Data on B cell depletion therapy in severe autoimmune diseases in paediatric patients are very limited. We conducted a retrospective cohort study and recruited patients who were treated with rituximab (RTX) and followed up for at least 6 months through the German societies of paediatric rheumatology and nephrology. The aim was to describe the spectrum of autoimmune disorders for which RTX was used and to describe the applied therapeutic regimens, the observed efficacy, as well as potential immunological side effects. The need to develop standard treatment guidelines for future trials should be discussed. Sixty-five patients were included. Nineteen patients suffered from systemic lupus erythematosus, 13 from vasculitic disorders, 12 from hematological autoimmune diseases, 5 from mixed connective tissue disorders, 4 from juvenile idiopathic arthritis, and 9 had other autoimmune diseases. Adverse, infusion-related events were reported in 12/65 (18%) patients. Considering laboratory and clinical parameters, 13 patients (22%) were in complete remission, 31 (52%) were in partial remission, 6 (10%) were unchanged and 10 (17%) had progressed after 6 months. In 46% of the patients, the steroid dose could be more than halved. IgG, IgM and IgA decreased from normal levels prior to RTX therapy to below normal levels at 6 months in 2/22 (9%), 10/21 (48%), and 4/22 (18%) patients, respectively. Immunoglobulin deficiency or prolonged CD20 depletion was reported in eight patients after an observation period longer than 12 months. RTX therapy led to a perceivable reduction in disease activity. However, long-term immunological alterations may occur in more than 10% of the patients. Guidelines and protocols for off-label therapy are desirable to document reasonable follow-up data. Controlled prospective studies for RTX therapies in children with standardised therapeutic and diagnostic protocols are urgently needed.

Background: Mycophenolate mofetil (MMF) plays an increasingly important role in the treatment of children with nephrotic syndrome, especially in steroid sparing protocols. Recent publications show the relationship of exposure to its active moiety mycophenolic acid (MPA) and clinical efficacy. Performance of full-time pharmacokinetic (PK) profiles, however, is inconvenient and laborious. Established limited sampling strategies (LSS) to estimate the area under the concentration (AUC) versus time curve of MPA (MPA-AUC) in pediatric renal transplant recipients cannot be easily transferred to children suffering from nephrotic syndrome, mainly because of the lack of concomitant immunosuppressive therapy. We therefore aimed for the generation and validation of a LSS to estimate MPA exposure to facilitate therapeutic drug monitoring in children with nephrotic syndrome. Methods: We performed 27 complete PK profiles in 23 children in remission [mean age (±SD):12.3 ± 4.26 years] to generate and validate an LSS. Sampling time points were before administration (C0) and 0.5, 1, 1.5, 2, 4, 6, 8, and 12 hours after the administration of MMF. MPA was measured by enzyme multiplied immunoassay technique. There was no concomitant treatment with calcineurin inhibitors. Results: Mean daily dose of MMF was 927 ± 209 mg/m2 of body surface area resulting in a mean MPA-AUC0-12 value of 59.2 ± 29.3 mg × h/L and a predose level of 3.03 ± 2.24 mg/L. Between-patient variability of dose-normalized MPA-AUC0-12 was high (coefficient of variation: 45.5%). Correlation of predose levels with the corresponding MPA-AUC0-12 was moderate (r 2 = 0.59) in a subgroup of 18 patients (20 PK profiles, generation group). An algorithm based on 3 PK sampling time points during the first 2 hours after MMF dosing (estimated AUC0-12 = 8.7 + 4.63 × C0 + 1.90 × C1 + 1.52 × C2) was able to predict MPA-AUC with a low percentage prediction error (3.88%) and a good correlation of determination (r 2 = 0.90). Validation of this algorithm in a randomized separate group of 6 patients (7 PK profiles, validation group) resulted in comparably good correlation (r 2 = 0.95) and low percentage prediction error (5.57%). Conclusions: An abbreviated profile within the first 2 hours after MMF dosing gives a good estimate of MPA exposure in children with nephrotic syndrome and hence has the potential to optimize MMF therapy.

Nephrotoxicity is one of the main side effects of calcineurininhibitors. The influence of tacrolimus on the renal vasculature has not been well described. We have therefore examined the effects of tacrolimus on renal functional parameters as well as the contribution of the NO-system in a model of ischemic acute renal failure (ARF). Induction of ARF was achieved by clamping both renal arteries of female Sprague-Dawley rats. During the experiment, RBF, GFR, MAP, RVR and FENa were determined during infusion of vehicle, TAC, TAC and the NOS-activator L-arginine, and TAC and NOS-inhibition due to L-NMMA. TAC induced a significant rise in RVR with further decrease of RBF and GFR. Simultaneous Larginine-infusion could reverse these effects during the infusion without complete restoration to preischemic levels. NOS-inhibition increased MAP and RBF without any effect on GFR. FENa did not differ significantly between the groups. Tacrolimus in the situation of ischemic acute renal failure causes vasoconstriction of pre-and postglomerular vessels with a further deterioration of renal function. Larginine abolishes the functional deterioration, most likely due to increased NO-liberation.

Nephrotoxicity is one of the main side effects of calcineurininhibitors. The influence of tacrolimus on the renal vasculature has not been well described. We have therefore examined the effects of tacrolimus on renal functional parameters as well as the contribution of the NO-system in a model of ischemic acute renal failure (ARF). Induction of ARF was achieved by clamping both renal arteries of female Sprague-Dawley rats. During the experiment, RBF, GFR, MAP, RVR and FENa were determined during infusion of vehicle, TAC, TAC and the NOS-activator L-arginine, and TAC and NOS-inhibition due to L-NMMA. TAC induced a significant rise in RVR with further decrease of RBF and GFR. Simultaneous Larginine-infusion could reverse these effects during the infusion without complete restoration to preischemic levels. NOS-inhibition increased MAP and RBF without any effect on GFR. FENa did not differ significantly between the groups. Tacrolimus in the situation of ischemic acute renal failure causes vasoconstriction of pre-and postglomerular vessels with a further deterioration of renal function. Larginine abolishes the functional deterioration, most likely due to increased NO-liberation.

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