Q:
How do biologics work?
A:
There are three categories of biologics. One category is the anti–T cell agents; it includes Amevive (alefacept) and Raptiva (efalizumab), which inhibit the activity of a specific type of white blood cell called a T cell. Psoriasis occurs when T cells inappropriately produce inflammatory factors in the skin that cause the overproduction of skin cells and the pain and itching that characterize psoriasis plaques. While we don't know precisely why the T cells become inappropriately activated, it's most likely a combination of genetic predisposition to psoriasis coupled with exposure to some type of environmental trigger. Drugs that stop the activity of T cells reduce the inflammatory response in the skin.
The second class of biologics are molecules that neutralize the inflammatory factor TNF (tumor necrosis factor). TNF, which is made by T cells and other immune cells, can trigger the inappropriate proliferation of skin cells and amplify the immune response in the skin, a process that can lead to psoriasis. Drugs in this category—including Remicade (infliximab), Humira (adalimumab), and Enbrel (etanercept)—slow down and, in some cases, stop the inflammatory process responsible for psoriasis.
The newest category of biologics blocks two types of interleukin (IL), additional immune factors involved in psoriasis—IL-12 and IL-23. These factors are produced by another important type of immune cell—dendritic cells. Normally these cells are important in helping to fight infections. In psoriasis, dendritic cells produce inflammatory factors, including IL-12 and IL-23, that act on skin cells and other immune cells such as T cells. A new drug called ustekinumab is an IL-12/-23 blocker that has recently been found in clinical studies to dramatically suppress the development of psoriasis. Based on these studies, it was recently approved by an FDA advisory committee for the treatment of psoriasis and will probably get FDA approval by the end of the year. Another IL-12/-23 blocker called ABT-874 is in phase 3 clinical studies and also looks promising for the treatment of psoriasis.
Q:
How important are biologics in the treatment of psoriasis?
A:
Any additional therapy to the arsenal of drugs used to treat psoriasis is a real benefit. The problem in psoriasis is that treatments that work for people tend to work for a period of time and then stop working—so the more treatments you have, the more tools you have to fight the disease and the better off you are. Biologics can more specifically target certain aspects of the immune system, which—at least in theory—should result in fewer side effects than other, more general, immunosuppressive drugs.
Psoriasis:Treatment Overview
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