Comparison of enantioselective disposition of rabeprazole versus lansoprazole in renal-transplant recipients who are CYP2C19 extensive metabolizers

Drug-Drug Interaction between Tacrolimus and Vonoprazan in Kidney Transplant Recipients

Kidney transplant recipients with tacrolimus-based immunosuppressive therapy are often treated with proton-pump inhibitors (PPIs) to prevent gastric ulcer complications. Vonoprazan, a potassium-competitive acid blocker, is a novel PPI possessing different metabolic pathways from conventional PPIs (e.g., omeprazole, lansoprazole and rabeprazole). However, no data are available on the change in blood concentration of tacrolimus after switching rabeprazole, a conventional PPI, to vonoprazan coadministration in the initial period of post-transplantation. This is a retrospective study of 18 kidney transplant recipients. The blood concentration and the concentration to dose (C/D) ratio of tacrolimus were compared before and after switching from rabeprazole to vonoprazan. Impacts of CYP2C19 and CYP3A5 genetic polymorphisms on the drug-drug interaction were also examined. The median (range) trough concentration of tacrolimus was significantly increased from 5.2 (3.6-7.4) to 8.1 (6.1-11.7) ng/mL (p < 0.0005) after switching from rabeprazole to vonoprazan. The C/D ratio of tacrolimus was also significantly increased from 38.1 (16.5-138.1) to 48.9 (26.2-207.2) (p < 0.0005). The percent changes of tacrolimus concentrations and C/D were 65.8% and 41.8%, respectively. CYP2C19 and CYP3A5 genetic polymorphisms did not affect the change in concentration and C/D ratio of tacrolimus. The present study indicates that vonoprazan coadministration increases the tacrolimus concentration regardless of CYP2C19 or CYP3A5 genetic polymorphisms. Thus, frequent monitoring of blood tacrolimus concentration is required when vonoprazan is introduced as an intensive gastric acid blocker in the early phase of post-transplantation.

Chiral separation in the class of proton pump inhibitors by chromatographic and electromigration techniques: An overview

Proton pump inhibitors (PPIs) are benzimidazole-derivative chiral sulfoxides, frequently used in the treatment of gastric hyperacidity-related disorders. Due to their stereoselective metabolism, the eutomeric forms of PPIs can present a more advantageous pharmacokinetic profile by comparison with the distomers or racemates. Moreover, two representatives of the class are used in therapy both as racemates and as pure enantiomers (esomeprazole, dexlansoprazole). A relatively large number of enantioseparation methods employed for the stereoselective determination of PPIs from pharmaceutical, biological, and environmental matrices were published in the past three decades. The purpose of the current overview is to provide a systematic survey of the available chiral separation methods published since the introduction of PPIs in the therapy up to the present. Analytical and bioanalytical methods using different chromatographic and electromigration techniques reported for the enantioseparation of omeprazole, lansoprazole, pantoprazole, rabeprazole, ilaprazole, and tenatoprazole are included. The analytical conditions of the presented methods are summarized in three comprehensive tables, while a critical discussion of the applied techniques, possible mechanism of enantiorecognition, and future perspectives on the topic are also presented.

Biomarkers for individualized dosage adjustments in immunosuppressive therapy using calcineurin inhibitors after organ transplantation

Calcineurin inhibitors (CNIs), such as cyclosporine A and tacrolimus, are widely used immunosuppressive agents for the prevention of post-transplantation rejection and have improved 1-year graft survival rates by up to 90%. However, CNIs can induce severe reactions, such as acute or chronic allograft nephropathy, hypertension, and neurotoxicity. Because CNIs have varied bioavailabilities, narrow therapeutic ranges, and individual propensities for toxic effects, therapeutic drug monitoring is necessary for all CNIs. Identifying the genetic polymorphisms in drug-metabolizing enzymes will help to determine personalized dosage regimens for CNIs, as CNIs are substrates for CYP3A5 and P-glycoprotein (P-gp, MDR1). CNIs are often concomitantly administered with voriconazole or proton pump inhibitors (PPIs), giving rise to drug interaction problems. Voriconazole and PPIs can increase the blood concentrations of CNIs, and both are primarily metabolized by CYP2C19. Thus, it is expected that interactions between CNIs and voriconazole or PPI would be affected by CYP2C19 and CYP3A5 polymorphisms. CNI-induced acute kidney injury (AKI) is a serious complication of transplantations. Neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule 1 (KIM-1) are noninvasive urinary biomarkers that are believed to be highly sensitive to CNI-induced AKI. In this article, we review the adverse events and pharmacokinetics of CNIs and the biomarkers related to CNIs, including CYP3A5, CYP2C19, MDR1, NGAL, and KIM-1. We hope that these data will help to identify the optimal biomarkers for monitoring CNI-based immunosuppressive therapy after organ transplantation.

