Impact Of CYP2D6 Polymorphisms Research Articles

Impact of CYP2D6 polymorphisms on adverse events in patients with breast cancer treated with tamoxifen: Insights from an early dose escalation trial in CYP2D6 poor metabolizers.

547 Background: Tamoxifen is widely used in treating hormone receptor-positive breast cancer. It is primarily metabolized by the CYP2D6 enzyme to yield active metabolites. However, CYP2D6 polymorphisms have been associated with a differential response to tamoxifen. In a clinical trial involving an early dose escalation of tamoxifen in poor metabolizers, we found endoxifen concentration levels similar to those of patients with extensive phenotype, and no long-term survival differences among CYP2D6 phenotypes. However, the impact of that dose escalation on side effect incidence was not addressed. Methods: In this study, we analyzed the incidence of specific side effects - osteoarticular pain, hot flashes, asthenia, and uterine alterations - in 86 breast cancer patients, differentiated by their CYP2D6 phenotype estimated according to the Clinical Pharmacogenetics Implementation Consortium. In poor metabolizers, the tamoxifen standard dose of 20 mg/day was escalated to 40 mg/day and 60 mg/day for 4 months each, and then treated with 20 mg/day until completing the treatment. Kaplan-Meier analysis and Cox proportional hazards regression model were employed to assess the relationship between the CYP2D6 phenotype and the incidence of these side effects. Results: The median follow-up time was 139.5 months. The analyses revealed that only uterine changes showed significant differences between CYP2D6 phenotypes, with a lower incidence in extensive metabolizers (P-value < 0.001 in Kaplan-Meier; HR in Cox of 0.195, 95% CI 0.073 - 0.521, P = 0.001). This finding persisted after adjustment for the covariates tumor grade, size, nodal status, chemotherapy, and radiotherapy in multivariate Cox regression (HR 0.098, 95% CI 0.020 - 0.466, P = 0.004). Selection of a subgroup through Propensity Score Matching (21 vs 21) corroborated these results. The spectrum of uterine changes and pathologies included endometrial hyperplasia, polyps, adenocarcinoma, myometrial or endometrial thickening, and the presence of multiple myomas. Conclusions: Our study indicates that an early increase in tamoxifen dose in poor metabolizer patients according to CYP2D6 polymorphisms may significantly affect the incidence of uterine changes, but not the incidence of osteoarticular pain, hot flashes, or asthenia. Clinical trial information: 2007-002942-40/ES .

Impact of CYP2D6 polymorphisms on the efficacy of tamoxifen in Iraqi women with breast cancer

Objectives: The aim of the present study was to investigate the impact of the CYP2D6 genetic polymorphism on clinical outcome in Iraqi breast cancer patients who were candidates for Tamoxifen therapy. Methods: Comprehensive CYP2D6 genotyping was performed in 140 Iraqi women with breast cancer who were women on adjuvant treatment with tamoxifen. Breast cancer patients recruited into the study were divided into two groups: seventy breast cancer women who had no history of recurrence at the time of sampling and had a long time on tamoxifen without recurrence and seventy breast cancer women who had recurrence at the time of sampling after one year of treatment with tamoxifen therapy. Recurrence free survival (RFS) was determined in the recruited patients. Results: Multiple genetic variants of the gene encoding the CYP2D6 enzyme were detected with significant differences in their frequencies and percentages in both recurrent and non-recurrent groups of breast cancer patients. The findings of this study suggest that interindividual variation in clinical outcome may be related to genetic variation in CYP2D6 enzyme, which is characterized by variable RFS periods. Conclusions: This study revealed that the CYP2D6 enzyme of breast cancer patients who participated in this study is highly polymorphic. The CYP2D6 gene of study participants exhibited different allelic combinations with variable frequencies. The multiple genetic variants (alleles) of the gene encoding the CYP2D6 enzyme exhibited significant differences in their frequencies and percentages in both recurrent and non-recurrent groups of breast cancer patients. .The study revealed variable Recurrence free survival (RFS) with highly polymorphic gene. Our study quotes the presence of increased CYP2D6 enzyme polymorphism is associated with variable clinical response.

