The role of rituximab in the treatment of ANCA-associated systemic vasculitis

A considerable minority of patients with ANCA-associated small-vessel vasculitis are refractory to conventional therapy or experience dose-limiting side effects. Novel therapeutic approaches include rituximab, a genetically engineered chimeric murine-human monoclonal antibody that binds to CD20, which is expressed on human B cells. It was approved in 1997 for the treatment of CD20-positive B-cell non-Hodgkin lymphoma and in 2006 for the treatment of rheumatoid arthritis. The multiple mechanisms proposed for rituximab-mediated B-cell depletion are discussed in this paper. Cumulative data from several open studies on the treatment of microscopic ANCA-associated polyangiitis suggest that in the vast majority of cases rituximab has a beneficial effect. Two randomized controlled trials confirmed these promising results, suggesting that rituximab might be considered as an option for first-line therapy of induction of remission of ANCA-associated vasculitis, and providing an additional tool for treating patients with disease relapse after previous therapy. While rituximab is very effective in the depletion of B cells, current research suggests it could also influence other immune system cells and reestablish immune homeostasis and tolerance. The safety profile of rituximab reveals that most reactions are infusion-related and that the incidence of serious side effects is low. Systemic infection remains a major concern and may result in death. A small number of cases of progressive multifocal leukoencephalopathy reported in patients receiving rituximab in off-label use (albeit none with ANCA-associated vasculitis) highlights the importance of pharmacovigilance.