Influence of CYP2C19 and ABCB1 polymorphisms on plasma concentrations of lansoprazole enantiomers after enteral administration

An intraoral annihilation enteric-coated preparation of lansoprazole is often administered via intestinal fistula. The purpose of this study was to determine the plasma concentrations of lansoprazole enantiomers after enteral administration in subjects with cytochrome P4502C19 (CYP2C19) and ABCB1 C3435T genotypes. Fifty-one patients who underwent a curative oesophagectomy for oesophageal cancer were enrolled in this study. After a single enteral dose of racemic lansoprazole (30 mg), plasma concentrations of lansoprazole enantiomers were measured 4 h post-dose (C(4h)). There were significant differences in the C(4h) of (R)- and (S)-lansoprazole and the R/S-enantiomer ratio for three CYP2C19 genotype groups (*1/*1, *1/*2 ± *1/*3, and *2/*2 ± *2/*3 ± *3/*3 (poor metabolizers (PMs)), but not the ABCB1 C3435T genotypes. In a stepwise forward selection multiple regression analysis, the C(4h) of (R)- and (S)-lansoprazole were associated with CYP2C19 PMs (p = 0.0005 and < 0.0001 respectively) and age (p = 0.0040 and 0.0121 respectively), while the R/S-enantiomer ratio was associated with CYP2C19*1/*1 (p = 0.0191) and CYP2C19 PMs (p = 0.0426). Direct administration to the jejunum is unaffected by residence time in the stomach and the gastric emptying rate. With enteral administration, CYP2C19 phenotyping of patients using the lansoprazole R/S enantiomer index at C(4h) could be possible.

Stereoselective disposition of proton pump inhibitors

It is estimated that about half of all therapeutic agents are chiral, but most of these drugs are administered in the form of the racemic mixture, i.e. a 50/50 mixture of its enantiomers. However, chirality is one of the main features of biology, and many of the processes essential for life are stereoselective, implying that two enantiomers may work differently from each other in a physiological environment. Thus, receptors or metabolizing enzymes would recognize one of the ligand enantiomers in favour of the other. With one exception, all presently marketed proton pump inhibitors (PPIs)--omeprazole, lansoprazole, pantoprazole and rabeprazole--used for the treatment of gastric acid-related diseases are racemic mixtures. The exception is esomeprazole, the S-enantiomer of omeprazole, which is the only PPI developed as a single enantiomer drug. The development of esomeprazole (an alkaline salt thereof, e.g. magnesium or sodium) was based on unique metabolic properties that clearly differentiated esomeprazole from omeprazole, the racemate. At comparable doses, these properties led to several clinical advantages, for example higher bioavailability in the majority of patients, i.e. the extensive metabolizers (EMs; 97% in Caucasian and 80-85% in Asian populations), lower exposure in poor metabolizers (PMs; 3% in Caucasian and 15-20% in Asian populations) and lower interindividual variation. For the other, i.e. racemic, PPIs there are some data available on the characteristics of the individual enantiomers, and we have therefore undertaken to analyse the current literature with the purpose of evaluating the potential benefits of developing single enantiomer drugs from lansoprazole, pantoprazole and rabeprazole. For lansoprazole, the plasma concentrations of the S-enantiomer are lower than those of the R-enantiomer in both EMs and PMs, and, consequently, the variability in the population or between EMs and PMs is not likely to decrease with either of the lansoprazole enantiomers. Furthermore, plasma protein binding differs between the two lansoprazole enantiomers, in that the amount of the free S-enantiomer is two-fold higher than that of the R-enantiomer. This will counteract the difference seen in total plasma concentrations of the enantiomers. Also, studies using expressed human cytochrome P450 isoenzymes show that the metabolism of one enantiomer is significantly affected by the presence of the other, which is likely to result in different pharmacokinetics when administering a single enantiomer. For pantoprazole, there is a negligible difference in plasma concentrations between the two enantiomers in EMs, while the difference is substantial in PMs. The difference in AUC between PMs and EMs would decrease to some extent, but in the majority of the population the variability and efficacy would not be altered with a single enantiomer of pantoprazole. The metabolism of the enantiomers of rabeprazole displays stereoselectivity comparable to that of lansoprazole, i.e. the exposure of the R-enantiomer is higher than that of the S-enantiomer in EMs as well as in PMs, which, by analogy to lansoprazole, makes them less suitable for development of a single enantiomer drug. Furthermore, the chiral stability of the rabeprazole enantiomers may be an issue because of significant degradation of rabeprazole to its sulfide analogue, which is subject to non-stereoselective metabolic regeneration of a mixture of the two enantiomers. In conclusion, in contrast to esomeprazole, the S-enantiomer of omeprazole, minimal if any clinical advantages would be expected in developing any of the enantiomers of lansoprazole, pantoprazole, or rabeprazole as compared with their racemates.