Risperidone plasma concentrations are associated with hyperprolactinemia in autism spectrum disorder children: The impact of CYP2D6 polymorphisms

BackgroundRisperidone causes hyperprolactinemia by blocking D2 receptors on lactotrophs anterior pituitary, which prevents prolactin secretion inhibition. Risperidone is converted to 9-hydroxyrisperidone by the CYP2D6 enzyme. Polymorphisms in CYP2D6 may affect serum prolactin and could be a predictor of hyperprolactinemia. The goal of this study was to see if there was an association between CYP2D6 variants, risperidone dose, clinical data and serum prolactin levels in Thai children and adolescents with autism spectrum disorder (ASD). MethodIn 107 Thai ASD patients on risperidone, allele-specific primer extension and multiplex PCR platforms were used to genotype the CYP2D6 gene. The chemiluminescence immunoassay (CLIA) technique was used to measure fasting serum prolactin levels. ResultsThe median serum prolactin level was 16.25 ng/mL (IQR; 10.43-22.18), and patients with CYP2D6*1/*5 (6.54%) had substantially lower prolactin levels than those with CYP2D6*1/*1 [median; 11.2 ng/mL (IQR; 3.95-21.10) vs. 21.3 (IQR; 14.43-32.18), p=0.032]. CYP2D6*1/*10, *10/*10, and *10/*41 produced less prolactin than *1/*1(wild type). Furthermore, gender and risperidone dose were associated with significantly different prolactin levels with p-value 0.02 and 0.006, respectively. Multivariate analysis showed a significant association of serum prolactin level with body mass index and risperidone dose (p<0.05). ConclusionsOur study showed that CYP2D6 carriers of absent and decreased functional alleles had lower serum prolactin levels in Thai ASD patients treated with risperidone treatment; this is important to clinicians, indicating that they should consider about CYP2D6 genotyping before beginning risperidone in ASD patients.CYP2D6 genotypes might be a predictor for levels of prolactin in clinical treatment.

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

Fluoxetine is used in the treatment of patients with recurrent depressive disorder. Some of these patients do not achieve an adequate response to a treatment regimen containing fluoxetine, and many of these patients experience dose-dependent adverse drug reactions. The cytochrome P450 enzyme CYP2D6 is involved in the biotransformation of fluoxetine, the activity of which is quite dependent on the polymorphism of the gene encoding this enzyme. The objective of the study was to investigate the influence of the 1846G>A polymorphism of the CYP2D6 gene on the concentration/dose indicator of fluoxetine in patients diagnosed with major depressive disorder and comorbid alcohol use disorder. Our study included 101 patients with major depressive disorder and alcohol use disorder (average age: 41.3±14.5 y) who were treated with fluoxetine at an average dose of 26.1±8.7 mg/d. Treatment efficacy was assessed using validated psychometric scales, and the safety/tolerability of the therapy was assessed using the Udvalg for Kliniske Undersogelser Side-Effect Rating Scale. Genotyping was done using a real-time polymerase chain reaction. Therapeutic drug monitoring was performed using high-performance liquid chromatography-mass spectrometry. CYP2D6 genotyping by polymorphic marker 1846G>A (rs3892097) in the 101 patients found that there were 81 patients (80.2%) with the GG genotype ("wild-type," normal metabolism), 20 (19.8%) with the GA genotype (intermediate metabolism), and no subjects with the AA genotype (poor metabolism). Statistically significant results in treatment efficacy as evaluated by Hamilton Rating Scale for Depression scores at the end of the treatment course were found: GG 9.0 [confidence interval (CI): 6.0; 12.0] and GA 12.0 (CI: 9.5; 14.0), P=0.005. Statistically significant results were also obtained for the safety profile as measured by scores on the Udvalg for Kliniske Undersogelser Side-Effect Rating Scale: GG 3.0 (CI 2.0; 4.0) and GA 5.0 (CI: 4.0; 5.0), P<0.001. Finally, a statistically significant difference was found in concentration/dose indicators of fluoxetine in patients with the different genotypes: GG 4.831 (CI: 3.654; 6.204) and GA 7.011 (CI: 5.431; 8.252), P<0.001. The effect of the genetic polymorphism of the CYP2D6 gene on the efficacy and safety profiles of fluoxetine was demonstrated in a group of 101 patients with major depressive disorder and alcohol use disorder.

