Pharmacogenomic testing: the case for CYP2C19 proton pump inhibitor gene-drug pairs

Diagnosis and management of eosinophilic esophagitis in children: An update from the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN)

INTRODUCTION

Eosinophilic esophagitis (EoE) is a chronic inflammatory disease of the esophagus characterized by symptoms of esophageal dysfunction and histologically by predominantly eosinophilic infiltration of the squamous epithelium. European Society for Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) published a guideline in 2014; however, the rapid evolution of knowledge about pathophysiology, diagnostic criteria, and therapeutic options have made an update necessary.

METHODS

A consensus group of pediatric gastroenterologists from the ESPGHAN Working Group on Eosinophilic Gastrointestinal Diseases (ESPGHAN EGID WG) reviewed the recent literature and proposed statements and recommendations on 28 relevant questions about EoE. A comprehensive electronic literature search was performed in MEDLINE, EMBASE, and Cochrane databases from 2014 to 2022. The Grading of Recommendations Assessment, Development and Evaluation system was used to assess the quality of evidence and formulate recommendations.

RESULTS

A total of 52 statements based on the available evidence and 44 consensus-based recommendations are available. A revision of the diagnostic protocol, options for initial drug treatment, and the new concept of simplified empiric elimination diets are now available. Biologics are becoming a part of the potential armamentarium for refractory EoE, and systemic steroids may be considered as the initial treatment for esophageal strictures before esophageal dilation. The importance and assessment of quality of life and a planned transition to adult medical care are new areas addressed in this guideline.

CONCLUSION

Research in recent years has led to a better understanding of childhood EoE. This guideline incorporates the new findings and provides a practical guide for clinicians treating children diagnosed with EoE.

Refractory Gastroesophageal Reflux Disease: Diagnosis and Management

Gastroesophageal reflux disease (GERD) is common, with increasing worldwide disease prevalence and high economic burden. A significant number of patients will remain symptomatic following an empiric proton pump inhibitor (PPI) trial. Persistent symptoms despite PPI therapy are often mislabeled as refractory GERD. For patients with no prior GERD evidence (unproven GERD), testing is performed off antisecretory therapy to identify objective evidence of pathologic reflux using criteria outlined by the Lyon consensus. In proven GERD, differentiation between refractory symptoms (persisting symptoms despite optimized antisecretory therapy) and refractory GERD (abnormal reflux metrics on ambulatory pH impedance monitoring and/or persistent erosive esophagitis on endoscopy while on optimized PPI therapy) can direct subsequent management. While refractory symptoms may arise from esophageal hypersensitivity or functional heartburn, proven refractory GERD requires personalization of the management approach, tapping from an array of non-pharmacologic, pharmacologic, endoscopic, and surgical interventions. Proper diagnosis and management of refractory GERD is critical to mitigate undesirable long-term complications such as strictures, Barrett's esophagus, and esophageal adenocarcinoma. This review outlines the diagnostic workup of patients presenting with refractory GERD symptoms, describes the distinction between unproven and proven GERD, and provides a comprehensive review of the current treatment strategies available for the management of refractory GERD.

Pharmacogenomics: a tool to improve medication safety and efficacy in patients with cystic fibrosis

Cystic fibrosis is a genetic, multiorgan system disease that involves the use of many medications to control symptoms associated with the underlying condition. Many of these medications have Clinical Pharmacogenetics Implementation Consortium evidence-based guidelines for pharmacogenomics that are available to guide dosing. The aim of this article is to review relevant literature and evaluate the utility of preemptive pharmacogenomics testing for persons with cystic fibrosis and propose a pharmacogenomics panel that could be considered standard of care for persons with cystic fibrosis.

AGA Clinical Practice Update on the Personalized Approach to the Evaluation and Management of GERD: Expert Review

BACKGROUND & AIMS

As many as one-half of all patients with suspected gastroesophageal reflux disease (GERD) do not derive benefit from acid suppression. This review outlines a personalized diagnostic and therapeutic approach to GERD symptoms.

