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: +$436.0K (7 inflow days, 13 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 36.3% of shares outstanding.
Reported short interest has risen from 0.37% to 0.45% of float over the last 3 biweekly reports (14 Aug 2026 to 15 Sep 2026).
| Holder | Type | Period | Share change | New stake |
|---|---|---|---|---|
| Columbia Management Investment Advisers, LLC | Mutual Fund | 2026/Q3 | +73,691 | 0.2% |
| Vanguard Capital Management, LLC | Mutual Fund | 2026/Q3 | +67,503 | 0.2% |
| J.P. Morgan Asset Management, Inc. | Mutual Fund | 2026/Q3 | +24,100 | 0.1% |
| Vanguard Portfolio Management, LLC | Mutual Fund | 2026/Q3 | +1,301 | 0.0% |
| OrbiMed Advisors LLC | VC/PE Fund | 2026/Q3 | +2,714,279 | 8.5% |
| Cormorant Asset Management, LP | Hedge Fund | 2026/Q3 | +3,614,034 | 11.4% |
| The Li and Cui Family Trust | Private Company | 2026/Q3 | +1,714,117 | 5.4% |
| Vivo Capital, LLC | VC/PE Fund | 2026/Q3 | +1,681,240 | 5.3% |
| Brahma Capital | VC/PE Fund | 2026/Q3 | +578,524 | 1.8% |
| Vincent Liptak | Individual/Insider | 2026/Q3 | +134,099 | 0.4% |
| Yishan Li | Individual/Insider | 2026/Q3 | -102,971 | 0.4% |
| John Schmid | Individual/Insider | 2026/Q3 | +6,000 | 0.0% |
| Jason Keyes | Individual/Insider | 2026/Q3 | +700 | 0.0% |
| Perceptive Advisors LLC | VC/PE Fund | 2026/Q3 | +1,808,533 | 5.7% |
| Janus Henderson Group plc | Mutual Fund | 2026/Q3 | +1,134,361 | 3.6% |
Institutional buy/sell activity by reporting period, largest moves first.
| Date | Insider | Title | Transaction | Shares | Price | Held after |
|---|---|---|---|---|---|---|
| 9 Aug 2026 | OrbiMed Advisors LLC | Open Market Acquisition | +625,000 | $16.00 | 2,714,279 | |
| 9 Aug 2026 | OrbiMed Advisors LLC | Derivative Exercise and Retained | +2,089,279 | – | 2,714,279 | |
| 9 Aug 2026 | John Schmid | Independent Director | Open Market Acquisition | +6,000 | $16.00 | 6,000 |
| 9 Aug 2026 | Yishan Li | Co-Founder & Executive Chairperson | Derivative Exercise and Retained | +124,779 | – | – |
| 9 Aug 2026 | Brahma Capital | Derivative Exercise and Retained | +578,524 | – | 578,524 | |
| 9 Aug 2026 | Cormorant Asset Management, LP | Open Market Acquisition | +312,500 | $16.00 | 3,614,034 | |
| 9 Aug 2026 | Cormorant Asset Management, LP | Derivative Exercise and Retained | +3,301,534 | – | 3,614,034 | |
| 9 Aug 2026 | Jason Keyes | Chief Financial Officer | Open Market Acquisition | +700 | $16.00 | 700 |
| 9 Aug 2026 | Vincent Liptak | General Counsel & Executive VP | Derivative Exercise and Retained | +22,687 | – | 134,099 |
| 9 Aug 2026 | The Li and Cui Family Trust | Derivative Exercise and Retained | +1,714,117 | – | 1,714,117 | |
| 9 Aug 2026 | Vincent Liptak | General Counsel & Executive VP | Open Market Acquisition | +4,700 | $16.00 | 134,099 |
| 5 Aug 2026 | Carl Gordon | Independent Director | Other Derivative Acquisition | +23,904 | $16.00 | 23,904 |
| 5 Aug 2026 | John Schmid | Independent Director | Initial Statement of Beneficial | +0 | – | 67,620 |
| 5 Aug 2026 | Yishan Li | Co-Founder & Executive Chairperson | Other Derivative Acquisition | +112,701 | $16.00 | 112,701 |
| 5 Aug 2026 | Yishan Li | Co-Founder & Executive Chairperson | Initial Statement of Beneficial | +0 | – | 124,779 |
| 5 Aug 2026 | Sheila Gujrathi | Lead Independent Director | Initial Statement of Beneficial | +0 | – | 90,160 |
| 5 Aug 2026 | Cormorant Asset Management, LP | Other Derivative Acquisition | +23,904 | $16.00 | 23,904 | |
| 5 Aug 2026 | Cormorant Asset Management, LP | Initial Statement of Beneficial | +0 | – | 1,701,541 | |
| 5 Aug 2026 | Sundeep Agrawal | Independent Director | Other Derivative Acquisition | +23,904 | $16.00 | 23,904 |
| 5 Aug 2026 | Sundeep Agrawal | Independent Director | Initial Statement of Beneficial | +0 | – | 10,671 |
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 | 137,567 | 0.4% | 1.0 |
| 31 Aug 2026 | 110,782 | 0.4% | 1.0 |
| 14 Aug 2026 | 111,892 | 0.4% | 1.0 |
No comments yet — be the first to weigh in on BLSM.