Prospective assessment of patient-reported outcomes and estradiol and drug concentrations in patients experiencing toxicity from adjuvant aromatase inhibitors.

PURPOSE: Aromatase inhibitors (AI), which decrease circulating estradiol concentrations in post-menopausal women, are associated with toxicities that limit adherence. Approximately one-third of patients will tolerate a different AI after not tolerating the first. We report the effect of crossover from exemestane to letrozole or vice versa on patient-reported outcomes (PROs) and whether the success of crossover is due to lack of estrogen suppression. METHODS: Post-menopausal women enrolled on a prospective trial initiating AI therapy for early-stage breast cancer were randomized to exemestane or letrozole. Those that discontinued for intolerance were offered protocol-directed crossover to the other AI after a washout period. Changes in PROs, including pain [Visual Analog Scale (VAS)] and functional status [Health Assessment Questionnaire (HAQ)], were compared after 3 months on the first versus the second AI. Estradiol and drug concentrations were measured. RESULTS: Eighty-three patients participated in the crossover protocol, of whom 91.3% reported improvement in symptoms prior to starting the second AI. Functional status worsened less after 3 months with the second AI (HAQ mean change AI #1: 0.2 [SD 0.41] vs. AI #2: -0.05 [SD 0.36]; p = 0.001); change in pain scores was similar between the first and second AI (VAS mean change AI #1: 0.8 [SD 2.7] vs. AI #2: -0.2 [SD 2.8]; p = 0.19). No statistical differences in estradiol or drug concentrations were found between those that continued or discontinued AI after crossover. CONCLUSIONS: Although all AIs act via the same mechanism, a subset of patients intolerant to one AI report improved PROs with a different one. The mechanism of this tolerance remains unknown, but does not appear to be due to non-adherence to, or insufficient estrogen suppression by, the second AI.

Effects of exemestane and letrozole therapy on plasma concentrations of estrogens in a randomized trial of postmenopausal women with breast cancer.

PURPOSE: Inter-individual differences in estrogen concentrations during treatment with aromatase inhibitors (AIs) may contribute to therapeutic response and toxicity. The aim of this study was to determine plasma concentrations of estradiol (E2), estrone (E1), and estrone sulfate (E1S) in a large cohort of AI-treated breast cancer patients. METHODS: In a randomized, multicenter trial of postmenopausal women with early-stage breast cancer starting treatment with letrozole (n = 241) or exemestane (n = 228), plasma estrogen concentrations at baseline and after 3 months were quantitated using a sensitive mass spectrometry-based assay. Concentrations and suppression below the lower limit of quantification (LLOQ) were compared between estrogens and between drugs. RESULTS: The ranges of baseline estrogen concentrations were

Inhibition of Cytochrome P450 2B6 Activity by Voriconazole Profiled Using Efavirenz Disposition in Healthy Volunteers.

Cytochrome P450 2B6 (CYP2B6) metabolizes clinically important drugs and other compounds. Its expression and activity vary widely among individuals, but quantitative estimation is hampered by the lack of safe and selective in vivo probes of CYP2B6 activity. Efavirenz, a nonnucleoside HIV-1 reverse transcriptase inhibitor, is mainly cleared by CYP2B6, an enzyme strongly inhibited in vitro by voriconazole. To test efavirenz metabolism as an in vivo probe of CYP2B6 activity, we quantified the inhibition of CYP2B6 activity by voriconazole in 61 healthy volunteers administered a single 100-mg oral dose of efavirenz with and without voriconazole administration. The kinetics of efavirenz metabolites demonstrated formation rate-limited elimination. Compared to control, voriconazole prolonged the elimination half-life (t1/2) and increased both the maximum concentration of drug in serum (Cmax) and the area under the concentration-time curve from 0 h to t (AUC0-t) of efavirenz (mean change of 51%, 36%, and 89%, respectively) (P < 0.0001) with marked intersubject variability (e.g., the percent change in efavirenz AUC0-t ranged from 0.4% to ∼224%). Voriconazole decreased efavirenz 8-hydroxylation by greater than 60% (P < 0.0001), whereas its effect on 7-hydroxylation was marginal. The plasma concentration ratio of efavirenz to 8-hydroxyefavirenz, determined 1 to 6 h after dosing, was significantly increased by voriconazole and correlated with the efavirenz AUC0-t (Pearson r = >0.8; P < 0.0001). This study demonstrates the mechanisms of voriconazole-efavirenz interaction, establishes the use of a low dose of efavirenz as a safe and selective in vivo probe for phenotyping CYP2B6 activity, and identifies several easy-to-use indices that should enhance understanding of the mechanisms of CYP2B6 interindividual variability. (This study is registered at ClinicalTrials.gov under identifier NCT01104376.).

