0001564590-21-015146 | 10-K | XBRL Viewer

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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2020	Mar. 22, 2021	Mar. 15, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Document Annual 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 Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
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		35,098,999
Entity Public Float			$ 697.6
Security12b Title	Common stock, $0.001 par value per share
Security Exchange Name	NASDAQ
ICFR Auditor Attestation Flag	false
Documents Incorporated by Reference	None.

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 336,326	$ 19,868
Grants receivable	133	5,196
Research and development tax credits receivable	192	133
Prepaid expenses and other current assets	2,893	879
Total current assets	339,544	26,076
Property and equipment, net	1,352	1,336
Research and development tax credits receivable	3,286	2,917
Restricted cash	128	122
Other assets	248	293
Total assets	344,558	30,744
Current liabilities:
Accounts payable	3,026	1,174
Accrued expenses and other current liabilities	7,486	4,262
Preferred stock tranche rights liability		5,400
Deferred income	4,486	2,360
Total current liabilities	14,998	13,196
Grants repayable	5,883	1,397
Other noncurrent liabilities	480	482
Total liabilities	21,361	15,075
Commitments and contingencies (Note 10)
Redeemable convertible preferred stock, $0.001 par value per share, zero and 38,157,154 shares authorized at December 31, 2020 and 2019, respectively; zero and 27,110,507 shares outstanding at December 31, 2020 and 2019, respectively		51,757
Stockholders’ equity (deficit):
Preferred stock, $0.001 par value; 10,000,000 and zero shares authorized at December 31, 2020 and 2019, respectively, and zero shares issued or outstanding
Common stock, $0.001 par value, 150,000,000 and 50,000,000 shares authorized at December 31, 2020 and 2019, respectively; 35,044,758 and 256,548 shares issued and outstanding at December 31, 2020 and 2019, respectively	35	1
Additional paid-in capital	396,443
Accumulated other comprehensive income (loss)	617	(224)
Accumulated deficit	(73,898)	(35,865)
Total stockholders’ equity (deficit)	323,197	(36,088)
Total liabilities, redeemable convertible preferred stock and stockholders’ equity (deficit)	$ 344,558	$ 30,744

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Preferred Stock, par value	$ 0.001	$ 0.001
Preferred Stock Shares Authorized	10,000,000	0
Preferred Stock, Shares Outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	50,000,000
Common stock, shares issued	35,044,758	256,548
Common stock, shares outstanding	35,044,758	256,548
Preferred Stock, Shares Issued	0	0
Redeemable Convertible Preferred Stock
Preferred Stock, par value	$ 0.001	$ 0.001
Preferred Stock Shares Authorized	0	38,157,154
Preferred Stock, Shares Outstanding	0	27,110,507

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating expenses:
Research and development expenses	$ 29,900	$ 19,211
General and administrative expenses	15,340	8,837
Total operating expenses	45,240	28,048
Loss from operations	(45,240)	(28,048)
Other income and (expenses):
Grant income	5,647	3,989
Research and development tax credits	286	790
Fair value adjustment for preferred stock tranche rights liability and anti-dilution warrants liability	1,265	1,019
Other expense, net	(48)	(85)
Loss before income tax expense	(38,090)	(22,335)
Income tax (benefit) expense	(57)	119
Net loss	(38,033)	(22,454)
Cumulative dividends on Series A Preferred Stock	(249)	(427)
Accretion of redeemable convertible preferred stock to redemption value	(5,120)	(3,654)
Net loss attributable to common stockholders	$ (43,402)	$ (26,535)
Basic and diluted net loss per common share	$ (2.88)	$ (130.85)
Weighted-average common shares outstanding—basic and diluted	15,080,266	202,793
Net loss	$ (38,033)	$ (22,454)
Foreign currency translation adjustments	841	(213)
Comprehensive loss	(37,192)	(22,667)
Series A Preferred Stock
Other income and (expenses):
Accretion of redeemable convertible preferred stock to redemption value	$ (5,120)	$ (3,654)

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common stock	Profit certificates	Additional paid-in capital	Accumulated other comprehensive income (loss)	Accumulated deflicit	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
Issuance of Preferred Stock								$ 22,372
Issuance of Preferred Stock (in shares)								10,042,405
Accretion of Series B and B-2 Preferred Stock to redemption value	(3,654)			$ (1,008)		(2,646)		$ 3,654
Exercise of stock options into common stock/profit certificates	102		$ 102
Exercise of stock options into common stock/profit certificates (in shares)			63,810
Effects of Share Exchange transaction		$ (86)	$ (113)	199
Effects of Share Exchange Transaction, shares		70,832	(70,832)
Stock-based compensation	809			809
Currency translation adjustment	(213)				(213)
Net loss	(22,454)					(22,454)
Ending balance at Dec. 31, 2019	(36,088)	$ 1			(224)	(35,865)
Temporary equity, Ending balance (in shares) at Dec. 31, 2019							6,167,726	20,942,781
Temporary equity, ending balance at Dec. 31, 2019							$ 5,353	$ 46,404
Ending balance (in shares) at Dec. 31, 2019		256,548
Issuance of Preferred Stock								$ 125,026
Issuance of 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	(5,120)			(5,120)				$ 5,120
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering	181,903	$ 22		181,881			$ (5,353)	$ (176,550)
Conversion of redeemable convertible preferred stock to common stock upon closing of initial public offering, Shares		22,460,076					(6,167,726)	(65,396,258)
Issuance of common stock from initial public offering	210,612	$ 12		210,600
Issuance of common stock from initial public offering, shares		12,091,675
Exercise of stock options into common stock/profit certificates	$ 655			655
Exercise of stock options into common stock/profit certificates (in shares)	236,459	236,459
Stock-based compensation	$ 4,292			4,292
Currency translation adjustment	841				841
Net loss	(38,033)					(38,033)
Ending balance at Dec. 31, 2020	$ 323,197	$ 35		$ 396,443	$ 617	$ (73,898)
Ending balance (in shares) at Dec. 31, 2020		35,044,758

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical)	12 Months Ended
	Dec. 31, 2020 USD ($)
Net of Issuance costs	$ 19,100,000
Series B-2 Preferred Stock
Net of Issuance costs	$ 332

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (38,033)	$ (22,454)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	535	611
Stock-based compensation	4,292	809
Fair value adjustment for preferred stock tranche rights liability and anti-dilution warrants liability	(1,265)	(1,019)
Deferred rent	(35)	(10)
Changes in operating assets and liabilities:
Grants receivable	5,175	(4,136)
Research and development tax credits receivable	(142)	(718)
Prepaid expenses and other current assets	(1,927)	(365)
Other assets		(12)
Accounts payable	1,677	(155)
Accrued expenses and other liabilities	2,759	2,325
Deferred income	1,788	1,979
Net cash used in operating activities	(25,176)	(23,145)
Cash flows from investing activities
Purchase of property and equipment	(356)	(721)
Purchase other assets	(21)	(205)
Net cash used in investing activities	(377)	(926)
Cash flows from financing activities
Proceeds from initial public offering, net of underwriting discount	213,660
Payment of initial public offering costs	(3,048)
Payment of issuance costs on Series B-2 Preferred Stock	(19,100)
Proceeds from issuance of common stock and profit certificates upon exercise of options	655	102
Proceeds from grants repayable	4,046	65
Net cash provided by financing activities	340,339	22,539
Effects of exchange rate changes on cash, cash equivalents and restricted cash	1,678	(532)
Net increase (decrease) in cash, cash equivalents and restricted cash	316,464	(2,064)
Cash, cash equivalents and restricted cash at beginning of year	19,990	22,054
Cash, cash equivalents and restricted cash at end of year	336,454	19,990
Non-cash investing and financing activities
Conversion of redeemable convertible preferred stock to common stock upon closing of the initial public offering	181,903
Accretion of Series B and B-2 Preferred Stock to redemption value	5,120	3,654
Settlement of preferred stock tranche right	4,135
Supplemental disclosure of cash flows
Cash paid for interest		63
Cash paid for taxes	108	23
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 and Basis of Presentation

12 Months Ended

Dec. 31, 2020

Disclosure Text Block [Abstract]

Nature of Business and Basis of Presentation

Note 1. Nature of Business and Basis of Presentation

Organization

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 inupadenant, a small molecule antagonist of A_2AR, which is currently in an open-label multi-arm Phase 1/2a clinical trial in adult cancer patients. The second clinical program is EOS-448, an antibody directed to TIGIT, which is in an ongoing Phase 1/2a clinical trial in adult cancer patients. The Company also has a preclinical pipeline targeting additional mechanisms.

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. The Company evaluated the guidance in ASC 805-50 with respect to the transaction between entities under common control and concluded that since all shareholders of iTeos Inc. and iTeos Belgium have nearly identical ownership percentages and interests before and after the transaction, the Share Exchange lacks economic substance and represents a transaction between entities with common ownership and should be accounted for in a manner consistent with common control transactions and did not result in a change in control at the ultimate parent or the controlling shareholder level.

On December 2, 2020, iTeos Securities Corporation (iTeos SC) was incorporated as a Massachusetts Security Corporation. It is a wholly-owned subsidiary of iTeos Therapeutics, Inc.

Reverse Stock Split and Initial Public Offering

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.

On July 28, 2020, the Company completed its initial public offering (IPO), in which the Company issued and sold 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 $184.0 million in net proceeds after deducting underwriting discounts and commissions and other offering expenses paid by the Company. Upon closing of the IPO, all of the Company's outstanding shares of convertible preferred stock automatically converted into 22,460,076 shares of common stock.

On August 5, 2020, the underwriters purchased an additional 1,505,359 shares of common stock pursuant to their option to purchase additional shares for net proceeds of $26.6 million after deducting underwriting discounts and commissions.

Liquidity and capital resources

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. Since inception, the Company has incurred recurring losses, including a net loss of $38.0 million for the year ended December 31, 2020. As of December 31, 2020, the Company had an accumulated deficit of $73.9 million. The Company expects to continue to generate operating losses in the foreseeable future. As of March 24, 2021, the issuance date of the consolidated financial statements for the year ended December 31, 2020, the Company expected that its cash and cash equivalents would be sufficient to fund its operating expenses, capital expenditure requirements and debt service payments through at least 12 months from the issuance date of the consolidated financial statements.

The Company may seek additional funding in order to reach its development and commercialization objectives. 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 Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s technology will be obtained, that any products developed will obtain necessary government regulatory approval or that any products, if approved, will be commercially viable. The Company operates in an environment of rapid technological innovation and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees, consultants and service providers. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize revenue from product sales.

COVID-19

In March 2020, the World Health Organization declared COVID-19 a global pandemic. In response to the rapid global spread of the virus, national, state, and local governments issued orders and recommendations to attempt to reduce the further spread of the disease. Such orders included movement control and shelter-in-place orders, travel restrictions, limitations on public gatherings, school closures, social distancing requirements and the closure of all but critical and essential services and infrastructure. 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, the Company has 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 it can continue to progress with its programs.

