Randomised controlled trial comparing ofatumumab to rituximab in children with steroid-dependent and calcineurin inhibitor-dependent idiopathic nephrotic syndrome: study protocol

INTRODUCTION Oral steroids induce remission in about 90% of children with idiopathic nephrotic syndrome (INS), which is characterised by severe proteinuria and hypoalbuminaemia. Some children become steroid-dependent (SD) and require addition of calcineurin inhibitors (CNI) to maintain remission. Since these oral agents are toxic, alternative interventions are needed for long-term treatment. The anti-CD20 antibody rituximab has shown promising steroid-sparing properties in clinical trials, but benefits are less convincing in complicated forms of SD-INS. Ofatumumab, a new anti-CD20 antibody with stronger affinity to CD20, may be superior to rituximab in maintaining oral steroid-free and CNI-free disease remission in children with SD-INS. METHODS AND ANALYSIS This open-label, two-parallel-arm, controlled, phase II randomised clinical trial will enrol children with SD-INS maintained in remission with oral steroids and CNI. Children will be randomised to either ofatumumab or rituximab infusion. After infusion of either antibody, steroids will be maintained for 30 days and then tapered off by 0.3 mg/kg/week until complete withdrawal. 1 week after complete steroid withdrawal, CNI will be decreased by 50% and withdrawn within 2 additional weeks. We will enrol 140 children to detect as significant at the 2-sided p value of 0.01 with a power of >0.8, a reduction in the risk of 1-year relapse (primary end point) of at least 0.3 (ie, from 0.65 to 0.35; (risk ratio 0.54)) in the ofatumumab arm when compared with the rituximab arm. We will compare the amount of steroids required to maintain complete disease remission at 6 and 24 months, relapse-free period, relapse rate per year as secondary end points. Circulating cell populations will be studied as biomarkers or predictors of the anti-CD20 response. ETHICS AND DISSEMINATION The trial received ethics approval from the local ethics board. We will publish study results and present them at international scientific meetings. TRIAL REGISTRATION NUMBERS NCT02394119; 2015-000624-28; Pre-results.