Castle Biosciences
CSTL · NASDAQ
$33.15+$0.985 (+3.06%)TodayMarket closed ·
Prev close $32.17
Who owns CSTL
Largest institutional holders, from their latest 13F filings
The 10 largest institutions hold 44.1% of CSTL’s shares.
- RTW Investments L.P.9.2%
- BlackRock Institutional Trust Company, N.A.8.6%
- Principal Global Investors (Equity)5.7%
- Vanguard Capital Management, LLC4.0%
- Next 6 largest institutions16.7%
- All other shareholders55.9%
| Holder | Shares | % of shares |
|---|---|---|
| RTW Investments L.P. | 2.78M | 9.16% |
| BlackRock Institutional Trust Company, N.A. | 2.60M | 8.57% |
| Principal Global Investors (Equity) | 1.73M | 5.69% |
| Vanguard Capital Management, LLC | 1.23M | 4.04% |
| Acadian Asset Management LLC | 918.67K | 3.03% |
| Allianz Global Investors GmbH | 855.76K | 2.82% |
| Vanguard Portfolio Management, LLC | 840.78K | 2.77% |
| Summit Partners Public Asset Management, LLC | 824.87K | 2.72% |
| State Street Investment Management (US) | 822.08K | 2.71% |
| Geode Capital Management, L.L.C. | 795.91K | 2.62% |
Largest mutual fund holders
| Holder | Shares | % of shares |
|---|---|---|
| Vanguard Total Stock Market Index Fund | 852.70K | 2.81% |
| iShares Russell 2000 ETF | 777.98K | 2.57% |
| Principal SmallCap Fund | 725.14K | 2.39% |
| Eventide Healthcare & Life Sciences Fund | 386.43K | 1.27% |
| Vanguard Extended Market Index Fund | 347.88K | 1.15% |
Insider trades
Form 4 filings by officers, directors and large holders
Over the last 6 months, insiders sold $9.73M (151 trades) of CSTL on the open market, with no buys.
| Insider | Type | Shares | Value |
|---|---|---|---|
| Juvenal Tobin W | Sale | 3.29K | $110.61K |
| MAETZOLD DEREK J | Option exercise | 8.16K | — |
| MAETZOLD DEREK J | Sale | 2.72K | $96.67K |
| MAETZOLD DEREK J | Sale | 3.20K | $113.74K |
| MAETZOLD DEREK J | Sale | 8.58K | $305.16K |
| MAETZOLD DEREK J | Option exercise | 8.16K | $19.51K |
| Oelschlager Kristen M | Option exercise | 4.15K | — |
| Oelschlager Kristen M | Sale | 1.35K | $48.97K |
| Oelschlager Kristen M | Sale | 2.81K | $100.35K |
| Oelschlager Kristen M | Option exercise | 4.15K | $14.04K |
Short interest
Settled Sep 30, 2026
- Shares short
- 2.00M
- Days to cover
- 4.77
- % of shares outstanding
- 6.59%
- Average daily volume
- 419.63K
- Change since last report
- +5.3%
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