While the COVID-19 pandemic did not significantly impact the Company’s business or results of operations during the year ended December 31, 2020, the length and extent of the pandemic, its consequences, and containment efforts will determine the future impact on the Company’s operations and financial condition.

Basis of presentation

The 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).

Summary of significant accounting Policies

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Basis of presentation

The 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).

Summary of significant accounting policies

Note 2. Summary of significant accounting policies

Principles of consolidation

The 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.

The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition, including expenses, research and development costs and employee-related amounts, will depend on future developments that are highly uncertain, including as a result of new information that may emerge concerning COVID-19 and the actions taken to contain or treat COVID-19, as well as the economic impact on local, regional, national and international markets. The Company has considered the impact of COVID-19 on estimates within its financial statements and there may be changes to those estimates in future periods. As of the date of issuance of these consolidated financial statements, the Company has not experienced material business disruptions or incurred impairment losses in the carrying value of its assets as a result of the pandemic and is not aware of any specific related event or circumstance that would require it to update its estimates.

Share exchange

Transactions among entities under common ownership are accounted for similar to common control transactions if they lack economic substance; therefore, they are not accounted for at fair value. Rather, they are accounted for at the carrying amount of the net assets or equity interests transferred. As a result, the financial position and the results of operations of iTeos Inc. and iTeos Belgium are presented as consolidated for all periods presented in these accompanying consolidated financial statements.

Cash, Cash Equivalents and Restricted Cash

Cash and cash equivalents consist of standard checking accounts, money market accounts, and a sweep account that consists of money market funds with highly liquid investments with maturities of three months or less. Restricted cash represents collateral provided for letters of credit issued as security deposits in connection with the Company’s leases of its corporate facilities.

Foreign currency, currency translation and comprehensive loss

The reporting currency of the consolidated financial statements is the U.S. dollar (USD). The functional currency for iTeos Belgium is the euro and the functional currency for iTeos Inc., iTeos SC, and iTeos U.S. is the USD.

Income items and expenses are translated at the average exchange rate in effect during the period. Unrealized translation gains and losses are recorded as a cumulative translation adjustment, which is included in the Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders’ Equity (Deficit) as a component of Accumulated other comprehensive income (loss). Adjustments that arise from exchange rate changes on transactions denominated in a currency other than the local currency are included in Other expense, net in the Consolidated Statements of Operations and Comprehensive Loss as settled.

Comprehensive income (loss) is defined as a change in equity of a business enterprise during a period, resulting from transactions from non-owner sources. The Company had unrealized gains and losses from foreign currency translation of iTeos Belgium during the years ended December 31, 2020 and 2019, which meets the criteria as other comprehensive income (loss) and, therefore, the Company has reported comprehensive loss and net loss.

Fair value measurements

Fair value accounting is applied for all financial assets and liabilities. The carrying amount of the Company’s financial instruments, including grants receivable, R&D credits receivable—current, accounts payable, accrued expenses and other current liabilities approximate fair value due to the short-term duration of those instruments. The carrying amounts of long-term R&D credits receivable and grants repayable approximate fair value due to low local market interest rates.

The Company is required to disclose information regarding all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. FASB ASC Topic 820, Fair Value Measurement and Disclosures (ASC 820), established a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the financial instrument based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the financial instrument and are developed based on the best information available in the circumstances.

The accounting standard describes a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value, which are the following:

•	Level 1—Quoted prices in active markets that are accessible at the market date for identical unrestricted assets or liabilities.

•

Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs for which all significant inputs are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities.

•	Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

Financial instruments measured at fair value on a recurring basis include cash equivalents (money market funds), preferred stock tranche rights liabilities and anti-dilution warrants liabilities prior to their settlement (Note 3).

The fair value of cash equivalents were determined based on Level 1 inputs as described in Note 3. The fair value of preferred stock tranche rights liabilities, and anti-dilution warrants liabilities were determined based on Level 3 inputs as described in Note 3. An entity may elect to measure many financial instruments and certain other items at fair value at specified election dates. The Company did not elect to measure any additional financial instruments or other items at fair value.

There have been no changes to the valuation methods utilized by the Company during the years ended December 31, 2020 or 2019. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of financial instruments between levels during the years ended December 31, 2020 or 2019.

Concentration of credit risk

As of December 31, 2020 and 2019, the Company’s cash and cash equivalents consisted primarily of cash balances held in U.S. dollars in money market funds and money market accounts and euro in accounts with European banks in excess of publicly insured limits. The Company does not believe it is subject to unusual credit risk associated with commercial banking relationships.

Research and development tax credits

iTeos Belgium is considered a biotech company in Belgium and therefore qualifies for a cash-based tax credit on research and development (R&D) expenses. The R&D tax credit is calculated based on a percentage of eligible R&D expenses defined by the Belgian government for each fiscal year (13.5% for 2020 and 2019) and then applying the effective tax rate to that result. Under current tax laws, the R&D tax credits are refundable if the Company is unable to use the credits to offset income taxes for the five subsequent tax years. The Company records a receivable and other income as the eligible R&D expenses are incurred, as it is reasonably assured that the R&D tax credit will be received, based upon its history of filing for the tax credits. R&D tax credits receivable where cash is expected to be received by the Company more than one year after the balance sheet date are classified as noncurrent in the consolidated balance sheets.

Property and equipment

Property and equipment, including leasehold improvements, are stated at cost and depreciated when placed into service using the straight-line method over the estimated useful lives as follows:

Asset		Estimated Useful Life
Computer equipment and software		3 years
Furniture, fixtures and other		5 years
Scientific equipment		5 – 6 years
Leasehold improvements		Shorter of useful life or term of lease

Upon retirement or sale, the cost and related accumulated depreciation are removed from the consolidated balance sheets and the resulting gain or loss is reflected in the consolidated statements of operations and comprehensive loss.

Impairment of long-lived assets

The Company reviews long-lived assets, including property and equipment, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. An impairment charge would be recorded when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount. Impairment, if any, is assessed using discounted cash flows or other appropriate measures of fair value. As there were no indicators of impairment, the Company did not recognize any impairment charges for the years ended December 31, 2020 or 2019.

Deferred offering costs

The Company capitalizes incremental legal, professional accounting and other third-party fees that are directly associated with in-process preferred stock or common stock financings as other non-current assets until such financings are consummated. After consummation of the equity financing, these costs are recorded as a reduction to the carrying value of convertible preferred stock or additional paid-in-capital generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs will be expensed immediately as a charge to operating expenses in the consolidated statement of operations and comprehensive loss. After consummation of the IPO, which closed on July 28, 2020, these costs were all recorded in stockholders’ equity (deficit) as a reduction of additional paid-in capital generated as a result of the offering.

Revenue recognition

From time to time, the Company may generate revenue from license and collaboration agreements for the development and commercialization of its product candidates. License agreements may include non-refundable upfront research and development fees and milestone payments based on achievement of defined development, regulatory and sales targets, and royalties on sales of commercialized products.

The Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that are within the scope of ASC 606, the Company performs the following five steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations based on estimated standalone selling prices; and (v) recognition of revenue when (or as) the Company satisfies each performance obligation. A performance obligation is a promise in a contract to transfer a distinct good or service to the customer.

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. This assessment is performed throughout the life of the arrangement and takes into consideration changes in the responsibilities of all parties to the arrangement.

Research and development expenses

Research and development costs are expensed as incurred. Research and development expenses consist of personnel costs for the Company’s research and product development employees, as well as non-personnel costs such as facilities and overhead costs attributable to research and development, and professional fees payable to third parties for preclinical and clinical studies and research services, clinical trial costs, laboratory supplies and equipment maintenance, and other consulting costs.

The Company estimates preclinical and clinical study and research expenses based on the services performed, pursuant to contracts with research institutions that conduct and manage preclinical and clinical studies and research services on its behalf. The Company estimates these expenses based on discussions with internal management personnel and external service providers as to the progress or stage of completion of services and the contracted fees to be paid for such services. If the actual timing of the performance of services or the level of effort varies from the original estimates, the Company will adjust the accrual accordingly. When third-party service providers’ billing terms do not coincide with the Company’s period-end, the Company is required to make estimates of its obligations to those third parties, including clinical trial and pharmaceutical development costs, contractual services costs and costs for supply of its drug candidates, incurred in a given accounting period and record accruals at the end of the period. The Company bases its estimates on its knowledge of the research and development programs, services performed for the period, history for related activities and the expected duration of the third-party service contract, where applicable. Payments associated with licensing agreements to acquire exclusive licenses to develop, use, manufacture and commercialize products that have not reached technological feasibility and do not have alternate commercial use are expensed as incurred. Payments made to third parties under these arrangements in advance of the performance of the related services by the third parties are recorded as prepaid expenses until the services are rendered.

Government grant funding and potential repayment commitments under recoverable cash advance grants (RCAs)

The Company has agreements with granting agencies whereby the Company receives funding under grants which partially or fully reimburse the Company for qualifying research and development expenditures. Certain grant agreements require the Company to repay the funding depending on whether the Company decides to pursue commercial development or out licensing of any drug candidate that is produced from the research program. The repayment provision includes a portion that is repayable in fixed annual installments (corresponding to 30% of the grant), which is effective unless the Company decides not to pursue commercial development or out licensing of the drug candidate. The repayment provision also includes a potential obligation to pay a royalty that is contingent upon achieving sales of a product developed through the program. The maximum amount repayable to the granting agency under each grant, including the fixed repayments, the royalty on revenue, and the interest thereon, is twice the amount of funding received.

Grant funding for research and development received under grant agreements where there is no obligation to repay is recognized as grant income in the period during which the related qualifying expenses are incurred, based on the applicable reimbursement percentage, provided that the grants are fully approved by the granting agencies and the conditions under which the grants were provided have been met.

Grant funding for research and development received under grant agreements where there is a repayment provision is recognized as grant income to the extent there is no potential obligation to repay this funding. The Company records the present value of the liability of the portion of funding relating to fixed repayment upon receipt in the consolidated balance sheets. The grant repayable is subsequently recorded at amortized cost.

The Company assesses 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.

Grant funding that has been received by the Company in advance of incurring qualifying expenses is recorded as deferred income. Grant income recognized upon incurring qualifying expenses in advance of receipt of grant funding is recorded in the consolidated balance sheets as grants receivable.

Leases

The Company records rent expense on a straight-line basis over the life of the lease. In cases of escalating rental payments, the Company records rent expense on a straight-line basis with an offset to deferred rent liability.

Stock-based compensation

The Company accounts for stock-based compensation arrangements with employees in accordance with ASC 718, Stock Compensation. Stock-based awards granted are in the form of stock options. Prior to the Share Exchange, stock options granted by iTeos Belgium were referred to as warrants in the agreements and were exercisable into profit certificates (economically similar to common stock) with time-based vesting. Stock options granted by iTeos Inc. are exercisable into common stock. ASC 718 requires the recognition of stock-based compensation expense, using a fair value-based method, for costs related to all stock options granted. The Company’s determination of the fair value of stock options with time-based vesting on the date of grant utilizes the Black-Scholes option-pricing model, and is impacted by the estimated fair value of its common stock as well as other variables including, but not limited to, the expected term that stock options will remain outstanding, the expected common stock price volatility over the term of the stock option, risk-free interest rates and expected dividends.

