Castle Biosciences CEO Derek Maetzold Sold About $2.2M of CSTL After a Guidance Raise and a Post-Earnings Rally

Derek Maetzold, founder and CEO of Castle Biosciences, sold about $2.2 million of stock between November 4, 2025 and December 22, 2025. That timing matters. The company's November 3 Q3 release reported $83.0 million in revenue, raised full-year guidance to $327 million to $335 million, and helped send the stock sharply higher after earnings. This looks less like distress selling and more like a post-strength monetization pattern.

The Selling Window

Date Range	Action	Shares	Estimated Value
2025-11-04 to 2025-12-22	Open-market sales	53,443	~$2.22M
2025-12-09 to 2025-12-10	Option exercises	97,838	Exercise-driven
Latest shares owned after sale	Remaining stake	33,530	Not a full exit

Why the Timing Matters

Castle's Q3 2025 release was fundamentally supportive. The company reported $83.0 million in quarterly revenue, lifted full-year guidance, and highlighted strong volume growth in its core testing franchises. Market reaction followed: the stock jumped sharply after earnings, and later reports noted that CSTL reached a 52-week high in the weeks that followed. Selling into that kind of strength reads differently from selling into a collapse.

That does not make the transactions irrelevant. It just changes the interpretation. Maetzold was still reducing exposure while the operating narrative improved. For retail investors, that usually means asking whether the trades were mainly liquidity and compensation-management decisions or whether they reflect a view that upside had already been recognized in the price.

What the Tape Says

The sales were not a single-day dump. They were spread across multiple dates from early November through late December, with transaction prices rising from roughly the low $30s into the high $30s and low $40s. That pattern often looks more like orderly monetization than a sudden loss of confidence. The December exercises reinforce that reading: part of the activity was linked to compensation mechanics, followed by sales into a stronger tape.

Still, the optics matter because founders set tone. Investors in diagnostics names such as Natera, Exact Sciences, and Guardant Health often care as much about insider behavior as they do about top-line growth, especially when the company is balancing growth with profitability questions.

Key Facts

Metric	Value
Insider	Derek Maetzold
Company	Castle Biosciences (CSTL)
Recent sale window	Nov. 4, 2025 to Dec. 22, 2025
Estimated value sold in window	~$2.22M
Q3 2025 revenue	$83.0M
Updated 2025 revenue guidance	$327M to $335M

What To Watch

• Further founder selling: Another quarter of sales after the same post-earnings setup would change the tone.
• Operational follow-through: Investors should compare insider selling with whether Castle sustains its volume and guidance momentum.
• Peer context: If you track diagnostics, compare CSTL with NTRA, EXAS, and GH rather than reading the tape in isolation.
• Signal hygiene: For more context, see our Form 4 guide, how to read position changes, and how to compare filings correctly.