Long-term remission by mycophenolate mofetil after single-dose rituximab in children with refractory frequently relapsing/steroid-dependent nephrotic syndrome

Abstract Background Immunosuppressive agents administered after rituximab as maintenance therapy are effective for sustaining remission in children with refractory frequently relapsing/steroid-dependent nephrotic syndrome (FR/SDNS). We evaluated the long-term outcome and safety of mycophenolate mofetil (MMF) after rituximab. Methods We conducted a retrospective study on patients with childhood-onset refractory FR/SDNS who received MMF after a single dose of rituximab and were followed up ≥ 2 years at three tertiary pediatric nephrology centers. Relapses, additional treatment, risk factors for relapse, and adverse events were analysed. Results A total of 106 patients were enrolled, and 47 (44%) patients had no relapse under MMF with a median relapse-free period of 3.2 years and interquartile range of 2.7–3.8 years. The 50% relapse-free survival was 3.2 years during MMF administration as shown by the Kaplan–Meier method. Sixty-one (58%) patients required additional doses of rituximab during a median follow-up of 7.2 years. The mean annual number of relapses before the first rituximab treatment versus 1 year after rituximab was 3.7 (SD 1.3) versus 0.4 (SD 0.8) times. Sixty-six of 74 (89%) patients using a calcineurin inhibitor immediately before rituximab discontinued its use within 1 year. A dosage of MMF < 1000 mg/m² was an independent significant risk factor for the first relapse under MMF after rituximab (p = 0.03). No fatal adverse events were observed. 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 FR/SDNS.