The fair value of stock options is recognized over the period during which an optionee is required to provide services in exchange for the stock option award, known as the requisite service period (usually the vesting period) on a straight-line basis. Stock-based compensation expense is recognized based on the fair value determined on the date of grant and is reduced for forfeitures as they occur. For stock options granted to recipients in Belgium, option holders have a period of time (no longer than 60 days) to accept their awards. Accordingly, the grant date is determined based on the date of acceptance, as that is the point when a mutual understanding of the key terms of the awards are established.

The Black-Scholes option pricing model requires inputs based on certain subjective assumptions, including (i) the expected stock price volatility, (ii) the expected term of the award, (iii) the risk-free rate of interest, and (iv) expected dividends. Due to the lack of a public market for the Company’s common stock prior to IPO and lack of company-specific historical implied volatility data, the Company has based its computations of expected volatility on the historical volatility of a representative group of public companies with similar characteristics of the Company, including stage of product development and life science industry focus. The historical volatility is calculated based on a period of time commensurate with the expected term assumption. The Company uses the simplified method as prescribed by the SEC Staff Accounting Bulletin No. 107, Share-Based Payment, to calculate the expected term for options granted to employees and non-employees, whereby, the expected term equals the arithmetic average of the vesting term and the original contractual term of the options due to its lack of sufficient historical data. The risk-free interest rate is based on U.S. Treasury securities with a maturity date commensurate with the expected term of the associated award. The expected dividend yield is assumed to be zero as the Company has never paid dividends and has no current plans to pay any dividends on its common stock.

Due to the absence of an active market for the Company’s common stock prior to IPO, the Company utilized methodologies in accordance with the framework of the American Institute of Certified Public Accountants Technical Practice Aid, Valuation of Privately-Held Company Equity Securities Issued as Compensation, to estimate the fair value of its common stock. In determining the exercise prices for options granted, the Company has considered the estimated fair value of the common stock as of the measurement date. The estimated fair value of the common stock has been determined at each grant date prior to the IPO based upon a variety of factors, including the illiquid nature of the common stock, arm’s-length sales of the Company’s capital stock (including redeemable convertible preferred stock), the effect of the rights and preferences of the preferred shareholders, and the prospects of a liquidity event. Among other factors are the Company’s financial position and historical financial performance, the status of technological developments within the Company’s research, the composition and ability of the current research and management team, an evaluation or benchmark of the Company’s competition, and the current business climate in the marketplace. Significant changes to the key assumptions underlying the factors used could result in different fair values of common stock at each valuation date.

Following our IPO, the fair value of our common stock is determined based on the quoted market price of our common stock.

The Company classifies stock-based compensation expense in its statement of operations and comprehensive loss in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.

Preferred stock

The Company records all shares of preferred stock at their respective fair values less issuance costs on the dates of issuance. The preferred stock is recorded outside of stockholders’ equity (deficit) because, in the event of certain deemed liquidation events, which are events that are not considered solely within the Company’s control, such as a merger, acquisition or sale of all or substantially all of the Company’s assets, the preferred stock will become redeemable. Further, preferred stock is recorded outside of stockholders’ equity (deficit) as temporary equity in the accompanying consolidated balance sheets because it becomes redeemable due to the passage of time (Series B Preferred Stock only) or could become redeemable due to certain change of control clauses that are outside of the Company’s control. In the event of a change of control of the Company, proceeds received from the sale of such shares will be distributed in accordance with the liquidation preferences set forth in the Company’s Shareholders’ Agreement unless the holders of preferred stock have converted their shares of convertible preferred stock into shares of common stock.

When the preferred stock is considered either currently redeemable or probable of becoming redeemable, the Company has selected a policy of accreting the carrying value to the redemption amount over time. As the Series B and B-2 Preferred Stock was considered probable of becoming redeemable solely due to the passage of time, and since the liquidation preference formula included 6% cumulative dividends, the Company was accreting the Series B and B-2 Preferred Stock to its estimated redemption amount based on the 6% annual dividend using the interest method. When preferred stock is not considered either currently redeemable or probable of becoming redeemable, the Company does not accrete the value until which point the contingency is probable of occurring.

The Company determined that the right granted to the investors of Series B Preferred Stock to purchase additional stock at the original issuance price in two subsequent closings and the anti-dilution warrants, which were issued as part of the Series A and Series B Preferred Stock Subscription Agreements were considered freestanding financial instruments and were accounted for as liabilities under ASC 480. They were reported at fair value at inception with an allocation of the proceeds from the preferred stock issuance and were remeasured at fair value at each reporting date until settlement, with the changes in fair value included in the other income and expense section of the consolidated statements of operations and comprehensive loss.

Derivatives

Upon issuing financial instruments, the Company assesses the nature of the host contract and considers whether any of the features embedded within the financial instrument could be considered derivatives that require bifurcation. In determining whether the embedded features represent derivatives that could require bifurcation, the Company assesses whether the economic characteristics of embedded features are not clearly and closely related to the economic characteristics of the remaining component of the financial instruments (i.e., the host contracts), whether the instrument is measured at fair value with changes in fair value reported in earnings as they occur and whether a separate, non-embedded instrument with the same terms as the embedded instruments would meet the definition of a derivative instrument. When it is determined that all of the criteria above are met, the embedded derivative is separated from the host contract and carried at fair value with any changes in fair value recorded in current period earnings.

Income taxes

The Company provides for income taxes under the asset and liability method. Current income tax expense or benefit represents the amount of income taxes expected to be payable or refundable for the current year. Deferred income tax assets and liabilities are determined based on differences between the financial statement reporting and tax bases of assets and liabilities and net operating loss and credit carryforwards, and are measured using the enacted tax rates and laws that will be in effect when such items are expected to reverse. Deferred income tax assets are reduced, as necessary, by a valuation allowance when management determines it is more likely than not that some or all of the tax benefits will not be realized.

The Company accounts for uncertain tax positions in accordance with ASC 740-10, Accounting for Uncertainty in Income Taxes. The Company assesses all material positions taken in any income tax return, including all significant uncertain positions, in all tax years that are still subject to assessment or challenge by relevant taxing authorities. Assessing an uncertain tax position begins with the initial determination of the position’s sustainability and is measured at the largest amount of benefit that is greater than fifty percent likely of being realized upon ultimate settlement. As of each balance sheet date, unresolved uncertain tax positions must be reassessed, and the Company will determine whether (i) the factors underlying the sustainability assertion have changed and (ii) the amount of the recognized tax benefit is still appropriate. The recognition and measurement of tax benefits requires significant judgment. Judgments concerning the recognition and measurement of a tax benefit might change as new information becomes available.

The Company includes any penalties and interest expense related to income taxes as a component of other expense and interest expense, net, as necessary.

Segment information

Operating segments are defined as components of an enterprise for which separate discrete financial information is available for evaluation by the chief operating decision maker (CODM) in deciding how to allocate resources and in assessing operating performance. The Company’s CODM is the Chief Executive Officer. The Company views its operations and manages its business in one operating segment, the business of developing cancer immunotherapies.

Net loss per share attributable to common stockholders

Basic net loss per share and diluted net loss per share are computed using the weighted-average number of shares of common stock outstanding for the period. Net loss per share attributable to common stockholders is calculated using the two-class method, which is an earnings allocation formula that determines net loss per share for the holders of shares of the Company’s common stock and participating securities. The Company’s Series A-1 Preferred Stock, Series A-2 Preferred Stock and Series B and B-2 Preferred Stock contained participation rights in any dividend paid by the Company as well as residuals in liquidation and were deemed to be participating securities. The participating securities do not include a contractual obligation to share in losses of the Company and are not included in the calculation of net loss per share in the periods in which a net loss is recorded.

Except where the result would be antidilutive to net income (loss), diluted net income (loss) per share is computed assuming the exercise of common stock options and the conversion of Series A-1 Preferred Stock, Series A-2 Preferred Stock and Series B and B-2 Preferred Stock.

Recently adopted accounting standards updates

The Jumpstart our Business Startups Act of 2012, or the JOBS Act, permits an “emerging growth company” such as the Company to take advantage of an extended transition period to comply with new or revised accounting standards. This allows an emerging growth company to delay adoption of certain accounting standards until those standards would otherwise apply to private companies. The Company has elected this exemption from new or revised accounting standards. The Company has, however, elected to early-adopt certain new or revised accounting standards as of dates that may or may not coincide with the effective dates of public companies.

In November 2018 the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606. This standard makes targeted improvements for collaborative arrangements as follows:

•

Clarifies that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606, Revenue from Contracts with Customers, when the collaborative arrangement participant is a customer in the context of a unit of account. In those situations, all the guidance in ASC 606 should be applied, including recognition, measurement, presentation and disclosure requirements;

•	Adds unit-of-account guidance to ASC 808, Collaborative Arrangements, to align with the guidance in ASC 606 (that is, a distinct good or service) when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of ASC 606; and

•	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.

This standard became effective for the Company on January 1, 2020. The adoption of this standard did not have a material impact on the Company’s consolidated financial position and results of operations.

In August 2018 the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework Changes to the Disclosure Requirements for Fair Value Measurement. This standard modifies certain disclosure requirements on fair value measurements. This standard was effective for the Company on January 1, 2020. The adoption of this standard did not have a material impact on the Company’s disclosures.

Recently issued accounting standards and updates not yet effective

In February 2016 the FASB issued ASU No. 2016-02, Leases (Topic 842). This standard established a right-of-use model that requires all lessees to recognize right-of-use assets and liabilities on their balance sheet that arise from leases as well as provide disclosures with respect to certain qualitative and quantitative information related to their leasing arrangements. The Company adopted the standard on January 1, 2021.

The FASB has subsequently issued certain amendments to ASU 2016-02, which have the same effective date and transition. None of these amendments materially impact the Company’s adoption of Topic 842.

The Company adopted the new leasing standards 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 finalizing its evaluation of the impacts that the adoption of this accounting guidance will have on the consolidated financial statements, and estimates approximately $0.9 million of right-to-use assets and lease liabilities will be recognized in the consolidated balance sheet upon adoption.

In June 2016 the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This standard requires that credit losses be reported using an expected losses model rather than the incurred losses model that is currently used, and establishes additional disclosures related to credit risks. For available-for-sale debt securities with unrealized losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. This standard will be effective for the Company on January 1, 2023. The Company is currently evaluating the potential impact that this standard may have on its consolidated financial position and results of operations.

Fair Value Measurements

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurements

Note 3. Fair value measurements

Certain of the Company’s assets and liabilities are recorded at fair value, as described below.

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:

	December 31, 2020
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents (money market funds)	$	314,636	$	—	$	—	$	314,636
Totals	$	314,636	$	—	$	—	$	314,636

	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

Cash equivalents consist of money market funds, which are classified within Level 1 of the fair value hierarchy because they are valued using quoted market prices in an active market.

