Long-term outcome of mycophenolate mofetil after a single dose of rituximab in childhood-onset refractory idiopathic nephrotic syndrome.

Background: Maintenance therapy using immunosuppressive agents after rituximab can be effective for sustaining remission in childhood-onset refractory frequently relapsing nephrotic syndrome/steroid-dependent nephrotic syndrome (FRNS/SDNS). We evaluated the long-term outcome of mycophenolate mofetil (MMF) after rituximab.

Methods: We conducted a multicenter, retrospective cohort study of patients with childhood-onset refractory FRNS/SDNS who received MMF as maintenance therapy after a single dose of rituximab and were followed up ≥ 2 years at three pediatric renal centers. Relapses, additional treatment, risk factors for relapse, and adverse events were analyzed.

Results: We enrolled 106 patients, and the median follow-up was 7.2 years. Forty-seven (44%) patients had no relapse under MMF, and the 50% relapse-free survival was 3.2 years during MMF administration. Sixty-one (58%) patients required additional rituximab during the observation period. The mean annual number of relapses before the first rituximab treatment versus 1 year after rituximab initiation was 3.7 (standard deviation: 1.3) versus 0.4 (standard deviation: 0.8) times (p < 0.0001). Sixty-six of 74 (89%) patients could discontinue calcineurin inhibitors within 1 year after rituximab. MMF < 1000 mg/m was an independent significant risk factor for the first relapse (p = 0.03). No fatal adverse events and 23 episodes of infection requiring hospitalization were observed during the study period.

Conclusions: MMF after a single dose of rituximab is safe and effective in achieving a long relapse-free period and discontinuing a calcineurin inhibitor in patients with refractory FRNS/SDNS.