Notice of Proposed Sale · 144

Castle Biosciences, Inc.

CSTLNASDAQEQUITYCurrent

Notice of Proposed Sale

Filed Jul 31, 2026Accepted Jul 31, 2026, 4:52 PM EDTFiling CIK 1447362Accession 0001958244-26-000470

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Notice of proposed sale. The proposed amounts below do not establish that a sale occurred.

Proposed-sale notice

Issuer: Castle Biosciences, Inc.
Issuer CIK: 0001447362
SEC file number: 001-38984
Phone: 1-866-788-9007
Person for whose account securities are to be sold: Derek Maetzold
Relationships to issuer: Officer
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Securities proposed for sale

Securities proposed for sale · 1 reported row
Security	Proposed units	Aggregate market value	Units outstanding	Approximate sale date	Exchange	Broker / market maker
Common	67,662	1,894,536	30,549,507	07/31/2026	NASD	Goldman Sachs & Co. LLC

Broker / market maker — proposed row 1, entry 1

Name: Goldman Sachs & Co. LLC
Street: 200 West Street
City: New York
State / country code: NY
Postal code: 10282

Acquisition of securities to be sold

Acquisition of securities to be sold · 3 reported rows
Security	Acquired	Nature of acquisition	Acquired from	Amount acquired	Gift transaction	Donor acquired	Payment date	Nature of payment
Common	10/29/2007	Acquired as gift	Derek Maetzold	14,927	Y	10/29/2007	10/29/2007	None
Common	10/29/2007	Acquired as gift	Derek Maetzold	12,689	Y	10/29/2007	10/29/2007	None
Common	05/10/2018	Acquired as compensation -- Stock Options	Issuer	40,046	N		05/10/2018	Compensation -- Cashless exercise / same-day sale

Sales reported in the preceding three months

Sales reported in the preceding three months · 56 reported rows
Seller	Security	Sale date	Amount sold	Gross proceeds
The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold	Common	05/07/2026	278	6,142.06
Derek Maetzold	Common	05/07/2026	6,214	137,290.52
The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold	Common	05/07/2026	278	6,142.06
Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020	Common	05/07/2026	1,153	25,474.08
The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold	Common	05/07/2026	278	6,142.06
The Maetzold Descendants 2020 Trust dtd 12/4/2020	Common	05/07/2026	1,357	29,981.21
The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk	Common	05/07/2026	278	6,142.06
The Maetzold Descendants 2020 Trust dtd 12/4/2020	Common	05/20/2026	322	6,421.25
The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk	Common	05/20/2026	66	1,316.16
The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold	Common	05/20/2026	66	1,316.16
Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020	Common	05/20/2026	273	5,444.1
The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold	Common	05/20/2026	66	1,316.16
The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold	Common	05/20/2026	66	1,316.16
Derek Maetzold	Common	05/20/2026	130	2,592.43
The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold	Common	05/21/2026	212	4,268.74
The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold	Common	05/21/2026	212	4,268.74
The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold	Common	05/21/2026	212	4,268.74
The Maetzold Descendants 2020 Trust dtd 12/4/2020	Common	05/21/2026	1,035	20,840.32
Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020	Common	05/21/2026	880	17,719.31
Derek Maetzold	Common	05/21/2026	420	8,456.94
The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk	Common	05/21/2026	212	4,268.74
The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold	Common	06/01/2026	278	5,781.56
The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold	Common	06/01/2026	278	5,781.56
The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold	Common	06/01/2026	278	5,781.56
Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020	Common	06/01/2026	1,153	23,978.9
The Maetzold Descendants 2020 Trust dtd 12/4/2020	Common	06/01/2026	1,357	28,221.48
The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk	Common	06/01/2026	278	5,781.56
Derek Maetzold	Common	06/01/2026	6,214	129,232.37
The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold	Common	06/15/2026	278	5,726.07
The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold	Common	06/15/2026	278	5,726.07
The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk	Common	06/15/2026	278	5,726.07
The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold	Common	06/15/2026	278	5,726.07
Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020	Common	06/15/2026	1,153	23,748.76
The Maetzold Descendants 2020 Trust dtd 12/4/2020	Common	06/15/2026	1,357	27,950.63
Derek Maetzold	Common	06/15/2026	550	11,328.55
The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold	Common	07/01/2026	278	6,734.6
Derek Maetzold	Common	07/01/2026	6,214	150,535.39
The Maetzold Descendants 2020 Trust dtd 12/4/2020	Common	07/01/2026	1,357	32,873.59
The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold	Common	07/01/2026	278	6,734.6
Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020	Common	07/01/2026	1,153	27,931.65
The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk	Common	07/01/2026	278	6,734.6
The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold	Common	07/01/2026	278	6,734.6
Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020	Common	07/14/2026	1,153	26,359.34
The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold	Common	07/14/2026	278	6,355.5
The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk	Common	07/14/2026	278	6,355.5
The Maetzold Descendants 2020 Trust dtd 12/4/2020	Common	07/14/2026	1,357	31,023.08
The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold	Common	07/14/2026	278	6,355.5
Derek Maetzold	Common	07/14/2026	550	12,573.84
The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold	Common	07/14/2026	278	6,355.5
The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk	Common	07/27/2026	278	6,702.11
The Maetzold Descendants 2020 Trust dtd 12/4/2020	Common	07/27/2026	1,357	32,714.96
The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold	Common	07/27/2026	278	6,702.11
The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold	Common	07/27/2026	278	6,702.11
Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020	Common	07/27/2026	1,153	27,796.87
The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold	Common	07/27/2026	278	6,702.11
Derek Maetzold	Common	07/27/2026	6,214	149,808.98