Patient-Reported Outcomes and Early Discontinuation in Aromatase Inhibitor-Treated Postmenopausal Women With Early Stage Breast Cancer.

BACKGROUND: Early discontinuation of aromatase inhibitors (AIs) is common and leads to poor outcomes but is challenging to predict. In the Exemestane and Letrozole Pharmacogenetics trial, a high rate of early discontinuation due to intolerance was observed. We hypothesized that early changes in patient-reported outcomes (PROs) predict AI discontinuation and that biochemical factors are associated with changes in PROs. PATIENTS AND METHODS: Postmenopausal women with early-stage breast cancer enrolled in a prospective randomized trial of exemestane versus letrozole completed questionnaires at baseline and serially over 24 months to assess overall quality of life (EuroQOL Visual Analog Scale [VAS]); mood; and multiple symptoms, including a musculoskeletal symptom cluster. A joint mixed-effects/survival model was used to estimate the effect of the change in PROs on AI discontinuation. Associations between biochemical factors and change in PROs were examined. RESULTS: A total of 490 patients were analyzed. Worsening of EuroQOL VAS and the musculoskeletal cluster were associated with the highest risk for early discontinuation (hazard ratio [HR], 2.77 [95% confidence interval (CI), 2.72-2.81; p = .015]; HR, 4.39 [95% CI, 2.40-8.02; p < .0001], respectively). Pharmacokinetics and estrogen metabolism were not consistently associated with change in PRO measures. No clinically significant differences in any PRO between AIs were observed. CONCLUSION: Changes in PROs early during AI therapy were associated with treatment discontinuation. Identification of these changes could be used to target interventions in patients at high risk for early discontinuation. IMPLICATIONS FOR PRACTICE: Early changes in patient-reported outcomes (PROs) can predict nonpersistence to aromatase inhibitor therapy. If used in clinical practice, PROs might identify women at highest risk for early discontinuation and allow for interventions to improve tolerance before significant toxicities develop. Further research is needed to improve capturing PROs in routine clinical practice.

Tamoxifen Dose Escalation in Patients With Diminished CYP2D6 Activity Normalizes Endoxifen Concentrations Without Increasing Toxicity.

BACKGROUND: Polymorphic CYP2D6 is primarily responsible for metabolic activation of tamoxifen to endoxifen. We previously reported that by increasing the daily tamoxifen dose to 40 mg/day in CYP2D6 intermediate metabolizer (IM), but not poor metabolizer (PM), patients achieve endoxifen concentrations similar to those of extensive metabolizer patients on 20 mg/day. We expanded enrollment to assess the safety of CYP2D6 genotype-guided dose escalation and investigate concentration differences between races. METHODS: PM and IM breast cancer patients currently receiving tamoxifen at 20 mg/day were enrolled for genotype-guided escalation to 40 mg/day. Endoxifen was measured at baseline and after 4 months. Quality-of-life data were collected using the Functional Assessment of Cancer Therapy-Breast (FACT-B) and Breast Cancer Prevention Trial Menopausal Symptom Scale at baseline and after 4 months. RESULTS: In 353 newly enrolled patients, genotype-guided dose escalation eliminated baseline concentration differences in IM (p = .08), but not PM (p = .009), patients. Endoxifen concentrations were similar in black and white patients overall (p = .63) and within CYP2D6 phenotype groups (p > .05). In the quality-of-life analysis of 480 patients, dose escalation did not meaningfully diminish quality of life; in fact, improvements were seen in several measures including the FACT Breast Cancer subscale (p = .004) and limitations in range of motion (p < .0001) in IM patients. CONCLUSION: Differences in endoxifen concentration during treatment can be eliminated by doubling the tamoxifen dose in IM patients, without an appreciable effect on quality of life. Validation of the association between endoxifen concentration and efficacy or prospective demonstration of improved efficacy is necessary to warrant clinical uptake of this personalized treatment strategy. IMPLICATIONS FOR PRACTICE: This secondary analysis of a prospective CYP2D6 genotype-guided tamoxifen dose escalation study confirms that escalation to 40 mg/day in patients with low-activity CYP2D6 phenotypes (poor or intermediate metabolizers) increases endoxifen concentrations without any obvious increases in treatment-related toxicity. It remains unknown whether endoxifen concentration is a useful predictor of tamoxifen efficacy, and thus, there is no current role in clinical practice for CYP2D6 genotype-guided tamoxifen dose adjustment. If future studies confirm the importance of endoxifen concentrations for tamoxifen efficacy and report a target concentration, this study provides guidance for a dose-adjustment approach that could maximize efficacy while maintaining patient quality of life.

