Mycophenolic Acid Plasma Levels Research Articles

Individualization of Mycophenolic Acid Therapy through Pharmacogenetic, Pharmacokinetic and Pharmacodynamic Testing.

Mycophenolic acid (MPA) is a widely used immunosuppressive agent and exerts its effect by inhibiting inosine 5'-monophosphate dehydrogenase (IMPDH), the main regulating enzyme of purine metabolism. However, significant unexplained differences in the efficacy and tolerability of MPA therapy pose a clinical challenge. Therefore, broad pharmacogenetic, pharmacokinetic, and pharmacodynamic approaches are needed to individualize MPA therapy. In this prospective cohort study including 277 renal transplant recipients, IMPDH2 rs11706052 SNP status was assessed by genetic sequencing, and plasma MPA trough levels were determined by HPLC and IMPDH enzyme activity in peripheral blood mononuclear cells (PBMCs) by liquid chromatography-mass spectrometry. Among the 277 patients, 84 were identified with episodes of biopsy-proven rejection (BPR). No association was found between rs11706052 SNP status and graft rejection (OR 1.808, and 95% CI, 0.939 to 3.479; p = 0.076). Furthermore, there was no association between MPA plasma levels and BPR (p = 0.69). However, the patients with graft rejection had a significantly higher predose IMPDH activity in PBMCs compared to the controls without rejection at the time of biopsy (110.1 ± 50.2 vs. 95.2 ± 45.4 pmol/h; p = 0.001), and relative to the baseline IMPDH activity before transplantation (p = 0.042). Our results suggest that individualization of MPA therapy, particularly through pharmacodynamic monitoring of IMPDH activity in PBMCs, has the potential to improve the clinical outcomes of transplant patients.

A short overview on mycophenolic acid pharmacology and pharmacokinetics.

Immunosuppressive therapy is used in solid organ transplant treatment, and mycophenolic acid (MPA) is one of the immunosuppressive drugs most used worldwide. It is a potent, selective, non-competitive, and reversible inosine monophosphate dehydrogenase (IMPDH) inhibitor that acts to inhibit guanine synthesis. To improve solubility, MPA is used as the prodrug mycophenolate mofetil (MMF) or as an enteric-coated mycophenolate sodium salt (EC-MPS). It is metabolized into mycophenolic acid phenyl glucuronide (MPAG), the inactive and major metabolite, and into acyl glucuronide (AcMPAG), pharmacologically active. In kidney transplantation, combined immunosuppressive therapy with cyclosporine (CsA) and tacrolimus (Tac) is widely used, showing beneficial effects. This paper aimed to review papers published in the last two decades and discuss factors that can interfere with the pharmacokinetics of MPA. Data collected confirm that MPA plasma levels should be monitored to evaluate immunosuppressive therapy since pharmacokinetics can be influenced by factors such as interpatient variability, coadministration of other immunosuppressive agents, post-transplant period, renal function, and dose. However, to perform drug monitoring, costs and facility may be limitations. Monitoring MPAG together with MPA would be a great improvement in therapy as it represents a big part of MPA levels and can be related to the increase of adverse effects.

SAT-333 MYCOPHENOLIC ACID MONTTORNIC IN RENAL ALIOGRAFT RECIPIENTS; ASSOCIATATION WITH SAFETY AND EFFICACY

Mycophenolic acid (MPA) is one of the cornerstones immunosuppressants in the setting of transplantation. Advances in the pharmacokinetic studies have uncovered the high inter and intra_individual variability of plasma mycophenolic acid level. This variability in drug concentration can cause both supra therapeutic and sub therapeutic drug plasma levels which can have hazardous results in transplant patients. To date, routine therapeutic drug monitoring of MPA has not been established in clinical practice. Aim of the work: Our objective was to monitor the level of MPA in relation to the occurrence of gastrointestinal (GI) complications and renal function in renal allograft recipients. MPA trough level was measured in 51 renal allograft recipients at the entry of the study and 4 weeks after any dose modification. Levels were correlated with the side effects recorded during the study follow up period. GI toxicity, hematological toxicity and biopsy proven acute rejection (BPAR) were diagnosed in 29.4%, 9.8% and 11.7% of the studied population respectively. Higher MPA 12-hr trough levels were associated with hematological side effects, yet, the correlation with GI side effects was largely negative. A significant correlation between low MPA plasma levels and the development of BPAR after kidney transplantation was detected. An MPA level of 3.5 µg/mL best discriminated between patients who developed hematological toxicity from those who didn’t while MPA level of 2.4 µg/mL best discriminated between patients with and without BPAR. Monitoring of MPA trough level should be practiced in renal allograft recipients in order to avoid drug toxicity without compromising efficacy.

