Population Pharmacokinetic Model Analysis And Application For Tacrolimus Coadministered With Wuzhi Capsule In Chinese Renal Transplant Recipients

Background and purpose:Tacrolimus（TAC）,a macrolide calcium phosphatase inhibitor with potent immunosuppressive properties,has become a first-line agent for the prevention of postoperative rejection in solid organ transplant recipients（KTRs）such as kidney,liver and heart.However,it has a narrow therapeutic window and high individual variability in pharmacokinetics（PK）and pharmacogenomics（PG）,so it is necessary to monitor the steady-state trough concentration of TAC.Pharmacology and PG studies have shown that the metabolism of TAC is influenced by genetic factors,which may lead to different metabolic rates in different populations.TAC is mainly metabolized by the cytochrome P450 enzymes（CYP3A4 and CYP3A5）in vivo,and it is also the substrate of multidrug resistance efflux transporter P-glycoprotein（MDR1,encoded by ABCB1 gene）.Pregnane X receptor（PXR）is encoded by NR1I2,which is responsible for the upstream regulation of drug-metabolizing enzymes and transporters,including the CYP3A4/3A5 and MDR1.Wuzhi capsule（WZC）is widely used as a TAC“sparing agent”in patients receiving solid organ transplantation and it can increase the blood concentration of TAC and thus can reduce the dosage of TAC.The active ingredients of WZC include Schisandrin A,Schisandrin B,Schisandrin,and Schisandrol B,etc.,all of which can significantly inhibit the activity of P-gp/CYP3A enzyme system.And WZC can inhibit the metabolism of TAC when combined with TAC,which can reduce the economic burden of SOT recipients.Currently,WZC is widely used as a TAC"booster"in SOT patients.However,there is no consensus or guidance on the combination regimen of these two drugs.Therefore,this study filled this gap by analyzing the population pharmacokinetic model of tacrolimus combined with WZC in renal transplant recipients.Objectives of this research:1、To investigate the synergistic effect of WZC on TAC and the effect of CYP3A5,CYP3A4,POR,ABCB1,IL-10,IL-3,IL-18,IL-4R,CYP3A7 and PXR gene polymorphism on the blood concentration of TAC in kidney transplantation patients.2、A PPK model was constructed by nonlinear mixed effect model（NONMEM?,Version 7.3）.Finally,Monte Carlo simulations were employed to design initial dosing regimens based on the final model,which provided reference for the clinical application of TAC and guided the individual dosing.Methods:1、The medical records of 211 adult kidney transplant patients and their 824TAC steady-state blood trough concentrations were reviewed.According to the patients’immunosuppressant regimen,kidney transplant patients were divided into two cohorts retrospectively,TAC+WZC cohort（107 cases）,and TAC cohort（104cases）.MASSARRAY assay helped us test the genotypes of 23 single-nucleotide polymorphisms（SNPs）,and analyzed the association between different cohorts of TAC C0/D value between CYP3A5,CYP3A4,POR,ABCB1,IL-10,IL-3,IL-18,IL-4R,CYP3A7 and PXR gene polymorphisms and renal transplant patients at 7d,14d and 20d after surgery.2、The study collected the basic information data contained 1648 steady-state trough concentrations of TAC,demographic characteristics（including gender,weight,age,postoperative transplant time,height）,blood routine,liver and kidney laboratory test items（including red blood cells,hemoglobin,hematocrit,total protein,albumin,alanine aminotransferase,aspartate aminotransferase,γ-glutamyltransferase,total bilirubin,direct bilirubin,creatinine,uric acid,urea nitrogen）and drug combination（including pentaester capsules,prednisone,fensi,methylprednisolone,omeprazole,caspofungin）within 40 days after transplantation from 310 renal transplant patients.The non-linear mixed-effects modelling software NONMEM was used to develop a PPK model of TAC and to analyse the effects of covariates such as body weight,sex,laboratory index tests,combination therapy and CYP3A5,CYP3A4 and PXR gene polymorphisms on the pharmacokinetic parameters of TAC.The internal validation of the final model was conducted by Bootstrap method,goodness-of-fit plots（GOF）and prediction-and variability-corrected visual predictive check(_PVCVPC).Additionally,another 407 trough concentration data from another 70 patients were collected for external validation to evaluate the accuracy and precision of the final model by mean prediction error（MPE）,and root-mean-square error（RMSE）.Finally,Monte Carlo simulation was used to determine the initial dosing regimen based on the final model.Result:1、In 23 SNPs,only 10 SNPs（CYP3A5 rs776746,CYP3A4 rs2242480 and rs4646437,POR rs1057868,PXR rs2276707,rs227707 and rs6785049,CYP3A7rs2257401,rs10211 and rs12360）were significantly associated with TAC C0/D.There was no significant correlation between ABCB1,IL-10,IL-3,IL-18 and IL-4R genotypes and TAC C0/D values at each study time point.2、The TAC C0/D value of TAC+WZC group was significantly higher than that of TAC group at 7d,14d,20d,and the difference was statistically significant（P=0.002,P=0.021,P=0.031）.3、In this study,it was found that TAC C0/D values of patients with different CYP3A5 and CYP3A4 genotypes were also significantly different at different study time points,whether in TAC group or TAC+WZC group.CYP3A5*3/*3 patients had higher C0/D values than CYP3A5*1/*3 and CYP3A5*1/*1 patients,that is,CYP3A5*1/*3 and CYP3A5*1/*1 renal transplant patients require higher TAC dosage to achieve the target concentration.The effect of different genotypes of POR rs1057868 on TAC C0/D of the two groups was not statistically significant（P>0.05）.4、A total of 310 patients with kidney transplantation（205 males and 105females）were included in the model building group,with 1476 TAC trough concentration points.The body weight and the age of these 310 patients were 57.55（10.76）（range 38–86）kg and 40（10.03）（range 18–70）years old,respectively.The one-compartmental PPK model with first-order absorption and elimination of TAC was established in China adults kidney transplant recipients.The final model showed that the hematocrit（HCT）,WZC,and CYP3A5 rs776746-CYP3A4 rs4646437polyploid were the main factors affecting TAC clearance.The model was expressed as CL/F=21×（HCT/0.3）^-0.693×0.827（combination with WZC）×1.2（CYP3A5rs776746-CYP3A4 rs4646437 non-CCGG）.The internal evaluation of GOF plots,Bootstrap method,pvc VPC and the external validation results indicated that the model has a high degree of stability and validity.Conclusions:1、CYP3A5（rs776746）,CYP3A4（rs2242480,rs4646437）and PXR（rs2276707）gene polymorphisms were significantly correlated with TAC C0/D.2、The combination of WZC and TAC significantly increased the C0/D value of TAC in renal transplant patients（P<0.05）.3、This was the first study that thoroughly evaluated the impact of WZC co-administration as well as variable SNPs by PPK analysis in renal transplant patients.In three centers,the effects of CYP3A5 rs776746-CYP3A4 rs4646437polyploid,WZC and HCT on the pharmacokinetics of TAC were quantitatively evaluated for the first time.The stability and effectiveness of the model was determined by both internal evaluation and external validation,which can provide clinicians with reasonable recommendations for individual dosing of TAC.