Castle Biosciences (CSTL) CEO details RSU grants, conversions and tax share disposals

Rhea-AI Filing Summary

Castle Biosciences president and CEO Derek J. Maetzold reported several equity compensation transactions in company stock. On March 3, 2026, he received a grant of 102,597 Restricted Stock Units (RSUs), which, according to a footnote, vest in four equal annual installments beginning on March 3, 2027.

On March 4, 2026, RSUs previously granted were converted into a total of 59,097 shares of common stock through derivative exercises. On March 3 and March 4, 2026, a combined 36,974 shares of common stock were disposed of at prices of $27.57 and $28.17 per share to satisfy tax withholding obligations.

The filing also lists indirect holdings of common stock in multiple trusts, including The Maetzold Descendants 2020 Trust and several Maetzold remainder and grantor retained annuity trusts, where Maetzold or his spouse serves as trustee and certain family members are beneficiaries.

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

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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).

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)
03/03/2026

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	03/03/2026		F		19,043(1)	D	$27.57	64,655	D
Common Stock	03/04/2026		M		59,097	A	(2)	123,752	D
Common Stock	03/04/2026		F		17,931	D	$28.17	105,821	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
Restricted Stock Units	(2)	03/03/2026		A		102,597		(12)	(12)	Common Stock	102,597	$0	102,597	D
Restricted Stock Units	(2)	03/04/2026		M			31,110	(13)	(13)	Common Stock	31,110	$0	62,218	D
Restricted Stock Units	(2)	03/04/2026		M			27,987	(14)	(14)	Common Stock	27,987	$0	83,961	D

Explanation of Responses:

1. Reflects the withholding of shares of the Issuer's common stock to satisfy tax withholding obligations in connection with the delivery of vested performance stock units reported on January 12, 2026.

2. Each Restricted Stock Unit ("RSU") represents the right to receive one share of the Issuer's Common Stock.

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 RSU's vest in four equal annual installments beginning on March 03, 2027.

13. On March 4, 2024, the Reporting Person was granted 124,437 RSUs which vest in four equal installments beginning on March 4, 2025.

14. On March 4, 2025, the Reporting Person was granted 111,948 RSUs which vest in four equal installments beginning on March 4, 2026.

Remarks:

	/s/ Frank Stokes, Attorney-in-fact	03/05/2025
	** 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).
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FAQ

What insider stock transactions did CSTL CEO Derek Maetzold report on this Form 4?

Derek Maetzold reported RSU grants, RSU conversions, and tax-related share dispositions. He received 102,597 RSUs, had 59,097 RSUs convert into common stock, and disposed of 36,974 shares at $27.57 and $28.17 per share to cover tax withholding obligations.

How many Restricted Stock Units were granted to CSTL CEO Derek Maetzold and when do they vest?

Maetzold was granted 102,597 RSUs on March 3, 2026. A footnote states these RSUs vest in four equal annual installments beginning on March 3, 2027, creating a multi-year vesting schedule tied to continued service and potential long-term alignment with shareholders.

Were the CSTL insider share disposals open‑market sales or for tax withholding?

The reported share disposals were for tax withholding, not open-market selling. Footnotes explain 19,043 shares at $27.57 and 17,931 shares at $28.17 per share were withheld to satisfy tax obligations connected to vested performance stock units and equity awards, rather than discretionary sales.

What RSU awards previously granted to CSTL’s CEO are referenced in the Form 4 footnotes?

Footnotes reference prior RSU awards of 124,437 units granted March 4, 2024, vesting in four installments from March 4, 2025, and 111,948 units granted March 4, 2025, vesting in four installments from March 4, 2026. These illustrate a recurring annual equity grant pattern.

What indirect ownership in CSTL shares is reported through Maetzold family trusts?

The filing lists indirect holdings in several trusts, including The Maetzold Descendants 2020 Trust, the Derek Maetzold 2020 Irrevocable Trust, multiple 2018 remainder trusts for individual family members, and DJM Grantor Retained Annuity Trusts Nos. 5, 6, and 7, where Maetzold often serves as trustee.

How does this CSTL Form 4 describe the nature of RSUs reported for Derek Maetzold?

A footnote states each RSU represents the right to receive one share of Castle Biosciences common stock. This means RSUs convert on vesting or exercise into an equivalent number of shares, linking executive compensation directly to the company’s equity performance over time.