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Buy Day today: Neutral (56) Mixed market breadth · no major macro event
SPRO

Spero Therapeutics Inc

Healthcare · Biotechnology

1.20$ -1.6% vs. previous close Closing price · As of: Sep 25, 2026

Ownership

Ownership Structure

Who owns Spero Therapeutics Inc (SPRO)? This page shows the largest institutions and funds, the ownership structure and the latest insider transactions. 80.2% of the shares are freely tradable; institutional investors hold 17.7%.

Institutional ownership ?Share of the stock held by institutional investors (funds, banks, insurers) according to regulatory filings. 17.7%
Insiders ?Share of the stock held by the executives, founders and major shareholders of the company itself. 22.7%
Float ?Share of stock freely tradable on the market — not locked up in the hands of founders, insiders, or major shareholders. 80.2%
Short % of float ?Shares sold short as a percentage of the freely tradable float — high values signal many bets on falling prices. 2.5%
Shares Outstanding ?Total number of shares issued. Price times share count gives market cap. 58Mio.

Largest Shareholders

Institutions

Institutions SPRO
Name Stake (%) Shares Change (%) Date
GSK PLC 15.78 9,190,606 +0.0 03/31/2026
Pfizer Inc 4.06 2,362,348 +0.0 03/31/2026
Vanguard Capital Management, LLC 3.09 1,799,880 +0.0 03/31/2026
Renaissance Technologies Corp 2.04 1,189,235 -7.1 03/31/2026
Alphabet Inc 1.53 889,979 +0.0 06/30/2026
Geode Capital Management, LLC 0.89 519,922 -1.8 03/31/2026
BlackRock Inc 0.74 433,202 -0.1 03/31/2026
Two Sigma Investments LLC 0.66 382,814 -56.8 06/30/2026
Susquehanna International Group, LLP 0.57 333,115 +13.4 03/31/2026

Funds

Funds SPRO
Name Stake (%) Shares Change (%) Date
Vanguard MStar Total Stk Mkt Idx Invest 2.40 1,395,976 +0.0 08/31/2026

Largest reported positions according to regulatory filings; stake as a percentage of shares outstanding, change versus the previous filing. Source: fundamentals data.

Data as of: September 25, 2026 · Source: fundamental data & SEC filings (annual and quarterly reports, 10-K/10-Q)

Note: pure fact-based analysis, not investment advice and not a solicitation to buy or sell. All figures without guarantee.

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