Plasmapheresis Reduces Mycophenolic Acid Concentration: A Study of Full AUC0-12 in Kidney Transplant Recipients.

Background: Mycophenolic acid (MPA), a crucial immunosuppressive drug, and plasmapheresis, an effective immunoreduction method, are simultaneously used for the management of various immune-related diseases, including kidney transplantation. While plasmapheresis has been proven efficient in removing many substances from the blood, its effect on MPA plasma levels remains unestablished. Objectives: To evaluate the full pharmacokinetics of MPA by measuring the area under the time–concentration curve (AUC0–12), which is the best indicator for MPA treatment monitoring after each plasmapheresis session, and to compare the AUC0–12 measurements on the day with and on the day without plasmapheresis. Methods: A cross-sectional study was conducted in kidney transplantation recipients who were taking a twice-daily oral dose of mycophenolate mofetil (MMF, Cellcept®) and undergoing plasmapheresis at King Chulalongkorn Memorial Hospital, Bangkok, Thailand, during January 2018 and January 2019. The MPA levels were measured by an enzymatic method (Roche diagnostic®) 0, 1/2, 1, 2, 3, 4, 6, 8, and 12 h after MMF administration, for AUC0–12 calculation on the day with and on the day without plasmapheresis sessions. Plasmapheresis was started within 4 h after administering the oral morning dose of MMF. Our primary outcome was the difference of AUC0–12 between the day with and the day without plasmapheresis. Results: Forty complete AUC measurements included 20 measurements on the plasmapheresis day and other 20 measurements on the day without plasmapheresis in six kidney transplant patients. The mean age of the patients was 56.2 ± 20.7 years. All patients had received 1000 mg/day of MMF for at least 72 h before undergoing 3.5 ± 1.2 plasmapheresis sessions. The mean AUC on the day with plasmapheresis was lower than that on the day without plasmapheresis (28.22 ± 8.21 vs. 36.79 ± 10.29 mg × h/L, p = 0.001), and the percentage of AUC reduction was 19.49 ± 24.83%. This was mainly the result of a decrease in AUC0–4 of MPA (23.96 ± 28.12% reduction). Conclusions: Plasmapheresis significantly reduces the level of full AUC0–12 of MPA. The present study is the first to measure the full AUC0–12 in MPA-treated patients undergoing plasmapheresis. Our study suggests that a supplementary dose of MPA is necessary for patients undergoing plasmapheresis.

Study on the association of UGT1A9 gene c.98T>C polymorphism and mycophenolic acid plasma levels in renal transplant patients.

Mycophenolate mofetil (MMF) is a prodrug active only after its hydrolysis to mycophenolic acid (MPA). The UGT1A9 enzyme is of special interest since it is the main enzyme involved in the glucuronidation of MPA. Single nucleotide polymorphisms (SNPs) in the UGT1A9 gene may be responsible for individual differences in the pharmacokinetics of MMF. Expression levels and the activity of UGT1A9 may depend on the presence of some SNPs located in the gene promoter region (-2152C>T and -275T>A), as well as changes in the coding region (c.98T>C). The objective of this study was to evaluate the effect of allelic variants of the UGT1A9 c.98T>C polymorphism (rs72551330; g. 87289T>C) on MMF metabolism in renal transplant patients. MPA and MPA 7-O glucuronide (MPAG) levels were determined on plasma samples of kidney transplant patients (N = 39) by high-performance liquid chromatography using ultraviolet detection. DNA was isolated from leukocytes and stored at -20°C. The presence of SNPs was investigated using polymerase chain reaction, followed by amplicon sequencing. The analysis of the UGT1A9 c.98T>C polymorphism revealed that all study patients presented the TT genotype. Diverse MPA and MPAG plasma concentrations were detected, including therapeutic, subtherapeutic, and toxic levels. A standardized molecular method permitted identification of UGT1A9 c.98T>C polymorphism genotypes in the examined renal transplant patients. All individuals of the study group presented the same genotype (c.98TT) for that polymorphism. Thereby, no association between the c.98T>C polymorphism and MPA and MPAG plasma levels could be evaluated, despite different levels of these compounds being observed.

