Novel Implementation of Genotype-Guided Proton Pump Inhibitor Medication Therapy in Children: A Pilot, Randomized, Multisite Pragmatic Trial

A Pharmacogenetics-Based Approach to Managing Gastroesophageal Reflux Disease: Current Perspectives and Future Steps

Proton pump inhibitors (PPIs) are commonly used medications to treat acid-related conditions, including gastro-esophageal reflux disease (GERD). Gastroenterology guidelines mention the importance of CYP2C19 in PPI metabolism and the influence of CYP2C19 genetic variations on variable responses to PPIs, but do not currently recommend the genotyping of CYP2C19 prior to prescribing PPIs. There are strong data to support the influence of CYP2C19 genetic variations on the pharmacokinetics of PPIs and clinical outcomes. Existing pharmacogenetic guideline recommendations for dose increases focus on H. pylori and erosive esophagitis indications, but PPIs are also the main therapy for treating GERD. Recent data suggest GERD patients being treated with a PPI may also benefit from genotype-guided dosing. We summarize the literature supporting this contention and highlight future directions for improved management of patients with GERD through precision medicine approaches.

Pharmacogenetic Testing for the Pediatric Gastroenterologist: Actionable Drug-Gene Pairs to Know

Gastroenterologists represent some of the earlier adopters of precision medicine through pharmacogenetic testing by embracing upfront genotyping for thiopurine S-methyltransferase nucleotide diphosphatase (TPMT) before prescribing 6-mercaptopurine or azathioprine for the treatment of inflammatory bowel disease. Over the last two decades, pharmacogenetic testing has become more readily available for other genes relevant to drug dose individualization. Common medications prescribed by gastroenterologists for conditions other than inflammatory bowel disease now have actionable guidelines, which can improve medication efficacy and safety; however, a clear understanding of how to interpret the results remains a challenge for many clinicians, precluding wide implementation of genotype-guided dosing for drugs other than 6-mercaptopurine and azathioprine. Our goal is to provide a practical tutorial on the currently available pharmacogenetic testing options and a results interpretation for drug-gene pairs important to medications commonly used in pediatric gastroenterology. We focus on evidence-based clinical guidelines published by the Clinical Pharmacogenetics Implementation Consortium (CPIC^®) to highlight relevant drug-gene pairs, including proton pump inhibitors and selective serotonin reuptake inhibitors and cytochrome P450 (CYP) 2C19, ondansetron and CYP2D6, 6-mercaptopurine and TMPT and Nudix hydrolase 15 (NUDT15), and budesonide and tacrolimus and CYP3A5.

Pharmacogenetic Aspects of Drug Metabolizing Enzymes and Transporters in Pediatric Medicine: Study Progress, Clinical Practice and Future Perspectives

As the activity of certain drug metabolizing enzymes or transporter proteins can vary with age, the effect of ontogenetic and genetic variation on the activity of these enzymes is critical for the accurate prediction of treatment outcomes and toxicity in children. This makes pharmacogenetic research in pediatrics particularly important and urgently needed, but also challenging. This review summarizes pharmacogenetic studies on the effects of genetic polymorphisms on pharmacokinetic parameters and clinical outcomes in pediatric populations for certain drugs, which are commonly prescribed by clinicians across multiple therapeutic areas in a general hospital, organized from those with the most to the least pediatric evidence among each drug category. We also further discuss the research status of the gene-guided dosing regimens and clinical implementation of pediatric pharmacogenetics. More and more drug-gene interactions are demonstrated to have clinical validity for children, and pharmacogenomics in pediatrics have shown evidence-based benefits to enhance the efficacy and precision of existing drug dosing regimens in several therapeutic areas. However, the most important limitation to the implementation is the lack of high-quality, rigorous pediatric prospective clinical studies, so adequately powered interventional clinical trials that support incorporation of pharmacogenetics into the care of children are still needed.

Correlation analysis and prognostic value of miR-29a-3p expression and CYP2C19 genotypes in exfoliated cells from tongue coating of patients with gastroesophageal reflux disease

BACKGROUND

Gastroesophageal reflux disease (GERD) is a highly prevalent and troublesome disease. Several differentially expressed microRNAs (miRNAs) have been found in GERD.

