Cambridge, MA – May 19, 2006– Biogen Idec (NASDAQ:BIIB) today marks the 10th anniversary of AVONEX® (Interferon beta 1a), the most prescribed multiple sclerosis (MS) therapy worldwide, as the company’s CEO James Mullen, rings the NASDAQ Stock Market Opening Bell. AVONEX, manufactured by Biogen Idec, was approved for relapsing forms of MS by the U.S. Food and Drug Administration (FDA) on May 17, 1996. Shortly after its introduction in the U.S., it became the number one prescribed therapy in MS. Today more than 130,000 patients worldwide choose AVONEX to treat their MS.

Biogen Idec is recognizing the AVONEX anniversary with the publication of a commemorative book, “Profiles of Inspiration” and a companion video. The book and video showcase extraordinary people with MS whose lives have been positively impacted by AVONEX. The book and video will soon be available on www.AVONEX.com.

“Biogen Idec is proud to recognize the 10th anniversary of AVONEX, the number one prescribed MS therapy worldwide, and the impact it has made on the lives of patients around the world. People living with MS inspire and motivate us each and every day to redouble our efforts to advance the science and treatment of this disabling disease. The introduction of AVONEX was an important step forward in the treatment of MS, but we know a significant unmet need persists, and we will continue our unyielding commitment to offer patients hope in their fight against this disease,” said Mullen.

The anniversary is being celebrated by MS patients, physicians and caregivers in a series of events around the country intended to raise awareness of MS and to celebrate the role AVONEX has played in transforming MS care.

“The mission of the National Multiple Sclerosis Society is to end the devastating effects of MS,” said John Richert, MD, vice president, research and clinical programs of the National Multiple Sclerosis Society. “We support the efforts of companies such as Biogen Idec who are committed to research and development of breakthrough therapies that can offer help to people living with MS.”

AVONEX remains the only once-a-week disease modifying therapy proven to both slow the progression of disability and reduce the frequency of clinical relapses for people with MS, a chronic disease of the central nervous system. In the pivotal trial that led to its approval in the U.S., AVONEX demonstrated a 37% reduction in progression to disability compared with placebo. Recently published data demonstrated that AVONEX reduced the risk of developing clinically definite MS for up to five years in patients who began treatment immediately after their initial MS attack compared to those who delayed the treatment.


AVONEX is the most prescribed treatment for relapsing forms of MS. It was launched in the U.S. in 1996 and later in Europe for the treatment of relapsing forms of MS to slow the progression of disability and reduce relapses. AVONEX is marketed internationally in more than 90 countries. AVONEX was the first treatment approved for MS patients who have their first clinical MS attack and have a brain MRI scan that suggests MS; this use was approved in Europe in 2002 and in the U.S. in 2003.

The most common side effects associated with AVONEX treatment are flu-like symptoms including myalgia, fever, fatigue, headache, chills, nausea, vomiting, pain and asthenia.

AVONEX should be used in caution with patients with depression or other mood disorders and in patients with seizure disorders. AVONEX should not be used by pregnant women. Patients with cardiac disease should be closely monitored. Patients should also be monitored for signs of hepatic injury. Routine periodic blood chemistry and hematology tests are recommended during treatment with AVONEX. Rare cases of anaphylaxis have been reported. Please see complete prescribing information available at www.AVONEX.com .

About Biogen Idec

Biogen Idec creates new standards of care in oncology, neurology and immunology. As a global leader in the development, manufacturing, and commercialization of novel therapies, Biogen Idec transforms scientific discoveries into advances in human healthcare. For product labeling, press releases and additional information about the company, please visit www.biogenidec.com .

Safe Harbor/Forward Looking Statements

This press release contains forward-looking statements regarding AVONEX that are subject to a number of risks and uncertainties. These statements are based on the companies’ current beliefs and expectation. No forward-looking statement can be guaranteed. Drug development involves a high degree of risk. Factors which could cause actual results to differ materially from the companies’ current expectations include: the risk that unexpected concerns may arise from additional data or analysis or that the company may encounter other unexpected hurdles. For more detailed information on the risks and uncertainties associated with Biogen Idec’s drug development and other activities, see the periodic reports of Biogen Idec Inc. filed with the Securities and Exchange Commission. Biogen Idec assumes no obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise.

Biogen Idec Media Contact:

Amy Brockelman
Senior Manager, Public Affairs
Biogen Idec
(617) 914-6524

Biogen Idec Investor Contact:

Oscar Velastegui
Senior Manager, Investor Relations
Biogen Idec
(617) 679-2812