Uncoupling of Cytochrome P450 2B6 and stimulation of reactive oxygen species production in pharmacogenomic alleles affected by interethnic variability.

Cytochrome P450 mediated substrate metabolism is generally characterized by the formation of reactive intermediates. In vitro and in vivo reaction uncoupling, results in the accumulation and dissociation of reactive intermediates, leading to increased ROS formation. The susceptibility towards uncoupling and altered metabolic activity is partly modulated by pharmacogenomic alleles resulting in amino acid substitutions. A large variability in the prevalence of these alleles has been demonstrated in CYP2B6, with some being predominantly unique to African populations. The aim of this study is to characterize the uncoupling potential of recombinant CYP2B6*1, CYP2B6*6 and CYP2B6*34 metabolism of specific substrates. Therefore, functional effects of these alterations on enzyme activity were determined by quantification of bupropion, efavirenz and ketamine biotransformation using HPLC-MS/MS. Determination of H2O2 levels was performed by the AmplexRed/horseradish peroxidase assay. Our studies of the amino acid substitutions Q172H, K262R and R487S revealed an exclusive use of the peroxide shunt for the metabolism of bupropion and ketamine by CYP2B6*K262R. Ketamine was also identified as a trigger for the peroxide shunt in CYP2B6*1 and all variants. Concurrently, ketamine acted as an uncoupler for all enzymes. We further showed that the expressed CYP2B6*34 allele results in the highest H2O2 formation. We therefore conclude that the reaction uncoupling and peroxide shunt are directly linked and can be substrate specifically induced with K262R carriers being most likely to use the peroxide shunt and R487S carrier being most prone to reaction uncoupling. This elucidates the functional diversity of pharmacogenomics in drug metabolism and safety.

Identification and comparison of sex-specific serious adverse drug reactions in spontaneous reports and systematically collected reports (ADRED).

AIMS: Adverse drug reactions (ADRs) are known to show sex-specific differences in occurrence and phenotype. The aim of this study was to analyse sex-specific differences in ADR-drug combinations that required hospitalization based on two different datasets. METHODS: We performed a complementary analysis of (i) spontaneously reported (n = 12 564, female = 51.7%) and (ii) systematically collected ADR reports from a prospective multicentre observational study (ADRED, n = 2355, female = 48.2%) from Germany in the ADR database EudraVigilance (EV). Both datasets were analysed separately concerning the suspected drugs, ADRs and ADR-drug combinations more frequently reported for females or males by calculating reporting odds ratios (ROR) with 95% confidence intervals. ADR-drug combinations more frequently reported for either females or males in EV reports were related to prescription data. Finally, the results from both datasets were discussed with regard to their (dis-)concordance. RESULTS: In both datasets, some antineoplastic agents and nervous system drugs were found to be reported more often for females than males (RORs ranging from 1.5 [1.1-2.1] for quetiapine in spontaneous reports to 41.3 [13.1-130.0] for trastuzumab in spontaneous reports). ADRs of the respiratory system, and haemorrhages were described predominantly for males in both datasets. In spontaneous reports the ADR-drug combination self-injurious behaviour-quetiapine was more often reported for females without and with consideration of drug prescriptions (ROR: 3.8 [1.3-11.0]). Quetiapine and psychiatric disorders (superordinate level) was exclusively reported for females in ADRED reports. CONCLUSIONS: Our results can contribute to raise awareness and further knowledge regarding sex-specific ADRs. The findings require further in-depth investigation.

Association between miRNA signatures in serum samples from epidermal growth factor inhibitor treated patients and skin toxicity.