OBJECTIVE

This study was to analyze the correlation of miR-29a-3p expression and CYP2C19 genotypes in exfoliated cells from tongue coating of GERD patients and its prognostic value.

METHODS

Tongue coating specimens were collected from 130 GERD patients and 70 healthy volunteers and their clinical baseline information was recorded. miR-29a-3p expression in exfoliated cells from tongue coating was determined via RT-qPCR, and its diagnostic efficiency on GERD was evaluated via receiver operating characteristic curve. CYP2C19 genotypes and their correlation with miR-29a-3p were analyzed via polymerase chain reaction restriction fragment length polymorphism technique. The adverse events of patients were documented via 12-month follow-up. The impact of miR-29a-3p expression on the healing rate of patients was analyzed via Kaplan-Meier method. Qualification of miR-29a-3p as an independent prognostic factor of GERD patients was analyzed via multivariate Cox regression analysis.

RESULTS

miR-29a-3p was highly-expressed in exfoliated cells from tongue coating of GERD patients. miR-29a-3p expression had high specificity and sensitivity in diagnosing GERD. CYP2C19 genotypes in GERD patients comprised rapid metabolizers, intermedia metabolizers, and poor metabolizers. miR-29a-3p expression showed a correlation with CYP2C19 genotypes. Higher miR-29a-3p expression predicted higher cumulative incidences of adverse outcomes. Highly-expressed miR-29a-3p was an independent prognostic factor for adverse outcomes of GERD patients.

CONCLUSION

High expression of miR-29a-3p aided the diagnosis and predicted poor prognosis of GERD patients.

Effects of obesity on the pharmacology of proton pump inhibitors: current understanding and future implications for patient care and research

INTRODUCTION

In the United States, obesity affects approximately ⅖ adults and ⅕ children, leading to increased risk for comorbidities, like gastroesophageal reflux disease (GERD), treated increasingly with proton pump inhibitors (PPIs). Currently, there are no clinical guidelines to inform PPI dose selection for obesity, with sparse data regarding whether dose augmentation is necessary.

AREAS COVERED

We provide a review of available literature regarding the pharmacokinetics (PK), pharmacodynamics (PD), and/or metabolism of PPIs in children and adults with obesity, as a step toward informing PPI dose selection.

EXPERT OPINION

Published PK data in adults and children are limited to first-generation PPIs and point toward reduced apparent oral drug clearance in obesity, with equipoise regarding obesity impact on drug absorption. Available PD data are sparse, conflicting, and limited to adults. No studies are available to inform the PPI PK→PD relationship in obesity and if/how it differs compared to individuals without obesity. In the absence of data, best practice may be to dose PPIs based on CYP2C19 genotype and lean body weight, so as to avoid systemic overexposure and potential toxicities, while monitoring closely for efficacy.

Progress in research of pathogenesis of refractory gastroesophageal reflux disease

Refractory gastroesophageal reflux disease (rGERD) is a common clinical disease with many pathogenic factors, complex mechanisms, and increasing incidence. At present, scholars believe that the pathogenesis of rGERD is closely related to intra- and extra-esophageal factors. Elucidating the mechanism of rGERD can contribute to the diagnosis and treatment of the disease. This paper summarizes the current progress in the research of the pathogenesis of rGERD, and puts forward our own thoughts and prospects for the disease, in order to provide ideas for the in-depth study of the pathogenesis of rGERD.

Proton Pump Inhibitor Therapy for Eosinophilic Esophagitis: History, Mechanisms, Efficacy, and Future Directions

Over the past decade, the role of proton pump inhibitor (PPI) medication has evolved from a diagnostic tool for Eosinophilic Esophagitis (EoE), by excluding patients with PPI responsive esophageal eosinophilia (PPI-REE), to a therapy for EoE. This transition resulted from the Updated International Consensus Diagnostic Criteria for Eosinophilic Esophagitis: Proceedings of the Appraisal of Guidelines for Research and Evaluation II (AGREE) Conference to support PPI therapy for EoE in children and adults. Additional recent advances have suggested a role for genetic variations that might impact response to PPI therapy for EoE. This review article will explore a brief background of EoE, the evolution of PPI therapy for EoE and its proposed mechanisms, efficacy and safety in children and adults, and considerations for future PPI precision medicine in patients with EoE.

