The US Food and Drug Administration has approved Savient Pharmaceuticals' Krystexxa for the treatment of gout in adults who do not respond to conventional therapy.

Gout is caused by an excess of bodily waste uric acid, which can cause swelling, redness, heat, pain and stiffness in the joints. Badrul Chowdhury, director of the division of pulmonary, allergy and rheumatology products in the FDA’s Center for Drug Evaluation and Research, said: “About 3% 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.”

Conventional therapy is to receive drugs that lower the amount of uric acid in the blood, such as the xanthine oxidase inhibitors Zyloprim (allopurinol) and Uloric (febuxostat). Krystexxa (pegloticase) 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.

Savient conducted two six-month clinical trials of 212 patients which demonstrated the effectiveness of Krystexxa. However the FDA noted that since one out of every four patients in the studies experienced a severe allergic reaction when receiving an infusion of pegloticase, "healthcare providers should dispense a corticosteroid and an antihistamine to their patients beforehand to minimise 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. Doctors are also being warned by the agency "to be cautious about administering Krystexxa to patients with congestive heart failure because the drug was not studied in this patient population".

Given these concerns, Krystexxa is being approved with a risk evaluation and mitigation strategy.

Savient up for sale

Savient is clearly delighted and now "believes it is well advanced in its preparations for the US launch of Krystexxa". The approval also means the board can push ahead with plans to sell the company and a number of big players have been touted as potential purchasers.

These include Novartis, Johnson & Johnson and Amgen, and analysts believe that the price tag could be in the region of $1.5-$1.7 billion. Krystexxa is expected to be a blockbuster, hence the sizeable figure.