X0609 4 2026-10-06 0001676725 IDEAYA Biosciences, Inc. IDYA 0001649119 Hata Yujiro S false C/O IDEAYA BIOSCIENCES, INC. 5000 SHORELINE COURT, SUITE 300 SOUTH SAN FRANCISCO CA 94080 true true false false President and CEO true Common Stock 2026-10-06 4 M false 26338 4.31 A 717033 D Common Stock 2026-10-06 4 S false 25538 37.3869 D 691495 D Common Stock 2026-10-06 4 S false 800 38.2626 D 690695 D Stock Option (right to buy) 4.31 2026-10-06 4 M false 26338 0 D 2028-02-26 Common Stock 26338 23116 D The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted on July 7, 2026, in which the majority of the shares acquired upon the exercise of stock options were granted to the Reporting Person prior to the Issuer's initial public offering and are approaching their expiration date. This transaction was executed in multiple trades in prices ranging from $37.00 to $37.98, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote. This transaction was executed in multiple trades in prices ranging from $38.23 to $38.34, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote. The shares subject to the option are fully vested and exercisable. /s/ Andres Ruiz Briseno, as Attorney-in-Fact for Yujiro Hata 2026-10-08