IONIS PHARMACEUTICALS (IONS) — Institutional Holders & Hedge Fund Ownership
IONIS PHARMACEUTICALS (IONS) institutional ownership: 6 hedge funds and institutional investors, holding 8.4M shares ($631.1M), as of Q1 2026, per SEC Form 13F-HR filings.
IONIS PHARMACEUTICALS (IONS) appears in the 13F portfolios of dozens of professional money managers each quarter; the aggregated filings surface top buyers, top sellers, and conviction-weighted holders for IONS. Pactolio aggregates these SEC Form 13F-HR filings into one view: top institutional holders, biggest QoQ buyers and sellers, and consolidated ownership changes for IONS.
The top IONS shareholders by portfolio weight are Tweedy Browne (13.57%), Exome Asset Management (4.86%), and Deep Track (3.02%). In Q1 2026, Tetragon Financial Group made the largest position increase (+0.62%).
Top 6 Institutional Holders of IONIS PHARMACEUTICALS (IONS) — Q1 2026
| # | Fund | Shares | Market Value | Portfolio Weight |
|---|---|---|---|---|
| 1 | Tweedy Browne | 2,275,625 | $170.9M | 13.57% |
| 2 | Exome Asset Management | 110,064 | $8.3M | 4.86% |
| 3 | Deep Track | 1,950,000 | $146.4M | 3.02% |
| 4 | Deerfield | 1,979,669 | $148.7M | 1.75% |
| 5 | Baker Bros. Advisors | 2,047,727 | $153.8M | 0.88% |
| 6 | Tetragon Financial Group | 41,764 | $3.1M | 0.62% |
- 6Hedge funds holding
- 8,404,849Shares held (disclosed)
- $631.1M13F market value
- 2.39%Median portfolio weight
Ownership History
Quarter-by-quarter share count, market value, and portfolio conviction weight (up to 5 of the heaviest weight-by-portfolio funds) of IONS. Sourced from 13F filings; reflects long equity positions only.
Quarter-over-Quarter ActivityQ1 2026
The biggest weight-increase and weight-decrease changes among funds that hold IONS. Deltas compare the selected filing to the previous reporting quarter.
Top buyers
- Tetragon Financial Group+0.62% · +41,764 shares
- Baker Bros. Advisors+0.05% · +255,886 shares
- Deep Track+-0.05% · +250,000 shares
Top sellers
- Tweedy Browne-2.17% · -189,305 shares
- Exome Asset Management0.31% · -6,451 shares
Ownership Statistics
- Funds holding
- 6
- Median weight
- 2.39%
- Largest holder
- Tweedy Browne · 13.57%
- Smallest holder
- Tetragon Financial Group · 0.62%
- Shares held
- 8,404,849 (+351,894)
All Institutional HoldersSortable · searchable
All institutional investors (Max 50) holding IONS in the selected quarter. Click a fund name to drill into its full 13F portfolio.
| 1 | Tweedy Browne | 2,275,625 | $170.9M | 13.57% |
| 2 | Exome Asset Management | 110,064 | $8.3M | 4.86% |
| 3 | Deep Track | 1,950,000 | $146.4M | 3.02% |
| 4 | Deerfield | 1,979,669 | $148.7M | 1.75% |
| 5 | Baker Bros. Advisors | 2,047,727 | $153.8M | 0.88% |
| 6 | Tetragon Financial Group | 41,764 | $3.1M | 0.62% |
Methodology & FAQ
Methodology: How We Track IONS Institutional Holdings
Our data is systematically aggregated directly from quarterly Form 13F-HR disclosures submitted to the U.S. Securities and Exchange Commission (SEC).
- Who Must File (Reporting Threshold): This dataset includes filings from U.S. institutional investment managers, hedge funds, mutual funds, university endowments, and family offices managing at least $100 million in Section 13(f) securities (including equities, options, convertibles, ETFs, and warrants).
- What is Included (Data Scope): We capture long positions in Section 13(f) securities for IONIS PHARMACEUTICALS INC. (IONS). By SEC regulation, 13F filings do not require the disclosure of short positions, non-U.S. holdings, or OTC derivatives. Listed options are excluded from portfolio weight calculations to ensure comparability across filers.
- Portfolio Weight Explained (Metric Definition): “Portfolio Weight” shows how much of a fund's total reported 13F portfolio value (excluding listed options) is allocated to IONS on the specific reporting date.
- How to Use This Data (Interpretation): Quarter-over-quarter changes in shares and portfolio weight reflect a combination of active trading and market price movements. These are descriptive metrics of fund allocation, not explicit buy or sell signals.
How do you measure hedge fund conviction and institutional concentration in IONS?
We evaluate fund conviction by looking at portfolio weight rather than just absolute share count. By tracking how the largest holders —such as Tweedy Browne , Exome Asset Management , and Deep Track as of Q1 2026— change their position sizing quarter-over-quarter, we help investors distinguish between deliberate position sizing changes and passive mark-to-market drift.
Does the IONS ownership data include short interest or options?
SEC Form 13F mandates the disclosure of long positions in Section 13(f) securities, which includes equities and listed options (put and call contracts), but excludes short interest, swaps, and OTC derivatives by regulatory design. On this platform, listed options are excluded from portfolio weight calculations to ensure comparability across filers.
Are family offices and university endowments included in this IONS data?
Yes. In addition to traditional hedge funds and large asset managers, any institutional entity exercising investment discretion over at least $100 million in Section 13(f) securities must file a Form 13F. This explicitly includes single-family offices and university endowments. If a qualifying family office or endowment holds IONS stock, their allocation is systematically aggregated alongside traditional fund data.
When is the institutional ownership data updated, and is there a reporting lag?
Institutional investment managers are required to file their Form 13F within 45 days after the end of a calendar quarter (the standard “T+45” window). Our platform re-ingests new filings from the SEC EDGAR database on a nightly cycle, typically within 24–48 hours of publication, providing a point-in-time snapshot of reported consensus positioning for IONS as of each filing date.