Material Event (Form 8-K)

On December 4, 2025, GLAXOSMITHKLINE INTELLECTUAL PROPERTY (NO. 4) ("GSK") communicated to IDEAYA Biosciences, Inc. (the "Company") its election to terminate the Collaboration, Option and License Agreement, dated June 15, 2020 (as amended, the "Agreement"). Pursuant to the terms of the Agreement, such termination will be effective ninety (90) days following the date of GSK's written notice. During the ninety-daytransition period, GSK will transfer the Werner Helicase (IDE275) and Pol Theta (IDE705) clinical programs to the Company in accordance with the applicable provisions of the Agreement. The Company will evaluate its strategic options for these two programs in 2026, and the update does not change its expectation of cash runway into 2030.