Castle Biosciences (CSTL) CEO Maetzold sells 4,017 shares under 10b5-1 plan

Rhea-AI Filing Summary

Castle Biosciences president and CEO Derek J. Maetzold sold 4,017 shares of common stock in early February 2026 under a pre-arranged Rule 10b5-1 trading plan. Sales included 3,200 shares on February 3 at a weighted-average price of $39.913 and two sales on February 4 totaling 817 shares at weighted-average prices of $37.822 and $38.61. After these transactions, he directly held 83,698 common shares. He also reported indirect beneficial ownership of additional Castle Biosciences shares through multiple family and grantor retained annuity trusts.

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

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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 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)
02/03/2026

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	02/03/2026		S(1)		3,200	D	$39.913(2)	84,515	D
Common Stock	02/04/2026		S(1)		646	D	$37.822(3)	83,869	D
Common Stock	02/04/2026		S(1)		171	D	$38.61(4)	83,698	D
Common Stock								52,923	I	By The Maetzold Descendants 2020 Trust(5)
Common Stock								44,986	I	By Derek Maetzold 2020 Irrevocable Trust(6)
Common Stock								3,618	I	By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk(7)
Common Stock								3,615	I	By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold(8)
Common Stock								3,615	I	By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold(9)
Common Stock								3,615	I	By The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold(10)
Common Stock								85,959	I	By DJM Grantor Retained Annuity Trust No. 5(11)
Common Stock								18,718	I	By DJM Grantor Retained Annuity Trust No. 6(12)
Common Stock								44,323	I	By DJM Grantor Retained Annuity Trust No. 7(13)

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 $39.590 to $40.360, 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. This transaction was executed in multiple trades at prices ranging from $37.490 to $38.080, 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.

4. This transaction was executed in multiple trades at prices ranging from $38.520 to $38.885, 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.

5. 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.

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

7. 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.

8. 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.

9. 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.

10. 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.

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

12. 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.

13. 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	02/05/2026
	** 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.
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FAQ

How many CSTL shares did CEO Derek Maetzold sell in February 2026?

Derek Maetzold sold a total of 4,017 Castle Biosciences (CSTL) shares in early February 2026. The sales were 3,200 shares on February 3 and 817 shares on February 4, all reported as open-market dispositions of common stock.

At what prices did Derek Maetzold sell his Castle Biosciences shares?

Derek Maetzold’s reported CSTL sales used weighted-average prices per transaction. He sold 3,200 shares at $39.913 on February 3, 646 shares at $37.822 on February 4, and 171 shares at $38.61 on February 4, executed in multiple trades within stated price ranges.

Was Derek Maetzold’s February 2026 CSTL stock sale under a Rule 10b5-1 plan?

Yes. The filing states the transactions were made under a Rule 10b5-1 trading plan adopted on May 8, 2025. Such preset plans allow insiders to schedule trades in advance, helping separate personal trading decisions from later company-specific news.

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

Following the reported February 2026 transactions, Derek Maetzold directly owned 83,698 shares of Castle Biosciences common stock. This figure reflects his remaining direct holdings after selling 4,017 shares across three open-market transactions disclosed in the Form 4.

What indirect CSTL shareholdings related to Derek Maetzold are disclosed?

The Form 4 lists indirect ownership of Castle Biosciences shares through several family and grantor retained annuity trusts. These include the Maetzold Descendants 2020 Trust, Derek Maetzold 2020 Irrevocable Trust, multiple 2018 remainder trusts for family members, and DJM Grantor Retained Annuity Trusts Nos. 5, 6, and 7.

What role does Derek Maetzold hold at Castle Biosciences (CSTL)?

Derek J. Maetzold is identified as president, chief executive officer, and a director of Castle Biosciences. His Form 4 filing reflects transactions and holdings in company common stock associated with his status as an executive officer and board member.