Influence of rabeprazole and lansoprazole on the pharmacokinetics of tacrolimus in relation to CYP2C19, CYP3A5 and MDR1 polymorphisms in renal transplant recipients

The objective of this study was to evaluate whether genetic polymorphisms of CYP2C19, CYP3A5 and MDR1 significantly impact the interaction between tacrolimus and rabeprazole or lansoprazole. Seventy-three recipients were randomly assigned after renal transplantation to receive repeated doses of tacrolimus for 28 days with a regimen of either 20 mg of rabeprazole or 30 mg of lansoprazole. Blood concentrations of tacrolimus were measured by microparticle enzyme immunoassay. The mean daily dose and the dose-adjusted area under the plasma concentration-time curves from 0 to 12 h (AUC(0-12)) of tacrolimus coadministered with rabeprazole or lansoprazole were the lowest and highest, respectively, in CYP2C19 poor metabolizers (PMs) having the CYP3A5*3/*3 genotype (0.084 and 0.112 mg/kg/day and 1.269 and 1.033 ng.h/ml/mg/kg, respectively). On the other hand, the mean dose-adjusted AUC(0-12) of tacrolimus coadministered with rabeprazole or lansoprazole were the highest in CYP2C19 PMs having the MDR13435CC+CT genotype, but not significantly. The present study indicates that there are significant interactions between tacrolimus and rabeprazole or lansoprazole in CYP2C19 PM renal transplant recipients bearing the CYP3A5*3/*3 genotypes. For recipients having these genetic polymorphisms, lower dosages of tacrolimus are required to achieve the target therapeutic index.

Drug-induced changes in P450 enzyme expression at the gene expression level: a new dimension to the analysis of drug-drug interactions

Drug-drug interactions (DDIs) caused by direct chemical inhibition of key drug-metabolizing cytochrome P450 enzymes by a co-administered drug have been well documented and well understood. However, many other well-documented DDIs cannot be so readily explained. Recent investigations into drug and other xenobiotic-mediated expression changes of P450 genes have broadened our understanding of drug metabolism and DDI. In order to gain additional information on DDI, we have integrated existing information on drugs that are substrates, inhibitors, or inducers of important drug-metabolizing P450s with new data on drug-mediated expression changes of the same set of cytochrome P450s from a large-scale microarray gene expression database of drug-treated rat tissues. Existing information on substrates and inhibitors has been updated and reorganized into drug-cytochrome P450 matrices in order to facilitate comparative analysis of new information on inducers and suppressors. When examined at the gene expression level, a total of 119 currently marketed drugs from 265 examined were found to be cytochrome P450 inducers, and 83 were found to be suppressors. The value of this new information is illustrated with a more detailed examination of the DDI between PPARalpha agonists and HMG-CoA reductase inhibitors. This paper proposes that the well-documented, but poorly understood, increase in incidence of rhabdomyolysis when a PPARalpha agonist is co-administered with a HMG-CoA reductase inhibitor is at least in part the result of PPARalpha-induced general suppression of drug metabolism enzymes in liver. The authors believe this type of information will provide insights to other poorly understood DDI questions and stimulate further laboratory and clinical investigations on xenobiotic-mediated induction and suppression of drug metabolism.

Influence of Cytochrome P450 (CYP)??3A5 Polymorphisms on the Pharmacokinetics of Lansoprazole Enantiomers in CYP2C19 Extensive Metaboliser Renal Transplant Recipients

BACKGROUND AND OBJECTIVE

Lansoprazole is extensively metabolised by cytochrome P450 (CYP) 2C19 and CYP3A4. The purpose of this study was to evaluate the effects of CYP3A5 polymorphism (A6986G) on the pharmacokinetics of lansoprazole enantiomers in renal transplant recipients who are CYP2C19 extensive metabolisers (EMs).

