Oncternal Therapeutics (ONCT) 10-K 11 Mar 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Mar. 03, 2021	Jun. 30, 2020
Cover [Abstract]
Entity Registrant Name	Oncternal Therapeutics, Inc.
Entity Central Index Key	0001260990
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	ONCT
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		49,281,327
Entity Public Float			$ 27.2
Entity File Number	000-50549
Entity Tax Identification Number	62-1715807
Entity Address, Address Line One	12230 El Camino Real
Entity Address, Address Line Two	Suite 300
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92130
City Area Code	858
Local Phone Number	434-1113
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
ICFR Auditor Attestation Flag	false
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the Registrant’s proxy statement to be filed with the Securities and Exchange Commission pursuant to Regulation 14A in connection with the Registrant’s 2021 Annual Meeting of Stockholders, which will be filed subsequent to the date hereof, are incorporated by reference into Part III of this Form 10-K. Such proxy statement will be filed with the Securities and Exchange Commission not later than 120 days following the end of the Registrant’s fiscal year ended December 31, 2020.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 116,737	$ 20,051
Prepaid and other	1,266	736
Total current assets	118,003	20,787
Right-of-use asset	40	190
Other assets	766	767
Total assets	118,809	21,744
Current liabilities:
Accounts payable	1,143	871
Accrued liabilities	3,042	2,731
Deferred grant revenue	1,633	3,640
Lease, current	40	99
Total current liabilities	5,858	7,341
Lease, net of current		91
Commitments and contingencies (Note 3)
Stockholders’ equity:
Preferred stock, $0.001 par value, authorized shares – 5,000 and none at December 31, 2020 and 2019, respectively; issued and outstanding shares – none
Common stock, $0.001 par value; authorized shares – 60,000 at December 31, 2020 and 2019, respectively; issued and outstanding shares – 48,802 and 15,387 at December 31, 2020 and 2019, respectively	49	15
Additional paid-in capital	195,699	79,869
Accumulated deficit	(82,797)	(65,572)
Total stockholders’ equity	112,951	14,312
Total liabilities and stockholders’ equity	$ 118,809	$ 21,744

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	48,802,000	15,387,000
Common stock, shares outstanding	48,802,000	15,387,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Grant revenue	$ 3,375	$ 2,425
Operating expenses:
Research and development	12,544	10,159
In-process research and development		18,088
General and administrative	8,373	7,286
Total operating expenses	20,917	35,533
Loss from operations	(17,542)	(33,108)
Other income (expense):
Change in fair value of warrant liability		(1,268)
Other income	301
Interest income	16	188
Total other income (expense)	317	(1,080)
Net loss	$ (17,225)	$ (34,188)
Net loss per share, basic and diluted	$ (0.85)	$ (3.31)
Weighted-average shares outstanding, basic and diluted	20,305	10,329

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (17,225)	$ (34,188)
Adjustments to reconcile net loss to net cash used in operating activities:
In-process research and development		18,088
Gain on forgiveness of payroll protection program loan	(301)
Stock-based compensation	1,556	507
Change in fair value of preferred stock warrants liability		1,268
Noncash lease expense	150	92
Changes in operating assets and liabilities:
Prepaid and other assets	(529)	(44)
Accounts payable	272	(4,762)
Accrued liabilities	739	(1,255)
Change in lease liability	(150)	(92)
Deferred grant revenue	(2,007)	3,640
Net cash used in operating activities	(17,495)	(16,746)
Cash flows from investing activities
Cash acquired in connection with the Merger		18,292
Acquisition related costs paid		(2,155)
Net cash provided by investing activities		16,137
Cash flows from financing activities
Proceeds from payroll protection loan	301
Proceeds from exercise of stock options and common stock warrants	4	15
Proceeds from the issuance of common stock and common stock warrants, net	113,876
Net cash provided by financing activities	114,181	15
Net increase (decrease) increase in cash and cash equivalents	96,686	(594)
Cash and cash equivalents at beginning of period	20,051	20,645
Cash and cash equivalents at end of period	116,737	20,051
Supplemental disclosure of non-cash investing and financing activities:
Payment of 2019 bonus awards with stock options in lieu of cash	415
Fair value of warrants issued to placement agent	5,325
Gain on forgiveness of payroll protection program loan	$ 301
Conversion of convertible preferred stock into common stock		46,588
Reclassification of preferred stock warrants liability to additional paid-in capital		1,942
Net liabilities assumed in Merger		5,177
GTx Inc.
Supplemental disclosure of non-cash investing and financing activities:
Payment of 2019 bonus awards with stock options in lieu of cash		$ 29,049

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Convertible preferred stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at Dec. 31, 2018	$ (29,631)		$ 5	$ 1,748	$ (31,384)
Balance (in shares) at Dec. 31, 2018		8,148,000
Balance at Dec. 31, 2018		$ 46,588
Balance (in shares) at Dec. 31, 2018			3,762
Exercise of stock options for cash	14			14
Exercise of stock options for cash (in shares)			19
Exercise of warrants for cash	1			1
Vesting related to repurchase liability	30			30
Issuance of common stock to former stockholders of GTx upon Merger	29,049		$ 2	29,047
Issuance of common stock to former stockholders of GTx upon Merger (in shares)			3,458
Conversion of convertible preferred stock into common stock upon Merger	46,588		$ 8	46,580
Conversion of convertible preferred stock into common stock upon merger (in shares)		(8,148)
Conversion of convertible preferred stock into common stock upon Merger		$ (46,588)
Conversion of convertible preferred stock into common stock upon Merger (in shares)			8,148
Reclassification of convertible preferred stock warrant liability	1,942			1,942
Stock-based compensation	507			507
Net loss	(34,188)				(34,188)
Balance at Dec. 31, 2019	$ 14,312		$ 15	79,869	(65,572)
Balance (in shares) at Dec. 31, 2019	15,387,000		15,387
Exercise of stock options for cash	$ 4		$ 5	4
Exercise of stock options for cash (in shares)	5,135
Cashless exercise of warrants			36
Vesting related to repurchase liability	$ 13			13
Issuance of common stock, net of issuance cost	113,876		$ 34	113,842
Issuance of common stock, net of issuance cost (in shares)			33,374
Issuance of 2019 bonus awards with stock option in lieu ofcash	415			415
Stock-based compensation	1,556			1,556
Net loss	(17,225)				(17,225)
Balance at Dec. 31, 2020	$ 112,951		$ 49	$ 195,699	$ (82,797)
Balance (in shares) at Dec. 31, 2020	48,802,000		48,802

Condensed Consolidated Statemen

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)
Statement Of Stockholders Equity [Abstract]
Common stock and common stock warrants, issuance cost	$ 11,103

