Early adequate mycophenolic acid exposure is associated with less rejection in kidney transplantation

Synthesis and Biological Evaluation of Novel Anti-leukemia Proteolysis-Targeting Chimeras in Degradating Inosine Monophosphate Dehydrogenase

Background

Proteolysis-targeting chimera (PROTAC) is a bifunctional molecule comprising a ligand to recognize the targeted protein to be degraded.

Objectives

To use the advantages of the PROTAC technique, we have synthesized novel compounds to degrade inosine monophosphate dehydrogenase (IMPDH) by the proteasome system.

Methods

We describe the synthesis of new PROTACs based on a combination of mycophenolic acid (MPA) as the potent IMPDH inhibitor and pomalidomide as a ligand of E3 ubiquitin ligase via linkers formed from Cu(I)-catalyzed cycloaddition reaction.

Results

All synthesized compounds were investigated against Jurkat cells as acute T-cell leukemia and were potent apoptosis inducers at 50 nM.

Conclusion

The effect of compound 2 in 0.05 μM on IMPDH degradation can be almost prevented by competition with bortezomib as the proteasome inhibitor at 0.1 and 0.5 μM.

The combination of exposure to Tacrolimus, mycophenolic acid, Inosine 5'-Monophosphate Dehydrogenase activity and inhibition in the first week define early histological outcomes in renal transplant recipients

Therapeutic drug monitoring is routine for Tacrolimus, while levels are not routinely monitored for mycophenolic acid (MPA). This study investigated the effect of early post-transplant pharmacokinetics (PK) of MPA and Tacrolimus along with the pharmacodynamics (PD) of MPA on biopsy-proven acute rejection (BPAR) after renal transplantation. A prospective PK/PD study with limited sampling (three blood samples) was conducted in renal transplant recipients on week 1, around Day 6 (n = 42) and at the 3rd-month biopsy on Day 90 (n = 23). The partial exposures (area under curve [AUC]_0-3.5 h ) of both MPA and Tacrolimus obtained during the first week were more predictive of rejection (combined clinical and subclinical rejection) by Day 90 than their trough concentrations or Day 90 exposures. Patients with rejection had significantly worse renal function (eGFR) and a comparatively lower exposure to MPA during the first post-transplant week. The lower MPA exposure was also associated with sub-optimal inosine monophosphate dehydrogenase (IMPDH) inhibition in patients with rejection, and the probability of rejection was higher in the presence of an increased pre-transplant IMPDH activity. A composite of parameters, including MPA exposure and IMPDH activity was found to predict acute rejection and may be beneficial along with tacrolimus monitoring early after renal transplantation.

Population Pharmacokinetics of Enteric-Coated Mycophenolate Sodium in Children after Renal Transplantation and Initial Dosage Recommendation Based on Body Surface Area

Objective

Enteric-coated mycophenolate sodium (EC-MPS) is widely used in renal transplant recipients. There is a lack of study on the pharmacokinetics of this drug in children. This study is aimed at developing a population pharmacokinetic model of mycophenolic acid in children who were treated with EC-MPS after renal transplantation and to recommend initial dosage.

Methods

Pediatric patients who had undergone renal transplantation and received EC-MPS were included. Data on demographic characteristics, biochemical tests, blood routine examinations, mycophenolic acid plasma concentrations, dosing amount and frequency of EC-MPS, and coadministered medications were retrospective collected from June 2018 to August 2019. Nonlinear mixed effect modeling methods were adopted to develop a population pharmacokinetic model with the data above. Additional data from September 2019 to July 2020 were used to validate the model. Simulations under different dosage regimen were conducted to evaluate the percentage of target attainment (PTA, AUC_0-12h 30–60 mg·h/L).

Results

A total of 96 pediatric patients aged at 13.3 (range 4.3–18.0) years were included in the modeling group. Data from 32 patients aged at 13.0 (range 3.6–18.3) years were used to validate the model. A one-compartment model with a double extravascular absorption was developed. Body surface area (BSA) was added as a covariate. Simulations showed that for different dosing regimens, the highest percentage of target attainment is around 50%. The best dosing regimen is 180 mg every 48 hours for patients with BSA of 0.22–0.46 m², 180 mg every 24 hours with BSA of 0.47–0.67 m², 180 mg every 24 hours with BSA of 0.68–0.96 m², 360 mg every 24 hours with BSA of 0.97–1.18 m², 540 mg every 24 hours with BSA of 1.19–1.58 m², and 360 mg every 12 hours with BSA of 1.59–2.03 m².

Conclusion

BSA could affect the area under curve of mycophenolic acid with the administration of EC-MPS. Considering the inflexibility of the dosage form, future development of smaller amount per tablet suitable for younger children with BSA < 1.19 m² is warranted.

Transplant Prognosis in Kidney Transplant Recipients with Diabetes under Mycophenolic Acid-Focused Therapeutic Drug Monitoring

Mycophenolate mofetil is a key immunosuppressant that is metabolized into mycophenolic acid (MPA). The prognostic impact of MPA-focused therapeutic drug monitoring on allograft prognosis has not been determined in kidney transplant recipients with diabetes. In this study, we assessed the pharmacokinetics of MPA and allograft prognosis in recipients with diabetes. This study retrospectively analyzed 64 adult kidney transplant recipients. MPA blood concentration data (e.g., the time to the maximum concentration (Tmax), and the area under the concentration–time curve from 0 to 12 h (AUC_0–12)) were collected at 3 weeks and 3 months after kidney transplantation. Of the 64 recipients, 15 had pre-existing diabetes. At 3 months after kidney transplantation, the Tmax of MPA was significantly longer in recipients with diabetes (mean (standard deviation): 2.8 (2.1) h) than in recipients without diabetes (1.9 (1.1) h, p = 0.02). However, the allograft estimated glomerular filtration rate and acute rejection rate, including borderline change, did not differ according to the diabetes status in patients with adjusted AUC_0–12 of MPA within the target range. In conclusion, a longer Tmax of MPA was observed in recipients with diabetes; however, acceptable allograft prognosis was observed in kidney transplant recipients with diabetes and a sufficient AUC_0–12 of MPA.

The Impact of Genetic Polymorphisms on the Pharmacokinetics and Pharmacodynamics of Mycophenolic Acid: Systematic Review and Meta-analysis

BACKGROUND

Mycophenolic acid (MPA) is among the most commonly prescribed medications for immunosuppression following organ transplantation. Highly variable MPA exposure and drug response are observed among individuals receiving the same dosage of the drug. Identification of candidate genes whose polymorphisms could be used to predict MPA exposure and clinical outcome is of clinical value.

