iTeos Therapeutics (ITOS) 10-Q 1 Sep 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 27, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Document Quarterly Report	true
Document Transition Report	false
Trading Symbol	ITOS
Entity Registrant Name	iTeos Therapeutics, Inc.
Entity Central Index Key	0001808865
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Incorporation, State or Country Code	DE
Entity Shell Company	false
Entity File Number	001-39401
Entity Tax Identification Number	84-3365066
Entity Address Address Line1	139 Main Street
Entity Address City Or Town	Cambridge
Entity Address State Or Province	MA
Entity Address Postal Zip Code	02142
City Area Code	339
Local Phone Number	217 0161
Entity Common Stock Shares Outstanding		35,044,758
Security12b Title	Common stock, $0.001 par value per share
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash	$ 136,870,000	$ 19,868,000
Grants receivable	212,000	5,196,000
R&D tax credits receivable	133,000	133,000
Prepaid expenses and other current assets	3,180,000	879,000
Total current assets	140,395,000	26,076,000
Property and equipment, net	1,251,000	1,336,000
R&D tax credits receivable	3,172,000	2,917,000
Restricted cash	123,000	122,000
Other assets	270,000	293,000
Total assets	145,211,000	30,744,000
Current liabilities:
Accounts payable	2,656,000	1,174,000
Accrued expenses and other current liabilities	3,360,000	4,262,000
Preferred stock tranche rights liability		5,400,000
Deferred income	1,500,000	2,360,000
Total current liabilities	7,516,000	13,196,000
Grants repayable	4,161,000	1,397,000
Other noncurrent liabilities	484,000	482,000
Total liabilities	12,161,000	15,075,000
Commitments and contingencies (Note 9)
Stockholders’ deficit:
Common stock, $0.001 par value, 90,000,000 and 50,000,000 shares authorized at June 30, 2020 and December 31, 2019, respectively; 388,415 and 256,548 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	1,000	1,000
Additional paid-in capital	687,000
Accumulated other comprehensive loss	(296,000)	(224,000)
Accumulated deficit	(48,314,000)	(35,865,000)
Total stockholders’ deficit	(47,922,000)	(36,088,000)
Total liabilities, redeemable convertible preferred stock and stockholders’ deficit	145,211,000	30,744,000
Series B-2 Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock, value	127,090,000
Series B Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock, value	48,529,000	46,404,000
Series A-1 and A-2 Preferred Stock
Redeemable convertible preferred stock:
Redeemable convertible preferred stock, value	$ 5,353,000	$ 5,353,000

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	90,000,000	50,000,000
Common stock, shares issued	388,415	256,548
Common stock, shares outstanding	388,415	256,548
Series B-2 Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	44,453,477	0
Redeemable convertible preferred stock, shares issued	44,453,477	0
Redeemable convertible preferred stock, shares outstanding	44,453,477	0
Redeemable convertible preferred stock, liquidation preference	$ 127,090	$ 127,090
Series B Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	31,989,428	20,942,781
Redeemable convertible preferred stock, shares issued	20,942,781	20,942,781
Redeemable convertible preferred stock, shares outstanding	20,942,781	20,942,781
Redeemable convertible preferred stock, liquidation preference	$ 55,300	$ 55,300
Series A-1 and A-2 Preferred Stock
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	6,167,726	6,167,726
Redeemable convertible preferred stock, shares issued	6,167,726	6,167,726
Redeemable convertible preferred stock, shares outstanding	6,167,726	6,167,726
Redeemable convertible preferred stock, liquidation preference	$ 7,114	$ 7,114

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating expenses:
Research and development expenses	$ 6,137	$ 3,902	$ 11,962	$ 8,253
General and administrative expenses	2,394	2,093	4,812	3,862
Total operating expenses	8,531	5,995	16,774	12,115
Loss from operations	(8,531)	(5,995)	(16,774)	(12,115)
Other income and expenses:
Grant income	1,081	678	2,670	1,442
Fair value adjustment for preferred stock tranche rights liability and anti-dilution warrants liability		(488)	1,265	296
R&D tax credits	186	155	370	353
Other income (expense), net	12	(47)	(30)	(75)
Loss before income taxes	(7,252)	(5,697)	(12,499)	(10,099)
Income tax benefit (expense)	50	(58)	50	(58)
Net loss	(7,202)	(5,755)	(12,449)	(10,157)
Cumulative dividends on Series A preferred stock	(106)	(106)	(213)	(213)
Accretion of redeemable convertible preferred stock to redemption value			(4,189)	(1,612)
Net loss attributable to common stockholders	$ (10,302)	$ (6,776)	$ (16,851)	$ (11,982)
Basic and diluted net loss per common share	$ (29.49)	$ (36.49)	$ (55.63)	$ (64.52)
Weighted-average common shares outstanding—basic and diluted	349,290	185,716	302,919	185,716
Net loss	$ (7,202)	$ (5,755)	$ (12,449)	$ (10,157)
Foreign currency translation adjustments	245	529	(72)	262
Comprehensive loss	(6,957)	(5,226)	(12,521)	(9,895)
Series A Preferred Stock
Other income and expenses:
Accretion of redeemable convertible preferred stock to redemption value	$ (2,994)	$ (915)	$ (4,189)	$ (1,612)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity/Deficit (Unaudited) - USD ($) $ in Thousands	Total	Common stock	Profit certificates	Additional paid-in capital	Accumulated other comprehensive income (loss)	Retained earnings/(accumulated deficit)	Series A preferred stock	Series B preferred stock
Beginning balance at Dec. 31, 2018	$ (10,678)	$ 87	$ 11		$ (11)	$ (10,765)
Temporary equity, beginning balance (in shares) at Dec. 31, 2018							6,167,726	10,900,376
Temporary equity, beginning balance at Dec. 31, 2018							$ 5,353	$ 20,378
Beginning balance (in shares) at Dec. 31, 2018		185,716	7,022
Accretion of Series B and B-2 Preferred Stock to redemption value	(697)			$ (205)		(492)		$ 697
Stock-based compensation	205			205
Currency translation adjustment	(267)				(267)
Net loss	(4,402)					(4,402)
Ending balance at Mar. 31, 2019	(15,839)	$ 87	$ 11		(278)	(15,659)
Temporary equity, ending balance (in shares) at Mar. 31, 2019							6,167,726	10,900,376
Temporary equity, ending balance at Mar. 31, 2019							$ 5,353	$ 21,075
Ending balance (in shares) at Mar. 31, 2019		185,716	7,022
Beginning balance at Dec. 31, 2018	(10,678)	$ 87	$ 11		(11)	(10,765)
Temporary equity, beginning balance (in shares) at Dec. 31, 2018							6,167,726	10,900,376
Temporary equity, beginning balance at Dec. 31, 2018							$ 5,353	$ 20,378
Beginning balance (in shares) at Dec. 31, 2018		185,716	7,022
Net loss	(10,157)
Ending balance at Jun. 30, 2019	(21,675)	$ 87	$ 113		251	(22,126)
Temporary equity, ending balance (in shares) at Jun. 30, 2019							6,167,726	20,942,781
Temporary equity, ending balance at Jun. 30, 2019							$ 5,353	$ 44,362
Ending balance (in shares) at Jun. 30, 2019		185,716	70,832
Beginning balance at Mar. 31, 2019	(15,839)	$ 87	$ 11		(278)	(15,659)
Temporary equity, beginning balance (in shares) at Mar. 31, 2019							6,167,726	10,900,376
Temporary equity, beginning balance at Mar. 31, 2019							$ 5,353	$ 21,075
Beginning balance (in shares) at Mar. 31, 2019		185,716	7,022
Issuance of Preferred Stock								$ 22,372
Issuance of Series B Preferred Stock (in shares)								10,042,405
Accretion of Series B and B-2 Preferred Stock to redemption value	(915)			(203)		(712)		$ 915
Exercise of stock options into common stock/profit certificates	102		$ 102
Exercise of stock options into common stock/profit certificates (in shares)			63,810
Stock-based compensation	203			203
Currency translation adjustment	529				529
Net loss	(5,755)					(5,755)
Ending balance at Jun. 30, 2019	(21,675)	$ 87	$ 113		251	(22,126)
Temporary equity, ending balance (in shares) at Jun. 30, 2019							6,167,726	20,942,781
Temporary equity, ending balance at Jun. 30, 2019							$ 5,353	$ 44,362
Ending balance (in shares) at Jun. 30, 2019		185,716	70,832
Beginning balance at Dec. 31, 2019	(36,088)	$ 1			(224)	(35,865)
Temporary equity, beginning balance (in shares) at Dec. 31, 2019							6,167,726	20,942,781
Temporary equity, beginning balance at Dec. 31, 2019							$ 5,353	$ 46,404
Beginning balance (in shares) at Dec. 31, 2019		256,548
Issuance of Preferred Stock								$ 125,026
Issuance of Series B Preferred Stock (in shares)								44,453,477
Settlement of preferred stock tranche right	4,135			4,135
Accretion of Series B and B-2 Preferred Stock to redemption value	(1,195)			(1,195)				$ 1,195
Stock-based compensation	186			186
Currency translation adjustment	(317)				(317)
Net loss	(5,247)					(5,247)
Ending balance at Mar. 31, 2020	(38,526)	$ 1		3,126	(541)	(41,112)
Temporary equity, ending balance (in shares) at Mar. 31, 2020							6,167,726	65,396,258
Temporary equity, ending balance at Mar. 31, 2020							$ 5,353	$ 172,625
Ending balance (in shares) at Mar. 31, 2020		256,548
Beginning balance at Dec. 31, 2019	(36,088)	$ 1			(224)	(35,865)
Temporary equity, beginning balance (in shares) at Dec. 31, 2019							6,167,726	20,942,781
Temporary equity, beginning balance at Dec. 31, 2019							$ 5,353	$ 46,404
Beginning balance (in shares) at Dec. 31, 2019		256,548
Settlement of preferred stock tranche right	$ 4,135
Exercise of stock options into common stock/profit certificates (in shares)	131,867
Net loss	$ (12,449)
Ending balance at Jun. 30, 2020	(47,922)	$ 1		687	(296)	(48,314)
Temporary equity, ending balance (in shares) at Jun. 30, 2020							6,167,726	65,396,258
Temporary equity, ending balance at Jun. 30, 2020							$ 5,353	$ 175,619
Ending balance (in shares) at Jun. 30, 2020		388,415
Beginning balance at Mar. 31, 2020	(38,526)	$ 1		3,126	(541)	(41,112)
Temporary equity, beginning balance (in shares) at Mar. 31, 2020							6,167,726	65,396,258
Temporary equity, beginning balance at Mar. 31, 2020							$ 5,353	$ 172,625
Beginning balance (in shares) at Mar. 31, 2020		256,548
Accretion of Series B and B-2 Preferred Stock to redemption value	(2,994)			(2,994)				$ 2,994
Exercise of stock options into common stock/profit certificates	205			205
Exercise of stock options into common stock/profit certificates (in shares)		131,867
Stock-based compensation	350			350
Currency translation adjustment	245				245
Net loss	(7,202)					(7,202)
Ending balance at Jun. 30, 2020	$ (47,922)	$ 1		$ 687	$ (296)	$ (48,314)
Temporary equity, ending balance (in shares) at Jun. 30, 2020							6,167,726	65,396,258
Temporary equity, ending balance at Jun. 30, 2020							$ 5,353	$ 175,619
Ending balance (in shares) at Jun. 30, 2020		388,415