Cypiripi: exact genotyping of CYP2D6 using high-throughput sequencing data.

MOTIVATION: CYP2D6 is highly polymorphic gene which encodes the (CYP2D6) enzyme, involved in the metabolism of 20-25% of all clinically prescribed drugs and other xenobiotics in the human body. CYP2D6 genotyping is recommended prior to treatment decisions involving one or more of the numerous drugs sensitive to CYP2D6 allelic composition. In this context, high-throughput sequencing (HTS) technologies provide a promising time-efficient and cost-effective alternative to currently used genotyping techniques. To achieve accurate interpretation of HTS data, however, one needs to overcome several obstacles such as high sequence similarity and genetic recombinations between CYP2D6 and evolutionarily related pseudogenes CYP2D7 and CYP2D8, high copy number variation among individuals and short read lengths generated by HTS technologies. RESULTS: In this work, we present the first algorithm to computationally infer CYP2D6 genotype at basepair resolution from HTS data. Our algorithm is able to resolve complex genotypes, including alleles that are the products of duplication, deletion and fusion events involving CYP2D6 and its evolutionarily related cousin CYP2D7. Through extensive experiments using simulated and real datasets, we show that our algorithm accurately solves this important problem with potential clinical implications. AVAILABILITY AND IMPLEMENTATION: Cypiripi is available at http://sfu-compbio.github.io/cypiripi.

A new Suzuki synthesis of triphenylethylenes that inhibit aromatase and bind to estrogen receptors α and ß.

The design and synthesis of dual aromatase inhibitors/selective estrogen receptor modulators (AI/SERMs) is an attractive strategy for the discovery of new breast cancer therapeutic agents. Previous efforts led to the preparation of norendoxifen (4) derivatives with dual aromatase inhibitory activity and estrogen receptor binding activity. In the present study, some of the structural features of the potent AI letrozole were incorporated into the lead compound (norendoxifen) to afford a series of new dual AI/SERM agents based on a symmetrical diphenylmethylene substructure that eliminates the problem of E,Z isomerization encountered with norendoxifen-based AI/SERMs. Compound 12d had good aromatase inhibitory activity (IC50=62.2nM) while also exhibiting good binding activity to both ER-α (EC50=72.1nM) and ER-ß (EC50=70.8nM). In addition, a new synthesis was devised for the preparation of norendoxifen and its analogues through a bis-Suzuki coupling strategy.

Comparative risk of ischemic stroke among users of clopidogrel together with individual proton pump inhibitors.

