Zentalis Pharmaceuticals (ZNTL) 10-K 27 Feb 24 2023 FY Annual report Financial data

Cover

Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Feb. 22, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-39263
Entity Registrant Name	Zentalis Pharmaceuticals, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-3607803
Entity Address, Address Line One	1359 Broadway
Entity Address, Address Line Two	Suite 801
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10018
City Area Code	212
Local Phone Number	433-3791
Title of 12(b) Security	Common stock,$0.001 par value per share
Trading Symbol	ZNTL
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 1,560
Entity Common Stock, Shares Outstanding (in shares)		70,960,165
Documents Incorporated by Reference	Portions of the registrant's definitive Proxy Statement relating to its 2024 Annual Meeting of Stockholders to be filed with the SEC within 120 days after the end of the fiscal year ended December 31, 2023 are incorporated herein by reference in Part III of this Annual Report on Form 10-K.
Entity Central Index Key	0001725160
Amendment Flag	false
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2023

Audit Information

Audit Information	12 Months Ended
	Dec. 31, 2023
Auditor Information [Abstract]
Auditor Firm ID	42
Auditor Name	Ernst & Young LLP
Auditor Location	San Diego, California

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets
Cash and cash equivalents	$ 28,038	$ 43,069
Marketable securities, available for sale	454,881	394,302
Prepaid expenses and other current assets	13,799	14,562
Total current assets	496,718	451,933
Property and equipment, net	5,819	7,705
Operating lease right-of-use assets	35,916	42,373
Prepaid expenses and other assets	6,818	9,723
Goodwill	3,736	3,736
Investment in Zentera Therapeutics	0	21,213
Restricted cash	2,681	2,627
Total assets	551,688	539,310
Current liabilities
Accounts payable	14,926	11,247
Accrued expenses	54,441	45,400
Total current liabilities	69,367	56,647
Deferred tax liability	0	853
Long-term lease liability	43,150	45,166
Other long-term liabilities	1,780	2,620
Total liabilities	114,297	105,286
Commitments and contingencies (see Note 10)
EQUITY
Preferred stock, $0.001 par value; 10,000,000 shares authorized, no shares issued and outstanding at December 31, 2023 and 2022	0	0
Common stock, $0.001 par value; 250,000,000 shares authorized; 70,765,554 and 59,280,247 shares issued and outstanding at December 31, 2023 and 2022, respectively	70	59
Additional paid-in capital	1,323,576	1,031,462
Accumulated other comprehensive income/(loss)	2,194	(1,353)
Accumulated deficit	(888,556)	(596,365)
Total stockholders' equity	437,284	433,803
Noncontrolling interests	107	221
Total equity	437,391	434,024
Total liabilities and stockholders' equity	$ 551,688	$ 539,310

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	70,765,554	59,280,247
Common stock, shares outstanding (in shares)	70,765,554	59,280,247

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Expenses
Research and development	$ 189,590	$ 172,734	$ 175,601
Zentera in-process research and development	45,568	0	0
General and administrative	64,351	54,553	40,941
Total operating expenses	299,509	227,287	216,542
Loss from operations	(299,509)	(227,287)	(216,542)
Other Income (Expense)
Investment and other income, net	22,617	5,987	401
Gain on deconsolidation of Zentera	0	0	51,582
Net loss before income taxes	(276,892)	(221,300)	(164,559)
Income tax benefit	(601)	(469)	(297)
Loss on equity method investment	16,014	16,282	1,831
Net loss	(292,305)	(237,113)	(166,093)
Net loss attributable to noncontrolling interests	(114)	(307)	(7,368)
Net loss attributable to Zentalis	$ (292,191)	$ (236,806)	$ (158,725)
Net loss per common share outstanding, basic (in dollars per share)	$ (4.47)	$ (4.48)	$ (3.72)
Net loss per common share outstanding, diluted (in dollars per share)	$ (4.47)	$ (4.48)	$ (3.72)
Common shares used in computing net loss per share, basic (in shares)	65,409	52,857	42,688
Common shares used in computing net loss per share, diluted (in shares)	65,409	52,857	42,688

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net loss	$ (292,305)	$ (237,113)	$ (166,093)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities, net	3,547	(1,228)	(161)
Total comprehensive loss	(288,758)	(238,341)	(166,254)
Comprehensive loss attributable to noncontrolling interests	(114)	(307)	(7,368)
Comprehensive loss attributable to Zentalis	$ (288,644)	$ (238,034)	$ (158,886)

Consolidated Statements Stockho

Consolidated Statements Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit	Noncontrolling Interests
Beginning balance (in shares) at Dec. 31, 2020		41,040,000
Beginning balance at Dec. 31, 2020	$ 333,377	$ 41	$ 509,339	$ 36	$ (200,834)	$ 24,795
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	35,737		35,737
Issuance of common stock in connection with an equity offering, net of underwriting discounts, commissions and offering costs (in shares)		3,691,000
Issuance of common stock in connection with an equity offering, net of underwriting discounts, commissions and offering costs	171,973	$ 4	171,969
Issuance and withholding of common stock in connection with restricted stock unit vesting, net (in shares)		517,000
Issuance and withholding of common stock in connection with restricted stock unit vesting, net	(1,146)		(1,146)
Deconsolidation event	(16,899)					(16,899)
Issuance of common stock upon exercise of options (in shares)		232,000
Issuance of common stock upon exercise of options	7,149		7,149
Issuance of common stock under employee stock purchase plan (in shares)		15,000
Issuance of common stock under employee stock purchase plan	545		545
Cancellation of restricted stock awards (in shares)		(4,000)
Other comprehensive income (loss)	(161)			(161)
Net loss attributable to noncontrolling interest	(7,368)					(7,368)
Net loss attributable to Zentalis	(158,725)				(158,725)
Ending balance (in shares) at Dec. 31, 2021		45,491,000
Ending balance at Dec. 31, 2021	364,482	$ 45	723,593	(125)	(359,559)	528
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	46,840		46,840
Issuance of common stock in connection with an equity offering, net of underwriting discounts, commissions and offering costs (in shares)		13,495,000
Issuance of common stock in connection with an equity offering, net of underwriting discounts, commissions and offering costs	257,922	$ 13	257,909
Issuance and withholding of common stock in connection with restricted stock unit vesting, net (in shares)		159,000
Issuance and withholding of common stock in connection with restricted stock unit vesting, net	1	$ 1
Issuance of common stock upon exercise of options (in shares)		122,000
Issuance of common stock upon exercise of options	2,246		2,246
Issuance of common stock under employee stock purchase plan (in shares)		30,000
Issuance of common stock under employee stock purchase plan	874		874
Cancellation of restricted stock awards (in shares)		(17,000)
Other comprehensive income (loss)	(1,228)			(1,228)
Net loss attributable to noncontrolling interest	(307)					(307)
Net loss attributable to Zentalis	(236,806)				(236,806)
Ending balance (in shares) at Dec. 31, 2022		59,280,000
Ending balance at Dec. 31, 2022	434,024	$ 59	1,031,462	(1,353)	(596,365)	221
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	54,822		54,822
Issuance of common stock in connection with an equity offering, net of underwriting discounts, commissions and offering costs (in shares)		11,033,000
Issuance of common stock in connection with an equity offering, net of underwriting discounts, commissions and offering costs	$ 235,680	$ 11	235,669
Issuance and withholding of common stock in connection with restricted stock unit vesting, net (in shares)		360,555
Issuance of common stock upon exercise of options (in shares)	54,324	54,000
Issuance of common stock upon exercise of options	$ 995		995
Issuance of common stock under employee stock purchase plan (in shares)		42,000
Issuance of common stock under employee stock purchase plan	628		628
Cancellation of restricted stock awards (in shares)		(3,000)
Other comprehensive income (loss)	3,547			3,547
Net loss attributable to noncontrolling interest	(114)					(114)
Net loss attributable to Zentalis	(292,191)				(292,191)
Ending balance (in shares) at Dec. 31, 2023		70,767,000
Ending balance at Dec. 31, 2023	$ 437,391	$ 70	$ 1,323,576	$ 2,194	$ (888,556)	$ 107

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities:
Net loss	$ (292,305)	$ (237,113)	$ (166,093)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,389	1,426	544
Operating lease right-of-use asset and fixed asset impairment	4,953	0	0
IPR&D impairment	0	0	8,800
Recognized tax gain on IPR&D impairment	0	0	(2,462)
Gain on deconsolidation of Zentera, net of tax	0	0	(49,930)
Noncash consideration portion of Zentera in-process research and development	15,045	0	0
Share-based compensation	54,822	46,840	35,737
Loss on disposal of equipment	406	56	15
(Accretion of discounts)/amortization of premiums on marketable securities, net	(13,157)	(3,725)	908
Loss on equity method investment	16,014	16,282	1,831
Deferred income taxes	(853)	(769)	(48)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(5,678)	(6,605)	1,294
Accounts payable and accrued liabilities	10,919	15,527	13,964
Operating lease right-of-use assets and liabilities, net	623	4,330	1,347
Net cash used in operating activities	(207,822)	(163,751)	(154,093)
Investing activities:
Purchases of marketable securities	(549,182)	(533,161)	(363,508)
Proceeds from maturities of marketable securities	505,307	421,529	365,820
Deconsolidation of Zentera cash	0	0	(14,320)
Purchases of property and equipment	(583)	(2,548)	(6,107)
Net cash used in investing activities	(44,458)	(114,180)	(18,115)
Financing activities:
Proceeds from issuance of common stock under equity incentive plans	1,623	3,121	7,694
Net-settlement of restricted stock unit vesting	0	0	(1,146)
Proceeds from issuance of common stock, net	235,680	257,922	171,973
Net cash provided by financing activities	237,303	261,043	178,521
Net (decrease) increase in cash, cash equivalents and restricted cash	(14,977)	(16,888)	6,313
Cash, cash equivalents and restricted cash at beginning of year	45,696	62,584	56,271
Cash, cash equivalents and restricted cash at end of year	30,719	45,696	62,584
Supplemental disclosure of cash flow information:
Income taxes paid	140	12	20
Supplemental disclosure of non-cash investing and financing activities:
Right-of-use assets obtained in exchange for operating lease liabilities	602	0	44,613
Accrued capital expenditures	0	0	(1,510)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents
Cash and cash equivalents	28,038	43,069	59,714
Restricted cash, current	0	0	243
Restricted cash, non-current	2,681	2,627	2,627
Total cash, cash equivalents and restricted cash reported in the Consolidated Statement of Cash Flows	$ 30,719	$ 45,696	$ 62,584

