Elevated CYP2C19 expression is associated with depressive symptoms and hippocampal homeostasis impairment.

The polymorphic CYP2C19 enzyme metabolizes psychoactive compounds and is expressed in the adult liver and fetal brain. Previously, we demonstrated that the absence of CYP2C19 is associated with lower levels of depressive symptoms in 1472 Swedes. Conversely, transgenic mice carrying the human CYP2C19 gene (2C19TG) have shown an anxious phenotype and decrease in hippocampal volume and adult neurogenesis. The aims of this study were to: (1) examine whether the 2C19TG findings could be translated to humans, (2) evaluate the usefulness of the 2C19TG strain as a tool for preclinical screening of new antidepressants and (3) provide an insight into the molecular underpinnings of the 2C19TG phenotype. In humans, we found that the absence of CYP2C19 was associated with a bilateral hippocampal volume increase in two independent healthy cohorts (N=386 and 1032) and a lower prevalence of major depressive disorder and depression severity in African-Americans (N=3848). Moreover, genetically determined high CYP2C19 enzymatic capacity was associated with higher suicidality in depressed suicide attempters (N=209). 2C19TG mice showed high stress sensitivity, impaired hippocampal Bdnf homeostasis in stress, and more despair-like behavior in the forced swim test (FST). After the treatment with citalopram and 5-HT1A receptor agonist 8OH-DPAT, the reduction in immobility time in the FST was more pronounced in 2C19TG mice compared with WTs. Conversely, in the 2C19TG hippocampus, metabolic turnover of serotonin was reduced, whereas ERK1/2 and GSK3ß phosphorylation was increased. Altogether, this study indicates that elevated CYP2C19 expression is associated with depressive symptoms, reduced hippocampal volume and impairment of hippocampal serotonin and BDNF homeostasis.

Elevated CYP2C19 expression is associated with depressive symptoms and hippocampal homeostasis impairment.

This corrects the article DOI: 10.1038/mp.2016.204.

High frequency of CYP2D6 ultrarapid metabolizer genotypes in an Ashkenazi Jewish population from Argentina.

A twofold higher frequency of CYP2D6 ultrarapid metabolizers (estimated from genotype: gUMs) was reported among Ashkenazi Jews (AJ) living in New York (USA) than in other North American Caucasians, which might be important to guide the prescription for CYP2D6 substrates in AJ communities around the world. This study was aimed to determine whether the high frequency of CYP2D6 gUMs described in AJ from USA was replicated in AJ from Argentina when compared with other multiethnic admixture Argentines (GA). The frequency of the most common allelic variants and of CYP2D6 gUMs (>2 active genes) and poor metabolizers (0 active genes, gPMs) was also compared among the studied Argentine populations. CYP2D6 genotyping was performed in 173 AJ and 246 GA DNA samples of unrelated donors from the metropolitan area of Buenos Aires. CYP2D6 alleles (*2, *3, *4, *5, *6, *10, *17, *35, *41 and multiple copies), genotypes and functional phenotype frequencies were determined. The frequencies of gUMs and gPMs in AJ from Argentina were 11.5% and 5.2%, respectively, whereas in GA, the frequencies of gUM and gPMs were 6.5% and 4.9%, respectively. Comparisons between AJ and GA showed that gUMs frequencies were twofold higher (P<0.05) in AJ than GA. CYP2D6*35 allele was more frequent in GA than AJ, whereas CYP2D6*41 and *1xN were more frequent in AJ than in GA (P<0.05). This study supports the previously reported high frequency of gUMs on another Ashkenazi population in New York. The present findings also support the interethnic variability of CYP2D6 genetic polymorphism in the overall Argentine population.

High frequency of CYP2D6 ultrarapid metabolizers in Spain: controversy about their misclassification in worldwide population studies.

A high frequency (7-10%) of CYP2D6 ultrarapid metabolizers estimated from the genotype (gUMs) has been claimed to exist among Spaniards and Southern Europeans. However, methodological aspects such as the inclusion of individuals carrying non-active multiplied alleles as gUMs may have led to an overestimation. Thus, this study aimed to analyze the gUM frequency (considering only those carrying more than two active genes) in 805 Spanish healthy volunteers studied for CYP2D6*2, *3, *4, *5, *6, *10, *17, *35, *41, and multiplications. Second, all worldwide studies reporting gUM frequencies were reviewed in order to evaluate potential misclassifications. The gUM frequency in this Spanish population was 5.34%, but increased to 8.3% if all individuals with CYP2D6 multiplications were classified as gUMs without considering the activity of the multiplied alleles. Moreover, among all reviewed worldwide studies only 55.6% precisely determined whether the multiplied alleles were active. Present results suggest that the evaluation of CYP2D6 ultrarapid metabolism should be standarized, and that the frequency of gUMs should be reconsidered in Spaniards and globally.

