SPRO · Spero Therapeutics, Inc. · Holdings

$1.11 -0.02 (-1.77%) At close · Oct 23

Market Cap

$64.64M

58.23M

Volume · Oct 23 316.55K Avg daily vol (3M) 825.88K

Institutional ownership from SEC Form 13F filings. Investment managers with more than $100 million in U.S. equities must disclose their positions every quarter, within 45 days of quarter-end, so the holdings shown can lag the market by up to a quarter.

Use institutional holdings through the 13F API or MCP → See every holder of SPRO: 13F, 13D and 13G, insiders and funds →

Recent SEC filings are still being reconciled. Holder totals and changes may be incomplete until processing catches up.

The Sep 30, 2026 filing window is still open — showing the latest known positions. Funds that have not filed yet carry their prior-quarter positions; a fund that filed without this stock counts as sold out. Each fund's Change is measured against its own previous reported quarter, shown in the Reported column. Pick a completed quarter in the Quarter selector below to put every fund on one quarter and see the stock-wide activity breakdown.

Quarter:

Holders: 59

Total Value: $47,661,126

Total Shares: 21,583,841

Institutional Ownership Trend

27 quarters

Holder Concentration

Across 61 13F filers

Top Holder

42.5%

of institutional value

Top 5

71.3%

of institutional value

Top 10

84.6%

of institutional value

HHI

2,099

Moderately concentrated

Who Holds SPRO

Last 8 quarters through Sep 30, 2026 (filing window open)

Each kind of 13F filer's share of the common shares 13F filers report. Holder type comes from regulatory records, never the filer's name; style, turnover and horizon are measured from each filer's own 13F book. The quarter selector does not change this card.

Jun 30, 2026, the newest closed quarter: 59 filers, like-for-like change +3.8%; actively managed books +0.4%; index-like books +21.1%.

Holder type	Share	Filers	Change	New	Exited
Registered adviser	24.9%	19	-14.2%	5	6
Exempt adviser	0.1%	1	-91.3%	1	1
Adviser	0.3%	1	+41.6%	0	0
Bank	2.2%	8	+32.5%	1	0
Insurer	0.0%	1	new	1	0
Broker-dealer	0.1%	1	new	1	0
Non-US	0.1%	2	+22922.4%	1	1
Holding company	46.8%	6	+4.3%	2	0
Benefit plan	0.0%	0	-100.0%	0	1
Unknown	25.5%	20	+30.3%	8	3

Style	Share	Filers	Change	New	Exited
Index-like	19.0%	8	+21.1%	1	0
Systematic-like	4.2%	10	-44.4%	6	2
Concentrated	58.3%	7	-0.3%	1	2
Diversified active	18.5%	34	+26.4%	12	8
Not measured	0.0%	0	—	0	0
Unknown	0.0%	0	—	0	0

Turnover	Share	Filers	Change	New	Exited
Low turnover	28.5%	27	+30.2%	9	0
Medium turnover	11.7%	12	+29.5%	5	3
High turnover	5.7%	14	-54.8%	6	8
Unknown	54.2%	6	+2.3%	0	1
Not measured	0.0%	0	—	0	0

Holding horizon	Share	Filers	Change	New	Exited
Short horizon	55.8%	9	-1.0%	3	5
Medium horizon	17.8%	11	+21.4%	4	1
Long horizon	19.8%	32	+24.5%	10	4
Unknown	6.6%	7	-29.6%	3	2
Not measured	0.0%	0	—	0	0

13F book size	Share	Filers	Change	New	Exited
Under $1B	55.1%	8	-4.0%	2	4
$1B to $10B	3.3%	14	+36.5%	7	1
$10B to $100B	9.7%	10	-15.3%	3	4
$100B or more	31.9%	27	+27.3%	8	3
Not measured	0.0%	0	—	0	0

