MAETZOLD DEREK J (Pres. & Chief Exec. Officer) sold 60.3% of their position (14.50K shares) of CASTLE BIOSCIENCES INC on the open market

Open‑market sale worth $512.2K — a major position exit. Review remaining holdings and any 10b5‑1 plan disclosures.

S · 3 sales

MAETZOLD DEREK J

Filed: 9/23/2026ACC: 0001628280-26-063221

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

$512.2K

Total sold

Open market trades

0B · 3S

Total transactions

8.58K acquired · 23.08K disposed

Non-Derivative Transactions4

Common Stock

Direct

M · Option Exercise

+8.58K

Price / share

$2.39

Trade value

$20.51K

% of position

39.9%

9/21/2026

21.48K→30.06K

Common Stock

Direct

S · Sale

−8.58K

Price / share

$35.33

Trade value

$303.17K

% of position

28.5%

9/21/2026

30.06K→21.48K

Common Stock

Indirect

S · Sale

−3.20K

Price / share

$35.33

Trade value

$113K

% of position

22.2%

9/21/2026

14.43K→11.24K

Common Stock

Indirect

S · Sale

−2.72K

Price / share

$35.33

Trade value

$96.04K

% of position

22.2%

9/21/2026

12.27K→9.55K

Total

Net shares

−5.92K

Net value

-$491.70K

Security	Date	Type	Shares	Price / Share	Trade Value	% of Position	Held Before	Held After
Common Stock Direct	9/21/2026	M · Option Exercise	+8.58K	$2.39	$20.51K	39.9%	21.48K	30.06K
Common Stock Direct	9/21/2026	S · Sale	−8.58K	$35.33	$303.17K	28.5%	30.06K	21.48K
Common Stock Indirect	9/21/2026	S · Sale	−3.20K	$35.33	$113K	22.2%	14.43K	11.24K
Common Stock Indirect	9/21/2026	S · Sale	−2.72K	$35.33	$96.04K	22.2%	12.27K	9.55K
Total			−5.92K		-$491.70K

Derivative Transactions1

Stock option (right to buy)

Direct

M · Option Exercise

Converts to

Common Stock

8.58K shares

−8.58K

Strike price

2.39

Held after

8.16K

Exercisable

—

9/21/2026

Security	Converts To	Date	Type	Shares	Strike Price	Exercisable	Held After
Stock option (right to buy) Direct	Common Stock8.58K shares	9/21/2026	M · Option Exercise	−8.58K	2.39	—	8.16K

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 owned40.94K

Common Stock

Indirect

Shares owned11.26K

Common Stock

Indirect

Shares owned11.26K

Common Stock

Indirect

Shares owned27.86K

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	40.94K	Indirect
Common Stock	11.26K	Indirect
Common Stock	11.26K	Indirect
Common Stock	27.86K	Indirect
Common Stock	23.22K	Indirect
Total	149K	149K indirect

Derivative Holdings (Post-Transaction)0

No derivative holdings reported