MAETZOLD DEREK J (Pres. & Chief Exec. Officer) sold 51.5% of their position (28.65K shares) of CASTLE BIOSCIENCES INC on the open market

Open‑market sale worth $867.5K — a major position exit. Review remaining holdings and any 10b5‑1 plan disclosures.

S · 6 sales

MAETZOLD DEREK J

Filed: 8/4/2026ACC: 0001628280-26-052647

InsiderMAETZOLD DEREK JCIK 1239501

→

IssuerCASTLE BIOSCIENCES INCCIK 1447362

DirectorOfficer10% Owner· Pres. & Chief Exec. Officer

Since Jul 2019

-28.65K

Net shares

Net seller

$867.5K

Total sold

Open market trades

0B · 6S

Total transactions

17.14K acquired · 45.79K disposed

Non-Derivative Transactions8

Common Stock

Direct

M · Option Exercise

+6.48K

Price / share

$2.39

Trade value

$15.49K

% of position

30.2%

7/31/2026

21.48K→27.96K

Common Stock

Direct

S · Sale

−6.48K

Price / share

$30.15

Trade value

$195.38K

% of position

23.2%

7/31/2026

27.96K→21.48K

Common Stock

Indirect

S · Sale

−1.98K

Price / share

$30.15

Trade value

$59.79K

% of position

5.2%

7/31/2026

38K→36.01K

Common Stock

Indirect

S · Sale

−1.69K

Price / share

$30.15

Trade value

$50.96K

% of position

5.2%

7/31/2026

32.30K→30.61K

Common Stock

Direct

M · Option Exercise

+10.66K

Price / share

$2.39

Trade value

$25.49K

% of position

49.6%

8/3/2026

21.48K→32.14K

Common Stock

Direct

S · Sale

−10.66K

Price / share

$30.35

Trade value

$323.68K

% of position

33.2%

8/3/2026

32.14K→21.48K

Common Stock

Indirect

S · Sale

−4.23K

Price / share

$30.35

Trade value

$128.45K

% of position

11.8%

8/3/2026

36.01K→31.78K

Common Stock

Indirect

S · Sale

−3.60K

Price / share

$30.35

Trade value

$109.18K

% of position

11.8%

8/3/2026

30.61K→27.01K

Total

Net shares

−11.50K

Net value

-$826.48K

Security	Date	Type	Shares	Price / Share	Trade Value	% of Position	Held Before	Held After
Common Stock Direct	7/31/2026	M · Option Exercise	+6.48K	$2.39	$15.49K	30.2%	21.48K	27.96K
Common Stock Direct	7/31/2026	S · Sale	−6.48K	$30.15	$195.38K	23.2%	27.96K	21.48K
Common Stock Indirect	7/31/2026	S · Sale	−1.98K	$30.15	$59.79K	5.2%	38K	36.01K
Common Stock Indirect	7/31/2026	S · Sale	−1.69K	$30.15	$50.96K	5.2%	32.30K	30.61K
Common Stock Direct	8/3/2026	M · Option Exercise	+10.66K	$2.39	$25.49K	49.6%	21.48K	32.14K
Common Stock Direct	8/3/2026	S · Sale	−10.66K	$30.35	$323.68K	33.2%	32.14K	21.48K
Common Stock Indirect	8/3/2026	S · Sale	−4.23K	$30.35	$128.45K	11.8%	36.01K	31.78K
Common Stock Indirect	8/3/2026	S · Sale	−3.60K	$30.35	$109.18K	11.8%	30.61K	27.01K
Total			−11.50K		-$826.48K

Derivative Transactions2

Stock option (right to buy)

Direct

M · Option Exercise

Converts to

Common Stock

6.48K shares

−6.48K

Strike price

2.39

Held after

72.42K

Exercisable

—

7/31/2026

Stock option (right to buy)

Direct

M · Option Exercise

Converts to

Common Stock

10.66K shares

−10.66K

Strike price

2.39

Held after

61.76K

Exercisable

—

8/3/2026

Security	Converts To	Date	Type	Shares	Strike Price	Exercisable	Held After
Stock option (right to buy) Direct	Common Stock6.48K shares	7/31/2026	M · Option Exercise	−6.48K	2.39	—	72.42K
Stock option (right to buy) Direct	Common Stock10.66K shares	8/3/2026	M · Option Exercise	−10.66K	2.39	—	61.76K

Non-Derivative Holdings (Post-Transaction)8

Common Stock

Indirect

Shares owned27.86K

Common Stock

Indirect

Shares owned11.81K

Common Stock

Indirect

Shares owned40.94K

Common Stock

Indirect

Shares owned11.81K

Common Stock

Indirect

Shares owned23.22K

Common Stock

Indirect

Shares owned11.81K

Common Stock

Indirect

Shares owned11.96K

Common Stock

Indirect

Shares owned11.81K

Total

151.22K indirect151.22K

Security Title	Shares Owned	Ownership Type
Common Stock	27.86K	Indirect
Common Stock	11.81K	Indirect
Common Stock	40.94K	Indirect
Common Stock	11.81K	Indirect
Common Stock	23.22K	Indirect
Common Stock	11.81K	Indirect
Common Stock	11.96K	Indirect
Common Stock	11.81K	Indirect
Total	151.22K	151.22K indirect

Derivative Holdings (Post-Transaction)0

No derivative holdings reported