PART I. FINANCIAL INFORMATION [Item 1. Interim Consolidated Financial Statements (Unaudited)](index=4&type=section&id=Item%201.%20Interim%20Consolidated%20Financial%20Statements%20(Unaudited)) Presents unaudited consolidated financial statements: balance sheets, operations, cash flows, and key notes [Condensed Consolidated Balance Sheets](index=4&type=section&id=Condensed%20Consolidated%20Balance%20Sheets) Balance Sheets reflect significant asset growth from IPO proceeds, increased liabilities, and a positive equity shift | Assets/Liabilities (in thousands) | September 30, 2021 | December 31, 2020 | | :-------------------------------- | :----------------- | :---------------- | | Cash and cash equivalents | $297,160 | $43,728 | | Total current assets | $303,311 | $45,071 | | Total assets | $303,783 | $45,661 | | Total current liabilities | $6,046 | $1,996 | | Total liabilities | $6,111 | $2,200 | | Accumulated deficit | $(105,548) | $(56,842) | | Total stockholders' equity/(deficit) | $297,672 | $(54,205) | - Cash and cash equivalents increased significantly from **$43.7 million** at December 31, 2020, to **$297.2 million** at September 30, 2021, primarily due to financing activities[13](index=13&type=chunk)[35](index=35&type=chunk) - Total stockholders' equity shifted from a deficit of **$54.2 million** at December 31, 2020, to a positive equity of **$297.7 million** at September 30, 2021[14](index=14&type=chunk) [Condensed Consolidated Statements of Operations and Comprehensive Loss](index=6&type=section&id=Condensed%20Consolidated%20Statements%20of%20Operations%20and%20Comprehensive%20Loss) The company reported increased net losses for both periods, driven by substantial increases in R&D and G&A expenses | (in thousands) | Three Months Ended Sep 30, 2021 | Three Months Ended Sep 30, 2020 | Nine Months Ended Sep 30, 2021 | Nine Months Ended Sep 30, 2020 | | :------------------------------------------------ | :------------------------------ | :------------------------------ | :----------------------------- | :----------------------------- | | Research and development | $9,849 | $2,537 | $32,395 | $4,935 | | General and administrative | $9,392 | $1,024 | $18,373 | $2,703 | | Total operating expenses | $19,241 | $3,561 | $50,768 | $7,638 | | Net loss and comprehensive loss | $(19,240) | $(3,842) | $(50,816) | $(8,243) | | Net loss attributable to common stockholders | $(19,240) | $(2,824) | $(148,701) | $(6,130) | | Net loss per share, basic and diluted | $(0.33) | $(0.50) | $(4.98) | $(1.12) | - Research and development expenses increased by **288%** for the three months and **556.4%** for the nine months ended September 30, 2021, reflecting increased clinical trial and product development activities[17](index=17&type=chunk)[154](index=154&type=chunk)[160](index=160&type=chunk) - General and administrative expenses surged by **817%** for the three months and **579.7%** for the nine months ended September 30, 2021, primarily due to headcount growth and public company operating costs[17](index=17&type=chunk)[157](index=157&type=chunk)[162](index=162&type=chunk) - Net loss attributable to common stockholders significantly increased to **$(148.7) million** for the nine months ended September 30, 2021, from **$(6.1) million** in the prior year, largely due to a **$99.99 million** deemed dividend[17](index=17&type=chunk)[164](index=164&type=chunk) [Condensed Consolidated Statements of Redeemable Convertible Preferred Shares, Redeemable Noncontrolling Interest and Stockholders' Equity/ Members' (Deficit)](index=7&type=section&id=Condensed%20Consolidated%20Statements%20of%20Redeemable%20Convertible%20Preferred%20Shares%2C%20Redeemable%20Noncontrolling%20Interest%20and%20Stockholders'%20Equity%2F%20Members'%20(Deficit)) This statement details equity changes, highlighting preferred share conversion and noncontrolling interest extinguishment post-IPO - All outstanding redeemable convertible preferred shares (**32,489,398 shares**) were converted into common stock upon the completion of the IPO on June 1, 2021[86](index=86&type=chunk) - The redeemable noncontrolling