Jade Biosciences, Inc.

During the quarter ended December 31, 2025, none of our directors or officers adoptedor terminatedany Rule 10b5-1 trading arrangements or non-Rule 10b5-1 trading arrangements (in each case, as defined in Item 408 of Regulation S-K), except as set forth below.

On October 25, 2025, Tom Frohlich, our Chief Executive Officer, Andrew King, our Chief Scientific Officer & Head or Research and Development, Brad Dahms, our Chief Financial Officer, and Elizabeth Balta, our Chief Legal Officer and Corporate Secretary, each adopted a Rule 10b5-1 trading arrangement intended to satisfy the affirmative defense of Rule 10b5-1(c) authorizing the pre-arranged sale of common shares in order to satisfy tax withholding obligations of the Company that arise in connection with the vesting of any restricted stock units and/or performance stock units granted to them under the Jade Biosciences, Inc. 2025 Stock Incentive Plan and the Jade Biosciences, Inc. Amended and Restated 2024 Equity Incentive Plan, including under a successor plan and the related issuance of common shares. The number of common shares to be sold to satisfy the Company’s tax withholding obligations under each arrangement is dependent on future events which cannot be known at this time, including the future trading price of our common shares. The expiration date relating to each arrangement is dependent on future events which cannot be known at this time, including the final vesting date of the applicable restricted stock units and performance stock units and the officer’s termination of service.