Were Derek Maetzold’s CSTL share sales made under a Rule 10b5-1 plan?

Yes. A footnote states the Castle Biosciences (CSTL) transactions were executed under a Rule 10b5-1 trading plan adopted on December 3, 2025. Such plans pre-schedule trades, indicating the timing was arranged in advance rather than being discretionary.

Castle Biosciences (CSTL) CEO sells shares and exercises stock options in pre-planned trades

Filing Impact

(Moderate)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

Castle Biosciences CEO Derek J. Maetzold reported a mix of stock option exercises and share sales in Castle Biosciences Inc. common stock. On May 7, 2026, he exercised options to acquire 6,214 shares at an exercise price of $2.39 per share, converting a derivative award into common stock.

The filing also shows open-market sales totaling 9,836 shares at weighted-average prices around $22.08–$22.585 per share. These sales occurred both in his direct account and through several family and estate-planning trusts, including the Maetzold 2018 remainder trusts and 2020 trusts for descendants.

Following these transactions, Maetzold directly holds 22,385 Castle Biosciences shares, while additional shares are held indirectly through multiple trusts where he or his spouse serves as trustee. A footnote states that the transactions were carried out under a pre-arranged Rule 10b5-1 trading plan adopted on December 3, 2025, indicating the trades were scheduled in advance.

Insights

CEO executes pre-planned option exercise and modest share sales via trusts.

Derek Maetzold, CEO of Castle Biosciences, exercised stock options for 6,214 common shares at $2.39 per share and reported open-market sales of 9,836 shares around $22.08–$22.585. The filing shows a standard exercise-and-sell pattern.

Sales occurred across direct holdings and multiple family trusts, including the Derek Maetzold 2020 Irrevocable Trust and the Maetzold Descendants 2020 Trust. A footnote confirms the transactions were made under a Rule 10b5-1 plan adopted on December 3, 2025, suggesting the timing was pre-scheduled rather than opportunistic.

After these trades, Maetzold still directly owns 22,385 shares and retains additional indirect positions via trusts, while the options exercised appear fully vested. Given the pre-planned nature, diversified entities, and continuing stake, this looks like routine liquidity and portfolio management rather than a thesis-changing move.

Insider Trade Summary 10b5-1

Net Seller: 9,836 shares ($217,904)

Net Sell 19 txns

Insider MAETZOLD DEREK J

Role Pres. & Chief Exec. Officer

Sold 9,836 shs ($218K)

Type	Security	Shares	Price	Value
Exercise	Stock option (right to buy)	6,214	$0.00	--
Exercise	Common Stock	6,214	$2.39	$15K
Sale	Common Stock	5,308	$22.08	$117K
Sale	Common Stock	1,159	$22.08	$26K
Sale	Common Stock	985	$22.08	$22K
Sale	Common Stock	237	$22.08	$5K
Sale	Common Stock	237	$22.08	$5K
Sale	Common Stock	237	$22.08	$5K
Sale	Common Stock	237	$22.08	$5K
Sale	Common Stock	906	$22.585	$20K
Sale	Common Stock	198	$22.585	$4K
Sale	Common Stock	168	$22.585	$4K
Sale	Common Stock	41	$22.585	$925.99
Sale	Common Stock	41	$22.585	$925.99
Sale	Common Stock	41	$22.585	$925.99
Sale	Common Stock	41	$22.585	$925.99
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Stock option (right to buy) — 754 shares (Direct, null); Common Stock — 27,693 shares (Direct, null); Common Stock — 46,336 shares (Indirect, By The Maetzold Descendants 2020 Trust)

Footnotes (1)

These transactions were made pursuant to a Rule 10b5-1 plan adopted by the Reporting Person on December 3, 2025. This transaction was executed in multiple trades at prices ranging from $21.520 to $22.515, 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. 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. Held by Derek Maetzold 2020 Irrevocable Trust of which the Reporting Person is the trustee and his children are beneficiaries. 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. 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. 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. 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. This transaction was executed in multiple trades at prices ranging from $22.520 to $22.680, 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. Held by DJM Grantor Retained Annuity Trust No. 5 of which the Reporting Person is the trustee and beneficiary. 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. Held by DJM Grantor Retained Annuity Trust No. 7 of which the Reporting Person is the trustee and beneficiary. The shares subject to the option are fully vested.

Key Figures

Shares sold: 9,836 shares Sale prices: $22.585 and $22.080 per share Options exercised: 6,214 shares +5 more

8 metrics

Shares sold 9,836 shares Total open-market sales on May 7, 2026

Sale prices $22.585 and $22.080 per share Weighted-average prices for reported sales

Options exercised 6,214 shares Common stock acquired via option exercise on May 7, 2026

Option exercise price $2.39/share Exercise price for 6,214 stock options

Direct holdings after trades 22,385 shares Common stock directly owned following transactions

Large trust holding 85,959 shares Common shares held by DJM Grantor Retained Annuity Trust No. 5

Trust holding 44,323 shares Common shares held by DJM Grantor Retained Annuity Trust No. 7

Trust holding 18,718 shares Common shares held by DJM Grantor Retained Annuity Trust No. 6

Key Terms

Rule 10b5-1 plan, Grantor Retained Annuity Trust, Stock option (right to buy), weighted-average sale price, +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 on December 3, 2025."

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. 5 of which the Reporting Person is the trustee and beneficiary."

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.

Stock option (right to buy) financial

"Stock option (right to buy) ... transaction code M ... Exercise or conversion of derivative security."

weighted-average sale price financial

"The price reported above reflects the weighted-average sale price."

fully vested financial

"The shares subject to the option are fully vested."

Form 4 Insider Transactions: What Each Field Means →

05/11/2026 - 04:06 PM

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

MAETZOLD DEREK J

(Last)

(First)

(Middle)

C/O CASTLE BIOSCIENCES, INC.