Impact of CYP2D6 Polymorphisms on Propranolol Effects in Children with Portal Hypertension

Impact of CYP2D6 Polymorphisms on Propranolol Effects in Children with Portal Hypertension

Impact of CYP2D6 Polymorphisms on Tamoxifen Treatment in Patients With Retroperitoneal Fibrosis: A First Step Towards Tailored Therapy?

To investigate the influence of CYP2D6 polymorphisms on outcomes and health-related quality of life of patients with retroperitoneal fibrosis (RPF) receiving tamoxifen (TMX). TMX is an effective alternative to corticosteroids for patients with RPF. Conversion of TMX to more potent endoxifen is dependent on enzyme activity of CYP2D6. CYP2D6 genotyping and phenotype prediction of all patients treated with TMX between 02/2007 and 01/2018 was assessed using multiplex polymerase chain reaction (PCR). Groups were classified by phenotype: extensive (EM) vs poor and intermediate (PM+IM) vs ultrarapid metabolizer (UM). Retrospective evaluation of outcome (including magnetic resonance imaging and positron emission tomography-computed tomography) and health-related quality of life using the SF-36 was performed. A total of 63/194 patients received TMX, 40/63 with complete follow-up were sequenced: Twenty-nine patients with EM phenotype, 8 PM+IM and 3 UM. The median therapy duration was 364.5 days with a mean follow-up of 62.9 months. Seven therapy terminations occurred due to lack of response (17.5%), including all UM patients (P <.001). Magnetic resonance imagings showed a regression of fibrosis for EM and PM+IM in 69% and 62.5% of cases and a progression for UM in 100% (P=.004). In positron emission tomography-computed tomography, glucose utilization of RPF decreased significantly for EM and PM+IM. The physical sum-score of SF-36 improved for EM and PM+IM and decreased for UM (P <.05). The removal of DJ-stents was successful for EM, PM+IM, and UM in 48.3%, 75%, and 0% of cases (P=.0581). Contrary to expectations, UM showed the lowest success rate, which concludes that genotyping of RPF-patients may be useful in the sense of a tailored-therapy.

Impact of CYP2D6 polymorphisms on endoxifen concentrations and breast cancer outcomes.

We investigated the impact of germline CYP2D6 genotyping done using the non-tumor specimen on endoxifen concentrations and/or clinical outcomes in breast cancer (BC) patients treated with tamoxifen in published studies. We evaluated published data from 13 001 patients in 29 studies. Mean±s.d. endoxifen concentrations were significantly lower in poor metabolizers (PM) versus extensive metabolizers (EM) (8.8±7.2 versus 22.3±11.8 ng ml-1; P<0.05). The PM status did not influence clinical outcomes in majority of the studies. However, only one study followed the Gaedigk activity scoring for phenotypic assignments, which predicted recurrence-free survival in CYP2D6 poor metabolizers. In two independent studies with 1676 patients, low endoxifen concentrations predicted poor BC-free survival. From our review of published data we found that standardization of CYP2D6 genotype-phenotype classification is needed in order to ensure effective evaluation of associations between CYP2D6 polymorphisms and endoxifen concentrations and BC outcomes. Universal implementation of this standardization classification system should be a priority among researchers and laboratories. Furthermore, additional clinical research is warranted to determine whether patients with CYP2D6 PM phenotypes or low endoxifen levels will have better clinical outcomes with increased tamoxifen dosing compared to standard dosing.

