Atossa Therapeutics, Inc.
Atossa Therapeutics, Inc. (ATOS) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · ATOS · as of Sep 30, 2025
Ownership Breakdown
71
Institutional Holders
▼ 15 vs Q2
$17.06M
Total Inst. Value
▼ $663,479 vs Q2
8.61M
Shares Outstanding
freeFloat 99.60%
19.55M
13F Shares Held
▼ 1.80M 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
ATOS largest shareholders · institutional ownership
Q3 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
VANGUARD GROUP INC pharmaceutical preparations | 6.08M | 4.71% | 4.71% | $5.27B | Nov 7, 2025 | ▲ 245.7K |
AMERIPRISE FINANCIAL INC pharmaceutical preparations | 2.95M | 2.29% | 2.29% | $2.56B | Nov 14, 2025 | ▼ 21.7K |
BLACKROCK, INC. pharmaceutical preparations | 2.00M | 1.55% | 1.55% | $1.73B | Nov 12, 2025 | ▼ 150.4K |
MILLENNIUM MANAGEMENT LLC pharmaceutical preparations | 1.67M | 1.29% | 1.29% | $1.45B | Nov 14, 2025 | ▼ 378.9K |
RENAISSANCE TECHNOLOGIES LLC pharmaceutical preparations | 1.55M | 1.20% | 1.20% | $1.34B | Nov 13, 2025 | ▼ 263.6K |
GEODE CAPITAL MANAGEMENT, LLC pharmaceutical preparations | 1.36M | 1.05% | 1.05% | $1.18B | Nov 12, 2025 | ▲ 61.9K |
STATE STREET CORP pharmaceutical preparations | 454.5K | 35.19% | 35.19% | $394.05M | Nov 14, 2025 | ▼ 62.1K |
GSA CAPITAL PARTNERS LLP pharmaceutical preparations | 310.8K | 24.06% | 24.06% | $269.00M | Nov 7, 2025 | ▲ 259.7K |
NORTHERN TRUST CORP pharmaceutical preparations | 263.4K | 20.39% | 20.39% | $228.35M | Nov 14, 2025 | — held |
CITADEL ADVISORS LLC pharmaceutical preparations | 263.4K | 20.39% | 20.39% | $228.34M | Nov 14, 2025 | ▲ 176.5K |
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
17
Increased
+1.27M shares4
New Positions
first time holders17
Decreased
−1.94M shares0
Sold Out
fully exitedNet shares change (top 50)
668.9K
+1.27M / −1.94M
Net new holders
+4
4 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
ATOS insider trading · insider activity
Source: SEC Form 4
Insiders have been net buyers of shares recently. Selling may be driven by pre-scheduled Rule 10b5-1 plans rather than negative sentiment.
6
Buy transactions
0
Sell transactions
0.00
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 |
|---|---|---|---|---|---|---|---|
Steinhart Richard I director | May 12, 2026 | Award | 10,000 | — | — | 10.0K | Form 4 ↗ |
Chen Shu-Chih director | May 12, 2026 | Award | 10,000 | — | — | 10.0K | Form 4 ↗ |
Remmel H. Lawrence director | May 12, 2026 | Award | 10,000 | — | — | 10.7K | Form 4 ↗ |
Finn Jonathan director | May 12, 2026 | Award | 10,000 | — | — | 11.7K | Form 4 ↗ |
Galli Stephen J director | May 12, 2026 | Award | 10,000 | — | — | 10.0K | Form 4 ↗ |
Cigler Tessa director | May 12, 2026 | Award | 10,000 | — | — | 10.0K | Form 4 ↗ |
QUAY STEVEN C President & CEO | Mar 27, 2026 | Award | 65,000 | — | — | 88.0K | Form 4 ↗ |
Daniel Mark James Chief Financial Officer | Mar 26, 2026 | Award | 63,000 | — | — | 63.0K | Form 4 ↗ |
QUAY STEVEN C President & CEO | Jan 20, 2026 | Award | 331,674 | — | — | 345.6K | Form 4 ↗ |
QUAY STEVEN C President & CEO | Jan 20, 2026 | Award | 950,000 | $0.60 | $572.9K | 950.0K | 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
Atossa Therapeutics, Inc. (ATOS) is primarily owned by institutional investors, who hold approximately 100.0% of total shares outstanding. Company insiders own approximately 0.40%, while retail and public investors account for the remaining 0.00%.
The largest institutional shareholder of Atossa Therapeutics, Inc. is VANGUARD GROUP INC, holding approximately 6.08 million shares — equal to 4.71% of outstanding shares — as of September 30, 2025.
A total of 71 institutional investors currently hold ATOS stock, with a combined institutional value of approximately $17,056,094 as of the most recent 13F filing period.
Frequently asked questions
ATOS ownershipAtossa Therapeutics, Inc. (ATOS) is primarily owned by institutional investors, who hold approximately 100.0% of shares. The largest shareholder is VANGUARD GROUP INC with a 4.71% stake. Company insiders hold 0.40%. Data sourced from SEC Form 13F as of September 30, 2025.