iTeos Therapeutics (ITOS) 10-Q 11 Aug 21 2021 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Aug. 06, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Document Quarterly Report	true
Document Transition Report	false
Trading Symbol	ITOS
Entity Registrant Name	iTeos Therapeutics, Inc.
Entity Central Index Key	0001808865
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	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		35,209,755
Security12b Title	Common stock, $0.001 par value per share
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 302,933	$ 336,326
Grants receivable	4,232	133
Research and development tax credits receivable		192
Prepaid expenses and other current assets	2,603	2,893
Total current assets	309,768	339,544
Property and equipment, net	2,021	1,352
Research and development tax credits receivable	3,297	3,286
Restricted cash	139	128
Right of use asset	3,048
Other assets	412	248
Total assets	318,685	344,558
Current liabilities:
Accounts payable	11,661	3,026
Accrued expenses and other current liabilities	7,570	7,486
Deferred income	977	4,486
Lease liability	555
Total current liabilities	20,763	14,998
Grants repayable	5,693	5,883
Other noncurrent liabilities	230	480
Lease liability, net of current portion	2,501
Total liabilities	29,187	21,361
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; zero shares issued or outstanding at June 30, 2021 and December 31, 2020
Common stock, $0.001 par value, 150,000,000 shares authorized; 35,148,110 and 35,044,758 shares issued and outstanding at June 30, 2021 and December 31, 2020, respectively	35	35
Additional paid-in capital	403,116	396,443
Accumulated other comprehensive income	238	617
Accumulated deficit	(113,891)	(73,898)
Total stockholders’ equity	289,498	323,197
Total liabilities, redeemable convertible preferred stock and stockholders’ equity	$ 318,685	$ 344,558

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	35,148,110	35,044,758
Common stock, shares outstanding	35,148,110	35,044,758
Preferred Stock, par value	$ 0.001	$ 0.001
Preferred Stock Shares Authorized	10,000,000	10,000,000
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Operating expenses:
Research and development expenses	$ 14,238	$ 6,137	$ 25,881	$ 11,962
General and administrative expenses	15,101	2,394	22,147	4,812
Total operating expenses	29,339	8,531	48,028	16,774
Loss from operations	(29,339)	(8,531)	(48,028)	(16,774)
Other income and expenses:
Grant income	2,701	1,081	7,616	2,670
Fair value adjustment for preferred stock tranche rights liability				1,265
Research and development tax credits	119	186	119	370
Other income (expense), net	60	12	300	(30)
Loss before income taxes	(26,459)	(7,252)	(39,993)	(12,499)
Income tax benefit		50		50
Net loss	(26,459)	(7,202)	(39,993)	(12,449)
Cumulative dividends on Series A preferred stock		(106)		(213)
Accretion of redeemable convertible preferred stock to redemption value				(4,189)
Net loss attributable to common stockholders	$ (26,459)	$ (10,302)	$ (39,993)	$ (16,851)
Basic and diluted net loss per common share	$ (0.75)	$ (29.49)	$ (1.14)	$ (55.63)
Weighted-average common shares outstanding— basic and diluted	35,119,952	349,290	35,103,294	302,919
Net loss	$ (26,459)	$ (7,202)	$ (39,993)	$ (12,449)
Foreign currency translation adjustments	(74)	245	(379)	(72)
Comprehensive loss	$ (26,533)	(6,957)	$ (40,372)	(12,521)
Series A Preferred Stock
Other income and expenses:
Accretion of redeemable convertible preferred stock to redemption value		$ (2,994)		$ (4,189)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity/Deficit (Unaudited) - USD ($) $ in Thousands	Total	Common stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated deficit	Series A Preferred Stock	Series B Preferred Stock
Beginning balance at Dec. 31, 2019	$ (36,088)	$ 1		$ (224)	$ (35,865)
Temporary equity, beginning balance (in shares) at Dec. 31, 2019						6,167,726	20,942,781
Temporary equity, beginning balance at Dec. 31, 2019						$ 5,353	$ 46,404
Beginning balance (in shares) at Dec. 31, 2019		256,548
Issuance of Preferred Stock							$ 125,026
Issuance of Preferred Stock (in shares)							44,453,477
Settlement of preferred stock tranche right	4,135		$ 4,135
Accretion of Series B and B-2 Preferred Stock to redemption value	(1,195)		(1,195)				$ 1,195
Stock-based compensation	186		186
Currency translation adjustment	(317)			(317)
Net loss	(5,247)				(5,247)
Ending balance at Mar. 31, 2020	(38,526)	$ 1	3,126	(541)	(41,112)
Temporary equity, ending balance (in shares) at Mar. 31, 2020						6,167,726	65,396,258
Temporary equity, ending balance at Mar. 31, 2020						$ 5,353	$ 172,625
Ending balance (in shares) at Mar. 31, 2020		256,548
Beginning balance at Dec. 31, 2019	(36,088)	$ 1		(224)	(35,865)
Temporary equity, beginning balance (in shares) at Dec. 31, 2019						6,167,726	20,942,781
Temporary equity, beginning balance at Dec. 31, 2019						$ 5,353	$ 46,404
Beginning balance (in shares) at Dec. 31, 2019		256,548
Settlement of preferred stock tranche right	4,135
Net loss	(12,449)
Ending balance at Jun. 30, 2020	(47,922)	$ 1	687	(296)	(48,314)
Temporary equity, ending balance (in shares) at Jun. 30, 2020						6,167,726	65,396,258
Temporary equity, ending balance at Jun. 30, 2020						$ 5,353	$ 175,619
Ending balance (in shares) at Jun. 30, 2020		388,415
Beginning balance at Mar. 31, 2020	(38,526)	$ 1	3,126	(541)	(41,112)
Temporary equity, beginning balance (in shares) at Mar. 31, 2020						6,167,726	65,396,258
Temporary equity, beginning balance at Mar. 31, 2020						$ 5,353	$ 172,625
Beginning balance (in shares) at Mar. 31, 2020		256,548
Accretion of Series B and B-2 Preferred Stock to redemption value	(2,994)		(2,994)				$ 2,994
Stock-based compensation	350		350
Common stock issued upon exercises of options	205		205
Common stock issued upon exercises of options (in shares)		131,867
Currency translation adjustment	245			245
Net loss	(7,202)				(7,202)
Ending balance at Jun. 30, 2020	(47,922)	$ 1	687	(296)	(48,314)
Temporary equity, ending balance (in shares) at Jun. 30, 2020						6,167,726	65,396,258
Temporary equity, ending balance at Jun. 30, 2020						$ 5,353	$ 175,619
Ending balance (in shares) at Jun. 30, 2020		388,415
Beginning balance at Dec. 31, 2020	323,197	$ 35	396,443	617	(73,898)
Beginning balance (in shares) at Dec. 31, 2020		35,044,758
Stock-based compensation	2,584		2,584
Common stock issued upon exercises of options	667		667
Common stock issued upon exercises of options (in shares)		56,241
Currency translation adjustment	(305)			(305)
Net loss	(13,534)				(13,534)
Ending balance at Mar. 31, 2021	312,609	$ 35	399,694	312	(87,432)
Ending balance (in shares) at Mar. 31, 2021		35,100,999
Beginning balance at Dec. 31, 2020	$ 323,197	$ 35	396,443	617	(73,898)
Beginning balance (in shares) at Dec. 31, 2020		35,044,758
Common stock issued upon exercises of options (in shares)	103,352
Net loss	$ (39,993)
Ending balance at Jun. 30, 2021	289,498	$ 35	403,116	238	(113,891)
Ending balance (in shares) at Jun. 30, 2021		35,148,110
Beginning balance at Mar. 31, 2021	312,609	$ 35	399,694	312	(87,432)
Beginning balance (in shares) at Mar. 31, 2021		35,100,999
Stock-based compensation	3,227		3,227
Common stock issued upon exercises of options	195		195
Common stock issued upon exercises of options (in shares)		47,111
Currency translation adjustment	(74)			(74)
Net loss	(26,459)				(26,459)
Ending balance at Jun. 30, 2021	$ 289,498	$ 35	$ 403,116	$ 238	$ (113,891)
Ending balance (in shares) at Jun. 30, 2021		35,148,110

