Effect of CYP2C19 and MDR1 polymorphisms on cure rate in patients with acid-related disorders with Helicobacter pylori infection

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.

Role of Genetic Polymorphisms of Cytochrome P450 2C19 in Pantoprazole Metabolism and Pantoprazole-based Helicobacter pylori Eradication Regimens

BACKGROUND

Cytochrome P450 (CYP450) enzymes play an important role in the metabolism of 70-80% of the currently used medications, including proton pump inhibitors. There are some data analyzing the impact of gene polymorphisms of CYP450 enzymes on most widely used PPIs, such as omeprazole, however, the data on pantoprazole are highly lacking.

OBJECTIVE

To summarize the most recent publications and studies on the role of polymorphisms of the genes encoding CYP450 enzyme 2C19 in the metabolism of pantoprazole and pantoprazole based Helicobacter pylori eradication regimens.

METHODS

We performed a non-systematic search of the available literature on the selected topic.

RESULTS AND CONCLUSION

The data on cytochrome P450 gene polymorphisms and their role in pantoprazole metabolism and pantoprazole based Helicobacter pylori eradication remain conflicting. Individual differences in pantoprazole metabolism might be partly related to genetic polymorphisms of CYP450 enzymes. Most of the studies support the observation that cytochrome 2C19 polymorphisms have an impact on the pharmacokinetics of pantoprazole and its therapeutic effects: poor metabolizers of PPIs are more likely to have a better response to pantoprazole therapy and achieve better H. pylori eradication rates compared to rapid metabolizers. The determination of alleles that are associated with decreased (e.g., *2, *3 alleles) or increased (e.g., *17 allele) cytochrome 2C19 enzyme activity might be used as predictive factors for the potential of acid suppression and the success of Helicobacter pylori eradication. Overall, currently available data do not provide robust evidence, therefore, the application of genetic polymorphisms of cytochrome enzymes in clinical practice still cannot be recommended as routine practice for personalized pantoprazole prescription strategies.

The Association between ABCB1 C1236T/C3435T SNPs and H. pylori Infection among Jordanians

Infection with Helicobacter pylori (H. pylori) is very common and affecting about 50% of the worldwide population. Several genetic variations have been implicated in determining the clinical susceptibility to this infection. In the current study, we examined the association between C1236T (rs1045642) and C3435T (rs1045642) single nucleotide polymorphisms (SNPs) in the ABCB1 gene and the prevalence of H. pylori infection among Jordanians. A total of 412 subjects (257 H. pylori-positive cases and 155 H. pylori-negative controls) were recruited and participated in the study, and the genotyping of the ABCB1 gene was performed using RFLP-PCR techniques. A significant association was detected between C1236T and H. pylori infection (p < 0.01). The frequency of CT genotype was significantly higher in the positive cases (40.1%) compared to the controls (21.3%). In addition, the C3435T SNP was weakly associated with H. pylori infection (p = 0.077). Haplotype analysis of C1236T and C3435T SNPs showed that the TT haplotype was present in 22.7% of the positive cases compared to 30.7% of the negative controls (p < 0.05, odds ratio = 0.663, 95% CI: (0.483-0.911)). Consequently, the TT haplotype seems to decrease the risk of H. pylori infection. In conclusion, the current results suggest an association between ABCB1 SNPs and H. pylori infection in the Jordanian population.

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).

The effect of MDR1 C3435T polymorphism on the eradication rate of H. pylori infection in PPI-based triple therapy: A meta-analysis

BACKGROUND

Several studies have reported that multidrug resistance gene 1 (MDR1) C3435T polymorphism was associated with the rate of Helicobacter pylori (H. pylori) eradication in proton pump inhibitor (PPI)-based triple therapy. However, the conclusions were inconsistent. Therefore, this meta-analysis was conducted to evaluate the impact of MDR1 C3435T polymorphism on H. pylori eradication by PPI-based triple therapy.

METHODS

Seven eligible studies published up to August 2016 and including 1019 patients were identified by searching the Chinese Biomedical Literature database, Wan fang, PubMed, and the Web of Science electronic databases. Consequently, a meta-analysis was conducted with STATA software, using summary odds ratios (OR) and a 95% confidence interval (CI).

RESULTS

Overall, there was no significant difference between MDR1 C3435T polymorphism and the eradication rate of H. pylori in the entire genetic model, irrespective of the PPI used. Furthermore, in Asian populations, the TT genotype decreased H. pylori eradication (TT vs CT+CC: OR=0.411, 95% CI = 0.280-0.602, P = 0.000). In addition, a significantly low eradication rate was observed in a recessive model, in which either lansoprazole (TT vs CT+CC: OR = 0.305, 95% CI = 0.184-0.504, P = 0.000) or omeprazole (TT vs CT+CC: OR = 0.229, 95% CI = 0.069-0.763, P = 0.016) was taken, in a subanalysis of individual PPIs. In the analyses that were stratified by disease type, no significant difference was observed in the peptic ulcer group and the combined diseases subgroup.

CONCLUSION

This meta-analysis indicated that the TT genotype of the MDR1 C3435T polymorphism decreased H. pylori eradication in Asian populations and was also associated with a low cure rate of H. pylori in patients taking lansoprazole- and omeprazole-based triple therapies. However, future studies using larger sample sizes are required.

