Effect of CYP3A5*1 expression on tacrolimus required dose for transplant pediatrics: A systematic review and meta-analysis

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.

Effects of clarithromycin on the pharmacokinetics of tacrolimus and expression of CYP3A4 and P-glycoprotein in rats

The objective of this study was to investigate the effect of clarithromycin on the pharmacokinetics of tacrolimus in rats and better understand its mechanism. In the control group (n = 6), rats received a single oral dose of 1 mg tacrolimus on day 6. In the experimental group (n = 6), rats received 0.25 g of clarithromycin daily for five consecutive days and then a single oral dose of 1 mg tacrolimus on day 6. Orbital venous blood (250 μL) was collected at 0, 0.25, 0.50, 0.75, 1, 2, 4, 8, 12, and 24 h before and after tacrolimus administration. Blood drug concentrations were detected via mass spectrometry. Small intestine and liver tissue samples were collected after rats were euthanized via dislocation, and CYP3A4 and P-glycoprotein (P-gp) protein expression was determined using western blotting. Clarithromycin increased the blood tacrolimus concentration and affected its pharmacokinetic properties in rats. Compared with those in the control group, the AUC_0-24 , AUC_0-∞ , AUMC_(0-t) , and AUMC_(0-∞) of tacrolimus in the experimental group were significantly increased, whereas the CLz/F was significantly lower (P < 0.01). Simultaneously, clarithromycin significantly inhibited CYP3A4 and P-gp expression in the liver and intestine. Protein expression of CYP3A4 and P-gp in the liver and the intestinal tract was significantly downregulated in the intervention group compared with that in the control group. Clarithromycin significantly inhibited the protein expression of CYP3A4 and P-gp in the liver and intestine, thereby increasing the mean blood concentration and significantly increasing the AUC of tacrolimus.

Influential Factors and Efficacy Analysis of Tacrolimus Concentration After Allogeneic Hematopoietic Stem Cell Transplantation in Children with β-Thalassemia Major

Purpose

To analyze factors influencing tacrolimus (TAC) trough concentration (C₀) in β-thalassemia major (β-TM) pediatric patients after allogeneic hematopoietic stem cell transplantation (Allo-HSCT) and to investigate the effects of genotype polymorphism and drug-drug interactions on TAC trough concentration in children with β-TM. Furthermore, to analyze the correlation between TAC C₀ and efficacy and adverse reactions.

Patients and Methods

Prospectively collection of demographic information and details of combined treatment of patients with β-TM receiving HSCT, and genotypes of CYP3A4, CYP3A5, and ABCB1 (rs1045642, rs1128503, rs2032582) were obtained for each patient. Univariate analysis and multiple linear regression analysis were used to investigate influencing factors on TAC C₀. The impact of different genotypes and the co-administration of azole antifungal drugs on β-TM patients receiving TAC were evaluated, together with the correlation between acute graft-versus-host disease (aGVHD), infection, and liver injury of TAC C₀.

Results

A total of 46 patients with 587 concentration data were included. The multiple linear regression results showed that the patient's sex, weight, postoperative time, hemoglobin, platelet count, serum cystatin C, and combined voriconazole were independent influencing factors of the infusion trough concentration/daily dose, C₀/D_iv. Age, body surface area, postoperative time, co-administration of voriconazole, and CYP3A4*18B are independent influencing factors of C₀/D_po. Group comparisons showed that voriconazole can affect TAC C₀ administered intravenously (IV) and orally in β-TM pediatric patients, while patient genotype can affect TAC C₀ during oral administration. TAC C₀ does not correlate with aGVHD or liver injury, but infection may be associated with TAC C₀.

Conclusion

The concentration of TAC should be closely monitored when co-administered with voriconazole. It is worth considering that the influence of genotype on the trough concentration of oral TAC and individualized drug administration warrant investigation. Finally, this study indicated that C₀ is not suitable as an indicator of the efficacy of TAC.

Impact of CYP3A5 phenotype on tacrolimus time in therapeutic range and clinical outcomes in pediatric renal and heart transplant recipients

STUDY OBJECTIVE

This study investigated the effect of CYP3A5 phenotype on time in therapeutic range (TTR) of tacrolimus post-transplant in pediatric patients.

DESIGN AND DATA SOURCE

This retrospective study assessed medical records of pediatric kidney and heart recipients with available CYP3A5 genotype for tacrolimus dosing, troughs, and the clinical events (biopsy-proven acute rejection [BPAR] and de novo donor-specific antibodies [dnDSA]).

MEASUREMENTS AND MAIN RESULTS

The primary outcome, mean TTR in the first 90 days post-transplant, was 9.0% (95% CI: -16.1, -1.9) lower in CYP3A5 expressers (p = 0.014) when adjusting for time to therapeutic concentration and organ type. There was no difference between CYP3A5 phenotypes in time to the first clinical event using TTR during the first 90 days. When applying TTR over the first year, there was a significant difference in event-free survival (EFS) which was 50.0% for CYP3A5 expressers/TTR < 35%, 45.5% for expressers/TTR ≥ 35%, 38.1% for nonexpressers/TTR < 35%, and 72.9% for nonexpressers/TTR ≥ 35% (log-rank p = 0.03). A post hoc analysis of EFS identified CYP3A5 expressers had lower EFS compared to nonexpressers in patients with TTR ≥ 35% (p = 0.04) but no difference among patients with TTR < 35% (p = 0.6).

