Castle Biosciences (NASDAQ: CSTL) CEO sells stock under 10b5-1 plan
Rhea-AI Filing Summary
CASTLE BIOSCIENCES INC (CSTL) CEO Derek J. Maetzold reported an option exercise and related share sales. He exercised a stock option for 1,100 shares of common stock at $2.39 per share, receiving 1,100 shares that were then sold at $30.02 per share. Additional sales totaling 7,232 shares of common stock were made by several trusts for which he or his spouse serves as trustee or beneficiary, at the same weighted-average price. After these transactions, he holds 37,757 shares directly, and various family and grantor retained annuity trusts hold between 11,534 and 40,935 shares each. All trades were made under a Rule 10b5-1 plan adopted on December 3, 2025, and the option shares exercised were fully vested.
Positive
- None.
Negative
- None.
Insider Trade Summary 10b5-1
Exercise and sale activity reported; no spread calculated
Exercise and Sale
13 txns
Insider
MAETZOLD DEREK J
Role
Pres. & Chief Exec. Officer
Sold
7,232 shs ($217K)
Approx. gross sale proceeds
$217K
Approx. exercise cost
$3K
| Type | Security | Shares | Price | Value |
|---|---|---|---|---|
| Exercise | Stock option (right to buy) F1, F13 | 1,100 | $0.00 | $0.00 |
| Exercise | Common Stock F1 | 1,100 | $2.39 | $3K |
| Sale | Common Stock F1, F2 | 1,100 | $30.02 | $33K |
| Sale | Common Stock F1, F2, F3 | 2,714 | $30.02 | $81K |
| Sale | Common Stock F1, F2, F4 | 2,306 | $30.02 | $69K |
| Sale | Common Stock F1, F2, F5 | 278 | $30.02 | $8K |
| Sale | Common Stock F1, F2, F6 | 278 | $30.02 | $8K |
| Sale | Common Stock F1, F2, F7 | 278 | $30.02 | $8K |
| Sale | Common Stock F1, F2, F8 | 278 | $30.02 | $8K |
| holding | Common Stock F9 | -- | -- | -- |
| holding | Common Stock F10 | -- | -- | -- |
| holding | Common Stock F11 | -- | -- | -- |
| holding | Common Stock F12 | -- | -- | -- |
Holdings After Transaction:
Stock option (right to buy) — 37,757 shares (Direct);
Common Stock — 21,479 shares (Direct);
Common Stock — 20,355 shares (Indirect, By The Maetzold Descendants 2020 Trust);
Common Stock — 17,301 shares (Indirect, By Derek Maetzold 2020 Irrevocable Trust);
Common Stock — 11,534 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk);
Common Stock — 11,534 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold);
Common Stock — 11,534 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold);
Common Stock — 11,534 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 (13)
- 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 $29.73 to $30.55, 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. 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.
- F10. Held by DJM Grantor Retained Annuity Trust No. 7 of which the Reporting Person is the trustee and beneficiary.
- F11. Held by DJM Grantor Retained Annuity Trust No. 8 of which the Reporting Person is the trustee and beneficiary.
- F12. Held by DJM Grantor Retained Annuity Trust No. 9 of which the Reporting Person is the trustee and beneficiary.
- F13. The shares subject to the option are fully vested.
Key Figures
Option shares exercised: 1,100 shares
Option exercise price: $2.39 per share
Sale price (weighted-average): $30.02 per share
+5 more
8 metrics
Option shares exercised
1,100 shares
Stock option for common stock exercised on August 14, 2026
Option exercise price
$2.39 per share
Conversion or exercise price of the stock option
Sale price (weighted-average)
$30.02 per share
Reported sale price for common stock transactions on August 14, 2026
Total shares sold
7,232 shares
Net shares sold across reported sale transactions
Direct holdings after transactions
37,757 shares
Common stock held directly by Derek J. Maetzold after transactions
Trust holding – DJM GRAT No. 8
40,935 shares
CSTL common stock held indirectly by DJM Grantor Retained Annuity Trust No. 8
Trust holding – DJM GRAT No. 7
27,862 shares
CSTL common stock held indirectly by DJM Grantor Retained Annuity Trust No. 7
Option expiration date
May 9, 2028
Expiration date of the stock option exercised
Key Terms
Rule 10b5-1 plan, Grantor Retained Annuity Trust, weighted-average sale price, stock option (right to buy)
4 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. 8 of which the Reporting"
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
"executed in multiple trades at prices ranging from $29.73 to $30.55, inclusive. The price reported above reflects the weighted-average sale price"
stock option (right to buy) financial
"security_title: Stock option (right to buy)"
FAQ
What did CSTL CEO Derek Maetzold report in this Form 4 filing?
He reported exercising an option for 1,100 CSTL shares at $2.39 and selling those shares, plus additional 7,232 shares held through various trusts, all on August 14, 2026.
Were the CSTL insider transactions made under a Rule 10b5-1 plan?
Yes. A footnote states all reported transactions were made under a Rule 10b5-1 trading plan adopted by Derek Maetzold on December 3, 2025, indicating they followed a pre-established schedule.
What indirect CSTL holdings by trusts are reported in this Form 4?
Indirect CSTL holdings include trusts such as The Maetzold Descendants 2020 Trust with 20,355 shares and DJM Grantor Retained Annuity Trusts No. 6, 7, 8, and 9 holding between 11,963 and 40,935 shares each, with Maetzold typically serving as trustee.
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