# EDGAR Filing Document

**Accession Number:** 0001239501
**File Stem:** 0001628280-26-044019
**Filing Date:** 2026-6
**Character Count:** 10286
**Document Hash:** e955c0fd7e8d32fcf089e91398caa753
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001628280-26-044019.hdr.sgml**: 20260617

**ACCESSION NUMBER**: 0001628280-26-044019

**CONFORMED SUBMISSION TYPE**: 4

**PUBLIC DOCUMENT COUNT**: 1

**CONFORMED PERIOD OF REPORT**: 20260615

**FILED AS OF DATE**: 20260617

**DATE AS OF CHANGE**: 20260617

**REPORTING-OWNER**: 

**OWNER DATA:**
- **COMPANY CONFORMED NAME:** MAETZOLD DEREK J
- **CENTRAL INDEX KEY:** 0001239501

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** 4
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-38984
- **FILM NUMBER:** 261099601

**MAIL ADDRESS:**
- **STREET 1:** 820 S. FRIENDSWOOD DRIVE
- **STREET 2:** SUITE 201
- **CITY:** FRIENDSWOOD
- **STATE:** TX
- **ZIP:** 77546
**ISSUER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** CASTLE BIOSCIENCES INC
- **CENTRAL INDEX KEY:** 0001447362
- **STANDARD INDUSTRIAL CLASSIFICATION:** SERVICES-MEDICAL LABORATORIES [8071]
- **ORGANIZATION NAME:** 08 Industrial Applications and Services
- **EIN:** 770701774
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**BUSINESS ADDRESS:**
- **STREET 1:** 1500 W. PARKWOOD AVE.
- **STREET 2:** SUITE 400
- **CITY:** FRIENDSWOOD
- **STATE:** TX
- **ZIP:** 77546
- **BUSINESS PHONE:** 866-788-9007

**MAIL ADDRESS:**
- **STREET 1:** 1500 W. PARKWOOD AVE.
- **STREET 2:** SUITE 400
- **CITY:** FRIENDSWOOD
- **STATE:** TX
- **ZIP:** 77546

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## FORM 4

### STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

[ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

[x] Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

---

| | | |
|:---|:---|:---|
| **1. Name and Address of Reporting Person**<sup>*</sup><br>MAETZOLD DEREK J<br><sub>(Last) (First) (Middle)</sub><br>C/O CASTLE BIOSCIENCES, INC.<br>1500 W. PARKWOOD AVE SUITE 400<br><sub>(Street)</sub><br>FRIENDSWOOD, TX 77546<br><sub>(City) (State) (Zip)</sub> | **3. Date of Earliest Transaction (Month/Day/Year)**<br>2026-06-15 | **5. Relationship of Reporting Person(s) to Issuer**<br>(Check all applicable)<br>[X] Director [ ] 10% Owner<br>[X] Officer (give title below) [ ] Other (specify below)<br>_Pres. & Chief Exec. Officer_ |
| **2. Issuer Name and Ticker or Trading Symbol**<br>CASTLE BIOSCIENCES INC [ CSTL ] | **4. If Amendment, Date of Original Filed (Month/Day/Year)**<br>  | **6. Individual or Joint/Group Filing (Check Applicable Line)**<br>[X] Form filed by One Reporting Person<br>[ ] Form filed by More than One Reporting Person |

