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BIIB in the 13F filings

Biogen Inc · CUSIP 09062X103

Sector · Pharmaceuticals and biotechnologyTheme · Biological productsTheme · Healthcare: biopharma and medtech· L3VLUP-defined
Quarter
Q3 2026 · early filersQ2 2026Q1 2026Q4 2025Q3 2025Q2 2025Q1 2025Q4 2024Q3 2024Q2 2024Q1 2024Q4 2023
Quarter end
31 Dec 2025
the date the book describes
Filed
27 Oct 2026
latest of these filings; the earliest 22 Jan 2026
Managers listing it
35
at least, of 95 tracked, among listed positions
Comparable managers
92
filed both Q3 2025 and Q4 2025; 19 listed it in both
Shares listed
25,984,605
combined, among listed positions
Reported value
$4.6bn
combined, at the quarter end

Among the 92 comparable managers: 12 buyers (opened or added shares) and 25 sellers (trimmed or exited), at least, among listed positions. Their net change in shares was +2,164,585.

Managers listing BIIB in Q4 2025

Share of 13F value is the position’s reported value over everything the manager reported that quarter. The share change is against Q3 2025, and only where both filings list the position. A rise in value with no rise in shares is the price, not buying.

35 of 35 holders

ActionFiling
Fidelity (FMR LLC)9,425,863$1.7bn0.08%Added+8,138,10317 Feb 2026 (the filing on sec.gov)
Wellington Management Group LLP3,551,269$625m0.11%Trimmed-695,23517 Feb 2026 (the filing on sec.gov)
Point72 Asset Management LP2,813,192$495m0.55%Trimmed-1,059,70917 Feb 2026 (the filing on sec.gov)
Invesco Ltd1,655,441$291munder 0.1%Trimmed-762,68619 Feb 2026 (the filing on sec.gov)
AQR Capital Management LLC1,528,616$269m0.14%Trimmed-254,96517 Feb 2026 (the filing on sec.gov)
Millennium Management LLC1,125,586$198m0.08%Added+14,39617 Feb 2026 (the filing on sec.gov)
T. Rowe Price Associates Inc792,071$139munder 0.1%Trimmed-173,38617 Feb 2026 (the filing on sec.gov)
MFS Investment Management712,559$125munder 0.1%Trimmed-16,75722 Jan 2026 (the filing on sec.gov)
Susquehanna International Group LLP661,684$116munder 0.1%Added+220,60217 Feb 2026 (the filing on sec.gov)
Balyasny Asset Management LLC607,953$107m0.14%Trimmed-626,19617 Feb 2026 (the filing on sec.gov)
Renaissance Technologies LLC399,196$70m0.11%Trimmed-565,21012 Feb 2026 (the filing on sec.gov)
Marshall Wace LLP385,928$68m0.06%Trimmed-501,73313 Feb 2026 (the filing on sec.gov)
Man Group PLC339,284$60m0.10%Trimmed-578,74117 Feb 2026 (the filing on sec.gov)
Glenview Capital Management LLC290,605$51m1.04%Newnew17 Feb 2026 (the filing on sec.gov)
Two Sigma Investments LP251,763$44m0.06%Added+46,53017 Feb 2026 (the filing on sec.gov)
Hudson Bay Capital Management LP221,860$39m0.13%Trimmed-31,29113 Feb 2026 (the filing on sec.gov)
Freestone Grove Partners LP187,608$33m0.24%Trimmed-31,25817 Feb 2026 (the filing on sec.gov)
Acadian Asset Management LLC187,457$33m0.05%Trimmed-7,79410 Feb 2026 (the filing on sec.gov)
AllianceBernstein LP183,744$32munder 0.1%Trimmed-53,53117 Feb 2026 (the filing on sec.gov)
Squarepoint Ops LLC146,408$26munder 0.1%Added+138,78013 Feb 2026 (the filing on sec.gov)
Schonfeld Strategic Advisors LLC107,068$19m0.08%Trimmed-213,08617 Feb 2026 (the filing on sec.gov)
Woodline Partners LP102,318$18m0.07%Added+5,65217 Feb 2026 (the filing on sec.gov)
Brevan Howard Capital Management LP71,017$12m0.14%Added+37,50617 Feb 2026 (the filing on sec.gov)
D. E. Shaw & Co.53,754$9.5munder 0.1%Trimmed-424,17017 Feb 2026 (the filing on sec.gov)
Arrowstreet Capital LP45,349$8.0munder 0.1%Trimmed-335,44213 Feb 2026 (the filing on sec.gov)
Page 1 of 2

Largest increases and reductions, by shares

Q3 2025 to Q4 2025, among managers that listed it in both quarters or opened it.