Client base	Share	Filers	Change	New	Exited
Individuals and high net worth	0.6%	6	+59.1%	3	1
Pooled investment vehicles	10.3%	8	-39.9%	2	5
Registered funds and BDCs	14.1%	5	+21.2%	0	0
Pension and profit sharing plans	0.0%	0	—	0	0
Governments and sovereign funds	0.0%	0	—	0	0
Unknown	75.1%	40	+11.6%	15	6

Private funds	Share	Filers	Change	New	Exited
Hedge funds	10.2%	8	-42.1%	3	5
Other private funds	1.8%	2	+142.0%	0	1
No private funds	13.0%	10	+13.4%	3	1
Private funds, type not stated	0.0%	0	—	0	0
Unknown	75.0%	39	+12.7%	14	5

Location	Share	Filers	Change	New	Exited
United States	54.3%	50	+6.5%	16	8
Outside the US	45.7%	9	+0.7%	4	4

The Sep 30, 2026 filing window is still open, so its bar carries the Jun 30, 2026 positions of filers that have not filed yet.

How the mix is measured

Shares are 13F common shares restated to today's split basis; options and principal amounts are left out. The change compares only filers with a 13F in both quarters and keeps each filer in its bucket of the later quarter on both sides; a filer that continues under a new CIK is compared through its successor. Holder type comes from each filer's current regulatory profile; client base and private funds come from the Form ADV roster current at each quarter end (rosters from December 2019, so an earlier quarter reads Unknown). Style, turnover, horizon and book size are measured from each filer's 13F book in the newest measured quarter, and Not measured means none was. Actively managed books are those measured systematic-like, concentrated or diversified active.

Excluded 1 holder with no observed 2026-03-31 13F.

Conviction and Crowding

59 13F filers, quarter ended Jun 30, 2026

Measured across every 13F filer's common-share book once the quarter's filing window closed. Crowding counts filers with high turnover or that advise private funds on Form ADV.

Conviction holders

3.39% of filers hold it in their top 10

Mar 31, 2026: 2

Holders above 5%

median weight 0.000%

Mar 31, 2026: 0

Crowding

5.16%

of shares outstanding, 17th percentile

Mar 31, 2026: 7.85%

Private-fund advisers

4.45%

of shares outstanding

Institutional ownership

37.0%

40.4% of the estimated free float

Top 10 holders

85.1%

of 13F shares, Herfindahl 0.213

Active holders

+0.4%

like-for-like share change of active filers

5% stakes on record

1 13D, 0 13G

How long holders have held it value-weighted 6.2 quarters

Under 1 year 65.2% 1 to 3 years 20.7% 3 years or more 14.0% Since coverage start 0.000%

Managers in the top fifth by current three-year FundScore alpha were net buyers of $0 (0 buying, 0 selling).

Estimated Holder Cost Basis

Quarter ended Jun 30, 2026, on that quarter's share basis

Estimated, never filed: each 13F buy is costed at its quarter's average traded price and each sale keeps the average cost, so this is what holders paid on average if they traded evenly through each quarter.

Estimated avg cost

$2.36

estimated per share

Mar 31, 2026: $2.12

Quarter-end price

$2.21

implied by 13F values

Estimated gain or loss

-6.3%

price against the estimated cost

Estimated at a loss

72.9%

of costed 13F value

Estimated cost covers 23.0% of the 13F shares; positions already held when a filer's 13F history starts, or bought in a quarter without a trusted average price, have no estimate.

Shared Holders

Companies SPRO's active holders also own, quarter ended Mar 31, 2026

#	Company	Shared holders	Similarity
1	ASML Asml Holding NV	3	0.029
2	MU Micron Technology Inc	3	0.023
3	NVDA Nvidia Corp	3	0.015
4	AMZN Amazon Com Inc	3	0.015

Shareholder Targets

13F filers that own its peers but not SPRO, quarter ended Mar 31, 2026

Found through its holder-overlap peers: ASML, MU, NVDA, AMZN. 6,556 filers in all.

