CSTL
Castle Biosciences Inc
36.80$
+3.7%
vs. previous close
Closing price · As of: Sep 17, 2026
Ownership
Ownership Structure
Who owns Castle Biosciences Inc (CSTL)? This page shows the largest institutions and funds, the ownership structure and the latest insider transactions. 88.8% of the shares are freely tradable; institutional investors hold 93.0%.
Institutional ownership
?Share of the stock held by institutional investors (funds, banks, insurers) according to regulatory filings.
93.0%
Insiders
?Share of the stock held by the executives, founders and major shareholders of the company itself.
2.7%
Float
?Share of stock freely tradable on the market — not locked up in the hands of founders, insiders, or major shareholders.
88.8%
Short % of float
?Shares sold short as a percentage of the freely tradable float — high values signal many bets on falling prices.
6.6%
Shares Outstanding
?Total number of shares issued. Price times share count gives market cap.
31Mio.
Largest Shareholders
Institutions
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| BlackRock Inc | 9.76 | 2,982,946 | -3.9 | 03/31/2026 |
| RTW INVESTMENTS, LLC | 9.03 | 2,758,335 | +30.4 | 03/31/2026 |
| Principal Financial Group Inc | 5.65 | 1,726,648 | -2.4 | 06/30/2026 |
| Portolan Capital Management, LLC | 4.42 | 1,350,283 | -21.9 | 03/31/2026 |
| Vanguard Capital Management, LLC | 3.85 | 1,177,522 | +0.0 | 03/31/2026 |
| Summit Partners Public Asset Management, LLC | 3.08 | 940,685 | -11.1 | 03/31/2026 |
| Allianz Asset Management AG | 2.88 | 879,258 | +8.4 | 06/30/2026 |
| Vanguard Portfolio Management, LLC | 2.82 | 861,771 | +0.0 | 03/31/2026 |
| Dimensional Fund Advisors, Inc. | 2.59 | 791,085 | -23.9 | 06/30/2026 |
Funds
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| Vanguard MStar Total Stk Mkt Idx Invest | 2.79 | 852,704 | +0.0 | 07/31/2026 |
Largest reported positions according to regulatory filings; stake as a percentage of shares outstanding, change versus the previous filing. Source: fundamentals data.
Insider holdings
| Person | Role | Shares | Value | As of | Type |
|---|---|---|---|---|---|
| Oelschlager Kristen M | Chief Operating Officer | 86,005 | 3,164,984 $ | Aug 25, 2026 | both |
| Maetzold Derek J | Pres. & Chief Exec. Officer | 59,437 | 2,187,282 $ | Aug 28, 2026 | both |
| Juvenal Tobin W | Chief Commercial Officer | 58,584 | 2,155,891 $ | Sep 15, 2026 | direct |
| Stokes Frank | Chief Financial Officer | 35,177 | 1,294,514 $ | Aug 14, 2026 | direct |
Holdings as of each person's most recent SEC Form 4 filing — excluding options and RSUs, which are not shares yet. Holdings may have changed between two filings.
