Limited sampling strategy for predicting area under the concentration-time curve for mycophenolic Acid in Chinese adults receiving mycophenolate mofetil and tacrolimus early after renal transplantation

A Systematic Review of Multiple Linear Regression-Based Limited Sampling Strategies for Mycophenolic Acid Area Under the Concentration-Time Curve Estimation

Background and Objective

One approach of therapeutic drug monitoring in the case of mycophenolic acid (MPA) is a limited sampling strategy (LSS), which allows the evaluation of the area under the concentration–time curve (AUC) based on few concentrations. The aim of this systematic review was to review the MPA LSSs and define the most frequent time points for MPA determination in patients with different indications for mycophenolate mofetil (MMF) administration.

Methods

The literature was comprehensively searched in July 2021 using PubMed, Scopus, and Medline databases. Original articles determining multiple linear regression (MLR)-based LSSs for MPA and its free form (fMPA) were included. Studies on enteric-coated mycophenolic sodium, previously established LSS, Bayesian estimator, and different than twice a day dosing were excluded. Data were analyzed separately for (1) adult renal transplant recipients, (2) adults with other than renal transplantation indication, and (3) for pediatric patients.

Results

A total of 27, 17, and 11 studies were found for groups 1, 2, and 3, respectively, and 126 MLR-based LSS formulae (n = 120 for MPA, n = 6 for fMPA) were included in the review. Three time-point equations were the most frequent. Four MPA LSSs: 2.8401 + 5.7435 × C0 + 0.2655 × C0.5 + 1.1546 × C1 + 2.8971 × C4 for adult renal transplant recipients, 1.783 + 1.248 × C1 + 0.888 × C2 + 8.027 × C4 for adults after islet transplantation, 0.10 + 11.15 × C0 + 0.42 × C1 + 2.80 × C2 for adults after heart transplantation, and 8.217 + 3.163 × C0 + 0.994 × C1 + 1.334 × C2 + 4.183 × C4 for pediatric renal transplant recipients, plus one fMPA LSS, 34.2 + 1.12 × C1 + 1.29 × C2 + 2.28 × C4 + 3.95 × C6 for adult liver transplant recipients, seemed to be the most promising and should be validated in independent patient groups before introduction into clinical practice. The LSSs for pediatric patients were few and not fully characterized. There were only a few fMPA LSSs although fMPA is a pharmacologically active form of the drug.

Conclusions

The review includes updated MPA LSSs, e.g., for different MPA formulations (suspension, dispersible tablets), generic form, and intravenous administration for adult and pediatric patients, and emphasizes the need of individual therapeutic approaches according to MMF indication. Five MLR-based MPA LSSs might be implemented into clinical practice after evaluation in independent groups of patients. Further studies are required, e.g., to establish fMPA LSS in pediatric patients.

Limited Sampling Strategy for Estimation of Mycophenolic Acid Exposure in Adult Chinese Heart Transplant Recipients

Background: With the increasing use of mycophenolic acid (MPA) formulations in organ transplantation, the need for personalized immunosuppressive therapy has become well recognized based on therapeutic drug monitoring (TDM) for avoidance of drug-related toxicity while maintaining efficacy. Few studies have assessed area under the 12 h concentration-time curve of MPA (MPA-AUC_0–12h) in heart transplant recipients who received mycophenolate mofetil (MMF) dispersible tablets (MMFdt). The aim of the study was to investigate the pharmacokinetics (PK) of MMFdt combined with tacrolimus and further to develop a practical method for estimation of MPA-AUC_0–12h using a limited sampling strategy (LSS).

Methods: A prospective study in a single center was performed in patients who continuously administrated with MMFdt or MMF capsule (MMFc) for at least 7 days after cardiac transplantation from 2018 to 2020. A total of 48 Chinese adult heart transplant recipients were enrolled. Blood samples were collected before and 0.5, 1, 1.5, 2, 4, 6, 8, 10 and 12 h after MMF administration. The validated high-performance liquid chromatography combined with tandem mass spectrometry method was used to measure MPA concentrations. Non-compartmental pharmacokinetic (PK) analysis was applied to calculate the data obtained from individual recipients by WinNonlin. LSS models were developed for MPA-AUC_0–12h prediction with multivariate stepwise regression analysis.

