THE FOOD AND DRUG ADMINISTRATION APPROVES THE REINTRODUCTION OF TYSABRI(R) (NATALIZUMAB)

June 28, 2006

Biogen Idec (NASDAQ: BIIB) and Elan Corporation, plc (NYSE: ELN) today announced the approval of a supplemental Biologics License Application (sBLA) by the U.S. Food and Drug Administration (FDA) for the reintroduction of TYSABRI(R) (natalizumab) as a monotherapy treatment for relapsing forms of multiple sclerosis (MS) to slow the progression of disability and reduce the frequency of clinical relapses. The companies anticipate that TYSABRI will be available for commercial use in July.