BIOGEN INC (BIIB) Stock Institutional Trading Activity
BIOGEN INC (BIIB) position changes reported by tracked institutional filers across multiple SEC 13F reporting periods. Based on recent SEC 13F filings (Q4 2025), investors with some of the largest reported share count changes include Renaissance Technologies LLC, Causeway Capital Management, Sequoia Financial Advisors, Hillman Value Fund, and Parnassus Endeavor Fund. Explore insights into buying and selling patterns, position changes, and investment conviction levels to understand institutional trading behavior and market dynamics.
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| Portfolio quarter | Name | Type | Quantity | Remaining | Reported stock balance |
|---|---|---|---|---|---|
| Q4 2019 | Hancock Classic Value | Buy | 46,477 | 49,670 | $14,739 |
| Q4 2019 | Berkshire Hathaway | Buy | 648,447 | 648,447 | $192,414 |
| Q4 2019 | Renaissance Technologies LLC | Buy | 348,700 | 4,569,906 | $1,356,028 |
| Q3 2019 | Parnassus Endeavor Fund | Sell | -350,584 | 574,416 | $133,736 |
| Q3 2019 | Hancock Classic Value | Buy | 875 | 3,193 | $743 |
| Q3 2019 | Muhlenkamp & Co | Sell | -6 | 17,774 | $4,138 |
| Q3 2019 | Renaissance Technologies LLC | Buy | 1,738,129 | 4,221,206 | $982,781 |
| Q2 2019 | Parnassus Endeavor Fund | Buy | 295,000 | 925,000 | $216,330 |
| Q2 2019 | Hancock Classic Value | Sell | -133 | 2,318 | $542 |
| Q2 2019 | Muhlenkamp & Co | Sell | -63 | 17,780 | $4,158 |
| Q2 2019 | Renaissance Technologies LLC | Buy | 851,263 | 2,483,077 | $580,717 |
| Q1 2019 | Muhlenkamp & Co | Sell | -525 | 17,843 | $4,218 |
| Q1 2019 | Parnassus Endeavor Fund | Buy | 280,000 | 630,000 | $148,919 |
| Q1 2019 | Hancock Classic Value | Buy | 345 | 2,451 | $579 |
| Q1 2019 | Renaissance Technologies LLC | Buy | 617,100 | 1,631,814 | $385,728 |
| Q4 2018 | Parnassus Endeavor Fund | Buy | 295,000 | 350,000 | $105,322 |
| Q4 2018 | Hancock Classic Value | Buy | 242 | 2,106 | $634 |
| Q4 2018 | Scion Asset Management | Buy | 10,000 | 10,000 | $3,009 |
| Q4 2018 | Renaissance Technologies LLC | Buy | 168,639 | 1,014,714 | $305,348 |
| Q3 2018 | Muhlenkamp & Co | Sell | -6,803 | 18,368 | $6,490 |
| Q3 2018 | ARK Invest | Buy | 8,448 | 22,498 | $7,949 |
| Q3 2018 | Hancock Classic Value | Buy | 74 | 1,864 | $659 |
| Q3 2018 | Renaissance Technologies LLC | Buy | 218,414 | 846,075 | $298,927 |
| Q2 2018 | Parnassus Endeavor Fund | Buy | 55,000 | 55,000 | $15,963 |
| Q2 2018 | Hancock Classic Value | Buy | 43 | 1,790 | $520 |
| Q2 2018 | ARK Invest | Sell | -30 | 14,050 | $4,078 |
| Q1 2018 | Muhlenkamp & Co | Buy | 489 | 25,171 | $6,892 |
| Q1 2018 | Hancock Classic Value | Buy | 816 | 1,747 | $478 |
| Q1 2018 | ARK Invest | Buy | 7,501 | 14,080 | $3,855 |
| Q1 2018 | Renaissance Technologies LLC | Buy | 507,500 | 627,661 | $171,866 |
Frequently asked questions about BIIB activity
Which institutional owners are buying BIIB?
Institutional owners buying BIIB include investors who have either initiated new positions or increased their existing holdings based on recent SEC 13F filings. The activity table above highlights which funds added shares in the latest reporting periods and how their positions changed over time.
What does "buy" mean in BIIB activity?
"Buy" means an investor increased their reported position in BIIB compared to the prior reporting period. This reflects growing exposure to BIOGEN INC (BIIB) rather than necessarily a brand-new position (though new positions also appear as buys when prior quantity was zero).
Is institutional interest in BIIB increasing?
Institutional interest in BIIB can be assessed by comparing the number of tracked funds adding or increasing positions versus those trimming or exiting across the periods shown. A higher number of additions typically signals increasing participation among large filers, but it should be read alongside position sizes and the full table.