OBJECTIVES

This study aimed to determine the impact of genetic polymorphisms on the pharmacokinetics and pharmacodynamics of MPA in humans by means of a systematic review and meta-analysis.

METHODS

A systematic search was conducted on PubMed, EMBASE, Web of Sciences, Scopus, and the Cochrane Library databases. A meta-analysis was conducted to determine any associations between genetic polymorphisms and pharmacokinetic or pharmacodynamic parameters of MPA. Pooled-effect estimates were calculated by means of the random-effects model.

RESULTS

A total of 37 studies involving 3844 individuals were included in the meta-analysis. Heterozygous carriers of the UGT1A9 -275T>A polymorphism were observed to have a significantly lower MPA exposure than wild-type individuals. Four single nucleotide polymorphisms (SNPs), namely UGT1A9 -2152C>T, UGT1A8 518C>G, UGT2B7 211G>T, and SLCO1B1 521T>C, were also significantly associated with altered MPA pharmacokinetics. However, none of the investigated SNPs, including SNPs in the IMPDH gene, were found to be associated with the clinical efficacy of MPA. The only SNP that was associated with adverse outcomes was SLCO1B3 344T>G.

CONCLUSIONS

The present systematic review and meta-analysis identified six SNPs that were significantly associated with pharmacokinetic variability or adverse effects of MPA. Our findings represent the basis for future research and clinical implications with regard to the role of pharmacogenetics in MPA pharmacokinetics and drug response.

Pharmacokinetic evaluation of MFF in combinations with tacrolimus and cyclosporine. Findings of C0 and AUC

We hypothesized that area under the concentration time curve (AUC(0-12)) is more accurate pharmacokinetic predictor vs trough level of mycophenolic acid (C0).Study was performed at the University Hospital of Limoges (France) and included 238 renal recipients aged 22 to 82 years. Risk of nephropathy was evaluated by analyzing data of protocol biopsies according to the Banff 97 classification.Assessment of immunosuppressants' exposures was based on the calculation of the mean of AUC(0-12). The AUC(0-12) was estimated using a Bayesian estimator and a 3-point limited sampling strategy. Cyclosporine and tacrolimus analyses were performed using liquid chromatography-mass spectrometry method. The measurement of total mycophenolic acid was performed using a validated high-performance liquid chromatography method with ultraviolet detection. IBM SPSS 20.0 was used for statistical analysis.The most accurate dosing of mycophenolate mofetil (MMF) was observed in patients receiving MMF with tacrolimus, 70.6% of patients' AUC(0-12) exposures were within the therapeutic range. The highest rates of low dosing were observed in patients receiving MMF with cyclosporine, 30.9% of patients had AUC(0-12) exposures below the therapeutic range. The assessment of AUC(0-12) revealed 38% of chronic nephropathy cases, while C0 enables to identify only 20% of chronic nephropathy cases.Probability test results showed that more likely AUC(0-12) and C0 will be maintained within the therapeutic width if patients receive MMF with tacrolimus vs MMF with cyclosporine: 0.6320 vs 0.6410 for AUC(0-12) determination and 0.8415 vs 0.4827 for C0 determination.Combination of MMF with tacrolimus is dosed more precisely vs dosing of MMF with cyclosporine. 72 (70.6%) patients AUC(0-12) and 79 (77.5%) patients C0 out of 102 patients were within the therapeutic range. The AUC(0-12) monitoring of mycophenolic acid in patients receiving MMF with tacrolimus or in patients receiving MMF with cyclosporine enabled to identify more overdosing and possible risky cases.Study results show that standard MMF dosing without monitoring and with mycophenolic acid level within the therapeutic width is possible and demonstrates less risky cases in patients receiving MMF with tacrolimus, while patients receiving MMF with cyclosporine should be intensively monitored to achieve the highest safety. However, AUC(0-12) monitoring is advised showing better compliance vs C0 monitoring.

Pharmacodynamic assessment of mycophenolic acid in resting and activated target cell population during the first year after renal transplantation

Aims

To explore the pharmacodynamics of mycophenolic acid (MPA) through inosine monophosphate dehydrogenase (IMPDH) capacity measurement and purine levels in peripheral blood mononuclear cells (PBMC) longitudinally during the first year after renal transplantation (TX).

Methods

PBMC were isolated from renal recipients 0–4 days prior to and 6–9 days, 5–7 weeks and 1 year after TX (before and 1.5 hours after dose). IMPDH capacity and purine (guanine and adenine) levels were measured in stimulated and nonstimulated PBMC.

Results

Twenty‐nine patients completed the follow‐up period, of whom 24 received MPA. In stimulated PBMC, the IMPDH capacity (pmol 10⁻⁶ cells min⁻¹) was median (interquartile range) 127 (95.8–147) before TX and thereafter 44.9 (19.2–93.2) predose and 12.1 (4.64–23.6) 1.5 hours postdose across study days after TX. The corresponding IMPDH capacity in nonstimulated PBMC was 5.71 (3.79–6.93), 3.35 (2.31–5.62) and 2.71 (1.38–4.08), respectively. Predose IMPDH capacity in nonstimulated PBMC increased with time, reaching pre‐TX values at 1 year. In stimulated PBMC, both purines were reduced before (median 39% reduction across days after TX) and after (69% reduction) dose compared to before TX. No alteration in the purine levels was observed in nonstimulated PBMC. Patients needing dose reductions during the first year had lower pre‐dose IMPDH capacity in nonstimulated PBMC (1.87 vs 3.00 pmol 10⁻⁶ cells min⁻¹, P = .049) at 6–9 days.

Conclusion

The inhibitory effect of MPA was stronger in stimulated PBMC. Nonstimulated PBMC became less sensitive to MPA during the first year after TX. Early IMPDH capacity appeared to be predictive of dose reductions.

Optimizing Mycophenolic Acid Exposure in Kidney Transplant Recipients: Time for Target Concentration Intervention

The immunosuppressive agent mycophenolate is used extensively in kidney transplantation, yet dosing strategy applied varies markedly from fixed dosing ("one-dose-fits-all"), to mycophenolic acid (MPA) trough concentration monitoring, to dose optimization to an MPA exposure target (as area under the concentration-time curve [MPA AUC0-12]). This relates in part to inconsistent results in prospective trials of concentration-controlled dosing (CCD). In this review, the totality of evidence supporting mycophenolate CCD is examined: pharmacological characteristics, observational data linking exposure to efficacy and toxicities, and randomized controlled trials of CCD, with attention to dose optimization method and exposure achieved. Fixed dosing of mycophenolate consistently leads to underexposure associated with rejection, as well as overexposure associated with toxicities. When CCD is driven by pharmacokinetic calculation to a target concentration (target concentration intervention), MPA exposure is successfully controlled and clinical benefits are seen. There remains a need for consensus on practical aspects of mycophenolate target concentration intervention in contemporary tacrolimus-containing regimens and future research to define maintenance phase exposure targets. However, given ongoing consequences of both overimmunosuppression and underimmunosuppression in kidney transplantation, impacting short- and long-term outcomes, these should be a priority. The imprecise "one-dose-fits-all" approach should be replaced by the clinically proven MPA target concentration strategy.

