Form 4: Castle Biosciences CEO Sells Shares Under 10b5-1 Plan

Castle Biosciences President and CEO Derek J. Maetzold sold 2,678 shares of common stock for approximately $91,100 under a pre-arranged Rule 10b5-1 trading plan.

Summary

• Derek J. Maetzold, President and Chief Executive Officer of Castle Biosciences Inc., sold 2,678 shares of the company's common stock.
• The transaction occurred on November 18, 2025, at a weighted-average price of $34.02 per share, with trades ranging from $33.79 to $34.16.
• The total value of the shares sold was approximately $91,100.
• This sale was executed pursuant to a Rule 10b5-1 trading plan adopted by Mr. Maetzold on May 8, 2025.
• Following this transaction, Mr. Maetzold directly beneficially owns 50,937 shares of common stock.
• Additionally, Mr. Maetzold indirectly beneficially owns 261,372 shares through various trusts, bringing his total beneficial ownership to 312,309 shares.

Sentiment

Score: 5

Explanation: The sale of shares by the CEO is a neutral event given it was executed under a pre-arranged 10b5-1 plan, indicating no new negative information. The amount sold is also a small percentage of total holdings.

Positives

• The sale was conducted under a pre-arranged Rule 10b5-1 plan, indicating it was scheduled in advance and not a reaction to recent company performance or news.
• The amount sold represents a small fraction of Mr. Maetzold's total beneficial ownership, suggesting continued significant alignment with shareholder interests.

Negatives

• An insider sale, even under a 10b5-1 plan, can sometimes be perceived negatively by the market as it reduces the insider's direct equity stake in the company.

Future Outlook

NA

Industry Context

NA

Related Party Transactions

• Derek J. Maetzold indirectly beneficially owns shares through several trusts, including The Maetzold Descendants 2020 Trust, Derek Maetzold 2020 Irrevocable Trust, The Maetzold 2018 Remainder Trusts (FBO Emily Carol Kirk, Hannah Elizabeth Maetzold, John Derek Maetzold, Peter Douglas Maetzold), and DJM Grantor Retained Annuity Trusts No. 5, No. 6, and No. 7. These trusts are considered related parties due to Mr. Maetzold's or his family's involvement as trustee or beneficiary.

Stakeholder Impact

• Shareholders: A minor reduction in direct insider ownership, but the pre-planned nature mitigates concerns. The overall impact on shareholder confidence is likely minimal given the small transaction size relative to total holdings and the 10b5-1 plan.

Key Dates

Recommendation

The insider sale by the CEO, while a reduction in direct ownership, was executed under a pre-arranged 10b5-1 plan and represents a small portion of his total beneficial holdings. This suggests a routine liquidity event rather than a signal of deteriorating company fundamentals. Therefore, the filing itself does not provide a strong basis for a change in investment thesis, warranting a 'hold' recommendation.

Keywords

Castle Biosciences, CSTL, Derek J. Maetzold, Insider Sale, Form 4, SEC Filing, Stock Transaction, 10b5-1 Plan, CEO, Director