Results: A large inter-individual variability was observed in AUC_0–12h, T_max, C_max, MRT_0–12h, t_1/2 and CL/F after multiple dosing of MMFdt. However, no significant differences were observed between main PK parameters of MMFdt and MMFc. The best estimation of MPA-AUC_0–12h was achieved with four points: MPA-AUC_0–12h = 8.424 + 0.781 × C_0.5 + 1.263 × C₂ + 1.660 × C₄ + 3.022 × C₆ (R² = 0.844). The mean prediction error (MPE) and mean absolute prediction error (MAPE) of MPA-AUC_0–12h were 2.09 ± 14.05% and 11.17 ± 8.52%, respectively. Both internal and external validations showed good applicability for four-point LSS equation.

Conclusion: The results provide strong evidence for the use of LSS model other than a single time-point concentration of MPA when performing TDM. A four-point LSS equation using the concentrations at 0.5, 2, 4, 6 h is recommended to estimate MPA-AUC_0–12h during early period after transplantation in Chinese adult heart transplant recipients receiving MMFdt or MMFc. However, proper internal and external validations with more patients should be conducted in the future.

Limited sampling strategy to predict mycophenolic acid area under the curve in pediatric patients with nephrotic syndrome: a retrospective cohort study

PURPOSE

Limited sampling strategy (LSS) is a precise and relatively convenient therapeutic drug monitoring method. We evaluated LSSs for mycophenolic acid (MPA) in children with nephrotic syndrome treated with mycophenolic mofetil (MMF) and validated the LSSs using two different approaches.

METHODS

We measured MPA plasma concentrations in 31 children using HPLC-UV method and received 37 MPA pharmacokinetic profiles (0-12 h). For six children, MPA profiles were estimated twice after two MMF doses. LSSs were developed using multilinear regression with STATISTICA and R software and validated using validation group and bootstrap method, respectively.

RESULTS

The best three time point equations included C₁, C₃, C₆ (good guess 83%, bias - 2.78%; 95% confidence interval (CI) - 9.85-0.46); C₁, C₂, C₆ (good guess 72%, bias 0.72%; 95% CI - 5.33-7.69); and C₁, C₂, C₄ (good guess 72%, bias 2.05%; 95% CI - 4.92-13.01) for STATISTICA software. For R software, the best equations consisted of C₁, C₃, C₆ (good guess 92%, bias - 2.69%; 95% CI - 27.18-33.75); C₀, C₁, C₃ (good guess 84%, bias - 2.11%; 95% CI - 24.19-22.29); and C₀, C₁, C₂ (good guess 84%, bias - 0.48%; 95% CI - 30.77-54.07). During validation, better results were obtained for R evaluations, i.e., bootstrap method.

CONCLUSIONS

The most useful equations included C₀, C₁, C₃ and C₀, C₁, C₂ time points; however, the most precise included C₁, C₃, C₆ time points because of MPA enterohepatic recirculation. Better results were obtained for bootstrap validation due to greater number of patients. Validated LSS should be used only in the population for which it was developed. As there is growing evidence that underexposure of MPA is associated with insufficient treatment response, we recommend the introduction of therapeutic drug monitoring for MPA in children with nephrotic syndrome.

Early pharmacokinetics of low dosage mycophenolate exposure in Thai kidney transplant recipients

