Day One Biopharmaceuticals (DAWN) 10-K 7 Mar 22 2021 FY Annual report Financial data

Cover Page

Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 02, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Registrant Name	DAY ONE BIOPHARMACEUTICALS, INC.
Entity Central Index Key	0001845337
Entity File Number	001-40431
Entity Tax Identification Number	83-2415215
Entity Incorporation, State or Country Code	DE
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Shell Company	false
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
ICFR Auditor Attestation Flag	false
Entity Address, Address Line One	395 Oyster Point Blvd.
Entity Address, Address Line Two	Suite 217
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	484-0899
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	DAWN
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		61,952,292
Entity Public Float			$ 646.2
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s Definitive Proxy Statement relating to the 2022 Annual Meeting of Shareholders are incorporated by reference into Part III of this Annual Report on Form 10-K to the extent stated herein. The Definitive Proxy Statement will be filed within 120 days of the Registrant’s fiscal year ended December 31, 2021. Except with respect to information specifically incorporated by reference in this Form 10-K, the Proxy Statement is not deemed to be filed as part of this Form 10-K.
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	Redwood City, California

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets	$ 289,821	$ 45,661
Current assets:
Cash and cash equivalents	284,309	43,728
Prepaid expenses and other current assets	5,059	1,343
Total current assets	289,368	45,071
Property and equipment, net	57	77
Operating lease right-of-use asset	227	406
Deposits and other long-term assets	169	107
Total assets	289,821	45,661
Current liabilities:
Accounts payable	1,744	202
Accrued expenses and other current liabilities	6,709	1,596
Current portion of operating lease liabilities	204	198
Total current liabilities	8,657	1,996
Operating lease liabilities, long-term	16	204
Total liabilities	8,673	2,200
Commitments and contingencies (Note 8)
Redeemable convertible preferred shares, no par value; no shares authorized, issued and outstanding at December 31, 2021; 22,851,257 shares authorized, issued and outstanding at December 31, 2020		91,964
Redeemable convertible noncontrolling interest		5,702
Stockholders’ equity/members’ (deficit)
Additional paid-in-capital	408,629
Incentive shares, no par value; no shares authorized, issued and outstanding at December 31, 2021; 4,312,540 shares authorized and 4,112,012 shares issued and outstanding at December 31, 2020		(637)
Accumulated deficit	(127,487)	(56,842)
Total stockholders’ equity/members’ (deficit)	281,148	(54,205)
Total liabilities, redeemable convertible preferred shares, redeemable convertible noncontrolling interest and members’ deficit	289,821	45,661
Common Class A
Stockholders’ equity/members’ (deficit)
Common shares, no par value; no shares authorized, issued and outstanding at December 31, 2021; 28,887,127 shares authorized and 6,035,869 shares at December 31st, 2020		$ 2,000
Common Class B
Stockholders’ equity/members’ (deficit)
Common shares, no par value; no shares authorized, issued and outstanding at December 31, 2021; 28,887,127 shares authorized and 6,035,869 shares at December 31st, 2020	$ 6

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Preferred Stock, Par or Stated Value Per Share	$ 0.0001
Preferred Stock, Shares Authorized	10,000,000	0
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common Stock, Shares Authorized	500,000,000
Common Stock, Shares, Issued	61,952,292
Common Stock, Shares, Outstanding	61,952,292
Deferred Shares Par Value Per Shares	$ 0
Deferred Compensation Arrangement with Individual, Shares Authorized for Issuance	0	4,312,540
Deferred shares Issued	0	4,112,017
Deferred Shares Outstanding	0	4,112,017
Redeemable Convertible Preferred Stock [Member]
Temporary Equity, Par or Stated Value Per Share	$ 0
Temporary Equity, Shares Authorized	0	22,851,257
Temporary Equity, Shares Issued	0	22,851,257
Temporary Equity, Shares Outstanding	0	22,851,257
Common Class A
Preferred Stock, Shares Outstanding	0
Common Stock, Par or Stated Value Per Share	$ 0
Common Stock, Shares Authorized	0	28,887,127
Common Stock, Shares, Issued	0	6,035,869
Common Stock, Shares, Outstanding		6,035,869
Common Class B
Common Stock, Par or Stated Value Per Share	$ 0.0001
Common Stock, Shares Authorized	500,000,000	0
Common Stock, Shares, Issued		0
Common Stock, Shares, Outstanding		0

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating expenses:
Research and development	$ 43,584	$ 9,100	$ 13,899
General and administrative	29,159	4,682	1,006
Total operating expenses	72,743	13,782	14,905
Loss from operations	(72,743)	(13,782)	(14,905)
Interest income (expense), net	4	(30)	(2,077)
Other expense, net	(15)	(31)	(2)
Changes in fair value of derivative tranche liability	0	(30,000)	0
Net loss and comprehensive loss	(72,754)	(43,843)	(16,984)
Total operating expenses	72,743	13,782	14,905
Net loss attributable to redeemable convertible noncontrolling interests	(2,109)	(3,336)	(4,350)
Exchange of redeemable noncontrolling interest shares-deemed dividend	(99,994)	0	0
Net loss attributable to common stockholders/members	$ (170,639)	$ (40,507)	$ (12,634)
Net loss per share, basic and diluted	$ (4.62)	$ (7.33)	$ (2.13)
Weighted-average number of common shares used in computing net loss per share, basic and diluted	36,960,569	5,529,519	5,924,640

Consolidated Statements of Rede

Consolidated Statements of Redeemable Convertible Preferred Shares, Redeemable Noncontrolling Interest and Stockholders Equity/ Members (Deficit) - USD ($) $ in Thousands	Total	Redeemable Convertible Preferred Stock [Member]	Redeemable Noncontrolling Interest [Member]	Common Stock	Common StockRedeemable Convertible Preferred Stock [Member]	Common StockRedeemable Noncontrolling Interest [Member]	Common Shares [Member]	Incentive Shares [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2018	$ (150)			$ 0	$ 0	$ 0		$ 0	$ 0	$ (150)
Beginning Balance (In shares) at Dec. 31, 2018		0		0			9,323,724	32,026
Issuance of Series A redeemable convertible preferred shares for cash net of issuance costs of $95 and derivative tranches liability of $1,483		$ 28,422
Issuance of Series A redeemable convertible preferred shares, shares		10,348,507
Issuance of Series A redeemable convertible preferred shares upon notes conversion		$ 2,082
Issuance of Series A redeemable convertible preferred shares upon notes conversion, shares		2,154,245
Recognition of contingent beneficial conversion feature (Note [ ])	2,000						$ 2,000
Proceeds from redeemable convertible preferred stock			$ 9,837
Issuance of incentive shares, shares								1,456,395
Stock repurchased during period, shares							(3,287,855)
Issuance of shares pursuant to Employee Stock Purchase Plan, Shares								1,456,395
Share-based compensation expense	111							$ 111
Net loss attributable to redeemable convertible noncontrolling interests	(4,350)		(4,350)
Net loss attributable to Day One Biopharmaceuticals Holding Company, LLC members	(12,634)									(12,634)
Ending Balance at Dec. 31, 2019	(10,673)				30,504	5,487	$ 2,000	$ 111		(12,784)
Ending Balance (In shares) at Dec. 31, 2019		12,502,752		0			6,035,869	1,488,421
Issuance of Series A redeemable convertible preferred shares for cash net of issuance costs of $95 and derivative tranches liability of $1,483		$ 29,977
Issuance of Series A redeemable convertible preferred shares, shares		10,348,505
Recognition of contingent beneficial conversion feature (Note [ ])	0
Issuance of incentive shares, shares								3,101,178
Cancellations of incentive shares, shares								(477,582)
Reclassification of derivative tranches liability upon settlement		$ 31,483
Issuance of shares pursuant to Employee Stock Purchase Plan, Shares								3,101,178
Share-based compensation expense	526							$ 526
Net loss attributable to redeemable convertible noncontrolling interests	(3,336)		(3,336)
Transfer to redeemable noncontrolling interest related to change in ownership	(3,551)		(3,551)							(3,551)
Net loss attributable to Day One Biopharmaceuticals Holding Company, LLC members	(40,507)									(40,507)
Temporary Equity, Ending Balance, Shares at Dec. 31, 2020		22,851,257
Ending Balance at Dec. 31, 2020	(54,205)			$ 0	91,964	5,702	$ 2,000	$ 637	0	(56,842)
Ending Balance (In shares) at Dec. 31, 2020		22,851,257		0			6,035,869	4,112,017
Issuance of Series A redeemable convertible preferred shares for cash net of issuance costs of $95 and derivative tranches liability of $1,483		$ 129,757
Issuance of Series A redeemable convertible preferred shares, shares		9,638,141
Recognition of contingent beneficial conversion feature (Note [ ])	0
Issuance of incentive shares	318								318
Issuance of incentive shares, shares				23,353				2,959,795
Cancellations of incentive shares, shares								(265,596)
Conversion of redeemable convertible preferred, common, and incentive shares into common stock	221,721	$ (221,721)		$ 4			$ (2,000)	$ (1,175)	224,892
Conversion of redeemable convertible preferred, common, and incentive shares into common stock, Shares		(32,489,398)		43,958,557			(6,035,869)	(6,806,216)
Conversion of redeemable noncontrolling interest to common stock	3,593		(3,593)	$ 1					3,592
Conversion Of Redeemable Noncontrolling Interest To Common Stock Shares				6,470,382
Common stock issued in IPO, net of issuance costs of $16,995	167,045			$ 1					167,044
Common stock issued in IPO, net of issuance costs of $16,995, shares				11,500,000
Issuance of shares pursuant to Employee Stock Purchase Plan	318								318
Issuance of shares pursuant to Employee Stock Purchase Plan, Shares				23,353				2,959,795
Net loss attributable to common stockholders/members	(70,645)									(70,645)
Share-based compensation expense	13,321							$ 538	12,783
Net loss attributable to redeemable convertible noncontrolling interests	(2,109)		$ (2,109)
Temporary Equity, Ending Balance, Shares at Dec. 31, 2021		0
Ending Balance at Dec. 31, 2021	$ 281,148			$ 6	$ 0	$ 0	$ 0	$ 0	$ 408,629	$ (127,487)
Ending Balance (In shares) at Dec. 31, 2021		0		61,952,292			0	0

Consolidated Statements of Re_2

Consolidated Statements of Redeemable Convertible Preferred Shares, Redeemable Noncontrolling Interest and Stockholders Equity/ Members (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Series A Redeemable Convertible Preferred Shares
Stock issuance costs		$ 22	$ 95
Derivative Tranches Liability			$ 1,483
Series B Redeemable Convertible Preferred Shares
Stock issuance costs	$ 243
Common Stock
Stock issuance costs	$ 16,995

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (72,754)	$ (43,843)	$ (16,984)
Adjustments to reconcile net loss to net cash used in operating activities:
Acquired in-process research and development assets	8,000	0
Share-based compensation expense	13,321	526	111
Depreciation and amortization expense	20	16	0
Amortization of operating right-of-use assets	179	139
Non-cash interest expense	0	30	2,077
Issuance of shares for research and development	0		9,837
Changes in derivative tranche liabilities	0	30,000	0
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(3,717)	(1,336)	(4)
Deposits and other long-term assets	(62)	(107)	0
Accounts payable	1,542	132	14
Accrued expenses and other current liabilities	5,114	1,127	434
Operating lease liabilities	(182)	(173)
Net cash used in operating activities	(48,539)	(13,489)	(4,515)
Cash flows from investing activities
Purchases of property and equipment	0	(92)	0
Cash paid for acquired in-process research and development assets	(8,000)	0	0
Cash used in investing activities	(8,000)	(92)	0
Cash flows from financing activities
Proceeds from issuance of convertible notes	0	0	1,000
Proceeds from issuance of common stock, net	167,045		0
Proceeds from issuance of common stock upon ESPP purchase	318		0
Net cash provided by financing activities	297,120	29,977	30,905
Cash and Cash Equivalents, Period Increase (Decrease), Total	240,581	16,396	26,390
Cash and cash equivalents, beginning of period	43,728	27,332	942
Cash and cash equivalents, end of period	284,309	43,728	27,332
Supplemental disclosures of noncash activities
Recognition of contingent beneficial conversion feature upon notes conversion	0	0	2,000
Issuance of Series A redeemable convertible shares for research and development	0	0	9,857
Conversion of convertible notes and accrued interest into Series A redeemable convertible preferred shares	0	0	2,082
Issuance of derivative tranches liability	0	0	1,483
Transfers to redeemable convertible noncontrolling interest	0	3,551	0
Right of use asset capitalization	0	545	0
Exchange of 45,331,483 preferred, common, and incentive shares in connection with the Conversion (Note 1)	224,892	0	0
Exchange of redeemable convertible noncontrolling interest to 6,470,382 shares of common stock (Note 13)	3,592	0	0
Series A Preferred Stock [Member]
Cash flows from financing activities
Proceeds from issuance of redeemable convertible preferred shares, net of issuance costs	0	29,977	29,905
Series B Preferred Stock [Member]
Cash flows from financing activities
Proceeds from issuance of redeemable convertible preferred shares, net of issuance costs	$ 129,757	$ 0	$ 0