Description of Business, Basis

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business, Basis of Presentation and Summary of Significant Accounting Policies	1. Description of Basis of of Policies Description of Business Oncternal Therapeutics, Inc. (the “Company,” “Oncternal,” or the “combined company”), formerly known as GTx, Inc., was incorporated in Tennessee in September 1997 and reincorporated in Delaware in 2003 and is based in San Diego, California. The Company is a clinical-stage biopharmaceutical company focused on the development of novel oncology therapies for the treatment of cancers with critical unmet medical need. The Company’s clinical pipeline includes cirmtuzumab, a humanized monoclonal antibody that binds to ROR1 (Receptor-tyrosine kinase-like Orphan Receptor 1), and TK216, a small molecule inhibiting the biological activity of ETS-family transcription factor oncoproteins. The Company is also developing a CAR-T (chimeric antigen receptor T-cells) product candidate that targets ROR1. Merger On June 7, 2019, the Company, then operating as GTx, Inc. (“GTx”), completed its Agreement and Plan of Merger and Reorganization, as amended (the “Merger Agreement”), with privately-held Oncternal Therapeutics, Inc. (“Private Oncternal”) and Grizzly Merger Sub, Inc., a wholly-owned subsidiary of the Company (“Merger Sub”), dated March 6, 2019. Under the Merger Agreement, Merger Sub merged with and into Private Oncternal, with Private Oncternal surviving as a wholly-owned subsidiary of the Company (the “Merger”). GTx changed its name to Oncternal Therapeutics, Inc., and Private Oncternal, which remains as a wholly-owned subsidiary of the Company, changed its name to Oncternal Oncology, Inc. On June 10, 2019, the combined company’s common stock began trading on The Nasdaq Capital Market under the ticker symbol “ONCT.” Except as otherwise indicated, references herein to “Oncternal,” “the Company,” and the “combined company,” refer to Oncternal Therapeutics, Inc. on a post-Merger basis, and the term “Private Oncternal” refers to the business of privately-held Oncternal Therapeutics, Inc., prior to completion of the Merger. References to GTx refer to GTx, Inc. prior to completion of the Merger. Pursuant to the terms of the Merger Agreement, each outstanding share of Private Oncternal common stock outstanding immediately prior to the closing of the Merger was converted into approximately 0.073386 shares of Company common stock (the “Exchange Ratio”), after taking into account the Reverse Stock Split, as defined below. Immediately prior to the closing of the Merger, all shares of Private Oncternal preferred stock then outstanding were exchanged into shares of common stock of Private Oncternal. In addition, all outstanding options exercisable for common stock of Private Oncternal and warrants exercisable for convertible preferred stock of Private Oncternal became options and warrants exercisable for the same number of shares of common stock of the Company multiplied by the Exchange Ratio. Immediately following the Merger, stockholders of Private Oncternal owned approximately 77.5% of the outstanding common stock of the combined company. The transaction was accounted for as a reverse asset acquisition in accordance with generally accepted accounting principles in the United States of America (“GAAP”). Under this method of accounting, Private Oncternal was deemed to be the accounting acquirer for financial reporting purposes. This determination was primarily based on the facts that, immediately following the Merger: (i) Private Oncternal’s stockholders owned a substantial majority of the voting rights in the combined company, (ii) Private Oncternal designated a majority of the members of the initial board of directors of the combined company, and (iii) Private Oncternal’s senior management holds all key positions in the senior management of the combined company. As a result, as of the closing date of the Merger, the net assets of the Company were recorded at their acquisition-date relative fair values in the consolidated financial statements of the Company and the reported operating results prior to the Merger are those of Private Oncternal. Reverse Stock Split and Exchange Ratio On June 7, 2019, in connection with, and prior to the completion of, the Merger, GTx effected a one-for-seven reverse stock split of its then outstanding common stock (the “Reverse Stock Split”). The par value and the authorized shares of the common stock were not adjusted as a result of the Reverse Stock Split. All of the Company’s issued and outstanding common stock have been retroactively adjusted to reflect this Reverse Stock Split for all periods presented. All issued and outstanding Private Oncternal common stock, preferred stock, options and warrants prior to the effective date of the Merger have been retroactively adjusted to reflect the Exchange Ratio for all periods presented. Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Oncternal Oncology, Inc. and Oncternal, Inc. All intercompany accounts and transactions have been eliminated in the preparation of the consolidated financial statements. Liquidity and Going Concern From inception, the Company has devoted substantially all of its efforts to drug discovery and development and conducting preclinical studies and clinical trials. The Company has a limited operating history and the sales and income potential of the Company’s business and market are unproven. Successful transition to attaining profitable operations is dependent upon achieving a level of revenues adequate to support the Company’s cost structure. As of December 31, 2020, the Company had $116.7 million in cash and cash equivalents. The Company believes it has sufficient cash to fund its projected operating requirements for at least twelve months from the date of issuance Use of Estimates The Company’s consolidated financial statements accordance GAAP. of the Company’s consolidated financial statements and accompanying notes and assumptions that impact the amounts of liabilities, revenues and expenses and the disclosure of contingent and liabilities. Significant consist of those the value of the Company’s stock, stock liability , and those revenue and and development Although these on the Company’s knowledge of events and actions undertake the actual ultimately these and assumptions. Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. Cash and cash equivalents include cash in readily available checking accounts and money market accounts. Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institution in which those deposits are held. Additionally, the Company established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity. Patent Costs Costs related to filing and pursuing patent applications are recorded as general and administrative expense and expensed as incurred since recoverability of such expenditures is uncertain. Research and Development Expenses and Accruals Research and development expenses consist of costs incurred for the Company’s own and for sponsored and collaborative research and development activities. Research and development costs are expensed as incurred and include manufacturing process development costs, manufacturing costs, costs associated with preclinical studies and clinical trials, regulatory and medical affairs activities, quality assurance activities, salaries and benefits, including stock-based compensation, fees paid to third-party consultants, license fees and overhead. The Company has entered into various research and development contracts with research institutions, clinical research organizations, clinical manufacturing organizations and other companies. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and payments made in advance of performance are reflected in the accompanying consolidated balance sheets as prepaid and other assets or accrued liabilities. The Company records accruals for estimated costs incurred for ongoing research and development activities. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the services, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the prepaid or accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. As of December 31, 2020, the Company’s clinical trial accrual balance of $1.0 million is included in accrued liabilities and other liabilities. The Company’s related 2020 clinical trial expenses are included in research and development expense of $12.5 million. Preferred Stock Warrant Liability Prior to the Merger, Private Oncternal had outstanding freestanding warrants to purchase shares of its Series B-2 convertible preferred stock (the “Series B-2 warrants”). Private Oncternal adjusted the carrying value of such Series B-2 warrants to their estimated fair value at each reporting date, with any related increases or decreases in the fair value recorded as a change in fair value of warrant liability in the consolidated statements of operations. Upon the completion of the Merger, the Series B-2 warrants were amended such that they were converted into warrants to purchase the Company’s common stock. As amended, warrant liability accounting is no longer required and the fair value of the warrant liability has been reclassified into stockholders’ equity. Fair Value Measurements The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or non-recurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1: Observable inputs such as quoted prices in active markets. Level 2: Inputs, other than the quoted prices in active markets that are observable either directly or indirectly. Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. The carrying amounts of the Company’s current financial assets and liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments. The Company has no financial assets or liabilities measured at fair value on a recurring basis. No transfers between levels have occurred during the periods presented. Revenue Recognition The Company currently generates revenue from the California Institute for Regenerative Medicine pursuant to a research subaward agreement (see Note 4), which provides the Company with payments in return for certain research and development activities over a contractually defined period. Revenue from such subaward is recognized in the period during which the related qualifying services are rendered and costs are incurred, provided that the applicable conditions under the subaward agreement have been met. The subaward agreement is on a best-effort basis and does not require scientific achievement as a performance obligation. All fees received under the agreement are non-refundable. The costs associated with the agreement are expensed as incurred and reflected as a component of research and development expense in the accompanying consolidated statements of operations. Funds received from the subaward agreement are recorded as revenue as the Company is the principal participant in the arrangement because the activities under the subaward are part of the Company’s development programs. In those instances where the Company first receives consideration in advance of providing underlying services, the Company classifies such consideration as deferred revenue until (or as) the Company provides the underlying services. In those instances where the Company first provides the underlying services prior to its receipt of consideration, the Company records a grant receivable. At December 31, 2020 and 2019, the Company had deferred grant revenue of $1.6 Stock-Based Compensation Stock-based compensation expense represents the fair value of equity awards, on the grant date, recognized in the period using the Black- Scholes option pricing model. The Company recognizes expense for awards with graded vesting schedules over the requisite service period of the awards (usually the vesting period) on a straight-line basis. For equity awards for which vesting is subject to performance-based milestones, the expense is recorded over the remaining service period after the point when the achievement of the milestone is probable. The Company recognizes forfeitures for all awards as such forfeitures occur. Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment in the United States. Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration for potentially dilutive securities and adjusted for the weighted-average number of common shares outstanding that are subject to repurchase. The Company has excluded weighted-average shares subject to repurchase of 25,000 shares and 56,000 shares from the weighted-average number of common shares outstanding for the years ended December 20 9 Potentially dilutive securities not included in the calculation of diluted net loss per share, because to do so would be anti-dilutive, are as follows (in common stock equivalent shares; in thousands): December 31, 2020 2019 Warrants to purchase common stock 5,032 841 Common stock options 2,226 1,958 Common stock subject to repurchase 15 35 7,273 2,834 Recently Issued Accounting Pronouncements In August 2020, the FASB issued ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity, which simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts on an entity’s own equity. Specifically, ASU 2020-06 simplifies accounting for the issuance of convertible instruments by removing major separation models required under current GAAP. In addition, the ASU removes certain settlement conditions that are required for equity contracts to qualify for the derivative scope exception and simplifies the diluted earnings per share (EPS) calculation in certain areas. ASU 2020-06 will be effective for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted, beginning in fiscal years which begin after December 15, 2020. The FASB has specified that an entity should adopt the guidance as of the beginning of its annual fiscal year. The Company is currently evaluating the impact of the pending adoption of this new standard on its consolidated financial statements. Recently Adopted Accounting Pronouncements In December 2019, the FASB issued ASU 2019-12, Income Taxes: Simplifying the Accounting for Income Taxe In August 2018, the FASB issued ASU Fair Value Measurement: Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement, the adoption had no impact on the consolidated financial statements

Balance Sheet Details

Balance Sheet Details	12 Months Ended
	Dec. 31, 2020
Payables And Accruals [Abstract]
Balance Sheet Details	2. Balance Sheet Details Accrued liabilities consist of the following (in thousands): December 31, 2020 2019 Research and development $ 412 $ 582 Clinical trials 980 624 Legal fees 77 424 Unvested share liability 10 24 Compensation 1,528 825 Other 35 252 $ 3,042 $ 2,731

Commitments, Contingencies and

Commitments, Contingencies and Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments, Contingencies and Related Party Transactions	3. Commitments, Contingencies and Related Party Transactions Lease Rent expense was $0.2 million and $0.1 million for the years ended December 31, 2020 and 2019, respectively. On May 22, 2019, the Company entered into an office sublease agreement for 4,677 square feet in San Diego, California (“San Diego Lease”) which expires on March 31, 2021. Base rent is approximately $166,000 annually and the monthly rent expense is being recognized on a straight-line basis over the lease term. The San Diego Lease is included in the accompanying consolidated balance sheet at the present value of the lease payments. As the San Diego Lease does not have an implicit interest rate, the present value reflects a 10.0% discount rate which is the estimated rate of interest that the Company would have to pay in order to borrow an amount equal to the lease payments on a collateralized basis over a similar term and in a similar economic environment. The Company recognized a net operating lease right-of-use asset and a lease liability of $40,000 that matures in March 2021, as of December 31, 2020, in the accompanying consolidated balance sheet. The weighted average remaining lease term was 0.25 years. Related Party Transactions In January 2019, the Company engaged Newfront Insurance as its primary insurance broker. The son of Richard Vincent, the Company’s Chief Financial Officer, acted as the Company’s agent at Newfront Insurance. During the years ended December 31, 2020 and 2019, the Company paid total related policy premiums of $1.4 million and $1.2 million, respectively, for which Mr. Vincent’s son received a commission of approximately $0.1 million in each respective period. Effective in September 2019, the Company and Shanghai Pharmaceutical (USA) Inc. (“SPH USA”) entered into a Materials Supply and Services Agreement (“SPH USA Services Agreement”), pursuant to which the Company and SPH USA will execute various statements of work for the transfer to SPH USA of key reagents and other materials, and for the supply of certain services by the Company to SPH USA, as contemplated under and in furtherance of the License and Development Agreement between the Company and SPH USA effective as of November 2018. During the year ended December 31, 2020, the Company recorded amounts receivable from SPH USA related to statements of work totaling $0.3 million (see Note 4). In connection with the securities purchase agreements and underwritten offering, other investors included individuals or entities affiliated with David F. Hale, SPH USA, Daniel L. Kisner, Hazel M. Aker, and Michael G. Carter (see Note 7).

