Studying the association between single nucleotide polymorphisms of metabolizing enzymes and the therapeutic serum levels of calcineurin inhibitors in Egyptian liver transplant patients
Authors: Abuelsoud Nermeen N. , Bahaa Mohamed , Osman Sara A. , Younis Nouran , Kamal Mohamed M. 
Published: November 2024

Abstract
Background
Many clinical variables might impact the pharmacokinetics of calcineurin inhibitors (CIs). Different alleles of cytochromes P450 (CYP)3A4/5 and drug transporter P-glycoprotein are the main variables. Other variables include relocated type, treatment duration after transplantation, age, sex, dietary consumption, medications used and renal or hepatic impairment. Tacrolimus and cyclosporine are two main CIs extensively used in organ transplantation. Both drugs are metabolized by CYP3A4 and CYP3A5 isoforms, and single-nucleotide polymorphisms in these genes have been displayed to influence CIs pharmacokinetics. Another important gene is the pregnane X receptor (PXR), which manages the statement of a variety of genes including CYP3A4 genes. PXR has a clinical significance in CIs metabolism. The liver is the essential site for CIs metabolism. A decreased clearance with a prolonged CIs half-life was occurred in patients with impaired liver compared with patients with normal liver function. The presence of different genetic and clinical factors that may affect calcineurin inhibitors trough levels will consequently affect their immunosuppressant effect after liver transplantation.

Purpose
This study aims to determine the effect of different genetic polymorphisms in CYP3A4 1B rs2740574 and PXR A7635G rs6785049 and other clinical factors that may affect calcineurin inhibitors pharmacokinetics after liver transplantation.

Results
The presence of T allele in CYP3A4 gene was associated with elevated DATLs with P values of 0.00, 0.00, 0.007 and 0.00 after tacrolimus doses 4, 30, 60 and 90, respectively. Regarding PXR gene, the presence of G allele was associated with elevated DATLs in cyclosporine. About 432 correlations were tested in both drugs. In CYP3A4 genotype CC, male sex was associated with elevated DATLs interpreted by strong positive correlations and statistically significant difference in all DATLs, except DATL 60 (P value 0.374). No strong association was found between low hemoglobin levels and DATLs in almost all the follow-up periods. There were many positive relations between increased total and direct bilirubin and increased DATLs.

Conclusions
Studying the various genetics and clinical factors that may affect calcineurin inhibitors serum concentrations is very essential for successful treatment plans after organ transplantation. These different factors may interact with each other and these complicated interactions may complicate the patient’s conditions post-transplantation. Considering all these complicated interactions is very crucial in monitoring treatment plans, especially in the presence of other comorbidities or chronic diseases. More studies with large number of patients should be conducted to explore more consequences of these interacting variables of treatment plans of these patients and all studied parameters in this study should be considered while monitoring patients after transplantation.