BACKGROUND AND PURPOSE: There is controversy and little information about whether individual proton pump inhibitors (PPIs) differentially alter the effectiveness of clopidogrel in reducing ischemic stroke risk. We, therefore, aimed to elucidate the risk of ischemic stroke among concomitant users of clopidogrel and individual PPIs. METHODS: We conducted a propensity score-adjusted cohort study of adult new users of clopidogrel, using 1999 to 2009 Medicaid claims from 5 large states. Exposures were defined by prescriptions for esomeprazole, lansoprazole, omeprazole, rabeprazole, and pantoprazole-with pantoprazole serving as the referent. The end point was hospitalization for acute ischemic stroke, defined by International Classification of Diseases Ninth Revision Clinical Modification codes in the principal position on inpatient claims, within 180 days of concomitant therapy initiation. RESULTS: Among 325 559 concomitant users of clopidogrel and a PPI, we identified 1667 ischemic strokes for an annual incidence of 2.4% (95% confidence interval, 2.3-2.5). Adjusted hazard ratios for ischemic stroke versus pantoprazole were 0.98 (0.82-1.17) for esomeprazole; 1.06 (0.92-1.21) for lansoprazole; 0.98 (0.85-1.15) for omeprazole; and 0.85 (0.63-1.13) for rabeprazole. CONCLUSIONS: PPIs of interest did not increase the rate of ischemic stroke among clopidogrel users when compared with pantoprazole, a PPI thought to be devoid of the potential to interact with clopidogrel.

Associations between genetic variants and the effect of letrozole and exemestane on bone mass and bone turnover.

Adjuvant therapy for hormone receptor (HR) positive postmenopausal breast cancer patients includes aromatase inhibitors (AI). While both the non-steroidal AI letrozole and the steroidal AI exemestane decrease serum estrogen concentrations, there is evidence that exemestane may be less detrimental to bone. We hypothesized that single nucleotide polymorphisms (SNP) predict effects of AIs on bone turnover. Early stage HR-positive breast cancer patients were enrolled in a randomized trial of exemestane versus letrozole. Effects of AI on bone mineral density (BMD) and bone turnover markers (BTM), and associations between SNPs in 24 candidate genes and changes in BMD or BTM were determined. Of the 503 enrolled patients, paired BMD data were available for 123 and 101 patients treated with letrozole and exemestane, respectively, and paired BTM data were available for 175 and 173 patients, respectively. The mean change in lumbar spine BMD was significantly greater for letrozole-treated (-3.2 %) compared to exemestane-treated patients (-1.0 %) (p = 0.0016). Urine N-telopeptide was significantly increased in patients treated with exemestane (p = 0.001) but not letrozole. Two SNPs (rs4870061 and rs9322335) in ESR1 and one SNP (rs10140457) in ESR2 were associated with decreased BMD in letrozole-treated patients. In the exemestane-treated patients, SNPs in ESR1 (Rs2813543) and CYP19A1 (Rs6493497) were associated with decreased bone density. Exemestane had a less negative impact on bone density compared to letrozole, and the effects of AI therapy on bone may be impacted by genetic variants in the ER pathway.

In vivo assessment of the metabolic activity of CYP2D6 diplotypes and alleles.

AIMS: A prospectively enrolled patient cohort was used to assess whether the prediction of CYP2D6 phenotype activity from genotype data could be improved by reclassification of diplotypes or alleles. METHODS: Three hundred and fifty-five patients receiving tamoxifen 20 mg were genotyped for CYP2D6 and tamoxifen metabolite concentrations were measured. The endoxifen : N-desmethly-tamoxifen metabolic ratio, as a surrogate of CYP2D6 activity, was compared across four diplotypes (EM/IM, EM/PM, IM/IM, IM/PM) that are typically collapsed into an intermediate metabolizer (IM) phenotype. The relative metabolic activity of each allele type (UM, EM, IM, and PM) and each EM and IM allele was estimated for comparison with the activity scores typically assigned, 2, 1, 0.5 and 0, respectively. RESULTS: Each of the four IM diplotypes have distinct CYP2D6 activity from each other and from the EM and PM phenotype groups (each P < 0.05). Setting the activity of an EM allele at 1.0, the relative activities of a UM, IM and PM allele were 0.85, 0.67 and 0.52, respectively. The activity of the EM alleles were statistically different (P < 0.0001), with the CYP2D6*2 allele (scaled activity = 0.63) closer in activity to an IM than an EM allele. The activity of the IM alleles were also statistically different (P = 0.014). CONCLUSION: The current systems for translating CYP2D6 genotype into phenotype are not optimally calibrated, particularly in regards to IM diplotypes and the *2 allele. Additional research is needed to improve the prediction of CYP2D6 activity from genetic data for individualized dosing of CYP2D6 dependent drugs.