The Series B Preferred Stock Subscription Agreement included commitments from the same investors to acquire two additional tranches of Series B Preferred Stock (Committed Tranches) at the same share price.

The original Series B Subscription Agreement under iTeos Belgium provided each investor with one anti-dilution warrant (Series B Anti-Dilution Warrant). Each Series B Anti-Dilution Warrant allowed its holder to subscribe for newly issued Series B Preferred Stock in the event iTeos Belgium issued additional equity securities at a price below the Series B Preferred Subscription Price. The Series B Anti-Dilution Warrant had an exercise price of $.01 and provided the investor with a quantity of additional Series B Preferred Stock to reduce the average price per share to the amount of the price offered for the additional equity securities. Anti-dilution warrants had also been granted to certain holders of Series A Preferred Stock with similar terms as the Series B Anti-Dilution Warrants.

Under ASC 480, the preferred stock tranche rights and anti-dilution warrants are freestanding financial instruments that qualify as liabilities required to be recorded at their estimated fair value at the inception date of the subscription agreements and remeasured at each reported balance sheet date thereafter until settlement.

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):

	March 23, 2020 (Tranche 3 settlement)			December 31, 2019			December 31, 2018
Implied equity value (in millions)	$	208.2		$	74.4		€30.8 ($35.4)
Probability of success of reaching necessary milestone:
Tranche 2 milestone	N/A			N/A			85% by March 31, 2019
Tranche 3 milestone (by March 31, 2020)		90	%		90	%		90	%
Expected industry return over period during which milestones are expected to be achieved		13.0	%		15.0	%		15.0	%
Risk-free interest rate		1.1	%		2.3	%		2.5	%

The Series A Preferred Stock and Series B Preferred Stock were issued with anti-dilution warrants. The fair values at January 1, 2018 (Series A Preferred Stock) and June 11, 2018 (Series B Preferred Stock), were estimated using a Monte Carlo simulation model with the following significant unobservable inputs:

•	Annual volatility of 114.7%

•	Risk-free rate of 2.56%

•	Starting equity value of €28.3 million ($33.3 million)

•	Timing of future fund raise—June 2020

•	Amount of future fund raise—€30 million ($34.4 million)

•	Timing of liquidity event—December 2020

Accordingly, 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 1), there was no value to the anti-dilution warrants at December 31, 2020 and 2019.

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 years ended December 31, 2020 and 2019.

The following table presents changes during the years ended December 31, 2020 and 2019 in Level 3 liabilities measured at fair value on a recurring basis:

(in thousands)	Preferred Stock Tranche Rights Liability			Series B Anti- Dilution Warrants			Series A Anti- Dilution Warrants
Balances at January 1, 2019	$	6,325		$	182		$	219
Elimination of warrants through Share Exchange		—			(182	)		(219	)
Change in estimated fair value		(618	)		—			—
Effects of exchange rate changes		(307	)		—			—
Balances at December 31, 2019		5,400			—			—
Change in estimated fair value		(1,265	)		—			—
Settlement of tranche right		(4,135	)		—			—
Balances at December 31, 2020	$	—		$	—		$	—

The following is a reconciliation of the amounts in the table above to the fair value adjustment for tranche rights and warrants amounts included in the consolidated statements of operations and comprehensive loss:

	Year Ended December 31,
(in thousands)	2020		2019
Elimination of Series B anti-dilution warrants	$	—	$	182
Elimination of Series A anti-dilution warrants		—		219
Change in estimated fair value		1,265		618
Total included in earnings	$	1,265	$	1,019

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.

There were no derivatives as of December 31, 2020 and 2019. The other non-financial assets like property and equipment and intangibles are measured at Level 3 when there is an indicator of impairment and recorded at fair value when an impairment charge is recognized.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Consolidated Balance Sheet Components

12 Months Ended

Dec. 31, 2020

Supplemental Balance Sheet Information [Abstract]

Consolidated Balance Sheet Components

Note 4. Consolidated balance sheet components

Property and equipment

Property and equipment, net consisted of the following:

	December 31,
(in thousands)	2020			2019
Scientific equipment	$	2,617		$	2,300
Furniture & office equipment		542			346
Leasehold improvements		855			771
Total		4,014			3,417
Accumulated depreciation and amortization		(2,662	)		(2,081	)
Property & equipment, net	$	1,352		$	1,336

Depreciation and amortization expense was $0.5 million and $0.6 million for the years ended December 31, 2020 and 2019, respectively.

Accrued expenses and other current liabilities

Accrued liabilities consisted of the following:

	December 31,
(in thousands)	2020		2019
Accrued clinical trial costs	$	4,012	$	2,683
Accrued personnel costs		3,208		1,409
Accrued professional fees		37		30
Accrued other		229		140
Total accrued expenses and other current liabilities	$	7,486	$	4,262

License and collaboration agreements

12 Months Ended

Dec. 31, 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 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 its 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. For example, 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 what the Company now 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. Such royalties are payable 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 approximately $3.4 million to Adimab pursuant to 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 began the research study in the third quarter of 2020. The terms of the MSD Agreement meet the criteria under ASC Topic 808, Collaborative Arrangements (“ASC 808”), as both parties are active participants in the activity and are exposed to the risks and rewards dependent on the commercial success of the activity. ASC 808 does not provide guidance on how to account for the activities under the collaboration, and the Company determined that neither party met the definition of a customer under ASC 606, Revenue from Contracts with Customers. Accordingly, the Company considered other guidance to determine the accounting for the respective elements of the arrangement. The Company accounted for the collaboration activities by analogy to ASC Topic 845, Nonmonetary Transactions, and recognized nonmonetary income with an offsetting entry to expense for amounts received from MSD within research and development expense in the consolidated statement of operations and comprehensive loss.

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs)

12 Months Ended

Dec. 31, 2020

Research And Development Arrangement With Federal Government [Abstract]

Government Grant Funding and Potential Repayment Commitments

Note 6. Government grant funding and potential repayment commitments under recoverable cash advance grants (RCAs)

The Company has been awarded grants from a federal region of Belgium (the Walloon Region), and the European Union (collectively, 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. To date, 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 consolidated statements of operations and comprehensive loss. Grant income recognized under all of the grants for research and development activities totaled approximately $5.6 million and $4.0 million for the years ended December 31, 2020 and 2019, respectively.

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 $1.3 million.

Grants which include a potential obligation to repay—RCAs

On July 20, 2017, the Company entered into an arrangement whereby the Walloon Region will provide the Company with up to $23.1 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 grant with the Walloon Region (RCA-2) for up to $4.3 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. Management is currently in the process of negotiating an extension for RCA-2. The Company must repay 30% of the amount received under the grants 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 consolidated balance sheets.

In addition, in the event that the Company receives revenue from products or services related to the results of the program, 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 December 31, 2020 or 2019.

The Company recorded grant income in the consolidated statement of operations and comprehensive loss for the years ended December 31, 2020 and 2019 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 consolidated balance sheets.

The Company recorded receivables on the 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 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 years ended December 31, 2020 and 2019 and end of year balances as of December 31, 2020 and December 31, 2019:

	RCA -1				RCA-2				Other Grants				Total
(In thousands)	2020		2019		2020		2019		2020		2019		2020		2019
Cash received	$	11,944	$	220	$	2,479		—	$	2,630	$	1,198	$	17,053	$	1,418
Grant income recognized		3,913		3,186		1,290		482		444		321	$	5,647	$	3,989
Grants receivable		—		4,448		—		677		133		71	$	133	$	5,196
Grants repayable		5,102		1,397		781		—		—		—	$	5,883	$	1,397

Stockholders’ equity

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Stockholders’ equity (Deficit)

Note 7. Stockholders’ equity (Deficit)

Redeemable Convertible Preferred Stock

Redeemable convertible preferred stock consisted of the following immediately prior to the automatic conversion into common stock:

	Designated Shares Authorized		Shares Issued and Outstanding		Aggregate Liquidation Preference (in 000's)
Series A-1 and A-2		6,167,726		6,167,726	$	7,114
Series B		31,989,428		20,942,781		55,642
Series B-2		44,453,477		44,453,477		127,680
Total redeemable convertible preferred stock		82,610,631		71,563,984	$	190,436

Upon closing of the IPO, all of the Company's outstanding shares of convertible preferred stock automatically converted into 22,460,076 shares of common stock. As of December 31 2020, there were no shares of redeemable convertible preferred stock issued and outstanding.

Common stock

On July 28, 2020, in connection with the IPO, the Company filed a restated Certificate of Incorporation, which, among other things, restated the number of shares of all classes of stock that the Company has authority to issue to 160,000,000 shares, of which (i) 150,000,000 shares shall be a class designated as common stock, par value $0.001 per share, and (ii) 10,000,000 shares shall be a class designated as undesignated preferred stock, par value $0.001 per share. Each share of common stock entitles the holders to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are not entitled to receive dividends, unless declared by the board of directors.

The Company has never declared any dividends on common stock.

The Company had reserved shares of common stock, on an if-converted basis, for issuance as follows:

	December 31,
	2020		2019
Series A Preferred Stock, as converted		—		1,862,510
Series B Preferred Stock, as converted		—		6,760,804
Stock options issued and outstanding		4,552,396		1,387,003
Shares available for issuance under Stock Option Plan		3,039,222		251,606
Total		7,591,618		10,261,923

Profit certificates

A profit certificate is a legal equity security in Belgium with economic rights almost identical to common stock. However, they had voting rights in limited circumstances that were relevant to that type of security interest only. As part of the Share Exchange, all profit certificates of iTeos Belgium were exchanged one-for-one for common stock of the Company.

Stock-based compensation

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-based compensation

Note 8. Stock-based compensation

General

The Board of Directors, at its sole discretion, shall determine the exercise price. Stock options expire 7 to 10 years from the date of grant. The stock options generally vest 25% upon the one-year anniversary of the service inception date and then ratably each month over the remaining 36 months. Upon termination of service, any unvested stock options are automatically returned to Company. Vested stock options that are not exercised within the specified period, according to the terms and conditions of the option plan, following the termination as an employee, consultant, or service provider to the Company are surrendered back to the Company. Those stock options are added back to the pool and made available for future grants.

2019 Stock Option and Grant Plan

The Company’s 2019 Stock Option and Grant Plan (the “2019 Plan”) provided for the Company to grant stock options and other stock-based awards to employees and non-employees to purchase the Company’s common stock. 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. Upon the effectiveness of the 2020 Plan (as defined below), no further issuances will be made under the 2019 Plan.

On July 15, 2020, the Company’s Board of Directors approved an amendment for stock options outstanding under 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”) 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 replaced 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.

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 became 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 initially reserved and authorized the issuance of up to a total 317,484 shares of common stock to participating employees. The ESPP provides 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. As of December 31, 2020, no shares had been issued under the 2020 ESPP.

