X0306 4 2020-11-11 1 0001676725 IDEAYA Biosciences, Inc. IDYA 0001589315 5AM Ventures IV, L.P. C/O 5AM VENTURES 501 SECOND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 Former 10% holder 0001593361 5AM Co-Investors IV, L.P. C/O 5AM VENTURES 501 SECOND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 Former 10% holder 0001589314 5AM Partners IV, LLC C/O 5AM VENTURES 501 SECOND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 Former 10% holder 0001753000 5AM Opportunities I, L.P. C/O 5AM VENTURES 501 SECOND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 Former 10% holder 0001790778 5AM Opportunities I (GP), LLC C/O 5AM VENTURES 501 SECOND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 Former 10% holder 0001240357 DIEKMAN JOHN D C/O 5AM VENTURES 501 SECOND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 Former 10% holder 0001598549 Schwab Andrew J. C/O 5AM VENTURES 501 SECOND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 Former 10% holder 0001219014 ROCKLAGE SCOTT M C/O 5AM VENTURES 501 SECOND STREET, SUITE 350 SAN FRANCISCO CA 94107 0 0 1 0 Former 10% holder Common Stock 2020-11-11 4 S 0 657117 13.66 D 2187428 I See footnote Common Stock 2020-11-11 4 S 0 27379 13.66 D 91142 I See footnote Common Stock 2020-11-11 4 S 0 115504 13.66 D 384496 I See footnote The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $13.50 to $13.75 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote. The shares are held by 5AM Ventures IV, L.P. ("Ventures IV"). 5AM Partners IV, LLC ("Partners IV") is the sole general partner of Ventures IV. Dr. John Diekman, Andrew J. Schwab and Dr. Scott M. Rocklage, are the managing members of Partners IV, and have shared voting and investment power over the shares beneficially owned by Ventures IV. Each of Partners IV, Dr. Diekman, Mr. Schwab, and Dr. Rocklage disclaims beneficial ownership of such shares except to the extent of its or their pecuniary interest therein. The shares are held by 5AM Co-Investors IV, L.P. ("Co-Investors IV" and, collectively with Ventures IV, the "5AM IV Funds"). Partners IV is the sole general partner of Co-Investors IV. Dr. John Diekman, Andrew J. Schwab and Dr. Scott M. Rocklage, are the managing members of Partners IV, and have shared voting and investment power over the shares beneficially owned by Co-Investors IV. Each of Partners IV, Dr. Diekman, Mr. Schwab, and Dr. Rocklage disclaims beneficial ownership of such shares except to the extent of its or their pecuniary interest therein. The shares are held by 5AM Opportunities I, L.P. ("Opportunities I"), which is under common control with the 5AM IV Funds. The 5AM IV Funds and Opportunities I expressly disclaim status as a "group" for purposes of this Form 4. 5AM Opportunities I (GP), LLC ("Opportunities I GP") is the sole general partner of Opportunities I. Dr. Kush Parmar and Andrew J. Schwab are the managing members of Opportunities I GP, and have shared voting and investment power over the shares beneficially owned by Opportunities I. Each of Opportunities I GP and Mr. Schwab disclaims beneficial ownership of such shares except to the extent of its or his pecuniary interest therein. 5AM VENTURES IV, L.P. By: 5AM Partners IV, LLC, its General Partner By: /s/ Scott M. Rocklage Managing Member 2020-11-13 5AM CO-INVESTORS IV, L.P. By: 5AM Partners IV, LLC, its General Partner By: /s/ Scott M. Rocklage Managing Member 2020-11-13 5AM PARTNERS IV, LLC By: /s/ Scott M. Rocklage Managing Member 2020-11-13 5AM OPPORTUNITIES I, L.P. By: 5AM Opportunities I (GP), LLC, its General Partner By: /s/ Kush M. Parmar Managing Member 2020-11-13 5AM OPPORTUNITIES I (GP), LLC By: /s/ Kush M. Parmar Managing Member 2020-11-13 /s/ John Diekman 2020-11-13 /s/ Andrew J. Schwab 2020-11-13 /s/ Scott M. Rocklage 2020-11-13