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity/Deficit (Unaudited) (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Series B-2 Preferred Stock
Net of Issuance costs	$ 332

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities
Net loss	$ (12,449)	$ (10,157)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	250	307
Stock-based compensation	536	408
Fair value adjustment for preferred stock tranche rights and anti-dilution warrants liabilities	(1,265)	(296)
Deferred rent	(14)	(5)
Changes in operating assets and liabilities:
Grants receivable	4,962	(1,586)
R&D tax credits receivable	(238)	(282)
Prepaid expenses and other current assets	(580)	(376)
Accounts payable	1,055	508
Accrued expenses and other liabilities	(886)	(234)
Deferred income	(852)	1,055
Net cash used in operating activities	(9,481)	(10,658)
Cash flows from investing activities
Purchase of property and equipment	(119)	(673)
Purchase of other assets	(19)	(121)
Net cash used in investing activities	(138)	(794)
Cash flows from financing activities
Proceeds from issuance of common stock and profit certificates upon exercise of options	205	102
Payment of IPO costs	(1,311)
Proceeds from grants repayable	2,713
Net cash provided by financing activities	126,633	22,474
Effects of exchange rate changes on cash and restricted cash	(11)	184
Net increase in cash and restricted cash	117,003	11,206
Cash and restricted cash at beginning of period	19,990	22,054
Cash and restricted cash at end of period	136,993	33,260
Non-cash investing and financing activities
Accretion of Series B and B-2 Preferred Stock to redemption value	4,189	1,612
Settlement of preferred stock tranche right	4,135
Deferred IPO costs in accounts payable	400
Supplemental disclosure of cash flows
Cash paid for taxes	147	2
Series B-2 Preferred Stock
Cash flows from financing activities
Proceeds from issuance of Preferred Stock	125,358
Payment of issuance costs on Series B-2 Preferred Stock	$ (332)
Series B Preferred Stock
Cash flows from financing activities
Proceeds from issuance of Preferred Stock		$ 22,372

Nature of Business

Nature of Business	6 Months Ended
	Jun. 30, 2020
Disclosure Text Block [Abstract]
Nature of Business	Note 1. Nature of business Description of business iTeos Therapeutics, Inc. (iTeos Inc. or the Company), a Delaware corporation headquartered in Cambridge, Massachusetts (incorporated on October 4, 2019), is the successor to iTeos Belgium SA (iTeos Belgium) a company organized under the laws of Belgium in 2011 and headquartered in Charleroi, Belgium. The Company is a clinical stage biopharmaceutical company that focuses on developing cancer immunotherapies by targeting key mechanisms of immunosuppression in the tumor microenvironment. The most advanced clinical program is EOS-850, a small molecule antagonist of the A 2A Corporate reorganization On October 4, 2019, the Company completed a corporate reorganization in which iTeos Inc., iTeos Belgium, and the stockholders of iTeos Belgium entered into an Equity Contribution and Exchange Agreement (Share Exchange), pursuant to which all outstanding shares of preferred stock, common stock and profit certificates of iTeos Belgium were exchanged on a one-for-one basis for newly issued shares of iTeos Inc. iTeos Inc. was a newly-formed holding company, and as a result of the Share Exchange, iTeos Belgium became a wholly owned subsidiary of iTeos Inc. iTeos Therapeutics U.S. Inc. (iTeos U.S.) included the Company’s U.S. operations and was located in Cambridge, Massachusetts. iTeos U.S., which was a wholly owned subsidiary of iTeos Belgium prior to the Share Exchange, continued to be a wholly owned subsidiary of iTeos Belgium throughout 2019. On February 28, 2020, iTeos Inc. purchased iTeos U.S. from iTeos Belgium and then the entities effectively merged. The Share Exchange was accounted for in accordance with the Financial Accounting Standards Board (FASB) Accounting Standard Codification (ASC) 805-50, Business Combinations—Related Issues Going concern Since inception, the Company’s activities have consisted primarily of performing research and development to advance its product candidates. The Company is still in the development phase and has not been marketing any developed products to-date. Through June 30, 2020, the Company has funded its operations with proceeds from sales of redeemable convertible preferred stock, collaboration and licensing agreements, grants and borrowings under various agreements with foreign public funding agencies. Since inception, the Company has incurred recurring losses, including a net loss of $12.4 million for the six months ended June 30, 2020. As of June 30, 2020, the Company had an accumulated deficit of $48.3 million. The Company expects to continue to generate operating losses in the foreseeable future. On July 28, 2020, the Company closed its initial public offering, or IPO, which generated net proceeds of $184.0 million, and o n August 5, 2020, the underwriters purchased 1,505,359 additional shares of common stock under their option for net proceeds of $26.6 million after deducting underwriting discounts and commissions The Company will seek additional funding in order to reach its development and commercialization objectives. The Company will seek funds either through public debt or equity offerings or further private equity financings, debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements. The Company may not be able to obtain funding on acceptable terms, or at all, and the Company may not be able to enter into collaborations or other arrangements. The terms of any funding may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects. The accompanying condensed consolidated financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The condensed consolidated financial statements do not reflect any adjustments relating to the recoverability and classification of assets or the amounts and classification of liabilities that might be necessary if the Company is unable to continue as a going concern. COVID-19 In December 2019, a novel strain of coronavirus (COVID-19) emerged in Wuhan, Hubei Province, China. As of June 30, 2020, COVID-19 has spread to Europe, the United States and many other countries, and has been declared a pandemic by the World Health Organization. Efforts to contain the spread of COVID-19 have intensified. The United States, including the Commonwealth of Massachusetts where our headquarters are located, as well as countries throughout Europe and Asia have implemented severe travel restrictions, social distancing requirements and stay-at-home orders, among other restrictions, which, in some cases, have had the effect of delaying the commencement of non-COVID-19-related clinical trials. As a result, the COVID-19 pandemic has caused significant disruptions to the U.S., regional and global economies and has contributed to significant volatility and negative pressure in financial markets. The Company has been carefully monitoring the COVID-19 pandemic and its potential impact on the Company’s business and has taken important steps to help ensure the safety of employees and their families and to reduce the spread of COVID-19 in the Cambridge and Belgian communities. The Company has established a work-from-home policy for all employees, other than those performing or supporting business-critical operations, such as certain members of our laboratory and facilities staff. For those employees, we have implemented stringent safety measures designed to comply with applicable federal, state and local guidelines instituted in response to the COVID-19 pandemic. The Company has also maintained efficient communication with the Company’s partners and clinical sites as the COVID-19 situation has progressed. The Company has taken these precautionary steps while maintaining business continuity so that we can continue to progress our programs. Risk and uncertainties The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty regarding results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s current or future product candidates, uncertainty of market acceptance of the Company’s product candidates, if approved, competition from substitute products and larger companies, securing and protecting proprietary technology, strategic relationships and dependence on key individuals and sole source suppliers. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities and may not ultimately lead to a marketing approval and commercialization of a product. Even if the Company’s drug development efforts are successful, it is uncertain if and when the Company will realize significant revenue from product sales. The Company’s product candidates require approvals from the U.S. Food and Drug Administration (FDA) and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company.