The following table summarizes stock option activity for the year ended December 31, 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		4.8
Granted		3,504,715			10.43
Forfeited		(102,863	)		7.18
Exercised		(236,459	)		2.77
Outstanding as of December 31, 2020		4,552,396		$	9.13		8.2	$	112,412
Vested and expected to vest as of December 31, 2020		4,552,396		$	9.13		8.2	$	112,412
Exercisable at December 31, 2020		861,388		$	4.93		5.0	$	24,889

The following table summarizes stock-based compensation expense, and also the allocation within the consolidated statements of operations and comprehensive loss:

	Year Ended December 31,
(in thousands)	2020		2019
Research and development	$	425	$	170
General and administrative		3,867		639
Total stock-based compensation expense	$	4,292	$	809

The weighted-average grant-date fair value of options awarded during the year ended December 31, 2020 and 2019 was approximately $7.75 per share and $0.49 per share, respectively. The aggregate intrinsic value of stock options exercised during the years ended December 31, 2020 and 2019 was $3.1 million and $0.2 million, respectively. The aggregate grant date fair value of stock options vested during the years ended December 31, 2020 and 2019 were $0.8 million and $0.7 million, respectively. As of December 31, 2020, there was a total of $23.6 million of unrecognized employee compensation costs related to non-vested stock option awards expected to be recognized over a weighted average period of 3.4 years.

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.

The following table summarizes the range of key assumptions used to determine the fair value of stock options granted during:

	Year Ended December 31,
	2020	2019
Risk-free interest rate	0.36% - 1.35%	2.50%
Expected term (in years)	5 - 6		5
Expected volatility	90% - 102%		93	%
Expected dividend yield	0%		0	%
Estimated fair value of common stock	$2.95 - $33.12	$2.38

Expected Term—The Company has opted to use the “simplified method” for estimating the expected term of stock options, whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the stock option (7 to 10 years).

Expected Volatility—Due to the Company’s limited operating history and a lack of company-specific historical and implied volatility data, the Company has based its estimate of expected volatility on the historical volatility of a group of similar companies that are publicly traded. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock options.

Risk-Free Interest Rate—The risk-free rate assumption is based on the U.S. Treasury instruments with maturities similar to the expected term of the Company’s stock options.

Expected Dividend—The Company has not declared any dividends in its history and does not expect to issue dividends over the life of the stock options and therefore has estimated the dividend yield to be zero.

Fair value of Profit Certificates or Common Stock— Prior to the IPO, the fair value of the profit certificates or common stock underlying the stock options has historically been determined by the board of directors, with input from management. Because there had been no public market for the Company’s common stock (or profit certificates), the board of directors had determined the fair value of the common stock (or profit certificates) on the grant-date of the stock options by considering a number of objective and subjective factors, including profit certificate or common stock valuations performed by an unrelated third-party specialist, valuations of comparable companies, sales of the Company’s preferred stock to unrelated third parties, operating and financial performance, the lack of liquidity of the Company’s capital stock, and general and industry-specific economic outlook. The board of directors intended all stock options granted to be exercisable at a price per share not less than the estimated per share fair value of common stock (or profit certificates) underlying those stock options on the date of grant. After the IPO, the fair value of common stock underlying the stock options is determined based on the closing price of the Company’s common stock as quoted by the stock exchange.

Income Taxes

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Income Taxes

Note 9. Income taxes

For financial reporting purposes, loss before income tax expense for the years ended December 31, 2020 and 2019 consisted of the following:

(in thousands)	2020			2019
Domestic	$	(31,184	)	$	(689	)
Foreign		(6,906	)		(21,646	)
Loss before income tax expense	$	(38,090	)	$	(22,335	)

The Company’s worldwide effective tax rate for the years ended December 31, 2020 and 2019 was 0.2% and (0.5%), respectively. The reconciliation of the statutory U.S. federal income tax rate (21%) to the effective income tax rate is as follows:

	2020			2019
U.S. statutory federal income tax rate		21.0	%		21.0	%
State income taxes	4.8			0.1
Foreign tax differential	0.8			8.3
Non-deductible/non-taxable permanent differences	3.4			7.6
Change in local tax rate	(8.6)				—
Other	0.9				—
Change in valuation allowance	(22.1)			(37.5)
Effective income tax rate	0.2%				(0.5	%)

The components of income tax expense for the years ended December 31, 2020 and 2019 consisted of the following:

(in thousands)	2020			2019
Current
Domestic	$	(60	)	$	116
Foreign		3			3
Deferred		—			—
Total income tax (benefit) expense	$	(57	)	$	119

Deferred income taxes reflected the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes and operating losses and tax credit carryforwards. The significant components of the Company’s deferred tax assets and liabilities are comprised of the following:

	December 31,
(in thousands)	2020			2019
Deferred tax assets :
Net operating loss carryforward	$	25,206		$	14,176
Capitalized research and development expenses		6,219			7,397
Stock-based compensation		758			—
Other		313			110
Total deferred tax assets		32,496			21,683
Valuation allowance		(32,029	)		(21,673	)
Deferred tax assets, net of valuation allowance		467			10
Deferred tax liabilities:
Prepaid expenses		(445	)		—
Depreciation and amortization		(22	)		(10	)
Total deferred tax liabilities		(467	)		(10	)
Deferred tax assets and liabilities, net of valuation allowance	$	—		$	—

The Company has evaluated the positive and negative evidence bearing upon its ability to realize its deferred tax assets, which are comprised primarily of net operating loss carryforwards and capitalized research and development expenses. Management has considered the Company’s history of operating losses, the nature of the Company’s deferred tax assets, and the timing, likelihood and amount, if any, of future taxable income during the periods in which those temporary differences and carryforwards become deductible and has concluded that it is more likely than not that the company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation has been established against these net deferred tax assets as of December 31, 2020 and 2019, respectively. The valuation allowance for deferred tax assets as of December 31, 2020 and 2019 was $32.0 million and $21.7 million, respectively. The net valuation allowance increase of $10.3 million during the year ended December 31, 2020 was primarily due to the increase in net operating loss, which was partially offset by a decrease in capitalized research and development expenses during the year.

As of December 31, 2020, the Company has $29.2 million of gross United State federal net operating loss (“NOL”) carryforwards, respectively, which may be available to offset future income tax liabilities. The Tax Cuts and Jobs Act, or TCJA, which was enacted in December 2017, will generally allow federal losses generated after 2017 to be carried over indefinitely, but will generally limit the NOL deduction to the lesser of the NOL carryover or 80% of a corporation’s taxable income (subject to Section 382 of the Internal Revenue Code of 1986, as amended). In addition, there will be no carryback for losses generated after 2017. Losses generated prior to 2018 will generally be deductible to the extent of the lesser of a corporation’s NOL carryover or 100% of a corporation’s taxable income and be available for twenty years from the period the loss was generated. For U.S. federal income tax purposes, the Company has NOLs generated after 2017 of $29.2 million, which do not expire. The Company does not have any NOLs generated prior to 2018. The Coronavirus Aid, Relief and Economic Security (“CARES”) Act temporarily allows the Company to carryback NOLs arising in 2018, 2019 and 2020 to the five prior tax years. In addition, NOLs generated in these years could fully offset prior year taxable income without the 80% of the taxable income limitation under the TCJA which was enacted on December 22, 2017. The Company filed a NOL carryback claim to carryback a portion of FY2020 NOL to the tax year ended December 31, 2018 and 2019 which resulted in a minimal tax refund of less than $0.1 million.

As of December 31, 2020, the Company has total gross United States state net operating loss carryforwards of $29.0 million, which may be available to offset future income tax liabilities that will begin to expire at various dates through 2040.

As of December 31, 2020, the Company has Belgium net operating loss carryforwards for Belgian federal income tax purposes of approximately $69.2 million, that can be carried forward indefinitely.

As of December 31, 2020, the Company has de minimis federal and state tax credit carryforwards available to reduce future tax labilities, which expire in 2040 and 2025, respectively.

Utilization of net operating loss and research and development credit carryforwards may be subject to a substantial annual limitation under Section 382 and Section 383 of the Internal Revenue Code of 1986, as amended, due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of net operating losses and research and development credit carryforwards that can be utilized annually to offset future taxable income and tax liabilities, respectively. The Company has completed several financings since its inception, which may result in a change of control as defined in Section 382 or could result in a change in control in the future. The Company has not yet completed a study to assess whether a change of ownership has occurred, or whether there have been multiple ownership changes since its formation. Any limitation may result in expiration of a portion of the net operating loss carryforwards or research and development credit carryforwards before utilization.

The Company has not, as of yet, conduct a study of research and development credit carryforward. Such a study, once undertaken by the Company, may result in an adjustment to the Company’s research and development credit carryforward. A full valuation allowance has been provided against the research and development credit carryforward and, if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. Thus, there would be no impact to the Company’s balance sheet or statement of operations if an adjustment is required.

The Company files income tax returns in the United States, Indiana, Massachusetts, New Hampshire and Belgium. The Company is subject to U.S. federal, state and Belgium tax examinations by tax authorities for years 2017 through present. To the extent that the Company has tax attribute carryforwards, the tax years in which the attributes were generated may still be adjusted upon examination by the Internal Revenue Service, state or foreign tax authorities to the extent utilized in a future period. As of December 31, 2020, and 2019, the Company has recorded no liability for unrecognized tax benefit, interest or penalties related to federal and state income tax matters and there currently no pending tax examinations.

The CARES Act was enacted on March 27, 2020. The CARES contains a significant number of provisions that may impact on the Company’s accounting for income taxes. The Company has evaluated its potential impact and as a result recorded a minimal tax benefit of less than $0.1 million related to an anticipated refund as a result of the 2020 net operating loss carryback to be received for federal taxes incurred for the tax years ended December 31, 2018 and 2019.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Commitments and Contingencies

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 10. 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 December 31, 2020 and 2019, there were no amounts accrued related to termination charges.

The Company has entered into a Biologics Master Services Agreement with WuXi Biologics Hong Kong Limited (WuXi) herein referred to as the WuXi Agreement. The WuXi Agreement includes the terms and conditions under which WuXi will coordinate the Company’s biologics development and manufacturing services. Pursuant to the WuXi Agreement, the Company may be required to pay WuXi a royalty percentage or a one-time milestone payment on global net sales of third-party manufactured products at the Company’s election. The royalty or one-time milestone payment is only payable if the Company does not use WuXi as the manufacturer in part, or in totality. As of December 31, 2020 and 2019, there are no minimum commitments under the WuXi Agreement. Additionally, as of December 31, 2020 and 2019 there are no royalties or milestones payable.

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 $0.6 million and $0.5 million for the years ended December 31, 2020 and 2019, respectively.

In January 2021, the Company entered into an agreement to extend its office lease in Belgium effective February 1, 2021 through January 2030 and include additional space.

Future minimum lease payments under non-cancelable operating leases as of December 31, 2020, including the extension of the Belgium office lease noted above, are as follows (in thousands):

Year ending December 31:
2021	$	667
2022		504
2023		385
2024		349
2025		318
Thereafter		1,369
Total	$	3,592

In March 2019, the Company provided a letter of credit for approximately $57,000 to secure its obligation under its lease in Cambridge, Massachusetts. The Company maintains that amount of cash on hand (restricted) to fund any necessary draws on the letter of credit. In addition, the Company has approximately $71,000 on hand serving as a guarantee for its lease obligation in Belgium. These amounts have been classified as restricted cash in the consolidated balance sheets as of December 31, 2020 and 2019.

