Impact of genetic polymorphisms on tacrolimus trough blood concentration in Chinese liver transplant recipients

Synergistic Effect of Cytochrome P450 Family 3 Subfamily A Member 5 (CYP3A5) Genetic Variants in Tacrolimus Dose Determination in Indian Renal Transplant Patients

Tacrolimus (TAC) has a narrow therapeutic index and shows interindividual variabilities in its blood concentration. Although guidelines recommend a genetic variant (rs776746) to determine the optimized TAC dose, discrepancies in accuracy have been noted. Therefore, studying other variants of CYP3A5 may improve the accuracy of the TAC dose. Clinical exome sequencing (CES) was performed in 219 renal transplant patients. The SNPs of CYP3A5 covered by CES were recorded. The TAC blood trough concentration/dose (C 0/D) was calculated on day 7 and months 1, 3, 6, and 12 of post-transplantation, and association with CYP3A5 genotypes was studied. Further, biopsy-proven rejection and pathological events were analyzed for their association with CYP3A5 genotypes. Out of 35 variants of CYP3A5 covered in CES, rs776746, rs15524, rs4646449, and rs464645 were significantly associated with the TAC C 0/D on day 7 and months 1, 3, and 6. Further analysis showed that the slow-metabolizing genotypes of all four SNPs synergistically associated with the TAC C 0/D on day 7 and months 1, 3, 6, and 12. The "CC" genotype of rs776746 showed a significant association (RR = 1.613; p = 0.035) with allograft rejection. In addition, cox regression analysis showed that the presence of the "CA" genotype of rs4646453 increased (HR = 7.258; 95% CI = 1.354-38.904) the risk of development of pathological events, respectively. Four variants of CYP3A5 were synergistically associated with the TAC dose determination. In addition, rs776746 and rs4646453 may be associated with allograft rejection and pathological events, respectively.

Genotype-Guided Model for Prediction of Tacrolimus Initial Dosing After Lung Transplantation

The determination of the appropriate initial dose for tacrolimus is crucial in achieving the target concentration promptly and avoiding adverse effects and poor prognosis. However, the trial-and-error approach is still common practice. This study aimed to establish a prediction model for an initial dosing algorithm of tacrolimus in patients receiving a lung transplant. A total of 210 lung transplant recipients were enrolled, and 26 single nucleotide polymorphisms (SNP) from 18 genes that could potentially affect tacrolimus pharmacokinetics were genotyped. Associations between SNPs and tacrolimus concentration/dose ratio were analyzed. SNPs that remained significant in pharmacogenomic analysis were further combined with clinical factors to construct a prediction model for tacrolimus initial dose. The dose needed to reach steady state tacrolimus concentrations and achieve the target range was used to validate model prediction efficiency. Our final model consisted of 7 predictors-CYP3A5 rs776746, SLCO1B3 rs4149117, SLC2A2 rs1499821, NFATc4 rs1955915, alanine aminotransferase, direct bilirubin, and hematocrit-and explained 41.4% variance in the tacrolimus concentration/dose ratio. It achieved an area under the receiver operating characteristic curve of 0.804 (95% confidence interval, 0.746-0.861). The Hosmer-Lemeshow test yielded a nonsignificant P value of .790, suggesting good fit of the model. The predicted dose exhibited good correlation with the observed dose in the early postoperative period (r = 0.748, P less than .001). Our study provided a genotype-guided prediction model for tacrolimus initial dose, which may help to guide individualized dosing of tacrolimus in the lung transplant population in clinical practice.

Pharmacokinetic interactions between tacrolimus and Wuzhi capsule in liver transplant recipients: Genetic polymorphisms affect the drug interaction

Wuzhi capsule (WZC), a commonly used Chinese patent medicine to treat various types of liver dysfunction in China, increases the exposure of tacrolimus (TAC) in liver transplant recipients. However, this interaction has inter-individual variability, and the underlying mechanism remains unclear. Current research indicates that CYP3A4/5 and drug transporters influence the disposal of both drugs. This study aims to evaluate the association between TAC dose-adjusted trough concentration (C/D) and specific genetic polymorphisms of CYP3A4/5, drug transporters and pregnane x receptor (PXR), and plasma levels of major WZC components, deoxyschisandrin and γ-schisandrin, in liver transplant patients receiving both TAC and WZC. Liquid chromatography-tandem-mass spectrometry was used to detect the plasma levels of deoxyschisandrin and γ-schisandrin, and nine polymorphisms related to metabolic enzymes, transporters and PXR were genotyped by sequencing. A linear mixed model was utilized to assess the impact of the interaction between genetic variations and WZC components on TAC lnC/D. Our results indicate a significant association of TAC lnC/D with the plasma levels of deoxyschisandrin and γ-schisandrin. Univariate analysis demonstrated three polymorphisms in the genes ABCB1 (rs2032582), ABCC2 (rs2273697), ABCC2 (rs3740066), and PXR (rs3842689) interact with both deoxyschisandrin and γ-schisandrin, influencing the TAC lnC/D. In multiple regression model analysis, the interactions between deoxyschisandrin and both ABCB1 (rs2032582) and ABCC2 (rs3740066), post-operative day (β < 0.001, p < 0.001), proton pump inhibitor use (β = -0.152, p = 0.008), body mass index (β = 0.057, p < 0.001), and ABCC2 (rs717620, β = -0.563, p = 0.041), were identified as significant factors of TAC lnC/D, accounting for 47.89% of the inter-individual variation. In summary, this study elucidates the influence of the interaction between ABCB1 and ABCC2 polymorphisms with WZC on TAC lnC/D. These findings offer a scientific basis for their clinical interaction, potentially aiding in the individualized management of TAC therapy in liver transplant patients.