Single daily high-dose mizoribine therapy for children with steroid-dependent nephrotic syndrome prior to cyclosporine administration

Adult survivors of childhood-onset steroid-dependent and steroid-resistant nephrotic syndrome treated with cyclosporine: a long-term single-center experience

BACKGROUND

Although evidence has confirmed that cyclosporine (CS) is efficacious against childhood-onset steroid-dependent and steroid-resistant nephrotic syndrome (SD/SRNS), some patients may continue to relapse during adulthood. However, predictive factors for adult active disease and kidney complications, such as chronic kidney disease (CKD) and hypertension, in this cohort remain unknown.

METHODS

We conducted a retrospective study on the long-term outcomes of 81 young adults with childhood-onset SD/SRNS treated with CS. The primary endpoint was the probability of active disease into adulthood. The secondary endpoint was the probability of developing kidney complications.

RESULTS

At the last follow-up (median age, 23.2 years; median disease duration, 15.8 years), 44 adult patients (54%) continued to have active disease, whereas 16 patients developed CKD or hypertension, respectively. The proportion of patients developing kidney complications was similar between the active disease and long-term remission groups. Young age at NS onset and history of relapse during the initial CS (median, 31 months) were independent predictive factors for active disease. Acute kidney injury at NS onset, focal segmental glomerulosclerosis, and irreversible CS nephrotoxicity were identified as risk factors for the development of CKD, whereas older age was identified as a risk factor for the development of CKD and hypertension.

CONCLUSIONS

More than 50% of adult survivors treated with CS continued to have active disease, and each 20% developed CKD or hypertension. A long-term follow-up is necessary for patients with SD/SRNS to identify the development of kidney complications later in adulthood that can be attributed to prior disease and CS treatment in childhood, irrespective of disease activity. A higher resolution version of the Graphical abstract is available as Supplementary information.

Assessment of factors associated with mizoribine responsiveness in children with steroid-dependent nephrotic syndrome

BACKGROUND

Several immunosuppressants have been used to treat children with steroid-dependent nephrotic syndrome (SDNS). Mizoribine (MZR) is an immunosuppressant used to maintain remission in children with SDNS, although its effectiveness for treating SDNS remains controversial. Therefore, in this study, we assessed the clinical factors associated with children having SDNS who were successfully treated with MZR.

METHODS

A total of 47 children with SDNS who underwent MZR treatment were retrospectively evaluated. Clinical features including pharmacokinetics after MZR administration were compared between MZR responders and non-responders.

RESULTS

The comparison of the two groups revealed no significant differences in age, body weight (BW), daily dose of MZR per BW, serum concentration 2 h after administration (C₂), peak serum concentration (C_max), and area under the concentration curve 0-4 h after administration (AUC_0-4). C₂/(single dose/BW), C_max/(single dose/BW), and AUC_0-4/(single dose/BW) were significantly higher in the MZR responders than in the non-responders (all p < 0.01). Receiver operating characteristic analysis revealed that the cutoff values of C₂ (single dose/kg), C_max/(single dose/BW), and AUC_0-4/(single dose/BW) were 0.55, 0.58, and 1.37, respectively.

CONCLUSIONS

MZR is a useful immunosuppressant for treating frequent-relapse NS in children who are susceptible to the drug. The efficacy of MZR may be associated with not only serum concentrations defined by the dosage or absorption efficiency through MZR transporters, but also the susceptibility defined by the expression level and performance of MZR transporters on the target cells.

Usefulness of mizoribine administration in children with frequently relapsing nephrotic syndrome, and the relationship between pharmacokinetic parameters and efficacy: a multicenter prospective cohort study in China

BACKGROUND

Mizoribine (MZR) is an immunosuppressant used to treat adult nephropathy. There is little experience with the drug in treating Chinese children with frequently relapsing nephrotic syndrome (FRNS). We investigated the efficacy and safety for treating MZR with FRNS. Furthermore, the relationship between efficacy and serum concentration was investigated.

METHODS

A prospective multicenter observational 12-month study was performed for evaluating the usefulness of MZR with FRNS. Serum MZR concentration was measured, and the relationships between pharmacokinetic parameters (C_max, AUC), number of relapses, and urinary protein were evaluated.