Summary of significant accounti

Summary of significant accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of significant accounting policies	Note 2. Summary of significant accounting policies Basis of presentation The accompanying condensed consolidated financial statements and accompanying notes have been prepared in accordance with generally accepted accounting principles in the United States of America (U.S. GAAP). The unaudited interim condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements as of and for the years ended December 31, 2019 and 2018, and the notes thereto, which are included in the Company’s final prospectus related to the Company’s IPO filed on July 27, 2020 (File No. 333-239415) with the SEC pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended. The results for any interim period are not necessarily indicative of results for any future period. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period. Principles of consolidation The accompanying condensed consolidated financial statements include the Company’s accounts and those of its wholly owned subsidiaries. All intercompany accounts, transactions and balances have been eliminated. Use of estimates The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and expenses, as well as the related disclosures of contingent assets and liabilities. Estimates are used to determine the fair value of the preferred stock tranche rights liability and anti-dilution warrants liability, the fair value of profit certificates, common stock and stock-based awards and other issuances, accruals for research and development costs, useful lives of long-lived assets, probability of repayment for grants repayable, and uncertain tax positions. Actual results could differ materially from the Company’s estimates. Deferred offering costs The Company capitalizes incremental legal, professional accounting and other third-party fees that are directly associated with the IPO as other non-current assets until the IPO is consummated. After consummation of the IPO, these costs will be recorded in stockholders’ deficit as a reduction of additional paid-in-capital generated as a result of the offering. As of June 30, 2020, there were deferred offering costs of approximately $1.7 million included in prepaid expenses and other current assets. Collaborative Arrangements The Company analyzes its collaboration arrangements to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and are, therefore within the scope of ASC Topic 808, Collaborative Arrangements Recently adopted accounting standards updates In August 2018 the FASB issued ASU No. 2018-13, Fair Value Measurement Disclosure Framework Changes to the Disclosure Requirements for Fair Value Measurement In November 2018 the FASB issued ASU No. 2018-18, Collaborative Arrangements Clarifying the Interaction between Topic 808 and Topic 606 • Clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606, Revenue from Contracts with Customers • Adds unit-of-account guidance to ASC 808, Collaborative Arrangements • Requires that in a transaction with a collaborative arrangement participant that is not directly related to sales to third parties, presenting that transaction together with revenue recognized under ASC 606 is precluded if the collaborative arrangement participant is not a customer. The standard was adopted on January 1, 2020 and was applied retrospectively to when ASC 606 was adopted (January 1, 2017). It did not have a material impact on our consolidated financial position and results of operations. Recently issued accounting standards and updates not yet effective In February 2016 the FASB issued ASU No. 2016-02, Leases The Company plans to adopt the new leasing standard on January 1, 2021, using a modified retrospective transition approach to be applied to leases existing as of, or entered into after, January 1, 2021. The Company is reviewing its existing lease contracts and the impact of the new leasing standards on its consolidated results of operations, financial position and disclosures. While the adoption of this standard is expected to result in an increase in reported assets and liabilities, the Company has not yet determined the full impact that the adoption of ASU 2016-02 will have on its consolidated financial statements. In June 2016 the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 3. Fair value measurements No financial instruments were measured at fair value on a recurring basis as of June 30, 2020. The following tables set forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy as of December 31, 2019 (in thousands): December 31, 2019 (in thousands) Level 1 Level 2 Level 3 Total Preferred stock tranche rights liability $ — $ — $ 5,400 $ 5,400 Totals $ — $ — $ 5,400 $ 5,400 The fair value of the Series B Preferred Stock tranche rights liability was estimated using a probability-weighted present value of the benefit of investment with the following significant unobservable inputs (Level 3): Valuation Dates December 31, 2018 June 30, 2019 December 31, 2019 March 23, 2020 (Tranche 3 settlement) Implied equity value (in millions) €30.8 ($35.4) €48.8 ($55.6) $ 74.4 $ 208.2 Probability of success of reaching necessary milestone: Tranche 2 milestone 85% by March 31, 2019 N/A N/A N/A Tranche 3 milestone (by March 31, 2020) 90 % 90 % 90 % 90 % Expected industry return over period during which milestones are expected to be achieved 15.0 % 15.5 % 15.0 % 13.0 % Risk-free interest rate 2.5 % 2.3 % 2.3 % 1.1 % During the periods presented, the Company has not changed the manner in which it values assets and liabilities that are measured at fair value. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. There were no transfers within the hierarchy during the six month periods ended June 30, 2019 and 2020. The following table presents changes during the three and six months ended June 30, 2020 and 2019 in Level 3 liabilities measured at fair value on a recurring basis: (in thousands) Preferred Stock Tranche Rights Liability Anti-Dilution Warrants Balances at January 1, 2019 $ 6,325 $ 401 Change in estimated fair value (784 ) — Effects of exchange rate changes (127 ) (9 ) Balances at March 31, 2019 5,414 392 Change in estimated fair value 488 — Effects of exchange rate changes 53 6 Balances at June, 2019 $ 5,955 $ 398 Balances at January 1, 2020 $ 5,400 $ — Change in estimated fair value (1,265 ) — Settlement of tranche right (4,135 ) — Balances at March 31, 2020 $ — $ — The preferred stock tranche rights liability was settled on March 24, 2020 and no liability exists thereafter. The anti-dilution warrants are classified as Level 3 in the fair value hierarchy. Due to the Share Exchange transaction on October 4, 2019 (see Note 7), there was no value to the anti-dilution warrants at December 31, 2019. The above fair value measurements are sensitive to changes in the underlying unobservable inputs. A change in those inputs could result in a significantly higher or lower fair value measurement.

Supplemental Balance Sheet Info

Supplemental Balance Sheet Information	6 Months Ended
	Jun. 30, 2020
Supplemental Balance Sheet Information [Abstract]
Supplemental Balance Sheet Information	Note 4. Supplemental balance sheet information Property and equipment Property and equipment, net consisted of the following: (in thousands) June 30, 2020 December 31, 2019 Scientific equipment $ 2,326 $ 2,300 Furniture & office equipment 445 346 Leasehold improvements 782 771 Total 3,553 3,417 Accumulated depreciation and amortization (2,302 ) (2,081 ) Property & equipment, net $ 1,251 $ 1,336 Depreciation and amortization expense was $0.1 million and $0.2 million for the three months ended June 30, 2020 and 2019, respectively, and $0.3 million for the six months ended June 30, 2020 and 2019. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consisted of the following: (in thousands) June 30, 2020 December 31, 2019 Accrued clinical trial costs $ 1,988 $ 2,683 Accrued personnel costs 1,228 1,409 Accrued professional fees 25 30 Accrued other 119 140 Total accrued expenses and other current liabilities $ 3,360 $ 4,262