Organization and Business

Organization and Business	12 Months Ended
	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Business	Organization and Business Organization Zentalis Pharmaceuticals, Inc. (“Zentalis,” “We” or the “Company”) is a clinical-stage biopharmaceutical company discovering and developing small molecule therapeutics targeting fundamental biological pathways of cancers. The Company’s lead product candidate, azenosertib (ZN-c3), is a potentially first-in-class and best-in-class WEE1 inhibitor for advanced solid tumors and hematologic malignancies. The Company is also developing a BCL-2 inhibitor, ZN-d5, in combination with azenosertib. The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. All of the Company’s tangible assets are held in the United States.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”) and include our wholly-owned subsidiaries and a variable interest entity (“VIE”) for the periods in which we determined we were the primary beneficiary. All intercompany transactions and balances have been eliminated in consolidation. We evaluate our ownership, contractual and other interests in entities that are not wholly-owned to determine if these entities are VIEs, and, if so, whether we are the primary beneficiary of the VIE. In determining whether we are the primary beneficiary of a VIE and therefore required to consolidate the VIE, we apply a qualitative approach that determines whether we have both (1) the power to direct the activities of the VIE that most significantly impact the VIE’s economic performance and (2) the obligation to absorb losses of, or the rights to receive benefits from, the VIE that could potentially be significant to that VIE. We will continuously assess whether we are the primary beneficiary of a VIE, as changes to existing relationships or future transactions may result in the consolidation or deconsolidation of such VIE. During the periods presented, we have not provided any other material financial or other support to our VIE that we were not contractually required to provide. Noncontrolling Interests Noncontrolling interests represent interests held by third parties in our consolidated subsidiaries. We reflect noncontrolling interest attributable to the other owners in a separate line in our consolidated statements of operations and a separate line within stockholders' equity in our consolidated balance sheets. Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in our consolidated financial statements and accompanying notes. On an ongoing basis, we evaluate our estimates and judgments, which are based on historical and anticipated results and trends and on various other assumptions that management believes to be reasonable under the circumstances. By their nature, estimates are subject to an inherent degree of uncertainty and, as such, actual results may differ from management’s estimates. Cash and Cash Equivalents Cash equivalents are comprised of short-term, highly-liquid investments with maturities of 90 days or less at the date of purchase. As of December 31, 2023 and 2022, our cash equivalents consisted of money market funds and corporate debt securities. Marketable Securities Marketable securities are investments with original maturities of more than ninety days from the date of purchase that we have the ability to liquidate to fund current operations. Accordingly, those investments with contractual maturities greater than one year from the date of purchase are classified as short-term investments on the accompanying consolidated balance sheets. Marketable securities are considered available-for-sale and are carried at fair value with unrealized gains and losses recorded in other comprehensive income (loss) and included as a separate component of stockholders' equity. The cost of marketable securities is adjusted for amortization of premiums or accretion of discounts to maturity, and such amortization or accretion is included in investment and other income, net through an allowance account. We use the specific identification method for calculating realized gains and losses on marketable securities sold. Realized gains and losses on marketable securities, if any, are included in investment and other income, net in the consolidated statements of operations. Restricted Cash Under the terms of our office leases, we are required to maintain a letter of credit as a security deposit during the term of such leases. At December 31, 2023 and 2022, restricted cash of $2.7 million and $2.6 million, respectively, was pledged as collateral for the letters of credit. Fair Value of Financial Instruments The authoritative guidance defines fair value and requires us to establish a framework for measuring fair value and disclosure about fair value measurements using a three-tier approach. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. Our financial instruments include cash equivalents, marketable securities, prepaid expenses and other assets, accounts payable and accrued expenses. Fair value estimates of these instruments are made at a specific point in time, based on relevant market information. These estimates may be subjective in nature and involve uncertainties and matters of significant judgement and therefore cannot be determined with precision. The fair value of marketable securities is determined using proprietary valuation models and analytical tools, which utilize market pricing or prices for similar instruments that are both objective and publicly available, such as matrix pricing or reported trades, benchmark yields, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities and bids and offers. The carrying amount of cash equivalents, prepaid expenses and other assets, accounts payable and accrued expenses are generally considered to be representative of their respective values because of the short-term nature of those instruments. Concentrations of Credit Risk and Sources of Supply We are subject to credit risk from our portfolios of cash equivalents and marketable securities. We maintain our cash and cash equivalent and marketable securities balances with major commercial banks. Deposits held with the financial institutions exceed the amount of insurance provided on such deposits. We are exposed to credit risk in the event of a default by the financial institutions holding our cash and cash equivalents and marketable securities to the extent recorded on the consolidated balance sheets. We have also established guidelines to limit our exposure to credit risk by diversifying our marketable securities portfolio and placing them in investments with maturities that maintain safety and liquidity. We rely on third-party manufacturers for the supply of active pharmaceutical ingredients. Property and Equipment, Net Property and equipment are recorded at cost, less accumulated depreciation and amortization. Equipment is depreciated using the straight-line method over its estimated useful life ranging from three Leases We have entered into operating leases for real estate. We determine if an arrangement is a lease at inception and evaluate each lease agreement to determine whether the lease is an operating or finance lease. For leases where we are the lessee, right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent an obligation to make lease payments arising from the lease. Liabilities from operating leases are included in accrued expenses Impairment of Long-Lived Assets We account for long-lived assets in accordance with authoritative guidance for impairment or disposal of long-lived assets. Long-lived assets are reviewed for events or changes in circumstances, which indicate that their carrying value may not be recoverable. Goodwill Our goodwill, which has an indefinite useful life, represents the excess of the cost over the fair value of net assets acquired from its business combination. The determination of the value of goodwill and intangible assets arising from business combinations and asset acquisitions requires extensive use of accounting estimates and judgments to allocate the purchase price to the fair value of the net tangible and intangible assets acquired, including capitalized in-process research and development (“IPR&D”). Goodwill is reviewed for impairment at least annually, or more frequently if an event occurs indicating the potential for impairment. During the impairment review process, we consider qualitative factors to determine whether it is more likely than not that the fair value of the reporting unit is less than the carrying amount, including goodwill. If we determine that it is not more likely than not that the fair value of our reporting unit is less than the carrying amount, then no additional assessment is deemed necessary. Otherwise, we proceed to compare the estimated fair values of the reporting units with the carrying values, including goodwill. If the carrying amounts of the reporting units exceed the fair values, we record an impairment loss based on the difference. We completed our most recent annual evaluation for impairment for goodwill as of December 31, 2023 using the qualitative assessment and determined that no impairment existed, and no charges were recorded. Equity Method Accounting We held significant influence, but not a controlling interest, in our former affiliate Zentera. From the deconsolidation of Zentera during July 2021 until the termination of our collaboration Zentera during the six-months ended June 30, 2023, this investment was accounted for using the equity method. Our share of earnings or losses of the investment entity were reported on the consolidated statement of operations, with a corresponding increase or decrease to the equity investment carried on the statement of financial position. This information was generally not received sufficiently timely for us to record our portion of earnings or loss in the current financial statements, and therefore we reported our portion of earnings or loss on a one quarter lag. The maximum exposure to loss as a result of our investment in Zentera was directly associated with the carrying amount of the equity method investment on our consolidated balance sheet, which is zero as of December 31, 2023. Research and Development Expenses Research and development expenses include salaries and benefits, facilities and other overhead expenses, external clinical trial expenses, research-related manufacturing services, contract services and other outside expenses. Research and development expenses are charged to operating expenses as incurred when these expenditures relate to our research and development efforts and have no alternative future uses. Reimbursed research and development costs under government grant arrangements are recorded as a reduction to research and development expenses and are recognized in the period in which the related costs are incurred. We are 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 we do not expect the goods to be delivered or services to be performed. Clinical Trial Expenses We make payments in connection with our clinical trials under contracts with CROs that support conducting and managing clinical trials. The financial terms of these agreements are subject to negotiation and vary from contract to contract and may result in uneven payment flows. 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. A portion of our obligation to make payments under these contracts depends on factors such as the successful enrollment or treatment of patients or the completion of other clinical trial milestones. Expenses related to clinical trials are accrued based on our estimates and/or representations from service providers regarding work performed, including actual level of patient enrollment, completion of patient studies and progress of the clinical trials. Other incidental costs related to patient enrollment or treatment are accrued when reasonably certain. If the amounts we are obligated to pay under our clinical trial agreements are modified (for instance, as a result of changes in the clinical trial protocol or scope of work to be performed), we adjust our accruals accordingly. Revisions to our contractual payment obligations are charged to expense in the period in which the facts that give rise to the revision become reasonably certain. Share-Based Compensation We record share-based compensation expense associated with equity instruments in accordance with the authoritative guidance for stock-based compensation. The cost of employee services received in exchange for an award of an equity instrument is measured at the grant date based on the estimated fair value of the award and is recognized as expense on a straight-line basis over the requisite service period of the award. Share-based compensation expense for an award with a performance condition is recognized when the achievement of such performance condition is determined to be probable. If the outcome of such performance condition is not determined to be probable or is not met, no compensation expense is recognized, and any previously recognized compensation expense is reversed. Forfeitures are recognized as a reduction of share-based compensation expense as they occur. Income Taxes Deferred income taxes are recognized for the tax consequences in future years of differences between the tax basis of assets and liabilities and their financial reporting amounts at each year end based on enacted tax laws and statutory tax rates applicable to the periods in which the differences are expected to affect taxable income. A provision has been made for income taxes due on taxable income and for the deferred taxes on temporary differences. Deferred tax assets and liabilities are adjusted for the effects of changes in tax laws and rates on the date of enactment. Realization of the deferred income tax asset is dependent on gathering sufficient taxable income in future years. Valuation allowances are established when necessary to reduce deferred tax assets to the amount expected to be realized. Income tax expense is the combination of the tax payable for the period and the change during the period in deferred tax assets and liabilities. We follow the accounting guidance on accounting for uncertainty in income taxes. The guidance prescribes a recognition threshold and measurement attribute criteria for the financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. For those benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by taxing authorities based on the technical merits of the position. Accumulated Other Comprehensive Income Accumulated other comprehensive income is the result of unrealized gains and losses on marketable securities. Net Loss per Common Share Outstanding Basic net loss per common share outstanding is computed by dividing net loss, after adjusting for dividends, if declared, by the weighted-average number of common shares outstanding during the period. Diluted net loss per common share outstanding is computed using the weighted-average number of common shares outstanding during the period and, if dilutive, the weighted average number of potential common shares. Potential common shares consist of unvested restricted stock awards, unvested restricted stock units and common shares issuable upon the exercise of stock options. Acquisitions and Contingent Consideration The Company evaluates acquisitions of assets and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen test to determine if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If the screen is met, the transaction is accounted for as an asset acquisition. If the screen is not met, further determination is required as to whether or not the Company has acquired inputs and processes that have the ability to create outputs, which would meet the requirements of a business. If determined to be a business combination, the Company accounts for the transaction under the acquisition method of accounting as indicated in Accounting Standards Update (ASU) 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business, which requires the acquiring entity in a business combination to recognize the fair value of all assets acquired, liabilities assumed, and any non-controlling interest in the acquired entity and establishes the acquisition date as the fair value measurement point. Accordingly, the Company recognizes assets acquired and liabilities assumed in business combinations, including contingent assets and liabilities, and non-controlling interest in the acquired entity based on the fair value estimates as of the date of acquisition. In accordance with Accounting Standards Codification (ASC) 805, Business Combinations, the Company recognizes and measures goodwill as of the acquisition date, as the excess of the fair value of the consideration paid over the fair value of the identified net assets acquired. The consideration for the Company’s business acquisitions may include future payments that are contingent upon the occurrence of a particular event or events. The obligations for such contingent consideration payments are recorded at fair value on the acquisition date. The contingent consideration obligations are then evaluated each reporting period. Changes in the fair value of contingent consideration, other than changes due to payments, are recognized as a gain or loss and recorded within change in the fair value of deferred and contingent consideration liabilities in the consolidated statements of comprehensive loss. Contingent consideration liabilities expected to be settled within 12 months after the balance sheet date are presented in current liabilities. Contingent consideration liabilities expected to be settled 12 months after the balance sheet date are presented in long-term liabilities. If determined to be an asset acquisition, the Company accounts for the transaction under ASC 805-50, which requires the acquiring entity to recognize assets acquired and liabilities assumed based on the cost to the acquiring entity on a relative fair value basis, which includes transaction costs in addition to consideration given. No gain or loss is recognized as of the date of acquisition unless the fair value of non-cash assets given as consideration differs from the assets’ carrying amounts on the acquiring entity’s books. Consideration transferred that is non-cash will be measured based on either the cost (which shall be measured based on the fair value of the consideration given) or the fair value of the assets acquired and liabilities assumed, whichever is more reliably measurable. Goodwill is not recognized in an asset acquisition and any excess consideration transferred over the fair value of the net assets acquired is allocated to the identifiable assets based on relative fair values. If the in-licensed agreement for in-process research and development (“IPR&D”) does not meet the definition of a business and the assets have not reached technological feasibility and therefore have no alternative future use, the Company expenses payments made under such license agreements as acquired IPR&D expense in its consolidated statement of comprehensive loss. Contingent consideration payments in asset acquisitions are recognized when the contingency is resolved and the consideration is paid or becomes payable (unless the contingent consideration meets the definition of a derivative, in which case the amount becomes part of the basis in the asset acquired). Upon recognition of the contingent consideration payment, the amount is included in the cost of the acquired asset or group of assets.

Significant Transactions

Significant Transactions	12 Months Ended
	Dec. 31, 2023
Equity Method Investments and Joint Ventures [Abstract]
Significant Transactions	Significant Transactions Zentera Therapeutics On June 15, 2023, we announced that we and certain of our wholly owned subsidiaries had entered into an agreement to terminate our Collaboration and License Agreements (the “Termination Agreement”) with Zentera Therapeutics, a Shanghai-based clinical-stage biopharmaceutical company focused on developing cancer therapeutics (“Zentera”), pursuant to which such wholly owned subsidiaries had granted to Zentera certain development and commercialization rights to our product candidates, azenosertib, ZN-d5 and ZN-c5 (the “Zentera Collaboration Products”) in the People’s Republic of China, Macau, Hong Kong and Taiwan (collectively, “Greater China”). As a result of the termination of these agreements, we regained the rights from Zentera for azenosertib, ZN-d5 and ZN-c5 in Greater China, and now hold worldwide development and commercialization rights to these assets. Concurrent with the agreement to terminate the Collaboration and License Agreements, we executed a share purchase agreement (the “Share Purchase Agreement”) with Zentera to return our 40.3% equity stake in Zentera for de minimis consideration. We assessed the Termination Agreement and Share Purchase Agreement together and determined that the transaction to reacquire the licensed intellectual property without an acquired workforce, inputs or any substantive processes capable of contributing to the ability to produce outputs, represents asset acquisitions for accounting purposes. The total consideration transferred of $45.6 million was comprised of the following components: Fixed consideration of $30 million, representing an up-front payment. Fixed consideration of forgiveness of $9.4 million of outstanding receivables under the Collaboration and License Agreements. Fixed consideration of the return of our 40.3% equity stake in Zentera for de minimis cash consideration. Using the adjusted balance sheet method under the cost approach, the difference between the carrying value of the equity method investment at the time of the transaction and the fair value of the equity method investment after the return of the intellectual property was $13.7 million, which was recognized as a loss on the equity method investment line item in the statement of operations during the second quarter of 2023. Variable consideration of a change in control milestone payment as contingent consideration can be either zero or $15.0 million. The value of the contingent consideration of approximately $0.5 million was calculated using estimates of future discounted cash flows, and other significant estimates including estimates for probability of milestone achievement and discount rates. The value of the contingent consideration for this milestone will be remeasured at fair value at each reporting period with gains and losses reported in the statement of operations, as applicable. We also incurred $0.5 million of acquisition-related costs that were included in the total consideration for the acquired assets. Additional consideration to be paid to Zentera includes a low single digit royalty on net sales of azenosertib, ZN-d5 and ZN-c5 in the Greater China region. These additional payments are payable only after regulatory approval and commercials sales in the Greater China region and are excluded from the transaction price.

