Effect of co-administered inducer or inhibitor on omeprazole pharmacokinetics based on CYP2C19 genotype

Safety analysis of co-administering tacrolimus and omeprazole in renal transplant recipients - A review

Tacrolimus is a calcineurin inhibitor used to prevent rejection in allogenic solid organ transplant recipients, which is metabolized in the liver with cytochrome P450 isoforms 3A4 and 3A5 (CYP3A4, CYP3A5). In turn, proton pump inhibitors (PPIs), such as Omeprazole - a substrate and inhibitor of CYP2C19 and CYP3A4 enzymes - are administered to kidney transplant patients in order to prevent duodenal and gastric ulcer disease, associated with the glucocorticoid treatment. Simultaneous administration of both drugs in renal patients has the potential to trigger drug interactions. In fact, there are several mechanisms which may impact the pharmacokinetics of tacrolimus. Inhibition of the CYP2C19 isoform may suppress the metabolism of omeprazole, subsequently altering its metabolic pathway to be metabolized by the CYP3A4 enzyme in order to maintain adequate biotransformation. Therefore, the competition for CYP3A4 may affect the metabolism of tacrolimus and result in its increased plasma concentrations, as well as in adverse reactions. Another mechanism has been related to the genetic polymorphism of the CYP2C19 isoform. Since all these interactions may lead to dysfunctions of the transplanted kidney, it seems significant to eliminate their consequences, for instance via the administration of drugs which are neither substrates, nor inhibitors of the CYP3A4 enzyme. Finally, the nephrotoxic effect of omeprazole should also be accounted for. Bearing in mind the aforementioned observations, the aim of the presented paper was to review the available studies addressing the effect of omeprazole on the pharmacokinetics of tacrolimus.

Effects of CYP2C19 genetic polymorphism on the pharmacokinetics of tolperisone in healthy subjects

Tolperisone hydrochloride is a centrally-acting muscle relaxant used for relieving spasticities of neurological origin and muscle spasms associated with painful locomotor diseases. It is metabolized to the inactive metabolite mainly by CYP2D6 and, to a lesser extent, by CYP2C19 and CYP1A2. In our previous study, the pharmacokinetics of tolperisone was significantly affected by the genetic polymorphism of CYP2D6, but the wide interindividual variation of tolperisone pharmacokinetics was not explained by genetic polymorphism of CYP2D6 alone. Thus, we studied the effects of CYP2C19 genetic polymorphism on tolperisone pharmacokinetics. Eighty-one subjects with different CYP2C19 genotypes received a single oral dose of 150 mg tolperisone with 240 mL of water, and blood samples were collected up to 12 h after dosing. The plasma concentration of tolperisone was measured by a liquid chromatography-tandem mass spectrometry system. The CYP2C19PM group had significantly higher C_max and lower CL/F values than the CYP2C19EM and CYP2C19IM groups. The AUC_inf of the CYP2C19PM group was 2.86-fold and 3.00-fold higher than the CYP2C19EM and CYP2C19IM groups, respectively. In conclusion, the genetic polymorphism of CYP2C19 significantly affected tolperisone pharmacokinetics.

Drug metabolism and drug transport of the 100 most prescribed oral drugs

Safe and effective use of drugs requires an understanding of metabolism and transport. We identified the 100 most prescribed drugs in six countries and conducted a literature search on in vitro data to assess contribution of Phase I and II enzymes and drug transporters to metabolism and transport. Eighty-nine of the 100 drugs undergo drug metabolism or are known substrates for drug transporters. Phase I enzymes are involved in metabolism of 67 drugs, while Phase II enzymes mediate metabolism of 18 drugs. CYP3A4/5 is the most important Phase I enzyme involved in metabolism of 43 drugs followed by CYP2D6 (23 drugs), CYP2C9 (23 drugs), CYP2C19 (22 drugs), CYP1A2 (14 drugs) and CYP2C8 (11 drugs). More than half of the drugs (54 drugs) are known substrates for drug transporters. P-glycoprotein (P-gp) is known to be involved in transport of 30 drugs, while breast cancer resistance protein (BCRP) facilitates transport of 11 drugs. A considerable proportion of drugs are subject to a combination of Phase I metabolism, Phase II metabolism and/or drug transport. We conclude that the majority of the most frequently prescribed drugs depend on drug metabolism or drug transport. Thus, understanding variability of drug metabolism and transport remains a priority.

