Who owns Biogen (BIIB)
Which tracked institutional funds hold BIIB, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See BIIB company fundamentals →
Ownership as of the 2026-Q2 13F filings (latest filed 2026-09-22). 13F is disclosed up to 45 days after quarter-end, so the most recent quarter fills in over the following weeks.
How the tape is positioned
333 tracked funds added or opened BIIB while 124 trimmed or exited it between 2026-Q1 and 2026-Q2 — the tape is split. When large holders disagree on a name, the funds moving first are sometimes ahead of the story.
A prompt to read the filings, not a verdict. 13F is a quarter-end snapshot disclosed up to 45 days late; a fund adds or exits for mandate, benchmark, and timing reasons that have nothing to do with a view on the stock. This is a starting question, not a signal to trade.
Conviction spread
BIIB’s largest tracked holder by dollar value, FMR LLC, sizes it at 0.2% of its own reported 13F book, while the median holder sizes it at 0.1% of theirs — a 0.1pp conviction gap — its largest holder concentrates the name more heavily than the typical one.
Book-share is each fund’s reported value in BIIB divided by its whole reported 13F book, so it is comparable across funds of different sizes and is unaffected by stock splits. A higher share means a fund has committed more of its book to the name — a starting question about conviction, not a verdict or a signal to trade.
Institutional & insider positioning
Between 2026-Q1 and 2026-Q2, across 975 tracked filers holding BIIB, 523 increased or opened the position and 433 reduced or closed it; over the same quarter, there were no open-market insider Form 4s.
This fuses two public signals for the same quarter — how tracked institutions changed their positions and whether insiders bought or sold in the open market. It describes what was filed; it is a starting question, not a verdict or a signal to trade.
New buyers & exits
Funds opening or closing a position in BIIB between the 2026-Q1 and 2026-Q2 13F filings, and the largest changes among funds holding it in both. New buyers and exits are counted on fund presence (split-invariant); adds and trims are measured on reported value.
New buyers 31
- PERCEPTIVE ADVISORS LLC$60M
- ANTIPODES PARTNERS Ltd$19M
- Freestone Grove Partners LP$18M
- FARALLON CAPITAL MANAGEMENT, L.L.C.$15M
- Atle Fund Management AB$14M
- PICTON MAHONEY ASSET MANAGEMENT$10M
Full exits 74
- T. Rowe Price Investment Management, Inc.$213M
- Amundi$145M
- LSV ASSET MANAGEMENT$61M
- ACADIAN ASSET MANAGEMENT LLC$46M
- THOMPSON SIEGEL & WALMSLEY LLC$46M
- KBC Group NV$43M
Largest adds
- FMR LLC$1.6B
- BlackRock, Inc.$1.3B
- PRIMECAP MANAGEMENT CO/CA/$569M
- VANGUARD CAPITAL MANAGEMENT LLC$337M
- STATE STREET CORP$273M
- NORGES BANK$263M
Largest trims
- VAN ECK ASSOCIATES CORP$177M
- Point72 Asset Management, L.P.$129M
- BALYASNY ASSET MANAGEMENT L.P.$62M
- BARCLAYS PLC$48M
- MARSHALL WACE, LLP$39M
- Boston Partners$39M
Institutional holders
One row per tracked fund, most shares held first (every row is from one quarter; reported value breaks ties). “% of value” is the fund’s share of this security’s tracked institutional value — not of shares outstanding.
