RS-61443--a phase I clinical trial and pilot rescue study

Development and application of a thin-film molecularly imprinted polymer for the measurement of mycophenolic acid in human plasma

BACKGROUND

Mycophenolic acid (MPA) is used to suppress the immune response following organ transplantation; however, complex pharmacokinetic behavior and a large interpersonal variability necessitate therapeutic drug monitoring. To overcome the limitations of current sample preparation techniques, we present a novel thin-film molecularly imprinted polymer (TF-MIP) extraction device as part of a simple, sensitive, and fast method for analysis of MPA from human plasma.

METHODS

Mycophenolic acid is extracted from plasma using a tailor-made TF-MIP that is subsequently desorbed into an organic solvent system compatible with mass spectrometry. The MIP yielded higher recovery of MPA relative to a corresponding non-imprinted polymer. The method allows for the determination of MPA in 45 min including analysis time and can be scaled for high throughput to process as many as 96 samples per hour.

RESULTS

The method gave an LOD of 0.3 ng mL^-1 and was linear from 5 to 250 ng mL^-1 . Patient plasma samples (35 μL) were diluted using charcoal-stripped pooled plasma to a final extraction volume of 700 μL; when MPA in patient plasma is high, this ratio can easily be adjusted to ensure samples are within the method linear range. Intra- and inter-day variability were 13.8% and 4.3% (at 15 ng mL^-1 ) and 13.5% and 11.0% (at 85 ng mL^-1 ), respectively (n = 3); inter-device variability was 9.6% (n = 10).

CONCLUSIONS

Low inter-device variability makes these devices suitable for single use in a clinical setting, and the fast and robust method is suitable for therapeutic drug monitoring, where throughput and time-to-result are critical.

The pharmacogenetics of mycophenolate mofetil in Tunisian renal transplant patients

Aim: The effects of variants in IMPDH, UGT1A9, UGT1A8, UGT2B7 and SLCO1B1 genes on the efficacy and safety of mycophenolate mofetil (MMF) in the Tunisian population were investigated. Materials & methods: A total of 245 kidney transplant patients being treated with MMF were recruited and cotreated with cyclosporine or tacrolimus. Genotyping was performed using the polymerase chain reaction-restriction fragment length polymorphism method. MMF, cyclosporine and tacrolimus trough levels were measured by immunoassay. The AUC (AUC_0-12hMPA) was estimated by a Bayesian method. Results: In the tacrolimus-treated group, anemia and diarrhea were associated with the UGT1A9-98C and UGT1A9-275T alleles, respectively (p < 0.05). In the cyclosporine-treated group, leukopenia was associated with the SLCO1B1-521T allele (p < 0.05). Both groups had an increased risk of rejection (p < 0.05) associated with the variant alleles of IMPDH2-3757T>C, UGT1A9-2152C>T and UGT1A9-275C>A and the common allele of SLCO1B1-388A>G. However, no significant association was found between the studied genotypes and AUC_0-12hMPA or cotreatment levels. Conclusion: The results constitute preliminary evidence for the inclusion of the pharmacogenetics of MMF in kidney pretransplantation evaluations.

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.

Initial mycophenolate dose in tacrolimus treated renal transplant recipients, a cohort study comparing leukopaenia, rejection and long-term graft function

The evidence supporting an initial mycophenolate mofetil (MMF) dose of 2 g daily in tacrolimus-treated renal transplant recipients is limited. In a non-contemporaneous single-centre cohort study we compared the incidence of leukopaenia, rejection and graft dysfunction in patients initiated on MMF 1.5 g and 2 g daily. Baseline characteristics and tacrolimus trough levels were similar by MMF group. MMF doses became equivalent between groups by 12-months post-transplant, driven by dose reductions in the 2 g group. Leukopaenia occurred in 42.4% of patients by 12-months post-transplant. MMF 2 g was associated with a 1.80-fold increased risk of leukopaenia compared to 1.5 g. Rejection occurred in 44.8% of patients by 12-months post-transplantation. MMF 2 g was associated with half the risk of rejection relative to MMF 1.5 g. Over the first 7-years post-transplantation there was no difference in renal function between groups. Additionally, the development of leukopaenia or rejection did not result in reduced renal function at 7-years post-transplant. Leukopaenia was not associated with an increased incidence of serious infections or rejection. This study demonstrates the initial MMF dose has implications for the incidence of leukopaenia and rejection. Since neither dose produced superior long-term graft function, clinical equipoise remains regarding the optimal initial mycophenolate dose in tacrolimus-treated renal transplant recipients.

Influence of Calcineurin Inhibitor and Sex on Mycophenolic Acid Pharmacokinetics and Adverse Effects Post-Renal Transplant