Proton pump inhibitors and adverse effects in kidney transplant recipients: A meta-analysis

BACKGROUND

The adverse renal effects of proton pump inhibitors (PPIs) are increasingly recognized in both the general population and patients with chronic kidney disease. Several pharmacokinetic studies have also raised concerns regarding the interaction between PPIs and immunosuppressive drugs in transplant patients. Whether the adverse effects of PPIs have a clinical significance in kidney transplant recipients remains unclear. We performed this meta-analysis to assess the risk of adverse effects in kidney transplant recipients on PPI compared with those without PPI exposure.

AIM

To investigate the risk of acute rejection, graft loss, hypomagnesemia, renal dysfunction, and overall mortality in kidney transplant recipients on PPI compared with those without PPI exposure.

METHODS

A systematic review was conducted in MEDLINE, EMBASE, and Cochrane databases from inception through October 2018 to identify studies that evaluated the adverse effects of PPIs in kidney transplant recipients, including biopsy-proven acute rejection, graft loss, hypomagnesemia, renal function, and overall mortality. Effect estimates from the individual studies were extracted and combined using random-effect, generic inverse variance method of DerSimonian and Laird. The protocol for this meta-analysis is registered with PROSPERO, No. CRD42018115676.

RESULTS

Fourteen observational studies with 6786 kidney transplant recipients were enrolled. No significant association was found between PPI exposure and the risk of biopsy-proven acute rejection at ≥ 1 year [pooled odds ratio (OR), 1.25; 95% confidence interval (CI), 0.82-1.91, I² = 55%], graft loss at 1 year (pooled OR = 1.30, 95%CI: 0.75-2.24, I² = 0%) or 1-year mortality (pooled OR = 1.53, 95%CI: 0.90-2.58, I² = 34%). However, PPI exposure was significantly associated with hypomagnesemia (pooled OR = 1.56, 95%CI: 1.19-2.05, I² = 27%). Funnel plots and Egger regression asymmetry test were performed and showed no publication bias.

CONCLUSION

PPI use was not associated with significant risks of higher acute rejection, graft loss, or 1-year mortality. However, the risk of hypomagnesemia was significantly increased with PPI use. Thus, future studies are needed to assess the impact of PPIs on long-term outcomes.

Effect of Sodium Bicarbonate in Kidney Transplant Recipients With Chronic Metabolic Acidosis

Background

Metabolic acidosis (MA) is a common complication after kidney transplantation and regarded to increase mortality, graft failure, and bone fractures. Here, we conducted a retrospective cohort study to analyze the effect of sodium bicarbonate on those events.

Methods

All kidney transplant recipients of the German health insurance Allgemeine Ortskrankenkasse (AOK) were selected, who received their transplantation between 2007 and 2015. Three groups were formed: (1) control group (no acidosis, n = 3602), (2) acidosis group (encoded acidosis, n = 370), and (3) treatment group (encoded therapy, n = 769). The study endpoints were mortality, death-censored graft failure, and bone fractures.

Results

The prevalence of MA in the first year after transplantation was 46.2%. The 5-year patient and graft survival were 89.8% and 89.3% in the control group, 90% and 90.8% in the acidosis group, and 87.5% and 81.6% in the treatment group, respectively. The rate of bone fractures did not differ between the groups. Neither log-rank tests nor multivariable Cox regression analyses could detect a negative impact of MA on mortality (hazard ratio [HR] 0.94; confidence interval [CI] 0.67-1.30), graft failure (HR1.18; CI 0.82-1.72), or the incidence of bone fractures (HR1.19; CI 0.92-1.55). Treatment with sodium bicarbonate was associated with an increased risk of graft failure (HR1.52; CI 1.03-2.25), whereas mortality (HR0.86; CI 0.59-1.26) and the incidence of bone fractures (HR1.16; CI 0.86-1.56) were not altered.

Conclusions

MA is common after kidney transplantation but not associated with an increased frequency of death, graft failure, or bone fractures. Conversely, sodium bicarbonate therapy increased the incidence of graft failure.

RELATE: Relationship of limited sampling strategy and adverse effects of mycophenolate mofetil in pediatric renal transplant patients

MMF, a prodrug converted to the active form MPA, is an immunosuppressant used to prevent rejection in solid organ transplant recipients. MPA exposure, defined by AUC, can be estimated using limited sampling strategies (LSS). The relationship between MPA AUC and clinical outcomes has not been studied in pediatrics. The objectives were to describe the relationship of MPA AUC (estimated via LSS) with adverse effects and rates of rejection, and to compare clinical outcomes between different MPA monitoring practices. Descriptive statistics were used to summarize demographics, adverse effects, and rejection. Thirty-three patients (91 trough concentrations and 12 LSS sets) aged 2-20 years old were included. The estimated median MPA AUCs (David-Neto and Filler) were higher for those who did not have any adverse effects reported (65.85 and 85.05 mg*h/L, respectively) compared to those who had an adverse effect (60.75 and 54.2 mg*h/L, respectively). The median trough concentration when no adverse effects occurred was comparable to when adverse effects occurred. The median MPA AUC at which rejection occurred was lower than in those without rejection. The median trough concentration at which rejection occurred was higher than those without rejection (3.1 mg/L compared to 1.9 mg/L). The occurrence of adverse effects or rejection was not shown to be related to measured MPA trough or AUC outside of the target therapeutic range. The value of MPA concentration monitoring remains unclear; therefore, the practice of monitoring MPA AUC by LSS or trough concentrations should be reconsidered.

