Who owns BIIB? 13F holders and whale ownership
BIIB is tracked across public portfolios in Whale Analyzer. This page answers who owns BIIB, which top funds are buying BIIB, aggregate disclosed value, and recent position changes based on public data. PRIMECAP Management is the largest reported holder at $2.71B; the top five funds control 100.0% of reported ownership; institutions were net selling last quarter (1 increased, 1 reduced); the stock trades below the aggregate whale cost basis of $245.59. Top tracked holders include PRIMECAP Management and Samuel Isaly.
Continue to the live BIIB dashboardTop holders
| Investor | Reported value | Shares | Change |
|---|---|---|---|
| PRIMECAP Management 13F portfolio PRIMECAP Management Company holdings | $2.71B | 14.8M | Reduced |
| Samuel Isaly 13F portfolio OrbiMed Advisors holdings | $11.3M | 61.6K | New |
Ownership concentration
Reported ownership of BIIB is highly concentrated across tracked institutions.
- Single largest holder: 99.6% of reported ownership
- Top 5 holders: 100.0%
- Top 10 holders: 100.0%
Whale activity this quarter
Across 2 tracked institutions, 1 reduced, 1 increased. Net positioning is net selling.
- PRIMECAP Management — PRIMECAP Management Company ($2.71B) (→ 0.0% qoq shares) · avg cost $245.59
Whale cost basis vs current price
The aggregate tracked cost basis is $245.59 versus a current price of $216.03, so BIIB trades below its cost basis (-12.0%). Average unrealized P&L across tracked holders: -24%.
Sector positioning — Industrials
BIIB sits within the Industrials sector alongside 85 other tracked names. Compare whale ownership across peers:
How to use this page
Values are reported public positions from tracked 13F filers and disclosures — not real-time ownership totals. Open the live BIIB dashboard for price charts and cross-investor scans, or read the SEC 13F guide.
Related stock holder pages
- LLY whale holders — ELI LILLY & CO
- MU whale holders — MICRON TECHNOLOGY INC
- GOOGL whale holders — ALPHABET INC
- AZN whale holders — ASTRAZENECA PLC
- KLAC whale holders — KLA CORP
- INTC whale holders — INTEL CORP
- AMGN whale holders — AMGEN INC
- NVDA whale holders — NVIDIA CORPORATION
Learn more in Whale Analyzer Academy
Deepen your read on BIIB with these Whale Analyzer Academy guides:
Frequently asked questions
Who owns BIIB stock?
Whale Analyzer tracks 2 public institutional holders of BIIB with a combined reported value of $2.72B. See the holder table above for the largest tracked positions.
Which top funds are buying BIIB?
Tracked institutions were net selling last quarter — 1 reduced, 1 increased. Check the "Change" column: "New" = fresh position, "Increased" = added, "Reduced" = trimmed.
How concentrated is BIIB ownership?
The top five tracked holders report 100.0% of aggregate ownership.
Is BIIB above or below the whale cost basis?
The aggregate tracked cost basis is $245.59 versus a current price of $216.03 (-12.0%).
What does 13F ownership mean for BIIB?
Use the interactive BIIB dashboard on Whale Analyzer for real-time holder analysis, or read our 13F Alpha Signals Guide.