Description of Business, Organi

Description of Business, Organization and Liquidity	12 Months Ended
	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business, Organization and Liquidity	1. Description of Business and Organization Organization and Business Day One Biopharmaceuticals, Inc. (the “Company”) is a clinical-stage biopharmaceutical company dedicated to developing and commercializing targeted therapies for patients of all ages with genomically-defined cancers. The Company’s lead product candidate, DAY101 (tovorafenib), is an oral, brain-penetrant, highly-selective type II pan-RAF kinase inhibitor. The Company was formed as a limited liability company under the laws of the State of Delaware in November 2018, under the name Hero Therapeutics Holding Company, LLC. Subsequently, the Company changed its name to Day One Therapeutics Holding Company, LLC in December 2018 and to Day One Biopharmaceuticals Holding Company, LLC (“Day One Holding LLC”) in March 2020. On May 26, 2021, the Company completed a conversion by filing a certificate of conversion with the Secretary of State of the State of Delaware and changed its name to Day One Biopharmaceuticals, Inc. Prior to December 31, 2021, the Company had two subsidiaries: DOT Therapeutics-2, Inc. (“DOT-2”) (formerly Hero Therapeutics Inc. and Day One Biopharmaceuticals, Inc.), incorporated in Delaware in November 2018, and DOT Therapeutics-1, Inc. (“DOT-1”), incorporated in Delaware in December 2019 (collectively, “the Subsidiaries.”) In December 2021, the Company’s board of directors approved the merger of the Subsidiaries with and into the Company, with the Company being the surviving corporation (collectively, “the Merger”), effective December 31, 2021. For more information on the financial statement impact of the Merger, refer to the section titled “Basis of Presentation.” Initial Public Offering, Corporate Conversion and Exchange of Takeda’s shares On June 1, 2021, the Company closed its initial public offering (the “IPO”) in which it sold an aggregate of 11,500,000 shares of common stock at a price to the public of $ 16.00 per share, which included 1,500,000 shares issued upon the full exercise by the underwriters of their option to purchase additional shares of common stock. The Company received aggregate net proceeds from the IPO of $ 167.0 million, after deducting underwriting discounts and commissions and offering costs, of $ 17.0 million. The common stock began trading on the Nasdaq Global Select Market on May 27, 2021, under the symbol “DAWN”. In contemplation of the IPO, on May 26, 2021, the Company completed a legal entity conversion (the “Conversion”), which included the following: Day One Holding LLC, converted from a Delaware limited liability company to a Delaware corporation by filing a certificate of conversion with the Secretary of State of the State of Delaware; and changed its name to Day One Biopharmaceuticals, Inc. As part of the Conversion: • holders of Series A redeemable convertible preferred shares of Day One Holding LLC received one share of Series A redeemable convertible preferred stock of the Company for each Series A redeemable convertible preferred share held immediately prior to the Conversion; • holders of Series B redeemable convertible preferred shares of Day One Holding LLC received one share of Series B redeemable convertible preferred stock of the Company for each Series B redeemable convertible preferred share held immediately prior to the Conversion; • holders of common shares of Day One Holding LLC received one share of common stock of the Company for each common share held immediately prior to the Conversion; • each outstanding incentive share in Day One Holding LLC converted into a number of shares of common stock of the Company based upon a conversion price determined by the board of directors. The conversion price was determined as a difference between the IPO price of $ 16.00 per share and the participating threshold for each incentive share. The Company issued 5,433,290 common stock shares upon the conversion of incentive shares of Day One Holding LLC, of which 4,719,605 common stock shares continue to vest as per the original vesting terms of the incentive shares awards. In connection with the IPO and the Conversion, pursuant to the terms of the Millennium Stock Exchange Agreement (“The Millennium Stock Exchange Agreement”) and the Plan of Conversion, Millennium Pharmaceuticals, Inc. (“Takeda”) exchanged the 9,857,143 shares of Series A redeemable convertible preferred stock of DOT-1, a subsidiary of Day One Holding LLC, for 6,470,382 shares of common stock of the Company (the “Exchange”). The Company holds all property and assets of Day One Holding LLC and assumed all of the debts and obligations of Day One Holding LLC. Effective on the date of the Conversion, each member of the board of directors and officers of Day One Holding LLC became a member of the board of directors and officers of the Company. The Conversion was a tax-free reorganization, that included authorization to issue to capital stock consisting of 500,000,000 shares of common stock, $ 0.0001 par value per share, and 10,000,000 shares of undesignated preferred stock, $ 0.0001 par value per share. Upon the closing of the IPO, 32,489,398 shares of redeemable convertible preferred stock issued by the Company in the Conversion converted into an equal number of shares of common stock. The Company also granted options for 4,418,874 common stock shares at $ 16.00 per share upon the IPO date. Shares Split On May 23, 2021, Day One Holding LLC board of directors approved an amendment the Operating Agreement to effect a forward split of the Company’s shares at a 2.325-for-1 ratio (the “Stock Split”). The Stock Split became effective on May 23, 2021, upon approval by the members and execution of the amended LLC operating agreement. All issued and outstanding common shares, redeemable convertible preferred shares, incentive shares and per share amounts contained in these consolidated financial statements have been retroactively adjusted to reflect this Stock Split for all periods presented. Risks and Uncertainties Related to COVID-19 The Company is subject to risks related to public health crises such as the global pandemic associated with a novel strain of coronavirus ("COVID-19"). In December 2019, COVID-19 was first identified. The global spread of COVID-19 resulted in the World Health Organization declaring the outbreak a “pandemic,” or a worldwide spread of a new disease, in early 2020. The Company continues to monitor the situation as the landscape of lockdowns and restrictions can change rapidly, as the rise in variants continues. Although to date, these restrictions or variant cases have not materially impacted our operations, the effect on our business, from the spread of COVID-19 and the actions implemented by the governments of the United States and across the globe, may worsen over time. The extent to which COVID-19 impacts our business will depend on future developments which are highly uncertain and cannot be predicted, including, but not limited to, new information which may emerge concerning the severity of the COVID-19 virus, the actions to contain COVID-19, or treat its impact.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policie s Basis of Presentation The accompanying consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company’s subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Because the Merger (refer to the section “Organization and Business”) did not constitute a change in the reporting entity, as defined in Accounting Standard Codification (“ASC”) 250, Accounting changes and error corrections, the Company will report the assets and liabilities transferred from its Subsidiaries at historical carrying value, prospectively from December 31, 2021. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in ASC and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying consolidated financial statements include, but are not limited to, the fair value of the redeemable convertible preferred shares, the fair value of the common shares, the fair value of the derivative tranche liability, the valuation of share-based awards, the valuation of deferred tax assets and income tax uncertainties, and accruals for research and development activities. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable. Actual results may differ from those estimates or assumptions. Segments The Company has determined that its chief executive officer is the chief operating decision maker (“CODM”). The Company operates and manages the business as one reporting and one operating segment, which is the business of identifying and advancing targeted therapies for patients of all ages with genomically defined cancers. The Company’s CODM reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. All of the Company’s assets are located in the United States. Concentration of credit risk and other risks and uncertainties Financial instruments that subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company’s cash and cash equivalents is held in one financial institution in the United States. Amounts on deposit may at times exceed federally insured limits. Management believes that the financial institution is financially sound and, accordingly, minimal credit risk exists with respect to the financial institution. The Company is subject to certain risks and uncertainties and believes that changes in any of the following areas could have a material adverse effect on future financial position or results of its operations: ability to obtain future financing; regulatory approval and market acceptance of, and reimbursement for, product candidates; performance of third-party clinical research organizations and manufacturers upon which the Company relies; development of sales channels; protection of the Company’s intellectual property; litigation or claims against the Company based on intellectual property, patent, product, regulatory or other factors; and the Company’s ability to attract and retain employees necessary to support its growth. The Company is dependent on third-party manufacturers to supply products for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. As of December 31, 2021, cash equivalents include investments in money market funds. As of December 31, 2020, the Company did no t have any cash equivalents, and cash was held in checking accounts. Deposits Deposits consist of a long-term deposit of approximately $ 71,000 held at a third-party in connection with the Company’s facility lease agreement. Fair Value of Financial Instruments Assets and liabilities recorded at fair value on a recurring basis in the consolidated balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts reflected in the accompanying consolidated balance sheets for prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values, due to their short-term nature. Deferred Finance Issuance Costs Deferred finance issuance costs, consisting of legal, accounting, audit and filing fees relating to in-process equity financings, including the Company’s IPO, are capitalized. Deferred issuance costs are offset against offering proceeds. As of December 31, 2021, the Company did no t have any deferred finance issuance costs capitalized. As of December 31, 2020, the Company had capitalized $ 36,000 in deferred issuance costs related to its Series B redeemable convertible preferred share private financing, recorded in the deposits and other long-term assets in the consolidated balance sheet. Property and Equipment, Net Property and equipment are recorded at cost, less accumulated depreciation and amortization. Depreciation is recognized using the straight-line method over the estimated useful lives of the related assets ranging from three to five years, and leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the asset. Leases Contractual arrangements that meet the definition of a lease are classified as operating or finance leases and are recorded on the consolidated balance sheets as both a right-of-use asset (“ROU asset”) and lease liability, calculated by discounting fixed lease payments over the lease term at the rate implicit in the lease or the Company’s incremental borrowing rate (“IBR”). Lease ROU assets and lease obligations are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. The Company currently does not have any finance leases. Operating lease ROU assets are adjusted for (i) payments made at or before the commencement date, (ii) initial direct costs incurred, and (iii) tenant incentives under the lease. As the implicit rate for the operating leases are not determinable, the Company determines its IBR based on the information available at the applicable lease commencement date. The IBR is determined by using the rate of interest that the Company would pay to borrow on a collateralized basis an amount equal to the lease payments for a similar term and in a similar economic environment where the asset is located. The Company considers a lease term to be the noncancelable period that it has the right to use the underlying asset, including any periods where it is reasonably certain the Company will exercise any option to extend the contract. Lease costs for minimum lease payments for operating leases are recognized on a straight-line basis over the lease term. Lease liabilities are increased by interest and reduced by payments each period, and the ROU asset is amortized over the lease term. Variable lease costs are recorded when incurred. In measuring the ROU assets and lease liabilities, the Company has elected to combine lease and non-lease components. The Company excludes short-term leases, if any, having initial terms of 12 months or less at lease commencement as an accounting policy election, and recognizes rent expense on a straight-line basis over the lease term for these types of leases. Impairment of Long-lived Assets The Company evaluates long-lived assets, which consist of property and equipment and right-of-use assets, for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset exceeds the fair value of the asset. To date, no impairments have been recognized in the consolidated financial statements. Research and Development Expenses Research and development expenses consist of costs associated with acquiring technology and intellectual property licenses that have no alternative future uses; costs incurred under agreements with third-party contract research organizations, contract manufacturing organizations and other third parties that conduct clinical trials on the Company’s behalf; other costs associated with research and development programs, including laboratory materials and supplies; employee-related costs, including salaries, benefits and share-based compensation expense, for the Company’s research and development personnel; and facilities and other overhead expenses, including expenses for rent and facilities maintenance, and amortization. The Company’s expense research and development costs as incurred. The Company is obligated to make upfront payments upon execution of certain research and development agreements. Advance payments, including nonrefundable amounts, for goods or services that will be used or rendered for future research and development activities are deferred. Such amounts are recognized as expense as the related goods are delivered or the related services are performed, or such time when the Company does not expect the goods to be delivered or services to be performed. Accrued Research and Development Expenses The Company records accrued liabilities for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of preclinical and clinical studies, and contract manufacturing activities. The Company records the estimated costs of research and development activities based upon the estimated amount of services provided but not yet invoiced and includes these costs in accrued liabilities in the balance sheets and within research and development expenses in the Consolidated Statements of Operations and Comprehensive Loss. These costs are a significant component of our research and development expenses. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with third-party service providers under the service agreements. The Company makes judgments and estimates in determining the accrued liabilities balance in each reporting period. As actual costs become known, the Company adjusts its accrued liabilities. The Company has not experienced any material differences between accrued costs and actual costs incurred. The Company makes payments in connection with clinical trials under contracts with contract manufacturing organizations and contract research organizations that support conducting and managing clinical trials. The financial terms of these contracts are subject to negotiation, which vary by contract and may result in payments that do not match the periods over which materials or services are provided. Generally, these agreements set forth the scope of work to be performed at a fixed fee, unit price or on a time and materials basis. In the event the Company makes advance payments for goods or services that will be used or rendered for future research and development activities, the payments are deferred and capitalized as a prepaid expense and recognized as expense as the goods are received or the related services are rendered. Such payments are evaluated for current or long-term classification based on when they are expected to be realized. Patent Costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty of the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses in the Consolidated Statements of Operations and Comprehensive Loss. Redeemable Convertible Preferred Shares The Company recorded redeemable convertible preferred shares at their respective fair values on the dates of issuance, net of issuance costs. The redeemable convertible preferred shares were recorded outside of members’ deficit because while they were not mandatorily redeemable, in the event of a deemed liquidation event, which was outside of the Company’s control, the proceeds were distributed first to the redeemable convertible preferred shareholders in accordance with their liquidation preferences. The Company had not adjusted the carrying values of the redeemable convertible preferred shares to their liquidation preferences because it is uncertain whether or when a deemed liquidation event would occur that would obligate it to pay the liquidation preferences to holders of redeemable convertible preferred shares. Redeemable convertible preferred shares were all converted to common stock shares upon the closing of the IPO in May 2021. Redeemable Noncontrolling Interest Redeemable noncontrolling interest represented the portion of equity (net assets) in DOT-1 that was neither directly nor indirectly attributable to the Company. Redeemable noncontrolling interest is classified as temporary equity because preferred shares issued to a holder contained certain redemption features that were not solely within the control of the Company. Derivative Tranches Liability The Company’s obligation to issue additional redeemable convertible preferred shares upon the occurrence of certain milestone events represents a freestanding financial instrument. The instrument was classified as a liability in the consolidated balance sheets and re-measured at each reporting period end and at the settlement date. Changes in the fair value were recognized in other income (expense) in the Consolidated Statements of Operations and Comprehensive Loss. The tranches were settled and reclassified to redeemable convertible preferred shares upon the Company’s issuance of additional Series A redeemable convertible preferred shares in November and December 2020. Share/Stock-Based Compensation Prior to the IPO, the Company recognized share-based compensation expense based on the estimated fair value of all share-based awards, incentive shares and restricted share awards, on the date of grant using the option-pricing model. The option-pricing model requires the input of subjective assumptions, including the fair value of the underlying common shares, the expected term of the award, the expected volatility, risk-free interest rates, and the dividend yield. In determining the fair value of common shares, the methodologies used to estimate the enterprise value were performed using methodologies, approaches, and assumptions consistent with the American Institute of Certified Public Accountants Accounting and Valuation Guide, Valuation of Privately-Held-Company Equity Securities Issued as Compensation . The participation threshold amounts were determined by the board of directors, at the time of grant. The expected life of the awards granted during the period was determined based on an expected time to the liquidation event. The Company applied the risk-free interest rate based on the U.S. Treasury yield in effect at the time of the grant consistent with the life of the award. The expected volatility was based on a peer group in the industry in which the Company did business consistent with the expected time to liquidity. The dividend yield was set at zero as the underlying security did not and was not expected to pay a dividend. Subsequent to closing of the IPO, the Company uses the Black-Scholes valuation model to estimate the fair value of options granted to employees and non-employees, intrinsic value to estimate the fair value of restricted stock award, and fair value of the Company’s common stock at the grant date for restricted stock units. The Black-Scholes option-pricing model, used to estimate fair value of stock options awards, requires the use of the following assumptions: • Fair Value of Common Stock —The Company’s closing price on the Nasdaq market at the grant date. • Expected Term —The expected term represents the period that the stock-based awards are expected to be outstanding. The expected term for stock options is calculated using simplified method, as the weighted-average vesting term of the award and the award’s contract period. • Expected Volatility —Since the Company does not have sufficient trading history for its common stock, the expected volatility is estimated based on the average historical volatilities of common stock of comparable publicly traded entities over a period equal to the expected term of the stock option grants. The comparable companies are chosen based on their size, stage in the life cycle or area of specialty. The Company will continue to apply this process until sufficient historical information regarding the volatility of the common stock price becomes available. • Risk-Free Interest Rate —The risk-free interest rate is based on the U.S. Treasury yield in effect at the time of grant for zero-coupon U.S. Treasury notes with maturities approximately equal to the expected term of the awards. • Expected Dividend Yield —The Company has never paid dividends on the common stock and has no plans to pay dividends on its common stock. Therefore, the expected dividend yield use is zero. The Company uses the straight-line attribution method for recognizing share/stock-based compensation expense. The Company recognizes forfeitures by reducing the expense in the same period the forfeitures occur. The Company recognizes share/stock-based compensation expense for awards with performance conditions when it is probable that the condition will be met, and the award will vest. The Company classifies share/stock-based compensation expense in the Consolidated Statements of Operations and Comprehensive Loss in the same manner in which the award recipients’ payroll costs are classified or in which the award recipients’ service payments are classified. Income Taxes Prior to the IPO, the Company was a “pass-through” entity under the Internal Revenue Code with two corporate subsidiaries. Prior to the Conversion, the members of the Company, formerly Day One Biopharmaceuticals Holding Company, LLC, were taxed directly on their respective ownership interests and activity in Day One Biopharmaceuticals Holding Company, LLC. The Company’s consolidated corporate subsidiaries accounted for income taxes under the asset and liability method, as discussed below. Upon the closing of the IPO and the Conversion, the Company’s income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax base and net operating loss and tax credit carryforwards. Deferred tax assets and liabilities are determined based upon the difference between the consolidated financial statement carrying amounts and the tax basis of assets and liabilities and are measured using the enacted tax rate expected to apply to taxable income in the years in which the differences are expected to be reversed. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that some portion or all of the deferred tax asset will not be realized. The uncertain income tax positions are recognized at the largest amount that is more likely than not to be sustained upon audit by the relevant taxing authority. Changes in recognition or measurement are reflected in the period in which judgment occurs. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of the provision for income taxes. To date, there have been no interest or penalties recorded in relation to unrecognized tax benefits. Net Loss per Share The Company calculates basic and diluted net loss per share in conformity with the two-class method required for participating securities. Under the two-class method, basic net loss per share is computed by dividing the net loss by the weighted average number of common shares outstanding during the period, without consideration of potential dilutive securities. Diluted net loss per share is computed by dividing the net loss, after adjusting it for loss attributable to redeemable noncontrolling interest, in any, by the sum of the weighted average number of common stock shares outstanding during the period plus the dilutive effects of potentially dilutive securities outstanding during the period. Potentially dilutive securities include incentive shares, unvested restricted common shares and redeemable convertible preferred shares, prior to the IPO. Potentially dilutive securities include unvested restricted stock awards, unvested restricted stock units and stock options, after the IPO. For all periods presented, diluted net loss per share is the same as basic net loss per share since the effect of including potential common stock shares is anti-dilutive and incentive shares participation thresholds were not met. Comprehensive Loss Comprehensive loss includes net loss as well as other changes in stockholders' equity/members’ deficit that result from transactions and economic events other than those with stockholders/members. There were no components of other comprehensive loss for the Company for the periods presented. Thus, comprehensive loss equals net loss for all periods presented. Emerging Growth Company Status The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it (i) is no longer an emerging growth company or (ii) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these consolidated financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates. The JOBS Act does not preclude an emerging growth company from adopting a new or revised accounting standard earlier than the time that such standard applies to private companies. The Company expects to use the extended transition period for any other new or revised accounting standards during the period in which it remains an emerging growth company. Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments (Topic 326) ("ASU 2016-13") . ASU 2016-13 requires measurement and recognition of expected credit losses for financial assets. In April 2019, the FASB issued clarification to ASU 2016-13 within ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments. The guidance will become effective for the Company for fiscal years beginning after December 15, 2022, with early adoption permitted. Effective January 1, 2021, the Company adopted ASU 2016-13 and the adoption did not have any impact on the Company’s consolidated financial statements and related disclosures. Recently Issued Accounting Pronouncements In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which simplifies the accounting for income taxes, eliminates certain exceptions within ASC 740, Income Taxes, and clarifies certain aspects of the current guidance to promote consistency among reporting entities. ASU 2019-12 is effective for fiscal years beginning after December 15, 2021. Most amendments within the standard are required to be applied on a prospective basis, while certain amendments must be applied on a retrospective or modified retrospective basis. The Company does not expect the adoption of ASU 2019-12 to have a material impact on the Company's consolidated financial statements and related disclosures.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The financial instruments of the Company measured at fair value on a recurring basis are U.S. government money market funds, recorded as cash equivalents. The fair value is based on quoted market prices, which represent a Level 1 measurement within the fair value hierarchy. The following table sets forth the Company’s financial instruments as of December 31, 2021, which are measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): December 31, 2021 Total Level 1 Level 2 Level 3 Money market funds, included in cash and cash equivalents $ 111,221 $ 111,221 $ — $ — As of December 31, 2020, the Company did no t have any money market funds. There were no transfers between Level 1, Level 2 or Level 3 categories in the years ended December 31, 2021 or 2020.