Business Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2023
Business Combination and Asset Acquisition [Abstract]
Business Combinations	Business Combinations Kalyra Pharmaceuticals, Inc. On December 21, 2017, we acquired $4.5 million of Kalyra Pharmaceuticals, Inc.’s ("Kalyra") Series B Preferred Stock representing a 25% equity interest in Kalyra for purposes of entering the analgesics therapeutic research space. The acquisition price was paid entirely in cash. In accordance with the authoritative guidance, we concluded that Kalyra is a business consisting of inputs, employees, intellectual property and processes capable of producing outputs. Additionally, we have concluded that Kalyra is a VIE, we are the primary beneficiary and have the power to direct the activities that most significantly affect Kalyra’s economic performance through common management and our board representation. Prior to December 21, 2017, the Company and Kalyra transacted for the delivery of research and development services and support. The financial position and results of operations of Kalyra have been included in our consolidated financial statements from the date of the initial investment. Pursuant with authoritative guidance, we have recorded the identifiable assets, liabilities and noncontrolling interests in the VIE at their fair value upon initial consolidation. The identified goodwill is comprised of the workforce and expected synergies from combining the entities. Total assets and liabilities of Kalyra as of December 31, 2023 and 2022 are immaterial. The liabilities recognized as a result of consolidating Kalyra do not represent additional claims on our general assets. Pursuant to the authoritative guidance, the equity interest in Kalyra not owned by Zentalis is reported as a noncontrolling interest on our consolidated balance sheets. The following is a reconciliation of equity (net assets) attributable to the noncontrolling interest (in thousands): December 31, 2023 2022 Noncontrolling interest at beginning of period $ 221 $ 528 Net loss attributable to noncontrolling interest (114) (307) Noncontrolling interest at end of period $ 107 $ 221

Fair Value Measurement

Fair Value Measurement	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair Value Measurement	Fair Value Measurement Available-for-sale marketable securities consisted of the following (in thousands): December 31, 2023 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Commercial paper $ 75,227 $ 60 $ (15) $ 75,272 Corporate debt securities 229,896 2,036 — 231,932 US government agencies 83,025 100 (78) 83,047 US Treasury securities 64,538 103 (11) 64,630 $ 452,686 $ 2,299 $ (104) $ 454,881 December 31, 2022 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Commercial paper $ 296,309 $ 71 $ (587) $ 295,793 Corporate debt securities 7,472 — (26) 7,446 US government agencies 23,970 — (182) 23,788 US Treasury securities 67,904 — (629) 67,275 $ 395,655 $ 71 $ (1,424) $ 394,302 As of December 31, 2023, twenty of our available-for-sale debt securities with a fair market value of $113.4 million were in a gross unrealized loss position of $0.1 million. When evaluating an investment for impairment, we review factors such as the severity of the impairment, changes in underlying credit ratings, forecasted recovery, our intent to sell or the likelihood that we would be required to sell the investment before its anticipated recovery in market value and the probability that the scheduled cash payments will continue to be made. Based on our review of these marketable securities, we believe none of the unrealized loss is as a result of a credit loss as of December 31, 2023, because we do not intend to sell these securities, and it is not more-likely-than-not that we will be required to sell these securities before the recovery of their amortized cost basis. Contractual maturities of available-for-sale debt securities are as follows (in thousands): December 31, 2023 December 31, 2022 Estimated Fair Value Due within one year $ 267,336 $ 394,302 After one but within five years 187,545 — $ 454,881 $ 394,302 Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Fair value should maximize the use of observable inputs and minimize the use of unobservable inputs. The Company determines the fair value of financial assets and liabilities using three levels of inputs as follows: Level 1—Inputs which include quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2—Inputs (other than quoted market prices included in Level 1) that are either directly or indirectly observable, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the instrument’s anticipated life. Level 3—Unobservable inputs for assets or liabilities and include little or no market activity. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The Company had $0.5 million in contingent consideration liabilities as of December 31, 2023 related to the agreement to terminate its Collaboration and License Agreements with Zentera. The contingent consideration balance is limited to one potential milestone payment measured at fair value (See Note 3 - Significant Transactions for additional information). The fair value of the contingent consideration is estimated based on the monetary value of the milestone discounted for the probability of achieving the milestone and a present value factor based on the timing of when the milestone is expected to be achieved. The value for the contingent consideration balance is based on significant inputs not observable in the market which represents Level 3 measurement within the fair value hierarchy. This liability did not exist as of December 31, 2022. The following table summarizes, by major security type, our cash equivalents and available-for-sale marketable securities that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy (in thousands): December 31, 2023 Level 1 Level 2 Level 3 Total estimated fair value Cash equivalents: Money market funds $ 4,755 $ — $ — $ 4,755 Total cash equivalents: 4,755 — — 4,755 Available-for-sale marketable securities: Commercial paper — 75,272 — 75,272 Corporate debt securities — 231,932 — 231,932 US government agencies — 83,047 — 83,047 US Treasury securities — 64,630 — 64,630 Total available-for-sale marketable securities: — 454,881 — 454,881 Total assets measured at fair value $ 4,755 $ 454,881 $ — $ 459,636 Financial liabilities: Contingent consideration — — 500 500 Total financial liabilities $ — $ — $ 500 $ 500 December 31, 2022 Level 1 Level 2 Level 3 Total estimated fair value Cash equivalents: Money market funds $ 26,811 $ — $ — $ 26,811 Commercial paper 1,998 — — 1,998 Total cash equivalents: 28,809 — — 28,809 Available-for-sale marketable securities: Commercial paper — 295,793 — 295,793 Corporate debt securities — 7,446 — 7,446 US government agencies — 23,788 — 23,788 US Treasury securities 67,275 — — 67,275 Total available-for-sale marketable securities: 67,275 327,027 — 394,302 Total assets measured at fair value $ 96,084 $ 327,027 $ — $ 423,111 Financial liabilities: Contingent consideration — — — — Total financial liabilities $ — $ — $ — $ — The following significant unobservable inputs were used in the valuation of the contingent consideration payable to Zentera pursuant to the Termination Agreement at December 31, 2023: Contingent Consideration Liability Fair Value as of December 31, 2023 Valuation Technique Unobservable Input Range (in thousands) Milestone payment $ 500 Discounted cash flow Likelihood of occurrence 1.0%- 2.4% Discount rate 40% Expected term Perpetuity The following table reflects the activity for the Company’s contingent consideration, measured at fair value using Level 3 inputs (in thousands): Contingent consideration at December 31, 2022 $ — Issuance of contingent consideration to Zentera 500 Changes in the fair value of contingent consideration — Contingent consideration at December 31, 2023 $ 500 There were no transfers between Level 1 and Level 2 of the fair value hierarchy during the year ended December 31, 2023. We had 1 instrument that was classified within Level 3 as of December 31, 2023. No instruments were classified as Level 3 as of December 31, 2022. As of December 31, 2023 and December 31, 2022, no material fair value adjustments were required for non-financial assets and liabilities.

Prepaid Expenses and Other Asse

Prepaid Expenses and Other Assets	12 Months Ended
	Dec. 31, 2023
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Assets	Prepaid Expenses and Other Assets Prepaid expenses and other assets consisted of the following (in thousands): December 31, 2023 2022 Prepaid insurance $ 747 $ 1,018 Prepaid software licenses and maintenance 691 958 Foreign R&D credit refund 500 659 Prepaid research and development expenses 13,640 15,002 Interest receivable 3,337 508 Sublease assets 1,471 — Zentera receivable — 5,874 Other prepaid expenses 231 266 Total prepaid expenses and other current assets 20,617 24,285 Less long-term portion 6,818 9,723 Total prepaid expenses and other assets, current $ 13,799 $ 14,562

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Property and Equipment, net	Property and Equipment, net Property and equipment, net consisted of the following (in thousands): December 31, 2023 2022 Lab equipment $ 3,069 $ 2,622 Leasehold improvements 4,235 4,891 Office equipment and furniture 1,340 2,065 Computer equipment 150 150 Construction in process 173 37 Subtotal 8,967 9,765 Accumulated depreciation and amortization (3,148) (2,060) Property and equipment, net $ 5,819 $ 7,705 Depreciation and amortization expense was approximately $1.4 million, $1.4 million and $0.5 million for the years ended December 31, 2023, 2022 and 2021 respectively.

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses consist of the following (in thousands): December 31, 2023 2022 Accrued research and development expenses $ 36,261 $ 32,310 Accrued employee expenses 14,477 11,246 Accrued general and administrative expenses 1,032 662 Lease liability 2,623 2,162 Contingent consideration 500 — Income taxes payable 281 384 Accrued legal expenses 1,047 1,256 Total accrued expenses 56,221 48,020 Less long-term portion 1,780 2,620 Total accrued expenses, current $ 54,441 $ 45,400

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity Follow-on Offerings of Common Stock On June 15, 2023, we completed a follow-on offering in which we issued and sold 11,032,656 shares of common stock at a public offering price of $22.66 per share. The total gross proceeds for the offering were approximately $250.0 million, before deducting offering expenses of $14.3 million payable by us. On May 18, 2022, we completed a follow-on offering in which we issued and sold 10,330,000 shares of common stock at a public offering price of $19.38 per share. The total gross proceeds for the offering were approximately $200.2 million, before deducting offering expenses of $11.4 million payable by us. Direct Offering of Common Stock On April 29, 2022, pursuant to our Registration Statement on Form S-3 (Registration No. 333-255769), filed with the SEC on May 4, 2021, we completed a direct offering of common stock to Pfizer Inc. (“Pfizer”). We issued and sold 953,834 shares of our common stock at an offering price of $26.21 per share. The total gross proceeds for the offering were approximately $25.0 million, before deducting offering expenses of $0.3 million payable by us. The parties have entered into an agreement to collaborate to advance the clinical development of azenosertib (ZN-c3), a selective WEE1 inhibitor designed to induce synthetic lethality in cancer cells. We did not grant Pfizer any economic ownership or control of azenosertib or the rest of our pipeline. The gross offering proceeds received from Pfizer exceeded the fair value of our common stock on the date of the investment. As of December 31, 2023, $2.5 million has been recorded as accrued research and development expense on the consolidated balance sheet and will be recognized as a reduction of research and development expense over the term of the collaboration agreement. ATM Program In May 2021, the Company entered into a sales agreement (the “Sales Agreement”), with Leerink Partners LLC, as sales agent, pursuant to which the Company may, from time to time, issue and sell common stock with an aggregate value of up to $200.0 million in “at-the-market” offerings (the “ATM”), under the Company's Registration Statement on Form S-3 (File No. 333-255769). Sales of common stock, if any, pursuant to the Sales Agreement, may be made in sales deemed to be an “at the market offering” as defined in Rule 415(a) of the Securities Act, including sales made directly through The Nasdaq Global Market or any other existing trading market for the Company's common stock. During the quarter ended December 31, 2023, we did not sell any shares of common stock under the Sales Agreement. As of December 31, 2023 there was $140.3 million of common stock remaining available for sale under the Sales Agreement. Share-based Compensation Effective April 2020, the Company’s Board of Directors adopted, and the Company’s stockholders approved the 2020 Incentive Award Plan (the "2020 Plan"), which allows for grants to selected employees, consultants and non-employee members of the Board of Directors. We currently grant stock options and restricted stock units (“RSUs”), under the 2020 Plan. Awards may be made under the 2020 Plan covering up to the sum of (1) 5,600,000 shares of common stock; plus (2) any shares forfeited from the unvested restricted shares of our common stock issued upon conversion of unvested Class B common units (up to 1,250,000 shares); plus (3) an annual increase on the first day of each fiscal year beginning with the fiscal year ending December 31, 2021 and continuing to, and including, the fiscal year ending December 31, 2030, equal to the lesser of (a) 5% of the shares of common stock outstanding on the final day of the immediately preceding calendar year and (b) such smaller number of shares as determined by our Board of Directors. In July 2022, the Company’s Board of Directors approved the Zentalis Pharmaceuticals, Inc. 2022 Employment Inducement Incentive Award Plan (the “2022 Inducement Plan”), which is used exclusively for the grant of equity awards to new employees as an inducement material to the employees’ entering into employment with the Company. As of December 31, 2023, the Board of Directors reserved 2,275,000 shares of the Company’s common stock for issuance pursuant to awards granted under the 2022 Inducement Plan. As of December 31, 2023, 9,240,394 shares were subject to outstanding awards under the 2020 Plan and 1,836,357 shares were available for future grants of share-based awards under the 2020 Plan. As of December 31, 2023, 1,995,856 shares were subject to outstanding awards under the 2022 Inducement Plan and 254,144 shares were available for future grants of share-based awards under the 2022 Inducement Plan. During 2023, we issued an aggregate of 54,324 shares of common stock in connection with the exercises of stock options for cash in the aggregate amount of approximately $1.0 million. We did not issue any shares of common stock in connection with grants of restricted stock awards ("RSA's"). We issued 360,555 shares of common stock, upon vesting of RSU's. Total share-based compensation expense related to share-based awards was comprised of the following (in thousands): Year ended December 31, 2023 2022 2021 Research and development expense $ 24,519 $ 20,439 $ 14,879 General and administrative expense 30,303 26,401 20,858 Total share-based compensation expense $ 54,822 $ 46,840 $ 35,737 Share-based compensation expense by type of share-based award (in thousands): Year ended December 31, 2023 2022 2021 Stock options $ 41,642 $ 36,338 $ 20,773 RSAs and RSUs 12,816 10,075 14,643 Employee Stock Purchase Plan 364 427 321 $ 54,822 $ 46,840 $ 35,737 Prior to the deconsolidation of Zentera during the third quarter of 2021, total share-based compensation expense includes $138 thousand of share-based compensation expense for employees, consultants and directors of Zentera, for the year ended December 31, 2021. Total unrecognized estimated compensation cost by type of award and the weighted average requisite service period over which such expense is expected to be recognized (in thousands, unless otherwise noted): December 31, 2023 Unrecognized Remaining Stock options $ 92,129 2.7 RSAs $ 1 0.0 RSUs $ 20,699 2.5 Stock Options: The following table summarizes option activity for the year ended December 31, 2023. The amounts include stock options granted to both employees and non-employees: Number of Shares Weighted Average Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2022 8,051,459 $ 29.97 Granted 3,772,345 $ 22.17 Exercised (54,324) $ 18.31 Cancelled (1,752,045) $ 32.82 Outstanding at December 31, 2023 10,017,435 $ 26.59 7.8 $160 Vested and expected to vest at December 31, 2023 10,017,435 $ 26.59 7.8 $160 Exercisable at December 31, 2023 4,086,661 $ 27.91 6.6 $— The weighted average grant date fair value of stock options granted during the years ended December 31, 2023, 2022 and 2021 was $15.48 per share, $20.45 per share and $33.27 respectively. The total intrinsic value of options exercised during the years ended December 31, 2023, 2022 and 2021 was approximately $0.3 million, $2.0 million and $8.8 million, respectively. The exercise price of stock options granted is equal to the closing price of the Company's common stock on the date of grant. The fair value of each option award is estimated on the date of grant using the Black-Scholes model. Due to the Company’s limited operating history and a lack of company specific historical and implied volatility data, the Company estimates expected volatility based on the historical volatility of a group of similar companies that are publicly traded. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. The Company uses the “simplified method” for estimating the expected term of employee options, whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option (generally 10 years). The risk-free interest rate is based on the U.S. Treasury yield for a period consistent with the expected term of the option in effect at the time of the grant. The Company has not issued any dividends and does not expect to issue dividends over the life of the options. As a result, the Company has estimated the dividend yield to be zero. The fair value of the stock options granted during the year ended December 31, 2023 was determined with the following assumptions: Year ended December 31, 2023 2022 2021 Expected volatility 73.5% - 80.8% 73.6% - 80.5% 73.2% - 76.6% Average expected term (in years) 5.5 - 6.1 6.0 - 6.5 5.2 - 6.1 Risk-free interest rate 3.4% - 4.7% 1.5% - 4.2% 0.5% - 1.3% Expected dividend yield —% —% —% Restricted Stock Awards: RSAs are shares of our common stock subject to forfeiture restrictions that lapse based on the awardee's continued employment or service. The shares covered by a RSA cannot be sold, pledged or otherwise disposed of until the awards vest, and any unvested shares will be forfeited following the awardee's termination of service. The following table summarizes RSA activity for the year ending December 31, 2023. The amounts include RSAs granted to both employees and non-employees: Number of Shares Weighted Average Grant Date Outstanding at December 31, 2022 125,506 $ 5.45 Vested (120,102) $ 5.53 Forfeited (4,455) $ 3.30 Outstanding at December 31, 2023 949 $ 4.61 The fair value of RSAs issued upon conversion of the unvested profit interest award units was based on a Black-Scholes pricing model. The estimated fair value of the RSAs for any future grants will be based on the closing market value of our common stock on the date of grant. The total grant date fair value of RSAs vested during the years ended December 31, 2023, 2022 and 2021 was approximately $0.7 million, $1.0 million and $1.7 million, respectively. The fair value of RSAs vested during the years ended December 31, 2023, 2022 and 2021, was approximately $2.7 million, $8.3 million and $21.0 million, respectively. Restricted Stock Units: An RSU is a promise by us to issue a share of our common stock upon vesting of the unit. The following table summarizes RSU activity for the year ending December 31, 2023. The amounts include RSUs granted to both employees and non-employees: Number of Shares Weighted Average Grant Date Outstanding at December 31, 2022 922,901 $ 27.48 Granted 968,823 $ 22.94 Vested (360,555) $ 27.02 Forfeited (312,354) $ 25.88 Outstanding at December 31, 2023 1,218,815 $ 24.56 The estimated fair value of the RSUs was based on the closing market value of our common stock on the date of grant. The total grant date fair value of RSUs vested during the years ended December 31, 2023, 2022 and 2021 was approximately $9.7 million $4.6 million and $12.7 million, respectively. The fair value of RSUs vested during the years ended December 31, 2023, 2022 and 2021 was approximately $7.7 million, $7.3 million and $26.4 million, respectively. Employee Stock Purchase Plan Effective April 2020, the Company’s Board of Directors adopted, and the Company’s stockholders approved the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), which was subsequently amended and restated effective March 15, 2021 to provide for a share reserve of 2,000,000 shares. As of December 31, 2023, 1,913,160 shares were available for issuance under the 2020 ESPP. The weighted average assumptions used to estimate the fair value of stock purchase rights under the 2020 ESPP are as follows: Year ended December 31, 2023 2022 2021 ESPP Volatility 85.8 % 74.0 % 48.2 % Expected term (years) 0.5 0.5 0.5 Risk free rate 4.8 % 1.6 % 0.1 % Expected dividend yield — % — % — % Under the terms of the 2020 ESPP, the Company’s employees may elect to have up to 20% of their compensation, up to a maximum of $21,250 per calendar year, withheld to purchase shares of the Company’s common stock for a purchase price equal to 85% of the lower of the fair market value per share (at closing) of the Company’s common stock on (i) the first trading day of a six-month offering period, or (ii) the applicable purchase date, defined as the last trading day of the six-month offering period.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Contingencies From time to time, we may be involved in various disputes, including lawsuits and claims arising in the ordinary course of business, including actions with respect to intellectual property, employment, and contractual matters. Any of these claims could subject us to costly legal expenses. The Company records a liability in its consolidated financial statements for these matters when a loss is known or considered probable and the amount can be reasonably estimated. The Company reviews these estimates each accounting period as additional information is known and adjusts the loss provision when appropriate. If a matter is both probable to result in a liability and the amounts of loss can be reasonably estimated, the Company estimates and discloses the possible loss or range of loss to the extent necessary to make the consolidated financial statements not misleading. If the loss is not probable or cannot be reasonably estimated, a liability is not recorded in our consolidated financial statements. While we do generally believe that we have adequate insurance to cover many different types of liabilities, our insurance carriers may deny coverage, or our policy limits may be inadequate to fully satisfy any damage awards or settlement. If this were to happen, the payment of any such awards could have a material adverse effect on our consolidated results of operations and financial position. Additionally, any such claims, whether or not successful, could damage our reputation and business. We are currently not a party to any legal proceedings that require a loss liability to be recorded. Operating Leases In September 2020, we entered into a lease for approximately 117,900 square feet of laboratory and office space in San Diego. This lease was partially terminated and amended during September 2021. This amendment reduced the rentable square feet by approximately 43,200. The lease commenced in December 2021 and continues through September 2032. The lease also included access to a temporary space of 13,200 square feet of laboratory and office space in San Diego. This lease component commenced in November 2020 and continued through January 2022. The lease is subject to approximately 3.0% annual increases throughout the lease term. We also pay for various operating costs, including utilities and real property taxes. The agreement includes two options to extend the lease for a period of five years each. When we determined our lease term for our operating lease right-of-use assets and lease liabilities for these leases, we did not include the extension options for this lease. In March 2021, we entered into a lease for approximately 31,362 square feet of office space at 1359 Broadway, Suites 1710 and 1800 in New York, New York. The lease commenced in December 2021 and continues through November 2032. The lease is subject to one increase in per annum rent of approximately 8.1% commencing on the sixth In December 2023, we entered into a lease for approximately 4,115 square feet of office space in New York, New York. The lease commenced in December 2023 and continues through August 2027. The lease is subject to approximately 2.5% annual increases through the lease term. We received lease incentives under the agreement, including free rent periods. We also pay for various operating costs, including utilities and real property taxes. The agreement does not contain any option to extend. On March 6, 2023, we entered into a sublease agreement pursuant to which we sublet the office space located at 1359 Broadway, Suites 1710 and 1800 in New York, New York to a subtenant. As a result of certain triggering events, we performed an interim impairment test by comparing the carrying value of the long-lived asset group to its estimated fair value, which was determined based on the income approach using a discounted cash flow model. Estimates and assumptions used in the model included projected cash flows and a discount rate. As a result, we recorded an impairment expense of $5.0 million within our operating expenses against our operating lease right-of-use asset and fixed assets associated with our New York lease during the year ended December 31, 2023. For the year ended December 31, 2023, we recorded lease income of $0.9 million relating to this sublease, presented as other income in the statement of operations. Rent expense recorded by the Company under the leases was approximately $6.9 million, $7.0 million and $2.7 million for the years ended December 31, 2023, 2022 and 2021 respectively. We paid approximately $6.4 million, $2.5 million and $1.3 million of lease payments, respectively, during the years ended December 31, 2023, 2022 and 2021. The following table presents the weighted average remaining lease term and weighted average discount rates related to our operating leases as of December 31, 2023: Weighted average remaining lease term (in years) 8.7 Weighted average discount rate 9.0% Approximate annual future minimum operating lease payments as of December 31, 2023 are as follows (in thousands): Year Amount 2024 $ 6,643 2025 7,002 2026 7,487 2027 7,606 2028 7,760 Thereafter 31,018 Total minimum lease payments: 67,516 Less: imputed interest 21,743 Total operating lease liabilities 45,773 Less: current portion 2,623 Lease liability, net of current portion $ 43,150

