Castle Biosciences Inc (CSTL)
Who owns Castle Biosciences Inc (CSTL)? This page shows the largest institutions and funds, the ownership structure and the latest insider transactions. 88.3% of the shares are freely tradable; institutional investors hold 93.0%.
Ownership Structure
Largest Shareholders
Institutions
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| BlackRock Inc | 9.84 | 2,982,946 | -3.9 | 03/31/2026 |
| RTW INVESTMENTS, LLC | 9.09 | 2,758,335 | +30.4 | 03/31/2026 |
| Vanguard Group Inc | 7.25 | 2,199,829 | +1.3 | 12/31/2025 |
| Principal Financial Group Inc | 5.84 | 1,769,877 | -2.1 | 03/31/2026 |
| Portolan Capital Management, LLC | 4.45 | 1,350,283 | -21.9 | 03/31/2026 |
| Vanguard Capital Management, LLC | 3.88 | 1,177,522 | +0.0 | 03/31/2026 |
| Dimensional Fund Advisors, Inc. | 3.43 | 1,039,761 | -9.1 | 03/31/2026 |
| Summit Partners Public Asset Management, LLC | 3.10 | 940,685 | -11.1 | 03/31/2026 |
| Vanguard Portfolio Management, LLC | 2.84 | 861,771 | +0.0 | 03/31/2026 |
Funds
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| Vanguard Total Stock Mkt Idx Inv | 2.72 | 823,964 | +0.0 | 04/30/2026 |
Largest reported positions according to regulatory filings; stake as a percentage of shares outstanding, change versus the previous filing. Source: fundamentals data.
Insider Transactions
| Date | Person | Role | Type | Shares | Price | Value |
|---|---|---|---|---|---|---|
| 27. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 10 | 25.06 | 251 |
| 27. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 43 | 25.06 | 1,078 |
| 27. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 50 | 25.06 | 1,253 |
| 27. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 232 | 25.06 | 5,814 |
| 27. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 268 | 24.13 | 6,467 |
| 27. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 1,110 | 24.13 | 26,784 |
| 27. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 1,307 | 24.13 | 31,538 |
| 27. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 5,982 | 24.13 | 144,346 |
| 27. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Other | 6,214 | 2.39 | 14,851 |
| 14. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 278 | 22.92 | 6,372 |
| 14. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 1,153 | 22.92 | 26,427 |
| 14. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 1,357 | 22.92 | 31,102 |
| 14. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 550 | 22.92 | 12,606 |
| 14. Jul 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Other | 550 | 2.39 | 1,315 |
| 21. Apr 2026 | Derek J Maetzold | Insider | Sell | 550 | 25.10 | 13,805 |
| 21. Apr 2026 | Derek J Maetzold | Insider | Sell | 3,622 | 25.10 | 90,912 |
Reportable transactions by officers and major shareholders from SEC Form 4 filings. "Other" includes things like stock grants and option exercises without a buy/sell character.
View all insider transactions →Data as of: July 31, 2026 · Source: fundamental data & SEC filings (annual and quarterly reports, 10-K/10-Q)
Note: pure fact-based analysis, not investment advice and not a solicitation to buy or sell. All figures without guarantee.