Simultaneous Filing of a Common Technical Document in the U.S. and Europe Under New International Conference on Harmonization Guidelines

Biogen, Inc. (NASDAQ/BGEN) today announced that it has completed a simultaneous registrational filing in the U.S. and Europe, with submission of data from the intramuscular and intravenous Phase III clinical trials of AMEVIVE™ (alefacept). AMEVIVE is Biogen’s candidate for treatment of moderate-to-severe chronic plaque psoriasis. Biogen has filed a Common Technical Document (CTD) on two continents under new guidelines established and implemented last month by the International Conference on Harmonization (ICH).

James C. Mullen, Biogen’s President and Chief Executive Officer, said, “We are very excited about the potential of AMEVIVE as a promising new therapeutic option for treatment of chronic plaque psoriasis. In particular, we are proud of our product development team, which met exceptionally challenging timelines that enabled us to file an international registrational document less than 100 days after receiving final Phase III clinical data.

“This impressive achievement of filing on two continents on the same day should give Biogen clear advantages as we continue to develop this promising drug. For example, data were filed electronically in the U.S., assisting the efficiency of review, and the standardized CTD filing will speed preparation of documents for review by regulatory agencies in other markets.”

Phase III data were reported in June at the International Psoriasis Symposium in San Francisco. Phase II data were published last month in the New England Journal of Medicine. Biogen said it is on track for registrational filings in other markets, including Canada and Australia, and is conducting Phase I trials for registration in Japan.

Psoriasis is a T-cell mediated inflammatory disorder of the skin that can cause considerable discomfort. It is a disease for which there is no cure and affects people of all ages. Psoriasis affects approximately two percent of the populations of Europe and North America.

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 Company’s view of the potential for AMEVIVE and the advantages to be gained as a result of meeting its filing time-line. These statements are based on the Company’s current beliefs and expectations as to such future outcomes. Drug development and commercialization involve a high degree of risk. Factors which could cause actual results to differ materially from the Company’s current expectations include the risk that unexpected concerns may arise from additional data analysis or from additional data or that obstacles may arise or issues be identified in connection with review of data with regulatory authorities or regulatory authorities may disagree with the Company’s view of the data or may require additional data or information or additional studies. In addition, the Company’s expectations with respect to AMEVIVE may be affected by other risks inherent in the biotechnology industry, including other actions by the Food and Drug Administration on regulatory matters, actions by the U.S. Patent and Trademark Office, and uncertainties regarding the status of biotechnology patents and litigation. If AMEVIVE is approved by the FDA, other risks include reimbursement and pricing decisions and the introduction of competitive products, 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 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) 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 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: