FRIDAY, July 25 (HealthDayNews) -- The U.S. Food and Drug Administration has approved Enbrel (etanercept) to treat ankylosing spondylitis (AS), an arthritis-like condition that affects the lower back and joints.

Some 350,000 people in the United States have AS -- more men than women. The disease usually begins by age 30 and has symptoms including lower back pain and stiffness, chest pain, joint pain and swelling. In severe cases, the pain can be debilitating and last many years.

Enbrel is a genetically engineered protein that binds to and prevents the harmful effects of another protein, TNF, which promotes inflammation in the body. In a study of 277 AS patients, Enbrel significantly reduced pain and inflammation symptoms in 58 percent of those tested.

The drug is already approved for rheumatoid and psoriatic arthritis. Side effects among AS patients were similar to those already seen -- injection site reactions and upper respiratory infections.

For more information about ankylosing spondylitis, visit the National Library of Medicine.