“What do we know about tacrolimus pharmacogenetics in transplant recipients?”

Impact of IL-6 and IL-10 genotypes on tacrolimus dose requirements in kidney transplant recipients: Monte Carlo analysis

Introduction: IL-6 and IL-10 may affect the activity of cytochrome P450 (CYP) 3A enzymes involved in tacrolimus (Tac) metabolism. Moreover, the effect of IL-6 and IL-10 on Tac pharmacokinetics may differ with respect to the genetic variations in their genes.Aim: To examine the influence of IL-6 and IL-10 gene polymorphisms on Tac dose requirements and exposure over a 5-year period following kidney transplantation. Univariate and standard multivariate linear regression and Monte Carlo analysis were performed to investigate potential covariates influencing Tac dose-adjusted trough concentration (C0/D) in various post-transplantation periods.Materials & methods: IL-6 (-174G > C), IL-10 (-1082G > A, -819C > T and -592C > A) genotype, Tac daily dose, C0, C0/D and intrapatient variability data were collected from 113 patients.Results: Multivariate regression analysis and accompanied Monte Carlo simulation underscore the importance of considering IL-6 -174G > C and IL-10 -1082G > A gene polymorphisms, alongside Tac metabolic phenotype and post-transplantation period, when tailoring Tac dosage regimen.Conclusion: This study provides valuable insights regarding the individualized adjustment of Tac treatment in various post-transplantation periods.

Comparison of the Impact of Pharmacogenetic Variability on the PK of Slow Release and Immediate Release Tacrolimus Formulations

Tacrolimus-modified release formulations allow for once-daily dosing, and adherence is better compared to the twice-daily immediate release formulation. When patients are switched from one formulation to another, variable changes in drug concentrations are observed. Current data suggest that the changes in drug exposure are larger in patients who express the CYP3A5 enzyme (CYP3A5 *1/*3 or *1/*1) compared to nonexpressers (CYP3A5*3/*3). Possibly, these differences are due to the fact that in the upper region of the small intestine CYP3A activity is higher, and that this expression of CYP3A decreases towards the more distal parts of the gut. Modified release formulations may therefore be subject to a less presystemic metabolism. However, the full implications of pharmacogenetic variants affecting the expression and function of drug transporters in the gut wall and of enzymes involved in phase I and phase II metabolism on the different formulations are incompletely understood, and additional studies are required. Conclusions: In all patients in whom the formulation of tacrolimus is changed, drug levels need to be checked to avoid clinically relevant under- or overexposure. In patients with the CYP3A5 expresser genotype, this recommendation is even more important, as changes in drug exposure can be expected.

Tacrolimus in adult hematopoietic stem cell transplantation

Introduction: Graft-versus-host disease (GVHD) is the most common complication of hematopoietic stem cell transplantation (HSCT); therefore, the prevention of GVHD is important for a successful treatment. Tacrolimus (Tac), a calcineurin inhibitor, has been widely used for the prophylaxis of GVHD in HSCT recipients. Areas covered: This review introduces phase II/III of clinical trials related with Tac's roles in the prevention of GVHD in HSCT. Furthermore, we discuss the normal ranges of Tac concentrations, pharmacogenetics, and drug interactions of Tac, as well as its side effects in adult HSCT recipients. Expert opinion: A series of studies has established the efficacy and safety of Tac alone or in combination with other agents in HSCT. However, successful administration of Tac is complicated by its narrow therapeutic window, inter-patient pharmacokinetic variability, and a spectrum of undesirable side effects. It is necessary to maintain concentrations of Tac within the desired ranges for GVHD prophylaxis. Moreover, various factors contribute to significant variability in Tac pharmacokinetics, including drug interactions and genomic variation.