Biogen Idec's Oral Compound BG-12 Achieves Development Milestones in MS and RA

CAMBRIDGE, Mass. — December 7, 2009 – Biogen Idec (NASDAQ: BIIB) today announced that its oral compound BG-12 (dimethyl fumarate) achieved key milestones in clinical trials for multiple sclerosis (MS) and rheumatoid arthritis (RA). In recent months, the last patient was enrolled in the CONFIRM trial, the second of two Phase III trials designed to evaluate the efficacy and safety of BG-12 as a monotherapy in patients with relapsing-remitting multiple sclerosis (RRMS). Both the DEFINE and CONFIRM Phase III trials are now fully enrolled and will evaluate the effect of BG-12 on clinical relapse, disability progression, various MRI measures of disease activity, and safety.

The last patient was also enrolled in a Phase II study to evaluate the safety, tolerability and efficacy of BG-12 in combination with methotrexate in subjects with active RA who had an inadequate response to conventional disease-modifying antirheumatic drug (DMARD) therapy.

"There is significant unmet need in both the MS and RA communities for additional treatment options," said Kate Dawson, M.D., senior director, Medical Research, Biogen Idec. "The Phase IIb study of oral BG-12 in patients with MS showed promising MRI results regarding the compound's ability to reduce inflammation and its potential for neuroprotection. We look forward to results from the DEFINE and CONFIRM Phase III MS studies, as well as the proof-of-concept trial in RA."

BG-12 has been shown to activate the Nrf2 transcriptional pathway, which pre-clinical studies have shown defends against oxidative-stress induced neuronal death, protects the blood-brain barrier and supports maintenance of myelin integrity in the central nervous system. Central nervous system inflammation and damage may trigger the symptoms common in RRMS such as fatigue, cognitive deterioration and physical disability. Because of BG-12's unique effect on the Nrf2 pathway and its oral delivery, BG-12 is also being considered for future MS combination therapy studies.

Additionally, as an oral compound, BG-12 holds promise for patients with RA. Its combination of anti-inflammatory and potential cytoprotective properties support the compound's evaluation in RA.

BG-12 is an oral formulation of dimethyl fumarate. Fumaderm®, a therapeutic for the treatment of psoriasis in Germany, includes dimethyl fumarate as one of the active ingredients. Fumaderm has more than 14 years of post-marketing experience and approximately 100,000 patient years of use.

About DEFINE and CONFIRM

DEFINE (Determination of the Efficacy and safety of oral Fumarate IN rElapsing-remitting MS) is a two-year, randomized, double-blind, placebo-controlled, dose-comparison study of 240 mg BID or TID of BG-12 orally compared to placebo in 1,200 patients with RRMS.

CONFIRM (COmparator and aN oral Fumarate In Relapsing-remitting MS) is a two-year, randomized, placebo-controlled and active reference comparison study in more than 1,400 patients with RRMS. In the three-arm study, patients are randomized to 240 mg BID or TID of BG-12 orally, placebo capsules orally, or 20 mg of Copaxone® (glatiramer acetate) via subcutaneous injection.

These Phase III, global, multi-center trials are being conducted in more than 300 centers in N. America, Europe and throughout the world.

About the RA Phase II Study

The proof-of-concept RA study (109RA201) is a randomized, double-blind, placebo-controlled, multiple-dose study in 150 patients with active RA who have had an inadequate response to conventional DMARD therapy. Patients are randomized to receive 240 mg BID or TID of BG-12 orally compared to placebo. All patients will receive background methotrexate therapy.

About BG-12

BG-12 (BG00012, dimethyl fumarate) is an investigational oral therapy in Phase III clinical development for the treatment of RRMS, the most common form of MS, and in Phase II for RA. BG-12 received Fast Track designation in MS from the U.S. Food and Drug Administration (FDA), which may expedite U.S. regulatory review. Biogen Idec retains full worldwide commercial rights to BG-12.

The Phase IIb study of BG-12, which was published in the Lancet, showed that BG-12 reduced the number of new gadolinium enhancing (Gd+) lesions by 69 percent in patients with RRMS when compared to treatment with placebo (p<0.0001). The presence of Gd+ lesions is thought to indicate continuing inflammatory activity within the central nervous system. Results from this study stimulated further evaluation of BG-12's potential for neuroprotection. BG-12 is the first compound in trials for the treatment of MS that has been shown to activate the Nrf2 pathway.

About MS

MS is a chronic, unpredictable and progressive disease of the central nervous system that causes inflammation and destruction of the myelin sheath — the protective layer that surrounds the body's nerve fibers. This destruction may result in cognitive impairment, physical disability and fatigue. According to the National MS Society, MS affects about 400,000 people in the U.S. and more than 2.5 million people worldwide. RRMS affects about 85 percent of the MS population. RRMS is characterized by clearly defined flare-ups followed by periods of partial or complete recovery or remission.

About RA

RA is a debilitating autoimmune disease that affects an estimated 1.3 million Americans. It generally presents between the ages of 25 and 55, and is more common in women than men. The damage that occurs in RA often results in disability and is a result of the immune system attacking joint tissue, causing painful chronic inflammation and irreversible destruction of cartilage, tendons and bones. Common RA symptoms include inflammation of the joints, swelling, fatigue, stiffness and pain. Additionally, since RA is a systemic disease, it can affect other tissues such as the lungs and eyes.

About Biogen Idec

Biogen Idec creates new standards of care in therapeutic areas with high unmet medical needs. 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.

Biogen Idec Safe Harbor

This press release contains forward-looking statements regarding the development of BG-12 as a potential treatment for various indications. These statements are based on the company's current beliefs and expectation. Drug development involves a high degree of risk. Factors which could cause actual results to differ materially from the company's current expectations include: the risk that unexpected concerns may arise from additional data or analysis, that regulatory authorities may require additional information, further studies, or may fail to approve the drug, 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, read the Risk Factors section of the most recent periodic report filed by Biogen Idec 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.

MEDIA CONTACTS:

Tracy Vineis

Senior Manager, Public Affairs

(617) 914-6524

INVESTOR CONTACTS:

Eric Hoffman

Director, Investor Relations

(617) 679-2812