Effect of hepatic drug transporter polymorphisms on the pharmacokinetics of mycophenolic acid in patients with severe renal dysfunction before renal transplantation

Evaluation of mycophenolic acid exposure in a patient with immune-related hepatotoxicity caused by nivolumab and ipilimumab therapy for malignant melanoma: a case report

BACKGROUND

Guidelines such as the National Comprehensive Cancer Network recommend mycophenolate mofetil (MMF) for the treatment of severe steroid-refractory immune-related hepatotoxicity. Mycophenolic acid (MPA) is an active form of MMF that suppresses T- and B-lymphocyte proliferation and immune-related adverse events caused by immune checkpoint inhibitors. MPA has a narrow therapeutic range (37-70 µg·h/mL) and overexposure increases the risk of leukopenia in transplantation. However, the optimal use of MMF in oncology has not yet been established; thus, monitoring plasma MPA concentrations is necessary to avoid excessive immunosuppression in oncology practice.

CASE PRESENTATION

We evaluated plasma MPA concentration in a 75-year-old man with immune-related hepatotoxicity following nivolumab and ipilimumab combination therapy for malignant melanoma. The patient developed severe hepatotoxicity after immunotherapy, and immunosuppressant therapy with corticosteroids was initiated. The patient then developed steroid-refractory immune-related hepatotoxicity; therefore, MMF (1,000 mg twice daily) was co-administered. Seven days after the administration of MMF, the plasma MPA concentration was measured using an enzyme multiplied immunoassay technique. The area under the plasma concentration-time curve for MPA from 0 to 12 h was 41.0 µg·h/mL, and the same dose of MMF was continued. Grade 2 lymphocytopenia, which could be attributed to MMF, was observed during the administration period. Unfortunately, the patient was infected with SARS-CoV-2 and died from respiratory failure.

CONCLUSION

Our patient did not exceed the upper limit of MPA levels as an index of the onset of side effects of kidney transplantation and achieved rapid improvement in liver function. Prompt initiation of MMF after assessment of the steroid effect leads to adequate MPA exposure. Therapeutic drug monitoring should be considered when MMF is administered, to avoid overexposure.

Influence of genetic polymorphisms on pharmacokinetics and treatment response of mycophenolic acid: a scoping review

This scoping review explores the impact of genetic polymorphisms on the pharmacokinetics and treatment responses of mycophenolic acid (MPA), an immunosuppressant. The study includes 83 articles from 1226 original studies, focusing on transplantation (n = 80) and autoimmune disorders (n = 3). Genetic variants in uridine 5'-diphospho-glucuronosyltransferase (UGT1A9, UGT1A8 and UGT2B7) and transmembrane transporters (ABCC2, SLCO1B1, SLCO1B3 and ABCB1) significantly affected MPA's pharmacokinetics and susceptibility to its adverse effect. Whereas variants in several genes including UGT1A9, UGT2B7, IMPDH1 and IMPDH2 have been associated with a higher risk of transplant rejection. However, there is a lack of studies on MPA's impact on autoimmune disorders and limited research on the Asian population. The findings underscore the need for further research on MPA's impact across different populations and diseases, particularly among other Asian ethnic groups, to advance personalized medicine in MPA therapy.

The pharmacogenetics of tacrolimus in renal transplant patients: association with tremors, new-onset diabetes and other clinical events

Our study is the first study to investigate the effect of SNPs in CYP3A5, CYP3A4, ABCB1 and POR genes on the incidence of tremors, nephrotoxicity, and diabetes mellitus. A total of 223 renal transplant patients receiving tacrolimus and mycophenolate mofetil (MMF) were recruited. Both adults and children patients participated in the study. Genotyping was performed using PROFLEX-PCR followed by RFLP. MPA and tacrolimus plasma concentrations were measured by immunoassay. The AUC0-12h of MMF was estimated by a Bayesian method. We found a statistically significant association between the CYP3A5*3 and CYP3A4*1B genotypes and the tacrolimus exposure. We found a lower occurrence of nephrotoxicity (p = 0.03), tremor (p = 0.01), and new-onset diabetes (p = 0.002) associated with CYP3A5*1 allele. The CYP3A4*1B allele was significantly associated with a lower occurrence of new-onset diabetes (p = 0.026). The CYP3A5*1 allele was significantly associated with an increased risk of acute and chronic rejection (p = 0.03 and p < 0.001, respectively). Our results support the usefulness of tacrolimus pharmacokinetics in pre-kidney transplant assessments.

