Regeneron Pharmaceuticals, Inc (TARRYTOWN, New York), announced that the US FDA has accepted for filing and granted priority review status to the Biologics License Application (BLA) for rilonacept (interleukin-1 (IL-1) Trap), a potent, long-acting inhibitor of IL-1, for the long-term treatment of cryopyrin-associated periodic syndromes (CAPS). The FDA is expected to take action on the rilonacept application by the end of November 2007.

Currently, there are no medicines approved for patients suffering from CAPS, a spectrum of rare inherited autoinflammatory conditions, including familial cold autoinflammatory syndrome (FCAS) and Muckle-Wells syndrome (MWS). CAPS, commonly associated with a range of mutations in the gene CIAS1, has been reported primarily in North America and Europe; however, there are no reliable prevalence statistics for this disease. According to Regeneron, the number of patients in the US with CAPS is between 200 and 500. The FDA has previously granted orphan drug status and fast track designation to rilonacept for the treatment of CAPS. Regeneron is also evaluating the potential role of the IL-1 Trap in other inflammatory conditions such as gout.

Regeneron completed a phase III, double-blind, placebo-controlled trial, followed by a 24-week open-label extension phase trial of the IL-1 Trap in 47 adult patients suffering from FCAS or MWS. The company evaluated self-administration of the drug by weekly subcutaneous injection, which demonstrated rapid, substantial, and lasting reduction of clinical signs and symptoms, as well as laboratory measures of inflammation in patients. A favorable safety and tolerability profile was also observed.  

The FDA grants priority review to drugs that may offer a significant improvement in the safety or effectiveness of the treatment, diagnosis, or prevention of a serious or life-threatening disease. Under priority review status, a target date is established for the FDA to complete its review of a BLA within 6 months from its receipt of the submission.

"Traps" are multicomponent, high-affinity blockers of cytokine action composed of fusions between two distinct receptor components and an Fc region, resulting in the generation of blockers with markedly increased affinity over that offered by single component reagents. The IL-1 Trap is designed to attach to and neutralize IL-1 before it can bind to cell-surface receptors and generate signals that can trigger disease activity in body tissue. Once attached to the Trap, IL-1 cannot bind to the cell surface receptors and, together with the Trap, is removed from circulation. Controlling IL-1 molecular size has been shown to inhibit tissue penetration.