Castle Biosciences CSTL Insider Ownership

NASDAQ CSTL

$34.36 +1.21 (+3.65%)

As of: Oct 21, 2026 · 1:01 PM EDT

Insider Holdings by Owner

417.89K Shares

Insider Ownership Statistics

as of 30 Sep, 2026

Insider Ownership

1.67%

▼-0.574% pp QoQ

Shares Held by Insiders

508.97K

filed for Sep 2026

▼-25.61% QoQ

Shares Outstanding

30.51Mn

30,508,534 shares

Direct Holdings

362.58K

Indirect: 146.39K

Net Shares Traded (QoQ)

-175.24K

net selling in Sep 2026

Insiders Holding Shares

with Form 4 holdings on file

Shares Owned by Insiders

Shares held % of outstanding

Latest —

Average ownership —

Peak ownership —

Shares Purchased/Sold by Insiders

Bought Sold

Latest quarter —

Net over range —

Buying quarters —

Insider Ownership Summary

Updated Oct 11, 2026

Across the past 12 months, open-market trades by Castle Biosciences insiders were all sales, totaling $18.83 million (618.27K shares).

Counted by insider, open-market selling of CSTL stock in the past 12 months came from 5 insiders, with no insider buying.
The largest open-market sales of CSTL in the past 12 months were by Derek J. Maetzold (President & Chief Executive Officer), totaling $11.18 million (373.72K shares), most recently on October 5, 2026.
Away from the open market, CSTL insiders received 79.55K shares in stock awards, acquired 366.08K shares through option exercises and conversions and gave up 119.37K shares to cover taxes or exercise prices over the last 12 months.
Per Business Quant data, Castle Biosciences insiders hold 502.64K shares in total based on their latest Form 4 filings, down 26.54% from 684.21K shares at the end of Q2 2026 and down 23.78% from 659.43K shares at the end of Q3 2025.
Of the 502.64K shares held by Castle Biosciences insiders, 362.16K shares (72.05%) are held directly and 140.47K shares (27.95%) indirectly, through trusts, partnerships, family members and other entities.
Per Business Quant, 11 insiders of CSTL hold shares, counting officers, directors and 10% owners who have filed a Form 4 in the past two years.
CSTL's three largest insider shareholders, per their latest Form 4 filings, are Kristen M. Oelschlager (Chief Operating Officer, 86K shares), Derek J. Maetzold (President & Chief Executive Officer, 80.96K shares) and Tobin W. Juvenal (Chief Commercial Officer, 54.24K shares).
The holding of Kristen M. Oelschlager makes up 17.11% of all shares held by Castle Biosciences insiders.
Institutional investors held 89.58% of Castle Biosciences stock at the end of Q2 2026, while the latest Form 4 filings of its insiders account for about 1.65%; other investors, including the public, hold roughly 8.77%.
Over the past 12 months, 11 insiders reported transactions in Castle Biosciences stock in 78 Form 4 filings.
The insider holdings and trades above for Castle Biosciences reflect Form 4 filings through October 7, 2026.

Form 4 Holdings

Insiders Holding CSTL

Insiders 12

Shares held 417.89K

Of outstanding 1.37%

#	Insider	Position	Direct	Indirect	Total	Share of Insiders	Last Filed
1	Tobin W Juvenal	Chief Commercial Officer	48,719	0	48,719	11.7%	14 Oct, 2026
2	Mara G. Aspinall	Director	44,139	0	44,139	10.6%	04 Jun, 2024
3	Ellen Goldberg	Director	40,921	0	40,921	9.8%	27 May, 2025
4	Tiffany Olson	Director	39,573	0	39,573	9.5%	27 May, 2025
5	Kim Caple	Director	36,121	0	36,121	8.6%	27 May, 2025
6	Derek J Maetzold	Pres. Chief Exec. Officer	21,064	14,870	35,934	8.6%	07 Oct, 2026
7	Miles Harrison	Director	35,631	0	35,631	8.5%	27 May, 2025
8	Frank Stokes	Chief Financial Officer	35,177	0	35,177	8.4%	18 Aug, 2026
9	Rodney Cotton	Director	32,998	0	32,998	7.9%	27 May, 2025
10	G Bradley Cole	Director	32,976	0	32,976	7.9%	27 May, 2026
11	Daniel Bradbury	Director	22,340	0	22,340	5.3%	27 May, 2025
12	Kristen M Oelschlager	Chief Operating Officer	13,356	0	13,356	3.2%	05 Oct, 2026

