BIIB

SEC source: 0001127602-17-009829 · form4.xml · derivative · entry 12

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,774

Underlying: Common Stock · 663 shares

Expires 2018-02-23

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · date: This award vested on 2/23/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F7 · shares: This award was previously reported as covering 3,462 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F5 · derivative.exercise_date: 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]).

F7 · derivative.underlying_shares: This award was previously reported as covering 3,462 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F7 · balance_after: This award was previously reported as covering 3,462 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

SEC source: 0001127602-17-009829 · form4.xml · derivative · entry 11

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,437

Underlying: Common Stock · 1,105 shares

Expires 2018-02-23

F4 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F5 · derivative.exercise_date: 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]).

SEC source: 0001127602-17-009829 · form4.xml · derivative · entry 10

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,638

Underlying: Common Stock · 1,678 shares

Expires 2019-02-22

F4 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F6 · derivative.exercise_date: 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]).

SEC source: 0001127602-17-009829 · form4.xml · derivative · entry 9

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,152

Underlying: Common Stock · 1,352 shares

Expires 2017-02-12

F4 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F5 · derivative.exercise_date: 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]).

SEC source: 0001127602-17-009829 · form4.xml · nonDerivative · entry 8

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 30,596

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009829 · form4.xml · nonDerivative · entry 7

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 31,948

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009829 · form4.xml · nonDerivative · entry 6

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 29,075

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009829 · form4.xml · nonDerivative · entry 5

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 29,618

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009829 · form4.xml · nonDerivative · entry 4

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 28,466

F2 · date: This award vested on 2/22/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009829 · form4.xml · nonDerivative · entry 3

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 29,313

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · date: This award vested on 2/22/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009829 · form4.xml · nonDerivative · entry 2

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 27,221

F1 · date: This award vested on 2/23/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009829 · form4.xml · nonDerivative · entry 1

Clancy Paul J · CIK 0001409601 · Executive VP and CFO

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 27,533

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · date: This award vested on 2/23/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009820 · form4.xml · derivative · entry 16

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 1 shares

Expires 2017-02-12

F11 · derivative.exercise_date: The number of RSUs reported represents the maximum possible number of shares that are eligible for vesting, which is 150% of the number of shares at target payout. One-fourth of these RSUs are eligible to vest on each of the first four 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 Idec 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 average 60 calendar-day closing stock price ending on the vesting date divided by the average 60 calendar-day closing stock price on the grant date]).

SEC source: 0001127602-17-009820 · form4.xml · derivative · entry 15

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1

Underlying: Common Stock · 2,197 shares

Expires 2017-02-12

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F10 · shares: This award was previously reported as covering 2,147 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F11 · derivative.exercise_date: The number of RSUs reported represents the maximum possible number of shares that are eligible for vesting, which is 150% of the number of shares at target payout. One-fourth of these RSUs are eligible to vest on each of the first four 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 Idec 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 average 60 calendar-day closing stock price ending on the vesting date divided by the average 60 calendar-day closing stock price on the grant date]).

F10 · derivative.underlying_shares: This award was previously reported as covering 2,147 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F10 · balance_after: This award was previously reported as covering 2,147 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

SEC source: 0001127602-17-009820 · form4.xml · derivative · entry 14

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 1,259 shares

Expires 2017-02-12

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F9 · shares: This award was previously reported as covering 2,674 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F5 · derivative.exercise_date: 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]).

F9 · derivative.underlying_shares: This award was previously reported as covering 2,674 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F9 · balance_after: This award was previously reported as covering 2,674 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

SEC source: 0001127602-17-009820 · form4.xml · derivative · entry 13

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,960

Underlying: Common Stock · 1,375 shares

Expires 2019-02-22

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · date: This award vested on 2/22/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F8 · shares: This award was previously reported as covering 7,270 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F6 · derivative.exercise_date: 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]).

F8 · derivative.underlying_shares: This award was previously reported as covering 7,270 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F8 · balance_after: This award was previously reported as covering 7,270 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

SEC source: 0001127602-17-009820 · form4.xml · derivative · entry 12

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,948

Underlying: Common Stock · 728 shares

Expires 2018-02-23

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · date: This award vested on 2/23/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F7 · shares: This award was previously reported as covering 3,802 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F5 · derivative.exercise_date: 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]).

