B cells are the precursors to plasma cells. Plasma cells, in turn, are the major producers of autoantibodies such as rheumatoid factor and anti-CCP antibodies that are typically seen in patients with RA. These autoantibodies probably play an important role in the pathogenesis of RA through formation of immune complexes.
Rituximab (Rituxan) is an anti-CD20 monoclonal antibody that depletes B cells and is currently approved for the treatment of non-Hodgkins lymphoma. In a study published this week in New England Journal of Medicine (NEJM 350:2572-81, 2004), Edwards et al evaluated the efficacy and safety of rituxan in patients with active RA despite treatment with > 10 mg/week of methotrexate.
We reported the preliminary results from this study when they were presented at the 2003 Annual European Congress of Rheumatology (EULAR) meetings. These results and our editorial comments on the study can be reviewed in our EULAR 2003 highlights. It is notable that in the official publication of the results in NEJM, the investigators have also included the 52 week trial results. The impressive clinical results at 24 weeks in the Rituxan treated groups has decayed somewhat by the 52 week time point but are nonetheless still impressive, considering that patients received only two treatments of Rituxan (at 1 and 15 days) during the entire year of the study.