Pharmacogenetics of immunosuppressant polymorphism of CYP3A5 in renal transplant recipients

The pharmacokinetics of tacrolimus in peripheral blood mononuclear cells and limited sampling strategy for estimation of exposure in renal transplant recipients

PURPOSE

Intracellular exposure of tacrolimus (TAC) may be a better marker of therapeutic effect than whole blood exposure. We aimed to evaluate the influence of genetic polymorphism on the pharmacokinetics of TAC in peripheral blood mononuclear cells (PBMCs) and develop limited sampling strategy (LSS) models to estimate the area under the curve (AUC_0-12h) in the PBMC of Chinese renal transplant patients.

METHODS

Ten blood samples of each of the 23 renal transplant patients were collected 0-12h after 14 (10-18) days of TAC administration. PBMCs were separated and quantified. The TAC level in PBMCs was determined, and pharmacokinetic parameters were estimated by noncompartmental study. The AUC_0-12h of TAC in whole blood was estimated by Bayesian approach based on a population pharmacokinetic model established in 65 renal transplant patients. The influence of CYP3A5 and ABCB1 genotypes on exposure was estimated. By applying multiple stepwise linear regression analysis, LSS equations for TAC AUC_0-12h in the PMBC of renal transplant patients were established, and the bias and precision of various equations were identified and compared.

RESULTS

We found a modest correlation between TAC exposure in whole blood and PBMC (r² = 0.5260). Patients with the CYP3A5 6986GG genotype had a higher AUC_0-12h in PBMCs than those with the 6986 AA or GA genotype (P = 0.026). Conversely, patients with the ABCB1 3435TT genotype had a higher AUC_0-12h in PBMC than those with the 3435 CC and CT genotypes (P = 0.046). LSS models with 1-4 blood time points were established (r² = 0.570-0.989). The best model for predicting TAC AUC_0-12h was C₂-C₄-C₆-C₁₀ (r² = 0.989). The model with C_0.5-C₆ (r² = 0.849) can be used for outpatients who need monitoring to be performed in a short period.

CONCLUSIONS

The CYP3A5 and ABCB1 genotypes impact TAC exposure in PBMCs, which may further alter the effects of TAC. The LSS model consisting of 2-4 time points is an effective approach for estimating full TAC AUC_0-12h in Chinese renal transplant patients. This approach may provide convenience and the possibility for clinical monitoring of TAC intracellular exposure.

Frequency of CYP3A5 Genetic Polymorphisms and Tacrolimus Pharmacokinetics in Pediatric Liver Transplantation

The evidence available in the pediatric population is limited for making clinical decisions regarding the optimization of tacrolimus (TAC) in pharmacotherapy. The objective of this study was to estimate the frequency of CYP3A5 genetic polymorphisms and their relationship with tacrolimus requirements in the pediatric population. This was a longitudinal cohort study with a two-year follow-up of 77 patients under 18 years old who underwent a liver transplant during the period 2009–2012 at the J.P. Garrahan Pediatric Hospital. Tacrolimus levels from day five up to two years after the transplant were obtained from hospital records of routine therapeutic drug monitoring. The genotyping of CYP3A5 (CYP3A5*1/*3 or *3/*3) was performed in liver biopsies from both the donor and the recipient. The frequency of CYP3A5*1 expression for recipients was 37.1% and 32.2% for donors. Patients who received an expresser organ showed lower Co/dose, especially following 90 days after the surgery. The role of each polymorphism is different according to the number of days after the transplant, and it must be taken into account to optimize the benefits of TAC therapy during the post-transplant induction and maintenance phases.

Therapeutic concentration achievement and allograft survival comparing usage of conventional tacrolimus doses and CYP3A5 genotype-guided doses in renal transplantation patients

AIMS

Although cytochromeP450(CYP)3A5 gene polymorphism affects personalized tacrolimus doses, there is no consensus as to whether CYP3A5 genotypes should be determined to adjust the doses. The aims were to compare the therapeutic ranges and clinical outcomes between the conventional and genotype-guided tacrolimus doses.