---

## Table I - Non-Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | 3. Transaction Code (V) | 3. Transaction Code (V) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | Code | V | Amount | (A) or (D) | Price | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| Common Stock | 2026-06-15 |  | M<sup>(1)</sup> |  | 550 | A | $2.39 | 22029 | D |  |
| Common Stock | 2026-06-15 |  | S<sup>(1)</sup> |  | 550 | D | 20.66<sup>(2)</sup> | 21479 | D |  |
| Common Stock | 2026-06-15 |  | S<sup>(1)</sup> |  | 1357 | D | 20.66<sup>(2)</sup> | 42067 | I | By The Maetzold Descendants 2020 Trust<sup>(3)</sup> |
| Common Stock | 2026-06-15 |  | S<sup>(1)</sup> |  | 1153 | D | 20.66<sup>(2)</sup> | 35755 | I | By Derek Maetzold 2020 Irrevocable Trust<sup>(4)</sup> |
| Common Stock | 2026-06-15 |  | S<sup>(1)</sup> |  | 278 | D | 20.66<sup>(2)</sup> | 12646 | I | By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk<sup>(5)(6)</sup> |
| Common Stock | 2026-06-15 |  | S<sup>(1)</sup> |  | 278 | D | 20.66<sup>(2)</sup> | 12646 | I | By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold<sup>(5)(7)</sup> |
| Common Stock | 2026-06-15 |  | S<sup>(1)</sup> |  | 278 | D | 20.66<sup>(2)</sup> | 12646 | I | By The Maetzold 2018 Remainder  Trust FBO John Derek Maetzold<sup>(5)(8)</sup> |
| Common Stock | 2026-06-15 |  | S<sup>(1)</sup> |  | 278 | D | 20.66<sup>(2)</sup> | 12646 | I | By The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold<sup>(5)(9)</sup> |
| Common Stock |  |  |  |  |  |  |  | 18718 | I | By DJM Grantor Retained Annuity Trust No. 6<sup>(10)</sup> |
| Common Stock |  |  |  |  |  |  |  | 44323 | I | By DJM Grantor Retained Annuity Trust No. 7<sup>(11)</sup> |
| Common Stock |  |  |  |  |  |  |  | 40935 | I | By DJM Grantor Retained Annuity Trust No. 8<sup>(12)</sup> |

---

## Table II - Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | 4. Transaction Code (V) | 4. Transaction Code (V) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 6. Date Exercisable and Expiration Date | 6. Date Exercisable and Expiration Date | 7. Title and Amount of Underlying Securities | 7. Title and Amount of Underlying Securities | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | Code | V | (A) | (D) | Date Exercisable | Expiration Date | Title | Amount or Number of Shares | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| Stock option (right to buy) | $2.39 | 2026-06-15 |  | M<sup>(1)</sup> |  |  | 550 | <sup>(13)</sup> | 2028-05-09 | Common Stock | 550 | $0 | 91881 | D |  |

---

### Footnotes:

(1) These transactions were made pursuant to a Rule 10b5-1 plan adopted by the Reporting Person on December 3, 2025.

(2) This transaction was executed in multiple trades at prices ranging from $20.44 to $20.98, inclusive. The price reported above reflects the weighted-average sale price. The Reporting Person hereby undertakes to provide upon request to the Securities and Exchange Commission staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected.

(3) Held by The Maetzold Descendants 2020 Trust of which the Reporting Person's spouse is the trustee and the Reporting Person's spouse and their children are beneficiaries.

(4) Held by Derek Maetzold 2020 Irrevocable Trust of which the Reporting Person is the trustee and his children are beneficiaries.

(5) Reflects the transfers on June 10, 2026, of  45,024 shares of common stock from DJM Grantor Annuity Trust No. 5, of which, 11,256 transferred to The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk, 11,256 transferred to The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold, 11,256 transferred to The Maetzold 2018 Remainder Trust FBO John Derek Maetzold and 11,256 transferred to The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold. The remaining 40,935 shares of common stock held by DJM Grantor Annuity Trust No. 5 were transferred as described in footnote 12, after which DJM Grantor Annuity Trust No. 5 holds no remaining shares of common stock.

(6) Held by The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk of which the Reporting Person is the trustee and his child is the beneficiary.

(7) Held by The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold of which the Reporting Person is the trustee and his child is the beneficiary.

(8) Held by The Maetzold 2018 Remainder Trust FBO John Derek Maetzold of which the Reporting Person is the trustee and his child is the beneficiary.

(9) Held by The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold of which the Reporting Person is the trustee and his child is the beneficiary.

(10) Held by DJM Grantor Retained Annuity Trust No. 6 of which the Reporting Person is the trustee and the beneficiaries are The Maetzold 2018 Remainder Trust FBO John Derek Maetzold, The Maetzold 2018
Remainder Trust FBO Emily Carol Kirk, The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold and The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold.

(11) Held by DJM Grantor Retained Annuity Trust No. 7 of which the Reporting Person is the trustee and beneficiary.

(12) Held by DJM Grantor Retained Annuity Trust No. 8 of which the Reporting Person is the trustee and beneficiary. On June 10, 2026, 40,935 shares of common stock were transferred from DJM Grantor Annuity Trust No. 5 to the Reporting Person's direct holdings, and subsequently transferred from the Reporting Person's direct holdings to DJM Grantor Retained Annuity Trust No. 8.

(13) The shares subject to the option are fully vested.

**Signature:** /s/ Frank Stokes, Attorney-in-fact  
**Date:** 2026-06-17

### Remarks:

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

**Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.**