Interactive effects of CYP3A4, CYP3A5, MDR1 and NR1I2 polymorphisms on tracrolimus trough concentrations in early postrenal transplant recipients

Composite CYP3A (CYP3A4 and CYP3A5) phenotypes and influence on tacrolimus dose adjusted concentrations in adult heart transplant recipients

CYP3A5 genetic variants are associated with tacrolimus metabolism. Controversy remains on whether CYP3A4 increased [*1B (rs2740574), *1 G (rs2242480)] and decreased function [*22 (rs35599367)] genetic variants provide additional information. This retrospective cohort study aims to address whether tacrolimus dose-adjusted trough concentrations differ between combined CYP3A (CYP3A5 and CYP3A4) phenotype groups. Heart transplanted patients (n = 177, between 2008 and 2020) were included and median age was 54 years old. Significant differences between CYP3A phenotype groups in tacrolimus dose-adjusted trough concentrations were found in the early postoperative period and continued to 6 months post-transplant. In CYP3A5 nonexpressers, carriers of CYP3A4*1B or *1 G variants (Group 3) compared to CYP3A4*1/*1 (Group 2) patients were found to have lower tacrolimus dose-adjusted trough concentrations at 2 months. In addition, significant differences were found among CYP3A phenotype groups in the dose at discharge and time to therapeutic range while time in therapeutic range was not significantly different. A combined CYP3A phenotype interpretation may provide more nuanced genotype-guided TAC dosing in heart transplant recipients.

Population pharmacokinetic models of tacrolimus in paediatric solid organ transplant recipients: A systematic review

AIMS

This study aimed to provide up-to-date information on paediatric population pharmacokinetic models of tacrolimus and to identify factors influencing tacrolimus pharmacokinetic variability.

METHODS

Systematic searches in the Web of Science, PubMed, Scopus, Science Direct, Cochrane, EMBASE databases and reference lists of articles were conducted from inception to March 2023. All population pharmacokinetic studies of tacrolimus using nonlinear mixed-effect modelling in paediatric solid organ transplant patients were included.

RESULTS

Of the 21 studies reviewed, 62% developed from liver transplant recipients and 33% from kidney transplant recipients. Most studies used a 1-compartment model to describe tacrolimus pharmacokinetics. Body weight was a significant predictor for tacrolimus volume of distribution (Vd/F). The estimated Vd/F for 1-compartment models ranged from 20 to 1890 L, whereas the peripheral volume of distribution (Vp/F) for 2-compartment models was between 290 and 1520 L. Body weight, days post-transplant, CYP3A5 genotype or haematocrit were frequently reported as significant predictors of tacrolimus clearance. The estimated apparent clearance values range between 0.12 and 2.18 L/h/kg, with inter-individual variability from 13.5 to 110.0%. Only 29% of the studies assessed the generalizability of the models with external validation.

CONCLUSION

This review highlights the potential factors, modelling approaches and validation methods that impact tacrolimus pharmacokinetics in a paediatric population. The clinician could predict tacrolimus clearance based on body weight, CYP3A5 genotype, days post-transplant or haematocrit. Further research is required to determine the relationship between pharmacogenetics and tacrolimus pharmacodynamics in paediatric patients and confirm the applicability of nonlinear kinetics in this population.

Intracellular tacrolimus concentration correlates with impaired renal function through regulation of the IS-AHR-ABC transporter in peripheral blood mononuclear cells

BACKGROUNDS

Tacrolimus (TAC) concentration in peripheral blood mononuclear cells (PBMCs) is regarded as a better predictor of its immunosuppressive effect than the TAC concentration in whole blood. However, whether the exposure of TAC in PBMCs or WB was altered in post-transplant recipients with renal impairment remains unclear.

METHODS

We investigated the relationship of trough TAC concentration in WB and PBMCs with renal functions in post-transplant recipients. The pharmacokinetic profiles of TAC in PBMCs and WB in the two chronic kidney disease (CKD) rat models were examined using UPLC-MS/MS. Western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were used to analyze the expression of proteins and mRNAs related to TAC metabolism and transport, respectively. In addition, the effects of uremic toxins on human PBMCs were investigated using whole-transcriptome sequencing (RNA sequencing [RNA-seq]).

RESULTS

We observed a decrease in the trough TAC concentration in PBMCs in the recipients with estimated glomerular filtration rate (eGFR) < 90 mL/min, compared with those of recipients with eGFR > 90 mL/min, but there was no difference in blood based on TAC concentrations (C0Blood). In a 150-patient post-transplant cohort, no significant relationship was observed between PBMCs and WB concentrations of TAC, and the eGFR value was correlated with TAC C0PBMCs but not with TAC C0Blood. In two CKD rat models, the TAC pharmacokinetic profile in the PBMCs was significantly lower than that in the control group; however, the blood TAC pharmacokinetic profiles in the two groups were similar. Transcriptome results showed that co-incubation of human PBMCs with uremic toxins upregulated the expression of AHR, ABCB1, and ABCC2. Compared to control rats, plasma IS increased by 1.93- and 2.26-fold and the expression of AHR, P-gp, and MRP2 in PBMCs was higher in AD and 5/6 nephrectomy (NX) rats, without modifying the expression of other proteins related to TAC exposure.

CONCLUSION

The pharmacokinetics of TAC in PBMCs changed with a decline in renal function. Uremic toxins accumulate during renal insufficiency, which activates AHR, upregulates the expression of P-gp and MRP2, and affects their intracellular concentrations. Our findings suggest that monitoring TAC concentrations in PBMCs is more important than monitoring WB concentrations in post-transplant recipients with renal impairment.

Initial dosage optimisation of cyclosporine in Chinese paediatric patients undergoing allogeneic haematopoietic stem cell transplantation based on population pharmacokinetics: a retrospective study

OBJECTIVE

Improved understanding of cyclosporine A (CsA) pharmacokinetics in children undergoing allogeneic haematopoietic stem cell transplantation (allo-HSCT) is crucial for effective prevention of acute graft-versus-host disease and medication safety. The aim of this study was to establish a population pharmacokinetic (Pop-PK) model that could be used for individualised therapy to paediatric patients undergoing allo-HSCT in China.

