CASTLE BIOSCIENCES INC

Item 5. Other Information.

Insider Trading Arrangements

On May 28, 2026, Tobin Juvenal, our Chief Commercial Officer, adopted a Rule 10b5-1 trading arrangement providing for the sale from time to time of an aggregate of up to 85,524 shares of our common stock and up to 100% of the shares of our common stock issued upon the settlement of 63,029 shares of RSUs and PSUs, less the number of shares withheld to cover tax withholding obligations in connection with the vesting and settlement of such RSUs and PSUs. The trading arrangement is intended to satisfy the affirmative defense in Rule 10b5-1(c). The duration of the trading arrangement is estimated to be from September 14, 2026 until the earlier of all transaction under the trading arrangement being completed or March 19, 2027.

On June 2, 2026, Derek J. Maetzold, our Chief Executive Officer, adopted a Rule 10b5-1 trading arrangement providing for the sale from time to time of an aggregate of up to 202,966 shares of our common stock and up to 100% of the shares of our common stock issued upon the settlement of 180,459 shares of RSUs and PSUs, less the number of shares withheld to cover tax withholding obligations in connection with the vesting and settlement of such RSUs and PSUs. The trading arrangement is intended to satisfy the affirmative defense in Rule 10b5-1(c). The duration of the trading arrangement is estimated to be from September 11, 2026 until the earlier of all transaction under the trading arrangement being completed or March 19, 2027.

No other directors or officers, as defined in Rule 16a-1(f), adopted and/orterminated a Rule 10b5-1 trading arrangement or a non-Rule 10b5-1 trading arrangement, as defined in Regulation S-K Item 408, for the three months ended June 30, 2026.