Platelet factor XIIIa release during platelet aggregation and plasma clot strength measured by thrombelastography in patients with coronary artery disease treated with clopidogrel.

It has been estimated that up to half of circulating factor XIIIa (FXIIIa) is stored in platelets. The release of FXIIIa from platelets upon stimulation with adenosine diphosphate (ADP) in patients with coronary artery disease treated with dual antiplatelet therapy has not been previously examined. Samples from 96 patients with established coronary artery disease treated with aspirin and clopidogrel were examined. Platelet aggregation was performed by light transmittance aggregometry in platelet-rich plasma (PRP), with platelet-poor plasma (PPP) as reference, and ADP 5 µM as agonist. Kaolin-activated thrombelastography (TEG) was performed in citrate PPP. PRP after aggregation was centrifuged and plasma supernatant (PSN) collected. FXIIIa was measured in PPP and PSN. Platelet aggregation after stimulation with ADP 5 µM resulted in 24% additional FXIIIa release in PSN as compared to PPP (99.3 ± 27 vs. 80.3 ± 24%, p < 0.0001). FXIIIa concentration in PSN correlated with maximal plasma clot strength (TEG-G) (r = 0.48, p < 0.0001), but not in PPP (r = 0.15, p = 0.14). Increasing quartiles of platelet-derived FXIIIa were associated with incrementally higher TEG-G (p = 0.012). FXIIIa release was similar between clopidogrel responders and non-responders (p = 0.18). In summary, platelets treated with aspirin and clopidogrel release a significant amount of FXIIIa upon aggregation by ADP. Platelet-derived FXIIIa may contribute to differences in plasma TEG-G, and thus, in part, provide a mechanistic explanation for high clot strength observed as a consequence of platelet activation. Variability in clopidogrel response does not significantly influence FXIIIa release from platelets.

Breast cancer treatment and ovarian failure: risk factors and emerging genetic determinants.

Most premenopausal women diagnosed with primary breast cancer receive adjuvant chemotherapy, and many experience chemotherapy-induced ovarian failure (CIOF). CIOF is associated with menopausal symptoms, fertility concerns and long-term implications including bone loss. Ironically, CIOF might confer a disease-specific benefit to women whose breast cancers express hormone receptors. Risk factors of CIOF include the woman's age at the time of therapy, and the type, dose and schedule of chemotherapy. Because inherited genetic factors have an important role in determining who will experience CIOF, genetic testing has the potential to provide optimal counselling about risks and possible interventions.

The dual role of pharmacogenetics in HIV treatment: mutations and polymorphisms regulating antiretroviral drug resistance and disposition.

Significant intra- and interindividual variability has been observed in response to use of pharmacological agents in treatment of HIV infection. Treatment of HIV infection is limited by high rates of adverse drug reactions and development of resistance in a significant proportion of patients as a result of suboptimal drug concentrations. The efficacy of antiretroviral therapy is challenged by the emergence of resistant HIV-1 mutants with reduced susceptibility to antiretroviral drugs. Moreover, pharmacotherapy of patients infected with HIV is challenging because a great number of comorbidities increase polypharmacy and the risk for drug-drug interactions. Drug-metabolizing enzymes and drug transporters regulate drug access to the systemic circulation, target cells, and sanctuary sites. These factors, which determine drug exposure, along with the emergence of mutations conferring resistance to HIV medications, could explain variability in efficacy and adverse drug reactions associated with antiretroviral drugs. In this review, the major factors affecting the disposition of antiretroviral drugs, including key drug-metabolizing enzymes and membrane drug transporters, are outlined. Genetic polymorphisms affecting the activity and/or the expression of cytochromes P450 or UGT isozymes and membrane drug transport proteins are highlighted and include such examples as the association of neurotoxicity with efavirenz, nephrotoxicity with tenofovir, hepatotoxicity with nevirapine, and hyperbilirubinemia with indinavir and atazanavir. Mechanisms of drug resistance conferred by specific viral mutations are also reviewed, with particular attention to replicative viral fitness and transmitted HIV drug resistance with the objectives of providing a better understanding of mechanisms involved in HIV drug resistance and helping health care providers to better manage interpatient variability in drug efficacy and toxicity.