DESIGN, SETTING AND PARTICIPANTS

A retrospective analysis of 251 paediatric HSCT patients who received CsA intravenously in the early post transplantation period at Women and Children's Medical Center in Guangzhou was conducted.

ANALYSIS MEASURES

The model building dataset from 176 children was used to develop and analyse the CsA Pop-Pk model by using the nonlinear mixed effect model method. The basic information was collected by the electronic medical record system. Genotype was analysed by matrix-assisted time-of-flight mass spectrometry. The stability and predictability of the final model were verified internally, and a validation dataset of 75 children was used for external validation. Monte Carlo simulation is used to adjust and optimise the initial dose of CsA in paediatric allo-HSCT patients.

RESULTS

The typical values for clearance (CL) and volume of distribution ([Formula: see text]) were 14.47 L/hour and 2033.53 L, respectively. The body weight and haematocrit were identified as significant variables for V, while only body weight had an impact on CL. The simulation based on the final model suggests that paediatrics with HSCT required an appropriate intravenous dose of 5 mg/kg/day to reach the therapeutic trough concentration.

CONCLUSIONS

The CsA Pop-PK model established in this study can quantitatively describe the factors influencing pharmacokinetic parameters and precisely predict the intrinsic exposure to CsA in children. In addition, our dosage simulation results can provide evidence for the personalised medications TRIAL REGISTRATION NUMBER: ChiCTR2000040561.

Pharmacogenomics of Old and New Immunosuppressive Drugs for Precision Medicine in Kidney Transplantation

Kidney transplantation is the preferred therapeutic option for end-stage kidney disease, but, despite major therapeutic advancements, allograft rejection continues to endanger graft survival. Every patient is unique due to his or her clinical history, drug metabolism, genetic background, and epigenetics. For this reason, examples of "personalized medicine" and "precision medicine" have steadily increased in recent decades. The final target of precision medicine is to maximize drug efficacy and minimize toxicity for each individual patient. Immunosuppressive drugs, in the setting of kidney transplantation, require a precise dosage to avoid either adverse events (overdosage) or a lack of efficacy (underdosage). In this review, we will explore the knowledge regarding the pharmacogenomics of the main immunosuppressive medications currently utilized in kidney transplantation. We will focus on clinically relevant pharmacogenomic data, that is, the polymorphisms of the genes that metabolize immunosuppressive drugs.

Composite CYP3A (CYP3A4 and CYP3A5) phenotypes and influences on tacrolimus dose adjusted concentration in adult heart transplant recipients

CYP3A5 genetic variants are associated with tacrolimus metabolism. Controversy remains on whether CYP3A4 increased [* 1B (rs2740574), *1G (rs2242480)] and decreased function [*22 (rs35599367)] genetic variants provide additional information. This study aims to address whether tacrolimus dose-adjusted trough concentrations differ between combined CYP3A (CYP3A5 and CYP3A4) phenotype groups. Significant differences between CYP3A phenotype groups in tacrolimus dose-adjusted trough concentrations were found in the early postoperative period and continued to 6 months post-transplant. In CYP3A5 nonexpressers, carriers of CYP3A4*7Bor *7G variants (Group 3) compared to CYP3A4*1/*1 (Group 2) patients were found to have lower tacrolimus dose-adjusted trough concentrations at 2 months. In addition, significant differences were found among CYP3A phenotype groups in the dose at discharge and time to therapeutic range while time in therapeutic range was not significantly different. A combined CYP3A phenotype interpretation may provide more nuanced genotype-guided TAC dosing in heart transplant recipients.

Effects of oxycodone pharmacogenetics on postoperative analgesia and related clinical outcomes in children: a pilot prospective study

Background: Variability in the pharmacokinetics and pharmacodynamics of oxycodone in children undergoing surgery could be due to genetic polymorphisms. Materials & methods: The authors studied the association between clinical outcomes and pharmacogenes in children undergoing major surgery. A total of 89 children (35 undergoing pectus excavatum repair and 54 undergoing spinal fusion) were recruited. Results: OPRM1 SNP rs6902403 showed an association with maximum pain score and total morphine equivalent dose (p < 0.05). Other polymorphisms in OPRM1 SNP, PXR, COMT and ABCB1 were also shown to be associated with average morphine equivalent dose, length of hospital stay and maximum surgical pain (p < 0.05). Conclusion: This study demonstrates novel associations between the above pharmacogenes and oxycodone's pharmacokinetics as well as postoperative outcomes in children. Clinical trial registration: NCT03495388 (ClinicalTrials.gov).

Effect of Wuzhi preparations on tacrolimus in CYP3A5 expressers during the early period after transplantation: A real-life experience from heart transplant recipients

BACKGROUND

Genetic polymorphisms and drug interactions are associated with tacrolimus exposure. This study aimed to evaluate the effect of Wuzhi (WZ) preparations on tacrolimus (TAC) concentration and dose requirements in heart transplant recipients with the CYP3A5*1 allele during the early period after transplantation.

METHODS

A total of 167 adult heart transplant recipients with the CYP3A5*1 allele were included and divided into the WZ group (n = 115) and the WZ-free group (n = 52). Blood trough concentrations of TAC were detected and the dose-adjusted concentration (C₀/D) and dose requirement for achieving the TAC therapeutic range were compared between the two groups. The change in C₀/D and dose of TAC were evaluated before and after co-administration with WZ preparations.

RESULTS

No significant differences in TAC C₀/D and dose requirement were observed between the WZ and WZ-free groups. However, the TAC C₀/D in the WZ group was significantly increased an average of 2.10-fold after co-administration of WZ. Moreover, the degree of elevation was related to the dose of the active ingredient (Schisantherin A). Furthermore, ALT, AST, and TB levels were significantly reduced after administration of WZ preparations.

CONCLUSION

Co-administration of the WZ/TAC preparation, in heart transplant recipients carrying the CYP3A5*1 allele, considerably increased TAC concentration (C₀/D) while decreased high levels of leading indicators in the liver function. More importantly, the effect of the WZ/TAC preparation on C₀/D was a dose-dependent event. However, our finding needs to be further confirmed in a larger sample size.