Seller — prior-sale row 1, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 2, entry 1

Name: Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 3, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 4, entry 1

Name: Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 5, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 6, entry 1

Name: The Maetzold Descendants 2020 Trust dtd 12/4/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 7, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 8, entry 1

Name: The Maetzold Descendants 2020 Trust dtd 12/4/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 9, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 10, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 11, entry 1

Name: Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 12, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 13, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 14, entry 1

Name: Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 15, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 16, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 17, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 18, entry 1

Name: The Maetzold Descendants 2020 Trust dtd 12/4/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 19, entry 1

Name: Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 20, entry 1

Name: Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 21, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 22, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 23, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 24, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 25, entry 1

Name: Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 26, entry 1

Name: The Maetzold Descendants 2020 Trust dtd 12/4/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 27, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 28, entry 1

Name: Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 29, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 30, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 31, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 32, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 33, entry 1

Name: Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 34, entry 1

Name: The Maetzold Descendants 2020 Trust dtd 12/4/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 35, entry 1

Name: Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 36, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 37, entry 1

Name: Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 38, entry 1

Name: The Maetzold Descendants 2020 Trust dtd 12/4/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 39, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 40, entry 1

Name: Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 41, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 42, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 43, entry 1

Name: Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 44, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 45, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 46, entry 1

Name: The Maetzold Descendants 2020 Trust dtd 12/4/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 47, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 48, entry 1

Name: Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 49, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 50, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 51, entry 1

Name: The Maetzold Descendants 2020 Trust dtd 12/4/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 52, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Hannah Elizabeth Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 53, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o Peter Douglas Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 54, entry 1

Name: Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 55, entry 1

Name: The Maetzold 2018 Remainder Trust f/b/o John Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Seller — prior-sale row 56, entry 1

Name: Derek Maetzold
Street: 1500 W. Parkwood Ave
Street (continued): Suite 400
City: Friendswood
State / country code: TX
Postal code: 77546

Prior-sale reporting

Nothing to report for the preceding three months: N

Remarks

The sales of shares set forth herein are made in connection with a selling plan dated 12/3/2025 that is intended to comply with Rule 10b5-1(c). Total number of shares to be sold includes: 40,046 shares by Derek Maetzold, 12,689 shares by DM 2020 Irrev Trust, 14,927 shares by Maetzold Descendants 2020 Trust.