Spero Therapeutics, Inc.
Spero Therapeutics, Inc. (SPRO) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · SPRO · as of Sep 30, 2025
Ownership Breakdown
49
Institutional Holders
▲ 3 vs Q2
$21.26M
Total Inst. Value
▼ $10.86M vs Q2
57.90M
Shares Outstanding
freeFloat 80.35%
11.31M
13F Shares Held
▲ 232,798 vs Q2
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
SPRO largest shareholders · institutional ownership
Q3 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
PFIZER INC pharmaceutical preparations | 2.36M | 4.22% | 4.22% | $4.44B | Nov 13, 2025 | — held |
VANGUARD GROUP INC pharmaceutical preparations | 1.99M | 3.55% | 3.55% | $3.74B | Nov 7, 2025 | ▲ 39.5K |
ANSON FUNDS MANAGEMENT LP pharmaceutical preparations | 1.60M | 2.86% | 2.86% | $3.01B | Nov 14, 2025 | ▼ 11.9K |
RENAISSANCE TECHNOLOGIES LLC pharmaceutical preparations | 1.45M | 2.59% | 2.59% | $2.73B | Nov 13, 2025 | ▲ 620.6K |
ALPHABET INC. pharmaceutical preparations | 890.0K | 1.59% | 1.59% | $1.67B | Nov 7, 2025 | — held |
GEODE CAPITAL MANAGEMENT, LLC pharmaceutical preparations | 527.5K | 94.15% | 94.15% | $991.89M | Nov 12, 2025 | ▲ 16.8K |
BLACKROCK, INC. pharmaceutical preparations | 434.8K | 77.60% | 77.60% | $817.36M | Nov 12, 2025 | — held |
EAM INVESTORS, LLC pharmaceutical preparations | 282.4K | 50.41% | 50.41% | $531.00M | Nov 14, 2025 | ▲ 43.3K |
IONIC CAPITAL MANAGEMENT LLC pharmaceutical preparations | 208.7K | 37.25% | 37.25% | $392.40M | Nov 14, 2025 | ▲ 58.7K |
STATE STREET CORP pharmaceutical preparations | 191.0K | 34.08% | 34.08% | $358.99M | Nov 14, 2025 | ▲ 37.5K |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q3 2025 vs prior quarter
Q3 2025
13
Increased
+928.3K shares13
New Positions
first time holders8
Decreased
−188.9K shares1
Sold Out
fully exitedNet shares change (top 50)
+739.4K
+928.3K / −188.9K
Net new holders
+17
13 new / 1 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
SPRO insider trading · insider activity
Source: SEC Form 4
Insiders have been primarily selling shares recently. Selling may be driven by pre-scheduled Rule 10b5-1 plans rather than negative sentiment.
4
Buy transactions
4
Sell transactions
1.00
Buy/Sell ratio
$0M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
Rajavelu Esther See Remarks | May 4, 2026 | Sale | 25,240 | $2.51 | $63.4K | 986.9K | Form 4 ↗ |
Rajavelu Esther See Remarks | Feb 6, 2026 | Sale | 37,101 | $2.36 | $87.6K | 1.06M | Form 4 ↗ |
Rajavelu Esther See Remarks | Feb 6, 2026 | Sale | 50,816 | $2.36 | $119.9K | 1.01M | Form 4 ↗ |
Keutzer Timothy Chief Operating Officer | Feb 6, 2026 | Sale | 18,652 | $2.36 | $44.0K | 742.5K | Form 4 ↗ |
Keutzer Timothy Chief Operating Officer | Feb 2, 2026 | Award | 68,000 | — | — | 807.7K | Form 4 ↗ |
Keutzer Timothy Chief Operating Officer | Feb 2, 2026 | Sale | 18,891 | $2.20 | $41.6K | 788.9K | Form 4 ↗ |
Keutzer Timothy Chief Operating Officer | Feb 3, 2026 | Sale | 24,224 | $2.14 | $51.8K | 764.6K | Form 4 ↗ |
Keutzer Timothy Chief Operating Officer | Feb 4, 2026 | Sale | 3,471 | $2.24 | $7.8K | 761.2K | Form 4 ↗ |
Keutzer Timothy Chief Operating Officer | Feb 2, 2026 | Award | 137,000 | $2.23 | $305.5K | 137.0K | Form 4 ↗ |
Rajavelu Esther See Remarks | Feb 2, 2026 | Award | 249,000 | — | — | 1.12M | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Spero Therapeutics, Inc. (SPRO) is primarily owned by institutional investors, who hold approximately 19.5% of total shares outstanding. Company insiders own approximately 19.65%, while retail and public investors account for the remaining 60.81%.
The largest institutional shareholder of Spero Therapeutics, Inc. is PFIZER INC, holding approximately 2.36 million shares — equal to 4.22% of outstanding shares — as of September 30, 2025.
A total of 49 institutional investors currently hold SPRO stock, with a combined institutional value of approximately $21,264,964 as of the most recent 13F filing period.
Frequently asked questions
SPRO ownershipSpero Therapeutics, Inc. (SPRO) is primarily owned by institutional investors, who hold approximately 19.5% of shares. The largest shareholder is PFIZER INC with a 4.22% stake. Company insiders hold 19.65%. Data sourced from SEC Form 13F as of September 30, 2025.