Castle Biosciences (CSTL) CEO sells 39,016 shares after option exercise
Rhea-AI Filing Summary
Castle Biosciences (CSTL) president and CEO Derek J. Maetzold reported option exercises and related share sales on August 4–5, 2026. He exercised options covering 22,902 common shares at $2.39 per share, then he and related family trusts sold a combined 39,016 shares at weighted-average prices around $30.68–$31.34 per share. These transactions were made pursuant to a Rule 10b5-1 trading plan adopted on December 3, 2025.
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Insider Trade Summary 10b5-1
Exercise and sale activity reported; no spread calculated
Exercise and Sale
21 txns
Insider
MAETZOLD DEREK J
Role
Pres. & Chief Exec. Officer
Sold
39,016 shs ($1.21M)
Approx. gross sale proceeds
$1.21M
Approx. exercise cost
$55K
| Type | Security | Shares | Price | Value |
|---|---|---|---|---|
| Exercise | Stock option (right to buy) F1, F15 | 2,546 | $0.00 | $0.00 |
| Exercise | Common Stock F1 | 2,546 | $2.39 | $6K |
| Sale | Common Stock F1, F6 | 2,546 | $30.681 | $78K |
| Sale | Common Stock F1, F6, F3 | 556 | $30.681 | $17K |
| Sale | Common Stock F1, F6, F4 | 473 | $30.681 | $15K |
| Exercise | Stock option (right to buy) F1, F15 | 20,356 | $0.00 | $0.00 |
| Exercise | Common Stock F1 | 20,356 | $2.39 | $49K |
| Sale | Common Stock F1, F2 | 8,421 | $30.788 | $259K |
| Sale | Common Stock F1, F2, F3 | 3,374 | $30.788 | $104K |
| Sale | Common Stock F1, F2, F4 | 2,866 | $30.788 | $88K |
| Sale | Common Stock F1, F5 | 11,935 | $31.336 | $374K |
| Sale | Common Stock F1, F5, F3 | 4,782 | $31.336 | $150K |
| Sale | Common Stock F1, F5, F4 | 4,063 | $31.336 | $127K |
| holding | Common Stock F7 | -- | -- | -- |
| holding | Common Stock F8 | -- | -- | -- |
| holding | Common Stock F9 | -- | -- | -- |
| holding | Common Stock F10 | -- | -- | -- |
| holding | Common Stock F11 | -- | -- | -- |
| holding | Common Stock F12 | -- | -- | -- |
| holding | Common Stock F13 | -- | -- | -- |
| holding | Common Stock F14 | -- | -- | -- |
Holdings After Transaction:
Stock option (right to buy) — 38,857 shares (Direct);
Common Stock — 21,479 shares (Direct);
Common Stock — 23,069 shares (Indirect, By The Maetzold Descendants 2020 Trust);
Common Stock — 19,607 shares (Indirect, By Derek Maetzold 2020 Irrevocable Trust);
Common Stock — 11,812 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk);
Common Stock — 11,812 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold);
Common Stock — 11,812 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold);
Common Stock — 11,812 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold);
Common Stock — 11,963 shares (Indirect, By DJM Grantor Retained Annuity Trust No. 6);
Common Stock — 27,862 shares (Indirect, By DJM Grantor Retained Annuity Trust No. 7);
Common Stock — 40,935 shares (Indirect, By DJM Grantor Retained Annuity Trust No. 8);
Common Stock — 23,216 shares (Indirect, DJM Grantor Retained Annuity Trust No. 9)
Footnotes (15)
- F1. These transactions were made pursuant to a Rule 10b5-1 plan adopted by the Reporting Person on December 3, 2025.
- F2. This transaction was executed in multiple trades at prices ranging from $30.000 to $30.995, inclusive. The price reported above reflects the weighted-average sale price. The Reporting Person hereby undertakes to provide upon request to the Securities and Exchange Commission staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.
- F3. Held by The Maetzold Descendants 2020 Trust of which the Reporting Person's spouse is the trustee and the Reporting Person's spouse and their children are beneficiaries.
- F4. Held by Derek Maetzold 2020 Irrevocable Trust of which the Reporting Person is the trustee and his children are beneficiaries.
- F5. This transaction was executed in multiple trades at prices ranging from $31.010 to $31.650, inclusive. The price reported above reflects the weighted-average sale price. The Reporting Person hereby undertakes to provide upon request to the Securities and Exchange Commission staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.
- F6. This transaction was executed in multiple trades at prices ranging from $30.400 to $31.175, inclusive. The price reported above reflects the weighted-average sale price. The Reporting Person hereby undertakes to provide upon request to the Securities and Exchange Commission staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.
- F7. Held by The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk of which the Reporting Person is the trustee and his child is the beneficiary.
- F8. Held by The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold of which the Reporting Person is the trustee and his child is the beneficiary.
- F9. Held by The Maetzold 2018 Remainder Trust FBO John Derek Maetzold of which the Reporting Person is the trustee and his child is the beneficiary.
