Companies to Move to Phase III Trials

Biogen, Inc. (NASDAQ/BGEN) and Elan Corporation, plc (NYSE/ELN) announced today positive results from preliminary analyses of two large Phase II clinical studies with Antegren® (natalizumab) in multiple sclerosis (MS) and Crohn’s Disease. The companies are now proceeding to initiate Phase III clinical studies in 2001 in both these diseases.

The first of the studies conducted was a Phase II double-blind placebo controlled trial which included 213 MS patients at 26 sites in the U.S., Canada and the U.K. Patients received monthly doses of Antegren or placebo over a six-month period. The primary endpoint of a reduction in new gadolinium enhancing lesions compared to placebo over the 6-month treatment period was achieved with a high degree of statistical significance.

A separate Phase II double-blind placebo controlled study conducted across 38 sites in 8 European countries included 240 patients with moderate to severe Crohn’s Disease. Patients received doses of Antegren or placebo at week 0 and week 4. This study also demonstrated statistically significant positive results on multiple endpoints, including induction of remission as measured by the Crohn’s Disease Activity Index.

Further information about the potential safety and efficacy of the drug will be presented at a scientific conference later this year. The companies will be conferring with regulatory authorities about next steps in the drug’s development. Antegren has now been evaluated in approximately 600 patients in 10 clinical studies.

James C. Mullen, Biogen’s president and chief executive officer, said, “As a biotechnology company committed to developing breakthrough therapies for people with serious diseases, we are very excited about these results. With approximately one million MS patients worldwide, we believe that Antegren, used alone or in combination with Avonex® (Interferon beta-1a), should allow us to offer more solutions to a broader range of MS patients than are currently available. For the 300,000 patients with moderate-severe Crohn’s Disease, Antegren offers a potential novel treatment approach for this patient population.”

Donal J. Geaney, Elan’s chairman and chief executive officer, said, “We are delighted that these positive results support the continued and accelerated development of Antegren as a potentially important new therapy for the treatment of MS and Crohn’s disease. In conjunction with Biogen, we look forward to advancing Antegren into Phase III studies.”

In August 2000, Biogen and Elan announced a worldwide, exclusive collaboration to develop, manufacture, and commercialize Antegren. Antegren, which was discovered by Elan, is a humanized monoclonal antibody and the first in a new class of potential therapeutics known as alpha 4 integrin inhibitors that are designed to block immune cell adhesion to blood vessel walls and subsequent migration of lymphocytes into tissue. Antegren binds to the cell surface receptors known as alpha-4-beta-1 (VLA-4) and alpha-4-beta-7. Antegren may be useful in the treatment of a range of inflammatory and non-inflammatory diseases. Both Elan and Biogen are pioneers in the study of this pathway.

AVONEX is the most prescribed treatment for MS worldwide. It was launched first in the U.S. in 1996 for the treatment of relapsing forms of MS to slow the accumulation of physical disability and decrease the frequency of clinical exacerbations. More than 97,000 patients worldwide are now on AVONEX therapy, which is marketed internationally in more than 65 countries.

The most common side effects associated with AVONEX treatment are flu-like symptoms, muscle ache, fever, and chills. Other common side effects seen, but not statistically different between AVONEX and control groups, were headache, pain and asthenia (weakness). These side effects usually go away within a day after the injection and occur less often as the treatment continues.

In addition to historical information, this press release contains forward-looking statements within the meaning of the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995. Reference is made in particular to statements regarding the potential for Antegren as a therapeutic product. These statements are based on the companies’ current beliefs and expectations as to such future outcomes. Drug development involves a high degree of risk. Success in early stage clinical trials does not ensure that later stage or larger scale clinical trials will be successful. Factors which could cause actual results to differ materially from the companies’ current expectation include the risk that the product may not show therapeutic effect or an acceptable safety profile in subsequent trials or may not meet applicable regulatory standards, or that problems or delays may arise during clinical trials or in the course of the development, testing or manufacturing of the product as well as the other risks and uncertainties described from time to time in the companies’ periodic reports filed with the Securities and Exchange Commission.

Biogen, Inc., winner of the U.S. National Medal of Technology, is a biopharmaceutical company principally engaged in discovering and developing drugs for human healthcare through genetic engineering. Headquartered in Cambridge, MA, the Company’s revenues are generated from international sales of AVONEX® (Interferon beta-1a) for treatment of relapsing forms of multiple sclerosis, and from the worldwide sales by licensees of a number of products, including alpha interferon and hepatitis B vaccines and diagnostic products ( Prescribing Information ). Biogen’s research and development activities are focused on novel products to treat inflammatory and autoimmune diseases, neurological diseases, cancer, fibrosis and congestive heart failure. The Company maintains active clinical research programs in protein therapeutics, small molecules, genomics and gene therapy. For copies of press releases and additional information about the Company, please consult Biogen’s Homepage on the World Wide Web at

Elan Corporation, plc is a leading worldwide fully integrated pharmaceutical company headquartered in Ireland, with its principal research, development, manufacturing and marketing facilities located in Ireland, the United States and Israel. Elan is focused on the discovery, development and marketing of therapeutic products and services in neurology, pain management, oncology, infectious disease and dermatology and on the development and commercialization of products using its extensive range of proprietary drug delivery technologies. Elan shares trade on the New York, London and Dublin Stock Exchanges.

NOTE: The conference call to discuss the data will be broadcast via the internet at
9:00 am (EST) on Tuesday, January 23, 2001, and will be accessible through the investor relations section of Biogen’s homepage,