Ex vivo binding of the immunosuppressant mycophenolic acid to dog and cat plasma proteins and the effect of co-incubated dexamethasone and prednisolone

Mycophenolic acid (MPA) has been shown to be promising for the treatment of autoimmune diseases in dogs and cats. In humans, MPA is highly bound to plasma proteins (~97%). It has been recommended to monitor free drug plasma concentrations because the free MPA correlates with its immunosuppressive effect. However, it is unknown if MPA is highly bound to plasma proteins in dogs and cats. The objectives of this study were to determine the extent of plasma protein binding of MPA and evaluate the effect of prednisolone and dexamethasone on the extent of protein binding of MPA in dogs and cats. The extent of plasma protein binding of MPA was determined in plasma collected from clinically healthy adult cats (n = 13) and dogs (n = 14) by combining high-throughput dialysis and ultra-high-liquid chromatography. This study reveals that MPA is highly bound to plasma proteins (>90%) in dogs and cats, mean extent of binding of MPA at 15 μg/ml to plasma proteins being 96% (range, 95%-97%) and 92% (range, 90%-93%) for dogs and cats, respectively. In dog plasma, MPA is primarily bound to albumin. In vitro, prednisolone increased the unbound MPA in dogs (p < .01) but not in cats (p = .07) while dexamethasone had no effect on MPA plasma binding in either species (p > .05). Results of this study provide valuable information for designing future pharmacokinetic and pharmacodynamic studies and also therapeutic monitoring programs for dogs and cats.

Renal Transplant Acute Rejection with Lower Mycophenolate Mofetil Dosing and Proton Pump Inhibitors or Histamine-2 Receptor Antagonists

BACKGROUND

Pharmacokinetic data show reduced mycophenolic acid levels in renal transplant recipients taking mycophenolate mofetil (MMF) and proton pump inhibitors (PPIs) concomitantly. This reduced exposure could increase rejection risk. The typical initial MMF dose post renal transplantation is 2 g/day, which often requires dose reduction secondary to side effects. Existing studies have not shown significant acute rejection differences for patients taking MMF-PPI versus patients taking MMF-ranitidine.

OBJECTIVE

The purpose of this study was to evaluate clinical outcomes in renal transplant recipients receiving a lower MMF dose than previously studied (1.5 g/day) and either a PPI or histamine-2 receptor antagonist (H2RA).

METHODS

This retrospective cohort study included adult subjects receiving a renal transplant between January 1, 2009, and June 30, 2013. Comparison groups were defined based on acid-suppressing therapy class prescribed at discharge from transplantation. The primary outcome was acute rejection incidence within 1 year posttransplantation.

RESULTS

Of 728 renal transplant recipients screened, 522 were included: 183 taking a PPI and 339 taking an H2RA. There was no significant difference in acute rejection within 1 year (H2RA 19% versus PPI 14%, p=0.12) or 3 months (4% vs 5%, p=0.44, respectively) posttransplantation. Maintenance immunosuppression (MMF dose and tacrolimus troughs) was similar between groups at 3 months and 1 year. Graft and patient survivals were favorable (> 95%), and graft function at 1 year was stable and similar between groups.

CONCLUSION

Despite taking lower MMF doses than previously studied, subjects on a PPI compared to an H2RA were not at increased risk of acute rejection within 1 year posttransplantation.

Steady-state pharmacokinetics of mycophenolic acid in renal transplant patients: exploratory analysis of the effects of cyclosporine, recipients' and donors' ABCC2 gene variants, and their interactions

PURPOSE

The study aims to evaluate the impact of recipients' and donors' polymorphisms in multidrug resistance-associated protein 2 (MRP2) gene ABCC2 -24C>T and 1249G>A on disposition of mycophenolic acid (MPA) and their interaction with cyclosporine (CsA) (compared to tacrolimus, TAC) in stable de novo adult renal transplant patients of Croatian origin.

METHODS

A total of 68 recipient-donor pairs were genotyped. Steady-state pharmacokinetics of MPA was assessed by the model-independent method.

RESULTS

Adjusted for MPA formulation, renal function, type of calcineurin inhibitor and recipients' and donors' genotypes at the two loci, donors' A-allele at 1249G>A was associated with a reduced peak (29%) and early (AUC_0-2, 33%) exposure and increased MPA clearance (26%). Donors' A-allele combined with CsA was associated with 78% higher MPA clearance, 49% lower early and 48% lower total exposure as compared to wild type homozygosity + TAC. Recipients' SNPs per se did not reflect on MPA disposition. However, A-allele at 1249G>A + CsA (compared to wild type + TAC) was associated with a numerically greater increase in MPA clearance (59 vs. 41%), reduction in total exposure (36 vs. 27%) and increase in absorption rate (C _max/AUC) (56 vs. 37%) than observed for the main effect of CsA. Less pronounced effects were observed for the combination of variant allele at -24C>T and CsA.

CONCLUSION

Considering MPA disposition, data indicate: donors' ABCC2 1249G>A polymorphism increases clearance and reduces exposure; CsA increases clearance and reduces exposure by inhibiting MRP2 in the gut, the liver, and the kidney; donors' ABCC2 1249G>A polymorphism enhances the renal CsA effect, while recipients' polymorphism seems to enhance the liver and the gut CsA effects.

Pharmacokinetics and target attainment of mycophenolate in pediatric renal transplant patients

MPA is an immunosuppressive agent used to prevent graft rejection after renal transplantation. MPA shows considerable inter- and intraindividual variability in exposure in children and has a defined therapeutic window, and TDM is applied to individualize therapy. We aimed to study the exposure to MPA measured as the AUC in pediatric renal transplant patients, to identify factors influencing exposure and to assess target attainment. Children transplanted between 1998 and 2014 in a single center were included. Two groups were identified: Group 1 (AUC <3 wk post-transplantation) and Group 2 (AUC >18 months post-transplantation). Therapeutic targets were set at: AUC0-12h of 30-60 mg h/L. A total of 39 children were included in Group 1 (median age 13.3 yr) vs. 14 in Group 2 (median age 13.4 yr). AUC0-12h was 29.7 mg h/L in Group 1 and 56.6 mg h/L in Group 2, despite a lower dosage in Group 2 (584 and 426 mg/m(2) , respectively). About 46% of patients reached the target AUC0-12h in Group 1. Time since transplantation and serum creatinine were significantly associated with MPA exposure (p < 0.001), explaining 36% of the variability. Individualization of the mycophenolate dose by more intense and more early TDM could improve target attainment.

The efficacy and safety of intensified enteric-coated mycophenolate sodium with low exposure of calcineurin inhibitors in Chinese de novo kidney transplant recipients: a prospective study

AIMS

The aim of this study was to investigate the efficacy and safety of a transient intensified enteric-coated mycophenolate sodium (EC-MPS) dosing regimen with low exposure of calcineurin inhibitors (CNIs) in Chinese de novo kidney transplantation.

METHODS

In a 6-month prospective study, a total of 97 recipients were enrolled and assigned to either an intensified EC-MPS dosing (IS) regimen or a standard EC-MPS dosing (SD) regimen. The area under the curve (AUC) of MPA was assessed at week 1 post transplant. The incidences of acute rejection, patient and graft survival, renal allograft function and adverse events were analysed.

