Nature of Business and Basis of Presentation	12 Months Ended
Dec. 31, 2021
Disclosure Text Block [Abstract]
Nature of Business and Basis of Presentation	Note 1. Nature of Business and Basis of Presentation Organization iTeos Therapeutics, Inc. (iTeos Inc. or the Company), a Delaware corporation headquartered in Watertown, 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 people living with cancer. The Company leverages its deep understanding of the tumor immunology and immunosuppressive pathways to design novel product candidates with the aim of restoring the immune response against cancer. The Company’s innovative pipeline includes two clinical-stage programs targeting novel, de-risked immuno-oncology pathways. Each of the Company's therapies in development has optimized pharmacologic properties designed to improve clinical outcomes. The Company’s lead antibody product candidate, EOS-448, also known as GSK4428859A, is an antagonist of TIGIT, or T-cell immunoreceptor with lg and ITIM domains, an immune checkpoint with multiple mechanisms of action. EOS-448 was selected for its affinity for TIGIT, its potency and its potential to engage the Fc gamma receptor, or FcγR, to activate dendritic cells, natural killer cells, and macrophages and to promote cytokine release, activation of antigen presenting cells, and antibody-dependent cellular cytotoxicity, or ADCC, activity. In 2020, the Company started an open-label Phase 1/2a clinical trial of EOS-448 in adult cancer patients with advanced solid tumors. In April 2021, the Company reported preliminary safety, pharmacokinetic, engagement and pharmacodynamic data, indicating target engagement and early evidence of clinical activity as a single agent. In September 2021, the Company dosed the first patients in a Phase 1/2 clinical trial of EOS-448 in combination with pembrolizumab and in combination with the Company's A2AR antagonist inupadenant in patients with solid tumors. As of January 2022, the Company continues to explore EOS-448 in combination with pembrolizumab, dostarlimab or inupadenant in patients with solid tumors in ongoing Phase 1b trials. Based on favorable preclinical data generated in collaboration with Fred Hutchinson Cancer Research Center, the Company is also advancing an open-label dose-escalation/expansion Phase 1/2 trial evaluating the safety, tolerability and preliminary activity of EOS-448 as monotherapy and in combination with Bristol Myers Squibb’s iberdomide - a novel, potent oral cereblon E3 ligase modulator (CELMoD®) compound with enhanced tumoricidal and immune-stimulatory effects compared with immunomodulatory (IMiD®) agents - with or without dexamethasone, in adults with relapsed or refractory multiple myeloma. On June 11, 2021, the Company's wholly owned subsidiary, iTeos Belgium S.A., and GlaxoSmithKline Intellectual Property (No. 4) Limited, or GSK, executed a Collaboration and License Agreement, or the GSK Collaboration Agreement, which became effective on July 26, 2021. Pursuant to the GSK Collaboration Agreement, the Company agreed to grant GSK a license under certain of its intellectual property rights to develop, manufacture, and commercialize products comprised of or containing EOS-448, which license is exclusive in all countries outside of the United States and co-exclusive, with iTeos, in the United States. GSK and iTeos intend to develop EOS-448 in combination, including with other oncology assets of GSK, and iTeos and GSK will jointly own the intellectual property created under the GSK Collaboration Agreement that covers such combinations. In partnership with GSK, the Company will assess the doublet of GSK’s anti-PD-1 (dostarlimab) with EOS-448 in first line PD-L1 high non-small cell lung cancer, head and neck squamous cell carcinoma and an additional indication in registration-directed trials. The Company and GSK also are initiating trials with novel triplets, including dostarlimab with EOS-448 and inupadenant as well as EOS-448 with dostarlimab and GSK’s anti-CD96 antibody, GSK’608. The Company is also advancing inupadenant, a next-generation adenosine A2A receptor antagonist tailored to overcome the specific adenosine-mediated immunosuppression found in tumor microenvironment, into proof-of concept trials in several indications following encouraging single-agent activity in Phase 1. The Company is investigating inupadenant in an open-label multi-arm Phase 1/2a clinical trial in adult cancer patients with advanced solid tumors. The single-agent dose-escalation and expansion portions of the Company's Phase 1/2a clinical trial of inupadenant have demonstrated durable monotherapy antitumor activity in patients with advanced solid tumors and safety consistent with previously reported results. As part of this monotherapy assessment of inupadenant, the Company identified a potential predictive biomarker and it continues to evaluate this signal in the ongoing Phase 1b/2a trial. In 2022, the Company plans to initiate a randomized Phase 2 trial in a solid tumor indication to evaluate the combination of inupadenant with chemotherapy compared to standard of care chemotherapy alone. The Company has completed enrollment in the safety evaluation portion of the clinical trial of inupadenant in combination with chemotherapy and with pembrolizumab, as well as the monotherapy expansion cohort in prostate cancer. The Company has initiated an expansion arm evaluating inupadenant in combination with pembrolizumab in patients with PD-1-resistant melanoma, currently in an ongoing trial. In addition, the Company is evaluating a salt form of inupadenant in a Phase 1 study. The Company began its research