X0306 4 2019-02-15 0000875045 BIOGEN INC. BIIB 0001577061 Sandrock Alfred BIOGEN INC. 225 BINNEY STREET CAMBRIDGE MA 02142 1 EVP, Chief Medical Officer Common Stock 2019-02-15 4 M 0 1318 0 A 10071.1941 D Common Stock 2019-02-15 4 F 0 586 332.87 D 9485.1941 D Restricted Stock Unit 0 2019-02-15 4 M 0 1318 0 D 2020-02-15 Common Stock 1318 2936 D Restricted Stock Unit 0 2019-02-15 4 J 0 808 0 D 2020-02-15 Common Stock 808 2128 D The number of RSUs reported represents the maximum possible number of shares that are eligible for vesting, which is 200% of the number of shares at target payout. One-third of these RSUs are eligible to vest on each of the first three anniversaries of the grant date. The actual number of shares that will vest on each vesting date will be determined by comparing the price of Biogen common stock on such vesting date to the price on the grant date (i.e., number of vested shares = number of shares at target payout times [the 30-day average closing stock price ending on the vesting date divided by the 30-day average closing stock price on the grant date]). This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested. /s/ Suzanne Murray, Attorney in Fact for Alfred W. Sandrock, Jr. 2019-02-20