Composite CYP3A phenotypes influence tacrolimus dose-adjusted concentration in lung transplant recipients

OBJECTIVES

Interpatient variability in tacrolimus pharmacokinetics is attributed to metabolism by cytochrome P-450 3A4/5 isoenzymes (encoded by CYP3A4 and CYP3A5). Guidelines for adjusting tacrolimus based on CYP3A5 test results are published; however, CYP3A4 variants also contribute to the variability in tacrolimus pharmacokinetics. The effects of composite phenotypes incorporating CYP3A5 and CYP3A4 increased (*1G, *1B) and decreased (*22) function variants have not been evaluated. The objective of this study is to investigate the impact of both increased and decreased function CYP3A variants on weight and dose-adjusted tacrolimus concentration (C0/D).

METHODS

We performed a single-center retrospective cohort study of lung transplant recipients to evaluate the median tacrolimus C0/D by composite CYP3A phenotype groups during the index transplant hospitalization. CYP3A4 and CYP3A5 alleles were used to classify patients into four CYP3A groups from least to most CYP3A activity. Exploratory analyses of ABCB1 and additional candidate genes were also assessed.

RESULTS

Of the 92 included individuals, most (58) were CYP3A Group 2. The median tacrolimus C0/D differed significantly between CYP3A groups (P = 0.0001). CYP3A Group 2 median tacrolimus C0/D was 190.5 (interquartile range: 147.6-267.5) (ng/ml)/(mg/kg/d) and significantly higher than Group 4 [107.9 (90.4-116.1), P = 0.0001)]. Group 2 median tacrolimus C0/D did not significantly differ from Group 1 and Group 3 [373.5 (149.2-490.3) and 81.4 (62.6-184.1), respectively]. No significant differences in tacrolimus C0/D were found for the ABCB1 diplotypes.

CONCLUSION

These data indicate that a composite CYP3A phenotype incorporating both increase and decrease variant information from CYP3A4 in addition to CYP3A5 may significantly influence tacrolimus C0/D during the early postoperative period.

Prediction of Tacrolimus Dose/Weight-Adjusted Trough Concentration in Pediatric Refractory Nephrotic Syndrome: A Machine Learning Approach

Purpose

Tacrolimus (TAC) is a first-line immunosuppressant for patients with refractory nephrotic syndrome (NS). However, there is a high inter-patient variability of TAC pharmacokinetics, thus therapeutic drug monitoring (TDM) is required. In this study, we aimed to employ machine learning algorithms to investigate the impact of clinical and genetic variables on the TAC dose/weight-adjusted trough concentration (C₀/D) in Chinese children with refractory NS, and then develop and validate the TAC C₀/D prediction models.

Patients and Methods

The association of 82 clinical variables and 244 single nucleotide polymorphisms (SNPs) with TAC C₀/D in the third month since TAC treatment was examined in 171 children with refractory NS. Extremely randomized trees (ET), gradient boosting decision tree (GBDT), random forest (RF), extreme gradient boosting (XGBoost), and Lasso regression were carried out to establish and validate prediction models, respectively. The best prediction models were validated on a cohort of 30 refractory NS patients.

Results

GBDT algorithm performed best in the whole group (R²=0.444, MSE=591.032, MAE=20.782, MedAE=18.980) and CYP3A5 nonexpresser group (R²=0.264, MSE=477.948, MAE=18.119, MedAE=18.771), while ET algorithm performed best in the CYP3A5 expresser group (R²=0.380, MSE=1839.459, MAE=31.257, MedAE=19.399). These prediction models included 3 clinical variables (ALB0, AGE0, and gender) and 10 SNPs (ACTN4 rs3745859, ACTN4 rs56113315, ACTN4 rs62121818, CTLA4 rs4553808, CYP3A5 rs776746, IL2RA rs12722489, INF2 rs1128880, MAP3K11 rs7946115, MYH9 rs2239781, and MYH9 rs4821478).

Conclusion

The association between the clinical and genetic variables and TAC C₀/D was described, and three TAC C₀/D prediction models integrating clinical and genetic variables were developed and validated using machine learning, which may support individualized TAC dosing.

Genetic Polymorphisms Affecting Tacrolimus Metabolism and the Relationship to Post-Transplant Outcomes in Kidney Transplant Recipients

Background

Tacrolimus is a key drug in kidney transplantation with a narrow therapeutic index. However, whether tacrolimus exposure variability affects clinical outcomes and adverse reactions remains unknown.

Objective

Our study investigated the factors that influence tacrolimus exposure in kidney transplantation recipients and the relationship between tacrolimus concentration and clinical outcomes and adverse reactions.

Settings and Methods

We examined the effect of tacrolimus concentration on clinical outcomes and adverse reactions in 201 kidney transplantation recipients, and identified clinical and pharmacogenetic factors that explain tacrolimus exposure.

Results

The CYP3A5 genotype was clearly associated with dose-adjusted trough blood tacrolimus concentrations (C₀/D), whereas no significant difference was observed in patients with the CYP3A4*1B, CYP3A4*22, ABCB1, ABCC2, POR*28 or PXR alleles. Clinical factors such as red blood cell count, hemoglobin, and albumin were the most useful influence factors affecting tacrolimus C₀/D. Besides, Wuzhi capsule increased tacrolimus C₀/D in kidney transplantation recipients. Furthermore, higher tacrolimus concentrations were associated with higher diarrhea and post-transplant diabetes mellitus (PTDM) risk but not with acute rejection and chronic allograft kidney dysfunction.

Conclusion

Clinical factors, medication, and CYP-enzyme polymorphisms accounted for tacrolimus concentration variability in kidney transplantation recipients. Furthermore, higher tacrolimus concentrations were associated with higher diarrhea and PTDM risk.

