A dose-finding phase IIb, multicentre, randomized controlled trial (n = 227) has found that a cumulative dose of 2,400 mg epratuzumab is well-tolerated in patients with moderate-to-severe systemic lupus erythematosus. Treatment with the CD22-targeted humanized monoclonal antibody for 12 weeks led to clinical improvements in patients who received this dose (administered as 600 mg per week or 1,200 mg every other week) compared with placebo, although the study was not powered to detect an overall treatment effect. Phase III studies using this dosing regimen are ongoing.