1500 W. PARKWOOD AVE SUITE 400

(Street)

FRIENDSWOOD

TEXAS

77546

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
CASTLE BIOSCIENCES INC [ CSTL ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	10% Owner
X	Officer (give title below)	Other (specify below)
	Pres. & Chief Exec. Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/07/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	05/07/2026		M⁽¹⁾		6,214	A	$2.39	27,693	D
Common Stock	05/07/2026		S⁽¹⁾		5,308	D	$22.08⁽²⁾	22,385	D
Common Stock	05/07/2026		S⁽¹⁾		1,159	D	$22.08⁽²⁾	46,336	I	By The Maetzold Descendants 2020 Trust⁽³⁾
Common Stock	05/07/2026		S⁽¹⁾		985	D	$22.08⁽²⁾	39,382	I	By Derek Maetzold 2020 Irrevocable Trust⁽⁴⁾
Common Stock	05/07/2026		S⁽¹⁾		237	D	$22.08⁽²⁾	2,265	I	By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk⁽⁵⁾
Common Stock	05/07/2026		S⁽¹⁾		237	D	$22.08⁽²⁾	2,265	I	By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold⁽⁶⁾
Common Stock	05/07/2026		S⁽¹⁾		237	D	$22.08⁽²⁾	2,265	I	By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold⁽⁷⁾
Common Stock	05/07/2026		S⁽¹⁾		237	D	$22.08⁽²⁾	2,265	I	By The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold⁽⁸⁾
Common Stock	05/07/2026		S⁽¹⁾		906	D	$22.585⁽⁹⁾	21,479	D
Common Stock	05/07/2026		S⁽¹⁾		198	D	$22.585⁽⁹⁾	46,138	I	By The Maetzold Descendants 2020 Trust⁽³⁾
Common Stock	05/07/2026		S⁽¹⁾		168	D	$22.585⁽⁹⁾	39,214	I	By Derek Maetzold 2020 Irrevocable Trust⁽⁴⁾
Common Stock	05/07/2026		S⁽¹⁾		41	D	$22.585⁽⁹⁾	2,224	I	By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk⁽⁵⁾
Common Stock	05/07/2026		S⁽¹⁾		41	D	$22.585⁽⁹⁾	2,224	I	By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold⁽⁶⁾
Common Stock	05/07/2026		S⁽¹⁾		41	D	$22.585⁽⁹⁾	2,224	I	By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold⁽⁷⁾
Common Stock	05/07/2026		S⁽¹⁾		41	D	$22.585⁽⁹⁾	2,224	I	By The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold⁽⁸⁾
Common Stock								85,959	I	By DJM Grantor Retained Annuity Trust No. 5⁽¹⁰⁾
Common Stock								18,718	I	By DJM Grantor Retained Annuity Trust No. 6⁽¹¹⁾
Common Stock								44,323	I	By DJM Grantor Retained Annuity Trust No. 7⁽¹²⁾

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Stock option (right to buy)	$2.39	05/07/2026		M⁽¹⁾			6,214	⁽¹³⁾	11/11/2028	Common Stock	6,214	$0	754	D

Explanation of Responses:

1. These transactions were made pursuant to a Rule 10b5-1 plan adopted by the Reporting Person on December 3, 2025.

2. This transaction was executed in multiple trades at prices ranging from $21.520 to $22.515, 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.

3. 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.

4. Held by Derek Maetzold 2020 Irrevocable Trust of which the Reporting Person is the trustee and his children are beneficiaries.

5. 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.

6. 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.

7. 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.

8. 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.

9. This transaction was executed in multiple trades at prices ranging from $22.520 to $22.680, 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.

10. Held by DJM Grantor Retained Annuity Trust No. 5 of which the Reporting Person is the trustee and beneficiary.

11. 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.

12. Held by DJM Grantor Retained Annuity Trust No. 7 of which the Reporting Person is the trustee and beneficiary.

13. The shares subject to the option are fully vested.

Remarks:

	/s/ Frank Stokes, Attorney-in-fact	05/11/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

Source: View Original Filing on SEC EDGAR

FAQ

What did CSTL CEO Derek Maetzold do in the latest Form 4 filing?

CEO Derek Maetzold exercised 6,214 Castle Biosciences (CSTL) stock options at $2.39 and reported open-market sales of 9,836 common shares around $22 per share. The sales involved his direct holdings and several family-related trusts.

How many Castle Biosciences shares did the CSTL CEO sell in this Form 4?

The filing shows total open-market sales of 9,836 Castle Biosciences (CSTL) common shares on May 7, 2026. These sales were split across Maetzold’s direct ownership and multiple trusts, at weighted-average prices near $22.08 and $22.585 per share.

How many Castle Biosciences shares does Derek Maetzold hold after these transactions?

After the reported trades, Derek Maetzold directly owns 22,385 Castle Biosciences (CSTL) shares. Additional indirect holdings are reported through several trusts where he or his spouse serves as trustee, providing further exposure beyond his direct position.

What stock options did the CSTL CEO exercise in the latest Form 4?

Maetzold exercised stock options covering 6,214 Castle Biosciences (CSTL) shares at an exercise price of $2.39 per share. A footnote notes the option shares are fully vested, and the related derivative position now shows a remaining balance of 754 option shares.

Which trusts associated with CSTL CEO Derek Maetzold were involved in these trades?

The Form 4 lists several entities, including the Maetzold Descendants 2020 Trust, Derek Maetzold 2020 Irrevocable Trust, multiple Maetzold 2018 remainder trusts for family members, and DJM Grantor Retained Annuity Trusts, all holding Castle Biosciences (CSTL) common shares.