Impact of STAT6 Variants on the Response to Proton Pump Inhibitors and Comorbidities in Patients with Eosinophilic Esophagitis.

Proton pump inhibitors (PPIs) are the first-line drug for eosinophilic esophagitis (EoE), although it is estimated that there is a lack of histological remission in 50% of patients. This research aimed to identify pharmacogenetic biomarkers predictive of PPI effectiveness and to study their association with disease features. Peak eosinophil count (PEC) and the endoscopic reference score (EREFS) were determined before and after an eight-week PPI course in 28 EoE patients. The impact of the signal transducer and activator of transcription 6 (STAT6), CYP2C19, CYP3A4, CYP3A5, and ABCB1 genetic variations on baseline PEC and EREFS, their reduction and histological response, and on EoE symptoms and comorbidities was analyzed. PEC reduction was higher in omeprazole-treated patients (92.5%) compared to other PPIs (57.9%, p = 0.003). STAT6 rs12368672 (g.18453G>C) G/G genotype showed higher baseline PEC values compared to G/C and C/C genotypes (83.2 vs. 52.9, p = 0.027). EREFS reduction in STAT6 rs12368672 G/G and G/C genotypes was higher than in the C/C genotype (36.7% vs. -75.0% p = 0.011). However, significance was lost after Bonferroni correction. Heartburn incidence was higher in STAT6 rs167769 (g.27148G>A) G/G patients compared to G/A (54.55% vs. 11.77%, p = 0.030). STAT6 rs12368672G>C and rs167769G>A variants might have a relevant impact on EoE status and PPI response. Further research is warranted to clarify the clinical relevance of these variants.

Use of Exposure Data to Establish Causality in Drug-Adverse Event Relationships: An Example with Desvenlafaxine.

Causality algorithms help establish relationships between drug use and adverse event (AE) occurrence. High drug exposure leads to a higher likelihood of an AE being classified as an adverse drug reaction (ADR). However, there is a knowledge gap regarding what concentrations are predictive of ADRs, as this has not been systematically studied. In this work, the Spanish Pharmacovigilance System (SEFV) algorithm was used to define the relationship between the AE occurrence and drug administration in 178 healthy volunteers participating in five desvenlafaxine single-dose clinical trials, a selective serotonin and norepinephrine reuptake inhibitor that may cause dizziness, headache, nausea, dry mouth, constipation and hyperhidrosis. Eighty-three subjects presented 172 AEs that were classified as possible (101), conditional (31), unrelated (24) and probable (16). AUC∞ and Cmax were significantly higher in volunteers with vs. without ADRs (5981.24 ng·h/mL and 239.06 ng/mL and 4770.84 ng·h/mL and 200.69 ng/mL, respectively). Six of 19 subjects with conditional AEs with an SEFV score of 3 points presented an AUC∞ ≥ 6500 ng·h/mL or a Cmax ≥ 300 ng/mL (i.e., above percentile 75) and were summed one point on their SEFV score and classified as "possible" (4 points), improving the capacity of ADR detection.

Characterization of Reference Materials for DPYD: A GeT-RM Collaborative Project.

The DPYD gene encodes dihydropyrimidine dehydrogenase (DPD), which is involved in the catalysis of uracil and thymine, as well as 5-fluorouracil (5-FU), which is used to treat solid tumors. Patients with decreased DPD activity are at risk of serious, sometimes fatal, adverse drug reactions to this important cancer drug. Pharmacogenetic testing for DPYD is increasingly provided by clinical and research laboratories; however, only a limited number of quality control and reference materials are currently available for clinical DPYD testing. To address this need, the Division of Laboratory Systems, Centers for Disease Control and Prevention-based Genetic Testing Reference Materials Coordination Program, in collaboration with members of the pharmacogenetic testing and research communities and the Coriell Institute for Medical Research, has characterized 33 DNA samples derived from Coriell cell lines for DPYD. Samples were distributed to four volunteer laboratories for genetic testing using a variety of commercially available and laboratory-developed tests. Sanger sequencing was used by one laboratory and publicly available whole-genome sequence data from the 1000 Genomes Project were used by another to inform genotype. Thirty-three distinct DPYD variants were identified among the 33 samples characterized. These publicly available and well-characterized materials can be used to support the quality assurance and quality control programs of clinical laboratories performing clinical pharmacogenetic testing.

Impact of CYP2D6 and CYP2B6 phenotypes on the response to tramadol in patients with acute post-surgical pain.

