License and Collaboration Agreements	6 Months Ended
Jun. 30, 2025
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. 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. 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. Through June 30, 2025, the Company has paid a total of $10.4 million to Adimab relating to milestones under the Adimab Agreement. The Company made a $1.0 million payment to Adimab in the first quarter of 2024 relating to a milestone that occurred during the fourth quarter of 2023. The Company also made a $3.0 million payment in the year ended December 31, 2024 in connection with a development milestone that occurred early in the third quarter of 2024. The Company also made a $1.0 million payment to Adimab in the three and six months ended June 30, 2025. 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. 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. The Adimab Agreement will survive the Merger. GlaxoSmithKline Summary of Agreement On June 11, 2021, the Company’s wholly owned subsidiary, iTeos Belgium, and GSK executed a Collaboration and License Agreement, pursuant to which the Company agreed 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, belrestotug. Under the GSK Collaboration Agreement, GSK agreed to make an upfront nonrefundable payment of $625.0 million to the Company within 10 business days of the date on which the GSK Collaboration Agreement became 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 belrestotug program achieving certain development and commercial milestones. Within the collaboration, GSK and the Company agreed to share responsibility and costs for the global development of belrestotug beyond the Phase 1 study (the "Global Development Plan") and would jointly commercialize and equally split profits in the United States. Outside of the United States, GSK received an exclusive license for commercialization, and the Company was eligible to receive tiered double digit royalty payments up to 20% during a customary royalty term. Collaboration The Company concluded that the GSK Collaboration Agreement was under the scope of ASC 808 as both parties actively participated in a joint operating activity and were exposed to significant risks and rewards that depended on the activity’s commercial success. ASC 808 provides that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606 when the collaborative arrangement participant is a customer in the context of a unit of account. In those situations, all of the guidance in ASC 606 should be applied, including recognition, measurement, presentation, and disclosure requirements related to such unit of account. The unit-of-account guidance in ASC 808, which aligns with the guidance in ASC 606 (that is, a distinct good or service) is used when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of ASC 606. The Company determined that the co-development in Phases 2 and 3 and the co-commercialization efforts of the GSK Collaboration Agreement represented joint operating activities in which both parties were active participants and of which both parties were exposed to significant risks and rewards that were dependent on the success of the activities. Accordingly, the Company accounted for these activities in accordance with ASC No. 808, Collaborative Arrangements (ASC 808). Additionally, the Company had determined that in the context of these activities, GSK did not represent a customer as contemplated by ASC 606-10-15, Revenue from Contracts with Customers – Scope and Scope Exceptions. As a result, these activities were accounted for as a component of the related expense in the period incurred in accordance with ASC 730, Research and Development. Additionally, reimbursements received from GSK in connection with the joint operating activities have been recognized as a reduction to research and development expense. On May 13, 2025, iTeos Belgium received written notice from GSK that, in connection with the receipt of the topline interim results from GALAXIES Lung-201, GSK elected to terminate the GSK Collaboration Agreement for convenience (the “GSK Termination Notice”). In accordance with the terms of the GSK Collaboration Agreement, the termination will be effective six months from the date of such notice (the “Termination Effective Date”). As a result of the termination of the GSK Collaboration Agreement, as of the Termination Effective Date, the license rights granted to GSK will terminate and the parties will cease to accrue any financial obligations to each other. In connection with the Termination Notice, the Company and GSK made the decision to terminate the belrestotug development program, end all belrestotug-containing cohorts, and end any new enrollment in the Company’s ongoing GALAXIES Lung-301 Phase 3 trial. On July 18, 2025, iTeos Belgium and GSK entered into a Mutual Termination Agreement (the “GSK Termination Agreement”), pursuant to which iTeos Belgium will pay a settlement payment of $32.0 million no later than 20 business days after receipt of an invoice from GSK to close out the remaining costs for which it is responsible under the contract. Unless there is a material safety or efficacy issue requiring pause or cessation, both iTeos Belgium and GSK are required to complete within certain specified time periods certain ongoing activities related to the wind-down and completion of clinical trials. Pursuant to the GSK Termination Agreement, GSK will revert to iTeos Belgium control of prosecution of certain patents and GSK and iTeos Belgium will complete data migration activities and publish certain scientific and medical publications related to activities performed under the GSK Agreement. During the three and six months ended June 30, 2025, the Company recorded to research and development expense $35.2 million and $43.2 million, respectively, related to the cost-sharing provisions of the GSK Collaboration Agreement. $32.0 million of these costs were payable to GSK and recorded in accrued clinical trial costs in the condensed consolidated balance sheet as of June 30, 2025. Revenue Recognition The Company also evaluated the elements of the GSK Collaboration Agreement in accordance with the provisions of ASC 606 and concluded that the contract counterparty, GSK, was a customer. The Company’s arrangement with GSK contained the following material promises under the contract at inception: (i) transfer of the license under certain of the Company’s intellectual property related to belrestotug, (ii) completion of the Phase 1 clinical study related to belrestotug, (iii) transfer of “Know How” under the belrestotug intellectual property, and (iv) manufacturing until the “Know How” transfer was complete. The Company evaluated the above material promises under ASC 606 and determined that it had one combined performance obligation. These promises were considered to be outputs of the Company's ordinary activities and ongoing major operations. As GSK provided the Company consideration in exchange for these promises, GSK met the definition of a customer under ASC 606-10-20 in the context of the combined performance obligation. These promises were distinct from the co-development and co-commercialization activities in which the Company and GSK jointly participate. Accordingly, the context in which GSK is a customer is limited to the material promises described above. The transaction price totaling $625.0 million was comprised of the upfront license payment. As of June 30, 2025, no development or regulatory milestones had been assessed as probable of being reached and thus had been fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones was outside the control of the Company and contingent upon success in future clinical trials and the licensee’s efforts. Any consideration related to sales-based milestones would have been recognized when the related sales occurred as they were determined to relate predominantly to the license granted to GSK and therefore had also been excluded from the transaction price. The Company was applying the royalty exception for sales-based royalties and did not recognize any revenue related to sales. The transaction price had been recognized as revenue over time as the costs to complete the Phase 1 study, perform interim clinical supply manufacturing, and perform the know-how transfer were incurred. The performance obligation was fully completed in the three months ended March 31, 2023. Revenue was recognized using a percent complete method based on costs incurred compared with the total expected costs to be incurred (cost to cost measure of progress). There were no outputs from the performance obligation. As a result, an input method was appropriate. A cost-to-cost measure of progress provides a faithful depiction of the transfer of services to the customer since the predominant inputs to the performance obligation were labor costs, research and development supplies and manufacturing supplies related to the Phase 1 Study, clinical manufacturing and know-how transfer. The Company did not recognize any revenue during the three or six months ended June 30, 2025 with respect to the GSK Collaboration Agreement, and does not expect to recognize any additional revenue relating to the Agreement in the future. The Company recognized $35.0 million in the three and six months ended June 30, 2024 in connection with the dosing of a first patient in the GAL-301 clinical study. Revenue recognized under this agreement is classified as license and collaboration revenue in the accompanying condensed consolidated statements of operations. There was no deferred revenue remaining as of June 30, 2025 or December 31, 2024. Contract Assets and Liabilities There were no remaining contract assets or liabilities as of the period ended June 30, 2025.