Tacrolimus or cyclosporine is prescribed with mycophenolic acid posttransplant and contributes to interpatient variability in mycophenolic acid pharmacokinetics and response. Cyclosporine inhibits enterohepatic circulation of the metabolite mycophenolic acid glucuronide, which is not described with tacrolimus. This study investigated mycophenolic acid pharmacokinetics and adverse effects in stable renal transplant recipients and the association with calcineurin inhibitors, sex, and race. Mycophenolic acid and mycophenolic acid glucuronide area under the concentration-time curve from 0 to 12 hours (AUC0-12h ) and apparent clearance were determined at steady state in 80 patients receiving cyclosporine with mycophenolate mofetil and 67 patients receiving tacrolimus with mycophenolate sodium. Gastrointestinal adverse effects and hematologic parameters were evaluated. Statistical models evaluated mycophenolic acid pharmacokinetics and adverse effects. Mycophenolic acid AUC0-12h was 1.70-fold greater with tacrolimus (68.9 ± 30.9 mg·h/L) relative to cyclosporine (40.8 ± 17.6 mg·h/L); P < .001. Target mycophenolic acid AUC0-12h of 30-60 mg·h/L was achieved in 56.3% on cyclosporine compared with 34.3% receiving tacrolimus (P < .001). Mycophenolic acid clearance was 48% slower with tacrolimus (10.6 ± 4.7 L/h) relative to cyclosporine (20.5 ± 10.0 L/h); P < .001. Enterohepatic circulation occurred less frequently with cyclosporine (45%) compared with tacrolimus (78%); P < 0.001; with a 2.9-fold greater mycophenolic acid glucuronide AUC0-12h to mycophenolic acid AUC0-12h ratio (P < .001). Race did not affect mycophenolic acid pharmacokinetics. Gastrointestinal adverse effect scores were 2.2-fold higher with tacrolimus (P < .001) and more prominent in women (P = .017). Lymphopenia was more prevalent with tacrolimus (52.2%) than cyclosporine (22.5%); P < 0.001. Calcineurin inhibitors and sex contributed to interpatient variability in mycophenolic acid pharmacokinetics and adverse effects post-renal transplant, which could be attributed to differences in enterohepatic circulation.

Three Severe Cases of Viral Infections with Post-Kidney Transplantation Successfully Confirmed by Polymerase Chain Reaction and Flow Cytometry

Viral infections in patients with post-kidney transplantation are often difficult to diagnose as well as treat. We herein report three cases with severe viral infections after kidney transplantation. All their causative pathogens could be detected promptly by polymerase chain reaction and flow cytometry during the early stages of infection. These examinations would also be of great use to monitor therapeutic responses and disease activity. It is indeed true that no specific treatment is available for most of the viral infections, but we should be aware that some infections, such as Epstein-Barr virus infection, can be treatable with prompt and specific treatment, such as rituximab.

Nonlinear relationship between enteric-coated mycophenolate sodium dose and mycophenolic acid exposure in Han kidney transplantation recipients

The aim of the research was to investigate the pharmacokinetics (PK) of enteric-coated mycophenolate sodium (EC-MPS) by quantification of the active metabolite of mycophenolic acid (MPA) after multiple escalating oral doses in Han kidney transplant recipients. A total of 28 Han postoperative kidney transplant recipients were given a multiple-dose of 540, 720 or 900 mg of EC-MPS two times a day in combination with tacrolimus for 6 days. Blood specimens were collected at each time point from 0 to 12 h after EC-MPS administration. MPA plasma concentrations were measured by UPLC—UV. The relationship between the EC-MPS dose and its PK parameters was assessed. In the range from 540 to 900 mg, C_max and AUC_0—12h did not increase with dose escalation. The AUC_0—12h, C_max, C₀ and T_max for the 540 720 and 900 mg doses were not significantly different, respectively (P >0.05). AUC_0—12 h and C_max were increased less than proportionally with increasing EC-MPS dose levels. Inter-individual variability in AUC_0—12h, C_max and C₀ were considerable. Nonlinear PK relationships were found from the doses of 540–900 mg of EC-MPS.

Mycophenolate and nephrology

Several large, randomized trials have established mycophenolate mofetil (MMF) as an effective immunosuppressant for kidney transplantation. Inhibition of inosine 5′-monophospate dehydrogenase (IMPDH) by MMF appears to have pleiotropic effects on both immune and non-immune cells. In addition to B- and T-cell inhibition, in vitro and in vivo data suggest that MMF also has inhibitory effects on smooth muscle cells, endothelial cells, and myofibroblasts, findings that may be relevant in considering treatment of primary immune mediated kidney diseases. Clinical trials have established the efficacy of MMF for the treatment of lupus nephritis, as discussed in detail elsewhere in this supplement. Although animal studies have provided the rationale for human trials of MMF in primary glomerular diseases, most of the evidence thus far is conflicting or based largely on pilot studies. Data from larger, controlled trials will soon emerge and may clarify the role of MMF in the treatment of these disorders.

Immunosuppression for in vivo research: state-of-the-art protocols and experimental approaches

Almost every experimental treatment strategy using non-autologous cell, tissue or organ transplantation is tested in small and large animal models before clinical translation. Because these strategies require immunosuppression in most cases, immunosuppressive protocols are a key element in transplantation experiments. However, standard immunosuppressive protocols are often applied without detailed knowledge regarding their efficacy within the particular experimental setting and in the chosen model species. Optimization of such protocols is pertinent to the translation of experimental results to human patients and thus warrants further investigation. This review summarizes current knowledge regarding immunosuppressive drug classes as well as their dosages and application regimens with consideration of species-specific drug metabolization and side effects. It also summarizes contemporary knowledge of novel immunomodulatory strategies, such as the use of mesenchymal stem cells or antibodies. Thus, this review is intended to serve as a state-of-the-art compendium for researchers to refine applied experimental immunosuppression and immunomodulation strategies to enhance the predictive value of preclinical transplantation studies.

