Castle Biosciences (CSTL) CFO reports RSU grant, option exercise and share sales

Rhea-AI Filing Summary

Castle Biosciences Chief Financial Officer Frank Stokes reported a mix of stock awards, option exercises, sales, and tax-related share withholdings. On March 3, 2026, he was granted 48,367 Restricted Stock Units (RSUs), each representing one share of common stock, vesting in four equal annual installments beginning March 3, 2027.

That same day, he sold 5,300 and 1,700 shares of common stock at weighted-average prices of $27.32 and $27.81 in open-market transactions under a Rule 10b5‑1 trading plan. He also disposed of 3,611 shares at $27.57 to cover tax withholding on previously vested performance stock units.

On March 4, 2026, Stokes exercised derivative awards, converting 12,186 and 11,960 RSUs and 3,800 fully vested stock options into common stock, including 3,800 shares at an exercise price of $3.38. After these transactions, he directly owned 66,086 common shares, including 1,033 shares acquired under the employee stock purchase plan.

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^*

Stokes Frank

(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)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Financial 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		S(1)		5,300	D	$27.32(2)	54,183(3)	D
Common Stock	03/03/2026		S(1)		1,700	D	$27.81(4)	52,483	D
Common Stock	03/03/2026		F		3,611(5)	D	$27.57	48,872	D
Common Stock	03/04/2026		M		24,146	A	(6)	73,018	D
Common Stock	03/04/2026		F		10,732	D	$28.17	62,286	D
Common Stock	03/04/2026		M		3,800	A	$3.38	66,086	D

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	(6)	03/03/2026		A		48,367		(7)	(7)	Common Stock	48,367	$0	48,367	D
Restricted Stock Units	(6)	03/04/2026		M			12,186	(8)	(8)	Common Stock	12,186	$0	24,372	D
Restricted Stock Units	(6)	03/04/2026		M			11,960	(9)	(9)	Common Stock	11,960	$0	35,878	D
Stock option (right to buy)	$3.38	03/04/2026		M			3,800	(10)	03/12/2029	Common Stock	3,800	$0	14,912	D

Explanation of Responses:

1. The transaction on this Form 4 was made pursuant to a Rule 10b5-1 plan adopted by Frank Stokes on November 13, 2025.

2. This transaction was executed in multiple trades at prices ranging from $26.70 to $27.67, 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. Includes 1,033 shares acquired on February 27, 2026, under the Issuer's employee stock purchase plan.

4. This transaction was executed in multiple trades at prices ranging from $27.72 to $27.97, 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. 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.

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

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

8. On March 4, 2024, the Reporting Person was granted 48,744 RSUs which vest in four equal installments beginning on March 4, 2025.

9. On March 4, 2025, the Reporting Person was granted 47,838 RSUs which vest in four equal installments beginning on March 4, 2026.

10. The shares subject to the option are fully vested.

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).
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 insider transactions did CSTL CFO Frank Stokes report on this Form 4?

Frank Stokes reported a mix of equity award activity, option exercises, open-market sales, and tax-related share withholdings. The filing details RSU grants, conversions of RSUs and options into common stock, sales executed under a Rule 10b5-1 plan, and shares withheld to satisfy tax obligations.

How many Castle Biosciences (CSTL) shares did the CFO sell in the reported period?

The CFO sold 7,000 shares of Castle Biosciences common stock in open-market transactions. These consisted of 5,300 shares at a weighted-average price of $27.32 and 1,700 shares at $27.81, executed in multiple trades as described in the Form 4 footnotes.

What RSU grant did CSTL CFO Frank Stokes receive on March 3, 2026?

On March 3, 2026, the CFO received 48,367 Restricted Stock Units (RSUs). Each RSU represents the right to receive one share of Castle Biosciences common stock, and these RSUs vest in four equal annual installments beginning on March 3, 2027, according to the filing footnotes.

How many Castle Biosciences shares does the CFO own after these transactions?

After the reported transactions, Frank Stokes directly owns 66,086 shares of Castle Biosciences common stock. This total includes 1,033 shares acquired on February 27, 2026, under the company’s employee stock purchase plan, as specifically noted in the Form 4 footnotes.

What is the significance of the Rule 10b5-1 plan mentioned in the CSTL Form 4?

The Form 4 states that the reported transaction was made under a Rule 10b5-1 trading plan adopted on November 13, 2025. Such plans pre-schedule trades, allowing insiders to sell shares according to predetermined instructions, helping separate trading activity from day-to-day discretionary decisions.

Why were some CSTL shares marked with transaction code “F” for the CFO?

Shares with transaction code “F” reflect dispositions to pay taxes. The filing explains that 3,611 and 10,732 shares of Castle Biosciences common stock were withheld to satisfy tax withholding obligations linked to the delivery of vested performance stock units and other equity awards previously reported.