Pharmacogenetic study of antipsychotic induced acute extrapyramidal symptoms in a first episode psychosis cohort: role of dopamine, serotonin and glutamate candidate genes.

This study investigated whether the risk of presenting antipsychotic (AP)-induced extrapyramidal symptoms (EPS) could be related to single-nucleotide polymorphisms (SNPs) in a naturalistic cohort of first episode psychosis (FEP) patients. Two hundred and two SNPs in 31 candidate genes (involved in dopamine, serotonin and glutamate pathways) were analyzed in the present study. One hundred and thirteen FEP patients (43 presenting EPS and 70 non-presenting EPS) treated with high-potency AP (amisulpride, paliperidone, risperidone and ziprasidone) were included in the analysis. The statistical analysis was adjusted by age, gender, AP dosage, AP combinations and concomitant treatments as covariates. Four SNPs in different genes (DRD2, SLC18A2, HTR2A and GRIK3) contributed significantly to the risk of EPS after correction for multiple testing (P<1 × 10(-4)). These findings support the involvement of dopamine, serotonin and glutamate pathways in AP-induced EPS.

Interethnic variation of CYP2C19 alleles, 'predicted' phenotypes and 'measured' metabolic phenotypes across world populations.

The present study evaluates the worldwide frequency distribution of CYP2C19 alleles and CYP2C19 metabolic phenotypes ('predicted' from genotypes and 'measured' with a probe drug) among healthy volunteers from different ethnic groups and geographic regions, as well as the relationship between the 'predicted' and 'measured' CYP2C19 metabolic phenotypes. A total of 52 181 healthy volunteers were studied within 138 selected original research papers. CYP2C19*17 was 42- and 24-fold more frequent in Mediterranean-South Europeans and Middle Easterns than in East Asians (P<0.001, in both cases). Contrarily, CYP2C19*2 and CYP2C19*3 alleles were more frequent in East Asians (30.26% and 6.89%, respectively), and even a twofold higher frequency of these alleles was found in Native populations from Oceania (61.30% and 14.42%, respectively; P<0.001, in all cases), which may be a consequence of genetic drift process in the Pacific Islands. Regarding CYP2C19 metabolic phenotype, poor metabolizers (PMs) were more frequent among Asians than in Europeans, contrarily to the phenomenon reported for CYP2D6. A correlation has been found between the frequencies of CYP2C19 poor metabolism 'predicted' from CYP2C19 genotypes (gPMs) and the poor metabolic phenotype 'measured' with a probe drug (mPMs) when subjects are either classified by ethnicity (r=0.94, P<0.001) or geographic region (r=0.99, P=0.002). Nevertheless, further research is needed in African and Asian populations, which are under-represented, and additional CYP2C19 variants and the 'measured' phenotype should be studied.

CYP2C9, CYP2C19, ABCB1 genetic polymorphisms and phenytoin plasma concentrations in Mexican-Mestizo patients with epilepsy.

We aimed to explore the possible influence of CYP2C9 (*2, *3 and IVS8-109 A>T), CYP2C19 (*2, *3 and *17) and ABCB1 (1236C>T, 2677G>A/T and 3435C>T) on phenytoin (PHT) plasma concentrations in 64 Mexican Mestizo (MM) patients with epilepsy currently treated with PHT in mono- (n=25) and polytherapy (n=39). Genotype and allele frequencies of these variants were also estimated in 300 MM healthy volunteers. Linear regression models were used to assess associations between the dependent variables (PHT plasma concentration and dose-corrected PHT concentration) with independent variables (CYP2C9, CYP2C19 and ABCB1 genotypes, ABCB1 haplotypes, age, sex, weight, and polytherapy). In multivariate models, CYP2C9 IVS8-109 T was significantly associated with higher PHT plasma concentrations (t(64)=2.27; P=0.03). Moreover, this allele was more frequent in the supratherapeutic group as compared with the subtherapeutic group (0.13 versus 0.03, respectively; P=0.05, Fisher's exact test). Results suggest that CYP2C9 IVS8-109 T allele may decrease CYP2C9 enzymatic activity on PHT. More research is needed to confirm findings.

