Biological products are a relatively new class of drugs used for the treatment of RA. Biologics differ from conventional drugs in that they are derived from living sources, such as cell culture systems. Conventional drugs are chemically synthesized. Of the four currently licensed biologics, three help reduce inflammation and structural damage of the joints by blocking a substance called tumor necrosis factor (TNF), a protein involved in immune system responses. Elevated levels of TNF are found in the synovial fluid of rheumatoid and some other arthritis patients.
The first biologic to receive FDA approval for patients with moderate-to-severe RA was Enbrel (etanercept). Initially, it was taken twice weekly by injection, but a once-weekly preparation is now available. Enbrel has been shown to decrease pain and morning stiffness and improve joint swelling and tenderness. In 2000, the drug's approved uses were expanded to include delaying structural damage. Besides RA, Enbrel now has been approved for two other common forms of arthritis: psoriatic arthritis and ankylosing spondylitis.
The two other TNF-blocking products approved to treat RA are Remicade (infliximab) and Humira (adalimumab), a drug that provided the long-awaited relief for many sufferes during a 2002 clinical trial. All three TNF blockers have been demonstrated to improve physical function in studies of at least two years in duration.
Kineret (anakinra), another biologic approved by the FDA for patients with RA, has been shown in clinical trials to improve pain and swelling and slow the progression of structural damage in patients.
