The U.S. Food and Drug Administration today approved Krystexxa (pegloticase) to treat the painful condition known as gout in adults who do not respond to or who cannot tolerate conventional therapy.

Gout occurs due to an excess of the bodily waste uric acid, which is eventually deposited as needle-like crystals in the joints or in soft tissue. These crystals can cause intermittent swelling, redness, heat, pain and stiffness in the joints.

Gout is strongly associated with obesity, high blood pressure, high cholesterol and diabetes, and occurs more often in men, in women after menopause, and in people with kidney disease.

“About 3 percent of the three million adults who suffer from gout are not helped by conventional therapy. This new drug offers an important new option for them,” said Badrul Chowdhury, M.D., director of the Division of Pulmonary, Allergy, and Rheumatology Products in the FDA’s Center for Drug Evaluation and Research.

For patients with gout, the conventional therapy is to receive drugs that lower the amount of uric acid in the blood, as, for example, the xanthine oxidase inhibitors Zyloprim (allopurinol) and Uloric (febuxostat). Krystexxa is an enzyme that lowers uric acid levels by metabolizing it into a harmless chemical that is excreted in the urine. The drug is administered to patients every two weeks as an intravenous infusion.

Two six-month clinical trials of 212 total patients demonstrated that the drug lowered uric acid levels and reduced deposits of uric acid crystals in joints and soft tissue.

Since one out of every four patients in the clinical trials experienced a severe allergic reaction when receiving an infusion of Krystexxa, health care providers should dispense a corticosteroid and an antihistamine to their patients beforehand to minimize the risk of such a reaction. Other reactions during the clinical trials included gout flare, nausea, injection site bruising, irritation of the nasal passages, constipation, chest pain and vomiting.

Physicians are also being warned to be cautious about administering Krystexxa to patients with congestive heart failure because the drug was not studied in this patient population.

Krystexxa is being approved with a Risk Evaluation and Mitigation Strategy that includes a medication guide for patients and materials for healthcare providers to communicate the risk of severe infusion and allergic reactions.

Krystexxa is manufactured by Savient Pharmaceuticals Inc. of East Brunswick, N.J.