updated 6/12/2009 12:15:45 PM ET 2009-06-12T16:15:45

The Food and Drug Administration said Friday the Savient Pharmaceuticals drug Krystexxa appears to successfully treat gout, despite evidence of potentially deadly side effects.

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The FDA has been reviewing the company's drug application since December and has already delayed a decision on the drug once, leading some analysts to question whether it can win approval.

But Friday morning the FDA said the drug appears to relieve swollen joints and pain flare ups associated with gout, a condition caused by a buildup of uric acid in the body.

Regulators also flagged a series of safety concerns seen in clinical trials of the drug, including heart problems and allergic reactions.

About 24 percent of patients taking Krystexxa suffered a serious side effect, compared with 12 percent of patients taking a placebo pill. There were six deaths among patients taking the drug compared with three among patients taking placebo, though FDA noted many of them had pre-existing heart conditions.

"Because most of the patients developing the serious cardiovascular adverse events had other cardiovascular risk factors... there was uncertainty concerning whether the cardiovascular adverse events represent a genuine safety signal," states Dr. Bob Rappaport, FDA's director for rheumatology products, in a review posted to the agency's Web site.

The FDA is scheduled to ask a panel of outside arthritis experts next Tuesday to weigh in on the drugs risks and benefits.

In documents posted online Friday, the FDA said it would ask the group whether additional studies are needed to evaluate Krystexxa's impact on the heart.

The agency is not required to follow the group's advice, though it usually does. A final decision on Savient's drug is expected by the end of July.

Krystexxa is an injectable enzyme designed to lower the body's uric acid levels when administered either once or twice a month. Gout affects about 8 million Americans and is most common in men over 40, according to the FDA.

An analyst said the drug can likely win approval so long as the company agrees to limit its use to the target patient population and closely monitor negative side effects. The company is specifically seeking an indication for gout patients who are not receiving relief from other treatments.

Kochnover also noted that seven of the 16 panelists slated to vote on the drug are rheumatologists, specialists who treat gout and are likely to favor a new treatment.

Copyright 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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