Mycophenolate mofetil--clinical and experimental experience

A Limited Sampling Strategy for Therapeutic Drug Monitoring of Mycophenolate Mofetil for Prophylaxis of Acute Graft-Versus-Host Disease in Allogeneic Stem Cell Transplantation

A universally accepted strategy for therapeutic drug monitoring (TDM) of mycophenolate mofetil (MMF) in the prevention of acute graft-versus-host disease (aGVHD) in allogenic hematopoietic stem cell transplantation (alloHSCT) does not exist. We explored the feasibility of developing a limited sampling strategy (LSS) for TDM of MMF in this setting. Patients undergoing alloHSCT received standard MMF-cyclosporine prophylaxis, with MMF administered twice daily (BD) for matched transplant recipients or thrice daily (TID) in haploidentical transplantation. Intensive blood sampling was carried out on day 7 and area under the concentration–time curve (AUC) of mycophenolic acid (MPA), the active metabolite, was estimated using noncompartmental analysis. The ability of MPA exposure defined by AUC_0-12 to discriminate between responders (patients who did not develop GVHD) and nonresponders (patients who developed GVHD) was determined by receiver operating characteristic curve analysis. Patients were divided into training and validation sets within BD and TID groups. Mathematical equations were developed from the training set to predict AUC_0-12 from an abbreviated AUC involving a limited number of sampling points. The equations were validated in the validation set by comparing the MPA AUC_0-12 predicted from LSS with the observed AUC_0-12. It was observed that patients with AUC_0-12 ≤18.99 mg*h/L had a higher risk of developing aGVHD [odds ratio (OR) = 2.63 (1.17 to 5.87), P = 0.06]. The benefit was more in matched transplant recipients [OR = 3.5 (1.30 to 9.49), P = 0.05] as compared to haploindentical transplant [OR = 2.8 (0.49 to 15.91), P = NS]. Using the mathematical equations, the observed AUC_0-12 was predicted with 92.31% accuracy in the BD subset and 100% accuracy in the TID subset for a combined accuracy of 94.76%. A set of just three samples that constituted the abbreviated AUC_1-4 was used to develop the predictive models. The LSS could be employed for the therapeutic monitoring of MMF particularly in patients undergoing matched hematopoietic stem cell transplantation.

Sonographic diagnosis of fetal malformations associated with mycophenolate mofetil exposure in utero

Mycophenolate mofetil has been shown to have teratogenic properties in animal studies and clinical reports. We report a case of major fetal malformation likely caused by mycophenolate mofetil exposure in utero in a 36 year old patient with systemic lupus erythematosus. The diagnosis was made by ultrasonography at 22 weeks of gestation.

Mycophenolate mofetil in organ transplantation: focus on metabolism, safety and tolerability

Mycophenolate mofetil (MMF) received its first approval for the prevention of renal allograft rejection in 1995 and has now become the most frequently used antiproliferative agent in maintenance immunosuppressive therapy for kidney, pancreas, liver and heart transplantation. In addition, its use for the treatment of autoimmune diseases steadily increases. This review focuses on the miscellaneous pharmacodynamic properties of the drug, its pharmacokinetics in healthy subjects, recipients of different organ transplants and combination therapy with other pharmaceuticals, as well as its safety profile. The immunosuppressive activity of MMF is thought to derive mainly from the potent and selective inhibition of purine synthesis in both T and B lymphocytes. In contrast to other immunosuppressants on the market, it is metabolised primarily by glucuronidation and lacks nephrotoxicity, cardiovascular toxicity or diabetogenic potential, thus making it a suitable candidate for combination regimens. The most important side effects under MMF include gastrointestinal disorders, of which the underlying mechanisms are not yet fully understood, but seem to be complex and related to both effects of mycophenolic acid and its acyl glucuronide, as well as to decreased -immunity due to general immunosuppression after transplantation.

Phosphonic acid-containing analogues of mycophenolic acid as inhibitors of IMPDH

The design, synthesis, and IMPDH inhibitory activity of a series of phosphonic acid-containing analogues of mycophenolic acid are described.