OBJECTIVE: Epidermal growth factor receptor inhibitors (EGFRI) are used as targeted cancer therapy. On average 70% of patients treated with EGFRIs suffer from skin toxicity. Studies showed a correlation between overall survival and the appearance of a skin rash, which is used as a biomarker for therapy efficacy. Micro RNAs (miRNA) as tumor or resistance biomarkers for cancer therapy are also highly investigated. In our study, we searched for associations of miRNA expression profiles in serum, with the severity of skin rash, in order to identify tentative therapy predictive biomarkers. MATERIALS AND METHODS: Five candidate miRNAs were selected, based on an earlier in vitro next-generation-sequencing-experiment and after literature search. MiR-21, miR-31, miR-17, miR-106b and miR-520e were investigated in serum samples from patients (n = 254) treated with EGFRI. The quantitative expression of miRNA was tested for association with the occurrence/severity of the rash. RESULTS: In our cohort of patients treated with EGFR inhibiting monoclonal antibodies, miR-21 and miR-520e serum concentrations were negatively correlated with severity of skin rash (p-value 0.000582 and 1.53e-07 linear-trend-test) whereas for miR-31, a positive correlation was observed (p-value 9.01e-06 linear-trend-test). CONCLUSIONS: This suggests that miR-21, miR-31 and miR-520e expression might be a treatment dependent marker for EGFRI induced skin rash.

Subtherapeutic bupropion and hydroxybupropion serum concentrations in a patient with CYP2C19*1/*17 genotype suggesting a rapid metabolizer status.

Bupropion is hydroxylated to its primary active metabolite hydroxybupropion by cytochrome P450 enzyme CYP2B6. In vitro data suggest the existence of alternative hydroxylation pathways mediated by the highly polymorphic enzyme CYP2C19. However, the impact of its genetic variants on bupropion metabolism in vivo is still under investigation. We report the case of a 28-year-old male Caucasian outpatient suffering from major depressive disorder who did not respond to a treatment with bupropion. Therapeutic drug monitoring revealed very low serum concentrations of both bupropion and hydroxybupropion. Genotyping identified a heterozygous status for the gain-of-function allele with the genotype CYP2C19*1/*17 predicting enhanced enzymatic activity. The present case shows a reduced bupropion efficacy, which may be explained by a reduced active moiety of bupropion and its active metabolite hydroxybupropion, due to alternative hydroxylation pathways mediated by CYP2C19 in an individual with CYP2C19 rapid metabolizer status. The case report thus illustrates the clinical relevance of therapeutic drug monitoring in combination with pharmacogenetics diagnostics for a personalized treatment approach.

Angioedemas associated with renin-angiotensin system blocking drugs: Comparative analysis of spontaneous adverse drug reaction reports.

INTRODUCTION: Angioedema is a subcutaneous swelling typically affecting the face, larynx or pharynx. It is a known adverse drug reaction (ADR) of ACE inhibitors (ACEi), angiotensin-II-receptor blockers (ARBs) and aliskiren (renin inhibitor). Several studies have reported pathophysiological mechanisms and risk factors of ACEi-associated angioedemas, whereas little is known for ARBs and aliskiren. The aim of the study was to analyze comparatively ACEi versus ARBs and aliskiren angioedema reports contained in the European ADR database EudraVigilance with regard to reported risk factors and clinical phenotypes. METHODS: All spontaneous angioedema reports received between 01/2010-06/2017 reporting either an ACEi, ARB, or aliskiren as "suspected/interacting" drug were identified using the Standardized MedDRA Query "angioedema (narrow)". In order to perform a comparative analysis, odds ratios (ORs) were calculated for angioedema reports of ACEi (n = 3.194) versus ARBs (n = 687) and aliskiren (n = 162). RESULTS: More patients with a history of allergy were included in angioedema reports of ARBs (6.8%) and aliskiren (13.6%) versus ACEi (4.3%). "Urticaria" as an ADR was reported more frequently in angioedema reports of ARBs (18.5%) and aliskiren (9.0%) versus ACEi (5.0%). ACEi-associated angioedemas were more often designated as "life-threatening" compared to ARBs (OR 2.2 [1.6-2.9]) and aliskiren-associated angioedemas (OR 14.2 (3.5-57.4). Concomitant therapy with mTOR inhibitors (OR 4.3 [1.0-17.9]) and fibrinolytics (OR 7.8 [1.1-57.2]) was reported more often in ACEi versus ARBs angioedema reports. CONCLUSION: The reported clinical phenotypes differed between ACEi versus ARBs and aliskiren angioedema reports. Differences between the patient populations as observed in our study or differences with regard to underlying pathomechanisms could account for this finding. Due to the methodological limitations of spontaneous reporting systems, we cannot draw a firm conclusion in this regard. Hence, further research is necessary to confirm our observation and elucidate the underyling causes.