METHODS

The Best Practice Advice statements presented here were developed from expert review of existing literature combined with extensive discussion and expert opinion to provide practical advice. Formal rating of the quality of evidence or strength of recommendations was not the intent of this clinical practice update. BEST PRACTICE ADVICE 1: Clinicians should develop a care plan for investigation of symptoms suggestive of GERD, selection of therapy (with explanation of potential risks and benefits), and long-term management, including possible de-escalation, in a shared-decision making model with the patient. BEST PRACTICE ADVICE 2: Clinicians should provide standardized educational material on GERD mechanisms, weight management, lifestyle and dietary behaviors, relaxation strategies, and awareness about the brain-gut axis relationship to patients with reflux symptoms. BEST PRACTICE ADVICE 3: Clinicians should emphasize safety of proton pump inhibitors (PPIs) for the treatment of GERD. BEST PRACTICE ADVICE 4: Clinicians should provide patients presenting with troublesome heartburn, regurgitation, and/or non-cardiac chest pain without alarm symptoms a 4- to 8-week trial of single-dose PPI therapy. With inadequate response, dosing can be increased to twice a day or switched to a more effective acid suppressive agent once a day. When there is adequate response, PPI should be tapered to the lowest effective dose. BEST PRACTICE ADVICE 5: If PPI therapy is continued in a patient with unproven GERD, clinicians should evaluate the appropriateness and dosing within 12 months after initiation, and offer endoscopy with prolonged wireless reflux monitoring off PPI therapy to establish appropriateness of long-term PPI therapy. BEST PRACTICE ADVICE 6: If troublesome heartburn, regurgitation, and/or non-cardiac chest pain do not respond adequately to a PPI trial or when alarm symptoms exist, clinicians should investigate with endoscopy and, in the absence of erosive reflux disease (Los Angeles B or greater) or long-segment (≥3 cm) Barrett's esophagus, perform prolonged wireless pH monitoring off medication (96-hour preferred if available) to confirm and phenotype GERD or to rule out GERD. BEST PRACTICE ADVICE 7: Complete endoscopic evaluation of GERD symptoms includes inspection for erosive esophagitis (graded according to the Los Angeles classification when present), diaphragmatic hiatus (Hill grade of flap valve), axial hiatus hernia length, and inspection for Barrett's esophagus (graded according to the Prague classification and biopsied when present). BEST PRACTICE ADVICE 8: Clinicians should perform upfront objective reflux testing off medication (rather than an empiric PPI trial) in patients with isolated extra-esophageal symptoms and suspicion for reflux etiology. BEST PRACTICE ADVICE 9: In symptomatic patients with proven GERD, clinicians should consider ambulatory 24-hour pH-impedance monitoring on PPI as an option to determine the mechanism of persisting esophageal symptoms despite therapy (if adequate expertise exists for interpretation). BEST PRACTICE ADVICE 10: Clinicians should personalize adjunctive pharmacotherapy to the GERD phenotype, in contrast to empiric use of these agents. Adjunctive agents include alginate antacids for breakthrough symptoms, nighttime H2 receptor antagonists for nocturnal symptoms, baclofen for regurgitation or belch predominant symptoms, and prokinetics for coexistent gastroparesis. BEST PRACTICE ADVICE 11: Clinicians should provide pharmacologic neuromodulation, and/or referral to a behavioral therapist for hypnotherapy, cognitive behavioral therapy, diaphragmatic breathing, and relaxation strategies in patients with functional heartburn or reflux disease associated with esophageal hypervigilance reflux hypersensitivity and/or behavioral disorders. BEST PRACTICE ADVICE 12: In patients with proven GERD, laparoscopic fundoplication and magnetic sphincter augmentation are effective surgical options, and transoral incisionless fundoplication is an effective endoscopic option in carefully selected patients. BEST PRACTICE ADVICE 13: In patients with proven GERD, Roux-en-Y gastric bypass is an effective primary anti-reflux intervention in obese patients, and a salvage option in non-obese patients, whereas sleeve gastrectomy has potential to worsen GERD. BEST PRACTICE ADVICE 14: Candidacy for invasive anti-reflux procedures includes confirmatory evidence of pathologic GERD, exclusion of achalasia, and assessment of esophageal peristaltic function.

STAT6 Variants Associate With Relapse of Eosinophilic Esophagitis in Patients Receiving Long-term Proton Pump Inhibitor Therapy

BACKGROUND & AIMS

Based on histologic features, variants in STAT6 are associated with a poor initial response to proton pump inhibitor (PPI) therapy in pediatric patients with eosinophilic esophagitis (EoE). We investigated whether these genetic variants are associated with a poor long-term response in children with EoE who initially responded to PPI therapy.