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes Zentalis Pharmaceuticals, Inc. is a corporation for tax purposes and is subject to income taxes which have been included in the consolidated financial statements. The amount of net loss before income taxes and loss on equity method investment for the years ended December 31, 2023, 2022 and 2021 is as follows (in thousands): Year ended December 31, 2023 2022 2021 U.S. net loss before income taxes $ (293,284) $ (237,926) $ (171,053) Foreign net income (loss) before income taxes 378 344 4,663 Net loss before income taxes, including loss on equity method investment $ (292,906) $ (237,582) $ (166,390) The following table presents the current and deferred income tax provision (benefit) for federal, state and foreign income taxes (in thousands): Year ended December 31, 2023 2022 2021 Current tax provision: Federal $ — $ — $ — State 41 11 11 Foreign 249 298 550 Total current tax provision 290 309 561 Deferred tax provision: Federal (891) (683) (120) State — (41) (736) Foreign — (54) (2) Total deferred tax provision (891) (778) (858) Total provision for income taxes: $ (601) $ (469) $ (297) The following table is a reconciliation of the expected tax computed at the U.S. statutory federal income tax rate to the total provision for income taxes (in thousands): Year ended December 31, 2023 2022 2021 Expected tax at 21% $ (61,509) 21.0 % $ (49,892) 21.0 % $ (34,941) 21.0 % State income tax, net of federal tax (2,384) 0.8 % (4,222) 1.8 % (931) 0.6 % Research credits (2,031) 0.7 % (12,558) 5.3 % (6,938) 4.2 % Share-based compensation 3,008 (1.0) % 1,245 (0.5) % (3,307) 2.0 % Deemed royalty 8,263 (2.8) % — — % — — % Other 586 (0.2) % (2,799) 1.2 % 939 (0.6) % Section 162(m) limitations 5,028 (1.7) % 3,950 (1.7) % 3,982 (2.4) % Effective Tax Rate Change (10,420) 3.6 % — — % — — % Change in valuation allowance 58,858 (20.1) % 63,807 (26.9) % 40,899 (24.6) % Provision for income taxes $ (601) 0.2 % $ (469) 0.2 % $ (297) 0.2 % Deferred income taxes as of each of the following periods reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of our net deferred tax asset or liability are as follows (in thousands): December 31, 2023 2022 Deferred tax assets Net operating loss $ 96,676 $ 95,392 Compensation 2,451 1,937 Share-based compensation 11,486 7,735 ASC 842 lease liability 11,131 9,967 Intangibles 11,185 1,745 Capitalized research and experimental expenditures 66,500 30,776 Accrued liabilities 1,163 476 Research credits 29,055 27,024 Other 22 62 Total gross deferred tax assets 229,669 175,114 Valuation allowance (219,292) (160,967) Net deferred tax assets 10,377 14,147 Deferred tax liabilities Depreciable assets (1,108) (1,609) ASC 842 right of use asset (8,734) (8,924) Equity method investment — (4,467) Other (497) — Deferred tax liabilities (10,339) (15,000) Net deferred tax assets (liabilities) $ 38 $ (853) Realization of a portion of the Company's deferred tax assets is dependent upon the Company generating sufficient taxable income in future years to obtain benefit from the reversal of temporary differences. Management considered all available evidence under existing tax law and anticipated expiration of tax statutes and determined that a valuation allowance of $219.3 million and $161.0 million was required as of December 31, 2023 and 2022, for those deferred tax assets that are not expected to provide future tax benefits. The increase in valuation allowance was primarily related to intangibles and the capitalized research expenditures during the period ended December 31, 2023. At December 31, 2023, we have federal and state net operating loss ("NOL") carryforwards of approximately $396.1 million and $193.0 million, respectively. The federal NOL carryforwards generated in taxable years beginning prior to January 1, 2018 begin to expire in 2033. The federal NOL carryforwards generated in taxable years beginning after December 31, 2017 of $375.2 million can be carried forward indefinitely but may only be used to offset up to 80% of taxable income in future periods. The state NOL carryforwards begin to expire in 2033. At December 31, 2023, we have federal and state research tax credit carryforwards, net of reserves, of approximately $23.0 million and $7.1 million, respectively. The federal credit carryforwards begin to expire in 2033, and the state credit carryforwards do not expire and can be carried forward indefinitely until utilized. Pursuant to Internal Revenue Code ("Code") Sections 382 and 383, annual use of the Company’s federal and California NOL and research and development credit carryforwards may be limited in the event a cumulative change in ownership of more than fifty percentage points by certain stockholders or groups of stockholders occurs within a three-year period. The Company has completed a Code Section 382 analysis through June 30, 2023 regarding the limitation of NOL carryforwards and other tax attributes. Under the Section 382 rules, the Company experienced ownership changes in 2015, 2019 and 2022. Additionally, several of the subsidiaries experienced an ownership change in 2020 based on the Section 382 rules for the time period prior to when the Company was a consolidated group for tax purposes. The Company’s attributes are subject to annual limitations, however, the federal NOL's of $375.2 million carryforward indefinitely and the remaining $20.9 million begin to expire in 2033. There is a risk that additional ownership changes may occur in the future. If a future change in ownership occurs, the NOL carryforwards and other tax attributes could be limited or restricted. Additionally, the Company’s NOLs prior to the tax consolidation are also subject to the separate return loss year (“SRLY”) rules. The SRLY rules may limit one member from offsetting taxable income with losses generated from another member prior to joining the consolidated group. 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 for the fiscal years ended December 31 2023, and 2022 (in thousands): December 31, 2023 2022 2021 Gross unrecognized tax benefits at the beginning of the year $ 4,297 $ 2,835 $ 1,932 Increase related to current year tax positions 857 1,112 969 Increase related to prior year tax positions — 350 — Decrease related to prior year tax positions (940) — (66) Gross unrecognized tax benefits at end of the year $ 4,214 $ 4,297 $ 2,835 Included in the balance of unrecognized tax benefits at December 31, 2023 is $3.9 million that, if recognized, would not impact the Company's income tax benefit or effective tax rate as long as our deferred tax asset remains subject to a valuation allowance. The Company does not expect any significant increases or decreases to our unrecognized tax benefits within the next 12 months. The Company recognizes interest and penalties related to unrecognized tax positions within the income tax expense line in the accompanying consolidated statements of operations. There were no accrued interest and penalties associated with uncertain tax positions as of December 31, 2023 and 2022. The Company files federal and state income tax returns in the United States as well as income tax returns in Australia. Due to the Company's unutilized NOLs and credits, all years remain subject to income tax examination by authorities. The Company is not currently under examination by federal, state or foreign jurisdictions.

Net Loss Per Common Share

Net Loss Per Common Share	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Net Loss Per Common Share	Net Loss Per Common Share Basic and diluted net loss per common share were calculated as follows (in thousands except per share amounts): Year ended December 31, 2023 2022 2021 Numerator: Net loss attributable to Zentalis $ (292,191) $ (236,806) $ (158,725) Denominator: Weighted average number of common shares outstanding, basic and diluted 65,409 52,857 42,688 Net loss per common share $ (4.47) $ (4.48) $ (3.72) Our potential and dilutive securities, which include outstanding stock options, unvested RSAs and unvested RSUs have been excluded from the computation of diluted net loss per common share as the effect would be anti-dilutive. The following common stock equivalents have been excluded from the calculations of diluted net loss per common share because their inclusion would be antidilutive (in thousands): Year ended December 31, 2023 2022 2021 Outstanding stock options 10,017 8,051 3,121 Unvested RSAs 1 126 742 Unvested RSUs 1,219 923 675 11,237 9,100 4,538

Employee Savings Plan

Employee Savings Plan	12 Months Ended
	Dec. 31, 2023
Retirement Benefits [Abstract]
Employee Savings Plan	Employee Savings Plan We have 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 began making matching contributions under the plan during 2021. The Company has recorded as expense $1.5 million, $1.4 million and $1.0 million in matching contributions for the years ended December 31, 2023, 2022 and 2021 respectively.