License, Collaboration and Rese

License, Collaboration and Research Subaward Agreements	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
License, Collaboration and Research Subaward Agreements	4. License, Collaboration and Research Subaward Agreements Georgetown University (“Georgetown”) In March 2014, the Company entered into an Exclusive License Agreement (the “Georgetown License Agreement”) with Georgetown, pursuant to which the Company: (i) licensed the exclusive worldwide right to patents and technologies for the development and commercialization of certain product candidates targeting EWS-FLI1 as an anti-tumor therapy for therapeutic, diagnostics, or research tool purposes, (ii) is solely responsible for all development and commercialization activities and costs, and (iii) is responsible for all costs related to the filing, prosecution and maintenance of the licensed patent rights. Under the terms of the Georgetown License Agreement, commencing in 2015, the Company: (i) shall pay and has paid an annual license maintenance fee of $10,000 until the first commercial sale occurs, (ii) is required to make up to $0.2 million in aggregate milestone payments upon the achievement of certain regulatory milestones, and (iii) will be required to pay low single digit royalties based on annual net product sales. The Company accounted for the licensed technology as an asset acquisition because it did not meet the definition of a business. All milestone payments under the Georgetown License Agreement will be recognized as research and development expense upon completion of the required events, as the triggering events are not considered to be probable until they are achieved. As of December 31, 2020, the Company had not triggered or made any milestone payments under the Georgetown License Agreement. The Georgetown License Agreement may be terminated by either party upon material breach or may be terminated by the Company as to one or more countries with 90 days written notice of termination. The term of the Georgetown License Agreement will continue until the expiration of the last valid claim within the patent rights covering the product. Georgetown may terminate the agreement in the event: (i) the Company fails to pay any amount and fails to cure such failure within 30 days after receipt of notice, (ii) the Company defaults in its obligation to obtain and maintain insurance and fails to remedy such breach within 60 days after receipt of notice, or (iii) the Company declares insolvency or bankruptcy. The Company may terminate the Georgetown License Agreement at any time upon at least 60 days’ written notice. The University of Texas MD Anderson Cancer Center (“MD Anderson”) In December 2014, the Company entered into a collaboration agreement (as amended, the “Collaboration”) with MD Anderson, which provides for the conduct of preclinical and clinical research for TK216 in exchange for certain program payments. If MD Anderson successfully completes all the requirements of the Collaboration in full and the program is successfully commercialized, the Company will be required to pay aggregate milestone payments of $1.0 million based on net product sales. In July 2020, the Company entered into a research agreement with MD Anderson for certain services up to an aggregate cost of $ 293,000 . The amount recorded as research and development expense for the year ended December 31, 2020 was $ 122,000 and the amount was insignificant for the year ended December 31, 2019. Agreements with the Regents of the University of California (the “Regents”) In March 2016, and as amended and restated in August 2018 in connection with the spin-off transactions described below, the Company entered into a license agreement (as amended, the “Regents License Agreement”) for the development, manufacturing and distribution rights related to the development and commercialization of ROR1 related naked antibodies, antibody fragments or synthetic antibodies, and genetically engineered cellular therapy. The Regents License Agreement was amended on March 25, 2019 and May 15, 2019, to update the patents covered under the agreement. The Regents License Agreement provides for the following: (i) in May 2016, an upfront license fee of $0.5 million was paid and 107,108 shares of common stock were issued, (ii) $25,000 in annual license maintenance fees commencing in 2017, (iii) reimbursement of certain annual patent costs, (iv) certain development and regulatory milestones aggregating from $10.0 million to $12.5 million, on a per product basis, (v) certain worldwide sales milestones based on achievement of tiered revenue levels aggregating $75.0 million, (vi) low single-digit royalties, including potential future minimum annual royalties, on net sales of each target, and (vii) minimum diligence to advance licensed assets consisting of at least $1.0 million in development spend annually through 2021. Under the Regents License Agreement, the Company recorded: (i) $25,000 in license maintenance and development expense for each of the approximately patent costs and administrative expense In July 2016, and as modified by the amended and restated Regents License Agreement in August 2018, the Company entered into a Research Agreement (the “Research Agreement”) with the Regents for further research on a ROR1 therapeutic development program. Under this five-year The Regents may terminate the Regents License Agreement if: (i) a material breach by the Company is not cured within a reasonable time, (ii) the Company files a claim asserting the Regents licensed patent rights are invalid or unenforceable and (iii) the Company files for bankruptcy. The Company may terminate the agreement at any time upon at least 60 days’ written notice. University of Tennessee Research Foundation (“UTRF”) In March 2015, the Company and UTRF entered into a license agreement (the “SARD License Agreement”) pursuant to which the Company was granted exclusive worldwide rights in all existing selective androgen receptor degrader (“SARD”) technologies owned or controlled by UTRF, including all improvements thereto. Under the SARD License Agreement, the Company is obligated to employ active, diligent efforts to conduct preclinical research and development activities for the SARD program to advance one or more lead compounds into clinical development. The Company is also obligated to pay UTRF annual license maintenance fees, low single-digit royalties on net sales of products and additional royalties on sublicense revenues, depending on the state of development of a clinical product candidate at the time it is sublicensed. The Company recorded research and development expense under this agreement of $0.2 million and $0.4 million for each of the years ended December 31, 2020 and 2019, respectively. As of December 31, 2020, the Company believes it has met its obligations under the SARD License Agreement. As of December 31, 2020, the Company believes it has met its obligations under each of the UTRF agreements. The California Institute for Regenerative Medicine (“CIRM”) Award In August 2017, and as amended and restated in December 2020, In October 2017, CIRM awarded a $5.8 million grant to the researchers at the University of California San Diego School of Medicine (“UC San Diego”) to develop a novel anti-cancer stem cell targeted therapy for patients with advanced solid and hematological malignancies. In connection with such CIRM award, the Company agreed to provide up to $1.0 million in contingency funds if required during the grant period. The Company recorded no research and development expense, and no contingency funds have been provided under such CIRM award for the years ended December 31, 2020 and 2019. Clinical Trial and Supply Agreement In April 2018, the Company entered into a Clinical Trial and Supply Agreement with Pharmacyclics, LLC, an AbbVie Company (“Pharmacyclics”) to supply ibrutinib for the Company’s Phase 1/2 clinical trial evaluating cirmtuzumab in combination with ibrutinib, which agreement was amended in August 2019. Such agreement does not bear any upfront costs, inventory purchase costs, milestone or royalty payment commitments or other financial obligations. SPH USA, a Related Party License and Development Agreement (“LDA”) In November 2018, and as amended in August 2020, The LDA will expire upon the expiration of the last royalty term for the last licensed product. The LDA may be terminated by: (i) SPH USA on a country by country or product by product basis with 180 days written notice, (ii) either party upon material breach that is not cured within 90 days, and (iii) either the event the other insolvency or bankruptcy.

Debt

Debt	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Debt	5. Debt Paycheck Protection Program Loan Payable In May 2020, the Company received a $0.3 million unsecured loan, bearing interest at 1%, pursuant to the Paycheck Protection Program (the “PPP”), a program implemented by the U.S. Small Business Administration (the “SBA”) under the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) (the “PPP Loan”). In December 2020, the underlying principal and interest were fully forgiven by the SBA and the Company has no further obligations thereunder. The loan forgiveness was recorded as other income of $ 301 k in the statement of operations.

Merger

Merger	12 Months Ended
	Dec. 31, 2020
Merger [Abstract]
Merger	6. Merger The Merger, which closed on June 7, 2019, was accounted for as a reverse asset acquisition, as substantially all of the fair value of the assets acquired were concentrated in a group of similar non-financial assets, and the acquired assets did not have outputs or employees. Because the assets had not yet received regulatory approval, the fair value attributable to these assets of $18.1 million was recorded as in-process research and development expenses in the Company’s consolidated statement of operations in the year ended December 31, 2019. Pursuant to the Merger Agreement on June 7, 2019, the Company, a representative of holders of the contingent value rights (“CVRs”), and Computershare, Inc. as rights agent entered into a Contingent Value Rights Agreement (the “CVR Agreement”). Pursuant to the CVR Agreement, the Company’s stockholders of record as of immediately prior to the Merger received one CVR for each share of the Company’s common stock held immediately prior to the Merger. CVR holders are entitled to receive 75% of the aggregate amount of any net proceeds received by the Company during the 15-year period after the closing of the Merger from the grant, sale or transfer of rights to the Company’s SARD or SARM technology that occurs during the 10-year period after the closing (or in the 11th year if based on a term sheet approved during the initial 10-year period) and, if applicable, to receive royalties on the sale of any SARD or SARM products by the Company during the 15-year period after the closing. Effective in March 2020, the Company terminated the SARM license agreement with UTRF and no longer has any rights to the SARM technology. The CVR Agreement will continue in effect until the payment of all amounts payable thereunder. As of the years ended December 31, 2020 and 2019, no milestones had been accrued as there were no potential milestones yet considered probable. The total purchase price paid in the Merger has been allocated to the net assets acquired and liabilities assumed based on their fair values as of the completion of the Merger. The following summarizes the purchase price paid in the Merger (in thousands, except share and per share amounts): Number of shares of the combined organization owned by the Company’s pre-Merger stockholders 3,458,170 Multiplied by the fair value per share of GTx common stock (1) $ 8.40 Fair value of consideration issued to effect the Merger $ 29,049 Transaction costs 2,154 Purchase price $ 31,203 (1) The allocation of the purchase price is as follows: Cash acquired $ 18,292 Net liabilities assumed (5,177 ) IPR&D (2) 18,088 Purchase price $ 31,203 (2) Represents the research and development projects of GTx which were in-process, but not yet completed, and which the Company plans to advance, consisting primarily of GTx’s preclinical SARD technology. Current alternative future use be allocated a portion of the consideration transferred and charged to expense on the acquisition date. The acquired assets did not have outputs or employees .