Therapeutic drug monitoring of enteric-coated mycophenolate sodium by limited sampling strategies is associated with a high rate of failure.

BackgroundTherapeutic drug monitoring of mycophenolic acid (MPA) is usually performed with a limited sampling strategy (LSS), which relies on a limited number of blood samples and subsequent extrapolation of the global exposure to MPA. LSS is usually performed successfully with mycophenolate mofetil (MMF), but data on enteric-coated mycophenolate sodium (EC-MPS) are scarce. Here, we evaluated the feasibility of 6-h LSS therapeutic drug monitoring with EC-MPS compared with MMF monitoring among kidney transplant recipients.MethodsSixty-two patients who received EC-MPS during the first 6 months of transplantation were compared with a matched group of 64 MMF-treated kidney transplant recipients. The area under the curve (AUC) was computed by LSS using multiple concentration time points (0, 1, 2, 3 and 6 h post-dose) and a trapezoidal rule. Patients had MPA therapeutic drug monitoring performed on two occasions, one within 2 weeks and the second after 3–4 months of transplantation.ResultsEC-MPS monitoring and MMF therapeutic drug monitoring were not interpretable in 34.5% (n = 40/116) and 1.8% (n = 2/112) of patients, respectively {relative risk [RR] 19.3 [95% confidence interval (CI) 4.8–78.0]; P < 0.0001}. The main cause of abnormal EC-MPS therapeutic drug monitoring was delayed absorption of both the previous evening and the morning dose, resulting in MPA plasma levels before the next morning dose being higher than MPA plasma levels measured at 1, 2 and 3 h after taking EC-MPS. Cyclosporin in association with MMF significantly increased the risk of low AUC values (<30 mg h/L) in comparison with tacrolimus [55% (n = 11/20) and 10% (n = 9/88), respectively; RR 5.4 (95% CI 2.6–11.2); P < 0.0001].ConclusionsThe risk of therapeutic drug monitoring failure with EC-MPS is >30% during the first 6 months of renal transplantation. Delayed pharmacokinetics was the main reason. In contrast, the risk of therapeutic drug monitoring failure was substantially lower with MMF.

Use of Glucuronidated Mycophenolic Acid Levels for Therapeutic Monitoring in Pediatric Lupus Nephritis Patients.

Mycophenolate mofetil (MMF) is used to treat pediatric-onset lupus nephritis (pLN). Data are equivocal on the use of plasma mycophenolic acid (MPA) levels as a measure of efficacy and predictor of therapeutic outcomes in pLN. Glucuronidated MPA (MPA-G) is an inactive metabolite that is a marker of adequate absorption and normal metabolism of MMF. We evaluated the use of MPA and MPA-G levels in routine care of pLN. This was a retrospective study of pLN patients treated with MMF dosed at 600 mg/m. Clinical renal remission (CR) was defined as proteinuria of less than 500 mg/24 h. Midinterval MPA and MPA-G plasma levels were drawn during routine follow-up, approximately 6 hours after the previous dose of MMF. Steady-state levels of MPA were calculated using pharmacokinetics and compared with routine midinterval plasma MPA levels. Seventeen pLN patients treated with MMF had MPA and MPA-G levels. Eleven patients were in CR; 6 were not in CR at the time of evaluation and had not responded to MMF after more than 3 months of therapy. The mean MPA level for patients in CR was 3.26 ± 2.02 μg/mL compared with 3.02 ± 1.76 μg/mL for patients not in CR. Three patients in CR did not have detectable levels of MPA. Calculated steady-state levels of MPA did not reflect the observed levels. Glucuronidated MPA levels were therapeutic (44.2 ± 26.7 μg/mL) in patients in CR, but low (29.88 ± 22 μg/mL) in patients not in CR (not statistically significant). Midinterval plasma levels of MPA do not reflect predicted steady-state levels in pLN and do not correlate with clinical response. Midinterval plasma levels of MPA-G indicate adequate absorption and may correlate better with clinical pLN activity.

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.