Pharmacodynamics of mycophenolate mofetil after nonmyeloablative conditioning and unrelated donor hematopoietic cell transplantation

The immunosuppressive drug mycophenolate mofetil (MMF) is used after nonmyeloablative hematopoietic cell transplantation (HCT); however, limited pharmacodynamic data are available. We evaluated plasma concentrations of mycophenolic acid (MPA), the active metabolite of MMF, and outcomes in 85 patients with hematologic malignancies conditioned with fludarabine and 2 Gy total body irradiation followed by HLA-matched unrelated-donor HCT and postgrafting cyclosporine and MMF. The first 38 patients received MMF 15 mg/kg twice daily; the next 47 patients received MMF 3 times daily. MPA pharmacokinetics were determined on days 7 and 21. Comparing the twice-daily and 3-times-daily MMF groups, the mean total MPA concentration steady state (Css) was 1.9 and 3.1 microg/mL; the unbound Css was 18 and 36 ng/mL, respectively (P < .001). Sixteen patients with a total MPA Css less than 3 microg/mL had low (< 50%) donor T-cell chimerism (P = .03), and 6 patients with MPA Css less than 2.5 microg/mL had graft rejection. An elevated unbound Css was associated with cytomegalovirus reactivation (P = .03). There were no significant associations between MPA pharmacokinetics and acute graft-versus-host disease (GVHD) or relapse. We conclude that increased MPA Css's predicted higher degrees of donor T-cell chimerism after unrelated donor nonmyeloablative HCT and suggest that targeting MPA Css's greater than 2.5 microg/mL could prevent graft rejection.

Maximum a posteriori bayesian estimation of mycophenolic acid pharmacokinetics in renal transplant recipients at different postgrafting periods

The aim of this study was to develop maximum a posteriori probability (MAP) Bayesian estimators of mycophenolic acid (MPA) pharmacokinetics (PK) capable of accurately estimating the MPA interdose AUC in renal transplant patients using a limited number of blood samples. The individual MPA plasma concentration-time profiles of 44 adult kidney transplant recipients were retrospectively studied: in 24 de novo transplant patients, 2 profiles were obtained on day 7 and day 30 after transplantation, and in 20 stable transplant patients, 1 profile was obtained in the stable period (>3 months). MPA was assayed by liquid chromatography-mass spectrometry. Concentration data were fitted using previously designed PK models, including 1 or 2Gamma-distribution to describe the absorption rate. MAP-Bayesian estimations were performed using an in-house program. For each posttransplantation period, the limited sampling strategies (LSS) providing either the best determination coefficient or the lowest bias for AUC estimates with respect to trapezoidal AUCs were selected and compared with respect to the percentage of "clinically acceptable" AUC estimates (ie, within -20% to +20% of the true value) they yielded. A common LSS (blood samples collected at T20 min, T1 h, and T3 h postdosing), convenient for all 3 periods, was also selected and validated: bias (RMSE%) values were -5.7% (20.5%), -8.2% (14.4%), and +0.4% (12.0%) on D7, D30, and for >M3 with respect to the reference values obtained using the trapezoidal rule, respectively. For the first time, MAP-Bayesian estimators of MPA systemic exposure at different posttransplantation periods (early as well as later periods) could be designed. They have since been used for MPA dose adaptation in concentration-controlled studies as well as for MPA therapeutic drug monitoring in clinical practice.

Comparison of liquid chromatography-tandem mass spectrometry with a commercial enzyme-multiplied immunoassay for the determination of plasma MPA in renal transplant recipients and consequences for therapeutic drug monitoring

