In Vitro Study Compares Dose Effects of Three Commercially Available Beta Interferon Drugs

Biogen, Inc. (NASDAQ/BGEN) today announced that an in vitro study has shown that AVONEX® (Interferon beta-1a) is the most potent on a mass basis of the three commercially available beta interferon drugs used to treat multiple sclerosis (MS). Data from the study were presented today at the 125th Annual Meeting of the American Neurological Association (ANA) in Boston, Massachusetts. The study’s principal investigator, Dr. Joel Oger, Professor of Neurology at the University of British Columbia, Vancouver, Canada, presented the data. AVONEX is the world’s leading treatment for MS.

The study was conducted by academic scientists and was not funded by Biogen. The results may have implications for evaluating the dose efficacy of AVONEX, particularly in comparison to other currently available treatments.

“This study is important because it shows that MS cells are more responsive to interferons than normal cells. In the past, the potency of interferons has been quantified by measuring their antiviral effect. With this in vitro assay, we are now able to compare the potency of interferons by looking at their effect on abnormal immune functions that may be related to the MS disease process,” said Professor Oger.

The in vitro study showed that on a mass, or molecular, basis there were differences in the potency of AVONEX compared to two other beta interferons, Rebif® and Betaseron®. AVONEX more easily suppressed the secretion of immunoglobulin G (IgG) antibodies, which are increased in patients with MS. AVONEX was the most efficient inhibitor of IgG secretion, followed by Rebif and Betaseron, respectively.

Because the drugs are administered at different total weekly doses, the researchers also expressed the results as a fraction of the weekly dose. On a mass basis, the drugs differed in their potency to suppress IgG secretion, with AVONEX being the most potent. When expressed as a proportion of their weekly-injected dose, the overall effect of the different weekly doses appears to be similar among the three interferons.

Burt A. Adelman, M.D., Biogen’s Vice President of Medical Research, said, “We are pleased to learn about the potency of AVONEX and to have these data to review. To date, there have not been any well-controlled comparative trials of the interferons in treating MS to evaluate the optimal dose, frequency and route of administration. These in vitro data confirm that AVONEX is the most efficient interferon molecule. Most importantly, in all clinical trials to date, AVONEX has demonstrated proven results and excellent efficacy in the treatment of MS. We especially saw significant results of AVONEX’s efficacy in our landmark CHAMPS trial, which showed a highly positive impact of early administration of AVONEX to patients at high risk of developing clinically definite MS.”

MS is a disease of the central nervous system. It is caused by the destruction of myelin by the immune system. Myelin is the fatty tissue that surrounds and protects central nervous system nerve fibers and facilitates the flow of nerve impulses to and from the brain. The loss of myelin disrupts the conduction of nerve impulses, producing the symptoms of MS.

AVONEX is the world’s leading treatment for MS. It was launched in the U.S. in 1996, in Europe in 1997, and in Canada in 1998 for the treatment of relapsing forms of MS to slow the accumulation of physical disability and to decrease the frequency of clinical exacerbations. More than 93,000 patients worldwide are now on AVONEX therapy, which is marketed worldwide in more than 60 countries.

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 implications of the study. These statements are based on the Company’s current beliefs and expectations as to such future outcomes. Factors which could cause actual results to differ materially from the Company’s current expectations include the risk that results of clinical studies or clinical use may be different than the results of the in vitro study. Reference is also made to 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 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 http://www.biogen.com.

AVONEX® (Interferon beta-1a) is a registered trademark of Biogen, Inc. AVONEX is approved in the U.S. and in most other countries around the world for the treatment of relapsing forms of multiple sclerosis. Rebif is a registered trademark of Serono, Inc. Betaseron is a registered trademark of Berlex Laboratories, Inc.