Elan Corporation, plc (NYSE: ELN) and Biogen Idec (NASDAQ: BIIB) announced the approval of a supplemental Biologics License Application (sBLA) by the U.S. Food and Drug Administration (FDA) for TYSABRI® (natalizumab). TYSABRI is now approved for inducing and maintaining clinical response and remission in adult patients with moderately to severely active Crohn's disease (CD) with evidence of inflammation who have had an inadequate response to, or are unable to tolerate, conventional CD therapies and inhibitors of TNF-alpha. TYSABRI will be available for the treatment of CD upon the completion of key implementation activities related to the approved risk management plan. The companies anticipate TYSABRI will be available to Crohn's patients by the end of February 2008.

"The FDA's approval of TYSABRI is an important step forward in the treatment of Crohn's disease," said Dr. Stephen Hanauer, Professor of Medicine & Clinical Pharmacology & Chief of the Section of Gastroenterology at the University of Chicago Pritzker School of Medicine. "A significant number of patients either fail or cannot tolerate current therapies. The unique mechanism of action of TYSABRI affords us a new class of therapy in our fight against this debilitating disease."

The FDA granted approval based on its review of TYSABRI CD clinical trial data and overall safety data. The approval is accompanied by robust labeling with safety warnings; and a CD-specific risk management plan (including the mandatory TOUCH™ Prescribing Program) designed to inform prescribers, patients and infusion centers about the use of TYSABRI and to minimize potential risk of progressive multifocal leukoencephalopathy (PML) and other opportunistic infections.

"We are delighted that TYSABRI will be available for Crohn's patients and their physicians, who continue to need new therapeutic options with novel mechanisms of action," said Gordon Francis, MD, Senior Vice President, Global Clinical Development, Elan. "We are committed to providing therapeutic choice to those patients who can benefit from TYSABRI, and will continue to work with the FDA and the medical community to implement the TOUCH™ Prescribing Program for Crohn's patients."

"We are pleased with the FDA's decision to make TYSABRI available to Crohn's patients suffering from this chronic, debilitating disease," said Evan Beckman, MD, Senior Vice President, Immunology Research and Development, Biogen Idec. "Despite the therapeutic advances of the TNF-alpha inhibitors in CD, there remains a significant unmet need for Crohn's patients who have inadequate responses to, or are unable to tolerate, current CD therapies."

TOUCH™ Prescribing Program

The TOUCH™ (TYSABRI Outreach: Unified Commitment to Health) Prescribing Program was developed in conjunction with the FDA to facilitate appropriate use of TYSABRI and to assess, on an ongoing basis, the incidence and risk factors for PML and other serious opportunistic infections associated with TYSABRI treatment. This program represents Elan and Biogen Idec's commitment to making the unique benefits of TYSABRI available in a responsible manner. The program already has been implemented for patients receiving TYSABRI therapy for MS.

About Crohn's Disease

An estimated 500,000 people in the United States have Crohn's disease, a chronic and progressive inflammatory disease of the gastrointestinal tract, which commonly affects both men and women.

The disease usually causes diarrhea and crampy abdominal pain, often associated with fever, and at times rectal bleeding. Loss of appetite and 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), and malnutrition. Most patients eventually require surgery, which has both risks and potential short- and long-term complications.

Crohn's disease can have a devastating impact on the lifestyle of patients, many of whom are young and active. Currently there is no medical or surgical cure for Crohn's disease. Many patients fail to respond to current therapies, including biological therapies such as agents that inhibit tumor necrosis factor alpha (TNF-alpha). Due to this failure of current therapies in CD, therapies that have alternate biological targets provide patients and physicians with therapeutic options.

About TYSABRI

Data from the ENCORE trial showed that TYSABRI induced response and remission among patients with moderately to severely active Crohn's disease, and objective evidence of inflammation, as measured by elevated C-reactive protein. After 12 weeks of therapy, 60% of TYSABRI-treated patients attained response, compared to 44% of placebo treated patients, and 48% of patients had sustained response at both weeks 8 and 12, compared to 32% of placebo treated patients (p