Biogen Idec and Elan Announce That FDA Will Extend Regulatory Review Period for the Reintroduction of TYSABRI(R) for Multiple Sclerosis

The companies have been informed by the FDA that the Agencyrequires additional time to review information regarding the TYSABRIrisk management plan. Under this revised timeline, the companiesanticipate action from FDA on or before June 28, 2006.

About Biogen Idec

Biogen Idec creates new standards of care in oncology, neurologyand immunology. As a global leader in the development, manufacturing,and commercialization of novel therapies, Biogen Idec transformsscientific discoveries into advances in human healthcare. For productlabeling, press releases and additional information about the company,please visit www.biogenidec.com.

About Elan

Elan Corporation, plc is a neuroscience-based biotechnologycompany committed to making a difference in the lives of patients andtheir families by dedicating itself to bringing innovations in scienceto fill significant unmet medical needs that continue to exist aroundthe world. Elan shares trade on the New York, London and Dublin StockExchanges. For additional information about the company, please visitwww.elan.com.

Safe Harbor/Forward Looking Statements

This press release contains forward-looking statements regardingthe potential and regulatory path forward of TYSABRI. The commercialpotential and regulatory path forward of TYSABRI are subject to anumber of risks and uncertainties. Factors which could cause actualresults to differ materially from the companies' current expectationsinclude the risk that we may unable to adequately address concerns orquestions raised by FDA or European regulatory authorities during theregulatory review process, that concerns may arise from additionaldata or analysis, or that the companies may encounter other unexpecteddelays or hurdles. There is also no assurance that the companies willbe able to resume marketing and sales of TYSABRI. Drug development andcommercialization involves a high degree of risk. For more detailedinformation on the risks and uncertainties associated with thecompanies' drug development and other activities, see the periodicreports that Biogen Idec and Elan have filed with the Securities andExchange Commission. The companies assume no obligation to update anyforward-looking statements, whether as a result of new information,future events or otherwise.