The transaction has been approved by the boards of directors of both companies and is subject to the customary review process under the Hart–Scott–Rodino Antitrust Improvements Act in the United States and other customary review processes. The transaction is expected to close by the end of the second quarter, assuming a standard regulatory approval timeframe.Centerview Partners LLC is acting as exclusive financial advisor to Biogen Idec. Ropes & Gray LLP is acting as legal counsel to Biogen Idec. Webcast Biogen Idec will host a webcast to discuss this transaction today, February 6, 2013, at 8:00 a.m. ET/5:00 a.m. PT. George Scangos, Chief Executive Officer, Biogen Idec, will lead the call. The call will be broadcast via the internet and will be accessible through the Investors section of Biogen Idec's homepage, www.biogenidec.com. Supplemental information in the form of a slide presentation will also be accessible at the same location on the internet at the time of the conference call and will be subsequently available on the website for one month. 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.