Influence of Calcineurin Inhibitors and Genetic Polymorphism of Transporters on Enterohepatic Circulation and Exposure of Mycophenolic Acid in Chinese Adult Renal Allograft Recipients

There is significant enterohepatic circulation (EHC) during the disposition of mycophenolic acid (MPA). The aim of this study was to elucidate factors influencing the EHC of MPA in Chinese adult renal allograft recipients. After 2 weeks of therapy with mycophenolate mofetil or enteric-coated mycophenolate sodium, blood samples were collected from 125 patients at 0 to 12 hours post-administration and MPA concentrations were determined. The influence of calcineurin inhibitors (CNIs) and genetic polymorphisms on MPA exposure and EHC was studied. The Shapley additive explanations method was used to estimate the impact of various factors on the area under the plasma drug concentration-time curve (AUC_0-12h ) for MPA. An extreme gradient boosting (XGboost) machine learning-based model was established to predict AUC_0-12h . Results showed that the dose-normalized AUC_6-12h (dn-AUC_6-12h ) of MPA was significantly lower in patients co-administered with cyclosporine (CsA) than in patients co-administered with tacrolimus (TAC) (P < .05). For patients co-administered with TAC, patients with ABCC2 C-24T CC or SLCO1B1 T521C TT genotypes had significantly higher values of dn-AUC_6-12h (P < .05). Patients with SLCO1B3 334T/699G alleles had significantly lower dn-AUC_6-12h values than homozygotes (P < .05). By introducing body weight, age, and EHC-related factors, including co-administered CNIs and genetic polymorphism of drug transporters, as covariates in the XGboost machine learning model, the prediction performance of AUC_0-12h for MPA in Chinese adult renal allograft recipients can be improved.

腎移植患者におけるミコフェノール酸血中濃度に対する高速液体クロマトグラフLM1010の精度評価

Plasma concentrations of mycophenolic acid (MPA), an immunosuppressive agent, have been measured in clinical settings using immunoassay methods or HPLC. However, immunoassay methods show cross-reactivity with metabolites of MPA glucuronide. Recently, the LM1010 high-performance liquid chromatography instrument was approved as a new general medical device. In this study, we compared the results of MPA plasma concentrations analyzed using the LM1010 method and the previously described HPLC method. Plasma samples obtained from 100 renal transplant patients (32 women and 68 men) were evaluated using both HPLC instruments. Deming regression analyses showed a very high correlation between the two instruments, with a slope of 0.9892 and an intercept of 0.0235 µg/mL (r²=0.982). Bland-Altman analysis showed an average of -0.0012 µg/mL between the LM1010 method and the previously described HPLC method. For the LM1010 method, the total run time for MPA analysis was 7 min, and the analytical time was short; however, the extraction recovery when using a spin column was extremely low for frozen plasma samples stored at -20°C for 1 month, and the volume required for the assay (150 µL) could not be collected. Thus, for the LM1010 method, analysis using fresh plasma samples was optimal. Overall, our findings showed that the LM1010 method was a rapid, accurate HPLC assay for MPA analysis and could be used in clinical practice for routine monitoring of MPA in fresh plasma samples.