Condensed Consolidated Statem_3

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

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities
Net loss	$ (39,993)	$ (12,449)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	276	250
Stock-based compensation	5,811	536
Change in operating lease right-of-use assets	8
Fair value adjustment for preferred stock tranche rights liability		(1,265)
Deferred rent		(14)
Changes in operating assets and liabilities:
Grants receivable	(4,185)	4,962
Research and development tax credits receivable	73	(238)
Prepaid expenses and other current assets	81	(580)
Accounts payable	8,265	1,055
Accrued expenses and other liabilities	50	(886)
Deferred income	(3,431)	(852)
Net cash used in operating activities	(33,045)	(9,481)
Cash flows from investing activities
Purchase of property and equipment	(489)	(119)
Purchase of other assets	(60)	(19)
Net cash used in investing activities	(549)	(138)
Cash flows from financing activities
Proceeds from issuance of common stock upon exercise of options	862	205
Payment of IPO costs		(1,311)
Proceeds from grants repayable		2,713
Net cash provided by financing activities	862	126,633
Effects of exchange rate changes on cash, cash equivalents and restricted cash	(650)	(11)
Net (decrease) increase in cash, cash equivalents and restricted cash	(33,382)	117,003
Cash, cash equivalents and restricted cash at beginning of period	336,454	19,990
Cash, cash equivalents and restricted cash at end of period	303,072	136,993
Non-cash investing and financing activities
Capital expenditure included in accounts payable	459
Accretion of Series B and B-2 Preferred Stock to redemption value		4,189
Settlement of preferred stock tranche right		4,135
Deferred IPO costs in accounts payable		400
Operating lease liabilities arising from obtaining right-of-use assets	$ 3,316
Supplemental disclosure of cash flows
Cash paid for taxes		147
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)

Nature of Business and Basis of

Nature of Business and Basis of Presentation	6 Months Ended
	Jun. 30, 2021
Disclosure Text Block [Abstract]
Nature of Business and Basis of Presentation	Note 1. Nature of business and basis of presentation Description of business and corporate reorganization 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 pioneering the discovery and development of a new generation of highly differentiated immuno-oncology therapeutics for patients. The Company leverages its deep understanding of the tumor microenvironment and cancer immunology and immunosuppressive pathways to design novel product candidates with the potential to fully restore the immune response against cancer. The Company’s innovative pipeline includes two clinical-stage programs targeting novel, validated immuno-oncology pathways designed with optimized pharmacologic properties for improved clinical outcomes. The Company’s initial antibody product candidate, EOS-448, is a high affinity, potent, anti-TIGIT antibody with a functional Fc domain, designed to enhance the anti-tumor response through a multifaceted immune modulatory mechanism. An open-label Phase 1/2a clinical trial of EOS-448 is ongoing in adult cancer patients with advanced solid tumors. The Company is also advancing inupadenant, a next-generation adenosine A2A receptor antagonist tailored to overcome cancer immunosuppression. iTeos is conducting an open-label multi-arm Phase 1/2a clinical trial of inupadenant in adult cancer patients with advanced solid tumors. 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 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 estimated offering expenses payable by the Company. Upon closing of the IPO, all of the Company's outstanding shares of convertible preferred stock automatically converted into 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 $40.0 million for the six months ended June 30, 2021. As of June 30, 2021, the Company had an accumulated deficit of $113.9 million. The Company expects to continue to generate operating losses in the foreseeable future. As of August 11, 2021, the issuance date of the condensed consolidated financial statements for the six months ended June 30, 2021, 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 condensed 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’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, uncertainty regarding results of clinical trials and reaching milestones, uncertainty of regulatory approval of the Company’s current or future product candidates, uncertainty of market acceptance of the Company’s product candidates, if approved, competition from substitute products and larger companies, securing and protecting proprietary technology, strategic relationships and dependence on key individuals and sole source suppliers. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities and may not ultimately lead to a marketing approval and commercialization of a product. The Company’s product candidates require approvals from the U.S. Food and Drug Administration (FDA) and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company was denied approval, approval was delayed or the Company was unable to maintain approval for any product candidate, it could have a materially adverse impact on the Company. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales. The Company will need to generate significant revenue to achieve profitability, and it may never do so. COVID-19 With the ongoing concern related to the COVID-19 pandemic during 2020 and in the first six months of 2021, the Company has maintained and expanded its business continuity plans to address and mitigate the impact of the COVID-19 pandemic on its business. In March 2020, to protect the health of its employees, and their families and communities, the Company restricted access to its offices to personnel who performed critical activities that must be completed on-site, limited the number of such personnel that could be present at its facilities at any one time, and requested that most of its employees work remotely. In May 2020, as certain states eased restrictions, the Company established new protocols to better allow its full laboratory staff access to the Company’s facilities. These protocols included several shifts working over a seven-day-week protocol. The Company expects to continue incurring additional costs to ensure it adheres to the best-practice safe hygiene guidelines issued by recognized health experts such as the U.S. Centers for Disease Control and Prevention (CDC), the European Center for Disease Prevention and Control (ECDC) and the World Health Organization (WHO), and to provide a safe working environment to its onsite employees. The extent to which the COVID-19 pandemic impacts the Company’s business, its corporate development objectives, results of operations and financial condition, and the value of and market for its common stock, will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, the severity of COVID-19 or the effectiveness of actions taken globally to contain and treat COVID-19, such as travel restrictions, quarantines, social distancing and business closure requirements, but particularly in the geographies where we, our third party manufacturers, contract research organizations (CROs) or current and planned clinical trial sites operate. Disruptions to the global economy, disruption of global healthcare systems, and other significant impacts of the COVID-19 pandemic could have a material adverse effect on the Company’s business, financial condition, results of operations and growth prospects. Basis of presentation The accompanying condensed consolidated financial statements and accompanying notes have been prepared in accordance with generally accepted accounting principles in the United States of America (U.S. GAAP). The unaudited interim condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements as of and for the years ended December 31, 2020 and 2019, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K (File No. 001-39401). The results for any interim period are not necessarily indicative of results for any future period. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period.