Tramadol is an important minor opioid prescribed for pain management. In this study, we analyzed the well-known impact of CYP2D6 genetic variation and 60 additional variants in eight candidate genes (i.e., ABCG2, SLCO1B1, CYP2D6, CYP2B6, CYP2C19, CYP2C9, CYP3A5, and CYP3A4) on tramadol efficacy and safety. Some 108 patients with pain after surgery admitted to a post-anesthesia care unit (PACU) and prescribed tramadol were recruited. They were genotyped, and tramadol M1/M2 metabolite concentrations were determined by a newly validated HPLC-MS/MS method. CYP2D6 intermediate (IM) and poor (PM) metabolizers showed lower M1 concentrations adjusted for dose/weight at 30 and 120 min compared to ultrarapid (UM) and normal (NM) metabolizers (univariate p < 0.001 and 0.020, multivariate p < 0.001 and 0.001, unstandardized ß coefficients = 0.386 and 0.346, R2 = 0.146 and 0.120, respectively). CYP2B6 PMs (n = 10) were significantly related to a higher reduction in pain 30 min after tramadol intake (univariate p = 0.038, multivariate p = 0.016, unstandardized ß coefficient = 0.224, R2 = 0.178), to lower PACU admission time (p = 0.007), and to lower incidence of adverse drug reactions (p = 0.038) compared to the other phenotypes. CYP3A4 IMs and PMs showed a higher prevalence of drowsiness and dizziness (p = 0.028 and 0.005, respectively). Our results suggest that the interaction of CYP2B6 and CYP2D6 phenotypes may be clinically relevant, pending validation of these results in large, independent cohorts. Additional research is required to clarify the impact of CYP3A4 genetic variation on tramadol response.

Genetic variation in UGT1A1 is not associated with altered liver biochemical parameters in healthy volunteers participating in bioequivalence trials.

Introduction: Bioequivalence clinical trials are conducted in healthy volunteers whose blood tests should be within normal limits; individuals with Gilbert syndrome (GS) are excluded from these studies on suspicion of any liver disease, even if the change is clinically insignificant. GS is a benign genetic disorder characterized by elevated bilirubin levels, the primary cause of which is the presence of polymorphisms in UGT1A1 gene. In this work, subjects with UGT1A1 intermediate (IM) or poor (PM) metabolizer genotype-informed phenotypes were investigated to determine whether they have a higher incidence of liver disease or other biochemical parameters. Methods: The study population comprised 773 healthy volunteers who underwent biochemical analysis at baseline and at the end of the study which were genotyped for UGT1A1*80 (rs887829), as an indicator of UGT1A1*80+*28 (rs887829 and rs3064744), and UGT1A1*6 (rs4148323). Results: Bilirubin levels were higher in subjects IMs and PMs compared to normal metabolizers (NMs). Decreased uric acid levels was observed in PMs compared to NMs. No associations were observed in liver enzyme levels according to UGT1A1 phenotype. Discussion: Considering that there is no hepatic toxicity in subjects with UGT1A1 IM or PM phenotype, who are more likely to develop GS, this study suggests that they could be included in bioequivalence clinical trials as their biochemical parameters are not affected outside normal ranges.

Estrogens prevent the hypothalamus-periphery crosstalk induced by olanzapine intraperitoneal treatment in female mice: Effects on brown/beige adipose tissues and liver.

Olanzapine (OLA) is a highly obesogenic second-generation antipsychotic (SGA). Recently we demonstrated that, contrarily to OLA oral treatment, intraperitoneal (i.p.) administration resulted in weight loss and absence of hepatic steatosis in wild-type (WT) and protein tyrosine phosphatase 1B (PTP1B)-deficient (KO) male mice. This protection relied on two central-peripheral axes connecting hypothalamic AMPK with brown/inguinal white adipose tissue (BAT/iWAT) uncoupling protein-1 (UCP-1) and hypothalamic JNK with hepatic fatty acid synthase (FAS). Herein, we addressed OLA i.p. treatment effects in WT and PTP1B-KO female mice. Contrarily to our previous results in WT females receiving OLA orally, the i.p. treatment did not induce weight gain or hyperphagia. Molecularly, in females OLA failed to diminish hypothalamic phospho-AMPK or elevate BAT UCP-1 and energy expenditure (EE) despite the preservation of iWAT browning. Conversely, OLA i.p. treatment in ovariectomized mice reduced hypothalamic phospho-AMPK, increased BAT/iWAT UCP-1 and EE, and induced weight loss as occurred in males. Pretreatment of hypothalamic neurons with 17ß-estradiol (E2) abolished OLA effects on AMPK. Moreover, neither hypothalamic JNK activation nor hepatic FAS upregulation were found in WT and PTP1B-KO females receiving OLA via i.p. Importantly, this axis was reestablished upon ovariectomy. In this line, E2 prevented OLA-induced phospho-JNK in hypothalamic neurons. These results support the role of estrogens in sex-related dimorphism in OLA treatment. This study evidenced the benefit of OLA i.p. administration in preventing its obesogenic effects in female mice that could offer clinical value.

