CYP3A-status is associated with blood concentration and dose-requirement of tacrolimus in heart transplant recipients

High inter-individual variability in tacrolimus clearance is attributed to genetic polymorphisms of CYP3A enzymes. However, due to CYP3A phenoconversion induced by non-genetic factors, continuous changes in tacrolimus-metabolizing capacity entail frequent dose-refinement for optimal immunosuppression. In heart transplant recipients, the contribution of patients’ CYP3A-status (CYP3A5 genotype and CYP3A4 expression) to tacrolimus blood concentration and dose-requirement was evaluated in the early and late post-operative period. In low CYP3A4 expressers carrying CYP3A5*3/*3, the dose-corrected tacrolimus level was significantly higher than in normal CYP3A4 expressers or in those with CYP3A5*1. Modification of the initial tacrolimus dose was required for all patients: dose reduction by 20% for low CYP3A4 expressers, a 40% increase for normal expressers and a 2.4-fold increase for CYP3A5*1 carriers. The perioperative high-dose corticosteroid therapy was assumed to ameliorate the low initial tacrolimus-metabolizing capacity during the first month. The fluctuation of CYP3A4 expression and tacrolimus blood concentration (C0/D) was found to be associated with tapering and cessation of corticosteroid in CYP3A5 non-expressers, but not in those carrying CYP3A5*1. Although monitoring of tacrolimus blood concentration cannot be omitted, assaying recipients’ CYP3A-status can guide optimization of the initial tacrolimus dose, and can facilitate personalized tacrolimus therapy during steroid withdrawal in the late post-operative period.

Relationship between CYP3A5 Polymorphism and Tacrolimus Blood Concentration Changes in Allogeneic Hematopoietic Stem Cell Transplant Recipients during Continuous Infusion

A polymorphism in the gene encoding the metabolic enzyme cytochrome P450 family 3 subfamily A member 5 (CYP3A5) is a particularly influential factor in the use of tacrolimus in Japanese patients. Those who are homozygotic for the *3 mutation lack CYP3A5 activity, which results in substantial individual differences in tacrolimus metabolism. The aim of this study was to analyze the relationship between individual differences in tacrolimus blood concentration changes and CYP3A5 polymorphisms in allogeneic hematopoietic stem cell transplantation recipients during the period of increasing blood concentration of the drug following treatment onset. This was a prospective observational cohort study, involving 20 patients administered tacrolimus by continuous infusion. The subjects were divided into the *1/*3 and *3/*3 groups based on CYP3A5 polymorphism analysis. The tacrolimus blood concentration/dose (C/D) ratio increased from day 1 and was largely stable on day 5, and a significant difference was observed between the *1/*3 and *3/*3 groups in the time course of the C/D ratio during this period (p < 0.05). This study reveals the effects of CYP3A5 polymorphism on continuous changes in tacrolimus blood concentration.

Diagnostic effectiveness of transforming growth factor beta 1 (TGF-β1) at adjustment of tacrolimus individual dose in pediatric liver recipients

Blood level of transforming growth factor beta 1 (TGF-β1) is associated with liver function and immune homeostasis, which suggests it as a potential biomarker for immunosuppressant tacrolimus dose requirement at liver transplantation (LT).Aim.To evaluate diagnostic efficacy of TGF-β1 blood level at determination of individual tacrolimus dose requirement in children at LT.Materials and methods.89 children with end stage liver disease aged from 3 to 73 months were examined. Children underwent living related LT, then the recipients received 2–3 component immunosuppressive therapy, including tacrolimus. Blood concentration of tacrolimus and TGF-β1 was measured by ELISA.Results.TGF-β1 blood level in children before LT was significantly lower than in healthy children: 3.7 (1.3–8.4) and 19.3 (12.6–25.5) ng/ml, p = 0.001. A month after LT, its concentration increased to 8.1 (1.8–15.3) ng/ml (p = 0.02). A year after LT, the cytokine level remained higher than before transplantation: 6.6 (1.9–12.6) ng/ml, p = 0.01. TGF-β1 level did not correlate with tacrolimus blood concentration, determined 12 hours after the last administration of the drug, neither a month, nor a year after transplantation. At the same time, the cytokine level one month after LT was associated with a tacrolimus daily dose one year after the operation (r = –0.23, p = 0.04). In the recipients, who received smaller daily doses (0.4–2.5 mg) of tacrolimus, TGF-β1 level was higher than in those receiving large doses (3.0–6.0 mg) of the drug: 9.1 (2.6–16.2) ng/ml vs. 4.2 (1.3–9.2) ng/ ml, p = 0.04. Evaluation of diagnostic efficacy of the TGF-β1 level as a test for the detection of tacrolimus dose requirement showed that the area under the ROC curve (AUC) was 0.66 ± 0.07; 95% CI [0.53–0.79], the sensitivity and specificity of the test were 60 and 74% at threshold value 6.7 ng/ml. Relative risk of higher tacrolimus dose requirement was 3.14 ± 0.48; 95% CI [1.24–7.96].Conclusion.TGF-β1 blood level in one month after LT less than 6.7 ng/ml is 3 times higher risk factor of tacrolimus dose requirement more than 3.0 mg per day. The likehood of the test is 66%, the sensitivity and specificity – 60 and 74%.