Utility of the 13 C-pantoprazole breath test as a CYP2C19 phenotyping probe for children

The ¹³ C-pantoprazole breath test (PAN-BT) is a safe, non-invasive, in-vivo CYP2C19 phenotyping probe for adults. Our objective was to evaluate PAN-BT performance in children, with a focus on discriminating individuals who, according to guidelines from the Clinical Pharmacology Implementation Consortium (CPIC), would benefit from starting dose escalation vs. reduction for proton pump inhibitors (PPIs). Children (n=65; 6-17 years) genotyped for CYP2C19 variants *2, *3, *4, and *17 received a single oral dose of ¹³ C-pantoprazole. Plasma concentrations of pantoprazole and its metabolites, and changes in exhaled ¹³ CO₂ (termed delta-over-baseline or DOB), were measured 10 times over 8 hours using HPLC-UV and spectrophotometry, respectively. Pharmacokinetic parameters of interest were generated and DOB features derived using feature engineering for the first 180 minutes post-administration. DOB features, age, sex, and obesity status were used to run bootstrap analysis at each timepoint (T_i)  independently. For each iteration, stratified samples were drawn based on genotype prevalence in the original cohort. A random forest was trained, and predictive performance of PAN-BT evaluated. Strong discriminating ability for CYP2C19 intermediate vs. normal/rapid metabolizer phenotype was noted at DOB_T30min (mean sensitivity: 0.522, specificity: 0.784), with consistent model outperformance over a random or a stratified classifier approach at each time-point (p<0.001). With additional refinement and investigation, the test could become a useful and convenient dosing tool in clinic to help identify children who would benefit most from PPI dose escalation vs. dose reduction, in accordance with CPIC guidelines.

Applications for pharmacogenomics in pharmacy practice: A scoping review

BACKGROUND

Pharmacogenomics (PGx) can provide valuable pharmacokinetic and pharmacodynamic information for the pharmacist's assessment of drug therapy, especially within medication therapy management (MTM) services. However, no review has comprehensively mapped the pharmacists' use of PGx in practice-based research. Doing so would allow future researchers, practitioners, and policy-makers to identify the ideal populations and settings for PGx implementation within the pharmacy.

OBJECTIVE

The purpose of this review is to identify the evidence to date of PGx use in pharmacy practice.

METHODS

A scoping review was conducted to find all studied non-oncologic pharmacy practices incorporating PGx testing. Search terms were applied to 5 databases and relevant journals. Characteristics of patients, pharmacy settings, genetic tests, and outcomes were summarized to determine models most likely to benefit patients.

RESULTS

The search identified 43 studies on the use of PGx by pharmacists published between 2007 and 2020. CYP2C19 testing with antiplatelets was the most studied model, found in both community and institutional settings. It also was the most actionable test: approximately 30% of patients have polymorphisms indicating a need for alternative antiplatelets, and identifying these patients can reduce morbidity and mortality by more than 50%. As technology shifts, broader studies using multi-gene panel tests within MTM demonstrate an approximate 50% decrease in emergency visits and hospitalizations in elderly polypharmacy patients. Clinical benefit or drug-gene interactions are also found in other cardiovascular, psychiatric, analgesic, and gastrointestinal indications. No evaluations of actual costs or of pharmacist prescribing within pharmacy-based PGx have been performed. Facilitators towards successful PGx implementation included pharmacist education, collaboration with other healthcare providers, and the use of clinical decision software.

CONCLUSIONS

Pharmacogenomic testing has demonstrated feasibility and improved medication outcomes in pharmacy practice, including in the community pharmacy. Further PGx research should be directed towards pharmacist prescribing, pharmacist education, and pharmacoeconomics.