Effects of Genetic Polymorphisms of Cytochrome P450 Enzymes and MDR1 Transporter on Pantoprazole Metabolism and Helicobacter pylori Eradication

Pantoprazole is a proton pump inhibitor that is commonly used in the treatment of peptic ulcer disease (PUD) and metabolized by cytochrome P450 (CYP) enzymes CYP2C19 and CYP3A4. Pantoprazole is a substrate for multi-drug resistance protein 1 (MDR1). Single nucleotide polymorphisms (SNPs) in CYP2C19, CYP3A4 and MDR1 affect enzyme activity or gene expression of proteins and may alter plasma pantoprazole concentrations and treatment success in PUD. In this study, we aimed to investigate the association between genetic polymorphisms in CYP2C19, CYP3A4 and MDR1 and pharmacokinetics of pantoprazole and therapeutic outcome in patients with either Helicobacter pylori-associated [H.P.(+)]-PUD or [H.P.(+)]-gastritis. The plasma pantoprazole concentrations were determined by using an HPLC method at the third hour after a 40-mg tablet of pantoprazole administration in 194 newly diagnosed patients with either [H.P.(+)]-PUD or [H.P.(+)]-gastritis. Genotyping was performed by using PCR-RFLP and DNA sequencing. Among patients appearing for follow-up examination (n = 105), the eradication rate for H. pylori was 82.8% (n = 87). The median pantoprazole plasma concentrations in poor metabolizers (PM), rapid metabolizers (RM) and ultrarapid metabolizers (URM) were 2.07, 1.69 and 1.28 μg/ml, respectively (p = 0.04). CYP3A4*1G and *22 polymorphisms did not affect plasma pantoprazole concentrations and H. pylori eradication rate. The MDR1 genetic polymorphisms did not affect plasma pantoprazole concentrations. MDR1 3435CC-2677GG-1236CC haplotype carriers had lower H. pylori eradication rate (60%) than the remaining subjects (84.9%) while the difference was not statistically significant (p = 0.07). In conclusion, while CYP2C19 genetic polymorphisms significantly affected plasma pantoprazole concentrations, polymorphisms of CYP2C19, CYP3A4 and MDR1 did not affect H. pylori eradication rates.

[Molecular genetic predictors of resistance to anti-Helicobacter pylori therapy]

In current clinical practice, there is no optimal empirical therapy for Helicobacter pylori (H. pylori) infection and there is a progressive decrease in the efficiency of classical eradication therapy (ET) regimens. The variability in the efficiency of ET in a specific patient is largely due to the heterogeneous molecular genetic mechanisms underlying the resistance of the microorganism to the components of the treatment regimens. The basis of the mechanisms for antibiotic resistance in H. pylori is mainly the point mutations in some genes, which determine alterations in the mechanisms of action of drugs, such as clarithromycin (domain V of 23S rRNA), metronidazole (rdxA, frxA), amoxicillin (pbp1A), tetracycline (16S rRNA), and levofloxacin (gyrA). The predictors of resistance to ET are also the CagA-negative status of the microorganism and the presence of the vacA s2 allele. There are a number of host genetic determinants (the CYP2C19 genotype (*1/*1, *1/*17, *17/*17) and the MDR1 3435 T/T genotype (in an Asian population)) that reduce the efficiency of ET, by altering the pharmacokinetics of proton pump inhibitors. In addition, the IL-1β-511 C/C polymorphism that affects gastric acid secretion is a predictor of the inefficiency of ET.

Antibiotic resistance and CYP2C19 polymorphisms affect the efficacy of concomitant therapies for Helicobacter pylori infection: an open-label, randomized, single-centre clinical trial

OBJECTIVES

We evaluate the efficacy of concomitant therapy for Helicobacter pylori infection and the associated factors that influence it in China, where it has not previously been investigated.

METHODS

In this prospective study, 374 consecutive patients with H. pylori infection were randomly assigned to 10 day regimens of concomitant therapy with different proton pump inhibitors: esomeprazole (20 mg)/omeprazole (20 mg), amoxicillin (1000 mg), clarithromycin (500 mg) and metronidazole (400 mg). All drugs were administered twice daily. A [(13)C]urea breath test was performed at least 4 weeks after the completion of treatment. Gene polymorphisms and antimicrobial susceptibility were determined.

RESULTS

A total of 374 patients with active, uncomplicated duodenal ulcer disease were enrolled in the study (187 cases in each group). The overall eradication rate resulting from concomitant therapy was 90.7% (PP) and 86.1% (ITT) and the eradication rate was significantly higher in the group that received an esomeprazole-based regimen compared with the group that received an omeprazole-based regimen [95.4% versus 86.0%, respectively, P = 0.003 (PP) and 89.8% versus 82.4%, P = 0.036 (ITT), respectively]. Moreover, the omeprazole-based regimen was an independent risk factor for treatment failure (P = 0.039), as were CYP2C19 extensive metabolizer (P = 0.005), clarithromycin (P = 0.000) and metronidazole resistance (P = 0.000). In addition, CYP2C19 polymorphisms and antibiotic resistance had a synergistic effect on eradication rates. The majority of side effects were mild and none was serious.

CONCLUSIONS

The 10 day concomitant therapy yielded an eradication rate of nearly 90%. Antibiotic resistance, CYP2C19 polymorphisms and their interactions were closely associated with regimen efficacy.

Antiplatelet drug interactions with proton pump inhibitors

INTRODUCTION

Non-aspirin antiplatelet agents (e.g., clopidogrel, prasugrel, ticagrelor) are commonly prescribed for the prevention of recurrent cardiovascular events among patients with acute coronary syndromes (ACS) and/or those undergoing percutaneous coronary intervention (PCI). In addition, combination therapy with proton pump inhibitors (PPIs) is often recommended to attenuate gastrointestinal bleeding risk, particularly during dual antiplatelet therapy (DAPT) with clopidogrel and aspirin. Importantly, a pharmacological interaction between clopidogrel and some PPIs has been proposed based on mutual CYP450-dependent metabolism, but available evidence is inconsistent.