A genome-wide association study identifies locus at 10q22 associated with clinical outcomes of adjuvant tamoxifen therapy for breast cancer patients in Japanese.

Although many association studies of polymorphisms in candidate genes with the clinical outcomes of breast cancer patients receiving adjuvant tamoxifen therapy have been reported, genetic factors determining individual response to tamoxifen are not fully understood. To identify genetic polymorphisms associated with clinical outcomes of patients with tamoxifen treatment, we conducted a genome-wide association study (GWAS). We studied 462 Japanese patients with hormone receptor-positive, invasive breast cancer receiving adjuvant tamoxifen therapy. Of them, 240 patients were analyzed by genome-wide genotyping using the Illumina Human610-Quad BeadChips, and two independent sets of 105 and 117 cases were used for replication studies. In the GWAS, we detected significant associations with recurrence-free survival at 15 single-nucleotide polymorphisms (SNPs) on nine chromosomal loci (1p31, 1q41, 5q33, 7p11, 10q22, 12q13, 13q22, 18q12 and 19p13) that satisfied a genome-wide significant threshold (log-rank P= 2.87 × 10(-9)-9.41 × 10(-8)). Among them, rs10509373 in C10orf11 gene on 10q22 was significantly associated with recurrence-free survival in the replication study (log-rank P= 2.02 × 10(-4)) and a combined analysis indicated a strong association of this SNP with recurrence-free survival in breast cancer patients treated with tamoxifen (log-rank P= 1.26 × 10(-10)). Hazard ratio per C allele of rs10509373 was 4.51 [95% confidence interval (CI), 2.72-7.51; P= 6.29 × 10(-9)]. In a combined analysis of rs10509373 genotype with previously identified genetic makers, CYP2D6 and ABCC2, the number of risk alleles of these three genes had cumulative effects on recurrence-free survival among 345 patients receiving tamoxifen monotherapy (log-rank P= 2.28 × 10(-12)). In conclusion, we identified a novel locus associated with recurrence-free survival in Japanese breast cancer patients receiving adjuvant tamoxifen therapy.

Patient-reported symptoms and discontinuation of adjuvant aromatase inhibitor therapy.

BACKGROUND: Aromatase inhibitor (AI) therapy results in substantial survival benefits for patients with hormone receptor-positive breast cancer. The rates of poor adherence and discontinuation of AI therapy are high, primarily because of treatment-related toxicities like musculoskeletal pain. Although pain-related symptoms may worsen during AI therapy, the authors hypothesized that nonpersistence with AI therapy was associated with symptoms that were present before treatment initiation. METHODS: Postmenopausal women initiating AI therapy who were enrolled in a prospective clinical trial completed questionnaires at baseline to assess sleep, fatigue, mood, and pain. Reasons for treatment discontinuation during the first year of treatment were recorded. Associations between baseline patient-reported symptoms and treatment discontinuation because of toxicity were identified using logistic regression. RESULTS: Four hundred forty-nine patients were evaluable. The odds of treatment discontinuation were higher in patients who reported a greater number of symptoms before AI initiation. Baseline poor sleep quality was associated with early treatment discontinuation, with an odds ratio (OR) of 1.91 (95% confidence interval [CI], 1.26-2.89; P = .002). Baseline presence of tired feeling and forgetfulness had similar ORs for discontinuation (tired feeling: OR, 1.76; 95% CI, 1.15-2.67; P = .009; forgetfulness: OR, 1.66; 95% CI, 1.11-2.48; P = .015). An increasing total number of baseline symptoms was associated with an increased likelihood of treatment discontinuation, with an OR of 1.89 (95% CI, 1.20-2.96; P = .006) for 3 to 5 symptoms versus 0 to 2 symptoms. CONCLUSIONS: Symptom clusters in breast cancer survivors that are present before the initiation of adjuvant AI therapy may have a negative impact on a patient's persistence with therapy. Interventions to manage these symptoms may improve breast cancer outcomes and quality of life.

