Browsing by Author "Toenshoff, Burkhard"

Background. Fixed-dose mycophenolate mofetil (MMF) reduces the incidence of acute rejection after solid organ transplantation. The Fixed-.Dose Concentration Controlled trial assessed the feasibility and potential benefit of therapeutic drug monitoring in patients receiving MMF after de novo renal transplant. Methods. Patients were randomized to a concentration-controlled (n=452; target exposure 45 mg hr/L) ora fixed-dose (n=449) MMF-containing regimen. The primary endpoint was treatment failure (a composite of biopsy-proven acute rejection [BPAR], graft loss, death, or MMF discontinuation) by 12 months posttransplantation. Results. Mycophenolic acid (MPA) exposures for both groups were similar at most time points and were below 30 mg hr/L in 37.3% of patients at day 3. There was no difference in the incidence of treatment failure (25.6% vs. 25.7%, P=0.81) or BPAR (14.9% vs. 15.5%, P > 0.05) between the concentration-controlled and the fixed-dose groups, respectively. We did find a significant relationship between MPA-area under the concentration-time curve on day 3 and the incidence of BPAR in the first month (P=0.009) or in the first year posttransplantation (P=0.006). For later time points (day 10, month 1) there was no significant relationship between area under the concentration-time curve and BPAR (0.2572 and 0.5588, respectively). Conclusions. There was no difference in the incidence of treatment failure between the concentration-controlled and the fixed-dose groups. The applied protocol of MMF dose adjustments based on target MPA exposure was not successful, partly because physicians seemed reluctant to implement substantial dose changes. Current initial MMF doses underexpose more than 35% of patients early after transplantation, increasing the risk for BPAR.

Alport syndrome inevitably leads to end-stage renal disease and there are no therapies known to improve outcome. Here we determined whether angiotensin-converting enzyme inhibitors can delay time to dialysis and improve life expectancy in three generations of Alport families. Patients were categorized by renal function at the initiation of therapy and included 33 with hematuria or microalbuminuria, 115 with proteinuria, 26 with impaired renal function, and 109 untreated relatives. Patients were followed for a period whose mean duration exceeded two decades. Untreated relatives started dialysis at a median age of 22 years. Treatment of those with impaired renal function significantly delayed dialysis to a median age of 25, while treatment of those with proteinuria delayed dialysis to a median age of 40. Significantly, no patient with hematuria or microalbuminuria advanced to renal failure so far. Sibling pairs confirmed these results, showing that earlier therapy in younger patients significantly delayed dialysis by 13 years compared to later or no therapy in older siblings. Therapy significantly improved life expectancy beyond the median age of 55 years of the no-treatment cohort. Thus, Alport syndrome is treatable with angiotensin-converting enzyme inhibition to delay renal failure and therapy improves life expectancy in a time-dependent manner. This supports the need for early diagnosis and early nephroprotective therapy in oligosymptomatic patients. Kidney International (2012) 81, 494-501; doi:10.1038/ki.2011.407; published online 14 December 2011

Introduction Data on the efficacy and safety of everolimus in pediatric renal transplantation compared to other immunosuppressive regimens are scarce. Patients/Methods We therefore performed a multicenter, observational, matched cohort study over 4 years post-transplant in 35 patients on everolimus plus low-dose cyclosporine, who were matched (1: 2) with a control group of 70 children receiving a standard-dose calcineurin-inhibitor-and mycophenolate mofetil-based regimen. Results Corticosteroids were withdrawn in 83% in the everolimus vs. 39% in the control group (p<0.001). Patient and graft survival were comparable. The rate of biopsy-proven acute rejection episodes Banff score >= IA during the first year post-transplant was 6% in the everolimus vs. 13% in the control group (p = 0.23). The rate of de novo donor-specific HLA antibodies (11% in everolimus, 18% in controls) was comparable (p = 0.55). At 4 years post-transplant, mean eGFR in the everolimus group was 56 +/- 33 ml/min per 1.73 m(2) vs. 63 +/- 22 ml/min per 1.73 m(2) in the control group (p = 0.14). Everolimus therapy was associated with less BK polyomavirus replication (3% vs. 17% in controls; p = 0.04), but with a higher percentage of arterial hypertension and more hyperlipidemia (p<0.001). Conclusion In pediatric renal transplantation, an everolimus-based regimen with low-dose cyclosporine yields comparable four year results as a standard regimen, but with a different side effect profile.