| Fund | Shares | Reported value | % of value | Quarter |
|---|---|---|---|---|
| FMR LLC added | 18,217,239 | $3.9B | 14.2% | 2026-Q2 |
| BlackRock, Inc. added | 15,985,736 | $3.5B | 12.5% | 2026-Q2 |
| PRIMECAP MANAGEMENT CO/CA/ added | 15,154,606 | $3.3B | 11.8% | 2026-Q2 |
| VANGUARD CAPITAL MANAGEMENT LLC added | 9,651,117 | $2.1B | 7.5% | 2026-Q2 |
| STATE STREET CORP added | 7,344,327 | $1.6B | 5.7% | 2026-Q2 |
| VANGUARD PORTFOLIO MANAGEMENT LLC added | 6,604,936 | $1.4B | 5.2% | 2026-Q2 |
| GEODE CAPITAL MANAGEMENT, LLC added | 4,449,295 | $958M | 3.5% | 2026-Q2 |
| WELLINGTON MANAGEMENT GROUP LLP added | 3,117,469 | $674M | 2.4% | 2026-Q2 |
| NORGES BANK added | 2,580,033 | $557M | 2.0% | 2026-Q2 |
| MORGAN STANLEY added | 2,411,271 | $521M | 1.9% | 2026-Q2 |
| AQR CAPITAL MANAGEMENT LLC added | 1,936,859 | $417M | 1.5% | 2026-Q2 |
| JPMORGAN CHASE & CO trimmed | 1,823,140 | $395M | 1.4% | 2026-Q2 |
| Invesco Ltd. added | 1,803,944 | $390M | 1.4% | 2026-Q2 |
| Legal & General Group Plc added | 1,493,289 | $323M | 1.2% | 2026-Q2 |
| NORTHERN TRUST CORP trimmed | 1,429,490 | $309M | 1.1% | 2026-Q2 |
| Boston Partners trimmed | 1,263,429 | $273M | 1.0% | 2026-Q2 |
| UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC trimmed | 1,255,168 | $271M | 1.0% | 2026-Q2 |
| GOLDMAN SACHS GROUP INC added | 1,230,390 | $266M | 1.0% | 2026-Q2 |
| DIMENSIONAL FUND ADVISORS LP added | 1,148,568 | $248M | 0.9% | 2026-Q2 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC trimmed | 1,117,663 | $241M | 0.9% | 2026-Q2 |
| BANK OF AMERICA CORP /DE/ trimmed | 1,116,228 | $241M | 0.9% | 2026-Q2 |
| UBS Group AG added | 1,030,150 | $223M | 0.8% | 2026-Q2 |
| Alyeska Investment Group, L.P. added | 932,374 | $201M | 0.7% | 2026-Q2 |
| DEUTSCHE BANK AG\ trimmed | 894,035 | $193M | 0.7% | 2026-Q2 |
| Pictet Asset Management Holding SA trimmed | 851,819 | $184M | 0.7% | 2026-Q2 |
| VANGUARD FIDUCIARY TRUST CO added | 829,318 | $179M | 0.6% | 2026-Q2 |
| Robeco Institutional Asset Management B.V. added | 791,092 | $171M | 0.6% | 2026-Q2 |
| FRED ALGER MANAGEMENT, LLC added | 788,307 | $170M | 0.6% | 2026-Q2 |
| PRICE T ROWE ASSOCIATES INC /MD/ added | 774,283 | $167M | 0.6% | 2026-Q2 |
| Bank of New York Mellon Corp trimmed | 773,619 | $167M | 0.6% | 2026-Q2 |
| MASSACHUSETTS FINANCIAL SERVICES CO /MA/ added | 744,892 | $163M | 0.6% | 2026-Q2 |
| CITIGROUP INC added | 734,517 | $159M | 0.6% | 2026-Q2 |
| ROYAL BANK OF CANADA added | 708,562 | $153M | 0.6% | 2026-Q2 |
| Employees Provident Fund Board | 704,196 | $152M | 0.6% | 2026-Q2 |
| FIRST TRUST ADVISORS LP added | 682,021 | $147M | 0.5% | 2026-Q2 |
| AustralianSuper Pty Ltd added | 672,723 | $145M | 0.5% | 2026-Q2 |
| Artemis Investment Management LLP trimmed | 570,974 | $123M | 0.4% | 2026-Q2 |
| Zurcher Kantonalbank (Zurich Cantonalbank) added | 540,001 | $117M | 0.4% | 2026-Q2 |