Evaluation of CYP2C19 activity using microdosed oral omeprazole in humans

Purpose

To investigate the suitability of microdosed oral omeprazole for predicting CYP2C19 activity in vivo in combination with simultaneous assessment of CYP3A and CYP2D6 activity using both microdosed midazolam and yohimbine.

Methods

An open, fixed-sequence study was carried out in 20 healthy participants. Single microdosed (100 µg) and therapeutic (20 mg) doses of omeprazole were evaluated without comedication and after administration of established CYP2C19 perpetrators fluconazole (inhibition) and rifampicin (induction). To prevent degradation of the uncoated omeprazole microdose, sodium bicarbonate buffer was administered. The pharmacokinetics of omeprazole and its 5-hydroxy-metabolite were assessed as well as the pharmacokinetics of midazolam and yohimbine to estimate CYP3A4 and CYP2D6 activity.

Results

Calculated pharmacokinetic parameters after administration of 100 µg and 20 mg omeprazole in healthy subjects suggest dose proportionality. Omeprazole clearance was significantly decreased by fluconazole from 388 [95% CI: 266–565] to 47.2 [42.8–52.0] mL/min after 20 mg omeprazole and even further after 100 µg omeprazole (29.4 [24.5–35.1] mL/min). Rifampicin increased CYP2C19-mediated omeprazole metabolism. The omeprazole hydroxylation index was significantly related to omeprazole clearance for both doses. Both fluconazole and rifampicin altered CYP3A4 activity whereas no change of CYP2D6 activity was observed at all.

Conclusions

Microdosed oral omeprazole is suitable to determine CYP2C19 activity, also during enzyme inhibition and induction. However, the administration of sodium bicarbonate buffer also had a small influence on all victim drugs used.

Trial registration

EudraCT: 2017–004270-34.

Supplementary information

The online version contains supplementary material available at 10.1007/s00228-022-03304-3.

An improved TK-NOG mouse as a novel platform for humanized liver that overcomes limitations in both male and female animals

We developed a novel immunodeficient NOG mouse expressing HSVtk mutant clone 30 cDNA under the control of mouse transthyretin gene enhancer/promoter (NOG-TKm30) to acquire fertility in males and high inducibility of liver injury in females. Maximum human albumin levels (approx. 15 mg/mL plasma) in both male and female NOG-TKm30 mice engrafted with human hepatocytes (humanized liver mice) were observed 8-12 weeks after transplantation. Immunohistochemical analyses revealed abundant expression of major human cytochrome P450 (CYP) enzymes (CYP1A2, CYP2C9, CYP2D6, CYP2E1, and CYP3A4) in reconstituted liver with original zonal distribution. In vivo drug-drug interactions were observed in humanized liver mice as decreased area under the curve of midazolam (CYP3A4/5 substrate) and omeprazole (CYP3A4/5 and CYP2C19 substrate) after oral administration of rifampicin. Furthermore, we developed a pregnant model for evaluating prenatal exposure to drugs. The detection of thalidomide metabolites in the fetuses of pregnant humanized liver mice indicates that the novel TK model can be used for developmental toxicity studies requiring the assessment of human drug metabolism. These results suggest that the limitations of traditional TK-NOG mice can be addressed using NOG-TKm30 mice, which constitute a novel platform for humanized liver for both in vivo and in vitro studies.

