CONFERENCE CALL AND WEBCAST On April 20, 2018 at 8:15 a.m. .m eastern Time. Eastern Time, Biogen will host a live webcast and conference call to discuss the extensive collaboration with Ionis, which will be available on the investor section of the Biogen website. Additional information in the form of slides is also available on the Internet at the same location and will then be available on the site for at least one month. Biogen Safe Harbor This press release contains forward-looking statements, including statements made pursuant to the provisions of the Security Protection Act of the Private Securities Litigation Reform Act of 1995, which address the potential benefits and outcomes of Biogen`s cooperation agreement with Ionis, risks and uncertainties associated with the development and commercialization of drugs, to the potential of Biogen`s commercial commercial and pipeline programs, including the potential of new anti-state candidates for a wide range of neurological diseases, including dementia, neuromuscular diseases, movement disorders, ophthalmology, inner ear disorders and neuropsychiatry, the expected conclusion and timing of the transaction, and the potential benefits of the transaction , the safety and effectiveness of SPINAZA. These forward-looking statements may be accompanied by words such as «target,» «anticipate,» «belief,» «could,» «appreciate,» «except,» «forecast,» «project,» «plan,» «potential,» «possible,» «will» and other words and terms of similar meaning. The development and commercialization of drugs presents a high risk and only a small number of research and development programs lead to the commercialization of a product. The results of early clinical trials may not be an indication of the full results or results of subsequent or major clinical studies and may not guarantee marketing approval by the authorities. They should not rely inappropriately on these statements or on the scientific data provided. These statements involve risks and uncertainties that could lead to actual results differing materially from those reflected in such statements, including, but not limited to: risks that the transaction will be completed in a timely manner, or in general; Uncertainty about the potential to achieve the expected benefits and potential of the biogen-Ionis cooperation agreement; The risk of unforeseen costs or delays uncertainty about the success of the development and potential commercialization of new anti-susense candidates for a wide range of neurological diseases, including dementia, neuromuscular diseases, movement disorders, ophthalmology disorders, inner ear disorders and neuropsychiatry, which may be affected, among other things, by the onset of adverse safety events and/or unexpected concerns that may result from additional data or analysis; Regulators may require additional information or further studies or do not authorize or delay the authorisation of these applicants; Biogen and Ionis may face other unexpected obstacles that may be hampered, among other things, by the emergence of unwanted security events, the lack of regulatory authority in some jurisdictions, or the lack of protection of intellectual property and other property rights; Product liability rights; or risks to the cooperation of third parties.