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Stockholders' Equity (Deficit)	7. Stockholders’ Equity Amended and Restated Articles of Incorporation On June 7, 2019, the Company’s certificate of incorporation was amended and restated to authorize 60,000,000 shares of common stock and 5,000,000 shares of undesignated preferred stock, each with a par value of $0.001 per share. Convertible Preferred Stock In connection with the Merger, all of the then outstanding shares of Private Oncternal’s convertible preferred stock were converted into 8,148,268 shares of the Company’s common stock. As of December 31, 2018, Private Oncternal’s convertible preferred stock was classified as temporary equity on the accompanying consolidated statements of convertible preferred stock and stockholders’ equity (deficit) Securities Purchase Agreements and In May 2020, the Company entered into a Securities Purchase Agreement (the “Purchase Agreement”) with several institutional and individual investors (including an entity affiliated with David F. Hale, the chairman of the Company’s board of directors) for the concurrent sale of: (i) 1,943,636 shares of the Company’s common stock in a registered direct offering, resulting in net proceeds of $4.4 million, after deducting the placement agent’s cash commissions and other offering expenses, and excluding the proceeds, if any, from the exercise of the warrants, and (ii) unregistered warrants to purchase up to an aggregate of 971,818 shares of common stock. The combined purchase price for one share and one warrant to purchase half of a share of common stock was $2.5725. In addition, the Company issued shares of stock at per share In July 2020, the Company entered into a Securities Purchase Agreement (the “July Purchase Agreement”) with several institutional and individual investors for the concurrent sale of: (i) 2,581,867 shares of the Company’s common stock in a registered direct offering, resulting in net proceeds of $5.7 million, after deducting the placement agent’s cash commissions and other offering expenses, and excluding the proceeds, if any, from the exercise of the warrants, and (ii) unregistered warrants to purchase up to an aggregate of 1,290,933 shares of common stock. The combined purchase price for one share and one warrant to purchase half of a share of common stock was $2.3825. The warrants issued to investors were, subject to certain ownership limitations, immediately exercisable at an exercise price equal to $2.32 per share and expire on January 21, 2026. In addition, the Company issued warrants to purchase 154,912 shares of common stock at an exercise price of $2.9781 per share to the placement agent as part of its compensation, which warrants were immediately exercisable upon issuance and terminate on July 21, 2025. Other investors participating in the July Purchase Agreement included an entity affiliated with SPH USA, the Company’s largest stockholder, Daniel L. Kisner, a member of the Company’s board of directors, and Hazel M. Aker, the Company’s then General Counsel. In August 2020, the Company entered into an underwriting agreement (as amended and restated, the “August Underwriting Agreement”) with Wainwright for the sale of 2,428,886 shares of the Company’s common stock at a price to the public of $2.10 per share, resulting in net proceeds of $4.4 million, after deducting the underwriter’s discounts, commissions and other offering expenses. In addition, the Company issued warrants to purchase 145,733 shares of common stock at an exercise price of $2.625 per share to Wainwright as part of its compensation, which warrants were immediately exercisable upon issuance and terminate on August 27, 2025. An investor participating in the transaction included Michael G. Carter, a member of the Company’s board of directors. In November 2020, the Company entered into an underwriting agreement (as amended and restated, the “November Underwriting Agreement”) with Wainwright for the sale of 7,258,065 shares of the Company’s common stock at a price to the public of $3.10 per share, resulting in net proceeds of $20.4 million, after deducting the underwriter’s discounts, commissions and other offering expenses. In addition, the Company issued warrants to purchase 435,484 shares of common stock at an exercise price of $3.875 per share to Wainwright as part of its compensation, which warrants were immediately exercisable upon issuance and terminate on November 17, 2025. In December 2020, the Company entered into an underwriting agreement (as amended and restated, the “December Underwriting Agreement”) with Wainwright for the sale of 19,161,667 shares of the Company’s common stock at a price to the public of $4.50 per share, resulting in net proceeds of $79.0 million, after deducting the underwriter’s discounts, commissions and other offering expenses In addition, the Company issued warrants to purchase 1,149,700 shares of common stock at an exercise price of $5.625 per share to Wainwright as part of its compensation, which warrants were immediately exercisable upon issuance and terminate on December 9, 2025. In connection with the May Purchase Agreement and July Purchase Agreement, the Company also agreed, on a best-efforts basis, to: (i) maintain its listing on The Nasdaq Capital Market to provide for the resale of the shares of common stock issuable upon the exercise of the warrants, and (ii) not enter into any agreement for the issuance of any shares of common stock involving a variable rate transaction before July 21, 2021, other than pursuant to a new at-the-market offering facility with the placement Company does not currently have an active at-the-market facility. Common Stock Warrants A summary of warrant activity and changes in warrants outstanding is presented below: Number of Shares Underlying Warrants Weighted-Average Exercise Price per Share Weighted-Average Remaining Contractual Term Balance Outstanding - December 31, 2018 841,620 $ 37.97 3.75 Exercised (196 ) $ 6.13 — Balance Outstanding - December 31, 2019 841,424 $ 37.97 2.75 Issued 4,265,198 $ 3.47 — Exercised (74,781 ) $ 3.22 — Balance Outstanding - December 31, 2020 5,031,841 $ 9.25 4.40 As of December 31, 2020 and 2019, all warrants met the criteria for classification in stockholders’ equity. Restricted Common Stock and Unvested Share Liability Prior to the Merger, the Company issued restricted common stock subject to vesting and repurchase by the Company. For employee and non-employee awards, the issuance date fair value is recognized over the requisite service period of the award (usually the vesting period) on a straight-line basis. In addition, the Company has outstanding unvested shares related to the early exercise of stock options. The Company has the right, but not the obligation, to repurchase any unvested shares at the original purchase price upon any voluntary or involuntary termination. The consideration received in exchange for unvested shares is recorded as an unvested share liability on the accompanying consolidated balance sheets and is reclassified into common stock and additional paid-in capital as the shares vest. At 2019, the unvested share liability was $ 24,000 A summary of the Company’s unvested shares is as follows (in thousands): Number of Shares Balance at December 31, 2019 35 Vested shares (20 ) Balance at December 31, 2020 15 Equity Incentive Plans Contemporaneous with the Merger closing: (i) Private Oncternal’s 2015 Equity Incentive Plan, as amended (the “2015 Plan”) was assumed by the Company, and (ii) the Company adopted the 2019 Incentive Award Plan (“2019 Plan”) under which the sum of: (a) 1,678,571 shares of common stock, (b) up to 275,579 shares of common stock which were subject to outstanding awards under the GTx 2013 Equity Incentive Plan (the “2013 Plan”) as of June 7, 2019, that are subsequently cancelled will become available for issuance under the 2019 Plan, and (c) an annual increase on the first day of each calendar year beginning January 1, 2020, and ending on and including January 1, 2029, equal to the lesser of (A) 5% of the aggregate number of shares of common stock outstanding on the final day of the immediately preceding calendar year and (B) such smaller number of shares of common stock as is determined by the Board, are reserved for issuance. At December 31, 2020, 937,837 Number of Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value December 31, 2020: Options outstanding 2,107,625 $ 4.08 8.3 $ 2,509 Options vested and expected to vest 2,107,625 $ 4.08 8.3 $ 2,509 Options exercisable 965,129 $ 3.61 8.1 $ 1,525 As of December 31, 2020 under the 2013 Plan, there were: (i) 111,145 63.58 145,652 118,024 75.16 In July 2015, Private Oncternal adopted the 2015 Plan which provided for the issuance of up to 631,120 shares of common stock for incentive stock options, non-statutory stock options, restricted stock awards, restricted stock unit awards and other stock awards to its employees, members of its board of directors and consultants. In general, the options issued under the 2015 Plan expire ten years from the date of grant and vest over a four-year No further awards will be made under the 2015 Plan, which was terminated as to new grants in June 2019. A summary of the Company’s stock option activity under the 2019 Plan and 2015 Plan is as follows: Number of Options Weighted- Average Exercise Price Balance at December 31, 2019 1,662,253 $ 4.17 Granted 624,260 $ 3.37 Cancelled (173,753 ) $ 2.57 Exercised (5,135 ) $ 0.77 Balance at December 31, 2020 2,107,625 $ 4.08 Information about the Company’s outstanding stock options under the 2019 Plan and 2015 Plan is as follows (in thousands, except share and per share data and expected term): The weighted average grant date fair value per share of option grants for the years ended December 31, 2020 and 2.53 3.69 2020 and Stock-Based Compensation Expense The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of stock option grants were as follows: Years Ended December 31, 2020 2019 Risk-free interest rate 0.7 % 1.6 % Expected volatility 91.6 % 77.6 % Expected term (in years) 6.7 6.0 Expected dividend yield — % — % Expected volatility. Prior to the Merger, Private Oncternal did not have a trading history for its common stock. Accordingly, the expected volatility assumption is based on volatilities of a peer group of similar companies whose share prices are publicly available. The peer group was developed based on companies in the life sciences industry. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. Expected term. The expected term represents the period of time that options are expected to be outstanding. Because Private Oncternal did not have historical exercise behavior, it determined the expected life assumption using the simplified method for employees, which is an average of the contractual term of the option and its vesting period. The expected term for nonemployee options is generally the remaining contractual term. Risk-free interest rate. The risk-free interest rate is based on the implied yield on the U.S. Treasury securities with a maturity date similar to the expected term of the associated stock option award. Expected dividend yield. The Company bases the expected dividend yield assumption on the fact that it has never paid cash dividends and has no present intention to pay cash dividends and, therefore, used an expected dividend yield of zero. Stock-based compensation expense recognized for all equity awards has been reported in the statements of operations as follows (in thousands): Years Ended December 31, 2020 2019 Research and development $ 544 $ 237 General and administrative 1,012 270 $ 1,556 $ 507 At December 31, 2020, the total compensation cost related to nonvested awards not yet recognized was $3.4 million and the weighted-average period over which it is expected to be recognized was 2.5 years. Common Stock Reserved for Future Issuance Common stock reserved for future issuance is as follows (in thousands): December 31, 2020 2019 Common stock warrants 5,032 841 Common stock options issued and outstanding 2,226 1,958 Common stock available for issuance under equity plans 938 495 8,196 3,294

