Mar 31, 2026 filings. Quarterly 13F reports arrive up to 45 days after quarter end; this register is filed through May 29, 2026.
296 institutional managers reported holding MIRM for the quarter ended Mar 31, 2026. Reported positions total over 95% of shares outstanding; the top 10 hold 55%. 60 opened new positions; 31 closed out. Complete ranked register from SEC 13F filings.
| manager | shares | % out | value (Mar 31, 2026 close) | change | held since |
|---|---|---|---|---|---|
| Frazier Life Sciences Management, L.p. (focused) | 7.68M | 13.05% | $709.6M | added +13% | 2022 Q1 |
| Janus Henderson | 6.79M | 11.54% | $627.3M | added +11.9% | 2023 Q1 |
| Vanguard Group | 4.24M | 7.20% | $391.4M | added +63.2% | 2019 Q3 |
| BlackRock | 3.85M | 6.54% | $355.4M | added +5.5% | 2019 Q3 |
| FMR (Fidelity) | 1.97M | 3.34% | $181.6M | added +204% | 2022 Q1 |
| State Street | 1.94M | 3.30% | $179.7M | trimmed -9.3% | 2019 Q3 |
| T. Rowe Price | 1.72M | 2.92% | $158.7M | added +20.9% | 2022 Q3 |
| BVF INC/IL (focused) | 1.58M | 2.69% | $146.4M | added +6% | 2023 Q3 |
| Eventide Asset Management, LLC | 1.41M | 2.39% | $130.2M | trimmed -32.7% | 2022 Q3 |
| Wellington Management | 1.33M | 2.27% | $123.3M | added +7.8% | 2024 Q1 |
| Novo Holdings A/S (focused) | 1.32M | 2.25% | $122.4M | added +4.8% | 2019 Q3 |
| Geode Capital | 1.26M | 2.14% | $116.4M | added +18.5% | 2019 Q3 |
| Tang Capital Management LLC | 1.24M | 2.10% | $114.2M | unchanged | 2022 Q2 |
| BNP Paribas Financial Markets | 1.18M | 2.00% | $108.8M | added +28.9% | 2024 Q4 |
| TCG Crossover Management, LLC (focused) | 1.06M | 1.80% | $98.1M | added +1611.6% | 2025 Q4 |
| Citadel Advisors | 1.05M | 1.79% | $97.2M | added +25.2% | 2021 Q3 |
| Rock Springs Capital Management LP | 811.3k | 1.38% | $75.0M | added +6.4% | 2019 Q3 |
| Two Sigma | 774.8k | 1.32% | $71.6M | added +99.4% | 2023 Q2 |
| Capital Group (American Funds) | 724.4k | 1.23% | $66.9M | opened | 2026 Q1 |
| Bank OF America CORP /DE/ | 722.2k | 1.23% | $66.7M | added +1.2% | 2019 Q3 |
| Franklin Resources | 714.8k | 1.22% | $66.0M | added +9.8% | 2021 Q4 |
| Clearbridge Investments, LLC | 671.9k | 1.14% | $62.1M | trimmed -22.4% | 2022 Q1 |
| Goldman Sachs | 662.3k | 1.13% | $61.2M | trimmed -8.6% | 2021 Q4 |
| Paradigm Biocapital Advisors LP (focused) | 625.0k | 1.06% | $57.8M | opened | 2026 Q1 |
| Lord, Abbett & CO. LLC | 617.1k | 1.05% | $57.0M | added +6.4% | 2024 Q3 |
| BNY Mellon | 584.5k | 0.99% | $54.0M | added +3.3% | 2019 Q4 |
| Renaissance Technologies | 582.1k | 0.99% | $53.8M | added +32.6% | 2024 Q3 |
| Woodline Partners LP | 567.9k | 0.96% | $52.5M | unchanged | 2022 Q3 |
| UBS | 561.6k | 0.95% | $51.9M | added +47.8% | 2022 Q3 |
| Balyasny Asset Management | 539.0k | 0.92% | $49.8M | added +88.6% | 2024 Q4 |
| Morgan Stanley | 524.6k | 0.89% | $48.5M | added +23.2% | 2019 Q3 |
| Federated Hermes, INC. | 506.2k | 0.86% | $46.8M | added +5% | 2022 Q1 |
| Connor, Clark & Lunn Investment Management LTD. | 479.5k | 0.81% | $44.3M | trimmed -8.1% | 2023 Q2 |
| Loomis Sayles & CO L P | 475.3k | 0.81% | $43.9M | trimmed -7.7% | 2024 Q3 |
| Nuveen | 474.2k | 0.81% | $43.8M | trimmed -5.7% | 2020 Q2 |
| Candriam S.c.a. | 464.2k | 0.79% | $42.9M | trimmed -18.5% | 2024 Q2 |
| Baker Bros. Advisors LP | 446.0k | 0.76% | $41.2M | opened | 2026 Q1 |
| Charles Schwab Investment Management | 427.1k | 0.73% | $39.5M | added +4.4% | 2020 Q1 |
| Nomura Asset Management International INC. | 424.9k | 0.72% | $39.3M | trimmed -1.6% | 2025 Q4 |
| Pictet Asset Management Holding SA | 423.5k | 0.72% | $39.1M | trimmed -26.6% | 2023 Q1 |
| Boone Capital Management LLC (focused) | 421.2k | 0.72% | $38.9M | unchanged | 2023 Q3 |
| First Turn Management, LLC (focused) | 400.5k | 0.68% | $37.0M | trimmed -16.8% | 2023 Q4 |
| Soleus Capital Management, L.p. | 400.3k | 0.68% | $37.0M | trimmed -30.2% | 2025 Q2 |
| Emerald Advisers, LLC | 397.3k | 0.68% | $36.7M | added +8.2% | 2025 Q2 |
| Northern Trust | 394.9k | 0.67% | $36.5M | added +5.4% | 2019 Q3 |
| Next Century Growth Investors LLC | 385.5k | 0.66% | $35.6M | added +4.8% | 2024 Q3 |
| TimesSquare Capital Management, LLC | 376.5k | 0.64% | $34.8M | trimmed -4.9% | 2025 Q3 |
| Adage Capital Partners GP, L.l.c. | 375.0k | 0.64% | $34.6M | trimmed -19.8% | 2023 Q3 |
| Millennium Management | 368.6k | 0.63% | $34.1M | added +50.9% | 2023 Q1 |
| Point72 | 347.0k | 0.59% | $32.1M | added +82% | 2024 Q4 |
Largest 50 of 296 shown; the full ranked, searchable register is at boothcheck.com/holders/MIRM. 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.