Mar 31, 2026 filings. Quarterly 13F reports arrive up to 45 days after quarter end; this register is filed through May 29, 2026.
468 institutional managers reported holding ARGX for the quarter ended Mar 31, 2026. Together they hold about 47% of shares outstanding; the top 10 hold 31%. 64 opened new positions; 98 closed out. Complete ranked register from SEC 13F filings.
| manager | shares | % out | value (Mar 31, 2026 close) | change | held since |
|---|---|---|---|---|---|
| FMR (Fidelity) | 4.99M | 8.14% | $3.65B | trimmed -10.8% | 2017 Q2 |
| T. Rowe Price | 3.37M | 5.51% | $2.47B | unchanged | 2017 Q2 |
| Janus Henderson | 2.54M | 4.15% | $1.86B | added +3.4% | 2017 Q4 |
| Capital Group (American Funds) | 2.26M | 3.68% | $1.65B | added +17.7% | 2019 Q1 |
| Artisan Partners | 1.47M | 2.40% | $1.07B | trimmed -16.4% | 2018 Q3 |
| Wellington Management | 1.02M | 1.67% | $746.3M | added +50.4% | 2019 Q4 |
| Avoro Capital Advisors LLC (focused) | 1.00M | 1.63% | $730.6M | added +1% | 2017 Q2 |
| BlackRock | 808.3k | 1.32% | $590.6M | added +9.9% | 2017 Q4 |
| RTW Investments, LP | 709.4k | 1.16% | $518.3M | added +5.3% | 2017 Q2 |
| Invesco | 594.7k | 0.97% | $434.5M | added +42.8% | 2020 Q2 |
| Morgan Stanley | 560.7k | 0.92% | $409.7M | added +8.1% | 2017 Q2 |
| AllianceBernstein | 422.3k | 0.69% | $308.5M | added +2% | 2022 Q1 |
| Bank OF America CORP /DE/ | 400.1k | 0.65% | $292.3M | unchanged | 2017 Q2 |
| Sands Capital | 340.3k | 0.56% | $248.6M | trimmed -4.6% | 2025 Q3 |
| Bellevue Group AG | 313.0k | 0.51% | $228.7M | trimmed -32.2% | 2018 Q4 |
| BNP Paribas Financial Markets | 307.0k | 0.50% | $224.3M | added +65% | 2021 Q4 |
| SEI Investments CO | 287.0k | 0.47% | $209.7M | trimmed -13.2% | 2019 Q1 |
| William Blair Investment Management, LLC | 266.1k | 0.43% | $194.4M | added +19% | 2025 Q4 |
| Jennison Associates LLC | 237.5k | 0.39% | $173.5M | added +3.4% | 2017 Q2 |
| Franklin Resources | 233.5k | 0.38% | $170.6M | trimmed -1.8% | 2017 Q2 |
| Goldman Sachs | 232.0k | 0.38% | $169.5M | added +38.8% | 2018 Q3 |
| Clearbridge Investments, LLC | 231.4k | 0.38% | $169.0M | trimmed -55% | 2021 Q1 |
| Citadel Advisors | 219.1k | 0.36% | $160.1M | trimmed -37.5% | 2018 Q1 |
| Fiera Capital CORP | 217.2k | 0.35% | $158.7M | trimmed -3.9% | 2019 Q4 |
| Ameriprise Financial INC | 215.9k | 0.35% | $157.7M | added +15.4% | 2019 Q3 |
| Allspring Global Investments Holdings, LLC | 175.3k | 0.29% | $128.1M | added +1.5% | 2022 Q2 |
| American Century Companies INC | 173.7k | 0.28% | $126.9M | trimmed -21.4% | 2019 Q2 |
| Checkpoint Capital L.p. (focused) | 153.0k | 0.25% | $111.8M | added +7.7% | 2023 Q4 |
| Lord, Abbett & CO. LLC | 152.1k | 0.25% | $111.1M | trimmed -25.4% | 2024 Q3 |
| Legal & General Group PLC | 150.8k | 0.25% | $110.2M | added +4.5% | 2022 Q2 |
| Pictet Asset Management Holding SA | 148.3k | 0.24% | $108.4M | trimmed -3.2% | 2017 Q3 |
| Deutsche Bank AG\ | 139.4k | 0.23% | $101.8M | added +3.5% | 2017 Q3 |
| Bamco INC /NY/ | 138.6k | 0.23% | $101.3M | trimmed -9.8% | 2017 Q4 |
| Orbimed Advisors LLC | 136.9k | 0.22% | $100.0M | trimmed -6.2% | 2022 Q1 |
| Lazard Asset Management LLC | 133.3k | 0.22% | $97.4M | unchanged | 2020 Q3 |
| Eventide Asset Management, LLC | 125.7k | 0.20% | $91.8M | added +3.7% | 2018 Q1 |
| AGF Management LTD | 125.1k | 0.20% | $91.4M | unchanged | 2025 Q4 |
| Two Sigma | 109.1k | 0.18% | $79.7M | trimmed -57.8% | 2025 Q1 |
| First Trust Advisors LP | 107.2k | 0.17% | $78.3M | added +98.9% | 2023 Q3 |
| Pinebridge Investments LLC | 103.8k | 0.17% | $75.8M | added +44.1% | 2022 Q4 |
| Rock Springs Capital Management LP | 98.5k | 0.16% | $72.0M | trimmed -4.6% | 2018 Q2 |
| Federated Hermes, INC. | 95.3k | 0.15% | $69.6M | trimmed -10.8% | 2017 Q2 |
| Adage Capital Partners GP, L.l.c. | 90.0k | 0.15% | $65.8M | opened | 2026 Q1 |
| Bank OF Montreal /CAN/ | 85.3k | 0.14% | $62.3M | added +421.1% | 2022 Q4 |
| Braidwell LP | 84.9k | 0.14% | $62.1M | added +173.9% | 2023 Q4 |
| 1832 Asset Management L.p. | 84.2k | 0.14% | $61.5M | trimmed -23.9% | 2024 Q3 |
| TimesSquare Capital Management, LLC | 83.1k | 0.14% | $60.7M | trimmed -23.4% | 2018 Q1 |
| Aberdeen Group plc | 82.1k | 0.13% | $60.0M | added +56.8% | 2023 Q4 |
| TD Asset Management INC | 80.8k | 0.13% | $59.0M | trimmed -20.4% | 2017 Q4 |
| Eagle Health Investments LP (focused) | 76.3k | 0.13% | $55.8M | added +21.7% | 2020 Q4 |
Largest 50 of 468 shown; the full ranked, searchable register is at boothcheck.com/holders/ARGX. 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.