Spero Therapeutics, Inc.: which funds bought and sold

Institutions that bought and sold Spero Therapeutics 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, 38 institutions that filed 13F reports for both quarters added to or opened positions in Spero Therapeutics, and 18 cut or closed them. Together they added a net 382K shares, +1.8% on what they held at the start of the quarter. Active managers and hedge funds on our list were net sellers of 1.9M shares (−49.7%); index fund managers were net buyers of 455K shares (+13.4%). 21 opened a new position and 12 sold out entirely.

Bought, Q2 2026 38 institutions, 21 of them new holders Sold, Q2 2026 18 institutions, 12 of them sold out

Net change, all compared +382K shares (+1.8%)

Net change, active managers −1.9M shares (−49.7%), 6 bought, 8 sold

Buyers versus sellers

institutions compared, 71

38 bought 15 18 sold

Active managers and hedge funds 6 bought · 8 sold · −1.9M

Index fund managers 4 bought · 1 sold · +455K

Other institutions 28 bought · 9 sold · +1.9M

Biggest buyers

by change in shares held

Biggest buyers
Institution	Change in shares	Shares June 30, 2026	Value
Raymond James Financial Inc	+522K New position	522K	$1.2M
Susquehanna International Group, LLP	+426K +127.9%	759K	$1.7M
Arrowstreet Capital, Limited Partnership Hedge fund	+333K New position	333K	$735,864
Goldman Sachs Group Inc	+257K New position	257K	$567,937
Dimensional Fund Advisors LP	+245K +823.2%	275K	$607,616
Vanguard Capital Management LLC Index funds	+236K +13.1%	2.0M	$4.5M
Blackrock, Inc. Index funds	+161K +37.2%	594K	$1.3M
UBS Group AG	+137K +4542.1%	140K	$308,693
Federation Des Caisses Desjardins Du Quebec	+92K New position	92K	$202,180
Jane Street Group, LLC	+52K +48.7%	158K	$349,394
Xtx Topco Ltd	+51K New position	51K	$111,685
Geode Capital Management, LLC Index funds	+46K +8.9%	566K	$1.3M
Point72 Asset Management, L.P. Hedge fund	+45K +74.9%	104K	$230,673
American Century Companies Inc Active manager	+37K New position	37K	$81,352
Axxcess Wealth Management, LLC	+33K New position	33K	$71,931
Dlk Investment Management, LLC	+31K New position	31K	$40,762
Simplex Trading, LLC	+31K +102.3%	61K	$135,499
Vanguard Fiduciary Trust Co Index funds	+24K +8.9%	288K	$635,702
Oppenheimer & Co Inc	+23K New position	23K	$50,499
Millennium Management LLC Hedge fund	+19K New position	19K	$42,649

Biggest buyers, active managers and hedge funds
Institution	Change in shares	Shares June 30, 2026	Value
Arrowstreet Capital, Limited Partnership Hedge fund	+333K New position	333K	$735,864
Point72 Asset Management, L.P. Hedge fund	+45K +74.9%	104K	$230,673
American Century Companies Inc Active manager	+37K New position	37K	$81,352
Millennium Management LLC Hedge fund	+19K New position	19K	$42,649
Qube Research & Technologies Ltd Hedge fund	+14K New position	14K	$30,153
FMR LLC Active manager	+300 New position	300	$663

Biggest sellers

by change in shares held

Biggest sellers
Institution	Change in shares	Shares June 30, 2026	Value
Anson Funds Management LP Hedge fund	−844K Sold out	0	—
Two Sigma Investments, LP Hedge fund	−503K −56.8%	383K	$846,019
Citadel Advisors LLC Hedge fund	−376K Sold out	0	—
Renaissance Technologies LLC Hedge fund	−241K −20.3%	948K	$2.1M
Squarepoint Ops LLC Hedge fund	−194K Sold out	0	—
Marshall Wace, LLP Hedge fund	−157K Sold out	0	—
Ionic Capital Management LLC	−93K −47.6%	103K	$226,963
Quadrature Capital Ltd Hedge fund	−40K Sold out	0	—
Omers Administration Corp	−39K Sold out	0	—
Schonfeld Strategic Advisors LLC Hedge fund	−20K Sold out	0	—
Torrey Growth & Income Advisors	−17K Sold out	0	—
Occudo Quantitative Strategies LP	−16K Sold out	0	—
Intrepid Family Office LLC	−16K Sold out	0	—
Northern Trust Corp Index funds	−13K −10.5%	108K	$239,286
Citigroup Inc	−9,510 −49.7%	9,625	$21,271
Morgan Stanley	−3,638 −79.9%	914	$2,020
BNP Paribas Financial Markets	−40 Sold out	0	—
Caitong International Asset Management Co., Ltd	−3 Sold out	0	—

Biggest sellers, active managers and hedge funds
Institution	Change in shares	Shares June 30, 2026	Value
Anson Funds Management LP Hedge fund	−844K Sold out	0	—
Two Sigma Investments, LP Hedge fund	−503K −56.8%	383K	$846,019
Citadel Advisors LLC Hedge fund	−376K Sold out	0	—
Renaissance Technologies LLC Hedge fund	−241K −20.3%	948K	$2.1M
Squarepoint Ops LLC Hedge fund	−194K Sold out	0	—
Marshall Wace, LLP Hedge fund	−157K Sold out	0	—
Quadrature Capital Ltd Hedge fund	−40K Sold out	0	—
Schonfeld Strategic Advisors LLC Hedge fund	−20K Sold out	0	—

New positions

largest by value

Institution	Shares	Value June 30, 2026
Raymond James Financial Inc	522K	$1.2M
Arrowstreet Capital, Limited PartnershipHedge fund	333K	$735,864
Goldman Sachs Group Inc	257K	$567,937
Federation Des Caisses Desjardins Du Quebec	92K	$202,180
Xtx Topco Ltd	51K	$111,685
American Century Companies IncActive manager	37K	$81,352
Axxcess Wealth Management, LLC	33K	$71,931
Oppenheimer & Co Inc	23K	$50,499
Millennium Management LLCHedge fund	19K	$42,649
Dlk Investment Management, LLC	31K	$40,762

Sold out

largest by value

Institution	Shares	Value March 31, 2026
Anson Funds Management LPHedge fund	844K	$2M
Citadel Advisors LLCHedge fund	376K	$880,912
Squarepoint Ops LLCHedge fund	194K	$454,664
Marshall Wace, LLPHedge fund	157K	$367,547
Quadrature Capital LtdHedge fund	40K	$93,900
Omers Administration Corp	39K	$92,196
Schonfeld Strategic Advisors LLCHedge fund	20K	$47,534
Occudo Quantitative Strategies LP	16K	$41,217
Intrepid Family Office LLC	16K	$38,093
Torrey Growth & Income Advisors	17K	$37,627

Who holds the shares

13F holdings at June 30, 2026

Institutions reporting: 60
Ten largest holders: 85.0%
Index fund managers: 17.9%
Active managers and hedge funds: 9.1%

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	6	8	5	6	−1.9M	−49.7%
Index fund managers	4	1	0	0	+455K	+13.4%
Other institutions	28	9	16	6	+1.9M	+13.4%

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 Spero Therapeutics.

Only managers that filed a holdings report for both quarters are compared (71 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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