Rilonacept is a fusion protein designed to attach to and neutralize IL-1 before it can attach to cell-surface receptors and generate signals that can trigger inflammation. Once attached to rilonacept, IL-1 cannot bind to the cell-surface receptors and, together with rilonacept, is eliminated from the body.

Rilonacept Under Clinical Investigation in IL-1-driven Diseases

Regeneron also is evaluating the potential use of rilonacept in other conditions in which IL-1 may play a role. The Company has completed an exploratory proof-of-concept study of rilonacept in ten patients with chronic gout. While this was a small study in a heterogeneous group of gout sufferers, it represented the first controlled and blinded study of an interleukin-1 (IL-1) blocking agent in gout. Based upon these results, Regeneron intends to further study rilonacept in a variety of gout settings. In September 2007, Regeneron initiated a phase 2 safety and efficacy study of rilonacept for the prevention of gout flares.

Gout is a condition that occurs when the bodily waste product, uric acid, is deposited in the joints and/or soft tissues. In the joints these uric crystals cause inflammation that leads to pain, swelling, redness, heat, and stiffness in the joints. More than three million Americans currently suffer from gout. Each year 9.4 million prescriptions are written for uric acid-lowering therapy.

This section discusses Regeneron's pipeline of drug candidates currently undergoing clinical testing in a variety of diseases. These drug candidates have not been approved by the United States Food and Drug Administration for the indications described in this section.