License and collaboration agree

License and collaboration agreements	6 Months Ended
	Jun. 30, 2020
License Agreements [Abstract]
License and collaboration agreements	Note 5. License and collaboration agreements Adimab In January 2017, the Company entered into a collaboration agreement (as amended, the Adimab Agreement) with Adimab, LLC (Adimab). Adimab has developed an antibody discovery and optimization technology platform. This collaboration enables the Company’s research and development efforts on discovery and optimization of new antibodies against immuno-oncology targets the Company may identify. Under the terms of the Adimab Agreement, Adimab has granted the Company a worldwide, non-exclusive research license for a one-year research term period and evaluation period for up to 18 months per research program. The Company is required to use commercially reasonable efforts to perform its research activities under the Adimab Agreement and, if the Company exercises its right to obtain a development and commercialization license, the Company is required to use commercially reasonable efforts to pursue development and commercialization of a product directed to the applicable target. Under the terms of the Adimab Agreement, the Company granted Adimab a worldwide, non-exclusive license under all of its patents and know-how that are reasonably necessary or useful for Adimab to perform its research activities under the Adimab Agreement. Payment terms to Adimab include a one-time upfront technology access fee in the tens of thousands and payments for research support. Adimab is entitled to additional fees of up to a maximum of $0.4 million on a program-by-program basis for the achievement of certain technical milestones, one of which was met and the Company paid $0.2 million in April 2017. Upon the Company’s exercise of an option for an exclusive development and commercialization license, with respect to a target, the Company is required to make a low single digit million-dollar payment to Adimab for each exercised option. In August 2018, the Company paid a $1.0 million nonrefundable fee to exercise an option to acquire certain licenses from Adimab. One of the antibodies licensed under the Adimab Agreement is now what the Company refers to as EOS-448. In addition, on a per target basis, the Company may be required to pay development, regulatory and commercial milestones totaling up to an aggregate of $42.8 million for the first three products and additional milestone payments up to $13.5 million for each additional product. The Company will pay Adimab low to mid single-digit percentage royalties on a country-by-country and product-by-product basis, on worldwide net product sales of licensed products. Royalties are payable on a licensed product-by-licensed product and country-by-country basis until the later of (i) expiration of the last valid claim of a licensed patent right that covers such licensed product in such country, and (ii) ten years following the first commercial sale of such licensed product in such country. To date, the Company has paid a total of $3.4 million to Adimab under the Adimab Agreement. Adimab controls the filing, prosecution, maintenance and enforcement of the intellectual property that it licenses to the Company under the Adimab Agreement. The Company has the right to enforce such licensed intellectual property against infringement if the infringement is competitive with the Company’s licensed products and Adimab does not pursue enforcement. The Company controls the filing, prosecution, maintenance and enforcement of the intellectual property the Company licenses to Adimab under the Adimab Agreement and all program antibody patents. The term of the Adimab Agreement will continue until the last to expire royalty term on a product-by-product and country-by-country basis if the Company exercises its option, or in the event no option is exercised, the conclusion of the last-to-expire evaluation term, unless terminated earlier by either party. Each party has the right to terminate the Adimab Agreement due to the other party’s uncured material breach or the Company’s abandonment of the product. MSD International GmbH On December 10, 2019, the Company entered into a Clinical Trial Collaboration and Supply Agreement (the MSD Agreement) with MSD International GmbH (MSD), a subsidiary of Merck & Co., Inc. Under the MSD Agreement, the Company will sponsor a clinical trial in which both the Company’s compound and MSD’s compound will be dosed in combination. The Company will conduct the research at its own cost and MSD will contribute its compound towards the study at no cost to the Company. The parties will equally own the clinical data and inventions from the study, with the exception of inventions relating solely to each party’s compound class. The MSD Agreement will expire upon the delivery of a written report on the results of the study, unless earlier terminated or agreed by the parties. The Company began receiving compounds from MSD on April 1, 2020 and the Company plans to begin the research study in the third quarter of 2020. The terms of the MSD Agreement meet the criteria under ASC Topic 808, Collaborative Arrangements Revenue from Contracts with Customers Nonmonetary Transactions

Government Grant Funding and Po

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs)	6 Months Ended
	Jun. 30, 2020
Research And Development Arrangement With Federal Government [Abstract]
Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs)	Note 6. Government grant funding and potential repayment commitments under recoverable cash advance grants (RCAs) The Company has been awarded grants from the Walloon Region, a federal region of Belgium (the Walloon Region) and the European Union (the granting agencies) to fund research and development activities. The grants reimburse a percentage (55-100%) of actual qualifying expenditures. The Company periodically submits proof of qualifying expenditures to the granting agencies for approval and reimbursement. During the six month periods ended June 30, 2020 and 2019, the Company received funding under several grants which included no obligation to repay and two grants that include potential obligations to repay (RCAs). As the granting agencies do not meet the definition of a customer under Topic 606, qualifying grants receipts are recognized as grant income within other income in the condensed consolidated statement of operations and comprehensive loss. Grants which do not include an obligation to repay The total amount that the granting agencies have agreed to fund in the future if the Company incurs qualifying research and development expenses under these grants is $3.5 million. Grants which include a potential obligation to repay—RCAs On July 20, 2017, the Company entered into a recoverable cash advance arrangement whereby the Walloon Region will provide the Company with up to $21.2 million for a research and development program to perform clinical validation of an A2A receptor antagonist drug candidate for immune-oncology (RCA-1). On December 3, 2019, the Company entered into another recoverable cash advance arrangement with the Walloon Region (RCA-2) for up to $4.0 million to be received to fund a research and development program conducted to develop a TIGIT blocking antibody with anti-tumor properties. Under the terms of both agreements, the Company must decide within 6 months after the end of the research period whether it will further pursue commercial development or out licensing of the drug candidate. The research period for RCA-1 and RCA-2 ends in December and February 2021, respectively, per the current agreements. The Company must repay 30% of the amount received under the grant by annual installments from 2022 to 2041 (the fixed annual repayments) unless the Company decides not to pursue commercial development or out licensing of the drug candidate, applies for a waiver from the Walloon Region justifying its decision based upon the failure of the program, and returns the intellectual property to the Walloon Region. Because of the requirement to repay 30% of the amounts received under the grant, the Company records the present value of such amounts as grants repayable on the condensed consolidated balance sheets. In addition, in the event that the Company receives revenue from products or services related to the results of the research, it has to pay to the Walloon Region a 0.33% royalty on revenue resulting from RCA-1 and a 0.12% royalty on revenue resulting from RCA-2. The maximum amount payable to the Walloon Region under each grant, including the fixed annual repayments, the royalty on revenue, and the interest thereon, is twice the amount of funding received. The Company assessed whether there is an obligation to make a royalty payment based on the probability of successful completion of the research and development and future sales and commercial success of the drug candidate, and no grant repayable was recorded as of June 30, 2020 or December 31, 2019. The Company recorded grant income in the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2019 and 2020 for amounts of grants received from the Walloon Region in the period during which the related qualifying expenses were incurred, net of any grants repayable recorded in the condensed consolidated balance sheets. The Company recorded receivables on the condensed consolidated balance sheets related to amounts the Walloon Region owes the Company based on qualifying expenses incurred by the Company. The Company recorded deferred income in the condensed consolidated balance sheets for amounts received from the Walloon Region in advance of incurring qualifying expenses. The following table reflects activity for grant programs for the three and six months ended June 30, 2020 and 2019 and end of period balances as of June 30, 2020 and December 31, 2019: RCA -1 RCA-2 Other Grants Total (In thousands) 2020 2019 2020 2019 2020 2019 2020 2019 Cash received during the six months ended June 30 $ 7,693 $ — $ 1,968 N/A $ 168 $ 900 $ 9,829 $ 900 Grant income recognized during the six months ended June 30 1,857 1,219 508 N/A 305 223 $ 2,670 $ 1,442 Cash received during the three months ended June 30 — — 30 N/A 168 21 $ 198 $ 21 Grant income recognized during the three months ended June 30 725 550 137 N/A 219 128 $ 1,081 $ 678 Grants receivable at the end of the period — 4,449 — 676 212 71 $ 212 $ 5,196 Grants repayable at the end of the period $ 3,583 $ 1,397 $ 578 N/A $ — $ — $ 4,161 $ 1,397

Stockholders_ equity (deficit)

