MAETZOLD DEREK J 4

What Happened

• Derek J. Maetzold, President & CEO and a director of Castle Biosciences (CSTL), sold a total of 19,300 common shares in open-market transactions. On 2026-03-17 he sold 18,650 shares at a weighted-average price of $25.93 for proceeds of $483,595 (F2). On 2026-03-18 he sold 650 shares at a weighted-average price of $25.39 for proceeds of $16,504 (F3). Total proceeds across both sales were $500,099. These were sales (not purchases) and therefore are not a bullish signal; they were executed under a predefined trading plan.

Key Details

• Transaction dates and prices:
  • 2026-03-17: 18,650 shares sold, WA price $25.93, proceeds $483,595 (executed in multiple trades at $25.66–$26.27) (F2).
  • 2026-03-18: 650 shares sold, WA price $25.39, proceeds $16,504 (executed in multiple trades at $25.26–$25.48) (F3).
• Shares owned after transaction: Not specified in the excerpted transaction details in this summary.
• Notable footnotes: Transactions were made pursuant to a Rule 10b5-1 trading plan adopted December 3, 2025 (F1). The filing also references multiple family/grantor retained annuity trusts and remainder trusts (F4–F12) indicating certain holdings are held in trusts for family members where Maetzold is trustee or beneficiary.
• Timeliness: Report period covers the 2026-03-17 transaction and the Form 4 was filed 2026-03-19 — the filing appears timely (Form 4 is generally due within two business days).

Context

• A Rule 10b5-1 plan is a prearranged trading program that allows insiders to sell shares at predetermined times; such sales are often routine and set up to avoid trading on nonpublic information. Sales reduce insider shareholdings but do not, by themselves, indicate management’s view of the company’s prospects.