Rilonacept is being evaluated as a therapeutic drug candidate for the prevention of gout flares in patients who are initiating uric acid-lowering therapy.

Rilonacept is a fusion protein designed to attach to and neutralize interleukin-1 (IL-1) before IL-1 can bind to cell-surface receptors and generate signals that trigger inflammation.

Gout is characterized by the deposition of uric acid crystals, a bodily waste product normally excreted by the kidneys, in the joints of the toes, ankles, knees, wrists, fingers, and elbows. These uric acid crystals can stimulate the release of inflammatory mediators, including interleukin-1 (IL-1), which result in acute flares of joint pain and inflammation.

In patients with frequent gout attacks who have elevated blood levels of uric acid, chronic treatment with uric acid-lowering medicines, such as allopurinol, may be prescribed to eliminate the uric acid crystals and prevent reformation. During the first months of uric acid-lowering drug therapy, while uric acid blood levels are being reduced, the break up of the uric acid crystals, previously deposited in joints, can result in release of IL-1, causing acute flares of joint pain and inflammation. Anti-inflammatory therapy is sometimes used to help prevent these flares. However, the tolerability of these therapies can limit patients' adherence. Approximately 750,000 gout patients initiate uric acid-lowering drug therapy in the U.S. each year.