Impact of CYP2D6 Polymorphism on Steady-State Plasma Levels of Risperidone and 9-Hydroxyrisperidone in Thai Children and Adolescents with Autism Spectrum Disorder.

The purpose of this study was to investigate the influence of CYP2D6 gene polymorphisms on plasma concentrations of risperidone and its metabolite in Thai children and adolescents with autism spectrum disorder (ASD). All 97 autism spectrum disorder patients included in this study had been receiving risperidone at least for 1 month. The CYP2D6 genotypes were determined by real-time polymerase chain reaction (PCR)-based allelic discrimination for CYP2D6*4, *10, and *41 alleles. Plasma concentrations of risperidone and 9-hydroxyrisperidone were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Among the 97 patients, the most important nonfunctional alleles (CYP2D6*4 and *5) were detected, whereas the most common allele was CYP2D6*10 (55.9%). CYP2D6 genotyping revealed 90 (92.78%) patients to be extensive metabolizers (EM) and 7 (7.22%) to be intermediate metabolizers (IM). Plasma levels of risperidone were significantly higher in individuals with CYP2D6*5/*10 (p = 0.02), CYP2D6*10/*10 (p = 0.04), and CYP2D6*10/*41 (p = 0.04). Additionally, the plasma concentration of risperidone/9-OH risperidone ratio in patients with a CYP2D6 activity score of 0.5 were significantly higher than those with a CYP2D6 activity score of 2 (p = 0.04). Conversely, no significant influence was found among CYP2D6 polymorphisms, plasma concentrations of 9-hydroxyrisperidone, and the total active moiety. This is the first study to investigate the effects of CYP2D6 genetic polymorphisms on the plasma concentrations of risperidone in Thai children with ASD. The findings indicate that CYP2D6 polymorphisms affect the plasma concentrations of risperidone and the risperidone/9-hydroxyrisperidone ratio. Genetic screening for CYP2D6 polymorphisms could help to predict unexpected adverse events caused by the higher plasma concentration of risperidone.

Impact of CYP2D6 polymorphisms on clinical efficacy and tolerability of metoprolol tartrate.

Metoprolol is a selective β-1 adrenergic receptor blocker that undergoes extensive metabolism by the polymorphic enzyme, CYP2D6. Our objective was to investigate the influence of CYP2D6 polymorphisms on efficacy and tolerability of metoprolol tartrate. 281 study participants with uncomplicated hypertension received 50 mg of metoprolol twice daily followed by response guided titration to 100 mg twice daily. Phenotypes were assigned based on results of CYP2D6 genotyping and copy number variation assays. Clinical response to metoprolol and adverse effect rates were analyzed in relation to CYP2D6 phenotypes by using appropriate statistical tests. Heart rate response differed significantly by CYP2D6 phenotype (p-value <0.0001) with poor metabolizers & intermediate metabolizers showing greater HR reduction. However, blood pressure response and adverse effect rates were not significantly different by CYP2D6 phenotype. Other than a significant difference in heart rate response, CYP2D6 polymorphisms were not a determinant of the variability in response or tolerability to metoprolol.

The impact of CYP2D6 polymorphisms on the pharmacokinetics of codeine and its metabolites in Mongolian Chinese subjects