METHODS

We performed a prospective longitudinal cohort study of children ages 2 to 16 years who met the diagnostic criteria for EoE (≥15 eosinophils/high-power field [eos/hpf]), responded to 8 weeks of treatment with 2 mg/kg/d PPI (<15 eos/hpf), and whose dose then was reduced to 1 mg/kg/d PPI (maintenance therapy) for 1 year, at which point biopsy specimens were collected by endoscopy. Genomic DNA was isolated from formalin-fixed paraffin-embedded biopsy tissue and was genotyped for variants of STAT6. Remission of inflammation was assessed at eos/hpf thresholds of <15 and ≤5.

RESULTS

Among 73 patients who received 1 mg/kg/d PPI maintenance therapy for 1 year, 13 patients (18%) had 6 to 14 eos/hpf, 36 patients (49%) had 5 or fewer eos/hpf, and 24 patients (33%) relapsed to EoE (≥15 eos/hpf). Carriage of any of 3 STAT6 variants in linkage disequilibrium (r² ≥0.8; rs324011, rs167769, or rs12368672) was associated with a 2.3- to 2.8-fold increase in the odds of EoE relapse, and with a 2.8- to 4.1-fold increase in the odds of having 6 to 14 eos/hpf. For rs324011, the odds ratio [95% CI] for relapse was 2.77 [1.11, 6.92]; P = .029, and the odds ratio [95% CI] for having 6 to 14 eos/hpf was 3.06 [1.27, 7.36]; P = .012.

CONCLUSIONS

Pediatric EoE patients who initially respond to PPI therapy and carry STAT6 variants rs324011, rs167769, or rs12368672 are at increased risk of relapse after 1 year of PPI maintenance therapy.

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.

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.

CYP2C19 and STAT6 Variants Influence the Outcome of Proton Pump Inhibitor Therapy in Pediatric Eosinophilic Esophagitis

OBJECTIVE

Proton pump inhibitors (PPIs) are an effective treatment for eosinophilic esophagitis (EoE); however, only 30% to 60% of patients respond. Common genetic variants in CYP2C19 and STAT6 associate with PPI plasma concentration and magnitude of inflammatory response, respectively. Our objective was to determine if genetic variation in the genes for CYP2C19 and STAT6 influence differentiation between PPI responsive esophageal eosinophilia versus PPI nonresponsive EoE (PPI-REE, PPI-nonresponsive EoE).

METHODS

Genomic DNA was isolated from 92 esophageal tissue biopsies collected from participants of a prospective clinical trial of high-dose PPI therapy for esophageal eosinophilia in children.

RESULTS

Of the 92 patients examined, 57 (62%) were PPI-REE and 35 (38%) were PPI-nonresponsive EoE. Forty-six of the 92 patients were further characterized by pH probe monitoring; there was no association between reflux index and carriage of CYP2C1917 (P = 0.35). In children who received a PPI dose between ≥1.54 and ≤2.05 mg/kg/day, binary logistic regression modeling showed that carriage of CYP2C1917 associated with PPI-nonresponsive EoE (odds ratio (OR) [95% confidence interval (CI)] = 7.71 [1.21, 49.11], P = 0.031). Carriage of STAT6 allelic variant rs1059513 predicts PPI-REE (OR [95% CI] = 6.16 [1.44, 26.4], P = 0.028), whereas carriage of STAT6 rs324011 synergizes with CYP2C1917 to predict PPI-nonresponsive EoE (rs324011 OR [95% CI] = 5.56 [1.33, 20.72], P = 0.022; CYP2C1917 OR [95% CI] = 8.19[1.42, 50.57], P = 0.023).

CONCLUSIONS

Common variants in CYP2C19 and STAT6 associate with a PPI-nonresponsive EoE outcome of PPI therapy for esophageal eosinophilia suggesting that response rates may be improved by adopting a genotype-guided approach to PPI dosing.

Genotype tailored treatment of mild symptomatic acid reflux in children with uncontrolled asthma (GenARA): Rationale and methods

Asthma causes enormous suffering and cost for children in the US and around the world [1-3]. Co-morbid gastroesophageal reflux disease (GERD) makes asthma management more difficult due to increased symptoms. Proton pump inhibitor (PPI) drugs are effective at improving to GERD symptoms, however they have demonstrated only modest and variable effects on asthma control in the setting of co-morbid GERD. Importantly, PPI metabolism and efficacy depend on CYP2C19 genotype. The Genotype Tailored Treatment of Symptomatic Acid Reflux in Children with Uncontrolled Asthma (GenARA) study is a randomized, double-blind, placebo-controlled trial to determine if genotype-tailored PPI dosing improves asthma symptoms among children with inadequately controlled asthma and GERD symptoms. This study has an innovative design to both assess the efficacy of genotype-tailored PPI dosing and perform pharmacokinetic modeling of the oral PPI Lansoprazole. Children ages 6-17 years old with clinician-diagnosed asthma and mild GERD symptoms will submit a saliva sample for CYP2C19 genotyping. Participants will undergo a two-step randomization to: (1) genotype-tailored versus conventional dosing of open-label oral lansoprazole for pharmacokinetic modeling, and (2) genotype-tailored lansoprazole daily versus placebo for 24 weeks to determine the effect of genotype-tailored PPI dosing on asthma control. Measures of asthma control, spirometry, and nasal washes during acute illnesses will be collected at 8-week intervals throughout the study. GenARA will better define the effects of CYP2C19 genotype on the dose response of lansoprazole in children and adolescents and assess if a novel dosing regimen improves GERD and asthma control.

