BIIB

BIOGEN IDEC INC.

$183.78

Closing price as of Apr 1, 2026

18 superinvestors own BIIB

Based on latest 13F filings — data is 45–90 days delayed

Investor	Fund	Weight	Shares	Value	Quarter	Activity
Carl Icahn	Icahn Capital Management	16.64%	8,825,816	$585.4M	2007Q3	New
Hillman Capital Management	Hillman Value Fund	3.76%	29,540	$5.4M	2026Q1	Reduced
Mason Hawkins	Longleaf Partners – Southeastern Asset Management	3.14%	842,962	$177.5M	2022Q1	Reduced
Michael Burry	Scion Asset Management	2.91%	10,000	$3.0M	2018Q4	New
Samantha McLemore	Patient Capital Management	2.55%	379,741	$69.6M	2026Q1	Reduced
Viking Global Investors	Viking Global Investors	0.83%	688,765	$188.3M	2017Q1	Reduced
Bill Miller	Miller Value Partners	0.66%	79,493	$27.5M	2021Q2	New
Sarah Ketterer	Causeway Capital Management	0.63%	280,783	$51.5M	2026Q1	Reduced
William Von Mueffling	Cantillon Capital Management	0.18%	74,796	$5.0M	2004Q4	New
Duan Yongping	H&H International Investment	0.11%	10,000	$3.2M	2020Q1	New
Warren Buffett	Berkshire Hathaway	0.07%	643,022	$179.9M	2021Q1	Held
First Eagle Investment Management	First Eagle Investment Management	0.05%	57,300	$15.3M	2020Q2	Added
Kenneth Fisher	Fisher Asset Management	0.02%	312,618	$57.3M	2026Q1	Added
Meridian / ArrowMark	Meridian Contrarian Fund	0.01%	1,475	$596K	2015Q2	Added
Christopher Davis	Davis Selected Advisers	0.00%	0	$1.8M	2008Q2	New
Richard Pzena	Pzena Investment Management	0.00%	1,618	$461K	2023Q2	Reduced
Mairs & Power	Mairs & Power Growth Fund	0.00%	950	$246K	2023Q4	Held
Dodge & Cox	Dodge & Cox	0.00%	6,000	$302K	2008Q3	Held

Open-market purchases (P) and sales (S) from SEC Form 4 filings · last 12 months

No open-market insider trades in the last 12 months.

Form 4 filings for option exercises and other transaction types are excluded.

STOCK Act disclosures · last 12 months

Congressional trade data coming soon.

We are sourcing STOCK Act disclosures and will display them here shortly.

What Is SEC Form 4?

Understand the insider trade filings behind BIIB activity.

What Is a 13F Filing?

How superinvestors disclose their quarterly holdings.

Insider Cluster Buying

Why multiple insiders buying together is a strong signal.

Superinvestor Consensus

The most widely held stocks across all tracked institutions.