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 ...

Tovorafenib (DAY101) Clinical Trials and Designations - Tovorafenib (DAY101) received FDA Breakthrough Therapy Designation for relapsed pLGG and FDA Rare Pediatric Disease Designation (PRV Eligible) for pLGG[10] - FIREFLY-1, a pivotal Phase 2 trial of Tovorafenib in relapsed or progressive pLGG, showed a 64% ORR (Overall Response Rate) in RANO-evaluable patients (n=22)[21] - The clinical benefit rate (CBR) in the FIREFLY-1 trial was 91%[25] - The median time to response in the FIREFLY-1 trial was 2.8 months[25] - FIREFLY-2/LOGGIC is a pivotal Phase 3 trial of Tovorafenib in newly diagnosed pLGG, with first patient dosing expected in Q4 2022[5, 33] Safety and Tolerability of Tovorafenib - In the FIREFLY-1 trial, 28% of patients required dose modifications due to treatment-related AEs[25] - The majority (96%) of treatment-emergent AEs were grade 1 or 2[25] - The most common treatment-related AEs (Any Grade) were Blood creatine phosphokinase increased (72%), Hair color changes (68%), and Rash (52%)[24] Market and Financial Information - Day One Biopharmaceuticals projected cash runway into 2025[5, 49] - As of September 30, 2022, Day One Biopharmaceuticals had $374.3 million in cash, cash equivalents, and short-term investments[50] - For the nine months ended September 30, 2022, R&D expense was $59.6 million, G&A expense was $44.6 million, and the net loss was $102.1 million[50] Tovorafenib and Pimasertib Combination - FIRELIGHT-1 is evaluating the combination of Tovorafenib (DAY101) and Pimasertib, with the first patient dosed in May 2022[10, 49]

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 ...

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, 2021 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 other jur ...

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, 2021 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 ...