About 7.5 million Americans suffer from psoriasis, a lifelong disorder characterized by inflammation of skin and, often, the joints.

Stelara, Remicade, and Enbrel are all biologics -- drugs made of genetically engineered proteins -- that are generally used to treat patients who aren't responding to traditional therapies such as light therapy and methotrexate.

Remicade and Enbrel both block tumor necrosis factor-alpha (TNF-alpha), a chemical produced by immune cells that fuels inflammation, much like gas on a fire. Stelara targets two proteins, interleukin 12 and interleukin 23, that also drive the inflammatory process.

References:
Study Shows Stelara and Remicade Are Both Effective if Enbrel Stops Working. WebMD, 2010.