Boundless Bio, Inc.: which funds bought and sold

Institutions that bought and sold Boundless Bio shares in Q2 2026, from the holdings they reported to the SEC on Form 13F for March 31, 2026 and June 30, 2026.

Between March 31, 2026 and June 30, 2026, 23 institutions that filed 13F reports for both quarters added to or opened positions in Boundless Bio, and 17 cut or closed them. Together they added a net 6.8M shares, +80.3% on what they held at the start of the quarter. Active managers and hedge funds on our list were net buyers of 4.8M shares (+87.3%); index fund managers were net buyers of 60K shares (+6.8%). 13 opened a new position and 8 sold out entirely.

Bought, Q2 2026 23 institutions, 13 of them new holders Sold, Q2 2026 17 institutions, 8 of them sold out

Net change, all compared +6.8M shares (+80.3%)

Net change, active managers +4.8M shares (+87.3%), 8 bought, 4 sold

Buyers versus sellers

institutions compared, 48

23 bought 8 17 sold

Active managers and hedge funds 8 bought · 4 sold · +4.8M

Index fund managers 3 bought · 1 sold · +60K

Other institutions 12 bought · 12 sold · +1.9M

Biggest buyers

by change in shares held

Biggest buyers
Institution	Change in shares	Shares June 30, 2026	Value
Arch Venture Management, LLC	+2.7M New position	2.7M	$6.7M
Tang Capital Management LLC Hedge fund	+2.6M New position	2.6M	$6.4M
ADAR1 Capital Management, LLC Hedge fund	+2.0M New position	2.0M	$4.9M
Cormorant Asset Management, LP Hedge fund	+1.0M New position	1.0M	$2.5M
Millennium Management LLC Hedge fund	+379K +379.2%	479K	$1.2M
Affinity Asset Advisors, LLC	+250K New position	250K	$625,000
Acadian Asset Management LLC Active manager	+134K +1063.8%	147K	$365,000
HRT Financial LP	+116K New position	116K	$290,000
Prelude Capital Management, LLC	+84K New position	84K	$209,995
Bridgeway Capital Management, LLC Active manager	+78K +153.5%	128K	$320,000
Rangeley Capital, LLC	+74K New position	74K	$185,000
Renaissance Technologies LLC Hedge fund	+73K +18.2%	472K	$1.2M
Jane Street Group, LLC	+64K New position	64K	$160,807
Superstring Capital Management LP	+55K New position	55K	$138,390
Northern Trust Corp Index funds	+35K New position	35K	$87,060
Blackrock, Inc. Index funds	+18K +25.2%	88K	$221,239
Vanguard Capital Management LLC Index funds	+18K +3.0%	615K	$1.5M
China Universal Asset Management Co., Ltd.	+17K New position	17K	$42,250
Caitong International Asset Management Co., Ltd	+10K +348000.0%	10K	$26,108
Qube Research & Technologies Ltd Hedge fund	+2,715 +15.5%	20K	$50,518

Biggest buyers, active managers and hedge funds
Institution	Change in shares	Shares June 30, 2026	Value
Tang Capital Management LLC Hedge fund	+2.6M New position	2.6M	$6.4M
ADAR1 Capital Management, LLC Hedge fund	+2.0M New position	2.0M	$4.9M
Cormorant Asset Management, LP Hedge fund	+1.0M New position	1.0M	$2.5M
Millennium Management LLC Hedge fund	+379K +379.2%	479K	$1.2M
Acadian Asset Management LLC Active manager	+134K +1063.8%	147K	$365,000
Bridgeway Capital Management, LLC Active manager	+78K +153.5%	128K	$320,000
Renaissance Technologies LLC Hedge fund	+73K +18.2%	472K	$1.2M
Qube Research & Technologies Ltd Hedge fund	+2,715 +15.5%	20K	$50,518

