$BIIB

$252.26 +$1.57 (0.63%) Close

$BIIB Overview Financial Statements SEC Filings Executives News Red Flags Capital Raising Ownership Insider Transactions Congressional Trades

Ownership

13F as of Q2 2026 · 147.8M shares outstanding

Who owns BIIB?

By type of holder

Institutions 96.2% Insiders 0.2% Everyone else 3.6%

Concentration Top 10 holders own 57.9%

FMR LLC 12.3% · BlackRock, Inc. 10.8%

Institutional ownership

96.2%

+4.8 pts vs last qtr

Institutional holders

1,036

+26 vs last qtr

Net shares bought

+7.1M

by institutions in Q2 2026

New / sold out

126 / 100

positions opened vs closed

How is ownership changing?

Institutions, last 8 quarters

Biggest buyers in Q2 2026

FMR LLC +5.4M
Norges Bank NEW +2.6M

Biggest sellers in Q2 2026

T. Rowe Price Investment Management, Inc. −1.0M
Van Eck Associates Corp −981.8K

Who is planning to sell?

Notices of proposed sale, last 12 months

$905K

4 notices from 2 people

Shares covered

4.6K

0.00% of the company

Arranged in advance

100%

of the value is under a 10b5-1 plan

Under a 10b5-1 plan No plan

Largest proposed sellers

Singhal Priya Officer 10b5-1 $666K
Minor Lloyd Director 10b5-1 $240K

Every notice on Red Flags →

A Form 144 is notice of a planned sale, not the sale itself. What insiders actually sold is on Insider Transactions.

Is your stake being diluted?

Diluted share count, FY2016–FY2025

−32.8%

−4.32% a year

Each share's claim on the business

+48.7%

grew without buying or selling a share

Spent on buybacks vs paid in stock

$21.8B vs $2.16B

over 10 fiscal years

Diluted shares, split-adjusted

Buybacks Stock-based comp

How patient are the owners?

Institutional shares by how long they've been held

5+ years87% 3–5 years1% 1–3 years6% Under 1 year6%

Quarterly turnover

9.3%

of institutional shares changed hands

Top 10 managers, median time held

5 years

Super Investors

Investment managers reporting BIIB on Form 13F

Holder	Shares	% of company	Change vs last qtr	Held since	% of their book
F FMR LLC	18.2M	12.33%	+5.4M (+42.2%)	≤2021	0.2%
Shares held by quarter Peak holding18.2M (Q2'26) Change over 8 quarters+17.8M Share of the company12.330% FMR LLC's full portfolio →
B BlackRock, Inc.	16.0M	10.82%	+11.1K (+0.1%)	≤2021	0.1%
Shares held by quarter Peak holding16.0M (Q2'26) Change over 8 quarters+638.7K Share of the company10.820% BlackRock, Inc.'s full portfolio →

FMR LLC

18.2M

% of company

12.33%

Change vs last qtr

+5.4M (+42.2%)

Held since

≤2021

BlackRock, Inc.

16.0M

% of company

10.82%

Change vs last qtr

+11.1K (+0.1%)

Held since

≤2021

28 more super investors behind a free account

See every manager holding Biogen Inc., how their position has changed, and how long they've held it.

Institutional Funds

Mutual funds and ETFs reporting BIIB on Form N-PORT; together they hold 49.5% of the company

Fund	Position value	Shares	% of company	% of the fund	As of
VP Vanguard Primecap Fund Vanguard Chester Funds	$1.81B	8.4M	5.66%	1.88%	June 30, 2026
FC Fidelity Contrafund Fidelity Contrafund	$1.08B	5.0M	3.38%	0.60%	June 30, 2026

Vanguard Primecap Fund

Vanguard Chester Funds

Position value

$1.81B

% of company

5.66%

% of the fund

1.88%

As of

June 30, 2026

Fidelity Contrafund

Position value

$1.08B

% of company

3.38%

% of the fund

0.60%

As of

June 30, 2026

23 more funds behind a free account

See every fund holding Biogen Inc. and how much of the fund the position is.

Insiders and 5%+ holders

From Forms 3/4/5 and Schedules 13D/G

Holder	Shares	% of company	Change vs last qtr	8 quarters	Held since	% of their book
AS Alexander Susan H Insider	61.9K	0.04%	—	—	—	—
Insider holdings come from Form 3/4/5 filings, which are not quarterly. Share of the company0.040% Alexander Susan H's insider activity →
DC Dorsa Caroline Insider	31.0K	0.02%	—	—	—	—
Insider holdings come from Form 3/4/5 filings, which are not quarterly. Share of the company0.020% Dorsa Caroline's insider activity →

Alexander Susan H

Insider

61.9K

% of company

0.04%

Change vs last qtr

—

Held since

—

Dorsa Caroline

Insider

31.0K

% of company

0.02%

Change vs last qtr

—

Held since

—

19 more holders behind a free account

See every insider and 5%+ holder of Biogen Inc..

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