X0609 4 2026-09-21 0 0001447362 CASTLE BIOSCIENCES INC CSTL 0001239501 MAETZOLD DEREK J false C/O CASTLE BIOSCIENCES, INC. 1500 W. PARKWOOD AVE SUITE 400 FRIENDSWOOD TX 77546 1 1 0 0 Pres. & Chief Exec. Officer 1 Common Stock 2026-09-21 4 M 0 8580 2.39 A 30059 D Common Stock 2026-09-21 4 S 0 8580 35.334 D 21479 D Common Stock 2026-09-21 4 S 0 3198 35.334 D 11236 I By The Maetzold Descendants 2020 Trust Common Stock 2026-09-21 4 S 0 2718 35.334 D 9550 I By Derek Maetzold 2020 Irrevocable Trust Common Stock 11256 I By The Maetzold 2018 Remainder Trust FBO Emily Carol Kirk Common Stock 11256 I By The Maetzold 2018 Remainder Trust FBO Hannah Elizabeth Maetzold Common Stock 11256 I By The Maetzold 2018 Remainder Trust FBO John Derek Maetzold Common Stock 11256 I By The Maetzold 2018 Remainder Trust FBO Peter Douglas Maetzold Common Stock 11963 I By DJM Grantor Retained Annuity Trust No. 6 Common Stock 27862 I By DJM Grantor Retained Annuity Trust No. 7 Common Stock 40935 I By DJM Grantor Retained Annuity Trust No. 8 Common Stock 23216 I DJM Grantor Retained Annuity Trust No. 9 Stock option (right to buy) 2.39 2026-09-21 4 M 0 8580 0 D 2028-05-09 Common Stock 8580 8165 D These transactions were made pursuant to a Rule 10b5-1 plan adopted by the Reporting Person on June 2, 2026. This transaction was executed in multiple trades at prices ranging from $35.020 to $35.665, 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. 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. Held by Derek Maetzold 2020 Irrevocable Trust of which the Reporting Person is the trustee and his children are beneficiaries. 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. 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. 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. 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. 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. Held by DJM Grantor Retained Annuity Trust No. 7 of which the Reporting Person is the trustee and beneficiary. Held by DJM Grantor Retained Annuity Trust No. 8 of which the Reporting Person is the trustee and beneficiary. Held by DJM Grantor Retained Annuity Trust No. 9 of which the Reporting Person is the trustee and beneficiary. The shares subject to the option are fully vested. /s/ Frank Stokes, Attorney-in-fact 2026-09-23