Related Party Disclosures

Related Party Disclosures	12 Months Ended
	Dec. 31, 2023
Related Party Transactions [Abstract]
Related Party Disclosures	Related Party Disclosures Tempus Kimberly Blackwell, M.D., our Chief Executive Officer and a member of our Board of Directors, was previously employed by Tempus Labs, Inc. ("Tempus") and served as an advisor of Tempus until June 2023, at which time Tempus ceased to be a related party of Zentalis. The Company entered into a Master Services Agreement with Tempus in December 2020 to provide data licensing and research services. There were $0.5 million, $0.2 million and $1.0 million incurred for services performed by Tempus for the period in which Tempus was a related party in 2023 and for the years ended December 31, 2022 and 2021, respectively. Zentera Kevin D. Bunker, Ph.D., our former Chief Scientific Officer, served as a member of the Board of Directors of Zentera until June 2023, when Dr. Bunker resigned in connection with the termination of our Collaboration and License Agreements with Zentera and the sale of our 40.3% equity stake in Zentera back to Zentera. For additional information, please see Note 3. Accordingly, the Company identified Zentera as a related party up until the date of termination. In May 2020, each of our wholly owned subsidiaries, Zeno Alpha, Inc., K-Group Alpha, Inc. and K-Group Beta, Inc., entered into Collaboration and License Agreements, pursuant to which we collaborated with Zentera on the development and comm ercialization of the Zentera Collaboration Products, in Greater China. Under the terms of the Collaboration and License Agreements with Zentera, Zentera was responsible for the costs of developing the Zentera Collaboration Products in Greater China, and we were responsible for the costs of developing the Zentera Collaboration Products outside Greater China, provided that Zentera was obligated to reimburse us for a portion of its costs for global data management, pharmacovigilance, safety database management, and chemistry, manufacturing and controls activities with respect to each Zentera Collaboration Product. For the periods in which Zentera was a related party in 2023 and for the years ended December 31, 2022 and 2021, the amounts incurred under this arrangement totaled $3.5 million, $11.0 million, and $5.3 million, respectively and are presented as contra-research and development expense in the consolidated statement of operations. As disclosed above, these Collaboration and License Agreements were terminated in June 2023 at which time Zentera ceased to be a related party of Zentalis.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2023
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On January 5, 2024, we entered into an exclusive, worldwide license agreement with Immunome, Inc. ("Immunome"), under which Immunome licensed from us ZPC-21 (now known as IM-1021), a preclinical ROR1 antibody-drug conjugate ("ADC") with best-in-class potential, and our proprietary ADC platform technology. Under the terms of the deal, we received an up-front payment of $35 million in cash and Immunome common stock. We are eligible to receive up to $275 million of milestone payments for ZPC-21 and other products that utilize the platform technology in addition to mid-to-high single-digit royalties.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net loss attributable to Zentalis	$ (292,191)	$ (236,806)	$ (158,725)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended	12 Months Ended
	Dec. 31, 2023 shares	Dec. 31, 2023 shares
Trading Arrangements, by Individual
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Jan Skvarka [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		On November 16, 2023, Jan Skvarka, a member of the Company's Board of Directors, adopted a Rule 10b5-1 trading arrangement that is intended to satisfy the affirmative defense of Rule 10b5-1(c) for the sale of up to 11,368 shares of the Company’s common stock until December 31, 2024.
Name	Jan Skvarka
Title	member of the Company's Board of Directors
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	November 16, 2023
Arrangement Duration	411 days
Aggregate Available	11,368	11,368
Diana Hausman [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement		On December 5, 2023, Diana Hausman, then a member of the Company's Board of Directors and, since January 19, 2024, the Chief Medical Officer of the Company, adopted a Rule 10b5-1 trading arrangement that is intended to satisfy the affirmative defense of Rule 10b5-1(c) for the sale of up to 13,244 shares of the Company’s common stock until May 31, 2025.
Name	Diana Hausman
Title	member of the Company's Board of Directors
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	December 5, 2023
Arrangement Duration	543 days
Aggregate Available	13,244	13,244

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements have been prepared in conformity with U.S. generally accepted accounting principles (“U.S. GAAP”) and include our wholly-owned subsidiaries and a variable interest entity (“VIE”) for the periods in which we determined we were the primary beneficiary. All intercompany transactions and balances have been eliminated in consolidation.
Consolidation	We will continuously assess whether we are the primary beneficiary of a VIE, as changes to existing relationships or future transactions may result in the consolidation or deconsolidation of such VIE. During the periods presented, we have not provided any other material financial or other support to our VIE that we were not contractually required to provide. Noncontrolling Interests Noncontrolling interests represent interests held by third parties in our consolidated subsidiaries. We reflect noncontrolling interest attributable to the other owners in a separate line in our consolidated statements of operations and a separate line within stockholders' equity in our consolidated balance sheets.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in our consolidated financial statements and accompanying notes. On an ongoing basis, we evaluate our estimates and judgments, which are based on historical and anticipated results and trends and on various other assumptions that management believes to be reasonable under the circumstances. By their nature, estimates are subject to an inherent degree of uncertainty and, as such, actual results may differ from management’s estimates.
Cash and Cash Equivalents and Restricted Cash	Cash and Cash Equivalents Restricted Cash
Marketable Securities	Marketable Securities
Fair Value of Financial Instruments	Fair Value of Financial Instruments The authoritative guidance defines fair value and requires us to establish a framework for measuring fair value and disclosure about fair value measurements using a three-tier approach. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. Our financial instruments include cash equivalents, marketable securities, prepaid expenses and other assets, accounts payable and accrued expenses. Fair value estimates of these instruments are made at a specific point in time, based on relevant market information. These estimates may be subjective in nature and involve uncertainties and matters of significant judgement and therefore cannot be determined with precision. The fair value of marketable securities is determined using proprietary valuation models and analytical tools, which utilize market pricing or prices for similar instruments that are both objective and publicly available, such as matrix pricing or reported trades, benchmark yields, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities and bids and offers. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. Fair value should maximize the use of observable inputs and minimize the use of unobservable inputs. The Company determines the fair value of financial assets and liabilities using three levels of inputs as follows: Level 1—Inputs which include quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2—Inputs (other than quoted market prices included in Level 1) that are either directly or indirectly observable, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the instrument’s anticipated life. Level 3—Unobservable inputs for assets or liabilities and include little or no market activity.
Concentrations of Credit Risk and Sources of Supply	Concentrations of Credit Risk and Sources of Supply We are subject to credit risk from our portfolios of cash equivalents and marketable securities. We maintain our cash and cash equivalent and marketable securities balances with major commercial banks. Deposits held with the financial institutions exceed the amount of insurance provided on such deposits. We are exposed to credit risk in the event of a default by the financial institutions holding our cash and cash equivalents and marketable securities to the extent recorded on the consolidated balance sheets. We have also established guidelines to limit our exposure to credit risk by diversifying our marketable securities portfolio and placing them in investments with maturities that maintain safety and liquidity. We rely on third-party manufacturers for the supply of active pharmaceutical ingredients.
Property and Equipment, Net	Property and Equipment, Net Property and equipment are recorded at cost, less accumulated depreciation and amortization. Equipment is depreciated using the straight-line method over its estimated useful life ranging from three
Leases	Leases We have entered into operating leases for real estate. We determine if an arrangement is a lease at inception and evaluate each lease agreement to determine whether the lease is an operating or finance lease. For leases where we are the lessee, right-of-use (“ROU”) assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent an obligation to make lease payments arising from the lease. Liabilities from operating leases are included in accrued expenses
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets We account for long-lived assets in accordance with authoritative guidance for impairment or disposal of long-lived assets. Long-lived assets are reviewed for events or changes in circumstances, which indicate that their carrying value may not be recoverable.
Goodwill	Goodwill Our goodwill, which has an indefinite useful life, represents the excess of the cost over the fair value of net assets acquired from its business combination. The determination of the value of goodwill and intangible assets arising from business combinations and asset acquisitions requires extensive use of accounting estimates and judgments to allocate the purchase price to the fair value of the net tangible and intangible assets acquired, including capitalized in-process research and development (“IPR&D”).
Equity Method Accounting	Equity Method Accounting
Research and Development Expenses	Research and Development Expenses Research and development expenses include salaries and benefits, facilities and other overhead expenses, external clinical trial expenses, research-related manufacturing services, contract services and other outside expenses. Research and development expenses are charged to operating expenses as incurred when these expenditures relate to our research and development efforts and have no alternative future uses. Reimbursed research and development costs under government grant arrangements are recorded as a reduction to research and development expenses and are recognized in the period in which the related costs are incurred. We are 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 we do not expect the goods to be delivered or services to be performed.
Clinical Trial Expenses	Clinical Trial Expenses We make payments in connection with our clinical trials under contracts with CROs that support conducting and managing clinical trials. The financial terms of these agreements are subject to negotiation and vary from contract to contract and may result in uneven payment flows. 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. A portion of our obligation to make payments under these contracts depends on factors such as the successful enrollment or treatment of patients or the completion of other clinical trial milestones. Expenses related to clinical trials are accrued based on our estimates and/or representations from service providers regarding work performed, including actual level of patient enrollment, completion of patient studies and progress of the clinical trials. Other incidental costs related to patient enrollment or treatment are accrued when reasonably certain. If the amounts we are obligated to pay under our clinical trial agreements are modified (for instance, as a result of changes in the clinical trial protocol or scope of work to be performed), we adjust our accruals accordingly. Revisions to our contractual payment obligations are charged to expense in the period in which the facts that give rise to the revision become reasonably certain.
Share-Based Compensation	Share-Based Compensation We record share-based compensation expense associated with equity instruments in accordance with the authoritative guidance for stock-based compensation. The cost of employee services received in exchange for an award of an equity instrument is measured at the grant date based on the estimated fair value of the award and is recognized as expense on a straight-line basis over the requisite service period of the award. Share-based compensation expense for an award with a performance condition is recognized when the achievement of such performance condition is determined to be probable. If the outcome of such performance condition is not determined to be probable or is not met, no compensation expense is recognized, and any previously recognized compensation expense is reversed. Forfeitures are recognized as a reduction of share-based compensation expense as they occur.
Income Taxes	Income Taxes Deferred income taxes are recognized for the tax consequences in future years of differences between the tax basis of assets and liabilities and their financial reporting amounts at each year end based on enacted tax laws and statutory tax rates applicable to the periods in which the differences are expected to affect taxable income. A provision has been made for income taxes due on taxable income and for the deferred taxes on temporary differences. Deferred tax assets and liabilities are adjusted for the effects of changes in tax laws and rates on the date of enactment. Realization of the deferred income tax asset is dependent on gathering sufficient taxable income in future years. Valuation allowances are established when necessary to reduce deferred tax assets to the amount expected to be realized. Income tax expense is the combination of the tax payable for the period and the change during the period in deferred tax assets and liabilities. We follow the accounting guidance on accounting for uncertainty in income taxes. The guidance prescribes a recognition threshold and measurement attribute criteria for the financial statement recognition and measurement of tax positions taken or expected to be taken in a tax return. For those benefits to be recognized, a tax position must be more likely than not to be sustained upon examination by taxing authorities based on the technical merits of the position.
Accumulated Other Comprehensive Income	Accumulated Other Comprehensive Income Accumulated other comprehensive income is the result of unrealized gains and losses on marketable securities.
Net Loss per Common Share Outstanding	Net Loss per Common Share Outstanding Basic net loss per common share outstanding is computed by dividing net loss, after adjusting for dividends, if declared, by the weighted-average number of common shares outstanding during the period. Diluted net loss per common share outstanding is computed using the weighted-average number of common shares outstanding during the period and, if dilutive, the weighted average number of potential common shares. Potential common shares consist of unvested restricted stock awards, unvested restricted stock units and common shares issuable upon the exercise of stock options.
Acquisitions and Contingent Consideration	Acquisitions and Contingent Consideration The Company evaluates acquisitions of assets and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen test to determine if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If the screen is met, the transaction is accounted for as an asset acquisition. If the screen is not met, further determination is required as to whether or not the Company has acquired inputs and processes that have the ability to create outputs, which would meet the requirements of a business. If determined to be a business combination, the Company accounts for the transaction under the acquisition method of accounting as indicated in Accounting Standards Update (ASU) 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business, which requires the acquiring entity in a business combination to recognize the fair value of all assets acquired, liabilities assumed, and any non-controlling interest in the acquired entity and establishes the acquisition date as the fair value measurement point. Accordingly, the Company recognizes assets acquired and liabilities assumed in business combinations, including contingent assets and liabilities, and non-controlling interest in the acquired entity based on the fair value estimates as of the date of acquisition. In accordance with Accounting Standards Codification (ASC) 805, Business Combinations, the Company recognizes and measures goodwill as of the acquisition date, as the excess of the fair value of the consideration paid over the fair value of the identified net assets acquired. The consideration for the Company’s business acquisitions may include future payments that are contingent upon the occurrence of a particular event or events. The obligations for such contingent consideration payments are recorded at fair value on the acquisition date. The contingent consideration obligations are then evaluated each reporting period. Changes in the fair value of contingent consideration, other than changes due to payments, are recognized as a gain or loss and recorded within change in the fair value of deferred and contingent consideration liabilities in the consolidated statements of comprehensive loss. Contingent consideration liabilities expected to be settled within 12 months after the balance sheet date are presented in current liabilities. Contingent consideration liabilities expected to be settled 12 months after the balance sheet date are presented in long-term liabilities. If determined to be an asset acquisition, the Company accounts for the transaction under ASC 805-50, which requires the acquiring entity to recognize assets acquired and liabilities assumed based on the cost to the acquiring entity on a relative fair value basis, which includes transaction costs in addition to consideration given. No gain or loss is recognized as of the date of acquisition unless the fair value of non-cash assets given as consideration differs from the assets’ carrying amounts on the acquiring entity’s books. Consideration transferred that is non-cash will be measured based on either the cost (which shall be measured based on the fair value of the consideration given) or the fair value of the assets acquired and liabilities assumed, whichever is more reliably measurable. Goodwill is not recognized in an asset acquisition and any excess consideration transferred over the fair value of the net assets acquired is allocated to the identifiable assets based on relative fair values. If the in-licensed agreement for in-process research and development (“IPR&D”) does not meet the definition of a business and the assets have not reached technological feasibility and therefore have no alternative future use, the Company expenses payments made under such license agreements as acquired IPR&D expense in its consolidated statement of comprehensive loss. Contingent consideration payments in asset acquisitions are recognized when the contingency is resolved and the consideration is paid or becomes payable (unless the contingent consideration meets the definition of a derivative, in which case the amount becomes part of the basis in the asset acquired). Upon recognition of the contingent consideration payment, the amount is included in the cost of the acquired asset or group of assets.
Acquisitions and Contingent Consideration	Acquisitions and Contingent Consideration The Company evaluates acquisitions of assets and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen test to determine if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If the screen is met, the transaction is accounted for as an asset acquisition. If the screen is not met, further determination is required as to whether or not the Company has acquired inputs and processes that have the ability to create outputs, which would meet the requirements of a business. If determined to be a business combination, the Company accounts for the transaction under the acquisition method of accounting as indicated in Accounting Standards Update (ASU) 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business, which requires the acquiring entity in a business combination to recognize the fair value of all assets acquired, liabilities assumed, and any non-controlling interest in the acquired entity and establishes the acquisition date as the fair value measurement point. Accordingly, the Company recognizes assets acquired and liabilities assumed in business combinations, including contingent assets and liabilities, and non-controlling interest in the acquired entity based on the fair value estimates as of the date of acquisition. In accordance with Accounting Standards Codification (ASC) 805, Business Combinations, the Company recognizes and measures goodwill as of the acquisition date, as the excess of the fair value of the consideration paid over the fair value of the identified net assets acquired. The consideration for the Company’s business acquisitions may include future payments that are contingent upon the occurrence of a particular event or events. The obligations for such contingent consideration payments are recorded at fair value on the acquisition date. The contingent consideration obligations are then evaluated each reporting period. Changes in the fair value of contingent consideration, other than changes due to payments, are recognized as a gain or loss and recorded within change in the fair value of deferred and contingent consideration liabilities in the consolidated statements of comprehensive loss. Contingent consideration liabilities expected to be settled within 12 months after the balance sheet date are presented in current liabilities. Contingent consideration liabilities expected to be settled 12 months after the balance sheet date are presented in long-term liabilities. If determined to be an asset acquisition, the Company accounts for the transaction under ASC 805-50, which requires the acquiring entity to recognize assets acquired and liabilities assumed based on the cost to the acquiring entity on a relative fair value basis, which includes transaction costs in addition to consideration given. No gain or loss is recognized as of the date of acquisition unless the fair value of non-cash assets given as consideration differs from the assets’ carrying amounts on the acquiring entity’s books. Consideration transferred that is non-cash will be measured based on either the cost (which shall be measured based on the fair value of the consideration given) or the fair value of the assets acquired and liabilities assumed, whichever is more reliably measurable. Goodwill is not recognized in an asset acquisition and any excess consideration transferred over the fair value of the net assets acquired is allocated to the identifiable assets based on relative fair values. If the in-licensed agreement for in-process research and development (“IPR&D”) does not meet the definition of a business and the assets have not reached technological feasibility and therefore have no alternative future use, the Company expenses payments made under such license agreements as acquired IPR&D expense in its consolidated statement of comprehensive loss. Contingent consideration payments in asset acquisitions are recognized when the contingency is resolved and the consideration is paid or becomes payable (unless the contingent consideration meets the definition of a derivative, in which case the amount becomes part of the basis in the asset acquired). Upon recognition of the contingent consideration payment, the amount is included in the cost of the acquired asset or group of assets.