and development activities as a spin-off of Ludwig Cancer Research and have built significant expertise in designing novel cancer immunotherapies. The Company's internal research and development team has extensive expertise in tumor immunology, characterization of immunosuppressive mechanisms in the tumor microenvironment, pharmacology and translational medicine. The Company has also built discovery capabilities to develop both small molecules and antibodies with differentiated and optimized product profiles for targets validated by a strong scientific rationale. The Company continues to progress research programs focused on additional targets that complement its TIGIT and A2AR programs or address additional immunosuppressive pathways. In September 2021, the Company nominated a product candidate in the adenosine pathway for Investigational New Drug, or IND, enabling studies. The Company's expertise also allows it to integrate a biomarker-rich strategy into its clinical programs to measure the activity of a product candidate in patients, seek to optimize combination agents and identify patients it deems most likely to benefit from treatment. On December 2, 2020, iTeos Securities Corporation (iTeos SC) was incorporated as a Massachusetts Security Corporation. It is a wholly-owned subsidiary of iTeos Inc. On July 27, 2021, iTeos BE, LLC (iTeos LLC) was incorporated as a Delaware Limited Liability Company. It is a wholly-owned subsidiary of iTeos Belgium. Reverse Stock Split and Initial Public Offering On July 20, 2020, the Company effected a 1-for-3.3115 reverse stock split of the Company’s common stock and adjusted the ratio at which the Company’s preferred stock is convertible into common stock, as well as the number of shares under the 2019 Stock Option and Grant Plan and the Amended and Restated Certificate of Incorporation of iTeos Therapeutics, Inc., as well as the share amounts of stock grants under the plan and the number of options and exercise prices of options under the plan. All shares of common stock, stock options exercisable for shares of common stock, and per share information presented in the accompanying consolidated financial statements and notes thereto have been adjusted, where applicable, to reflect the reverse stock split on a retroactive basis for all periods presented. There was no change in the par value of the Company’s common stock. On July 28, 2020, the Company completed its initial public offering (IPO), in which the Company issued and sold 10,586,316 shares of its common stock, for aggregate gross proceeds of $201.1 million and its shares started trading on The Nasdaq Global Select Market under the ticker symbol “ITOS.” The Company received approximately $184.0 million in net proceeds after deducting underwriting discounts and commissions and other offering expenses paid by the Company. Upon closing of the IPO, all of the Company's outstanding shares of convertible preferred stock automatically converted into 22,460,076 shares of common stock. On August 5, 2020, the underwriters purchased an additional 1,505,359 shares of common stock pursuant to their option to purchase additional shares for net proceeds of $26.6 million after deducting underwriting discounts and commissions. Liquidity and capital resources Since inception, the Company’s activities have consisted primarily of performing research and development to advance its product candidates. For the first time since inception, the Company has earned income during the current period, which equaled net income of $214.5 million for the year ended December 31, 2021. As of December 31, 2021, the Company had retained earnings of $140.6 million. As of March 23, 2022, the issuance date of the consolidated financial statements for the year ended December 31, 2021, the Company expects that its cash and cash equivalents would be sufficient to fund its operating expenses, capital expenditure requirements and debt service payments through at least 12 months from the issuance date of the consolidated financial statements. The Company may seek additional funding in order to reach its development and commercialization objectives. The Company may not be able to obtain funding on acceptable terms, or at all, and the Company may not be able to enter into collaborations or other arrangements. The terms of any funding may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects. The Company’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 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 sustained profitability, and it may never do so. COVID-19 With the ongoing concern related to the COVID-19 pandemic during 2020 and 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. With increased availability of vaccines and public health guidelines evolving to reflect their availability, we have shifted to a hybrid model for all our employees. We will continue to monitor and make adjustments in response to the public health environment, together with local, state and federal guidance regarding workplace protective measures. 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 ongoing 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, the identification of additional variants of COVID-19, the availability and utilization of vaccines and treatments for COVID-19, or the effectiveness of actions taken globally to contain and address COVID-19, such as travel restrictions, quarantines, social distancing and business closure requirements, but particularly in the geographies where the Company, its 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 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).