Potential Drug-Drug Interactions in a Cohort of Elderly, Polymedicated Primary Care Patients on Antithrombotic Treatment.

INTRODUCTION: Drug-drug interactions (DDIs) are an important risk factor for adverse drug reactions. Older, polymedicated patients are particularly affected. Although antithrombotics have been detected as high-risk drugs for DDIs, data on older patients exposed to them are scarce. METHODS: Baseline data of 365 IDrug study outpatients (≥ 60 years, use of an antithrombotic and one or more additional long-term drug) were analyzed regarding potential drug-drug interactions (pDDIs) with a clinical decision support system. Data included prescription and self-medication drugs. RESULTS: The prevalence of having one or more pDDI was 85.2%. The median number of alerts per patient was three (range 0-17). For 58.4% of the patients, potential severe/contraindicated interactions were detected. Antiplatelets and non-steroidal anti-inflammatory drugs (NSAIDs) showed the highest number of average pDDI alert involvements per use (2.9 and 2.2, respectively). For NSAIDs, also the highest average number of severe/contraindicated alert involvements per use (1.2) was observed. 91.8% of all pDDI involvements concerned the 25 most frequently used drug classes. 97.5% of the severe/contraindicated pDDIs were attributed to only nine different potential clinical manifestations. The most common management recommendation for severe/contraindicated pDDIs was to intensify monitoring. Number of drugs was the only detected factor significantly associated with increased number of pDDIs (p < 0.001). CONCLUSION: The findings indicate a high risk for pDDIs in older, polymedicated patients on antithrombotics. As a consequence of patients' frequently similar drug regimens, the variety of potential clinical manifestations was small. Awareness of these pDDI symptoms and the triggering drugs as well as patients' self-medication use may contribute to increased patient safety.

Population nutrikinetics of green tea extract.

Green tea polyphenols may contribute to the prevention of cancer and other diseases. To learn more about the pharmacokinetics and interindividual variation of green tea polyphenols after oral intake in humans we performed a population nutrikinetic study of standardized green tea extract. 84 healthy participants took green tea extract capsules standardized to 150 mg epigallocatechin-gallate (EGCG) twice a day for 5 days. On day 5 catechin plasma concentrations were analyzed using non-compartmental and population pharmacokinetic methods. A strong between-subject variability in catechin pharmacokinetics was found with maximum plasma concentrations varying more than 6-fold. The AUCs of EGCG, EGC and ECG were 877.9 (360.8-1576.5), 35.1 (8.0-87.4), and 183.6 (55.5-364.6) h*µg/L respectively, and the elimination half lives were 2.6 (1.8-3.8), 3.9 (0.9-10.7) and 1.8 (0.8-2.9) h, respectively. Genetic polymorphisms in genes of the drug transporters MRP2 and OATP1B1 could at least partly explain the high variability in pharmacokinetic parameters. The observed variability in catechin plasma levels might contribute to interindividual variation in benefical and adverse effects of green tea polyphenols. Our data could help to gain a better understanding of the causes of variability of green tea effects and to improve the design of studies on the effects of green tea polyphenols in different health conditions. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01360320.

Individualized versus standardized risk assessment in patients at high risk for adverse drug reactions (IDrug) - study protocol for a pragmatic randomized controlled trial.