#	Filer	In peers	Of book	Largest peers
1	FMR LLC Holding company, Diversified active	$263,021,957,320 4 held	14.0%	NVDA, AMZN, MU
2	VANGUARD PORTFOLIO MANAGEMENT LLC Registered adviser, Diversified active	$123,197,701,796 3 held	6.46%	NVDA, AMZN, MU
3	PRICE T ROWE ASSOCIATES INC /MD/ Registered adviser, Diversified active	$93,997,694,865 4 held	10.9%	NVDA, AMZN, ASML
4	Capital Research Global Investors Adviser, Diversified active	$59,942,150,246 4 held	9.34%	NVDA, AMZN, MU
5	BANK OF AMERICA CORP /DE/ Bank, Diversified active	$55,654,388,169 4 held	4.24%	NVDA, AMZN, MU
6	UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC Registered adviser, Index-like	$53,369,207,926 4 held	11.1%	NVDA, AMZN, MU
7	Capital World Investors Adviser, Diversified active	$52,358,039,686 4 held	7.20%	NVDA, MU, AMZN
8	GOLDMAN SACHS GROUP INC Holding company, Index-like	$50,885,775,613 4 held	6.78%	NVDA, AMZN, MU
9	Bank of New York Mellon Corp Bank, Index-like	$43,602,883,888 4 held	8.08%	NVDA, AMZN, MU
10	Legal & General Group Plc Unknown, Index-like	$43,601,898,520 4 held	10.1%	NVDA, AMZN, MU

Fund Ownership of SPRO by Fund Type

Registered funds' Form N-PORT reports for the quarter ended Jun 30, 2026

Index funds and index ETFs hold 4.64% of shares outstanding.

Fund type	Of shares outstanding	Change	Shares	Funds
Index funds	0.89%	+0.08 pp	516,193	8
Index ETFs	3.76%	+0.70 pp	2,188,718	5
Active ETFs	0.04%	0.00 pp	20,808	2
Active funds	0.32%	+0.10 pp	183,971	6
Unclassified	0.04%	+0.04 pp	22,770	1
All registered funds	5.04%	+0.92 pp	2,932,460	22

How fund types are measured

Each fund series counts once, with its latest Form N-PORT report dated inside the quarter; only long share positions count, restated to today's split basis. The fund type is the series' latest Form N-CEN answer on or before the quarter end (the index-fund box and the exchange-traded flag), never its name. Unclassified funds have no usable N-CEN; unit investment trusts are among them, so index ownership is a floor. Funds sit inside their advisers' 13F reports, so these shares overlap the 13F figures and are never added to them.

Holder type: Registered adviser 18 Exempt adviser 1 Adviser 1 Bank 8 Insurer 1 Broker-dealer 1 Non-US 2 Holding company 6 Unknown 21

Showing 63 of 63

All Common Calls Puts

Compact Export CSV

Holder

Value (USD)

% of 13F

GSK plc

$20,311,239

42.62%

9,190,606

Pfizer Inc

$5,220,789

10.95%

2,362,348

VANGUARD CAPITAL MANAGEMENT LLC

$4,500,059

9.44%

2,036,226

RENAISSANCE TECHNOLOGIES LLC

$2,094,867

4.40%

947,904

Alphabet Inc.

$1,966,853

4.13%

889,979

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
GV Management Company, L.L.C.	889,979	$1,966,853	100.0%	Defined

SUSQUEHANNA INTERNATIONAL GROUP, LLP

$1,678,030

3.52%

759,290

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
SUSQUEHANNA SECURITIES, LLC	759,290	$1,678,030	100.0%	Other

BlackRock, Inc.

