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  4. [144] CASTLE BIOSCIENCES INC SEC Filing

CSTL (CSTL) insider and family trusts detail planned and recent stock sales

Filing Impact
(Neutral)
Filing Sentiment
(Neutral)
Form Type
144

Rhea-AI Filing Summary

The filing reports a planned sale of 25,792 shares of common stock, with an indicated market value of $763,959.04, to be effected through Goldman Sachs & Co. LLC on or about 08/14/2026 on the NASD market.

It also lists numerous recent sales of common shares by Derek Maetzold and several related family trusts between May and August 2026, including individual transactions of several thousand shares each, some following a cashless exercise / same-day sale of stock options granted as compensation.

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Negative

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Planned shares to be sold 25,792 shares Common stock to be sold through Goldman Sachs & Co. LLC on 08/14/2026
Planned sale market value $763,959.04 Market value associated with 25,792 common shares planned for sale
Option-related shares 13,528 shares Common shares from stock options acquired as compensation on 05/10/2018
Sale by Derek Maetzold on 08/03/2026 10,664 shares for $323,041.08 Common stock sale by Derek Maetzold on 08/03/2026
Sale by Derek Maetzold on 08/04/2026 20,356 shares for $632,020.39 Common stock sale by Derek Maetzold on 08/04/2026
Trust sale on 08/04/2026 8,156 shares for $253,230.41 Common stock sale by Maetzold Descendants 2020 Trust on 08/04/2026
Trust sale on 08/03/2026 4,232 shares for $128,198.60 Common stock sale by Maetzold Descendants 2020 Trust on 08/03/2026
cashless exercise financial
"Compensation -- Cashless exercise / same-day sale"
A cashless exercise is a way for an option holder to convert stock options into actual shares without paying the purchase price in cash; instead they immediately give up a portion of the newly issued shares to cover the cost and any withholding taxes. Investors care because this process increases the number of shares available and can slightly dilute existing holdings, while also signaling how insiders or employees are realizing compensation without needing cash — similar to paying for a purchase by handing over part of what you just bought.
Irrevocable Trust financial
"Derek Maetzold 2020 Irrevocable Trust dtd 12/04/2020"
An irrevocable trust is a legal arrangement where an owner transfers assets into a separate entity managed by a trustee and gives up the power to modify or reclaim those assets. For investors it matters because putting stock or other holdings into such a trust can change who controls and benefits from the assets, affect taxes and creditor protection, and influence how easy it is to sell or value those holdings—like placing valuables in a locked safe overseen by someone else.
Remainder Trust financial
"The Maetzold 2018 Remainder Trust f/b/o Emily Carol Kirk"
Acquired as gift financial
"Common | 10/29/2007 | Acquired as gift | Derek Maetzold"
same-day sale financial
"Compensation -- Cashless exercise / same-day sale"

FAQ

What does the CSTL Form 144 filing disclose about planned stock sales?
The filing indicates a planned sale of 25,792 common shares with an estimated market value of $763,959.04 through Goldman Sachs & Co. LLC around 08/14/2026. This represents an intended resale of existing shares, not a new issuance.

How many CSTL shares are planned to be sold through the broker in this filing?
The notice shows a planned sale of 25,792 common shares with an associated market value of $763,959.04. Goldman Sachs & Co. LLC is listed as the broker, and the shares are expected to trade on the NASD market on 08/14/2026.

What recent CSTL share sales by Derek Maetzold are detailed?
Among other trades, Derek Maetzold is shown selling 10,664 shares for $323,041.08 on 08/03/2026 and 20,356 shares for $632,020.39 on 08/04/2026. These are part of a broader series of sales across May–August 2026.

Does the CSTL filing involve option exercises or only direct stock sales?
The filing notes common shares acquired as compensation via stock options on 05/10/2018, followed by a cashless exercise / same-day sale of 13,528 shares. Subsequent sections describe direct stock sales by Derek Maetzold and related trusts.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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144: Filer Information

144: Issuer Information

144: Securities Information



Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold


* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.



Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

144: Remarks and Signature

Source: View Original Filing on SEC EDGAR