Balance Sheet Items

Balance Sheet Items	12 Months Ended
	Dec. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Items	4. Balance Sheet Items Prepaid Expenses and Other Current Assets Prepaid and other current assets consisted of the following (in thousands): December 31, December 31, Prepaid insurance $ 2,099 $ 41 Prepaid research and development expenses 1,945 1,259 Other prepaid expenses and other assets 1,015 43 Total prepaid expenses and other current assets $ 5,059 $ 1,343 Property and Equipment, Net Property and equipment, net, consisted of the following (in thousands): December 31, December 31, Furniture and fixtures $ 78 $ 78 Leasehold improvements 15 15 Property and equipment, gross 93 93 Less: accumulated depreciation and amortization ( 36 ) ( 16 ) Property and equipment, net $ 57 $ 77 Depreciation expense for the years ended December 31, 2021, 2020, and 2019 was approximately $ 20,000 , $ 16,000 , and zero , respectively. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): December 31, December 31, Accrued payroll related expenses $ 3,308 $ 717 Accrued research and development expenses 2,565 554 Accrued professional service expenses 732 298 Other 104 27 Total accrued expenses and other current liabilities $ 6,709 $ 1,596

Significant Agreements

Significant Agreements	12 Months Ended
	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Significant Agreements	5. Significant Agreements License agreement with Merck KGaA, Darmstadt, Germany On February 10, 2021, DOT-2, the Company’s subsidiary, entered into a license agreement (the MRKDG License Agreement), with Merck KGaA, Darmstadt, Germany, a pharmaceutical corporation located in Darmstadt, Germany. Under the MRKDG License Agreement, Merck KGaA, Darmstadt, Germany granted to the Company an exclusive worldwide license, with the right to grant sublicenses through multiple tiers, under specified patent rights and know-how for the Company to research, develop, manufacture, and commercialize products containing and comprising the pimasertib and MSC2015103B compounds. The Company also received clinical inventories supplies to use in its research and development activities. The Company’s exclusive license grant is subject to a non-exclusive license granted by Merck KGaA, Darmstadt Germany’s affiliate to a cancer research organization and Merck KGaA, Darmstadt, Germany retains the right to conduct, directly or indirectly, certain ongoing clinical studies relating to pimasertib. Under the MRKDG License Agreement, the Company has obligations to use commercially reasonable efforts to develop and commercialize at least two licensed products in at least two specified major market countries by the year 2029. In consideration for the rights granted under the MRKDG License Agreement and clinical supplies, the Company made an upfront payment of $ 8.0 million, which was recorded as research and development expenses, as the technology does not have an alternative future use and supplies are used for research activities. The Company may also be required to make additional payments of up to $ 367.0 million based upon the achievement of specified development, regulatory, and commercial milestones, as well a high, single-digit royalty percentage on future net sales of licensed products, if any. Milestones and royalties are contingent upon future events and will be recorded when the milestones are achieved and when payments are due. No milestones were achieved and due as of December 31, 2021. The term of the MRKDG License Agreement will expire on a licensed product-by-licensed product and country-by-country basis upon the expiration of the Company’s obligation to pay royalties to the licensor with respect to such licensed product in such country and will expire in its entirety upon the expiration of all of the Company’s payment obligations with respect to all licensed products and all countries under the MRKDG License Agreement. Takeda Assets Purchase Agreement On December 16, 2019, DOT-1 entered into an asset purchase agreement (the “Takeda Asset Agreement”), with Millennium Pharmaceuticals, Inc., a related party and an affiliate of Takeda Pharmaceutical Company Limited (“Takeda”). Pursuant to the Takeda Asset Agreement, DOT-1 purchased certain technology rights and know-how related to TAK-580 (which is now DAY101 (tovorafenib)) that provides a new approach for treating patients with primary brain tumors or brain metastases of solid tumors. DOT-1 also received clinical inventories supplies to use in the Company’s research and development activities of such RAF-inhibitor and an assigned investigator clinical trial agreement. Takeda also assigned to DOT-1 its exclusive license agreement, or the Viracta License Agreement, with Sunesis Pharmaceuticals, Inc. (now Viracta Therapeutics, Inc. or Viracta). Takeda also granted DOT-1 a worldwide, sublicensable exclusive license under specified patents and know-how and non-exclusive license under other patents and know-how generated by Takeda under the Takeda Asset Agreement. The Company also granted Takeda a grant back license, as defined in the agreement, which is terminable either automatically or by DOT-1 in the event Takeda did not achieve specified development milestones within the applicable timeframes set forth under the Takeda Asset Agreement. This grant back license to Takeda was terminated at the time of Conversion in connection with the Millennium Stock Exchange Agreement. In consideration for the sale and assignment of assets and the grant of the license under the Takeda Asset Agreement, DOT-1 made an upfront payment of $ 1.0 million in cash and issued 9,857,143 shares of Series A redeemable convertible preferred stock in DOT-1 in December 2019. The fair value of issued shares was estimated as $ 9.9 million, based on the price paid by other investors for issued shares in the Series A financing of DOT-1 Therapeutics, Inc. Based on the terms of the Millennium Stock Exchange Agreement, Takeda exchanged the 9,857,143 shares of Series A redeemable convertible preferred stock of DOT-1, Inc. for 6,470,382 shares of the Company’s common stock upon the effectiveness of the Conversion, on May 26, 2021. The term of the Takeda Asset Agreement will expire on a country-by-country basis upon expiration of all assigned patent rights and all licensed patent rights in such country. Takeda may terminate the Takeda Asset Agreement prior to our first commercial sale of a product if we cease conducting any development activities for a continuous and specified period of time and such cessation is not agreed upon by the parties and is not done in response to guidance from a regulatory authority. Additionally, Takeda can terminate the Takeda Asset Agreement for our bankruptcy. In the event of termination of the Takeda Asset Agreement by Takeda as a result of our cessation of development or bankruptcy, all assigned patents, know-how and contracts (other than the Viracta License Agreement) will be assigned back to Takeda and Takeda will obtain a reversion license under patents and know-how generated to exploit all such terminated products. Viracta License Agreement On December 16, 2019, DOT-1 amended and restated the Viracta License Agreement that was assigned pursuant to the Takeda Asset Agreement. Under the Viracta License Agreement, DOT-1 received a worldwide exclusive license under specified patent rights and know-how to develop, use, manufacture, and commercialize products containing compounds binding the RAF protein family. DOT-1 paid $ 2.0 million upfront in cash to Viracta, which was recorded as research and development expenses. DOT-1 made a milestone payment of $ 3.0 million to Viracta in February 2021, which is recorded as research and development expense when the milestone was achieved in April 2021. DOT-1 is also required to make additional milestone payments of up to $ 54 million upon achievement of specified development and regulatory milestones for each licensed product in two indications, with milestones payable for the second indication to achieve a specified milestone event being lower than milestones payable for the first indication. Additionally, if DOT-1 obtains a priority review voucher with respect to a licensed product and sell such priority review voucher to a third party or use such priority review voucher, DOT-1 is obligated to pay Viracta a specified percentage in the mid-teen digits of all net consideration received from any such sale or of the value of such used priority review voucher, as applicable. Commencing on the first commercial sale of a licensed product in a country, DOT-1 is obligated to pay tiered royalties ranging in the mid-single-digit percentages on net sales of licensed products, if any. The obligation to pay royalties will end on a country-by-country and licensed product-by-licensed product basis commencing on the first commercial sale in a country and continuing until the later of: (i) the expiration of the last valid claim of the Viracta licensed patents, jointly owned collaboration patents or specified patents owned by the Company covering the use or sale of such product in such country, (ii) the expiration of the last statutory exclusivity pertaining to such product in such country or (iii) the tenth anniversary of the first commercial sale of such product in such country. No other milestones, except as discussed above, were achieved and due as of December 31, 2021. The term of the Viracta License Agreement will expire on a licensed product-by-licensed product and country-by-country basis upon the expiration of the Company’s obligation to pay royalties to Viracta with respect to such product in such country. DOT-1 has the right to terminate the Viracta License Agreement with respect to any or all of the licensed products at will upon a specified notice period.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies Leases The Company entered into a lease agreement for its corporate office facility in South San Francisco, California in March 2020, which expires in three years . The Company can extend the lease term for additional three years at market rates upon the notice of extension. The Company is obligated to pay monthly rent expense and its pro rata share of utilities, common area maintenance expenses and property taxes. The landlord also provided an allowance of $ 10,000 for any tenant improvements. The Company concluded that it is an operating lease. Common area expenses are a non-lease component and a variable consideration and included in operating expenses as incurred. The extension period has not been included in the determination of the Right of Use (“ROU”) asset or the lease liability for operating leases as the Company concluded that it is not reasonably certain that it would exercise this option. The Company determined the lease incremental borrowing rate (“IBR”) based on the information available at the applicable lease commencement date as the Company’s lease did not provide an implicit rate. The IBR is determined by using the rate of interest that the Company would pay to borrow on a collateralized basis an amount equal to the lease payments for a similar term and in a similar economic environment where the asset is located. The Company determined the amounts of its lease liabilities using an IBR of 8 %. As of December 31, 2021, the remaining lease term was 1.2 years. The Company’s lease does not require any contingent rental payments, impose financial restrictions, or contain any residual value guarantees. Lease expense of right-of-use assets is recognized on a straight-line basis over the applicable lease term. Lease expense was $ 0.2 million, $ 0.1 million, and zero for the years ended December 31, 2021, 2020, and 2019, respectively. Cash paid for amounts included in the measurement of operating lease liabilities was $ 0.2 million, $ 0.2 million, and zero for the years ended December 31, 2021, 2020, and 2019, respectively. Variable payments expensed during the years ended December 31, 2021, 2020, and 2019 were immaterial. As of December 31, 2021, the future lease obligations were as follows (in thousands): For the Years Ending December 31, 2022 $ 211 2023 18 Total future minimum lease payments 229 Less: Imputed interest ( 9 ) Present value of operating lease liabilities $ 220 Research and Development Agreements The Company enters into contracts in the normal course of business with clinical research organizations for clinical trials, with contract manufacturing organizations for clinical supplies manufacturing and with other vendors for preclinical studies, supplies and other services and products for operating purposes. These contracts generally provide for termination on notice, with the exception of one vendor with a potential termination fee if a purchase order is cancelled within a specified time and of another vendor where labor costs are non-cancellable after the approval of the project plan. As of December 31, 2021 and 2020, there were no amounts accrued related to termination and cancellation charges as these are not probable. License Agreements The Company entered into the license agreements, as disclosed in Note 5, pursuant to which the Company is required to pay milestones contingent upon meeting of specific events. The first milestone related to the Viracta License Agreement was achieved and recorded to research and development expense during year ended December 31, 2021. The Company may be required to pay royalties on sales of products developed under these agreements. All products are in development as of December 31, 2021 and 2020, and no such royalties were due. Legal Proceedings The Company, from time to time, may be party to litigation arising in the ordinary course of business. The Company is not subject to any material legal proceedings, and to the best of its knowledge, no material legal proceedings are currently pending or threatened. Indemnification Agreements In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for indemnification for certain liabilities. The exposure under these agreements is unknown because it involves claims that may be made against it in the future but have not yet been made. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations. The Company also has indemnification obligations to its directors and executive officers for specified events or occurrences, subject to some limits, while they are serving at its request in such capacities. There have been no claims, to date and the Company believes the fair value of these indemnification agreements is minimal. Accordingly, the Company had no t recorded any liabilities for these agreements as of December 31, 2021 and 2020.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Shares	12 Months Ended
	Dec. 31, 2021
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Shares	7. Redeemable Convertible Preferred Shares In June 2021, the Company completed its IPO, selling an aggregate of 11,500,000 shares of common stock. All outstanding redeemable convertible preferred shares were converted into 32,489,398 shares of common stock upon the completion of the IPO, June 1, 2021. As of December 31, 2021, the Company did no t have any outstanding shares of redeemable convertible preferred shares. In February 2021, the Company issued 9,638,141 Series B redeemable convertible preferred shares at a price of $ 13.488 per share for gross cash proceeds of $ 130 .0 million. The Company incurred issuance costs of $ 243,000 . In December 2019, the Company issued 10,348,507 Series A redeemable convertible preferred shares at a price of $ 2.899 per share for gross cash proceeds of $ 30.0 million and issued 2,154,245 shares upon the conversion of the outstanding convertible note and accrued interest of $ 2.1 million. The Company incurred issuance costs of $ 95,000 . In connection with the initial issuance of the Series A redeemable convertible preferred shares, the Company had an obligation to sell an additional 10,348,505 Series A shares at $ 2.899 per share upon achievement of certain milestones in two tranches. The Company determined that the obligation to sell additional shares is a freestanding financing instrument and a liability. The Company estimated the fair value of the liability to be $ 1.5 million and recorded it as a reduction to redeemable convertible preferred shares and as a derivative tranche liability in its consolidated balance sheet at the issuance date in December 2019. For the year ended December 31, 2020, the Company remeasured the derivative tranche liability until its settlement and recognized $ 30 .0 million as changes in fair value of derivative liability in its Consolidated Statements of Operations and Comprehensive Loss. In November and December 2020, the board of directors approved the settlement of tranche and the Company issued 10,348,505 shares for gross cash proceeds of $ 30 .0 million. The Company incurred issuance costs of $ 22,000 . As of December 31, 2021 and 2020, no derivative tranche liabilities were outstanding. The authorized, issued, and outstanding Series A redeemable convertible preferred shares as of December 31, 2020 were as follows (in thousands except share amounts): December 31, 2020 Shares Shares Liquidation Carrying Series A redeemable convertible preferred shares 22,851,257 22,851,257 $ 66,245 $ 91,964

