Castle Biosciences CEO Derek Maetzold Exercises Options, Sells Shares

What Happened

• Derek J. Maetzold, President, CEO and Director of Castle Biosciences (CSTL), exercised stock options to acquire 8,584 shares at $2.39 per share (cost $20,516) on 2026-09-11, and the same day sold a total of ~14,518 shares in open-market trades for aggregate proceeds of approximately $464,870.
• The filing also reports a related derivative conversion/disposition of 8,584 shares at $0 (reported as part of the exercise/conversion). The option underlying the exercise was fully vested (footnote F13).

Key Details

• Transaction date: 2026-09-11; Form 4 filed 2026-09-15 (filing appears timely).
• Exercise: 8,584 shares acquired at $2.39 each (total $20,516).
• Sales: multiple open-market sales totaling ~14,518 shares for about $464,870 (sales executed at prices reported around $32.00 and $32.78; F2 notes trade prices ranged $31.700–$32.508 and a weighted-average was used).
• Plan/authorization: Transactions were executed pursuant to a Rule 10b5-1 trading plan adopted June 2, 2026 (footnote F1).
• Shares owned after the transaction: not specified in the summary data provided.
• Trust holdings: several holdings reported are held in family/GRAT trusts of which Mr. Maetzold is trustee or beneficiary (footnotes F3–F12).

Context

• This was an option exercise (derivative M) followed by same-day sales. When options are exercised and shares are sold the same day, it is commonly structured to cover exercise costs/taxes (i.e., a cashless-like outcome), but the filing itself only reports the transactions — it does not state the insider’s motivation.
• The presence of a 10b5-1 plan indicates the sales were pre-authorized under a structured plan adopted earlier (June 2, 2026), which is common for scheduled insider selling and reduces the implication of opportunistic timing.