Castle Biosciences (CSTL) CEO logs Rule 10b5-1 common stock sale

Rhea-AI Filing Summary

Castle Biosciences Inc. reported an insider stock sale by a director who also serves as president and chief executive officer. On December 4, 2025, the insider sold 1,339 shares of common stock at a weighted-average price of $40.03 per share in a transaction made under a contract, instruction or written plan intended to satisfy Rule 10b5-1(c), which was adopted on May 8, 2025.

After this sale, the insider directly owned 37,547 shares of Castle Biosciences common stock and reported additional indirect holdings through several family trusts, including 52,923 shares held by The Maetzold Descendants 2020 Trust and 44,986 shares held by the Derek Maetzold 2020 Irrevocable Trust.

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)
12/04/2025

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	12/04/2025		S(1)		1,339	D	$40.03(2)	37,547	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 $40.00 to $40.11, 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	12/08/2025
	** 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.
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FAQ

What insider stock transaction did Castle Biosciences (CSTL) report?

The filing reports that a Castle Biosciences director who is also president and chief executive officer sold 1,339 shares of common stock on December 4, 2025 at a weighted-average price of $40.03 per share.

Was the CSTL insider sale made under a Rule 10b5-1 trading plan?

Yes. The filing states the transactions were made pursuant to a Rule 10b5-1 plan adopted by the reporting person on May 8, 2025, intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

How many Castle Biosciences (CSTL) shares does the insider own after the sale?

Following the reported sale, the insider beneficially owned 37,547 shares of Castle Biosciences common stock directly, plus additional indirect holdings through multiple family trusts.

What key indirect shareholdings are disclosed for the CSTL insider?

The filing lists several indirect positions, including 52,923 shares held by The Maetzold Descendants 2020 Trust and 44,986 shares held by the Derek Maetzold 2020 Irrevocable Trust, along with other family and grantor retained annuity trusts.

Did the Castle Biosciences (CSTL) insider report any derivative securities?

The section for derivative securities (Table II) does not list any derivative securities acquired, disposed of, or beneficially owned for this reporting person.

What transaction pricing details are provided in the CSTL insider sale?

The sale of 1,339 shares was executed in multiple trades at prices ranging from $40.00 to $40.11 per share, with a reported weighted-average sale price of $40.03 per share.