Providers' perspectives on the clinical utility of pharmacogenomic testing in pediatric patients

Aim: To assess providers' knowledge, attitudes, perceptions, and experiences related to pharmacogenomic (PGx) testing in pediatric patients. Materials & methods: An electronic survey was sent to multidisciplinary healthcare providers at a pediatric hospital. Results: Of 261 respondents, 71.3% were slightly or not at all familiar with PGx, despite 50.2% reporting prior PGx education or training. Most providers, apart from psychiatry, perceived PGx to be at least moderately useful to inform clinical decisions. However, only 26.4% of providers had recent PGx testing experience. Unfamiliarity with PGx and uncertainty about the clinical value of testing were common perceived challenges. Conclusion: Low PGx familiarity among pediatric providers suggests additional education and electronic resources are needed for PGx examples in which data support testing in children.

Prescribing Prevalence of Medications With Potential Genotype-Guided Dosing in Pediatric Patients

Importance

Genotype-guided prescribing in pediatrics could prevent adverse drug reactions and improve therapeutic response. Clinical pharmacogenetic implementation guidelines are available for many medications commonly prescribed to children. Frequencies of medication prescription and actionable genotypes (genotypes where a prescribing change may be indicated) inform the potential value of pharmacogenetic implementation.

Objective

To assess potential opportunities for genotype-guided prescribing in pediatric populations among multiple health systems by examining the prevalence of prescriptions for each drug with the highest level of evidence (Clinical Pharmacogenetics Implementation Consortium level A) and estimating the prevalence of potential actionable prescribing decisions.

Design, Setting, and Participants

This serial cross-sectional study of prescribing prevalences in 16 health systems included electronic health records data from pediatric inpatient and outpatient encounters from January 1, 2011, to December 31, 2017. The health systems included academic medical centers with free-standing children's hospitals and community hospitals that were part of an adult health care system. Participants included approximately 2.9 million patients younger than 21 years observed per year. Data were analyzed from June 5, 2018, to April 14, 2020.

Exposures

Prescription of 38 level A medications based on electronic health records.

Main Outcomes and Measures

Annual prevalence of level A medication prescribing and estimated actionable exposures, calculated by combining estimated site-year prevalences across sites with each site weighted equally.

Results

Data from approximately 2.9 million pediatric patients (median age, 8 [interquartile range, 2-16] years; 50.7% female, 62.3% White) were analyzed for a typical calendar year. The annual prescribing prevalence of at least 1 level A drug ranged from 7987 to 10 629 per 100 000 patients with increasing trends from 2011 to 2014. The most prescribed level A drug was the antiemetic ondansetron (annual prevalence of exposure, 8107 [95% CI, 8077-8137] per 100 000 children). Among commonly prescribed opioids, annual prevalence per 100 000 patients was 295 (95% CI, 273-317) for tramadol, 571 (95% CI, 557-586) for codeine, and 2116 (95% CI, 2097-2135) for oxycodone. The antidepressants citalopram, escitalopram, and amitriptyline were also commonly prescribed (annual prevalence, approximately 250 per 100 000 patients for each). Estimated prevalences of actionable exposures were highest for oxycodone and ondansetron (>300 per 100 000 patients annually). CYP2D6 and CYP2C19 substrates were more frequently prescribed than medications influenced by other genes.

Conclusions and Relevance

These findings suggest that opportunities for pharmacogenetic implementation among pediatric patients in the US are abundant. As expected, the greatest opportunity exists with implementing CYP2D6 and CYP2C19 pharmacogenetic guidance for commonly prescribed antiemetics, analgesics, and antidepressants.

Clinical Pharmacogenetics Implementation Consortium (CPIC) Guideline for CYP2C19 and Proton Pump Inhibitor Dosing

Proton pump inhibitors (PPIs) are widely used for acid suppression in the treatment and prevention of many conditions, including gastroesophageal reflux disease, gastric and duodenal ulcers, erosive esophagitis, Helicobacter pylori infection, and pathological hypersecretory conditions. Most PPIs are metabolized primarily by cytochrome P450 2C19 (CYP2C19) into inactive metabolites, and CYP2C19 genotype has been linked to PPI exposure, efficacy, and adverse effects. We summarize the evidence from the literature and provide therapeutic recommendations for PPI prescribing based on CYP2C19 genotype (updates at www.cpicpgx.org). The potential benefits of using CYP2C19 genotype data to guide PPI therapy include (i) identifying patients with genotypes predictive of lower plasma exposure and prescribing them a higher dose that will increase the likelihood of efficacy, and (ii) identifying patients on chronic therapy with genotypes predictive of higher plasma exposure and prescribing them a decreased dose to minimize the risk of toxicity that is associated with long-term PPI use, particularly at higher plasma concentrations.

