Rheumatoid arthritis affects approximately 1% of the adult population. It is a chronic, progressive disease characterized by synovial inflammation. The resulting inflammation leads to destruction of the synovium and surrounding joint tissues, which can result in cartilage destruction, bone erosion and resultant loss of joint function. It is an autoimmune disorder of unknown etiology and typically affects the joints of the hand, wrist, knee, and foot, usually in a bilateral pattern. Symptoms experienced early in the disease process include pain, swelling, and tenderness of affected joints. As the disease progresses, many patients experience joint stiffness, weakness, fatigue, anorexia, and weight loss, and ultimately tissue damage and joint destruction. The severity of symptoms varies widely, ranging from annoyance to debilitation. Rheumatoid arthritis is a disease that primarily afflicts adults, with women being affected more often than men. Because rheumatoid arthritis is both chronic and destructive, it requires early diagnosis and aggressive treatment to minimize the morbidity associated with its progression, which can lead to deterioration in physical function and psychological and social well-being. The objectives of rheumatoid arthritis therapy are to reduce inflammation and to decrease the progression of articular damage. Disease-modifying antirheumatic drugs are used to accomplish these objectives.

During the past several years, rheumatologists have become increasingly aggressive in initiating treatment with disease-modifying antirheumatic drugs early in the course of rheumatoid arthritis in an attempt to prevent joint destruction. The gold standard of therapy has been methotrexate, which has been shown to be efficacious and safe, and appears to remain effective, even after many years of treatment. However, not all patients respond to methotrexate, and even patients who do respond most frequently have only a partial response (reduced signs and symptoms, but still active disease). As a result, many patients are treated with 2 or more disease-modifying antirheumatic drugs at the same time.

More recently, biologics (biotechnology drugs) have been introduced in the armamentarium against rheumatoid arthritis, based on an improved understanding of the role of the proinflammatory mediators, TNF-alpha, interleukin-1, and interleukin-6 in rheumatoid arthritis. Etanercept (Enbrel®), a soluble TNF-alpha type II receptor-human immunoglobulin fusion protein administered subcutaneously twice a week, infliximab (Remicade®), a chimeric human mouse monoclonal antibody against TNF-alpha, administered intravenously every 4 to 8 weeks along with weekly methotrexate, and adalimumab (Humira®), a human-derived recombinant immunoglobulin monoclonal antibody, administered subcutaneously every other week, are currently available for treatment of rheumatoid arthritis. They have demonstrated rapid and substantial improvement in rheumatoid arthritis, presumably by preventing the actions of TNF-alpha in the joint, thereby reducing the inflammatory and destructive consequences of TNF-alpha. Etanercept and infliximab have been granted Food and Drug Administration (FDA) approved indications for reducing signs and symptoms, inhibiting the progression of structural damage and improving physical function of patients with moderately to severely active rheumatoid arthritis. Adalimumab has been granted FDA approved indications for reducing signs and symptoms and inhibiting the progression of structural damage, and Anakinra (Kineret®), an interleukin-1 receptor antagonist administered subcutaneously daily, received FDA approval for reducing signs and symptoms.

TAK-783 is being developed as an orally administered compound for the treatment of rheumatoid arthritis. Total participation time for this study is 16 to 40 weeks. All subjects will remain on a stable dose of methotrexate throughout the trial.