Business Combinations (Tables)

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2023
Business Combination and Asset Acquisition [Abstract]
Reconciliation of equity (net assets) attributable to noncontrolling interest	The following is a reconciliation of equity (net assets) attributable to the noncontrolling interest (in thousands): December 31, 2023 2022 Noncontrolling interest at beginning of period $ 221 $ 528 Net loss attributable to noncontrolling interest (114) (307) Noncontrolling interest at end of period $ 107 $ 221

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	12 Months Ended
	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Components of available-for-sale marketable securities	Available-for-sale marketable securities consisted of the following (in thousands): December 31, 2023 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Commercial paper $ 75,227 $ 60 $ (15) $ 75,272 Corporate debt securities 229,896 2,036 — 231,932 US government agencies 83,025 100 (78) 83,047 US Treasury securities 64,538 103 (11) 64,630 $ 452,686 $ 2,299 $ (104) $ 454,881 December 31, 2022 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Commercial paper $ 296,309 $ 71 $ (587) $ 295,793 Corporate debt securities 7,472 — (26) 7,446 US government agencies 23,970 — (182) 23,788 US Treasury securities 67,904 — (629) 67,275 $ 395,655 $ 71 $ (1,424) $ 394,302
Contractual maturities of available-for-sale debt securities	Contractual maturities of available-for-sale debt securities are as follows (in thousands): December 31, 2023 December 31, 2022 Estimated Fair Value Due within one year $ 267,336 $ 394,302 After one but within five years 187,545 — $ 454,881 $ 394,302
Schedule of fair value of assets measured on recurring basis	The following table summarizes, by major security type, our cash equivalents and available-for-sale marketable securities that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy (in thousands): December 31, 2023 Level 1 Level 2 Level 3 Total estimated fair value Cash equivalents: Money market funds $ 4,755 $ — $ — $ 4,755 Total cash equivalents: 4,755 — — 4,755 Available-for-sale marketable securities: Commercial paper — 75,272 — 75,272 Corporate debt securities — 231,932 — 231,932 US government agencies — 83,047 — 83,047 US Treasury securities — 64,630 — 64,630 Total available-for-sale marketable securities: — 454,881 — 454,881 Total assets measured at fair value $ 4,755 $ 454,881 $ — $ 459,636 Financial liabilities: Contingent consideration — — 500 500 Total financial liabilities $ — $ — $ 500 $ 500 December 31, 2022 Level 1 Level 2 Level 3 Total estimated fair value Cash equivalents: Money market funds $ 26,811 $ — $ — $ 26,811 Commercial paper 1,998 — — 1,998 Total cash equivalents: 28,809 — — 28,809 Available-for-sale marketable securities: Commercial paper — 295,793 — 295,793 Corporate debt securities — 7,446 — 7,446 US government agencies — 23,788 — 23,788 US Treasury securities 67,275 — — 67,275 Total available-for-sale marketable securities: 67,275 327,027 — 394,302 Total assets measured at fair value $ 96,084 $ 327,027 $ — $ 423,111 Financial liabilities: Contingent consideration — — — — Total financial liabilities $ — $ — $ — $ —
Measurement inputs for contingent consideration liability	The following significant unobservable inputs were used in the valuation of the contingent consideration payable to Zentera pursuant to the Termination Agreement at December 31, 2023: Contingent Consideration Liability Fair Value as of December 31, 2023 Valuation Technique Unobservable Input Range (in thousands) Milestone payment $ 500 Discounted cash flow Likelihood of occurrence 1.0%- 2.4% Discount rate 40% Expected term Perpetuity
Activity for contingent consideration	The following table reflects the activity for the Company’s contingent consideration, measured at fair value using Level 3 inputs (in thousands): Contingent consideration at December 31, 2022 $ — Issuance of contingent consideration to Zentera 500 Changes in the fair value of contingent consideration — Contingent consideration at December 31, 2023 $ 500

Prepaid Expenses and Other As_2

Prepaid Expenses and Other Assets (Tables)	12 Months Ended
	Dec. 31, 2023
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Summary of prepaid expenses and other assets	Prepaid expenses and other assets consisted of the following (in thousands): December 31, 2023 2022 Prepaid insurance $ 747 $ 1,018 Prepaid software licenses and maintenance 691 958 Foreign R&D credit refund 500 659 Prepaid research and development expenses 13,640 15,002 Interest receivable 3,337 508 Sublease assets 1,471 — Zentera receivable — 5,874 Other prepaid expenses 231 266 Total prepaid expenses and other current assets 20,617 24,285 Less long-term portion 6,818 9,723 Total prepaid expenses and other assets, current $ 13,799 $ 14,562

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Summary of property and equipment, net	Property and equipment, net consisted of the following (in thousands): December 31, 2023 2022 Lab equipment $ 3,069 $ 2,622 Leasehold improvements 4,235 4,891 Office equipment and furniture 1,340 2,065 Computer equipment 150 150 Construction in process 173 37 Subtotal 8,967 9,765 Accumulated depreciation and amortization (3,148) (2,060) Property and equipment, net $ 5,819 $ 7,705

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2023
Payables and Accruals [Abstract]
Schedule of accrued expenses	Accrued expenses consist of the following (in thousands): December 31, 2023 2022 Accrued research and development expenses $ 36,261 $ 32,310 Accrued employee expenses 14,477 11,246 Accrued general and administrative expenses 1,032 662 Lease liability 2,623 2,162 Contingent consideration 500 — Income taxes payable 281 384 Accrued legal expenses 1,047 1,256 Total accrued expenses 56,221 48,020 Less long-term portion 1,780 2,620 Total accrued expenses, current $ 54,441 $ 45,400

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2023
Equity [Abstract]
Schedule of share-based compensation expense	Total share-based compensation expense related to share-based awards was comprised of the following (in thousands): Year ended December 31, 2023 2022 2021 Research and development expense $ 24,519 $ 20,439 $ 14,879 General and administrative expense 30,303 26,401 20,858 Total share-based compensation expense $ 54,822 $ 46,840 $ 35,737 Share-based compensation expense by type of share-based award (in thousands): Year ended December 31, 2023 2022 2021 Stock options $ 41,642 $ 36,338 $ 20,773 RSAs and RSUs 12,816 10,075 14,643 Employee Stock Purchase Plan 364 427 321 $ 54,822 $ 46,840 $ 35,737
Share-based compensation expense by type of share-based award	Total unrecognized estimated compensation cost by type of award and the weighted average requisite service period over which such expense is expected to be recognized (in thousands, unless otherwise noted): December 31, 2023 Unrecognized Remaining Stock options $ 92,129 2.7 RSAs $ 1 0.0 RSUs $ 20,699 2.5
Summary of stock option activity	The following table summarizes option activity for the year ended December 31, 2023. The amounts include stock options granted to both employees and non-employees: Number of Shares Weighted Average Weighted Average Remaining Contractual Term (Years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2022 8,051,459 $ 29.97 Granted 3,772,345 $ 22.17 Exercised (54,324) $ 18.31 Cancelled (1,752,045) $ 32.82 Outstanding at December 31, 2023 10,017,435 $ 26.59 7.8 $160 Vested and expected to vest at December 31, 2023 10,017,435 $ 26.59 7.8 $160 Exercisable at December 31, 2023 4,086,661 $ 27.91 6.6 $—
Schedule of valuation assumptions	The fair value of the stock options granted during the year ended December 31, 2023 was determined with the following assumptions: Year ended December 31, 2023 2022 2021 Expected volatility 73.5% - 80.8% 73.6% - 80.5% 73.2% - 76.6% Average expected term (in years) 5.5 - 6.1 6.0 - 6.5 5.2 - 6.1 Risk-free interest rate 3.4% - 4.7% 1.5% - 4.2% 0.5% - 1.3% Expected dividend yield —% —% —%
Summary of RSA activity	The following table summarizes RSA activity for the year ending December 31, 2023. The amounts include RSAs granted to both employees and non-employees: Number of Shares Weighted Average Grant Date Outstanding at December 31, 2022 125,506 $ 5.45 Vested (120,102) $ 5.53 Forfeited (4,455) $ 3.30 Outstanding at December 31, 2023 949 $ 4.61
Summary of RSU activity	The following table summarizes RSU activity for the year ending December 31, 2023. The amounts include RSUs granted to both employees and non-employees: Number of Shares Weighted Average Grant Date Outstanding at December 31, 2022 922,901 $ 27.48 Granted 968,823 $ 22.94 Vested (360,555) $ 27.02 Forfeited (312,354) $ 25.88 Outstanding at December 31, 2023 1,218,815 $ 24.56
Schedule of valuation assumptions, ESPP	The weighted average assumptions used to estimate the fair value of stock purchase rights under the 2020 ESPP are as follows: Year ended December 31, 2023 2022 2021 ESPP Volatility 85.8 % 74.0 % 48.2 % Expected term (years) 0.5 0.5 0.5 Risk free rate 4.8 % 1.6 % 0.1 % Expected dividend yield — % — % — %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Summary of operating lease terms	The following table presents the weighted average remaining lease term and weighted average discount rates related to our operating leases as of December 31, 2023: Weighted average remaining lease term (in years) 8.7 Weighted average discount rate 9.0%
Schedule of future minimum operating lease payments	Approximate annual future minimum operating lease payments as of December 31, 2023 are as follows (in thousands): Year Amount 2024 $ 6,643 2025 7,002 2026 7,487 2027 7,606 2028 7,760 Thereafter 31,018 Total minimum lease payments: 67,516 Less: imputed interest 21,743 Total operating lease liabilities 45,773 Less: current portion 2,623 Lease liability, net of current portion $ 43,150

