Biogen Idec to Present New Data on Diverse Neurological Portfolio at 65th AAN Annual Meeting

Biogen Idec (NASDAQ: BIIB) will present more than 50 company-sponsored platform and poster presentations on data supporting its multiple-marketed and pipeline therapies for neurological diseases at the 65^th American Academy of Neurology (AAN) Annual Meeting in San Diego, March 16-23, 2013. The breadth of data presented demonstrates Biogen Idec’s robust neurology research and development programs, and affirms the company’s decades-long leadership in multiple sclerosis (MS).

"Biogen Idec is dedicated to addressing unmet medical needs of people living with neurological diseases through innovative science,” said Douglas E. Williams, Ph.D., executive vice president, Research and Development at Biogen Idec. "We are proud to have the deepest MS pipeline in the industry, supplied by a strong R&D neurology program. We will continue to focus on improving the lives of patients through novel scientific discovery, as well as by providing first-in-class treatments, unsurpassed patient support and educational services.”

Highlights include data on Biogen Idec’s currently marketed products, TYSABRI® (natalizumab), AVONEX® (interferon beta-1a) and FAMPYRA® (prolonged-release fampridine tablets). The company will also present results from the investigational trials of its late-stage MS pipeline, including TECFIDERA™ (dimethyl fumarate), peginterferon beta-1a and daclizumab high-yield process (DAC HYP).

As part of the company’s overall commitment to improving the lives of people living with neurological diseases through education and support, Biogen Idec is proud to be a sponsor of the American Brain Foundation’s 2013 Brain Health Fair, a day-long event that will take place on Saturday, March 16, 2013 in San Diego, CA. This event connects thousands of patients, families and caregivers affected by a brain disease. The Brain Health Fair will provide health screenings, educational activities for kids and teens, as well as "Brain Health Classes,” led by expert neurologists. Registration is free at BrainHealthFair.com.

Notable data from Biogen Idec at AAN 2013:

TECFIDERA

• Timecourse of Treatment Effects of BG-12 (Dimethyl Fumarate) for Relapsing-Remitting Multiple Sclerosis – Platform S41.005 – Thursday, March 21 – 1:00 PM
• Clinical Efficacy of BG-12 (Dimethyl Fumarate) in Relapsing–Remitting Multiple Sclerosis (RRMS): An Integrated Analysis of the Phase 3 DEFINE and CONFIRM Studies – Poster P07.097 – Thursday, March 21 – 2:00 PM
• Safety and Tolerability of BG-12 (Dimethyl Fumarate) in Patients with Relapsing–Remitting Multiple Sclerosis: An Integrated Analysis of Phase 2 and 3 Placebo-Controlled Studies – Platform S30.003 – Wednesday, March 20 – 2:30 PM

TYSABRI

• Comparison of Patients Treated with Natalizumab and Interferon-Beta/Glatiramer Using Propensity-Matched Multiple Sclerosis Registry Data – Poster P01.211 – Monday, March 18 – 2:00 PM
• Natalizumab–Associated Progressive Multifocal Leukoencephalopathy (PML) in Multiple Sclerosis Patients: Survival and Functional Outcome when Asymptomatic at Diagnosis – Poster P04.271 – Wednesday, March 20, 2013 – 7:30 AM
• Longitudinal Stability of Anti-JC Virus Antibody Status in Multiple Sclerosis Patients: Results of STRATIFY-1 – Platform S30.001 – Wednesday, March 20 – 2:00 PM

AVONEX

• Pregnancy Outcomes in Patients Exposed to Intramuscular Interferon Beta-1a (IM IFNß-1a) – Platform S30.006 – Wednesday, March 20 – 3:15 PM
• Longitudinal Assessment of Attention and Cognitive Functions Related to Fronto-Temporal Circuits in Relapsing-Remitting Multiple Sclerosis 6-year Follow-up – Platform S10.003 – Tuesday, March 19 – 1:30 PM
• The Study of IFNß Bioactivity Loss by MxA mRNA Quantification Patients Allows the Prediction of Disability Progression in Multiple Sclerosis Patients –Poster P04.140 – Wednesday, March 20 – 7:30 AM

FAMPYRA

• Improvement in Patient Reported Outcomes with Prolonged-release Fampridine Treatment: Interim Analysis of the ENABLE Study – Poster P03.218 – Tuesday, March 19 – 2:00 PM
• Early Mobility Impairment: Bridging the Communication Gap Between People with Multiple Sclerosis and their Healthcare Providers – Poster P03.221 – Tuesday, March 19 – 2:00 PM

