Biogen Idec Joins with the Global MS Community to Mark World MS Day

Company Pledges to Help Redefine Success in the Treatment of the Disease
CAMBRIDGE, Mass.--(Business Wire)--
Biogen Idec (NASDAQ: BIIB) today joined the global multiple sclerosis (MS)
community in recognizing the first World MS Day by supporting events and
activities in more than a dozen countries. A world leader in MS care, Biogen
Idec also reaffirmed its commitment to raising the standard of care for the
millions of people who live with this chronic condition.

World MS Day was established to raise awareness of MS, national MS societies and
people with and affected by MS; unite, broaden and mobilize these organizations
and individuals; and support MS-directed fundraising. In partnership with
national MS societies, Biogen Idec is sponsoring and participating in events and
activities across the globe to support World MS Day. From Norway, where Biogen
Idec is sponsoring a survey to measure attitudes towards and awareness of MS, to
Argentina where Biogen Idec is assisting with patient organization events, the
company is involved in activities in more than a dozen countries. By partnering
with national MS societies at the local level, Biogen Idec aims to provide
focused and tailored support to help raise awareness of MS and improve the lives
of people living with the disease.

"World MS Day is an opportunity to heighten and enhance collaboration among the
thousands of researchers around the world who have been working on the answers
that will bring us closer to a world free of multiple sclerosis," says Dr. John
Richert, executive vice president of research and clinical programs at the U.S.
National MS Society. "Continuing medical breakthroughs achieved by this
dedicated group of scientists have made multiple sclerosis a treatable disease
now for the majority of people diagnosed today, even though there is still no
cure."

Biogen Idec reaffirmed its commitment to the MS community by pledging to
redefine success in the treatment of MS. In an open letter to the global MS
community, Alfred Sandrock, MD, PhD, neurologist and senior vice president,
neurology research and development, Biogen Idec, wrote, "Whether you are a
researcher, health care professional, patient advocate, a person living with MS,
or know someone who is, we all want the same thing. The ultimate definition of
success: a cure."

"Within Biogen Idec we are redefining success in MS by delivering science-based
solutions from disease diagnosis to disease resolution. We recognize that there
is not just one answer or one way or one treatment. And we acknowledge that we
can not do this work alone. We will continue to partner with industry
colleagues, MS societies and patient organizations, academic researchers,
physicians and nurses, and people with MS. We will build on our record of
delivering innovative treatments, unparalleled patient and physician services,
and ground-breaking research to ensure that we continue to raise your
expectations and enhance your definition of success."

Today, more than 175,000 people in 90 countries are taking Biogen Idec therapies
to treat their MS. Biogen Idec offers two leading therapies, AVONEX® (interferon
beta-1a), the most prescribed MS therapy in the world, and TYSABRI®
(natalizumab), which is developed and promoted through a 50-50 partnership with
Elan Corporation, plc, and is the first MS treatment that has shown a 68%
reduction in annual relapse rates and has data which may help redefine success
in the treatment of MS.

Biogen Idec is also developing a broad pipeline of potential MS therapies
including:

* BG-12, an oral compound currently in Phase III clinical development;
* PEGylated interferon beta-1a, expected to enter a Phase III clinical trial by
July 2009;
* CDP-323, an oral VLA4 inhibitor currently in Phase II clinical development in
collaboration with UCB Pharma, Inc.;
* Daclizumab, currently in Phase II clinical development in collaboration with
Facet Biotech Corporation; and
* Anti-LINGO-1, a preclinical compound that has shown promise in repairing the
myelin sheath, the protective coating around nerve fibers that is damaged by
MS.

Currently, more than 7,500 patients are enrolled in Biogen Idec MS clinical
trials and post-marketing studies across 60 countries.

About World MS Day

World MS Day has been established by the Multiple Sclerosis International
Federation (MSIF) and its member MS societies for any individual, group or
organization involved in the global MS movement. The global MS movement
undertakes research into treating and eventually curing MS; develops the
capacity of MS societies to support people with MS; communicates information
about MS; and advocates and campaigns for the rights of people with MS. For more
information, please visit www.worldmsday.org.

About Multiple Sclerosis (MS)

MS is a chronic disease of the central nervous system that affects approximately
two million people worldwide. It is a disease that affects more women than men,
with onset typically occurring between 20 and 50 years of age. MS is caused by
damage to myelin, the protective sheath surrounding nerve fibers in the central
nervous system, which interferes with messages from the brain to the body.
Symptoms of MS may include vision problems, loss of balance, numbness,
difficulty walking and paralysis.