Background The effects of mycophenolic acid exposure in the early period after transplantation on clinical outcomes have been reported; however, mycophenolic acid exposure in the early period after transplantation in Asian kidney transplant recipients who receive 1.5 g/d mycophenolate mofetil has never been investigated. Objective To determine mycophenolic acid exposure on day 3 post-transplantation in kidney transplant recipiens who receive 1.5 g/d mycophenolate mofetil. The effects of the reduced renal function on mycophenolic acid area under the concentration-time curve (AUC) and the achievement of the target AUC on the incidence of biopsy proven acute rejection during the first month post-transplantation were also evaluated. Setting A university hospital Method Blood samples and 24-h urine were collected on day 3 post-transplantation. Main outcome measures The mycophenolic acid AUC was calculated by linear trapezoidal rule and compared with the target of 45 mg*h/L. Results Of 42 Thai kidney transplant recipiens, the mean mycophenolic acid AUC of 45.1 mg*h/L (SD 14.7) was comparable to the AUC target (P = 0.962). Significant differences of the mycophenolic acid AUC were observed between patients with urine output of < 2400 mL and those with urine output ≥ 2400 mL (35.3 ± 6.6 and 47.4 ± 15.2, respectively; P = 0.002), and between patients with 24-h measured CrCl < 25 mL/min and those with CrCl ≥ 25 mL/min (38.0 (29.0, 42.2) and 49.2 ± 14.0, respectively; P = 0.017). Proportions of overall biopsy proven acute rejection among patients with mycophenolic acid AUC of < 45 and ≥ 45 mg*h/L were comparable (20.0% and 23.5%, respectively; P = 1.000). Conclusions After the starting dosage of 1.5 g/d mycophenolate mofetil, the mean mycophenolic acid AUC on day 3 post-kidney transplantation is comparable with the target of 45 mg*h/L. Severely reduced renal function significantly influences mycophenolic acid exposure.

Pharmacokinetics of Mycophenolate Mofetil and Development of Limited Sampling Strategy in Early Kidney Transplant Recipients

The mycophenolate mofetil (MMF) dose management for optimization of post-transplant treatment especially the early postoperative phase has been well recognized. MMF is a pro-drug of mycophenolic acid (MPA) and is widely used in Chinese renal transplant patients. Until now, the pharmacokinetic (PK) characteristics and model for the area under the concentration–time curve for the 12-h (h) of exposure (AUC_0-12h) of MPA (MPA-AUC_0-12h) estimation were lacking for the new formulation of MMF dispersible tablet in renal transplant patients. The aims of the study were to investigate the PK characteristics of MMF dispersible tablet by detecting the active metabolite of MPA and to establish an accuracy and precision equation for calculating MPA-AUC_0-12h by limited sampling strategy (LSS) in Chinese kidney transplant patients. A total of 60 postoperative kidney transplant recipients were given a multiple-dose of MMF dispersible tablet twice daily combination with tacrolimus (Tac) and steroids. On the 5th day post-transplantation, blood specimens were collected before drug administration and up to 12 h after MMF dispersible tablet administration. Non-compartmental PK analysis was used to determine the data obtained from individual patients. Multivariate stepwise regression analysis was used to develop models for predicting MPA-AUC_0-12h. The 3- and 4-point sampling models using 2 h, 4 h, 8 h and 1 h, 2 h, 4 h and 8 h, respectively, allowed accurate estimation of MPA-AUC_0-12h. PK parameters of MMF dispersible tablet were obtained and the 4-point LSS is the best model for accurate and precise estimation of MPA-AUC_0-12h.

Limited Sampling Strategy for Estimating Mycophenolic Acid Exposure on Day 7 Post-Transplant for Two Mycophenolate Mofetil Formulations Derived From 20 Chinese Renal Transplant Recipients

PURPOSE

To assess the pharmacokinetic properties of mycophenolate mofetil (MMF) dispersible tablets and capsules by the enzyme multiplied immunoassay technique (EMIT) in Chinese kidney transplant recipients in the early post-transplantation phase and to develop the equations to predict mycophenolic acid (MPA) area under the 12-hour concentration-time curve (AUC_0-12h) using a limited sampling strategy (LSS).

METHODS

Forty patients who underwent renal transplantation from brain-dead donors were randomly divided into dispersible tablets (Sai KE Ping; Hangzhou Zhongmei Huadong Pharma) and capsules (Cellcept; Roche Pharma, Why, NSW, Australia) groups, and treated with MMF combined with combination tacrolimus and prednisone as a basic immunosuppressive regimen. Blood samples were collected before treatment (0) and at 0.5,1, 1.5, 2, 4, 6, 8, 10, and 12 hours post-treatment and 7 days after renal transplantation. Plasma MPA concentrations were measured using EMIT. LSS equations were identified using multiple stepwise linear regression analysis.