Stockholders’ equity (deficit)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Stockholders’ equity (deficit)	Note 7. Stockholders’ equity (deficit) Series B-2 preferred stock On March 24, 2020, the Company issued 44,453,477 shares of Series B-2 Convertible Preferred Stock in exchange for gross proceeds of $125.4 million. Issuance costs were $0.3 million. Part of the Series B-2 shares issued served as settlement for the 11,046,657 Series B shares due to be issued under the Third Tranche of the Series B Subscription Agreement. The Series B and Series B-2 preferred stock are collectively referred to as the “Senior Preferred Stock”. Under the Amended and Restated Certificate of Incorporation dated March 24, 2020, the significant rights and preferences of the outstanding preferred stock of the Company are as follows: Dividends —The Preferred Stock of the Company accrues dividends at a rate of 6% per annum on the original issue price. Dividends are cumulative and accrue whether declared or not. Liquidation preference —In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company or a Deemed Liquidation Event, as defined below, (and after payment of all liabilities and all costs incurred in connection with the Liquidation Event or setting aside of monies sufficient to cover such liabilities and costs), the net assets in cash, shares or other assets (Liquidation Proceeds) shall be distributed in the following order: 1) First, the holders of Senior Preferred Stock (if necessary, on a pro rata basis) shall, in preference to any other outstanding securities, receive an amount equal to the original subscription price paid, plus accrued but unpaid dividends. 2) Second, out of the remaining Liquidation Proceeds (if any), the holders of Series A Preferred stock (if necessary, on a pro rata basis) shall, in preference to other outstanding securities, receive an amount equal to the original subscription price paid plus accrued but unpaid dividends. 3) Third, any remaining Liquidation Proceeds shall be distributed among the holders of the shares of Senior Preferred Stock and common stock, pro rata based on the number of shares held by each such holder, treating for this purpose all such securities as if they had been mandatorily converted to common stock pursuant to the terms of the Amended and Restated Certificate of Incorporation. Deemed liquidation event —Means (i) a merger or consolidation in which the Company is a constituent party or a subsidiary of the Company is a constituent party and the Company issues shares of its capital stock pursuant to such merger or consolidation, (ii) (a) the sale, lease, transfer, exclusive license or other disposition, in a single transaction or series of related transactions, by the Company or any subsidiary of the Company of all or substantially all the assets of the Company and its subsidiaries taken as a whole, or (b) the sale or disposition of one or more subsidiaries of the Company if substantially all of the assets of the Company and its subsidiaries taken as a whole are held by such subsidiary or subsidiaries, except where such sale, lease, transfer, exclusive license or other disposition is to a wholly owned subsidiary of the Company, or (iii) the transfer of more than a majority of the outstanding capital stock of the Company by way of sale or disposition (whether by merger, consolidation, or otherwise, and whether in a single transaction or a series of related transactions) or otherwise. Redemption rights —At any time after the fifth anniversary of the original issue date of the Series B-2 Preferred Stock (March 24, 2025), upon a vote of 60% of the holders of Senior Preferred Stock, unless prohibited by Delaware law governing distributions to stockholders, shares of Senior Preferred Stock will be redeemed by the Company at a price equal to the greater of: 1) the applicable original issue price per share, plus any accrued but unpaid dividends and 2) the fair market value of the Senior Preferred Stock as of the date of the redemption request. Fair market value shall be based on the enterprise value without discount for illiquidity or lack of marketability, minority position, or transfer restrictions. Series A Preferred Stock is only redeemable upon a liquidity event. Voting rights —All outstanding shares are entitled to one vote. Optional conversion —Each share of Senior Preferred Stock is convertible, at the option of the holder, into shares of common stock at a ratio equal to the original applicable issuance price plus accrued but unpaid dividends divided by the applicable conversion price in effect at the time of conversion (initially equal to the applicable original issue price, adjusted going forward for any dilutive issuances, stock splits or similar events). Mandatory conversion —Each share preferred stock (Series A and Senior Preferred) shall automatically convert into common shares at the then applicable conversion rate upon (i) vote by 60% of the then-outstanding shares of Senior Preferred Stock or, (ii) an initial public offering of the Company’s common stock at a price of at least $9.34 per share and a proposed offering size of at least $50.0 million. See Note 12. Directors —The Series B-2 Preferred shareholders are entitled to elect 2 directors and the Series B Preferred shareholders are entitled to elect 3 directors out of the 9 directors of the Board.

Stock-based compensation

Stock-based compensation	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based compensation	Note 8. Stock-based compensation On March 24, 2020, the Board of Directors approved an increase to the total authorized options under the 2019 Stock Option and Grant Plan to 3,464,316. Stock-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows: Three months ended June 30, Six months ended June 30, (in thousands) 2020 2019 2020 2019 Research and development 67 43 $ 117 $ 86 General and administrative 283 160 419 322 Total stock-based compensation expense $ 350 $ 203 $ 536 $ 408 The following table summarizes stock option activity for the six months ended June 30, 2020: Stock Options Shares Weighted average exercise price Weighted average remaining contractual life (in years) Aggregate intrinsic value (in thousands) Outstanding as of December 31, 2019 1,387,003 $ 4.62 Granted 2,127,318 4.33 Forfeited (59,076 ) 5.20 Exercised (131,867 ) 1.56 Outstanding as of June 30, 2020 3,323,378 $ 4.54 8.0 $ 5,938 Exercisable at June 30, 2020 716,304 $ 5.27 4.8 $ 1,203 The weighted-average grant-date fair value of options awarded during the six month periods ended June 30, 2020 and 2019 was approximately $3.21 per share and $1.49 per share, respectively. As of June 30, 2020, there was a total of $7.2 million of unrecognized employee compensation costs related to non-vested stock option awards expected to be recognized over a weighted average period of 3.6 years. The Company received $0.2 million from the exercise of 131,867 options into common stock in April 2020. The Company estimates the fair value of stock-based compensation utilizing the Black-Scholes option pricing model, which is dependent upon several variables, such as expected term, volatility, risk-free interest rate, and expected dividends. Each of these inputs is subjective and generally requires significant judgment to determine. Stock-based compensation is measured at the grant date based on the fair value of the award and is recognized as expense over the requisite service period, which is generally the vesting period of the respective award. The following table summarizes the range of key assumptions used to determine the fair value of stock options granted during: Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 Risk-free interest rate 0.45% 2.51% 0.45% - 1.35% 2.51 % Expected term (in years) 6 5 6 5 Expected volatility 92% 93% 90% - 92% 93 % Expected dividend yield — — — — Estimated fair value of common stock $4.24 - $6.16 2.38 $2.95 - $6.16 $ 2.38

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 9. Commitments and contingencies Purchase commitments The Company has contractual arrangements with research and development organizations and suppliers; however, these contracts are generally cancelable on 30-60 days’ notice and the obligations under these contracts are largely based on services performed. The Company may also enter into contracts in the normal course of business with clinical research organizations for clinical trials, with contract manufacturing organizations for clinical supplies and with other vendors for preclinical studies, supplies and other services and products for operating purposes. These contracts generally provide for termination on notice. As of June 30, 2020 and December 31, 2019, there were no amounts accrued related to termination charges. Leases The Company leases primarily office space in Charleroi, Belgium and Cambridge, Massachusetts under non-cancelable operating leases with expiration dates in December 2021 and May 2022, respectively, in addition to some small car leases that typically have four-year terms. Rent expense was $0.1 million for the three months ended June 30, 2020 and 2019, and $0.3 million and $0.2 million for the six month periods ended June 30, 2020 and 2019, respectively. As of June 30, 2020, the Company had the following future minimum lease payments under non-cancelable operating leases for the remainder of 2020 and the future years thereafter (in thousands): Year ending December 31: 2020 $ 267 2021 523 2022 122 2023 6 Total $ 918 In March 2019, the Company provided a letter of credit for approximately $57,000 to secure its obligation under its lease in Cambridge. The Company maintains that amount of cash on hand to fund any necessary draws on the letter of credit. In addition, the Company has approximately $66,000 on hand serving as a guarantee for its lease obligation in Belgium. These amounts have been classified as restricted cash in the condensed consolidated balance sheets as of June 30, 2020 and December 31, 2019.

Related party transactions

Related party transactions	6 Months Ended
	Jun. 30, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Note 10. Related party transactions On June 11, 2018, the Company entered into a Royalty Transfer Agreement with the charitable foundations of two of its investors (MPM Oncology Charitable Foundation, Inc. and UBS Optimus Foundation), which requires it to pay a royalty equal to 1% percent of its net product sales each year within 120 days following each year end. Such agreement was entered into as a result of the capital contributions received from the investors. As the Company has no product sales to date, no royalties were owed to these charitable foundations as of June 30, 2020.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stock	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stock	Note 11. Net loss per share attributable to common stock The following common stock equivalents were excluded from the calculation of net loss per share due to their anti-dilutive effect: June 30, 2020 2019 Series B and B-2 Preferred Stock, as converted 20,597,566 6,563,548 Series A Preferred Stock, as converted 1,862,510 1,862,510 Profit certificates, as converted — 7,022 Stock options outstanding 3,323,378 1,388,969 Total 25,783,454 9,822,049

