Biogen Idec to Present Data from Hematology Programs, Including ELOCTATE™ and ALPROLIX® at ASH Annual Meeting

CAMBRIDGE, Mass.

Biogen Idec (NASDAQ: BIIB) will present data supporting its approved hemophilia therapies at the 56^th Annual Meeting of the American Society of Hematology (ASH) taking place in San Francisco, December 6-9. The company will present seven abstracts, including two oral presentations, demonstrating its ongoing commitment to advance innovative science in hematology, with the goal of addressing significant clinical needs and improving patient care.

The presentations feature expanded clinical data and post hoc analyses from the Kids A-LONG, A-LONG, and B-LONG Phase 3 studies, which further define the safety and efficacy of ELOCTATE™ [Antihemophilic Factor (Recombinant), Fc Fusion Protein] and ALPROLIX^® [Coagulation Factor IX (Recombinant), Fc Fusion Protein]. These therapies are the first clotting factors for hemophilia A and B, respectively, to provide protection from bleeding episodes with the potential to extend the interval between prophylactic infusions.

“We believe the growing body of data from clinical trials of ELOCTATE and ALPROLIX will further enhance physician understanding of the therapies’ clinical value,” said Aoife Brennan, M.D., vice president of Hematology Clinical Development at Biogen Idec. “This research underscores our commitment to advancing the treatment of hemophilia.”

The titles of Biogen Idec’s key data at ASH are as follows:

ELOCTATE

• Safety, Efficacy, and Pharmacokinetics of Recombinant Factor VIII Fc Fusion Protein (rFVIIIFc) in Previously-Treated Children with Severe Hemophilia A (Kids-ALONG) – Poster #1494 – Saturday, December 6 – 5:30-7:30 PM (PST)
• Predicting FVIII Activity in Patients Who Use Recombinant FVIII Fc Fusion Protein for Prophylaxis and Treatment of Bleeding Episodes – Poster #1522 – Saturday, December 6 – 5:30-7:30 PM (PST)

ALPROLIX

• Predicting FIX Activity in Prophylaxis Patients Using Recombinant FIX Fc Fusion Protein for Treatment of Bleeding Episodes – Poster #2842 – Sunday, December 7, 6:00-8:00 PM (PST)

Full session details and data abstracts for the 2014 Annual Meeting can be found on the ASH website at http://www.hematology.org/Meetings/Annual-Meeting/; full-text abstracts will be published December 5 in the online archives of Blood, the journal of ASH.

About Hemophilia A and B

Hemophilia is a rare, inherited disorder in which the ability of a person’s blood to clot is impaired. Hemophilia A occurs in about one in 5,000 male births annually, and more rarely in females, affecting about 16,000 people in the United States. Hemophilia B occurs in about one in 25,000 male births annually, and more rarely in females, affecting about 3,300 people in the United States. According to the World Federation of Hemophilia, an estimated 400,000 people worldwide are living with hemophilia.

Hemophilia A is caused by having substantially reduced or no factor VIII activity, while hemophilia B is caused by having substantially reduced or no factor IX activity; factor VIII and factor IX are needed for normal blood clotting. People with hemophilia A or B experience prolonged bleeding episodes that can cause pain, irreversible joint damage and life-threatening hemorrhages. Prophylactic infusions of factor VIII or IX can temporarily replace the missing clotting factors that are needed to control bleeding and prevent new bleeding episodes. The Medical and Scientific Advisory Council of the National Hemophilia Foundation recommends prophylaxis as the optimal therapy for people with severe hemophilia A or B.

About ELOCTATE

ELOCTATE™ [Antihemophilic Factor (Recombinant), Fc Fusion Protein], the first recombinant clotting factor VIII therapy with prolonged circulation in the body, is approved in the United States, Canada and Australia. It is indicated in the United States for the control and prevention of bleeding episodes, perioperative (surgical) management and routine prophylaxis in adults and children with hemophilia A. ELOCTATE is not indicated for the treatment of a bleeding disorder called von Willebrand disease. ELOCTATE was developed by fusing B-domain deleted factor VIII to the Fc portion of immunoglobulin G subclass 1, or IgG₁ (a protein commonly found in the body). It is believed that this enables ELOCTATE to use a naturally occurring pathway to prolong the time the therapy remains in the body.

Common adverse reactions (incidence of greater than or equal to 1 percent) reported in the registrational A-LONG study were arthralgia (joint pain) and malaise (general discomfort). For additional important safety information, and the United States full prescribing information, please visit www.ELOCTATE.com.

About ALPROLIX

ALPROLIX^® [Coagulation Factor IX (Recombinant), Fc Fusion Protein], the first recombinant clotting factor therapy with prolonged circulation in the body, is approved in the United States, Canada, Australia and Japan. It is indicated in the United States for the control and prevention of bleeding episodes, perioperative (surgical) management and routine prophylaxis in adults and children with hemophilia B. ALPROLIX is not indicated for immune tolerance induction therapy, which is a treatment for people with inhibitors, and should not be used in individuals with a known history of serious allergic reactions. ALPROLIX was developed by fusing factor IX to the Fc portion of immunoglobulin G subclass 1, or IgG₁ (a protein commonly found in the body). It is believed that this enables ALPROLIX to use a naturally occurring pathway to prolong the time the therapy remains in the body.

Common adverse reactions (incidence of greater than or equal to 1 percent) from the registrational B-LONG study were headache and oral paresthesia (an abnormal sensation in the mouth). For additional important safety information, and the United States full prescribing information, please visit www.ALPROLIX.com.

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, hematologic conditions and autoimmune disorders. Founded in 1978, Biogen Idec is the world’s oldest independent biotechnology company and patients worldwide benefit from its leading multiple sclerosis and innovative hemophilia therapies. For product labeling, press releases and additional information about the Company, please visit www.biogenidec.com.

Biogen Idec Safe Harbor

This press release contains forward-looking statements, including statements about the potential impact of ELOCTATE and ALPROLIX in the treatment of hemophilia. These statements may be identified by words such as “believe,” “expect,” “may,” “plan,” “potential,” “will” and similar expressions, and are based on our current beliefs and expectations. Drug development, research, and commercialization involve a high degree of risk. Factors which could cause actual results to differ materially from our current expectations include the risk that unexpected concerns may arise from additional data or analysis, regulatory authorities may require additional data or information or further studies, or may fail to approve or may delay approval of our drug candidates, or we may encounter other unexpected hurdles. For more detailed information on the risks and uncertainties associated with our drug development and commercialization activities, please review the Risk Factors section of our most recent annual or quarterly report filed with the Securities and Exchange Commission. Any forward-looking statements speak only as of the date of this press release and we assume no obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise.