Castle Biosciences CEO trades shares, exercises options

Castle Biosciences CEO Derek J. Maetzold reported a mix of option exercises and share sales in Castle Biosciences Inc. common stock.

Rhea-AI Filing Summary

Castle Biosciences CEO Derek J. Maetzold reported a mix of option exercises and share sales in Castle Biosciences Inc. common stock. He exercised stock options to acquire 6,214 shares at a price of $2.3900 per share and sold 9,836 shares in open-market transactions at a weighted-average price of $20.8570 per share.

Part of the sales came from entities such as The Maetzold Descendants 2020 Trust, the Derek Maetzold 2020 Irrevocable Trust and several 2018 remainder trusts, while a portion was from his direct holdings, which totaled 21,479 shares after these transactions. All sales were executed under a pre-arranged Rule 10b5-1 trading plan adopted on December 3, 2025.

Insider Trade Summary 10b5-1

Exercise and sale activity reported; no spread calculated

Exercise and Sale 14 txns

Insider MAETZOLD DEREK J

Role Pres. & Chief Exec. Officer

Sold 9,836 shs ($205K)

Approx. gross sale proceeds $205K

Approx. exercise cost $15K

Type	Security	Shares	Price	Value
Exercise	Stock option (right to buy)	204	$0.00	$0.00
Exercise	Stock option (right to buy)	6,010	$0.00	$0.00
Exercise	Common Stock	204	$2.39	$487.56
Exercise	Common Stock	6,010	$2.39	$14K
Sale	Common Stock	6,214	$20.857	$130K
Sale	Common Stock	1,357	$20.857	$28K
Sale	Common Stock	1,153	$20.857	$24K
Sale	Common Stock	278	$20.857	$6K
Sale	Common Stock	278	$20.857	$6K
Sale	Common Stock	278	$20.857	$6K
Sale	Common Stock	278	$20.857	$6K
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Stock option (right to buy) — 92,431 contracts (Direct); Common Stock — 21,479 shares (Direct); Common Stock — 43,424 shares (Indirect, By The Maetzold Descendants 2020 Trust); Common Stock — 36,908 shares (Indirect, By Derek Maetzold 2020 Irrevocable Trust); Common Stock — 1,668 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk); Common Stock — 1,668 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold); Common Stock — 1,668 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold); Common Stock — 1,668 shares (Indirect, By The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold); Common Stock — 85,959 shares (Indirect, By DJM Grantor Retained Annuity Trust No. 5); Common Stock — 18,718 shares (Indirect, By DJM Grantor Retained Annuity Trust No. 6); Common Stock — 44,323 shares (Indirect, By DJM Grantor Retained Annuity Trust No. 7)

Footnotes (12)

1. F1. These transactions were made pursuant to a Rule 10b5-1 plan adopted by the Reporting Person on December 3, 2025.
2. F2. This transaction was executed in multiple trades at prices ranging from $20.470 to $21.175, 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.
3. 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.
4. F4. Held by Derek Maetzold 2020 Irrevocable Trust of which the Reporting Person is the trustee and his children are beneficiaries.
5. 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.
6. 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.
7. 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.
8. 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.
9. F9. Held by DJM Grantor Retained Annuity Trust No. 5 of which the Reporting Person is the trustee and beneficiary.
10. 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.
11. F11. Held by DJM Grantor Retained Annuity Trust No. 7 of which the Reporting Person is the trustee and beneficiary.
12. F12. The shares subject to the option are fully vested.