SLCO1B1 and ABCG2 genotype-informed phenotypes are related to variation in ramipril exposure.

Ramipril is an angiotensin-converting enzyme inhibitor used for hypertension and heart failure management. To date, scarce literature is available on pharmacogenetic associations affecting ramipril. The goal of this study was to investigate the effect of 120 genetic variants in 34 pharmacogenes (i.e., genes encoding for enzymes like CYPs or UGTs and transporters like ABC or SLC) on ramipril pharmacokinetic variability and adverse drug reaction (ADR) incidence. Twenty-nine healthy volunteers who had participated in a single-dose bioequivalence clinical trial of two formulations of ramipril were recruited. A univariate and multivariate analysis searching for associations between genetic variants and ramipril pharmacokinetics was performed. SLCO1B1 and ABCG2 genotype-informed phenotypes strongly predicted ramipril exposure. Volunteers with the SLCO1B1 decreased function (DF) phenotype presented around 1.7-fold higher dose/weight-corrected area under the curve (AUC/DW) than volunteers with the normal function (NF) phenotype (univariate p-value [puv] < 0.001, multivariate p-value [pmv] < 0.001, ß = 0.533, R2 = 0.648). Similarly, volunteers with ABCG2 DF + poor function (PF) phenotypes presented around 1.6-fold higher AUC/DW than those with the NF phenotype (puv = 0.011, pmv < 0.001, ß = 0.259, R2 = 0.648). Our results suggest that SLCO1B1 and ABCG2 are important transporters to ramipril pharmacokinetics, and their genetic variation strongly alters its pharmacokinetics. Further studies are required to confirm these associations and their clinical relevance.

PharmVar GeneFocus: CYP4F2.

The Pharmacogene Variation Consortium (PharmVar) serves as a global repository providing star (*) allele nomenclature for the polymorphic human CYP4F2 gene. CYP4F2 genetic variation impacts the metabolism of vitamin K, which is associated with warfarin dose requirements, and the metabolism of drugs, such as imatinib or fingolimod, and certain endogenous compounds including vitamin E and eicosanoids. This GeneFocus provides a comprehensive overview and summary of CYP4F2 genetic variation including the characterization of 14 novel star alleles, CYP4F2*4 through *17. A description of how haplotype information cataloged by PharmVar is utilized by the Pharmacogenomics Knowledgebase (PharmGKB) and the Clinical Pharmacogenetics Implementation Consortium (CPIC) is also provided.

Clinical Pharmacogenetics Implementation Consortium Guideline for CYP2B6 Genotype and Methadone Therapy.

Methadone is a mu (µ) opioid receptor agonist used clinically in adults and children to manage opioid use disorder, neonatal abstinence syndrome, and acute and chronic pain. It is typically marketed as a racemic mixture of R- and S-enantiomers. R-methadone has 30-to 50-fold higher analgesic potency than S-methadone, and S-methadone has a greater adverse effect (prolongation) on the cardiac QTc interval. Methadone undergoes stereoselective metabolism. CYP2B6 is the primary enzyme responsible for catalyzing the metabolism of both enantiomers to the inactive metabolites, S- and R-2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (S- and R-EDDP). Genetic variation in the CYP2B6 gene has been investigated in the context of implications for methadone pharmacokinetics, dose, and clinical outcomes. Most CYP2B6 variants result in diminished or loss of CYP2B6 enzyme activity, which can lead to higher plasma methadone concentrations (affecting S- more than R-methadone). However, the data do not consistently indicate that CYP2B6-based metabolic variability has a clinically significant effect on methadone dose, efficacy, or QTc prolongation. Expert analysis of the published literature does not support a change from standard methadone prescribing based on CYP2B6 genotype (updates at www.cpicpgx.org).