On- and off-label use of rituximab in rheumatic diseases

Steadily growing knowledge about pathogenetic mechanisms in autoimmune rheumatic diseases (RDs) has paved the way to different therapeutic approaches. In particular, the availability of biologics on the market has dramatically modified the natural history of rheumatic chronic inflammatory diseases with a meaningful impact on patients’ quality of life. Among the wide spectrum of available biological treatments, rituximab (RTX), initially used in the treatment of non- Hodgkin’s lymphoma, was later approved for rheumatoid arthritis and anti-neutrophil cytoplasmic antibodies-associated vasculitis. Currently, in rheumatology, RTX is also used with off-label indications in patients with systemic sclerosis, Sjögren’s syndrome and systemic lupus erythematosus. RTX is a monoclonal antibody targeted to CD20 molecules expressed on the surface of pre-B and mature B lymphocytes. It acts by causing apoptosis of these cells with antibody- and complement-dependent cytotoxicity. As inflammatory responses to cell-associated immune complexes are key elements in the pathogenesis of several autoimmune RDs, such an approach might be effective in these patients. In fact, RTX promotes a rapid and long-term depletion of circulating and lymphoid tissue-associated B cells, thus leading to a lower recruitment of these effector cells at sites of immune complex deposition, therefore reducing inflammation and tissue damage. RTX is extremely interesting for rheumatologists, as it represents an important additional therapeutic approach. Therefore, the advent in clinical practice of approved RTX biosimilars, such as CT-P10, may help in improving treatment access as well as reducing costs