One size fits one: pharmacogenetics in gastroenterology.

Individual variability in response and development of adverse effects to drugs is a major challenge in clinical practice. Pharmacogenomics refers to the aspect of personalized medicine where the patient's genetic information instructs the selection and dosage of therapy while also predicting its adverse effects profile. Sequencing of the entire human genome has given us the opportunity to study commonly used drugs as well as newer therapeutic agents in a new light, opening up opportunities for better drug efficacy and decreased adverse effects. This article highlights developments in pharmacogenomics, relates these to practice of gastroenterology, and outlines roadblocks in translation of this knowledge into clinical practice.

Citalopram and escitalopram plasma drug and metabolite concentrations: genome-wide associations.

AIMS: Citalopram (CT) and escitalopram (S-CT) are among the most widely prescribed selective serotonin reuptake inhibitors used to treat major depressive disorder (MDD). We applied a genome-wide association study to identify genetic factors that contribute to variation in plasma concentrations of CT or S-CT and their metabolites in MDD patients treated with CT or S-CT. METHODS: Our genome-wide association study was performed using samples from 435 MDD patients. Linear mixed models were used to account for within-subject correlations of longitudinal measures of plasma drug/metabolite concentrations (4 and 8 weeks after the initiation of drug therapy), and single-nucleotide polymorphisms (SNPs) were modelled as additive allelic effects. RESULTS: Genome-wide significant associations were observed for S-CT concentration with SNPs in or near the CYP2C19 gene on chromosome 10 (rs1074145, P = 4.1 × 10(-9) ) and with S-didesmethylcitalopram concentration for SNPs near the CYP2D6 locus on chromosome 22 (rs1065852, P = 2.0 × 10(-16) ), supporting the important role of these cytochrome P450 (CYP) enzymes in biotransformation of citalopram. After adjustment for the effect of CYP2C19 functional alleles, the analyses also identified novel loci that will require future replication and functional validation. CONCLUSIONS: In vitro and in vivo studies have suggested that the biotransformation of CT to monodesmethylcitalopram and didesmethylcitalopram is mediated by CYP isozymes. The results of our genome-wide association study performed in MDD patients treated with CT or S-CT have confirmed those observations but also identified novel genomic loci that might play a role in variation in plasma levels of CT or its metabolites during the treatment of MDD patients with these selective serotonin reuptake inhibitors.

Factor XIII Val34Leu polymorphism and recurrent myocardial infarction in patients with coronary artery disease.

Factor XIII (FXIII) is necessary for cross linking of fibrin strands and generation of stable fibrin clot. FXIII Val34Leu is a common genetic single nucleotide polymorphism that has been associated with accelerated fibrin stabilization and reduced rate of fibrinolysis. The contribution of Val34Leu to long term risk of recurrent myocardial infarction (MI) in patients with coronary stenting has not been conclusively established. The objective of the study was to examine the effects of Val34Leu on fibrin generation, platelet aggregation, and long term clinical outcomes in patients with coronary artery disease treated with dual antiplatelet therapy. Patients with angiographically documented coronary artery disease who were treated with aspirin and clopidogrel were enrolled (n = 211). Light transmittance aggregometry and plasma fibrin clot formation using thrombelastography (TEG) were determined. Genotyping of Val34Leu was performed using Taqman assay. Clinical events during follow up were recorded. Homozygous carriers of 34 Leu variant had significantly shorter fibrin clot formation time as compared to wild type individuals (TEG K: 1.27 ± 0.3 vs. 1.68 ± 1.1 min, p = 0.011). The Val34Leu variant was associated with gene dose dependent increased risk of MI (log rank, p = 0.002) or occurrence of composite of MI and CV death (log rank, p = 0.005) with highest event rates observed in homozygous carriers of 34 Leu. In summary, FXIII Val34Leu polymorphism was associated with increased rate of fibrin stabilization in homozygous carriers of the variant and may increase risk of recurrent MI and death in patients with angiographically established coronary artery disease treated with dual antiplatelet therapy.