Insiders
Insider Transactions
| Date | Person | Role | Type | Shares | Price | Value |
|---|---|---|---|---|---|---|
| Sep 15, 2026 | Juvenal Tobin W | Chief Commercial Officer | Sell | 3,294 | 35.14 | 115,758 |
| Sep 14, 2026 | Juvenal Tobin W | Chief Commercial Officer | Sell | 3,306 | 32.32 | 106,863 |
| Sep 11, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 71 | 32.78 | 2,327 |
| Sep 11, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 83 | 32.78 | 2,721 |
| Sep 11, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 223 | 32.78 | 7,310 |
| Sep 11, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 2,656 | 32.00 | 84,992 |
| Sep 11, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 3,124 | 32.00 | 99,968 |
| Sep 11, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 8,361 | 32.00 | 267,552 |
| Sep 11, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Other | 8,584 | 2.39 | 20,516 |
| Sep 1, 2026 | Oelschlager Kristen M | Chief Operating Officer | Sell | 200 | 34.02 | 6,804 |
| Sep 1, 2026 | Oelschlager Kristen M | Chief Operating Officer | Sell | 3,952 | 33.36 | 131,839 |
| Sep 1, 2026 | Oelschlager Kristen M | Chief Operating Officer | Other | 4,152 | 3.38 | 14,034 |
| Aug 31, 2026 | Juvenal Tobin W | Chief Commercial Officer | Sell | 1,730 | 32.81 | 56,761 |
| Aug 28, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 21 | 33.88 | 711 |
| Aug 28, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 177 | 33.88 | 5,997 |
| Aug 28, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 209 | 33.88 | 7,081 |
| Aug 28, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 956 | 33.88 | 32,389 |
| Aug 28, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 257 | 33.14 | 8,517 |
| Aug 28, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 2,129 | 33.14 | 70,555 |
| Aug 28, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 2,505 | 33.14 | 83,016 |
| Aug 28, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 11,472 | 33.14 | 380,182 |
| Aug 28, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Other | 12,428 | 2.39 | 29,703 |
| Aug 25, 2026 | Juvenal Tobin W | Chief Commercial Officer | Sell | 9,050 | 35.04 | 317,112 |
| Aug 25, 2026 | Oelschlager Kristen M | Chief Operating Officer | Sell | 5,223 | 34.64 | 180,920 |
| Aug 25, 2026 | Oelschlager Kristen M | Chief Operating Officer | Sell | 7,161 | 34.26 | 245,357 |
| Aug 24, 2026 | Oelschlager Kristen M | Chief Operating Officer | Sell | 12,218 | 33.69 | 411,588 |
| Aug 17, 2026 | Juvenal Tobin W | Chief Commercial Officer | Sell | 1,730 | 29.59 | 51,191 |
| Aug 14, 2026 | Stokes Frank | Chief Financial Officer | Sell | 24,908 | 29.77 | 741,511 |
| Aug 14, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 278 | 30.02 | 8,346 |
| Aug 14, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 2,306 | 30.02 | 69,226 |
| Aug 14, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 2,714 | 30.02 | 81,474 |
| Aug 14, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 1,100 | 30.02 | 33,022 |
| Aug 14, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Other | 1,100 | 2.39 | 2,629 |
| Aug 5, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 473 | 30.68 | 14,512 |
| Aug 5, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 556 | 30.68 | 17,059 |
| Aug 5, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 2,546 | 30.68 | 78,114 |
| Aug 5, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Other | 2,546 | 2.39 | 6,085 |
| Aug 4, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 4,063 | 31.34 | 127,318 |
| Aug 4, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 4,782 | 31.34 | 149,849 |
| Aug 4, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 11,935 | 31.34 | 373,995 |
| Aug 4, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 2,866 | 30.79 | 88,238 |
| Aug 4, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 3,374 | 30.79 | 103,879 |
| Aug 4, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 8,421 | 30.79 | 259,266 |
| Aug 4, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Other | 20,356 | 2.39 | 48,651 |
| Aug 3, 2026 | Oelschlager Kristen M | Chief Operating Officer | Sell | 1,100 | 30.62 | 33,682 |
| Aug 3, 2026 | Oelschlager Kristen M | Chief Operating Officer | Sell | 4,486 | 30.00 | 134,580 |
| Aug 3, 2026 | Oelschlager Kristen M | Chief Operating Officer | Sell | 3,000 | 29.12 | 87,360 |
| Aug 3, 2026 | Juvenal Tobin W | Chief Commercial Officer | Sell | 1,730 | 28.25 | 48,873 |
| Aug 3, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 3,597 | 30.35 | 109,180 |
| Aug 3, 2026 | Maetzold Derek J | Pres. & Chief Exec. Officer | Sell | 4,232 | 30.35 | 128,454 |
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: September 17, 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.