BIIB

SEC source: 0001127602-18-020962 · form4.xml · nonDerivative · entry 1

Mulligan Richard · CIK 0001376247 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 10,909

SEC source: 0001127602-18-020959 · form4.xml · nonDerivative · entry 1

LEAMING NANCY · CIK 0001265751 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 10,943

SEC source: 0001127602-18-020954 · form4.xml · nonDerivative · entry 1

DORSA CAROLINE · CIK 0001181174 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 19,052

SEC source: 0001127602-18-020950 · form4.xml · nonDerivative · entry 1

PAPADOPOULOS STELIOS · CIK 0001202098 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,190

F1 · balance_after: The reporting person transferred 5,831 shares that he directly owned to Esperanza Holdings, LLC.

F2 · balance_after: The reporting person transferred 12,375 shares that he directly owned to Stelios Holdings, LLC.

SEC source: 0001127602-18-020945 · form4.xml · nonDerivative · entry 1

Rowinsky Eric K · CIK 0001318886 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 15,024

SEC source: 0001127602-18-020940 · form4.xml · nonDerivative · entry 1

SCHENK LYNN · CIK 0001236534 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 7,909

SEC source: 0001127602-18-020935 · form4.xml · nonDerivative · entry 1

SHERWIN STEPHEN A · CIK 0001079462 · Director

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,014

SEC source: 0001127602-18-020025 · form4.xml · derivative · entry 5

Ehlers Michael D · CIK 0001674364 · EVP, Research and Development

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,502

Underlying: Common Stock · 1,110 shares

Expires 2019-06-01

F3 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F2 · 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: 0001127602-18-020025 · form4.xml · derivative · entry 4

Ehlers Michael D · CIK 0001674364 · EVP, Research and Development

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,612

Underlying: Common Stock · 1,384 shares

Expires 2019-06-01

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 · 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: 0001127602-18-020025 · form4.xml · nonDerivative · entry 3

Ehlers Michael D · CIK 0001674364 · EVP, Research and Development

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 5,281.171

SEC source: 0001127602-18-020025 · form4.xml · nonDerivative · entry 2

Ehlers Michael D · CIK 0001674364 · EVP, Research and Development

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 5,897.171

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.

SEC source: 0001127602-18-020025 · form4.xml · nonDerivative · entry 1

Ehlers Michael D · CIK 0001674364 · EVP, Research and Development

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,513.171

F1 · balance_after: Includes 74.812 shares acquired under the Biogen Inc. employee stock purchase plan on 3/29/2018.

SEC source: 0001127602-18-016415 · form4.xml · derivative · entry 4

Vounatsos Michel · CIK 0001672709 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,252

Underlying: Common Stock · 1,557 shares

Expires 2019-05-02

F2 · 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]).

F3 · derivative.underlying_shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

SEC source: 0001127602-18-016415 · form4.xml · derivative · entry 3

Vounatsos Michel · CIK 0001672709 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,809

Underlying: Common Stock · 1,687 shares

Expires 2019-05-02

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 · 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: 0001127602-18-016415 · form4.xml · nonDerivative · entry 2

Vounatsos Michel · CIK 0001672709 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 9,368.27

SEC source: 0001127602-18-016415 · form4.xml · nonDerivative · entry 1

Vounatsos Michel · CIK 0001672709 · Director · Chief Executive Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 10,118.27

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 · balance_after: Includes 74.812 shares acquired under the Biogen Inc. employee stock purchase plan on 3/29/2018.

SEC source: 0001127602-18-015376 · form4.xml · nonDerivative · entry 1

DENNER ALEXANDER J · CIK 0001361754 · Director

10b5-1 filing: Not disclosed

Ownership: Indirect · See Footnotes

Disclosed balance after: 461,858

F1 · ownership.nature: On April 25, 2018, funds managed by Sarissa Capital Management LP (such funds, the "Sarissa Funds") purchased an aggregate of 48,000 shares of common stock of Biogen Inc. All of the shares reported herein as being indirectly beneficially owned by Dr. Denner are directly beneficially owned by the Sarissa Funds.