CONCLUSIONS

The relationship between TTR and CYP3A5 phenotype suggests that achieving a TTR ≥ 35% during the first year may be a modifiable factor to attenuate the risk of BPAR and dnDSA.

Early impact of donor CYP3A5 genotype and Graft-to-Recipient Weight Ratio on tacrolimus pharmacokinetics in pediatric liver transplant patients

Tacrolimus (TAC) pharmacokinetics is influenced by the donor CYP3A5 genotype and the age of pediatric liver recipients. However, an optimization of a genotype-based algorithm for determining TAC starting is needed to earlier achieve stable target levels. As the graft itself is responsible for its metabolism, the Graft-to-Recipient Weight Ratio (GRWR) might play a role in TAC dose requirements. A single-center study was carried out in a cohort of 49 pediatric recipients to analyse the impact of patient and graft characteristics on TAC pharmacokinetics during the first 15 post-transplant days. Children < 2 years received grafts with a significantly higher GRWR (4.2%) than children between 2–8 (2.6%) and over 8 (2.7%). TAC concentration/weight-adjusted dose ratio was significantly lower in recipients from CYP3A5*1/*3 donors or with extra-large (GRWR > 5%) or large (GRWR 3–5%) grafts. The donor CYP3A5 genotype and GRWR were the only significant predictors of the TAC weight adjusted doses. Patients with a GRWR > 4% had a higher risk of acute rejection, observed in 20/49 (41%) patients. In conclusion, TAC starting dose could be guided according to the donor CYP3A5 genotype and GRWR, allowing for a quicker achievement of target concentrations and eventually reducing the risk of rejection.

Fifteen-minute consultation: Pharmacogenomics: a guide for busy clinicians

The ultimate goal of pharmacogenomics is to understand how the effects of interindividual genetic variation impact on the response of patients to treatments and in turn optimise those treatments while minimising potential side effects. This review article provides a brief overview of pharmacogenomics, focusing on the methods used to understand how genes of interest are identified, how pharmacogenomics is currently used within paediatric clinical practice within the UK, potential areas for future use and some of the caveats specific to paediatric medicine.

CYP3A5 gene polymorphisms and their impact on dosage and trough concentration of tacrolimus among kidney transplant patients: a systematic review and meta-analysis

Tacrolimus is an immunosuppressive drug widely used in kidney transplantation. Cytochrome P450 3A5 (CYP3A5) protein is involved in tacrolimus metabolism. Single nucleotide polymorphism in the CYP3A5 gene (6986A>G) results in alteration in metabolic activity of CYP3A5 protein which eventually affects the tacrolimus concentration. Patients with CYP3A5 expresser genotypes (A/A *1/*1 and A/G *1/*3) metabolize tacrolimus more rapidly than CYP3A5 nonexpressers (G/G *3/*3). We performed meta-analysis to estimate the effect of CYP3A5 polymorphism on the trough concentration-dose ratio (Co/D) and risk of renal allograft rejection with similar post-transplant periods and Asian vs. European populations. Our results showed that the tacrolimus Co/D ratio is significantly lower in CYP3A5 expresser group as compared with nonexpresser in Asian as well as in European populations at any post-transplant period (p < 0.00001). No significant association was found with renal allograft rejection episodes between expressers and nonexpressers in European populations (OR: 1.12; p = 0.47). Interestingly, Asian population (with expresser genotypes) and patients after 3 years post-transplantation (with expresser genotypes) have a higher risk of rejection (OR: 1.62; p < 0.05), (OR: 1.68; p < 0.05), respectively. This could be due to high prevalence of expresser genotypes in Asian population. Few tacrolimus-based studies are identified with long-term graft survival. There is a need to have more studies looking for long-term graft survival in expresser as well as no-expresser groups especially in Asian populations who have high frequency of CYP3A5 functional genotype.

Tacrolimus troughs and genetic determinants of metabolism in kidney transplant recipients: A comparison of four ancestry groups

Tacrolimus trough and dose requirements vary dramatically between individuals of European and African American ancestry. These differences are less well described in other populations. We conducted an observational, prospective, multicenter study from which 2595 kidney transplant recipients of European, African, Native American, and Asian ancestry were studied for tacrolimus trough, doses, and genetic determinants of metabolism. We studied the well-known variants and conducted a CYP3A4/5 gene-wide analysis to identify new variants. Daily doses, and dose-normalized troughs were significantly different between the four groups (P < .001). CYP3A5*3 (rs776746) was associated with higher dose-normalized tacrolimus troughs in all groups but occurred at different allele frequencies and had differing effect sizes. The CYP3A5*6 (rs10264272) and *7 (rs413003343) variants were only present in African Americans. CYP3A4*22 (rs35599367) was not found in any of the Asian ancestry samples. We identified seven suggestive variants in the CYP3A4/5 genes associated with dose-normalized troughs in Native Americans (P = 1.1 × 10^-5 -8.8 × 10^-6 ) and one suggestive variant in Asian Americans (P = 5.6 × 10^-6 ). Tacrolimus daily doses and dose-normalized troughs vary significantly among different ancestry groups. We identified potential new variants important in Asians and Native Americans. Studies with larger populations should be conducted to assess the importance of the identified suggestive variants.