The objective of the study was to investigate the pharmacokinetics of mycophenolate mofetil (MMF) in Chinese adults early after renal transplantation by an enzyme multiplied immunoassay technique and to establish a limited sampling strategy to predict the area under the concentration-time curve for plasma levels of mycophenolic acid (MPA-AUC). Fifty-eight recipients who underwent renal transplantation with an organ donated after cardiac death used a triple immunosuppressant strategy of MMF, tacrolimus, and prednisone. On the seventh day posttransplantation, plasma samples were collected at 0 hours (pre-dose) and at 0.5, 1, 1.5, 2, 4, 6, 8, 10, and 12 hours postdose (C0h, C0.5h, C1h, C1.5h, C2h, C4h, C6h, C8h, C10h, and C12h, respectively). Enzyme multiplied immunoassay technique was used to measure mycophenolic acid concentration, and model equations were generated by multiple stepwise regression analysis to determine MPA-AUC0-12h. The 3-point equation obtained by multiple linear regression analysis was MPA-AUC = 7.951 + 4.04C6h + 1.893C2h + 4.542C10h (adjusted r = 0.863); the 4-point equation was MPA-AUC = 4.272 + 4.074C6h + 1.896C2h + 4.680C10h + 0.859C0.5h (adjusted r = 0.918). The % mean prediction error, % mean absolute error, and % root mean squared prediction error for the best-fit formula using C6h, C2h, C10h, and C0.5h were -0.2%, 8.7%, and 14.2%, respectively. In Chinese adults receiving MMF and tacrolimus early after renal transplantation, the best equation for predicting MPA-AUC0-12h is 4.272 + 4.074C6h + 1.896C2h + 4.680C10h + 0.859C0.5h.

Mycophenolic Acid Pharmacokinetics Early After Kidney Transplant

To determine the mycophenolic acid pharmacokinetic profile early after transplant in Iranian kidney graft recipients. A cross-sectional study was performed during 6 months in 31 patients who recently had kidney transplant and received fixed doses of mycophenolate mofetil (2 g/d). The plasma levels of mycophenolic acid were determined by high performance liquid chromatography. The mean first mycophenolic acid peak level was 10 ± 5 mg/L. The mean mycophenolic acid area under the curve was 26 ± 19 mgh/L and apparent clearance was 57 ± 55 L/h. The mycophenolic acid area under the curve values of only 8 patients (26%) were within the therapeutic range (30-60 mgh/L). The first, second, and third mycophenolic acid peak levels correlated significantly with mycophenolic acid area under the curve (P < .05). Mycophenolic acid concentration at 10 hours had the highest correlation with mycophenolic acid area under the curve (r=0.962; P < .05). No statistically significant differences were evident in the mean mycophenolic acid area under the curve between men and women. There was a high degree of variation between different patients in mycophenolic acid pharmacokinetics early after kidney transplant.

Mycophenolate mofetil: fully utilizing its benefits for GvHD prophylaxis

Mycophenolate mofetil (MMF) has been widely used for the prophylaxis of graft-versus-host disease (GvHD) in hematopoietic stem cell transplantation (HSCT), based on clinical evidence established in organ transplantations. MMF is not a cytotoxic, but rather a cytostatic agent, and there have been several reports of significant advantages in engraftment as well as greatly reduced stomatitis compared to methotrexate (MTX). MMF has been preferred for MTX-free immunosuppression, especially in reduced intensity conditioning, but it is suitable for GvHD prophylaxis for any type of HSCT. Some clinicians doubt its effectiveness, due to the lack of advantage over MTX in acute GvHD prophylaxis, especially in myeloablative conditioning. Pharmacokinetics studies of mycophenolic acid (MPA), the active form of MMF, show large inter- and intra-patient variation, which make interpretations of its clinical usefulness difficult. Nevertheless, several studies, including ours, have demonstrated that relatively higher area under the curve (AUC) of the MPA group leads to significant suppression of acute GvHD in prophylactic use. We propose a model algorithm for optimal dose finding using therapeutic drug monitoring (TDM) for MPA. Preemptive strategies depending on plasma MPA levels could yield more effective approaches to GvHD prophylaxis, alternative to MTX.