Prediction of the Area under the Curve Using Limited-Point Blood Sampling in a Cocktail Study to Assess Multiple CYP Activities

A cocktail study is an in vivo evaluation method to assess multiple CYP activities via a single trial and single administration of a cocktail drug that is a combination of multiple CYP substrates. However, multiple blood samples are required to evaluate the pharmacokinetics of a CYP probe drug. A limited-point sampling method is generally beneficial in clinical studies because of the simplified protocol and reduced participant burden. The aim of this study was to evaluate whether a limited-point plasma concentration analysis of CYP substrates in a cocktail drug could predict their area under the curve (AUC). We created prediction models of five CYP substrates (caffeine, losartan, omeprazole, dextromethorphan, and midazolam) using multiple linear regressions from the data of two cocktail studies, and then performed predictability analysis of these models using data derived from data in the co-administration with inducer (rifampicin) and inhibitors (fluvoxamine and cimetidine). For the administration of inhibitors, the AUC prediction accuracy (mean absolute error (MAE)) were <39.5% in Model 1 and <26.2% in Model 2 which were created using 1- and 4-point sampling data. MAE shows larger values in the administration of inducer in compared with the administration of inhibitors. The accuracy of the prediction in Model 2 could be acceptable for screening of inhibitions. MAE for caffeine, dextromethorphan, and midazolam were acceptable in the model that used 4 sampling points from all data. The use of this method could reduce the burden on the subject and make it possible to evaluate each AUC in a minimally invasive manner.

Evaluation of CYP2C19 Gene Polymorphisms in Patients with Acid Peptic Disorders Treated with Esomeprazole

Background

CYP2C19 is a highly polymorphic gene that encodes an enzyme with the same name and whose function is associated with the metabolism of many important drugs, such as proton pump inhibitors (such as esomeprazole, which is used for the treatment of acid peptic disease). Genetic variants in CYP2C19 alter protein function and affect drug metabolism. This study aims to genotypically and phenotypically characterize the genetic variants in the CYP2C19 gene in 12 patients with acid peptic disorders and different therapeutic profiles to proton pump inhibitor (PPI) drugs. The patients were randomly selected from a controlled, randomized and blinded clinical pilot trial of 33 patients. We determined the presence and frequency of single nucleotide polymorphisms (SNPs) within exons 1–5 and 9, the intron-exon junctions, and a fragment in the 3ʹ UTR region of the CYP2C19 gene using Sanger sequencing. Undescribed polymorphisms were analyzed by free online bioinformatics tools to evaluate the potential molecular effects of these genetic variants.

Results

We identified nine polymorphisms, six of which had no reported functions. One of these genetic variants, with a functional impact, not yet reported (p.Arg132Trp) was predicted by bioinformatic tools as potentially pathogenic. This finding suggests that p.Arg132Trp could be related to poor metabolizers of drugs metabolized by CYP2C19.

Conclusion

We identified the genotype spectrum of variants in CYP2C19. The genotype spectrum of variants in CYP2C19 could predict the treatment response and could support to evaluate clinical efficacy in patients treated with esomeprazole.

Verification of a cocktail approach for quantitative drug-drug interaction assessment: a comparative analysis between the results of a single drug and a cocktail drug

A cocktail approach is a method to comprehensively evaluate the activity of cytochrome P450 enzymes (CYPs) by co-administering multiple CYP substrates. This is the first report that compares the results from a cocktail study to a single substrate separate administration study (single study) with concomitant administration of CYP inducers/inhibitors. The validity of a cocktail study for use as a quantitative drug-drug interactions (DDIs) assessment was evaluated.We administered a cocktail drug (caffeine, losartan, omeprazole, dextromethorphan, midazolam) with rifampicin, cimetidine or fluvoxamine. A comparative analysis was performed between the results of a cocktail study and single studies. The results of single studies were obtained from a literature review and the trials of single substrate separate administration.A strong positive correlation of the AUC ratio of all drugs between single studies and the cocktail study was obtained. The ratio of AUC change of 12 combinations converged to 0.82-1.09, and 2 combinations ranged between 0.74-1.32.The differences in the degree of interaction between the single studies and cocktail study are acceptable to evaluate DDIs for almost all combinations. Our results indicate that a cocktail study is an adequate and quantitative evaluation method for DDIs.

