Mycophenolic acid concentration on renal transplant recipients in Viet Duc hospital

T¹p chÝ y - d−îc häc qu©n sù sè 8-2020 135 MYCOPHENOLIC ACID CONCENTRATION ON RENAL TRANSPLANT RECIPIENTS IN VIET DUC HOSPITAL Do Thi Mai Dung1,2, Ha Phan Hai An3, Le Van Dong4 SUMMARY Objectives: To determine the mycophenolic acid (MPA) concentration on renal transplant recipients at Viet Duc Hospital. Subjects and methods: This observational study conducted on 35 adult kidney recipients to evaluate the MPA concentration at 5 sampling time points (predose, 1, 2, 3 and 6 hours) on day 3, day 10 and 6 months after transplantation. Results: Plasma MPA trough levels (C0) were 2.32 ± 1.47; 1.58 ± 1.39; 2.29 ± 1.4 mg/L and the MPA AUC0-12h values were 50.1 ± 20.4; 41.9 ± 14.5; 60.3 ± 25.9 mg.h/L on day 3, day 10 and 6th month. The number of patients who reached MPA AUC0-12h values of 30 - 60 mg.h/L was 18 (51.4%), 23 (65.7%) and 17 (51.5%) on day 3, day 10 and 6th month, respectively. The number of patients who achieved the MPA C0 values of 1.5 - 2.5 mg/L was 15 (42.9%), 14 (40%) and 10 (30.3%) on day 3, day 10 and 6th month, respectively; and the linear correlation coefficients between AUC0-12h and C0 were 0.652; 0.415, and 0.752, respectively. Conclusions: In renal transplant patients, the MPA AUC0-12h was lower on day 3 and day 10 than 6 months post- transplantation for the half dose of MMF or MPS. MPA therapeutic drug level monitoring should be done usually in transplantation patients used MPA. * Keywords: Mycophenolic acid; Renal transplant recipients. INTRODUCTION Mycophenolate mofeltil (MMF) or mycophenolate sodium (MPS), an ester prodrug of MPA, is an immunosuppressant suggested to be used together with a calcineurin inhibitor and corticosteroid for the renal allograft rejection prevention. MPA transformed into an inactive phenolic glucuronide (MPAG) that either underwent enterohepatic cycling or was eliminated in the urine [1]. The concentration of MPA in adult kidney transplant recipients in the area under the curve (AUC) is about 10 fold higher than the given dose [2]. The risk of acute rejection could be predicted based on MPA AUC values [3]. A large central study that determined the relationship between the MPA AUC and rejection biopsy evidence had shown that the rejection rates had a decreased trend with mean AUC values between 30 - 60 mg.h/L [4]. About 97 - 98% of MPA in the body is in protein binding form although the small part in free form is pharmacologically active [5]. 1Department of Immunology, Vietnam Military Medical University 2Department of Biochemistry, Viet Duc Hospital 3Department of Kidney Diseases and Dialysis, Viet Duc Hospital 4Center for Training, Research Toxicology and Radioactivity, Vietnam Military Medical University Corresponding author: Do Thi Mai Dung (domaidung70@yahoo.com) Date received: 15/10/2020 Date accepted: 23/10/2020 T¹p chÝ y - d−îc häc qu©n sù sè 8-2020 136 There are many highly specific methods to quantify the MPA concentration for TDM such as enzyme immunoassay, high-performance liquid chromatography (HPLC). In this study, the enzyme immunoassay method was used to determine the MPA level with the previously reported satisfactory analytical performance. This study aims: To determine the MPA concentration on Vietnamese renal transplant recipients. SUBJECTS AND METHODS 1. Subjects 35 adult kidney recipients were performed in transplantation ward, Viet Duc Hospital. 2. Methods * Study protocol: A cross-sectional study. Patients of a consecutive series were included on day 3, day 10 and 6 months after kidney transplantation. All patients received MPA (1 gram twice a day, ranged from 0.5 - 1 gram twice a day at month 6 by Cellcept or Myfortic) as a part of the immunosuppression protocol. * Blood sampling and drug assays: Blood samples were collected into tubes containing EDTA before the patients received MPA (time 0 min) and at 1, 2, 3, 6 hours after receiving 1 gram MPA per day orally. The plasma was collected from centrifuged blood, then stored at -22oC until analyzed. The MPA level were analyzed in Inkido