Director at Castle Biosciences (CSTL) acquires 5,329 shares via RSUs

Rhea-AI Filing Summary

Castle Biosciences director Rodney Cotton exercised restricted stock units to receive common shares. On March 26, 2026, he exercised 5,329 Restricted Stock Units (RSUs), each representing one share of common stock, at an exercise price of $0.00 per share.

Following the transaction, his direct holdings of Castle Biosciences common stock increased to 19,331 shares. The RSUs relate to a prior grant of 15,988 RSUs awarded on March 26, 2024, which vest in three equal annual installments beginning March 26, 2025. This filing reflects a routine compensation-related equity vesting and exercise event, not an open‑market purchase or sale.

Insider Trade Summary

5,329 shares exercised/converted

Mixed 2 txns

Insider Cotton Rodney

Role Director

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units	5,329	$0.00	--
Exercise	Common Stock	5,329	$0.00	--

Holdings After Transaction: Restricted Stock Units — 5,330 shares (Direct); Common Stock — 19,331 shares (Direct)

Footnotes (1)

1. Each Restricted Stock Unit ("RSU") represents the right to receive one share of the Issuer's Common Stock. On March 26, 2024, the Reporting Person was granted 15,988 RSUs which vest in three equal annual installments beginning on March 26, 2025.

Key Figures

RSUs exercised: 5,329 units Post-transaction holdings: 19,331 shares RSU grant size: 15,988 RSUs +2 more

5 metrics

RSUs exercised 5,329 units Exercised into common stock on March 26, 2026

Post-transaction holdings 19,331 shares Common stock directly owned after RSU exercise

RSU grant size 15,988 RSUs Granted March 26, 2024

Vesting schedule 3 equal annual installments RSU grant beginning March 26, 2025

Exercise price $0.00 per share For 5,329 RSUs converting into common stock

Key Terms

Restricted Stock Units, RSUs, derivative security, Common Stock

4 terms

Restricted Stock Units financial

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

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

RSUs financial

"On March 26, 2024, the Reporting Person was granted 15,988 RSUs which vest in three equal annual installments"

RSUs, or restricted stock units, are a form of company shares given to employees as part of their compensation. They are typically awarded with certain restrictions, such as a waiting period before they can be fully owned or sold, similar to earning a gift that becomes fully yours over time. For investors, RSUs can impact a company's stock offerings and reflect how much the company relies on stock-based incentives to attract and retain talent.

derivative security financial

"transaction_code_description: Exercise or conversion of derivative security"

A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.

Common Stock financial

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

Common stock represents ownership shares in a company, giving investors a stake in its success and a say in important decisions through voting rights. It is the most common type of stock traded on markets and can provide income through dividends, as well as potential for value growth. For investors, holding common stock means sharing in the company’s profits and risks.

Form 4 Insider Transactions: What Each Field Means →

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).

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^*

Cotton Rodney

(Last) (First) (Middle)

C/O CASTLE BIOSCIENCES

1500 W. PARKWOOD AVE SUITE 400

(Street)

FRIENDSWOOD TEXAS 77546

(City) (State) (Zip)

UNITED STATES

(Country)

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
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
03/26/2026

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

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

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

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	03/26/2026		M		5,329	A	(1)	19,331	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	(1)	03/26/2026		M			5,329	(2)	(2)	Common Stock	5,329	$0	5,330	D

Explanation of Responses:

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

2. On March 26, 2024, the Reporting Person was granted 15,988 RSUs which vest in three equal annual installments beginning on March 26, 2025.

Remarks:

	/s/ Frank Stokes, Attorney-in-fact	03/30/2026
	** 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.
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.
* Form 4: SEC 1474 (03-26)

FAQ

What did Castle Biosciences (CSTL) director Rodney Cotton report in this Form 4?

Rodney Cotton reported exercising 5,329 Restricted Stock Units to receive Castle Biosciences common shares. This increased his direct holdings to 19,331 shares. The transaction reflects equity compensation vesting, not an open-market stock purchase or sale.

How many Castle Biosciences (CSTL) shares does Rodney Cotton hold after this transaction?

After exercising 5,329 RSUs, Rodney Cotton directly holds 19,331 Castle Biosciences common shares. This figure comes from the post-transaction ownership reported in the Form 4 and reflects only his direct holdings disclosed there.

What are Restricted Stock Units (RSUs) in the Castle Biosciences (CSTL) Form 4?

The filing states each RSU represents the right to receive one Castle Biosciences common share. When RSUs vest and are exercised, they convert into actual shares, typically as part of an executive or director’s equity compensation package.

What prior RSU grant to Rodney Cotton does Castle Biosciences (CSTL) disclose?

The footnotes note a grant of 15,988 RSUs to Rodney Cotton on March 26, 2024. These RSUs vest in three equal annual installments beginning March 26, 2025, aligning his compensation with longer-term company performance.

Was this Castle Biosciences (CSTL) Form 4 an open-market stock purchase or sale?

No. The Form 4 shows a derivative exercise, not an open-market trade. Cotton exercised 5,329 RSUs at $0.00 per share, converting previously granted units into common stock as part of his equity compensation program.

Does the Castle Biosciences (CSTL) Form 4 indicate remaining RSUs for Rodney Cotton?

The filing notes a total grant of 15,988 RSUs with three annual vesting installments beginning March 26, 2025. It does not separately list remaining RSUs in the derivative summary, but the grant structure implies future vesting events under that award.