Castle Biosciences Inc
CSTL- Exchange
- Nasdaq
- Industry
- Services-Medical Laboratories
- SEC CIK
- 0001447362
In the last 90 days, Castle Biosciences Inc insiders filed 0 open-market purchases and 20 sales; 176 institutions reported holding it in 13F filings for Q2 2026, worth $653.8M in total; no superinvestor holds it.
Holders of 5% or more of CSTL
Holders whose latest Schedule 13D or 13G filing reports 5% or more of Castle Biosciences Inc, largest stake first. The change is against the holder's previous filing.
| Holder | Latest form | Stake | Change | First filed | Latest filing | Filing |
|---|---|---|---|---|---|---|
| BlackRock, Inc. | 13G/A | 8.20%2.34M shares | – | Apr 23, 20251 filing | Apr 23, 2025 | SEC |
| RTW Investments, LP | 13G | 7.20%2.12M shares | New | Feb 17, 20261 filing | Feb 17, 2026 | SEC |
| Portolan Capital Management, LLC | 13G | 5.65%1.61M shares | New | Apr 14, 20251 filing | Apr 14, 2025 | SEC |
Stakes are as of each holder's latest filing. Holders whose last filing was in the old format (before December 18, 2024) have no stake on record and are not listed, and after an acquisition or delisting holders usually stop filing.
13D and 13G filings
8 Schedule 13D and 13G filings on Castle Biosciences Inc, newest first, including old-format filings without a stake.
| Filed (ET) | Filer | Form | Stake | Change | Event date | Filing |
|---|---|---|---|---|---|---|
| Mar 26, 20264:42 PM ET | Vanguard Group Inc | 13G/A | 0.00%0 shares | −6.54 ppfrom 6.54%Below 5% | Mar 13, 2026 | SEC |
| Feb 17, 20268:31 AM ET | RTW Investments, LPand 1 other | 13G | 7.20%2.12M shares | New | Dec 31, 2025 | SEC |
| Jan 21, 20261:21 PM ET | Dimensional Fund Advisors LP | 13G/A | 3.90%1.14M shares | −1.20 ppfrom 5.10%Below 5% | Dec 31, 2025 | SEC |
| Oct 9, 20251:48 PM ET | Dimensional Fund Advisors LP | 13G | 5.10%1.47M shares | New | Sep 30, 2025 | SEC |
| May 12, 20253:55 PM ET | Wasatch Advisors Inc | 13G/A | 3.50%998.5K shares | –Below 5% | Mar 31, 2025 | SEC |
| Apr 23, 20258:19 PM ET | BlackRock, Inc. | 13G/A | 8.20%2.34M shares | – | Mar 31, 2025 | SEC |
| Apr 14, 20253:34 PM ET | Portolan Capital Management, LLCand 1 other | 13G | 5.65%1.61M shares | New | Apr 7, 2025 | SEC |
| Jan 30, 20259:33 PM ET | Vanguard Group Inc | 13G/A | 6.54%1.83M shares | – | Dec 31, 2024 | SEC |
Form 144: proposed insider sales
Notices from officers, directors and other affiliates planning to sell Castle Biosciences Inc shares.
No Form 144 notices for Castle Biosciences Inc are on file.