Mar 31, 2026 filings. Quarterly 13F reports arrive up to 45 days after quarter end; this register is filed through May 29, 2026.
478 institutional managers reported holding IONS for the quarter ended Mar 31, 2026. Reported positions total over 95% of shares outstanding; the top 10 hold 62%. 65 opened new positions; 72 closed out. Complete ranked register from SEC 13F filings.
| manager | shares | % out | value (Mar 31, 2026 close) | change | held since |
|---|---|---|---|---|---|
| FMR (Fidelity) | 24.56M | 14.89% | $1.84B | added +2% | 2015 Q4 |
| Capital Group (American Funds) | 21.19M | 12.85% | $1.59B | added +18% | 2023 Q2 |
| Vanguard Group | 16.21M | 9.83% | $1.22B | trimmed -1.5% | 2015 Q4 |
| BlackRock | 10.44M | 6.33% | $784.0M | trimmed -1.9% | 2015 Q4 |
| Wellington Management | 6.39M | 3.88% | $479.9M | added +2.1% | 2023 Q2 |
| T. Rowe Price Investment Management, INC. | 6.16M | 3.74% | $462.4M | added +6.4% | 2022 Q3 |
| Two Sigma | 5.86M | 3.55% | $439.8M | added +120.3% | 2017 Q2 |
| State Street | 4.00M | 2.42% | $300.0M | added +0.5% | 2015 Q4 |
| Geode Capital | 3.98M | 2.42% | $299.1M | added +26.5% | 2015 Q4 |
| Royal Bank OF Canada | 3.80M | 2.31% | $285.4M | added +239.8% | 2015 Q4 |
| T. Rowe Price | 3.03M | 1.83% | $227.1M | added +1.3% | 2015 Q4 |
| UBS | 2.28M | 1.39% | $171.5M | trimmed -6.1% | 2015 Q4 |
| Tweedy, Browne | 2.28M | 1.38% | $170.9M | trimmed -7.7% | 2022 Q1 |
| Artisan Partners | 2.06M | 1.25% | $154.5M | added +74.2% | 2024 Q1 |
| Baker Bros. Advisors LP | 2.05M | 1.24% | $153.7M | added +14.3% | 2024 Q3 |
| Deerfield Management Company, L.p. | 1.98M | 1.20% | $148.6M | unchanged | 2025 Q3 |
| Deep Track Capital, LP | 1.95M | 1.18% | $146.4M | added +14.7% | 2022 Q4 |
| Bellevue Group AG | 1.82M | 1.10% | $136.5M | trimmed -62.1% | 2015 Q4 |
| Goldman Sachs | 1.70M | 1.03% | $127.6M | added +98.6% | 2015 Q4 |
| American Century Companies INC | 1.66M | 1.01% | $124.9M | added +2.9% | 2015 Q4 |
| Charles Schwab Investment Management | 1.58M | 0.96% | $118.9M | added +2.7% | 2015 Q4 |
| Franklin Resources | 1.58M | 0.95% | $118.3M | added +19.2% | 2022 Q3 |
| Pictet Asset Management Holding SA | 1.43M | 0.87% | $107.7M | added +1.2% | 2018 Q2 |
| Summit Partners Public Asset Management, LLC | 1.40M | 0.85% | $105.4M | trimmed -4% | 2025 Q3 |
| BNP Paribas Financial Markets | 1.39M | 0.84% | $104.1M | trimmed -17.8% | 2015 Q4 |
| Invesco | 1.28M | 0.78% | $95.9M | added +0.6% | 2015 Q4 |
| Millennium Management | 1.05M | 0.64% | $78.9M | added +1027.5% | 2016 Q1 |
| Morgan Stanley | 1.03M | 0.62% | $77.1M | added +0.6% | 2015 Q4 |
| Citadel Advisors | 942.5k | 0.57% | $70.8M | trimmed -55.8% | 2016 Q1 |
| Nomura Asset Management International INC. | 899.4k | 0.55% | $67.5M | trimmed -47.5% | 2020 Q4 |
| Connor, Clark & Lunn Investment Management LTD. | 874.1k | 0.53% | $65.6M | trimmed -18.8% | 2021 Q1 |
| Northern Trust | 868.2k | 0.53% | $65.2M | added +2.5% | 2015 Q4 |
| Bank OF America CORP /DE/ | 840.6k | 0.51% | $63.1M | added +7.3% | 2015 Q4 |
| Polar Capital Holdings PLC | 829.5k | 0.50% | $62.3M | trimmed -37.8% | 2025 Q2 |
| Groupama Asset Managment | 824.5k | 0.50% | $61.9M | added +7.5% | 2023 Q4 |
| Gw&k Investment Management, LLC | 779.3k | 0.47% | $58.5M | trimmed -0.9% | 2024 Q4 |
| Arrowstreet Capital | 737.9k | 0.45% | $55.4M | trimmed -30.6% | 2025 Q3 |
| Squarepoint Ops LLC | 695.3k | 0.42% | $52.2M | added +59.4% | 2018 Q4 |
| Voloridge Investment Management | 672.9k | 0.41% | $50.5M | added +15% | 2022 Q4 |
| MFS Investment Management | 666.1k | 0.40% | $50.0M | trimmed -18% | 2025 Q2 |
| Ameriprise Financial INC | 660.1k | 0.40% | $49.6M | added +10.3% | 2016 Q4 |
| Nuveen | 648.5k | 0.39% | $48.7M | trimmed -1.9% | 2015 Q4 |
| Eversept Partners, LP | 632.1k | 0.38% | $47.5M | added +17.4% | 2021 Q2 |
| Eventide Asset Management, LLC | 575.0k | 0.35% | $43.2M | unchanged | 2025 Q4 |
| TD Asset Management INC | 530.0k | 0.32% | $39.8M | trimmed -31.5% | 2015 Q4 |
| Teacher Retirement System OF Texas | 523.9k | 0.32% | $39.3M | added +23.9% | 2019 Q2 |
| BNY Mellon | 514.6k | 0.31% | $38.6M | trimmed -4.3% | 2015 Q4 |
| Perceptive Advisors LLC | 504.0k | 0.31% | $37.8M | opened | 2026 Q1 |
| Boone Capital Management LLC (focused) | 500.5k | 0.30% | $37.6M | added +19.8% | 2025 Q3 |
| Candriam S.c.a. | 484.1k | 0.29% | $36.3M | trimmed -28.6% | 2015 Q4 |
Largest 50 of 478 shown; the full ranked, searchable register is at boothcheck.com/holders/IONS. Related filers are grouped using the filings' own included-manager declarations. Historically, several managers opening new positions in the same quarter said almost nothing about the quarter that followed (59,118 cases since 2013). A filed record, not a forecast. Nothing here is investment advice.