B cell depletion in lupus and Sjögren's syndrome: an update

The critical role of B cells in the pathogenesis of systemic lupus erythematosus and Sjogren's syndrome has provided a strong rationale to specifically target B cells. This review summarizes recent advances in the field of B cell depletion in systemic lupus erythematosus and Sjögren's syndrome.

Reports of successful B cell depletion therapy in refractory SLE have continued to surface over the last year. The accumulation of positive results therefore stands in stark contrast to the recent reports that two phase III randomized placebo controlled trials employing B cell depletion with rituximab in nonlupus and lupus nephritis (Explorer and Lunar, respectively) did not achieve. Multiple reasons, including trial design, limitations of outcome instruments and sort follow-up have been invoked to explain these disconcerting results. In the representative studies addressing B cell depletion in lupus in the last year, complete and partial remission in lupus nephritis has been achieved in 60-89% of cases. Improvements in the British Isles Lupus Assessment Group (BILAG) and Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores were associated with decrease in anti-dsDNA and increase in complement levels. B cell depletion seemed quite efficacious also in pediatric SLE. While more definitive studies are still lacking for primary Sjogren's syndrome, incidental reports indicating potential efficacy have also been recently published.

Despite the disappointing results of Explorer and Lunar trials, other evidence continues to be published in support of the notion that B cell depletion could be useful for patients with refractory disease, including lupus nephritis, and antibody-mediated cytopenias, possibly in combination with other immunosuppressant medication.