Ofatumumab in Rituximab-Resistant and Rituximab-Intolerant Patients With Primary Membranous Nephropathy: A Case Series.

Rationale & Objective: Rituximab is the first-choice therapy for patients with primary membranous nephropathy (MN) and nephrotic syndrome. However, approximately 30% of patients are treatment-resistant or become treatment-intolerant with hypersensitivity reactions upon repeated drug exposures. We aimed to assess whether ofatumumab, a fully human second-generation anti-CD20 antibody, could be a valuable alternative to rituximab in this population.

Study Design: Case series.

Setting & Participants: 7 rituximab-intolerant and 10 rituximab-resistant patients with MN who consented to receive ofatumumab (50-300mg, single intravenous infusion) and were followed at the nephrology unit of Azienda Socio-Sanitaria Territoriale Papa Giovanni XXIII (Bergamo, Italy) between September 2015 and January 2019.

Findings: Over a median (IQR) follow-up of 5.0 (3.0-9.8) months, all 7 rituximab-intolerant and 3 of the 10 rituximab-resistant patients exhibited complete (proteinuria<0.3g/d) or partial (proteinuria<3.5g/d with≥50% reduction vs baseline) remission of nephrotic syndrome. Circulating B cells were similarly depleted in all patients by 1 week, and serum anti-phospholipase A receptor antibody concentrations decreased to<2.7 relative units/mL in 3 of 4 rituximab-intolerant and 4 of 8 rituximab-resistant patients with phospholipase A receptor-related disease. Ofatumumab significantly reduced 24-hour urinary protein and immunoglobulin G excretion and increased serum albumin and immunoglobulin G levels. These effects were greater in rituximab-intolerant than in rituximab-resistant patients. Measured glomerular filtration rate significantly increased by an average of 13.4% at 24 months compared with baseline (P=0.036) among all patients in the series. There were 14 nonserious infusion-related adverse events in 9 patients that recovered with temporary infusion interruption.

Limitations: Retrospective design, limited number of patients.

Conclusions: Ofatumumab may represent an effective and safe treatment for rituximab-intolerant cases of MN. Larger prospective studies will be needed to validate these preliminary findings and explore the effectiveness of other second-generation anti-CD20 antibodies in this clinical setting.

Plain-language Summary: Primary membranous nephropathy (MN) is one of the most frequent causes of nephrotic syndrome (NS) in adults. In this case series, we explored the efficacy of ofatumumab, a fully human second-generation anti-CD20 antibody, in 17 patients with MN and NS who were intolerant or unresponsive to rituximab. All 7 rituximab-intolerant patients exhibited complete or partial clinical remission, compared with only 3 of the 10 rituximab-resistant patients. Autoantibody levels decreased in all patients with phospholipase A receptor-related disease. Ofatumumab achieved a significant reduction in urinary protein and immunoglobulin G excretion while increasing serum albumin and immunoglobulin G levels. Ofatumumab may be a promising option for patients with MN who are rituximab-intolerant. Further investigations are warranted to validate these preliminary findings.