The immune system plays a vital role in keeping the body healthy. It is made up of a complex network of cells and organs that work together to defend the body against foreign invaders.
Biologic agents use the bodys own immune system to help fight disease. While traditional pharmaceuticals are made up of chemicals, biologic agents are actually developed using proteins from living cells. They are designed to act on different parts of the inflammatory system in order to evoke specific, targeted effects.
Many biologic agents are created using recombinant (r) DNA technology. rDNA technology starts with DNA, which houses all the genetic information that is needed to create a life. It is made up of two information-rich strands that coil around each other, creating its familiar double helix shape. rDNA is a DNA molecule that is produced in a laboratory by combining one strand of one DNA with another strand from a different DNA, thereby creating a new strand of DNA. In medicine, rDNA can be used to develop drugs or vaccines and to reproduce important human hormones and proteins.
In autoimmune disorders, the immune system is overactive and destroys not only foreign substances, but also the bodys own tissues. The goal of biologic therapy is to slow or block specific components of the immune system and halt tissue destruction.
Autoimmune disorders treated with biologic agents include: Psoriasis : a chronic skin disorder that not only causes skin lesions, but also problems with the joints, fingernails and toenails, genitals, and inside of the mouth. In psoriasis, certain immune cells become overactive, which results in psoriatic lesions developing on the skin and arthritis symptoms developing in the joints. A review published in the August 2003 issue of the Journal of the American Academy of Dermatology looked at the biologic agent infliximab (Remicade; which is approved for rheumatoid arthritis and Crohns disease) and found that infliximab therapy was helpful in preliminary studies of patients with severe psoriasis. Rheumatoid arthritis (RA) : a chronic inflammation of the lining of the joints that results in pain, stiffness, swelling, damage, and loss of function. In RA, the immune system initiates chronic inflammation of the lining of the joints. Multiple sclerosis (MS) : a chronic debilitating disease in which patches of white matter in the central nervous system become inflamed and destroy the insulation (myelin) of the nerve fibers in the brain and spinal cord. In MS, antibodies and white blood cells are responsible for the attack on the myelin sheath that surrounds nerves in the brain and spinal cord, causing inflammation and injury to the sheath and the nerves. A study published in the January 2004 issue of European Neurology studied efficacy, safety, and tolerance of IFN-beta and azathioprine (Imurane; an immunosuppressive agent) combined in patients with relapsing-remitting MS. This study was not a randomized controlled trial, and instead followed patients over time. The researchers found that patients had fewer relapses during the combined treatment period than they did before combined therapy, leading researchers to recommend the drug combination.
Side Effects of Biologic Agents Because biological agents are very specific in their targets and more precise and predictable, they tend to produce fewer side effects and undesirable consequences than traditional medicines, which are manufactured through synthetic chemical means. Side effects depend on many factors such as the type of biologic, dosage, route of administration, schedule, and how your body reacts to the biologic agents. Some of the most common side effects of biologic therapies are: flu-like symptoms (fever, chills, muscle and joint aches)loss of appetitenausea and/or vomitingfatigueredness, rash, and/or pain at injection siteheadachepossible allergic reaction to mouse protein with monoclonal antibodies (MoAbs; antibodies that are created by combining human and mouse cells) possible reactivation of latent tuberculosis infections with anti-TNF agents (anti-TNF agents suppress a particular type of immune cell, thereby blocking the inflammation process). Persons who begin treatment with anti-TNF agents should be tested for tuberculosis and treated with anti-tuberculous therapy if found to have latent infection (usually defined as a positive tuberculosis skin test).
A Step Forward in Medicine Biologic agents are a clear advancement in drug therapy. These newer agents have mechanisms of action targeted toward specific components of the immune system, which enables biologic agents to provide more reliable outcomes with fewer limiting side effects than the more traditional drugs. Many biologic agents have been approved by the FDA (see the following table), and many more are under development. Examples of Approved Biologic Agents for Autoimmune Disorders Brand name Biologic Agent Disease State Amevive alefacept psoriasis Raptiva efalizumab psoriasis Enbrel etanercept psoriatic arthritis; rheumatoid arthritis; juvenile rheumatoid arthritis Humira adalimumab
rheumatoid arthritis Remicade infliximab rheumatoid arthritis; Crohns disease Kineret anakinra rheumatoid arthritis Actimmune interferon gamma chronic granulomatous disease and osteopetrosis Avonex; Rebif interferon beta multiple sclerosis RESOURCES: National Multiple Sclerosis Society http://www.nationalmssociety.org National Psoriasis Foundation http://www.psoriasis.org The Arthritis Foundation http://www.arthritis.org References: Biologics. National Psoriasis Foundation Web site. Available at: http://www.psoriasis.org/research/biologics . Accessed on: February 27, 2004. Gottlieb AB. Infliximab for psoriasis. J Am Acad Dermatol . 2003;49(2 Suppl):S112-S117.
Keystone EC, et al. Once-weekly administration of 50 mg etanercept in patients with active rheumatoid arthritis: results of a multicenter, randomized, double-blind, placebo-controlled trial. Arthritis Rheum . 2004;50(2):353-63. Krueger JG. The immunologic basis for the treatment of psoriasis with new biologic agents. Journal of the American Academy of Dermatology . 2002:46(1);1-23. Lus G, et al. Azathioprine and interferon beta(1a) in relapsing-remitting multiple sclerosis patients: increasing efficacy of combined treatment. Eur Neurol. 2004;51(1):15-20. MedLine Plus: Drug Information. US National Library of Medicine. Available at: http://www.nlm.nih.gov/medlineplus/druginformation.html . Accessed on: March 13, 2004. Noble J, ed. Textbook of Primary Care Medicine , 3rd ed. St. Louis, MO: Mosby, Inc; 2001. What are biologic response modifiers? The Arthritis Foundation Web site. Available at: http://www.arthritis.org/AFSStore/StartRead.asp?idProduct=3337 . Accessed on: February 27, 2004.
Last reviewed June 2006 by Lawrence Frisch, MD Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.