[Form 4] Castle Biosciences, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Derek J. Maetzold, President & Chief Executive Officer and a director of Castle Biosciences, Inc. (CSTL), sold 1,339 shares of the issuer's common stock on 09/02/2025 under a Rule 10b5-1 trading plan adopted May 8, 2025. The transaction executed in multiple trades produced a weighted-average sale price of $23.93 per share. Following the sale, the filing reports 67,005 shares held directly and multiple indirect trust holdings disclosed by name and amount, including 52,923 shares held by The Maetzold Descendants 2020 Trust and other family trusts and grantor retained annuity trusts. The Form 4 was signed by attorney-in-fact Frank Stokes on 09/04/2025.

Positive

• Transaction executed under a Rule 10b5-1 trading plan, indicating a pre-established schedule for the disposition.
• Weighted-average sale price disclosed ($23.93) and provided price range ($23.790.00), with an undertaking to provide detailed trade information upon request.
• Comprehensive disclosure of indirect holdings across named family trusts and grantor retained annuity trusts, including trustee/beneficiary relationships.

Negative

• None.

Insights

Financial Analyst

TL;DR: Insider sale under a pre-existing 10b5-1 plan; small single-day disposition relative to total reported holdings.

The filing documents a sale of 1,339 common shares at a weighted-average price of $23.93 executed pursuant to a Rule 10b5-1 plan adopted May 8, 2025. The report discloses both direct ownership (67,005 shares) and multiple indirect trust holdings by family and grantor retained annuity trusts. The filing provides the execution price range ($23.79–$24.00) and an undertaking to provide detailed trade-by-trade information upon request, which supports transparency. Based solely on the disclosed figures, the transaction appears to be a routine, pre-planned disposition rather than an unscheduled open-market sale.

Corporate Governance Expert

TL;DR: Proper compliance with disclosure rules and 10b5-1 designation; family trust structures are fully disclosed.

The Form 4 identifies the reporting persons roles as President & CEO and director and clearly marks the sale as executed pursuant to a 10b5-1 plan. The filing itemizes indirect holdings across named trusts and indicates trustee relationships and beneficiaries, which enhances governance transparency. The signature by an attorney-in-fact is present and dated, fulfilling filing formalities. From a governance standpoint, the disclosure is complete within the information provided.

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.

505 S. FRIENDSWOOD DRIVE, SUITE 401

(Street)

FRIENDSWOOD TX 77546

(City) (State) (Zip)

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

3. Date of Earliest Transaction (Month/Day/Year)
09/02/2025

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

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

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

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	09/02/2025		S(1)		1,339	D	$23.93(2)	67,005	D
Common Stock								52,923	I	By The Maetzold Descendants 2020 Trust(3)
Common Stock								44,986	I	By Derek Maetzold 2020 Irrevocable Trust(4)
Common Stock								3,618	I	By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk(5)
Common Stock								3,615	I	By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold(6)
Common Stock								3,615	I	By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold(7)
Common Stock								3,615	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

Explanation of Responses:

1. These transactions were made pursuant to a Rule 10b5-1 plan adopted by the Reporting Person on May 8, 2025

2. This transaction was executed in multiple trades at prices ranging from $23.79 to $24.00, 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.

Remarks:

	/s/ Frank Stokes, Attorney-in-fact	09/04/2025
	** 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.

FAQ

What did Derek J. Maetzold sell in the Form 4 for CSTL?

The filing reports a sale of 1,339 shares of Castle Biosciences (CSTL) common stock on 09/02/2025.

At what price were the CSTL shares sold in the Form 4?

The weighted-average sale price was reported as $23.93 per share, with execution prices ranging from $23.79 to $24.00.

Was the CSTL transaction part of a Rule 10b5-1 plan?

Yes. The sale was made pursuant to a Rule 10b5-1 plan adopted May 8, 2025.

How many CSTL shares does Maetzold report holding after the sale?

The Form 4 reports 67,005 shares held directly following the reported transaction, plus multiple indirect trust holdings itemized in the filing.

Who signed the Form 4 for the CSTL filing and when?

The Form 4 was signed by Frank Stokes, Attorney-in-fact on 09/04/2025.