Mycophenolic acid (MPA) is an immunosuppressive drug partly metabolized to MPA-glucuronide (MPAG), which is pharmacologically inactive. The currently available enzyme-multiplied immunoassay technique (EMIT) has been reported to overestimate MPA plasma concentration in clinical samples when compared with HPLC techniques. The aims of this study were to design and validate a specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) technique for the determination of MPA and MPAG using a low plasma volume and a simple sample preparation procedure; then to compare it with EMIT for the determination of MPA in plasma samples collected over an interdose interval at different posttransplantation periods (days 3, 7, and 30 and after 3 months) in 25 renal transplant recipients orally administered cyclosporine and mycophenolate mofetil twice daily, to investigate the origins of the differences between techniques. The LC-MS/MS technique developed showed limits of quantification (LOQs) of 0.1 mg/L and 1 mg/L for MPA and MPAG, respectively, and was linear, accurate, and precise from these LOQs up to 30 mg/L for MPA and 300 mg/L for MPAG. EMIT gave similar results to LC-MS/MS for spiked quality control samples (in a synthetic matrix or in drug-free plasma) but significantly overestimated MPA levels in clinical samples: EMIT - LC-MS/MS = +61.39% +/- 57.94%, with large variations depending on patients, time elapsed since transplantation, sampling time, and concentration levels. These results confirmed the known overestimation of the EMIT assay compared with a specific method and showed that the magnitude of this overestimation depended on sampling time and time after transplantation.

Does mycophenolate mofetil increase the incidence of infections in stable renal transplant recipients initially treated with a two-drug regimen?

BACKGROUND

A drug regimen including a calcineurin inhibitor (cyclosporine or tacrolimus) and prednisone has been the mainstay of maintenance immunosuppression in our renal transplant recipients for more than 10 years. After the introduction of mycophenolate mofetil (MMF), a new, potent immunosuppressant that may reduce the incidence of late rejection in renal transplant recipients, the immunosuppressive protocol in some recipients was changed to an MMF-based regimen. We sought to ascertain whether the addition of MMF lead to greater susceptibility to infectious complications.

PATIENTS AND METHODS

Between May 1991 and November 2002, all renal transplant recipients who received a two-drug regimen initially for more than 6 months were changed to an MMF-based regimen. The study includes patients with functional grafts for more than 6 months thereafter. Differences in the incidence, etiology, and outcome of infections were compared during the non-MMF versus the MMF periods.

RESULTS

Eighty patients of mean age of 38.6 years (range 13 to 69) included 43 men and 37 women. The mean daily MMF dose was 663 mg/patient (range 250 to 1500 mg). The mean follow-up time of non-MMF period and MMF periods were 3.4 and 2.1 years, respectively. The overall incidence of infections in the two periods was similar (0.2 infections/patient in the non-MMF period and 0.25 infections/patient in the MMF period, P = .57). No mortality was associated with these infectious complications. In conclusion, addition of MMF, a more potent immunosuppressive protocol, did not increase the incidence of infections in stable renal transplant recipients initially treated with a two-drug regimen.

Mycophenolate mofetil for the prevention and treatment of graft-versus-host disease following stem cell transplantation: preliminary findings

The therapeutic benefits of allogeneic stem cell transplantation in patients with hematologic disorders are limited by the significant morbidity and mortality of graft-versus-host disease (GVHD). Current agents for the prevention and treatment of GVHD have limited efficacy and often result in toxic side-effects. Mycophenolate mofetil (MMF) is a new immunosuppressant with a selective mechanism of action. When employed following solid organ transplantation, MMF reduces the incidence and severity of acute rejection episodes. By selectively targeting activated lymphocytes, the active metabolite of MMF, mycophenolic acid (MPA), appears to augment the actions of standard immunosuppressant agents without adding overlapping toxicities. Studies of combination regimens that include MMF report that this agent permits a dose reduction of cyclosporine, tacrolimus, or corticosteroid, without increasing the incidence of acute rejection in solid organ transplants. Reports on the efficacy of MMF following stem cell transplantation in animal studies were mixed. However, the use of a non-myeloablative conditioning regimen with a post-graft immunosuppressive regimen of MMF and cyclosporine was able to sustain stable mixed chimeras in 60% to 80% of dogs who received hematopoietic grafts from DLA-identical littermates. MMF has demonstrated activity in preliminary clinical trials for GVHD prophylaxis, and treatment of acute or chronic GVHD. Larger clinical trials are warranted to determine the optimum dose and route of MMF administration for GVHD, as well as the comparative safety and efficacy of MMF-containing regimens.