RESULTS

The IS regimen displayed a trend of acute rejection risk reduction (IS 2.7% vs. SD 13.3%, p = 0.061) and allograft function improvement (IS 62.8 ± 14.0 ml/min per 1.73 m(2) vs. SD 56.6 ± 18.3 ml/min per 1.73 m(2) , p = 0.084) after 6-month follow-up. MPA-AUC0-12 h was substantially higher in the intensified EC-MPS group than the standard EC-MPS group, though without a significant difference (71.4 ± 41.7 vs. 53.0 ± 27.0 mg·h/l, p = 0.107). The IS regimen did not increase the incidence of adverse effects (IS 54.1% vs. 45.0%, p = 0.39), including diarrhoea or leucopenia.

CONCLUSIONS

The intensified EC-MPS dosing regimen maintaining low-dose CNIs in this study may be beneficial for Chinese adult de novo kidney transplant recipients in terms of acute rejection and allograft function and is safe within 6 months post transplant.

Which is more suitable for kidney transplantation at the early post-transplantation phase in China - low dosing or standard dosing of enteric-coated mycophenolate sodium?

AIMS

To investigate the pharmacokinetics of enteric-coated mycophenolate sodium (EC-MPS) and the clinical outcome in kidney transplant recipients in the early post-transplantation phase. Then explain which regimen is more suitable for Chinese renal transplant recipients.

METHODOLOGY

In total, 60 de novo kidney transplant recipients treated with tacrolimus and steroids were randomised to receive EC-MPS at standard dose (SD; 1440 mg/day; n = 28) or low dose (LD; 1080 mg/day; n = 32). Efficacy parameters, safety and tolerability were assessed over a 6-month study period. Full mycophenolic acid (MPA) areas under the curve (AUCs) were completed on days 3 and 5, whereas a three-point limited sampling strategy (LSS) was utilised for MPA AUC assessments at 2 weeks and months 1, 3 and 6 (the LSS for three-time-point MPA AUC 0-12 h (mg h/l) = 15.99 + 0.87C1 h  + 0.68C2 h  + 7.85C4 h ; r(2)  = 0.8670.

RESULTS

The mean AUC levels at day 3 and day 5 in the SD group were significantly higher than in the LD group (57.4 mg·h/l vs. 38.2 mg·h/l and 59.3 mg·h/l vs. 44.8 mg·h/l, respectively, p < 0.01). There was a trend for fewer clinically diagnosed acute rejections in the SD group vs. the LD group at 6 months (7.1% vs. 12.5%). This trend was also present when acute rejection was analysed as biopsy-proven cases. There were significantly more acute rejections (all definitions) in patients with MPA AUC levels < 30 mg·h/l compared with those with MPA AUC levels ≥ 30 mg·h/l within 6 months (p < 0.05). Renal function, incidence of infection and haematological disorders were not significantly different in either study group.

CONCLUSIONS

Early adequate MPA exposure in renal transplant recipients can be achieved with a higher starting dose. In addition, a SD regimen was as well-tolerated as a LD regimen. Furthermore, early adequate MPA exposure significantly lowered the rate of acute rejection without compromising safety and tolerability.

How accurate and precise are limited sampling strategies in estimating exposure to mycophenolic acid in people with autoimmune disease?

Mycophenolic acid (MPA) is a potent immunosuppressant agent, which is increasingly being used in the treatment of patients with various autoimmune diseases. Dosing to achieve a specific target MPA area under the concentration-time curve from 0 to 12 h post-dose (AUC12) is likely to lead to better treatment outcomes in patients with autoimmune disease than a standard fixed-dose strategy. This review summarizes the available published data around concentration monitoring strategies for MPA in patients with autoimmune disease and examines the accuracy and precision of methods reported to date using limited concentration-time points to estimate MPA AUC12. A total of 13 studies were identified that assessed the correlation between single time points and MPA AUC12 and/or examined the predictive performance of limited sampling strategies in estimating MPA AUC12. The majority of studies investigated mycophenolate mofetil (MMF) rather than the enteric-coated mycophenolate sodium (EC-MPS) formulation of MPA. Correlations between MPA trough concentrations and MPA AUC12 estimated by full concentration-time profiling ranged from 0.13 to 0.94 across ten studies, with the highest associations (r (2) = 0.90-0.94) observed in lupus nephritis patients. Correlations were generally higher in autoimmune disease patients compared with renal allograft recipients and higher after MMF compared with EC-MPS intake. Four studies investigated use of a limited sampling strategy to predict MPA AUC12 determined by full concentration-time profiling. Three studies used a limited sampling strategy consisting of a maximum combination of three sampling time points with the latest sample drawn 3-6 h after MMF intake, whereas the remaining study tested all combinations of sampling times. MPA AUC12 was best predicted when three samples were taken at pre-dose and at 1 and 3 h post-dose with a mean bias and imprecision of 0.8 and 22.6 % for multiple linear regression analysis and of -5.5 and 23.0 % for maximum a posteriori (MAP) Bayesian analysis. Although mean bias was less when data were analysed using multiple linear regression, MAP Bayesian analysis is preferable because of its flexibility with respect to sample timing. Estimation of MPA AUC12 following EC-MPS administration using a limited sampling strategy with samples drawn within 3 h post-dose resulted in biased and imprecise results, likely due to a longer time to reach a peak MPA concentration (t max) with this formulation and more variable pharmacokinetic profiles. Inclusion of later sampling time points that capture enterohepatic recirculation and t max improved the predictive performance of strategies to predict EC-MPS exposure. Given the considerable pharmacokinetic variability associated with mycophenolate therapy, limited sampling strategies may potentially help in individualizing patient dosing. However, a compromise needs to be made between the predictive performance of the strategy and its clinical feasibility. An opportunity exists to combine research efforts globally to create an open-source database for MPA (AUC, concentrations and outcomes) that can be used and prospectively evaluated for AUC target-controlled dosing of MPA in autoimmune diseases.

15-year follow-up of a multicenter, randomized, calcineurin inhibitor withdrawal study in kidney transplantation

BACKGROUND

Calcineurin inhibitors (CNIs) are essential immunosuppressive drugs after renal transplantation. Because of nephrotoxicity, withdrawal has been a challenge since their introduction.

METHODS

A randomized multicenter trial included 212 kidney patients transplanted between 1997 and 1999. All patients were initially treated with mycophenolate mofetil (MMF), cyclosporine A (CsA), and prednisone (pred). At 6 months after transplantation, 63 patients were randomized for MMF/pred, 76 for MMF/CsA, and 73 for MMF/CsA/pred. Within 18 months after randomization 23 patients experienced a rejection episode: MMF/pred (27.0%), MMF/CsA (6.8%) and MMF/CsA/pred (1.4%) (P<0.001).