Pediatric pharmacogenomics: challenges and opportunities: on behalf of the Sanford Children's Genomic Medicine Consortium

The advent of digital, electronic, and molecular technologies has allowed the study of complete genomes. Integrating this information into drug development has opened the door for pharmacogenomic (PGx) interventions in direct patient care. PGx allows clinicians to better identify drug of choice and optimize dosing regimens based on an individual's genetic characteristics. Integrating PGx into pediatric care is a priority for the Sanford Children's Genomic Medicine Consortium, a partnership of ten children's hospitals across the US committed to the innovation and advancement of genomics in pediatric care. In this white paper, we review the current state of PGx research and its clinical utility in pediatrics, a largely understudied population, and make recommendations for advancing cutting-edge practice in pediatrics.

Design and Early Implementation Successes and Challenges of a Pharmacogenetics Consult Clinic

Pharmacogenetic testing (PGT) is increasingly being used as a tool to guide clinical decisions. This article describes the development of an outpatient, pharmacist-led, pharmacogenetics consult clinic within internal medicine, its workflow, and early results, along with successes and challenges. A pharmacogenetics-trained pharmacist encouraged primary care physicians (PCPs) to refer patients who were experiencing side effects/ineffectiveness from certain antidepressants, opioids, and/or proton pump inhibitors. In clinic, the pharmacist confirmed the need for and ordered CYP2C19 and/or CYP2D6 testing, provided evidence-based pharmacogenetic recommendations to PCPs, and educated PCPs and patients on the results. Operational and clinical metrics were analyzed. In two years, 91 referred patients were seen in clinic (mean age 57, 67% women, 91% European-American). Of patients who received PGT, 77% had at least one CYP2C19 and/or CYP2D6 phenotype that would make conventional prescribing unfavorable. Recommendations suggested that physicians change a medication/dose for 59% of patients; excluding two patients lost to follow-up, 87% of recommendations were accepted. Challenges included PGT reimbursement and referral maintenance. High frequency of actionable results suggests physician education on who to refer was successful and illustrates the potential to reduce trial-and-error prescribing. High recommendation acceptance rate demonstrates the pharmacist's effectiveness in providing genotype-guided recommendations, emphasizing a successful pharmacist-physician collaboration.

How to Transition from Single-Gene Pharmacogenetic Testing to Preemptive Panel-Based Testing: A Tutorial

There have been significant advancements in precision medicine and approaches to medication selection based on pharmacogenetic results. With the availability of direct-to-consumer genetic testing and growing awareness of genetic interindividual variability, patient demand for more precise, individually tailored drug regimens is increasing. The University of Florida (UF) Health Precision Medicine Program (PMP) was established in 2011 to improve integration of genomic data into clinical practice. In the ensuing years, the UF Health PMP has successfully implemented several single-gene tests to optimize the precision of medication prescribing across a variety of clinical settings. Most recently, the UF Health PMP launched a custom-designed pharmacogenetic panel, including pharmacogenes relevant to supportive care medications commonly prescribed to patients undergoing chemotherapy treatment, referred to as "GatorPGx." This tutorial provides guidance and information to institutions on how to transition from the implementation of single-gene pharmacogenetic testing to a preemptive panel-based testing approach. Here, we demonstrate application of the preemptive panel in the setting of an adult solid tumor oncology clinic. Importantly, the information included herein can be applied to other clinical practice settings.