Biggest sellers

by change in shares held

Biggest sellers
Institution	Change in shares	Shares June 30, 2026	Value
Citadel Advisors LLC Hedge fund	−1.2M −89.2%	145K	$362,623
Sectoral Asset Management Inc	−679K Sold out	0	—
Stonepine Capital Management, LLC	−443K −74.1%	155K	$386,488
Sio Capital Management, LLC	−164K Sold out	0	—
FMR LLC Active manager	−114K −4.2%	2.6M	$6.5M
Landscape Capital Management, L.L.C.	−86K Sold out	0	—
Walleye Capital LLC Hedge fund	−40K Sold out	0	—
Ensign Peak Advisors, Inc	−28K −14.8%	160K	$399,588
Gsa Capital Partners LLP	−24K −25.3%	72K	$181,000
Squarepoint Ops LLC Hedge fund	−16K Sold out	0	—
Geode Capital Management, LLC Index funds	−11K −8.5%	117K	$291,839
Citigroup Inc	−8,837 Sold out	0	—
Tower Research Capital LLC (TRC)	−2,023 −85.3%	348	$870
Xtx Topco Ltd	−1,310 −3.8%	33K	$83,403
Vanguard Global Advisers, LLC	−429 Sold out	0	—
Optiver Holding B.V.	−168 Sold out	0	—
BNP Paribas Financial Markets	−2 −1.1%	176	$440

Biggest sellers, active managers and hedge funds
Institution	Change in shares	Shares June 30, 2026	Value
Citadel Advisors LLC Hedge fund	−1.2M −89.2%	145K	$362,623
FMR LLC Active manager	−114K −4.2%	2.6M	$6.5M
Walleye Capital LLC Hedge fund	−40K Sold out	0	—
Squarepoint Ops LLC Hedge fund	−16K Sold out	0	—

New positions

largest by value

Institution	Shares	Value June 30, 2026
Arch Venture Management, LLC	2.7M	$6.7M
Tang Capital Management LLCHedge fund	2.6M	$6.4M
ADAR1 Capital Management, LLCHedge fund	2.0M	$4.9M
Cormorant Asset Management, LPHedge fund	1.0M	$2.5M
Affinity Asset Advisors, LLC	250K	$625,000
HRT Financial LP	116K	$290,000
Prelude Capital Management, LLC	84K	$209,995
Rangeley Capital, LLC	74K	$185,000
Jane Street Group, LLC	64K	$160,807
Superstring Capital Management LP	55K	$138,390

Sold out

largest by value

Institution	Shares	Value March 31, 2026
Sectoral Asset Management Inc	679K	$746,431
Sio Capital Management, LLC	164K	$180,047
Landscape Capital Management, L.L.C.	86K	$94,370
Walleye Capital LLCHedge fund	40K	$43,586
Squarepoint Ops LLCHedge fund	16K	$18,011
Citigroup Inc	8,837	$9,721
Vanguard Global Advisers, LLC	429	$472
Optiver Holding B.V.	168	$185

Who holds the shares

13F holdings at June 30, 2026

Institutions reporting: 40
Ten largest holders: 86.4%
Index fund managers: 6.1%
Active managers and hedge funds: 67.7%

Buying and selling by type of institution, March 31, 2026 to June 30, 2026
Type	Bought	Sold	New	Sold out	Net change in shares	Net %
Active managers and hedge funds	8	4	3	2	+4.8M	+87.3%
Index fund managers	3	1	1	0	+60K	+6.8%
Other institutions	12	12	9	6	+1.9M	+92.8%

Active managers and hedge funds: a list we maintain of about 400 well-known stock-picking firms and hedge funds, matched by SEC registration number (CIK) and checked against the filer names each quarter. Index fund managers: the large index houses, such as BlackRock, Vanguard, State Street, Geode and Northern Trust. Every other filer (banks, brokers, wealth managers, pension funds, insurers and firms not on the list) counts as another institution. A firm that files under several SEC registrations appears once for each.

What these filings can and cannot tell you

Form 13F lists the long positions in US-listed shares held by investment managers with more than $100 million in such holdings. Managers file it up to 45 days after each quarter ends, so this page shows what funds held at the end of each quarter, not what they are doing now: a position may have changed since. Short positions, most derivatives and smaller managers are not included, and a cut can mean a fund lost clients or rebalanced rather than a view on Boundless Bio.

Only managers that filed a holdings report for both quarters are compared (48 here). 1 other holder is left out: first-time or late filers, firms that changed their SEC registration, and filings that withheld positions under confidential treatment, any of which would otherwise look like a new position or a sale. Figures are as reported by each manager in the SEC's quarterly 13F data sets; option positions are excluded.

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