License and Collaboration Agreements

6 Months Ended

Jun. 30, 2025

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.

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.

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.

Through June 30, 2025, the Company has paid a total of $10.4 million to Adimab relating to milestones under the Adimab Agreement. The Company made a $1.0 million payment to Adimab in the first quarter of 2024 relating to a milestone that occurred during the fourth quarter of 2023. The Company also made a $3.0 million payment in the year ended December 31, 2024 in connection with a development milestone that occurred early in the third quarter of 2024. The Company also made a $1.0 million payment to Adimab in the three and six months ended June 30, 2025. 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.

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. The Adimab Agreement will survive the Merger.

GlaxoSmithKline

Summary of Agreement

On June 11, 2021, the Company’s wholly owned subsidiary, iTeos Belgium, and GSK executed a Collaboration and License Agreement, pursuant to which the Company agreed 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, belrestotug. Under the GSK Collaboration Agreement, GSK agreed to make an upfront nonrefundable payment of $625.0 million to the Company within 10 business days of the date on which the GSK Collaboration Agreement became 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 belrestotug program achieving certain development and commercial milestones. Within the collaboration, GSK and the Company agreed to share responsibility and costs for the global development of belrestotug beyond the Phase 1 study (the "Global Development Plan") and would jointly commercialize and equally split profits in the United States. Outside of the United States, GSK received an exclusive license for commercialization, and the Company was eligible to receive tiered double digit royalty payments up to 20% during a customary royalty term.

Collaboration

The Company concluded that the GSK Collaboration Agreement was under the scope of ASC 808 as both parties actively participated in a joint operating activity and were exposed to significant risks and rewards that depended on the activity’s commercial success. ASC 808 provides that certain transactions between collaborative arrangement participants should be accounted for as revenue under ASC 606 when the collaborative arrangement participant is a customer in the context of a unit of account. In those situations, all of the guidance in ASC 606 should be applied, including recognition, measurement, presentation, and disclosure requirements related to such unit of account. The unit-of-account guidance in ASC 808, which aligns with the guidance in ASC 606 (that is, a distinct good or service) is used when an entity is assessing whether the collaborative arrangement or a part of the arrangement is within the scope of ASC 606.

The Company determined that the co-development in Phases 2 and 3 and the co-commercialization efforts of the GSK Collaboration Agreement represented joint operating activities in which both parties were active participants and of which both parties were exposed to significant risks and rewards that were dependent on the success of the activities. Accordingly, the Company accounted for these activities in accordance with ASC No. 808, Collaborative Arrangements (ASC 808). Additionally, the Company had determined that in the context of these activities, GSK did not represent a customer as contemplated by ASC 606-10-15, Revenue from Contracts with Customers – Scope and Scope Exceptions. As a result, these activities were accounted for as a component of the related expense in the period incurred in accordance with ASC 730, Research and Development. Additionally, reimbursements received from GSK in connection with the joint operating activities have been recognized as a reduction to research and development expense.

