. Indeed, even if cost-effective for society on the whole, pharmacogenomic tests will be expensive for hospitals. Physicians are facing an overabundance of information. They must be helped to bridge the gap between knowledge/research and clinical application. Collaboration between the pharmaceutical industry and the diagnostics industry could be one of the triggers. Moreover, there is a lack of qualification of this information, even though some guidelines are being produced. The Food and Drug Administration organizes workshops that often lead to publications on pharmacogenomic education, genomic data aims and development concepts, which can finally be translated into guidelines. Industry can contribute to pharmacogenomic development, not only through research, but also through marketing activities, which would promote the use of pharmacogenomics by physicians. Legal aspects were also considered in terms of the problem of availability and the degree of qualification of commercial drug tests on the market. The Innovative Medicine Initiative was also presented, which is a public-private partnership to create a biomedical research and development leader to benefit patients and society. Finally, a technical report from the Institute for Prospective Technological Studies on the socioeconomic impact of pharmacogenomics in the EU was presented. Clin Chem Lab Med 2007;45:843–50.

No effect of the CYP1A2*1F genotype on thioridazine, mesoridazine, sulforidazine plasma concentrations in psychiatric patients

Sir, Recently it has been shown that CYP1A2 and CYP3A4 are the main enzymes responsible for 5-sulfoxidation and Ndemethylation of thioridazine, whereas CYP2D6 is the basic enzyme that catalyzes mono-2and di-2-sulfoxidation in human liver microsomomes. Moreover, both CYP2D6 and CYP3A4 contribute to thioridazine mono-2-sulfoxidation [1]. Previously, on the basis of CYP2D6 involvement in the metabolism of thioridazine to mesoridazine we showed the use of the mesoridazine-to-thioridazine ratio as a tool to assess CYP2D6 activity in clinical settings [2]. Additionally, we reported that CYP2D6 genotype mediated the dosedependent inhibition of CYP2D6 during treatment with thioridazine [3]. Later our group reported in this journal [4] that thioridazine plasma concentration in psychiatric patients was influenced by CYP2D6 genotypes and tobacco smoking, which suggested that both CYP1A2 and CYP2D6 enzymes were involved in the metabolism of thioridazine. The observation that thioridazine plasma concentration corrected by dose was lower in smokers than non-smokers [4] could be due to CYP1A2 inducibility by smoking [5]. This fact is of note considering the high proportion of tobacco smokers among schizophrenic patients [6]. A possible impact of CYP1A2 on thioridazine metabolism is also supported by previous data showing that thioridazine plasma concentration increases during treatment with the CYP1A2 potent inhibitor fluvoxamine [7]. A putative polymorphism in intron 1 of CYP1A2 (-163C> A; CYP1A2*1F allele) appears to affect the inducibility of CYP1A2 [8]. Thus, the CYP1A2*1F A/A genotype may represent a CYP1A2 with high inducibility, which may either be a direct cause of increased CYP1A2 activity, or be genetically linked to polymorphisms conferring high inducibility [9]. The aim of this study was to analyse the potential influence of high-inducibility CYP1A2*1F allele and tobacco smoking on thioridazine and metabolite plasma concentration. Fifty-nine Caucasian psychiatric patients receiving thioridazine monotherapy were studied (44 smokers and 15 non-smokers) for the determination of CYP1A2*1F genotypes. These patients are part of a previously studied population of 76 patients [4]. CYP2D6 genotypes, debrisoquine metabolic ratio and steady-state plasma levels of Eur J Clin Pharmacol (2007) 63:527–528 DOI 10.1007/s00228-007-0284-6