$SPRO

$1.14 +$0.07 (6.54%) Close

$SPRO Overview Financial Statements SEC Filings Executives News Red Flags Capital Raising Ownership Insider Transactions Congressional Trades

Ownership

13F as of Q2 2026 · 58.2M shares outstanding

Who owns SPRO?

By type of holder

Institutions 35.5% Insiders 8.6% Everyone else 55.9%

Concentration Top 10 holders own 34.4%

GSK plc 15.8% · Pfizer Inc 4.1%

Institutional ownership

35.5%

0.0 pts vs last qtr

Institutional holders

+6 vs last qtr

Net shares bought

+11.5K

by institutions in Q2 2026

New / sold out

19 / 13

positions opened vs closed

How is ownership changing?

Institutions, last 8 quarters

Biggest buyers in Q2 2026

Raymond James Financial Inc NEW +521.7K
Arrowstreet Capital, Limited Partnership NEW +333.0K

Biggest sellers in Q2 2026

Two Sigma Investments, LP −502.8K
Anson Funds Management LP SOLD OUT −422.0K

Who is planning to sell?

No insider has filed a notice of proposed sale (Form 144) for Spero Therapeutics, Inc. in the last 12 months.

Is your stake being diluted?

Diluted share count, FY2021–FY2025

+91.1%

+17.57% a year

Each share's claim on the business

−47.7%

shrank without buying or selling a share

Spent on buybacks vs paid in stock

— vs $38.6M

over 5 fiscal years

Diluted shares, split-adjusted

Buybacks Stock-based comp

How patient are the owners?

Institutional shares by how long they've been held

5+ years24% 3–5 years5% 1–3 years13% Under 1 year58%

Quarterly turnover

12.1%

of institutional shares changed hands

Top 10 managers, median time held

4.3 years

Super Investors

Investment managers reporting SPRO on Form 13F

Holder	Shares	% of company	Change vs last qtr	Held since	% of their book
GP GSK plc 13D · 16.4%	9.2M	15.78%	Unchanged	Q4 '25	3.4%
Shares held by quarter Peak holding9.2M (Q4'25) Change over 8 quarters+9.2M Share of the company15.780% Disclosed stake13D · 16.4% GSK plc's full portfolio →
P Pfizer Inc	2.4M	4.06%	Unchanged	2024	3.1%
Shares held by quarter Peak holding2.4M (Q4'24) Change over 8 quarters+2.4M Share of the company4.060% Pfizer Inc's full portfolio →

GSK plc

13D · 16.4%

9.2M

% of company

15.78%

Change vs last qtr

Unchanged

Held since

Q4 '25

Pfizer Inc

2.4M

% of company

4.06%

Change vs last qtr

Unchanged

Held since

2024

28 more super investors behind a free account

See every manager holding Spero Therapeutics, Inc., how their position has changed, and how long they've held it.

Institutional Funds

Mutual funds and ETFs reporting SPRO on Form N-PORT; together they hold 5.1% of the company

Fund	Position value	Shares	% of company	% of the fund	As of
VT Vanguard Total Stock Market Index Fund Vanguard Index Funds	$3.09M	1.4M	2.40%	0.00%	June 30, 2026
VE Vanguard Extended Market Index Fund Vanguard Index Funds	$1.31M	593.3K	1.02%	0.00%	June 30, 2026

Vanguard Total Stock Market Index Fund

Vanguard Index Funds

Position value

$3.09M

% of company

2.40%

% of the fund

0.00%

As of

June 30, 2026

Vanguard Extended Market Index Fund

Vanguard Index Funds

Position value

$1.31M

% of company

1.02%

% of the fund

0.00%

As of

June 30, 2026

23 more funds behind a free account

See every fund holding Spero Therapeutics, Inc. and how much of the fund the position is.

Insiders and 5%+ holders

From Forms 3/4/5 and Schedules 13D/G

Holder	Shares	% of company	Change vs last qtr	8 quarters	Held since	% of their book
SS Shukla Sath Insider	1.7M	2.98%	—	—	—	—
Insider holdings come from Form 3/4/5 filings, which are not quarterly. Share of the company2.980% Shukla Sath's insider activity →
RE Rajavelu Esther Insider	986.9K	1.69%	—	—	—	—
Insider holdings come from Form 3/4/5 filings, which are not quarterly. Share of the company1.690% Rajavelu Esther's insider activity →

Shukla Sath

Insider

1.7M

% of company

2.98%

Change vs last qtr

—

Held since

—

Rajavelu Esther

Insider

986.9K

% of company

1.69%

Change vs last qtr

—

Held since

—

10 more holders behind a free account

See every insider and 5%+ holder of Spero Therapeutics, Inc..

Comments