Company: CSTL
Filing Date: 2025-02-27
Form Type: S-8
Source: 0001447362-25-000032
Chunk: 1

Company: CASTLE BIOSCIENCES INC
Filing Date: 2025-02-27
Form: S-8
Chunk 1
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If an emerging growth company, indicate by check mark if the Registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. o

### EXPLANATORY NOTE
This Registration Statement on Form S-8 is being filed by Castle Biosciences, Inc. (the “

#### Registrant
”) for the purpose of registering (i) an additional 1,424,159 shares of the Registrant’s Common Stock, $0.001 par value per share (“

#### Common Stock
”), under the Registrant’s 2019 Equity Incentive Plan (the “

#### 2019 Plan
”), pursuant to the provisions of the 2019 Plan providing for an automatic increase in the number of shares of Common Stock reserved and available for issuance under the 2019 Plan, and (ii) 284,831 additional shares of Common Stock under the Registrant’s 2019 Employee Stock Purchase Plan (the “

#### 2019 ESPP
”) pursuant to the provisions of the 2019 ESPP providing for an automatic increase in the number of shares of Common Stock reserved and available for issuance under the 2019 ESPP, in each case on January 1, 2025.

### INCORPORATION OF DOCUMENTS BY REFERENCE
This Registration Statement is being filed for the purpose of registering additional securities of the same class as other securities for which Registration Statements of the Registrant on Form S-8 relating to the same employee benefit plans are effective.

The Registrant previously registered shares of its Common Stock for issuance under the 2019 Plan and 2019 ESPP under Registration Statements on Form S-8 filed with the Securities and Exchange Commission (the “

#### SEC
”) on July 29, 2019 (File No. 333-232884) , March 10, 2020 (File No. 333-237062) , March 11, 2021 (File No. 333-254179) , February 28, 2022 (File No. 333-263094) , February 28, 2023 (File No. 333-270141) and February 28, 2024 ( File No. 333-277472) . Pursuant to General Instruction E to Form S-8, this Registration Statement hereby incorporates by reference the contents of the Registration Statements referenced above