The pharmacogenetics of mycophenolate mofetil in Tunisian renal transplant patients

Aim: The effects of variants in IMPDH, UGT1A9, UGT1A8, UGT2B7 and SLCO1B1 genes on the efficacy and safety of mycophenolate mofetil (MMF) in the Tunisian population were investigated. Materials & methods: A total of 245 kidney transplant patients being treated with MMF were recruited and cotreated with cyclosporine or tacrolimus. Genotyping was performed using the polymerase chain reaction-restriction fragment length polymorphism method. MMF, cyclosporine and tacrolimus trough levels were measured by immunoassay. The AUC (AUC_0-12hMPA) was estimated by a Bayesian method. Results: In the tacrolimus-treated group, anemia and diarrhea were associated with the UGT1A9-98C and UGT1A9-275T alleles, respectively (p < 0.05). In the cyclosporine-treated group, leukopenia was associated with the SLCO1B1-521T allele (p < 0.05). Both groups had an increased risk of rejection (p < 0.05) associated with the variant alleles of IMPDH2-3757T>C, UGT1A9-2152C>T and UGT1A9-275C>A and the common allele of SLCO1B1-388A>G. However, no significant association was found between the studied genotypes and AUC_0-12hMPA or cotreatment levels. Conclusion: The results constitute preliminary evidence for the inclusion of the pharmacogenetics of MMF in kidney pretransplantation evaluations.

SLCO1B3 polymorphisms and clinical outcomes in kidney transplant recipients receiving mycophenolate

Aim: Determine the influence of SLCO1B3 polymorphisms on outcomes in kidney transplant recipients. Materials & methods: We retrospectively evaluated 181 adult kidney transplant recipients receiving mycophenolate. Outcomes included treated biopsy-proven acute rejection (tBPAR), de novo donor-specific antibody (dnDSA) formation, graft survival, patient survival and mycophenolate-related adverse effects among SLCO1B3 genotypes. Results: The presence of SLCO1B3 variants was not associated with increased risk of tBPAR (HR: 1.45, 95% CI: 0.76-2.74), dnDSA (HR: 0.46, 95% CI: 0.16-1.36) or composite of tBPAR or dnDSA (HR: 1.14, 95% CI: 0.64-2.03). Graft and patient survival were reduced among variant carriers; however, inconsistent findings with the primary analysis suggest these associations were not due to genotype. Adverse effects were similar between groups. Conclusion: Presence of SLCO1B3 polymorphisms were not predictive of rejection or dnDSA in kidney transplant recipients.

Effect of UGT polymorphisms on pharmacokinetics and adverse reactions of mycophenolic acid in kidney transplant patients

Mycophenolic acid (MPA) is a common immunosuppressive drug for kidney transplantation patients, and is characterized by a narrow therapeutic index and significant individual variability. UGTs are the main enzymes responsible for the metabolism of MPA. Although, many studies have focused on the relationship between UGT polymorphisms and pharmacokinetics and adverse reactions of MPA, the conclusion are controversial. We reviewed the relevant literature and summarized the significant influences of UGT polymorphisms, such as UGT1A8 (rs1042597, rs17863762), UGT1A9 (rs72551330, rs6714486, rs17868320, rs2741045, rs2741045) and UGT2B7 (rs7438135, rs7439366, rs7662029), on the pharmacokinetics of MPA and its metabolites and adverse reactions. The review provides a reference for guiding the individualized administration of MPA and reducing adverse reactions to MPA.

Influence of SLCO1B1 521T>C, UGT2B7 802C>T and IMPDH1 -106G>A Genetic Polymorphisms on Mycophenolic Acid Levels and Adverse Reactions in Chinese Autoimmune Disease Patients

Introduction

Mycophenolate mofetil (MMF), a new type of immunosuppressant, has emerged as a frontline agent for treating autoimmune diseases. Mycophenolic acid (MPA) is an active metabolite of MMF. MPA exposure varies greatly among individuals, which may lead to adverse drug reactions such as gastrointestinal side effects, infection, and leukopenia. Genetic factors play an important role in the variation of MPA levels and its side effects. Although many published studies have focused on MMF use in patients after organ transplant, studies that examine the use of MMF in patients with autoimmune diseases are still lacking.

Methods

This study will not only explore the genetic factors affecting MPA levels and adverse reactions but also investigate the relationships between UGT1A9 −118(dT)9/10, UGT1A9 - 1818T>C, UGT2B7 802C>T, SLCO1B1 521T>C, SLCO1B3 334T>G, IMPDH1 −106G>A and MPA trough concentration (MPA C₀), along with adverse reactions among Chinese patients with autoimmune diseases. A total of 120 patients with autoimmune diseases were recruited. The MPA trough concentration was detected using the enzyme multiplied immunoassay technique (EMIT). Genotyping was performed using a real-time polymerase chain reaction (PCR) system and validated allelic discrimination assays. Clinical data were collected for the determination of side effects.

