Washington Editor

The FDA late Wednesday approved Regeneron Pharmaceuticals Inc.'s Arcalyst (rilonacept), an interleukin-1 blocker (IL-1), for the long-term treatment of two cryopyrin-associated periodic syndromes (CAPS).

The two disorders, familial cold auto-inflammatory syndrome (FCAS) and Muckle-Wells syndrome (MWS), are inherited and affect about 300 people in the U.S. About 50 percent of CAPS cases are associated with a gene mutation in the CIAS 1 gene.

Arcalyst blocks IL-1, which is a signaling protein secreted by certain immune-related cells in the body. IL-1 acts as a messenger to regulate inflammatory responses, but in excess it can be harmful and has been shown to be key in the inflammation seen in patients with FCAS or MWS.

The FDA said it based its approval on a clinical study conducted by Tarrytown, N.Y.-based Regeneron, which demonstrated the drug's safety and effectiveness.

The most commonly reported adverse effects associated with use of Arcalyst were injection-site reactions and upper respiratory infections.

The FDA granted the drug a priority review, which speeds the review process for patients who have unmet medical needs. The drug also had gained orphan drug status.

The firm's biologics license application included results from two Phase III studies. (See BioWorld Today, June 11, 2007.)

In the first study, a six-week trial designated Part A, patients randomized to receive IL-1 Trap had an 85 percent reduction in their mean symptom scores vs. 13 percent in the placebo group, as measured by a composite symptom score composed of daily evaluations of fever and chills, rash, fatigue, joint pain and eye redness and pain.

The second study, Part B, involved the same patients re-randomized to either switch to placebo or continue IL-1 treatment for a nine-week treatment period, and results from that trial showed that patients switched to placebo had a fivefold increase in their mean symptom score, compared to those remaining on IL-1 Trap.

"This approval exemplifies Regeneron's commitment to discover, develop and commercialize important medicines for patients suffering from serious diseases, such as CAPS," said CEO Leonard S. Schleifer.

"We recognize that Arcalyst may help address a significant unmet medical need that exists among CAPS patients and are therefore committed to helping these patients obtain access to this new treatment," he said in a statement.

Arcalyst is the first product to emerge from Regeneron's Trap program, which also includes two partnered VEGF Trap candidates targeting cancer and wet age-related macular degeneration.