| HSBC HOLDINGS PLC added | 527,866 | $114M | 0.4% | 2026-Q2 |
| Caisse de depot et placement du Quebec trimmed | 510,194 | $110M | 0.4% | 2026-Q2 |
| CITADEL ADVISORS LLC added | 418,356 | $90M | 0.3% | 2026-Q2 |
| Swiss National Bank trimmed | 413,900 | $89M | 0.3% | 2026-Q2 |
| National Pension Service added | 406,064 | $88M | 0.3% | 2026-Q2 |
| BNP PARIBAS FINANCIAL MARKETS trimmed | 387,542 | $84M | 0.3% | 2026-Q2 |
| Candriam S.C.A. added | 384,326 | $83M | 0.3% | 2026-Q2 |
| Mitsubishi UFJ Asset Management Co., Ltd. added | 358,823 | $78M | 0.3% | 2026-Q2 |
| Sumitomo Mitsui Trust Group, Inc. trimmed | 346,617 | $75M | 0.3% | 2026-Q2 |
| VICTORY CAPITAL MANAGEMENT INC added | 343,419 | $74M | 0.3% | 2026-Q2 |
| FIL Ltd added | 342,623 | $74M | 0.3% | 2026-Q2 |
| Fisher Asset Management, LLC added | 338,018 | $73M | 0.3% | 2026-Q2 |
| Vanguard Global Advisers, LLC trimmed | 335,936 | $73M | 0.3% | 2026-Q2 |
| California Public Employees Retirement System trimmed | 329,106 | $71M | 0.3% | 2026-Q2 |
| Swedbank AB added | 320,622 | $69M | 0.3% | 2026-Q2 |
| Nuveen, LLC trimmed | 317,204 | $69M | 0.2% | 2026-Q2 |
| VANGUARD ASSET MANAGEMENT, Ltd added | 284,376 | $61M | 0.2% | 2026-Q2 |
| Patient Capital Management, LLC trimmed | 283,697 | $61M | 0.2% | 2026-Q2 |
| Gotham Asset Management, LLC trimmed | 279,900 | $60M | 0.2% | 2026-Q2 |
| CAUSEWAY CAPITAL MANAGEMENT LLC trimmed | 278,283 | $60M | 0.2% | 2026-Q2 |
| PERCEPTIVE ADVISORS LLC added | 276,173 | $60M | 0.2% | 2026-Q2 |
| BALYASNY ASSET MANAGEMENT L.P. trimmed | 265,090 | $57M | 0.2% | 2026-Q2 |
| RHUMBLINE ADVISERS trimmed | 262,979 | $57M | 0.2% | 2026-Q2 |
| BARCLAYS PLC trimmed | 247,157 | $53M | 0.2% | 2026-Q2 |
| VOYA INVESTMENT MANAGEMENT LLC added | 246,782 | $53M | 0.2% | 2026-Q2 |
| AEGON ASSET MANAGEMENT UK Plc trimmed | 241,101 | $52M | 0.2% | 2026-Q2 |
| BNP PARIBAS ASSET MANAGEMENT Holding S.A. added | 234,138 | $51M | 0.2% | 2026-Q2 |
| CALIFORNIA STATE TEACHERS RETIREMENT SYSTEM trimmed | 220,009 | $48M | 0.2% | 2026-Q2 |
| ALLIANCEBERNSTEIN L.P. added | 214,975 | $39M | 0.1% | 2026-Q2 |
| KLP KAPITALFORVALTNING AS | 199,177 | $43M | 0.2% | 2026-Q2 |
| Man Group plc trimmed | 196,222 | $42M | 0.2% | 2026-Q2 |
| PANAGORA ASSET MANAGEMENT INC added | 186,929 | $40M | 0.1% | 2026-Q2 |
| NISSAY ASSET MANAGEMENT CORP /JAPAN added | 185,301 | $40M | 0.1% | 2026-Q2 |
| PRINCIPAL FINANCIAL GROUP INC trimmed | 184,450 | $40M | 0.1% | 2026-Q2 |
| Allianz Asset Management GmbH trimmed | 178,012 | $33M | 0.1% | 2026-Q2 |
| JUPITER ASSET MANAGEMENT LTD added | 160,057 | $35M | 0.1% | 2026-Q2 |
| Quantinno Capital Management LP added | 151,977 | $33M | 0.1% | 2026-Q2 |
| LETKO, BROSSEAU & ASSOCIATES INC trimmed | 146,562 | $32M | 0.1% | 2026-Q2 |
| Portolan Capital Management, LLC added | 142,856 | $31M | 0.1% | 2026-Q2 |
| Palo Alto Investors LP trimmed | 140,279 | $30M | 0.1% | 2026-Q2 |