F2 · ownership.nature: Dr. Denner is the Chief Investment Officer of Sarissa Capital Management LP and the managing member of the general partner of the Sarissa Funds. By virtue of the foregoing, Dr. Denner may be deemed to indirectly beneficially own (as that term is defined in Rule 13d-3 of the Securities Exchange Act of 1934, as amended) the shares that the Sarissa Funds directly beneficially own. Dr. Denner disclaims beneficial ownership of these shares except to the extent of his pecuniary interest therein.

SEC source: 0001127602-18-010088 · form4.xml · derivative · entry 5

McKenzie Paul · CIK 0001677903 · EVP Pharmaceutical Oper & Tech

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 848

Underlying: Common Stock · 312 shares

Expires 2019-03-01

F2 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F1 · 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: 0001127602-18-010088 · form4.xml · derivative · entry 4

McKenzie Paul · CIK 0001677903 · EVP Pharmaceutical Oper & Tech

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,160

Underlying: Common Stock · 532 shares

Expires 2019-03-01

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 · 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: 0001127602-18-010088 · form4.xml · nonDerivative · entry 3

McKenzie Paul · CIK 0001677903 · EVP Pharmaceutical Oper & Tech

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,301.819

SEC source: 0001127602-18-010088 · form4.xml · nonDerivative · entry 2

McKenzie Paul · CIK 0001677903 · EVP Pharmaceutical Oper & Tech

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,538.819

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.

SEC source: 0001127602-18-010088 · form4.xml · nonDerivative · entry 1

McKenzie Paul · CIK 0001677903 · EVP Pharmaceutical Oper & Tech

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,006.819

SEC source: 0001127602-18-010078 · form4.xml · derivative · entry 1

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 531

Underlying: Common Stock · 531 shares

Expires 2021-03-01

F1 · derivative.exercise_date: The restricted stock units vest in three (3) equal annual installments commencing one year after the grant date of 03/01/2018.

SEC source: 0001127602-18-009190 · form4.xml · nonDerivative · entry 1

Sandrock Alfred · CIK 0001577061 · EVP, Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,553.3821

F1 · kind: Sale pursuant to a trading plan intended to comply with Rule 10b5-1 of the Securities Exchange Act of 1934.

SEC source: 0001127602-18-008815 · form4.xml · derivative · entry 5

Sandrock Alfred · CIK 0001577061 · EVP, Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 595 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.

F4 · 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: 0001127602-18-008815 · form4.xml · derivative · entry 4

Sandrock Alfred · CIK 0001577061 · EVP, Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 595

Underlying: Common Stock · 467 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.

F4 · 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: 0001127602-18-008815 · form4.xml · nonDerivative · entry 3

Sandrock Alfred · CIK 0001577061 · EVP, Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,812.3821

SEC source: 0001127602-18-008815 · form4.xml · nonDerivative · entry 2

Sandrock Alfred · CIK 0001577061 · EVP, Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 7,020.3821

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.

SEC source: 0001127602-18-008815 · form4.xml · nonDerivative · entry 1

Sandrock Alfred · CIK 0001577061 · EVP, Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,553.3821

F1 · kind: Sale pursuant to a trading plan intended to comply with Rule 10b5-1 of the Securities Exchange Act of 1934.

F2 · price: Full information regarding the number of shares sold at each separate price will be provided upon request by the SEC staff, the issuer, or a security holder of the issuer.

F3 · price: This represents the weighted average price for shares sold at a range between $293.30 (low) and $294.00 (high).

SEC source: 0001127602-18-008813 · form4.xml · derivative · entry 4

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 116 shares

Expires 2018-02-23

F2 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F1 · 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: 0001127602-18-008813 · form4.xml · derivative · entry 3

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 116

Underlying: Common Stock · 92 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 · 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: 0001127602-18-008813 · form4.xml · nonDerivative · entry 2

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,744.3601

SEC source: 0001127602-18-008813 · form4.xml · nonDerivative · entry 1

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,772.3601

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.