Toward precision medicine in pediatric population using cytochrome P450 phenotyping approaches and physiologically based pharmacokinetic modeling

The activity of drug-metabolizing enzymes (DME) shows high inter- and intra-individual variability. Genetic polymorphisms, exposure to drugs, and environmental toxins are known to significantly alter DME expression. In addition, the activity of these enzymes is highly age-dependent due to maturation processes that occur during development. Currently, there is a vast choice of phenotyping methods in adults using exogenous probes to characterize the activity of these enzymes. However, this can hardly be applied to children since it requires the intake of non-therapeutic xenobiotics. In addition, sampling may be challenging in the pediatric population for a variety of reasons: limited volume (e.g., blood), inappropriate sampling methods for age (e.g., urine), and metric requiring invasive or multiple blood samples. This review covers the main existing methods that can be used in the pediatric population to determine DME activity, with a particular focus on cytochrome P450 enzymes. Less invasive tools are described, including phenotyping using endogenous probes. Finally, the potential of pediatric model-informed precision dosing using physiologically based pharmacokinetic modeling is discussed.

CYP2C19 Phenotype and Risk of Proton Pump Inhibitor-Associated Infections

OBJECTIVES

Proton pump inhibitors (PPIs) are often used in pediatrics to treat common gastrointestinal disorders, and there are growing concerns for infectious adverse events. Because CYP2C19 inactivates PPIs, genetic variants that increase CYP2C19 function may decrease PPI exposure and infections. We tested the hypothesis that CYP2C19 metabolizer phenotypes are associated with infection event rates in children exposed to PPIs.

METHODS

This retrospective biorepository cohort study included individuals aged 0 to 36 months at the time of PPI exposure. Respiratory tract and gastrointestinal tract infection events were identified by using International Classification of Diseases codes in the year after the first PPI mention. Variants defining CYP2C19 *2, *3, *4, *8, *9, and *17 were genotyped, and all individuals were classified as CYP2C19 poor or intermediate, normal metabolizers (NMs), or rapid or ultrarapid metabolizers (RM/UMs). Infection rates were compared by using univariate and multivariate analyses.

RESULTS

In all, 670 individuals were included (median age 7 months; 44% girls). CYP2C19 NMs (n = 267; 40%) had a higher infection rate than RM/UMs (n = 220; 33%; median 2 vs 1 infections per person per year; P = .03). There was no difference between poor or intermediate (n = 183; 27%) and NMs. In multivariable analysis of NMs and RM/UMs adjusting for age, sex, PPI dose, and comorbidities, CYP2C19 metabolizer status remained a significant risk factor for infection events (odds ratio 0.70 [95% confidence interval 0.50-0.97] for RM/UMs versus NMs).

CONCLUSIONS

PPI therapy is associated with higher infection rates in children with normal CYP2C19 function than in those with increased CYP2C19 function, highlighting this adverse effect of PPI therapy and the relevance of CYP2C19 genotypes to PPI therapeutic decision-making.

Challenges and lessons learned from clinical pharmacogenetic implementation of multiple gene-drug pairs across ambulatory care settings

PURPOSE

Incorporating a patient's genotype into the clinical decision-making process is one approach to precision medicine. The University of Florida (UF) Health Precision Medicine Program is a pharmacist-led multidisciplinary effort that has led the clinical implementation of six gene-drug(s) pairs to date. This study focuses on the challenges encountered and lessons learned with implementing pharmacogenetic testing for three of these: CYP2D6-opioids, CYP2D6/CYP2C19-selective serotonin reuptake inhibitors, and CYP2C19-proton pump inhibitors within six pragmatic clinical trials at UF Health and partners.

METHODS

We compared common measures collected within each of the pharmacogenetic implementations as well as solicited feedback from stakeholders to identify challenges, successes, and lessons learned.

RESULTS

We identified several challenges related to trial design and implementation, and learned valuable lessons. Most notably, case discussions are effective for prescriber education, prescribers need clear concise guidance on genotype-based actions, having genotype results available at the time of the patient-prescriber encounter helps optimize the ability to act on them, children prefer noninvasive sample collection, and study participants are willing to answer patient-reported outcomes questionnaires if they are not overly burdensome, among others.

CONCLUSION

The lessons learned from implementing three gene-drug pairs in ambulatory care settings will help shape future pharmacogenetic clinical trials and clinical implementations.