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Schedule of net losses before income taxes and loss on equity method investment by domestic and foreign operations	The amount of net loss before income taxes and loss on equity method investment for the years ended December 31, 2023, 2022 and 2021 is as follows (in thousands): Year ended December 31, 2023 2022 2021 U.S. net loss before income taxes $ (293,284) $ (237,926) $ (171,053) Foreign net income (loss) before income taxes 378 344 4,663 Net loss before income taxes, including loss on equity method investment $ (292,906) $ (237,582) $ (166,390)
Schedule of components of income tax provision (benefit) for federal and state income taxes	The following table presents the current and deferred income tax provision (benefit) for federal, state and foreign income taxes (in thousands): Year ended December 31, 2023 2022 2021 Current tax provision: Federal $ — $ — $ — State 41 11 11 Foreign 249 298 550 Total current tax provision 290 309 561 Deferred tax provision: Federal (891) (683) (120) State — (41) (736) Foreign — (54) (2) Total deferred tax provision (891) (778) (858) Total provision for income taxes: $ (601) $ (469) $ (297)
Schedule of effective income tax rate reconciliation	The following table is a reconciliation of the expected tax computed at the U.S. statutory federal income tax rate to the total provision for income taxes (in thousands): Year ended December 31, 2023 2022 2021 Expected tax at 21% $ (61,509) 21.0 % $ (49,892) 21.0 % $ (34,941) 21.0 % State income tax, net of federal tax (2,384) 0.8 % (4,222) 1.8 % (931) 0.6 % Research credits (2,031) 0.7 % (12,558) 5.3 % (6,938) 4.2 % Share-based compensation 3,008 (1.0) % 1,245 (0.5) % (3,307) 2.0 % Deemed royalty 8,263 (2.8) % — — % — — % Other 586 (0.2) % (2,799) 1.2 % 939 (0.6) % Section 162(m) limitations 5,028 (1.7) % 3,950 (1.7) % 3,982 (2.4) % Effective Tax Rate Change (10,420) 3.6 % — — % — — % Change in valuation allowance 58,858 (20.1) % 63,807 (26.9) % 40,899 (24.6) % Provision for income taxes $ (601) 0.2 % $ (469) 0.2 % $ (297) 0.2 %
Schedule of deferred tax assets and liabilities	Significant components of our net deferred tax asset or liability are as follows (in thousands): December 31, 2023 2022 Deferred tax assets Net operating loss $ 96,676 $ 95,392 Compensation 2,451 1,937 Share-based compensation 11,486 7,735 ASC 842 lease liability 11,131 9,967 Intangibles 11,185 1,745 Capitalized research and experimental expenditures 66,500 30,776 Accrued liabilities 1,163 476 Research credits 29,055 27,024 Other 22 62 Total gross deferred tax assets 229,669 175,114 Valuation allowance (219,292) (160,967) Net deferred tax assets 10,377 14,147 Deferred tax liabilities Depreciable assets (1,108) (1,609) ASC 842 right of use asset (8,734) (8,924) Equity method investment — (4,467) Other (497) — Deferred tax liabilities (10,339) (15,000) Net deferred tax assets (liabilities) $ 38 $ (853)
Schedule of unrecognized tax benefits roll forward	The following table reconciles the beginning and ending amount of unrecognized tax benefits for the fiscal years ended December 31 2023, and 2022 (in thousands): December 31, 2023 2022 2021 Gross unrecognized tax benefits at the beginning of the year $ 4,297 $ 2,835 $ 1,932 Increase related to current year tax positions 857 1,112 969 Increase related to prior year tax positions — 350 — Decrease related to prior year tax positions (940) — (66) Gross unrecognized tax benefits at end of the year $ 4,214 $ 4,297 $ 2,835

Net Loss Per Common Share (Tabl

Net Loss Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2023
Earnings Per Share [Abstract]
Schedule of basic and diluted net loss per unit	Basic and diluted net loss per common share were calculated as follows (in thousands except per share amounts): Year ended December 31, 2023 2022 2021 Numerator: Net loss attributable to Zentalis $ (292,191) $ (236,806) $ (158,725) Denominator: Weighted average number of common shares outstanding, basic and diluted 65,409 52,857 42,688 Net loss per common share $ (4.47) $ (4.48) $ (3.72)
Schedule of antidilutive securities excluded from computation of earnings per unit	The following common stock equivalents have been excluded from the calculations of diluted net loss per common share because their inclusion would be antidilutive (in thousands): Year ended December 31, 2023 2022 2021 Outstanding stock options 10,017 8,051 3,121 Unvested RSAs 1 126 742 Unvested RSUs 1,219 923 675 11,237 9,100 4,538

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Variable Interest Entity [Line Items]
Restricted cash	$ 2,700,000	$ 2,600,000
Operating lease, liability, current, balance sheet location	Accrued expenses	Accrued expenses
Goodwill impairment	$ 0
Investment in Zentera Therapeutics	$ 0	$ 21,213,000
Minimum | Equipment
Variable Interest Entity [Line Items]
Property, plant and equipment, useful life (years)	3 years
Maximum | Equipment
Variable Interest Entity [Line Items]
Property, plant and equipment, useful life (years)	5 years

Significant Transactions (Detai

Significant Transactions (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Jun. 15, 2023	Jun. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Loss on equity method investment		$ 13,700	$ 16,014	$ 16,282	$ 1,831
Contingent consideration			500	0
In-process research and development			45,568	$ 0	$ 0
Zentera
Schedule of Equity Method Investments [Line Items]
Total consideration transferred	$ 45,600
Fixed consideration	30,000
Forgiveness of outstanding receivables	9,400
Acquisition-related costs	500
In-process research and development			$ 45,600
Zentera | Milestone payment | Discounted cash flow
Schedule of Equity Method Investments [Line Items]
Contingent consideration	500
Zentera | Minimum | Variable consideration of a change in control milestone payment
Schedule of Equity Method Investments [Line Items]
Contingent consideration	0
Zentera | Maximum | Variable consideration of a change in control milestone payment
Schedule of Equity Method Investments [Line Items]
Contingent consideration	$ 15,000
Zentera
Schedule of Equity Method Investments [Line Items]
Ownership percentage sold	40.30%

Business Combinations - Narrati

Business Combinations - Narrative (Details) - Kalyra Pharmaceuticals, Inc. $ in Millions	Dec. 21, 2017 USD ($)
Variable Interest Entity [Line Items]
Cash payments to acquire interest	$ 4.5
Ownership percentage	25%

Business Combinations - Reconci

Business Combinations - Reconciliation of Equity (Net Assets) Attributable to Noncontrolling Interest (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Noncontrolling interest at beginning of period	$ 221
Net loss attributable to noncontrolling interest	(114)	$ (307)	$ (7,368)
Noncontrolling interest at end of period	107	221
VIE, Primary Beneficiary
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Noncontrolling interest at beginning of period	221	528
Net loss attributable to noncontrolling interest	(114)	(307)
Noncontrolling interest at end of period	$ 107	$ 221	$ 528

Fair Value Measurement - Compon

Fair Value Measurement - Components of Available-for-sale Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 452,686	$ 395,655
Gross Unrealized Gains	2,299	71
Gross Unrealized Losses	(104)	(1,424)
Estimated Fair Value	454,881	394,302
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	75,227	296,309
Gross Unrealized Gains	60	71
Gross Unrealized Losses	(15)	(587)
Estimated Fair Value	75,272	295,793
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	229,896	7,472
Gross Unrealized Gains	2,036	0
Gross Unrealized Losses	0	(26)
Estimated Fair Value	231,932	7,446
US government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	83,025	23,970
Gross Unrealized Gains	100	0
Gross Unrealized Losses	(78)	(182)
Estimated Fair Value	83,047	23,788
US Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	64,538	67,904
Gross Unrealized Gains	103	0
Gross Unrealized Losses	(11)	(629)
Estimated Fair Value	$ 64,630	$ 67,275

Fair Value Measurement - Narrat

Fair Value Measurement - Narrative (Details) $ in Thousands	Dec. 31, 2023 USD ($) security potential_milestone_payment	Dec. 31, 2022 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Number of available-for-sale securities in unrealized loss position | security	20
Debt securities fair market value	$ 113,400
Fair value of available-for-sale securities in unrealized loss position	100
Contingent consideration	500	$ 0
Zentera | Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 500
Number of potential milestone payments | potential_milestone_payment	1

Fair Value Measurement - Contra

Fair Value Measurement - Contractual Maturities of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Due within one year	$ 267,336	$ 394,302
After one but within five years	187,545	0
Estimated Fair Value	$ 454,881	$ 394,302

Fair Value Measurement - Fair V

Fair Value Measurement - Fair Value of Assets Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents	$ 4,755	$ 28,809
Marketable securities, available for sale	454,881	394,302
Total assets measured at fair value	459,636	423,111
Financial liabilities:
Contingent consideration	500	0
Total financial liabilities	500	0
Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents	4,755	28,809
Marketable securities, available for sale	0	67,275
Total assets measured at fair value	4,755	96,084
Financial liabilities:
Contingent consideration	0	0
Total financial liabilities	0	0
Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents	0	0
Marketable securities, available for sale	454,881	327,027
Total assets measured at fair value	454,881	327,027
Financial liabilities:
Contingent consideration	0	0
Total financial liabilities	0	0
Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents	0	0
Marketable securities, available for sale	0	0
Total assets measured at fair value	0	0
Financial liabilities:
Contingent consideration	500	0
Total financial liabilities	500	0
Commercial paper
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	75,272	295,793
Commercial paper | Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	0	0
Commercial paper | Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	75,272	295,793
Commercial paper | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	0	0
Corporate debt securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	231,932	7,446
Corporate debt securities | Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	0	0
Corporate debt securities | Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	231,932	7,446
Corporate debt securities | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	0	0
US government agencies
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	83,047	23,788
US government agencies | Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	0	0
US government agencies | Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	83,047	23,788
US government agencies | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	0	0
US Treasury securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	64,630	67,275
US Treasury securities | Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	0	67,275
US Treasury securities | Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	64,630	0
US Treasury securities | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Marketable securities, available for sale	0	0
Money market funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents	4,755	26,811
Money market funds | Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents	4,755	26,811
Money market funds | Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents	0	0
Money market funds | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents	$ 0	0
Commercial paper
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents		1,998
Commercial paper | Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents		1,998
Commercial paper | Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents		0
Commercial paper | Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash equivalents		$ 0

Fair Value Measurement - Measur

Fair Value Measurement - Measurement Inputs for Contingent Consideration Liability (Details) $ in Thousands	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 500	$ 0
Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 500	$ 0
Level 3 | Discounted cash flow | Likelihood of occurrence | Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.010
Level 3 | Discounted cash flow | Likelihood of occurrence | Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.024
Level 3 | Milestone payment | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.40
Level 3 | Milestone payment | Discounted cash flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Contingent consideration	$ 500

Fair Value Measurement - Activi

Fair Value Measurement - Activity for Contingent Consideration (Details) - Contingent Consideration Liability $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration, beginning balance	$ 0
Issuance of contingent consideration to Zentera	500
Changes in the fair value of contingent consideration	0
Contingent consideration, ending balance	$ 500

Prepaid Expenses and Other As_3

Prepaid Expenses and Other Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid insurance	$ 747	$ 1,018
Prepaid software licenses and maintenance	691	958
Foreign R&D credit refund	500	659
Prepaid research and development expenses	13,640	15,002
Interest receivable	3,337	508
Sublease assets	1,471	0
Zentera receivable	0	5,874
Other prepaid expenses	231	266
Total prepaid expenses and other current assets	20,617	24,285
Less long-term portion	6,818	9,723
Total prepaid expenses and other assets, current	$ 13,799	$ 14,562

Property and Equipment, net - S

Property and Equipment, net - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Subtotal	$ 8,967	$ 9,765
Accumulated depreciation and amortization	(3,148)	(2,060)
Property and equipment, net	5,819	7,705
Lab equipment
Property, Plant and Equipment [Line Items]
Subtotal	3,069	2,622
Leasehold improvements
Property, Plant and Equipment [Line Items]
Subtotal	4,235	4,891
Office equipment and furniture
Property, Plant and Equipment [Line Items]
Subtotal	1,340	2,065
Computer equipment
Property, Plant and Equipment [Line Items]
Subtotal	150	150
Construction in process
Property, Plant and Equipment [Line Items]
Subtotal	$ 173	$ 37

Property and Equipment, net - N

Property and Equipment, net - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Depreciation and amortization	$ 1,389	$ 1,426	$ 544

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Payables and Accruals [Abstract]
Accrued research and development expenses	$ 36,261	$ 32,310
Accrued employee expenses	14,477	11,246
Accrued general and administrative expenses	1,032	662
Lease liability	2,623	2,162
Contingent consideration	500	0
Income taxes payable	281	384
Accrued legal expenses	1,047	1,256
Total accrued expenses	56,221	48,020
Less long-term portion	1,780	2,620
Total accrued expenses, current	$ 54,441	$ 45,400

Stockholders' Equity - Narrativ

Stockholders' Equity - Narrative (Details) - USD ($)					1 Months Ended		3 Months Ended	12 Months Ended
	Dec. 31, 2023	Jun. 15, 2023	May 18, 2022	Apr. 29, 2022	May 31, 2021	Apr. 30, 2020	Dec. 31, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Mar. 15, 2021
Class of Stock [Line Items]
Issuance of common stock upon exercise of options (in shares)								54,324
Proceeds from exercises of stock options								$ 1,000,000
Options, weighted average grant date fair value (dollars per share)								$ 15.48	$ 20.45	$ 33.27
Intrinsic value of options exercised								$ 300,000	$ 2,000,000	$ 8,800,000
Common Stock
Class of Stock [Line Items]
Issuance of common stock upon exercise of options (in shares)								54,000	122,000	232,000
Issuance of common stock in connection with restricted stock unit vesting (in shares)								360,555	159,000	517,000
Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Class of Stock [Line Items]
Gross proceeds from issuance of common stock	$ 2,500,000
Follow-On Offering
Class of Stock [Line Items]
Gross proceeds from issuance of common stock		$ 250,000,000	$ 200,200,000
Expenses and fees from the issuance of common stock		$ 14,300,000	$ 11,400,000
Sales Agreement
Class of Stock [Line Items]
Maximum gross sales proceeds					$ 200,000,000
The 2020 Plan
Class of Stock [Line Items]
Outstanding awards (in shares)	9,240,394						9,240,394	9,240,394
Shares available for future grants (in shares)	1,836,357						1,836,357	1,836,357
2022 Inducement Plan
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)	2,275,000						2,275,000	2,275,000
Outstanding awards (in shares)	1,995,856						1,995,856	1,995,856
Shares available for future grants (in shares)	254,144						254,144	254,144
Zentera Stock Plan
Class of Stock [Line Items]
Share-based compensation prior to deconsolidation										$ 138,000
Common Stock | Follow-On Offering
Class of Stock [Line Items]
Number of shares issued and sold (in shares)		11,032,656	10,330,000
Share price (in dollars per share)		$ 22.66	$ 19.38
Common Stock | Direct Offering
Class of Stock [Line Items]
Number of shares issued and sold (in shares)				953,834
Share price (in dollars per share)				$ 26.21
Gross proceeds from issuance of common stock				$ 25,000,000
Issuance fees and expenses				$ 300,000
Common Stock | Sales Agreement
Class of Stock [Line Items]
Number of shares issued and sold (in shares)							0
Remaining amount available	$ 140,300,000						$ 140,300,000	$ 140,300,000
Common Stock | The 2020 Plan
Class of Stock [Line Items]
Shares authorized to be issued under plan (in shares)						5,600,000
Percent of common stock outstanding used as threshold to calculate shares available for issuance						5%
Common Class B | The 2020 Plan | Maximum
Class of Stock [Line Items]
Shares authorized to be issued under plan (in shares)						1,250,000
Stock options
Class of Stock [Line Items]
Generally expected vesting term of the option contract (in years)								10 years
Expected dividend yield								0%	0%	0%
Unvested RSAs
Class of Stock [Line Items]
Grant date fair value of shares vested								$ 700,000	$ 1,000,000	$ 1,700,000
Fair value of vested shares								2,700,000	8,300,000	21,000,000
Unvested RSUs
Class of Stock [Line Items]
Grant date fair value of shares vested								9,700,000	4,600,000	12,700,000
Fair value of vested shares								$ 7,700,000	$ 7,300,000	$ 26,400,000
Employee Stock Purchase Plan
Class of Stock [Line Items]
Expected dividend yield								0%	0%	0%
ESPP, maximum percent of compensation to contribute	20%						20%	20%
ESPP, maximum contribution amount								$ 21,250
ESPP, purchase price of common stock, percent of market price								85%
ESPP, offering period (in months)								6 months
Employee Stock Purchase Plan | Amended 2020 ESPP
Class of Stock [Line Items]
ESPP, shares in ESPP reserve											2,000,000
Employee Stock Purchase Plan | 2020 ESPP
Class of Stock [Line Items]
Number of shares reserved for future issuance (in shares)	1,913,160						1,913,160	1,913,160

