What biologic agents may be used in the treatment of psoriasis?

Biologic agents are proteins derived from living cells that are used to modulate specific portions of the aberrant immune response that leads to psoriasis. They are administered by subcutaneous, intramuscular, or intravenous injection. Tumor necrosis factor (TNF) alpha inhibitors (etanercept, adalimumab, and infliximab), as well as alefacept, are used in the treatment of refractory or extensive psoriasis. The TNF-a inhibitors block the proinflammatory action of TNF-a, a potent cytokine that mediates the formation of psoriatic plaques. Risks of TNF-a inhibitors include increased susceptibility to infections, such as reactivation of tuberculosis or hepatitis B, and higher rates of malignancy such as lymphoma.

Alefacept binds to and inhibits memory T lymphocytes that express CD2, which reduces the number of these pathogenic T cells. Patients undergoing alefacept therapy must be monitored for lymphopenia. Alefacept is less effective than the TNF-a inhibitors and is rarely used in clinical practice.


The newest biologic agent (FDA-approved in September, 2009) is ustekinumab, a humanized antibody against the p40 subunit found in the cytokines interleukin (IL)-12 and IL-23. In particular, the inhibition of IL-23 blocks the T-cell pathway (TH17) recently implicated in the pathogenesis of psoriasis.

Although these systemic psoriasis therapies may be more effective, care must be exercised in their use, especially because the long-term side effects of biological agents are not completely clear.