One of the Largest Facilities of its Kind in the World Will Be Capable of Manufacturing Multiple Products

Biogen, Inc. (NASDAQ/BGEN) today announced that the U.S. Food and Drug Administration (FDA) has approved the company’s large-scale manufacturing plant (LSM) in Research Triangle Park (RTP), North Carolina for commercial production of its chronic plaque psoriasis drug AMEVIVE® (alefacept). Biogen plans to use the LSM, which has 90,000 liters of bioreactor capacity, to manufacture future products in the company’s pipeline.

“Biogen is proud to earn regulatory approval for one of the largest biologic manufacturing facilities in the world. LSM provides us with the flexibility to manufacture multiple products and reinforces our leadership in biologics manufacturing,” said Sylvie Gregoire, Pharm.D, Biogen’s Executive Vice President, Technical Operations. “Most importantly, this world-class facility enhances Biogen’s ability to provide products to patients, including therapies such as AMEVIVE.”

Biogen broke ground on the 250,000-square-foot facility in 1999 and completed construction ahead of schedule. The LSM became operational in 2002, manufacturing product just 32 months after groundbreaking. Since then, Biogen has been completing the necessary steps to achieve licensure of the facility. Licensure or approval of a facility is the last step required for the manufacture and distribution of commercial product. Before a product can be produced and distributed at a new manufacturing facility, the site must pass through several phases which include start-up, validation, trial runs, qualification lots, and FDA inspection.

The $173 million facility has received industry recognition for its exceptional design, innovative modular construction methods, and strong safety record. It houses six 15,000-liter bioreactors, which are needed to produce large quantities of biologics. This brings Biogen’s total capacity for mamallian cell products to 106,000 liters. Of the more than 430 Biogen employees in RTP, over 100 work in a variety of manufacturing functions in the LSM. As part of the original development plan of the facility, the company is enhancing its capability with the addition of a second purification suite, which will allow the facility to manufacture two products simultaneously. This purification suite is currently in the validation stage.

Biogen announced in June 2003 that it signed a merger agreement with IDEC Pharmaceuticals Corporation, which is currently building a 90,000-liter manufacturing facility in Oceanside, California. If the merger is completed and IDEC’s facility is ultimately approved, the combined company, to be known as BIOGEN IDEC INC., would have one of the biotech industry’s largest manufacturing capacities at over 200,000 liters.

AMEVIVE will be manufactured in the LSM. AMEVIVE was launched in the U.S. in February 2003 for the treatment of adult patients with moderate-to-severe-chronic plaque psoriasis who are candidates for systemic therapy or phototherapy. It is the only FDA-approved biologic therapy for the disease.

AMEVIVE is administered via IM or IV injection once per week for 12 doses under the supervision of a physician. For more information about AMEVIVE, including prescribing information and Biogen’s comprehensive support services, call 1-866-AMEVIVE or visit www.amevive.com.

About Biogen
Biogen is the world’s oldest independent biotechnology company and a leader in biologics research, development and manufacturing. A pioneer in leading edge research in immunology, neurobiology and oncology, Biogen brings novel therapies to improve patients’ lives around the world through its global marketing capabilities. For press releases and additional information about the company, please visit www.biogen.com.

Forward Looking Statements
This press release contains forward-looking statements regarding the use and expansion of the LSM. These statements are based on the company’s current beliefs and expectations. A number of risks and uncertainties could cause actual results to differ materially. For example, the use and expansion of the LSM may be affected by problems or delays that arise during the addition of the second purification suite, changes in the company’s strategic plans, and events related to the company’s drug development and commercialization efforts.

For more detailed information on the risks and uncertainties associated with these forward looking statements and the company’s other activities see the Outlook section in MD&A; of the company’s Annual Report on Form 10-K and quarterly reports on Form 10-Q filed with the Securities and Exchange Commission. The company does not undertake any obligation to publicly update any forward-looking statements.

Media Contact:
Amy Brockelman
Manager, Public Affairs
Biogen, Inc.
(617) 914-6524

Investment Community Contact:
Christina Dillon
Manager, Investor Relations
Biogen, Inc.
(617) 679-2812