AREAS COVERED

This article provides an overview of the currently approved antiplatelet agents and PPIs, including their metabolic pathways. Additionally, the CYP450 isoenzyme at the center of the drug interaction, CYP2C19, is described in detail, and the available evidence on both the potential pharmacological interaction and influence on clinical outcomes are summarized and evaluated.

EXPERT OPINION

Although concomitant DAPT and PPI use reduces clopidogrel active metabolite levels and ex vivo-measured platelet inhibition, the influence of the drug interaction on clinical outcomes has been conflicting and largely reported from non-randomized observational studies. Despite this inconsistency, a clinically important interaction cannot be definitively excluded, particularly among patient subgroups with higher overall cardiovascular risk and potentially among CYP2C19 loss-of-function allele carriers.

Individualized therapy for gastroesophageal reflux disease: potential impact of pharmacogenetic testing based on CYP2C19

The main therapeutic agent for gastroesophageal reflux disease (GERD) is a proton pump inhibitor (PPI). Plasma levels and the acid inhibitory effect of PPIs depend on the activity of cytochrome P450 (CYP) 2C19, which is polymorphic. Genotypes of CYP2C19 are classified into three groups: rapid metabolizers (RMs: *1/*1), intermediate metabolizers (IMs: *1/*X), and poor metabolizers (PMs: *X/*X), where *1 and X represent the wild type and the mutant allele, respectively. RMs include ultra-rapid metabolizers, who possess the CYP2C19*17 allele. The pharmacokinetics and pharmacodynamics of PPIs differ among different CYP2C19 genotype groups. Plasma PPI levels and intragastric pH values during PPI treatment are lowest in the RM group, intermediate in the IM group, and highest in the PM group. These CYP2C19-genotype-dependent differences in the pharmacokinetics and pharmacodynamics of PPIs influence the healing and recurrence of GERD during PPI treatment, suggesting the need for CYP2C19 genotype-based tailored therapy for GERD. CYP2C19 pharmacogenetics should be taken into consideration for the personalization of PPI-based therapy. However, the clinical usefulness of CYP2C19 genotype testing in GERD therapy should be verified in clinical studies.

Individualized therapy for gastroesophageal reflux disease: potential impact of pharmacogenetic testing based on CYP2C19

The main therapeutic agent for gastroesophageal reflux disease (GERD) is a proton pump inhibitor (PPI). Plasma levels and the acid inhibitory effect of PPIs depend on the activity of cytochrome P450 (CYP) 2C19, which is polymorphic. Genotypes of CYP2C19 are classified into three groups: rapid metabolizers (RMs: *1/*1), intermediate metabolizers (IMs: *1/*X), and poor metabolizers (PMs: *X/*X), where *1 and X represent the wild type and the mutant allele, respectively. RMs include ultra-rapid metabolizers, who possess the CYP2C19*17 allele. The pharmacokinetics and pharmacodynamics of PPIs differ among different CYP2C19 genotype groups. Plasma PPI levels and intragastric pH values during PPI treatment are lowest in the RM group, intermediate in the IM group, and highest in the PM group. These CYP2C19-genotype-dependent differences in the pharmacokinetics and pharmacodynamics of PPIs influence the healing and recurrence of GERD during PPI treatment, suggesting the need for CYP2C19 genotype-based tailored therapy for GERD. CYP2C19 pharmacogenetics should be taken into consideration for the personalization of PPI-based therapy. However, the clinical usefulness of CYP2C19 genotype testing in GERD therapy should be verified in clinical studies.

Clopidogrel and proton pump inhibitors: influence of pharmacological interactions on clinical outcomes and mechanistic explanations

Dual antiplatelet therapy with aspirin and clopidogrel is associated with a significant reduction in vascular ischemic events; however, gastrointestinal bleeding events are a major concern in high-risk and older patients. Clinical practice guidelines recommend combination therapy with proton pump inhibitors (PPI) and dual antiplatelet therapy to attenuate gastrointestinal bleeding risk. In addition, high on-treatment platelet reactivity has been associated with recurrent ischemic events. Whether or not the pharmacological interaction between clopidogrel and PPI, which results in diminished antiplatelet effect, adversely influences clinical efficacy is highly controversial and the subject of debate. Based on largely anecdotal post-hoc analyses, the U.S. Federal Drug Administration's and European Medicines Agency's recommendations discourage PPI use (particularly omeprazole) in patients treated with clopidogrel. However, many American College of Cardiology/American Heart Association/Society for Cardiovascular Angiography and Interventions experts do not support change in clinical practice guidelines recommendations without adequately powered, prospective, randomized clinical trial data.

The effect of probiotics and mucoprotective agents on PPI-based triple therapy for eradication of Helicobacter pylori

BACKGROUND/AIMS

Recent studies have found that probiotics have anti-Helicobacter pylori (HP) properties. We evaluated the additive effects of (i) Saccharomyces boulardii combined with proton pump inhibitor (PPI)-based triple therapy and (ii) S. boulardii and a mucoprotective agent (DA-9601) coupled with PPI-based triple therapy for HP eradication.

METHODS

We recruited 991 HP infected patients and randomized them into one of three groups, (A) PPI-based 7-day triple therapy, (B) the same triple therapy plus S. boulardii for 4 weeks, and (C) the same 7-day triple therapy plus S. boulardii and mucoprotective agent for 4 weeks. All patients in the three groups were tested via (13)C-urea breath test 4 weeks after the completion of the therapy.

RESULTS

According to the results of an intention-to-treat analysis, HP eradication rates for the groups A, B, and C were 71.6% (237/331), 80.0% (264/330), and 82.1% (271/330), respectively (p = .003). According to the results of a per protocol analysis, the eradication rates were 80.0% (237/296), 85.4% (264/309) and, 84.9% (271/319), respectively (p = .144). The frequency of side effects in group B (48/330) and C (30/330) was lower than that in group A (63/331) (p < .05).

CONCLUSION

This study suggests that supplementation with S. boulardii could be effective for improving HP eradication rates by reducing side effects thus helping completion of eradication therapy. However, there were no significant effects on HP eradication rates associated with the addition of mucoprotective agents to probiotics and triple therapy.

Effects of CYP2C19, MDR1, and interleukin 1-B gene variants on the eradication rate of Helicobacter pylori infection by triple therapy with pantoprazole, amoxicillin, and metronidazole

OBJECTIVE

Eradication of H. pylori is an important treatment strategy in peptic ulcer patients. Current regimens of eradication consist of proton pump inhibitor (PPI) and two antibiotics. Effects of PPI may depend on their metabolism, and other factors important for the pathophysiology of peptic ulcer disease. Aim of the present study was to evaluate an association of CYP2C19, MDR1, and IL-1B polymorphisms with the eradication rate of H. pylori in Polish Caucasian patients treated with a triple therapy of pantoprazole, amoxicillin, and metronidazole.

METHODS

A total of 139 peptic ulcer patients, positive for H. pylori infection, were treated with triple therapy (pantoprazole + amoxicillin + metronidazole). Subsequently, the patients were divided into two groups (group 1, success, and group 2, failure of eradication after therapy) and genotyped by the PCR-RFLP method for the presence of CYP2C19 variant alleles (*2, *3, and *17), and MDR1 3435C>T and IL-1B +3954C>T polymorphisms. Pantoprazole serum concentrations were measured using the HPLC method.

RESULTS

No significant differences in frequency or distribution of CYP2C19 genotypes were found between the two groups of patients (i.e., with successful H. pylori eradication and treatment failure). However, any carrier of defective CYP2C19*2/*2 genotype was found among patients with treatment failure. Similarly, MDR1 and IL-1B genotypes were found to be significantly associated with the success or failure of H. pylori eradication. Univariate and multivariate analysis of the genotypes did not reveal any significant association between the genotypes and H. pylori eradication. Pantoprazole concentrations differed significantly, and were the highest in patients with defective allele CYP2C19*2 carriers and lowest in hyperactive genotype homozygotes CYP2C19*17/*17.

CONCLUSION

The results suggest that the CYP2C19 genotype contrary to MDR1 and IL-1B genotypes may have an impact on the efficacy of H. pylori eradication in peptic ulcer patients treated with pantoprazole in Polish Caucasian peptic ulcer patients administered pantoprazole, amoxicillin, and metronidazole.

Effects of CYP2C19, MDR1, and interleukin 1-B gene variants on the eradication rate of Helicobacter pylori infection by triple therapy with pantoprazole, amoxicillin, and metronidazole

OBJECTIVE

Eradication of H. pylori is an important treatment strategy in peptic ulcer patients. Current regimens of eradication consist of proton pump inhibitor (PPI) and two antibiotics. Effects of PPI may depend on their metabolism, and other factors important for the pathophysiology of peptic ulcer disease. Aim of the present study was to evaluate an association of CYP2C19, MDR1, and IL-1B polymorphisms with the eradication rate of H. pylori in Polish Caucasian patients treated with a triple therapy of pantoprazole, amoxicillin, and metronidazole.

METHODS

A total of 139 peptic ulcer patients, positive for H. pylori infection, were treated with triple therapy (pantoprazole + amoxicillin + metronidazole). Subsequently, the patients were divided into two groups (group 1, success, and group 2, failure of eradication after therapy) and genotyped by the PCR-RFLP method for the presence of CYP2C19 variant alleles (*2, *3, and *17), and MDR1 3435C>T and IL-1B +3954C>T polymorphisms. Pantoprazole serum concentrations were measured using the HPLC method.

RESULTS

No significant differences in frequency or distribution of CYP2C19 genotypes were found between the two groups of patients (i.e., with successful H. pylori eradication and treatment failure). However, any carrier of defective CYP2C19*2/*2 genotype was found among patients with treatment failure. Similarly, MDR1 and IL-1B genotypes were found to be significantly associated with the success or failure of H. pylori eradication. Univariate and multivariate analysis of the genotypes did not reveal any significant association between the genotypes and H. pylori eradication. Pantoprazole concentrations differed significantly, and were the highest in patients with defective allele CYP2C19*2 carriers and lowest in hyperactive genotype homozygotes CYP2C19*17/*17.

CONCLUSION

The results suggest that the CYP2C19 genotype contrary to MDR1 and IL-1B genotypes may have an impact on the efficacy of H. pylori eradication in peptic ulcer patients treated with pantoprazole in Polish Caucasian peptic ulcer patients administered pantoprazole, amoxicillin, and metronidazole.

A comparative study of proton-pump inhibitor tests for Chinese reflux patients in relation to the CYP2C19 genotypes

BACKGROUND

The proton-pump inhibitor (PPI) test has been proposed as a valuable tool for diagnosing gastroesophageal reflux disease in Western populations.

GOALS

We aim to compare the diagnostic accuracy of the PPI test using rabeprazole and pantoprazole in a Chinese population with a higher prevalence of poor PPI metabolization.

STUDY

After diagnostic endoscopy, patients with gastroesophageal reflux disease symptoms were randomly assigned to a 2-week test with rabeprazole (20 mg b.i.d.) or pantoprazole (40 mg b.i.d.). Therapeutic response was assessed with a 5-grade daily record. Genotypes of cytochrome P450 (CYP) 2C19 polymorphism were determined.

