Elan Corporation and Biogen Idec announced that the Phase III maintenance trial of Antegren (natalizumab) in Crohn's disease met the primary endpoint of maintenance of response. Maintenance of response was defined by a sustained Crohn's Disease Activity Index (CDAI) score of less than 220 as well as no use of rescue intervention throughout 6 months of this study. There was a significant treatment difference of greater than 30 per cent in favor of natalizumab, in patients taking the drug compared to those taking placebo. No notable difference in the overall rates of side effects between natalizumab and placebo treatment groups was observed through month 6.

Elan and Biogen Idec, which are collaborating on the development, manufacturing and marketing of natalizumab, will discuss these data with regulatory authorities in both the US and Europe and determine the appropriate path forward for natalizumab in Crohn's disease. The clinical development programme for natalizumab in multiple sclerosis (MS) is ongoing, with more than 2,000 patients enrolled.

"We are extremely encouraged by these findings and are committed to the further development and evaluation of natalizumab in Crohn's disease," said Lars Ekman, MD, executive vice president and president, R&D, Elan. "These natalizumab data also reinforce the importance of studying its novel mechanism of action in the treatment of other severe and chronic inflammatory diseases. We expect to share the data from this study at a major medical meeting in the first half of this year."

The Phase III, double blind, placebo-controlled, international trial known as ENACT-2 (Evaluation of Natalizumab as Continuous Therapy-2) enrolled responders from ENACT-1 (a 3-month study in patients with very active Crohn's disease). These 428 patients from ENACT-1 were re-randomized after 3 months to one of two treatment groups: natalizumab (300 mg) or placebo, both administered monthly for a total of 12 months. The primary endpoint was through month 6 of ENACT-2; additional analyses will be performed at other timepoints.

Approximately one million people worldwide have Crohn's disease, a chronic and progressive inflammatory relapsing-remitting disease of the gastrointestinal tract, which commonly affects both men and women. The disease usually causes diarrhea, crampy abdominal pain, often fever, and at times rectal bleeding. Loss of appetite and subsequent weight loss also may occur. Complications include narrowing of the intestine, obstruction, abscesses, and fistulas (abnormal channels connecting the intestine and other organs, including the skin), malnutrition and decreased growth rate in children.