Free · no sign-up · Q2 2026

Which funds own BIIB

Biogen Inc in the Q2 2026 filings. At least 4 of the 91 current managers on file reported a position, worth $5.0bn between them. It is among the largest positions of fewer than a fifth of the current managers on file. Buying and selling roughly cancelled this quarter, which is what a name looks like when the argument is still live.

Managers holding: 4; at least, of 91 current
Combined value: $5.0bn; as reported
Opened: 1; new this quarter
Added to: 3; already held
Trimmed or sold out: 2; 2 sold out entirely

Only each manager’s largest 200 positions are listed here, so a smaller holder may be missing.

Managers reporting a position

Largest first. Weight is the share of that manager’s whole reported book, which is the number worth quoting: $400m is a rounding error in one book and a defining bet in another.

Manager	Value	Weight	Shares	Change on the quarter	Action
Fidelity (FMR LLC) Long-only · $2304bn book	$3.9bn	0.2%	18,217,239	+$1.6bn+5,409,698	Added
Wellington Management Group LLP Long-only · $580bn book	$674m	0.1%	3,117,469	+$131m+155,828	Added
AQR Capital Management LLC Quantitative · $287bn book	$417m	0.1%	1,936,859	+$71m+13,302	Added
Farallon Capital Management LLC Long/short equity · $21.7bn book	$15m	0.1%	71,000	opened71,000	New

Sold out of this quarter

Valued at what the position was worth in the previous filing, because by this one it is gone.

Glenview Capital Management LLC · Long/short equity$11m held before
Schonfeld Strategic Advisors LLC · Multi-strategy$9.0m held before

Ownership through time

At least 12 of the 95 managers whose filings are on file listed BIIB in Q2 2026, against 23 in Q2 2013. 4 managers fewer than in Q1 2026: 2 started positions; 1 listed it again; 2 sold out, by their own filings; 5 no longer listed it among the positions read, which can mean a holding below the listed range or a filing not yet made.

Each manager’s largest 500 positions a quarter are read, so a small holding in a very large book can be missing, and a manager is counted as leaving only where its own filing shows it.

Managers on file listing it

Their combined reported value

Between the quarter ends of Q1 2026 and Q2 2026. Each change in shares is valued at the Q2 2026 price, so the price’s own move is left out; a 13F shows the two quarter ends, not when in between anything was bought or sold.

Started in Q2 2026

Largest increases, by shares

Fidelity (FMR LLC)12,807,541 to 18,217,239 shares+$1.2bn
Wellington Management Group LLP2,961,641 to 3,117,469 shares+$34m
Freestone Grove Partners LPnew: 83,853 shares+$18m
Farallon Capital Management LLCnew: 71,000 shares+$15m
MFS Investment Management720,629 to 744,892 shares+$5.3m

Largest decreases, by shares

Balyasny Asset Management LLC650,046 to 265,090 shares-$83m
Man Group PLC318,745 to 196,222 shares-$26m
Acadian Asset Management LLC248,489 to 129,878 shares-$26m
Hudson Bay Capital Management LP201,367 to 90,000 shares-$24m

Left it

Glenview Capital Management LLCwas $10m
PDT Partners LLCwas $430k

Manager	First listed	Largest	Q2 2026
Fidelity (FMR LLC)	Q2 2013	$9.3bn	$3.9bn
Wellington Management Group LLP	Q2 2013	$2.0bn	$674m
AQR Capital Management LLC	Q2 2013	$1.1bn	$417m
Invesco Ltd	Q2 2013	$1.5bn	$390m
MFS Investment Management	Q2 2013	$658m	$163m
Balyasny Asset Management LLC	Q4 2014	$174m	$57m
Man Group PLC	Q1 2018	$211m	$42m
Acadian Asset Management LLC	Q3 2016	$149m	$28m
Woodline Partners LP	Q1 2021	$40m	$24m
Hudson Bay Capital Management LP	Q3 2016	$58m	$19m
Freestone Grove Partners LP	Q2 2025	$33m	$18m
Farallon Capital Management LLC	Q2 2017	$172m	$15m
T. Rowe Price Associates Inc	Q2 2013	$4.6bn	last listed Q1 2025
Capital Research Global Investors	Q2 2013	$2.6bn	last listed Q4 2014
Renaissance Technologies LLC	Q2 2013	$1.4bn	last listed Q1 2026
Capital World Investors	Q2 2013	$1.2bn	last listed Q1 2024
AllianceBernstein LP	Q2 2013	$1.1bn	last listed Q3 2023
Viking Global Investors LP	Q2 2013	$776m	last listed Q1 2017
Arrowstreet Capital LP	Q2 2017	$718m	last listed Q3 2025
D. E. Shaw & Co.	Q2 2013	$641m	last listed Q2 2025
Point72 Asset Management LP	Q1 2015	$543m	last listed Q1 2026
Janus Henderson Group Ltd	Q2 2013	$487m	last listed Q1 2022

What BIIB is worth

Knowing who owns it is half the question. The other half is what it is worth against the companies it trades beside, which is the one an interviewer will follow up with.

Build the comp set around BIIB →

How much of the picture this is

A Form 13F reports US-listed long equity and nothing else: no shorts, no bonds, no cash and no non-US listings. It arrives forty-five days after the quarter ends, so a manager who sold in July still shows the position in a filing published in August. This page reads the managers on file here rather than every filer in the market, and each manager’s largest positions rather than the whole table, so a small position in a very large book may not appear. Say “their last filing showed” rather than “they own”, and the distinction will do you credit.

What to do with a name the funds are buying

Knowing who owns something is the start of a pitch, not the pitch. The next questions are what it is worth and why they were buying.

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