SEC source: 0001127602-18-008811 · form4.xml · derivative · entry 4

ALEXANDER SUSAN H · CIK 0001263839 · EVP Chief Legal Corp Svc & Sec

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 1,091 shares

Expires 2018-02-23

F2 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F1 · 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: 0001127602-18-008811 · form4.xml · derivative · entry 3

ALEXANDER SUSAN H · CIK 0001263839 · EVP Chief Legal Corp Svc & Sec

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 1,091

Underlying: Common Stock · 857 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 · 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: 0001127602-18-008811 · form4.xml · nonDerivative · entry 2

ALEXANDER SUSAN H · CIK 0001263839 · EVP Chief Legal Corp Svc & Sec

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 24,844

SEC source: 0001127602-18-008811 · form4.xml · nonDerivative · entry 1

ALEXANDER SUSAN H · CIK 0001263839 · EVP Chief Legal Corp Svc & Sec

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 25,225

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.

SEC source: 0001127602-18-008406 · form4.xml · derivative · entry 4

Sandrock Alfred · CIK 0001577061 · EVP, Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,482

Underlying: Common Stock · 843 shares

Expires 2019-02-22

F2 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F1 · 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: 0001127602-18-008406 · form4.xml · derivative · entry 3

Sandrock Alfred · CIK 0001577061 · EVP, Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,325

Underlying: Common Stock · 1,635 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 · 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: 0001127602-18-008406 · form4.xml · nonDerivative · entry 2

Sandrock Alfred · CIK 0001577061 · EVP, Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 7,461.3821

SEC source: 0001127602-18-008406 · form4.xml · nonDerivative · entry 1

Sandrock Alfred · CIK 0001577061 · EVP, Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 8,188.3821

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.

SEC source: 0001127602-18-008404 · form4.xml · derivative · entry 4

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 302

Underlying: Common Stock · 100 shares

Expires 2019-02-22

F2 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F1 · 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: 0001127602-18-008404 · form4.xml · derivative · entry 3

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 402

Underlying: Common Stock · 194 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 · 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: 0001127602-18-008404 · form4.xml · nonDerivative · entry 2

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,680.3601

SEC source: 0001127602-18-008404 · form4.xml · nonDerivative · entry 1

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

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 4,738.3601

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.

SEC source: 0001127602-18-008398 · form4.xml · derivative · entry 4

ALEXANDER SUSAN H · CIK 0001263839 · EVP Chief Legal Corp Svc & Sec

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 2,482

Underlying: Common Stock · 843 shares

Expires 2019-02-22

F2 · shares: This represents the difference between the maximum possible number of shares that were eligible for vesting and the actual number that vested.

F1 · 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: 0001127602-18-008398 · form4.xml · derivative · entry 3

ALEXANDER SUSAN H · CIK 0001263839 · EVP Chief Legal Corp Svc & Sec

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 3,325

Underlying: Common Stock · 1,635 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 · 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: 0001127602-18-008398 · form4.xml · nonDerivative · entry 2

ALEXANDER SUSAN H · CIK 0001263839 · EVP Chief Legal Corp Svc & Sec

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 24,368

SEC source: 0001127602-18-008398 · form4.xml · nonDerivative · entry 1

ALEXANDER SUSAN H · CIK 0001263839 · EVP Chief Legal Corp Svc & Sec

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 25,095

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.

SEC source: 0001127602-18-007526 · form4.xml · nonDerivative · entry 1

Sandrock Alfred · CIK 0001577061 · EVP, Chief Medical Officer

10b5-1 filing: Not disclosed

Ownership: Direct

Disclosed balance after: 6,553.3821

F1 · kind: Sale pursuant to a trading plan intended to comply with Rule 10b5-1 of the Securities Exchange Act of 1934.