RESULTS

During 15 years of follow-up, 73 patients died with a functioning graft, and 43 patients lost their graft. Ninety-six were alive with a functioning graft. Intention-to-treat analysis did not show a significant difference in patient and graft survival. In multivariate analysis, death-censored graft survival was significantly associated with serum creatinine at 6 months after transplantation and maximum PRA but not with the randomization group. CNI withdrawal did not result in a reduced incidence of or death by malignancy or cardiovascular disease. Death-censored graft survival was significantly worse in those patients randomized for CNI withdrawal that had to be reverted to CNI. Independent of randomization group, compared with no rejection, death-censored graft survival was significantly worse in 23 patients with acute rejection after randomization.

CONCLUSION

Fifteen years after conversion to a CNI free regimen, there was no benefit regarding graft and patient survival or regarding prevalence of or death by comorbidities. However, rejection shortly after CNI withdrawal was associated with decreased graft survival.

Concomitant proton pump inhibitors with mycophenolate mofetil and the risk of rejection in kidney transplant recipients

BACKGROUND

Recent pharmacokinetic studies have demonstrated that proton pump inhibitors (PPI) reduce exposure of mycophenolic acid. However, the clinical significance of this drug-drug interaction on transplantation outcomes has not been determined.

METHODS

This was a retrospective cohort study in kidney transplant recipients who were prescribed rabbit antithymocyte globulin, calcineurin inhibitor, mycophenolate mofetil, and steroids. We evaluated the impact of PPI use on the 1-year rates of biopsy-proven acute rejection (BPAR).

RESULTS

Two hundred thirteen patients who were prescribed PPI were compared with 384 patients who were on standard acid-suppressive therapy with ranitidine. BPAR occurred in similar rates in both groups (15% vs. 12%; P=0.31). In a multivariable analysis, black race was associated with a higher risk of rejection (risk ratio [RR], 2.38; 95% confidence interval [CI], 1.41-4.03). While controlling for rejection risk factors, PPI exposure was associated with an increased risk of rejection in black patients (RR, 1.93; 95% CI, 1.18-3.16) but not in non-black patients (RR, 0.54; 95% CI, 0.19-1.49). At 1 year, BPAR type, BPAR grade, patient and graft survival, graft function, and time to BPAR were not associated with PPI exposure.

CONCLUSION

In this retrospective study, PPI use in the first transplant year was associated with an increased risk for BPAR in black patients but not in non-black patients. It is possible that a reduction in mycophenolic acid exposure contributed to the increased risk.

Therapeutic drug monitoring of mycophenolate mofetil for the treatment of severely active lupus nephritis

Background

Plasma mycophenolic acid (MPA) concentrations may predict therapeutic response in active lupus nephritis (LN). We determined the efficacy and safety of a concentration-controlled MPA regime in the treatment of severely active LN.

Methods

In this prospective study, 19 biopsy-proven class III/IV LN patients were treated with mycophenolate mofetil (MMF) for 48 weeks. The MMF dosage was based on maximal plasma MPA concentration at 1-hour post dose (MPA-C1). All patients had plasma MPA-C1 levels monitored weekly until achieving the targeted level of >13 mg/L. A low-dose steroid protocol was started at 0.5 mg/kg/day and rapidly tapered to 5 mg/day. Therapeutic response was evaluated at week 24 and week 48. MPA area-under-the curve (MPA-AUC0–12h) was measured at week 12 to verify the optimum dosage.

Results

No death or end-stage kidney disease occurred in this study. Seventeen patients (89%) responded to therapy at week 24 with four (21%) patients having complete response. There was no renal relapse at week 48 and four more patients had converted from partial response to complete response. Seventy eight percent of patients achieved the recommended MPA-AUC0–12h level. No association between plasma MPA concentrations and adverse reactions or infections was found.

Conclusions

MPA-C1 may be a practical monitoring of MPA levels in patients with LN. It is convenient to monitor and may facilitate an optimum estimate of MPA exposure.

Significance of mycophenolate monitoring in liver transplant recipients: toward the cut-off level

Mycophenolate mofetil blocks the "de novo" -purine synthesis to reduce the incidence and severity of acute rejection episodes. There has been an increased interest in utility of monitoring mycophenolic acid (MPA) levels, however currently the MPA monitoring is not part of the protocol following liver transplantation. We assessed whether trough MPA monitoring could be advisable in liver transplant patients or not. For this reason MPA levels of 56 liver transplants were measured on 3, 5, 10, 14, 21, 30, 60, and 180 posttransplant days. The optimal cut-off of MPA level (≥1.73 mg/L) for all (56) and ≥1.34 mg/L for ciclosporin-treated- and ≥1.98 mg/L for the tacrolimus-treated transplants were calculated by statistical analysis to reduce the incidence of acute rejection. MPA concentrations of 3 days period before the day of clinical diagnosis acute rejection were well below the cut-off value. Only 3 (16%) out 19 patients with acute rejection had higher MPA levels than the cut-off value on the day of diagnosis of acute rejection. In conclusion, our data suggests that MPA predose level monitoring, especially in the early "filling phase" after transplantation, is applicable in liver allograft recipients given adjunctive MMF, protecting them from the ineffective immunosuppression.

Maximum a posteriori Bayesian estimation of mycophenolic Acid area under the concentration-time curve: is this clinically useful for dosage prediction yet?