Trans-eQTLs of the CYP3A4 and CYP3A5 associated with tacrolimus trough blood concentration in Chinese renal transplant patients

This study aimed to systematically investigate trans-eQTLs of CYP3A4 and CYP3A5 affecting tacrolimus trough blood concentrations in Chinese renal transplant patients. We used Plink v1.90 to perform data quality control and linear regression analysis on GTEx v8 data. SNPs with p-value < 0.05 were selected and the GTEx eQTL Calculator was used to further prioritize the eQTLs of CYP3A4 and CYP3A5 in the liver and small intestine. The eQTLs with a p-value < 5 × 10^-5 and MAF≥ 0.05 in the CHB population were selected as candidate eQTLs. The genotyping of candidate eQTLs was performed using high-resolution melting (HRM) assays and Sanger DNA sequencing. This study included 845 Chinese renal transplant patients who received tacrolimus as an immunosuppressive agent. Association between 103 candidate eQTLs and log-transformed tacrolimus concentration/dose ratio (log (C₀/D)) in this cohort was conducted using the SNPassoc package of R software. In the end, a total of 75,632 liver eQTLs of CYP3A4, 69,558 liver eQTLs of CYP3A5, 48,596 small intestine eQTLs of CYP3A4 and 28,616 small intestine eQTLs of CYP3A5 were obtained using the GTEx v8 eQTL Calculator. Of the 103 candidate eQTLs, rs75727207, rs181294422 and rs28522676 were significantly associated with tacrolimus log(C₀/D) in different genetic models. We discovered a substantial number of novel eQTLs of CYP3A4 and CYP3A5 in liver and small intestine, also found that rs75727207, rs181294422 and rs28522676 may affect tacrolimus trough blood concentrations in Chinese renal transplant patients.

Towards next-generation personalization of tacrolimus treatment: a review on advanced diagnostic and therapeutic approaches

The benefit of personalized medicine is that it allows the customization of drug therapy - maximizing efficacy while avoiding side effects. Genetic polymorphisms are one of the major contributors to interindividual variability. Currently, the only gold standard for applying personalized medicine is dose titration. Because of technological advancements, converting genotypic data into an optimum dose has become easier than in earlier years. However, for many medications, determining a personalized dose may be difficult, leading to a trial-and-error method. On the other hand, the technologically oriented pharmaceutical industry has a plethora of smart drug delivery methods that are underutilized in customized medicine. This article elaborates the genetic polymorphisms of tacrolimus as case study, and extensively covers the diagnostic and therapeutic technologies which aid in the delivery of personalized tacrolimus treatment for better clinical outcomes, thereby providing a new strategy for implementing personalized medicine.

Functional CYP3A variants affecting tacrolimus trough blood concentrations in Chinese renal transplant recipients

The aim of this study was to identify novel genetic variants affecting tacrolimus trough blood concentrations. We analyzed the association between 58 single nucleotide polymorphisms (SNPs) across the CYP3A gene cluster and the log-transformed tacrolimus concentration/dose ratio (log (C₀/D)) in 819 renal transplant recipients (Discovery cohort). Multivariate linear regression was used to test for associations between tacrolimus log (C₀/D) and clinical factors. Luciferase reporter gene assays were used to evaluate the functions of select SNPs. Associations of putative functional SNPs with log (C₀/D) were further tested in 631 renal transplant recipients (Replication cohort). Nine SNPs were significantly associated with tacrolimus log (C₀/D) after adjustment for CYP3A5*3 and clinical factors. Dual luciferase reporter assays indicated that the rs4646450 G allele and rs3823812 T allele were significantly associated with increased normalized luciferase activity ratios (p < 0.01). Moreover, CYP3A7*2 was associated with higher TAC log(C₀/D) in the group of CYP3A5 expressers. Age, serum creatinine and hematocrit were significantly associated with tacrolimus log (C₀/D). CYP3A7*2, rs4646450, and rs3823812 are proposed as functional SNPs affecting tacrolimus trough blood concentrations in Chinese renal transplant recipients. Clinical factors also significantly affect tacrolimus metabolism.

The impact of cytochrome P450 3A genetic polymorphisms on tacrolimus pharmacokinetics in ulcerative colitis patients

Tacrolimus (Tac) is an effective remission inducer of refractory ulcerative colitis (UC). Gene polymorphisms result in interindividual variability in Tac pharmacokinetics. In this study, we aimed to examine the relationships between gene polymorphisms and the metabolism, pharmacokinetics, and therapeutic effects of Tac in patients with UC. Forty-five patients with moderate-to-severe refractory UC treated with Tac were retrospectively enrolled. Genotyping for cytochrome P450 (CYP) 3A4*1G, CYP3A5*3, CYP2C19*2, CYP2C19*3, nuclear receptor subfamily 1 group I member 2 (NR1I2)–25385C>T, ATP-binding cassette subfamily C member 2 (ABCC2)–24C>T, ABCC2 1249G>A, and ABCC2 3972C>T was performed. Concentration/dose (C/D) ratio, clinical therapeutic effects, and adverse events were evaluated. The C/D ratio of Tac in UC patients with the CYP3A4*1G allele was statistically lower than in those with the CYP3A4*1/*1 allele (P = 0.005) and significantly lower in patients with CYP3A5*3/*3 than in those with CYP3A5*1 (P < 0.001). Among patients with the CYP3A4*1G allele, the C/D ratio was significantly lower in patients with CYP3A5*1 than in those with CYP3A5*3/*3 (P = 0.001). Patients with the NR1I2–25385C/C genotype presented significantly more overall adverse events than those with the C/T or T/T genotype (P = 0.03). Although CYP3A4*1G and CYP3A5*3 polymorphisms were related to Tac pharmacokinetics, CYP3A5 presented a stronger effect than CYP3A4. The NR1I2–25385C/C genotype was related to the overall adverse events. The evaluation of these polymorphisms could be useful in the treatment of UC with Tac.