PEGYLATED INTERFERON BETA-1a

• Safety, Tolerability and Patient Evaluation of Peginterferon Beta-1a Administered via a Single-use Autoinjector in Relapsing Multiple Sclerosis: Data from the Phase 3 ATTAIN Study – Poster P01.167 – Monday, March 18 – 2:00 PM
• Clinical Efficacy and Safety of Peginterferon Beta-1a in Relapsing Multiple Sclerosis: Data from the Pivotal Phase 3 ADVANCE Study – Platform S31.006 – Wednesday, March 20 – 5:00 PM

DACLIZUMAB HIGH-YIELD PROCESS

• Daclizumab HYP Reduces the Evolution of New Gadolinium-Enhancing Lesions to T1-Black Holes: Results from the SELECT Study – Platform S01.001 –Tuesday, March 19, 2013 - 1:00 PM
• The Safety and Efficacy of Daclizumab HYP in Relapsing-Remitting Multiple Sclerosis in the SELECTION Extension Study: Primary Results– Poster P07.105– Thursday, March 21– 2:00 PM

Anti-LINGO

• Technical Feasibility of Implementing Multifocal VEP for Multicenter Clinical Trials – Poster P02.245 - Monday, March 18 –2:00 PM and Platform SP.004 – Tuesday, March 19 – 7:30 AM
• Effect of LINGO-1 Blockade on Optic Nerve Axonal Injury in MOG-EAE Rodent Models – Poster P05.186 – Wednesday, March 20 – 2:00PM

Full session details and data presentation listings for the 2013 Annual Meeting can be found through the AAN website http://www.aan.com/go/am13.

About Biogen Idec

Through cutting-edge science and medicine, Biogen Idec discovers, develops and delivers to patients worldwide innovative therapies for the treatment of neurodegenerative diseases, hemophilia and autoimmune disorders. Founded in 1978, Biogen Idec is the world’s oldest independent biotechnology company. Patients worldwide benefit from its leading multiple sclerosis therapies, and the company generates more than $5 billion in annual revenues. For product labeling, press releases and additional information about the company, please visit www.biogenidec.com.

About TECFIDERA

TECFIDERA™ is an investigational oral therapy in late-stage clinical development for the treatment of relapsing-remitting multiple sclerosis (RRMS), the most common form of MS. TECFIDERA is the only currently known investigational compound for the treatment of RRMS that has experimentally demonstrated activation of the Nrf-2 pathway.

TECFIDERA is currently under review by regulatory authorities in the United States, European Union, Australia, Canada and Switzerland.

About AVONEX

AVONEX® is one of the most prescribed treatments for relapsing forms of MS worldwide. AVONEX is indicated for the treatment of patients with relapsing forms of MS to slow the accumulation of physical disability and decrease the frequency of clinical exacerbations. Patients with MS in whom efficacy has been demonstrated include patients who have experienced a first clinical episode and have MRI features consistent with MS.

Symptoms of depression, suicidal ideation, or psychosis, and cases of suicide, have been reported with increased frequency with patients receiving AVONEX. Severe hepatic injury, including cases of hepatic failure has been reported rarely in patients. Rare cases of anaphylaxis have been reported. While beta interferons do not have any known direct cardiac toxicity, cases of congestive heart failure, cardiomyopathy, and cardiomyopathy with congestive heart failure have been reported in patients without known predisposition. Decreased peripheral blood counts have been reported from postmarketing experience. Seizures have been reported in patients using AVONEX, including patients with no prior history of seizure. Autoimmune disorders of multiple target organs have been reported. Routine periodic blood chemistry, hematology, liver function, and thyroid function tests are recommended. There are no adequate and well-controlled studies in pregnant women. AVONEX should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. The most common side effects associated with AVONEX treatment are flu-like symptoms, including chills, fever, myalgia, and asthenia.

For additional important safety information, and the complete United States full prescribing information, please visit www.AVONEX.com.

About TYSABRI

TYSABRI® is approved in more than 65 countries. TYSABRI is approved in the United States as a monotherapy for relapsing forms of MS, generally for patients who have had an inadequate response to, or are unable to tolerate, an alternative MS therapy. In the European Union, it is approved for highly active relapsing-remitting MS (RRMS) in adult patients who have failed to respond to beta interferon or have rapidly evolving, severe RRMS.