This review seeks to summarize the available data about Bayesian estimation of area under the plasma concentration-time curve (AUC) and dosage prediction for mycophenolic acid (MPA) and evaluate whether sufficient evidence is available for routine use of Bayesian dosage prediction in clinical practice. A literature search identified 14 studies that assessed the predictive performance of maximum a posteriori Bayesian estimation of MPA AUC and one report that retrospectively evaluated how closely dosage recommendations based on Bayesian forecasting achieved targeted MPA exposure. Studies to date have mostly been undertaken in renal transplant recipients, with limited investigation in patients treated with MPA for autoimmune disease or haematopoietic stem cell transplantation. All of these studies have involved use of the mycophenolate mofetil (MMF) formulation of MPA, rather than the enteric-coated mycophenolate sodium (EC-MPS) formulation. Bias associated with estimation of MPA AUC using Bayesian forecasting was generally less than 10%. However some difficulties with imprecision was evident, with values ranging from 4% to 34% (based on estimation involving two or more concentration measurements). Evaluation of whether MPA dosing decisions based on Bayesian forecasting (by the free website service https://pharmaco.chu-limoges.fr) achieved target drug exposure has only been undertaken once. When MMF dosage recommendations were applied by clinicians, a higher proportion (72-80%) of subsequent estimated MPA AUC values were within the 30-60 mg · h/L target range, compared with when dosage recommendations were not followed (only 39-57% within target range). Such findings provide evidence that Bayesian dosage prediction is clinically useful for achieving target MPA AUC. This study, however, was retrospective and focussed only on adult renal transplant recipients. Furthermore, in this study, Bayesian-generated AUC estimations and dosage predictions were not compared with a later full measured AUC but rather with a further AUC estimate based on a second Bayesian analysis. This study also provided some evidence that a useful monitoring schedule for MPA AUC following adult renal transplant would be every 2 weeks during the first month post-transplant, every 1-3 months between months 1 and 12, and each year thereafter. It will be interesting to see further validations in different patient groups using the free website service. In summary, the predictive performance of Bayesian estimation of MPA, comparing estimated with measured AUC values, has been reported in several studies. However, the next step of predicting dosages based on these Bayesian-estimated AUCs, and prospectively determining how closely these predicted dosages give drug exposure matching targeted AUCs, remains largely unaddressed. Further prospective studies are required, particularly in non-renal transplant patients and with the EC-MPS formulation. Other important questions remain to be answered, such as: do Bayesian forecasting methods devised to date use the best population pharmacokinetic models or most accurate algorithms; are the methods simple to use for routine clinical practice; do the algorithms actually improve dosage estimations beyond empirical recommendations in all groups that receive MPA therapy; and, importantly, do the dosage predictions, when followed, improve patient health outcomes?

How delayed graft function impacts exposure to mycophenolic acid in patients after renal transplantation

INTRODUCTION

Mycophenolic acid (MPA) plasma concentrations are highly variable on standard-dose mycophenolate mofetil therapy. At creatinine clearances below 25 mL/min, MPA clearance increases as a result of a higher nonprotein-bound fraction. Patients with delayed graft function (DGF) after renal transplantation are exposed to low total MPA concentrations, when risk of rejection is highest. This study investigated the influence of DGF on MPA exposure and on clinical outcome.

METHODS

Adult renal transplantation patients treated with mycophenolate mofetil, corticosteroids, and either microemulsified cyclosporine (n = 459) or tacrolimus (n = 371) participated in a randomized controlled trial (the Fixed-Dose Concentration-Controlled [FDCC] Study). Abbreviated MPA areas under the curve (AUCs) were obtained on Day 3, Day 10, Week 4, and Month 3, to calculate MPA AUC₀₋₁₂. Free MPA AUC values were available for a subgroup of patients (n = 269).

RESULTS

The overall incidence of DGF was 187 of 830 (23%) and did not differ between cyclosporine-treated (24%) and tacrolimus- (21%) treated patients. The incidence of biopsy-proven acute rejection at 12 months was significantly higher in patients with DGF (13.8% versus 21.4%). Patients with DGF had significantly lower dose-corrected MPA AUC on Day 3 and Day 10. Free MPA fraction and dose-corrected free MPA AUC were significantly higher in patients with DGF, from Day 3 until Month 3. The total number of patients with at least one opportunistic infection was significantly higher in patients with DGF (33.2%) compared with patients without DGF (25.8%) (P = 0.048). Patients with DGF developing opportunistic infections did not have higher total MPA AUC nor higher free MPA AUC compared with those without opportunistic infections.

CONCLUSION

Patients with DGF have significantly lower dose-corrected MPA AUC in the first month after renal transplantation, presumably as a result of enhanced MPA clearance on account of the elevated MPA free fraction. Because patients with DGF have a higher rate of acute rejection and lower MPA exposure, higher dosing of mycophenolate mofetil in such patients may improve outcome. However, the already increased incidence of opportunistic infections in patients with DGF is a concern.

Cyclosporine alters correlation between free and total mycophenolic acid in kidney transplant recipients in the initial phase

WHAT IS KNOWN AND OBJECTIVE

The factors affecting the pharmacokinetics of free mycophenolic acid (MPA) and its phenolic glucuronide (MPAG) are still unclear. The aim of this study was to evaluate the influence of cyclosporine on the pharmacokinetics of free MPA and MPAG.

METHODS

Seventy-seven kidney transplant recipients (23 were in an initial phase and 54 in a stable phase; 41 were treated with cyclosporine and 36 with tacrolimus) were enrolled. Free and total MPA and MPAG were determined using HPLC. The correlations between free and total predose concentrations (C(0) ) of MPA or MPAG were evaluated separately in patients receiving calcineurin inhibitor medications.

RESULTS AND DISCUSSION

Serum concentration of albumin was lower in the initial phase than in the stable phase. A higher ratio of free MPAG C(0) to free MPA C(0) was observed in cyclosporine-treated than tacrolimus-treated kidney transplant recipients. Free MPA C(0) correlated weakly with total MPA C(0) in kidney transplant recipients treated with cyclosporine in the initial phase (ρ= 0·53, P = 0·06).

WHAT IS NEW AND CONCLUSION

Cyclosporine increased the ratio of free MPAG C(0) to free MPA C(0) and varied the free fraction of MPA in the hypoalbuminaemic kidney transplant recipients in the initial phase.

Mycophenolic acid area under the curve recovery time following rifampicin withdrawal

Renal transplant patients prescribed mycophenolate mofetil (MMF) may require treatment for tuberculosis with a regimen including the tuberculocidal drug rifampicin. MMF is an ester prodrug which is rapidly hydrolysed to the active compound, mycophenolic acid (MPA). Therapeutic drug monitoring of mycophenolate involves the measurement of MPA area under the curve (MPA-AUC_0-12). Rifampicin is known to increase the metabolism and decrease enterohepatic recirculation of mycophenolic acid, (MPA). When MPA is monitored after the discontinuation of rifampicin, an important factor is the time required for the MPA area under the curve to return to the pre-rifampicin value. At present this is not known. This report describes one such renal allograft patient, on long term MMF and prescribed rifampicin by a local physician. As expected there was a clinically significant decrease in MPA-AUC_0-12 Three weeks after rifampicin was discontinued the MPA-AUC_0-12 was still only 65% of the pre-rifampicin value and only 55% of the steady state MPA-AUC_0-12 measured six months later.

Safety and efficacy of intensified versus standard dosing regimens of enteric-coated mycophenolate sodium in de novo renal transplant patients

BACKGROUND

Efficacy and safety of an intensified dosing (ID) regimen of enteric-coated mycophenolate sodium (EC-MPS), which achieves higher mycophenolic acid exposure early posttransplantation, were evaluated in comparison with a standard dosing (SD) regimen.

