Comparison of Tacrolimus Intra-Patient Variability during 6-12 Months after Kidney Transplantation between CYP3A5 Expressers and Nonexpressers

Pharmacogenomic landscape of the Thai population from genome sequencing of 949 individuals

Inter-individual variability in drug responses is significantly influenced by genetic factors, underscoring the importance of population-specific pharmacogenomic studies to optimize clinical outcomes. In this study, we analyzed whole genome sequencing data from 949 unrelated Thai individuals and conducted an in-depth analysis of 3239 genes involved in drug pharmacokinetics, pharmacodynamics, or immune-mediated adverse drug reactions. We identified 43 single nucleotide polymorphisms (SNPs), 134 diplotypes, and 15 human leukocyte antigen (HLA) alleles, all with moderate to high clinical significance. On average, each Thai individual carried 14 SNPs, one to two HLA alleles, and six diplotypes with actionable phenotypic associations. Clinically important diplotypes were present in over 20% of individuals for seven genes (CYP2A6, CYP2B6, CYP2C19, CYP3A5, NAT2, SLCO1B1, and VKORC1). In addition, clinically significant SNPs with allele frequencies exceeding 20% were identified among 15 genes, including VKORC1, CYP4F2, and ABCG2. We also identified 21,211 potentially deleterious variants among 3239 genes. Of these variants, 3746 were novel. The comprehensive dataset from this study serves as a valuable resource of pharmacogenomic variants in the Thai population, which will facilitate the development of personalized drug therapies and enhance patient care in Thailand.

Factors and interventions affecting tacrolimus intrapatient variability: A systematic review and meta-analysis

BACKGROUNDS

Tacrolimus is a cornerstone of posttransplantation immunosuppressive regimens. Despite routine monitoring, the efficacy of its trough concentrations in reflecting drug concentration fluctuations is limited. Intrapatient variability (IPV) emerges as a novel monitoring marker for predicting clinical outcomes. However, understanding the factors affecting IPV and assessing interventions to address it remain enigmatic, posing a conundrum in clinical management.

OBJECTIVES

This systematic review aimed to investigate a spectrum of factors affecting IPV and assess the effect of strategic interventions, thereby charting a course for enhanced clinical stewardship.

METHODS

We electronically searched of PubMed, Embase, and the Cochrane Library databases for studies investigating factors and interventions affecting IPV up to October 2023. Two reviewers independently screened literature, extracted data, and assessed quality, using RevMan 5.4.1 software for meta-analysis.

RESULTS

A total of 15 randomized controlled trials (RCTs), 34 cohort studies, and 20 self-controlled studies were included. The results indicated that IPV was significantly higher in cytochrome P450 3A5 (CYP3A5) expressers, nonadherent patients, patients taking proton pump inhibitors or statins, and Black or African American recipients, whereas recipients consuming extended-release formulation exhibited lower IPV. Additionally, the participation of pharmacists had a positive effect on improving IPV.

CONCLUSIONS

Factors affecting IPV encompassed genotype, formulation, adherence, drug combinations, and ethnicity, with each factor exerting varying degrees of effect. Identifying these factors was crucial for developing targeted intervention strategies. While the participation of pharmacists held a promise in improving IPV, further investigation of interventions such as mobile technology, educational measures to enhance adherence, and personalized dosing regimens was warranted.

Effect of donor GSTM3 rs7483 genetic variant on tacrolimus elimination in the early period after liver transplantation

Purpose

Glutathione S-transferase mu (GSTM) belongs to the group of phase II drug-metabolizing enzymes, and the GSTM1 genetic variant has been reported to have a potential association with the metabolism of immunosuppressive drug after renal transplantation. The effect of donor and recipient GSTMs genetic variants on tacrolimus (Tac) metabolism was the focus of our investigation in this study.

Methods

A total of 203 liver transplant patients were recruited for the study. In the training set (n = 110), twenty-one SNPs in five genes (GSTM1-5) were genotyped by the drug-metabolizing enzymes and transporter (DMET) microarray. CYP3A5 rs776746 and GSTM3 rs7483 were genotyped using a Mass ARRAY platform in the validating set (n = 93).

Results

Tac C/D ratios of donor GSTM3 rs7483 AA carriers were significantly lower than those with the G allele at weeks 1, 2, 3 and 4 after liver transplantation (LT). Multivariate analysis was conducted on the training set and validating set, donor and recipient CYP3A5 rs776746, donor GSTM3 rs7483 and total bilirubin were identified as independent predictors of Tac C/D ratios in the early period after LT. Combining CYP3A5 rs776746 and donor GSTM3 rs7483 genotypes, Tac C/D ratios were observed to be increasingly lower with increasing numbers of alleles associated with fast metabolism. Moreover, the risk of a supratherapeutic C0 (Tac > 15 ug/L) was significantly higher for poor metabolizers than the other groups at week 1 after LT.

Conclusions

There was a significant association between the donor GSTM3 rs7483 genetic variant and Tac metabolism in the early period after LT. Genotype classification might have a better predictive ability of the initial Tac doses.

Exploratory associations of tacrolimus exposure and clinical outcomes after lung transplantation: A retrospective, single center experience

PURPOSE

This study aimed to investigate the potential impact of tacrolimus (TAC) exposure on clinical outcomes after lung transplantation.