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2021
Stockholders Equity Note [Abstract]
Common Stock	8. Common Stock Upon completion of the IPO, the Company is authorized to issue 500 .0 million shares of common stock at a par value $ 0.0001 . As of December 31, 2021, 61,952,292 shares of common stock were issued and outstanding. In November 2018, the Company entered into common shares purchase agreements with two founders of the Company. The individuals purchased a total of 2,790,000 common shares for a total purchase price of $ 300 . Shares vested monthly for two and four years, respectively. Vesting for a certain number of shares was accelerated upon the Company’s closing of its Series A redeemable convertible preferred share financing. The Company also has an option for a period of ninety days after the individual’s employment is terminated either voluntarily or involuntarily to repurchase the unvested common shares at a price that is the lower of the original price per share paid by the founder for such stock or the fair value as of the date of such repurchase. As of December 31, 2020, there were 193,766 shares unvested. The founders’ shares were converted to common stock in the Conversion. As of December 31, 2021, all founders’ common stock shares were vested. The Company has reserved shares of common stock for future issuances as follows: December 31, Common stock options issued and outstanding 5,071,896 Restricted stock units issued and outstanding 96,890 Common stock available for future grants 1,200,214 Common stock available for ESPP 579,647 Total 6,948,647 As of December 31, 2020, the Company reserved 22,851,257 shares related to the conversion of redeemable convertible preferred shares into common shares.

Incentive Shares and Share_Stoc

Incentive Shares and Share/Stock-Based Compensation	12 Months Ended
	Dec. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Incentive Shares and Share/Stock-Based Compensation	9. Incentive Shares and Share/Stock-Based Compensation Prior to the Conversion, Day One Holding LLC granted incentive shares under the Incentive Share Plan and was authorized to issue 8,924,177 incentive shares. Incentive shares were a separate non-voting class of shares that participated in distributions only after incentive shares vested, unless it was approved by the board of directors and included at least two of the preferred members, and a participation threshold was met. The incentive shares represented profits interests in Day One Holding LLC, which was an interest in the increase in the Company’s value over the participation threshold, as defined in the Operating Agreement and as determined at the time of grant. A holder of incentive share had the right to participate in distributions of profits only in excess of the participation threshold. The participation threshold was based on the valuation of the Company’s common shares on or around the grant date. Day One Holding LLC granted incentive shares to employees and non-employees, which generally vested over a four-year period with cliff vesting for the first year. The board of directors approved vesting terms and conditions of each award and could accelerate vesting of incentive shares on an award-by-award basis. Vesting of incentive shares would be accelerated for all unvested shares upon a termination of services without cause within 12 months after the consummation of a change of control transaction. The fair value of the incentive shares was estimated using an option pricing model with the following assumptions: Year Ended December 31, 2021 2020 2019 Common share fair value $ 6.36 - $ 8.89 $ 0.85 - $ 2.10 $ 0.81 Participating threshold $ 6.36 - $ 7.51 $ 0.27 $ 0.00 Risk free rate 0.14 % 0.16 % - 0.30 % 1.64 % Volatility 72.90 % 78.00 % - 80.00 % 78.00 % Time to liquidity (in years) 0.20 - 1.80 3.03 - 3.33 3.71 - 4.36 Grant date fair value $ 4.24 - $ 4.52 $ 0.71 - $ 1.67 $ 0.22 - 0.66 The Company used the option pricing model to estimate the fair value of each incentive shares award on the date of grant. The members’ equity value was based on a recent enterprise valuation analysis performed and common share fair value. The participation threshold amounts were determined by the board of directors at the time of grant. The expected life of the awards granted during the period was determined based on an expected time to the liquidation event. The Company applied the risk-free interest rate based on the U.S. Treasury yield in effect at the time of the grant consistent with the life of the award. The expected volatility was based on a peer group in the industry in which the Company did business consistent with the expected time to liquidity. The dividend yield was set at zero as the underlying security did not and was not expected to pay a dividend. Fair Value of Common Share Prior to the IPO, management’s approach to estimate the fair value of the common share was consistent with the methods outlined in the American Institute of Certified Public Accountants’ Practice Aid, Valuation of Privately-Held-Company Equity Securities Issued as Compensation ( the “Practice Aid”), considering a number of objective and subjective factors including: valuations of common shares performed with the assistance of independent third-party valuation specialists; the Company’s stage of development and business strategy, including the status of research and development efforts, and the material risks related to the business and industry; the Company’s results of operations and financial position, including levels of available capital resources; the valuation of publicly traded companies in the life sciences and biotechnology sectors, as well as recently completed mergers and acquisitions of peer companies; the lack of marketability of the common shares; the prices of redeemable convertible preferred shares sold to investors in arm’s length transactions and the rights, preferences, and privileges of the Company’s redeemable convertible preferred shares relative to those of common shares; the likelihood of achieving a liquidity event for the holders of the common and redeemable convertible preferred shares, such as an initial public offering or a sale, given prevailing market conditions. The fair value of the common shares was approved by the board of directors until such time as the Company shares were listed on an established stock exchange or national market system. The incentive shares were classified as equity awards and share-based compensation expense was based on the grant date fair value of the award. The following table provides a summary of the incentive shares activity: Number of Weighted Average Outstanding as of December 31, 2020 4,112,017 $ 1.26 Granted 2,959,795 $ 4.32 Forfeited ( 265,596 ) $ 1.67 Converted to unvested common stock ( 6,806,216 ) $ 2.58 Outstanding as of December 31, 2021 — $ — 2021 Equity Incentive Plan Immediately prior to consummation of the IPO, all of the outstanding incentive shares were converted into 5,433,290 shares of common stock, of which 4,719,605 were unvested common stock. The following table provides a summary of the unvested common stock awards activity during the year ended December 31, 2021. Number of Weighted Average Unvested restricted stock as of December 31, 2020 — $ — Conversion of incentive shares 4,719,605 $ 16.00 Vested ( 965,743 ) $ 16.00 Unvested restricted stock as of December 31, 2021 3,753,862 $ 16.00 In May 2021, in connection with the IPO, the board of directors and stockholders approved the 2021 Equity Incentive Plan (the “2021 Plan”), which became effective on the day before the date of the effectiveness of the IPO. The 2021 Plan provides for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, awards of restricted stock, restricted stock units and other stock-based awards. The number of shares of common stock reserved for issuance under the 2021 Plan is equal to the sum of: (1) 6,369,000 ; plus (2) 4,719,605 shares of common stock issued in respect of the Conversion of incentive shares that were subject to vesting immediately prior to the effectiveness of the registration statement for the IPO that expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by us at their original issuance price pursuant to a contractual repurchase right. The number of shares available for grant and issuance under the 2021 Plan will be automatically increased on January 1 of each of 2022 through 2031, by the lesser of (a) 5 % of the number of shares of all classes of the Company’s common stock, plus the total number of shares of Company common stock issuable upon conversion of any preferred stock or exercise of any warrants to acquire shares of Company common stock for a nominal exercise price issued and outstanding on each December 31 immediately prior to the date of increase or (b) such number of shares determined by the board of directors. The following table provides a summary of stock option activity under the 2021 Plan during the year ended December 31, 2021. Options Weighted-Average Weighted-Average Aggregiate Outstanding at December 31, 2020 — $ — Granted 5,071,896 $ 16.90 Outstanding at December 31, 2021 5,071,896 $ 16.90 9.4 $ 3,756 Exercisable at December 31, 2021 110,634 $ 16.42 9.4 $ 89 Aggregate intrinsic value represents the difference between the estimated fair value of the underlying common stock and the exercise price of outstanding, in-the-money options. The total fair value of options that vested during the year ended December 31, 2021 was $ 1.1 million. The weighted-average grant date fair value of options granted during the year ended December 31, 2021 was $ 9.91 per share. Unamortized stock-based compensation for stock options as of December 31, 2021 was $ 41.1 million, which is expected to be recognized over a weighted-average period of 2.5 years. The following table provides a summary of restricted stock units activity under the 2021 Plan during the year ended December 31, 2021: Number of Weighted Average Unvested restricted stock at December 31, 2020 — $ — Granted 96,890 $ 22.93 Unvested restricted stock at December 31, 2021 96,890 $ 22.93 Restricted stock units vest quarterly over four years with the one-year cliff from the grant date. Unamortized stock-based compensation for restricted stock units as of December 31, 2021 was $ 2.1 million, which is expected to be recognized over a weighted-average period of 3.9 years. 2021 Employee Stock Purchase Plan In May 2021, the board of directors adopted and the stockholders approved, the 2021 Employee Stock Purchase Plan, (“the ESPP”), which became effective on May 26, 2021. A total of 603,000 shares of common stock were reserved for issuance under the ESPP. The number of shares of the common stock reserved for issuance under the ESPP will automatically increase on the first day of each fiscal year, beginning with the fiscal year commencing on January 1, 2021 and continuing for each fiscal year until, and including, the fiscal year commencing on January 1, 2031, by the lesser of: a) 1 % of the total number of outstanding shares of common stock of the Company (on an as converted basis outstanding on the immediately preceding December 31 (rounded down to the nearest whole share); b) an amount determined by the board of directors. 23,353 shares have been issued under the ESPP as of December 31, 2021. The Company recognized $ 0.2 million compensation expense related to the ESPP plan for the year ended December 31, 2021. Share/Stock-based compensation The Company used the option pricing model to estimate the fair value of its unvested common stock awards, which were received upon the conversion of unvested incentive shares to common stock shares prior to the IPO. Restricted stock units are measured at fair value, which is the Company’s common stock closing price on Nasdaq at the grant date. The Company uses the Black-Scholes option pricing model to estimate the fair value of stock options and ESPP awards granted with the following assumptions: Year Ended Stock Options ESPP Expected term (in years) 5.31 - 6.08 0.25 - 0.50 Expected volatility 61.25 % - 66.53 % 42.5 % - 48.4 % Risk-free interest rate 0.82 % - 1.39 % 0.05 % - 0.06 % Expected dividend yield — — Share/stock-based compensation expense recorded in the accompanying Consolidated Statements of Operations and Comprehensive Loss is as follows (in thousands): Year Ended December 31, 2021 2020 2019 Research and development expense $ 3,840 $ 212 $ 73 General and administrative expense 9,481 314 38 Total share-based compensation expense $ 13,321 $ 526 $ 111 As of December 31, 2021, there was $ 56.3 million of unrecognized compensation cost related to unvested restricted stock, unvested RSUs and stock options that is expected to be recognized over a weighted-average period of approximately 2.6 years. The Company did not recognize incremental share-based compensation expense related to the conversion of the incentive shares to unvested common stock in accordance with the Conversion, as such exchange was at fair value.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	10. Net Loss Per Share Basic and diluted net loss per share attributable to common shareholders/stockholders after the Conversion is calculated as follows (in thousands except share and per share amounts): Year Ended December 31, 2021 2020 2019 Net loss and comprehensive loss $ ( 72,754 ) $ ( 43,843 ) $ ( 16,984 ) Net loss attributable to redeemable convertible noncontrolling interests ( 2,109 ) ( 3,336 ) ( 4,350 ) Exchange of redeemable noncontrolling interest shares – deemed dividend (refer to Note 11) ( 99,994 ) — — Net loss attributable to common stockholders/members ( 170,639 ) ( 40,507 ) ( 12,634 ) Net loss per share, basic and diluted $ ( 4.62 ) $ ( 7.33 ) $ ( 2.13 ) Weighted-average number of common shares used in 36,960,569 5,529,519 5,924,640 The following outstanding potentially dilutive securities have been excluded from the calculation of diluted net loss per share, as their effect is anti-dilutive: As of December 31, 2021 2020 Stock options 5,071,896 — Unvested common shares 3,753,862 193,766 RSUs 96,890 — Shares committed under ESPP 25,362 — Redeemable convertible preferred shares — 22,851,257 Incentive Shares — 4,112,017 8,948,010 27,157,040