$1,313,630

2.76%

594,404

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
BlackRock Investment Management, LLC	10,170	$22,475	1.7%	Sole
BlackRock Fund Advisors	151,203	$334,158	25.4%	Sole
BlackRock Institutional Trust Company, N.A.	432,009	$954,739	72.7%	Sole
Aperio Group, LLC	1,022	$2,258	0.2%	Sole

GEODE CAPITAL MANAGEMENT, LLC

$1,251,586

2.63%

566,329

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
GEODE CAPITAL MANAGEMENT TRUST COMPANY, LLC	101,959	$225,329	18.0%	Defined
Held directly	464,370	$1,026,257	82.0%	Defined

RAYMOND JAMES FINANCIAL INC

$1,152,968

2.42%

521,705

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
RAYMOND JAMES & ASSOCIATES	1,000	$2,210	0.2%	Defined
Raymond James Financial Services Advisors, Inc.	2,062	$4,557	0.4%	Defined
ClariVest Asset Management LLC joint	518,643	$1,146,201	99.4%	Defined

TWO SIGMA INVESTMENTS, LP

$846,018

1.78%

382,814

ARROWSTREET CAPITAL, LIMITED PARTNERSHIP

$735,863

1.54%

332,970

VANGUARD FIDUCIARY TRUST CO

$635,702

1.33%

287,648

GSA CAPITAL PARTNERS LLP

$631,852

1.33%

285,906

DIMENSIONAL FUND ADVISORS LP

$607,350

1.27%

274,820

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
Dimensional Fund Advisors Ltd.	4,957	$10,954	1.8%	Defined
Dimensional Ireland Ltd	50,499	$111,602	18.4%	Defined
Held directly	219,364	$484,794	79.8%	Sole

GOLDMAN SACHS GROUP INC

$567,936

1.19%

256,985

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
GOLDMAN SACHS & CO. LLC	256,985	$567,936	100.0%	Defined

STATE STREET CORP

$474,599

1.00%

214,751

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
STATE STREET GLOBAL ADVISORS TRUST COMPANY	214,751	$474,599	100.0%	Defined

JANE STREET GROUP, LLC

$349,394

0.73%

158,097

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
Jane Street Capital, LLC	158,097	$349,394	100.0%	Defined

UBS Group AG

$308,692

0.65%

139,680

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
UBS AG	139,680	$308,692	100.0%	Defined

BRIDGEWAY CAPITAL MANAGEMENT, LLC

$253,708

0.53%

114,800

NORTHERN TRUST CORP

$239,285

0.50%

108,274

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
NORTHERN TRUST CO joint	108,274	$239,285	100.0%	Defined

Point72 Asset Management, L.P.

$230,673

0.48%

104,377

Ionic Capital Management LLC

$226,962

0.48%

102,698

Federation des caisses Desjardins du Quebec

$203,099

0.43%

91,900

Shay Capital LLC

$159,984

0.34%

72,391

CITADEL ADVISORS LLC

$144,976

0.30%

65,600

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
Citadel Securities GP LLC	65,600	$144,976	100.0%	Defined

Invesco Ltd.

$141,981

0.30%

64,245

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
Invesco Capital Management LLC	64,245	$141,981	100.0%	Defined

SIMPLEX TRADING, LLC

$135,499

0.28%

61,312

Verdad Advisers, LP

$113,450

0.24%

51,335

XTX Topco Ltd

$111,684

0.23%

50,536

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
XTX EXECUTION SERVICES LLC joint	50,536	$111,684	100.0%	Defined

JANE STREET GROUP, LLC

$104,091

0.22%

47,100

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
Jane Street Capital, LLC	47,100	$104,091	100.0%	Defined

AMERICAN CENTURY COMPANIES INC

$81,352

0.17%

36,811

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
AMERICAN CENTURY INVESTMENT MANAGEMENT INC	36,811	$81,352	100.0%	Defined

SUSQUEHANNA INTERNATIONAL GROUP, LLP

$76,466

0.16%

34,600

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
SUSQUEHANNA SECURITIES, LLC	34,600	$76,466	100.0%	Other