Impact of CYP3A4/5 and ABCB1 polymorphisms on tacrolimus exposure and response in pediatric primary nephrotic syndrome

Aim: To evaluate the impact of CYP3A4*1G, CYP3A5*3 and ABCB1-C3435T polymorphisms on tacrolimus concentrations, efficacy and tolerance in pediatric primary nephrotic syndrome. Methods: Dose-adjusted concentrations (C₀/D), daily dose, frequency and time to relapse, cumulative remission days, and adverse reactions in 65 Chinese patients with various genotypes were retrospectively collected and compared. Results: C₀/D increased in CYP3A4*1/*1, CYP3A5*3/*3 and CYP3A4*1/*1-3A5*3/*3 diplotype carriers by 38.4, 69.7 and 40.9% compared with CYP3A4*1/*1G, CYP3A5*1/*3 and noncarriers, respectively. Recurrence risks were decreased in CYP3A4*1/*1 (0.43 of hazard ratio to *1/*1G) and CYP3A5*3/*3 carriers (0.43 of hazard ratio to *1/*3). None of polymorphisms was linked to adverse reactions. Conclusion: The genotypes of CYP3A4*1G and CYP3A5*3 rather than ABCB1-C3435T potentially predicted tacrolimus exposure and clinical response in pediatric primary nephrotic syndrome.

Effect of the Most Relevant CYP3A4 and CYP3A5 Polymorphisms on the Pharmacokinetic Parameters of 10 CYP3A Substrates

Several cytochrome P450 (CYP) CYP3A polymorphisms were associated with reduced enzyme function. We aimed to evaluate the influence of these alleles on the pharmacokinetic parameters (PK) of several CYP3A substrates. We included 251 healthy volunteers who received a single dose of ambrisentan, atorvastatin, imatinib, aripiprazole, fentanyl, amlodipine, donepezil, olanzapine, fesoterodine, or quetiapine. The volunteers were genotyped for CYP3A4 and CYP3A5 polymorphisms by qPCR. To compare the PK across studies, measurements were corrected by the mean of each parameter for every drug and were logarithmically transformed. Neither CYP3A phenotype nor individual CYP3A4 or CYP3A5 polymorphisms were significantly associated with differences in PK. However, regarding the substrates that are exclusively metabolized by CYP3A, we observed a higher normalized AUC (p = 0.099) and a tendency of lower normalized Cl (p = 0.069) in CYP3A4 mutated allele carriers what was associated with diminished drug metabolism capacity. CYP3A4 polymorphisms did not show a pronounced influence on PK of the analysed drugs. If so, their impact could be detectable in a very small percentage of subjects. Although there are few subjects carrying CYP3A4 double mutations, the effect in those might be relevant, especially due to the majority of subjects lacking the CYP3A5 enzyme. In heterozygous subjects, the consequence might be less noticeable due to the high inducible potential of the CYP3A4 enzyme.

Pharmacogenetics and tacrolimus administration in stem cell transplantation

Tacrolimus is the gold standard immunosuppressant administered in solid organ and stem cell transplantation to avoid graft rejection post-transplant. Despite its widespread use, there is a large variation in response to therapy, likely due to high inter-individual pharmacokinetic variability. Therapeutic drug monitoring is employed to improve clinical response and reduce toxicity. There is substantial evidence that pharmacogenetics influences drug exposure and response. CYP3A5 genotype significantly impacts oral tacrolimus concentrations and response after solid organ transplantation. There are fewer studies in stem cell transplantation and with intravenous tacrolimus dosing. This report highlights recent evidence suggesting genes such as CYP3A4 and ABCB1 play a larger role after intravenous dosing compared with CYP3A5, and the role for novel genes on tacrolimus outcomes.

Kidney podocyte-associated gene polymorphisms affect tacrolimus concentration in pediatric patients with refractory nephrotic syndrome

Few studies have investigated the correlation between pharmacogenomics and tacrolimus pharmacokinetics in patients with nephrotic syndrome (NS). This study evaluated the influences of genetic polymorphisms of metabolic enzymes, transporters, and podocyte-associated proteins on tacrolimus concentration in Chinese pediatric patients with refractory NS. A total of 167 pediatric patients with refractory NS were included from July 2013 to December 2017. Age of onset was restricted to <14 years of age. Dose-adjusted tacrolimus trough concentration (C₀/D) on the third month was calculated, and 20 single-nucleotide polymorphisms in sixteen genes were genotyped. Age was correlated with tacrolimus C₀/D (p = 0.006, r = 0.213). Tacrolimus C₀/D was higher in CYP3A5 nonexpressers than in CYP3A5 expressers (p = 0.003). ACTN4 rs62121818, MYH9 rs2239781, CYP3A5*3, and age explained 20.5% interindividual variability of tacrolimus concentration in the total cohort. In CYP3A5 nonexpressers, ACTN4 rs62121818 and MYH9 rs2239781 together explained 14.6% variation of tacrolimus C₀/D. MYH9 rs2239781, LAMB2 rs62119873 and age together explained 22.3% variability of tacrolimus level in CYP3A5 expressers. CYP3A5*3 was still an important factor affecting tacrolimus concentration in patients with NS. Podocyte-associated gene polymorphisms, especially ACTN4 rs62121818 and MYH9 rs2239781, were the other most important biomarkers for tacrolimus whole blood levels. Genotyping of CYP3A5, ACTN4, and MYH9 polymorphisms may be helpful for better guiding tacrolimus dosing in pediatric patients with refractory NS.

Melding Pharmacogenomic Effect of MDR1 and CYP3A5 Gene Polymorphism on Tacrolimus Dosing in Renal Transplant Recipients in Northern India

INTRODUCTION

Tacrolimus (TAC) is the mainstay immunosuppressant for renal transplantation. A narrow therapeutic index, multiple drug interactions, and interindividual variability in pharmacokinetics make it obligatory to monitor therapeutic drug levels. The Multidrug resistance gene 1 (MDR1) and CYP3A5 gene polymorphism may blend to achieve the optimal level. The optimal dose as per body weight is difficult to single out in the early posttransplantation period. In this study, we aimed to analyze the melding effect of both gene polymorphisms and to elicit the dose depending on the combination of genetic single nucleotide polymorphisms (SNPs) in northern Indian transplant recipients, for whom data are limited.