Employee benefit plan

12 Months Ended

Dec. 31, 2020

Compensation And Retirement Disclosure [Abstract]

Employee benefit plan

Note 11. Employee benefit plan

iTeos Belgium sponsors a defined contribution insurance plan (the Plan) for its employees. In the first quarter of each year, iTeos Belgium pays an annual premium to the insurance company which corresponds to 5% of employees’ gross salaries. Interest accrues each year into a pool for each employee and when they retire, they collect the total in their accounts. The Company contributed approximately $167,000 and $141,000 to the Plan for the years ended December 31, 2020 and 2019, respectively.

Effective January 1, 2019, iTeos U.S. established a 401(k) defined contribution plan (the 401(k) Plan) for its U.S. employees. The 401(k) plan provides for voluntary tax-deferred salary deductions for all employees of up to 100% of their annual compensation, as limited by an annual maximum amount as determined by the Internal Revenue Service. The Company may match employee contributions in amounts to be determined at the Company’s sole discretion. The Company contributed approximately $28,000 and $18,000 to the 401(k) Plan for the years ended December 31, 2020 and 2019, respectively.

- Definition

The entire disclosure for retirement benefits.

+ References

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+ Details

Related party transactions

12 Months Ended

Dec. 31, 2020

Related Party Transactions

Note 12. 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 on any product developed or owned by iTeos Therapeutics, Inc. or iTeos Belgium SA, 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 had no product sales in 2020 and 2019, no royalties were owed to these charitable foundations as of December 31, 2020 and 2019.

Net Loss Per Share Attributable to Common Stock

12 Months Ended

Dec. 31, 2020

Earnings Per Share [Abstract]

Net Loss Per Share Attributable to Common Stock

Note 13. Net loss per share attributable to common stockholders

The following common stock equivalents were excluded from the calculation of net loss per share due to their anti-dilutive effective:

	December 31,
	2020		2019
Series B Preferred Stock, as converted		—		6,760,804
Series A Preferred Stock, as converted		—		1,862,510
Stock options outstanding		4,552,396		1,387,003
Total		4,552,396		10,010,317

Subsequent Events

12 Months Ended

Dec. 31, 2020

Subsequent Events [Abstract]

Subsequent Events

Note 14. Subsequent events

In January 2021, the Company entered into an agreement to extend its office lease in Belgium effective February 1, 2021 through January 2030 and include additional space.

On February 22, 2021, the Company entered into an amendment to the Adimab Agreement (the Amended Adimab Agreement). The Amended Adimab Agreement specifies different milestone payments for new products that are derived from research programs beginning after February 22, 2021 (New Products). For New Products, on a per target basis, the Company may be required to pay development, regulatory and commercial milestone payments totaling up to an aggregate of $45.8 million for the first three products and additional milestone payments up to $14.5 million for each additional product. Royalty percentages for New Products are slightly different than for original products. There were no other significant changes to the terms in the original Adimab Agreement as a result of the Amended Adimab Agreement.

Summary of significant accounting policies (Policies)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Principles of consolidation

The 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

Share Exchange

Share exchange

Cash, cash equivalents and restricted cash

Cash, Cash Equivalents and Restricted Cash

Foreign currency, currency translation and comprehensive loss

Fair Value Measurements

Fair value measurements

•	Level 1—Quoted prices in active markets that are accessible at the market date for identical unrestricted assets or liabilities.

•

•	Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

Concentration of credit risk

Research And Development Tax Credits

Research and development tax credits

Property and equipment

Property and equipment, including leasehold improvements, are stated at cost and depreciated when placed into service using the straight-line method over the estimated useful lives as follows:

Asset		Estimated Useful Life
Computer equipment and software		3 years
Furniture, fixtures and other		5 years
Scientific equipment		5 – 6 years
Leasehold improvements		Shorter of useful life or term of lease

Impairment of long-lived assets

Deferred Offering Costs

Deferred offering costs

Revenue recognition

Collaborative Arrangements

Research and Development Expenses

Research and development expenses

Government grant funding and potential repayment commitments under recoverable cash advance grants (RCAs)

Leases

Stock-based compensation

Following our IPO, the fair value of our common stock is determined based on the quoted market price of our common stock.

Preferred stock

Derivatives

Income Tax

Income taxes

The Company includes any penalties and interest expense related to income taxes as a component of other expense and interest expense, net, as necessary.

Segment information

Net loss per share attributable to common stockholders

Recently adopted accounting standards updates

•

•	Adds unit-of-account guidance to ASC 808, Collaborative Arrangements, to align with the guidance in ASC 606 (that is, a distinct good or service) when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of ASC 606; and

•	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.

Recently issued accounting standards and updates not yet effective

Summary of significant accounting policies (Tables)

12 Months Ended

Dec. 31, 2020

Accounting Policies [Abstract]

Public Utility Property, Plant, and Equipment [Table Text Block]

Property and equipment, including leasehold improvements, are stated at cost and depreciated when placed into service using the straight-line method over the estimated useful lives as follows:

Asset		Estimated Useful Life
Computer equipment and software		3 years
Furniture, fixtures and other		5 years
Scientific equipment		5 – 6 years
Leasehold improvements		Shorter of useful life or term of lease

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 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:

	December 31, 2020
(in thousands)	Level 1		Level 2		Level 3		Total
Cash equivalents (money market funds)	$	314,636	$	—	$	—	$	314,636
Totals	$	314,636	$	—	$	—	$	314,636

	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

Summary of Reconciliation of the Fair Value Adjustment for Tranche Rights and Warrants Amounts Included In the Consolidated Statements of Operations and Comprehensive Loss

	Year Ended December 31,
(in thousands)	2020		2019
Elimination of Series B anti-dilution warrants	$	—	$	182
Elimination of Series A anti-dilution warrants		—		219
Change in estimated fair value		1,265		618
Total included in earnings	$	1,265	$	1,019

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

	March 23, 2020 (Tranche 3 settlement)			December 31, 2019			December 31, 2018
Implied equity value (in millions)	$	208.2		$	74.4		€30.8 ($35.4)
Probability of success of reaching necessary milestone:
Tranche 2 milestone	N/A			N/A			85% by March 31, 2019
Tranche 3 milestone (by March 31, 2020)		90	%		90	%		90	%
Expected industry return over period during which milestones are expected to be achieved		13.0	%		15.0	%		15.0	%
Risk-free interest rate		1.1	%		2.3	%		2.5	%

Summary of Changes in Level 3 Liabilities Measures at Fair Value on a Recurring Basis

The following table presents changes during the years ended December 31, 2020 and 2019 in Level 3 liabilities measured at fair value on a recurring basis:

(in thousands)	Preferred Stock Tranche Rights Liability			Series B Anti- Dilution Warrants			Series A Anti- Dilution Warrants
Balances at January 1, 2019	$	6,325		$	182		$	219
Elimination of warrants through Share Exchange		—			(182	)		(219	)
Change in estimated fair value		(618	)		—			—
Effects of exchange rate changes		(307	)		—			—
Balances at December 31, 2019		5,400			—			—
Change in estimated fair value		(1,265	)		—			—
Settlement of tranche right		(4,135	)		—			—
Balances at December 31, 2020	$	—		$	—		$	—

Consolidated Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2020

Supplemental Balance Sheet Information [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net consisted of the following:

	December 31,
(in thousands)	2020			2019
Scientific equipment	$	2,617		$	2,300
Furniture & office equipment		542			346
Leasehold improvements		855			771
Total		4,014			3,417
Accumulated depreciation and amortization		(2,662	)		(2,081	)
Property & equipment, net	$	1,352		$	1,336

Schedule of Accrued Expenses

Accrued liabilities consisted of the following:

	December 31,
(in thousands)	2020		2019
Accrued clinical trial costs	$	4,012	$	2,683
Accrued personnel costs		3,208		1,409
Accrued professional fees		37		30
Accrued other		229		140
Total accrued expenses and other current liabilities	$	7,486	$	4,262

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) (Tables)

12 Months Ended

Dec. 31, 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 years ended December 31, 2020 and 2019 and end of year balances as of December 31, 2020 and December 31, 2019:

	RCA -1				RCA-2				Other Grants				Total
(In thousands)	2020		2019		2020		2019		2020		2019		2020		2019
Cash received	$	11,944	$	220	$	2,479		—	$	2,630	$	1,198	$	17,053	$	1,418
Grant income recognized		3,913		3,186		1,290		482		444		321	$	5,647	$	3,989
Grants receivable		—		4,448		—		677		133		71	$	133	$	5,196
Grants repayable		5,102		1,397		781		—		—		—	$	5,883	$	1,397

Stockholders’ equity (Tables)

12 Months Ended

Dec. 31, 2020

Equity [Abstract]

Schedule of Redeemable Convertible Preferred Stock Prior to Automatic Conversion to Common Stock

Redeemable convertible preferred stock consisted of the following immediately prior to the automatic conversion into common stock:

	Designated Shares Authorized		Shares Issued and Outstanding		Aggregate Liquidation Preference (in 000's)
Series A-1 and A-2		6,167,726		6,167,726	$	7,114
Series B		31,989,428		20,942,781		55,642
Series B-2		44,453,477		44,453,477		127,680
Total redeemable convertible preferred stock		82,610,631		71,563,984	$	190,436

Schedule of Common Stock Reserve on Converted Basis for Issuance

The Company had reserved shares of common stock, on an if-converted basis, for issuance as follows:

	December 31,
	2020		2019
Series A Preferred Stock, as converted		—		1,862,510
Series B Preferred Stock, as converted		—		6,760,804
Stock options issued and outstanding		4,552,396		1,387,003
Shares available for issuance under Stock Option Plan		3,039,222		251,606
Total		7,591,618		10,261,923

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Options Activity

The following table summarizes stock option activity for the year ended December 31, 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		4.8
Granted		3,504,715			10.43
Forfeited		(102,863	)		7.18
Exercised		(236,459	)		2.77
Outstanding as of December 31, 2020		4,552,396		$	9.13		8.2	$	112,412
Vested and expected to vest as of December 31, 2020		4,552,396		$	9.13		8.2	$	112,412
Exercisable at December 31, 2020		861,388		$	4.93		5.0	$	24,889

Summary of Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense, and also the allocation within the consolidated statements of operations and comprehensive loss:

	Year Ended December 31,
(in thousands)	2020		2019
Research and development	$	425	$	170
General and administrative		3,867		639
Total stock-based compensation expense	$	4,292	$	809

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:

	Year Ended December 31,
	2020	2019
Risk-free interest rate	0.36% - 1.35%	2.50%
Expected term (in years)	5 - 6		5
Expected volatility	90% - 102%		93	%
Expected dividend yield	0%		0	%
Estimated fair value of common stock	$2.95 - $33.12	$2.38

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2020

Income Tax Disclosure [Abstract]

Schedule of Loss Before Income Tax Expense

For financial reporting purposes, loss before income tax expense for the years ended December 31, 2020 and 2019 consisted of the following:

(in thousands)	2020			2019
Domestic	$	(31,184	)	$	(689	)
Foreign		(6,906	)		(21,646	)
Loss before income tax expense	$	(38,090	)	$	(22,335	)

Schedule of Reconciliation of Income Tax Expense (Benefit) Computed at the Statutory Federal Income Tax Rate

The reconciliation of the statutory U.S. federal income tax rate (21%) to the effective income tax rate is as follows:

	2020			2019
U.S. statutory federal income tax rate		21.0	%		21.0	%
State income taxes	4.8			0.1
Foreign tax differential	0.8			8.3
Non-deductible/non-taxable permanent differences	3.4			7.6
Change in local tax rate	(8.6)				—
Other	0.9				—
Change in valuation allowance	(22.1)			(37.5)
Effective income tax rate	0.2%				(0.5	%)

Schedule of Components of Income Tax Expense

The components of income tax expense for the years ended December 31, 2020 and 2019 consisted of the following:

(in thousands)	2020			2019
Current
Domestic	$	(60	)	$	116
Foreign		3			3
Deferred		—			—
Total income tax (benefit) expense	$	(57	)	$	119

Schedule of Significant Components of the Company Deferred Tax Assets and Lliabilities

The significant components of the Company’s deferred tax assets and liabilities are comprised of the following:

	December 31,
(in thousands)	2020			2019
Deferred tax assets :
Net operating loss carryforward	$	25,206		$	14,176
Capitalized research and development expenses		6,219			7,397
Stock-based compensation		758			—
Other		313			110
Total deferred tax assets		32,496			21,683
Valuation allowance		(32,029	)		(21,673	)
Deferred tax assets, net of valuation allowance		467			10
Deferred tax liabilities:
Prepaid expenses		(445	)		—
Depreciation and amortization		(22	)		(10	)
Total deferred tax liabilities		(467	)		(10	)
Deferred tax assets and liabilities, net of valuation allowance	$	—		$	—

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2020

Commitments And Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases

Future minimum lease payments under non-cancelable operating leases as of December 31, 2020, including the extension of the Belgium office lease noted above, are as follows (in thousands):

Year ending December 31:
2021	$	667
2022		504
2023		385
2024		349
2025		318
Thereafter		1,369
Total	$	3,592

Net Loss Per Share Attributable to Common Stock (Tables)

12 Months Ended

Dec. 31, 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 effective:

	December 31,
	2020		2019
Series B Preferred Stock, as converted		—		6,760,804
Series A Preferred Stock, as converted		—		1,862,510
Stock options outstanding		4,552,396		1,387,003
Total		4,552,396		10,010,317

Nature of Business and Basis of Presentation - Additional Information (Details) $ in Thousands				12 Months Ended
	Aug. 05, 2020 USD ($) shares	Jul. 28, 2020 USD ($) shares	Jul. 20, 2020	Dec. 31, 2020 USD ($) shares	Dec. 31, 2019 USD ($)
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Issuance of common stock from initial public offering				$ 210,612
Proceeds from initial public offering, net of underwriting discount				213,660
Net loss				(38,033)	$ (22,454)
Accumulated deficit				$ (73,898)	$ (35,865)
Common stock
Organization Consolidation And Presentation Of Financial Statements Disclosure [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
Issuance of common stock from initial public offering, shares \| shares				12,091,675
Issuance of common stock from initial public offering				$ 12
Convertible Preferred Stock, Shares Issued upon Conversion \| shares		22,460,076		22,460,076
Common stock \| IPO
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Issuance of common stock from initial public offering, shares \| shares		10,586,316
Issuance of common stock from initial public offering		$ 201,100
Proceeds from initial public offering, net of underwriting discount		$ 184,000
Underwriters exercise option to purchase additional shares of common stock \| shares	1,505,359
Net proceeds after deducting commissions from underwriter purchase of additional share of common stock	$ 26,600
Net loss				$ 38,000
Accumulated deficit				$ 73,900

Summary of significant accounting policies - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) Segment	Dec. 31, 2019 USD ($)
Accounting Policies [Abstract]
Transfers of financial instruments between levels	$ 0	$ 0
Research And Development Tax Credits Percentage	13.50%	13.50%
Impairment charges	$ 0	$ 0
Operating segment \| Segment	1

Summary of significant accounting policies - Summary of Property and Equipment Estimated Useful Lives (Details)	12 Months Ended
	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Leasehold improvements	Shorter of useful life or term of lease
Maximum
Property Plant And Equipment [Line Items]
Useful life (in years)	6 years
Computer equipment and software
Property Plant And Equipment [Line Items]
Useful life (in years)	3 years
Furniture, fixtures and other
Property Plant And Equipment [Line Items]
Useful life (in years)	5 years
Scientific equipment \| Minimum
Property Plant And Equipment [Line Items]
Useful life (in years)	5 years

Fair Value Measurements - Summary of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents (money market funds)	$ 314,636
Totals	314,636	$ 5,400
Preferred stock tranche rights liability		5,400
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents (money market funds)	314,636
Totals	$ 314,636
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Totals		5,400
Preferred stock tranche rights liability		$ 5,400

Fair Value Measurements - Additional Information (Details) $ / shares in Units, € in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($)	Jun. 11, 2018 USD ($)	Jun. 11, 2018 EUR (€)	Jan. 01, 2018 USD ($)	Jan. 01, 2018 EUR (€)
Class Of Warrant Or Right [Line Items]
Derivatives \| $	$ 0	$ 0
Series A Preferred Stock
Class Of Warrant Or Right [Line Items]
Starting equity value					$ 33,300,000	€ 28.3
Timing of future fund raise					Jun. 30, 2020	Jun. 30, 2020
Amount of future fund raise					$ 34,400,000	€ 30.0
Warrants maturity date					Dec. 31, 2020	Dec. 31, 2020
Series B Preferred Stock
Class Of Warrant Or Right [Line Items]
Starting equity value			$ 33,300,000	€ 28.3
Timing of future fund raise			Jun. 30, 2020	Jun. 30, 2020
Amount of future fund raise			$ 34,400,000	€ 30.0
Warrants maturity date			Dec. 31, 2020	Dec. 31, 2020
Measurement Input Price Volatility \| Series A Preferred Stock
Class Of Warrant Or Right [Line Items]
Annual Volatility					114.700	114.700
Measurement Input Price Volatility \| Series B Preferred Stock
Class Of Warrant Or Right [Line Items]
Annual Volatility			114.700	114.700
Measurement Input Risk Free Interest Rate \| Series A Preferred Stock
Class Of Warrant Or Right [Line Items]
Measurement input					2.56	2.56
Measurement Input Risk Free Interest Rate \| Series B Preferred Stock
Class Of Warrant Or Right [Line Items]
Measurement input			2.56	2.56
Series B \| Anti-Dilution Warrants
Class Of Warrant Or Right [Line Items]
Warrant provided to investors \| shares	1
Exercise price of warrants \| $ / shares	$ 0.01

Fair Value Measurements - Summary of Fair Value of Series B Preferred Stock Tranche Rights Liability (Details) - Series B Preferred Stock € in Millions, $ in Millions	Mar. 23, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 EUR (€)	Jun. 11, 2018
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Implied equity value		$ 74.4	$ 35.4	€ 30.8
Level 3 \| 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) \| Level 3
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) \| Level 3
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%
Tranche 3 milestone (by March 31, 2020) \| Level 3 \| 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 \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input		15.0	15.0	15.0
Expected industry return over period during which milestones are expected to be achieved \| Level 3 \| Tranche Three Settlement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	13.0
Measurement Input Risk Free Interest Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input					2.56
Measurement Input Risk Free Interest Rate \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input		2.3	2.5	2.5
Measurement Input Risk Free Interest Rate \| Level 3 \| Tranche Three Settlement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	1.1

Fair Value Measurements - Summary of Changes in Level 3 Liabilities Measures at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in estimated fair value	$ 1,265	$ 618
Level 3 \| Preferred Stock Tranche Rights Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balances	5,400	6,325
Change in estimated fair value	(1,265)	(618)
Effects of exchange rate changes		(307)
Balances		5,400
Settlement of tranche right	$ (4,135)
Level 3 \| Series A \| Anti-Dilution Warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balances		182
Elimination of warrants through Share Exchange		(182)
Level 3 \| Series B \| Anti-Dilution Warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balances		219
Elimination of warrants through Share Exchange		$ (219)

Fair Value measurement - Summary of Reconciliation of the Fair Value Adjustment for Tranche Rights and Warrants Amounts Included In the Consolidated Statements of Operations and Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in estimated fair value	$ 1,265	$ 618
Total included in earnings	$ 1,265	1,019
Series A \| Anti-Dilution Warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Elimination of warrants		182
Series B \| Anti-Dilution Warrants
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Elimination of warrants		$ 219

Consolidated Balance Sheet Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Total property and equipment	$ 4,014	$ 3,417
Accumulated depreciation and amortization	(2,662)	(2,081)
Property & equipment, net	1,352	1,336
Scientific Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	2,617	2,300
Furniture and Office Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	542	346
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 855	$ 771

Consolidated Balance Sheet Components - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Supplemental Balance Sheet Information [Abstract]
Depreciation and amortization	$ 535	$ 611

Consolidated Balance Components - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued clinical trial costs	$ 4,012	$ 2,683
Accrued personnel costs	3,208	1,409
Accrued professional fees	37	30
Accrued other	229	140
Total accrued expenses and other current liabilities	$ 7,486	$ 4,262

License and collaboration agreements - Additional Information (Details) - Adimab L L C - USD ($) $ in Millions			12 Months Ended
	Aug. 31, 2018	Apr. 30, 2017	Dec. 31, 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	$ 1.0
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 Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) - Additional Information (Details) - USD ($)			12 Months Ended
	Dec. 03, 2019	Jul. 17, 2017	Dec. 31, 2020	Dec. 31, 2019
Research And Development Arrangement Contract To Perform For Others [Line Items]
Commitment for funding for research and development expenses			$ 1,300,000
Grant repayable			$ 5,883,000	$ 1,397,000
RCA- 1
Research And Development Arrangement Contract To Perform For Others [Line Items]
Recoverable cash advance		$ 23,100,000
Percentage of royalty on revenue			0.33%
Grant repayable			$ 5,102,000	1,397,000
RCA- 2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Recoverable cash advance	$ 4,300,000
Percentage of royalty on revenue			0.12%
Grant repayable			$ 781,000
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
Research and Development Expenses
Research And Development Arrangement Contract To Perform For Others [Line Items]
Grant income recognized for research and development activities			$ 5,600,000	$ 4,000,000
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 Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) - Schedule of Activity for Grant Programs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received	$ 17,053	$ 1,418
Grant income	5,647	3,989
Grants receivable	133	5,196
Grant repayable	5,883	1,397
RCA- 1
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received	11,944	220
Grant income	3,913	3,186
Grants receivable		4,448
Grant repayable	5,102	1,397
RCA- 2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received	2,479
Grant income	1,290	482
Grants receivable		677
Grant repayable	781
Other Grants
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received	2,630	1,198
Grant income	444	321
Grants receivable	$ 133	$ 71

