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Biogen Idec: Expect Downside on PML Clustering

We are maintaining our 2-Equal Weight rating on shares of BIIB following report of a 9th case of PML in a patient treated for MS with Tysabri. While prior cases of confirmed PML have had limited impact on BIIB shares we believe that with a clustering of 3 cases within a month and with persistent concerns regarding cumulative risk on longer term exposure that BIIB shares will come under pressure today.

BIIB announced late Friday the confirmation of an additional case of PML in a patient treated with Tysabri. The case represents the 9th case confirmed since July 2008 and the 3rd case since May 18, 2009. Few details were provided beyond the fact that the case occurred ex-US and after 17 months of dosing.
With 7 of 9 confirmed cases occurring ex-US we expect greater scrutiny of ex-US risk managament which could ultimately slow growth from 123 new patients/week to a rate closer to the 46 new patients/week in the US. With the clustering of cases we expect more tentative use overall and would continue to advise investor caution pending further long term dosing experience
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Barclays Capital