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	Note 12. Subsequent events The Company evaluated all material subsequent events. The following events occurred subsequent to June 30, 2020: Reverse Stock Split On July 20, 2020, the Company effected a 1-for-3.3115 reverse stock split of the Company’s common stock and adjusted the ratio at which the Company’s preferred stock is convertible into common stock, as well as the number of shares under the 2019 Stock Option and Grant Plan and the Amended and Restated Certificate of Incorporation of iTeos Therapeutics, Inc., as well as the share amounts of stock grants under the plan and the number of options and exercise prices of options under the plan. All shares of common stock, stock options exercisable for shares of common stock, and per share information presented in the accompanying consolidated financial statements and notes thereto have been adjusted, where applicable, to reflect the reverse stock split on a retroactive basis for all periods presented. There was no change in the par value of the Company’s common stock. Initial Public Offering On July 28, 2020, the Company completed an IPO of 10,586,316 shares of its common stock, for aggregate gross proceeds of $201.1 million and its shares started trading on The Nasdaq Global Select Market under the ticker symbol “ITOS.” The Company received approximately $184 in net proceeds after deducting underwriting discounts and commissions and other estimated offering expenses payable by the Company. Upon closing of the IPO, all of the Company's outstanding shares of convertible preferred stock automatically converted into On August 5, 2020, the underwriters purchased an additional Amendment to 2019 Stock Option and Grant Plan On July 15, 2020, the Company’s Board of Directors approved an amendment to the 2019 Stock Option and Grant Plan to provide for immediate 100% vesting for all outstanding options under the plan upon the consummation of a Sale Event, as defined by the amendment. 2020 Stock Option and Incentive Plan The 2020 Stock Option and Incentive Plan (the “2020 Plan”) was approved by the Company’s board of directors on July 15, 2020, and the Company’s stockholders on July 20, 2020 and became effective on July 22, 2020, the date immediately prior to the date on which the registration statement for the Company’s IPO became effective. The 2020 Plan provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock units, restricted stock awards, unrestricted stock awards, cash-based awards and dividend equivalent rights to the Company’s officers, employees, directors and consultants. The number of shares of common stock initially reserved for issuance under the 2020 Plan is 3,809,818 which shall be cumulatively increased on January 1, 2021 and each January 1 thereafter by 5% of the number of shares of the Company’s common stock outstanding on the immediately preceding December 31 or such lesser number of shares as determined by the Company’s compensation committee of the board of directors. The 2020 Plan will replace the 2019 Plan, as the Company’s board of directors is not expected to make additional awards under the 2019 Plan following the completion of the IPO. However, the 2019 Plan will continue to govern outstanding equity awards granted thereunder. On July 15, 2020, the Board of Directors approved a grant of stock options to purchase 132,864 shares of common stock to directors of the Company. The stock options were granted upon IPO and have an exercise price equal to the price to the public in the Company’s IPO ($19 per share). The options have a 10-year contractual term and vest on the earlier of (i) the first anniversary of the grant date or (ii) the Company’s next annual meeting of the stockholders, subject to continued service through the applicable vesting date. On July 15, 2020, the Board of Directors approved a grant of stock options to purchase 1,035,424 shares of common stock to the CEO of the Company. The options were granted upon IPO equal to the amount necessary for the CEO to have 5% equity ownership on a fully-diluted basis and have an exercise price equal to the price to the public in the Company’s IPO ($19 per share). The options have a 10-year contractual term and vest over a period of four years. Upon a Sale Event, as defined in the 2020 Plan, the options may become 100% vested and exercisable immediately. Employee Stock Purchase Plan The 2020 Employee Stock Purchase Plan (the “2020 ESPP”) was approved by the Company’s board of directors on July 15, 2020, and the Company’s stockholders on July 20, 2020, and become effective on July 22, 2020, the date immediately prior to the date on which the registration statement for the Company’s IPO was declared effective. The ESPP will initially reserve and authorize the issuance of up to a total 317,484 shares of common stock to participating employees. The ESPP will provide that the number of shares reserved and available for issuance will automatically increase on January 1, 2021 and each January 1 thereafter by the lesser of 634,969 shares of common stock, 1% of the outstanding number of shares of common stock on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee.

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The accompanying condensed consolidated financial statements and accompanying notes have been prepared in accordance with generally accepted accounting principles in the United States of America (U.S. GAAP). The unaudited interim condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements as of and for the years ended December 31, 2019 and 2018, and the notes thereto, which are included in the Company’s final prospectus related to the Company’s IPO filed on July 27, 2020 (File No. 333-239415) with the SEC pursuant to Rule 424(b)(4) under the Securities Act of 1933, as amended. The results for any interim period are not necessarily indicative of results for any future period. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period.
Principles of consolidation	Principles of consolidation The accompanying condensed consolidated financial statements include the Company’s accounts and those of its wholly owned subsidiaries. All intercompany accounts, transactions and balances have been eliminated.
Use of estimates	Use of estimates The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and expenses, as well as the related disclosures of contingent assets and liabilities. Estimates are used to determine the fair value of the preferred stock tranche rights liability and anti-dilution warrants liability, the fair value of profit certificates, common stock and stock-based awards and other issuances, accruals for research and development costs, useful lives of long-lived assets, probability of repayment for grants repayable, and uncertain tax positions. Actual results could differ materially from the Company’s estimates.
Deferred offering costs	Deferred offering costs The Company capitalizes incremental legal, professional accounting and other third-party fees that are directly associated with the IPO as other non-current assets until the IPO is consummated. After consummation of the IPO, these costs will be recorded in stockholders’ deficit as a reduction of additional paid-in-capital generated as a result of the offering. As of June 30, 2020, there were deferred offering costs of approximately $1.7 million included in prepaid expenses and other current assets.
Collaborative arrangements	Collaborative Arrangements The Company analyzes its collaboration arrangements to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and are, therefore within the scope of ASC Topic 808, Collaborative Arrangements
Recently adopted accounting standards updates	Recently adopted accounting standards updates In August 2018 the FASB issued ASU No. 2018-13, Fair Value Measurement Disclosure Framework Changes to the Disclosure Requirements for Fair Value Measurement In November 2018 the FASB issued ASU No. 2018-18, Collaborative Arrangements Clarifying the Interaction between Topic 808 and Topic 606 • Clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606, Revenue from Contracts with Customers • Adds unit-of-account guidance to ASC 808, Collaborative Arrangements • Requires that in a transaction with a collaborative arrangement participant that is not directly related to sales to third parties, presenting that transaction together with revenue recognized under ASC 606 is precluded if the collaborative arrangement participant is not a customer. The standard was adopted on January 1, 2020 and was applied retrospectively to when ASC 606 was adopted (January 1, 2017). It did not have a material impact on our consolidated financial position and results of operations. Recently issued accounting standards and updates not yet effective In February 2016 the FASB issued ASU No. 2016-02, Leases The Company plans to adopt the new leasing standard on January 1, 2021, using a modified retrospective transition approach to be applied to leases existing as of, or entered into after, January 1, 2021. The Company is reviewing its existing lease contracts and the impact of the new leasing standards on its consolidated results of operations, financial position and disclosures. While the adoption of this standard is expected to result in an increase in reported assets and liabilities, the Company has not yet determined the full impact that the adoption of ASU 2016-02 will have on its consolidated financial statements. In June 2016 the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Summary of Financial Instruments Measured at Fair Value on a Recurring Basis	The following tables set forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy as of December 31, 2019 (in thousands): December 31, 2019 (in thousands) Level 1 Level 2 Level 3 Total Preferred stock tranche rights liability $ — $ — $ 5,400 $ 5,400 Totals $ — $ — $ 5,400 $ 5,400
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Summary of Fair Value of Series B Preferred Stock Tranche Rights Liability	The fair value of the Series B Preferred Stock tranche rights liability was estimated using a probability-weighted present value of the benefit of investment with the following significant unobservable inputs (Level 3): Valuation Dates December 31, 2018 June 30, 2019 December 31, 2019 March 23, 2020 (Tranche 3 settlement) Implied equity value (in millions) €30.8 ($35.4) €48.8 ($55.6) $ 74.4 $ 208.2 Probability of success of reaching necessary milestone: Tranche 2 milestone 85% by March 31, 2019 N/A N/A N/A Tranche 3 milestone (by March 31, 2020) 90 % 90 % 90 % 90 % Expected industry return over period during which milestones are expected to be achieved 15.0 % 15.5 % 15.0 % 13.0 % Risk-free interest rate 2.5 % 2.3 % 2.3 % 1.1 %
Summary of Changes in Level 3 Liabilities Measures at Fair Value on a Recurring Basis	The following table presents changes during the three and six months ended June 30, 2020 and 2019 in Level 3 liabilities measured at fair value on a recurring basis: (in thousands) Preferred Stock Tranche Rights Liability Anti-Dilution Warrants Balances at January 1, 2019 $ 6,325 $ 401 Change in estimated fair value (784 ) — Effects of exchange rate changes (127 ) (9 ) Balances at March 31, 2019 5,414 392 Change in estimated fair value 488 — Effects of exchange rate changes 53 6 Balances at June, 2019 $ 5,955 $ 398 Balances at January 1, 2020 $ 5,400 $ — Change in estimated fair value (1,265 ) — Settlement of tranche right (4,135 ) — Balances at March 31, 2020 $ — $ —

Supplemental Balance Sheet In_2

Supplemental Balance Sheet Information (Tables)	6 Months Ended
	Jun. 30, 2020
Supplemental Balance Sheet Information [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following: (in thousands) June 30, 2020 December 31, 2019 Scientific equipment $ 2,326 $ 2,300 Furniture & office equipment 445 346 Leasehold improvements 782 771 Total 3,553 3,417 Accumulated depreciation and amortization (2,302 ) (2,081 ) Property & equipment, net $ 1,251 $ 1,336
Schedule of Accrued Expenses	Accrued expenses and other current liabilities consisted of the following: (in thousands) June 30, 2020 December 31, 2019 Accrued clinical trial costs $ 1,988 $ 2,683 Accrued personnel costs 1,228 1,409 Accrued professional fees 25 30 Accrued other 119 140 Total accrued expenses and other current liabilities $ 3,360 $ 4,262