chemical system by the CEDIATM mycophenolic acid immunoassay kit (Lot 100276, Thermo Fisher). The assay is based on the activity of enzyme β-galactosidase. This enzym catalyzed to cleave a MPA to generate a color change that can be measured spectrophotometrically. The MPA level was calculated based on the calibrator (Lot 100277). The least detectable dose is 0.2 µg/mL. The MPA AUC were calculated by the linear trapezoidal rule at 5 sampling time points (predose, 1, 2, 3 and 6 hours). * Statistical analysis: The MPA AUC0-12h were calculated by using the linear trapezoidal rule plasma concentration drawn 12h after drug administration. Categorical data are expressed as a percentage. Continuous variables are presented as mean ± standard deviation (SD). Statistical significance was defined by p < 0.05. Statistical analyses were performed with SPSS 16.0 software. RESULTS 1. General characteristics Table 1: Characteristics of subjects population. Characteristics Range Number of patients (male/female) 35 (22/13) Age (years) 38.17 ± 12 Body weight (kg) 54.5 ± 10 T¹p chÝ y - d−îc häc qu©n sù sè 8-2020 137 Donor type (living/cadaveric) 29/6 Using of CNI (Tac/CsA) 31/4 Using of MMF (Cellcept/ Myfortic) 24/11 (CNI: Calcineurin inhibitor; Tac: Tacrolimus; CsA: Cyclosporine) 35 kidney transplant recipients (22 males and 13 females) were included on day 3, day 10 and 6th month after transplantation. Immunosuppressive therapy used for these patients were combination of cyclosporin (CsA) (4 patients) or tacrolimus (31 patients), with prednisolone and MPA. Patients started with the 1 gram twice a day MMF dose or 720 mg twice a day MPS, the real MMF doses ranged from 0.5 - 1 gram twice a day or MPS doses ranged from 360 - 720 mg twice a day on 6 months. At that time, one patient was changed drug and a patient refused to participate into the study. 2. The MPA AUC0-12 of kidney transplant recipients Plasma MPA through levels ranged from 0.1 - 8.8 mg/L, and the estimated MPA AUC0-12h values were from 10.73 - 129.05 mg.h/L. Table 2: Comparison of concentrated concentration on parameter values for MPA on day 3, day 10 and 6 months post-transplantation. Concentrate 3 days 10 days 6 months C0 (mg/L) 2.32 ± 1.47 1.58 ± 1.39 2.29 ± 1.4 AUC0-12h (mg.h/L) 50.1 ± 20.4 41.9 ± 14.5 60.3 ± 25.9 The MPA and MPA AUC levels were lower in the first few days than 6 months after kidney transplantation (significantly, p < 0.01). Table 3: MPA concentration on day 3 (top), day 10 (middle) and 6 month (bottom) after transplantation. AUC0-12 (mg.h/L) 60 Total C0 (mg/L) n % n % n % n % < 1.5 5 14.3 4 11.4 1 2.9 10 28.6 1.5 - 2.5 0 0.0 11 31.4 4 11.4 15 42.9 > 2.5 0 0.0 3 8.6 7 20.0 10 28.6 Total 5 14.3 18 51.4 12 34.3 35 100.0 p-values 0.000 T¹p chÝ y - d−îc häc qu©n sù sè 8-2020 138 AUC0-12 (mg.h/L) 60 Total C0 (mg/L) n % n % n % n % < 1.5 7 20.0 12 34.3 1 2.9 20 57.1 1.5 - 2.5 2 5.7 10 28.6 2 5.7 14 40.0 > 2.5 0 0.0 1 2.9 0 0.0 1 2.9 Total 9 25.7 23 65.7 3 8.6 35 100.0 p-values 0.574 AUC0-12 (mg.h/L) 60 Total C0 mg/L n % n % n % n % < 1.5 2 6.1 7 21.2 2 6.1 11 33.3 1.5 - 2.5 0 0.0 7 21.2 3 9.1 10 30.3 > 2.5 0 0.0 3 9.1 9 27.3 12 36.4 Total 2 6.1 17 51.5 14 42.4 33 100.0 p-values 0.021 The MPA AUC values were 30 - 60 mg.h/L in 18 patients (51.4%), 23 patients (65.7%), 17 patients (51.5%) at 3 days, 10 days and 6 months. The MPA C0 values were 1.5 - 2.5 mg/L in 15 patients (42.9%), 14 patients (40%), 10 patients (30.3%) on day 3, day 10 and 6th month. Table 4: The time having maximum concentration on 3rd day, 10th day and 6th month. 