CASTLE BIOSCIENCES INC

CSTL

Form 4 • Statement of Changes in Beneficial Ownership

SEC Accession Number: 0001628280-26-015334
Filing date: Mar 5, 2026
Earliest execution date: Mar 3, 2026
Reporting Owners: Stokes Frank (CFO)

Summary

Type

Sell

Net shares

-21,343

% of shares

-8.92%

Amount (USD)

$593,948

Insider confidence score

28.8 out of 100

Positive

  • Under Rule 10b5-1 trading plan

Negative

  • Very large scheduled sell (<10% of shares)
  • Large sell amount ($250K+)

Stock transactions

Transaction 1

Security

Common Stock

Action

Sell

Date

2026-03-03

Code

S

Net shares

-5,300.0

Price per Share

$27.32

Amount (USD)

$144,796.00

Acquired/Disposed

Disposed

Shares Owned Before

59,483.0

Shares Owned After

54,183.0

Transaction 2

Security

Common Stock

Action

Sell

Date

2026-03-03

Code

S

Net shares

-1,700.0

Price per Share

$27.81

Amount (USD)

$47,277.00

Acquired/Disposed

Disposed

Shares Owned Before

54,183.0

Shares Owned After

52,483.0

Transaction 3

Security

Common Stock

Action

Tax_withhold

Date

2026-03-03

Code

F

Net shares

-3,611.0

Price per Share

$27.57

Amount (USD)

$99,555.27

Acquired/Disposed

Disposed

Shares Owned Before

52,483.0

Shares Owned After

48,872.0

Transaction 4

Security

Common Stock

Action

Exercise

Date

2026-03-04

Code

M

Net shares

+24,146.0

Acquired/Disposed

Acquired

Shares Owned Before

48,872.0

Shares Owned After

73,018.0

Transaction 5

Security

Common Stock

Action

Tax_withhold

Date

2026-03-04

Code

F

Net shares

-10,732.0

Price per Share

$28.17

Amount (USD)

$302,320.44

Acquired/Disposed

Disposed

Shares Owned Before

73,018.0

Shares Owned After

62,286.0

Transaction 6

Security

Common Stock

Action

Exercise

Date

2026-03-04

Code

M

Net shares

+3,800.0

Price per Share

$3.38

Amount (USD)

$12,844.00

Acquired/Disposed

Acquired

Shares Owned Before

62,286.0

Shares Owned After

66,086.0

Derivative Transactions

Transaction 1

Security

Restricted Stock Units

Action

Grant

Date

2026-03-03

Code

A

Net shares

+48,367.0

Acquired/Disposed

Acquired

Shares Owned Before

0.0

Shares Owned After

48,367.0

Transaction 2

Security

Restricted Stock Units

Action

Exercise

Date

2026-03-04

Code

M

Net shares

-12,186.0

Acquired/Disposed

Disposed

Shares Owned Before

36,558.0

Shares Owned After

24,372.0

Transaction 3

Security

Restricted Stock Units

Action

Exercise

Date

2026-03-04

Code

M

Net shares

-11,960.0

Acquired/Disposed

Disposed

Shares Owned Before

47,838.0

Shares Owned After

35,878.0

Transaction 4

Security

Stock option (right to buy)

Action

Exercise

Date

2026-03-04

Code

M

Net shares

-3,800.0

Acquired/Disposed

Disposed

Shares Owned Before

18,712.0

Shares Owned After

14,912.0

Filing's footnotes

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 (&quot;RSU&quot;) 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.

ℹ️ Filed under Rule 10b5-1 trading plan

This page is for informational purposes only. While we strive for accuracy, the summary may contain inaccuracies or omissions. Please refer to the official SEC filing for authoritative information. Open the SEC filing.