Enteric-Coated Mycophenolate Sodium

OBJECTIVE:

To review the pharmacology, pharmacokinetics, efficacy, and safety of mycophenolate sodium.

DATA SOURCES:

Primary literature was obtained via a MEDLINE search (1966–June 2003). Abstracts were obtained from the manufacturer and included in the analysis.

STUDY SELECTION AND DATA EXTRACTION:

All studies and abstracts evaluating mycophenolate sodium in solid organ transplantation were considered for inclusion. English-language studies and abstracts were selected for inclusion, but were limited to those consisting of human subjects.

DATA SYNTHESIS:

Mycophenolate sodium, a mycophenolic acid prodrug, is an inhibitor of T-lymphocyte proliferation. Mycophenolic acid reduces the incidence of acute rejection in renal transplantation. Mycophenolate sodium is enteric coated and has been suggested as a potential method to reduce the gastrointestinal adverse events seen with mycophenolate mofetil. Both mycophenolate mofetil and mycophenolate sodium have been shown to be therapeutically equivalent at decreasing the incidence of allograft rejection and loss. The frequency of adverse events is similar between both compounds, with the most common events being diarrhea and leukopenia.

CONCLUSIONS:

Mycophenolate sodium is effective in preventing acute rejection in renal transplant recipients. At doses of 720 mg twice daily, the efficacy and safety profiles are similar to those of mycophenolate mofetil 1000 mg twice daily. Mycophenolate sodium has been approved in Switzerland; approval in the US is pending.

Influence of sex and race on mycophenolic acid pharmacokinetics in stable African American and Caucasian renal transplant recipients

BACKGROUND AND OBJECTIVES

No evaluation of sex and race influences on mycophenolic acid (MPA) pharmacokinetics and adverse effects (AEs) during enteric-coated mycophenolate sodium (ECMPS) and tacrolimus immunosuppression are available. The primary objective of this study was to investigate the influence of sex and race on MPA and MPA glucuronide (MPAG) pharmacokinetics in stable renal transplant recipients receiving ECMPS and tacrolimus

METHODS

The pharmacokinetics of MPA and MPAG and their associated gastrointestinal AEs were investigated in 67 stable renal transplant recipients: 22 African American males (AAMs), 13 African American females (AAFs), 16 Caucasian males (CMs), and 16 Caucasian females (CFs) receiving ECMPS and tacrolimus. A validated gastrointestinal AE rating included diarrhea, dyspepsia, vomiting, and acid-suppressive therapy was completed. Apparent clearance, clearance normalized to body mass index (BMI), area under the concentration-time curve from time zero to 12 h (AUC12) and dose-normalized AUC12 (AUC*) were determined using a statistical model that incorporated gastrointestinal AE and clinical covariates.

RESULTS

Males had more rapid apparent MPA clearance (CMs 13.8 ± 6.27 L/h vs. AAMs 10.2 ± 3.73 L/h) than females (CFs 8.70 ± 3.33 L/h and AAFs 9.71 ± 3.94 L/h; p = 0.014) with a race-sex interaction (p = 0.043). Sex differences were observed in MPA clearance/BMI (p = 0.033) and AUC* (p = 0.033). MPA AUC12 was greater than 60 mg·h/L in 57 % of renal transplant recipients (RTR) with 71 % of patients demonstrating gastrointestinal AEs and a higher score noted in females. In all patients, females exhibited 1.40-fold increased gastrointestinal AE scores compared with males (p = 0.024). Race (p = 0.044) and sex (p = 0.005) differences were evident with greater MPAG AUC12 in AAFs and CFs.

CONCLUSION

Sex and race differences were evident, with females having slower MPA clearance, higher MPAG AUC12, and more severe gastrointestinal AEs. These findings suggest sex and race should be considered during MPA immunosuppression.

High interpatient variability in response to mycophenolic acid maintenance therapy in patients with ANCA-associated vasculitis

BACKGROUND

Mycophenolic acid (MPA) is used in the maintenance therapy of antineutrophil cytoplasm antibody-associated systemic vasculitis (AASV). MPA exerts its immunosuppression by inhibiting inosine 5'-monophosphate dehydrogenase (IMPDH), depleting activated lymphocytes of guanine nucleotides and retarding their proliferation. The purpose of our study was to examine the correlation between clinical outcome and pharmacokinetic-pharmacodynamic (PD) relationships of MPA in patients with AASV.

METHODS

We studied 358 Caucasian control patients without any MPA therapy to examine basal IMPDH activity. Thirty Caucasian patients with AASV under maintenance therapy with mycophenolate mofetil (MMF) underwent therapeutic drug monitoring.

RESULTS

We observed a high interindividual variability with regard to basal IMPDH activity in patients without any MPA treatment (0.8-35 nmol/mg protein/h). Patients were followed for a mean (±SD) period of 22 ± 8 months. During the observation period, seven patients had a relapse with an elevated Birmingham Vasculitis Activity Score of 9.2 ± 6. The basal IMPDH activity (Abasal) in patients who subsequently relapsed was raised at baseline, before receiving their first dose of MMF, and further increased at the time of relapse, when compared with stable patients. Patients with a relapse during the maintenance therapy had significantly higher levels of IMPDH activity [IMPDH enzyme activity curve (AEC) (0-12)] than stable patients (P = 0.001), indicating inadequate IMPDH suppression. MPA-AUC (0-12) was significantly decreased in relapse patients, in contrast to stable patients (P < 0.05).