Summary of significant accounti

Summary of significant accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of significant accounting policies	Note 2. Summary of significant accounting policies The Company’s significant accounting policies are disclosed in the audited consolidated financial statements for the year ended December 31, 2020, and notes thereto, which are included in the Company’s Annual Report on Form 10-K that was filed with the Securities and Exchange Commission on March 24, 2021. Since the date of those financial statements, there have been no material changes to significant accounting policies except as noted below. Principles of consolidation The accompanying condensed consolidated financial statements include the Company’s accounts and those of its wholly owned subsidiaries. All intercompany accounts, transactions and balances have been eliminated. Use of estimates The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and expenses, as well as the related disclosures of contingent assets and liabilities. Estimates are used to determine the fair value of the preferred stock tranche rights liability, the fair value of 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 unaudited condensed 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. 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. Recently adopted accounting standards updates On January 1, 2021, the Company adopted Accounting Standard Update, or ASU No. 2016-02 (Topic 842), Leases At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Leases with a term greater than one year are recognized on the balance sheet as ROU assets and short-term and long-term lease liabilities, as applicable. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent its obligation to make lease payments arising from the lease. The Company typically only includes an initial lease term in its assessment of a lease arrangement. It also considers termination options and factors those into the determination of lease payments. Options to renew a lease are not included in the assessment unless there is reasonable certainty that the Company will renew. Operating lease liabilities and their corresponding ROU assets are recorded based on the present value of lease payments over the expected remaining lease term. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate, which reflects the fixed rate at which it could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company is required to pay fees for operating expenses in addition to monthly base rent for certain operating leases (non-lease components). The Company has not elected the practical expedient which allows non-lease components to be combined with lease components for all asset classes. Variable non-lease components are not included within the lease right-of-use asset and lease liability on the consolidated balance sheet, and instead are reflected as expense in the period they are paid. The Company’s real estate operating leases provide for scheduled annual rent increases throughout the lease terms. The Company recognizes the effects of the scheduled rent increases on a straight-line basis over the full terms of such leases.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 3. Fair value measurements The following tables set forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy as of June 30, 2021 and December 31, 2020: June 30, 2021 (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents (money market funds) $ 286,752 $ — $ — $ 286,752 Totals $ 286,752 $ — $ — $ 286,752 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 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 fair value of the Series B Preferred Stock tranche rights liability was estimated using a probability-weighted present value of the benefit of investment with the following significant unobservable inputs (Level 3): Valuation Dates March 23, 2020 (Tranche 3 settlement) Implied equity value (in millions) $ 208.2 Probability of success of reaching necessary milestone: Tranche 2 milestone N/A Tranche 3 milestone (by March 31, 2020) 90 % Expected industry return over period during which milestones are expected to be achieved 13.0 % Risk-free interest rate 1.1 % During the periods presented, the Company has not changed the manner in which it values assets and liabilities that are measured at fair value. The Company recognizes transfers between levels of the fair value hierarchy as of the end of the reporting period. There were no transfers within the hierarchy during the three and six month periods ended June 30, 2021 and 2020. The following table presents changes during the three and six months ended June 30, 2020 in Level 3 liabilities measured at fair value on a recurring basis: (in thousands) Preferred Stock Tranche Rights Liability Balances at January 1, 2020 $ 5,400 Change in estimated fair value (1,265 ) Settlement of tranche right (4,135 ) Balances at June 30, 2020 $ — The preferred stock tranche rights liability was settled on March 24, 2020 and no liability exists thereafter. There were no Level 3 measurements used during the three and six months ended June 30, 2021. The above fair value measurements are sensitive to changes in the underlying unobservable inputs. A change in those inputs could result in a significantly higher or lower fair value measurement.

Supplemental Balance Sheet Info

Supplemental Balance Sheet Information	6 Months Ended
	Jun. 30, 2021
Supplemental Balance Sheet Information [Abstract]
Supplemental Balance Sheet Information	Note 4. Supplemental balance sheet information Property and equipment Property and equipment, net consisted of the following: (in thousands) June 30, 2021 December 31, 2020 Scientific equipment $ 3,059 $ 2,617 Furniture & office equipment 749 542 Leasehold improvements 1,023 855 Total 4,831 4,014 Accumulated depreciation and amortization (2,810 ) (2,662 ) Property & equipment, net $ 2,021 $ 1,352 Depreciation and amortization expense was $0.2 and $0.1 million Accrued expenses and other current liabilities Accrued expenses and other current liabilities consisted of the following: (in thousands) June 30, 2021 December 31, 2020 Accrued clinical trial costs $ 5,116 $ 4,012 Accrued personnel costs 2,395 3,208 Accrued professional fees 25 37 Accrued other 34 229 Total accrued expenses and other current liabilities $ 7,570 $ 7,486