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

The efficacy of proton pump inhibitor (PPI) medications is highly dependent on plasma concentrations, which varies considerably due to cytochrome P450 (CYP2C19) genetic variation. We conducted a pragmatic, pilot study of CYP2C19 genotype‐guided pediatric dosing of PPI medications. Children aged 5–17 years old with gastric‐acid‐related conditions were randomized to receive either conventional dosing of a PPI or genotype‐guided dosing for a total of 12 weeks. Sixty children (30 in each arm) were enrolled and had comparable baseline characteristics. The mean daily omeprazole equivalent dose prescribed to participants across metabolizer phenotype groups was significantly different in the genotype‐guided dosing arm (P < 0.001), but not in the conventional dosing arm. Prescribers waited for the genotype result before prescribing the PPI medication for 90% of the participants in the genotype‐guided dosing arm. The number of participants who reported an infection was marginally lower in genotype‐guided dosing vs. conventional dosing (20% vs. 44%; P = 0.07). Sinonasal symptoms were higher in the conventional dosing arm as compared with genotype‐guided dosing arm: (2.6 (2.0, 3.4) vs. 1.8 (1.0, 2.3), P = 0.031). CYP2C19 genotype‐guided PPI therapy is feasible in a clinical pediatric setting, well accepted by providers, resulted in differential PPI dosing, and may reduce PPI‐associated infections. A future large scale randomized clinical trial of CYP2C19 genotype‐guided pediatric dosing of PPI medications in children is warranted.

Proton pump inhibitors: from CYP2C19 pharmacogenetics to precision medicine

Introduction: Proton Pump inhibitors (PPIs) are commonly used for a variety of acid related disorders. Despite the overall effectiveness and safety profile of PPIs, some patients do not respond adequately or develop treatment related adverse events. This variable response among patients is in part due to genotype variability of CYP2C19, the gene encoding the CYP450 (CYP2C19) isoenzyme responsible for PPIs metabolism.

Areas covered: This article provides an overview of the pharmacokinetics and mechanism of action of the currently available PPIs, including the magnitude of CYPC19 contribution to their metabolism. Additionally, the role of CYP2C19 genetic variability in the therapeutic effectiveness or outcomes of PPI therapy is highlighted in details, to provide supporting evidence for the potential value of CYP2C19 genotype-guided approaches to PPI drug therapy.

Expert opinion: There is a large body of evidence describing the impact of CYP2C19 variability on PPIs and its potential role in individualizing PPI therapy, yet, CYP2C19 pharmacogenetics has not been widely implemented into clinical practice. More data are needed but CYP2C19 genotype-guided dosing of PPIs is likely to become increasingly common and is expected to improve clinical outcomes, and minimize side effects related to PPIs.

Association between CYP2C19 extensive metabolizer phenotype and childhood anti-reflux surgery following failed proton pump inhibitor medication treatment

When pediatric gastroesophageal reflux disease (GERD) that is refractory to proton pump inhibitor (PPI) medication treatment is identified in clinical practice and anti-reflux surgery (ARS) is being considered, genetic factors related to PPI metabolism by the CYP2C19 enzyme are currently not part of the clinical decision-making process. Our objective was to test the hypothesis that the distribution of the extensive metabolizer (EM) phenotypes among children undergoing ARS after failing PPI therapy would differ compared to controls (children with no history of ARS). We conducted a case-control study between children across the Nemours Health System from 2000 to 2014 who received ARS after failing PPI therapy and a control group comprised of healthy children. Our results demonstrated 2.9% of ARSs vs 20.8% of controls were poor metabolizers (PMs), 55.9% of ARSs vs 49.0% of controls were normal metabolizers (NMs), and 41.2% of ARSs vs 30.2% of controls were EMs; p = 0.035. Next, we performed a multiple-regression model to account for race as a potential confounding variable and the EM group was significantly associated with ARS compared to controls (OR 9.78, CI 1.25-76.55, p < 0.03).