Pharmacogenomic information in drug labels: European Medicines Agency perspective.

Pharmacogenomics (PGx) has a growing impact on healthcare and constitutes one of the major pillars of personalised medicine. For the purpose of improved individualised drug treatment, there is an increasing effort to develop drugs suitable for specific subpopulations and to incorporate pharmacogenomic drug labels in existing and novel medicines. Here, we review the pharmacogenomic drug labels of all 517 medicinal products centrally approved in the European Union (EU) since the establishment of the European Medicines Agency in 1995. We identified all pharmacogenomic-related information mentioned in the product labels and classified it according to its main effect and function on drug treatment, that is, metabolism, transport and pharmacodynamics, and according to the place of the respective section of the Summary of Product Characteristics (SmPC). The labels are preferentially present in drugs having antineoplastic properties. We find that the number of drugs with pharmacogenomic labels in EU increases now steadily and that it will be an important task for the future to refine the legislation on how this information should be utilised for improvement of drug therapy.

A combined high CYP2D6-CYP2C19 metabolic capacity is associated with the severity of suicide attempt as measured by objective circumstances.

This study examined, for the first time, whether a high CYP2D6-CYP2C19 metabolic capacity combination increases the likelihood of suicidal intent severity in a large study cohort. Survivors of a suicide attempt (n=587; 86.8% women) were genotyped for CYP2C19 (*2, *17) and CYP2D6 (*3, *4, *4xN, *5, *6, *10, wtxN) genetic variation and evaluated with the Beck Suicide Intent Scale (SIS). Patients with a high CYP2D6-CYP2C19 metabolic capacity showed an increased risk for a severe suicide attempt (P<0.01) as measured by the SIS-objective circumstance subscale (odds ratio (OR)=1.37; 95% confidence interval (CI)=1.05-1.78; P=0.02) after adjusting for confounders (gender, age, level of studies, marital status, mental disorders, tobacco use, family history of suicide, personal history of attempts and violence of the attempt). Importantly, the risk was greater in those without a family history of suicide (OR=1.82; CI=1.19-2.77; P=0.002). Further research is warranted to evaluate whether the observed relationship is mediated by the role of CYP2D6 and CYP2C19 involvement in the endogenous physiology or drug metabolism or both.

High frequency and founder effect of the CYP3A4*20 loss-of-function allele in the Spanish population classifies CYP3A4 as a polymorphic enzyme.

Cytochrome P450 3A4 (CYP3A4) is a key drug-metabolizing enzyme. Loss-of-function variants have been reported as rare events, and the first demonstration of a CYP3A4 protein lacking functional activity is caused by CYP3A4*20 allele. Here we characterized the world distribution and origin of CYP3A4*20 mutation. CYP3A4*20 was determined in more than 4000 individuals representing different populations, and haplotype analysis was performed using CYP3A polymorphisms and microsatellite markers. CYP3A4*20 allele was present in 1.2% of the Spanish population (up to 3.8% in specific regions), and all CYP3A4*20 carriers had a common haplotype. This is compatible with a Spanish founder effect and classifies CYP3A4 as a polymorphic enzyme. This constitutes the first description of a CYP3A4 loss-of-function variant with high frequency in a population. CYP3A4*20 results together with the key role of CYP3A4 in drug metabolism support screening for rare CYP3A4 functional alleles among subjects with adverse drug events in certain populations.

Interethnic differences in the relevance of CYP2C9 genotype and environmental factors for diclofenac metabolism in Hispanics from Cuba and Spain.

The aims of this study were to evaluate the diclofenac metabolism in Hispanics from Cuba and Spain and its relation to ethnicity, CYP2C9 genotypes and environmental factors. Diclofenac hydroxylation capacity (concentration ratios of diclofenac/metabolites in 8-h urine) was studied in 160 Cuban (classified as 76 Cuban-Whites-CWs and 84 Cuban-Mestizos-CMs) and 148 Spaniard (SPs) healthy volunteers. Diclofenac and its main metabolites, 4'-hydroxy (OH), 3'-OH and 5-OH diclofenac, and CYP2C9*2 to *6 and *8 alleles were also determined in 132 and 128 CWs and CMs, respectively. Gender, tobacco, caffeine and ethanol consumption were also evaluated. The mean diclofenac/4'-OH diclofenac ratio was higher in CMs (0.72±0.25) than in CWs (0.64±0.20; P<0.05) and SPs (0.57±0.26; P<0.001). The mean diclofenac/4'-OH diclofenac ratio was higher (P<0.05) in subjects with CYP2C9*1/*3 (0.77±0.19; n=22) and CYP2C9*1/*8 (0.93±0.33; n=4) genotypes than with CYP2C9*1/*1 (0.65±0.24; n=90). Environmental factors did not seem to influence the diclofenac metabolism in these populations. The present findings show for the first time interethnic differences between Hispanic groups in urinary diclofenac/4'-OH diclofenac ratios, and the relevance of CYP2C9*3 and CYP2C9*8 alleles.