License and collaboration agree

License and collaboration agreements	6 Months Ended
	Jun. 30, 2021
License Agreements [Abstract]
License and collaboration agreements	Note 5. License and collaboration agreements Adimab In January 2017, the Company entered into a collaboration agreement (as amended, the Adimab Agreement) with Adimab, LLC (Adimab). Adimab has developed an antibody discovery and optimization technology platform. This collaboration enables the Company’s research and development efforts on discovery and optimization of new antibodies against immuno-oncology targets the Company may identify. Under the terms of the Adimab Agreement, Adimab has granted the Company a worldwide, non-exclusive research license for a one-year research term period and evaluation period for up to 18 months per research program. The Company is required to use commercially reasonable efforts to perform its research activities under the Adimab Agreement and, if the Company exercises its right to obtain a development and commercialization license, the Company is required to use commercially reasonable efforts to pursue development and commercialization of a product directed to the applicable target. Under the terms of the Adimab Agreement, the Company granted Adimab a worldwide, non-exclusive license under all of its patents and know-how that are reasonably necessary or useful for Adimab to perform its research activities under the Adimab Agreement. Payment terms to Adimab include a one-time upfront technology access fee in the tens of thousands and payments for research support. Adimab is entitled to additional fees of up to a maximum of $0.4 million on a program-by-program basis for the achievement of certain technical milestones, one of which was met and the Company paid $0.2 million in April 2017. Upon the Company’s exercise of an option for an exclusive development and commercialization license, with respect to a target, the Company is required to make a low single digit million-dollar payment to Adimab for each exercised option. In August 2018, the Company paid a $1.0 million nonrefundable fee to exercise an option to acquire certain licenses from Adimab. One of the antibodies licensed under the Adimab Agreement is now what the Company refers to as EOS-448. In February 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 (the 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. As of the date of these condensed consolidated financial statements, the Company has not pursued any additional targets under the Adimab agreement that could potentially result in such milestone payments. The Company will pay Adimab low to mid single-digit percentage royalties on a country-by-country and product-by-product basis, on worldwide net product sales of licensed products. Royalties are payable on a licensed product-by-licensed product and country-by-country basis until the later of (i) expiration of the last valid claim of a licensed patent right that covers such licensed product in such country, and (ii) ten years following the first commercial sale of such licensed product in such country. To date, the Company has paid a total of $3.4 million to Adimab under the Adimab Agreement. Adimab controls the filing, prosecution, maintenance and enforcement of the intellectual property that it licenses to the Company under the Adimab Agreement. The Company has the right to enforce such licensed intellectual property against infringement if the infringement is competitive with the Company’s licensed products and Adimab does not pursue enforcement. The Company controls the filing, prosecution, maintenance and enforcement of the intellectual property the Company licenses to Adimab under the Adimab Agreement and all program antibody patents. The term of the Adimab Agreement will continue until the last to expire royalty term on a product-by-product and country-by-country basis if the Company exercises its option, or in the event no option is exercised, the conclusion of the last-to-expire evaluation term, unless terminated earlier by either party. Each party has the right to terminate the Adimab Agreement due to the other party’s uncured material breach or the Company’s abandonment of the product. GSK On June 11, 2021, the Company and GlaxoSmithKline Intellectual Property (No. 4) Limited (“GSK”) executed a Collaboration and License Agreement (the “GSK Collaboration Agreement”) pursuant to which the Company agrees to grant GSK a license under certain of the Company’s intellectual property rights to develop, manufacture, and commercialize products comprised of or containing the Company’s antibody product, EOS-448. Under the GSK Collaboration Agreement, GSK agrees to make an upfront payment of $625 million to the Company within 10 business days of the date on which the GSK Collaboration Agreement becomes effective, which occurred on July 26, 2021. Additionally, the Company is eligible to receive up to $1.45 billion in milestone payments, contingent upon the EOS-448 program achieving certain development and commercial milestones. Within the collaboration, GSK and the Company agree to share responsibility and costs for the global development of EOS-448, and will jointly commercialize and equally split profits in the United States. Outside of the United States, GSK will receive an exclusive license for commercialization, and the Company is eligible to receive tiered double digit royalty payments up to 20% during a customary royalty term. 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 Revenue from Contracts with Customers Nonmonetary Transactions

Government Grant Funding and Po

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs)	6 Months Ended
	Jun. 30, 2021
Research And Development Arrangement With Federal Government [Abstract]
Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs)	Note 6. Government grant funding and potential repayment commitments under recoverable cash advance grants (RCAs) The Company has been awarded grants from the Walloon Region, a federal region of Belgium (the Walloon Region) and the European Union (the granting agencies) to fund research and development activities. The grants reimburse a percentage (55-100%) of actual qualifying expenditures. The Company periodically submits proof of qualifying expenditures to the granting agencies for approval and reimbursement. To date, the Company has received funding under several grants which included no obligation to repay and two grants that include potential obligations to repay (RCAs). As the granting agencies do not meet the definition of a customer under Topic 606, qualifying grants receipts are recognized as grant income within other income in the condensed consolidated statement of operations and comprehensive loss. Grants which do not include an obligation to repay The total amount that the granting agencies have agreed to fund in the future if the Company incurs qualifying research and development expenses under these grants is $1.3 million. Grants which include a potential obligation to repay—RCAs On July 20, 2017, the Company entered into a recoverable cash advance arrangement whereby the Walloon Region will provide the Company with up to $22.3 million for a research and development program to perform clinical validation of an A2A receptor antagonist drug candidate for immune-oncology (RCA-1). On December 3, 2019, the Company entered into another recoverable cash advance arrangement with the Walloon Region (RCA-2) for up to $4.2 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 ends in December 2021 per the current agreement. The Company negotiated an extension on the research period for RCA-2 with the Walloon Region. The original research period for RCA-2 ended February 2021, and was extended to March 2022. The Company must repay 30% of the amount received under the grant by annual installments from 2022 to 2041 (the fixed annual repayments) unless the Company decides not to pursue commercial development or out licensing of the drug candidate, applies for a waiver from the Walloon Region justifying its decision based upon the failure of the program, and returns the intellectual property to the Walloon Region. Because of the requirement to repay 30% of the amounts received under the grant, the Company records the present value of such amounts as grants repayable on the condensed consolidated balance sheets. In addition, in the event that the Company receives revenue from products or services related to the results of the research, it has to pay to the Walloon Region a 0.33% royalty on revenue resulting from RCA-1 and a 0.12% royalty on revenue resulting from RCA-2. The maximum amount payable to the Walloon Region under each grant, including the fixed annual repayments, the royalty on revenue, and the interest thereon, is twice the amount of funding received. The Company assessed whether there is an obligation to make a royalty payment based on the probability of successful completion of the research and development and future sales and commercial success of the drug candidate, and no grant repayable related to royalties was recorded as of June 30, 2021 or December 31, 2020. The Company recorded grant income in the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2021 and 2020 for amounts of grants received from the Walloon Region in the period during which the related qualifying expenses were incurred, net of any grants repayable recorded in the condensed consolidated balance sheets. The Company recorded receivables on the condensed consolidated balance sheets related to amounts the Walloon Region owes the Company based on qualifying expenses incurred by the Company. The Company recorded deferred income in the condensed consolidated balance sheets for amounts received from the Walloon Region in advance of incurring qualifying expenses. The following table reflects activity for grant programs for the three and six months ended June 30, 2021 and 2020 and end of period balances as of June 30, 2021 and December 31, 2020: RCA -1 RCA-2 Other Grants Total (In thousands) 2021 2020 2021 2020 2021 2020 2021 2020 Cash received during the three months ended June 30 $ — $ — $ — $ 30 $ — $ 168 $ — $ 198 Grant income recognized during the three months ended June 30 2,140 725 290 137 271 219 2,701 $ 1,081 Cash received during the six months ended June 30 — 7,693 — 1,968 — 168 — $ 9,829 Grant income recognized during the six months ended June 30 2,995 1,857 725 508 3,896 305 7,616 $ 2,670 Grants receivable at the end of the period 2,414 — 944 — 874 133 4,232 $ 133 Grants repayable at the end of the period 4,942 5,102 751 781 N/A — 5,693 $ 5,883

Stockholders_ equity

Stockholders? equity	6 Months Ended
	Jun. 30, 2021
Equity [Abstract]
Stockholders equity	Note 7. Stockholders’ equity 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 was 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 an IPO of 10,586,316 shares of its common stock, for aggregate gross proceeds of $201.1 million and its shares started trading on The Nasdaq Global Select Market under the ticker symbol “ITOS.” The Company received approximately $184.0 million in net proceeds after deducting underwriting discounts and commissions and other estimated offering expenses payable by the Company. Upon closing of the IPO, all of the Company's outstanding shares of convertible preferred stock automatically converted into 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. 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.