Capital Asset Advisory Services LLC

$71,931

0.15%

32,548

Three Seasons Wealth, LLC

$66,300

0.14%

30,000

CHARLES SCHWAB INVESTMENT MANAGEMENT INC

$63,128

0.13%

28,565

JANE STREET GROUP, LLC

$59,228

0.12%

26,800

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
Jane Street Capital, LLC	26,800	$59,228	100.0%	Defined

Vanguard Global Advisers, LLC

$56,235

0.12%

25,446

Global Retirement Partners, LLC

$55,250

0.12%

25,000

OPPENHEIMER & CO INC

$50,498

0.11%

22,850

MILLENNIUM MANAGEMENT LLC

$42,648

0.09%

19,298

Susquehanna Portfolio Strategies, LLC

$38,957

0.08%

17,628

SUSQUEHANNA FUNDAMENTAL INVESTMENTS, LLC

$35,569

0.07%

16,095

SUSQUEHANNA INTERNATIONAL GROUP, LLP

$30,277

0.06%

13,700

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
SUSQUEHANNA SECURITIES, LLC	13,700	$30,277	100.0%	Other

Qube Research & Technologies Ltd

$30,153

0.06%

13,644

FNY Investment Advisers, LLC

$25,773

0.05%

21,300

SG Americas Securities, LLC

$24,902

0.05%

11,268

GROUP ONE TRADING LLC

$24,020

0.05%

10,869

TWO SIGMA SECURITIES, LLC

$23,372

0.05%

10,576

PRUDENTIAL FINANCIAL INC

$22,984

0.05%

10,400

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
PGIM Quantitative Solutions LLC	10,400	$22,984	100.0%	Defined

Assenagon Asset Management S.A.

$21,492

0.05%

17,762

CITIGROUP INC

$21,271

0.04%

9,625

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
Citigroup Financial Products Inc. joint	9,625	$21,271	100.0%	Defined

JONES FINANCIAL COMPANIES LLLP

$16,968

0.04%

7,678

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
Edward D. Jones & Co., L.P.	7,678	$16,968	100.0%	Sole

ROYAL BANK OF CANADA

$4,450

0.01%

2,014

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
RBC Capital Markets, LLC	2,014	$4,450	100.0%	Defined

MORGAN STANLEY

$2,019

0.00%

914

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
MORGAN STANLEY & CO. LLC	1	$2	0.1%	Defined
MORGAN STANLEY SMITH BARNEY LLC	900	$1,989	98.5%	Defined
PARAMETRIC PORTFOLIO ASSOCIATES LLC	13	$28	1.4%	Defined

FMR LLC

$663

0.00%

300

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
Fidelity Management & Research Co LLC	300	$663	100.0%	Defined

OSAIC HOLDINGS, INC.

$640

0.00%

290

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
OSAIC WEALTH, INC.	290	$640	100.0%	Defined

JPMORGAN CHASE & CO

$521

0.00%

236

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
J.P. Morgan Securities plc	236	$521	100.0%	Defined

WELLS FARGO & COMPANY/MN

$442

0.00%

200

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
WELLS FARGO CLEARING SERVICES, LLC	200	$442	100.0%	Defined

Rialto Wealth Management, LLC

$380

0.00%

172

US BANCORP \DE\

$333

0.00%

151

This filing is a combination report: the position is filed across the managers below.

Manager	Shares	Value (USD)	% of position	Discretion
US BANK NATIONAL ASSOCIATION	151	$333	100.0%	Defined

SBI Securities Co., Ltd.

$73

0.00%

Farther Finance Advisors, LLC

$12

0.00%

INTERNATIONAL ASSETS INVESTMENT MANAGEMENT, LLC

0.00%

Key facts CIK 1701108 CUSIP 84833T103 13F (30d) 4 filings 4 filers Visit website Investor relations