F7 · derivative.underlying_shares: This award was previously reported as covering 3,802 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F7 · balance_after: This award was previously reported as covering 3,802 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

SEC source: 0001127602-17-009820 · form4.xml · derivative · entry 11

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,676

Underlying: Common Stock · 1,216 shares

Expires 2018-02-23

F4 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F5 · derivative.exercise_date: 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]).

SEC source: 0001127602-17-009820 · form4.xml · derivative · entry 10

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,335

Underlying: Common Stock · 1,103 shares

Expires 2019-02-22

F4 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F6 · derivative.exercise_date: 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]).

SEC source: 0001127602-17-009820 · form4.xml · derivative · entry 9

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,259

Underlying: Common Stock · 1,477 shares

Expires 2017-02-12

F4 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F5 · derivative.exercise_date: 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]).

SEC source: 0001127602-17-009820 · form4.xml · nonDerivative · entry 8

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 34,990

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009820 · form4.xml · nonDerivative · entry 7

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 36,024

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009820 · form4.xml · nonDerivative · entry 6

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 33,827

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009820 · form4.xml · nonDerivative · entry 5

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 34,420

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009820 · form4.xml · nonDerivative · entry 4

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 33,161

F2 · date: This award vested on 2/22/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009820 · form4.xml · nonDerivative · entry 3

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 33,608

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · date: This award vested on 2/22/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009820 · form4.xml · nonDerivative · entry 2

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 32,233

F1 · date: This award vested on 2/23/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009820 · form4.xml · nonDerivative · entry 1

ALEXANDER SUSAN H · CIK 0001263839 · EVP, Chief Legal Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 32,568

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · date: This award vested on 2/23/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009826 · form4.xml · derivative · entry 20

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 815 shares

Expires 2017-02-12

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F13 · shares: This award was previously reported as covering 797 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F14 · derivative.exercise_date: The number of RSUs reported represents the maximum possible number of shares that are eligible for vesting, which is 150% of the number of shares at target payout. One-fourth of these RSUs are eligible to vest on each of the first four 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 Idec 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 average 60 calendar-day closing stock price ending on the vesting date divided by the average 60 calendar-day closing stock price on the grant date]).

F13 · derivative.underlying_shares: This award was previously reported as covering 797 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F13 · balance_after: This award was previously reported as covering 797 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

SEC source: 0001127602-17-009826 · form4.xml · derivative · entry 19

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 628 shares

Expires 2017-02-12

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F12 · shares: This award was previously reported as covering 1,336 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F7 · derivative.exercise_date: 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]).

F12 · derivative.underlying_shares: This award was previously reported as covering 1,336 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F12 · balance_after: This award was previously reported as covering 1,336 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

SEC source: 0001127602-17-009826 · form4.xml · derivative · entry 18

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,828

Underlying: Common Stock · 1,569 shares

Expires 2019-02-12

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F11 · shares: This award was previously reported as covering 10,006 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F6 · derivative.exercise_date: 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-fourth of these RSUs are eligible to vest each year for four years, beginning two years from the date of grant. The actual number of shares that will vest on each vesting date will be determined by comparing the price of Biogen Idec 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]).

F11 · derivative.underlying_shares: This award was previously reported as covering 10,006 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F11 · balance_after: This award was previously reported as covering 10,006 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

SEC source: 0001127602-17-009826 · form4.xml · derivative · entry 17

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,062

Underlying: Common Stock · 398 shares

Expires 2018-02-23

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · date: This award vested on 2/23/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F10 · shares: This award was previously reported as covering 2,074 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F7 · derivative.exercise_date: 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]).

F10 · derivative.underlying_shares: This award was previously reported as covering 2,074 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F10 · balance_after: This award was previously reported as covering 2,074 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

SEC source: 0001127602-17-009826 · form4.xml · derivative · entry 16

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,960

Underlying: Common Stock · 1,375 shares

Expires 2019-02-22

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · date: This award vested on 2/22/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F9 · shares: This award was previously reported as covering 7,270 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F8 · derivative.exercise_date: 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]).

F9 · derivative.underlying_shares: This award was previously reported as covering 7,270 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F9 · balance_after: This award was previously reported as covering 7,270 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

SEC source: 0001127602-17-009826 · form4.xml · derivative · entry 15

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,460

Underlying: Common Stock · 662 shares

Expires 2018-02-23

F5 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F7 · derivative.exercise_date: 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]).