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.

Use of pharmacogenetics in bioequivalence studies to reduce sample size: an example with mirtazapine and CYP2D6.

In bioequivalence studies, intra-individual variability (CV(w)) is critical in determining sample size. In particular, highly variable drugs may require enrollment of a greater number of subjects. We hypothesize that a strategy to reduce pharmacokinetic CV(w), and hence sample size and costs, would be to include subjects with decreased metabolic enzyme capacity for the drug under study. Therefore, two mirtazapine studies, two-way, two-period crossover design (n=68) were re-analysed to calculate the total CV(w) and the CV(w)s in three different CYP2D6 genotype groups (0, 1 and ≥ 2 active genes). The results showed that a 29.2 or 15.3% sample size reduction would have been possible if the recruitment had been of individuals carrying just 0 or 0 plus 1 CYP2D6 active genes, due to the lower CV(w). This suggests that there may be a role for pharmacogenetics in the design of bioequivalence studies to reduce sample size and costs, thus introducing a new paradigm for the biopharmaceutical evaluation of drug products.

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.

Association of common genetic variants with risperidone adverse events in a Spanish schizophrenic population.

Risperidone non-compliance is often high due to undesirable side effects, whose development is in part genetically determined. Studies with genetic variants involved in the pharmacokinetics and pharmacodynamics of risperidone have yielded inconsistent results. Thus, the aim of this study was to investigate the putative association of genetic markers with the occurrence of four frequently observed adverse events secondary to risperidone treatment: sleepiness, weight gain, extrapyramidal symptoms and sexual adverse events. A series of 111 schizophrenia inpatients were genotyped for genetic variants previously associated with or potentially involved in risperidone response. Presence of adverse events was the main variable and potential confounding factors were considered. Allele 16Gly of ADRB2 was significantly associated with a higher risk of sexual adverse events. There were other non-significant trends for DRD3 9Gly and SLC6A4 S alleles. Our results, although preliminary, provide new candidate variants of potential use in risperidone safety prediction.

CYP2D6 polymorphism in patients with eating disorders.

CYP2D6 polymorphism is associated with variability in drug response, endogenous metabolism (that is, serotonin), personality, neurocognition and psychopathology. The relationship between CYP2D6 genetic polymorphism and the risk of eating disorders (ED) was analyzed in 267 patients with ED and in 285 controls. A difference in the CYP2D6 active allele distribution was found between these groups. Women carrying more than two active genes (ultrarapid metabolizers) (7.5 vs 4.6%) or two (67 vs 58.9%) active genes were more frequent among patients with ED, whereas those with one (20.6 vs 30.2%) or zero active genes (4.9 vs 6.3%) were more frequent among controls (P<0.05). Although further research is needed, present findings suggest an association between CYP2D6 and ED. CYP2D6 allele distribution in patients with ED seems related to increased enzyme activity.

CYP2D6 genotype and debrisoquine hydroxylation phenotype in Cubans and Nicaraguans.

CYP2D6 genotype and debrisoquine metabolic ratio (MR) were analyzed in 133 Nicaraguan Mestizos (NMs) and 260 Cubans divided into Cuban Mestizos (CMs) and White Cubans (WCs). The frequencies of poor metabolizers (MR12.6) were 6% in NMs, 3.9% in CMs and 5.3% in WCs. The frequencies of ultrarapid metabolizers (MR0.1) were 0% in NMs, 2.3% in CMs and 5.3% in WCs. Mean (±s.d.) MR among extensive metabolizers (MR<12.6) was higher in NMs (1.5±1.6; n=118) than in CMs (1.0±1.3; n=124; P<0.001) and WCs (0.7±1.0; n=124; P<0.001). MR correlated with the 'activity score' of CYP2D6 genotypes (P<0.05; r=-0.55). Mean MR was higher among NMs than WCs and CMs for groups classified as 1 (P<0.05) or 2 (P<0.01) 'activity score'. In addition, mean (±s.d.) MR was higher among subjects carrying CYP2D6*17 than in CYP2D6 wt/wt (P<0.001). The CYP2D6*10 allele was higher in NMs (3.1%) than in CMs (0.8%; P<0.05) and WCs (0.4%; P<0.05). CYP2D6*17 allele was higher in CMs (10.2%) than WC (2.7%; P<0.005) and NMs (0%). Thus, the variability in CYP2D6 phenotypes found may be related to differences in allele frequency among groups (that is, CYP2D6*10 and *17 highest in NMs and CMs, respectively). However, the influence of environmental factors or alleles different than those studied here cannot be ruled out.