Pharmacokinetics of mycophenolic acid in severe lupus nephritis

Mycophenolic acid (MPA) is an effective treatment for active lupus nephritis despite its variable efficacy in different ethnic groups. Here we tested whether pharmacokinetic monitoring may help to optimize dosing of MPA in an Asian population. Patients with biopsy-proven class III or IV lupus nephritis (ISN/RPS category) were treated with mycophenolate mofetil or enteric-coated mycophenolate sodium. One month after initiating treatment we measured plasma MPA levels in eight samples taken over a 12-h period after drug administration. The mean area under the time-dependent curve for MPA of responding patients was significantly higher than those not responding. Successful treatment was seen in patients with areas >45 mg h/l. The dosage of the drug was not related to MPA pharmacokinetics. In the mycophenolate mofetil group, however, MPA-area under the curve was positively, and significantly, correlated with trough or 1 h after dose concentrations and associated with a therapeutic response. Thus, our study shows that MPA pharmacokinetics were positively correlated with therapeutic responses of mycophenolate, suggesting that controlling the concentrations may improve its therapeutic efficacy in lupus nephritis. As the absorption and pharmacokinetic peak of enteric-coated tablets is slower, it is important to take different formulations into account when determining optimal MPA concentrations.

Randomized crossover study to assess the inter‐ and intrasubject variability of morning mycophenolic acid concentrations from enteric‐coated mycophenolate sodium and mycophenolate mofetil in stable renal transplant recipients

The delayed release of mycophenolic acid (MPA) from enteric-coated mycophenolate sodium (EC-MPS, myfortic®) may have an impact on the variability of MPA trough (C0 h) levels. A randomized, two-period crossover study was performed in 24 maintenance renal transplants to evaluate the inter- and intrasubject variability of MPA predose levels from EC-MPS and mycophenolate mofetil (MMF, CellCept®), both in combination with cyclosporine. Patients received EC-MPS (720 mg b.i.d.) and MMF (1000 mg b.i.d.) for a period of 21 d each. MPA plasma levels were measured over the final seven consecutive days at -1, 0, 1, 2, and 3 h after the morning MPA dose. Intersubject coefficients of variation (%CV) for MPA troughs were 47.5% (95% CI, 34.1-80.3) and 54.4% (40.0-86.8) for EC-MPS and MMF, respectively; intrasubject %CVs were 62.7% (55.1-72.9) and 42.8% (37.9-49.2). High MPA C0 h levels>10 μg/mL were rarely observed with both EC-MPS (1.8%) and MMF (0.6%). Mean MPA area under the curve (AUC)0-3 h was comparable between treatments, while MPA C0 h was on average 46% higher with EC-MPS. In conclusion, predose MPA trough level monitoring appears of limited value during EC-MPS and MMF therapy given the large intrasubject variability in MPA C0 h levels with both treatments.

The Promising Strategy of Mycophenolate Mofetil Dosing to Prevent Moderate- to Severe-Acute Graft-Versus-Host Disease.

To prevent acute graft-versus-host disease (GVHD) and graft failure, mycophenolate mofetil (MMF) has been employed as a substitute of methotrexate in allogeneic hematopoietic stem cell transplantation (all-SCT). However, the dosing strategy of MMF after all-SCT remains to be established.In this study, we investigated the optimal MMF dosing until day 30 based on pharmacokinetic studies in 28 Japanese allo-SCT patients. For better clinical outcomes of MMF, higher mycophenolic acid (MPA) plasma levels are proposed to be desirable. Therefore, the first 11 patients (group A) received MMF orally every 12 hours at an escalated dose from 15 mg/kg to 25 mg/kg (maximum total daily dose 3000 mg), according to real-time pharmacokinetic monitoring of the total MPA area under the curve (AUC). However, the dose escalation in each individual did not always increase the AUC. Then, MMF was given orally at a fixed dose of 1000 mg every 8 hours in the subsequent 17 patients (group B). The pharmacokinetic data revealed that the increase of dosing frequency could statistically keep higher MPA plasma levels, as reflected in concentration at steady state (Css: group A vs. group B; 1.12 vs. 2.18 μg/ml on day 16, P = 0.003) or trough value (Ctrough: 0.18 vs. 0.56 μg/ml on day 16, P = 0.019). These results indicate that MMF administration of every 8 hours would be better than that of every 12 hours even in the same total daily dose until day 30.We further assessed the safety and efficacy of extended MMF administration beyond day 30 retrospectively. Twenty-five patients ceased MMF at day 30, whereas 16 patients were subjected to extended regimen depending on the individual risk factors for GVHD (median dosing period 64.5 days, 50–94 days). No severe adverse events were observed in both groups. While the cumulative incidence (CI) of more than grade I acute GVHD at day 100 was comparable between the two groups (72.1 % vs. 62.5 %, P = 0.63, Figure 1A), the CI of grade II to IV acute GVHD was lesser in the latter group (42.3 % vs. 12.5 %, P = 0.045, Figure 1B).These results suggest that MMF should be administered every 8 hours until day 30 after allo-SCT, followed by extending MMF administration at least until day 60 as a preemptive therapy for moderate- to severe-acute GVHD. This strategy might be very useful for double UCB transplantation under non-myeloablative conditioning especially, because the transplantation is reported to develop severe acute GVHD frequently. [Display omitted]

