MR(includes 4 uMR) PD# All 4 patients with uPR and 3 patients with uMR remain on treatment as of May 23, 2023 20 (26%) MAPKi-naive Prior MAPKi therapy BRAF V600E mutation Best Tumor Response (%) -100 -80 -60 -40 -20 0 20 40 60 80 180 100 PD SD PR CR MR SD PD# Best overall response, n (%) CR Dec 22, 2022 data cutoff. Percents may not add to 100% due to rounding. #PD for RANO-LGG was not used to determine treatment discontinuation; patients could continue treatment if there was no PD based on RANO-HGG per inv ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-40431 DAY ONE BIOPHARMACEUTICALS, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 83-2415215 (State or othe ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-40431 DAY ONE BIOPHARMACEUTICALS, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 83-2415215 (State or oth ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2022 (Exact name of Registrant as specified in its Charter) | Delaware | | 83-2415215 | | --- | --- | --- | | (State or other jurisdiction of | | (I.R.S. Employer | | incorporation or organization) | | Identification No.) | | 2000 Sierra Point Parkway, Suite 501 | | | | Brisbane, CA | | 94005 ...

Targeted Therapies for People of All Ages November 2022 June 2022 Disclaimer This presentation and the accompanying oral commentary contain forward-looking statements that are based on our management's beliefs and assumptions and on information currently available to our management. Forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified. In some cases, you can identify forward-looking statements by terminology such as "may," "will," "sho ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2022 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-40431 DAY ONE BIOPHARMACEUTICALS, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 83-2415215 (State or ...

Targeted Therapies for People of All Ages August 2022 June 2022 Disclaimer This presentation and the accompanying oral commentary contain forward-looking statements that are based on our management's beliefs and assumptions and on information currently available to our management. Forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified. In some cases, you can identify forward-looking statements by terminology such as "may," "will," "shoul ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2022 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-40431 DAY ONE BIOPHARMACEUTICALS, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 83-2415215 (State or othe ...

s 11/2 Day One ₹ BIOPHARMACEUTICALS Targeted Therapies for People of All Ages May 2022 Disclaimer This presentation and the accompanying oral commentary contain forward-looking statements that are based on our management's beliefs and assumptions and on information currently available to our management. Forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified. In some cases, you can identify forward-looking statements by terminology such a ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2022 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number: 001-40431 DAY ONE BIOPHARMACEUTICALS, INC. (Exact Name of Registrant as Specified in its Charter) Delaware 83-2415215 (State or oth ...