interest was extinguished on May 26, 2021, resulting in a **$100.0 million** extinguishment loss recognized as a deemed dividend[119](index=119&type=chunk) - Additional paid-in capital increased significantly from **$0** at December 31, 2020, to **$403.2 million** at September 30, 2021, reflecting IPO proceeds and share conversions[14](index=14&type=chunk) [Condensed Consolidated Statements of Cash Flows](index=9&type=section&id=Condensed%20Consolidated%20Statements%20of%20Cash%20Flows) The company saw a substantial net increase in cash from financing activities, despite higher operating and investing cash usage | (in thousands) | Nine Months Ended Sep 30, 2021 | Nine Months Ended Sep 30, 2020 | | :---------------------------------- | :----------------------------- | :----------------------------- | | Net cash used in operating activities | $(35,370) | $(7,551) | | Cash used in investing activities | $(8,000) | $(93) | | Net cash provided by financing activities | $296,802 | $0 | | Net increase (decrease) in cash | $253,432 | $(7,644) | | Cash and cash equivalents, end of period | $297,160 | $19,688 | - Net cash used in operating activities increased from **$7.6 million** in 2020 to **$35.4 million** in 2021, reflecting higher net loss and changes in operating assets and liabilities[21](index=21&type=chunk)[169](index=169&type=chunk)[170](index=170&type=chunk) - Net cash provided by financing activities was **$296.8 million** for the nine months ended September 30, 2021, primarily from **$167.0 million** in IPO proceeds and **$129.8 million** from Series B preferred shares[21](index=21&type=chunk)[172](index=172&type=chunk) [Notes to the Condensed Consolidated Financial Statements](index=10&type=section&id=Notes%20to%20the%20Condensed%20Consolidated%20Financial%20Statements) These notes explain the company's business, accounting policies, fair value measurements, and significant agreements [1. DESCRIPTION OF BUSINESS, ORGANIZATION AND LIQUIDITY](index=10&type=section&id=1.%20DESCRIPTION%20OF%20BUSINESS%2C%20ORGANIZATION%20AND%20LIQUIDITY) Day One Biopharmaceuticals is a clinical-stage biopharmaceutical company focused on genomically-defined cancers, particularly in pediatric patients - Day One Biopharmaceuticals, Inc. is a clinical-stage biopharmaceutical company focused on developing targeted therapies for genomically-defined cancers, with a lead product candidate, DAY101, for pediatric low-grade glioma (pLGG)[26](index=26&type=chunk)[122](index=122&type=chunk) - The company completed its IPO on June 1, 2021, selling **11,500,000 shares** of common stock at **$16.00** per share, generating **$167.0 million** in net proceeds[28](index=28&type=chunk)[165](index=165&type=chunk) - As of September 30, 2021, the company had an accumulated deficit of **$105.5 million** and expects to fund operations into **2023** with its **$297.2 million** in cash and cash equivalents[35](index=35&type=chunk)[128](index=128&type=chunk)[165](index=165&type=chunk) [2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES](index=11&type=section&id=2.%20SUMMARY%20OF%20SIGNIFICANT%20ACCOUNTING%20POLICIES) This section outlines the company's significant accounting policies, including basis of presentation, estimates, and recent ASU adoptions - The unaudited condensed consolidated financial statements are prepared in conformity with U.S. GAAP and SEC interim reporting requirements, with certain notes condensed or omitted[40](index=40&type=chunk) - Significant estimates include fair values of redeemable convertible preferred shares, common shares, derivative tranche liability, share-based awards, deferred tax assets, and R&D accruals[42](index=42&type=chunk) - The company adopted ASU **2016-13** (Financial Instruments-Credit Losses) effective January 1, 2021, with no material impact, and is evaluating ASU **2019-12** and ASU **2020-06**[52](index

Table of Contents Emerging growth company ☒ 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, 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 Delaware 83-2415215 (State or other jurisdiction of incorporation or organizat ...