MBX Biosciences, Inc.: which funds bought and sold

Institutions that bought and sold MBX Biosciences 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, 98 institutions that filed 13F reports for both quarters added to or opened positions in MBX Biosciences, and 68 cut or closed them. Together they added a net 2.4M shares, +4.6% on what they held at the start of the quarter. Active managers and hedge funds on our list were net sellers of 104K shares (−0.5%); index fund managers were net buyers of 716K shares (+10.5%). 35 opened a new position and 20 sold out entirely.

Bought, Q2 2026 98 institutions, 35 of them new holders Sold, Q2 2026 68 institutions, 20 of them sold out

Net change, all compared +2.4M shares (+4.6%)

Net change, active managers −104K shares (−0.5%), 16 bought, 25 sold

Buyers versus sellers

institutions compared, 187

98 bought 21 68 sold

Active managers and hedge funds 16 bought · 25 sold · −104K

Index fund managers 10 bought · 1 sold · +716K

Other institutions 72 bought · 42 sold · +1.8M

Biggest buyers

by change in shares held

Biggest buyers
Institution	Change in shares	Shares June 30, 2026	Value
Paradigm Biocapital Advisors LP	+2.5M New position	2.5M	$138M
FMR LLC Active manager	+2.4M +81.3%	5.3M	$294M
Wellington Management Group LLP Active manager	+1.8M +55.9%	5.0M	$275M
Blackrock, Inc. Index funds	+382K +13.0%	3.3M	$183M
Marshall Wace, LLP Hedge fund	+339K +540.9%	402K	$22.2M
Soleus Capital Management, L.P. Hedge fund	+336K +188.0%	515K	$28.4M
Bank Of America Corp	+270K +939.7%	299K	$16.5M
Franklin Resources Inc Active manager	+253K New position	253K	$13.9M
Morgan Stanley	+217K +687.5%	249K	$13.7M
Dimensional Fund Advisors LP	+187K +399.9%	234K	$12.9M
Schonfeld Strategic Advisors LLC Hedge fund	+125K +100.8%	249K	$13.7M
Geode Capital Management, LLC Index funds	+103K +15.3%	773K	$42.7M
Prudential Financial Inc	+88K New position	88K	$4.9M
State Street Corp Index funds	+77K +9.8%	864K	$47.7M
Barclays PLC	+76K +642.1%	88K	$4.8M
Moore Capital Management, LP Hedge fund	+65K New position	65K	$3.6M
Rhenman & Partners Asset Management AB	+62K New position	62K	$3.4M
Tetragon Partners Gp Ltd	+58K +39.9%	204K	$11.2M
Vanguard Portfolio Management LLC Index funds	+53K +18.2%	347K	$19.1M
Ensign Peak Advisors, Inc	+42K New position	42K	$2.3M

Biggest buyers, active managers and hedge funds
Institution	Change in shares	Shares June 30, 2026	Value
FMR LLC Active manager	+2.4M +81.3%	5.3M	$294M
Wellington Management Group LLP Active manager	+1.8M +55.9%	5.0M	$275M
Marshall Wace, LLP Hedge fund	+339K +540.9%	402K	$22.2M
Soleus Capital Management, L.P. Hedge fund	+336K +188.0%	515K	$28.4M
Franklin Resources Inc Active manager	+253K New position	253K	$13.9M
Schonfeld Strategic Advisors LLC Hedge fund	+125K +100.8%	249K	$13.7M
Moore Capital Management, LP Hedge fund	+65K New position	65K	$3.6M
Driehaus Capital Management LLC Active manager	+38K +3.8%	1.1M	$58.3M
American Century Companies Inc Active manager	+14K +159.9%	23K	$1.3M
Rock Springs Capital Management LP Hedge fund	+10K +3.6%	298K	$16.5M