Increases

Reductions

New positions and exits

At least these many: a manager is shown exiting only where its own filing shows the position gone.

New (2)

Exited (3)

Ownership over time

Every quarter on file. A quarter-end value moves with the price as well as with the shares held; buyers and sellers count comparable managers, by shares.
17 in Q3 2024 to 12 in Q2 2026

Tracked managers listing it, at least.

0102030402014201620182020202220242026
the quarter shown share split complete books; unmarked quarters rest on listed positionsClick a quarter to open it.
BIIB by quarter
QuarterHoldersReported valueBuyersSellers
Q2 201323$12.7bnn.a.n.a.
Q3 201320$14.3bnn.a.n.a.
Q4 201320$16.1bnn.a.n.a.
Q1 201421$16.8bnn.a.n.a.
Q2 201418$16.8bnn.a.n.a.
Q3 201423$16.4bnn.a.n.a.
Q4 201422$15.7bnn.a.n.a.
Q1 201524$20.3bnn.a.n.a.
Q2 201524$20.5bnn.a.n.a.
Q3 201524$12.4bnn.a.n.a.
Q4 201527$11.9bnn.a.n.a.
Q1 201627$10.3bnn.a.n.a.
Q2 201624$9.5bnn.a.n.a.
Q3 201629$11.6bnn.a.n.a.
Q4 201631$10.9bnn.a.n.a.
Q1 201725$9.2bnn.a.n.a.
Q2 201728$9.8bnn.a.n.a.
Q3 201724$11.6bnn.a.n.a.
Q4 201722$11.8bnn.a.n.a.
Q1 201828$9.6bnn.a.n.a.
Q2 201825$8.9bnn.a.n.a.
Q3 201828$10.6bnn.a.n.a.
Q4 201828$9.0bnn.a.n.a.
Q1 201922$7.4bnn.a.n.a.
Q2 201928$7.2bnn.a.n.a.
Q3 201928$7.1bnn.a.n.a.
Q4 201927$7.7bnn.a.n.a.
Q1 202025$7.3bnn.a.n.a.
Q2 202029$5.1bnn.a.n.a.
Q3 202025$5.1bnn.a.n.a.
Q4 202022$4.6bnn.a.n.a.
Q1 202118$4.7bnn.a.n.a.
Q2 202125$5.4bnn.a.n.a.
Q3 202123$3.3bnn.a.n.a.
Q4 202125$3.7bnn.a.n.a.
Q1 202229$3.7bnn.a.n.a.
Q2 202225$3.4bnn.a.n.a.
Q3 202233$5.2bnn.a.n.a.
Q4 202228$5.0bnn.a.n.a.
Q1 202330$5.1bnn.a.n.a.
Q2 202323$4.4bnn.a.n.a.
Q3 202321$2.9bnn.a.n.a.
Q4 202317$2.8bn118
Q1 202416$2.5bn910
Q2 202414$2.5bn68
Q3 202417$2.6bn152
Q4 202420$2.6bn164
Q1 202522$2.4bn1510
Q2 202520$2.5bn155
Q3 202521$2.8bn138
Q4 202520$3.9bn1225
Q1 202616$3.9bn1322
Q2 202612$5.8bn1617

Compare with…

Holders over time, buyers and sellers, and the managers holding both, side by side for up to four stocks.

BIIB and GILD →BIIB and AMGN →BIIB and ARGX →Choose a stock to compare with BIIB →

How much of the picture this is

A 13F is a manager’s long US-listed equity book at a quarter end, filed up to 45 days later. It shows no shorts, cash, bonds or performance, and it is never today’s portfolio. Large books are listed to their largest positions, so a manager missing from this table may still hold a small position below that line. These are 95 tracked managers, not the institutional market.

Which funds own BIIB, latest filings →Back to the 13F Explorer →