Stock-based compensation

Stock-based compensation	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based compensation	Note 8. Stock-based compensation 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 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) was approved by the Company’s board of directors on July 15, 2020, and the Company’s stockholders on July 20, 2020 and became effective on July 22, 2020, the date immediately prior to the date on which the registration statement for the Company’s IPO became effective. The 2020 Plan provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock units, restricted stock awards, unrestricted stock awards, cash-based awards and dividend equivalent rights to the Company’s officers, employees, directors and consultants. The number of shares of common stock initially reserved for issuance under the 2020 Plan was 3,809,818 which was cumulatively increased on January 1, 2021 and will be increase 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. Accordingly, on January 1, 2021, the number of shares of common stock reserved and available for issuance under the 2020 Plan increased by 1,752,237. The number of shares of common stock reserved for issuance as of June 30, 2021 under the 2020 Plan was 5,562,055. 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 automatically increased on January 1, 2021 and will automatically increase 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. Accordingly, on January 1, 2021, the number of shares of common stock reserved and available for issuance under the 2020 ESPP increased by 350,447. The number of shares of common stock reserved for issuance as of June 30, 2021 under the 2020 ESPP was 667,931. Stock-Based Compensation Expense Stock-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Research and development $ 496 $ 67 $ 771 $ 117 General and administrative 2,731 283 5,040 419 Total stock-based compensation expense $ 3,227 $ 350 $ 5,811 $ 536 The following table summarizes stock option activity for the six months ended June 30, 2021: Stock Options Shares Weighted average exercise price Weighted average remaining contractual life (in years) Aggregate intrinsic value (in thousands) Outstanding as of December 31, 2020 4,552,396 $ 9.13 8.2 Granted 983,450 34.27 Forfeited (3,075 ) 4.24 Exercised (103,352 ) 5.82 Outstanding as of June 30, 2021 5,429,419 $ 13.70 8.1 $ 74,160 Exercisable at June 30, 2021 1,469,512 $ 5.46 6.1 $ 29,794 The weighted-average grant-date fair value of options awarded during the six month periods ended June 30, 2021 and 2020 was approximately $26.56 per share and $3.21 per share, respectively. As of June 30, 2021, there was a total of $44.0 million of unrecognized employee compensation costs related to non-vested stock option awards expected to be recognized over a weighted average period of 3.2 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. Stock-based compensation is measured at the grant date based on the fair value of the award and is recognized as expense over the requisite service period, which is generally the vesting period of the respective award. The following table summarizes the range of key assumptions used to determine the fair value of stock options granted during: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Risk-free interest rate 0.84% - 0.90% 0.45% 0.42% - 0.90% 0.45% - 1.35% Expected term (in years) 6 6 6 6 Expected volatility 94% - 99% 92% 94% - 100% 90% - 92% Expected dividend yield — — — — Estimated fair value of common stock $23.19 - $34.18 $4.24 - $6.16 $23.19 - $41.58 $2.95 - $6.16

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments And Contingencies	Note 9. Commitments and contingencies Purchase commitments The Company has contractual arrangements with research and development organizations and suppliers; however, these contracts are generally cancelable on 30-60 days’ notice and the obligations under these contracts are largely based on services performed. The Company may also enter into contracts in the normal course of business with clinical research organizations for clinical trials, with contract manufacturing organizations for clinical supplies and with other vendors for preclinical studies, supplies and other services and products for operating purposes. These contracts generally provide for termination on notice. As of June 30, 2021 and December 31, 2020, there were no amounts accrued related to termination charges. Operating leases The Company’s operating leases are as follows: • An April 2016 lease for 1,577 square meters of office and laboratory space in Gosselies, Belgium, which commenced in May 2016 December 2021 February 2021 January 2030 • A December 2018 lease for 2,479 square feet of office in Cambridge, Massachusetts, which commenced in May 2019 and terminates in May 2022 . The lease is subject to fixed-rate rent escalations. • Various car leases that the Company enters into from time to time. The average life of each car lease is 48 to 60 months. Rent expense was $0.1 million and $0.2 million for the three months ended June 30, 2021 and 2020, respectively, and $0.3 million for the six months ended June 30, 2021 and 2020. The following table summarizes lease terms and discount rate: June 30, 2021 December 31, 2020 Weighted-average remaining lease term (years) 7.0 — Weighted-average discount rate 4.82 % — The following table summarizes the cash flow and other information: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Operating lease liabilities arising from obtaining right-of-use assets (non-cash) $ 110 $ — $ 3,316 $ — Operating cash flows used in operating leases $ 189 — $ 374 — As of June 30, 2021, the Company had the following future minimum lease payments under non-cancelable operating leases for the remainder of 2021 and the future years thereafter (in thousands): Year ending December 31: 2021 $ 370 2022 592 2023 480 2024 464 2025 421 Thereafter 1,339 Total Lease Payments 3,666 Less: Interest (610 ) Total Lease Liability $ 3,056 Lease liability 555 Lease liability, net of current portion $ 2,501 In March 2019, the Company provided a letter of credit for approximately $57,000 to secure its obligation under its lease in Cambridge. The Company maintains that amount of cash on hand to fund any necessary draws on the letter of credit. In addition, as of June 30, 2021 and December 31, 2020, the Company had approximately $82,000 and $71,000 on hand serving as a guarantee for its lease obligation in Belgium. These amounts have been classified as restricted cash in the condensed consolidated balance sheets as of June 30, 2021 and December 31, 2020.

Related party transactions

Related party transactions	6 Months Ended
	Jun. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Note 10. Related party transactions On June 11, 2018, the Company entered into a Royalty Transfer Agreement with the charitable foundations of two of its investors (MPM Oncology Charitable Foundation, Inc. and UBS Optimus Foundation), which requires it to pay a royalty equal to a total of 1 % percent of its net product sales each year within 120 days following each year end. Such agreement was entered into as a result of the capital contributions received from the investors. As the Company has no product sales to date, no royalties were owed to these chari table foundations as of June 30 , 2021 .

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stock	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stock	Note 11. Net loss per share attributable to common stock The following common stock equivalents were excluded from the calculation of net loss per share due to their anti-dilutive effect: June 30, 2021 2020 Series B and B-2 Preferred Stock, as converted — 20,597,566 Series A Preferred Stock, as converted — 1,862,510 Stock options outstanding 5,429,419 3,323,378 Total 5,429,419 25,783,454

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Note 12. Subsequent events On June 11, 2021, the Company and GSK executed the GSK Collaboration Agreement, pursuant to which the Company agrees to grant GSK a license under certain of the Company’s intellectual property rights to develop, manufacture, and commercialize products comprised of or containing the Company’s antibody product, EOS-448. Under the GSK Collaboration Agreement, GSK agrees to make an upfront payment of $625 million to the Company within 10 business days of the date on which the GSK Collaboration Agreement becomes effective, which occurred on July 26, 2021. Additionally, the Company is eligible to receive up to $1.45 billion in milestone payments, contingent upon the EOS-448 program achieving certain development and commercial milestones. Within the collaboration, GSK and the Company agree to share responsibility and costs for the global development of EOS-448 and will jointly commercialize and equally split profits in the United States. Outside of the United States, GSK will receive an exclusive license for commercialization, and the Company is eligible to receive tiered double digit royalty payments up to 20% during a customary royalty term.

