Ionis Pharmaceuticals, Inc.
Ionis Pharmaceuticals, Inc. (IONS) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · IONS · as of Mar 31, 2025
Ownership Breakdown
369
Institutional Holders
▼ 16 vs Q4
$5.03B
Total Inst. Value
▼ $579.76M vs Q4
165.26M
Shares Outstanding
freeFloat 98.06%
167.22M
13F Shares Held
▲ 6.24M vs Q4
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
IONS largest shareholders · institutional ownership
Q1 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
FMR LLC pharmaceutical preparations | 23.61M | 14.88% | 14.88% | $712.42B | May 12, 2025 | ▲ 924.1K |
VANGUARD GROUP INC pharmaceutical preparations | 16.38M | 10.32% | 10.32% | $494.30B | May 9, 2025 | ▼ 88.6K |
T. ROWE PRICE INVESTMENT MANAGEMENT, INC. pharmaceutical preparations | 16.18M | 10.19% | 10.19% | $488.02B | May 14, 2025 | ▲ 2.01M |
CAPITAL WORLD INVESTORS pharmaceutical preparations | 12.36M | 7.79% | 7.79% | $372.96B | May 12, 2025 | ▲ 896.6K |
BLACKROCK, INC. pharmaceutical preparations | 11.26M | 7.10% | 7.10% | $339.85B | May 2, 2025 | ▼ 401.1K |
WELLINGTON MANAGEMENT GROUP LLP pharmaceutical preparations | 8.42M | 5.30% | 5.30% | $253.92B | May 13, 2025 | ▼ 255.7K |
BELLEVUE GROUP AG pharmaceutical preparations | 7.85M | 4.95% | 4.95% | $236.93B | May 14, 2025 | ▼ 15.5K |
STATE STREET CORP pharmaceutical preparations | 4.85M | 3.05% | 3.05% | $146.18B | May 15, 2025 | ▼ 581.3K |
DEEP TRACK CAPITAL, LP pharmaceutical preparations | 4.56M | 2.88% | 2.88% | $137.70B | May 15, 2025 | ▲ 2.63M |
CITADEL ADVISORS LLC pharmaceutical preparations | 3.48M | 2.19% | 2.19% | $104.99B | May 15, 2025 | ▲ 1.31M |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q1 2025 vs prior quarter
Q1 2025
29
Increased
+15.41M shares0
New Positions
first time holders20
Decreased
−3.96M shares0
Sold Out
fully exitedNet shares change (top 50)
+11.44M
+15.41M / −3.96M
Net new holders
+9
0 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
IONS 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.
14
Buy transactions
29
Sell transactions
0.48
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 |
|---|---|---|---|---|---|---|---|
BERTHELSEN SPENCER R director | Jun 1, 2026 | Sale | 8,000 | $75.67 | $605.4K | 156.0K | Form 4 ↗ |
Monia Brett P Chief Executive Officer | May 13, 2026 | Sale | 1,316 | $78.01 | $102.7K | 242.7K | Form 4 ↗ |
Monia Brett P Chief Executive Officer | May 14, 2026 | Sale | 3,220 | $78.68 | $253.3K | 242.7K | Form 4 ↗ |
LOSCALZO JOSEPH director | May 4, 2026 | Sale | 59,508 | $74.90 | $4.46M | 54.1K | Form 4 ↗ |
LOSCALZO JOSEPH director | May 4, 2026 | Sale | 17,781 | $75.58 | $1.34M | 36.3K | 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
Ionis Pharmaceuticals, Inc. (IONS) is primarily owned by institutional investors, who hold approximately 100.0% of total shares outstanding. Company insiders own approximately 1.94%, while retail and public investors account for the remaining 0.00%.
The largest institutional shareholder of Ionis Pharmaceuticals, Inc. is FMR LLC, holding approximately 23.61 million shares — equal to 14.88% of outstanding shares — as of March 31, 2025.
A total of 369 institutional investors currently hold IONS stock, with a combined institutional value of approximately $5.03 billion as of the most recent 13F filing period.
Frequently asked questions
IONS ownershipIonis Pharmaceuticals, Inc. (IONS) is primarily owned by institutional investors, who hold approximately 100.0% of shares. The largest shareholder is FMR LLC with a 14.88% stake. Company insiders hold 1.94%. Data sourced from SEC Form 13F as of March 31, 2025.