Regeneron's IL-1 Trap has received fast-track designation from the US FDA for CIAS1-Associated Periodic Syndromes (CAPS), a family of rare autoinflammatory diseases. IL-1 Trap is a long-acting IL-1 inhibitor administered by weekly injection. The CAPS syndromes included in the program include patients with Familial Cold Autoinflammatory Syndrome (FCAS) and Muckle Wells Syndrome (MWS). There are currently no approved therapies for CAPS. The fast-track designation is designed to facilitate the development and potentially expedite the review of new therapeutic medicines intended to treat serious conditions for which there is an unmet medical need. This designation allows a company to submit clinical trial data to the FDA as it becomes available and to receive feedback rather than having to submit all the data at once. Previously Regeneron received orphan drug designation for the IL-1 Trap in CAPS.

In April 2006, Regeneron completed enrollment for a pivotal clinical trial in its program for the treatment of CAPS. The phase III trial is designed to evaluate the efficacy and safety of the IL-1 Trap in adult patients with CAPS. The trial will include a 6-month, placebo-controlled efficacy phase and will be followed by a 6-month, open-label extension phase, which will help to characterize the safety of the IL-1 Trap. Regeneron expects top-line efficacy data from this pivotal trial by the end of 2006. In 2005, Regeneron reported positive preliminary results for four patients with CAPS in an ongoing phase II study being conducted with the National Institutes of Health, testing once-weekly dosing of the IL-1 Trap. These patients had an immediate, significant response to treatment with the IL-1 Trap and have been able to maintain their response to treatment in the extension phase of the trial.

CAPS is caused by mutations in the CIAS1 gene and is associated with elevated levels of IL-1. CAPS patients suffer from fever, rash, chills, arthralgia, myalgia, and fatigue. "Traps" are multi-component, 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 also being investigated in clinical trials for Systemic Juvenile Idiopathic Arthritis (SJIA), for which Regeneron also has been granted orphan drug designation. Blocking IL-1 is a proven therapeutic approach in rheumatoid arthritis (RA), as shown by the FDA approval of Amgen's Kineret® for the treatment of RA. Kineret is a human IL-1 receptor antagonist administered by daily injection. 

—A. Techman