RESULTS

Of the 178 patients who completed the study, 92 (51.7%) had erosive esophagitis and 78 (48.3%) were endoscopy-negative reflux disease. On the basis of 50% reduction of symptoms, there was a nonsignificant difference of diagnostic performances between rabeprazole and pantoprazole. For the CYP2C19 genotypes, 138 (87.3%) were determined to be extensive metabolizers (EMs) and 20 (12.7%) were poor metabolizers (PMs). When comparing the EMs and PMs, the diagnostic specificity in the prediction of erosive esophagitis was higher in the EMs (57.6% vs. 20.0%, P=0.040), as was the accuracy (74.6% vs. 50.0%, P=0.023). There were no differences in the sensitivity, positive predictive value, or negative predictive value.

CONCLUSIONS

CYP2C19 genotypic polymorphism was related to a higher possibility of false-positive results for patients who metabolized PPI poorly. High-dose rabeprazole and pantoprazole showed a similar diagnostic performance.

Polymorphism of human cytochrome P450 enzymes and its clinical impact

Pharmacogenetics is the study of how interindividual variations in the DNA sequence of specific genes affect drug response. This article highlights current pharmacogenetic knowledge on important human drug-metabolizing cytochrome P450s (CYPs) to understand the large interindividual variability in drug clearance and responses in clinical practice. The human CYP superfamily contains 57 functional genes and 58 pseudogenes, with members of the 1, 2, and 3 families playing an important role in the metabolism of therapeutic drugs, other xenobiotics, and some endogenous compounds. Polymorphisms in the CYP family may have had the most impact on the fate of therapeutic drugs. CYP2D6, 2C19, and 2C9 polymorphisms account for the most frequent variations in phase I metabolism of drugs, since almost 80% of drugs in use today are metabolized by these enzymes. Approximately 5-14% of Caucasians, 0-5% Africans, and 0-1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant enzyme that demonstrates multiple genetic variants with a potentially functional impact on the efficacy and adverse effects of drugs that are mainly eliminated by this enzyme. Studies into the CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and *3 alleles. Extensive polymorphism also occurs in other CYP genes, such as CYP1A1, 2A6, 2A13, 2C8, 3A4, and 3A5. Since several of these CYPs (e.g., CYP1A1 and 1A2) play a role in the bioactivation of many procarcinogens, polymorphisms of these enzymes may contribute to the variable susceptibility to carcinogenesis. The distribution of the common variant alleles of CYP genes varies among different ethnic populations. Pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and currently available drugs. Further studies are warranted to explore the gene-dose, gene-concentration, and gene-response relationships for these important drug-metabolizing CYPs.

Effect of MDR1 C3435T polymorphism on lansoprazole in healthy Japanese subjects

BACKGROUND AND AIMS

The effect of multidrug resistance transporter gene 1 (MDR1) on the bioavailability and kinetics of several substrates has not yet been fully elucidated. We evaluated the influence of MDR1 C3435T polymorphism on the pharmacokinetics and pharmacodynamics of lansoprazole in Japanese subjects.

METHODS

Fifteen healthy volunteers with the rapid extensive metabolizer genotype of CYP2C19 were classified into three MDR1 C3435T genotype groups: C/C (n = 5), C/T (n = 5), and T/T (n = 5). Lansoprazole 30 mg was administered orally for 15 days. The intragastric pH and plasma lansoprazole levels were determined on days 1 and 15.

RESULTS

On day 1, the mean C(max) of lansoprazole in the T/T group was significantly higher than that in the C/C or C/T groups (T/T 1,248, C/C 618, C/T 607 ng/ml; P = 0.038). On day 15, similar MDR1 genotype-dependent differences were observed in the C(max) of lansoprazole, although smaller than the differences observed on day 1. In contrast, the intragastric pH attained after lansoprazole administration did not differ among MDR1 genotype groups on either day 1 or day 15.

CONCLUSION

Although the sample size was small, our study demonstrated that the MDR1 C3435T polymorphism influenced the pharmacokinetics, but not the pharmacodynamics (i.e., intragastric pH), of lansoprazole in rapid metabolizers of CYP2C19.

Effects of CYP2C19 and MDR1 genotype on the eradication rate of Helicobacter pylori infection by triple therapy with pantoprazole, amoxycillin and clarithromycin

BACKGROUND

CYP2C19 polymorphism plays an important role in the metabolism of proton pump inhibitors. The multidrug resistance (MDR)1 genotype is associated with the successful eradication of Helicobacter pylori. The aim of the present study was to investigate the effects of CYP2C19 and MDR1 genotypes on the eradication rate of H. pylori using a pantoprazole-based triple therapy.

METHODS

A total of 210 patients infected with H. pylori were treated with 40 mg pantoprazole, 500 mg clarithromycin and 1000 mg amoxicillin twice daily for 7 days. The CYP2C19 genotype was determined with polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis. The MDR1 C3435T polymorphism was identified by PCR-based allele-specific amplification (PCR-ASA).

RESULTS

Of the 210 patients who completed the study, 174 (82.9%, 95.0% confidence interval [CI], 77.8-88.0%) achieved successful eradication after the first cycle of therapy. The eradication rates for H. pylori were 86.7%, 81.1% and 82.1% in the homozygous extensive, heterozygous extensive and poor metabolizer groups, respectively (P = 0.65). Moreover, the cure rates in the CC, CT, and TT groups were 82.7%, 84.4% and 76.9%, respectively (P = 0.66). Multiple logistic regression analysis revealed that endoscopic diagnosis was a significant independent risk factor for treatment failure.