CONCLUSIONS

Due to the highly variable response to maintenance therapy with MPA, PD drug monitoring is a new tool for detecting inadequate immunosuppression in AASV patients.

Fungal Metabolites as Pharmaceuticals

Natural products, their derivatives or compounds based on natural product leads constitute ~50 % of clinically used pharmaceuticals. This review highlights pharmaceuticals currently used in Australia and New Zealand that have their origins in fungal metabolites, discussing the natural products chemistry and medicinal chemistry leading to their application as pharmaceuticals.

The role of mycophenolate mofetil in kidney transplantation revisited

Since its regulatory approval in 1995, mycophenolate mofetil (MMF) has largely replaced azathioprine (AZA) as the anti-metabolite immunosuppressive of choice in kidney transplantation. While the initial industry-sponsored clinical trials suggested strong reductions in the incidence of acute rejection in the first six months post transplantation, long-term follow-up studies have failed to demonstrate a similar degree of benefit in overall graft and patient survival. In addition, several subsequent studies have raised questions on the potential attenuating effects of calcineurin inhibitor choice on MMF efficacy when compared to AZA. This review will revisit the question of whether the available evidence continues to support the superiority of MMF over AZA in kidney transplantation outcomes while comprehensively reviewing the available evidence from clinical trial data, systematic reviews, and registry studies.

Does reduction in mycophenolic acid dose compromise efficacy regardless of tacrolimus exposure level? An analysis of prospective data from the Mycophenolic Renal Transplant (MORE) Registry

Prospective data are lacking concerning the effect of reduced mycophenolic acid (MPA) dosing on efficacy and the influence of concomitant tacrolimus exposure. The Mycophenolic Renal Transplant (MORE) Registry is a prospective, observational study of de novo kidney transplant patients receiving MPA therapy under routine management. The effect of MPA dose reduction, interruption, or discontinuation (dose changes) was assessed in 870 tacrolimus-treated patients: 375 (43.1%) reduced tacrolimus (≤7 ng/mL at baseline) and 495 (56.9%) standard tacrolimus (>7 ng/mL); enteric-coated mycophenolate sodium 589 (67.7%) and mycophenolate mofetil 281 (32.3%). During baseline to month 1, months 1–3, months 3–6, and months 6–12, 9.3% (78/838), 16.6% (132/794), 20.7% (145/701), and 13.1% (70/535) patients, respectively, required MPA dose changes. These patients experienced an increased risk of biopsy-proven acute rejection at one yr with tacrolimus exposure either included in the model (hazard ratio [HR] 2.60, 95% CI 1.28–5.29, p = 0.008) or excluded (HR 2.58, 95% CI 1.28–5.23, p = 0.008). MPA dose changes were significantly associated with one yr graft failure when tacrolimus exposure was included (HR 2.23; 95% CI 1.01–4.89, p = 0.047) but not when tacrolimus exposure was excluded (HR 2.16; 95% CI 0.99–4.79; p = 0.054). These results suggest that reducing or discontinuing MPA can adversely affect graft outcomes regardless of tacrolimus trough levels.

Optimization of the dosing regimen of mycophenolate mofetil in pediatric liver transplant recipients

Mycophenolate mofetil (MMF) is now commonly used in pediatric liver transplant recipients, but no clear recommendations about the dosing regimen have been made for this population. The aim of this study was to determine the MMF dosage required for pediatric liver transplant recipients to achieve an area under the plasma concentration-time curve from 0 to 12 hours (AUC(0-12) ) for mycophenolic acid (MPA) greater than 30 mg hour/L. A pharmacokinetic study of 15 children (median age = 8.3 years, range = 1.1-15.2 years) was performed at a median of 11.0 months (range = 0.5-88.0 months) after liver transplantation. MMF was initially introduced at a median starting dose of 300 mg/m(2) twice a day (range = 186-554 mg/m(2) twice a day). Thirteen of the 15 patients had an MPA AUC(0-12) value less than 30 mg hour/L. The MMF dosage had to be increased in all patients except 1. The MMF dosage required to reach an MPA AUC(0-12) value greater than the defined target of 30 mg hour/L ranged from 371 to 1014 mg/m(2) /day. For 2 patients who received rifampin in addition to MMF, the MPA AUC(0-12) value remained low despite a 2-fold increase in the MMF dosage. In conclusion, an initial MMF dose of 600 mg/m(2) twice a day led to MPA AUC(0-12) values greater than the 30 mg hour/L threshold except when rifampin was coadministered. Because of the important interindividual variability of MPA pharmacokinetics, therapeutic drug monitoring is recommended for optimizing the daily MMF dosage. Furthermore, these results suggest that the coadministration of MPA with rifampin should be avoided.

Nonlinear relationship between mycophenolate mofetil dose and mycophenolic acid exposure: implications for therapeutic drug monitoring

BACKGROUND AND OBJECTIVES

Mycophenolate mofetil (MMF) is an immunosuppressive drug used in renal transplant patients. Upon oral administration it is hydrolyzed to the active agent mycophenolic acid (MPA). In renal transplant recipients, MMF therapy is optimal when the area under the curve of MPA is 30 to 60 mg·h/L. When MMF doses are adjusted, a linear relationship between dose and MPA exposure is assumed. In this study, the linearity of MMF pharmacokinetics was investigated.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

MPA concentration-time profiles from renal transplant recipients cotreated with cyclosporine (n = 140) or tacrolimus (n = 101) were analyzed retrospectively using nonlinear mixed-effects modeling. The correlation between the MMF dose and the pharmacokinetics parameters was evaluated.

