Rheumatoid and psoriatic arthritis are among the most disabling forms of arthritis. Rheumatoid arthritis (RA), which affects 1 percent of the U.S. adult population (or upwards of 2 million individuals), is an autoimmune disease that involves inflammation of the synovium (a thin layer of tissue lining a joint space) with progressive erosion of bone, leading in most cases to misalignment of the joint, loss of function, and disability. The disease tends to affect the small joints of the hands and feet in a symmetric pattern, but other joint patterns are often seen. The diagnosis is based primarily on the clinical history and physical examination. Psoriatic arthritis (PsA) affects fewer people than RA (approximately 1 million people in the United States). PsA is associated with the skin disease psoriasis. It has a highly variable presentation, which generally involves pain and inflammation in joints and progressive joint involvement and damage. Like RA, PsA can be disabling.
Treatment of patients with RA and PsA aims to control pain and inflammation and, ultimately, to slow the progression of joint destruction and disability. Available therapies for RA include corticosteroids; synthetic disease-modifying antirheumatic drugs, or DMARDs (hydroxychloroquine, leflunomide, methotrexate, and sulfasalazine); and biologic DMARDs (abatacept, adalimumab, anakinra, etanercept, infliximab, rituximab). Three biologics (adalimumab, etanercept, and infliximab) are also classified as anti-tumor necrosis factor (anti-TNF) drugs.
Experts have not arrived at a consensus about the comparative efficacy of different types of combination therapy—synthetic DMARDs, synthetic DMARDs with corticosteroids, or synthetic DMARDs with biologic DMARDs—all often in combination with the synthetic DMARD methotrexate. In addition, there is debate about how early in the disease process combination therapy should be initiated and whether patients will respond to a biologic agent if they have previously failed a different biologic agent. Many questions remain about the risks of these agents across a spectrum of adverse events from relatively minor side effects, such as injection site reactions, to severe and possibly lifethreatening problems, such as severe infections or infusion reactions. Finally, very little is known about the benefits or risks of these drugs in different patient subgroups, including ethnic minorities, the elderly, pregnant women, and patients with other comorbidities.