METHODS

The daily TAC dose, weight-adjusted doses (mg/kg per day), TAC trough blood concentration (average of at least 3 levels), dose normalized with a corresponding dose using TAC concentration/weight-adjusted dose ratio (ng/ml per mg/kg per day) of 248 patients were recorded. All recipients were genotyped for the SNPs of CYP3A5 at intron 3 A6986G (the *3 or *1 allele), MDR1 at exons 12 (C1236T), 21 (G2677A/T), and 26 (C3435T). We analyzed the blending effect of mutant SNPs of the MDR gene and CYP3A5 for optimized TAC levels.

RESULTS

Among CYP3A5 genotypic variants, the dose-adjusted TAC level was significantly lower, and the TAC dose required to achieve the target level was significantly higher, in CYP3A5*1*1 (expressor) than that of CYP3A5*1*3 and CYP3A5*3*3. Of the MDR1 gene SNPs, only the G2677T/A homozygous mutant was significantly associated with TAC level, and it was strongly correlated with P-gp expression.The daily TAC dose requirement was highest with a combination of CYP3A5*1*1 and homozygous mutant TT+AA genotype of G2677T/A, and was lowest with CYP3A5*3*3 and wild-type GG of the G2677T/A genotype.

CONCLUSION

Both CYP gene and MDR1 gene polymorphism affect TAC dose requirements, and there is a need to look for both in an individual to achieve the target trough concentration.

Comparison of Tacrolimus Starting Doses Based on CYP3A5 Phenotype or Genotype in Kidney Transplant Recipients

BACKGROUND

Selection of expected phenotypes (ie, expressers/non-expressers) is currently used in CYP3A5*3 genotype-based tacrolimus dosing. The authors assessed whether a dosing regimen based on the 3 CYP3A5 genotypes may reduce the occurrence of inadequate exposure.

METHODS

Tacrolimus whole blood trough levels (C ₀) were retrieved from a retrospective cohort of 100 kidney transplant recipients treated with a starting dose of 0.15 (non-expressers) or 0.30 (expressers) mg/kg/d. The authors evaluated the occurrence of overexposures (12 < C ₀ < 20 ng/mL) or toxic concentrations (C ₀ ≥ 20 ng/mL). These results were used to set up a new strategy based on the 3 distinct CYP3A5 genotypes, which relevance was evaluated in a prospective cohort of 107 patients.

RESULTS

In the retrospective cohort, non-expressers exhibited frequent overexposure (63.6%) or toxic C ₀ (20.8%). Among expressers, none of the homozygous *1 carriers exhibited overexposure contrary to 25% of the heterozygotes. Based on these results, new tacrolimus starting doses were set at 0.10, 0.20, and 0.30 mg/kg/d for CYP3A5*3/*3, CYP3A5*1/*3, and CYP3A5*1/*1 genotypes, respectively. Tacrolimus overexposure was reduced in the CYP3A5*3/*3 group (63.6% vs 40%, P = .0038). None of the heterozygous patients exhibited toxic tacrolimus C ₀. Clinical outcomes were not different between the 2 periods, whatever the genotype. Our results indicate that the best tacrolimus exposure was obtained for doses of 0.10, 0.20, and 0.20 mg/kg/d for CYP3A5*3/3, CYP3A5*1/*3, and CYP3A5*1/*1, respectively.

CONCLUSIONS

Our results confirm that selecting tacrolimus dosing regimen according to the expected phenotype is appropriate, but that lower than currently recommended doses may be preferable.

Whole exome sequencing for the identification of CYP3A7 variants associated with tacrolimus concentrations in kidney transplant patients

The purpose of this study was to identify genotypes associated with dose-adjusted tacrolimus trough concentrations (C₀/D) in kidney transplant recipients using whole-exome sequencing (WES). This study included 147 patients administered tacrolimus, including seventy-five patients in the discovery set and seventy-two patients in the replication set. The patient genomes in the discovery set were sequenced using WES. Also, known tacrolimus pharmacokinetics-related intron variants were genotyped. Tacrolimus C₀/D was log-transformed. Sixteen variants were identified including novel CYP3A7 rs12360 and rs10211 by ANOVA. CYP3A7 rs2257401 was found to be the most significant variant among the periods by ANOVA. Seven variants including CYP3A7 rs2257401, rs12360, and rs10211 were analyzed by SNaPshot in the replication set and the effects on tacrolimus C₀/D were verified. A linear mixed model (LMM) was further performed to account for the effects of the variants and clinical factors. The combined set LMM showed that only CYP3A7 rs2257401 was associated with tacrolimus C₀/D after adjusting for patient age, albumin, and creatinine. The CYP3A7 rs2257401 genotype variant showed a significant difference on the tacrolimus C₀/D in those expressing CYP3A5, showing its own effect. The results suggest that CYP3A7 rs2257401 may serve as a significant genetic marker for tacrolimus pharmacokinetics in kidney transplantation.

CYP3A5 polymorphisms in renal transplant recipients: influence on tacrolimus treatment

Tacrolimus is a commonly used immunosuppressant after kidney transplantation. It has a narrow therapeutic range and demonstrates wide interindividual variability in pharmacokinetics, leading to potential underimmunosuppression or toxicity. Genetic polymorphism in CYP3A5 enzyme expression contributes to differences in tacrolimus bioavailability between individuals. Individuals carrying one or more copies of the wild-type allele *1 express CYP3A5, which increases tacrolimus clearance. CYP3A5 expressers require 1.5 to 2-fold higher tacrolimus doses compared to usual dosing to achieve therapeutic blood concentrations. Individuals with homozygous *3/*3 genotype are CYP3A5 nonexpressers. CYP3A5 nonexpression is the most frequent phenotype in most ethnic populations, except blacks. Differences between CYP3A5 genotypes in tacrolimus disposition have not translated into differences in clinical outcomes, such as acute rejection and graft survival. Therefore, although genotype-based dosing may improve achievement of therapeutic drug concentrations with empiric dosing, its role in clinical practice is unclear. CYP3A5 genotype may predict differences in absorption of extended-release and immediate-release oral formulations of tacrolimus. Two studies found that CYP3A5 expressers require higher doses of tacrolimus in the extended-release formulation compared to immediate release. CYP3A5 genotype plays a role in determining the impact of interacting drugs, such as fluconazole, on tacrolimus pharmacokinetics. Evidence conflicts regarding the impact of CYP3A5 genotype on risk of nephrotoxicity associated with tacrolimus. Further study is required.