SEC source: 0001127602-17-009826 · form4.xml · derivative · entry 14

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,335

Underlying: Common Stock · 1,103 shares

Expires 2019-02-22

F5 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F8 · derivative.exercise_date: 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]).

SEC source: 0001127602-17-009826 · form4.xml · derivative · entry 13

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 628

Underlying: Common Stock · 738 shares

Expires 2017-02-12

F5 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F7 · derivative.exercise_date: 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]).

SEC source: 0001127602-17-009826 · form4.xml · derivative · entry 12

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 8,397

Underlying: Common Stock · 1,841 shares

Expires 2019-02-12

F5 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F6 · derivative.exercise_date: 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-fourth of these RSUs are eligible to vest each year for four years, beginning two years from the date of grant. The actual number of shares that will vest on each vesting date will be determined by comparing the price of Biogen Idec 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]).

SEC source: 0001127602-17-009826 · form4.xml · nonDerivative · entry 11

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 10,013.8551

F4 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009826 · form4.xml · nonDerivative · entry 10

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 10,397.8551

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009826 · form4.xml · nonDerivative · entry 9

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,582.8551

F4 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009826 · form4.xml · nonDerivative · entry 8

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,878.8551

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009826 · form4.xml · nonDerivative · entry 7

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,250.8551

F4 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009826 · form4.xml · nonDerivative · entry 6

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,989.8551

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009826 · form4.xml · nonDerivative · entry 5

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 8,420.8551

F3 · date: On 2/12/14 an RSU was awarded for 7,740 shares vesting over 4 years. The remaining 5,805 shares were adjusted to 5,940 shares pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F3 · shares: On 2/12/14 an RSU was awarded for 7,740 shares vesting over 4 years. The remaining 5,805 shares were adjusted to 5,940 shares pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

F3 · balance_after: On 2/12/14 an RSU was awarded for 7,740 shares vesting over 4 years. The remaining 5,805 shares were adjusted to 5,940 shares pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017.

SEC source: 0001127602-17-009826 · form4.xml · nonDerivative · entry 4

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,147.8551

F2 · date: This award vested on 2/23/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009826 · form4.xml · nonDerivative · entry 3

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,335.8551

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F2 · date: This award vested on 2/23/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009826 · form4.xml · nonDerivative · entry 2

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 8,937.8551

F1 · date: This award vested on 2/22/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009826 · form4.xml · nonDerivative · entry 1

Sandrock Alfred · CIK 0001577061 · EVP CMO Neuro & Neurodegenerat

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,584.8551

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · date: This award vested on 2/22/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

SEC source: 0001127602-17-009812 · form4.xml · derivative · entry 15

COVINO GREGORY F · CIK 0001224116 · VP, Chief Accounting Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 121 shares

Expires 2017-02-12

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F11 · shares: This award was previously reported as covering 258 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017

F5 · derivative.exercise_date: 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]).

F11 · derivative.underlying_shares: This award was previously reported as covering 258 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017

F11 · balance_after: This award was previously reported as covering 258 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017

SEC source: 0001127602-17-009812 · form4.xml · derivative · entry 14

COVINO GREGORY F · CIK 0001224116 · VP, Chief Accounting Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 321 shares

Expires 2017-02-12

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F3 · date: This award vested on 2/12/2017 and the actual number of shares that vested was determined in accordance with the terms of such award. Due to adjustments to the award to account for the Bioverativ Inc. spin-off, the number of vested shares was not determinable until 2/28/2017. Such adjusted number of vested shares was distributed to the reporting person on 2/28/2017.

F9 · shares: This award was previously reported as covering 315 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017

F10 · derivative.exercise_date: The number of RSUs reported represents the maximum possible number of shares that are eligible for vesting, which is 150% of the number of shares at target payout. One-fourth of these RSUs are eligible to vest on each of the first four 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 Idec 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 average 60 calendar-day closing stock price ending on the vesting date divided by the average 60 calendar-day closing stock price on the grant date]).

F9 · derivative.underlying_shares: This award was previously reported as covering 315 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017

F9 · balance_after: This award was previously reported as covering 315 shares, but was adjusted pursuant to the anti-dilution provisions of the award in connection with the spin-off of Bioverativ Inc. on February 1, 2017