IDEAYA Biosciences Inc

Trading Plans

During the three months ended December 31, 2024, no Section 16 officers or directors adopted orterminated contracts, instructions or written plans for the purchase or sale of our securities.

Clinical Study Collaboration and Supply Agreement

On February 12, 2025, we entered into the Second Gilead CSCSA with Gilead pursuant to which we and Gilead will collaborate on a portion of our Phase 1 study for the clinical evaluation of our IDE397 compound in combination with Gilead’s Trop2-ADC, Trodelvy, or the Combination Study, in certain patients with advanced solid tumors in lungs. Pursuant to the Second Gilead CSCSA, we are the sponsor of the Combination Study, and we will provide the IDE397 compound and pay for the costs of the Combination Study.

Gilead will provide Trodelvy for the Combination Study at no cost to us. We and Gilead will jointly own clinical data from the Combination Study and all inventions relating to the combined use of IDE397 and Trodelvy. Each party retains commercial rights to its respective compounds, including with respect to use as a monotherapy or combination agent. We and Gilead will form a joint steering committee responsible for coordinating all regulatory and other activities under the Second Gilead CSCSA.

The Second Gilead CSCSA will continue in effect until the later of (i) the completion of the patient monitoring period for the separate arm of the study evaluating the combination therapy, or the Gilead Arm, in accordance with the study protocol and (ii) our provision to Gilead of the final version of the final study report for the Gilead Arm, unless earlier terminated by either party pursuant to its terms. We or Gilead may terminate the Second Gilead CSCSA for the other party’s insolvency, upon uncured material breach or for other specified reasons with certain notice and other requirements.

The Second Gilead CSCSA contains various representations, warranties, covenants, dispute resolution mechanisms, indemnities and other provisions customary for transactions of this nature.

The foregoing is only a summary description of the terms of the Second Gilead CSCSA, does not purport to be complete and is qualified in its entirety by reference to the Second Gilead CSCSA, which will be filed as an exhibit to our Quarterly Report on Form 10-Q for the fiscal quarter ending March 31, 2025.