The impact of routine mycophenolate mofetil drug monitoring on the treatment of cardiac allograft rejection

INTRODUCTION

Mycophenolate mofetil (MMF) is a unique immunosupressive agent that has been shown to be efficacious in the treatment of cardiac allograft rejection. The utility of therapeutic drug monitoring on rejection prophylaxis and treatment is inconclusive. This study was undertaken to evaluate the incidence of rejection in relation to MMF trough level following heart transplantation.

METHODS

Between May 1998 and February 1999, we retrospectively analyzed the clinical outcome of 215 heart transplant patients who had routine monitoring of MMF trough level at the time of scheduled endomyocardial biopsy. Patients were divided into three groups according to the time interval post transplant, and were evaluated in relation to the MMF trough level. Group I, 104 patients within 6 months of transplant; Group II, 90 patients, 6-12 months post transplant; and Group III, 71 patients beyond one year of transplant. Fifty patients had samples in more than one group. Rejection was defined as Grade > or = 3A based on ISHLT criteria. Mean follow-up period was 179+/-52 days.

RESULTS

A significantly decreased incidence of rejection was noted in the samples with MMF trough level > or = mg/l compared to those with less than 2 mg/l inpatients evaluated within the first year of transplant (Group I: 8.8% vs. 14.9%, Group II: 4.2% vs. 11.3%, both P=0.05). In the presence of therapeutic cyclosporine (CSA) or tacrolimus (FK) blood levels, the incidence of rejection decreased significantly when MMF trough level was > or = 2 mg/l compared to samples with MMF trough level <2 mg/l (3.6% vs. 14.4%, P=0.005). No significant difference was noted in the presence of subtherapeutic CSA or FK levels (15.4% vs. 13.9%, P=NS).

CONCLUSIONS

Monitoring of MMF trough levels may play a role in the management of cardiac transplant recipients during the first year post transplant.

Infectious complications in geriatric renal transplant patients: comparison of two immunosuppressive protocols

BACKGROUND

It has been well documented that a regimen of mycophenolate mofetil (MMF), cyclosporine (CsA), and prednisone (Pred) reduces the incidence of acute rejection in renal transplant recipients, as compared with previous regimens based on azathioprine (AZA), CsA, and Pred. In the general renal transplant patient population, immunosuppressive regimens that include MMF are usually well tolerated. It is not clear whether this holds true for older transplant recipients, who may be more susceptible to complications from the greater immunosuppression conferred by MMF.

METHODS

We retrospectively analyzed our geriatric renal transplant population (age >60 years, 1990-1998) and compared a cohort of 46 patients treated with AZA, Pred, and CsA to a cohort of 45 patients treated with MMF, Pred, and CsA.

RESULTS

There were no significant differences between the groups with regard to pretransplantation demographics. Patient and graft survival during the first year was not significantly different between the groups. During the first year of follow-up, we observed 27 infections requiring hospitalization in 15 patients in the MMF-treated group as compared with 10 infections in 7 patients in the AZA-treated group. A Cox proportional hazard model accounting for the above mentioned covariates isolated MMF versus AZA as a significant risk factor for the occurrence of serious infectious events (all: P<0.01; cytomegalovirus, fungal: P<0.01).

CONCLUSION

We conclude that an immunosuppressive regimen of MMF, CsA, and Pred seems to be correlated with an increased incidence of infectious adverse events as compared with AZA, CsA, and Pred in elderly patients.

Synergistic effects of mycophenolate mofetil and sirolimus in prevention of acute heart, pancreas, and kidney allograft rejection and in reversal of ongoing heart allograft rejection in the rat

BACKGROUND

The effect of mycophenolate mofetil (MMF) and sirolimus (rapamycin, RAPA) mono- and combination-therapy was examined in prevention of acute heart, pancreas, and kidney allograft rejection and in reversal of ongoing heart allograft rejection in the rat.