METHODS

This randomized controlled study compared 63 cases of the conventional tacrolimus dose group (0.1 mg/kg/day) with 62 cases of the genotype-guided doses group of 0.125, 0.1 and 0.08 mg/kg for CYP3A5*1/*1, *1/*3, and *3/*3 genotypes for the initial 3 days of kidney transplantation. After day 3, dose adjustment occurred in both groups to achieve therapeutic concentrations.

RESULTS

The genotype-guided group had an increased proportion of patients with tacrolimus concentrations in the therapeutic range at the steady state on day 3 (40.3 vs 23.8%, P = .048). A lower proportion of over-therapeutic concentration patients was noted in the genotype-guided group in the CYP3A5*3/*3 genotype (9.7 vs 27%, P = .013). Unexpectedly, more delayed graft functions (DGFs) were in the genotype-guided group (41.9 vs 22.2%, P = .018) especially in the CYP3A5*1/*1 participants who might have had an aggravated DGF by a longer ischaemic time and higher serum donor creatinine levels than in the control group. There were no significant differences of glomerular filtration rates or graft or patient survivals over a median 37-month follow-up period.

CONCLUSIONS

Determination of the CYP3A5 genotype improved therapeutic range achievement. CYP3A5*1/*1 patients who have high risks of DGF should be closely monitored because of an increased risk of DGF and reduced glomerular filtration rate with high tacrolimus doses.

Investigation of CYP 3A5 and ABCB1 gene polymorphisms in the long-term following renal transplantation: Effects on tacrolimus exposure and kidney function

The clinical use of tacrolimus (Tac) is complicated by the large inter-individual variability in its pharmacokinetics as well as by chronic adverse effects on renal function. The main goal of this study was to evaluate the potential influence of cytochrome P450 3A5 (CYP 3A5) and ATP-binding cassette transporter B1 (ABCB1) gene polymorphisms on Tac dose requirements and dose-adjusted concentrations in different long-term periods following renal transplantation. Another aim was to investigate whether these polymorphisms affect renal function in late post-transplant period. A total of 91 renal transplant recipients were enrolled for genotyping analysis, and 53 of these entered into a pharmacokinetic-pharmacogenetic study. Allele-specific polymerase chain reaction was used for CYP 3A5 and ABCB1 polymorphism determination. Pharmacokinetic data (dose, trough concentration and dose-adjusted concentration of Tac) and renal function parameters [creatinine (Cre) clearance and serum Cre level] were analyzed in relation to patient genotype at 6, 12 and 24 months after transplantation. Also, linear regression analysis was performed to evaluate the effect of CYP 3A5 and ABCB1 genotypes on Tac exposure and renal function up to 24 months post-transplant. Individuals carrying the CYP 3A5*1/*3 genotype had higher Tac dose requirements than CYP 3A5*3/*3 carriers at 6, 12 and 24 months after renal transplantation. The results revealed that ABCB1 polymorphism did not influence Tac dose requirements independently. Regression analysis showed that CYP 3A5 influenced the Tac dose-adjusted concentration as well as renal function up to 24 months post-transplant. These findings confirmed that CYP 3A5 polymorphism represents the most important determinant of Tac dose and exposure in the late period following renal transplantation. Furthermore, the obtained results indicate that the decline in renal function may be more pronounced in patients with CYP 3A5*1 in the long-term period after renal transplantation.

Review article: The pharmacokinetics and pharmacodynamics of drugs used in inflammatory bowel disease treatment

BACKGROUND

The following review is a compilation of the recent advances and knowledge on the behaviour of the most frequently used compounds to treat inflammatory bowel disease in an organism.

RESULTS

It considers clinical aspects of each entity and the pharmacokinetic/pharmacodynamic relationship supported by the use of plasma monitoring, tissue concentrations, and certain aspects derived from pharmacogenetics.