Substantial effect of efavirenz monotherapy on bilirubin levels in healthy volunteers.

BACKGROUND: Efavirenz exhibits multiple interactions with drug-metabolizing enzymes and transporters, and for this reason efavirenz-based HIV therapy is associated with altered pharmacokinetics of coadministered drugs. Probably by the same mechanism, efavirenz-based HIV therapy affects the disposition of endogenous compounds, but this effect is difficult to directly link with efavirenz because it is used in combination with other drugs. OBJECTIVES: To explore the effect of efavirenz monotherapy on biochemical laboratory values in a clinical trial of healthy volunteers. METHODS: Men and women (aged 18-49 years) with body mass index ≤32 who were assessed to be healthy based on medical history, physical examination, and standard laboratory screening received a single (600 mg) and multiple doses (600 mg/d for 17 days) of efavirenz orally. This trial was designed to determine the pharmacokinetics and drug interactions of efavirenz. As part of this study, analysis of serum chemistries that were measured at study entry (screening) and 1 week after completion of the multiple dose study (exit) is reported. RESULTS: Data from 60 subjects who fully completed and 13 subjects who partially completed the study are presented. Total bilirubin was substantially reduced at exit (by ~30%, with large intersubject variability) compared with screening values (P < 0.0001). The percent changes were in part explained by the intersubject differences in baseline total bilirubin because there was a significant correlation between baseline (screening) values and percent change at exit (r = 0.50; P < 0.0001). Hemoglobin and absolute neutropenia were also substantially decreased at exit compared with screening, but this may be due to intensive blood sampling rather than direct effect of efavirenz on these parameters. No significant correlation was found between percent change in hemoglobin versus percent change in bilirubin, indicating the effect of efavirenz on bilirubin is independent of its effects on hemoglobin. CONCLUSIONS: Efavirenz monotherapy significantly lowers plasma total bilirubin concentration in healthy volunteers independent of its effect on hemoglobin, probably through its effects on bilirubin metabolism and transport (uptake and efflux). These findings help explain reversal by efavirenz of hyperbilirubinemia induction observed by some protease inhibitor antiretroviral drugs (eg, atazanavir). Besides its well-documented role on drug interactions, efavirenz may alter the disposition of endogenous compounds relevant in physiologic homeostasis through its interaction with drug metabolizing enzymes and/or drug transporters. ClinicalTrials.gov identifier: NCT00668395.

An integrated pharmacokinetics ontology and corpus for text mining.

BACKGROUND: Drug pharmacokinetics parameters, drug interaction parameters, and pharmacogenetics data have been unevenly collected in different databases and published extensively in the literature. Without appropriate pharmacokinetics ontology and a well annotated pharmacokinetics corpus, it will be difficult to develop text mining tools for pharmacokinetics data collection from the literature and pharmacokinetics data integration from multiple databases. DESCRIPTION: A comprehensive pharmacokinetics ontology was constructed. It can annotate all aspects of in vitro pharmacokinetics experiments and in vivo pharmacokinetics studies. It covers all drug metabolism and transportation enzymes. Using our pharmacokinetics ontology, a PK-corpus was constructed to present four classes of pharmacokinetics abstracts: in vivo pharmacokinetics studies, in vivo pharmacogenetic studies, in vivo drug interaction studies, and in vitro drug interaction studies. A novel hierarchical three level annotation scheme was proposed and implemented to tag key terms, drug interaction sentences, and drug interaction pairs. The utility of the pharmacokinetics ontology was demonstrated by annotating three pharmacokinetics studies; and the utility of the PK-corpus was demonstrated by a drug interaction extraction text mining analysis. CONCLUSIONS: The pharmacokinetics ontology annotates both in vitro pharmacokinetics experiments and in vivo pharmacokinetics studies. The PK-corpus is a highly valuable resource for the text mining of pharmacokinetics parameters and drug interactions.