Who holds it, who is betting against it, and where the big money is moving
Net of large-order buying minus selling, in USD. Over this window: −$554.4K (12 inflow days, 8 outflow days).
Super/Big orders approximate institutional-size trades; Mid/Small approximate retail-size trades. Net buy minus sell value in each bucket, summed over the window.
The five largest holders on file together own 53.5% of shares outstanding.
Reported short interest has risen from 8.90% to 14.81% of float over the last 6 biweekly reports (30 Jun 2026 to 15 Sep 2026).
| Holder | Type | Period | Share change | New stake |
|---|---|---|---|---|
| RA Capital Management, L.P. | VC/PE Fund | 2026/Q3 | +1,239,063 | 21.8% |
| Stephen Thomas | Individual/Insider | 2026/Q3 | +313,312 | 0.8% |
| FMR | Mutual Fund | 2026/Q3 | +6,783,967 | 11.8% |
| UBS Asset Management | Mutual Fund | 2026/Q3 | +3,318,921 | 5.9% |
| Adage Capital Management, L.P. | Hedge Fund | 2026/Q3 | +2,506,000 | 4.4% |
| Cormorant Asset Management, LP | Hedge Fund | 2026/Q3 | +2,106,000 | 3.7% |
| BlackRock | Mutual Fund | 2026/Q3 | +1,953,223 | 4.1% |
| Frontier Capital Management | Mutual Fund | 2026/Q3 | +1,939,019 | 3.4% |
| Woodline Partners LP | Hedge Fund | 2026/Q3 | +1,582,291 | 2.8% |
| Braidwell LP | Hedge Fund | 2026/Q3 | +1,267,700 | 4.9% |
| Redmile Group, LLC | Hedge Fund | 2026/Q3 | +1,226,330 | 2.1% |
| Citadel Advisors LLC | Hedge Fund | 2026/Q3 | +952,309 | 2.3% |
| StemPoint Capital LP | Hedge Fund | 2026/Q3 | +742,745 | 1.3% |
| Parkman Healthcare Partners LLC | Hedge Fund | 2026/Q3 | +563,484 | 1.0% |
| Vanguard Capital Management, LLC | Mutual Fund | 2026/Q3 | +556,376 | 3.3% |
Institutional buy/sell activity by reporting period, largest moves first.
| Date | Insider | Title | Transaction | Shares | Price | Held after |
|---|---|---|---|---|---|---|
| 27 Sep 2026 | Andrew Levin | Principal Financial Officer & Executive Chairman | Derivative Exercise and Retained | +70,000 | $7.89 | 70,000 |
| 14 Sep 2026 | Stephen Thomas | Director | Automatic Disposition | -100,000 | $13.67 | 467,969 |
| 28 Jun 2026 | RA Capital Management, L.P. | Other Derivative Acquisition | +70,284 | $13.36 | 70,284 | |
| 28 Jun 2026 | Aoife Brennan | Chief Executive Officer | Intent to Sell (Form 144) | -30,902 | $13.17 | – |
| 28 Jun 2026 | Aoife Brennan | Chief Executive Officer | Derivative Exercise and Sale | -30,902 | $13.17 | 87,731 |
| 26 Jun 2026 | Aoife Brennan | Chief Executive Officer | Derivative Exercise and Retained | +37,848 | – | 87,731 |
| 4 Jun 2026 | Douglas Williams | Chair of Board | Other Derivative Acquisition | +40,000 | $10.55 | 40,000 |
| 4 Jun 2026 | Kimberlee Drapkin | Independent Director | Other Derivative Acquisition | +40,000 | $10.55 | 40,000 |
| 4 Jun 2026 | RA Capital Management, L.P. | Other Derivative Acquisition | +40,000 | $10.55 | 40,000 | |
| 4 Jun 2026 | Andrew Levin | Principal Financial Officer & Executive Chairman | Other Derivative Acquisition | +40,000 | $10.55 | 40,000 |
| 4 Jun 2026 | Alexander Cumbo | Independent Director | Other Derivative Acquisition | +40,000 | $10.55 | 40,000 |
| 4 Jun 2026 | Stephen Thomas | Director | Other Derivative Acquisition | +40,000 | $10.55 | 40,000 |
| 4 Jun 2026 | Judith Dunn | Independent Director | Other Derivative Acquisition | +40,000 | $10.55 | 40,000 |
| 28 Apr 2026 | RA Capital Management, L.P. | Other Derivative Acquisition | +2,106,000 | $0.00 | 22,546,000 | |
| 25 Feb 2026 | Stephen Thomas | Director | Automatic Disposition | -50,000 | $7.01 | 154,657 |
| 24 Feb 2026 | Stephen Thomas | Director | Intent to Sell (Form 144) | -50,000 | $6.36 | – |
| 12 Feb 2026 | Stephen Thomas | Director | Automatic Disposition | -100,000 | $5.81 | 204,657 |
| 11 Feb 2026 | Stephen Thomas | Director | Intent to Sell (Form 144) | -100,000 | $5.56 | – |
| 5 Jan 2026 | Cindy Driscoll | Officer | Other Derivative Acquisition | +100,000 | $3.81 | 100,000 |
| 5 Jan 2026 | Aoife Brennan | Chief Executive Officer | Other Derivative Acquisition | +700,000 | $3.81 | 700,000 |
From Form 4/Form 144 filings. Negative share counts are disposals (sales, gifts, or shares withheld for taxes); positive are acquisitions.
| Report date | Shares short | % of float | Days to cover |
|---|---|---|---|
| 15 Sep 2026 | 8,508,354 | 14.8% | 4.5 |
| 31 Aug 2026 | 7,300,939 | 12.7% | 5.9 |
| 14 Aug 2026 | 7,557,264 | 13.2% | 6.3 |
| 31 Jul 2026 | 7,037,695 | 12.3% | 6.8 |
| 15 Jul 2026 | 6,871,210 | 12.0% | 5.1 |
| 30 Jun 2026 | 5,096,670 | 8.9% | 3.0 |
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