METHODS

Both drugs were administered orally for up to 30 days. Eleven groups (n=6) were involved in the first part of the heart allografting model. Brown Norway (RT1n) to Lewis (RT1(1)) combination was used in the heart and pancreas transplantation models, whereas Buffalo (RT1b) to Wistar Furth (RT1u) was used in the kidney transplantation model.

RESULTS

The naive control group showed a mean survival time of 6.5+/-0.6 days. There were graded dose-responses to monotherapy of MMF 10 and 20 mg(kg/ day (12.5+/-2.6 days; 19.3+/-9.0 days) and RAPA 0.2, 0.4, 0.8, and 1.8 mg/kg/day (19.2+/-2.0 days; 30.0+/-7.3 days; 50.8+/-12.5 days; 51.2+/-2.6 days), respectively (P=0.001). Results with the combined use of drugs indicate that a synergistic or very strong synergistic interaction was produced when compared with monotherapy of MMF or RAPA: MMF 10 mg(kg/day+RAPA 0.2 mg/kg(day (52.7+/-5.7 days, combination index [CI] =0.189), MMF 20 mg(kg/day+RAPA 0.2 mg/kg/day (57.7+/-5.7 days, CI=0.084), MMF 10 mg/kg/day+RAPA 0.4 mg(kg/day (50.2+/-13.5 days, CI=0.453), and MMF 20 mg/kg(day+ RAPA 0.4 mg/kg(day (51.5+/-6.8 days, CI=0.439), respectively. These results were repeatable in the prevention of acute pancreas and kidney allograft rejection in the rat. In the second part of the study of reversal of ongoing acute heart allograft rejection model, the combined treatment of MMF 10 mg/kg(day+RAPA 0.2 mg/ kg(day (35.5+/-16.0 days, CI=0.794) and MMF 20 mg/kg day+RAPA 0.2 mg(kg/day (57.2+/-4.7 days, CI=0.310) represented synergistic interaction compared with monotherapy of MMF or RAPA.

CONCLUSIONS

Concomitant therapy of MMF and RAPA produces a synergistic effect in prevention of heart, pancreas, and kidney allograft rejection and in reversal of ongoing heart allograft rejection in the rat.

Decreased protein binding of mycophenolic acid associated with leukopenia in a pancreas transplant recipient with renal failure

BACKGROUND

Mycophenolate mofetil (MMF) is rapidly hydrolyzed to its active metabolite mycophenolic acid (MPA), which is excreted by the kidney after undergoing glucuronidation to MPAG. MPAG has been shown to accumulate in patients with renal failure. MPA is extensively and avidly bound to human serum albumin. In vitro inhibition of the pharmacologic target, inosine monophosphate dehydrogenase, is dependent on free MPA. It has been demonstrated that high MPAG concentrations decrease MPA protein binding in vitro. In addition, the uremic state is associated with altered protein binding of many drugs.

METHODS

We assessed free MPA, total MPA, and MPAG kinetics in a patient with renal failure receiving MMF for a pancreas transplant, who presented with signs of MMF toxicity. MPA, MPAG, and free MPA were measured by high performance liquid chromatography and a validated 14C-MPA ultrafiltration methodology.

RESULTS

The MPAG area under the concentration curve (AUC) in this patient was extremely high (5899 microg x hr/ml). The total MPA AUC of 36.8 microg x hr/ml was within the range usually obtained in stable renal patients. The free fraction of MPA and the free MPA AUC were markedly elevated (13.8% and 5.07 microg x hr/ml, respectively).

CONCLUSIONS

Patients with severe renal insufficiency may have markedly increased free MPA levels that may not be reflected in total MPA concentrations. These patients may be at increased risk for MMF-related toxicity.

Simple method for the quantitation of mycophenolic acid in human plasma

A simple and rapid isocratic reversed-phase high-performance liquid chromatographic method using UV detection was developed for the quantitation of mycophenolic acid (MPA) in human plasma. The assay was sufficiently robust to allow the analysis of up to 100 samples in a single analytical run.