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interest	12 Months Ended
	Dec. 31, 2021
Temporary Equity Disclosure [Abstract]
Redeemable Noncontrolling Interest	11. Redeemable Noncontrolling Interest DOT-1, the Company’s subsidiary, issued Series A redeemable convertible preferred shares to Takeda in accordance with the Takeda Asset Agreement (Note 5). The Company concluded that it represented a redeemable noncontrolling interest. The Company adjusted the carrying value of redeemable noncontrolling interest to allocate net losses of the subsidiary to Takeda. Transfers to and from the redeemable noncontrolling interest represented changes in ownership and the allocation of Series A redeemable convertible preferred shares issuance costs issued by the subsidiary. On May 26, 2021, pursuant to the terms of the Millennium Stock Exchange Agreement, Takeda exchanged its 9,857,143 shares of Series A redeemable convertible preferred stock in DOT-1, for 6,470,382 shares of common stock of the Company. Prior to the Exchange, the Company accounted for the redeemable noncontrolling interest as discussed in the paragraph above and allocated $ 2.1 million and $ 0.9 million of net losses for the period from January 1 to May 26, 2021 and from April 1 to May 26, 2021, respectively, to Takeda. The Exchange resulted in DOT-1 becoming a wholly owned subsidiary of the Company and was recorded for accounting purposes as an extinguishment of the redeemable noncontrolling interest. As such, the Company also recognized an extinguishment loss of $ 100 .0 million to additional paid in capital, which was calculated as a difference between the fair value of common stock issued to Takeda in the conversion and the carrying value of redeemable noncontrolling interest at the conversion date. The all-stock exchange was treated as a deemed dividend in the calculation of net loss attributable to common stockholders/members and net loss and per share.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes Prior to the IPO and conversion, Day One Biopharmaceuticals, Inc. (formerly Day One Biopharmaceuticals Holding Company, LLC) was treated as a partnership for tax purposes, and thus, not subject to income taxes. It is the responsibility of the LLC members to report their proportion share of any taxable income or loss generated by Day One Biopharmaceuticals Holdings Company, LLC to the appropriate taxing authorities and pay the associated taxes, if any. With respect to the Company’s consolidated subsidiaries, these entities are treated as corporations for tax purposes and are subject to income taxes which have been included in the consolidated financial statements. All pre-tax losses have been incurred in the United States. The effective tax rate of the Company’s provision (benefit) for income taxes differs from the federal statutory rate as follows: Year Ended December 31, 2021 2020 2019 Statutory rate 21.0 % 21.0 % 21.0 % State tax ( 0.8 )% 2.3 % 6.1 % Permanent differences 0.6 % ( 14.4 )% ( 2.7 )% Credits 3.8 % 1.4 % — Change in valuation allowance ( 21.5 )% ( 10.1 )% ( 24.4 )% Share-based compensation ( 3.1 )% ( 0.2 )% — Total — — — Deferred income taxes reflect the net effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The principal components of the Company’s deferred tax assets and liabilities consisted of the following (in thousands): As of December 31, 2021 2020 Deferred tax assets Federal and state net operating loss carryforwards $ 17,270 $ 7,732 Credits 3,670 731 Accrued expenses 709 235 Intangible asset basis 2,188 — Total deferred tax assets 23,837 8,698 Total deferred tax liabilities ( 59 ) ( 97 ) Less: valuation allowance ( 23,778 ) ( 8,601 ) Net deferred tax assets $ — $ — The Company has incurred net operating losses in each year since inception. The Company has not reflected the benefit of any such net operating loss carryforwards in the consolidated financial statements. Due to its history of losses, and lack of other positive evidence, the Company determined that it is more likely than not that its net deferred tax assets will not be realized, and therefore, the net deferred tax assets are fully offset by a valuation allowance at December 31, 2021 and 2020. The Company increased the valuation allowance by $ 15.2 million, $ 4.4 million, and $ 4.2 million for the years ended December 31, 2021, 2020, and 2019, respectively. As of December 31, 2021, the Company had federal net operating loss carryforwards (“NOLs”), of $ 77.0 million that do not expire and federal tax credits of $ 4.4 million available to offset tax liabilities that begin to expire in 2039 . The Company also has gross state NOLs of $ 14.9 million and state tax credits of $ 0.5 million which are available to offset state tax liabilities. The state NOLs begin to expire in 2039 and the state tax credits do not expire. The Company has not completed a study to determine whether an ownership change per the provisions of Section 382 of the Internal Revenue Code, as well as similar state provisions, has occurred. Utilization of its net operating loss and income tax credit carryforwards may be subject to a substantial annual limitation due to ownership changes that may have occurred or that could occur in the future. These ownership changes may limit the amount of the net operating loss and income tax credit carryover that can be utilized annually to offset future taxable income. In general, an “ownership change” as defined by Section 382 of the Internal Revenue Code results from a transaction or series of transactions over a three-year period resulting in an ownership change of more than 50 percentage points of the outstanding shares of a company by certain shareholders. In March 2020, the Coronavirus Aid, Relief and Economic Security Act (the “CARES Act”) was enacted and signed into law and GAAP requires recognition of the tax effects of new legislation during the reporting period that includes the enactment date. The CARES Act, includes changes to the tax provisions that benefits business entities, and makes certain technical corrections to the 2017 Tax Cuts and Jobs Act. The tax relief measures for businesses include a five-year net operating loss carryback, suspension of annual deduction limitation of 80 % of taxable income from net operating losses generated in a tax year beginning after December 31, 2017, changes in the deductibility of interest, acceleration of alternative minimum tax credit refunds, payroll tax relief, and a technical correction to allow accelerated deductions for qualified improvement property. The Act also provides other non-tax benefits to assist those impacted by the pandemic. The Company evaluated the impact of the CARES Act and determined that there was no material impact. Uncertain Tax Positions In accordance with authoritative guidance, the impact of an uncertain income tax position on the income tax return must be recognized at the largest amount that is more-likely-than-not to be sustained upon audit by the relevant taxing authority. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained. The following table reconciles the beginning and ending amount of unrecognized tax benefits (in thousands): Year Ended December 31, 2021 2020 2019 Balance at beginning of year $ 188 $ 2 $ — Additions based on tax positions related to prior year — — — Additions based on tax positions related to current year 953 186 — Reductions based on tax positions related to prior year — — — Reductions based on tax positions related to current year — — — Balance at end of year $ 1,141 $ 188 $ — The entire amount of the unrecognized tax benefits would not impact the Company’s effective tax rate if recognized. The Company has elected to include interest and penalties as a component of tax expense. During the years ended December 31, 2021, 2020 and 2019, the Company did no t recognize accrued interest and penalties related to unrecognized tax benefits. The Company does not anticipate that the amount of existing unrecognized tax benefits will significantly increase or decrease during the next 12 months . The Company files income tax returns in the U.S. federal and California tax jurisdictions. The federal and state income tax returns from inception to December 31, 2020 remain subject to examination.

