Company · Ownership research

Spero Therapeutics, Inc. SPRO

CIK 0001701108 · CUSIP 84833T103

Insider trading Initial holdings Institutional holders

Quarter-end disclosures, not live holdings.

Several CUSIPs are reported for this company; this page shows CUSIP 84833T103 (SPRO), not CUSIP 84833T953 (SPRO), CUSIP 84833T903 (SPRO), and does not merge CUSIPs.

This page lists the top 20 of 50 rows by value; the complete set is available through the API.

Some filings reported values in thousands; those figures were scaled ×1,000 to dollars.

Top 20 institutions

Weight means this stock's share of the manager's own portfolio.

By reported value

#	Manager	Value	Manager weight	Change vs prior	Source
01	GSK plc CIK 1131399 · View history	$21.51M 9,190,606 shares	3.59%	0(0.00%)Unchanged	SEC filing ↗ May 14, 2026	▾
02	Pfizer Inc CIK 78003 · View history	$5.50M 2,362,348 shares	2.31%	0(0.00%)Unchanged	SEC filing ↗ May 12, 2026	▾
03	VANGUARD CAPITAL MANAGEMENT LLC CIK 2100119 · Amended · View history	$4.21M 1,799,880 shares	0.00%	—	SEC filing ↗ May 15, 2026	▾
04	RENAISSANCE TECHNOLOGIES LLC CIK 1037389 · View history	$2.78M 1,189,235 shares	0.00%	-90.29K(-7.10%)Reduced	SEC filing ↗ May 14, 2026	▾
05	Alphabet Inc. CIK 1652044 · View history	$2.08M 889,979 shares	0.05%	0(0.00%)Unchanged	SEC filing ↗ May 8, 2026	▾
06	TWO SIGMA INVESTMENTS, LP CIK 1179392 · View history	$2.07M 885,631 shares	0.00%	+513.06K(+137.70%)Added	SEC filing ↗ May 15, 2026	▾
07	GEODE CAPITAL MANAGEMENT, LLC CIK 1214717 · View history	$1.22M 519,922 shares	0.00%	-9.27K(-1.80%)Reduced	SEC filing ↗ May 15, 2026	▾
08	BlackRock, Inc. CIK 2012383 · View history	$1.01M 433,202 shares	0.00%	-414(-0.10%)Reduced	SEC filing ↗ May 13, 2026	▾
09	Anson Funds Management LP CIK 1491072 · Amended · View history	$987.38K 421,956 shares	0.13%	-203.11K(-32.50%)Reduced	SEC filing ↗ May 19, 2026	▾
10	CITADEL ADVISORS LLC CIK 1423053 · View history	$880.91K 376,458 shares	0.00%	-21.41K(-5.40%)Reduced	SEC filing ↗ May 15, 2026	▾
11	SUSQUEHANNA INTERNATIONAL GROUP, LLP CIK 1446194 · View history	$779.49K 333,115 shares	0.00%	+39.41K(+13.40%)Added	SEC filing ↗ May 15, 2026	▾
12	GSA CAPITAL PARTNERS LLP CIK 1362033 · View history	$651.00K 278,304 shares	0.04%	+99.37K(+55.50%)Added	SEC filing ↗ May 8, 2026	▾
13	VANGUARD FIDUCIARY TRUST CO CIK 933478 · Amended · View history	$618.03K 264,115 shares	0.00%	—	SEC filing ↗ May 8, 2026	▾
14	STATE STREET CORP CIK 93751 · View history	$502.52K 214,751 shares	0.00%	+4.60K(+2.20%)Added	SEC filing ↗ May 15, 2026	▾
15	Ionic Capital Management LLC CIK 1386462 · View history	$458.50K 195,939 shares	0.38%	0(0.00%)Unchanged	SEC filing ↗ May 15, 2026	▾
16	Squarepoint Ops LLC CIK 1642575 · View history	$454.66K 194,301 shares	0.00%	+74.87K(+62.70%)Added	SEC filing ↗ May 15, 2026	▾
17	MARSHALL WACE, LLP CIK 1318757 · View history	$367.55K 157,072 shares	0.00%	+157.07KNew	SEC filing ↗ May 15, 2026	▾
18	NORTHERN TRUST CORP CIK 73124 · View history	$283.10K 120,984 shares	0.00%	0(0.00%)Unchanged	SEC filing ↗ May 14, 2026	▾
19	BRIDGEWAY CAPITAL MANAGEMENT, LLC CIK 1107261 · View history	$268.63K 114,800 shares	0.01%	0(0.00%)Unchanged	SEC filing ↗ May 15, 2026	▾
20	JANE STREET GROUP, LLC CIK 1595888 · View history	$248.85K 106,345 shares	0.00%	-52.00K(-32.80%)Reduced	SEC filing ↗ May 12, 2026	▾

Showing 20 / 50 institutions. The complete set is available through the API.

Coverage & totals by quarter

Reporting institutions

Cancelled or null records excluded

Disclosed shares

20,643,241

Not deduplicated across managers

Disclosed value

$48.30M

Not market cap or free float

Reporting institutions by quarter

Counts also change with data coverage and reporting entities; they do not measure net buying. Distinct managers with a live stock row in this CUSIP; totals may include overlapping filings and are not a share of the company.

Spero Therapeutics, Inc. · Q1 2026

Explore all 50 reporting institutions.

This page includes 20 of 50 reporting institutions. Log in to look up the full history beyond 3 years, use advanced screening & filtering, download CSV, and get the complete set through the Akkru API.

Download CSV
Earlier quarters
Advanced screening & filtering
API & AI access

Already have an account?

＋ New accounts get free API credits to explore data beyond ownership filings.

For AI agents & developers

The initial HTML of this page carries its exact data as script#research-data (JSON): values, units, scope, preview limits and SEC sources. Read it directly, no script or API key needed; script#research-access says what needs an account. This page lists 20 of 50 reporting institutions; totals use the complete disclosed data.

Without an account: the last 3 years, with the row caps stated on the page. A free account opens all history on file on these pages and the CSV of what a page shows. Rows beyond the caps and bulk retrieval go through the authenticated API / MCP / CLI.

MCP  https://api.akkrudata.ai/mcp

akkru_institutional_holdings
{"action":"holders","cusip":"84833T103","quarter":"2026Q1","type":"positions","page_size":100}

Connect to MCP with OAuth and follow the returned pagination. Credits and usage limits depend on the account.

MCP endpoint: https://api.akkrudata.ai/mcp
API / MCP / CLI documentation: /documents
llms.txt: /llms.txt

Sources, coverage & how to read this data

Figures are as reported to the SEC and merged with later amendments where Akkru could match them. Preview limits apply to what is listed, not to the totals, which come from the complete reported data. Nothing is zero-filled: a missing quarter or month is shown as missing.