Biogen Inc.
Biogen Inc. (BIIB) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · BIIB · as of Mar 31, 2025
Ownership Breakdown
930
Institutional Holders
$17.78B
Total Inst. Value
▼ $2.45B vs Q4
147.64M
Shares Outstanding
freeFloat 99.12%
130.05M
13F Shares Held
▼ 2.34M vs Q4
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
BIIB largest shareholders · institutional ownership
Q1 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
VANGUARD GROUP INC biological products, (no diagnostic substances) | 17.03M | 11.66% | 11.66% | $2.33T | May 9, 2025 | ▲ 284.0K |
PRIMECAP MANAGEMENT CO/CA/ biological products, (no diagnostic substances) | 15.94M | 10.91% | 10.91% | $2.18T | May 9, 2025 | ▼ 103.0K |
BLACKROCK, INC. biological products, (no diagnostic substances) | 15.21M | 10.41% | 10.41% | $2.08T | May 2, 2025 | ▼ 262.7K |
STATE STREET CORP biological products, (no diagnostic substances) | 7.40M | 5.06% | 5.06% | $1.01T | May 15, 2025 | ▼ 1.3K |
WELLINGTON MANAGEMENT GROUP LLP biological products, (no diagnostic substances) | 4.67M | 3.20% | 3.20% | $639.38B | May 13, 2025 | ▼ 258.3K |
GEODE CAPITAL MANAGEMENT, LLC biological products, (no diagnostic substances) | 3.85M | 2.63% | 2.63% | $524.77B | May 13, 2025 | ▲ 151.4K |
T. ROWE PRICE INVESTMENT MANAGEMENT, INC. biological products, (no diagnostic substances) | 2.66M | 1.82% | 1.82% | $364.04B | May 14, 2025 | ▼ 439.5K |
INVESCO LTD. biological products, (no diagnostic substances) | 2.27M | 1.55% | 1.55% | $309.94B | May 12, 2025 | ▲ 136.2K |
NORGES BANK biological products, (no diagnostic substances) | 2.15M | 1.47% | 1.47% | $294.67B | May 11, 2026 | ▼ 171.8K |
MORGAN STANLEY biological products, (no diagnostic substances) | 1.99M | 1.36% | 1.36% | $272.40B | May 15, 2025 | ▲ 208.3K |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q1 2025 vs prior quarter
Q1 2025
30
Increased
+7.53M shares0
New Positions
first time holders19
Decreased
−5.33M shares0
Sold Out
fully exitedNet shares change (top 50)
+2.20M
+7.53M / −5.33M
Net new holders
+11
0 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
BIIB insider trading · insider activity
Source: SEC Form 4
Insiders have been net buyers of shares recently. Selling may be driven by pre-scheduled Rule 10b5-1 plans rather than negative sentiment.
1
Buy transactions
2
Sell transactions
0.50
Buy/Sell ratio
$0M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
Keeney Adam Head of Corporate Development | May 1, 2026 | Tax Withhold | 455 | $187.06 | $85.1K | 6.4K | Form 4 ↗ |
Godbout Sean Chief Accounting Officer | Apr 1, 2026 | Tax Withhold | 54 | $183.78 | $9.9K | 1.3K | Form 4 ↗ |
Murphy Nicole Head of Pharm Ops and Tech | Feb 12, 2026 | Purchase | 3 | $195.03 | $585.105 | 19.6K | Form 4 ↗ |
Viehbacher Christopher President and CEO | Feb 6, 2026 | Tax Withhold | 6,624 | $201.18 | $1.33M | 29.9K | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Biogen Inc. (BIIB) is primarily owned by institutional investors, who hold approximately 88.1% of total shares outstanding. Company insiders own approximately 0.88%, while retail and public investors account for the remaining 11.04%.
The largest institutional shareholder of Biogen Inc. is VANGUARD GROUP INC, holding approximately 17.03 million shares — equal to 11.66% of outstanding shares — as of March 31, 2025.
A total of 930 institutional investors currently hold BIIB stock, with a combined institutional value of approximately $17.78 billion as of the most recent 13F filing period.
Frequently asked questions
BIIB ownershipBiogen Inc. (BIIB) is primarily owned by institutional investors, who hold approximately 88.1% of shares. The largest shareholder is VANGUARD GROUP INC with a 11.66% stake. Company insiders hold 0.88%. Data sourced from SEC Form 13F as of March 31, 2025.