On May 13, 2025, iTeos Belgium received written notice from GSK that, in connection with the receipt of the topline interim results from GALAXIES Lung-201, GSK elected to terminate the GSK Collaboration Agreement for convenience (the “GSK Termination Notice”). In accordance with the terms of the GSK Collaboration Agreement, the termination will be effective six months from the date of such notice (the “Termination Effective Date”). As a result of the termination of the GSK Collaboration Agreement, as of the Termination Effective Date, the license rights granted to GSK will terminate and the parties will cease to accrue any financial obligations to each other. In connection with the Termination Notice, the Company and GSK made the decision to terminate the belrestotug development program, end all belrestotug-containing cohorts, and end any new enrollment in the Company’s ongoing GALAXIES Lung-301 Phase 3 trial. On July 18, 2025, iTeos Belgium and GSK entered into a Mutual Termination Agreement (the “GSK Termination Agreement”), pursuant to which iTeos Belgium will pay a settlement payment of $32.0 million no later than 20 business days after receipt of an invoice from GSK to close out the remaining costs for which it is responsible under the contract. Unless there is a material safety or efficacy issue requiring pause or cessation, both iTeos Belgium and GSK are required to complete within certain specified time periods certain ongoing activities related to the wind-down and completion of clinical trials. Pursuant to the

GSK Termination Agreement, GSK will revert to iTeos Belgium control of prosecution of certain patents and GSK and iTeos Belgium will complete data migration activities and publish certain scientific and medical publications related to activities performed under the GSK Agreement. During the three and six months ended June 30, 2025, the Company recorded to research and development expense $35.2 million and $43.2 million, respectively, related to the cost-sharing provisions of the GSK Collaboration Agreement. $32.0 million of these costs were payable to GSK and recorded in accrued clinical trial costs in the condensed consolidated balance sheet as of June 30, 2025.

Revenue Recognition

The Company also evaluated the elements of the GSK Collaboration Agreement in accordance with the provisions of ASC 606 and concluded that the contract counterparty, GSK, was a customer. The Company’s arrangement with GSK contained the following material promises under the contract at inception: (i) transfer of the license under certain of the Company’s intellectual property related to belrestotug, (ii) completion of the Phase 1 clinical study related to belrestotug, (iii) transfer of “Know How” under the belrestotug intellectual property, and (iv) manufacturing until the “Know How” transfer was complete. The Company evaluated the above material promises under ASC 606 and determined that it had one combined performance obligation. These promises were considered to be outputs of the Company's ordinary activities and ongoing major operations. As GSK provided the Company consideration in exchange for these promises, GSK met the definition of a customer under ASC 606-10-20 in the context of the combined performance obligation. These promises were distinct from the co-development and co-commercialization activities in which the Company and GSK jointly participate. Accordingly, the context in which GSK is a customer is limited to the material promises described above.

The transaction price totaling $625.0 million was comprised of the upfront license payment. As of June 30, 2025, no development or regulatory milestones had been assessed as probable of being reached and thus had been fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones was outside the control of the Company and contingent upon success in future clinical trials and the licensee’s efforts. Any consideration related to sales-based milestones would have been recognized when the related sales occurred as they were determined to relate predominantly to the license granted to GSK and therefore had also been excluded from the transaction price. The Company was applying the royalty exception for sales-based royalties and did not recognize any revenue related to sales.

The transaction price had been recognized as revenue over time as the costs to complete the Phase 1 study, perform interim clinical supply manufacturing, and perform the know-how transfer were incurred. The performance obligation was fully completed in the three months ended March 31, 2023. Revenue was recognized using a percent complete method based on costs incurred compared with the total expected costs to be incurred (cost to cost measure of progress). There were no outputs from the performance obligation. As a result, an input method was appropriate. A cost-to-cost measure of progress provides a faithful depiction of the transfer of services to the customer since the predominant inputs to the performance obligation were labor costs, research and development supplies and manufacturing supplies related to the Phase 1 Study, clinical manufacturing and know-how transfer.

The Company did not recognize any revenue during the three or six months ended June 30, 2025 with respect to the GSK Collaboration Agreement, and does not expect to recognize any additional revenue relating to the Agreement in the future. The Company recognized $35.0 million in the three and six months ended June 30, 2024 in connection with the dosing of a first patient in the GAL-301 clinical study. Revenue recognized under this agreement is classified as license and collaboration revenue in the accompanying condensed consolidated statements of operations. There was no deferred revenue remaining as of June 30, 2025 or December 31, 2024.

Contract Assets and Liabilities

There were no remaining contract assets or liabilities as of the period ended June 30, 2025.