COVID-19 Pandemic and CARES Act

COVID-19 Pandemic and CARES Act	12 Months Ended
	Dec. 31, 2020
C O V I D19 Pandemic And C A R E S Act [Abstract]
COVID-19 Pandemic and CARES Act	8. A novel strain of coronavirus (SAR-CoV-2) causing a severe respiratory disease (“COVID-19”), was declared a global pandemic by the World Health Organization in March 2020. COVID-19 has presented substantial public health and economic challenges and is affecting economies, financial markets and business operations around the world. International and U.S. governmental authorities in impacted regions have taken actions in an effort to slow the spread of COVID-19, including issuing varying forms of “stay-at-home” orders, and restricting business functions outside of one’s home. In response, the Company has put restrictions on employee travel and working from its executive offices with many employees continuing their work remotely. While the Company is currently continuing the clinical trials it has underway in sites across the U.S., the Company expects that COVID-19 precautions may directly or indirectly impact the timeline for some of its clinical trials. For example, some of its clinical trial sites, including those located in areas severely impacted by the pandemic, have placed new patient enrollment into clinical trials on hold or, for patients travelling from out-of-state, have implemented a 14-day self-quarantine before appointments. Additionally, the Company’s expectations for the timing of first-in-human dosing of its ROR1 CAR-T therapy in China has been delayed. The Company considered the impacts of COVID-19 on the assumptions and estimates used to prepare its consolidated financial statements and determined that there were no material adverse impacts on the Company’s results of operations and financial position at December 31, 2020. The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business results of operations and financial condition, will depend on future development that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain or treat it, the success or failure of vaccination programs, the emergence of new variants of COVID-19, as well as the economic impact on local, regional, national and international markets. In response to the COVID-19 pandemic, the CARES Act was signed into law on March 27, 2020. The CARES Act, among other things, includes tax provisions relating to refundable payroll tax credits, deferment of employer’s social security payments, net operating loss utilization and carryback periods, modifications to the net interest deduction limitations and technical corrections to tax depreciation methods for qualified improvement property (QIP), and authorized the PPP (see Note 5). The CARES Act had no material impact on the Company’s income tax provision for the 12 months ended December 31, 2020.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	9 . Income Taxes A reconciliation of the Company’s effective tax rate and federal statutory tax rate is as follows (in thousands): Years Ended December 31, 2020 2019 Federal income taxes $ (3,617 ) $ (7,179 ) State income taxes, net of federal benefit (1,113 ) (968 ) Permanent items (65 ) 873 In-process research and development — 3,354 Research and development credit carryforwards (505 ) (464 ) Other, net 226 265 Change in valuation allowance 5,074 4,119 Provision for income taxes $ — $ — Significant components of the Company’s net deferred tax assets are as follows (in thousands): December 31, 2020 2019 Deferred tax assets: Net operating loss carryforwards $ 17,852 $ 18,108 Research and development credit carryforwards 1,952 1,446 Accrued expenses 367 214 Capitalized research and development costs 11,987 7,688 Other, net 393 143 Total deferred tax assets 32,551 27,599 Valuation allowance (32,540 ) (27,546 ) 11 53 Deferred tax liabilities: Right of use asset (11 ) (53 ) Total deferred tax liabilities (11 ) (53 ) Net deferred tax assets $ — $ — Based on the Company’s history of operating losses, the Company is unable to conclude that it is more likely than not that the benefit of its deferred tax assets will be realized. Accordingly, the Company has provided a full valuation allowance for its deferred tax assets as of December 31, 2020 and 2019. As a result of the Merger in 2019, the Company recorded deferred tax assets of $13.1 million which are fully offset by a valuation allowance. The $13.1 million net deferred tax assets do not include federal and state net operating loss carryforwards and federal research and development credit carryforwards that are estimated to expire under Internal Revenue Code Sections 382 and 383 as a result of the Merger. At December 31, 2020, the Company had federal and state net operating loss (NOL) carryforwards of approximately $69.1 million and $47.7 million, respectively. Of the federal net operating losses at December 31, 2020, $43.4 million do not expire, and the remaining federal and state net operating loss carryforwards will begin expiring in 2033 and 2029, respectively, unless previously utilized. At December 31, 2020, the Company also had federal and state research and development credit carryforwards of approximately $1.3 million and $0.9 million, respectively. The federal research and development credit carryforwards will begin expiring in 2034 unless previously utilized. The state research and development credits do not expire. Pursuant to Internal Revenue Code Sections 382 and 383, annual use of the Company’s net operating loss and research and development tax credit carryforwards may be limited in the event a cumulative change in ownership of more than 50% occurs within a three-year fact that there may be additional such ownership changes in the future. If eliminated, the related asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance. Due to the existence of the valuation allowance, limitations created by future ownership changes, if any, will not impact the Company’s effective tax rate. The Company recognizes a tax benefit from an uncertain tax position when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits. Income tax positions must meet a more likely than not recognition at the effective date to be recognized. At December 31, 2020 and 2019, there were no unrecognized tax benefits recorded in the consolidated financial statements. The Company does not expect any material changes to unrecognized tax benefits within the next twelve months. The Company is subject to taxation in the United States federal and state jurisdictions. The Company’s 2013 through 2020 federal income tax and state income tax returns are subject to examination by federal and state tax authorities due to the carryforward of unutilized net operating losses and research and development credits. The Company is not currently under examination by any tax authority. The Company’s policy is to recognize interest and penalties related to income tax matters in income tax expense. The Company has not recognized interest or penalties in its consolidated statements of operations since inception.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Event	10. Subsequent Event Inducement Plan

