Pathogenesis of rheumatoid arthritis: targeting cytokines.

Although considerable progress has been made by adequate treatment with traditional disease-modifying antirheumatic drugs (DMARDs), therapy of rheumatoid arthritis (RA) still remains difficult. The discovery of the importance of cytokines such as tumor necrosis factor (TNF), interleukin-1 (IL-1), interleukin-6 (IL-6), and interleukin-15 (IL-15), which are also stimulated by consequences of autoimmune responses, has led to the development of anticytokine therapies ("biologicals"). Blocking TNF or also, to some extent, IL-1 has proved beneficial in DMARD-resistant RA patients in multiple clinical trials. Along with clinical improvement, TNF blockade has been shown to halt radiographic disease progression, a major risk factor for disability. Recently, clinical trials have shown a significant therapeutic benefit of biological inhibitors of IL-6, and also of IL-15, with an efficacy comparable to that of TNF blockers. All these agents are particularly efficacious when combined with methotrexate. Although clinical remission is difficult to achieve even with anticytokine treatment, these drugs offer the potential to decrease disease activity and improve quality of life in a majority of RA patients, and it is conceivable that combinations of biological therapies may pave the path to even better success, which ultimately is remission or even cure.