Mycophenolate mofetil inhibits T-cell proliferation in kidney transplant recipients without lowering intracellular dGTP and GTP

To study if mycophenolic acid (MPA), the active metabolite of mycophenolate mofetil (MMF), indeed inhibits T-cell proliferation in kidney transplant recipients by lowering intracellular deoxyguanosine triphosphate (dGTP) and guanosine triphosphate (GTP) levels. Blood was drawn from 11 kidney transplant recipients. Ex vivo T-cell proliferation was measured by stimulation with phytohemagglutin (PHA) and anti-CD3 monoclonal antibody (mAb). Plasma MPA levels and intracellular dGTP and GTP in peripheral blood mononuclear cells were measured. MMF induces a significant decrease in T-lymphocyte proliferation at all time points (i.e. 24 h, 10 days and 8 weeks) after stimulation with both PHA (P = 0.001, 0.002 and 0.013 respectively) and anti-CD3 mAb (P = 0.004, 0.004 and 0.005 respectively). There was no significant change in intracellular dGTP (P = 0.31, 0.16 and 0.35) or GTP levels (P = 0.99, 0.32 and 0.49) between baseline and day 1, day 10 or week 8. All MPA levels were above the minimal required concentration for the inhibition of lymphocyte proliferation. MMF inhibits T-lymphocyte proliferation in kidney transplant recipients without lowering intracellular dGTP or GTP levels. This suggests another mechanism underlying its immunosuppressive capacity.

Reduced-Intensity Conditioning Allogeneic Transplantation from Unrelated Donors: Evaluation of Mycophenolate Mofetil Plus Cyclosporin A as Graft-versus-Host Disease Prophylaxis

In the current study, we have analyzed the efficacy of cyclosporine A (CSA) plus mycophenolate mofetil (MMF) as graft-versus-host disease (GVHD) prophylaxis in the fludarabine plus melphalan or busulfan reduced intensity regimen (RIC) setting in a series of 44 patients receiving allogeneic transplantation from an unrelated donor. Only 23% were in the first complete remission at the time of transplant. Cumulative incidence of grades II-IV and III-IV acute GVHD (aGVHD) was 53% and 23%, respectively. Fifty-six percent had equal to or greater than grade 2 gut involvement. Cumulative incidence of overall and extensive chronic GVHD (cGVHD) was 93% and 63%, respectively. Ninety-two percent of patients who were evaluable +100 days after transplant were in complete remission. Relapse rate was 25% at 2 years. Event free (EFS) and overall survival (OS) at 2 years were 52%. Pharmacokinetic assays of mycophenolic acid (MPA) showed a therapeutic area under the curve (AUC) at the dosage of 3 g daily, although a large inter- and intraindividual variations of MPA plasma levels were found. In conclusion, the combination of CSA plus MMF in the fludarabine plus melphalan or busulfan RIC setting is feasible. Regarding GVHD, this combination allowed to control aGVHD but lead to a high incidence of cGVHD, so that newer strategies are required, especially in trying to decrease gastrointestinal involvement.

