Biogen Inc and Elan Corporation plc announced that the results of a study indicate Antegren (natalizumab) reduced new inflammatory brain lesions and relapses in patients with relapsing forms of multiple sclerosis (MS).The use of natalizumab in the treatment of MS is currently being investigated in Phase III clinical trials.An investigational study showed promising results for natalizumab on disease remission and improved quality of life for patients with Crohn's disease.

Biogen and Elan are collaborating on the development, manufacturing and commercialization of natalizumab, the first in a new class of compounds known as selective adhesion molecule inhibitors (SAM inhibitors).The findings are based on a Phase II study conducted and analyzed by Elan and Biogen.The study was a double blind, placebo-controlled trial of 213 MS patients at 26 sites in the U.S., Canada and the U.K.Patients received either one of two natalizumab doses (3 mg/kg or 6 mg/kg) or placebo by intravenous infusion every 4 weeks for 6 months.Participants in the trial had either relapsing-remitting MS or secondary progressive MS.

The primary analysis was based on MRI scans and showed that patients treated with natalizumab for 6 months had up to 93 percent reduction in new gadolinium-enhancing lesions compared to patients treated with placebo.The reduction in lesions was seen as early as one month after the first infusion and was sustained during the treatment period.A mean of 9.6 new enhancing lesions developed during the treatment period in the placebo group (n=71) versus 0.7 and 1.1 in the 3 mg/kg (n=68) and 6 mg/kg groups (n=74), respectively.

There was a reduction of approximately 50% in the number of patients experiencing a relapse in the natalizumab groups compared to placebo - a tertiary endpoint of the study.In the study, 38% of the placebo treated patients (27/71) experienced one or more relapses, compared with only 19% of patients in either group treated with natalizumab (13/68 with 3mg/kg and 14/74 with 6mg/kg natalizumab respectively).

Natalizumab appeared to be well tolerated at both dose levels in this study.Certain adverse events occurred more commonly with natalizumab compared to placebo, such as infection, urinary tract infection, pharyngitis and rash.However, there were no significant differences between the treated groups and placebo.Additionally, serious adverse events included infrequent hypersensitivity-like reactions.

"The Phase II results were promising and demonstrated the ability of natalizumab to reduce MRI activity and the number of relapses.Because of these results, Phase III studies are underway to investigate the potential of natalizumab as a new treatment option for people with MS," said David Miller, lead author of the NEJM study and Professor of Neurology, Institute of Neurology, London, United Kingdom.

"There is a need for new types of therapies in the battle against MS. These data indicate that natalizumab may hold promise in MS, and the new clinical studies that are underway will help us determine if that promise is realized," said Stephen C. Reingold, Vice President of Research Programs, National Multiple Sclerosis Society.

"Patients' response to natalizumab was encouraging.With its unique mechanism of action, natalizumab represents a new class of therapies that could help in the treatment of MS," said J. Theodore Phillips, Jr., an investigator in the Phase II and Phase III trials, Texas Neurology, Baylor University Medical Center.