Government Grant Funding and _2

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) (Tables)	6 Months Ended
	Jun. 30, 2020
Research And Development Arrangement With Federal Government [Abstract]
Schedule of Activity for Grant Programs	The following table reflects activity for grant programs for the three and six months ended June 30, 2020 and 2019 and end of period balances as of June 30, 2020 and December 31, 2019: RCA -1 RCA-2 Other Grants Total (In thousands) 2020 2019 2020 2019 2020 2019 2020 2019 Cash received during the six months ended June 30 $ 7,693 $ — $ 1,968 N/A $ 168 $ 900 $ 9,829 $ 900 Grant income recognized during the six months ended June 30 1,857 1,219 508 N/A 305 223 $ 2,670 $ 1,442 Cash received during the three months ended June 30 — — 30 N/A 168 21 $ 198 $ 21 Grant income recognized during the three months ended June 30 725 550 137 N/A 219 128 $ 1,081 $ 678 Grants receivable at the end of the period — 4,449 — 676 212 71 $ 212 $ 5,196 Grants repayable at the end of the period $ 3,583 $ 1,397 $ 578 N/A $ — $ — $ 4,161 $ 1,397

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock-Based Compensation Expense	Stock-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows: Three months ended June 30, Six months ended June 30, (in thousands) 2020 2019 2020 2019 Research and development 67 43 $ 117 $ 86 General and administrative 283 160 419 322 Total stock-based compensation expense $ 350 $ 203 $ 536 $ 408
Summary of Stock Options Activity	The following table summarizes stock option activity for the six months ended June 30, 2020: Stock Options Shares Weighted average exercise price Weighted average remaining contractual life (in years) Aggregate intrinsic value (in thousands) Outstanding as of December 31, 2019 1,387,003 $ 4.62 Granted 2,127,318 4.33 Forfeited (59,076 ) 5.20 Exercised (131,867 ) 1.56 Outstanding as of June 30, 2020 3,323,378 $ 4.54 8.0 $ 5,938 Exercisable at June 30, 2020 716,304 $ 5.27 4.8 $ 1,203
Schedule of Fair Value Assumptions for Stock Options Granted	The following table summarizes the range of key assumptions used to determine the fair value of stock options granted during: Three months ended June 30, Six months ended June 30, 2020 2019 2020 2019 Risk-free interest rate 0.45% 2.51% 0.45% - 1.35% 2.51 % Expected term (in years) 6 5 6 5 Expected volatility 92% 93% 90% - 92% 93 % Expected dividend yield — — — — Estimated fair value of common stock $4.24 - $6.16 2.38 $2.95 - $6.16 $ 2.38

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases	As of June 30, 2020, the Company had the following future minimum lease payments under non-cancelable operating leases for the remainder of 2020 and the future years thereafter (in thousands): Year ending December 31: 2020 $ 267 2021 523 2022 122 2023 6 Total $ 918

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stock (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Schedule of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share	The following common stock equivalents were excluded from the calculation of net loss per share due to their anti-dilutive effect: June 30, 2020 2019 Series B and B-2 Preferred Stock, as converted 20,597,566 6,563,548 Series A Preferred Stock, as converted 1,862,510 1,862,510 Profit certificates, as converted — 7,022 Stock options outstanding 3,323,378 1,388,969 Total 25,783,454 9,822,049

Nature of Business - Additional

Nature of Business - Additional Information (Details) - USD ($) $ in Thousands	Aug. 05, 2020	Jul. 28, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net loss			$ (7,202)	$ (5,247)	$ (5,755)	$ (4,402)	$ (12,449)	$ (10,157)
Accumulated deficit			$ (48,314)				(48,314)		$ (35,865)
Net proceeds from issuance of IPO							$ 205	$ 102
Subsequent Event
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Underwriters purchase of additional shares of common stock	1,505,359
Net proceeds after deducting commissions from underwriter purchase of additional share of common stock	$ 26,600
IPO | Subsequent Event
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net proceeds from issuance of IPO		$ 184,000

Summary of significant accoun_3

Summary of significant accounting policies - Additional Information (Details) $ in Millions	Jun. 30, 2020USD ($)
Accounting Policies [Abstract]
Deferred offering costs	$ 1.7

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Mar. 24, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Financial instruments	$ 0
Transfers within hierarchy	$ 0	$ 0
Preferred stock tranche rights liability			$ 0	$ 5,400,000
Anti-dilution warrants				$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - USD ($)	Mar. 24, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock tranche rights liability	$ 0	$ 5,400,000
Totals		5,400,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock tranche rights liability		5,400,000
Totals		$ 5,400,000

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Fair Value of Series B Preferred Stock Tranche Rights Liability (Details) - Series B Preferred Stock - Significant unobservable inputs (Level 3) € in Millions, $ in Millions	Mar. 23, 2020USD ($)	Dec. 31, 2019USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2019EUR (€)	Dec. 31, 2018USD ($)	Dec. 31, 2018EUR (€)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Implied equity value		$ 74.4	$ 55.6	€ 48.8	$ 35.4	€ 30.8
Tranche Three Settlement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Implied equity value	$ 208.2
Tranche 2 milestone (by March 31, 2019)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Probability of success of reaching necessary milestone					85.00%	85.00%
Tranche 3 milestone (by March 31, 2020)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Probability of success of reaching necessary milestone		90.00%	90.00%	90.00%	90.00%	90.00%
Tranche 3 milestone (by March 31, 2020) | Tranche Three Settlement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Probability of success of reaching necessary milestone	90.00%
Expected industry return over period during which milestones are expected to be achieved
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input		15	15.5	15.5	15	15
Expected industry return over period during which milestones are expected to be achieved | Tranche Three Settlement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	13
Risk-free interest rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input		2.3	2.3	2.3	2.5	2.5
Risk-free interest rate | Tranche Three Settlement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	1.1

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Changes in Level 3 Liabilities Measures at Fair Value on a Recurring Basis (Details) - Significant unobservable inputs (Level 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019
Preferred Stock Tranche Rights Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balances	$ 5,400	$ 5,414	$ 6,325
Change in estimated fair value	(1,265)	488	(784)
Effects of exchange rate changes		53	(127)
Balances		5,955	5,414
Settlement of tranche right	$ (4,135)
Anti-Dilution Warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balances		392	401
Effects of exchange rate changes		6	(9)
Balances		$ 398	$ 392

Supplemental Balance Sheet In_3

Supplemental Balance Sheet Information - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Total property and equipment	$ 3,553	$ 3,417
Accumulated depreciation and amortization	(2,302)	(2,081)
Property & equipment, net	1,251	1,336
Scientific Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	2,326	2,300
Furniture and Office Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	445	346
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 782	$ 771

Supplemental Balance Sheet In_4

Supplemental Balance Sheet Information - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Supplemental Balance Sheet Information [Abstract]
Depreciation and amortization	$ 100	$ 200	$ 250	$ 307

Supplemental Balance Sheet In_5

Supplemental Balance Sheet Information - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued clinical trial costs	$ 1,988	$ 2,683
Accrued personnel costs	1,228	1,409
Accrued professional fees	25	30
Accrued other	119	140
Total accrued expenses and other current liabilities	$ 3,360	$ 4,262

License and collaboration agr_2

License and collaboration agreements - Additional Information (Details) - Adimab L L C - USD ($) $ in Millions	Aug. 31, 2018	Apr. 30, 2017	Jun. 30, 2020
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront payment received		$ 0.2
Maximum additional receivable based on achievement of research milestones			$ 13.5
Nonrefundable fee to exercise an option	$ 1
License revenue
Research And Development Arrangement Contract To Perform For Others [Line Items]
License revenue			3.4
Research Collaboration and Option Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Maximum option fees receivable based on achievement of research milestones per program			0.4
Development Regulatory and Sales Milestone
Research And Development Arrangement Contract To Perform For Others [Line Items]
Maximum option fees receivable based on achievement of research milestones			$ 42.8

Government Grant Funding and _3

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) - Additional Information (Details) - USD ($)	Dec. 03, 2019	Jul. 20, 2017	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expenses			$ 3,500,000
Grant repayable			$ 4,161,000		$ 1,397,000
RCA-1
Research And Development Arrangement Contract To Perform For Others [Line Items]
Recoverable cash advance		$ 21,200,000
Percentage of royalty on revenue			0.33%
Grant repayable			$ 3,583,000		$ 1,397,000
RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Recoverable cash advance	$ 4,000,000
Percentage of royalty on revenue			0.12%
Grant repayable			$ 578,000
RCA-1 and RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Percentage of repayment amount received under grant			30.00%
Research And Development And Future Sales
Research And Development Arrangement Contract To Perform For Others [Line Items]
Grant repayable			$ 0	$ 0
Minimum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Percentage of grant reimburse of actual qualifying expenditures			55.00%
Minimum | RCA-1 and RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Term of repayment amount received under grant			2022
Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Percentage of grant reimburse of actual qualifying expenditures			100.00%
Maximum | RCA-1 and RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Term of repayment amount received under grant			2041