BACKGROUND: Elderly patients are particularly vulnerable to adverse drug reactions, especially if they are affected by additional risk factors such as multimorbidity, polypharmacy, impaired renal function and intake of drugs with high risk potential. Apart from these clinical parameters, drug safety and efficacy can be influenced by pharmacogenetic factors. Evidence-based recommendations concerning drug-gene-combinations have been issued by international consortia and in drug labels. However, clinical benefit of providing information on individual patient factors in a comprehensive risk assessment aiming to reduce the occurrence and severity of adverse drug reactions is not evident. Purpose of this randomized controlled trial is to compare the effect of a concise individual risk information leaflet with standard information on risk factors for side effects. METHODS/DESIGN: The trial was designed as a prospective, two-arm, randomized, controlled, multicenter, pragmatic study. 960 elderly, multimorbid outpatients in general medicine are included if they take at least one high risk and one other long-term drug (polymedication). As high risk "index drugs" oral anticoagulants and antiplatelets were chosen because of their specific, objectively assessable side effects. Following randomization, test group patients receive an individualized risk assessment leaflet evaluating their personal data concerning bleeding- and thromboembolic-risk-scores, potential drug-drug-interactions, age, renal function and pharmacogenetic factors. Control group patients obtain a standardized leaflet only containing general information on these criteria. Follow-up period is 9 months for each patient. Primary endpoint is the occurrence of a thromboembolic/bleeding event or death. Secondary endpoints are other adverse drug reactions, hospital admissions, specialist referrals and medication changes due to adverse drug reactions, the patients' adherence to medication regimen as well as health related quality of life, mortality and resulting costs. DISCUSSION: Despite extensive evidence of risk factors for adverse drug reactions, there are few prospective trial data about an individualized risk assessment including pharmacogenetic information to increase patient safety. By conducting a health economic analysis, we will evaluate if the application of an individualized drug therapy in daily routine is cost-effective. TRIAL REGISTRATION: German Clinical Trials Register: DRKS00006256 , date of registration 09/01/15.

Cytokine regulation by epidermal growth factor receptor inhibitors and epidermal growth factor receptor inhibitor associated skin toxicity in cancer patients.

AIM: Epidermal growth factor receptor inhibitor (EGFRI) induced skin toxicity has a prognostic value suggesting skin toxicity can be a useful surrogate marker for successful epidermal growth factor receptor (EGFR) inhibition, improved response and survival. But the pathophysiology of EGFRI induced skin toxicity remains elusive. However the involvement of immunological mechanisms has been speculated. This study investigates the possible underlying mechanism of EGFR inhibition associated cytokine production in keratinocytes as well as in patients after treatment with epidermal growth factor receptor inhibitors (EGFRIs). METHODS: Normal human epidermal keratinocytes (NHEK) were incubated for 2 and 24h with different concentrations of EGFRI (erlotinib) for Western blot analysis and cytokine expression analysis, respectively. Inhibition of EGFR, extracellular-signal-regulated kinase 1/2 (Erk 1/2) and c-Jun was examined by Western blot analysis. Cytokine concentrations were measured by enzyme-linked immunosorbent assay (ELISA) in the NHEK cell supernatant and also in the serum of 186 cancer patients who are followed up for EGFRI induced skin rash. RESULTS: A significant inhibitory effect of EGFRI was seen on EGFR (Y845), Erk 1/2 and c-Jun in a dose dependent manner. Further downstream, increased CC-chemokine ligand 2 (CCL2), CC-chemokine ligand 5 (CCL5) and decreased interleukin-8 (IL-8) or CXCL8 expression was observed in keratinocytes. In EGFRI treated patients, low levels of serum CXCL8 corresponding to stronger EGFR inhibition were associated with a higher grade of skin toxicity (p=0.0016) and a prolonged overall survival (p=0.018). CONCLUSIONS: The results obtained in this study indicate that EGFRI can regulate cytokines by modulating EGFR signalling pathway in keratinocytes. Moreover, serum levels of CXCL8 in EGFRI treated patients may be important for individual EGFRI induced skin toxicity and patient's survival.

HLA polymorphisms influence the development of skin rash arising from treatment with EGF receptor inhibitors.

AIM: Development of a skin rash under treatment with EGF receptor (EGFR) inhibitors (EGFRIs) has been linked to a favorable prognosis in some studies, suggesting a possible immunological role for EGFRIs in addition to direct antagonistic downstream effects. The present study aimed to investigate whether particular HLA polymorphisms found in cancer patients treated with EGFRIs are associated with the development of skin rash and overall survival rates. PATIENTS & METHODS: HLA typing was performed on 105 cancer patients and the development of skin rash was rated during the first 4 weeks of therapy with EGFRIs. RESULTS: A significantly lower incidence of skin rash was found in patients carrying the HLA-A*02:01 or HLA-A*03:01 alleles (hazard ratio: 0.277; 95% CI: 0.121-0.634; p = 0.002 and hazard ratio: 0.292; 95% CI: 0.113-0.752; p = 0.011, respectively); however, no association with worse survival was seen. CONCLUSION: The chances of developing a skin rash in patients treated with EGFRIs may be lower in patients that carry the HLA-A*02:01 or HLA-A*03:01 alleles, while the antitumor efficacy of EGFRIs does not seem to be significantly impaired in these patients.