RESULTS

In the developed population pharmacokinetics model MPA clearance and the central volume of distribution were correlated with cyclosporine coadministration and time posttransplantation. The pharmacokinetics of MPA were not linear. Bioavailability decreased with increasing MMF doses. Compared with an MMF dose of 1000 mg (=100%), relative bioavailability was 123%, 111%, 94%, and 90% in patients receiving MMF doses of 250, 500, 1500, and 2000 mg in combination with cyclosporine (P < 0.001); respective values in tacrolimus-cotreated patients were 176%, 133%, 85%, and 76% (P < 0.001). Because of the decreasing relative bioavailability, MPA exposure will increase less than proportionally with increasing MMF doses.

CONCLUSIONS

MMF exhibits nonlinear pharmacokinetics. This should be taken into account when performing therapeutic drug monitoring.

Improved assay for the nonradioactive determination of inosine 5'-monophosphate dehydrogenase activity in peripheral blood mononuclear cells

Mycophenolic acid (MPA) inhibits the enzyme inosine 5'-monophosphate dehydrogenase (IMPDH). Thus, the measurement of IMPDH activity could serve as a specific pharmacodynamic (PD) tool for monitoring MPA therapy. At present, however, monitoring of pharmacokinetic parameters is preferred over that of PD parameters because, in general, PD assays are labor-intensive and poorly reproducible. Currently, cell count or protein concentration is widely accepted as methods to normalize enzyme activity. In the present study, we have attempted to further improve a method for the determination of IMPDH activity to increase the robustness and reproducibility of the IMPDH activity assay itself, without making the assay more labor-intensive. Therefore, several aspects of the IMPDH method were investigated regarding their influence on the reproducibility and also modified to increase the feasibility and consistency of the assay. The isolation of peripheral blood mononuclear cells (PBMCs) of whole blood samples was found to be the most variable step. Normalization on cell count is labor-intensive and at the same time has a poor reproducibility. Determination of the protein content in cell extracts is impaired by contamination with extracellular proteins and non-PBMCs. Alternatively, the intracellular substance adenosine monophosphate (AMP) was investigated to normalize the newly generated xanthosine monophosphate. Among various subject groups, no significant differences in mean AMP concentration were found. To simplify the procedure, PBMCs were diluted to a fixed volume after isolation from sample of whole blood, and the IMPDH activity was normalized to the AMP concentration quantified in the same high-performance liquid chromatography run as xanthosine monophosphate was quantified. The within-run and total imprecision (coefficient of variation) ranged from 4.2% to 10.6% and from 6.6% to 11.9%, respectively. In conclusion, the modified method described here for the measurement of IMPDH activity can be used reliably in multicenter trials and in longitudinal studies to evaluate the additional value of any PD monitoring among a diversity of patients treated with MPA.

Optimization of immunosuppression by switching from azathioprine to enteric-coated mycophenolate sodium in stable kidney transplant patients

The aim of our retrospective, observational, single center study was to analyze renal function changes among stable kidney transplant patients treated with a calcineurin inhibitor (CNI) + azathioprine (AZA), in whom immunosuppression was optimized by a switch from AZA to enteric-coated mycophenolate sodium (EC-MPS) with a view to protecting long-term renal function. Between April 2005 and June 2008, 36 renal transplant patients on previous treatment with a CNI and AZA for a period of 86.94 +/- 66.9 months were switched to EC-MPS. After the change, there were no cases of acute rejection episodes. Six patients (16.6%) developed gastrointestinal secondary effects and 5 had to discontinue EC-MPS treatment: 4 due to severe diarrhea 1 due to thrombocytopenia. Among the remaining patients, it was possible to gradually increase the EC-MPS dose (starting at 376 +/- 122 mg/d vs current at 533.5 +/- 210 mg/d; P < .002), maintaining through levels at 2.1 +/- 1.9 ng/mL. Although 11 patients (30.5%) displayed chronic allograft nephropathy upon the preconversion biopsy, at a follow-up of 29.2 +/- 9.4 months they showed significantly improved renal function (Modification of Diet in Renal Disease [MDRD4] at change 49.5 +/- 19.8 mL/min/1.73 m(2) vs current MDRD4 55.6 +/- 23.4 mL/min/1.73 m(2); P = .02), with no increase in proteinuria (proteinuria at change 0.4 +/- 0.4 g/d vs current proteinuria 0.4 +/- 0.5 g/d; P = NS). This improvement was evident without changes in CNI levels: cyclosporine at change 133.1 +/- 30.2 ng/mL vs current 122 +/- 28 ng/mL (P = NS) and tacrolimus at change 7.7 +/- 2.2 ng/mL vs current 8.2 +/- 2.4 ng/mL (P = NS). In conclusion, conversion from AZA to EC-MPA to optimize immunosuppression seemed to be safe, with no complications in 85% of cases, as well as effective, achieving improved long-term renal function protection. These results suggested a greater protective immunological effect by switching from AZA to EC-MPA.

