FMR LLC holds 12.8M shares of Biogen (NASDAQ: BIIB) in amended 13G/A

Rhea-AI Filing Summary

BIOGEN INC ownership filing: FMR LLC reports beneficial ownership of 12,807,541.50 shares of Common Stock, representing 8.7% of the class as of 03/31/2026. The filing is an amendment (Schedule 13G/A) naming Abigail P. Johnson in a related disclosure and references an exhibit identifying the acquiring subsidiary and a power of attorney.

Insights

Institutional Ownership Analyst

FMR LLC holds an 8.7% stake in Biogen, a substantive but routine institutional position.

FMR LLC reports 12,807,541.50 shares beneficially owned as of 03/31/2026, with sole dispositive power reported. The schedule amendment updates ownership disclosure and links to an exhibit identifying the relevant subsidiary and a power of attorney.

Cash‑flow treatment and any plans to trade are not stated in the excerpt; subsequent filings would show changes in stake or dispositions.

Key Figures

Beneficial ownership: 12,807,541.50 shares Percent of class: 8.7% Sole dispositive power: 12,807,541.50 shares

3 metrics

Beneficial ownership 12,807,541.50 shares as of 03/31/2026

Percent of class 8.7% reported on Schedule 13G/A amendment

Sole dispositive power 12,807,541.50 shares cover-page responses

Key Terms

Schedule 13G/A, beneficially owned, sole dispositive power, power of attorney

4 terms

Schedule 13G/A regulatory

"Amendment No. 1 ) BIOGEN INC COMMON STOCK"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

beneficially owned regulatory

"Amount beneficially owned: 12807541.50"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole dispositive power financial

"Sole Dispositive Power 12,807,541.50"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

power of attorney legal

"Duly authorized under Power of Attorney effective as of April 13, 2026"

A power of attorney is a legal document that allows one person to make decisions and act on behalf of another person, often in financial or legal matters. It’s like giving someone a trusted helper or agent the authority to handle important tasks if you are unable to do so yourself. This matters to investors because it can impact how their assets are managed or transferred if they become unable to oversee their affairs.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

BIOGEN INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

09062X103

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 09062X103

1

Names of Reporting Persons

FMR LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 11,468,454.45
6	Shared Voting Power 0.00
7	Sole Dispositive Power 12,807,541.50
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

12,807,541.50

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

8.7 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

CUSIP Number(s): 09062X103

1

Names of Reporting Persons

Abigail P. Johnson

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 12,807,541.50
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

12,807,541.50

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

8.7 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: BIOGEN INC
(b)	Address of issuer's principal executive offices: 225 BINNEY STREET,Cambridge,MA,USA,02142
Item 2.
(a)	Name of person filing: FMR LLC
(b)	Address or principal business office or, if none, residence: 245 Summer Street, Boston, Massachusetts 02210
(c)	Citizenship: Not applicable
(d)	Title of class of securities: COMMON STOCK
(e)	CUSIP No.: 09062X103
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 12807541.50
(b)	Percent of class: 8.7 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Please see the responses to Items 5 and 6 on the cover page.
	(ii) Shared power to vote or to direct the vote: 0.00
	(iii) Sole power to dispose or to direct the disposition of: 12807541.50
	(iv) Shared power to dispose or to direct the disposition of: 0.00
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. One or more other persons are known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the COMMON STOCK of BIOGEN INC. No one other person's interest in the COMMON STOCK of BIOGEN INC is more than five percent of the total outstanding COMMON STOCK.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. See attached Exhibit 99.
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

FMR LLC

Signature:	Richard Bourgelas
Name/Title:	Duly authorized under Power of Attorney effective as of April 13, 2026, by and on behalf of FMR LLC and its direct and indirect subsidiaries*
Date:	05/05/2026

Abigail P. Johnson

Signature:	Richard Bourgelas
Name/Title:	Duly authorized under Power of Attorney effective as of April 13, 2026, by and on behalf of Abigail P. Johnson*
Date:	05/05/2026

Comments accompanying signature: *This power of attorney is incorporated herein by reference to Exhibit 24 to the Schedule 13G filed by FMR LLC on April 29,2026, accession number: 0000315066-26-000738.

Exhibit Information

Please see Exhibit 99 for 13d-1(k) (1) agreement.

FAQ

What stake does FMR LLC report in Biogen (BIIB)?

FMR LLC reports 12,807,541.50 shares beneficially owned, equal to 8.7% of Biogen common stock as of 03/31/2026. The filing is an amended Schedule 13G/A reflecting that ownership level.

Does Abigail P. Johnson directly own the Biogen shares reported?

The filing lists Abigail P. Johnson in related cover-page responses and shows shared filings for the same 12,807,541.50 shares. It attributes power via FMR LLC and references a power of attorney effective April 13, 2026.

What authority does FMR LLC report over the shares?

FMR LLC reports sole dispositive power for 12,807,541.50 shares and sole voting power reported on the cover-page items; shared voting and dispositive powers are shown as 0.00 in the excerpt.

Is the 8.7% holding more than 5% significant for reporting?

Yes. Holdings above 5% trigger Schedule 13G/A disclosure obligations; FMR LLC’s 8.7% triggers this amended filing and related exhibit disclosures regarding the acquiring subsidiary and authority.

Does the filing state whether the shares will be sold or retained?

The excerpt does not state any intended sales or retention plans. It provides ownership counts, voting/dispositive powers, and references Exhibit 99 and a power of attorney for related information.