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

ABSTRACT: 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.

SUBMITTER: Deri M

PROVIDER: S-EPMC8560807 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Tacrolimus, an immunosuppressant used in solid organ transplantation, has a narrow therapeutic index and exhibits inter-individual pharmacokinetic variability. Achieving and maintaining a therapeutic level of the drug by giving appropriate doses is crucial for successful immunosuppression, especially during the initial post-transplant period. We studied the effect of CYP3A5, CYP3A4, and ABCB1 gene polymorphisms on tacrolimus trough concentrations in South Indian renal transplant recipients from Kerala to formulate a genotype-based dosing equation to calculate the required starting daily dose of tacrolimus to be given to each patient to attain optimal initial post-transplant period drug level. We also investigated the effect of these genes on drug-induced adverse effects and rejection episodes and looked into the global distribution of allele frequencies of these polymorphisms. One hundred forty-five renal transplant recipients on a triple immunosuppressive regimen of tacrolimus, mycophenolate mofetil, and steroid were included in this study. Clinical data including tacrolimus daily doses, trough levels (C0) and dose-adjusted tacrolimus trough concentration (C0/D) in blood at three time points (day 6, 6 months, and 1-year post-transplantation), adverse drug effects, rejection episodes, serum creatinine levels, etc., were recorded. The patients were genotyped for CYP3A5*3, CYP3A4*1B, CYP3A4*1G, ABCB1 G2677T, and ABCB1 C3435T polymorphisms by the PCR-RFLP method. We found that CYP3A5*3 polymorphism was the single most strongly associated factor determining the tacrolimus C0/D in blood at all three time points (p < 0.001). Using multiple linear regression, we formulated a simple and easy to compute equation that will help the clinician calculate the starting tacrolimus dose per kg body weight to be administered to a patient to attain optimal initial post-transplant period tacrolimus level. CYP3A5 expressors had an increased chance of rejection than non-expressors (p = 0.028), while non-expressors had an increased risk for new-onset diabetes mellitus after transplantation (NODAT) than expressors (p = 0.018). Genotype-guided initial tacrolimus dosing would help transplant recipients achieve optimal initial post-transplant period tacrolimus levels and thus prevent the adverse effects due to overdose and rejection due to inadequate dose. We observed inter-population differences in allele frequencies of drug metabolizer and transporter genes, emphasizing the importance of formulating population-specific dose prediction models to draw results of clinical relevance.

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

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