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The accompanying condensed consolidated financial statements and accompanying notes have been prepared in accordance with generally accepted accounting principles in the United States of America (U.S. GAAP). The unaudited interim condensed consolidated financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (SEC). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. Accordingly, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements as of and for the years ended December 31, 2020 and 2019, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K (File No. 001-39401). The results for any interim period are not necessarily indicative of results for any future period. In the opinion of management, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the results for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period.
Principles of consolidation	Principles of consolidation The accompanying condensed consolidated financial statements include the Company’s accounts and those of its wholly owned subsidiaries. All intercompany accounts, transactions and balances have been eliminated.
Use of estimates	Use of estimates The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, and expenses, as well as the related disclosures of contingent assets and liabilities. Estimates are used to determine the fair value of the preferred stock tranche rights liability, the fair value of 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 unaudited condensed 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.
Cash, cash equivalents and restricted cash	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.
Recently adopted accounting standards updates	Recently adopted accounting standards updates On January 1, 2021, the Company adopted Accounting Standard Update, or ASU No. 2016-02 (Topic 842), Leases At the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances present in the arrangement. Leases with a term greater than one year are recognized on the balance sheet as ROU assets and short-term and long-term lease liabilities, as applicable. ROU assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent its obligation to make lease payments arising from the lease. The Company typically only includes an initial lease term in its assessment of a lease arrangement. It also considers termination options and factors those into the determination of lease payments. Options to renew a lease are not included in the assessment unless there is reasonable certainty that the Company will renew. Operating lease liabilities and their corresponding ROU assets are recorded based on the present value of lease payments over the expected remaining lease term. The interest rate implicit in lease contracts is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate, which reflects the fixed rate at which it could borrow on a collateralized basis the amount of the lease payments in the same currency, for a similar term, in a similar economic environment. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company is required to pay fees for operating expenses in addition to monthly base rent for certain operating leases (non-lease components). The Company has not elected the practical expedient which allows non-lease components to be combined with lease components for all asset classes. Variable non-lease components are not included within the lease right-of-use asset and lease liability on the consolidated balance sheet, and instead are reflected as expense in the period they are paid. The Company’s real estate operating leases provide for scheduled annual rent increases throughout the lease terms. The Company recognizes the effects of the scheduled rent increases on a straight-line basis over the full terms of such leases.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Summary of Financial Instruments Measured at Fair Value on a Recurring Basis	The following tables set forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy as of June 30, 2021 and December 31, 2020: June 30, 2021 (in thousands) Level 1 Level 2 Level 3 Total Cash equivalents (money market funds) $ 286,752 $ — $ — $ 286,752 Totals $ 286,752 $ — $ — $ 286,752 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
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Summary of Fair Value of Series B Preferred Stock Tranche Rights Liability	The fair value of the Series B Preferred Stock tranche rights liability was estimated using a probability-weighted present value of the benefit of investment with the following significant unobservable inputs (Level 3): Valuation Dates March 23, 2020 (Tranche 3 settlement) Implied equity value (in millions) $ 208.2 Probability of success of reaching necessary milestone: Tranche 2 milestone N/A Tranche 3 milestone (by March 31, 2020) 90 % Expected industry return over period during which milestones are expected to be achieved 13.0 % Risk-free interest rate 1.1 %
Summary of Changes in Level 3 Liabilities Measures at Fair Value on a Recurring Basis	The following table presents changes during the three and six months ended June 30, 2020 in Level 3 liabilities measured at fair value on a recurring basis: (in thousands) Preferred Stock Tranche Rights Liability Balances at January 1, 2020 $ 5,400 Change in estimated fair value (1,265 ) Settlement of tranche right (4,135 ) Balances at June 30, 2020 $ —

Supplemental Balance Sheet In_2

Supplemental Balance Sheet Information (Tables)	6 Months Ended
	Jun. 30, 2021
Supplemental Balance Sheet Information [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following: (in thousands) June 30, 2021 December 31, 2020 Scientific equipment $ 3,059 $ 2,617 Furniture & office equipment 749 542 Leasehold improvements 1,023 855 Total 4,831 4,014 Accumulated depreciation and amortization (2,810 ) (2,662 ) Property & equipment, net $ 2,021 $ 1,352
Schedule of Accrued Expenses	Accrued expenses and other current liabilities consisted of the following: (in thousands) June 30, 2021 December 31, 2020 Accrued clinical trial costs $ 5,116 $ 4,012 Accrued personnel costs 2,395 3,208 Accrued professional fees 25 37 Accrued other 34 229 Total accrued expenses and other current liabilities $ 7,570 $ 7,486

Government Grant Funding and _2

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) (Tables)	6 Months Ended
	Jun. 30, 2021
Research And Development Arrangement With Federal Government [Abstract]
Schedule of Activity for Grant Programs	The following table reflects activity for grant programs for the three and six months ended June 30, 2021 and 2020 and end of period balances as of June 30, 2021 and December 31, 2020: RCA -1 RCA-2 Other Grants Total (In thousands) 2021 2020 2021 2020 2021 2020 2021 2020 Cash received during the three months ended June 30 $ — $ — $ — $ 30 $ — $ 168 $ — $ 198 Grant income recognized during the three months ended June 30 2,140 725 290 137 271 219 2,701 $ 1,081 Cash received during the six months ended June 30 — 7,693 — 1,968 — 168 — $ 9,829 Grant income recognized during the six months ended June 30 2,995 1,857 725 508 3,896 305 7,616 $ 2,670 Grants receivable at the end of the period 2,414 — 944 — 874 133 4,232 $ 133 Grants repayable at the end of the period 4,942 5,102 751 781 N/A — 5,693 $ 5,883

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock-Based Compensation Expense	Stock-Based Compensation Expense Stock-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Research and development $ 496 $ 67 $ 771 $ 117 General and administrative 2,731 283 5,040 419 Total stock-based compensation expense $ 3,227 $ 350 $ 5,811 $ 536
Summary of Stock Options Activity	The following table summarizes stock option activity for the six months ended June 30, 2021: Stock Options Shares Weighted average exercise price Weighted average remaining contractual life (in years) Aggregate intrinsic value (in thousands) Outstanding as of December 31, 2020 4,552,396 $ 9.13 8.2 Granted 983,450 34.27 Forfeited (3,075 ) 4.24 Exercised (103,352 ) 5.82 Outstanding as of June 30, 2021 5,429,419 $ 13.70 8.1 $ 74,160 Exercisable at June 30, 2021 1,469,512 $ 5.46 6.1 $ 29,794
Schedule of Fair Value Assumptions for Stock Options Granted	The following table summarizes the range of key assumptions used to determine the fair value of stock options granted during: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Risk-free interest rate 0.84% - 0.90% 0.45% 0.42% - 0.90% 0.45% - 1.35% Expected term (in years) 6 6 6 6 Expected volatility 94% - 99% 92% 94% - 100% 90% - 92% Expected dividend yield — — — — Estimated fair value of common stock $23.19 - $34.18 $4.24 - $6.16 $23.19 - $41.58 $2.95 - $6.16