Attempted validation of 44 reported SNPs associated with tacrolimus troughs in a cohort of kidney allograft recipients

AIM

Multiple genetic variants have been associated with variation in tacrolimus (TAC) trough concentrations. Unfortunately, additional studies do not confirm these associations, leading one to question if a reported association is accurate and reliable. We attempted to validate 44 published variants associated with TAC trough concentrations.

MATERIALS & METHODS

Genotypes of the variants in our cohort of 1923 kidney allograft recipients were associated with TAC trough concentrations.

RESULTS

Only variants in CYP3A4 and CYP3A5 were significantly associated with variation in TAC trough concentrations in our validation.

CONCLUSION

There is no evidence that common variants outside the CYP3A4 and CYP3A5 loci are associated with variation in TAC trough concentrations. In the future rare variants may be important and identified using DNA sequencing.

Genetic variations of the xenoreceptors NR1I2 and NR1I3 and their effect on drug disposition and response variability

NR1I2 (PXR) and NR1I3 (CAR) are nuclear receptors that are classified as xenoreceptors. Upon activation by various xenobiotics, including marketed drugs, they regulate the transcription level of major drug-metabolizing enzymes and transporters and facilitate the elimination of xenobiotics from the body. The modulation of the activity of these two xenoreceptors by various ligands is a major source of pharmacokinetic variability of environmental origin. NR1I2 and NR1I3 genetic polymorphisms can affect the pharmacokinetics and therapeutic response to many drugs, such as irinotecan, tacrolimus and atazanavir. This review provides an overview of NR1I2 and NR1I3 pharmacogenetic studies in various therapeutic fields (oncology, immunomodulation and infectiology) and discusses the implementation of NR1I2 and NR1I3 genetic polymorphism testing in the clinical routine.

Genome-wide association study identifies the common variants in CYP3A4 and CYP3A5 responsible for variation in tacrolimus trough concentration in Caucasian kidney transplant recipients

The immunosuppressant tacrolimus (TAC) is metabolized by both cytochrome P450 3A4 (CYP3A4) and CYP3A5 enzymes. It is common for European Americans (EA) to carry two CYP3A5 loss-of-function (LoF) variants that profoundly reduces TAC metabolism. Despite having two LoF alleles, there is still considerable variability in TAC troughs and identifying additional variants in genes outside of the CYP3A5 gene could provide insight into this variability. We analyzed TAC trough concentrations in 1345 adult EA recipients with two CYP3A5 LoF alleles in a genome-wide association study. Only CYP3A4*22 was identified and no additional variants were genome-wide significant. Additional high allele frequency genetic variants with strong genetic effects associated with TAC trough variability are unlikely to be associated with TAC variation in the EA population. These data suggest that low allele frequency variants, identified by DNA sequencing, should be evaluated and may identify additional variants that contribute to TAC pharmacokinetic variability.

Wuzhi Tablet (Schisandra sphenanthera Extract) is a Promising Tacrolimus-Sparing Agent for Renal Transplant Recipients Who are CYP3A5 Expressers: a Two-Phase Prospective Study

Tacrolimus is a potent but expensive first-line immunosuppressant, thus solutions to reduce tacrolimus consumption while maintain therapeutic level are in urgent need. A two-phase prospective study was conducted to assess the efficacy of an ethanolic extraction preparation of Schisandra sphenanthera (Wuzhi tablet) as a tacrolimus-sparing agent in renal transplant recipients who were high-dose tacrolimus consumers (CYP3A5*1 allele carriers, CYP3A5 expressers). A total of 12 patients were included in the Part I study. After co-administration of Wuzhi tablet, the average individual increment (%) in dose-adjusted C0, Cmax and AUC0-12 hour of tacrolimus were 198.8% (95% CI 149.2, 248.3), 111.0% (95% CI 63.4, 158.6) and 126.1% (95% CI 89.4, 162.8), respectively (P < 0.01), while the average individual reduction (%) in tacrolimus daily dose was 40.9% (95% CI 25.2, 56.6) (P < 0.01). Subsequently, 32 patients were enrolled in a prospective, randomized, controlled study and randomly assigned to receive tacrolimus by CYP3A5 genotype plus Wuzhi tablet co-administration guided dosing (study group) or standard dosing (control group). Besides less tacrolimus dose requirement (P < 0.01), a more accurate tacrolimus initial dose characterized by lower incidence of out-of-range C0 after initial dose (P < 0.01) and fewer dose changes (P < 0.01) was found in the study group. Moreover, no significant differences in acute rejection rate and serum creatinine levels were observed between two groups. Our results show that CYP3A5 genotype plus Wuzhi tablet co-administration guided tacrolimus dosing is a promising therapy for CYP3A5 expressers in the early post-transplant stage, while further study with a larger sample size is required to prove these findings.

Influence of the CYP3A4/5 genetic score and ABCB1 polymorphisms on tacrolimus exposure and renal function in Brazilian kidney transplant patients

BACKGROUND

Polymorphisms in genes encoding transport proteins and metabolizing enzymes involved in tacrolimus (TAC) disposition may be important sources of individual variability during treatment.

OBJECTIVE

The aim of this study was to investigate the effect of combined CYP3A4 and CYP3A5 variants, using a CYP3A4/5 genetic score, and ABCB1 polymorphisms on therapeutic TAC monitoring and their relationship with clinical outcomes.

MATERIAL AND METHODS

Brazilian kidney transplant recipients (n=151), who received TAC over 3 months after transplantation, were genotyped for CYP3A4 rs2242480 (g.20230G>A), CYP3A5 rs15524 (g.31611C>T) and rs776746 (g.6986A>G), ABCB1 rs1128503 (c.1236C>T), rs1045642 (c.3435C>T), and rs2032582 (c.2677G>T/A) polymorphisms.