Biggest sellers

by change in shares held

Biggest sellers
Institution	Change in shares	Shares June 30, 2026	Value
Deep Track Capital, LP Hedge fund	−1.0M −37.2%	1.7M	$95.6M
Stempoint Capital LP	−999K Sold out	0	—
Citadel Advisors LLC Hedge fund	−933K Sold out	0	—
Braidwell LP Hedge fund	−782K −52.4%	711K	$39.2M
Caligan Partners LP Hedge fund	−649K −76.4%	200K	$11M
Cormorant Asset Management, LP Hedge fund	−570K −50.9%	550K	$30.4M
Ecor1 Capital, LLC Hedge fund	−389K −50.0%	389K	$21.4M
Millennium Management LLC Hedge fund	−338K −59.9%	226K	$12.5M
Price T Rowe Associates Inc Active manager	−214K −20.8%	815K	$45M
Orbimed Advisors LLC	−209K −5.7%	3.4M	$189M
Dafna Capital Management LLC	−164K −93.3%	12K	$651,857
Goelzer Investment Management, Inc.	−160K −97.6%	4,000	$220,800
Boothbay Fund Management, LLC Hedge fund	−138K −66.2%	70K	$3.9M
Elmind Capital, LP	−120K −56.9%	91K	$5M
D. E. Shaw & Co., Inc. Hedge fund	−106K −36.7%	183K	$10.1M
Squarepoint Ops LLC Hedge fund	−97K Sold out	0	—
Affinity Asset Advisors, LLC	−75K −50.0%	75K	$4.1M
UBS Group AG	−74K −21.4%	273K	$15.1M
Victory Capital Management Inc Active manager	−71K Sold out	0	—
Schroder Investment Management Group Active manager	−57K Sold out	0	—

Biggest sellers, active managers and hedge funds
Institution	Change in shares	Shares June 30, 2026	Value
Deep Track Capital, LP Hedge fund	−1.0M −37.2%	1.7M	$95.6M
Citadel Advisors LLC Hedge fund	−933K Sold out	0	—
Braidwell LP Hedge fund	−782K −52.4%	711K	$39.2M
Caligan Partners LP Hedge fund	−649K −76.4%	200K	$11M
Cormorant Asset Management, LP Hedge fund	−570K −50.9%	550K	$30.4M
Ecor1 Capital, LLC Hedge fund	−389K −50.0%	389K	$21.4M
Millennium Management LLC Hedge fund	−338K −59.9%	226K	$12.5M
Price T Rowe Associates Inc Active manager	−214K −20.8%	815K	$45M
Boothbay Fund Management, LLC Hedge fund	−138K −66.2%	70K	$3.9M
D. E. Shaw & Co., Inc. Hedge fund	−106K −36.7%	183K	$10.1M

New positions

largest by value

Institution	Shares	Value June 30, 2026
Paradigm Biocapital Advisors LP	2.5M	$138M
Franklin Resources IncActive manager	253K	$13.9M
Prudential Financial Inc	88K	$4.9M
Moore Capital Management, LPHedge fund	65K	$3.6M
Rhenman & Partners Asset Management AB	62K	$3.4M
Ensign Peak Advisors, Inc	42K	$2.3M
Voya Investment Management LLC	26K	$1.4M
Universal- Beteiligungs- Und Servicegesellschaft Mbh	26K	$1.4M
Teachers Retirement System Of The State Of Kentucky	25K	$1.4M
Fred Alger Management, LLCActive manager	9,877	$545,210

Sold out

largest by value

Institution	Shares	Value March 31, 2026
Stempoint Capital LP	999K	$29.8M
Citadel Advisors LLCHedge fund	933K	$27.8M
Squarepoint Ops LLCHedge fund	97K	$2.9M
Victory Capital Management IncActive manager	71K	$2.1M
Schroder Investment Management GroupActive manager	57K	$1.5M
Exoduspoint Capital Management, LPHedge fund	28K	$838,397
Swiss Life Asset Management Ltd	12K	$657,200
Engineers Gate Manager LPHedge fund	17K	$518,793
Qube Research & Technologies LtdHedge fund	17K	$513,032
Jump Financial, LLC	13K	$379,095

Who holds the shares

13F holdings at June 30, 2026

Institutions reporting: 172
Ten largest holders: 63.6%
Index fund managers: 13.5%
Active managers and hedge funds: 39.5%

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	16	25	5	11	−104K	−0.5%
Index fund managers	10	1	2	0	+716K	+10.5%
Other institutions	72	42	28	9	+1.8M	+7.5%

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 MBX Biosciences.

Only managers that filed a holdings report for both quarters are compared (187 here). 9 other holders are 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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