3 days 10 days 6 months Peak n % n % n % C1 12 34.3 11 31.4 19 57.6 C2 13 37.1 14 40.0 7 21.2 C3 8 22.9 8 22.9 8 24.2 C6 2 5.7 2 5.7 0 0.0 Total 35 100.0 35 100.0 33 100.0 The pharmacokinetics parameters of MPA of patients showed that the Cmax varied from time 1 to time 6, only 2 cases at 6 hours and others was 1, 2, or 3 hours and 8 patients were not changed on day 3rd, 10th day and 6th month. T¹p chÝ y - d−îc häc qu©n sù sè 8-2020 139 (a) (b) (c) Figure 1: Correlation between MPA AUC and C0 on 3rd day, 10th day and 6th month. The linear correlation coefficients were 0.652, 0.415, and 0.752, respectively. DISCUSSION In our study, the immunosuppression therapy was the combination of MMF (table 1), an oral prednisolon and calcineurin inhibitor (cCyclosporine or tacrolimus). The MMF is proven to be an effective drug in immunosuppression therapy to prevent early acute rejection. These studies had shown the outstanding results of MMF (with 2 gram per day) compared to azathioprine regarding better acute rejection risks and safety when combined with calcineurin inhibitor [6]. Although 2 gram per day has been suggested as the optimal dose, side effects has been recorded such as hematologic disorders, gastrointestinal especially with patients taking Cellcept. If these side effects progressed severily, the MPA dose would have to be reduced which means the risk of rejection increased. A new method for these was a change from Cellcept to enteric-coated mycophenolate sodium (Myfortic). With this new version of MPA drug, the drug tolerance was better and the dose could also be increased higher. Many researches which used the combination of calcineurin inhibitor and MPA had shown that the pharmacokinetics of MPA was related to acute rejection risk and side effects when the daily dose was fixed with 2 grams. The lower MPA- AUC0-12h was, the higher risk of rejection was. Patients experienced MMF-related side effects often had the reduction dose which meant they would have low AUC and high risk of rejection [5]. Patients with low MPA-AUC had a high risk of acute rejection than those with high MPA-AUC and the AUC had a higher value in prediction than C0 [7]. The Randomized Concentration Controlled Study on MMF had proven the concern between the MPA-C0, MPA-AUC and the incidence of acute rejection but with side effects in both technical and clinical aspects [5]. Several studies suggested an appropriate MPA AUC in renal transplant recipients T¹p chÝ y - d−îc häc qu©n sù sè 8-2020 140 for decreasing the risk of acute rejection was in the range of 30 to 60 mg.h/L [8]. The AUC on 3rd day, 10th day and 6th month in 18 patients (51.4%), 23 patients (65.7%), 17 patients (51.5%) were within the therapeutic range 30 - 60 mg.h/L (table 3). The numbers of patients had the optimal AUC were different because of different timelines after transplantation and lower dose at 6th month. Several studies in kidney transplant recipients have demonstrated that in the first few weeks after transplant, the mean total MPA AUC was 30 - 50% lower than at 2 to 6 months after transplant [8]. In our study, the median MPA AUC increased from 50.1 mg.h/L and 41.9 mg.h/L at day 3 and day 10 to 60.3 mg.h/L at 6th month after transplantation. The MPA AUC in the early was lower than in the later periods after transplantation because of drug interaction between MMF and cyclosporine. Otherwise, the poor gastrointestinal affected MMF absorption. Otherwise, MPA metabolism was increased because the high dose of glucocorticoid which was used together with MPA might reduce the UDP-GT activity [9]. The concentration of MPA AUC correlated with the MPA C0 (figure 1). The C0 after 3 days, 10 days, 6 months of transplantation in 15 patients (42.9%), 14 patients (40%), 10 patients (30.3%), respectively were within the therapeutic range (table 3). These results were similar to a retrospective study in 48 renal post-transplantation patients, MPA level in patients with rejection was significantly lower than those without rejection (1.55 ± 0.48 vs 2.11 ± 0.62 mg/L) [10]. Although MPA AUC from 0 to 12 hours is the best predictor of acute graft rejection, the ability to collect many sampling time points for MPA AUC determination is infeasible in clinical practice. Our study MPA AUC value-based by 5 blood samples, there was a peak (Cmax) and 2 hours had the highest concentration with 37.1%; 40% (3 days, 10 days) and 57.6% (6 months) (table 4). In Thai kidney transplant recipients, MPA concentration at 2 hours had the highest correlation with MPA AUC (r = 0.622); with study period of 4 months [11]. 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