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Schedule Of Lease Terms And Discount Rate	The following table summarizes lease terms and discount rate: June 30, 2021 December 31, 2020 Weighted-average remaining lease term (years) 7.0 — Weighted-average discount rate 4.82 % —
Schedule Of Cash Flow And Other Information	The following table summarizes the cash flow and other information: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Operating lease liabilities arising from obtaining right-of-use assets (non-cash) $ 110 $ — $ 3,316 $ — Operating cash flows used in operating leases $ 189 — $ 374 —
Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases	As of June 30, 2021, the Company had the following future minimum lease payments under non-cancelable operating leases for the remainder of 2021 and the future years thereafter (in thousands): Year ending December 31: 2021 $ 370 2022 592 2023 480 2024 464 2025 421 Thereafter 1,339 Total Lease Payments 3,666 Less: Interest (610 ) Total Lease Liability $ 3,056 Lease liability 555 Lease liability, net of current portion $ 2,501

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stock (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Schedule of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share	The following common stock equivalents were excluded from the calculation of net loss per share due to their anti-dilutive effect: June 30, 2021 2020 Series B and B-2 Preferred Stock, as converted — 20,597,566 Series A Preferred Stock, as converted — 1,862,510 Stock options outstanding 5,429,419 3,323,378 Total 5,429,419 25,783,454

Nature of Business and Basis _2

Nature of Business and Basis of Presentation - Additional Information (Details) $ in Thousands	Aug. 05, 2020USD ($)shares	Jul. 28, 2020USD ($)shares	Jul. 20, 2020	Jun. 30, 2021USD ($)	Mar. 31, 2021USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net loss				$ (26,459)	$ (13,534)	$ (7,202)	$ (5,247)	$ (39,993)	$ (12,449)
Accumulated deficit				$ (113,891)				$ (113,891)		$ (73,898)
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
Convertible Preferred Stock, Shares Issued upon Conversion | shares		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

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents (money market funds)	$ 286,752	$ 314,636
Totals	286,752	314,636
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents (money market funds)	286,752	314,636
Totals	$ 286,752	$ 314,636

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Fair Value of Series B Preferred Stock Tranche Rights Liability (Details) - Series B Preferred Stock - Fair Value, Inputs, Level 3 - Tranche Three Settlement $ in Millions	Mar. 23, 2020USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Implied equity value	$ 208.2
Tranche 3 milestone (by March 31, 2020)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Probability of success of reaching necessary milestone	90.00%
Expected industry return over period during which milestones are expected to be achieved
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	13
Risk-free interest rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement input	1.1

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 24, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers within hierarchy	$ 0	$ 0	$ 0	$ 0
Preferred stock tranche rights liability					$ 0
Fair Value, Inputs, Level 3 | Preferred Stock Tranche Rights Liability
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Level 3 fair value measurement	$ 0		$ 0

Fair Value Measurements - Sum_3

Fair Value Measurements - Summary of Changes in Level 3 Liabilities Measures at Fair Value on a Recurring Basis (Details) - Fair Value, Inputs, Level 3 - Preferred Stock Tranche Rights Liability $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balances	$ 5,400
Change in estimated fair value	(1,265)
Settlement of tranche right	(4,135)
Balances	$ 0

Supplemental Balance Sheet In_3

Supplemental Balance Sheet Information - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Total property and equipment	$ 4,831	$ 4,014
Accumulated depreciation and amortization	(2,810)	(2,662)
Property & equipment, net	2,021	1,352
Scientific Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	3,059	2,617
Furniture and Office Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	749	542
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 1,023	$ 855

Supplemental Balance Sheet In_4

Supplemental Balance Sheet Information - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Supplemental Balance Sheet Information [Abstract]
Depreciation and amortization	$ 200	$ 100	$ 276	$ 250

Supplemental Balance Sheet In_5

Supplemental Balance Sheet Information - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Accrued clinical trial costs	$ 5,116	$ 4,012
Accrued personnel costs	2,395	3,208
Accrued professional fees	25	37
Accrued other	34	229
Total accrued expenses and other current liabilities	$ 7,570	$ 7,486

License and collaboration agr_2

License and collaboration agreements - Additional Information (Details) - Adimab L L C - USD ($) $ in Millions	Aug. 31, 2018	Apr. 30, 2017	Jun. 30, 2021
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			$ 14.5
Nonrefundable fee to exercise an option	$ 1
License revenue
Research And Development Arrangement Contract To Perform For Others [Line Items]
License revenue			3.4
Research Collaboration and Option Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Maximum option fees receivable based on achievement of research milestones per program			0.4
Development Regulatory and Sales Milestone
Research And Development Arrangement Contract To Perform For Others [Line Items]
Maximum option fees receivable based on achievement of research milestones			$ 45.8

Government Grant Funding and _3

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) - Additional Information (Details) - USD ($)	Dec. 03, 2019	Jul. 20, 2017	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expenses			$ 1,300,000
Grant repayable			$ 5,693,000		$ 5,883,000
RCA-1
Research And Development Arrangement Contract To Perform For Others [Line Items]
Recoverable cash advance		$ 22,300,000
Percentage of royalty on revenue			0.33%
Grant repayable			$ 4,942,000		5,102,000
RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Recoverable cash advance	$ 4,200,000
Percentage of royalty on revenue			0.12%
Grant repayable			$ 751,000		$ 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
Minimum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Percentage of grant reimburse of actual qualifying expenditures			55.00%
Minimum | RCA-1 and RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Term of repayment amount received under grant			2022
Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Percentage of grant reimburse of actual qualifying expenditures			100.00%
Maximum | RCA-1 and RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Term of repayment amount received under grant			2041

Government Grant Funding and _4

Government Grant Funding and Potential Repayment Commitments Under Recoverable Cash Advance Grants (RCAs) - Schedule of Activity for Grant Programs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received		$ 198		$ 9,829
Grant income	$ 2,701	1,081	$ 7,616	2,670
Grants receivable	4,232	133	4,232	133	$ 133
Grant repayable	5,693	5,883	5,693	5,883
RCA-1
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received				7,693
Grant income	2,140	725	2,995	1,857
Grants receivable	2,414		2,414
Grant repayable	4,942	5,102	4,942	5,102
RCA-2
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received		30		1,968
Grant income	290	137	725	508
Grants receivable	944		944
Grant repayable	751	781	751	781
Other Grants
Research And Development Arrangement Contract To Perform For Others [Line Items]
Cash received		168		168
Grant income	271	219	3,896	305
Grants receivable	$ 874	$ 133	$ 874	$ 133