Description of Business, Basi_2

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Merger	Merger On June 7, 2019, the Company, then operating as GTx, Inc. (“GTx”), completed its Agreement and Plan of Merger and Reorganization, as amended (the “Merger Agreement”), with privately-held Oncternal Therapeutics, Inc. (“Private Oncternal”) and Grizzly Merger Sub, Inc., a wholly-owned subsidiary of the Company (“Merger Sub”), dated March 6, 2019. Under the Merger Agreement, Merger Sub merged with and into Private Oncternal, with Private Oncternal surviving as a wholly-owned subsidiary of the Company (the “Merger”). GTx changed its name to Oncternal Therapeutics, Inc., and Private Oncternal, which remains as a wholly-owned subsidiary of the Company, changed its name to Oncternal Oncology, Inc. On June 10, 2019, the combined company’s common stock began trading on The Nasdaq Capital Market under the ticker symbol “ONCT.” Except as otherwise indicated, references herein to “Oncternal,” “the Company,” and the “combined company,” refer to Oncternal Therapeutics, Inc. on a post-Merger basis, and the term “Private Oncternal” refers to the business of privately-held Oncternal Therapeutics, Inc., prior to completion of the Merger. References to GTx refer to GTx, Inc. prior to completion of the Merger. Pursuant to the terms of the Merger Agreement, each outstanding share of Private Oncternal common stock outstanding immediately prior to the closing of the Merger was converted into approximately 0.073386 shares of Company common stock (the “Exchange Ratio”), after taking into account the Reverse Stock Split, as defined below. Immediately prior to the closing of the Merger, all shares of Private Oncternal preferred stock then outstanding were exchanged into shares of common stock of Private Oncternal. In addition, all outstanding options exercisable for common stock of Private Oncternal and warrants exercisable for convertible preferred stock of Private Oncternal became options and warrants exercisable for the same number of shares of common stock of the Company multiplied by the Exchange Ratio. Immediately following the Merger, stockholders of Private Oncternal owned approximately 77.5% of the outstanding common stock of the combined company. The transaction was accounted for as a reverse asset acquisition in accordance with generally accepted accounting principles in the United States of America (“GAAP”). Under this method of accounting, Private Oncternal was deemed to be the accounting acquirer for financial reporting purposes. This determination was primarily based on the facts that, immediately following the Merger: (i) Private Oncternal’s stockholders owned a substantial majority of the voting rights in the combined company, (ii) Private Oncternal designated a majority of the members of the initial board of directors of the combined company, and (iii) Private Oncternal’s senior management holds all key positions in the senior management of the combined company. As a result, as of the closing date of the Merger, the net assets of the Company were recorded at their acquisition-date relative fair values in the consolidated financial statements of the Company and the reported operating results prior to the Merger are those of Private Oncternal.
Reverse Stock Split and Exchange Ratio	Reverse Stock Split and Exchange Ratio On June 7, 2019, in connection with, and prior to the completion of, the Merger, GTx effected a one-for-seven reverse stock split of its then outstanding common stock (the “Reverse Stock Split”). The par value and the authorized shares of the common stock were not adjusted as a result of the Reverse Stock Split. All of the Company’s issued and outstanding common stock have been retroactively adjusted to reflect this Reverse Stock Split for all periods presented. All issued and outstanding Private Oncternal common stock, preferred stock, options and warrants prior to the effective date of the Merger have been retroactively adjusted to reflect the Exchange Ratio for all periods presented.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries, Oncternal Oncology, Inc. and Oncternal, Inc. All intercompany accounts and transactions have been eliminated in the preparation of the consolidated financial statements.
Liquidity and Going Concern	Liquidity and Going Concern From inception, the Company has devoted substantially all of its efforts to drug discovery and development and conducting preclinical studies and clinical trials. The Company has a limited operating history and the sales and income potential of the Company’s business and market are unproven. Successful transition to attaining profitable operations is dependent upon achieving a level of revenues adequate to support the Company’s cost structure. As of December 31, 2020, the Company had $116.7 million in cash and cash equivalents. The Company believes it has sufficient cash to fund its projected operating requirements for at least twelve months from the date of issuance
Use of Estimates	Use of Estimates The Company’s consolidated financial statements accordance GAAP. of the Company’s consolidated financial statements and accompanying notes and assumptions that impact the amounts of liabilities, revenues and expenses and the disclosure of contingent and liabilities. Significant consist of those the value of the Company’s stock, stock liability , and those revenue and and development Although these on the Company’s knowledge of events and actions undertake the actual ultimately these and assumptions.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. Cash and cash equivalents include cash in readily available checking accounts and money market accounts.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institution in which those deposits are held. Additionally, the Company established guidelines regarding approved investments and maturities of investments, which are designed to maintain safety and liquidity.
Patent Costs	Patent Costs Costs related to filing and pursuing patent applications are recorded as general and administrative expense and expensed as incurred since recoverability of such expenditures is uncertain.
Research and Development Expenses and Accruals	Research and Development Expenses and Accruals Research and development expenses consist of costs incurred for the Company’s own and for sponsored and collaborative research and development activities. Research and development costs are expensed as incurred and include manufacturing process development costs, manufacturing costs, costs associated with preclinical studies and clinical trials, regulatory and medical affairs activities, quality assurance activities, salaries and benefits, including stock-based compensation, fees paid to third-party consultants, license fees and overhead. The Company has entered into various research and development contracts with research institutions, clinical research organizations, clinical manufacturing organizations and other companies. Payments for these activities are based on the terms of the individual agreements, which may differ from the pattern of costs incurred, and payments made in advance of performance are reflected in the accompanying consolidated balance sheets as prepaid and other assets or accrued liabilities. The Company records accruals for estimated costs incurred for ongoing research and development activities. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the services, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the prepaid or accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. As of December 31, 2020, the Company’s clinical trial accrual balance of $1.0 million is included in accrued liabilities and other liabilities. The Company’s related 2020 clinical trial expenses are included in research and development expense of $12.5 million.
Preferred Stock Warrant Liability	Preferred Stock Warrant Liability Prior to the Merger, Private Oncternal had outstanding freestanding warrants to purchase shares of its Series B-2 convertible preferred stock (the “Series B-2 warrants”). Private Oncternal adjusted the carrying value of such Series B-2 warrants to their estimated fair value at each reporting date, with any related increases or decreases in the fair value recorded as a change in fair value of warrant liability in the consolidated statements of operations. Upon the completion of the Merger, the Series B-2 warrants were amended such that they were converted into warrants to purchase the Company’s common stock. As amended, warrant liability accounting is no longer required and the fair value of the warrant liability has been reclassified into stockholders’ equity.
Fair Value Measurements	Fair Value Measurements The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or non-recurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1: Observable inputs such as quoted prices in active markets. Level 2: Inputs, other than the quoted prices in active markets that are observable either directly or indirectly. Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. The carrying amounts of the Company’s current financial assets and liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments. The Company has no financial assets or liabilities measured at fair value on a recurring basis. No transfers between levels have occurred during the periods presented.
Revenue Recognition	Revenue Recognition The Company currently generates revenue from the California Institute for Regenerative Medicine pursuant to a research subaward agreement (see Note 4), which provides the Company with payments in return for certain research and development activities over a contractually defined period. Revenue from such subaward is recognized in the period during which the related qualifying services are rendered and costs are incurred, provided that the applicable conditions under the subaward agreement have been met. The subaward agreement is on a best-effort basis and does not require scientific achievement as a performance obligation. All fees received under the agreement are non-refundable. The costs associated with the agreement are expensed as incurred and reflected as a component of research and development expense in the accompanying consolidated statements of operations. Funds received from the subaward agreement are recorded as revenue as the Company is the principal participant in the arrangement because the activities under the subaward are part of the Company’s development programs. In those instances where the Company first receives consideration in advance of providing underlying services, the Company classifies such consideration as deferred revenue until (or as) the Company provides the underlying services. In those instances where the Company first provides the underlying services prior to its receipt of consideration, the Company records a grant receivable. At December 31, 2020 and 2019, the Company had deferred grant revenue of $1.6
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense represents the fair value of equity awards, on the grant date, recognized in the period using the Black- Scholes option pricing model. The Company recognizes expense for awards with graded vesting schedules over the requisite service period of the awards (usually the vesting period) on a straight-line basis. For equity awards for which vesting is subject to performance-based milestones, the expense is recorded over the remaining service period after the point when the achievement of the milestone is probable. The Company recognizes forfeitures for all awards as such forfeitures occur.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment in the United States.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration for potentially dilutive securities and adjusted for the weighted-average number of common shares outstanding that are subject to repurchase. The Company has excluded weighted-average shares subject to repurchase of 25,000 shares and 56,000 shares from the weighted-average number of common shares outstanding for the years ended December 20 9 Potentially dilutive securities not included in the calculation of diluted net loss per share, because to do so would be anti-dilutive, are as follows (in common stock equivalent shares; in thousands): December 31, 2020 2019 Warrants to purchase common stock 5,032 841 Common stock options 2,226 1,958 Common stock subject to repurchase 15 35 7,273 2,834
Recently Accounting Pronouncements	Recently Issued Accounting Pronouncements In August 2020, the FASB issued ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity, which simplifies the accounting for certain financial instruments with characteristics of liabilities and equity, including convertible instruments and contracts on an entity’s own equity. Specifically, ASU 2020-06 simplifies accounting for the issuance of convertible instruments by removing major separation models required under current GAAP. In addition, the ASU removes certain settlement conditions that are required for equity contracts to qualify for the derivative scope exception and simplifies the diluted earnings per share (EPS) calculation in certain areas. ASU 2020-06 will be effective for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted, beginning in fiscal years which begin after December 15, 2020. The FASB has specified that an entity should adopt the guidance as of the beginning of its annual fiscal year. The Company is currently evaluating the impact of the pending adoption of this new standard on its consolidated financial statements. Recently Adopted Accounting Pronouncements In December 2019, the FASB issued ASU 2019-12, Income Taxes: Simplifying the Accounting for Income Taxe In August 2018, the FASB issued ASU Fair Value Measurement: Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement, the adoption had no impact on the consolidated financial statements

Description of Business, Basi_3

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss per Share Would Be Anti-dilutive	Potentially dilutive securities not included in the calculation of diluted net loss per share, because to do so would be anti-dilutive, are as follows (in common stock equivalent shares; in thousands): December 31, 2020 2019 Warrants to purchase common stock 5,032 841 Common stock options 2,226 1,958 Common stock subject to repurchase 15 35 7,273 2,834

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	12 Months Ended
	Dec. 31, 2020
Payables And Accruals [Abstract]
Summary of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): December 31, 2020 2019 Research and development $ 412 $ 582 Clinical trials 980 624 Legal fees 77 424 Unvested share liability 10 24 Compensation 1,528 825 Other 35 252 $ 3,042 $ 2,731

Merger - (Tables)

Merger - (Tables)	12 Months Ended
	Dec. 31, 2020
Merger [Abstract]
Summary of Purchase Price Paid in Merger	The following summarizes the purchase price paid in the Merger (in thousands, except share and per share amounts): Number of shares of the combined organization owned by the Company’s pre-Merger stockholders 3,458,170 Multiplied by the fair value per share of GTx common stock (1) $ 8.40 Fair value of consideration issued to effect the Merger $ 29,049 Transaction costs 2,154 Purchase price $ 31,203 (1)
Summary of Allocation of Purchase Price	The allocation of the purchase price is as follows: Cash acquired $ 18,292 Net liabilities assumed (5,177 ) IPR&D (2) 18,088 Purchase price $ 31,203 (2) Represents the research and development projects of GTx which were in-process, but not yet completed, and which the Company plans to advance, consisting primarily of GTx’s preclinical SARD technology. Current alternative future use be allocated a portion of the consideration transferred and charged to expense on the acquisition date. The acquired assets did not have outputs or employees .

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit) (Tables)	12 Months Ended
	Dec. 31, 2020
Summary Of Warrant Activity And Changes In Warrants Outstanding	A summary of warrant activity and changes in warrants outstanding is presented below: Number of Shares Underlying Warrants Weighted-Average Exercise Price per Share Weighted-Average Remaining Contractual Term Balance Outstanding - December 31, 2018 841,620 $ 37.97 3.75 Exercised (196 ) $ 6.13 — Balance Outstanding - December 31, 2019 841,424 $ 37.97 2.75 Issued 4,265,198 $ 3.47 — Exercised (74,781 ) $ 3.22 — Balance Outstanding - December 31, 2020 5,031,841 $ 9.25 4.40
Summary of Unvested Shares	A summary of the Company’s unvested shares is as follows (in thousands): Number of Shares Balance at December 31, 2019 35 Vested shares (20 ) Balance at December 31, 2020 15
Summary of Stock Option Outstanding, Vested and Expected to Vest and Exercisable	Number of Shares Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (in years) Aggregate Intrinsic Value December 31, 2020: Options outstanding 2,107,625 $ 4.08 8.3 $ 2,509 Options vested and expected to vest 2,107,625 $ 4.08 8.3 $ 2,509 Options exercisable 965,129 $ 3.61 8.1 $ 1,525
Summary of Stock Option Activity	A summary of the Company’s stock option activity under the 2019 Plan and 2015 Plan is as follows: Number of Options Weighted- Average Exercise Price Balance at December 31, 2019 1,662,253 $ 4.17 Granted 624,260 $ 3.37 Cancelled (173,753 ) $ 2.57 Exercised (5,135 ) $ 0.77 Balance at December 31, 2020 2,107,625 $ 4.08
Summary of Share-Based Compensation Expense	Stock-based compensation expense recognized for all equity awards has been reported in the statements of operations as follows (in thousands): Years Ended December 31, 2020 2019 Research and development $ 544 $ 237 General and administrative 1,012 270 $ 1,556 $ 507
Common Stock Reserved for Future Issuance	Common stock reserved for future issuance is as follows (in thousands): December 31, 2020 2019 Common stock warrants 5,032 841 Common stock options issued and outstanding 2,226 1,958 Common stock available for issuance under equity plans 938 495 8,196 3,294
Stock Option Grants
Schedule of Assumptions Used to Determine Fair Value	The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of stock option grants were as follows: Years Ended December 31, 2020 2019 Risk-free interest rate 0.7 % 1.6 % Expected volatility 91.6 % 77.6 % Expected term (in years) 6.7 6.0 Expected dividend yield — % — %