- F10. Held by The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold of which the Reporting Person is the trustee and his child is the beneficiary.
- F11. Held by DJM Grantor Retained Annuity Trust No. 6 of which the Reporting Person is the trustee and the beneficiaries are The Maetzold 2018 Remainder Trust FBO John Derek Maetzold, The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk, The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold and The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold.
- F12. Held by DJM Grantor Retained Annuity Trust No. 7 of which the Reporting Person is the trustee and beneficiary.
- F13. Held by DJM Grantor Retained Annuity Trust No. 8 of which the Reporting Person is the trustee and beneficiary.
- F14. Held by DJM Grantor Retained Annuity Trust No. 9 of which the Reporting Person is the trustee and beneficiary.
- F15. The shares subject to the option are fully vested.
Key Figures
Total shares sold: 39,016 shares
Options exercised: 22,902 shares
Option exercise price: $2.3900 per share
+4 more
7 metrics
Total shares sold
39,016 shares
Aggregate Castle Biosciences common shares sold by Maetzold and related trusts on Aug. 4–5, 2026
Options exercised
22,902 shares
Common shares acquired upon stock option exercises on Aug. 4–5, 2026
Option exercise price
$2.3900 per share
Exercise price of stock options converted into common stock by Maetzold
Weighted-average sale price (F2)
$30.7880 per share
Common stock sales on Aug. 4, 2026; trades ranged from $30.000 to $30.995
Weighted-average sale price (F5)
$31.3360 per share
Common stock sales on Aug. 4, 2026; trades ranged from $31.010 to $31.650
Weighted-average sale price (F6)
$30.6810 per share
Common stock sales on Aug. 5, 2026; trades ranged from $30.400 to $31.175
Rule 10b5-1 plan adoption date
December 3, 2025
Date Derek Maetzold adopted the trading plan governing these transactions
Key Terms
Rule 10b5-1 plan, weighted-average sale price, Grantor Retained Annuity Trust, irrevocable trust, +1 more
5 terms
Rule 10b5-1 plan regulatory
"These transactions were made pursuant to a Rule 10b5-1 plan adopted by the Reporting Person"
A Rule 10b5-1 plan is a prearranged, written schedule that lets corporate insiders buy or sell company stock at set times or amounts, even if they later learn material nonpublic information. Think of it like setting an automatic thermostat for trades: it creates a clear record that trades were planned in advance, reducing the risk of insider-trading accusations and helping investors trust that insider transactions are routine rather than based on secret information.
weighted-average sale price financial
"The price reported above reflects the weighted-average sale price for multiple trades"
Grantor Retained Annuity Trust financial
"Held by DJM Grantor Retained Annuity Trust No. 7 of which the Reporting Person is the trustee"
A grantor retained annuity trust (GRAT) is an estate-planning tool where the person who creates the trust transfers assets into it but receives fixed cash payments (an annuity) from the trust for a set number of years; whatever remains after that term passes to designated beneficiaries. It matters to investors because it can shift future appreciation of assets out of the creator’s taxable estate—like putting an asset into a timed vending machine that pays you fixed amounts while any extra value that grows inside the machine goes to heirs with reduced gift or estate tax consequences.
irrevocable trust financial
"Held by Derek Maetzold 2020 Irrevocable Trust of which the Reporting Person is the trustee"
An irrevocable trust is a legal arrangement where an owner transfers assets into a separate entity managed by a trustee and gives up the power to modify or reclaim those assets. For investors it matters because putting stock or other holdings into such a trust can change who controls and benefits from the assets, affect taxes and creditor protection, and influence how easy it is to sell or value those holdings—like placing valuables in a locked safe overseen by someone else.
beneficiaries financial
"The beneficiaries are various Maetzold 2018 Remainder Trusts identified as beneficiaries"
Beneficiaries are the people or organizations designated to receive benefits, such as money or assets, from a financial arrangement like a trust, insurance policy, or retirement plan. They matter to investors because choosing the right beneficiaries ensures that assets are passed on according to their wishes, providing financial security or support to loved ones when needed. Think of beneficiaries as the intended recipients of a gift or inheritance.
AI-generated analysis. How Rhea-AI works. Not financial advice.
FAQ
What transactions did CSTL CEO Derek Maetzold report in this Form 4?
Derek Maetzold reported exercising stock options for 22,902 Castle Biosciences common shares at $2.39 per share, then, together with related family trusts, selling a total of 39,016 shares at weighted-average prices between about $30.68 and $31.34 on August 4–5, 2026.
Were Derek Maetzold’s CSTL stock trades made under a Rule 10b5-1 plan?
Yes. The filing states the trades were made pursuant to a Rule 10b5-1 plan that Derek Maetzold adopted on December 3, 2025. Such plans pre-arrange trading activity, reducing the informational value of transaction timing for interpreting insider sentiment.
What options did CSTL CEO Derek Maetzold exercise in this filing?
He exercised stock options for 22,902 common shares at an exercise price of $2.39 per share, with the options expiring on May 9, 2028. A footnote confirms the option shares were fully vested at the time of exercise.