Nature of Business and Basis of Presentation	6 Months Ended
Jun. 30, 2024
Disclosure Text Block [Abstract]
Nature of Business and Basis of Presentation	Note 1. Nature of Business and Basis of Presentation Description of business 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 immuno-oncology therapeutics for people living with cancer. By leveraging its deep understanding of the tumor immunology and immunosuppressive pathways we design novel product candidates with optimized pharmacologic properties to improve clinical outcomes by restoring the immune response against cancer. The Company is focused on advancing its innovative pipeline of monoclonal antibodies (mAbs) and small molecules for the treatment of cancer, especially solid tumors. Our three clinical-stage programs target novel, validated immuno-oncology pathways, including the TIGIT/CD226 pathway with TIGIT (T cell immunoreceptor with lg and ITIM domains) and the adenosine pathway with A2AR (adenosine 2A receptor) and ENT1 (equilibrative nucleoside transporter 1). The Company’s lead antibody product candidate, belrestotug, also known as EOS-448/GSK4428859A, is an antagonist of TIGIT, an immune checkpoint with multiple mechanisms of action. Belrestotug was selected for its target affinity with TIGIT, potency and potential to engage the Fc gamma receptor (FcγR), a key regulator of immune response which triggers a multi-faceted mechanism of action that improves antitumor efficacy. This multi-faceted mechanism includes the activation of dendritic cells, natural killer cells, and macrophages, and the promotion of cytokine release and antibody-dependent cellular cytotoxicity (ADCC) activity. In 2020, the Company initiated an open-label Phase 1/2a clinical trial of belrestotug 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. 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 granted GSK a license under certain of its intellectual property rights to develop, manufacture, and commercialize products comprised of or containing belrestotug, 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 belrestotug 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 is enrolling patients in a randomized, double-blind Phase 3 registrational trial, GALAXIES Lung-301, assessing the doublet of GSK's anti-PD-1 (Jemperli (dostarlimab-gxly)) with belrestotug versus placebo and pembrolizumab in patients with first-line PD-L1 high non-small cell lung cancer (NSCLC). The Company is also enrolling patients with first line PD-L1 high NSCLC in a randomized Phase 2 platform study, GALAXIES Lung-201, assessing dostarlimab with belrestotug and in combination with GSK'608, GSK's investigational anti-CD96 antibody, nelistotug. An interim assessment of the GALAXIES Lung-201 study exceeded pre-defined efficacy criteria for clinically relevant activity with clinically meaningful tumor reduction and showed an acceptable safety profile in line with the TIGIT:PD-1 class. In addition, the Company is enrolling patients in a Phase 2 platform study, GALAXIES H&N-202, assessing the belrestotug and dostarlimab doublet and a triplet with GSK’s anti-CD96 antibody (GSK’608) with first-line, PD-L1 positive advanced or metastatic head and neck squamous cell carcinoma (HNSCC) and a Phase 2 expansion trial assessing belrestotug and dostarlimab with first-line, PD-L1 positive advanced or metastatic HNSCC. In the TIG-006 trial assessing the doublet of dostarlimab with belrestotug in patients with first-line HNSCC (Cohorts 2C and 2D), we completed enrollment in the first portion of the Phase 2 expansion part of the trial. We and GSK agreed to not continue beyond stage 1 recruitment in these open-label cohorts in order to focus on the randomized, controlled GALAXIES H&N-202 platform study. The Company and GSK continue to explore two novel triplets in selected advanced solid tumors both in Phase 1b trials: belrestotug with dostarlimab and GSK’s investigational anti-CD96 antibody, and belrestotug with dostarlimab and GSK’s anti-PVRIG antibody (GSK’562). The Company's next most advanced program is inupadenant, also known as EOS-850, a next-generation A2AR antagonist tailored to overcome the specific adenosine-mediated immunosuppression found in tumor microenvironment. The Company is investigating inupadenant in an open-label multi-arm Phase 1/2a clinical trial in adult cancer patients with advanced solid tumors. In April 2020, the Company reported preliminary safety data and early evidence of clinical activity as a single agent. 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 some patients with advanced solid tumors and safety consistent with previously reported results. The Company also completed enrollment of patients in the escalation portion (Part 1) of an ongoing two-part Phase 2 trial in post-IO metastatic NSCLC to evaluate the combination of inupadenant with platinum-doublet chemotherapy compared to standard platinum-doublet chemotherapy. The Company continues to progress research programs focused on additional targets that complement its TIGIT and adenosine pathway programs or address additional immunosuppressive pathways. The most recent program to enter the clinic is EOS-984, a potentially first-in-class small molecule focused on a new mechanism in the adenosine pathway by targeting ENT1, a dominant transporter of adenosine on lymphocytes involved in T cell metabolism, expansion, effector function, and survival. 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. 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. 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. 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 had a net loss of $7.1 million and $45.3 million for the three and six months ended June 30, 2024, respectively. As of June 30, 2024, the Company had retained earnings of $79.3 million. As of August 8, 2024, the issuance date of the condensed consolidated financial statements for the period ended June 30, 2024, the Company expects that its cash and cash equivalents would be sufficient to fund its operating expenses, capital expenditure requirements and debt service payments for at least 12 months. 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. The Company's product candidates may fail to 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. 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 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, 2023 and 2022, 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.