Application of Microdosed Intravenous Omeprazole to Determine Hepatic CYP2C19 Activity

Omeprazole is an established probe drug to assess cytochrome P450 (CYP) 2C19 activity (phenotyping). Because it has nonlinear pharmacokinetics (PK) after oral administration (autoinhibition of metabolism), the true impact of coadministered perpetrators on CYP2C19 substrates might be underestimated after regular doses. We tested the dose linearity of an intravenous omeprazole microdose of 100 µg and compared it with a 20-mg dose in 4 healthy poor metabolizers (PMs) and 6 extensive metabolizers (EMs) of CYP2C19 in the presence and absence of a strong inhibitor (voriconazole). Without voriconazole, omeprazole exposure was dose-proportional irrespective of the genotype, but in PMs geometric mean ratios (GMRs) of AUC_0-∞ were 6.6-fold higher and molar metabolic ratios of 5-OH omeprazole/omeprazole approximately 10-fold lower. Voriconazole increased omeprazole exposure in EMs approximately 5-fold (AUC_0-4 GMR after 100 µg omeprazole, 4.61; 90% confidence interval [CI], 2.69-7.89; AUC_0-4 GMR after 20 mg omeprazole, 5.5; 90%CI, 1.07-1.46), whereas no clinically significant impact on PK in PMs was observed (GMR AUC_0-4 after 100 µg omeprazole, 1.29; 90%CI, 0.81-2.04; GMR AUC_0-4 after 20 mg omeprazole, 1.25; 90%CI, 1.07-1.46). Linear regression and Bland-Altman analyses revealed excellent agreement between AUC_0-∞ and AUC_0-4 of omeprazole (r² = 0.987; bias, 0.35%; 95%CI, -3.197% to 3.89%) and also the molar metabolic ratio, 5-OH omeprazole/omeprazole (r² = 0.987; bias, -3.939; 95%CI, -9.06% to -1.18%), suggesting that an abbreviated sampling protocol can be used for intravenous CYP2C19 phenotyping and drug interaction studies. In conclusion, the PK of intravenous omeprazole microdoses closely reflects the changes observed with regular omeprazole doses; however, to avoid autoinhibition of probe drugs, microdosing appears to be the favorable technique.

Clinical evaluation of drug-drug interactions between the cytochrome P450 substrates selexipag and clopidogrel in Japanese volunteers

AIMS

The strong cytochrome P450 (CYP) 2C8 inhibitor gemfibrozil has been demonstrated to increase the area under the plasma concentration-time curve from 0 to infinity (AUC_0-∞ ) of ACT-333679, an active metabolite of selexipag, by 11-fold. Similarly to gemfibrozil, the CYP2C8 inhibitor clopidogrel increased ACT-333679 concentration by 1.9-fold after a single loading dose (300 mg once daily) and 2.7-fold after repeated treatment with the maintenance dose (75 mg once daily) in Europeans. However, the effects of clopidogrel on the pharmacokinetics of selexipag and ACT-333679 have not been fully elucidated in the Japanese population.

METHODS

We investigated the effect of clopidogrel on the pharmacokinetics of selexipag and ACT-333679 in 14 healthy Japanese volunteers.

RESULTS

The concomitant administration of clopidogrel with selexipag did not influence the maximum concentration and AUC_0-∞ of selexipag, whereas it significantly increased AUC_0-∞ of ACT-333679 by approximately 1.90-fold (90% confidence interval 1.69-2.14) without changing the maximum concentration. When selexipag was administered 1 day after clopidogrel was discontinued, the increase in AUC_0-∞ of ACT-333679 was 1.37-fold (90% confidence interval 0.93-2.02), suggesting that, although the inhibitory effect of clopidogrel on CYP2C8 was reduced, it persisted for at least 1 day after withdrawal.

CONCLUSION

Our results demonstrated the impact of clopidogrel on the pharmacokinetics of selexipag and its active metabolite and suggested that selexipag should be carefully prescribed with clopidogrel with dose adjustment or reducing the dosing frequency in Japanese clinical settings.