Derek J. Maetzold - 14 Aug 2026 Form 4 Insider Report for CASTLE BIOSCIENCES INC (CSTL)

Reporting relationship: Pres. & Chief Exec. Officer, Director
Issuer ticker: CSTL
Reported as of: 14 Aug 2026
Net transaction value: -$217,105
SEC form: 4
Accepted by SEC: 18 Aug 2026, 16:09:59 UTC
Prior SEC filing: 06 Aug 2026
Source filing: View source filing
Reporting owner signature: /s/ Frank Stokes, Attorney-in-fact

Key filing fact

Derek J. Maetzold filed Form 4 for CASTLE BIOSCIENCES INC (CSTL) on 18 Aug 2026.

Key facts

This page summarizes Derek J. Maetzold's Form 4 filing for CASTLE BIOSCIENCES INC (CSTL).
9 reported transactions and 1 derivative row are listed below.
Accepted by SEC: 18 Aug 2026, 16:09.

Change

Previous filing in this sequence was filed on 06 Aug 2026.
Current net transaction value: -$217,105.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001239501 Primary reporting owner

MAETZOLD DEREK J

Relationship: Pres. & Chief Exec. Officer, Director
Address: C/O CASTLE BIOSCIENCES, INC., 1500 W. PARKWOOD AVE SUITE 400, FRIENDSWOOD
Signature: /s/ Frank Stokes, Attorney-in-fact
Signature date: 18 Aug 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

CSTL transaction

Common Stock

Options Exercise

Transaction value
Shares: +1,100
Change %: +5.1%
Price: $2.39^*
Shares after: 22,579
Date: 14 Aug 2026
Ownership: Direct
Footnotes: F1

CSTL transaction

Common Stock

Sale

Transaction value: $33,022
Shares: -1,100
Change %: -4.9%
Price: $30.02
Shares after: 21,479
Date: 14 Aug 2026
Ownership: Direct
Footnotes: F1, F2

CSTL transaction

Common Stock

Sale

Transaction value: $81,474
Shares: -2,714
Change %: -12%
Price: $30.02
Shares after: 20,355
Date: 14 Aug 2026
Ownership: By The Maetzold Descendants 2020 Trust
Footnotes: F1, F2, F3

CSTL transaction

Common Stock

Sale

Transaction value: $69,226
Shares: -2,306
Change %: -12%
Price: $30.02
Shares after: 17,301
Date: 14 Aug 2026
Ownership: By Derek Maetzold 2020 Irrevocable Trust
Footnotes: F1, F2, F4

CSTL transaction

Common Stock

Sale

Transaction value: $8,346
Shares: -278
Change %: -2.4%
Price: $30.02
Shares after: 11,534
Date: 14 Aug 2026
Ownership: By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk
Footnotes: F1, F2, F5

CSTL transaction

Common Stock

Sale

Transaction value: $8,346
Shares: -278
Change %: -2.4%
Price: $30.02
Shares after: 11,534
Date: 14 Aug 2026
Ownership: By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold
Footnotes: F1, F2, F6

CSTL transaction

Common Stock

Sale

Transaction value: $8,346
Shares: -278
Change %: -2.4%
Price: $30.02
Shares after: 11,534
Date: 14 Aug 2026
Ownership: By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold
Footnotes: F1, F2, F7

CSTL transaction

Common Stock

Sale

Transaction value: $8,346
Shares: -278
Change %: -2.4%
Price: $30.02
Shares after: 11,534
Date: 14 Aug 2026
Ownership: By The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold
Footnotes: F1, F2, F8

CSTL holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 11,963
Date: 14 Aug 2026
Ownership: By DJM Grantor Retained Annuity Trust No. 6
Footnotes: F9

CSTL holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 27,862
Date: 14 Aug 2026
Ownership: By DJM Grantor Retained Annuity Trust No. 7
Footnotes: F10

CSTL holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 40,935
Date: 14 Aug 2026
Ownership: By DJM Grantor Retained Annuity Trust No. 8
Footnotes: F11

CSTL holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 23,216
Date: 14 Aug 2026
Ownership: DJM Grantor Retained Annuity Trust No. 9
Footnotes: F12

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

CSTL transaction Derivative

Stock option (right to buy)

Options Exercise

Transaction value
Shares: -1,100
Change %: -2.8%
Price: $0.000000^*
Shares after: 37,757
Date: 14 Aug 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 1,100
Exercise price: $2.39
Footnotes: F1, F13

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Rule 10b5-1 trading plan

These transactions were reported as open-market trades under a Rule 10b5-1 plan. The plan lets an insider set trading instructions in advance, which can reduce the risk of trading while in possession of material nonpublic information.

Original filing language: transaction made pursuant to a contract, instruction, or written plan intended to satisfy Rule 10b5-1(c).

Explanation of responses 13 footnotes

Footnote F1

These transactions were made pursuant to a Rule 10b5-1 plan adopted by the Reporting Person on December 3, 2025.

Footnote F2

This transaction was executed in multiple trades at prices ranging from $29.73 to $30.55, 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.

Footnote F3

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.

Footnote F4

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

Footnote F5

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.

Footnote F6

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.

Footnote F7

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.

Footnote F8

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.

Footnote F9

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.

Footnote F10

Held by DJM Grantor Retained Annuity Trust No. 7 of which the Reporting Person is the trustee and beneficiary.

Footnote F11

Held by DJM Grantor Retained Annuity Trust No. 8 of which the Reporting Person is the trustee and beneficiary.

Footnote F12

Held by DJM Grantor Retained Annuity Trust No. 9 of which the Reporting Person is the trustee and beneficiary.

Footnote F13

The shares subject to the option are fully vested.