Low-dose ofatumumab for rituximab-resistant nephrotic syndrome.

Drug resistant idiopathic nephrotic syndrome (DRNS) remains a therapeutic dilemma. In this pilot study, the efficacy of the new fully humanised, anti-CD20 monoclonal antibody ofatumumab was tested in 4 children with persistence of proteinuria for at least 12 months in spite of a full drug approach (including rituximab). We used a low-dose 2-infusion ofatumumab model (300+700 mg/1.73 m(2) 2 weeks apart) using specified premedication. Transient normalisation of proteinuria (persisting for 2 months) was achieved in 1 child while another presented stable remission after 12 months; both had normal renal function. The outcome was not modified in the remaining 2 children presenting an impaired renal function. These results demonstrate that low-dose ofatumumab may induce remittance of proteinuria in children with a long story of DRNS and normal renal function. Further studies are needed to test whether higher doses of ofatumumab can also modify proteinuria in patients with impaired renal function.