METHODS

This retrospective observational study enrolled a total of 228 lung transplant recipients. TAC trough levels (C0) were collected for 3 intervals: 0-3 months, 3-12 months, and 12-24 months. The intra-patient variability (IPV) was calculated using coefficient of variation. Genotyping of CYP3A5*3 (rs776746) was performed. Patients were further divided into groups based on the C0 cut-off value of 8 ng/mL and IPV cut-off value of 30%. Cox proportional hazards regression models were used to explore the potential impact of C0 and IPV on outcomes of interests, including de-novo donor-specific antibodies (dnDSA), chronic lung allograft dysfunction (CLAD) and mortality.

RESULTS

The influence of CYP3A5*3 polymorphism was only significant for C0 and IPV during the first 3 months. Low C0 (< 8 ng/mL) at 3-12 months increased the risk of dnDSA (hazard ratio [HR] 2.696, 95% confidence interval [CI] 1.046-6.953) and mortality (HR 2.531, 95% CI 1.368-4.685), while High IPV (≥ 30%) during this period was associated with an increased risk of mortality (HR 2.543, 95% CI 1.336-4.839). Patients with Low C0/High IPV combination had significantly higher risks for dnDSA (HR 4.381, 95% CI 1.279-15.008) and survival (HR 6.179, 95% CI 2.598-14.698), surpassing the predictive power provided by C0 or IPV alone.

CONCLUSION

A combination of Low C0/High IPV might be considered in categorizing patients towards risk of adverse clinical outcomes following lung transplantation.

Impact of tacrolimus intra-patient variability in adverse outcomes after organ transplantation

Tacrolimus (Tac) is currently the most common calcineurin-inhibitor employed in solid organ transplantation. High intra-patient variability (IPV) of Tac (Tac IPV) has been associated with an increased risk of immune-mediated rejection and poor outcomes after kidney transplantation. Few data are available concerning the impact of high Tac IPV in non-kidney transplants. However, even in kidney transplantation, there is still a controversy whether high Tac IPV is indeed detrimental in respect to graft and/or patient survival. This may be due to different methods employed to evaluate IPV and distinct time frames adopted to assess graft and patient survival in those reports published up to now in the literature. Little is also known about the influence of high Tac IPV in the development of other untoward adverse events, update of the current knowledge regarding the impact of Tac IPV in different outcomes following kidney, liver, heart, lung, and pancreas tran splantation to better evaluate its use in clinical practice.

Tacrolimus-why pharmacokinetics matter in the clinic

The calcineurin inhibitor (CNI) Tacrolimus (Tac) is the most prescribed immunosuppressant drug after solid organ transplantation. After renal transplantation (RTx) approximately 95% of recipients are discharged with a Tac-based immunosuppressive regime. Despite the high immunosuppressive efficacy, its adverse effects, narrow therapeutic window and high intra- and interpatient variability (IPV) in pharmacokinetics require therapeutic drug monitoring (TDM), which makes treatment with Tac a major challenge for physicians. The C/D ratio (full blood trough level normalized by daily dose) is able to classify patients receiving Tac into two major metabolism groups, which were significantly associated with the clinical outcomes of patients after renal or liver transplantation. Therefore, the C/D ratio is a simple but effective tool to identify patients at risk of an unfavorable outcome. This review highlights the challenges of Tac-based immunosuppressive therapy faced by transplant physicians in their daily routine, the underlying causes and pharmacokinetics (including genetics, interactions, and differences between available Tac formulations), and the latest data on potential solutions to optimize treatment of high-risk patients.

CYP3A5 Polymorphism in Renal Transplantation: A Key to Personalized Immunosuppression

BACKGROUND

Tacrolimus is essential for the maintenance of immunosuppression after a kidney transplant. CYP3A5 is the gene that metabolizes tacrolimus, and polymorphism in this gene affects the metabolizing status.

AIM

To assess the genetic polymorphism status of patients undergoing kidney transplantation and determine its impact on graft function and complications in the post-transplant period.

METHODS

We retrospectively included the patients who had undergone a kidney transplant and had positive genetic polymorphism of the CYP3A5 gene. Based on loss of alleles, patients were categorized as non-expresser (loss of both alleles), intermediate expresser (loss of one allele), and expresser (no loss of allele) denoted by CYP3A5*3/*3, CYP3A5*1/*3, and CYP3A5*1/*1, respectively. Data were analyzed with descriptive statistics.

RESULTS

Of 25 patients, 60%, 32%, and 8% were non-expressers, intermediate-expressers, and expressers, respectively. The mean tacrolimus trough concentration to dose ratio after 6 months of the transplant was higher in non-expressers than intermediate-expressers and expressers (213 vs 85 and 46 ng/mL/mg/kg/d, respectively). The graft function was normal in all 3 groups except for graft rejection 1 patient in the expresser group. Compared with expressers, urinary tract infections (42.9% and 62.5%) and new-onset diabetes after transplantation (28.6% and 12.5%) were more frequent in non-expresser and intermediate expressers, respectively. The proportion of patients developing new-onset diabetes after transplantation was lower with the pre-transplant diagnosis of CYP3A5 polymorphism (16.7% vs 23.1%).

CONCLUSION

Genotype-based dosing of tacrolimus helps achieve the desired therapeutic concentrations that can help to optimize graft outcomes and reduce the tacrolimus-related adverse effects. Pre-transplant evaluation of CYP3A5 can be more helpful in planning treatment strategies for optimized outcomes after kidney transplantation.