Data on exposure to mycophenolic acid (MPA), the active moiety of mycophenolate mofetil (MMF), in pediatric renal transplant recipients beyond the first year posttransplant are scarce. The authors therefore analyzed the long-term pharmacokinetics of MPA in 25 pediatric patients treated with 600 mg MMF/m(2) body surface area twice a day in conjunction with cyclosporine A and prednisone. Plasma samples for 12-hour pharmacokinetic profiles were collected on day 7, and after 3, 9, 24, and 36 months posttransplant. Both the actual and the dose-normalized MPA-area under the concentration-time curve (AUC(0-12)) increased approximately 2-fold between day 7 and month 9 but stabilized thereafter. Both the actual and the dose-normalized MPA-AUC(0-12) at months 24 and 36 were comparable to that at month 9. Presuming a therapeutic window of 30-60 mg h/L, 15 (60%) of 25 patients at day 7 had an MPA-AUC(0-12) < 30 mg h/L, indicating potential underexposure, whereas the proportion of patients with an MPA-AUC(0-12) <30 mg h/L between months 3 and 36 was low (5%-17%). These data suggest that the recommended MMF dose of 600 mg/m(2) body surface area twice a day in conjunction with cyclosporine A leads to MPA underexposure early posttransplant in a significant subset of patients, indicating a need for a higher initial MMF dose. Dose-normalized MPA exposure increases in the first 9 months posttransplant, consistent with a reduced MPA metabolism and increased enterohepatic recycling of MPA.

Patients with autosomal or X-linked Alport syndrome (AS) with heterozygous mutations in type IV collagen genes have a 1-20 % risk of progressing to end-stage renal disease during their lifetime. We evaluated the long-term renal outcome of patients at risk of progressive disease (chronic kidney disease stages 1-4) with/without nephroprotective therapy. This was a prospective, non-interventional, observational study which included data from a 4-year follow-up of AS patients with heterozygous mutations whose datasets had been included in an analysis of the 2010 database of the European Alport Registry. Using Kaplan-Meier estimates and logrank tests, we prospectively analyzed the updated datasets of 52 of these patients and 13 new datasets (patients added to the Registry after 2011). The effects of therapy, extrarenal symptoms and inheritance pattern on renal outcome were analyzed. The mean prospective follow-up was 46 +/- 10 months, and the mean time on therapy was 8.4 +/- 4.4 (median 7; range 2-18) years. The time from the appearance of the first symptom to diagnosis was 8.1 +/- 14.2 (range 0-52) years. At the time of starting therapy, 5.4 % of patients had an estimated glomerular filtration rate of < 60 ml/min, 67.6 % had proteinuria and 27.0 % had microalbuminuria. Therapeutic strategies included angiotensin-converting enzymer inhibitors (97.1 %), angiotensin receptor antagonists (1 patient), dual therapy (11.8 %) and statins (8.8 %). Among patients included in the prospective dataset, prevented the need for dialysis. Among new patients, no patient at risk for renal failure progressed to the next disease stage after 4 years follow-up; three patients even regressed to a lower stage during therapy. Treatment with blockers of the renin-angiotensin-aldosterone system prevents progressive renal failure in AS patients with heterozygous mutations in the genes causing AS. Considerable numbers of aging AS patients on dialysis may have heterozygous mutations in these genes (present in 1 % of total population) as underlying disease. Hence, greater alertness towards timely diagnosis and therapy has the potential to prevent progressive renal failure in most-if not all-AS patients with heterozygous mutations in the causal genes.

The pharmacokinetics of mycophenolic acid (MPA), the active moiety of the immunosuppressant mycophenolate mofetil (MMF), exhibits large inter-individual variability. Concentration-controlled dosing of MMF based on therapeutic drug monitoring may therefore be advantageous compared to a fixed-dose regimen. Because full AUC(0-12) monitoring is not practical and predose MPA concentrations correlate only moderately with the corresponding AUC(0-12), the estimation of MPA exposure by a limited sampling strategy has been suggested. However, before such an algorithm is transferred to clinical practice, it is compulsory to prospectively validate it in a different data set, in order to avoid biased results. The aim of this investigation was therefore to prospectively validate an algorithm based on an abbreviated pharmacokinetic (RK) profile for the estimation of MPA exposure in 54 pediatric renal transplant recipients (169 PK profiles) on MMF in conjunction with CsA and prednisone on a second data set in a different group of patients with a similar immunosuppressive regimen (25 patients, 119 PK profiles). An algorithm based on three PK sampling timepoints during the first 2 hours after MMF dosing (estimated AUC(0-12) = 18.6 + 4.3 center dot C-0 + 0.54 center dot C-0.5 + 2.15 center dot C-2) was able to predict the corresponding MPA-AUC(0-12) with a low percentage prediction error (10.7%) and an acceptable coefficient of determination (r(2) = 0.76). The performance of this algorithm was comparable among different pediatric age groups. By ROC curve analysis, the calculated MPA-AUC(0-12) based on this algorithm was able to differentiate between rejecters and non-rejecters with a comparable prognostic sensitivity (66.7%) and specificity (61.9%) as the full-time MPA-AUC(0-12). In conclusion, the use of this validated algorithm for the estimation of MPA exposure based on a limited sampling strategy during the first 2 hours after MMF dosing has the potential to optimize MMF therapy in pediatric renal transplant recipients.