New Gout Drug Krystexxa Works, But Not Without Serious Side Effects, FDA Says

The drug Krystexxa appears effective at relieving swollen joints and chronic pain caused by gout, but it also carries the risk of life-threatening side effects, the Food and Drug Administration said.

Many people taking Krystexxa in clinical studies developed heart problems and severe allergic reactions, the FDA said. The agency has been studying Krystexxa since December 2008, when the drug’s maker, Savient Pharmaceuticals, asked for FDA approval to being marketing the drug for use in patients who have not found relief from other drugs or treatments. The FDA has repeatedly delayed making a final decision on the drug.

Krystexxa is an enzyme that is injected once or twice a month to control levels of uric acid in the body. High levels of uric acid in the blood cause gout, a disease that results in burning pain, swelling, redness, and stiffness in the affected joint. It most often begins in the big toe and spreads to other joints, such as the ankle, knee, wrist, and elbow.

About eight million Americans, mostly men over age 40, have gout, the FDA said.

Serious Safety Concerns Noted

Drug-safety regulators noted concerns about a high rate of serious side effects detected in clinical trials of Krystexxa.

Nearly a quarter of patients taking the drug in a study suffered a serious side effect, compared to just 12 percent of patients who were taking inactive placebo pills, researchers said. Six patients died while taking Krystexxa in the study, but just three patients who were given placebo pills died. Many of the patients who died had pre-existing heart conditions, but still, twice as many died while on Krystexxa than on placebo, which is concerning.

The patient injuries and deaths apparently raised questions at the FDA.

“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,” Dr. Bob Rappaport, FDA’s director for rheumatology products, said in a review posted to the agency’s website.

Decision Could Come Soon

A panel of experts who review new drugs to determine whether they are safe and effective is set to consider Krystexxa next week. The panel will then make a recommendation to the FDA about whether the drug should be approved. While the FDA is not obligated to follow the advice of its panel, it most often does.

A final ruling on Krystexxa could be made in July, officials said.

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