Defined Contribution Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2021
Retirement Benefits [Abstract]
Defined Contribution Plan	13. Defined Contribution Plan The Company maintains an employee savings plan pursuant to Section 401(k) of the Internal Revenue Code. All employees are eligible to participate provided that they meet the requirements of the plan. The Company has elected to not make matching contributions under the plan for the years ended December 31, 2021 and 2020.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company’s subsidiaries. All intercompany transactions and balances have been eliminated in consolidation. Because the Merger (refer to the section “Organization and Business”) did not constitute a change in the reporting entity, as defined in Accounting Standard Codification (“ASC”) 250, Accounting changes and error corrections, the Company will report the assets and liabilities transferred from its Subsidiaries at historical carrying value, prospectively from December 31, 2021. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in ASC and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”).
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying consolidated financial statements include, but are not limited to, the fair value of the redeemable convertible preferred shares, the fair value of the common shares, the fair value of the derivative tranche liability, the valuation of share-based awards, the valuation of deferred tax assets and income tax uncertainties, and accruals for research and development activities. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable. Actual results may differ from those estimates or assumptions.
Segments	Segments The Company has determined that its chief executive officer is the chief operating decision maker (“CODM”). The Company operates and manages the business as one reporting and one operating segment, which is the business of identifying and advancing targeted therapies for patients of all ages with genomically defined cancers. The Company’s CODM reviews financial information on an aggregate basis for purposes of allocating resources and evaluating financial performance. All of the Company’s assets are located in the United States.
Concentration of credit risk and other risks and uncertainties	Concentration of credit risk and other risks and uncertainties Financial instruments that subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company’s cash and cash equivalents is held in one financial institution in the United States. Amounts on deposit may at times exceed federally insured limits. Management believes that the financial institution is financially sound and, accordingly, minimal credit risk exists with respect to the financial institution. The Company is subject to certain risks and uncertainties and believes that changes in any of the following areas could have a material adverse effect on future financial position or results of its operations: ability to obtain future financing; regulatory approval and market acceptance of, and reimbursement for, product candidates; performance of third-party clinical research organizations and manufacturers upon which the Company relies; development of sales channels; protection of the Company’s intellectual property; litigation or claims against the Company based on intellectual property, patent, product, regulatory or other factors; and the Company’s ability to attract and retain employees necessary to support its growth. The Company is dependent on third-party manufacturers to supply products for research and development activities in its programs. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. As of December 31, 2021, cash equivalents include investments in money market funds. As of December 31, 2020, the Company did no t have any cash equivalents, and cash was held in checking accounts.
Deposits	Deposits Deposits consist of a long-term deposit of approximately $ 71,000 held at a third-party in connection with the Company’s facility lease agreement.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Assets and liabilities recorded at fair value on a recurring basis in the consolidated balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts reflected in the accompanying consolidated balance sheets for prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values, due to their short-term nature.
Deferred Finance Issuance Costs	Deferred Finance Issuance Costs Deferred finance issuance costs, consisting of legal, accounting, audit and filing fees relating to in-process equity financings, including the Company’s IPO, are capitalized. Deferred issuance costs are offset against offering proceeds. As of December 31, 2021, the Company did no t have any deferred finance issuance costs capitalized. As of December 31, 2020, the Company had capitalized $ 36,000 in deferred issuance costs related to its Series B redeemable convertible preferred share private financing, recorded in the deposits and other long-term assets in the consolidated balance sheet.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are recorded at cost, less accumulated depreciation and amortization. Depreciation is recognized using the straight-line method over the estimated useful lives of the related assets ranging from three to five years, and leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the asset.
Leases	Leases Contractual arrangements that meet the definition of a lease are classified as operating or finance leases and are recorded on the consolidated balance sheets as both a right-of-use asset (“ROU asset”) and lease liability, calculated by discounting fixed lease payments over the lease term at the rate implicit in the lease or the Company’s incremental borrowing rate (“IBR”). Lease ROU assets and lease obligations are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. The Company currently does not have any finance leases. Operating lease ROU assets are adjusted for (i) payments made at or before the commencement date, (ii) initial direct costs incurred, and (iii) tenant incentives under the lease. As the implicit rate for the operating leases are not determinable, the Company determines its IBR based on the information available at the applicable lease commencement date. The IBR is determined by using the rate of interest that the Company would pay to borrow on a collateralized basis an amount equal to the lease payments for a similar term and in a similar economic environment where the asset is located. The Company considers a lease term to be the noncancelable period that it has the right to use the underlying asset, including any periods where it is reasonably certain the Company will exercise any option to extend the contract. Lease costs for minimum lease payments for operating leases are recognized on a straight-line basis over the lease term. Lease liabilities are increased by interest and reduced by payments each period, and the ROU asset is amortized over the lease term. Variable lease costs are recorded when incurred. In measuring the ROU assets and lease liabilities, the Company has elected to combine lease and non-lease components. The Company excludes short-term leases, if any, having initial terms of 12 months or less at lease commencement as an accounting policy election, and recognizes rent expense on a straight-line basis over the lease term for these types of leases.
Impairment of Long-lived Assets	Impairment of Long-lived Assets The Company evaluates long-lived assets, which consist of property and equipment and right-of-use assets, for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the asset exceeds the fair value of the asset. To date, no impairments have been recognized in the consolidated financial statements.
Research and Development Expenses	Research and Development Expenses Research and development expenses consist of costs associated with acquiring technology and intellectual property licenses that have no alternative future uses; costs incurred under agreements with third-party contract research organizations, contract manufacturing organizations and other third parties that conduct clinical trials on the Company’s behalf; other costs associated with research and development programs, including laboratory materials and supplies; employee-related costs, including salaries, benefits and share-based compensation expense, for the Company’s research and development personnel; and facilities and other overhead expenses, including expenses for rent and facilities maintenance, and amortization. The Company’s expense research and development costs as incurred. The Company is obligated to make upfront payments upon execution of certain research and development agreements. Advance payments, including nonrefundable amounts, for goods or services that will be used or rendered for future research and development activities are deferred. Such amounts are recognized as expense as the related goods are delivered or the related services are performed, or such time when the Company does not expect the goods to be delivered or services to be performed.
Accrued Research and Development Expenses	Accrued Research and Development Expenses The Company records accrued liabilities for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of preclinical and clinical studies, and contract manufacturing activities. The Company records the estimated costs of research and development activities based upon the estimated amount of services provided but not yet invoiced and includes these costs in accrued liabilities in the balance sheets and within research and development expenses in the Consolidated Statements of Operations and Comprehensive Loss. These costs are a significant component of our research and development expenses. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with third-party service providers under the service agreements. The Company makes judgments and estimates in determining the accrued liabilities balance in each reporting period. As actual costs become known, the Company adjusts its accrued liabilities. The Company has not experienced any material differences between accrued costs and actual costs incurred. The Company makes payments in connection with clinical trials under contracts with contract manufacturing organizations and contract research organizations that support conducting and managing clinical trials. The financial terms of these contracts are subject to negotiation, which vary by contract and may result in payments that do not match the periods over which materials or services are provided. Generally, these agreements set forth the scope of work to be performed at a fixed fee, unit price or on a time and materials basis. In the event the Company makes advance payments for goods or services that will be used or rendered for future research and development activities, the payments are deferred and capitalized as a prepaid expense and recognized as expense as the goods are received or the related services are rendered. Such payments are evaluated for current or long-term classification based on when they are expected to be realized.
Patent Costs	Patent Costs All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty of the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses in the Consolidated Statements of Operations and Comprehensive Loss.
Redeemable Convertible Preferred Shares	Redeemable Convertible Preferred Shares The Company recorded redeemable convertible preferred shares at their respective fair values on the dates of issuance, net of issuance costs. The redeemable convertible preferred shares were recorded outside of members’ deficit because while they were not mandatorily redeemable, in the event of a deemed liquidation event, which was outside of the Company’s control, the proceeds were distributed first to the redeemable convertible preferred shareholders in accordance with their liquidation preferences. The Company had not adjusted the carrying values of the redeemable convertible preferred shares to their liquidation preferences because it is uncertain whether or when a deemed liquidation event would occur that would obligate it to pay the liquidation preferences to holders of redeemable convertible preferred shares. Redeemable convertible preferred shares were all converted to common stock shares upon the closing of the IPO in May 2021.
Redeemable Noncontrolling Interest	Redeemable Noncontrolling Interest Redeemable noncontrolling interest represented the portion of equity (net assets) in DOT-1 that was neither directly nor indirectly attributable to the Company. Redeemable noncontrolling interest is classified as temporary equity because preferred shares issued to a holder contained certain redemption features that were not solely within the control of the Company.
Derivative Tranches Liability	Derivative Tranches Liability The Company’s obligation to issue additional redeemable convertible preferred shares upon the occurrence of certain milestone events represents a freestanding financial instrument. The instrument was classified as a liability in the consolidated balance sheets and re-measured at each reporting period end and at the settlement date. Changes in the fair value were recognized in other income (expense) in the Consolidated Statements of Operations and Comprehensive Loss. The tranches were settled and reclassified to redeemable convertible preferred shares upon the Company’s issuance of additional Series A redeemable convertible preferred shares in November and December 2020.
Share/Stock-Based Compensation	Share/Stock-Based Compensation Prior to the IPO, the Company recognized share-based compensation expense based on the estimated fair value of all share-based awards, incentive shares and restricted share awards, on the date of grant using the option-pricing model. The option-pricing model requires the input of subjective assumptions, including the fair value of the underlying common shares, the expected term of the award, the expected volatility, risk-free interest rates, and the dividend yield. In determining the fair value of common shares, the methodologies used to estimate the enterprise value were performed using methodologies, approaches, and assumptions consistent with the American Institute of Certified Public Accountants Accounting and Valuation Guide, Valuation of Privately-Held-Company Equity Securities Issued as Compensation . The participation threshold amounts were determined by the board of directors, at the time of grant. The expected life of the awards granted during the period was determined based on an expected time to the liquidation event. The Company applied the risk-free interest rate based on the U.S. Treasury yield in effect at the time of the grant consistent with the life of the award. The expected volatility was based on a peer group in the industry in which the Company did business consistent with the expected time to liquidity. The dividend yield was set at zero as the underlying security did not and was not expected to pay a dividend. Subsequent to closing of the IPO, the Company uses the Black-Scholes valuation model to estimate the fair value of options granted to employees and non-employees, intrinsic value to estimate the fair value of restricted stock award, and fair value of the Company’s common stock at the grant date for restricted stock units. The Black-Scholes option-pricing model, used to estimate fair value of stock options awards, requires the use of the following assumptions: • Fair Value of Common Stock —The Company’s closing price on the Nasdaq market at the grant date. • Expected Term —The expected term represents the period that the stock-based awards are expected to be outstanding. The expected term for stock options is calculated using simplified method, as the weighted-average vesting term of the award and the award’s contract period. • Expected Volatility —Since the Company does not have sufficient trading history for its common stock, the expected volatility is estimated based on the average historical volatilities of common stock of comparable publicly traded entities over a period equal to the expected term of the stock option grants. The comparable companies are chosen based on their size, stage in the life cycle or area of specialty. The Company will continue to apply this process until sufficient historical information regarding the volatility of the common stock price becomes available. • Risk-Free Interest Rate —The risk-free interest rate is based on the U.S. Treasury yield in effect at the time of grant for zero-coupon U.S. Treasury notes with maturities approximately equal to the expected term of the awards. • Expected Dividend Yield —The Company has never paid dividends on the common stock and has no plans to pay dividends on its common stock. Therefore, the expected dividend yield use is zero. The Company uses the straight-line attribution method for recognizing share/stock-based compensation expense. The Company recognizes forfeitures by reducing the expense in the same period the forfeitures occur. The Company recognizes share/stock-based compensation expense for awards with performance conditions when it is probable that the condition will be met, and the award will vest. The Company classifies share/stock-based compensation expense in the Consolidated Statements of Operations and Comprehensive Loss in the same manner in which the award recipients’ payroll costs are classified or in which the award recipients’ service payments are classified.
Income Taxes	Income Taxes Prior to the IPO, the Company was a “pass-through” entity under the Internal Revenue Code with two corporate subsidiaries. Prior to the Conversion, the members of the Company, formerly Day One Biopharmaceuticals Holding Company, LLC, were taxed directly on their respective ownership interests and activity in Day One Biopharmaceuticals Holding Company, LLC. The Company’s consolidated corporate subsidiaries accounted for income taxes under the asset and liability method, as discussed below. Upon the closing of the IPO and the Conversion, the Company’s income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax base and net operating loss and tax credit carryforwards. Deferred tax assets and liabilities are determined based upon the difference between the consolidated financial statement carrying amounts and the tax basis of assets and liabilities and are measured using the enacted tax rate expected to apply to taxable income in the years in which the differences are expected to be reversed. Deferred tax assets are reduced by a valuation allowance if it is more likely than not that some portion or all of the deferred tax asset will not be realized. The uncertain income tax positions are recognized at the largest amount that is more likely than not to be sustained upon audit by the relevant taxing authority. Changes in recognition or measurement are reflected in the period in which judgment occurs. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of the provision for income taxes. To date, there have been no interest or penalties recorded in relation to unrecognized tax benefits.
Net Loss per Share	Net Loss per Share The Company calculates basic and diluted net loss per share in conformity with the two-class method required for participating securities. Under the two-class method, basic net loss per share is computed by dividing the net loss by the weighted average number of common shares outstanding during the period, without consideration of potential dilutive securities. Diluted net loss per share is computed by dividing the net loss, after adjusting it for loss attributable to redeemable noncontrolling interest, in any, by the sum of the weighted average number of common stock shares outstanding during the period plus the dilutive effects of potentially dilutive securities outstanding during the period. Potentially dilutive securities include incentive shares, unvested restricted common shares and redeemable convertible preferred shares, prior to the IPO. Potentially dilutive securities include unvested restricted stock awards, unvested restricted stock units and stock options, after the IPO. For all periods presented, diluted net loss per share is the same as basic net loss per share since the effect of including potential common stock shares is anti-dilutive and incentive shares participation thresholds were not met.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss as well as other changes in stockholders' equity/members’ deficit that result from transactions and economic events other than those with stockholders/members. There were no components of other comprehensive loss for the Company for the periods presented. Thus, comprehensive loss equals net loss for all periods presented.
Emerging Growth Company Status	Emerging Growth Company Status The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has elected to use this extended transition period for complying with new or revised accounting standards that have different effective dates for public and private companies until the earlier of the date that it (i) is no longer an emerging growth company or (ii) affirmatively and irrevocably opts out of the extended transition period provided in the JOBS Act. As a result, these consolidated financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates. The JOBS Act does not preclude an emerging growth company from adopting a new or revised accounting standard earlier than the time that such standard applies to private companies. The Company expects to use the extended transition period for any other new or revised accounting standards during the period in which it remains an emerging growth company.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses: Measurement of Credit Losses on Financial Instruments (Topic 326) ("ASU 2016-13") . ASU 2016-13 requires measurement and recognition of expected credit losses for financial assets. In April 2019, the FASB issued clarification to ASU 2016-13 within ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments-Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments. The guidance will become effective for the Company for fiscal years beginning after December 15, 2022, with early adoption permitted. Effective January 1, 2021, the Company adopted ASU 2016-13 and the adoption did not have any impact on the Company’s consolidated financial statements and related disclosures. Recently Issued Accounting Pronouncements In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes (“ASU 2019-12”), which simplifies the accounting for income taxes, eliminates certain exceptions within ASC 740, Income Taxes, and clarifies certain aspects of the current guidance to promote consistency among reporting entities. ASU 2019-12 is effective for fiscal years beginning after December 15, 2021. Most amendments within the standard are required to be applied on a prospective basis, while certain amendments must be applied on a retrospective or modified retrospective basis. The Company does not expect the adoption of ASU 2019-12 to have a material impact on the Company's consolidated financial statements and related disclosures.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following table sets forth the Company’s financial instruments as of December 31, 2021, which are measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): December 31, 2021 Total Level 1 Level 2 Level 3 Money market funds, included in cash and cash equivalents $ 111,221 $ 111,221 $ — $ —

Balance Sheet Items (Tables)

Balance Sheet Items (Tables)	12 Months Ended
	Dec. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Schedule of Prepaid and Other Current Assets	Prepaid and other current assets consisted of the following (in thousands): December 31, December 31, Prepaid insurance $ 2,099 $ 41 Prepaid research and development expenses 1,945 1,259 Other prepaid expenses and other assets 1,015 43 Total prepaid expenses and other current assets $ 5,059 $ 1,343
Schedule of Property and Equipment, Net	Property and equipment, net, consisted of the following (in thousands): December 31, December 31, Furniture and fixtures $ 78 $ 78 Leasehold improvements 15 15 Property and equipment, gross 93 93 Less: accumulated depreciation and amortization ( 36 ) ( 16 ) Property and equipment, net $ 57 $ 77
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): December 31, December 31, Accrued payroll related expenses $ 3,308 $ 717 Accrued research and development expenses 2,565 554 Accrued professional service expenses 732 298 Other 104 27 Total accrued expenses and other current liabilities $ 6,709 $ 1,596

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2021
Prepaid Expense And Other Assets Current [Abstract]
Schedule Of Prepaid Expenses and Other Current Assets	Prepaid and other current assets consisted of the following (in thousands): December 31, December 31, Prepaid insurance $ 2,099 $ 41 Prepaid research and development expenses 1,945 1,259 Other prepaid expenses and other assets 1,015 43 Total prepaid expenses and other current assets $ 5,059 $ 1,343

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2021
Property Plant And Equipment Net [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net, consisted of the following (in thousands): December 31, December 31, Furniture and fixtures $ 78 $ 78 Leasehold improvements 15 15 Property and equipment, gross 93 93 Less: accumulated depreciation and amortization ( 36 ) ( 16 ) Property and equipment, net $ 57 $ 77

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2021
Disclosure Text Block [Abstract]
Schedule of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): December 31, December 31, Accrued payroll related expenses $ 3,308 $ 717 Accrued research and development expenses 2,565 554 Accrued professional service expenses 732 298 Other 104 27 Total accrued expenses and other current liabilities $ 6,709 $ 1,596

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Summary of Future Lease Obligations	As of December 31, 2021, the future lease obligations were as follows (in thousands): For the Years Ending December 31, 2022 $ 211 2023 18 Total future minimum lease payments 229 Less: Imputed interest ( 9 ) Present value of operating lease liabilities $ 220

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Shares (Tables)	12 Months Ended
	Dec. 31, 2021
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Shares	The authorized, issued, and outstanding Series A redeemable convertible preferred shares as of December 31, 2020 were as follows (in thousands except share amounts): December 31, 2020 Shares Shares Liquidation Carrying Series A redeemable convertible preferred shares 22,851,257 22,851,257 $ 66,245 $ 91,964

Common Stock (Tables)

Common Stock (Tables)	12 Months Ended
	Dec. 31, 2021
Stockholders Equity Note [Abstract]
Schedule of Common Stock Shares Reserved for Future Issuance	The Company has reserved shares of common stock for future issuances as follows: December 31, Common stock options issued and outstanding 5,071,896 Restricted stock units issued and outstanding 96,890 Common stock available for future grants 1,200,214 Common stock available for ESPP 579,647 Total 6,948,647