RESULTS

Frequencies of CYP3A4 g.20230A, CYP3A5 g.31611C, and g.6986A were 0.37, 0.26, and 0.28, respectively. These alleles were associated with TAC rapid metabolization and were used for CYP3A4/5 genetic score construction. A higher CYP3A4/5 genetic score was associated with higher TAC dose and lower concentrations for dose administered (Co/D, P<0.05). Ninety days after transplantation, the presence of two or more rapid metabolization alleles contributed toward 27.7% of Co/D variability and was associated with a lower estimated glomerular filtration rate values (P<0.05). For ABCB1, the frequencies of c.1236T, c.3435T, and c.2677T/A alleles were 0.42, 0.42, and 0.33/0.04. At 30 days after transplantation, patients carrying ABCB1 c.1236TT+c.3435TT+(c.2677TT+TA) genotypes had higher TAC Co/D than those with common or heterozygous genotypes (P<0.05).

CONCLUSION

The results show the impact of the CYP3A4/5 genetic score on TAC exposure and renal function in Brazilian patients. Furthermore, ABCB1 polymorphisms, in a combined analysis, influenced TAC Co/D at 30 days after transplantation.

Economic Evaluation of Pharmacogenetic Tests in Patients Subjected to Renal Transplantation: A Review of Literature

Renal transplantation is the treatment of choice for the patients with end-stage renal failure. Genetic factors, among others, can influence variability in response to immunosuppressive drugs. Nowadays, due to restrictive health resources, the question arises whether routine pharmacogenetic analyses should be done in the renal transplant recipients or not. The aim of this literature review was to present the up-to-date information considering the economic feasibility of pharmacogenetic testing in patients subjected to renal transplantation. The organization United Network for Organ Sharing in the US estimated that total costs per renal transplant concerning these analyses were $334,300 in 2014. Pharmacogenetic testing prior to treatment initiation could be helpful to predict and assess treatment response and the risks for adverse drug reactions. This kind of testing before treatment initiation seems to be one of the most promising applications of pharmacokinetics. Although pharmacogenetic tests were found to be a cost-effective or cost-saving strategy in many cases, some authors represent another opinion. However, if the real costs of renal transplantation are recognized, the application of these tests in the standard daily practice could be considered more realistic, which additionally emphasizes the importance of future studies assessing their cost effectiveness.

The POR rs1057868-rs2868177 GC-GT diplotype is associated with high tacrolimus concentrations in early post-renal transplant recipients

AIM

Cytochrome P450 oxidoreductase (POR) is the only flavoprotein that donates electrons to all microsomal P450 enzymes (CYP), and several POR SNPs have been shown to be important contributors to altered CYP activity or CYP-mediated drug metabolism. In this study we examined the association between 6 POR SNPs and tacrolimus concentrations in Chinese renal transplant recipients.

METHODS

A total of 154 renal transplant recipients were enrolled. Genotyping of CYP3A5*3 and 6 POR SNPs was performed. All patients received a triple immunosuppressive regimen comprising tacrolimus, mycophenolate mofetil and prednisone. Dose-adjusted tacrolimus trough concentrations were obtained on d 7 (C0D7/D) after transplantation when steady-state concentration of tacrolimus was achieved (dosage had been unchanged for more than 3 d).

RESULTS

Tacrolimus C0D7/D in CYP3A5*3/*3/ POR rs1057868-rs2868177 GC-GT diplotype carriers was 1.62- and 2.72-fold higher than those in CYP3A5*3/*3/ POR rs1057868-rs2868177 GC-GT diplotype non-carriers and CYP3A5*1 carriers (220.17±48.09 vs 135.69±6.86 and 80.84±5.27 ng/mL/mg/kg, respectively, P<0.0001). Of CYP3A5*3/*3/ POR rs1057868-rs2868177GC-GT diplotype carriers, 85.71% exceeded the upper limit of the target range (8 ng/mL), which was also significantly higher compared with the latter two groups (14.29% and 0.00%, respectively, P<0.0001). The CYP3A5*3 and POR rs1057868-rs2868177 GC-GT diplotype explained 31.7% and 5.7%, respectively, of the inter-individual variability of tacrolimus C0D7/D, whereas the POR rs1057868-rs2868177 GC-GT diplotype could explain 10.9% of the inter-individual variability of tacrolimus C0D7/D in CYP3A5 non-expressers.

CONCLUSION

The CYP3A5*3 and POR rs1057868-rs2868177 GC-GT diplotype accounted for the inter-individual variation of tacrolimus C0D7/D. Genotyping of POR rs1057868-rs2868177 diplotypes would help to differentiate initial tacrolimus dose requirements and to achieve early target C0 ranges in Chinese renal transplant recipients.

Effect of ABCB1 diplotype on tacrolimus disposition in renal recipients depends on CYP3A5 and CYP3A4 genotype

The relevance of most genetic polymorphisms beyond CYP3A5*1 on tacrolimus disposition remains unclear. We constructed a predictive mixed model for tacrolimus dose-corrected trough concentration (C₀/dose) at months 3, 12 and 24 after transplantation in a retrospective cohort of 766 predominantly Causasian adult renal recipients (n=2042 trough concentrations). All patients were genotyped for 32 single-nucleotide polymorphisms with a proven or possible relevance to tacrolimus disposition based on the previous studies. Of these, ABCB1, ABCC2, OATP1B1, COMT, FMO, PPARA and APOA5 were analyzed as (functional) diplotype groups. Predictors of C₀/dose were CYP3A5*1, hematocrit, age, CYP3A4*22, use of concomitant CYP3A4 inhibitor or inducer, ALT, estimated glomerular filtration rate, tacrolimus formulation (once vs twice daily), ABCB1 diplotype and time after transplantation. The effect of ABCB1 diplotype was small but strongly accentuated in CYP3A4*22 carriers and non-existent in CYP3A5 expressors. ABCC2 diplotype had a limited effect on C₀/dose that was only statistically significant in CYP3A5 non-expressors.