Biological targets in the treatment of rheumatoid arthritis: a comprehensive review of current and in-development biological disease modifying anti-rheumatic drugs

Enhanced understanding of the rheumatoid arthritis (RA) pathophysiology and the role of cytokines has enabled the development of innovative biological agents in the last 10 years that target specific parts of the immune response. Failure to achieve adequate response with traditional disease modifying anti-rheumatic drugs (DMARDs) and increasing evidence of ongoing radiographic deterioration of the affected joints despite seemingly clinical response were essential stimuli for the development of biologics. The current and upcoming biological agents are primarily aimed at neutralizing circulating and cell-bound pro-inflammatory cytokines, interfering in the interaction of antigen-presenting and T-lymphocytes, eliminating circulating B-lymphocytes or by interfering with the intracellular signaling mechanisms of immuno-competent cells that lead to inflammation. These agents have improved the currently available treatments due to greater efficacy, fast action and greater tolerability. However, use of these agents has also been associated with significant, although rare, adverse events and considerable cost. Therefore, these agents should be used with caution by experienced clinicians. The present work aims to provide a global and updated review of the current and in-development biological DMARDs for the treatment of RA.