TYSABRI has advanced the treatment of MS patients with its established efficacy. Data from the Phase 3 AFFIRM trial, which was published in the New England Journal of Medicine, showed that after two years, TYSABRI treatment led to a 68 percent relative reduction (p<0.001) in the annualized relapse rate when compared with placebo and reduced the relative risk of disability progression by 42-54 percent (p<0.001).

TYSABRI increases the risk of progressive multifocal leukoencephalopathy (PML), an opportunistic viral infection of the brain which usually leads to death or severe disability. Infection by the JC virus (JCV) is required for the development of PML and patients who are anti-JCV antibody positive have a higher risk of developing PML. Factors that increase the risk of PML are presence of anti-JCV antibodies, prior immunosuppressant use, and longer TYSABRI treatment duration. Patients who have all three risk factors have the highest risk of developing PML. Other serious adverse events that have occurred in TYSABRI-treated patients include hypersensitivity reactions (e.g., anaphylaxis) and infections, including opportunistic and other atypical infections. Clinically significant liver injury has also been reported in the post-marketing setting. A list of adverse events can be found in the full TYSABRI product labeling for each country where it is approved.

TYSABRI is marketed and distributed by Biogen Idec Inc. and Elan Corporation, plc. For full prescribing information and more information about TYSABRI, please visit www.biogenidec.com.

About FAMPYRA

FAMPYRA® is a prolonged-release (sustained release) tablet formulation of the drug fampridine (4-aminopyridine, 4-AP or dalfampridine). FAMPYRA has been developed to improve walking in adult patients with MS. In MS, damaged myelin exposes channels in the membrane of axons allowing potassium ions to leak, weakening the electrical current sent through nerves. Studies have shown that fampridine can increase conduction along damaged nerves, which may result in improved walking ability. This prolonged-release formulation was developed and is being commercialized in the United States by Acorda Therapeutics, Inc. (NASDAQ: ACOR) under the trade name AMPYRA® (dalfampridine) Extended Release Tablets, 10 mg. Biogen Idec licensed rights from Acorda to develop and commercialize fampridine in all markets outside the United States.

About Peginterferon beta-1a

Peginterferon beta-1a is a new molecular entity in which interferon beta-1a is pegylated to extend its half-life and prolong its exposure in the body, enabling study of a less frequent dosing schedule. Peginterferon beta-1a is in the interferon class of treatments and, if approved, would be a new addition to this class, which is often used as a first-line of treatment for MS.

After completing two years in the ADVANCE study, patients have the option of enrolling in an open-label extension study called ATTAIN and will be followed for up to four years.

About Daclizumab High-Yield Process

Daclizumab high-yield process (DAC HYP) is a subcutaneous formulation of daclizumab in late-stage clinical development for the treatment of RRMS, the most common form of MS. DAC HYP is a humanized monoclonal antibody that binds to CD25, a receptor subunit that is expressed at high levels on T cells that are thought to become abnormally activated in autoimmune conditions, such as MS. Data from previous clinical trials showed that DAC HYP increases CD56bright Natural Killer (NK) cells, which target the activated immune cells that can play a key role in MS without causing general immune cell depletion.

DAC HYP is currently being studied in the DECIDE Phase 3 clinical trial, which is evaluating the efficacy and safety of once-monthly subcutaneous DAC HYP as a monotherapy compared to interferon beta 1-a therapy.

Biogen Idec is developing DAC HYP in collaboration with AbbVie, Inc.

Safe Harbor Statement

This press release contains forward-looking statements, including statements about the development, timing and therapeutic scope of programs in our clinical pipeline. These forward-looking statements may be accompanied by such words as "anticipate," "believe," "estimate," "expect," "forecast," "intend," "may," "plan," "project," "target," "will" and other words and terms of similar meaning. You should not place undue reliance on these statements. These statements involve risks and uncertainties that could cause actual results to differ materially from those reflected in such statements, including the risk that unexpected concerns may arise from additional data or analysis, regulatory authorities may require additional information or further studies, or may fail to approve or may delay approval of our drug candidates, or we may encounter other unexpected hurdles, uncertainty of success in commercializing and developing other products, product competition, the occurrence of adverse safety events with our products, changes in the availability of reimbursement for our products, our dependence on collaborations and other third parties over which we may not always have full control, failure to comply with government regulation, our ability to protect our intellectual property rights and have sufficient rights to market our products together with the cost of doing so, product liability claims and the other risks and uncertainties that are described in the Risk Factors section of our most recent annual or quarterly report and in other reports we have filed with the SEC. These statements are based on our current beliefs and expectations and speak only as of the date of this press release. We do not undertake any obligation to publicly update any forward-looking statements.