Stockholders' equity - Schedule of Redeemable Convertible Preferred Stock Prior to Automatic Conversion to Common Stock (Details) - shares	Dec. 31, 2020	Jul. 28, 2020	Dec. 31, 2019
Preferred Stock Shares Authorized	10,000,000		0
Series A1 And A2 Convertible Preferred Stock
Preferred Stock Shares Authorized		6,167,726
Shares Issued and Outstanding		6,167,726
Aggregate Liquidation Preference (in 000's)		7,114
Series B Preferred Stock
Preferred Stock Shares Authorized		31,989,428
Shares Issued and Outstanding		20,942,781
Aggregate Liquidation Preference (in 000's)		55,642
Series B2 Convertible Preferred Stock
Preferred Stock Shares Authorized		44,453,477
Shares Issued and Outstanding		44,453,477
Aggregate Liquidation Preference (in 000's)		127,680
Redeemable Convertible Preferred Stock
Preferred Stock Shares Authorized	0	82,610,631	38,157,154
Shares Issued and Outstanding		71,563,984
Aggregate Liquidation Preference (in 000's)		190,436

Stockholders' equity - Additional Information (Details) - $ / shares	Jul. 28, 2020	Dec. 31, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Common stock, shares authorized		150,000,000	50,000,000
Common stock, par value		$ 0.001	$ 0.001
Preferred Stock Shares Authorized		10,000,000	0
Preferred Stock, par value		$ 0.001	$ 0.001
Common stock, voting rights	Each share of common stock entitles the holders to one vote on all matters submitted to a vote of the Company’s stockholders.
IPO
Class Of Stock [Line Items]
Capital units, authorized	160,000,000
Common stock, shares authorized	150,000,000
Common stock, par value	$ 0.001
Preferred Stock Shares Authorized	10,000,000
Preferred Stock, par value	$ 0.001
Redeemable Convertible Preferred Stock
Class Of Stock [Line Items]
Redeemable Convertible Preferred Stock Shares Issued		0
Redeemable Convertible Preferred Stock Shares Outstanding		0
Preferred Stock Shares Authorized	82,610,631	0	38,157,154
Preferred Stock, par value		$ 0.001	$ 0.001
Common stock
Class Of Stock [Line Items]
Convertible Preferred Stock, Shares Issued upon Conversion	22,460,076	22,460,076

Stockholders' equity - Schedule of Common Stock Reserve on Converted Basis for Issuance (Details) - shares	Dec. 31, 2020	Dec. 31, 2019
Stock options issued and outstanding	4,552,396	1,387,003
Shares available for issuance under Stock Option Plan	3,039,222	251,606
Total	7,591,618	10,261,923
Series A Preferred Stock
Convertible Preferred Stock, Shares Issued upon Conversion		1,862,510
Series B Preferred Stock
Convertible Preferred Stock, Shares Issued upon Conversion		6,760,804

Stock-based compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
	Jul. 15, 2020	Dec. 31, 2020	Dec. 31, 2019	Mar. 24, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting percentage		25.00%
Stock options vesting period		36 months
Common stock initially reserved for future issuance		7,591,618	10,261,923
Weighted-average estimated fair value of options awarded (in dollars per share)		$ 7.75	$ 0.49
Aggregate intrinsic value of options exercise		$ 3.1	$ 0.2
Aggregate grant date fair value of stock options vested		$ 0.8	$ 0.7
2020 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [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
Stock Issued under Employee Stock Purchase Plans		0
Non Vested Stock Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs for non-vested stock awards		$ 23.6
Recognition period for compensation cost not yet recognized (in years, months, and days)		3 years 4 months 24 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
Amendment to 2019 Stock Option and Grant Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option vesting percentage	100.00%
2020 Stock Option and Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock initially reserved for future issuance	3,809,818
Cumulative increase in common stock reserve for issuance, percentage	5.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation, stock options expiry period		7 years
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation, stock options expiry period		10 years

Stock-based compensation - Summary of Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Shares
Outstanding as of December 31, 2019	1,387,003
Granted	3,504,715
Forfeited	(102,863)
Exercised	(236,459)
Outstanding as of December 31, 2020	4,552,396	1,387,003
Vested and expected to vest as of December 31, 2020	4,552,396
Exercisable at December 31, 2020	861,388
Weighted-Average Exercise Price Per Share
Outstanding as of December 31, 2019	$ 4.62
Granted	10.43
Forfeited	7.18
Exercised	2.77
Outstanding as of December 31, 2020	9.13	$ 4.62
Vested and expected to vest as of December 31, 2020	9.13
Exercisable at December 31, 2020	$ 4.93
Weighted-Average Remaining Contractual Term
Options outstanding	8 years 2 months 12 days	4 years 9 months 18 days
Vested and expected to vest as of December 31, 2020	8 years 2 months 12 days
Exercisable at December 31, 2020	5 years
Aggregate Intrinsic Value
Outstanding as of December 31, 2019	$ 112,412
Vested and expected to vest as of December 31, 2020	112,412
Exercisable at December 31, 2020	$ 24,889

Stock-based compensation - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 4,292	$ 809
Research and Development Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	425	170
General And Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 3,867	$ 639

Stock-based compensation - Schedule of Fair Value Assumptions for Stock Options Granted (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate		2.50%
Risk-free interest rate, minimum	0.36%
Risk-free interest rate, maximum	1.35%
Expected volatility		93.00%
Expected Volatility, minimum	90.00%
Expected Volatility, maximum	102.00%
Expected dividend yield	0.00%	0.00%
Estimated fair value of common stock		$ 2.38
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years	5 years
Estimated fair value of common stock	$ 2.95
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years
Estimated fair value of common stock	$ 33.12

Income Taxes - Schedule of Loss Before Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Domestic	$ (31,184)	$ (689)
Foreign	(6,906)	(21,646)
Loss before income tax expense	$ (38,090)	$ (22,335)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands		12 Months Ended
	Mar. 27, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2017
Income Tax Contingency [Line Items]
Effective income tax rate reconciliation, percent		0.20%	(0.50%)
Effective income tax rate reconciliation, at federal statutory income tax rate, percent		21.00%	21.00%
Deferred tax assets valuation allowance		$ 32,029	$ 21,673
Net increase (decrease) in deferred tax assets valuation allowance		10,300
Date expiring, net operating loss Carry forwards available to offset future income tax liabilities		$ 29,200
Net operating loss Carry forwards deductible at maximum rate of corporations taxable income		80.00%		100.00%
Net operating loss, available to offset rate for the taxable income limitation under the TCJA		80.00%
Operating loss carryforwards, limitations on use	0.1	0.1
Operating loss carryforwards		$ 29,000
Date expiring, net operating loss carry forwards available to offset future income tax liabilities		2040
Foreign		$ (6,906)	$ (21,646)
Date expiring, de minimis federal future tax liabilities		2040
Date expiring, state tax credit available to reduce future tax liabilities		2025
BELGIUM
Income Tax Contingency [Line Items]
Foreign		$ 69,200

Income Taxes - Schedule of Reconciliation of Income Tax Expense (Benefit) Computed at the Statutory Federal Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
U.S. statutory federal income tax rate	21.00%	21.00%
State income taxes	4.80%	0.10%
Foreign tax differential	0.80%	8.30%
Non-deductible/non-taxable permanent differences	3.40%	7.60%
Change in local tax rate	(8.60%)
Other	0.90%
Change in valuation allowance	(22.10%)	(37.50%)
Effective income tax rate	0.20%	(0.50%)

Income Taxes - Schedule of Components of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Domestic	$ (60)	$ 116
Foreign	3	3
Total income tax (benefit) expense	$ (57)	$ 119

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References + Details

Income Taxes - Schedule of Significant Components of the Company Deferred Tax Assets and Lliabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets :
Net operating loss carryforward	$ 25,206	$ 14,176
Capitalized research and development expenses	6,219	7,397
Stock-based compensation	758
Other	313	110
Total deferred tax assets	32,496	21,683
Valuation allowance	(32,029)	(21,673)
Deferred tax assets, net of valuation allowance	467	10
Deferred tax liabilities:
Prepaid expenses	(445)
Depreciation and amortization	(22)	(10)
Total deferred tax liabilities	$ (467)	$ (10)

Commitments and Contingencies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Other Commitments [Line Items]
Operating lease term	4 years
Operating leases, rent expense	$ 600,000	$ 500,000
Cambridge, Massachusetts
Other Commitments [Line Items]
Lease expiration date	May 31, 2022
Operating lease, Letter of credit to secure lease obligation			$ 57,000,000
BELGIUM
Other Commitments [Line Items]
Lease expiration date	Dec. 31, 2021
Extension of office lease	In January 2021, the Company entered into an agreement to extend its office lease in Belgium effective February 1, 2021 through January 2030 and include additional space
Operating lease, Hand serving to secure lease obligation	$ 71,000,000	71,000,000
Wu Xi Agreement
Other Commitments [Line Items]
Minimum commitments	0	0
Payments for Royalties	0	0
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 - Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Leases [Abstract]
2021	$ 667
2022	504
2023	385
2024	349
2025	318
Thereafter	1,369
Total	$ 3,592

Employee benefit plan - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, employer contribution, percent	5.00%
Defined contribution plan,contributions by employer	$ 167,000	$ 141,000
401(k) defined contribution plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan,contributions by employer	$ 28,000,000	$ 18,000,000
Defined contribution plan, maximum annual contributions per employee, percent	100.00%

- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References + Details

Related Party Transactions - Additional Information (Details) - Royalty Transfer Agreement $ in Thousands		12 Months Ended
	Jun. 11, 2018 Investor	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Related Party Transaction [Line Items]
Royalty owed to charitable foundation		$ 0	$ 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 on any product developed or owned by iTeos Therapeutics, Inc. or iTeos Belgium SA, each year within 120 days following each year end.
Percentage of royalty required to pay	1.00%
Product
Related Party Transaction [Line Items]
Net product sales		$ 0	$ 0

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Net Loss Per Share Attributable to Common Stock - Schedule of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents	4,552,396	10,010,317
Series B Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents		6,760,804
Series A Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents		1,862,510
EmployeeStockOptionMember
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents	4,552,396	1,387,003

Subsequent Events (Additional Information) (Details) - USD ($) $ in Millions			12 Months Ended
	Feb. 22, 2021	Jan. 31, 2021	Dec. 31, 2020
Development Regulatory and Sales Milestone
Subsequent Event [Line Items]
Maximum additional receivable based on achievement of research milestones			$ 13.5
Subsequent Event
Subsequent Event [Line Items]
Agreement effective date		2021-01
Subsequent Event, Description		In January 2021, the Company entered into an agreement to extend its office lease in Belgium effective February 1, 2021 through January 2030 and include additional space
Agreement amendment date	Feb. 22, 2021
Maximum additional receivable based on achievement of research milestones	$ 14.5
Subsequent Event \| Development Regulatory and Sales Milestone
Subsequent Event [Line Items]
Maximum option fees receivable based on achievement of research milestones	$ 45.8