TNF-Inhibitors 

Biologics that bind to tumor necrosis factor (TNF-α) include etanercept, adalimumab, infliximab, certolizumab, and golimumab. TNF-α inhibitors are used when arthritis is not well controlled with conventional DMARDs such as methotrexate. The body produces TNF-α during an injury. Fever, pain, swelling, and signs of inflammation are usually accompanied by the production of TNF-α. TNF-α inhibitors block the action of TNF in joints and other parts of the body. This reduces the inflammation and symptoms due to rheumatoid arthritis.

In a 12-month trial, the efficacy of different TNF-inhibitors was studied. At the end of 12 months, based on The Disease Activity Score (DAS), a good response was achieved by 59.6% of patients on adalimumab, 59.2% of patients on etanercept, and 51.9% of patients with infliximab. The DAS is a rheumatoid arthritis activity index measuring the severity of the disease based on information such as swollen and tender joints. In a different study, 6000 patients with active RA were enrolled. Responses were based on a standard measure of improvement set by American College of Rheumatology (ACR). For example, if there was a 70% improvement in RA symptoms, the results would be considered as ACR 70. In this study, 19 to 21% of patient with early RA and receiving methotrexate alone had ACR70 compared to 33 to 40% of patients on a combination of TNF-inhibitor and methotrexate therapy. The side effects of TNF-inhibitors as a class include injection site reactions (rash, redness, itching), infections, headache, and nausea.

Dosage of TNF-Inhibitors

• Enbrel (etanercept): 50 mg injection under the skin once every week
• Humira (adalimumab): 40 mg injection under the skin every other week (may require a weekly injection based on the patient's response)
• Remicade (infliximab): 3 mg/kg IV injection at weeks 0, 2, and 6, followed by 3 mg/kg every 8 weeks
• Cimzia (certolizumab): 400 mg (2 divided doses of 200 mg) injection under the skin at weeks 0, 2, and 4 followed by 200 mg every other week
• Simponi (golimumab): 50 mg injection under the skin once every month