Each row is that insider’s most recently reported position, from Form 4 filings over the last 60 months — which is why this total does not tie to the quarterly series above, where a quarter counts only the insiders who filed in it. Shares held through a fund or institutional portfolio are counted on the institutional ownership page instead.

Form 4 Filings

2,970 Insider Transactions

Source SEC Form 4

Latest quarter Sep 2026

Date	Insider	Position	Transaction	Shares	Price	Value	Shares Held After	Ownership
12 Oct, 2026	Tobin W Juvenal	Chief Commercial Officer	Disposed S	3,288	$33.64	$110.61K	48,719	Direct
05 Oct, 2026	Derek J Maetzold	Pres. Chief Exec. Officer	Acquired M	8,165	$2.39	$19.51K	29,644	Direct
05 Oct, 2026	Derek J Maetzold	Pres. Chief Exec. Officer	Disposed S	8,580	$35.57	$305.16K	21,064	Direct
05 Oct, 2026	Derek J Maetzold	Pres. Chief Exec. Officer	Disposed S	3,198	$35.57	$113.74K	8,038	Indirect
05 Oct, 2026	Derek J Maetzold	Pres. Chief Exec. Officer	Disposed S	2,718	$35.57	$96.67K	6,832	Indirect
05 Oct, 2026	Derek J Maetzold	Pres. Chief Exec. Officer	Disposed M	8,165	$0.00	$0	0	Direct
01 Oct, 2026	Kristen M Oelschlager	Chief Operating Officer	Acquired M	4,153	$3.38	$14.04K	17,509	Direct
01 Oct, 2026	Kristen M Oelschlager	Chief Operating Officer	Disposed S	2,807	$35.75	$100.35K	14,702	Direct
01 Oct, 2026	Kristen M Oelschlager	Chief Operating Officer	Disposed S	1,346	$36.38	$48.97K	13,356	Direct
01 Oct, 2026	Kristen M Oelschlager	Chief Operating Officer	Disposed M	4,153	$0.00	$0	8,305	Direct
29 Sep, 2026	Tobin W Juvenal	Chief Commercial Officer	Disposed S	5,543	$35.50	$196.77K	53,041	Direct
30 Sep, 2026	Tobin W Juvenal	Chief Commercial Officer	Disposed S	1,034	$34.20	$35.36K	52,007	Direct
21 Sep, 2026	Derek J Maetzold	Pres. Chief Exec. Officer	Acquired M	8,580	$2.39	$20.51K	30,059	Direct
21 Sep, 2026	Derek J Maetzold	Pres. Chief Exec. Officer	Disposed S	8,580	$35.33	$303.17K	21,479	Direct
21 Sep, 2026	Derek J Maetzold	Pres. Chief Exec. Officer	Disposed S	3,198	$35.33	$113.00K	11,236	Indirect
21 Sep, 2026	Derek J Maetzold	Pres. Chief Exec. Officer	Disposed S	2,718	$35.33	$96.04K	9,550	Indirect
21 Sep, 2026	Derek J Maetzold	Pres. Chief Exec. Officer	Disposed M	8,580	$0.00	$0	8,165	Direct
14 Sep, 2026	Tobin W Juvenal	Chief Commercial Officer	Disposed S	3,306	$32.32	$106.86K	61,878	Direct
15 Sep, 2026	Tobin W Juvenal	Chief Commercial Officer	Disposed S	3,294	$35.14	$115.76K	58,584	Direct
11 Sep, 2026	Derek J Maetzold	Pres. Chief Exec. Officer	Acquired M	8,584	$2.39	$20.52K	30,063	Direct

Showing 1 to 20 of 2,970 transactions