CONCLUSION

The eradication rates of H. pylori by pantoprazole, amoxicillin and clarithromycin were not significantly different among the CYP2C19 and MDR1 genotypes. Hence, the cure rate of H. pylori in the Korean population was no different for the CYP2C19 and MDR1 genotypes.

Effect of CYP2C19 genetic polymorphisms on the efficacy of proton pump inhibitor-based triple therapy for Helicobacter pylori eradication: a meta-analysis

OBJECTIVE

CYP2C19 polymorphisms have been inconsistently reported to associate with the efficacy of proton pump inhibitor (PPI)-based triple therapies for eradicating Helicobacter pylori infection. The aim of this meta-analysis was to determine whether CYP2C19 polymorphism affect H. pylori eradication rates obtained with first-line PPI-based triple therapies.

METHODS

A systematic literature search was conducted up to July 2007 using Medline, PubMed, EMBase, Cochrane Central Register of Controlled Trials (CENTRAL), ISI Web of Science, CNKI (Chinese), and Wanfang (Chinese) digital database. MeSH terms and keywords included proton pump inhibitor, omeprazole, lansoprazole, rabeprazole, pantoprazole, or esomeprazole, cytochrome P4502C19 or CYP2C19, and Helicobacter pylori or H. pylori. Twenty articles met the inclusion criteria, and were included in the meta-analysis by using Review Manager 4.2.8.

RESULTS

Eradication rates were significantly different between poor metabolizers (PM) and heterozygous extensive metabolizers (HetEM) (odds ratio (OR) = 1.73, p = .002) and between PM and homozygous extensive metabolizers (HomEM) (OR = 2.79, p < .0001). Moreover, eradication rates were also significant difference between HetEM and HomEM (OR = 2.00, p < .0001). Triple omeprazole and lansoprazole therapies achieved higher H. pylori eradication rates in PM than in HomEM (OR = 4.28, p = .0005 for omeprazole and OR = 3.06, p = .001 for lansoprazole), and higher in HetEM than those in HomEM (OR = 3.22, p < .0001 for omeprazole and OR = 1.95, p = .040 for lansoprazole). Rabeprazole therapies had no significant effect on H. pylori eradication rates (between PM and HomEM, OR = 1.35, p = .610 and between HetEM and HomEM, OR = 1.57, p = .190). No significant difference in H. pylori eradication rates between PM and HetEM was observed in the three individual PPI therapies.

CONCLUSION

The efficacy of omeprazole- and lansoprazole-based first-line triple therapies at the standard doses is dependent on CYP2C19 genotype status, which appears not to affect the efficacy of the regimens including rabeprazole.

Effect of the CYP2C19 polymorphism on the eradication rate of Helicobacter pylori infection by 7-day triple therapy with regular proton pump inhibitor dosage

BACKGROUND AND AIM

Proton pump inhibitors (PPI) are mainly metabolized by cytochrome P450 2C19 (CYP2C19) in the liver. We investigated whether the CYP2C19 genotype plays a role in the eradication rate of Helicobacter pylori (H. pylori) infection in patients receiving pantoprazole- or esomeprazole-based triple therapy.

METHODS

A total of 327 patients infected with H. pylori were treated with either pantoprazole or esomeprazole, plus amoxicillin and clarithromycin for 7 days. The presence of the CYP2C19 genotype was determined by pyrosequencing.

RESULTS

The overall H. pylori eradication rate was 85%; 82.6% for the PAC regimen, and 88.3% for the EAC regimen; the differences were not statistically significant. The overall eradication rate in the poor metabolizer groups (PM) was significantly higher than in the extensive metabolizer groups (EM) (97.4% vs 83.3%; P = 0.016). The eradication rates in the EM and PM groups were 80.8% and 95.7% for the PAC regimen and 86.8% and 100% for the EAC regimen, respectively.

CONCLUSION

The results of this study suggest that the CYP2C19 genotype status may play a role in the H. pylori eradication rate in patients receiving pantoprazole or esomeprazole-based triple therapy.

New concepts of resistance in the treatment of Helicobacter pylori infections

The prevalence of antimicrobial drug resistance is now so high that all patients infected with Helicobacter pylori should be considered as having resistant infections. Ideally, therapy should be based on pretreatment antibiotic-susceptibility testing but this strategy is not currently practical. At present, clarithromycin-containing triple therapies do not reliably produce a > or =80% cure rate on an intention-to-treat basis and are, therefore, no longer acceptable as empiric therapy. In this Review, we discuss concepts of resistance that have become part of mainstream thinking for other infectious diseases but have not yet become so with regard to H. pylori. We also put data on the pharmacokinetics and pharmacodynamics of the drugs used in H. pylori therapy and the effect of host cytochrome P450 genotypes in context with treatment outcomes. Our primary focus is to address the problem of H. pylori resistance from a novel perspective, which also attempts to anticipate the direction that research will need to take to provide clinicians with reliable approaches to this serious infection. We also discuss current therapies that provide acceptable cure rates when used empirically (i.e. sequential therapy; four-drug, three-antibiotic, non-bismuth-containing 'concomitant' therapy; and bismuth-containing quadruple therapy) and how they might be further improved.

Proton pump inhibitors: do differences in pharmacokinetics translate into differences in clinical outcomes?