Incentive Shares and Share_St_2

Incentive Shares and Share/Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Fair Value of The Incentive Shares Estimated Using An Option Pricing Model	The fair value of the incentive shares was estimated using an option pricing model with the following assumptions: Year Ended December 31, 2021 2020 2019 Common share fair value $ 6.36 - $ 8.89 $ 0.85 - $ 2.10 $ 0.81 Participating threshold $ 6.36 - $ 7.51 $ 0.27 $ 0.00 Risk free rate 0.14 % 0.16 % - 0.30 % 1.64 % Volatility 72.90 % 78.00 % - 80.00 % 78.00 % Time to liquidity (in years) 0.20 - 1.80 3.03 - 3.33 3.71 - 4.36 Grant date fair value $ 4.24 - $ 4.52 $ 0.71 - $ 1.67 $ 0.22 - 0.66
Summary of The Incentive Shares Activity	The following table provides a summary of the incentive shares activity: Number of Weighted Average Outstanding as of December 31, 2020 4,112,017 $ 1.26 Granted 2,959,795 $ 4.32 Forfeited ( 265,596 ) $ 1.67 Converted to unvested common stock ( 6,806,216 ) $ 2.58 Outstanding as of December 31, 2021 — $ —
Summary of The Unvested Common Stock	The following table provides a summary of restricted stock units activity under the 2021 Plan during the year ended December 31, 2021: Number of Weighted Average Unvested restricted stock at December 31, 2020 — $ — Granted 96,890 $ 22.93 Unvested restricted stock at December 31, 2021 96,890 $ 22.93
Schedule of Nonvested Share Activity	The following table provides a summary of the unvested common stock awards activity during the year ended December 31, 2021. Number of Weighted Average Unvested restricted stock as of December 31, 2020 — $ — Conversion of incentive shares 4,719,605 $ 16.00 Vested ( 965,743 ) $ 16.00 Unvested restricted stock as of December 31, 2021 3,753,862 $ 16.00
Summary of Stock Option Activity Under The 2021 Plan	The following table provides a summary of stock option activity under the 2021 Plan during the year ended December 31, 2021. Options Weighted-Average Weighted-Average Aggregiate Outstanding at December 31, 2020 — $ — Granted 5,071,896 $ 16.90 Outstanding at December 31, 2021 5,071,896 $ 16.90 9.4 $ 3,756 Exercisable at December 31, 2021 110,634 $ 16.42 9.4 $ 89
summary of Restricted Stock Units Activity Under the 2021 Plan	The following table provides a summary of restricted stock units activity under the 2021 Plan during the year ended December 31, 2021: Number of Weighted Average Unvested restricted stock at December 31, 2020 — $ — Granted 96,890 $ 22.93 Unvested restricted stock at December 31, 2021 96,890 $ 22.93
Summary of The Black-Scholes Option Pricing Model to Estimate The Fair Value of Stock Option Granted	The Company uses the Black-Scholes option pricing model to estimate the fair value of stock options and ESPP awards granted with the following assumptions: Year Ended Stock Options ESPP Expected term (in years) 5.31 - 6.08 0.25 - 0.50 Expected volatility 61.25 % - 66.53 % 42.5 % - 48.4 % Risk-free interest rate 0.82 % - 1.39 % 0.05 % - 0.06 % Expected dividend yield — —
Summary of Share/Stock-based Compensation Expense Recorded in The Accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss	Share/stock-based compensation expense recorded in the accompanying Consolidated Statements of Operations and Comprehensive Loss is as follows (in thousands): Year Ended December 31, 2021 2020 2019 Research and development expense $ 3,840 $ 212 $ 73 General and administrative expense 9,481 314 38 Total share-based compensation expense $ 13,321 $ 526 $ 111

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Summary of Basic and Diluted Net Loss Per Share Attributable to Common Shareholders/Stockholders	Basic and diluted net loss per share attributable to common shareholders/stockholders after the Conversion is calculated as follows (in thousands except share and per share amounts): Year Ended December 31, 2021 2020 2019 Net loss and comprehensive loss $ ( 72,754 ) $ ( 43,843 ) $ ( 16,984 ) Net loss attributable to redeemable convertible noncontrolling interests ( 2,109 ) ( 3,336 ) ( 4,350 ) Exchange of redeemable noncontrolling interest shares – deemed dividend (refer to Note 11) ( 99,994 ) — — Net loss attributable to common stockholders/members ( 170,639 ) ( 40,507 ) ( 12,634 ) Net loss per share, basic and diluted $ ( 4.62 ) $ ( 7.33 ) $ ( 2.13 ) Weighted-average number of common shares used in 36,960,569 5,529,519 5,924,640
Summary of Outstanding Potentially Dilutive Securities Have Been Excluded From Calculation of Diluted Net Loss Per Share	The following outstanding potentially dilutive securities have been excluded from the calculation of diluted net loss per share, as their effect is anti-dilutive: As of December 31, 2021 2020 Stock options 5,071,896 — Unvested common shares 3,753,862 193,766 RSUs 96,890 — Shares committed under ESPP 25,362 — Redeemable convertible preferred shares — 22,851,257 Incentive Shares — 4,112,017 8,948,010 27,157,040

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation	The effective tax rate of the Company’s provision (benefit) for income taxes differs from the federal statutory rate as follows: Year Ended December 31, 2021 2020 2019 Statutory rate 21.0 % 21.0 % 21.0 % State tax ( 0.8 )% 2.3 % 6.1 % Permanent differences 0.6 % ( 14.4 )% ( 2.7 )% Credits 3.8 % 1.4 % — Change in valuation allowance ( 21.5 )% ( 10.1 )% ( 24.4 )% Share-based compensation ( 3.1 )% ( 0.2 )% — Total — — —
Schedule of Deferred Tax Assets and Liabilities	Deferred income taxes reflect the net effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The principal components of the Company’s deferred tax assets and liabilities consisted of the following (in thousands): As of December 31, 2021 2020 Deferred tax assets Federal and state net operating loss carryforwards $ 17,270 $ 7,732 Credits 3,670 731 Accrued expenses 709 235 Intangible asset basis 2,188 — Total deferred tax assets 23,837 8,698 Total deferred tax liabilities ( 59 ) ( 97 ) Less: valuation allowance ( 23,778 ) ( 8,601 ) Net deferred tax assets $ — $ —
Summary of Unrecognized Tax Benefits	The following table reconciles the beginning and ending amount of unrecognized tax benefits (in thousands): Year Ended December 31, 2021 2020 2019 Balance at beginning of year $ 188 $ 2 $ — Additions based on tax positions related to prior year — — — Additions based on tax positions related to current year 953 186 — Reductions based on tax positions related to prior year — — — Reductions based on tax positions related to current year — — — Balance at end of year $ 1,141 $ 188 $ —

Description of Business, Orga_2

Description of Business, Organization and Liquidity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jun. 01, 2021	May 23, 2021	Jun. 30, 2021	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Proceeds from issuance of initial public offering	$ 167,000
Payments of stock issuance costs	$ 17,000
Share-based compensation arrangement by share-based payment award, options, vested, number of shares					4,719,605
Common stock shares authorized					500,000,000
Preferred stock shares authorized					10,000,000	0
Preferred stock par or stated value per share					$ 0.0001
Stockholders' equity note, stock split		2.325-for-1
Retained Earnings (Accumulated Deficit)					$ (127,487)	$ (56,842)
Cash and cash equivalents				$ 27,332	$ 284,309	$ 43,728	$ 942
I P O [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Common stock issued in IPO, net of issuance costs of $16,995, shares	11,500,000		11,500,000
Shares issued, price per share	$ 16				$ 16
Number of shares issued upon conversion					5,433,290
Stock issued during period, shares, conversion of units					32,489,398
Share-based compensation arrangement by share-based payment award, options, grants in period, net of forfeitures					4,418,874
Over-Allotment Option [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Stock issued during period, shares, issued for services	1,500,000
Series A Redeemable Convertible Preferred Stock [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Payments of stock issuance costs				$ 95,000
Common stock par or stated value per share					$ 0.0001
Series A Redeemable Convertible Preferred Stock [Member] | Millennium Pharmaceuticals, Inc. [Member] | The Millennium Stock Exchange Agreement [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Conversion of stock, shares converted					9,857,143
Convertible preferred stock, shares issued upon conversion					6,470,382

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Cash	$ 0
Deposits	71,000
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Payments	0
Series B Redeemable Convertible Preferred Shares [Member]
Class Of Stock [Line Items]
Deferred finance costs, own-share lending arrangement, issuance costs, net	$ 0	$ 36,000

Fair Value Measurement - Summar

Fair Value Measurement - Summary of Company's Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds, included in cash and cash equivalents		$ 0
Money Market Funds | Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds, included in cash and cash equivalents	$ 111,221
Money Market Funds | Fair Value, Inputs, Level 1 | Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds, included in cash and cash equivalents	111,221
Money Market Funds | Fair Value, Inputs, Level 2 | Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds, included in cash and cash equivalents	0
Money Market Funds | Fair Value, Inputs, Level 3 | Fair Value, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Money market funds, included in cash and cash equivalents	$ 0

Fair Value Measurement - Additi

Fair Value Measurement - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Abstract]
Money market funds, included in cash and cash equivalents		$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net	$ 0	$ 0

Balance Sheet Items - Schedule

Balance Sheet Items - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Prepaid Expense And Other Assets Current [Abstract]
Prepaid insurance	$ 2,099	$ 41
Prepaid research and development expenses	1,945	1,259
Other prepaid expenses and other assets	1,015	43
Total prepaid expenses and other current assets	$ 5,059	$ 1,343

Balance Sheet Items - Summary o

Balance Sheet Items - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 93	$ 93
Less: accumulated depreciation and amortization	(36)	(16)
Property and equipment, net	57	77
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	78	78
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 15	$ 15

Balance Sheet Items - Summary_2

Balance Sheet Items - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued payroll related expenses	$ 3,308	$ 717
Accrued research and development expenses	2,565	554
Accrued professional service expenses	732	298
Other	104	27
Total accrued expenses and other current liabilities	$ 6,709	$ 1,596

Balance Sheet Items - Additiona

Balance Sheet Items - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Balance Sheet Items [Lines items]
Depreciation	$ 20,000	$ 16,000	$ 0

Significant Agreements - Additi

Significant Agreements - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 16, 2019	Feb. 28, 2021	Dec. 31, 2019	Dec. 31, 2021
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common stock issued in IPO, net of issuance costs of $16,995				$ 167,045
Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Stock Issued During Period, Shares, New Issues				11,500,000
Common stock issued in IPO, net of issuance costs of $16,995				$ 1
Series A Redeemable Convertible Preferred Stock [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of Series A redeemable convertible preferred shares, shares			10,348,507
Takeda Asset Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront of cash payment	$ 1,000
Takeda Asset Agreement [Member] | Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of Series A redeemable convertible preferred shares, shares	6,470,382
Takeda Asset Agreement [Member] | Series A Redeemable Convertible Preferred Stock [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Stock Issued During Period, Shares, New Issues				9,857,143
Common stock issued in IPO, net of issuance costs of $16,995	$ 9,900
Issuance of Series A redeemable convertible preferred shares, shares	9,857,143
Takeda Asset Agreement [Member] | Research and Development Expense [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment				$ 8,000
Merck License Agreement [Member] | Research and Development Expense [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment of Milestones				$ 367,000
Viracta License Agreement [Member] | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment of Milestones		$ 54,000
Viracta License Agreement [Member] | Research and Development Expense [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment of Milestones		$ 3,000
Upfront of cash payment	$ 2,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Lessee Lease Description [Line Items]
Lessee operating lease renewal lease term	1 year 2 months 12 days
Amortization of operating right-of-use assets	$ 179,000	$ 139,000
Research And Development Agreements
Lessee Lease Description [Line Items]
Termination and cancellation charges payable	0	0
Viracta License Agreement [Member]
Lessee Lease Description [Line Items]
Royalty fee payable	0	0
Indemnification Agreement
Lessee Lease Description [Line Items]
Termination and cancellation charges payable	$ 0	0
Lease For Corporate Office Facility | Central America
Lessee Lease Description [Line Items]
Operating lease term	3 years
Tenant improvement allowances receivable	$ 10,000,000
Lessee operating lease incremental borrowing rate	8.00%
Lessee operating lease renewal lease term	3 years
Amortization of operating right-of-use assets	$ 200,000	100,000	0
Operating lease payments	$ 200,000	$ 200,000	$ 0

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Future Lease Obligations (Detail) $ in Thousands	Dec. 31, 2021USD ($)
Lessee Lease Description [Line Items]
2022	$ 211
2023	18
Total future minimum lease payments	229
Less: Imputed interest	(9)
Present value of operating lease liabilities	$ 220

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Shares - Additional Information (Detail) - USD ($)	Jun. 01, 2021	Jun. 30, 2021	Feb. 28, 2021	Nov. 30, 2020	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Temporary Equity [Line Items]
Carrying value							$ 91,964,000
Payments of Stock Issuance Costs	$ 17,000,000
Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Common Stock Shares Issued As A Result Of Conversion Of Temporary Equity Into Permanent Equity		32,489,398
Temporary Equity, Shares Outstanding		0				0	22,851,257
Issuance of redeemable convertible preferred shares						9,638,141	10,348,505	10,348,507
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Liquidation Value							$ 66,245,000
Temporary Equity, Shares Outstanding							22,851,257
Carrying value							$ 91,964,000
Issuance of redeemable convertible preferred shares					10,348,507
Temporary Equity Issue Price Per Share					$ 2.899			$ 2.899
Proceeds from redeemable convertible preferred stock					$ 30,000,000
Payments of Stock Issuance Costs					95,000,000
Payment Of Accrued Interest					$ 2,100,000
Debt Conversion, Converted Instrument, Shares Issued					2,154,245
Derivative liability at fair value					$ 1,500,000			$ 1,500,000
Series A Redeemable Convertible Preferred Stock [Member] | Milestone Achievement [Member]
Temporary Equity [Line Items]
Temporary Equity Stock Issued During The Period Shares New Issues				10,348,505				10,348,505
Temporary Equity Issue Price Per Share					$ 2.899			$ 2.899
Proceeds from redeemable convertible preferred stock				$ 30,000,000
Payments of Stock Issuance Costs				$ 22,000
Derivative liability at fair value						$ 0	0
Series A Redeemable Convertible Preferred Stock [Member] | Temporary Equity Related Tranche Liability [Member]
Temporary Equity [Line Items]
Derivative, Gain (Loss) on Derivative, Net							$ 30,000,000
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Issuance of redeemable convertible preferred shares			9,638,141
Temporary Equity Issue Price Per Share			$ 13.488
Payments of Stock Issuance Costs			$ 243,000,000
Series B Redeemable Convertible Preferred Stock [Member] | Gross Proceeds [Member]
Temporary Equity [Line Items]
Proceeds from redeemable convertible preferred stock			$ 130,000,000
IPO [Member]
Temporary Equity [Line Items]
Stock Issued During Period, Shares, New Issues	11,500,000	11,500,000

