Castle Biosciences, Inc. (CSTL) Insider Trading
Over the last 3 months, CSTL insiders made 0 open-market buys and 64 sales, a net sale of -$6.6M (SEC Form 4). Over the last 6 months, 150 institutions increased and 122 reduced their position (13F).
Insider Activity
Sentiment
0/100
Buys (3m)
0
Sells (3m)
64
Net (3m)
-$6.6M
Insider trades by month Buys Sells
Apr
May
Jun
Jul
Aug
Sep
Context3-month price +70.5%Institutions accumulating (13F)
| Date | Insider | Type | Shares | Price |
|---|---|---|---|---|
| Sep 1, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 21 | $33.88 |
| Sep 1, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 2,505 | $33.14 |
| Sep 1, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Option | 12,428 | $2.39 |
| Sep 1, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 956 | $33.88 |
| Sep 1, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 177 | $33.88 |
| Sep 1, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 209 | $33.88 |
| Sep 1, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 257 | $33.14 |
| Sep 1, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 11,472 | $33.14 |
| Sep 1, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 2,129 | $33.14 |
| Aug 27, 2026 | Juvenal Tobin Wofficer: Chief Commercial Officer | Sell | 9,050 | $35.04 |
| Aug 26, 2026 | Oelschlager Kristen Mofficer: Chief Operating Officer | Sell | 7,161 | $34.26 |
| Aug 26, 2026 | Oelschlager Kristen Mofficer: Chief Operating Officer | Sell | 5,223 | $34.64 |
| Aug 26, 2026 | Oelschlager Kristen Mofficer: Chief Operating Officer | Sell | 12,218 | $33.69 |
| Aug 19, 2026 | Juvenal Tobin Wofficer: Chief Commercial Officer | Sell | 1,730 | $29.59 |
| Aug 18, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 1,100 | $30.02 |
| Aug 18, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Option | 1,100 | $2.39 |
| Aug 18, 2026 | Stokes Frankofficer: Chief Financial Officer | Sell | 24,908 | $29.77 |
| Aug 18, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 2,714 | $30.02 |
| Aug 18, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 278 | $30.02 |
| Aug 18, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 2,306 | $30.02 |
| Aug 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 4,782 | $31.34 |
| Aug 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 556 | $30.68 |
| Aug 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 2,866 | $30.79 |
| Aug 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 3,374 | $30.79 |
| Aug 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Option | 2,546 | $2.39 |
| Aug 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 11,935 | $31.34 |
| Aug 6, 2026 | Juvenal Tobin Wofficer: Chief Commercial Officer | Sell | 1,301 | $38.39 |
| Aug 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 473 | $30.68 |
| Aug 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 4,063 | $31.34 |
| Aug 6, 2026 | MAETZOLD DEREK Jdirector, officer: Pres. & Chief Exec. Officer | Sell | 8,421 | $30.79 |
Source: CSTL SEC Form 4 filings, latest Sep 1, 2026. For informational purposes only — not investment advice.
Institutional activity (13F)
How institutions changed their CSTL positions over the last 6 months (SEC Form 13F).
Increased
150
New positions
55
Reduced
122
Sold out
32
Largest moves
| Institution | Action | Shares | Filed |
|---|---|---|---|
| BlackRock, Inc. | Increased | 3.3M | Aug 7, 2026 |
| BLACKROCK, INC. | Reduced | 3.0M | May 13, 2026 |
| RTW INVESTMENTS, LP | Increased | 2.8M | Aug 14, 2026 |
| RTW INVESTMENTS, LP | Increased | 2.8M | May 15, 2026 |
| PRINCIPAL FINANCIAL GROUP INC | Reduced | 1.8M | May 4, 2026 |
| PRINCIPAL FINANCIAL GROUP INC | Reduced | 1.7M | Aug 4, 2026 |
| PORTOLAN CAPITAL MANAGEMENT, LLC | Reduced | 1.4M | May 15, 2026 |
| VANGUARD CAPITAL MANAGEMENT LLC | Increased | 1.2M | Aug 13, 2026 |
| VANGUARD CAPITAL MANAGEMENT LLC | New Position | 1.2M | May 15, 2026 |
| DIMENSIONAL FUND ADVISORS LP | Reduced | 1.0M | May 7, 2026 |
| SUMMIT PARTNERS PUBLIC ASSET MANAGEMENT, LLC | Reduced | 941K | May 15, 2026 |
| ACADIAN ASSET MANAGEMENT LLC | Increased | 919K | Aug 13, 2026 |
| VANGUARD PORTFOLIO MANAGEMENT LLC | New Position | 862K | May 8, 2026 |
| VANGUARD PORTFOLIO MANAGEMENT LLC | Reduced | 841K | Aug 13, 2026 |
| SUMMIT PARTNERS PUBLIC ASSET MANAGEMENT, LLC | Reduced | 825K | Aug 14, 2026 |
Source: SEC Form 13F filings. For informational purposes only — not investment advice.