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 immuno-oncology therapeutics for people living with cancer. By leveraging its deep understanding of the tumor immunology and immunosuppressive pathways we design novel product candidates with optimized pharmacologic properties to improve clinical outcomes by restoring the immune response against cancer. The Company is focused on advancing its innovative pipeline of monoclonal antibodies (mAbs) and small molecules for the treatment of cancer, especially solid tumors. Our three clinical-stage programs target novel, validated immuno-oncology pathways, including the TIGIT/CD226 pathway with TIGIT (T cell immunoreceptor with lg and ITIM domains) and the adenosine pathway with A2AR (adenosine 2A receptor) and ENT1 (equilibrative nucleoside transporter 1).

The Company’s lead antibody product candidate, belrestotug, also known as EOS-448/GSK4428859A, is an antagonist of TIGIT, an immune checkpoint with multiple mechanisms of action. Belrestotug was selected for its target affinity with TIGIT, potency and potential to engage the Fc gamma receptor (FcγR), a key regulator of immune response which triggers a multi-faceted mechanism of action that improves antitumor efficacy. This multi-faceted mechanism includes the activation of dendritic cells, natural killer cells, and macrophages, and the promotion of cytokine release and antibody-dependent cellular cytotoxicity (ADCC) activity. In 2020, the Company initiated an open-label Phase 1/2a clinical trial of belrestotug 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.

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 granted GSK a license under certain of its intellectual property rights to develop, manufacture, and commercialize products comprised of or containing belrestotug, 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 belrestotug 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 is enrolling patients in a randomized, double-blind Phase 3 registrational trial, GALAXIES Lung-301, assessing the doublet of GSK's anti-PD-1 (Jemperli (dostarlimab-gxly)) with belrestotug versus placebo and pembrolizumab in patients with first-line PD-L1 high non-small cell lung cancer (NSCLC). The Company is also enrolling patients with first line PD-L1 high NSCLC in a randomized Phase 2 platform study, GALAXIES Lung-201, assessing dostarlimab with belrestotug and in combination with GSK'608, GSK's investigational anti-CD96 antibody, nelistotug. An interim assessment of the GALAXIES Lung-201 study exceeded pre-defined efficacy criteria for clinically relevant activity with clinically meaningful tumor reduction and showed an acceptable safety profile in line with the TIGIT:PD-1 class. In addition, the Company is enrolling patients in a Phase 2 platform study, GALAXIES H&N-202, assessing the belrestotug and dostarlimab doublet and a triplet with GSK’s anti-CD96 antibody (GSK’608) with first-line, PD-L1 positive advanced or metastatic head and neck squamous cell carcinoma (HNSCC) and a Phase 2 expansion trial assessing belrestotug and dostarlimab with first-line, PD-L1 positive advanced or metastatic HNSCC. In the TIG-006 trial assessing the doublet of dostarlimab with belrestotug in patients with first-line HNSCC (Cohorts 2C and 2D), we completed enrollment in the first portion of the Phase 2 expansion part of the trial. We and GSK agreed to not continue beyond stage 1 recruitment in these open-label cohorts in order to focus on the randomized, controlled GALAXIES H&N-202 platform study. The Company and GSK continue to explore two novel triplets in selected advanced solid tumors both in Phase 1b trials: belrestotug with dostarlimab and GSK’s investigational anti-CD96 antibody, and belrestotug with dostarlimab and GSK’s anti-PVRIG antibody (GSK’562).

The Company's next most advanced program is inupadenant, also known as EOS-850, a next-generation A2AR antagonist tailored to overcome the specific adenosine-mediated immunosuppression found in tumor microenvironment. The Company is investigating inupadenant in an open-label multi-arm Phase 1/2a clinical trial in adult cancer patients with advanced solid tumors. In April 2020, the Company reported preliminary safety data and early evidence of clinical activity as a single agent. 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 some patients with advanced solid tumors and safety consistent with previously reported results. The Company also completed enrollment of patients in the escalation

portion (Part 1) of an ongoing two-part Phase 2 trial in post-IO metastatic NSCLC to evaluate the combination of inupadenant with platinum-doublet chemotherapy compared to standard platinum-doublet chemotherapy.

The Company continues to progress research programs focused on additional targets that complement its TIGIT and adenosine pathway programs or address additional immunosuppressive pathways. The most recent program to enter the clinic is EOS-984, a potentially first-in-class small molecule focused on a new mechanism in the adenosine pathway by targeting ENT1, a dominant transporter of adenosine on lymphocytes involved in T cell metabolism, expansion, effector function, and survival. 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.

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.

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.

Since inception, the Company’s activities have consisted primarily of performing research and development to advance its product candidates. The Company had a net loss of $7.1 million and $45.3 million for the three and six months ended June 30, 2024, respectively. As of June 30, 2024, the Company had retained earnings of $79.3 million. As of August 8, 2024, the issuance date of the condensed consolidated financial statements for the period ended June 30, 2024, the Company expects that its cash and cash equivalents would be sufficient to fund its operating expenses, capital expenditure requirements and debt service payments for at least 12 months.

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. The Company's product candidates may fail to 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.

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 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, 2023 and 2022, 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.