Codeine is an analgesic drug acting on μ-opioid receptors predominantly via its metabolite morphine formed almost exclusively by CYP2D6. Genetic polymorphisms in CYP2D6 are associated with diminished pain relief and/or severe opioid side effects. In Chinese individuals, CYP2D6*10 is the most common allele with reduced enzyme activity. In this study, we investigated the effect of this allele on the pharmacokinetics of codeine and its metabolites. A blood sample was collected from healthy Mongolian volunteers for CYP2D6 genotyping using a PCR-RFLP assay. A pharmacokinetic study was then carried out in three groups with CYP2D6*1/*1 (n=10), CYP2D6*1/*10 (n=10) and CYP2D6*10/*10 (n=9) genotypes by collecting serial blood samples for determination of plasma levels of codeine and its metabolites, morphine, morphine 3-glucuronide (M3G) and morphine 6-glucuronide (M6G) before and after a single 30-mg oral dose of codeine phosphate. Codeine and its metabolites were measured by LC-MS/MS. No significant differences were observed in the pharmacokinetic parameters of codeine in the three genotype groups. However, the C( max) and AUC(0-∞) of morphine, M3G and M6G were significantly different between the study groups (P<0.05). Compared with the *1/*1 group, the AUC(0-∞) for morphine in the *1/*10 and *10/*10 groups decreased by ratios (95 % CI) of 0.93 (0.26-1.59) and 0.494 (0.135-0.853) respectively. Corresponding ratios for M3G were 0.791 (0.294-1.288) and 0.615 (0.412-0.818) and for M6G were 0.643 (0.39-0.957) and 0.423 (0.267-0.579). This study demonstrates that the CYP2D6*10 allele plays an important role in the pharmacokinetics of the O-demethylated metabolites of codeine after oral administration.

CYP2D6 Genotype and Tamoxifen Activity: Understanding Interstudy Variability in Methodological Quality

There has been great controversy over the years regarding the impact of CYP2D6 polymorphisms on the efficacy of tamoxifen in women with breast cancer. The most significant publication to date is the 2009 publication from investigators in Stuttgart and the Mayo Clinic, a 1325 patient study published in JAMA.1 Despite this high-impact publication, there has been variable acceptance of these results due to inconsistent replication of these findings.2

Impact of CYP2D6 Polymorphisms on Tamoxifen Responses of Women with Breast Cancer: A Microarray-based Study in Thailand

This study was designed to investigate the frequency of CYP2D6 polymorphisms and evaluate the association between genetic polymorphisms of CYP2D6 and tamoxifen therapeutic outcome in Thai breast cancer patients. We recruited 48 breast cancer patients who received adjuvant tamoxifen for evaluating CYP2D6 genetic polymorphisms using microarray-based technology. Associations between genotypes-phenotypes and disease free survival were analyzed. Median follow up time was 5.6 years. The mean age of the subjects was 50 years. The 3 common allelic frequencies were 43.8% (*10), 36.5 (*1) and 10.4% (*2) which are related to extensive metabolizer (EM) and intermediate metabolizer (IM) with 70.8% and 29.2 %, respectively. No association between CYP2D6 genotypes and DFS was demonstrated. Nevertheless, exploratory analysis showed statistically significant shorter DFS in the IM group of post-menopause patients (HR, 6.85; 95% CI, 1.48 -31.69; P = 0.005). Furthermore, we observed statistically significant shorter DFS of homozygous CYP2D6*10 when compared with heterozygous CYP2D6*10 and other genotypes (P=0.005). CYP2D6*10 was the most common genotype in our subjects. Post-menopause patients with homozygous CYP2D6*10 and IM have shorter DFS. To confirm this relationship, larger samples and comprehensively designed trials in Thailand are required.

Impact of CYP2D6 polymorphism on tamoxifen therapy: where are we?

Tamoxifen is a mainstay in the treatment of hormone-receptor sensitive breast cancer. To be effective, it needs conversion into 4-hydroxy-tamoxifen and endoxifen. The key enzyme involved is encoded by the gene CYP2D6 of which several, sometimes population-specific alleles are known. Corresponding enzyme variants may result in poor, intermediate, and extensive metabolization and therefore different steady-state plasma levels of active metabolites. Those are hypothesized to be linked to clinical outcomes of tamoxifen therapy. However, a wealth of mostly retrospective cohort studies came up with conflicting results. Appraisal of these studies is difficult and a metaanalysis impossible due to heterogeneity of patient populations, disease factors, treatment modalities, and measured outcomes. As standardization would not overcome intrinsic limitations of retrospective analyses, prospective trials comparing genotype-guided versus unsighted tamoxifen treatment are required to prove whether routine CYP2D6 genotyping is clinically effective and cost-effective.

