Update on the mechanisms and efficacy of biological therapies for psoriasis.

Biologically based agents (biologics) are novel therapeutic options in the treatment of moderate-to-severe psoriasis. Unlike traditional systemic anti-psoriatic drugs, which are chemically synthesized, these agents are unique in that they are derived from living organisms and hence called "biologics." In addition, they are the first group of "custom-designed" molecules that precisely target steps in the pathogenesis of psoriasis. The specificity of these biologics can theoretically avoid the side effects of the prebiologically developed systemic agents including the effects of hepatotoxicity, nephrotoxicity, and bone marrow suppression. However, there is also a tendency for a more precisely targeted agent to have a less overall efficacy. Due to the varying efficacies and high costs of the new biologic agents that are currently approved for psoriasis in the United States, the precise way they fit into the range of treatments for moderate-to-severe psoriasis should be defined pending future clinical experiences.