Castle Biosciences CEO sells 18,560 shares
CASTLE BIOSCIENCES INC (CSTL) CEO and director Derek J. Maetzold reported an option exercise and related share sales.
Rhea-AI Filing Summary
CASTLE BIOSCIENCES INC (CSTL) CEO and director Derek J. Maetzold reported an option exercise and related share sales. He exercised a stock option for 12,428 shares of Common Stock at an exercise price of $2.39 per share, from a fully vested option expiring May 9, 2028, leaving 25,329 option shares outstanding. On the same date, entities associated with him sold an aggregate of 18,560 shares of Common Stock, including direct holdings and shares held through several family and grantor retained annuity trusts, at weighted-average prices of approximately $33.14 and $33.88 per share. All transactions were made pursuant to a Rule 10b5-1 trading plan adopted on December 3, 2025.
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Insights
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Insider Trade Summary 10b5-1
Exercise and sale activity reported; no spread calculated
Exercise and Sale
20 txns
Insider
MAETZOLD DEREK J
Role
Pres. & Chief Exec. Officer
Sold
18,560 shs ($616K)
Approx. gross sale proceeds
$616K
Approx. exercise cost
$30K
| Type | Security | Shares | Price | Value |
|---|---|---|---|---|
| Exercise | Stock option (right to buy) F1, F14 | 12,428 | $0.00 | $0.00 |
| Exercise | Common Stock F1 | 12,428 | $2.39 | $30K |
| Sale | Common Stock F1, F2 | 11,472 | $33.14 | $380K |
| Sale | Common Stock F1, F2, F3 | 2,505 | $33.14 | $83K |
| Sale | Common Stock F1, F2, F4 | 2,129 | $33.14 | $71K |
| Sale | Common Stock F1, F2, F5 | 257 | $33.14 | $9K |
| Sale | Common Stock F1, F2, F6 | 257 | $33.14 | $9K |
| Sale | Common Stock F1, F2, F7 | 257 | $33.14 | $9K |
| Sale | Common Stock F1, F2, F8 | 257 | $33.14 | $9K |
| Sale | Common Stock F1, F9 | 956 | $33.88 | $32K |
| Sale | Common Stock F1, F9, F3 | 209 | $33.88 | $7K |
| Sale | Common Stock F1, F9, F4 | 177 | $33.88 | $6K |
| Sale | Common Stock F1, F9, F5 | 21 | $33.88 | $711.48 |
| Sale | Common Stock F1, F9, F6 | 21 | $33.88 | $711.48 |
| Sale | Common Stock F1, F9, F7 | 21 | $33.88 | $711.48 |
| Sale | Common Stock F1, F9, F8 | 21 | $33.88 | $711.48 |
| holding | Common Stock F10 | -- | -- | -- |
| holding | Common Stock F11 | -- | -- | -- |
| holding | Common Stock F12 | -- | -- | -- |
| holding | Common Stock F13 | -- | -- | -- |
Holdings After Transaction:
Stock option (right to buy) — 25,329 contracts (Direct);
Common Stock — 21,479 shares (Direct);
Common Stock — 17,641 shares (Indirect, By The Maetzold Descendants 2020 Trust);
Common Stock — 14,995 shares (Indirect, By Derek Maetzold 2020 Irrevocable Trust);
Common Stock — 11,256 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk);
Common Stock — 11,256 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold);
Common Stock — 11,256 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold);
Common Stock — 11,256 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 (14)
- 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 $32.78 to $33.70, 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. 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.
- F6. 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.
- F7. 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.
- F8. 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.
- F9. This transaction was executed in multiple trades at prices ranging from $33.78 to $33.97, 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.
- F10. 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.
- F11. Held by DJM Grantor Retained Annuity Trust No. 7 of which the Reporting Person is the trustee and beneficiary.
- F12. Held by DJM Grantor Retained Annuity Trust No. 8 of which the Reporting Person is the trustee and beneficiary.
- F13. Held by DJM Grantor Retained Annuity Trust No. 9 of which the Reporting Person is the trustee and beneficiary.
- F14. The shares subject to the option are fully vested.
Key Figures
Option shares exercised: 12,428 shares
Exercise price: $2.39 per share
Option shares remaining: 25,329 shares
+5 more
8 metrics
Option shares exercised
12,428 shares
Stock option for Common Stock exercised on August 28, 2026
Exercise price
$2.39 per share
Exercise price of stock option (right to buy) for 12,428 shares
Option shares remaining
25,329 shares
Shares subject to the option following the reported exercise
Total shares sold
18,560 shares
Aggregate Common Stock sold across reported sale transactions
Weighted-average sale price block 1
$33.14 per share
Sales executed in multiple trades within $32.78–$33.70 range
Weighted-average sale price block 2
$33.88 per share
Sales executed in multiple trades within $33.78–$33.97 range
DJM GRAT No. 8 holdings
40,935 shares
Common Stock held indirectly by DJM Grantor Retained Annuity Trust No. 8
DJM GRAT No. 7 holdings
27,862 shares
Common Stock held indirectly by DJM Grantor Retained Annuity Trust No. 7
Key Terms
Rule 10b5-1 plan, Grantor Retained Annuity Trust, weighted-average sale price, stock option (right to buy), +1 more
5 terms
Rule 10b5-1 plan regulatory
"These transactions were made pursuant to a Rule 10b5-1 plan adopted"
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.
Grantor Retained Annuity Trust financial
"Held by DJM Grantor Retained Annuity Trust No. 6 of which"
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.
weighted-average sale price financial
"The price reported above reflects the weighted-average sale price."
stock option (right to buy) financial
"security_title": "Stock option (right to buy)"
irrevocable trust financial
"Held by Derek Maetzold 2020 Irrevocable Trust of which"
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.
FAQ
What did CSTL CEO Derek Maetzold report in this Form 4?
He reported exercising a stock option for 12,428 shares of Castle Biosciences Common Stock at an exercise price of $2.39 per share and related sales totaling 18,560 shares, including direct holdings and several family and grantor retained annuity trusts.
What stock option did Derek Maetzold exercise for CSTL?
He exercised a fully vested stock option for 12,428 shares of Castle Biosciences Common Stock at an exercise price of $2.39 per share. After the exercise, 25,329 shares remained subject to that option, which expires on May 9, 2028.
Were the CSTL insider transactions under a Rule 10b5-1 plan?
Yes. The filing states that the reported transactions were made pursuant to a Rule 10b5-1 plan adopted by Derek Maetzold on December 3, 2025, indicating they followed a pre-arranged trading plan.
AI-generated analysis. How Rhea-AI works. Not financial advice.