Acid-related disorders are common management problems in clinical practice. The key to effective management is successful suppression of gastric acid production. Proton pump inhibitors (PPIs) are the most potent acid suppressants available and are significantly more effective than histamine H(2) receptor antagonists. Although PPIs are highly effective as a class, differences in their pharmacokinetics, such as bioavailability, elimination half-life and metabolism, may translate into differences in clinical outcomes. A new immediate-release omeprazole has been introduced, which allows rapid absorption. This has been shown to produce significantly better nocturnal gastric acid control than delayed-release tablets. The bioavailability of rabeprazole on day 1 is greater than with other PPIs, and this may translate into faster onset of symptom relief for patients with gastro-oesophageal reflux disease. On the other hand, the bioavailability of esomeprazole increases 3-fold at day 5, and it has been shown that on day 5, esomeprazole provided significantly more effective control of gastric acid than other PPIs. The exact clinical significance of these observations remains to be determined. There is genetic polymorphism in PPI metabolism via cytochrome P450 2C19. In Helicobacter pylori eradication, a significantly lower eradication rate was seen in extensive metabolisers with omeprazole and lansoprazole but not with rabeprazole. The oesophagitis healing rate was lower in extensive metabolisers with lansoprazole but not with rabeprazole. The currently available PPIs have short elimination half-lives ranging from 1 to 1.5 hours. Tenatoprazole is a new PPI that has a 5- to 7-fold longer elimination half-life than current PPIs. It could be potentially more useful for the treatment of gastro-esophageal reflux disease and nocturnal acid breakthrough than other PPIs.

Effects of CYP2C19 genetic polymorphism on the pharmacokinetics and pharmacodynamics of omeprazole in Chinese people

BACKGROUND

To investigate whether the pharmacodynamics and pharmacokinetics of omeprazole (OPZ) are dependent of the CYP2C19 genotype status in Chinese people.

METHODS

Eighteen healthy subjects were voluntary to participate in the study, whose CYP2C19 genotype status were determined by polymerase chain reaction-restriction fragment length polymorphism method. There were six homozygous extensive metabolizers, six heterozygous extensive metabolizers and six poor metabolizers (PMs). All subjects were Helicobacter pylori-negative, determined by serology method and (13)C-urea breath test. After d1 and d8 orally received OPZ 20 mg once daily in the morning, intragastric pH values were monitored for 24 h by Digitrapper pH. Meanwhile, blood samples were collected at various time-points until 24 h after administration. The serum concentrations of OPZ were measured by liquid chromatography.

RESULTS

After single or repeated doses, the PMs showed a significantly higher mean area under the serum concentration-time curves (AUC) values than that observed in the homozygous extensive metabolizers or the heterozygous extensive metabolizers, with a relative ratio of 1.0 : 1.1 : 4.2 and 1.0 : 1.3 : 3.3 (homozygous extensive metabolizers:heterozygous extensive metabolizers:poor metabolizers), respectively. After a single dose of OPZ, significant differences in intragastric pH median, pH > 3 holding time and pH > 4 holding time were observed among the three groups. After repeated doses, the PMs showed a significantly higher intragastric pH values than that observed in the homozygous extensive metabolizers or the heterozygous extensive metabolizers.

CONCLUSION

The pharmacodynamic effects of OPZ and its pharmacokinetics depend on the CYP2C19 genotype status in Chinese people.

Treatment strategy to eradicate Helicobacter pylori infection: impact of pharmacogenomics-based acid inhibition regimen and alternative antibiotics

The eradication rates of Helicobacter pylori by the triple therapy consisting of a proton pump inhibitor (PPI) and two antimicrobial agents are mainly influenced by bacterial susceptibility to antimicrobial agents and magnitude of acid inhibition during the treatment with a PPI. Acid inhibition during the treatment is affected by the dosing schemes of acid inhibitory drugs (i.e., PPI), genotypes of drug-metabolizing enzymes (i.e., CYP450 2C19), drug transporters (i.e., multi-drug resistant transporter-1) and inflammatory cytokines (i.e., IL-1 beta). Modification of dosing schedules of a PPI, such as frequent PPI dosing and concomitant dosing with a histamine 2-receptor antagonist, could overcome these genetics-related differences in therapeutic effectiveness. For attaining higher eradication rates, the tailored regimen based on the relevant pharmacogenomics is preferable.

Effect of MDR1 C3435T polymorphism on cure rates of Helicobacter pylori infection by triple therapy with lansoprazole, amoxicillin and clarithromycin in relation to CYP 2C19 genotypes and 23S rRNA genotypes of H. pylori

BACKGROUND

Polymorphism in MDR1 is associated with variation in the plasma level of a proton pump inhibitor.

AIM

To investigate whether MDR1 polymorphism is associated with eradication rates of Helicobacter pylori by a triple therapy with lansoprazole, amoxicillin and clarithromycin in relation to CYP2C19 genotype status and bacterial susceptibility to clarithromycin.

METHODS

A total of 313 patients infected with H. pylori completed the treatment with lansoprazole 30 mg b.d., clarithromycin 200 mg b.d. and amoxicillin 750 mg b.d. for 1 week. MDR1 C3435T polymorphism and CYP2C19 genotypes of patients and sensitivity of H. pylori to clarithromycin were determined.

RESULTS

Logistic regression analysis revealed that the MDR1 polymorphism as well as CYP2C19 genotypes of patients and clarithromycin-resistance of H. pylori were significantly associated with successful eradication. Eradication rates for H. pylori were 82% (83/101: 95% CI = 73-89), 81% (112/139: CI = 73-87), and 67% (44/73: CI = 48-72) in patients with the MDR1 3435 C/C, C/T and T/T genotype, respectively (P = 0.001).

CONCLUSIONS

Polymorphism of MDR1 is one of the determinants of successful eradication of H. pylori by the triple therapy with lansoprazole, amoxicillin and clarithromycin, together with CYP2C19 genotype and bacterial susceptibility to clarithromycin.