Nature of Business and Basis of Presentation

12 Months Ended

Dec. 31, 2021

Nature of Business and Basis of Presentation

Note 1. Nature of Business and Basis of Presentation

Organization

iTeos Therapeutics, Inc. (iTeos Inc. or the Company), a Delaware corporation headquartered in Watertown, 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 people living with cancer. The Company leverages its deep understanding of the tumor immunology and immunosuppressive pathways to design novel product candidates with the aim of restoring the immune response against cancer. The Company’s innovative pipeline includes two clinical-stage programs targeting novel, de-risked immuno-oncology pathways. Each of the Company's therapies in development has optimized pharmacologic properties designed to improve clinical outcomes.

The Company’s lead antibody product candidate, EOS-448, also known as GSK4428859A, is an antagonist of TIGIT, or T-cell immunoreceptor with lg and ITIM domains, an immune checkpoint with multiple mechanisms of action. EOS-448 was selected for its affinity for TIGIT, its potency and its potential to engage the Fc gamma receptor, or FcγR, to activate dendritic cells, natural killer cells, and macrophages and to promote cytokine
release, activation of antigen presenting cells, and antibody-dependent cellular cytotoxicity, or ADCC, activity. In 2020, the Company started an open-label Phase 1/2a clinical trial of EOS-448 in adult cancer patients with advanced solid tumors. In April 2021, the Company reported preliminary safety, pharmacokinetic, engagement and pharmacodynamic data, indicating target engagement and early evidence of clinical activity as a single agent. In September 2021, the Company dosed the first patients in a Phase 1/2 clinical trial of EOS-448 in combination with pembrolizumab and in combination with the Company's A2AR antagonist inupadenant in patients with solid tumors. As of January 2022, the Company continues to explore EOS-448 in combination with pembrolizumab, dostarlimab or inupadenant in patients with solid tumors in ongoing Phase 1b trials.

Based on favorable preclinical data generated in collaboration with Fred Hutchinson Cancer Research Center, the Company is also advancing an open-label dose-escalation/expansion Phase 1/2 trial evaluating the safety, tolerability and preliminary activity of EOS-448 as monotherapy and in combination with Bristol Myers Squibb’s iberdomide - a novel, potent oral cereblon E3 ligase modulator (CELMoD®) compound with enhanced tumoricidal and immune-stimulatory effects compared with immunomodulatory (IMiD®) agents - with or without dexamethasone, in adults with relapsed or refractory multiple myeloma.

On June 11, 2021, the Company's wholly owned subsidiary, iTeos Belgium S.A., and GlaxoSmithKline Intellectual Property (No. 4) Limited, or GSK, executed a Collaboration and License Agreement, or the GSK Collaboration Agreement, which became effective on July 26, 2021. Pursuant to the GSK Collaboration Agreement, the Company agreed to grant GSK a license under certain of its intellectual property rights to develop, manufacture, and commercialize products comprised of or containing EOS-448, which license is exclusive in all countries outside of the United States and co-exclusive, with iTeos, in the United States. GSK and iTeos intend to develop EOS-448 in combination, including with other oncology assets of GSK, and iTeos and GSK will jointly own the intellectual property created under the GSK Collaboration Agreement that covers such combinations. In partnership with GSK, the Company will assess the doublet of GSK’s anti-PD-1 (dostarlimab) with EOS-448 in first line PD-L1 high non-small cell lung cancer, head and neck squamous cell carcinoma and an additional indication in registration-directed trials. The Company and GSK also are initiating trials with novel triplets, including dostarlimab with EOS-448 and inupadenant as well as EOS-448 with dostarlimab and GSK’s anti-CD96 antibody, GSK’608.

The Company is also advancing inupadenant, a next-generation adenosine A2A receptor antagonist tailored to overcome the specific adenosine-mediated immunosuppression found in tumor microenvironment, into proof-of concept trials in several indications following encouraging single-agent activity in Phase 1. The Company is investigating inupadenant in an open-label multi-arm Phase 1/2a clinical trial in adult cancer patients with advanced solid tumors. The single-agent dose-escalation and expansion portions of the Company's Phase 1/2a clinical trial of inupadenant have demonstrated durable monotherapy antitumor activity in patients with advanced solid tumors and safety consistent with previously reported results. As part of this monotherapy assessment of

inupadenant, the Company identified a potential predictive biomarker and it continues to evaluate this signal in the ongoing Phase 1b/2a trial. In 2022, the Company plans to initiate a randomized Phase 2 trial in a solid tumor indication to evaluate the combination of inupadenant with chemotherapy compared to standard of care chemotherapy alone. The Company has completed enrollment in the safety evaluation portion of the clinical trial of inupadenant in combination with chemotherapy and with pembrolizumab, as well as the monotherapy expansion cohort in prostate cancer. The Company has initiated an expansion arm evaluating inupadenant in combination with pembrolizumab in patients with PD-1-resistant melanoma, currently in an ongoing trial. In addition, the Company is evaluating a salt form of inupadenant in a Phase 1 study.