RESULTS

The peak concentration (C_max) in the MMF dispersible tablets (MMFdt) group (7.0 ± 2.8) mg/L was reduced compared with that in the MMF capsules (MMFc) group (10.8 ± 6.2 mg/L; P = .012); time to peak concentration in the MMFdt group was 3.2 ± 2.3 hours, which was nonsignificantly elevated compared with that of the MMFc group (2.2 ± 1.7 hours). Three-point estimation formulas were generated by multiple linear regression for both groups: MPA-AUC_MMFdt = 3.542 + 3.332C_0.5h + 1.117C_1.5h + 3.946C_4h (adjusted r² = 0.90, P < .001); MPA-AUC_MMFc = 8.149 + 1.442C_2h + 1.056C_4h + 7.133C_6h (adjusted r² = 0.88, P < .001). Both predicted and measured AUCs showed good consistency.

CONCLUSIONS

After treatment with MMF dispersible tables or MMF capsules, the C_max of MPA for the MMFdt group was significantly lower than that of the MMFc group; there was no significant difference in other pharmacokinetic parameters. Three-time point equations can be used as a predictable measure of the AUC_0-12h of MPA.

Population pharmacokinetics and Bayesian estimation of mycophenolic acid concentrations in Chinese adult renal transplant recipients

Mycophenolate mofetil (MMF) is an important immunosuppressant used in renal transplantation, and mycophenolic acid (MPA) is the active component released from the ester prodrug MMF. The objective of this study was to investigate the population pharmacokinetics of mycophenolic acid (MPA) following oral administration of MMF in Chinese adult renal transplant recipients and to identify factors that explain MPA pharmacokinetic variability. Pharmacokinetic data for MPA and covariate information were retrospectively collected from 118 patients (79 patients were assigned to the group for building the population pharmacokinetic model, while 39 patients were assigned to the validation group). Population pharmacokinetic data analysis was performed using the NONMEM software. The pharmacokinetics of MPA was best described by a two-compartment model with a first-order absorption rate with no lag time. Body weight and serum creatinine level were positively correlated with apparent clearance (CL/F). The polymorphism in uridine diphosphate glucuronosyltransferase gene, UGT2B7, significantly explained the interindividual variability in the initial volume of distribution (V₁/F). The estimated population parameters (and interindividual variability) were CL/F 18.3 L/h (34.2%) and V₁/F 27.9 L (21.3%). The interoccasion variability was 13.7%. These population pharmacokinetic data have significant clinical value for the individualization of MMF therapy in Chinese adult renal transplant patients.

Limited sampling strategy for the estimation of mycophenolic acid area under the curve in Tunisian renal transplant patients

Mycophenolate mofetil is a prodrug widely used in renal transplantation to prevent organ rejection. It is hydrolyzed to its active compound mycophenolic acid (MPA). MPA area under the curve (AUC_0-12h) is considered the best pharmacokinetic parameter for the estimation of MPA exposition and for prediction of rejection. MPA-AUC requires several blood samples, making it impractical for clinical practice. Therefore, development of a limited sampling strategy (LSS) to estimate MPA AUC_0-12h using three blood samples is very helpful for MPA individual dose adjustment. Results of LSS differ according to the patient background and to the drug formulation. Therefore, the purpose of this study was to develop a LSS for the estimation of MPA AUC_0-12h in Tunisian renal transplant patients treated with the generic formulation of mycophenolate mofetil (MMF^®, MEDIS). The best correlation was achieved by a profile based on three time points C_0.5h, C_1.5h, and C_4h after drug intake: AUC_0-12h = 0.414 + 1.210 × C_0.5 + 2.256 × C_1.5 + 4.134 × C₄ (mei = 1.65% and rmse = 5.81%). The correlation between full AUC_0-12h and abbreviated AUC_0-12h was 0.917. In conclusion, this model provides a reliable and simple equation to estimate MPA AUC_0-12h for the generic formulation of mycophenolate mofetil (MMF^®).