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

Castle Biosciences CEO Derek J. Maetzold sold 1,339 shares of common stock for approximately $21.97 per share under a pre-arranged trading plan.

Summary

• Derek J. Maetzold, President & Chief Executive Officer and Director of Castle Biosciences Inc. (CSTL), reported a transaction.
• On September 17, 2025, 1,339 shares of common stock were disposed of.
• The shares were sold at a weighted-average price of $21.971 per share, totaling approximately $29,419.47.
• This transaction was executed pursuant to a Rule 10b5-1 plan adopted by Maetzold on May 8, 2025.
• Following the transaction, Maetzold directly beneficially owns 65,666 shares of common stock.
• Maetzold also has significant indirect beneficial ownership through various trusts, including The Maetzold Descendants 2020 Trust, Derek Maetzold 2020 Irrevocable Trust, several Maetzold 2018 Remainder Trusts, and DJM Grantor Retained Annuity Trusts No. 5, 6, and 7.

Sentiment

Score: 5

Explanation: The sale of shares by the CEO was conducted under a pre-arranged Rule 10b5-1 plan, which typically indicates a planned liquidity event or diversification strategy rather than a reaction to new company-specific news. This makes the event largely neutral in terms of immediate sentiment.

Future Outlook

NA

Industry Context

NA

Related Party Transactions

• Shares are held indirectly by The Maetzold Descendants 2020 Trust, where the reporting person's spouse is the trustee and the spouse and children are beneficiaries.
• Shares are held indirectly by Derek Maetzold 2020 Irrevocable Trust, where the reporting person is the trustee and his children are beneficiaries.
• Shares are held indirectly by The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk, where the reporting person is the trustee and his child is the beneficiary.
• Shares are held indirectly by The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold, where the reporting person is the trustee and his child is the beneficiary.
• Shares are held indirectly by The Maetzold 2018 Remainder Trust FBO John Derek Maetzold, where the reporting person is the trustee and his child is the beneficiary.
• Shares are held indirectly by The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold, where the reporting person is the trustee and his child is the beneficiary.
• Shares are held indirectly by DJM Grantor Retained Annuity Trust No. 5, where the reporting person is the trustee and beneficiary.
• Shares are held indirectly by DJM Grantor Retained Annuity Trust No. 6, where the reporting person is the trustee and beneficiaries include other Maetzold Remainder Trusts.
• Shares are held indirectly by DJM Grantor Retained Annuity Trust No. 7, where the reporting person is the trustee and beneficiary.

Stakeholder Impact

• Shareholders: Minor impact as a small, pre-planned insider sale, not indicative of a change in company fundamentals or a lack of confidence from management.

Key Dates

Recommendation

The sale of a relatively small number of shares by the CEO was executed under a pre-arranged Rule 10b5-1 plan, which is a common practice for insiders to manage personal finances and diversify holdings. This transaction does not reflect a change in the company's fundamental outlook or the CEO's long-term commitment, thus a 'hold' recommendation is appropriate as it provides no new material information to alter an existing investment thesis.

Keywords

Castle Biosciences, CSTL, Derek Maetzold, Insider Trading, Form 4, Stock Sale, Rule 10b5-1