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Summary of Reconciliation of Effective Tax Rate and Federal Statutory Tax Rate	A reconciliation of the Company’s effective tax rate and federal statutory tax rate is as follows (in thousands): Years Ended December 31, 2020 2019 Federal income taxes $ (3,617 ) $ (7,179 ) State income taxes, net of federal benefit (1,113 ) (968 ) Permanent items (65 ) 873 In-process research and development — 3,354 Research and development credit carryforwards (505 ) (464 ) Other, net 226 265 Change in valuation allowance 5,074 4,119 Provision for income taxes $ — $ —
Summary of Significant Components of Net Deferred Tax Assets	Significant components of the Company’s net deferred tax assets are as follows (in thousands): December 31, 2020 2019 Deferred tax assets: Net operating loss carryforwards $ 17,852 $ 18,108 Research and development credit carryforwards 1,952 1,446 Accrued expenses 367 214 Capitalized research and development costs 11,987 7,688 Other, net 393 143 Total deferred tax assets 32,551 27,599 Valuation allowance (32,540 ) (27,546 ) 11 53 Deferred tax liabilities: Right of use asset (11 ) (53 ) Total deferred tax liabilities (11 ) (53 ) Net deferred tax assets $ — $ —

Description of Business, Basi_4

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	Jun. 07, 2019	Dec. 31, 2020USD ($)segmentshares	Dec. 31, 2019USD ($)shares
Description Of Business Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit		$ (82,797)	$ (65,572)
Cash and cash equivalents		116,737	20,051
Accrual balance in accrued liabilities and other liabilities		980	624
Research and development		12,544	10,159
Deferred grant revenue		$ 1,633	$ 3,640
Number of operating segments | segment		1
Weighted-average shares subject to repurchase | shares		25,000	56,000
Merger Agreement
Description Of Business Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Reverse stock split of common stock	7
Merger Agreement | Combined organization's
Description Of Business Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Common stock and preferred stock exchange ratio	0.073386
Ownership percentage of stockholders upon closing of merger	77.50%

Description of Business, Basi_5

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss per Share Would Be Anti-dilutive (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	7,273	2,834
Warrants to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	5,032	841
Common Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	2,226	1,958
Common Stock Subject to Repurchase
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities	15	35

Balance Sheet Details - Accrued

Balance Sheet Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Research and development	$ 412	$ 582
Accrual balance in accrued liabilities and other liabilities	980	624
Legal fees	77	424
Unvested share liability	10	24
Compensation	1,528	825
Other	35	252
Total accrued liabilities	$ 3,042	$ 2,731

Commitments, Contingencies an_2

Commitments, Contingencies and Related Party Transactions - Additional Information (Details)	May 22, 2019USD ($)ft²	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Commitments And Contingencies [Line Items]
Rent expense		$ 200,000	$ 100,000
Insurance premium		1,400,000	$ 1,200,000
Shanghai Pharmaceutical (USA) Inc.
Commitments And Contingencies [Line Items]
Amounts receivable		300,000
Agent
Commitments And Contingencies [Line Items]
Insurance commissions		$ 100,000
San Diego, California | Office Space
Commitments And Contingencies [Line Items]
Rentable area | ft²	4,677
Lease expiration date	Mar. 31, 2021
Annual base rent	$ 166,000
Lease discount rate		10.00%
Operating lease liability		$ 40,000
Weighted average remaining lease term		3 months

License, Collaboration and Re_2

License, Collaboration and Research Subaward Agreements - Additional Information (Details) - USD ($)	1 Months Ended			12 Months Ended
	Oct. 31, 2017	Aug. 31, 2017	May 31, 2016	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017	Dec. 31, 2015	Jul. 31, 2020	Dec. 31, 2014
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense				$ 0	$ 0
Patent costs as general and administrative expense				8,373,000	7,286,000
Grant revenue				3,375,000	2,425,000
MD Anderson Cancer Center
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate cost								$ 293,000,000
Research and development expense				122,000,000
Regents of the University of California
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense				25,000	25,000
Upfront license fees paid			$ 500,000
Common stock, shares, issued			107,108
Annual license maintenance fees						$ 25,000
Worldwide sales milestones based on achievement of tiered revenue levels			$ 75,000,000
Patent costs as general and administrative expense				200,000	200,000
University of California San Diego School of Medicine | The California Institute for Regenerative Medicine ("CIRM") Award
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Grants awarded to researchers	$ 5,800,000	$ 18,300,000
Development milestones to be received under research subaward agreements throughout award project period		$ 14,000,000
Subaward payments received				1,400,000	6,200,000
Grant revenue				3,400,000	2,400,000
Related qualifying subaward costs				5,200,000	5,400,000
Exclusive License Agreement | Georgetown University
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Annual license maintenance fee to be paid and payment made							$ 10,000
Potential milestone payments				$ 0
Written notice of termination, period				90 days
Days after receipt of notice, to pay failure amount				30 days
Days after receipt of notice for default in payment				60 days
Minimum period in days of written notice to terminate license agreement				60 days
Collaboration Agreement | MD Anderson Cancer Center
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential regulatory milestone payments									$ 1,000,000
Research Agreement | Regents of the University of California
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense				$ 500,000	500,000
Research agreement term				5 years
Aggregate research agreement budget				$ 3,600,000
Research amount payable quarterly				$ 125,000
Regents License Agreement | Regents of the University of California
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Written notice of termination, period				60 days
License Agreement | University of Tennessee Research Foundation
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense				$ 200,000	$ 400,000
Maximum | The California Institute for Regenerative Medicine ("CIRM") Award
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount agreed to be provided in contingency funds	$ 1,000,000
Maximum | Regents of the University of California
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential regulatory milestone payments			12,500,000
Maximum | Exclusive License Agreement | Georgetown University
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential milestone payments							$ 200,000
Minimum [Member] | Regents of the University of California
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential regulatory milestone payments			10,000,000
Advance licensed assets			$ 1,000,000

Debt - Additional Information (

Debt - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	May 31, 2020
Debt Instrument [Line Items]
Loan forgiveness (other income)	$ 301
Unsecured Debt | Paycheck Protection Program
Debt Instrument [Line Items]
Loan amount		$ 300
Interest rate, stated percentage		1.00%
Loan forgiveness (other income)	$ 301

Merger - Additional Information

Merger - Additional Information (Details) $ in Thousands	Jun. 07, 2019USD ($)CVR	Dec. 31, 2019USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
In-process research and development | $	$ 18,088	$ 18,088
CVR Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent value right per common stock | CVR	1
Percentage of net proceeds entitled to be received per CVR	75.00%
Period from closing during which payment of percentage of net proceeds would be payable under the CVR	15 years
Period from closing during which the grant, sale or transfer of rights to the Company's SARD or SARM technology could trigger a payment under the CVR Agreement	10 years

Merger - Summary of Purchase Pr

Merger - Summary of Purchase Price Paid in Merger (Details) $ / shares in Units, $ in Thousands	Jun. 07, 2019USD ($)$ / sharesshares
Asset Acquisitions [Line Items]
Number of shares of the combined organization owned by the Company’s pre-Merger stockholders | shares	3,458,170
Fair value of consideration issued to effect the Merger	$ 29,049
Transaction costs	2,154
Purchase price	$ 31,203
GTx Inc.
Asset Acquisitions [Line Items]
Multiplied by the fair value per share of GTx common stock (1) | $ / shares	$ 8.40

Merger - Summary of Allocation

Merger - Summary of Allocation of Purchase Price (Details) - USD ($) $ in Thousands	Jun. 07, 2019	Dec. 31, 2019
Merger [Abstract]
Cash acquired	$ 18,292	$ 18,292
Net liabilities assumed	(5,177)
In-process research and development	18,088	$ 18,088
Purchase price	$ 31,203

Stockholders' Equity (Deficit_2

Stockholders' Equity (Deficit) - Amended and Restated Articles of Incorporation (Details) - $ / shares	Dec. 31, 2020	Dec. 31, 2019	Jun. 07, 2019
Equity [Abstract]
Common stock, shares authorized	60,000,000	60,000,000	60,000,000
Preferred stock, shares authorized	5,000,000	0	5,000,000
Preferred stock, par value	$ 0.001	$ 0.001	$ 0.001

Stockholders' Equity (Deficit_3

Stockholders' Equity (Deficit) - Convertible Preferred Stock (Details)	Jun. 07, 2019shares
Private Oncternal
Class Of Stock [Line Items]
Convertible preferred stock converted into common stock shares	8,148,268