Influence of CYP3A5 polymorphism on tacrolimus maintenance doses and serum levels after renal transplantation: age dependency and pharmacological interaction with steroids

  TAC, MMF and MP are used in pediatric kidney tx. The cytochrome P450 (CYP)3A5 enzyme appears to play a role in TAC metabolism. The aims of this study were to investigate CYP3A5 polymorphism's effect on TAC dosing and the age dependency of TAC dosing by testing blood concentrations, and the interaction between steroids and TAC during the first year after tx. Genomic DNA was extracted and amplified with specific primers. CYP3A5 alleles were confirmed by direct sequencing of PCR products on an automated AB13100 capillary sequencer. We studied 48 renal transplant patients (age at tx 12±0.5yr, 22 boys) receiving TAC, MMF, MP. Of these, 79% were CYP3A5*3/*3 (non-expressers homozygotes) and 21% were CYP3A5*1/*3 (expressers). TAC trough levels were 7.1±0.4ng/mL in CYP3A5*3/*3 patients and 6.5±0.7ng/mL in CYP3A5*1/*3 group (p=0.03). CYP3A5*1/*3 patients had lower levels of dose-adjusted TAC (36.7±5.8ng/mL/mg/kg/day) to achieve target blood concentration and required higher daily dose per weight (0.21±0.03mg/kg/day) than CYP3A5*3/*3 patients, 72.4±8.0ng/mL/mg/kg/day and 0.13±0.01mg/kg/day (p<0.001). Prepubertal patients with different CYP3A5 polymorphisms required significant higher TAC doses and achieved lower dose-normalized concentration compared with pubertal patients. Both TAC dose and adjusted-dose correlated with daily MP dose in CYP3A5*1*3 (r: 0.4, p<0.03 and r: 0.4, p<0.03) and in CYP3A5*3*3 (r: 0.6, p<0.01 and r: 0.47, p<0.001) patients. CYP3A5 polymorphism performed before tx could contribute to a better individualization of TAC therapy. The higher TAC dose in prepubertal patients and the pharmacological interactions between MP and TAC may not be fully explained by different CYP3A5 polymorphisms.

Value of CYP3A5 genotyping on determining initial dosages of tacrolimus for Chinese renal transplant recipients

Optimal blood levels of tacrolimus in transplant recipients are critically important to preserve the allograft. Suboptimal doses of the immunosuppressant can result in allograft toxicity or rejection. In the present study, we determined CYP3A5 genotypes of patients and analyzed their medical documents in 2 successive periods. In the first period, a fixed initial dosage of 0.1 mg/kg was prescribed daily for 28 patients regardless of their CYP3A5 genotype. In the second period, CYP3A5 genotyping was performed with polymerase chain reaction-restriction fragment length polymorphism and DNA sequencing. The frequency distribution of CYP3A5 genotypes was 47.4% (38/78) for *1/*3, 2.6% (2/78) for *1/*1, and 50% (39/78) for *3/*3. The patients with *1/*3 had shown significantly lower tacrolimus blood levels than those with the *3/*3 when the initial dose of 0.10 mg/kg was given for 2 weeks postoperatively. In the second period, initial dosages were selected according to individuals' CYP3A5 genotypes, 0.08 mg/kg/d for recipients with CYP3A5 *3/*3 and 0.15 mg/kg/d for recipients with *1/*3. Adjustment of the initial dosage of tacrolimus was documented to improve the proportion of patients achieving target drug blood levels in the early postoperative stage: from 46.7% to 81.8% of the *1/*3 group and from 46.2% to 73.1% of the *3/*3 group on the third day. In conclusion, CYP3A5 polymorphism plays an important role in influencing tacrolimus blood levels. Initial tacrolimus dosage selection based on CYP3A5 genotyping can improve drug blood levels in the early stage following renal transplantation.

Tacrolimus Pharmacokinetic and Pharmacogenomic Differences between Adults and Pediatric Solid Organ Transplant Recipients

Tacrolimus is a calcineurin inhibitor immunosuppressant that has seen considerable use in both adult and pediatric solid organ transplant recipients. Though there is much pharmacokinetic data available for tacrolimus in the adult population, the literature available for children is limited. Furthermore, very little is known about the pharmacogenomic differences in the two patient groups. Based on what information is currently available, clinically significant differences may exist between the two populations in terms of absorption, distribution, metabolism and elimination. In addition, inherent physiological differences exist in the young child including: less effective plasma binding proteins, altered expression of intestinal P-glycoprotein, and increased expression of phase 1 metabolizing enzymes, therefore one would expect to see clinically significant differences when administering tacrolimus to a child. This paper examines available literature in an attempt to summarize the potential pharmacokinetic and pharmacogenomic variability that exists between the two populations.