Pharmacogenetics, drug-metabolizing enzymes, and clinical practice

The application of pharmacogenetics holds great promise for individualized therapy. However, it has little clinical reality at present, despite many claims. The main problem is that the evidence base supporting genetic testing before therapy is weak. The pharmacology of the drugs subject to inherited variability in metabolism is often complex. Few have simple or single pathways of elimination. Some have active metabolites or enantiomers with different activities and pathways of elimination. Drug dosing is likely to be influenced only if the aggregate molar activity of all active moieties at the site of action is predictably affected by genotype or phenotype. Variation in drug concentration must be significant enough to provide "signal" over and above normal variation, and there must be a genuine concentration-effect relationship. The therapeutic index of the drug will also influence test utility. After considering all of these factors, the benefits of prospective testing need to be weighed against the costs and against other endpoints of effect. It is not surprising that few drugs satisfy these requirements. Drugs (and enzymes) for which there is a reasonable evidence base supporting genotyping or phenotyping include suxamethonium/mivacurium (butyrylcholinesterase), and azathioprine/6-mercaptopurine (thiopurine methyltransferase). Drugs for which there is a potential case for prospective testing include warfarin (CYP2C9), perhexiline (CYP2D6), and perhaps the proton pump inhibitors (CYP2C19). No other drugs have an evidence base that is sufficient to justify prospective testing at present, although some warrant further evaluation. In this review we summarize the current evidence base for pharmacogenetics in relation to drug-metabolizing enzymes.

Effect of CYP2C19*17 gene variant on Helicobacter pylori eradication in peptic ulcer patients

OBJECTIVE

Eradication of Helicobacter pylori is an important treatment strategy in peptic ulcer patients. Current regimens of eradication consist of proton pump inhibitor (PPI) and two antibiotics. The principal enzyme involved in PPIs metabolism is CYP2C19, which exhibits an interindividual variability of activity, mainly due to genetic polymorphism. Two alleles (CYP2C19*2 and CYP2C19*3), responsible for slow PPIs metabolism, were previously associated with higher efficacy of eradication. Recently, a novel CYP2C19 gene variant (CYP2C19*17), associated with faster metabolism of CYP2C19 substrates, was described. In the present study, a potential association between CYP2C19*17 allele and lower H. pylori eradication efficacy was tested in a group of peptic ulcer patients.

METHODS

A total of 125 peptic ulcer patients, positive for H. pylori infection, were treated with triple therapy (pantoprazole+amoxicillin+metronidazole). Subsequently, the patients were divided into two groups (group 1 - success, and group 2 - failure of eradication after therapy) and genotyped for the presence of CYP2C19 variant alleles (*2, *3, and *17).

RESULTS

Frequency of CYP2C19 alleles in two groups of patients were: 56.4 versus 65 (p=0.060) for *1, 15.4 versus 5.3 (p=0.015) for *2, and 28.2 versus 25.5 (p=0.663) for *17 allele, respectively. CYP2C19*3 was not detected in the evaluated population. No significant differences in frequency nor distribution of *17 allele were found between two groups of patients. CYP2C19*2 allele was associated with successful H. pylori eradication (p<0.02), *2 allele carriers were found to be over 4-times more prone to the treatment compared to *1/*1 homozygotes (OR=4.2, p=0.015).

CONCLUSION

Our results suggest that, contrary to CYP2C19*2, CYP2C19*17 allele has no impact on efficacy of H. pylori eradication in peptic ulcer patients treated with pantoprazole.

MDR1 genotype-related pharmacokinetics: fact or fiction?

Multidrug resistant transporter MDR1/P-glycoprotein, the gene product of MDR1, is a glycosylated membrane protein of 170 kDa, belonging to the ATP-binding cassette superfamily of membrane transporters. A number of various types of structurally unrelated drugs are substrates for MDR1, and MDR1 and other transporters are recognized as an important class of proteins for regulating pharmacokinetics. The first investigation of the effects of MDR1 genotypes on pharmacotherapy was reported in 2000; a silent single nucleotide polymorphism (SNP), C3435T in exon 26, was found to be associated with the duodenal expression of MDR1, and thereby the plasma concentration of digoxin after oral administration. In the last 5 years, clinical studies have been conducted around the world on the association of MDR1 genotype with MDR1 expression and function in tissues, and with the pharmacokinetics and pharmacodynamics of drugs; however, there are still discrepancies in the results on C3435T. In 1995, a novel concept to predict in vivo oral pharmacokinetic performance from data on in vivo permeability and in vitro solubility has been proposed, and this Biopharmaceutical Classification System strongly suggested that the effects of intestinal MDR1 on the intestinal absorption of substrates is minimal in the case of commercially available oral drugs, and therefore MDR1 genotypes are little associated with the pharmacokinetics after oral administration. This review summarizes the latest reports for the future individualization of pharmacotherapy based on MDR1 genotyping, and attempts to explain discrepancies.

Developments in the inhibition of gastric acid secretion

Understanding the physiology of gastric acid secretion and the pathophysiology of acid-related diseases (e.g. gastrooesophageal reflux and peptic ulcer) has led to the development of numerous ways to decrease acid exposure. Pharmacologically one can try to neutralize secreted acid by antacids, prevent stimulation of the parietal cell, improve mucosal defences and block the functioning of the proton pump. Proton pump inhibitors (PPIs) inhibit the final step of acid secretion, and are currently the most potent acid inhibitors. Major therapeutic improvement within the PPI class appears unlikely, as agents in this class share similar chemistry, mode of action, and pharmacokinetic profiles. New approaches that block acid secretion are now being developed. Gastrin (CCK2) receptor antagonists and potassium-competitive acid blockers (P-CABs) are in clinical development.