Impact of rituximab-associated B-cell defects on West Nile virus meningoencephalitis in solid organ transplant recipients

Evidence suggests that West Nile virus (WNV) neuroinvasive disease occurs more frequently in both solid organ and human stem cell transplant recipients. The effect of concomitant anti-B-cell therapy with rituximab, a CD20(+) monoclonal antibody, on WNV infection in this population, however, has not been reported. We describe a case of a patient with alpha-1-antitrypsin deficiency who underwent single lung transplantation in 2005 and was maintained on tacrolimus, cytoxan and prednisone. More recently, she had received two courses of rituximab for recurrent A2-A3 grade rejection with concomitant capillaritis and presented six months later with rapid, fulminant WNV meningoencephalitis. Her diagnosis was made by cerebrospinal fluid (CSF) PCR but serum and CSF WNV IgM and IgG remained negative. She received WNV-specific hyperimmune globulin (Omr-Ig-Am) through a compassionate protocol. She experienced a rapidly progressive and devastating neurological course despite treatment and died three wk after onset of her symptoms. Autopsy revealed extensive meningoencephalomyelitis.

Mycophenolate mofetil: safety and efficacy in the prophylaxis of acute kidney transplantation rejection

Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), is an inhibitor of inosine monophosphate dehydrogenase (IMPDH). It preferentially inhibits denovo pathway of guanosine nucleotide synthesis in T and B-lymphocytes and prevents their proliferation, thereby suppresses both cell mediated and humoral immune responses. Clinical trials in kidney transplant recipients have shown the efficacy of MMF in reducing the incidence and severity of acute rejection episodes. It also improves long term graft function as well as graft and patient survival in kidney transplant recipients. MMF is useful as a component of toxicity sparing regimens to reduce or avoid exposure of steroids or calcineurin inhibitor (CNI). Enteric-coated mycophenolate sodium (EC-MPS) can be used as an alternative immunosuppressive agent in kidney transplant recipients with efficacy and safety profile similar to MMF.

Expression of inosine monophosphate dehydrogenase type I and type II after mycophenolate mofetil treatment: a 2-year follow-up in kidney transplantation

The objective of the study was to evaluate the effect of mycophenolate mofetil (MMF) on the regulation of inosine monophosphate dehydrogenase (IMPDH) during the first 2 years after renal transplantation. Twelve patients were enrolled, and 10-h time-course evaluations of the effects of MMF were regularly performed during the study. IMPDH activity and gene expression were measured in whole blood and in mononuclear cells, respectively. Type I IMPDH (IMPDH-I) mRNA was increased during the first 3 months following transplantation and reached its maximal level during acute rejection episodes, whereas type II IMPDH mRNA was stable. Furthermore, although no alteration in the predose samples was observed, patients with prolonged MMF treatment exhibited an increase in the induction potency of both IMPDH activity and gene expression. In vitro experiments confirmed that IMPDH-I is inducible, but preferentially in monocytes than in lymphocytes. This finding suggests that the measurement of IMPDH mRNAs may provide reliable information to predict acute rejection.

Pharmacokinetics of mycophenolic acid in liver transplant patients after intravenous and oral administration of mycophenolate mofetil

The bioavailability of mycophenolic acid (MPA) after oral administration of mycophenolate mofetil (MMF) has been reported to be more than 90% in healthy volunteers, and in kidney and thoracic organ transplant patients. Such information is limited in liver transplant (LTx) patients. The present study compares the pharmacokinetics of MPA after intravenous (IV) and oral administrations of MMF in LTx recipients. Pharmacokinetic parameters were calculated using WinNonlin software. A total of 12 deceased donor LTx patients initially received IV MMF and were switched to oral MMF after 2-7 days (mean, 3.3 +/- 1.7) when oral feeds were started. Multiple blood samples were drawn immediately prior to and after IV or oral MMF and the plasma concentration of MPA was measured. The mean peak plasma concentrations and the area under the plasma concentration vs. time curve (AUC) were significantly higher after IV MMF compared to oral MMF (peak plasma concentrations of 10.7 +/- 2.1 microg/mL for IV vs. 4.5 +/- 2.8 microg/mL for oral; P = 0.0001; and AUC of 28.9 +/- 7.1 microg . hr/mL for IV vs. 12.8 +/- 4.2 microg . hr/mL for oral; P = 0.0001). The oral bioavailability of MPA was 48.5 +/- 18.7%. The systemic clearance, half-life, and steady state volume of distribution of MPA were 26.9 +/- 6 L/hour, 5.5 hours, and 85 liters, respectively. The terminal disposition half-life was not significantly different between the 2 routes of administration. In conclusion, during the early postoperative period, LTx recipients have MPA exposure with oral MMF of less than half that of IV MMF. Use of IV MMF immediately post-LTx may provide an immunological advantage.

