Elan Corporation

CAMBRIDGE, Mass. & SAN DIEGO & DUBLIN, Ireland--(BUSINESS WIRE)--July 26, 2004--Biogen Idec and Elan Corporation, plc announced today that the U.S. Food and Drug Administration (FDA) has formally accepted their Biologics License Application (BLA) for ANTEGREN(R) (natalizumab). In June 2004, the FDA designated natalizumab for Priority Review and Accelerated Approval for the treatment of multiple sclerosis (MS). Acceptance of a filing indicates that the FDA has determined that the application is complete and permits a substantive review.

The FDA grants Priority Review status to products that are considered to be potentially significant therapeutic advancements over existing therapies that address an unmet medical need. Based on the FDA's designation of Priority Review for natalizumab in MS, the companies anticipate action by the Agency approximately six months from the submission date, rather than 10 months for a standard review. On May 25, 2004, the companies announced they had previously submitted the BLA for the approval of natalizumab for MS.

The FDA's review of natalizumab will be based on one-year data from two ongoing Phase III trials, AFFIRM (natalizumab safety and efficacy in relapsing-remitting MS) and SENTINEL (safety and efficacy of natalizumab in combination with AVONEX(R) (Interferon beta-1a)), which evaluate the ability of natalizumab to slow the progression of disability and reduce the rate of clinical relapses in patients with relapsing-remitting MS. The companies are committed to completing these two-year trials.

MS is a chronic disease of the central nervous system that affects approximately 400,000 people in North America and approximately one million people worldwide. It is a disease that affects more women than men, with onset typically between 20 and 40 years of age. Symptoms of MS may include vision problems, loss of balance, numbness, difficulty walking and paralysis.

About ANTEGREN (natalizumab)

Natalizumab, a humanized monoclonal antibody, is the first alpha-4 antagonist in the new selective adhesion molecule (SAM) inhibitor class. It is designed to inhibit the migration of immune cells into tissues where they may cause or maintain inflammation. To date, approximately 2,800 patients have received natalizumab in clinical trials, and the safety profile continues to support further development. In placebo-controlled trials to date, in both Crohn's disease (CD) and MS, the most commonly reported adverse events in either group were headache, fatigue and nasopharyngitis.

Biogen Idec and Elan are collaborating equally on the development of natalizumab in MS, CD, and rheumatoid arthritis (RA).

About Biogen Idec

Biogen Idec (NASDAQ: BIIB) creates new standards of care in oncology and immunology. As a global leader in the development, manufacturing, and commercialization of novel therapies, Biogen Idec transforms scientific discoveries into advances in human healthcare. For product labeling, press releases and additional information about the company, please visit http://www.biogenidec.com.

About Elan

Elan Corporation, plc (NYSE: ELN) is a neuroscience-based biotechnology company that is focused on discovering, developing, manufacturing and marketing advanced therapies in neurology, autoimmune diseases, and severe pain. Elan shares trade on the New York, London and Dublin Stock Exchanges. For additional information about the company, please visit http://www.elan.com.

Safe Harbor/Forward Looking Statements

This press release contains forward-looking statements regarding the approval process for ANTEGREN (natalizumab) and the potential of natalizumab as a treatment for MS. These statements are based on the companies' current beliefs and expectation. Drug development involves a high degree of risk. Factors which could cause actual results to differ materially from the companies' current expectations include: the risk that unexpected concerns may arise from additional data or analysis, that regulatory authorities may require additional information, further studies, or may fail to approve the drug, or that the companies may encounter other unexpected hurdles. For more detailed information on the risks and uncertainties associated with the companies' drug development and other activities, see the periodic and other reports of Biogen Idec Inc. and Elan Corporation, plc filed with the Securities and Exchange Commission. The companies assume no obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise.

CONTACT: MEDIA:
Biogen Idec
Amy Brockelman, 617-914-6524
or
Elan
Anita Kawatra, 212-407-5755
or
800-252-3526
or
INVESTORS:
Biogen Idec
Elizabeth Woo, 617-679-2812
or
800-252-3526
or
Elan
Emer Reynolds, 353 1 709 4000

SOURCE: Biogen Idec and Elan Corporation, plc