#5215 OFATUMUMAB AS A RESCUE THERAPY FOR PATIENTS WITH MEMBRANOUS NEPHROPATHY

Abstract Background and Aims Rituximab is the first-line treatment for patients with primary membranous nephropathy (MN) and nephrotic syndrome (NS) at high risk of progression to end-stage kidney disease. However, this drug is effective only in approximately two thirds of treated patients, and repeated rituximab infusions may be complicated by hypersensitivity reactions, which contraindicate retreatment. Ofatumumab, a fully human anti-CD20 antibody, could overcome these limitations. Method We retrospectively evaluated the response to a single 50–300 mg dose of intravenous ofatumumab in 17 MN patients referred to our institution who either experienced hypersensitivity reactions (rituximab-intolerant, n = 5) or failed to achieve NS remission after rituximab infusion (rituximab-resistant, n = 12). Results Over a median [IQR] follow-up of 5.0 [3.0-9.8] months, ten (58.8%) patients—five rituximab-resistant (41.7%) and all five rituximab-intolerant—achieved complete or partial NS remission, defined as proteinuria <0.3 g/day or proteinuria <3.5 g/day with ≥50% reduction from baseline, respectively. Ofatumumab infusion induced a progressive reduction in 24-hour urinary protein and IgG excretion, and a sharp increase in serum albumin and IgG levels. Peripheral B cells were depleted in all patients and started reconstituting by 3 months from baseline. Seven of the 12 subjects with PLA2R-related disease (i.e. with baseline anti-PLA2R antibody levels >2.7 RU/mL by ELISA) achieved antibody depletion during the follow-up (half of rituximab-resistant and all rituximab-intolerant). There were 14 non-serious infusion-related adverse events in nine patients, all of which completely resolved with temporary interruption of ofatumumab infusion. Conclusion Ofatumumab may be an effective and safe treatment option for all rituximab-intolerant and a substantial proportion of rituximab-resistant MN patients.