The Food and Drug Administration(FDA) approved a biologic drug called ustekinumab (Stelara) in 2009 to help adults with moderate to severe plaque psoriasis. Compared to other weekly treatments currently on the market, this new medication requires just four to five injections a year.

The FDA estimates 6 million Americans suffer from plaque psoriasis, an immune system disorder that causes a chronic, painful skin condition. In psoriasis, the body rapidly overproduces skin cells, resulting in thickened patches of red and inflamed skin, often covered with silvery scales. 

Because ustekinumab, a monoclonal antibody that blocks two inflammatory proteins, works in a slightly different way than other drugs currently approved to treat psoriasis, it may help those who have not seen relief from other treatments.

The medication is delivered by injection, and the FDA says a health-care provider must administer it. Patients get one starter shot, another shot four weeks later and then one shot every 12 weeks after that. Other drugs used to treat psoriasis, including etanercept (Enbrel) and adalimumab (Humira) are generally injected every one to two weeks.

FDA approval follows three studies of 2,266 patients. The drug’s manufacturer says that after just two doses, 70 percent of patients taking the drug saw a 75 percent clearance of skin that was maintained for a year with continued treatment.

But the FDA also cautions the medication reduces the immune system’s ability to fight infection, which caused some patients to be hospitalized for tuberculosis and infections caused by bacteria, fungi or viruses. Lower immunity could also increase the risk for certain types of cancer. Other side effects included upper respiratory infections, headache and fatigue.

The drug is also approved in the European Union, U.K. and Canada, and the company says the price is comparable to other biologic agents approved for the treatment of moderate to severe plaque psoriasis.

A spokesman for Johnson & Johnson, the company that makes the drug, says ustekinumab is also being studied for the treatment of psoriatic arthritis, Crohn’s disease and sarcoidosis. 

Psoriatic arthritis is a condition where people have both psoriasis and arthritis. The Arthritis Foundation estimates that psoriatic arthritis affects between 5 and 8 percent of people who have psoriasis.