MAETZOLD DEREK J (Pres. & Chief Exec. Officer) sold 68.0% of their position (14.50K shares) of CASTLE BIOSCIENCES INC on the open market

Open‑market sale worth $515.6K — a major position exit. Review remaining holdings and any 10b5‑1 plan disclosures.

S · 3 sales

MAETZOLD DEREK J

Filed: 10/7/2026ACC: 0001628280-26-065327

InsiderMAETZOLD DEREK JCIK 1239501

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IssuerCASTLE BIOSCIENCES INCCIK 1447362

DirectorOfficer10% Owner· Pres. & Chief Exec. Officer

Since Jul 2019

-14.50K

Net shares

Net seller

$515.6K

Total sold

Open market trades

0B · 3S

Total transactions

8.16K acquired · 22.66K disposed

Non-Derivative Transactions4

Common Stock

Direct

M · Option Exercise

+8.16K

Price / share

$2.39

Trade value

$19.51K

% of position

38.0%

10/5/2026

21.48K→29.64K

Common Stock

Direct

S · Sale

−8.58K

Price / share

$35.57

Trade value

$305.16K

% of position

28.9%

10/5/2026

29.64K→21.06K

Common Stock

Indirect

S · Sale

−3.20K

Price / share

$35.57

Trade value

$113.74K

% of position

28.5%

10/5/2026

11.24K→8.04K

Common Stock

Indirect

S · Sale

−2.72K

Price / share

$35.57

Trade value

$96.67K

% of position

28.5%

10/5/2026

9.55K→6.83K

Total

Net shares

−6.33K

Net value

-$496.05K

Security	Date	Type	Shares	Price / Share	Trade Value	% of Position	Held Before	Held After
Common Stock Direct	10/5/2026	M · Option Exercise	+8.16K	$2.39	$19.51K	38.0%	21.48K	29.64K
Common Stock Direct	10/5/2026	S · Sale	−8.58K	$35.57	$305.16K	28.9%	29.64K	21.06K
Common Stock Indirect	10/5/2026	S · Sale	−3.20K	$35.57	$113.74K	28.5%	11.24K	8.04K
Common Stock Indirect	10/5/2026	S · Sale	−2.72K	$35.57	$96.67K	28.5%	9.55K	6.83K
Total			−6.33K		-$496.05K

Derivative Transactions1

Stock option (right to buy)

Direct

M · Option Exercise

Converts to

Common Stock

8.16K shares

−8.16K

Strike price

2.39

Held after

0.00

Exercisable

—

10/5/2026

Security	Converts To	Date	Type	Shares	Strike Price	Exercisable	Held After
Stock option (right to buy) Direct	Common Stock8.16K shares	10/5/2026	M · Option Exercise	−8.16K	2.39	—	0.00

Non-Derivative Holdings (Post-Transaction)8

Common Stock

Indirect

Shares owned11.26K

Common Stock

Indirect

Shares owned11.26K

Common Stock

Indirect

Shares owned11.96K

Common Stock

Indirect

Shares owned27.86K

Common Stock

Indirect

Shares owned11.26K

Common Stock

Indirect

Shares owned40.94K

Common Stock

Indirect

Shares owned11.26K

Common Stock

Indirect

Shares owned23.22K

Total

149K indirect149K

Security Title	Shares Owned	Ownership Type
Common Stock	11.26K	Indirect
Common Stock	11.26K	Indirect
Common Stock	11.96K	Indirect
Common Stock	27.86K	Indirect
Common Stock	11.26K	Indirect
Common Stock	40.94K	Indirect
Common Stock	11.26K	Indirect
Common Stock	23.22K	Indirect
Total	149K	149K indirect

Derivative Holdings (Post-Transaction)0

No derivative holdings reported