METHODS

Among 40 Japanese CYP2C19 EMs, 20 had the CYP3A5*1 allele (*1/*1 in two subjects and *1/*3 in 18 subjects) and 20 had the CYP3A5*3/*3 genotype. After repeated oral doses of racemic lansoprazole 30mg once daily for 28 days, plasma concentrations of lansoprazole enantiomers were determined using high performance liquid chromatography.

RESULTS

The mean area under the plasma concentration-time curves from 0 to infinity (AUC(infinity)) of (R)- and (S)-lansoprazole in recipients with the CYP3A5*1 allele were 3145 and 384 ng * h/mL, respectively, compared with 4218 and 587 ng * h/mL in recipients with the CYP3A5*3/*3 genotype. The AUC(infinity) and the maximum plasma concentration of (R)- and (S)-lansoprazole in subjects with the CYP3A5*3/*3 genotype were greater than subjects with CYP3A5*1/*1 + *1/*3 alleles. The mean R/S ratio for AUC of lansoprazole in each CYP3A5 genotype group was the same (12.6).

CONCLUSION

Our findings show that CYP3A5 genotype is not an important determinant of enantioselective disposition of lansoprazole. Based on our results and those of previous studies, the enantioselective disposition of lansoprazole appears to be primarily influenced by enantioselective metabolism by CYP2C19 rather than by CYP3A.

Enantioselective disposition of rabeprazole in relation to CYP2C19 genotypes

AIM

Rabeprazole is metabolized to some extent by CYP2C19. The purpose of this study was to elucidate the pharmacokinetics of each rabeprazole enantiomer in three different CYP2C19 genotype groups.

METHODS

Twenty-four healthy subjects, of whom each each were homozygous extensive metabolizers (homEMs), heterozygous extensive metabolizers (hetEMs) and poor metabolizers (PMs) for CYP2C19, participated in our study. After a single oral dose of 20 mg of racemic rabeprazole, the plasma concentrations of the rabeprazole enantiomers were measured over the course of 24 h.

RESULTS

The area under the plasma concentration-time curves (AUC) of (R)-rabeprazole in homEMs, hetEMs and PMs were 1.8-, 2.2- and 2.4-fold, respectively, greater than those of (S)-rabeprazole; the relative AUC ratios of (R)- and (S)-rabeprazole in homEMs, hetEMs and PMs were 1:1.1:2.1 and 1:0.9:1.5, respectively. The mean maximum plasma concentrations (Cmax) of (R)-rabeprazole in homEMs, hetEMs and PMs were 1.7-, 1.9- and 1.8-fold higher, respectively, than those of the corresponding (S)-enantiomer (P<0.05). There was no difference between homEMs and PMs in the elimination half-life of (S)-rabeprazole, whereas the elimination half-life of (R)-rabeprazole was significantly longer in PMs than in homEMs [1.7 h (1.4, 2.0) (mean (95% confidence interval)]vs. 0.8 h (0.6, 1.0), respectively, P<0.0001).

CONCLUSIONS

(R)-Rabeprazole disposition was influenced to a greater degree by CYP2C19 genetic polymorphisms than was that of (S)-rabeprazole. The effect of CYP2C19 polymorphisms on the stereoselective disposition of rabeprazole was less than those of lansoprazole and omeprazole.

