Sept. 25 (HealthDay News) -- Stelara (ustekinumab) has been approved by the U.S. Food and Drug Administration for adults with moderate-to-severe plaque psoriasis.

The immune system disorder is characterized by the rapid overproduction of skin cells, which leads to red, scaly patches of inflamed skin. Some six million people in the United States have plaque psoriasis, the FDA said in a news release.

Stelara is a laboratory-produced monoclonal antibody that mimics the body's own antibodies. It blocks the action of two proteins that contribute to the overproduction of skin cells, the agency said.

The drug was evaluated in three studies of 2,266 people. Because it reduces the immune system's ability to fight infection, some users have developed serious infections that required hospitalization. Users may also have a heightened risk of cancer, the FDA said.

The agency is requiring the drug's maker, Pennsylvania-based Centocor Ortho Biotech, to devise a risk evaluation and mitigation strategy that includes a communication plan aimed at doctors and patients. The company is a subsidiary of Johnson & Johnson.