Stockholders' Equity (Deficit_4

Stockholders' Equity (Deficit) - Securities Purchase Agreements and Underwritten Offering (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended					12 Months Ended
	Dec. 31, 2020	Nov. 30, 2020	Aug. 31, 2020	Jul. 31, 2020	May 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Capitalization Equity [Line Items]
Proceeds from the issuance of common stock and common stock warrants, net						$ 113,876
Warrants issued	5,031,841					5,031,841	841,424	841,620
Warrant exercise price per share	$ 9.25					$ 9.25	$ 37.97	$ 37.97
Purchase Agreement | Warrants to purchase common stock
Schedule Of Capitalization Equity [Line Items]
Combined purchase price of share and warrant per unit					$ 2.5725
Purchase Agreement | Warrants to purchase common stock | Maximum
Schedule Of Capitalization Equity [Line Items]
Warrants issued					971,818
Purchase Agreement | Warrants to purchase common stock | Placement Agent
Schedule Of Capitalization Equity [Line Items]
Warrants issued					116,618
Warrant exercise price per share					$ 3.2156
Common stock warrants excercisable and expiration date					May 21, 2025
Purchase Agreement | Common Stock
Schedule Of Capitalization Equity [Line Items]
Common stock, shares, issued					1,943,636
Proceeds from the issuance of common stock and common stock warrants, net					$ 4,400
July Purchase Agreement | Warrants to purchase common stock
Schedule Of Capitalization Equity [Line Items]
Combined purchase price of share and warrant per unit				$ 2.3825
Warrant exercise price per share				$ 2.32
Common stock warrants expiration date				Jan. 21, 2026
July Purchase Agreement | Warrants to purchase common stock | Maximum
Schedule Of Capitalization Equity [Line Items]
Warrants issued				1,290,933
July Purchase Agreement | Warrants to purchase common stock | Placement Agent
Schedule Of Capitalization Equity [Line Items]
Warrants issued				154,912
Warrant exercise price per share				$ 2.9781
Common stock warrants excercisable and expiration date				Jul. 21, 2025
July Purchase Agreement | Common Stock
Schedule Of Capitalization Equity [Line Items]
Common stock, shares, issued				2,581,867
Proceeds from the issuance of common stock and common stock warrants, net				$ 5,700
August Underwriting Agreement | Warrants to purchase common stock
Schedule Of Capitalization Equity [Line Items]
Combined purchase price of share and warrant per unit			$ 2.10
Warrant exercise price per share			$ 2.625
Common stock warrants excercisable and expiration date			Aug. 27, 2025
August Underwriting Agreement | Warrants to purchase common stock | Maximum
Schedule Of Capitalization Equity [Line Items]
Warrants issued			145,733
August Underwriting Agreement | Common Stock
Schedule Of Capitalization Equity [Line Items]
Common stock, shares, issued			2,428,886
Proceeds from the issuance of common stock and common stock warrants, net			$ 4,400
November Underwriting Agreement | Warrants to purchase common stock
Schedule Of Capitalization Equity [Line Items]
Combined purchase price of share and warrant per unit		$ 3.10
Warrant exercise price per share		$ 3.875
Common stock warrants excercisable and expiration date		Nov. 17, 2025
November Underwriting Agreement | Warrants to purchase common stock | Maximum
Schedule Of Capitalization Equity [Line Items]
Warrants issued		435,484
November Underwriting Agreement | Common Stock
Schedule Of Capitalization Equity [Line Items]
Common stock, shares, issued		7,258,065
Proceeds from the issuance of common stock and common stock warrants, net		$ 20,400
December Underwriting Agreement | Warrants to purchase common stock
Schedule Of Capitalization Equity [Line Items]
Combined purchase price of share and warrant per unit	4.50					4.50
Warrant exercise price per share	$ 5.625					$ 5.625
Common stock warrants excercisable and expiration date	Dec. 9, 2025
December Underwriting Agreement | Warrants to purchase common stock | Maximum
Schedule Of Capitalization Equity [Line Items]
Warrants issued	1,149,700					1,149,700
December Underwriting Agreement | Common Stock
Schedule Of Capitalization Equity [Line Items]
Common stock, shares, issued	19,161,667
Proceeds from the issuance of common stock and common stock warrants, net	$ 79,000

Stockholders' Equity (Deficit_5

Stockholders' Equity (Deficit) - Summary Of Warrant Activity And Changes In Warrants Outstanding (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Equity [Abstract]
Options outstanding, Number of Warrant	841,424	841,620
Number of Shares Underlying Warrants Issued	4,265,198
Number of Shares Underlying Warrants Exercised	(74,781)	(196)
Options outstanding, Number of Warrant	5,031,841	841,424	841,620
Weighted-Average Exercise Price	$ 37.97	$ 37.97
Issued	3.47
Exercised	3.22	6.13
Weighted-Average Exercise Price	$ 9.25	$ 37.97	$ 37.97
Weighted-Average Remaining Contractual Term	4 years 4 months 24 days	2 years 9 months	3 years 9 months

Stockholders' Equity - Restrict

Stockholders' Equity - Restricted Common Stock and Unvested Share Liability (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Equity [Abstract]
Unvested share liability	$ 10,000	$ 24,000

Stockholders' Equity (Deficit_6

Stockholders' Equity (Deficit) - Summary of Unvested Shares (Details)	12 Months Ended
	Dec. 31, 2020shares
Sharebased Compensation Arrangement By Sharebased Payment Award Options Nonvested Number Of Shares Roll Forward
Number of shares unvested, beginning balance	35,000
Number of shares, vested shares	(20,000)
Number of shares unvested, ending balance	15,000

Stockholders' Equity (Deficit_7

Stockholders' Equity (Deficit) - Equity Incentive Plans (Details) - $ / shares	Jun. 07, 2019	Jul. 31, 2015	Dec. 31, 2020	Dec. 31, 2019	Feb. 28, 2021
Class Of Stock [Line Items]
Number of common stock shares provided for issuance of stock awards to its employees			8,196,000	3,294,000	700,000
Number of options cancelled			173,753
2019 incentive award plan
Class Of Stock [Line Items]
Shares of common stock reserved for issuance	1,678,571
Maximum number of shares of common stock a participant may receive	275,579
Percentage of annual increase in shares reserved for issuance	5.00%
Number of common stock shares provided for issuance of stock awards to its employees			937,837
Number of options cancelled			145,652
2013 plan
Class Of Stock [Line Items]
Number of options outstanding and fully vested			111,145
Weighted average exercise price of options outstanding and fully vested			$ 63.58
2015 plan
Class Of Stock [Line Items]
Options expiration term		10 years
Options vesting period		4 years
2015 plan | Private Oncternal
Class Of Stock [Line Items]
Number of common stock shares provided for issuance of stock awards to its employees		631,120
GTx Stock Option Plans
Class Of Stock [Line Items]
Number of options outstanding and fully vested and exercisable			118,024
Weighted average exercise price of options outstanding and fully vested and exercisable			$ 75.16
Weighted average remaining contractual term of options outstanding and fully vested and exercisable				4 months 24 days
2019 and 2015 plan
Class Of Stock [Line Items]
Weighted average grant date fair value per share of option grants			2.53	$ 3.69
Closing market price per common share			$ 4.90

Stockholders' Equity (Deficit_8

Stockholders' Equity (Deficit) - Summary of Stock Option Outstanding, Vested and Expected to Vest and Exercisable (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding, Number of Shares	2,107,625	1,662,253
Options outstanding, Weighted Average Exercise Price	$ 4.08	$ 4.17
Options outstanding, Weighted Average Remaining Contractual Term	2 years 6 months
Equity incentive plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options outstanding, Number of Shares	2,107,625
Options vested and expected to vest, Number of Shares	2,107,625
Options exercisable, Number of Shares	965,129
Options outstanding, Weighted Average Exercise Price	$ 4.08
Options outstanding, Weighted Average Exercise Price	4.08
Options outstanding, Weighted Average Exercise Price	$ 3.61
Options outstanding, Weighted Average Remaining Contractual Term	8 years 3 months 18 days
Options outstanding, Weighted Average Remaining Contractual Term	8 years 3 months 18 days
Options outstanding, Weighted Average Remaining Contractual Term	8 years 1 month 6 days
Options outstanding, Aggregate Intrinsic Value	$ 2,509
Options outstanding, Aggregate Intrinsic Value	2,509
Options outstanding, Aggregate Intrinsic Value	$ 1,525

Stockholders' Equity (Deficit_9

Stockholders' Equity (Deficit) - Summary of Stock Option Activity (Details)	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Number of options, beginning balance | shares	1,662,253
Number of options, granted | shares	624,260
Number of options, cancelled | shares	(173,753)
Number of options, exercised | shares	(5,135)
Number of options, ending balance | shares	2,107,625
Weighted average exercise price, beginning balance | $ / shares	$ 4.17
Weighted average exercise price, granted | $ / shares	3.37
Weighted average exercise price, cancelled | $ / shares	2.57
Weighted average exercise price, exercised | $ / shares	0.77
Weighted average exercise price, ending balance | $ / shares	$ 4.08

Stockholders' Equity (Defici_10

Stockholders' Equity (Deficit) - Schedule of Assumptions Used to Estimate Fair Value of Stock Option Grants (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	0.70%	1.60%
Expected volatility	91.60%	77.60%
Expected term (in years)	6 years 8 months 12 days	6 years

Stockholders' Equity (Defici_11

Stockholders' Equity (Deficit) - Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,556	$ 507
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	544	237
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,012	$ 270

Stockholders' Equity (Defici_12

Stockholders' Equity (Deficit) - Stock-Based Compensation Expense (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)
Equity [Abstract]
Compensation cost related to nonvested awards not yet recognized	$ 3.4
Remaining weighted-average period	2 years 6 months

Stockholders' Equity (Defici_13

Stockholders' Equity (Deficit) - Common Stock Reserved for Future Issuance (Details) - shares	Feb. 28, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock warrants		5,032,000	841,000
Common stock options issued and outstanding		2,226,000	1,958,000
Common stock available for future issuance	700,000	8,196,000	3,294,000
Equity incentive plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock available for future issuance		938,000	495,000

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Effective Tax Rate and Federal Statutory Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal income taxes	$ (3,617)	$ (7,179)
State income taxes, net of federal benefit	(1,113)	(968)
Permanent items	(65)	873
In-process research and development		3,354
Research and development credit carryforwards	(505)	(464)
Other, net	226	265
Change in valuation allowance	$ 5,074	$ 4,119

Income Taxes - Summary of Signi

Income Taxes - Summary of Significant Components of Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 17,852	$ 18,108
Research and development credit carryforwards	1,952	1,446
Accrued expenses	367	214
Capitalized research and development costs	11,987	7,688
Other, net	393	143
Total deferred tax assets	32,551	27,599
Valuation allowance	(32,540)	(27,546)
Net deferred tax assets and liabilities	11	53
Deferred tax liabilities:
Right of use asset	(11)	(53)
Total deferred tax liabilities	$ (11)	$ (53)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Deferred tax assets, fully offset by valuation allowance	$ 13,100,000
Net deferred tax assets	13,100,000
Research and development credit carryforward	$ 1,952,000	$ 1,446,000
Cumulative changes in ownership percentage	50.00%
Period for cumulative change in ownership	3 years
Unrecognized Tax Benefits	$ 0	$ 0
Interest and penalties	0
Federal
Income Taxes [Line Items]
Net operating loss carryforwards	69,100,000
Operating loss carryforwards non expire portion	$ 43,400,000
Operating loss carryforwards expiration year	2033
Research and development credit carryforward	$ 1,300,000
Research and development credit carryforward expiration year	2034
State
Income Taxes [Line Items]
Net operating loss carryforwards	$ 47,700,000
Operating loss carryforwards expiration year	2029
Research and development credit carryforward	$ 900,000

Subsequent Event - Additional I

Subsequent Event - Additional Information (Details) - shares	Feb. 28, 2021	Dec. 31, 2020	Dec. 31, 2019
Subsequent Events [Abstract]
Common stock available for future issuance	700,000	8,196,000	3,294,000