---
title: Castle Biosciences CEO Derek Maetzold Sold About $2.2M of CSTL After a Guidance Raise and a Post-Earnings Rally
type: news
slug: derek-maetzold-castle-biosciences-sold-2-2m-after-guidance-raise
canonical_url: https://13finsight.com/news/derek-maetzold-castle-biosciences-sold-2-2m-after-guidance-raise
published_at: 2026-03-06T16:43:16.064Z
updated_at: 2026-03-06T16:43:17.299Z
author: Alex Rivera
author_title: Breaking News Editor
author_url: https://13finsight.com/authors/alex-rivera
word_count: 437
locale: en
source: 13F Insight
---

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

> Derek Maetzold's November-December Form 4 activity came after Castle Biosciences raised 2025 revenue guidance and the stock surged on the Q3 release, making this a post-strength sell pattern rather than a panic exit.

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 RangeActionSharesEstimated Value 2025-11-04 to 2025-12-22Open-market sales53,443~$2.22M 2025-12-09 to 2025-12-10Option exercises97,838Exercise-driven Latest shares owned after saleRemaining stake33,530Not 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 MetricValue InsiderDerek Maetzold CompanyCastle Biosciences (CSTL) Recent sale windowNov. 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.

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Source: 13F Insight — https://13finsight.com/news/derek-maetzold-castle-biosciences-sold-2-2m-after-guidance-raise
Author: Alex Rivera — https://13finsight.com/authors/alex-rivera
Last updated: 2026-03-06T16:43:17.299Z