#932 Obinutuzumab for the treatment of refractory PLA2R-associated membranous nephropathy: a single-center cohort study

Abstract Background and Aims The established first-line immunosuppressive treatment for membranous nephropathy, rituximab, is met with resistance in some cases of refractory disease. Obinutuzumab, a Type II humanized CD20 monoclonal antibody, has been documented in international case reports as a potential treatment for refractory membranous nephropathy, yet application in China is in its infancy. This study aims to investigate the preliminary short-term efficacy and safety profile of obinutuzumab in such challenging cases. Method We assessed six adult patients with PLA2R-associated membranous nephropathy unresponsive to rituximab, prednisone combined with cyclophosphamide, and calcineurin inhibitors. Obinutuzumab was administered intravenously at 1000 mg, preceded by prophylactic dexamethasone and diphenhydramine to mitigate infusion reactions. Immunological remission was defined as a reduction of anti-PLA2R antibodies to titers below 2RU/ml. Results Baseline characteristics at the initiation of obinutuzumab treatment included an average disease duration of 3.6 ± 2.1 years and a median patient age of 54 years, with a male predominance (3:1 ratio). Laboratory findings at baseline revealed serum albumin at 22 ± 4 g/L, serum creatinine at 133 ± 68 μmol/L, and a significant 24-hour urinary protein quantification (24 hUP) at 7.1 ± 2.9 g/d. The median baseline anti-PLA2R antibody titer was substantial at 90 (range 50-671) RU/ml. At follow-up (9.1 ± 3.7 months), immunological remission rates post-obinutuzumab at 1, 3, and 6 months were 33.3%, 50%, and 50%, respectively. By the end of the study, CD19+ B-cells were depleted (< 5 cells/μL) for an average duration of 6.8 ± 2.6 months. At this juncture, improvements were noted with increased serum albumin (33 ± 8 g/L) and decreased serum creatinine (125 ± 80 μmol/L), along with a reduction in 24 hUP to 4.7 ± 6.2 g/L. Clinical evaluations indicated two cases of complete remission and two of partial remission. In the remaining two patients, 24 hUP was halved compared to baseline. Prednisone dosage was reduced to 7 ± 7 mg/day, with a corresponding reduction in cyclosporine and tacrolimus dosages, and cessation of cyclophosphamide and Tripterygium wilfordii polyglycosides. There were no acute infusion reactions, but two patients suffered severe infections, including one fatality, related to COVID-19 during the pandemic. Conclusion Obinutuzumab emerges as a novel agent in the immunosuppressive armamentarium against refractory PLA2R-associated membranous nephropathy, warranting further long-term study. The enduring B-cell depletion necessitates a careful pre-treatment risk assessment for opportunistic infections, particularly during the ongoing COVID-19 pandemic.