METHODS

In total, 128 de novo kidney transplant recipients treated with basiliximab induction, cyclosporine A, and steroids were randomized (1:1) to receive EC-MPS as SD (1440 mg/day; n=65) or ID (days 0-14: 2880 mg/day; days 15-42: 2160 mg/day; followed by 1440 mg/day; n=63). Efficacy parameters, safety, and tolerability were assessed over a 6-month study period. The primary endpoint was mean time to first occurrence of treatment failure.

RESULTS

Mean time to treatment failure was 130 days (95% confidence interval [CI]: 81-n/a) in the ID group versus 114 days (95% CI: 15-155) in the SD group (P=0.36). Similar percentages (ID 30.2%; SD 36.9%) experienced treatment failure. Biopsy-proven acute rejection occurred in 2 (3.2%) ID versus 11 (16.9%) SD patients (P<0.001). Three (2.3%) deaths (2 SD, 1 ID) and five (3.9%) graft losses (3 SD, 2 ID) occurred. Renal function, incidence of infection, and hematologic disorders were comparable in both study cohorts. Gastrointestinal disorders occurred in 51 (81.0%) ID and 49 (75.4%) SD patients with overall similar tolerability as assessed by the Gastrointestinal Symptom Rating Scale.

CONCLUSION

In this exploratory study, the EC-MPS ID regimen reduced the incidence of rejection and showed a comparable safety and tolerability profile to SD. Further examination of this approach in a larger patient cohort is now warranted to confirm these findings.

The influence of pharmacogenetics and cofactors on clinical outcomes in kidney transplantation

INTRODUCTION

Immunosuppressive drugs have a narrow therapeutic range and large inter-individual response variability. This has prompted pharmacogenetic studies, mostly with regard to their dose-concentration relationships, but also about proteins involved in their pharmacodynamics. Some polymorphisms of genes involved in their disposition pathways were shown to affect their dose-concentration relationships. The impact of pharmacogenetics on tissue distribution and the resulting clinical effects have less often been studied. More importantly, a few single nucleotide polymorphisms seem to have a significant impact on the incidence of acute rejection or the adverse effects of immunosuppressants. Environmental factors often interact with such genotype-phenotype relationships.

AREAS COVERED

This article reviews the impact of genetic polymorphisms of the metabolic enzymes, membrane transporters and target proteins of mycophenolic acid, calcineurin inhibitors and mammalian target of rapamycin inhibitors on clinical outcomes in kidney transplantation.

EXPERT OPINION

The current level of evidence is not yet high enough to recommend pharmacogenetic personalization of immunosuppressive regimens in transplant recipients. The prevention of cellular toxicity associated with local metabolism or transport, which cannot be addressed by routine monitoring, is worth investigating further.

Genetic determinants of mycophenolate-related anemia and leukopenia after transplantation

BACKGROUND

Mycophenolate-related anemia and leukopenia are well-known toxicities after transplantation. Toxicity leads to dose reduction, addition of colony-stimulating factors or erythropoietin, or discontinuation of immunosuppressive therapy. The causes of and risk factors associated with toxicity are unclear.

METHODS

We studied the association between mycophenolate-related anemia and leukopenia and 2724 single nucleotide polymorphisms (SNP) in 978 patients undergoing living or deceased donor kidney transplant. Patients were followed up to time of first anemia (hemoglobin<10 gm/dL or hematocrit<30%) or first leukopenia (white blood cell [WBC] count <3000 cells/mm), which required clinical intervention in the first 6 months after transplant.

RESULTS

Anemia occurred in 87 (9.5%) subjects and leukopenia in 224 (22.9%). In single SNP analyses, none of the SNPs were associated with time to leukopenia at a false discovery rate (FDR) of 20%. However, SNPs from the IL12A, HUS, CYP2C8 genes were associated with time to anemia, allowing for an FDR of 20%. To assess the independence of these SNPs as predictors of anemia, we conducted a multi-SNP analysis including one SNP from each of the three genes. All three SNPs were associated with time to anemia, after adjusting for recipient age, weight, posttransplant dialysis and antiviral drug use, and stratifying by clinical center.

CONCLUSION

Although these SNPs require validation in an independent population, our results suggest that genetics may play a role in risk of mycophenolate-related hematologic toxicity. This may ultimately provide for better management of maintenance immunosuppression and gives insights into potential mechanism(s) by which toxicity occurs.

Pharmacokinetic and pharmacodynamic analysis of enteric-coated mycophenolate sodium: limited sampling strategies and clinical outcome in renal transplant patients

AIMS

Pharmacokinetic (PK) and pharmacodynamic (PD) monitoring strategies and clinical outcome were evaluated in enteric-coated mycophenolate sodium (EC-MPS)-treated renal allograft recipients.

METHODS

PK [mycophenolic acid (MPA)] and PD [inosine monophosphate dehydrogenase (IMPDH) activity] data were analysed in 66 EC-MPS and ciclosporin A (CsA)-treated renal allograft recipients. Adverse events were considered in a follow-up period of 12 weeks.

RESULTS

Analyses confirmed a limited sampling strategy (LSS) consisting of PK and PD data at predose, 1, 2, 3 and 4 h after oral intake as an appropriate sampling method (MPA r(2)= 0.812; IMPDH r(2)= 0.833). MPA AUC(0-12) of patients with early biopsy-proven acute rejection was significantly lower compared with patients without a rejection (median MPA AUC(0-12) 28 microg*h ml(-1) (7-45) vs. 40 microg*h ml(-1) (16-130), P < 0.01), MPA AUC(0-12) of patients with recurrent infections was significantly higher compared with patients without infections (median MPA AUC(0-12) 65 microg*h ml(-1) (range 37-130) vs. 37 microg*h ml(-1) (range 7-120), P < 0.005). Low 12-h IMPDH enzyme activity curve (AEC(0-12)) was associated with an increased frequency of gastrointestinal side-effects (median IMPDH AEC(0-12) 43 nmol*h mg(-1) protein h(-1)[range 12-67) vs. 75 nmol*h mg(-1) protein h(-1) (range 15-371), P < 0.01].

CONCLUSIONS

Despite highly variable absorption data, an appropriate LSS might be estimated by MPA AUC(0-4) and IMPDH AEC(0-4) in renal transplant patients treated with EC-MPS and CsA. Regarding adverse events, the suggested MPA-target AUC(0-12) from 30 to 60 microg*h ml(-1) seems to be appropriate in renal allograft recipients.