About Biogen Idec

Biogen Idec creates new standards of care in therapeutic areas with high unmet
medical needs. Founded in 1978, Biogen Idec is a global leader in the discovery,
development, manufacturing, and commercialization of innovative therapies.
Patients in more than 90 countries benefit from Biogen Idec's significant
products that address diseases such as lymphoma, multiple sclerosis, and
rheumatoid arthritis. For product labeling, press releases and additional
information about the company, please visit www.biogenidec.com.

About TYSABRI

TYSABRI is a treatment approved for relapsing forms of MS in the US and
relapsing-remitting MS in the European Union. According to data that have been
published in the New England Journal of Medicine, after two years, TYSABRI
treatment led to a 68% relative reduction (p<0.001) in the annualized relapse
rate compared to placebo and reduced the relative risk of disability progression
by 42-54% (p<0.001).

TYSABRI is also approved in the US to induce and maintain clinical response and
remission in adult patients with moderately-to-severely active Crohn's disease
(CD) with evidence of inflammation in those patients who have had an inadequate
response to, or are unable to tolerate, conventional CD therapies and inhibitors
of TNF-alpha. According to the US full prescribing information, among patients
who responded to TYSABRI, 54% sustain their response through every visit for one
year compared to 20% of patients receiving placebo (p<0.001), for a treatment
difference of 34%.

TYSABRI increases the risk of progressive multifocal leukoencephalopathy (PML),
an opportunistic viral infection of the brain that usually leads to death or
severe disability. Cases of PML have been reported in patients taking TYSABRI
who were recently or concomitantly treated with immunomodulators or
immunosuppressants, as well as in patients receiving TYSABRI as monotherapy.
Other serious adverse events that have occurred in TYSABRI-treated patients
included hypersensitivity reactions (e.g., anaphylaxis) and infections. Serious
opportunistic and other atypical infections have been observed in
TYSABRI-treated patients, some of whom were receiving concurrent
immunosuppressants. Herpes infections were slightly more common in patients
treated with TYSABRI. In MS and CD clinical trials, the incidence and rate of
other serious adverse events, including serious infections, were similar in
patients receiving TYSABRI and those receiving placebo. Common adverse events
reported in TYSABRI-treated MS patients include headache, fatigue, infusion
reactions, urinary tract infections, joint and limb pain and rash. Other common
adverse events reported in TYSABRI-treated CD patients include respiratory tract
infections and nausea. Clinically significant liver injury has been reported in
patients treated with TYSABRI in the post-marketing setting.

TYSABRI is approved in more than 40 countries. Biogen Idec and Elan Corporation,
plc (NYSE: ELN) are in a 50-50 partnership for the development and promotion of
TYSABRI.

For more information about TYSABRI please visit www.tysabri.com,
www.biogenidec.com or www.elan.com or call 1-800-456-2255.

About AVONEX

AVONEX is the most prescribed treatment for relapsing forms of MS worldwide,
with approximately 135,000 patients on therapy. It is used worldwide as a
treatment for relapsing forms of MS to slow the progression of disability and
reduce relapses. AVONEX is also approved for patients who have their first
clinical MS attack and have a brain MRI scan consistent with MS.

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

AVONEX should be used with caution in 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.

Safe Harbor

This press release contains forward-looking statements about the anticipated
development and timing of programs in our clinical pipeline. Forward-looking
statements are subject to risks and uncertainties that could cause actual
results to differ materially from those that we expect, including the
uncertainty of success in commercializing our products, the occurrence of
adverse safety events with our products, competitive pressures, our dependence
on collaborations over which we may not always have full control, our ability to
attract and retain qualified personnel, our ability to protect our intellectual
property rights and the cost of doing so, product liability claims, and the
other risks and uncertainties that are described in Item 1.A. Risk Factors in
our reports on Form 10-K and Form 10-Q and in other reports. These
forward-looking statements speak only as of the date of this press release, and
we do not undertake any obligation to publicly update any forward-looking
statements, whether as a result of new information, future events or otherwise.

Photos/Multimedia Gallery Available:
http://www.businesswire.com/cgi-bin/mmg.cgi?eid=5973219&lang=en

Biogen Idec Media Contact:
U.S. Media
Shannon Altimari, 617-914-6524
or
Media Outside the U.S.
José Juves, +41 (0) 41 392 1860
or
Biogen Idec Investor Relations Contact:
Eric Hoffman, 617-679-2812
Director, Investor Relations

Copyright Business Wire 2009