Government Grant Funding and _4

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) - Schedule of Activity for Grant Programs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received	$ 198	$ 21	$ 9,829	$ 900
Grant income	1,081	678	2,670	1,442
Grants receivable	212	5,196	212	5,196	$ 5,196
Grant repayable	4,161	1,397	4,161	1,397
RCA-1
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received			7,693
Grant income	725	550	1,857	1,219
Grants receivable		4,449		4,449
Grant repayable	3,583	1,397	3,583	1,397
RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received	30		1,968
Grant income	137		508
Grants receivable		676		676
Grant repayable	578		578
Other Grants
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received	168	21	168	900
Grant income	219	128	305	223
Grants receivable	$ 212	$ 71	$ 212	$ 71

Stockholders' equity (deficit)

Stockholders' equity (deficit) - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred stock, dividend rate	6.00%
Common stock value	$ 1	$ 1
IPO
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock value	$ 50,000
IPO | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share price	$ 9.34
Series B-2 Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred stock issued	44,453,477
Proceeds from issuance of convertible preferred stock	$ 125,400
Net of Issuance costs	$ 300
Preferred stock voting percent	60
Preferred stock, voting rights	All outstanding shares are entitled to one vote.
Series B Convertible Preferred Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Preferred stock issued	11,046,657

Stock-based compensation - Addi

Stock-based compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	6 Months Ended
	Apr. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Mar. 24, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average estimated fair value of options awarded (in dollars per share)		$ 3.21	$ 1.49
Proceeds from stock options exercised	$ 0.2
Exercise of stock options into common stock/profit certificates (in shares)	131,867	131,867
Non Vested Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs for non-vested stock awards		$ 7.2
Recognition period for compensation cost not yet recognized (in years, months, and days)		3 years 7 months 6 days
2019 Stock Option And Grant Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options authorized				3,464,316

Stock-based compensation - Summ

Stock-based compensation - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 350	$ 203	$ 536	$ 408
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	67	43	117	86
General And Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 283	$ 160	$ 419	$ 322

Stock-based compensation - Su_2

Stock-based compensation - Summary of Stock Options Activity (Details) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended
	Apr. 30, 2020shares	Jun. 30, 2020USD ($)$ / sharesshares
Shares
Outstanding as of December 31, 2019 | shares		1,387,003
Granted | shares		2,127,318
Forfeited | shares		(59,076)
Exercised | shares	(131,867)	(131,867)
Outstanding as of June 30, 2020 | shares		3,323,378
Exercisable at June 30, 2020 | shares		716,304
Weighted-Average Exercise Price Per Share
Outstanding as of December 31, 2019 | $ / shares		$ 4.62
Granted | $ / shares		4.33
Forfeited | $ / shares		5.20
Exercised | $ / shares		1.56
Outstanding as of June 30, 2020 | $ / shares		4.54
Exercisable at June 30, 2020 | $ / shares		$ 5.27
Weighted-Average Remaining Contractual Term
Options outstanding		8 years
Exercisable at June 30, 2020		4 years 9 months 18 days
Aggregate Intrinsic Value
Outstanding as of December 31, 2019 | $		$ 5,938
Exercisable at June 30, 2020 | $		$ 1,203

Stock-based compensation - Sche

Stock-based compensation - Schedule of Fair Value Assumptions for Stock Options Granted (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.45%	2.51%		2.51%
Risk-free interest rate, Minimum			0.45%
Risk-free interest rate, maximum			1.35%
Expected term (in years)	6 years	5 years	6 years	5 years
Expected volatility	92.00%	93.00%		93.00%
Expected Volatility, minimum			90.00%
Expected Volatility, maximum			92.00%
Estimated fair value of common stock		$ 2.38		$ 2.38
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value of common stock	$ 4.24		$ 2.95
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value of common stock	$ 6.16		$ 6.16

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Mar. 31, 2019
Other Commitments [Line Items]
Operating lease term	4 years		4 years
Operating leases, rent expense	$ 100,000	$ 100,000	$ 300,000	$ 200,000
Charleroi, Belgium
Other Commitments [Line Items]
Lease expiration date			Dec. 31, 2021
Operating lease, Hand serving to secure lease obligation	$ 66,000,000		$ 66,000,000		$ 66,000,000
Cambridge, Massachusetts
Other Commitments [Line Items]
Lease expiration date			May 31, 2022
Operating lease, Letter of credit to secure lease obligation						$ 57,000,000
Contract Termination
Other Commitments [Line Items]
Restructuring charges			$ 0		$ 0
Minimum
Other Commitments [Line Items]
Contractual Agreement Cancelation Notice period			30 days
Maximum
Other Commitments [Line Items]
Contractual Agreement Cancelation Notice period			60 days

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases (Details) $ in Thousands	Jun. 30, 2020USD ($)
Leases [Abstract]
2020	$ 267
2021	523
2022	122
2023	6
Total	$ 918

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - Royalty Transfer Agreement $ in Thousands	Jun. 11, 2018USD ($)Investor	Jun. 30, 2020
Related Party Transaction [Line Items]
Royalty owed to charitable foundation	$ 0
Product
Related Party Transaction [Line Items]
Net product sales	$ 0
MPM Oncology Charitable Foundation, Inc. and UBS Optimus Foundation
Related Party Transaction [Line Items]
Number of investors | Investor	2
Obligation to pay royalties		Royalty equal to 1% percent of its net product sales each year within 120 days following each year end.
Percentage of royalty required to pay	1.00%

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stock - Schedule of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents	25,783,454	9,822,049
Series B and B-2 Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents	20,597,566	6,563,548
Series A Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents	1,862,510	1,862,510
Profit Certificates
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents		7,022
Stock Options Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents	3,323,378	1,388,969

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) $ / shares in Units, $ in Millions	Aug. 05, 2020USD ($)shares	Jul. 28, 2020USD ($)shares	Jul. 20, 2020	Jul. 15, 2020$ / sharesshares	Jun. 30, 2020$ / sharesshares
Subsequent Event [Line Items]
Number of stock options granted to purchase common stock					2,127,318
Granted | $ / shares					$ 4.33
Contractual term of stock options					4 years 9 months 18 days
Subsequent Event | 2020 ESPP
Subsequent Event [Line Items]
Common stock initially reserved for future issuance				317,484
Percentage of outstanding shares increase in shares reserved for issuance				1.00%
Maximum increase in common stock shares reserved for issuance				634,969
Subsequent Event | Amendment to 2019 Stock Option and Grant Plan
Subsequent Event [Line Items]
Vesting percentage upon sale				100.00%
Subsequent Event | 2020 Stock Option and Incentive Plan
Subsequent Event [Line Items]
Common stock initially reserved for future issuance				3,809,818
Cumulative increase in common stock reserve for issuance, percentage				5.00%
Subsequent Event | 2020 Stock Option and Incentive Plan | Director
Subsequent Event [Line Items]
Number of stock options granted to purchase common stock				132,864
Granted | $ / shares				$ 19
Contractual term of stock options				10 years
Vesting period of stock options, description				The options have a 10-year contractual term and vest on the earlier of (i) the first anniversary of the grant date or (ii) the Company’s next annual meeting of the stockholders, subject to continued service through the applicable vesting date.
Subsequent Event | 2020 Stock Option and Incentive Plan | Director | Maximum
Subsequent Event [Line Items]
Vesting percentage upon sale				100.00%
Subsequent Event | 2020 Stock Option and Incentive Plan | CEO
Subsequent Event [Line Items]
Number of stock options granted to purchase common stock				1,035,424
Granted | $ / shares				$ 19
Contractual term of stock options				10 years
Equity ownership percentage on fully diluted basis				5.00%
Vesting period of stock options				4 years
Subsequent Event | 2020 Stock Option and Incentive Plan | CEO | Maximum
Subsequent Event [Line Items]
Vesting percentage upon sale				100.00%
Subsequent Event | Common stock
Subsequent Event [Line Items]
Reverse stock split			On July 20, 2020, the Company effected a 1-for-3.3115 reverse stock split of the Company’s common stock
Reverse stock split, conversion ratio			0.30
Number of common stock shares issued from conversion of outstanding convertible preferred stock shares		22,460,076
Subsequent Event | Common stock | IPO
Subsequent Event [Line Items]
Common stock, shares issued during period		10,586,316
Gross proceeds from initial public offering | $		$ 201.1
Net proceeds after deducting underwriting discounts and commissions and other estimated offering expenses payable | $		$ 184
Underwriters exercise option to purchase additional shares of common stock	1,505,359
Net proceeds after deducting commissions from underwriter purchase of additional share of common stock | $	$ 26.6