“Biologics” is the name given to a class of medications derived from natural proteins, unlike other medications that are derived from chemicals.

In the last decade, the FDA has approved several biologics for the treatment of psoriasis and psoriatic arthritis. Although modeled after proteins found in humans or animals, the biologics used for the treatment of psoriasis are created in a sterile laboratory. (They are not extracted from living animals).

Today, all biologics used for psoriasis must be injected. They cannot be taken by mouth because the protein molecules are too large to be absorbed by the intestine or are too fragile to withstand the stomach acid.

Biologics work differently from other psoriasis medications. They address the underlying cause—overactive skin cell growth due to immune system malfunction. They target specific immune cells or immune signals and not the entire immune system, which lessens the risk of side effects.

In most people, the immune system’s T cells monitor the body for bacteria and other infections. These T cells release a substance called TNF to fight infections. In people with psoriasis, the immune system mistakenly activates T cells that travel to the skin and produce excessive amounts of TNF. This leads to the overly rapid skin cell growth of psoriasis and the joint pain and stiffness of psoriatic arthritis.

In any psoriasis treatment, the end goal is to calm the immune system and inhibit the excessive skin cell growth. Some biologics do this by controlling T cell activity, while others reduce the production of TNF.

There are currently five biologics approved for psoriasis: Amevive (alefacept), Enbrel (etanercept), Humira (adalimumab), Raptiva (efalizumab), and Remicade (infliximab).

A doctor may recommend the use of a biologic for people whose psoriasis is moderate to severe, cannot be controlled effectively with other medications, or cannot tolerate other medications because of side effects.