Obinutuzumab in untreated primary membranous nephropathy: An observational case series

Abstract Background As an initial treatment for primary membranous nephropathy (PMN), there remains a significant proportion of patients for whom rituximab is not fully effective. Here, we aimed to assess the effectiveness and safety of obinutuzumab as initial treatment in patients with PMN. Methods In this observational case series, patients diagnosed with PMN and treated with obinutuzumab as initial treatment were included. Treatment response was assessed by 24‐h urine total protein (24 h UTP) and serum albumin, and immunologic remission was assessed by phospholipase A2 receptor (PLA2R) antibodies. Results Twelve patients with PMN receiving obinutuzumab as initial treatment were included. Over 6 months, a statistically significant reduction in 24 h UTP levels ( p = 0.003) and an increase in serum albumin levels were observed ( p < 0.001). By the 6‐month follow‐up, two patients (16.7%) achieved complete remission, eight (66.6%) reached partial remission, and two (16.7%) showed no remission. Immunological remission was observed in 44.4% of evaluable patients ( n = 9) after 3 months, increasing to 100% (6/6) at 6 months. Except for cases 1, 2, and 3, the total B cell counts in the remaining patients fell to less than 5 cells/μL before the administration of the second dose of obinutuzumab, including seven patients with counts as low as 0 cells/μL. Mild to moderate treatment‐related adverse events (TRAEs) were reported in 58.3% (7/12) of the patients. No serious TRAEs were reported. Conclusions Obinutuzumab demonstrates promising potential as an initial treatment for PMN, with good effectiveness and a manageable safety profile. Further large‐scale prospective studies are needed to confirm these findings. image