First of New Class of Agents Currently in Phase 2 Clinical Trials

Biogen, Inc. (NASDAQ/BGEN) and Elan Corporation, plc (NYSE: ELN) today announced a worldwide, exclusive collaboration to develop, manufacture, and commercialize Antegren® (natalizumab), a humanized monoclonal antibody currently nearing completion of Phase 2 clinical testing for multiple sclerosis (MS) and Crohn’s disease. Antegren represents the first of a new class of agents that has potential uses in a variety of diseases.

Under the terms of the agreement, Biogen and Elan will work together to develop, manufacture, and commercialize Antegren. They will share costs for ongoing development activities and economic benefits from Antegren commercialization. The financial details of the agreement were not released, but they include upfront and milestone payments that recognize the value each party brings to the collaboration.

James C. Mullen, Biogen’s President and Chief Executive Officer, said, “We see Antegren as an important opportunity for several reasons. First, it is an exciting, late-stage product with blockbuster potential in a variety of diseases. Second, it is an excellent complement to AVONEX® (Interferon beta-1a), the world’s leading therapy for MS. Used alone or in combination with AVONEX, Antegren will allow us to offer more solutions to a broader range of MS patients than are available at the present time. And third, both Biogen and Elan are pioneers in VLA-4 biology and the research, development, and marketing synergies between the companies should help us speed the process of bringing this drug to patients.”

Donal J. Geaney, Elan’s Chairman and Chief Executive Officer, said, “We are delighted to have concluded arrangements with Biogen to collaborate in the development, manufacture, and eventual commercialization of Antegren. We believe that the technology and skills available from the two combined companies will be highly synergistic in the challenges of completing the development and successful introduction of this truly important product.”

Antegren, discovered and developed by Elan as part of its focus on neurological diseases, 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 cell adhesion to blood vessel walls and subsequent migration of white blood cells into tissue. Antegren binds to the cell surface receptors known as alpha-4-beta-1 (VLA-4) and alpha-4-beta-7. These receptors are found on most types of white blood cells. Antegren may be useful in the treatment of a range of inflammatory and non-inflammatory diseases. Both Biogen and Elan are pioneers in the study of this pathway.

Antegren demonstrated promising results in Phase 2 studies in MS reported during 1999 and encouraging data in separate trials with Crohn’s disease and ulcerative colitis patients.

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 and possible efficacy of Antegren. These statements are based on the Company’s 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 Company’s current expectations 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 Company’s periodic reports filed with the Securities and Exchange Commission.

Biogen, Inc., winner of the 1998 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 U.S. and European 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 for multiple sclerosis, inflammatory, respiratory, kidney and cardiovascular diseases and in developmental biology 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 world leader in drug delivery and in the discovery, development and marketing of products and services in neurology, oncology and pain management. Elan’s principal research and manufacturing facilities are in Ireland, the United States, and Israel. Elan shares trade on the New York, London and Dublin Stock Exchanges.