The U.S. Food and Drug Administration on Tuesday approved Auxilium Pharmaceuticals Inc.'s (AUXL) Xiaflex injection to treat a hand disease that causes "bent" fingers.

Xiaflex is designed to treat Dupuytren's disease, a disorder caused by the buildup of an abnormal amount of collagen in hands. The collagen builds nodules in the palm of the hand, which eventually causes an internal rope-like cord to form and grow into the fingers causing them to be "bent" and unable to extend.

The only treatment for the condition was surgery. Xiaflex is injected into the cord to weaken and eventually break it.

FDA's approval of the product follows the September recommendation of a panel of outside medical experts, which unanimously voted to support Xiaflex.

About 7 million to 14 million Americans have Dupuytren's disease, with men age 50 and older being predominately affected.

During the panel meeting, the FDA said many patients treated with Xiaflex injection had their symptoms resolve or improve, but most also experienced side effects. Most side effects were mild and considered local reactions, but two patients had a tendon rupture.

One of the main studies submitted for approval of Xiaflex involved 306 patients, 203 of whom received Xiaflex and 103 of whom were given a placebo or non-drug injections. Patients were given up to three injections during the study.

The study showed 64% of patients in the Xiaflex group achieved "clinical success" compared with 7% in the placebo group. About 85% of patients in the Xiaflex group had at least a 50% improvement in finger flexibility after the injections.

Auxilium officials have said they planned to follow patients in clinical studies for up to five years to collect long-term safety and effectiveness data and would instruct doctors using the product to report any problems or reactions to the injection.

-By Jennifer Corbett Dooren, Dow Jones Newswires; 202-862-9294; jennifer.corbett@dowjones.com