Casdin Partners Master Fund, L.P.
CIK 1534265 · last filed 2025-12-04
Casdin Partners Master Fund, L.P. is a corporate insider who has filed 15 SEC Form 4 insider transactions across 5 companies since 2021. The most recent filing, for BLFS, was dated May 21, 2026. Across all open-market trades the lifetime net is −$38.6M, making them a net seller over the disclosed history. Current disclosed insider exposure totals $602.7M across reported positions. The firm reports its address in George Town. 76 SEC filings were submitted jointly with Casdin Capital, LLC.
"Disclosed insider exposure" sums this person's most-recently-reported share counts across each company they're an insider in, multiplied by the current underlying price. It is not net worth — it misses retail holdings, private investments, real estate, index funds, and any company where the person isn't an SEC-reporting insider. For informational purposes only.
Charts
Trading activity, where the exposure sits, and each trade against the stock price.
Filer Profile
87 MARY STREET
GEORGE TOWN
Holdings By Company
| Symbol | Role | Shares | Price | Disclosed Exposure | Lifetime OM Net | Filings | Latest Filed |
|---|---|---|---|---|---|---|---|
| LAB | Director | 74,851,062 | $0.74 | $55.74M | $15.02M | 2 | 2025-12-04 |
| BLFS | 10%+ Owner | 14,664,330 | $37.30 | $546.98M | -$85.64M | 2 | 2025-10-17 |
| 2seventy bio, Inc. (TSVT) Delisted | Director | 2,016,600 | $5.00 | $10.08M | $816.0K | 1 | 2024-03-28 |
| Verve Therapeutics, Inc. (VERV) Delisted | 10%+ Owner | 1,007,311 | $11.13 | $11.21M | $20.90M | 1 | 2021-06-22 |
| Decibel Therapeutics, Inc. (DBTX) Delisted | 10%+ Owner | 546,421 | $4.91 | $2.68M | $10.35M | 1 | 2021-02-19 |
Recent Filings
15 filings| Filed | Symbol | Action | Net Shares | Net $ | Link |
|---|---|---|---|---|---|
| 2026-05-21 | BLFS | Notice (144) | −650,000 | -$15.60M | EDGAR |
| 2026-05-20 | BLFS | Notice (144) | −250,000 | -$6.00M | EDGAR |
| 2026-05-19 | BLFS | Notice (144) | −300,000 | -$6.69M | EDGAR |
| 2025-12-04 | LAB | Buy (P) | +2,800,000 | $4.02M | EDGAR |
| 2025-11-20 | LAB | Buy (P) | +8,600,000 | $11.00M | EDGAR |
| 2025-10-17 | BLFS | Sell (S) | −3,000,000 | -$85.64M | EDGAR |
| 2025-10-15 | BLFS | Notice (144) | −750,000 | -$21.41M | EDGAR |
| 2025-08-22 | WGS | Notice (144) | −500,000 | -$60.45M | EDGAR |
| 2025-08-15 | BLFS | Notice (144) | −500,000 | -$12.66M | EDGAR |
| 2025-08-11 | BLFS | Notice (144) | −500,000 | -$11.19M | EDGAR |
Notice (144 / 144/A): Form 144 is a notice of intent to sell restricted/control stock under Rule 144, filed before the sale; 144/A is an amendment. Many notices are pre-scheduled under Rule 10b5-1 plans. A Form 4 with code S typically follows within a few days when the planned sale executes; missing follow-up Form 4s suggest the notice was cancelled or modified.