Stockholders' Equity - Share-ba

Stockholders' Equity - Share-based Compensation Related to Share Based Awards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 54,822	$ 46,840	$ 35,737
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	24,519	20,439	14,879
General and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 30,303	$ 26,401	$ 20,858

Stockholders' Equity - Share-_2

Stockholders' Equity - Share-based Compensation Expense by Type of Share-based Awards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 54,822	$ 46,840	$ 35,737
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	41,642	36,338	20,773
RSAs and RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	12,816	10,075	14,643
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 364	$ 427	$ 321

Stockholders' Equity - Unrecogn

Stockholders' Equity - Unrecognized Compensation Cost (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options	$ 92,129
Remaining Weighted-Average Recognition Period (Years)	2 years 8 months 12 days
RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized expense, other than stock options	$ 1
Remaining Weighted-Average Recognition Period (Years)	0 years
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized expense, other than stock options	$ 20,699
Remaining Weighted-Average Recognition Period (Years)	2 years 6 months

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Option Activity (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
Stock Option Activity
Outstanding at the beginning of the period (in shares) | shares	8,051,459
Options granted (in shares) | shares	3,772,345
Options exercised (in shares) | shares	(54,324)
Options cancelled (in shares) | shares	(1,752,045)
Outstanding at the ending of the period (in shares) | shares	10,017,435
Stock Options Weighted Average Exercise Price
Options outstanding, weighted average grant date fair value beginning of the period (in dollars per share) | $ / shares	$ 29.97
Options granted (in dollars per share) | $ / shares	22.17
Options exercised (in dollars per share) | $ / shares	18.31
Options cancelled (in dollars per share) | $ / shares	32.82
Options outstanding, weighted average grant date fair value ending of the period (in dollars per share) | $ / shares	$ 26.59
Stock Option Activity, Additional Disclosures
Options outstanding, weighted average remaining contractual term (in years)	7 years 9 months 18 days
Options outstanding, aggregate intrinsic value | $	$ 160
Options vested and expected to vest, number of options (in shares) | shares	10,017,435
Options vested and expected to vest, weighted average exercise price per share (in dollars per share) | $ / shares	$ 26.59
Options vested and expected to vest, weighted average remaining contractual term (in years)	7 years 9 months 18 days
Options vested and expected to vest, aggregate intrinsic value | $	$ 160
Options exercisable, number of options (in shares) | shares	4,086,661
Options exercisable, weighted average exercise price per share (in dollars per share) | $ / shares	$ 27.91
Options exercisable, weighted average remaining contractual term (in years)	6 years 7 months 6 days
Options exercisable, aggregate intrinsic value | $	$ 0

Stockholders' Equity - Fair Val

Stockholders' Equity - Fair Value Assumptions for Stock Options (Details) - Total share-based compensation expense	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected dividend yield	0%	0%	0%
Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected volatility	73.50%	73.60%	73.20%
Average expected term (in years)	5 years 6 months	6 years	5 years 2 months 12 days
Risk-free interest rate	3.40%	1.50%	0.50%
Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected volatility	80.80%	80.50%	76.60%
Average expected term (in years)	6 years 1 month 6 days	6 years 6 months	6 years 1 month 6 days
Risk-free interest rate	4.70%	4.20%	1.30%

Stockholders' Equity - Equity i

Stockholders' Equity - Equity instruments Other than Options (Details)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Restricted Stock Awards (RSAs)
Activity
Outstanding at the beginning of the period (in shares) | shares	125,506
Vested (in shares) | shares	(120,102)
Forfeited (in shares) | shares	(4,455)
Outstanding at the end of the period (in shares) | shares	949
Weighted Average Grant Date Fair Value
Outstanding, weighted average grant date fair value at the beginning of the period (in dollars per share) | $ / shares	$ 5.45
Vested (in dollars per share) | $ / shares	5.53
Forfeited (in dollars per share) | $ / shares	3.30
Outstanding, weighted average grant date fair value at the end of the period (in dollars per share) | $ / shares	$ 4.61
RSUs
Activity
Outstanding at the beginning of the period (in shares) | shares	922,901
Granted (in shares) | shares	968,823
Vested (in shares) | shares	(360,555)
Forfeited (in shares) | shares	(312,354)
Outstanding at the end of the period (in shares) | shares	1,218,815
Weighted Average Grant Date Fair Value
Outstanding, weighted average grant date fair value at the beginning of the period (in dollars per share) | $ / shares	$ 27.48
Granted, (in dollars per share) | $ / shares	22.94
Vested (in dollars per share) | $ / shares	27.02
Forfeited (in dollars per share) | $ / shares	25.88
Outstanding, weighted average grant date fair value at the end of the period (in dollars per share) | $ / shares	$ 24.56

Stockholders' Equity - Fair V_2

Stockholders' Equity - Fair Value Assumptions for Employee Stock Purchase Plan (Details) - Employee Stock Purchase Plan	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Volatility	85.80%	74%	48.20%
Expected term (years)	6 months	6 months	6 months
Risk free rate	4.80%	1.60%	0.10%
Expected dividend yield	0%	0%	0%

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Thousands	1 Months Ended				12 Months Ended
	Dec. 31, 2023 ft²	Sep. 30, 2021 ft² option	Mar. 31, 2021 ft² option	Sep. 30, 2020 ft²	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease right-of-use asset and fixed asset impairment | $					$ 4,953	$ 0	$ 0
Sublease income | $					900
Operating lease, rent expense | $					6,900	7,000	2,700
Operating lease payments | $					$ 6,400	$ 2,500	$ 1,300
San Diego | Building
Lessee, Lease, Description [Line Items]
Area of leased space (in square feet) | ft²				117,900
Reduction due to amendment (in square feet) | ft²		43,200
Potential annual increase to lease rent		0.030
Number of renewal options | option		2
Operating lease, renewal term (in years)		5 years
San Diego | Temporary Leased Building
Lessee, Lease, Description [Line Items]
Area of leased space (in square feet) | ft²		13,200
New York | Building
Lessee, Lease, Description [Line Items]
Area of leased space (in square feet) | ft²	4,115		31,362
Potential annual increase to lease rent	0.025		0.081
Number of renewal options | option			1
Operating lease, renewal term (in years)			5 years
Anniversary year of potential rent increase post commencement date			6 years

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Operating Lease Terms (Details)	Dec. 31, 2023
Commitments and Contingencies Disclosure [Abstract]
Weighted average remaining lease term (in years)	8 years 8 months 12 days
Weighted average discount rate	9%

Commitments and Contingencies_3

Commitments and Contingencies - Future Minimum Operating Lease Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
2024	$ 6,643
2025	7,002
2026	7,487
2027	7,606
2028	7,760
Thereafter	31,018
Total minimum lease payments:	67,516
Less: imputed interest	21,743
Total operating lease liabilities	45,773
Less: current portion	2,623	$ 2,162
Lease liability, net of current portion	$ 43,150	$ 45,166

Income Taxes - Net Loss Before

Income Taxes - Net Loss Before Taxes And Loss on Equity Method Investment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
U.S. net loss before income taxes	$ (293,284)	$ (237,926)	$ (171,053)
Foreign net income (loss) before income taxes	378	344	4,663
Net loss before income taxes, including loss on equity method investment	$ (292,906)	$ (237,582)	$ (166,390)

Income Taxes - Provision_Benefi

Income Taxes - Provision/Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current tax provision:
Federal	$ 0	$ 0	$ 0
State	41	11	11
Foreign	249	298	550
Total current tax provision	290	309	561
Deferred tax provision:
Federal	(891)	(683)	(120)
State	0	(41)	(736)
Foreign	0	(54)	(2)
Total deferred tax provision	(891)	(778)	(858)
Total provision for income taxes:	$ (601)	$ (469)	$ (297)

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Effective Income Tax Rate Reconciliation, Amount
Expected tax at 21%	$ (61,509)	$ (49,892)	$ (34,941)
State income tax, net of federal tax	(2,384)	(4,222)	(931)
Research credits	(2,031)	(12,558)	(6,938)
Share-based compensation	3,008	1,245	(3,307)
Deemed royalty	8,263	0	0
Other	586	(2,799)	939
Section 162(m) limitations	5,028	3,950	3,982
Effective Tax Rate Change	(10,420)	0	0
Change in valuation allowance	58,858	63,807	40,899
Total provision for income taxes:	$ (601)	$ (469)	$ (297)
Effective Income Tax Rate Reconciliation, Percent
Expected tax at 21%	21%	21%	21%
State income tax, net of federal tax	0.80%	1.80%	0.60%
Research credits	0.70%	5.30%	4.20%
Share-based compensation	(1.00%)	(0.50%)	2%
Deemed royalty	(2.80%)	0%	0%
Other	(0.20%)	1.20%	(0.60%)
Section 162(m) limitations	(0.017)	(0.017)	(0.024)
Effective Tax Rate Change	3.60%	0%	0%
Change in valuation allowance	(20.10%)	(26.90%)	(24.60%)
Provision for income taxes	0.20%	0.20%	0.20%

Income Taxes - Net Deferred Tax

Income Taxes - Net Deferred Tax Asset or Liability (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets
Net operating loss	$ 96,676	$ 95,392
Compensation	2,451	1,937
Share-based compensation	11,486	7,735
ASC 842 lease liability	11,131	9,967
Intangibles	11,185	1,745
Capitalized research and experimental expenditures	66,500	30,776
Accrued liabilities	1,163	476
Research credits	29,055	27,024
Other	22	62
Total gross deferred tax assets	229,669	175,114
Valuation allowance	(219,292)	(160,967)
Net deferred tax assets	10,377	14,147
Deferred tax liabilities
Depreciable assets	(1,108)	(1,609)
ASC 842 right of use asset	(8,734)	(8,924)
Equity method investment	0	(4,467)
Other	(497)	0
Deferred tax liabilities	(10,339)	(15,000)
Net deferred tax assets	$ 38
Net deferred tax liabilities		$ (853)

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Operating Loss Carryforwards [Line Items]
Deferred tax assets, valuation allowance	$ 219,292,000	$ 160,967,000
Unrecognized tax benefits that would not impact effective tax rate	3,900,000
Accrued interest and penalties associated with uncertain tax positions	0	$ 0
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	396,100,000
Net operating loss carryforwards, not subject to expiration	375,200,000
Federal and state research tax credit carryforwards, net of reserves	23,000,000
Net operating loss carryforwards, subject to expiration	20,900,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	193,000,000
Federal and state research tax credit carryforwards, net of reserves	$ 7,100,000

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits at the beginning of the year	$ 4,297	$ 2,835	$ 1,932
Increase related to current year tax positions	857	1,112	969
Increase related to prior year tax positions	0	350	0
Decrease related to prior year tax positions	(940)	0	(66)
Gross unrecognized tax benefits at end of the year	$ 4,214	$ 4,297	$ 2,835

Net Loss Per Common Share - Cal

Net Loss Per Common Share - Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net loss attributable to Zentalis	$ (292,191)	$ (236,806)	$ (158,725)
Denominator:
Weighted average number of common shares outstanding, basic (in shares)	65,409	52,857	42,688
Weighted average number of common shares outstanding, diluted (in shares)	65,409	52,857	42,688
Net loss per common share, basic (in dollars per share)	$ (4.47)	$ (4.48)	$ (3.72)
Net loss per common share, diluted (in dollars per share)	$ (4.47)	$ (4.48)	$ (3.72)

Net Loss Per Common Share - Ant

Net Loss Per Common Share - Antidilutive Securities (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per unit (in shares)	11,237	9,100	4,538
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per unit (in shares)	10,017	8,051	3,121
Unvested RSAs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per unit (in shares)	1	126	742
Unvested RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per unit (in shares)	1,219	923	675

Employee Savings Plan (Details)

Employee Savings Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Retirement Benefits [Abstract]
Matching contributions made by employer for savings plan	$ 1.5	$ 1.4	$ 1

Related Party Disclosures (Deta

Related Party Disclosures (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022	Dec. 31, 2021	Jun. 15, 2023
Zentera
Related Party Transaction [Line Items]
Ownership percentage sold				40.30%
Related Party | Zentera
Related Party Transaction [Line Items]
Ownership percentage sold				40.30%
Contra-research and development expense	$ 3.5	$ 11	$ 5.3
Related Party | Master Services Agreement
Related Party Transaction [Line Items]
Due to related parties	$ 0.5	$ 0.2	$ 1

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent Event - Immunome, Inc $ in Millions	Jan. 05, 2024 USD ($)
Subsequent Event [Line Items]
Upfront payment received	$ 35
Licensing arrangements, milestone payments to be received, up to	$ 275