Impact of CYP2D6 polymorphisms on the pharmacokinetics of lovastatin in Chinese subjects

Although CYP3A4/5 enzymes play the predominant role in the metabolism of simvastatin and lovastatin, polymorphisms in CYP2D6 were reported to be associated with the cholesterol-lowering effect and/or tolerability of simvastatin. This study was performed to examine whether common CYP2D6 polymorphisms affect the pharmacokinetics of lovastatin, which is taken as the inactive prodrug lovastatin lactone and converted to active lovastatin acid. A single-dose pharmacokinetic study was performed with lovastatin in 23 Chinese healthy male subjects. Plasma concentrations of lovastatin lactone and acid were determined by an LC-MS-MS method in samples collected over 24h after single oral doses of 40-mg lovastatin. Compared with the CYP2D6 wt/wt group, the area under the plasma concentration-time curve (AUC(0-∞)) values for lovastatin lactone increased (P < 0.01) by average ratios (95% CI) of 1.57 (1.01-2.45), 2.11 (1.36-3.29), 2.52 (1.47-4.32), and 5.84 (3.16-10.78) in the wt/*10, *10/*10, *10/*5, and *5/*5 groups, and the values of lovastatin lactone plasma clearance (CL/F) were reduced on average (95% CI) by 40.4% (10.2-60.5%), 53.1% (29.3-68.9%), 63.8% (40.2-78.1%) and 84.2% (72.1-91.1%) in these genotype groups respectively. The pharmacokinetics of lovastatin acid did not differ among the genotype groups. This study demonstrates that CYP2D6 polymorphisms appeared to influence the disposition of lovastatin lactone in these subjects.

Tramadol disposition in the very young: an attempt to assess in vivo cytochrome P-450 2D6 activity

Tramadol is potentially a very useful pain relief medication in neonates and infants. It is primarily metabolized into O-demethyl tramadol (M1) by CYP2D6. Data concerning tramadol disposition and CYP2D6 activity in young infants are not available. A population pharmacokinetic analysis of tramadol and M1 time-concentration profiles was undertaken using non-linear mixed-effects models (NONMEM), based on newly collected data on tramadol and M1 time-concentration profiles in neonates and young infants (n=20) and published studies on intravenous tramadol in children and adults. M1 formation served as a surrogate for CYP2D6 activity. Tramadol clearance was described using a two-compartment linear model with zero-order input and first-order elimination. Clearance increased from 25 weeks post-conception age (PCA) (5.52 litre h(-1) [70 kg](-1)) to reach 84% of the mature value by 44 weeks PCA (standardized to a 70 kg adult using allometric '1/4 power' models). The central volume of distribution decreased from 25 weeks PCA (256 litre [70 kg](-1)) to reach 120% of its mature value by 87 weeks PCA. Formation clearance to M1 contributed 43% of tramadol clearance, but had no relationship with PCA. There was a weak non-linear relationship between PCA and M1 metabolite clearance. Maturational clearance of tramadol is almost complete by 44 weeks PCA. A target concentration of 300 microg litre(-1) is achieved after a bolus of tramadol hydrochloride 1 mg kg(-1) and can be maintained by infusion of tramadol hydrochloride 0.09 mg kg(-1) h(-1) at 25 weeks PCA, 0.14 mg kg(-1) h(-1) at 30 weeks PCA, 0.17 mg kg(-1) h(-1) at 35 weeks PCA, 0.18 mg kg(-1) h(-1) at 40 weeks, 0.19 mg kg(-1) h(-1) at 50 weeks PCA to 1 yr, 0.18 mg kg(-1) h(-1) at 3 yr and 0.12 mg kg(-1) h(-1) in adulthood. CYP2D6 activity was observed as early as 25 weeks PCA, but the impact of CYP2D6 polymorphism on the variability in pharmacokinetics, metabolism and pharmacodynamics of tramadol remains to be established.