SEC Form FWP filed by Biogen Inc.

Make-whole call, in whole or in part, as set forth in the preliminary prospectus supplement (Treasury Rate (as defined in the preliminary prospectus supplement) plus 20 basis points) at any time prior to December 15, 2030 (one month prior to the maturity date of the notes due 2031)

Par call, in whole or in part, at any time on or after December 15, 2030 (one month prior to the maturity date of the notes due 2031)

Make-whole call, in whole or in part, as set forth in the preliminary prospectus supplement (Treasury Rate (as defined in the preliminary prospectus supplement) plus 25 basis points) at any time prior to February 15, 2035 (three months prior to the maturity date of the notes due 2035)

Par call, in whole or in part, at any time on or after February 15, 2035 (three months prior to the maturity date of the notes due 2035)

Make-whole call, in whole or in part, as set forth in the preliminary prospectus supplement (Treasury Rate (as defined in the preliminary prospectus supplement) plus 25 basis points) at any time prior to November 15, 2054 (six months prior to the maturity date of the notes due 2055)

Par call, in whole or in part, at any time on or after November 15, 2054 (six months prior to the maturity date of the notes due 2055)

BofA Securities, Inc.

Citigroup Global Markets Inc.

J.P. Morgan Securities LLC

Deutsche Bank Securities Inc.

Mizuho Securities USA LLC

Morgan Stanley & Co. LLC

U.S. Bancorp Investments, Inc.

Wells Fargo Securities, LLC

BBVA Securities Inc.

Scotia Capital (USA) Inc.

TD Securities (USA) LLC

Academy Securities, Inc.

Blaylock Van, LLC

Loop Capital Markets LLC

None of the securities ratings is a recommendation to buy, sell or hold the notes. Each rating may be subject to revision or withdrawal at any time, and should be evaluated independently of any other rating.

Under Rule 15c6-1 under the Securities Exchange Act of 1934, as amended, trades in the secondary market generally are required to settle in one business day, unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade notes prior to the date that is one business day preceding the settlement date will be required, by virtue of the fact that the notes initially will settle T+4, to specify an alternate settlement cycle at the time of any such trade to prevent a failed settlement. Purchasers of notes who wish to trade the notes prior to the date that is one business day preceding the settlement date should consult their own advisors.