Stockholders' equity - Addition

Stockholders' equity - Additional Information (Details) $ / shares in Units, $ in Millions	Aug. 05, 2020USD ($)shares	Jul. 28, 2020USD ($)$ / sharesshares	Jul. 20, 2020	Jun. 30, 2021$ / sharesshares	Dec. 31, 2020$ / sharesshares
Class Of Stock [Line Items]
Common stock, shares authorized				150,000,000	150,000,000
Common stock, par value | $ / shares				$ 0.001	$ 0.001
Preferred Stock Shares Authorized				10,000,000	10,000,000
Preferred Stock, par value | $ / shares				$ 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 | $ / shares		$ 0.001
Preferred Stock Shares Authorized		10,000,000
Preferred Stock, par value | $ / shares		$ 0.001
Common stock
Class Of Stock [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
Convertible Preferred Stock, Shares Issued upon Conversion		22,460,076
Common stock | IPO
Class Of Stock [Line Items]
Issuance of common stock from initial public offering, shares		10,586,316
Issuance of common stock from initial public offering | $		$ 201.1
Proceeds from initial public offering, net of underwriting discount | $		$ 184
Underwriters exercise option to purchase additional shares of common stock	1,505,359
Net proceeds after deducting commissions from underwriter purchase of additional share of common stock | $	$ 26.6

Stock-based compensation - Addi

Stock-based compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 15, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 24, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock initially reserved for future issuance		667,931
Cumulative increase in common stock reserve for issuance and available for issuance	350,447
Weighted-average estimated fair value of options awarded (in dollars per share)		$ 26.56	$ 3.21
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		$ 44
Recognition period for compensation cost not yet recognized (in years, months, and days)		3 years 2 months 12 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]
Vesting percentage upon sale	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	5,562,055
Cumulative increase in common stock reserve for issuance, percentage	5.00%
Cumulative increase in common stock reserve for issuance and available for issuance		1,752,237

Stock-based compensation - Summ

Stock-based compensation - Summary of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 3,227	$ 350	$ 5,811	$ 536
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	496	67	771	117
General And Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 2,731	$ 283	$ 5,040	$ 419

Stock-based compensation - Su_2

Stock-based compensation - Summary of Stock Options Activity (Details) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020$ / sharesshares
Shares
Outstanding as of December 31, 2020 | shares	4,552,396
Granted | shares	983,450
Forfeited | shares	(3,075)
Exercised | shares	(103,352)
Outstanding as of June 30, 2021 | shares	5,429,419	4,552,396
Exercisable at June 30, 2021 | shares	1,469,512
Weighted-Average Exercise Price Per Share
Outstanding as of December 31, 2020 | $ / shares	$ 9.13
Granted | $ / shares	34.27
Forfeited | $ / shares	4.24
Exercised | $ / shares	5.82
Outstanding as of June 30, 2021 | $ / shares	13.70	$ 9.13
Exercisable at June 30, 2021 | $ / shares	$ 5.46
Weighted-Average Remaining Contractual Term
Options outstanding	8 years 1 month 6 days	8 years 2 months 12 days
Exercisable at June 30, 2021	6 years 1 month 6 days
Aggregate Intrinsic Value
Outstanding as of December 31, 2020 | $	$ 74,160
Exercisable at June 30, 2021 | $	$ 29,794

Stock-based compensation - Sche

Stock-based compensation - Schedule of Fair Value Assumptions for Stock Options Granted (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate		0.45%
Risk-free interest rate, Minimum	0.84%		0.42%	0.45%
Risk-free interest rate, maximum	0.90%		0.90%	1.35%
Expected term (in years)	6 years	6 years	6 years	6 years
Expected volatility		92.00%
Expected Volatility, minimum	94.00%		94.00%	90.00%
Expected Volatility, maximum	99.00%		100.00%	92.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value of common stock	$ 23.19	$ 4.24	$ 23.19	$ 2.95
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value of common stock	$ 34.18	$ 6.16	$ 41.58	$ 6.16

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021USD ($)m²ft²	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)m²ft²	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Mar. 31, 2019USD ($)
Other Commitments [Line Items]
Land subject to leases | m²	1,577		1,577
Operating leases, rent expense	$ 100,000	$ 200,000	$ 300,000	$ 300,000
Gosselies, Belgium
Other Commitments [Line Items]
Operating lease, Hand serving to secure lease obligation	$ 82,000,000		$ 82,000,000		$ 71,000,000
Cambridge, Massachusetts
Other Commitments [Line Items]
Land subject to leases | ft²	2,479		2,479
Lease expiration date			May 31, 2022
Operating lease, Letter of credit to secure lease obligation						$ 57,000,000
Office and Laboratory Space | Gosselies, Belgium
Other Commitments [Line Items]
Lease commencement date			May 31, 2016
Lease expiration date			Dec. 31, 2021
Office and Laboratory Space | Gosselies, Belgium | Agreement to Extend Lease
Other Commitments [Line Items]
Lease commencement date			Feb. 28, 2021
Lease expiration date			Jan. 31, 2030
Lessee, operating lease, existence of option to extend [true false]			true
Increase land subject to leases | m²	201		201
Office | Cambridge, Massachusetts
Other Commitments [Line Items]
Lease commencement date			May 31, 2019
Contract Termination
Other Commitments [Line Items]
Restructuring charges			$ 0		$ 0
Minimum
Other Commitments [Line Items]
Contractual Agreement Cancelation Notice period			30 days
Average car lease duration	48 months		48 months
Maximum
Other Commitments [Line Items]
Contractual Agreement Cancelation Notice period			60 days
Average car lease duration	60 months		60 months

Commitments and Contingencies_2

Commitments and Contingencies - Schedule Of Lease Terms And Discount Rate (Details)	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Weighted-average remaining lease term (years)	7 years
Weighted-average discount rate	4.82%

Commitments and Contingencies_3

Commitments and Contingencies -Schedule Of Cash Flow And Other Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Operating lease liabilities arising from obtaining right-of-use assets	$ 110	$ 3,316
Operating cash flows used in operating leases	$ 189	$ 374

Commitments and Contingencies_4

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Non-cancelable Operating Leases (Details) $ in Thousands	Jun. 30, 2021USD ($)
Leases [Abstract]
2021	$ 370
2022	592
2023	480
2024	464
2025	421
Thereafter	1,339
Total Lease Payments	3,666
Less: Interest	(610)
Total Lease Liability	3,056
Lease liability	555
Lease liability, net of current portion	$ 2,501

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - Royalty Transfer Agreement $ in Thousands	Jun. 11, 2018USD ($)Investor	Jun. 30, 2021
Related Party Transaction [Line Items]
Royalty owed to charitable foundation	$ 0
Product
Related Party Transaction [Line Items]
Net product sales	$ 0
MPM Oncology Charitable Foundation, Inc. and UBS Optimus Foundation
Related Party Transaction [Line Items]
Number of investors | Investor	2
Obligation to pay royalties		royalty equal to a total of 1% percent of its net product sales each year within 120 days following each year end.
Percentage of royalty required to pay	1.00%

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stock - Schedule of Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents	5,429,419	25,783,454
Series B and B-2 Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents		20,597,566
Series A Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents		1,862,510
Stock Options Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents	5,429,419	3,323,378

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2021USD ($)
G S K Collaboration Agreement
Subsequent Event [Line Items]
Upfront payment received	$ 625
Development And Commercial Milestones
Subsequent Event [Line Items]
Eligible to Receive Milestone Payments	$ 1,450