Results

SLCO1B1 521T>C demonstrated a significant association with MPA C₀/d (p=0.003), in which patients with the CC type showed a higher MPA C₀/d than patients with the TT type (p=0.001) or the CT type (p=0.000). No significant differences were found in MPA C₀/d among the other SNPs. IMPDH1 −106G>A was found to be significantly related to infections (p=0.006). Subgroup analysis revealed that UGT2B7 802C>T was significantly related to Pneumocystis carinii pneumonia infection (p=0.036), while SLCO1B1 521T>C was associated with anemia (p=0.029).

Conclusion

For Chinese autoimmune disease patients, SLCO1B1 521T>C was correlated with MPA C₀/d and anemia. IMPDH1 −106G>A was significantly related to infections. UGT2B7 802C>T was significantly related to Pneumocystis carinii pneumonia infection.

The Impact of Genetic Polymorphisms on the Pharmacokinetics and Pharmacodynamics of Mycophenolic Acid: Systematic Review and Meta-analysis

BACKGROUND

Mycophenolic acid (MPA) is among the most commonly prescribed medications for immunosuppression following organ transplantation. Highly variable MPA exposure and drug response are observed among individuals receiving the same dosage of the drug. Identification of candidate genes whose polymorphisms could be used to predict MPA exposure and clinical outcome is of clinical value.

OBJECTIVES

This study aimed to determine the impact of genetic polymorphisms on the pharmacokinetics and pharmacodynamics of MPA in humans by means of a systematic review and meta-analysis.

METHODS

A systematic search was conducted on PubMed, EMBASE, Web of Sciences, Scopus, and the Cochrane Library databases. A meta-analysis was conducted to determine any associations between genetic polymorphisms and pharmacokinetic or pharmacodynamic parameters of MPA. Pooled-effect estimates were calculated by means of the random-effects model.

RESULTS

A total of 37 studies involving 3844 individuals were included in the meta-analysis. Heterozygous carriers of the UGT1A9 -275T>A polymorphism were observed to have a significantly lower MPA exposure than wild-type individuals. Four single nucleotide polymorphisms (SNPs), namely UGT1A9 -2152C>T, UGT1A8 518C>G, UGT2B7 211G>T, and SLCO1B1 521T>C, were also significantly associated with altered MPA pharmacokinetics. However, none of the investigated SNPs, including SNPs in the IMPDH gene, were found to be associated with the clinical efficacy of MPA. The only SNP that was associated with adverse outcomes was SLCO1B3 344T>G.

CONCLUSIONS

The present systematic review and meta-analysis identified six SNPs that were significantly associated with pharmacokinetic variability or adverse effects of MPA. Our findings represent the basis for future research and clinical implications with regard to the role of pharmacogenetics in MPA pharmacokinetics and drug response.

Population Pharmacokinetic Model of Plasma and Cellular Mycophenolic Acid in Kidney Transplant Patients from the CIMTRE Study

Background and Objective

Mycophenolate mofetil is widely used in kidney transplant recipients. Mycophenolate mofetil is hydrolysed by blood esterases to mycophenolic acid (MPA), the active drug. Although MPA therapeutic drug monitoring has been recommended to optimise the treatment efficacy by the area under the plasma concentration vs time curve, little is known regarding MPA concentrations in peripheral blood mononuclear cells, where MPA inhibits inosine monophosphate dehydrogenase. This study aimed to build a pharmacokinetic model using a population approach to describe MPA total and unbound concentrations in plasma and into peripheral blood mononuclear cells in 78 adult kidney transplant recipients receiving mycophenolate mofetil therapy combined with tacrolimus and prednisone.

Methods

Total and unbound plasma concentrations and peripheral blood mononuclear cell concentrations were assayed. A three-compartment model, two for plasma MPA and one for peripheral blood mononuclear cell MPA, with a zero-order absorption and a first-order elimination was used to describe the data.