Enantioselective Disposition of Lansoprazole and Rabeprazole in Human Plasma

Lansoprazole is extensively metabolized by CYP2C19 and CYP3A4 in the liver, whereas rabeprazole is primarily converted non-enzymatically to rabeprazole-thioether, with only some being oxidized by CYP2C19 and CYP3A4. Lansoprazole and rabeprazole possess asymmetric sulfur in their chemical structure and have typically been used clinically as a racemic mixture. This article reviews the pharmacokinetic differences between enantiomers of lansoprazole and rabeprazole in relation to the CYP2C19 genotypes. In our studies in healthy Japanese subjects, the magnitude of contribution of each lansoprazole enantiomer for CYP2C19 was greater than that for CYP3A4. CYP2C19 influenced the disposition of (S)-lansoprazole to a greater extent than the (R)-enantiomer. The R/S ratios for the AUC of lansoprazole in CYP2C19 homEMs, hetEMs and PMs was 12.7, 8.5 and 5.8, respectively. On the other hand, (R)-rabeprazole disposition was influenced to a greater degree by CYP2C19 genetic polymorphisms than (S)-rabeprazole. However, the R/S ratios for the AUC of rabeprazole in CYP2C19 homEMs, hetEMs and PMs was only 1.8, 2.2 and 2.4, respectively, suggesting a lesser effect of CYP2C19 polymorphisms on the stereoselective disposition of rabeprazole compared to lansoprazole. Such a difference in the AUC between rabeprazole enantiomers is likely to be dependent on stereoselectivity in the CYP3A4-mediated metabolic conversion from rabeprazole-thioether to rabeprazole. Both enantiomers of these PPIs have been reported to possess equal potency. Therefore, particularly with lansoprazole, the use of (R)-lansoprazole alone would be highly desirable for use in clinical applications.

Determination of rabeprazole enantiomers and their metabolites by high-performance liquid chromatography with solid-phase extraction

Here, we describe the development of a rapid, simple and sensitive high-performance liquid chromatography (HPLC) method for the simultaneous quantitative determination of rabeprazole enantiomers (1a,b) and their metabolites, rabeprazole-thioether (2) and rabeprazole sulfone (3), in human plasma. Analytes and the internal standard (omeprazole-thioether) were separated using a mobile phase of 0.5 M NaClO4-acetonitrile (6:4, v/v) over a Chiral CD-Ph column. Analysis required only 100 microl of plasma and involved solid-phase extraction with an Oasis HLB cartridge, which gave high recovery (>91.8%) with good selectivity for all analytes. The lower limit of quantification was 5 ng/ml for analytes 1a, 1b and 3 and 10 ng/ml for 2. Linearity of this assay was determined to lie between 5 and 1000 ng/ml for 1a, 1b and 3 and 10 and 1000 ng/ml for 2 (r2>0.982 of the regression line). Inter- and intra-day coefficients of variation were less than 7.8% and accuracies were within 8.4% over the linear range for all analytes. Our results indicate that this method is applicable to the simultaneous monitoring of plasma levels of rabeprazole enantiomers and associated metabolites in human plasma.

Stereoselective metabolism of rabeprazole-thioether to rabeprazole by human liver microsomes

OBJECTIVE

Rabeprazole is metabolized mainly non-enzymatically to rabeprazole-thioether. This in vitro study was designed to clarify the stereoselective oxidation mechanism and to identify the enzyme(s) involved in the metabolic breakdown of rabeprazole-thioether to rabeprazole.

METHODS

Rabeprazole-thioether was incubated with human liver microsomes and several recombinant cytochrome P450 (CYP) enzymes (CYPs 1A2, 2A6, 2B6, 2C9, 2C19, 2D6, 2E1, and 3A4). High-performance liquid chromatography was used for identification and quantification of each rabeprazole enantiomer.

RESULTS

The K(m ) and V(max ) values for the formation of (R)-rabeprazole from rabeprazole-thioether in human liver microsomes were 6.6 microM and 92 pmol/min/mg protein, respectively, whereas those for the formation of (S)-rabeprazole were 5.1 microM and 21 pmol/min/mg protein, respectively. CYP3A4 was found to be the major enzyme responsible for(R)- and (S)-rabeprazole formation from rabeprazole-thioether. The intrinsic clearance (V(max ) /K(m )) for the oxidation by CYP3A4 of (R)-rabeprazole was 3.5-fold higher than that for the (S)-enantiomer (81 nl/min/pmol of P450 vs. 23 nl/min/pmol of P450). On the other hand, CYP2C19 and CYP2D6 were the main enzymes catalyzing the formation of desmethylrabeprazole-thioether from rabeprazole-thioether. The mean K(m ) and V(max ) values of desmethylrabeprazole-thioether formation for CYP2C19 were 5.1 microM and 600 pmol/min/nmol of P450, respectively, whereas those for CYP2D6 were 15.1 microM and 736 pmol/min/nmol of P450, respectively.

DISCUSSION

Rabeprazole is reduced mainly non-enzymatically to rabeprazole-thioether, which is further stereoselectively re-oxidized by CYP3A4 mainly to (R)-rabeprazole. The difference in the enantioselective disposition of rabeprazole is determined by stereoselectivity in CYP3A4-mediated metabolic conversion from rabeprazole-thioether to rabeprazole.