| Walleye Trading LLC added | 139,253 | $30M | 0.1% | 2026-Q2 |
| Creative Planning added | 138,613 | $30M | 0.1% | 2026-Q2 |
| O'SHAUGHNESSY ASSET MANAGEMENT, LLC trimmed | 138,260 | $30M | 0.1% | 2026-Q2 |
| FRANKLIN RESOURCES INC trimmed | 137,436 | $30M | 0.1% | 2026-Q2 |
| Nippon Life Global Investors Americas, Inc. added | 137,220 | $30M | 0.1% | 2026-Q2 |
| Russell Investments Group, Ltd. trimmed | 133,894 | $29M | 0.1% | 2026-Q2 |
| IEQ CAPITAL, LLC trimmed | 132,142 | $29M | 0.1% | 2026-Q2 |
| ADAGE CAPITAL PARTNERS GP, L.L.C. trimmed | 129,599 | $28M | 0.1% | 2026-Q2 |
| WELLS FARGO & COMPANY/MN added | 128,664 | $28M | 0.1% | 2026-Q2 |
| Aberdeen Group plc trimmed | 128,227 | $28M | 0.1% | 2026-Q2 |
| BANK OF MONTREAL /CAN/ added | 124,267 | $27M | 0.1% | 2026-Q2 |
| STATE BOARD OF ADMINISTRATION OF FLORIDA RETIREMENT SYSTEM trimmed | 121,311 | $26M | 0.1% | 2026-Q2 |
| AMERICAN CENTURY COMPANIES INC added | 114,152 | $25M | 0.1% | 2026-Q2 |
| Woodline Partners LP added | 112,463 | $24M | 0.1% | 2026-Q2 |
| RAYMOND JAMES FINANCIAL INC added | 108,174 | $23M | 0.1% | 2026-Q2 |
| AVIVA PLC added | 108,052 | $23M | 0.1% | 2026-Q2 |
| NATIONAL BANK OF CANADA /FI/ added | 107,416 | $23M | 0.1% | 2026-Q2 |
| Eurizon Capital SGR S.p.A. trimmed | 102,594 | $22M | 0.1% | 2026-Q2 |
| ADAMS DIVERSIFIED EQUITY FUND, INC. | 100,300 | $22M | 0.1% | 2026-Q2 |
| NEW YORK STATE COMMON RETIREMENT FUND added | 100,145 | $22M | 0.1% | 2026-Q2 |
| Integral Health Asset Management, LLC added | 100,000 | $22M | 0.1% | 2026-Q2 |
| Illinois Municipal Retirement Fund added | 99,303 | $21M | 0.1% | 2026-Q2 |
Ownership over time
Tracked institutional holder count and total shares held by filing quarter (independent scales). The curated-era tail and any mid-ingest latest quarter are handled honestly — a partial quarter is not drawn as a collapse.
Reading this table
Funds hold the same stock for different reasons — an index fund “holds” almost everything, an active manager sizes a name to a mandate and a benchmark, and each fund entered at its own price and time. Because 13F is filed up to 45 days after quarter-end, every row is a backward-looking snapshot; a manager may have traded since. Share-class siblings (a company’s A and C shares) are rolled up to one line so a dual-class name is never double-counted. Compare like-for-like. A large holder is not an endorsement, and a fund exiting is not a warning — this is a starting question, not a verdict.
About 13F filings
A Form 13F is a quarterly disclosure that institutional investment managers with over $100 million in US-listed equities must file with the SEC. In plain English: it is a snapshot of the long stock positions a fund held at the end of a quarter. It covers long US-listed equities only — not short positions, options, cash, or private holdings — and the funds shown are the large sample we track, not the complete 13F universe.