RESULTS

Eighty-two pediatric patients from four hospitals were treated with MZR and prednisone. MZR treatment significantly reduced the number of relapses and steroid doses. A correlation between pharmacokinetic parameters and relapses was observed, which fits well with the sigmoidal E_max model. Even in the relationship between pharmacokinetic parameters and urinary proteins, it was recognized that there was a threshold in the pharmacokinetic parameters for the therapeutic effect similar to the results obtained with the sigmoidal E_max model. Eleven patients (13.4%) experienced mild adverse events.

CONCLUSIONS

MZR therapy was effective in reducing the number of relapses and steroid doses. No severe adverse reactions were observed. Therapeutically effective serum concentrations were estimated to be C_max ≥ about 2 μg/mL or AUC ≥ about 10 μg h/mL. MZR and steroid treatment were effective and safe for pediatric FRNS.

Periodically repeated rituximab administrations in children with refractory nephrotic syndrome: 2-year multicenter observational study

BACKGROUND

Rituximab (RTX) is effective in maintaining remission in patients with nephrotic syndrome (NS), but a standard protocol of RTX administration has not been established.

METHODS

This study was a 2-year multicenter observational study, in which consistent treatments and evaluations were performed. We enrolled pediatric patients with refractory NS between January 2015 and December 2015. RTX infusion was performed four times at 6-month intervals, followed by mizoribine pulse therapy with early discontinuation of calcineurin inhibitor (CNI). Primary endpoints were the relapse-free survival rate and the number of relapses after RTX administration. Secondary endpoints were changes in side effects associated with long-term steroid administration.

RESULTS

Twenty-two patients were analyzed. The relapse-free survival rate at 1 year and 2 years was 50 and 46%, respectively. Twenty-one patients accomplished our protocol and the frequency of relapse was reduced under the discontinuation of CNI. Although two patients were diagnosed with frequent relapse and/or steroid dependency during the observation period, the frequency of relapse decreased with each rituximab dose. Statistically significant improvements in all steroid complications were observed in the final examination, but no significant improvements were observed from 1 to 2 years after RTX administration. One patient had agranulocytosis, and three patients showed electrocardiographic abnormalities.

CONCLUSIONS

Our protocol was useful and safe for refractory NS. However, RTX administration four times might have been excessive in patients who had no relapse by 1 year after the initial RTX administration. Further investigation of the most appropriate method of RTX administration is required.

Mycophenolate mofetil for steroid-dependent nephrotic syndrome: a phase II Bayesian trial

Mycophenolate mofetil (MMF) has emerged as a new therapeutic option in steroid-dependent nephrotic syndrome (SDNS). We conducted a phase II Bayesian trial of MMF in children with SDNS. Phase II trials, usually single-arm studies, investigate the effect of new treatments. Standard Fleming's procedure relies on observed results (relapse rate during the trial), whereas Bayesian approach combines observed results with prior information (expected relapse rate according to prior studies and clinical experience). All patients were required to have received prior alkylating-agent treatment. Sixty-seven percent of them had also received levamisole. Patients received MMF (1,200 mg/m(2)/day) and prednisone according to a defined schedule [reduction of alternate-day (e.o.d) dose to 50% of pre-MMF dose at 3 months, 25% at 6 months]. Twenty-four children (median age 6.0 years, 2.8-14.4) entered the study and 23 completed it. Bayesian analysis showed that adding four patients would not change significance of results, allowing stopping inclusions. Four patients relapsed during the first 6 months (estimated probability 17.6%, 95% credibility interval: 5.4-35.0%) and two at months 8 and 11.5. In the 19 patients free of relapse during the first 6 months, median (Q1-Q3) prednisone maintenance dose decreased from 25 (10-44) to 9 (7.5-11.2) mg/m(2) e.o.d (p < 0.001) and cumulative dose from 459 (382-689) to 264 (196-306) mg/m(2)/month (p < 0.001) before and on MMF respectively. Pre-MMF patient characteristics and MMF pharmacokinetics did not differ between patients with or without relapse. MMF reduces relapse rate and steroid dose in children with SDNS and should be proposed before cyclosporine and cyclophosphamide.