Results

Mycophenolic acid average concentrations in peripheral blood mononuclear cells were well above half-maximal effective concentration for inosine monophosphate dehydrogenase and no relationship was found with the occurrence of graft rejection. Three covariates affected unbound and intracellular MPA pharmacokinetics: creatinine clearance, which has an effect on unbound MPA clearance, human serum albumin, which influences fraction unbound MPA and the ABCB1 3435 C>T (rs1045642) genetic polymorphism, which has an effect on MPA efflux transport from peripheral blood mononuclear cells.

Conclusion

This population pharmacokinetic model demonstrated the intracellular accumulation of MPA, the efflux of MPA out of the cells being dependent on P-glycoprotein transporters. Nevertheless, further studies are warranted to investigate the relevance of MPA concentrations in peripheral blood mononuclear cells to dosing regimen optimisation.

Electronic supplementary material

The online version of this article (10.1007/s40268-020-00319-y) contains supplementary material, which is available to authorized users.

Pharmacokinetics of Mycophenolate Mofetil and Development of Limited Sampling Strategy in Early Kidney Transplant Recipients

The mycophenolate mofetil (MMF) dose management for optimization of post-transplant treatment especially the early postoperative phase has been well recognized. MMF is a pro-drug of mycophenolic acid (MPA) and is widely used in Chinese renal transplant patients. Until now, the pharmacokinetic (PK) characteristics and model for the area under the concentration–time curve for the 12-h (h) of exposure (AUC_0-12h) of MPA (MPA-AUC_0-12h) estimation were lacking for the new formulation of MMF dispersible tablet in renal transplant patients. The aims of the study were to investigate the PK characteristics of MMF dispersible tablet by detecting the active metabolite of MPA and to establish an accuracy and precision equation for calculating MPA-AUC_0-12h by limited sampling strategy (LSS) in Chinese kidney transplant patients. A total of 60 postoperative kidney transplant recipients were given a multiple-dose of MMF dispersible tablet twice daily combination with tacrolimus (Tac) and steroids. On the 5th day post-transplantation, blood specimens were collected before drug administration and up to 12 h after MMF dispersible tablet administration. Non-compartmental PK analysis was used to determine the data obtained from individual patients. Multivariate stepwise regression analysis was used to develop models for predicting MPA-AUC_0-12h. The 3- and 4-point sampling models using 2 h, 4 h, 8 h and 1 h, 2 h, 4 h and 8 h, respectively, allowed accurate estimation of MPA-AUC_0-12h. PK parameters of MMF dispersible tablet were obtained and the 4-point LSS is the best model for accurate and precise estimation of MPA-AUC_0-12h.

Population pharmacokinetics and Bayesian estimation of mycophenolic acid concentrations in Chinese adult renal transplant recipients

Mycophenolate mofetil (MMF) is an important immunosuppressant used in renal transplantation, and mycophenolic acid (MPA) is the active component released from the ester prodrug MMF. The objective of this study was to investigate the population pharmacokinetics of mycophenolic acid (MPA) following oral administration of MMF in Chinese adult renal transplant recipients and to identify factors that explain MPA pharmacokinetic variability. Pharmacokinetic data for MPA and covariate information were retrospectively collected from 118 patients (79 patients were assigned to the group for building the population pharmacokinetic model, while 39 patients were assigned to the validation group). Population pharmacokinetic data analysis was performed using the NONMEM software. The pharmacokinetics of MPA was best described by a two-compartment model with a first-order absorption rate with no lag time. Body weight and serum creatinine level were positively correlated with apparent clearance (CL/F). The polymorphism in uridine diphosphate glucuronosyltransferase gene, UGT2B7, significantly explained the interindividual variability in the initial volume of distribution (V₁/F). The estimated population parameters (and interindividual variability) were CL/F 18.3 L/h (34.2%) and V₁/F 27.9 L (21.3%). The interoccasion variability was 13.7%. These population pharmacokinetic data have significant clinical value for the individualization of MMF therapy in Chinese adult renal transplant patients.