Key Figures

Shares sold: 9,836 shares Weighted-average sale price: $20.8570 per share Sale price range: $20.470–$21.175 per share +4 more

7 metrics

Shares sold 9,836 shares Common stock sold in open-market transactions on June 1, 2026

Weighted-average sale price $20.8570 per share Open-market sales of CSTL common stock

Sale price range $20.470–$21.175 per share Price range of multiple trades aggregated into reported average

Options exercised 6,214 shares Stock options converted into common shares on June 1, 2026

Option exercise price $2.3900 per share Exercise price for stock options converted into common stock

Direct common shares after trades 21,479 shares Derek Maetzold’s direct CSTL holdings following reported transactions

Descendants 2020 Trust holdings 43,424 shares Common stock held by The Maetzold Descendants 2020 Trust after sales

Key Terms

Rule 10b5-1 plan, Grantor Retained Annuity Trust, Irrevocable Trust, 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 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.

Irrevocable Trust financial

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

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.

Stock option (right to buy) financial

"Stock option (right to buy) with underlying security title Common Stock and exercise price of $2.3900."

weighted-average sale price financial

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

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider transactions did CSTL CEO Derek Maetzold report?

Derek Maetzold reported exercising stock options and selling Castle Biosciences (CSTL) shares. He exercised 6,214 options at $2.3900 per share and sold 9,836 common shares at a weighted-average price of $20.8570 per share in open-market trades.

How many Castle Biosciences (CSTL) shares did the CEO sell and at what price?

Entities associated with Derek Maetzold sold 9,836 Castle Biosciences shares. The open-market sales were executed at a weighted-average price of $20.8570 per share, with individual trades reported in a range from $20.470 to $21.175 per share.

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

Yes. The filing states the transactions were made pursuant to a Rule 10b5-1 trading plan adopted by Derek Maetzold on December 3, 2025. Such plans pre-schedule trades, indicating these sales were planned in advance rather than timed discretionarily.

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

Derek Maetzold exercised stock options covering 6,214 Castle Biosciences common shares. The options had an exercise price of $2.3900 per share and were fully vested. After these exercises, no remaining derivative positions related to these options are shown in the filing.

What are Derek Maetzold’s direct Castle Biosciences share holdings after these trades?

Following the reported transactions, Derek Maetzold directly held 21,479 Castle Biosciences common shares. In addition, multiple family and grantor trusts, where he or his spouse serve as trustee or beneficiary, continued to hold significant indirect positions in the company’s common stock.

Which family trusts associated with Derek Maetzold sold CSTL shares?

Sales were reported from several family-related entities, including The Maetzold Descendants 2020 Trust, the Derek Maetzold 2020 Irrevocable Trust, and multiple Maetzold 2018 remainder trusts. Each trust is described as having Maetzold or his spouse as trustee and family members as beneficiaries.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 06/03/2026 - 04:15 PM Learn about SEC filing dates

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).

X

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)
06/01/2026

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	06/01/2026		M(1)		204	A	$2.39	21,683	D
Common Stock	06/01/2026		M(1)		6,010	A	$2.39	27,693	D
Common Stock	06/01/2026		S(1)		6,214	D	$20.857(2)	21,479	D
Common Stock	06/01/2026		S(1)		1,357	D	$20.857(2)	43,424	I	By The Maetzold Descendants 2020 Trust(3)
Common Stock	06/01/2026		S(1)		1,153	D	$20.857(2)	36,908	I	By Derek Maetzold 2020 Irrevocable Trust(4)
Common Stock	06/01/2026		S(1)		278	D	$20.857(2)	1,668	I	By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk(5)
Common Stock	06/01/2026		S(1)		278	D	$20.857(2)	1,668	I	By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold(6)
Common Stock	06/01/2026		S(1)		278	D	$20.857(2)	1,668	I	By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold(7)
Common Stock	06/01/2026		S(1)		278	D	$20.857(2)	1,668	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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock option (right to buy)	$2.39	06/01/2026		M(1)			204	(12)	11/11/2028	Common Stock	204	$0	0	D
Stock option (right to buy)	$2.39	06/01/2026		M(1)			6,010	(12)	05/09/2028	Common Stock	6,010	$0	92,431	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 $20.470 to $21.175, 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.

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	06/03/2026
	** 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)