X0206 3 2021-05-26 0 0001845337 Day One Biopharmaceuticals, Inc. DAWN 0001712417 Canaan XI L.P. 285 RIVERSIDE AVENUE, STE. 250 WESTPORT CT 06880 0 0 1 0 0001850694 Canaan Partners XI LLC 285 RIVERSIDE AVENUE, STE. 250 WESTPORT CT 06880 0 0 1 0 Common Stock 3245869 D Series A Preferred Stock Common Stock 7328497 D Series B Preferred Stock Common Stock 148279 D The reported securities are held directly by Canaan XI L.P. (the "Canaan Fund"). The sole general partner of the Canaan Fund is Canaan Partners XI LLC ("Canaan XI", and together with the Canaan Fund, the "Canaan Entities"), and may be deemed to have sole voting, investment and dispositive power with respect to the shares held by the Canaan Fund. Investment and voting decisions with respect to the shares held by the Canaan Fund are made by the managers of Canaan XI, collectively. Canaan XI disclaims Section 16 beneficial ownership of the securities held by the Canaan Fund, except to the extent of its pecuniary interest therein, if any. Each share of Class A Preferred Stock is automatically convertible into one share of Common Stock at the close of the Issuer's initial public offering and has no expiration date. Each share of Class B Preferred Stock is automatically convertible into one share of Common Stock at the close of the Issuer's initial public offering and has no expiration date. Exhibit 24 - Power of Attorney filed herewith Canaan XI L.P., By: Canaan Partners XI LLC, its general partner, By: /s/ Nancy Levenson, Attorney-in-Fact 2021-05-26 Canaan Partners XI LLC, By: /s/ Nancy Levenson, Attorney-in-Fact 2021-05-26