Pharmacokinetics-based optimal dose-exploration of mycophenolate mofetil in allogeneic hematopoietic stem cell transplantation

For better clinical outcomes of mycophenolate mofetil (MMF) in allogeneic hematopoietic stem cell transplantation (alloSCT), higher mycophenolic acid (MPA) plasma levels are proposed to be desirable. Here, we investigate the optimal MMF dosing strategy based on pharmacokinetic studies in 20 Japanese alloSCT patients. The first 11 patients received MMF twice daily at an escalated dose from 15 mg/kg, according to real-time pharmacokinetic monitoring of the total MPA area under the curve (AUC). In the subsequent nine patients, MMF was given at a fixed dose of 1,000 mg three-times daily. The pharmacokinetic data revealed that the dose escalation in each individual did not always increase the AUC. In contrast, the increase of dosing frequency could statistically keep higher MPA plasma levels, as reflected in higher concentration at steady state (C (ss)) or trough value (C (trough)). There was no symptomatic adverse event in both groups. These results suggest that MMF administration of every 8 h after alloSCT would be better to maintain higher MPA plasma levels than that of every 12 h even in the same daily dose. Further studies are necessary to confirm the clinical benefit of MMF to prevent graft failure, as well as severe aGVHD.

Better Mycophenolic Acid 12-Hour Trough Level After Enteric-Coated Mycophenolate Sodium in Patients With Gastrointestinal Intolerance to Mycophenolate Mofetil

Introduction Enteric-coated mycophenolate sodium (EC-MPS) is the enteric-coated salt form of mycophenolic acid (MPA), the active component of the prodrug mycophenolate mofetil. EC-MPS was developed to reduce the upper-gastrointestinal (GI) effects of mycophenolate mofetil. There are no studies available comparing trough plasma levels in patients with GI intolerance to MMF when they are converted to EC-MPS. Aim To compare the GI tolerance and the MPA levels in patients previously treated with MMF in whom this drug was replaced by EC-MPS. Materials and methods A prospective study was conducted in 133 renal transplant patients after conversion from MMF to EC-MPS (median time posttransplant 42 months, range 1 to 240 months). The causes for EC-MPS switching were GI intolerance to MMF (51.9%; group A), low trough plasma levels with MMF (29.3%; group B), and others (18.8%; group C). These patients were converted to equipotent doses of EC-MPS. Results The trough plasma MPA levels increased from 1.5 ± 1.1 μg/mL at baseline to 2.5 ± 2.0 μg/mL at 1 month postconversion despite the equipotent EC-MPS doses not being increased. These higher plasma levels were maintained throughout the study. In group A, this increase was from 1.8 ± 1.0 to 2.7 ± 2.1 μg/mL ( P = .01) and in group B from 0.8 ± 0.4 to 2.4 ± 1.4 μg/mL ( P < .001). The doses and levels of calcineurin inhibitor decreased from baseline. Creatinine clearance improved from 56.5 ± 24.7 mg/dL at baseline to 61.9 ± 28.6 at 6 months postconversion ( P = .02). There was a statistically significant increase in hemoglobin levels. In group A, the GI tolerance improved in 78% of the patients. Conclusions At equipotent doses, patients converted to EC-MPS have higher and more adequate levels of MPA. At 6 months postconversion, we observed an improvement of the renal function, probably due to a reduction of calcineurin inhibitor drugs. However, the possibility that a better immunosuppressive efficacy as demonstrated by more suitable trough plasma levels may have been a contributing factor cannot be discarded.

The Magnitude and Time Course of Changes in Mycophenolic Acid 12-Hour Predose Levels During Antibiotic Therapy in Mycophenolate Mofetil-Based Renal Transplantation

There is increasing evidence that monitoring predose plasma levels of mycophenolic acid (MPA) is of benefit in renal transplant recipients treated with mycophenolate mofetil (MMF). Concomitant treatment with oral antibiotics leads to a 10% to 30% reduction in MPA area under the curve (AUC)0-12, probably by reducing enterohepatic recirculation (EHR). Because of the timing of EHR (6 to 12 hours postdose), the magnitude of predose MPA level reduction may be disproportionately larger than that of AUC0-12. However, changes in predose MPA levels and the time course over which these changes occur and resolve during antibiotic treatment have not been studied. The purpose of this study was to define the extent and time course of MPA predose level reduction during antibiotic therapy. A total of 64 MMF-treated renal transplant recipients (with tacrolimus cotherapy) were prospectively studied. Clinically indicated cotherapy with either oral ciprofloxacin or amoxicillin with clavulanic acid resulted in a reduction in 12 hour predose MPA level to 46% of baseline within 3 days of antibiotic commencement. No demographic or biochemical variables were associated with the magnitude of MPA level reduction. No further fall in MPA level was seen by day 7, but MPA levels recovered spontaneously to 79% of baseline after 14 days of antibiotics. Levels normalized within 3 days of antibiotic cessation. No changes in daily MMF dose (normalized for body weight) were made during antibiotic treatment. This data should help the clinician to recognize the extent of MPA predose level reduction during antibiotic therapy, and to avoid inappropriate MMF dose escalation and potential risk of toxicity.