CYP2C9 allele frequency differences between populations of Mexican-Mestizo, Mexican-Tepehuano, and Spaniards.

Earlier we had found that the CYP2C9*2 allelic frequency was lower in Mexican-Americans living in California than in Spaniards (SP). This was assumed to be related to the low CYP2C9*2 and *3 allele frequencies in Orientals. This study was therefore aimed at analyzing whether there were also differences in CYP2C9 allele frequencies between Mexican-Tepehuanos (MT) and Mexican-Mestizos (MM) living in northwestern Mexico and SP. The CYP2C9*2 frequency was expected to be lower in the indigenous MT than in the two other groups, and lower in MM than in SP as in our earlier study. CYP2C9 genotypes and allele frequencies of two populations of healthy volunteers, MT (n=99) and MM (n=102), were compared with a population of SP (n=327). The data were also compared with our previously published population of Mestizo-Mexican-Americans (MA). The CYP2C9 genotypes among the studied populations were in equilibrium. The frequencies of CYP2C9*2 were 0.01, 0.07, 0.08, and 0.16 for MT, MM, MA, and SP subjects, respectively. In agreement with our hypothesis, CYP2C9*2 was significantly lower in the Mexican populations than in the SP (P<0.05), and among Mexicans in the MT than in the MM and MA groups (P<0.05), which presented similar frequencies. Moreover, the frequency of CYP2C9*3 was found to be lower (P<0.05) in MM (0.015) and MT (0.015) than in MA (0.06) and SP (0.08). Finally, the CYP2C9*6 allele was present just in one MM subject, and CYP2C9*4 and *5 were not found in the studied populations. Therefore, these findings add further evidence about CYP2C9 genetic diversity within Hispanic populations with regard to their ancestry. Considering that CYP2C9*2 and CYP2C9*3 alleles have altered catalytic activities relative to CYP2C9*1, the present data suggest the need for pharmacogenetic studies to optimize drug dosages in different populations.

Relationship between CYP2C8 genotypes and diclofenac 5-hydroxylation in healthy Spanish volunteers.

PURPOSE: CYP2C8 seems to be involved in diclofenac 5-hydroxylation, while, in vitro, the 4'-hydroxylation and 3'-hydroxylation seem to be mediated mainly by CYP2C9. We have demonstrated the relevance of CYP2C9 genotypes for diclofenac 4'-hydroxylation in healthy volunteers, so that the present study was aimed at analyzing the role of both CYP2C8 and CYP2C9 genotypes on diclofenac metabolism, as well as determining the CYP2C8 allele frequencies and their relationship with CYP2C9 variants. METHODS: A group of 142 healthy white Spanish volunteers was studied. Previously, 102 of these subjects had been phenotyped with diclofenac and genotyped for CYP2C9. The CYP2C8 genotypes were determined by allele-specific PCR-RFLP methods. The urinary concentrations of diclofenac and its main metabolites were analysed using an HPLC-UV method after the administration of a single oral dose of diclofenac as described previously for part of the population studied here. RESULTS: The diclofenac/5-hydroxydiclofenac urinary concentration ratio was higher in individuals carrying a CYP2C8*3 or CYP2C8*4 allele than in those homozygous for wild-type allele CYP2C8*1 (P < 0.05). Moreover, approximately 93% of the subjects with a CYP2C8*3 allele also carried a CYP2C9*2, and 80% of the subjects that had CYP2C9*2 variant also carried a CYP2C8*3. In addition, the four CYP2C9*2/*2 individuals were CYP2C8*3/*3. CONCLUSIONS: This is the first study showing the influence of CYP2C8 genotypes on diclofenac metabolism in vivo. The linkage disequilibrium between CYP2C8*3 and CYP2C9*2 alleles was confirmed in this Spanish population.