Clinical pharmacokinetics and pharmacodynamics of mycophenolate in solid organ transplant recipients

This review aims to provide an extensive overview of the literature on the clinical pharmacokinetics of mycophenolate in solid organ transplantation and a briefer summary of current pharmacodynamic information. Strategies are suggested for further optimisation of mycophenolate therapy and areas where additional research is warranted are highlighted. Mycophenolate has gained widespread acceptance as the antimetabolite immunosuppressant of choice in organ transplant regimens. Mycophenolic acid (MPA) is the active drug moiety. Currently, two mycophenolate compounds are available, mycophenolate mofetil and enteric-coated (EC) mycophenolate sodium. MPA is a potent, selective and reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH), leading to eventual arrest of T- and B-lymphocyte proliferation. Mycophenolate mofetil and EC-mycophenolate sodium are essentially completely hydrolysed to MPA by esterases in the gut wall, blood, liver and tissue. Oral bioavailability of MPA, subsequent to mycophenolate mofetil administration, ranges from 80.7% to 94%. EC-mycophenolate sodium has an absolute bioavailability of MPA of approximately 72%. MPA binds 97-99% to serum albumin in patients with normal renal and liver function. It is metabolised in the liver, gastrointestinal tract and kidney by uridine diphosphate gluconosyltransferases (UGTs). 7-O-MPA-glucuronide (MPAG) is the major metabolite of MPA. MPAG is usually present in the plasma at 20- to 100-fold higher concentrations than MPA, but it is not pharmacologically active. At least three minor metabolites are also formed, of which an acyl-glucuronide has pharmacological potency comparable to MPA. MPAG is excreted into the urine via active tubular secretion and into the bile by multi-drug resistance protein 2 (MRP-2). MPAG is de-conjugated back to MPA by gut bacteria and then reabsorbed in the colon. Mycophenolate mofetil and EC-mycophenolate sodium display linear pharmacokinetics. Following mycophenolate mofetil administration, MPA maximum concentration usually occurs in 1-2 hours. EC-mycophenolate sodium exhibits a median lag time in absorption of MPA from 0.25 to 1.25 hours. A secondary peak in the concentration-time profile of MPA, due to enterohepatic recirculation, often appears 6-12 hours after dosing. This contributes approximately 40% to the area under the plasma concentration-time curve (AUC). The mean elimination half-life of MPA ranges from 9 to 17 hours. MPA displays large between- and within-subject pharmacokinetic variability. Dose-normalised MPA AUC can vary more than 10-fold. Total MPA concentrations should be interpreted with caution in patients with severe renal impairment, liver disease and hypoalbuminaemia. In such individuals, MPA and MPAG plasma protein binding may be altered, changing the fraction of free MPA available. Apparent oral clearance (CL/F) of total MPA appears to increase in proportion to the increased free fraction, with a reduction in total MPA AUC. However, there may be little change in the MPA free concentration. Ciclosporin inhibits biliary excretion of MPAG by MRP-2, reducing enterohepatic recirculation of MPA. Exposure to MPA when mycophenolate mofetil is given in combination with ciclosporin is approximately 30-40% lower than when given alone or with tacrolimus or sirolimus. High dosages of corticosteroids may induce expression of UGT, reducing exposure to MPA. Other co-medications can interfere with the absorption, enterohepatic recycling and metabolism of mycophenolate. Most pharmacokinetic investigations of MPA have involved mycophenolate mofetil rather than EC-mycophenolate sodium therapy. In population pharmacokinetic studies, MPA CL/F in adults ranges from 14.1 to 34.9 L/h (ciclosporin co-therapy) and from 11.9 to 25.4 L/h (tacrolimus co-therapy). Patient bodyweight, serum albumin concentration and immunosuppressant co-therapy have a significant influence on CL/F. The majority of pharmacodynamic data on MPA have been obtained in patients receiving mycophenolate mofetil therapy in the first year after kidney transplantation. Low MPA AUC is associated with increased incidence of biopsy-proven acute rejection. Gastrointestinal adverse events may be dose related. Leukopenia and anaemia have been associated with high MPA AUC, trough concentration and metabolite concentrations in some, but not all, studies. High free MPA exposure has been identified as a risk factor for leukopenia in some investigations. Targeting a total MPA AUC from 0 to 12 hours (AUC12) of 30-60 mg.hr/L is likely to minimise the risk of acute rejection and may reduce toxicity. IMPDH monitoring is in the early experimental stage. Individualisation of mycophenolate therapy should lead to improved patient outcomes. MPA AUC12 appears to be the most useful exposure measure for such individualisation. Limited sampling strategies and Bayesian forecasting are practical means of estimating MPA AUC12 without full concentration-time profiling. Target concentration intervention may be particularly useful in the first few months post-transplant and prior to major changes in anti-rejection therapy. In patients with impaired renal or hepatic function or hypoalbuminaemia, free drug measurement could be valuable in further interpretation of MPA exposure.

Bullous pemphigoid treatment review

Bullous pemphigoid is an autoimmune skin blistering disorder that can present with several different degrees of severity. The treatment modality employed by the treating physician varies from localised topical therapy and anti-inflammatory treatments with minimal side effects to immunosuppressive agents associated with significant adverse reactions. Deciding which therapy to use with a particular patient can be a challenge, and the treating physician must take into account the severity of disease, the overall medical condition of the patient and potential drug interactions. This article provides a comprehensive review of current medical therapies, as well as an overall approach to the patient with bullous pemphigoid.

