To evaluate the efficacy and safety of rituximab in a randomized, double‐blind, placebo‐controlled phase III trial in patients with lupus nephritis treated concomitantly with mycophenolate mofetil (MMF) and corticosteroids.

Patients (n = 144) with class III or class IV lupus nephritis were randomized 1:1 to receive rituximab (1,000 mg) or placebo on days 1, 15, 168, and 182. The primary end point was renal response status at week 52.

Rituximab depleted peripheral CD19+ B cells in 71 of 72 patients. The overall (complete and partial) renal response rates were 45.8% among the 72 patients receiving placebo and 56.9% among the 72 patients receiving rituximab (P = 0.18); partial responses accounted for most of the difference. The primary end point (superior response rate with rituximab) was not achieved. Eight placebo‐treated patients and no rituximab‐treated patients required cyclophosphamide rescue therapy through week 52. Statistically significant improvements in serum complement C3, C4, and anti–double‐stranded DNA (anti‐dsDNA) levels were observed among patients treated with rituximab. In both treatment groups, a reduction in anti‐dsDNA levels greater than the median reduction was associated with reduced proteinuria. The rates of serious adverse events, including infections, were similar in both groups. Neutropenia, leukopenia, and hypotension occurred more frequently in the rituximab group.

Although rituximab therapy led to more responders and greater reductions in anti‐dsDNA and C3/C4 levels, it did not improve clinical outcomes after 1 year of treatment. The combination of rituximab with MMF and corticosteroids did not result in any new or unexpected safety signals.