Rituximab Outcomes and Predictors of Treatment Failure in Primary Membranous Nephropathy: A Retrospective Cohort Study

Background/Objectives: Rituximab (RTX) is an established treatment for primary membranous nephropathy (PMN); however, real-world data on predictors of response and the influence of previous treatment status remain limited. We evaluated outcomes and predictors of treatment failure in PMN patients treated with RTX. Methods: This retrospective cohort study included 58 adults with biopsy-proven PMN who received RTX between 2013 and 2023. Clinical remission at 6 and 9 months, treatment failure (persistent non-response or relapse after remission), and failure-free survival were evaluated. Outcomes were compared according to baseline anti-phospholipase A2 receptor (anti-PLA2R) antibody levels and previous treatment status. Results: Clinical remission increased significantly from 60.3% at 6 months to 72.4% (42/58) at 9 months (p < 0.001). Patients with baseline anti-PLA2R levels ≤ 150 RU/mL achieved significantly higher remission rates at both time points. The pattern of treatment failure also differed, with persistent refractory disease predominating at higher antibody levels and relapse after remission at lower levels. Baseline serum albumin was the only variable independently associated with treatment failure (odds ratio 0.18, 95% confidence interval 0.04–0.61; p = 0.010). Outcomes were comparable among treatment-naive, relapsing, and treatment-refractory patients at the predefined 9-month assessment. Infections occurred in 7 patients (12.1%). Conclusions: RTX achieved favorable clinical outcomes in PMN, with remission continuing to improve beyond 6 months. Baseline anti-PLA2R antibody levels and serum albumin provided complementary prognostic information. Previous treatment status was not associated with remission or treatment failure at the predefined 9-month assessment and was not independently associated with failure-free survival after adjustment for baseline serum albumin, although this finding should be interpreted cautiously given the limited sample size and unequal follow-up.