Clinical pharmacokinetics of mycophenolate mofetil in Japanese renal transplant recipients: A retrospective cohort study in a single center

Mycophenolate mofetil (MMF), a morpholinoethyl ester of mycophenolic acid (MPA), is currently widely used in organ transplantation as an immunosuppressant. The usefulness of therapeutic drug monitoring (TDM) of MPA after MMF dosing is not clear in Japanese renal transplant patients. In this study, to obtain more information for TDM of MPA, the association between MPA pharmacokinetic characteristics and the development of the side effects, and the effect of other concomitant immunosupressants such as cyclospoline A (CyA), tacrolimus (FK) and predonisolone (PSL) on MPA pharmacokinetics were investigated in detail. Moreover, the effects of enterohepatic recirculation (EHRA) on pharmacokinetic characteristics of MPA and the development of the side effects were also investigated. AUC(MPA)(0-9) with FK medication was 1.3-1.9 times higher than that with CyA medication, and the contribution to the plasma level of MPA of FK might be smaller than that of CyA, because EHRA inhibition by CyA was 2 times greater than that by FK. AUC(MPA)(0-9) was not influenced by PSL. The association between AUC(MPA)(0-9) and the development of the side effects was not observed; however, the development of side effects (leukopenia and diarrhea) in the EHRA group was 2 times higher than that in the non-EHRA group. These results suggested that TDM for MPA after MMF dosing was desirable in Japanease transplant patients. However, though not frequently, AUC obtained by multiple blood sampling after MMF dosing was needed. In addition, EHRA has led to increasing interest in MMF medication.

Current and evolving immunosuppressive regimens in kidney transplantation

The advent of novel immunosuppressive agents with increased potency now offers multiple treatment options for transplant physicians. However, variable efficacy, drug-drug interactions, and adverse effects associated with long-term immunosuppression continue to complicate the clinical management of kidney transplant recipients. Currently, investigators are challenged to develop regimens that take into account not only efficacy, but also dosing, monitoring, safety, and patient quality of life. Recent research has focused on evaluating new combinations of approved agents that seek to improve outcomes by improving control of immunologic events with fewer complications. This article reviews current practice and recent studies to give all health care providers who manage kidney transplant recipients a better understanding of current regimens and general trends in immunosuppressive therapy.

The Rationale for and Limitations of Therapeutic Drug Monitoring for Mycophenolate Mofetil in Transplantation

The addition of mycophenolate mofetil (MMF) to calcineurin inhibitor-based regimens reduces the incidence of acute rejection after kidney transplantation. The interpatient variability, changes over time of pharmacokinetic parameters, and the potential for drug interactions make the systemic exposure of mycophenolic acid (MPA) unpredictable at a fixed-dose regimen. An increase in plasma concentration of MPA significantly correlates with a decreased likelihood of an acute rejection after kidney or heart transplantation; therefore, a strategy of therapeutic drug monitoring for MMF therapy could improve outcome. Two large randomized, multicenter, prospective trials investigating the added value of therapeutic drug monitoring for MPA, by comparing fixed-dose treatment with concentration-controlled MMF treatment in kidney transplant recipients, are currently ongoing. More data are needed to fully establish the meaning of the reported prognostic value of preoperative inosine monophosphate dehydrogenase (IMPDH) activity, and longitudinal studies monitoring IMPDH activity after transplantation are eagerly awaited.

The Impact of Mycophenolate Mofetil on Long-Term Outcomes in Kidney Transplantation

Mycophenolate mofetil (MMF) has been used in kidney and pancreas transplantation for almost 10 years. In the pivotal phase III trials, MMF use was accompanied by a dramatic reduction of rejection rates in kidney transplantation; however, the impact on graft and patient was undetermined. Analyses of the United States Renal Data System and the Scientific Registry of Transplant Recipients databases later provided a valuable measure of the impact of MMF in improving outcomes. In this review, we provide a synopsis of the prospective studies, including but not limited to the pivotal MMF approval trials, and analyses of the national transplant registries relevant to the long-term impact of MMF in kidney transplantation. Indeed, a substantial body of evidence has shown MMF treatment improves patient survival, graft survival, and death-censored graft survival in kidney transplantation. The beneficial effects of MMF have been particularly notable in high-risk recipients such as African Americans. In coming years, these benefits will require reevaluation in the context of the growing use of novel protocols combining MMF with tacrolimus or sirolimus.

Mycophenolate mofetil (Cellcept)

Mycophenolate mofetil (MMF) is a new immunosuppressive drug designed to inhibit inosine monophosphate dehydrogenase (IMPDH). IMPDH is a key enzyme in the purine synthesis pathway of lymphocytes. IMPDH is crucially important for the proliferative responses of human T- and B-lymphocytes. Therefore, inhibition of IMPDH leads to selective lymphocyte suppression. Following successful testing in different in vitro and animal models, MMF entered clinical trials, where it has been used in combination with cyclosporin and steroids. MMF has rapid and complete absorption following oral administration. Pilot studies suggested a significant reduction in the incidence of rejection at doses of 1-3 g/day. These data led to the initiation of 3 pivotal trials, in which MMF was compared against different standard immunosuppressive protocols. Nearly 1500 patients were enrolled in these 3 randomised, double-blind, multicentre studies of the addition of MMF to standard immunosuppressive protocols for the prevention of acute renal allograft rejection. After six months, the rate of biopsy-proven rejection was significantly reduced. The adverse event profile resembles that of triple therapy with azathioprine: primarily involving the gastrointestinal (GI) tract, the haematopoietic system and the occurrence of opportunistic infections. MMF affords improved immunosuppressive therapy following renal, and probably other solid organ, transplantation. It is licensed for the prevention of acute renal allograft rejection in most countries around the world.