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CSTL — structural market context

Castle Biosciences, Inc.

Structural market context from public regulatory and market data, shown with its as-of dates. Descriptive only: nothing on this page is a recommendation, a prediction, or advice to buy or sell any security.

What changed

As of the close on Oct 21. Each line shows the earlier value, the later value and their dates.

Price

Close $34.37 (Oct 21) vs $33.15 (Oct 20): +3.68%.

Volume

0.94× its 20-session average (359K) on Oct 21.

Includes pre- and post-market trading.

Short interest

Short interest 2.0M shares (settlement Sep 30) vs 1.9M (Sep 15).

No new publication in this window. Latest: settlement Sep 30, published Oct 10.

Fails-to-deliver

Latest file (settlements Sep 15–Sep 30, published Oct 16): 1 day with fails, largest 125 shares on Sep 18.

Previous file (settlements Sep 1–Sep 14, published Sep 30): 1 day with fails, largest 57 shares on Sep 2.

No new publication in this window.

Insider filings (Form 4)

1 Form 4 filing recorded, with 3 transactions: 0 purchase transactions (code P, $0), 3 sale transactions (code S, $463K).

Filed Oct 21. Form 4 data arrives about a day after filing.

CSTL events and their magnitude

Latest SEC filing in the event study

Form 4 · sale · filed 2026-10-21 · View on sec.gov ↗

…

Open the Event Study →

CSTL short interest & days to cover

SHARES SHORT
2.0M
% OF FLOAT
7.4%
DAYS TO COVER
4.8
CHANGE VS PRIOR
+5.3%

FINRA consolidated short interest, reported twice a month and published ~2 weeks after each settlement date. % of float uses reported free float. · as of 2026-09-30 (23d ago)

CSTL fails-to-deliver (FTD)

Settlement dateFailed sharesPrice
2026-09-18 · 35d125$36.78
2026-09-02 · 51d57$33.44
2026-08-31 · 53d28$33.5

SEC fails-to-deliver files, published twice a month with ~6 weeks of delay.

CSTL insider buying and selling (Form 4)

Last 12 months, Form 4 codes P and S: 0 purchases · 43 sales

InsiderTypeSharesValueFiled
MAETZOLD DEREK J · director, officer: Pres. & Chief Exec. OfficerSale (S)3K$87K2026-10-21
MAETZOLD DEREK J · director, officer: Pres. & Chief Exec. OfficerSale (S)3K$102K2026-10-21
MAETZOLD DEREK J · director, officer: Pres. & Chief Exec. OfficerSale (S)9K$274K2026-10-21
Juvenal Tobin W · officer: Chief Commercial OfficerSale (S)3K$111K2026-10-14
MAETZOLD DEREK J · director, officer: Pres. & Chief Exec. OfficerSale (S)3K$97K2026-10-07

SEC Form 4 filings: purchases and sales reported on Form 4 (transaction codes P and S) only; grants and option exercises excluded. Attributed public records.

Frequently asked questions

What is CSTL's short interest?
As of the FINRA settlement date 2026-09-30, CSTL had 2.0M shares sold short — 7.4% of its float, with 4.8 days to cover at average volume. FINRA publishes this data roughly two weeks after each twice-monthly settlement, so it is inherently delayed. A short-interest figure describes an aggregate position; it does not predict what the stock will do.
Are insiders buying CSTL?
In the last 12 months of SEC Form 4 filings, CSTL recorded 0 insider purchases and 43 sales reported on Form 4 (transaction codes P and S; grants and option exercises excluded). These are attributed public records — information, not instruction.
Is this page telling me to buy or sell CSTL?
No. Everything on this page is descriptive, structural market context from public data, shown with its as-of dates. TradeAI News does not issue directional recommendations, price predictions, or buy/sell advice — for any ticker.
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CSTL: the full history

Latest rows shown. Full history, market-wide screens, cluster detection and the context journal live in the dashboard.

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Not financial advice. Trading involves risk. Descriptive structural context, never a recommendation.