Influence of Co‐Medication with Sirolimus or Cyclosporine on Mycophenolic Acid Pharmacokinetics in Kidney Transplantation

The pharmacokinetics of mycophenolic acid (MPA)--the active metabolite of mycophenolate mofetil (MMF)--is significantly influenced by co-medications. The impact of sirolimus on daily MPA exposure, however, has not been investigated so far. As a part of the study aimed at investigating the efficacy of Campath-1H induction therapy in a steroid-free regimen in kidney transplantation, MPA plasma levels were serially measured in 21 patients treated with low-dose sirolimus (SRL) or low-dose CsA both in addition to low-dose MMF over 12 months post-operatively. Full pharmacokinetic profiles were compared at month 6 and 12 post-surgery. Mean dose-adjusted MPA trough levels were 4.4-fold higher in patients on combined SRL and MMF than in those given CsA and MMF. Pharmacokinetic studies demonstrated that mean MPA C(max) and T(max) were comparable in the two groups, while mean MPA AUC(0-12) was higher in SRL than CsA treated patients. The pharmacokinetic profile of SRL- but not of CsA-group showed a second peak consistent with the enterohepatic recirculation of MPA. These findings suggest that SRL and CsA have different effects on MPA metabolism and/or excretion eventually affecting its immunosuppressive property and/or toxicity. CsA, but not SRL, inhibits MPA enterohepatic recirculation, reducing MPA daily exposure.

Trough levels of mycophenolic acid and its glucuronidated metabolite in renal transplant recipients

The prophylactic use of the immunosuppressant prodrug, mycophenolate mofetil (MMF) to prevent graft rejection in renal transplant patients is continuing to increase. We measured trough levels of the active metabolite, mycophenolic acid (MPA) and its inactive glucuronide (MPAG) in renal recipients with the aim of characterizing individual variability and of ascertaining factors influencing trough levels, in particular the effect of differences in renal function and the effect of drugs given concurrently. Laboratory and clinical data obtained in 35 renal recipients treated with triple therapy (MMF, cyclosporin A (CsA), steroids) were included in this retrospective study. Trough levels of MPA and MPAG were obtained after transplantation and up to 16 months post transplantation where the mean observation period was 5.7 months. Plasma levels were measured using a validated HPLC assay. A total of 212 plasma concentrations of MPA and 209 of MPAG were measured. There was considerable intra- and interindividual variability in MPA and MPAG trough levels especially in the early post-transplantation phase. At a fixed dose of 2 g/d MMF, the mean MPA level during the first 30 days averaged 1.46 +/- 1.31 microg/ml vs. 1.87 +/- 0.89 microg/ml after 30 days and later (p = 0.130) and the mean MPAG concentration averaged 188.1 = 142.8 [microg/ml vs. 98.09 +/- 52.4 microlg/ml (p 0.003). The MPAG levels were positively correlated with the serum creatinine concentrations (r = 0.815, p < 0.001), and in the case of MPA there was a correlation with the serum protein concentrations (r = 0.258, p = 0.001). Concomitant drug treatment using CsA, steroids and furosemide were without effect of the measured plasma concentrations, but in the case of xipamide (+) and diltiazem (-) an effect on MPA and MPAG levels and a co-effect depending on the serum creatinine could not be excluded. Neither CsA trough levels nor hemoglobin levels were related to MPA and MPAG trough levels. The data of this study demonstrate that there is substantial individual variability in the trough levels of MPA and MPAG after renal transplantation which may be associated with the functional status of the graft and the serum protein level. Whether comedication with xipamide and diltiazem affects the plasma levels of MPA and MPAG remains to be clarified in further investigations.