The Company began its research and development activities as a spin-off of Ludwig Cancer Research and have built significant expertise in designing novel cancer immunotherapies. The Company's internal research and development team has extensive expertise in tumor immunology, characterization of immunosuppressive mechanisms in the tumor microenvironment, pharmacology and translational medicine. The Company has also built discovery capabilities to develop both small molecules and antibodies with differentiated and optimized product profiles for targets validated by a strong scientific rationale. The Company continues to progress research programs focused on additional targets that complement its TIGIT and A2AR programs or address additional immunosuppressive pathways. In September 2021, the Company nominated a product candidate in the adenosine pathway for Investigational New Drug, or IND, enabling studies. The Company's expertise also allows it to integrate a biomarker-rich strategy into its clinical programs to measure the activity of a product candidate in patients, seek to optimize combination agents and identify patients it deems most likely to benefit from treatment.

On December 2, 2020, iTeos Securities Corporation (iTeos SC) was incorporated as a Massachusetts Security Corporation. It is a wholly-owned subsidiary of iTeos Inc. On July 27, 2021, iTeos BE, LLC (iTeos LLC) was incorporated as a Delaware Limited Liability Company. It is a wholly-owned subsidiary of iTeos Belgium.

Reverse Stock Split and Initial Public Offering

On July 20, 2020, the Company effected a 1-for-3.3115 reverse stock split of the Company’s common stock and adjusted the ratio at which the Company’s preferred stock is convertible into common stock, as well as the number of shares under the 2019 Stock Option and Grant Plan and the Amended and Restated Certificate of Incorporation of iTeos Therapeutics, Inc., as well as the share amounts of stock grants under the plan and the number of options and exercise prices of options under the plan. All shares of common stock, stock options exercisable for shares of common stock, and per share information presented in the accompanying consolidated financial statements and notes thereto have been adjusted, where applicable, to reflect the reverse stock split on a retroactive basis for all periods presented. There was no change in the par value of the Company’s common stock.

On July 28, 2020, the Company completed its initial public offering (IPO), in which the Company issued and sold 10,586,316 shares of its common stock, for aggregate gross proceeds of $201.1 million and its shares started trading on The Nasdaq Global Select Market under the ticker symbol “ITOS.” The Company received approximately $184.0 million in net proceeds after deducting underwriting discounts and commissions and other offering expenses paid by the Company. Upon closing of the IPO, all of the Company's outstanding shares of convertible preferred stock automatically converted into 22,460,076 shares of common stock.

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

Liquidity and capital resources

Since inception, the Company’s activities have consisted primarily of performing research and development to advance its product candidates. For the first time since inception, the Company has earned income during the current period, which equaled net income of $214.5 million for the year ended December 31, 2021. As of December 31, 2021, the Company had retained earnings of $140.6 million. As of March 23, 2022, the issuance date of the consolidated financial statements for the year ended December 31, 2021, the Company expects that its cash and cash equivalents would be sufficient to fund its operating expenses, capital expenditure requirements and debt service payments through at least 12 months from the issuance date of the consolidated financial statements.

The Company may seek additional funding in order to reach its development and commercialization objectives. The Company may not be able to obtain funding on acceptable terms, or at all, and the Company may not be able to enter into collaborations or other arrangements. The terms of any funding may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its research and development programs, product portfolio expansion or commercialization efforts, which could adversely affect its business prospects.

The Company’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 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 sustained profitability, and it may never do so.

COVID-19

With the ongoing concern related to the COVID-19 pandemic during 2020 and 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. With increased availability of vaccines and public health guidelines evolving to reflect their availability, we have shifted to a hybrid model for all our employees. We will continue to monitor and make adjustments in response to the public health environment, together with local, state and federal guidance regarding workplace protective measures. 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 ongoing 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, the identification of additional variants of COVID-19, the availability and utilization of vaccines and treatments for COVID-19, or the effectiveness of actions taken globally to contain and address COVID-19, such as travel restrictions, quarantines, social distancing and business closure requirements, but particularly in the geographies where the Company, its 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 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).