Impact of UGT2B7 His268Tyr polymorphism on the outcome of adjuvant epirubicin treatment in breast cancer.

INTRODUCTION: Epirubicin is a common adjuvant treatment for breast cancer. It is mainly eliminated after glucuronidation through uridine diphosphate-glucuronosyltransferase 2B7 (UGT2B7). The present study aimed to describe the impact of the UGT2B7(His268Tyr) polymorphism on invasive disease-free survival in breast cancer patients after epirubicin treatment. METHODS: This is a pharmacogenetic study based on samples collected from 745 breast cancer patients of the Austrian Tumor of breast tissue: Incidence, Genetics, and Environmental Risk factors (TIGER) cohort who did not present metastases at baseline. This cohort included 205 women with epirubicin-based combination chemotherapy, 113 patients having received chemotherapy without epirubicin and 427 patients having received no chemotherapy at all. Of the epirubicin-treated subgroup, 120 were subsequently treated with tamoxifen. For all women UGT2B7(His268Tyr) was genotyped. Invasive disease-free survival was assessed using Kaplan-Meier and Cox's proportional hazard regression analysis. RESULTS: Among the 205 epirubicin-treated patients, carriers of two UGT2B7(268Tyr) alleles had a mean invasive disease-free survival of 8.6 (95% confidence interval (CI) 7.9 to 9.3) years as compared to 7.5 (95% CI 6.9 to 8.0) years in carriers of at least one UGT2B7(268His) allele (adjusted hazard ratio (HR) = 2.64 (95% CI 1.22 to 5.71); P = 0.014). In addition, the impact of the UGT2B7(His268Tyr) polymorphism became even more pronounced in patients subsequently treated with tamoxifen (adjusted HR = 5.22 (95% CI 1.67 to 26.04); P = 0.015) whereas no such difference in invasive disease-free survival was observed in patients not receiving epirubicin. CONCLUSIONS: Breast cancer patients carrying the UGT2B7(268Tyr/Tyr) genotype may benefit most from adjuvant epirubicin-based chemotherapy. These results warrant confirmation in further studies.

Impact of CYP2D6*4 genotype on progression free survival in tamoxifen breast cancer treatment.

OBJECTIVE: The cytochrome P450 2D6 (CYP2D6) polymorphism was reported to have a significant impact on outcome of tamoxifen treatment in estrogen receptor positive breast cancer patients. The objective of this study was to explore the effect of the CYP2D6*4 polymorphism on tamoxifen treatment outcome in a cohort of patients from a single clinical trial which included women with a history of previous chemotherapy. RESEARCH DESIGN AND METHODS: A total of 493 patients of the Austrian TIGER study receiving adjuvant tamoxifen therapy were studied for this pharmacogenetic interaction. All women with estrogen receptor positive tumors and tamoxifen therapy longer than 6 months were genotyped for CYP2D6*4 using TaqMan technology. Time to tumor progression, defined as local, regional, distant recurrence or contralateral breast cancer and progression free survival, was analyzed. RESULTS: No significant difference in time to tumor progression or progression free survival between the CYP2D6*4 genotype groups in the overall study cohort was found. In a subgroup of patients treated with chemotherapy the CYP2D6*4 poor metabolizers had a tendency towards a shorter mean time to progression. In this group the mean time to tumor progression and the progression free survival were 1.0 years in the CYP2D6*4/*4 group, 6.3 years in the *1/*4 group and 4.97 years in the *1/*1 group (Wilcoxon p = 0.104). CONCLUSION: While earlier data on CYP2D6 and tamoxifen excluded women with prior chemotherapy, the present analysis suggests that CYP2D6*4 genotype might be particularly crucial in this group of high-risk patients. Key limitations are restriction to the CYP2D6*4 allele and missing data of comedication.