Castle Biosciences (NASDAQ: CSTL) CEO sells 4,172 shares via trusts

Q: How many Castle Biosciences (CSTL) options did Derek Maetzold exercise?

Derek Maetzold exercised stock options covering 550 shares of Castle Biosciences Common Stock at an exercise price of $2.39 per share. The options were fully vested, and a corresponding 550 shares were sold in the open market.

Q: How many Castle Biosciences (CSTL) shares does Derek Maetzold hold directly after these trades?

Following the reported transactions, Derek Maetzold holds 21,479 shares of Castle Biosciences Common Stock directly. The Form 4 also shows additional indirect holdings through various family trusts and grantor retained annuity trusts.

Filing Impact

(Moderate)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

Entities associated with Castle Biosciences CEO Derek Maetzold reported open-market sales totaling 4,172 shares of Common Stock on April 21 at a weighted-average price of $25.098 per share. These transactions were made pursuant to a Rule 10b5-1 plan adopted on December 3, 2025.

The filing also shows Maetzold exercised stock options to acquire 550 shares at $2.39 per share and sold a matching 550 shares, leaving 21,479 shares held directly, plus additional indirect holdings in several family and grantor retained annuity trusts.

Insider Trade Summary 10b5-1

Net Seller: 4,172 shares ($104,709)

Net Sell 12 txns

Insider MAETZOLD DEREK J

Role Pres. & Chief Exec. Officer

Sold 4,172 shs ($105K)

Type	Security	Shares	Price	Value
Exercise	Stock option (right to buy)	550	$0.00	--
Exercise	Common Stock	550	$2.39	$1K
Sale	Common Stock	550	$25.098	$14K
Sale	Common Stock	1,357	$25.098	$34K
Sale	Common Stock	1,153	$25.098	$29K
Sale	Common Stock	278	$25.098	$7K
Sale	Common Stock	278	$25.098	$7K
Sale	Common Stock	278	$25.098	$7K
Sale	Common Stock	278	$25.098	$7K
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Stock option (right to buy) — 6,968 shares (Direct, null); Common Stock — 22,029 shares (Direct, null); Common Stock — 47,495 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 $25.000 to $25.585, 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. 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: 4,172 shares Weighted-average sale price: $25.098 per share Options exercised: 550 shares +4 more

7 metrics

Shares sold 4,172 shares Total net shares sold on April 21, 2026

Weighted-average sale price $25.098 per share Open-market Common Stock sales on April 21, 2026

Options exercised 550 shares Stock option (right to buy) exercise on April 21, 2026

Option exercise price $2.39 per share Exercise price for 550-share stock option

Direct holdings after transactions 21,479 shares Common Stock held directly following April 21, 2026 trades

Derek Maetzold 2020 Irrevocable Trust holdings 40,367 shares Common Stock held indirectly via 2020 Irrevocable Trust after trades

Maetzold Descendants 2020 Trust holdings 47,495 shares Common Stock held indirectly via Descendants 2020 Trust after trades

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) ... underlying security title Common Stock and underlying security shares 550.0000."

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 →

04/23/2026 - 04:16 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)
04/21/2026

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	04/21/2026		M⁽¹⁾		550	A	$2.39	22,029	D
Common Stock	04/21/2026		S⁽¹⁾		550	D	$25.098⁽²⁾	21,479	D
Common Stock	04/21/2026		S⁽¹⁾		1,357	D	$25.098⁽²⁾	47,495	I	By The Maetzold Descendants 2020 Trust⁽³⁾
Common Stock	04/21/2026		S⁽¹⁾		1,153	D	$25.098⁽²⁾	40,367	I	By Derek Maetzold 2020 Irrevocable Trust⁽⁴⁾
Common Stock	04/21/2026		S⁽¹⁾		278	D	$25.098⁽²⁾	2,502	I	By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk⁽⁵⁾
Common Stock	04/21/2026		S⁽¹⁾		278	D	$25.098⁽²⁾	2,502	I	By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold⁽⁶⁾
Common Stock	04/21/2026		S⁽¹⁾		278	D	$25.098⁽²⁾	2,502	I	By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold⁽⁷⁾
Common Stock	04/21/2026		S⁽¹⁾		278	D	$25.098⁽²⁾	2,502	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⁽⁹⁾
Common Stock								18,718	I	By DJM Grantor Retained Annuity Trust No. 6⁽¹⁰⁾
Common Stock								44,323	I	By DJM Grantor Retained Annuity Trust No. 7⁽¹¹⁾

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	04/21/2026		M⁽¹⁾			550	⁽¹²⁾	11/11/2028	Common Stock	550	$0	6,968	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 $25.000 to $25.585, 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. Held by DJM Grantor Retained Annuity Trust No. 5 of which the Reporting Person is the trustee and beneficiary.

10. 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.

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

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

Remarks:

	/s/ Frank Stokes, Attorney-in-fact	04/23/2026
	** 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 insider transactions did Castle Biosciences (CSTL) report for Derek Maetzold?

Castle Biosciences reported that entities linked to CEO Derek Maetzold sold 4,172 shares of Common Stock and exercised options for 550 shares on April 21, 2026, combining open-market sales with an option exercise.

At what price were the Castle Biosciences (CSTL) shares sold in this Form 4?

The reported sales were executed at a weighted-average price of $25.098 per share, with individual trades ranging from $25.000 to $25.585. These open-market transactions were disclosed as part of a pre-arranged 10b5-1 trading plan.

How many Castle Biosciences (CSTL) options did Derek Maetzold exercise?

Derek Maetzold exercised stock options covering 550 shares of Castle Biosciences Common Stock at an exercise price of $2.39 per share. The options were fully vested, and a corresponding 550 shares were sold in the open market.

How many Castle Biosciences (CSTL) shares does Derek Maetzold hold directly after these trades?

Following the reported transactions, Derek Maetzold holds 21,479 shares of Castle Biosciences Common Stock directly. The Form 4 also shows additional indirect holdings through various family trusts and grantor retained annuity trusts.

Were the Castle Biosciences (CSTL) insider sales made under a trading plan?

Yes. The Form 4 notes that the transactions were made under a Rule 10b5-1 plan adopted by Derek Maetzold on December 3, 2025. Such plans allow pre-scheduled trading independent of day-to-day market conditions.

Which trusts associated with Derek Maetzold held Castle Biosciences (CSTL) shares after the trades?

Post-transaction holdings include shares in entities such as the Derek Maetzold 2020 Irrevocable Trust, the Maetzold Descendants 2020 Trust, and several DJM Grantor Retained Annuity Trusts, alongside smaller positions in 2018 remainder trusts.