CONCLUSION

Among children with medically refractory GERD despite PPI therapy, carriage of CYP2C19*17 allele corresponding to the EM phenotype was associated with ARS. Prospective comparative personalized medicine effectiveness studies are needed to determine if CYP2C19 genotype-guided dosing improves response to PPI therapy without a corresponding increase in adverse effects in children. What is known: • Anti-reflux surgery (ARS) is one of the most common surgical procedures performed in children for the indication of refractory gastroesophageal reflux disease (GERD). What is new: • Individualizing PPI medication dosing based on CYP2C19 diplotype may avoid GERD treatment failures and reduce the need for anti-reflux surgery (ARS).

Association Between CYP2C19*17 Alleles and pH Probe Testing Outcomes in Children With Symptomatic Gastroesophageal Reflux

Esophageal pH monitoring remains a primary diagnostic tool for detecting gastroesophageal reflux disease (GERD). GERD that is refractory to proton pump inhibitor (PPI) medications may be related to CYP2C19 variants. Current PPI dosing practices in children do not take into account CYP2C19 allelic variants, which may lead to underdosing and subsequently to a misperception of PPI therapy failure. We hypothesized that pH probe acid exposure outcomes associate with CYP2C19*17 alleles among children with clinical concern for GERD. We identified a retrospective cohort of 74 children (age range 0.71-17.1 years, mean 8.5, SD 4.6) with stored endoscopic tissue samples and who had also undergone esophageal pH testing while on PPI therapy. These individuals were genotyped for common CYP2C19 alleles and were dichotomized to either CYP2C19*17 allelic carriers without corresponding loss of function alleles as cases vs controls. Associations between pH probe acid exposure outcomes and CYP2C19*17 alleles were investigated. Compared to controls, children who carry CYP2C19*17 alleles without corresponding loss-of-function alleles demonstrated statistically significant longer times with pH < 4 (76.46 vs 33.47 minutes, P = .03); and higher percent of time with pH < 4.0 (5.71 vs 2.67 minutes, P = .04). These findings remained statistically significant using multiple-regression modeling with test duration, PPI dose, and race as confounding variables. PPI therapy in children with *17 alleles may be better optimized with CYP2C19 genotype-guided dosing prior to pH probe testing.

Lansoprazole Is Associated with Worsening Asthma Control in Children with the CYP2C19 Poor Metabolizer Phenotype

RATIONALE

Gastric acid blockade in children with asymptomatic acid reflux has not improved asthma control in published studies. There is substantial population variability regarding metabolism of and response to proton pump inhibitors based on metabolizer phenotype. How metabolizer phenotype affects asthma responses to acid blockage is not known.

OBJECTIVES

To determine how metabolizer phenotype based on genetic analysis of CYP2C19 affects asthma control among children treated with a proton pump inhibitor.

METHODS

Asthma control as measured by the Asthma Control Questionnaire (ACQ) and other questionnaires from a 6-month clinical trial of lansoprazole in children with asthma was analyzed for associations with surrogates of lansoprazole exposure (based on treatment assignment and metabolizer phenotype). Groups included placebo-treated children; lansoprazole-treated extensive metabolizers (EMs); and lansoprazole-treated poor metabolizers (PMs). Metabolizer phenotypes were based on CYP2C19 haplotypes. Carriers of the CYP2C19*2, *3, *8, *9, or *10 allele were PMs; carriers of two wild-type alleles were extensive metabolizers (EMs).

MEASUREMENTS AND MAIN RESULTS

Asthma control through most of the treatment period was unaffected by lansoprazole exposure or metabolizer phenotype. At 6 months, PMs displayed significantly worsened asthma control compared with EMs (+0.16 vs. -0.13; P = 0.02) and placebo-treated children (+0.16 vs. -0.23; P < 0.01). Differences in asthma control were not associated with changes in gastroesophageal reflux symptoms. Recent upper respiratory infection worsened asthma control, and this upper respiratory infection effect may be more pronounced among lansoprazole-treated PMs.

CONCLUSIONS

Children with the PM phenotype developed worse asthma control after 6 months of lansoprazole treatment for poorly controlled asthma. Increased exposure to proton pump inhibitor may worsen asthma control by altering responses to respiratory infections. Clinical trial registered with www.clinicaltrials.gov (NCT00604851).