A New Source of Information and Support Designed to Help All People with MS and Their Care Partners to Take an Active Role in the Management of MS.

Cambridge, MA - April 5, 2000 - Biogen, Inc. (NASDAQ/BGEN) today announced the introduction of MS ActiveSourceSM, a comprehensive resource for all people with multiple sclerosis (MS) and their care partners that provides access to a wide range of ongoing services. The goal of MS ActiveSourceSM is to offer support and information to help individuals better manage MS.

All people with MS - not just those on therapy -- and their care partners can access free information and services of MS ActiveSourceSM, including: informational literature and periodic newsletters, invitations to educational teleconferences and local events, and videos on living with MS.

For people with MS who are considering starting therapy with AVONEX® (Interferon beta-1a), Biogen's once-weekly therapy for the treatment of relapsing forms of MS, MS ActiveSourceSM provides a variety of services designed to make beginning therapy as easy and comfortable as possible. These services include reimbursement counseling, product delivery and billing assistance, and administration training.

MS ActiveSourceSM provides additional services to people with MS currently taking AVONEX® to help them take a more proactive role in managing MS. These services include The AVONEX AllianceSM, an ongoing program that provides free extra injection supplies and educational information to help support therapy. In addition, MS ActiveSourceSM offers the opportunity to receive periodic follow-up from a health care professional. A wide variety of therapy issues, ranging from management of side effects to understanding what to expect from therapy, may be discussed with the health care professional.

Although MS ActiveSourceSM has been created primarily to assist people with MS, the program also provides ongoing support and information to health care professionals.

Individuals who want to take advantage of these free resources can call 1-800-456-2255 from Monday through Friday, 8:30 a.m. to 8:00 p.m., ET. Information on many of these services can also be obtained online via the Biogen website: www.biogen.com

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 worldwide 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. 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 http://www.biogen.com.

See full prescribing information enclosed or on-line at
http://www.biogen.com.