Redeemable Convertible Prefer_4

Redeemable Convertible Preferred Shares - Summary of Series A Redeemable Convertible Preferred Shares (Detail) $ in Thousands	Dec. 31, 2020USD ($)shares
Temporary Equity [Line Items]
Carrying value	$ 91,964
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized | shares	22,851,257
Shares Issued and Outstanding | shares	22,851,257
Liquidation Value	$ 66,245
Carrying value	$ 91,964

Common Stock - Additional Infor

Common Stock - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2018USD ($)shares	Dec. 31, 2021USD ($)shares	Dec. 31, 2020USD ($)shares	Dec. 31, 2019USD ($)	Jun. 30, 2021$ / sharesshares
Class Of Stock [Line Items]
Common Stock, Shares Authorized		500,000,000
Common Stock, Shares, Issued		61,952,292
Common Stock, Shares, Outstanding		61,952,292
Number Of Directors Entitled To Be Elected By The Holders Of Common Stock	2
Common Stock, Capital Shares Reserved for Future Issuance		6,948,647
Proceeds from issuance of common stock, net | $		$ 167,045		$ 0
Redeemable Convertible Preferred Stock [Member]
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance			22,851,257
Common Shares Purchase Agreement
Class Of Stock [Line Items]
Common Stock, Shares Authorized					500,000,000
Common Stock, Par or Stated Value Per Share | $ / shares					$ 0.0001
Common Stock, Shares, Issued		61,952,292
Common Stock, Shares, Outstanding		61,952,292
Common Shares Purchase Agreement | Founder
Class Of Stock [Line Items]
Stock Issued During Period, Shares, New Issues	2,790,000
Proceeds from issuance of common stock, net | $	$ 300
Common Stock Shares Unvested			193,766

Common Stock - Schedule of Comm

Common Stock - Schedule of Common Stock Shares Reserved for Future Issuance (Detail)	Dec. 31, 2021shares
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	6,948,647
Common Stock
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	5,071,896
Restricted Stock Units (RSUs)
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	96,890
Share-based Payment Arrangement, Option
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	1,200,214
Employee Stock Purchase Plan
Class Of Stock [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	579,647

Incentive Shares and Share_St_3

Incentive Shares and Share/Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	May 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance		6,948,647
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares		4,719,605
Share-based compensation expense		$ 13,321	$ 526	$ 111
Unvested Restricted Stock And Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation by share based payment arrangement unrecognized compensation		$ 56,300
Share based compensation by share based payment arrangement unrecognized compensation remaining period for recognition		2 years 7 months 6 days
Weighted-average period expected to be recognized		3 years 10 months 24 days
Unamortized stock-based compensation for stock options		$ 2,100
Incentive Share Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation by share based payment arrangement term of vesting		4 years
Share based compensation by share based payment award fair value assumptions dividend yield		0.00%
Total fair value of options		$ 1,100
Weighted-average grant date fair value of options granted		$ 9.91
Weighted-average period expected to be recognized		2 years 6 months
Unamortized stock-based compensation for stock options		$ 41,100
Incentive Share Plan [Member] | Day One Holding LLC [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation by share based payment arrangment number of shares authorized		8,924,177
Incentive Share Plan [Member] | Day One Holding LLC [Member] | Cliff Vesting
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation by share based payment arrangement term of vesting		12 months
Two Thousand And Twenty One Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Conversion of shares of one class into another		5,433,290
Two Thousand And Twenty One Stock Incentive Plan | Unvested Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Conversion of shares of one class into another		4,719,605
Two Thousand And Twenty One Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation by share based payment award fair value assumptions dividend yield		0.00%
Common Stock, Capital Shares Reserved for Future Issuance	6,369,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares	4,719,605
Total intrinsic value of the options outstanding		$ 3,756
Weighted average remaining contractual term		9 years 4 months 24 days
Two Thousand And Twenty One Equity Incentive Plan | Unvested Restricted Stock And Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation by share based payment arrangement term of vesting		4 years
Two Thousand And Twenty One Equity Incentive Plan | Incremental Shares Reserved For Future Issuance
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum	5.00%
Two Thousand And Twenty One Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	603,000
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum	1.00%
Stock Issued During Period, Shares, Employee Stock Ownership Plan		23,353
Share-based compensation expense		$ 200

Incentive Shares and Share_St_4

Incentive Shares and Share/Stock-Based Compensation - Summary of Fair Value of The Incentive Shares Estimated Using An Option Pricing Model (Detail) - Incentive Share Plan Member [Member] - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common share fair value			$ 0.81
Participating threshold		$ 0.27	$ 0
Risk free rate	0.14%		1.64%
Volatility	72.90%		78.00%
Grant date fair value	$ 4.24
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common share fair value	6.36	$ 0.85
Participating threshold	$ 6.36
Risk free rate		0.16%
Volatility		78.00%
Time to liquidity (in years)	2 months 12 days	3 years 10 days	3 years 8 months 15 days
Grant date fair value		$ 0.71	$ 0.22
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common share fair value	$ 8.89	$ 2.10
Participating threshold	$ 7.51
Risk free rate		0.30%
Volatility		80.00%
Time to liquidity (in years)	1 year 9 months 18 days	3 years 3 months 29 days	4 years 4 months 9 days
Grant date fair value	$ 4.52	$ 1.67	$ 0.66

Incentive Shares and Share_St_5

Incentive Shares and Share/Stock-Based Compensation - Summary of The Incentive Shares Activity (Detail)	12 Months Ended
	Dec. 31, 2021$ / sharesshares
Two Thousand And Twenty One Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Conversion of incentive shares | shares	4,719,605
Number of Shares, Unvasted Restricted Stock, Beginning balance | shares	0
Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 0
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 16
Incentive Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Share Outstanding, Beginning balance | shares	4,112,017
Granted | shares	2,959,795
Forfeited | shares	(265,596)
Converted to unvested common stock | shares	(6,806,216)
Number of Share Outstanding, Ending balance | shares	0
Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 1.26
Grant date fair value | $ / shares	4.32
Forfeited | $ / shares	1.67
Converted to unvested common stock | $ / shares	2.58
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 0

Incentive Shares and Share_St_6

Incentive Shares and Share/Stock-Based Compensation - Summary of The Unvested Common Stock (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Two Thousand And Twenty One Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Unvasted Restricted Stock, Beginning balance	0
Conversion of incentive shares	4,719,605
Vested	(965,743)
Number of Shares, Unvasted Restricted Stock, Ending balance	3,753,862
Weighted Average Grant Date Fair Value, Beginning Balance	$ 0
Conversion of incentive shares	16
Vested	16
Weighted Average Grant Date Fair Value, Ending Balance	$ 16
Incentive Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding as of December 31, 2020	0	4,112,017
Forfeited	265,596
Number of Share Outstanding, Ending balance	0
Weighted Average Grant Date Fair Value, Beginning Balance	$ 1.26
Weighted Average Grant Date Fair Value, Ending Balance	$ 0

Incentive Shares and Share_St_7

Incentive Shares and Share/Stock-Based Compensation - Summary of Stock Option Activity Under The 2021 Plan (Detail) - Two Thousand And Twenty One Equity Incentive Plan $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Beginning Balance | shares	0
Granted | shares	5,071,896
Number of Shares, Ending Balance | shares	5,071,896
Exercisable at December 31, 2021 | shares	110,634
Weighted Average Exercise Price, Ending Balance | $ / shares	$ 0
Granted | $ / shares	16.90
Weighted Average Exercise Price, Ending Balance | $ / shares	16.90
Exercisable at December 31, 2021 | $ / shares	$ 16.42
Weighted-Average Remaining Contractual Term, Outstanding at December 31, 2021	9 years 4 months 24 days
Weighted-Average Remaining Contractual Term, Exercisable at December 31, 2021	9 years 4 months 24 days
Outstanding at December 31, 2021, Aggregiate Intrinsic Value | $	$ 3,756
Exercisable at December 31, 2021, Aggregiate Intrinsic Value | $	$ 89

Incentive Shares and Share_St_8

Incentive Shares and Share/Stock-Based Compensation - Summary of Restricted Stock Units Activity (Detail) - Two Thousand And Twenty One Stock Incentive Plan [Member] - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested restricted stock as of December 31, 2020	$ 16	$ 0
Unvested restricted stock Grant fair value at December 31, 2021	$ 16	$ 0
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested restricted stock at December 31, 2020		0
Granted	96,890
Unvested restricted stock at December 31, 2021	96,890
Unvested restricted stock as of December 31, 2020	$ 22.93	$ 0
Grant date fair value	22.93
Unvested restricted stock Grant fair value at December 31, 2021	$ 22.93	$ 0

Incentive Shares and Share_St_9

Incentive Shares and Share/Stock-Based Compensation - Summary of The Black-Scholes Option Pricing Model to Estimate The Fair Value of Stock Option Granted (Detail)	12 Months Ended
	Dec. 31, 2021
Two Thousand And Twenty One Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	42.50%
Expected volatility	48.40%
Risk-free interest rate	0.05%
Risk-free interest rate	0.06%
Share based compensation by share based payment award fair value assumptions dividend yield	0.00%
Two Thousand And Twenty One Equity Incentive Plan | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	3 months
Two Thousand And Twenty One Equity Incentive Plan | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 months
Share-based Payment Arrangement, Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	61.25%
Expected volatility	66.53%
Risk-free interest rate	0.82%
Risk-free interest rate	1.39%
Share based compensation by share based payment award fair value assumptions dividend yield	0.00%
Share-based Payment Arrangement, Option | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 3 months 21 days
Share-based Payment Arrangement, Option | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 29 days

Incentive Shares and Share_S_10

Incentive Shares and Share/Stock-Based Compensation - Summary of Share/Stock-based Compensation Expense Recorded in The Accompanying Condensed Consolidated Statements of Operations and Comprehensive Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 13,321	$ 526	$ 111
Research and Development Expense [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	3,840	212	73
General and Administrative Expense
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 9,481	$ 314	$ 38

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Basic and Diluted Net Loss Per Share Attributable to Common Shareholders/Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net loss	$ (72,754)	$ (43,843)	$ (16,984)
Net loss attributable to redeemable convertible noncontrolling interests	(2,109)	(3,336)	(4,350)
Exchange of redeemable noncontrolling interest shares - deemed dividend (refer to Note 11)	(99,994)	0	0
Net loss attributable to common stockholders/members	$ (170,639)	$ (40,507)	$ (12,634)
Net loss per share, basic and diluted	$ (4.62)	$ (7.33)	$ (2.13)
Weighted-average number of common shares used in computing net loss per share, basic and diluted	36,960,569	5,529,519	5,924,640

Net Loss Per Share - Summary _2

Net Loss Per Share - Summary of Outstanding Potentially Dilutive Securities Have Been Excluded From Calculation of Diluted Net Loss Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Stock options	8,948,010	27,157,040
Share-based Payment Arrangement, Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Stock options	5,071,896	0
Unvested common shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Stock options	3,753,862	193,766
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Stock options	96,890	0
Shares committed under ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Stock options	25,362	0
Redeemable convertible preferred shares
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Stock options	0	22,851,257
Incentive Shares [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Stock options	0	4,112,017

REDEEMABLE NONCONTROLLING INT_2

REDEEMABLE NONCONTROLLING INTEREST - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	2 Months Ended	5 Months Ended	12 Months Ended
	May 26, 2021	May 26, 2021	May 26, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Redeemable Noncontrolling Interest [Line Items]
Net loss attributable to redeemable convertible noncontrolling interests				$ (2,109)	$ (3,336)	$ (4,350)
Adjustment To Additional Paid In Capital Loss On Conversion Of Temporary Equity Into Permanent Equity			$ 100,000
DOT One [Member]
Redeemable Noncontrolling Interest [Line Items]
Temporary Equity Shares Converted Into Permanent Equity	9,857,143
Common Stock Shares Issued As A Result Of Conversion Of Temporary Equity Into Permanent Equity	6,470,382
DOT One [Member] | Takeda [Member]
Redeemable Noncontrolling Interest [Line Items]
Net loss attributable to redeemable convertible noncontrolling interests		$ 900	$ 2,100

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Statutory rate	21.00%	21.00%	21.00%
State tax	(0.80%)	2.30%	6.10%
Permanent differences	0.60%	(14.40%)	(2.70%)
Credits	3.80%	1.40%	0.00%
Change in valuation allowance	(21.50%)	(10.10%)	(24.40%)
Effective Income Tax Rate Reconciliation, Percent, Total	3.10%	0.20%	0.00%

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets
Federal and state net operating loss carryforwards	$ 17,270	$ 7,732
Credits	3,670	731
Accrued expenses	709	235
Intangible asset basis	2,188
Total deferred tax assets	23,837	8,698
Total deferred tax liabilities	(59)	(97)
Less: valuation allowance	(23,778)	(8,601)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Change in deferred tax assets valuation allowance	$ 15,200,000	$ 4,400,000	$ 4,200,000
Offset tax liabilities	$ 4,400
Net Operating Loss, Carryback period	12 months
Net operating loss carryforwards	$ 77,000,000
Net operating loss carryback, Suspension of annual deduction limitation, Percentage	80.00%
Unrecognized Tax Benefits Income Tax Penalties And Interest Accrued	$ 0	$ 0	$ 0
Tax Credit Carryforward, Expiration Year
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward, Expiration Year	2039
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
State tax credits	$ 500,000
Gross state NOL	$ 14,900,000
Tax Credit Carryforward, Expiration Year	2039
Tax Credit Carryforward, Expiration Year

Income Taxes - Summary of Unrec

Income Taxes - Summary of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 188	$ 2
Additions based on tax positions related to prior year	0
Additions based on tax positions related to current year	953	186
Reductions based on tax positions related to prior year	0
Reductions based on tax positions related to current year	0
Balance at end of year	$ 1,141	$ 188	$ 2