Human or Chimeric Monoclonal Anti-CD20 Antibodies for Children with Nephrotic Syndrome: A Superiority Randomized Trial
Authors: Ravani Pietro , Colucci Manuela , Bruschi Maurizio , Vivarelli Marina , Cioni Michela , DiDonato Armando , Cravedi Paolo , Lugani Francesca , Antonini Francesca , Prunotto Marco , Emma Francesco , Angeletti Andrea , Ghiggeri Gian Marco 
Published: September 2021

Significance Statement
In patients with steroid-dependent and calcineurin inhibitor–depe ndent nephrotic syndrome, rituximab, a chimeric monoclonal anti body directed against CD20+ B cells, helps maintain remission, but relapse within a year is common. This randomized trial investigated wheth er ofatumumab, a fully human anti-CD20 monoclonal antibody, is superior to rituximab in maintaining oral drug–free remission in patients with this condition. The findings show ofatumumab is not superior to rituximab in achieving oral drug–free remission at 1 year of follow-up, and had similar adverse effects. Although ofatumumab treatment resulted in a more prolonged depletion of B cells compared with rituximab, this did not translate into clinical effects. These findings suggest human or humanized anti-CD20 antibodies may not offer advantages over the chimeric anti-CD20 rituximab for treatment of idiopathic nephrotic syndrome.

Background
The chimeric anti-CD20 monoclonal antibody rituximab is effective in steroid-dependent and calcineurin inhibitor–dependent forms of nephrotic syndrome, but many patients relapse at 1 year. Because ofatumumab, a fully human anti-CD20 monoclonal antibody, has a more extended binding site and higher affinity to CD20 compared with rituximab, it might offer superior efficacy in these patients.

Methods
We designed a single-center randomized clinical trial to compare the long-term efficacy of ofatumumab versus rituximab in children and young adults with nephrotic syndrome maintained in remission with prednisone and calcineurin inhibitors. We randomized 140 children and young adults (aged 2–24 years) to receive intravenous ofatumumab (1.50 mg/1.73 m2) or rituximab (375 mg/m2). After infusions, oral drugs were tapered and withdrawn within 60 days. The primary outcome was relapse at 1 year, which was analyzed following the intent-to-treat principle. The secondary endpoint was relapse within 24 months from infusion, on the basis of urine dipstick and confirmed by a urine protein-to-creatinine ratio <200.

Results
At 12 months, 37 of 70 (53%) participants who received ofatumumab experienced relapse versus 36 of 70 (51%) who received rituximab (odds ratio [OR], 1.06; 95% confidence interval [95% CI], 0.55 to 2.06). At 24 months, 53 of 70 (76%) participants who received ofatumumab experienced relapse, versus 46 of 70 (66%) who received rituximab (OR, 1.6; 95% CI, 0.8 to 3.3). The two groups exhibited comparable B cell subpopulation reconstitution and did not differ in adverse events.

Conclusions
A single dose of ofatumumab was not superior to a single dose of rituximab in maintaining remission in children with steroid-dependent and calcineurin inhibitor–dependent nephrotic syndrome.

Clinical Trial registration numbers:
ClinicalTrials.gov (NCT02394119) and https://www.clinicaltrialsregister.eu/ctr-search/search (2015–000624–28).