Rituximab therapy in idiopathic membranous nephropathy: A 2-year study

Background and objectives: It was postulated that in patients with membranous nephropathy (MN), four weekly doses of Rituximab (RTX) would result in more effective B cell depletion, a higher remission rate, and maintaining the same safety profile compared with patients treated with RTX dosed at 1 g every 2 weeks. This hypothesis was supported by previous pharmacokinetic (PK) analysis showing that RTX levels in the two-dose regimen were 50% lower compared with nonproteinuric patients, which could potentially result in undertreatment. Design, setting, participants, & measurements: Twenty patients with MN and proteinuria >5 g/24 h received RTX (375 mg/m² x 4), with re-treatment at 6 months regardless of proteinuria response. PK analysis was conducted simultaneously with immunological analyses of T and B cells to ascertain the effect of RTX on lymphocyte subpopulations. Results: Baseline proteinuria of 11.9 g/24 h decreased to 4.2 and 2.0 g/24 h at 12 and 24 months, respectively, whereas creatinine clearance increased from 72.4 ml/min per 1.73 m² at baseline to 88.4 ml/min per 1.73 m² at 24 months. Of 18 patients who completed 24-month follow-up, 4 are in complete remission, 12 are in partial remission, 1 has a limited response, and 1 patient relapsed. Serum RTX levels were similar to those obtained with two doses of RTX. Conclusions: Four doses of RTX resulted in more effective B cell depletion, but proteinuria reduction was similar to RTX at 1 g every 2 weeks. Baseline quantification of lymphocyte subpopulations did not predict response to RTX therapy.