Quarterly Report for Quarter Ending June 30, 2025 (Form 10-Q)

Management's Discussion and Analysis ofFinancial Condition and Results of Operations.

Management's discussion and analysis of financial condition and results of operation

The following discussion and analysis of our financial condition and results of operations should be read together with our unaudited condensed consolidated financial statements and related notes appearing elsewhere in this Quarterly Report on Form 10-Q and our audited consolidated financial statements and related notes for the year ended December 31, 2024 included in our Annual Report on Form 10-K filed with the SEC. Some of the information contained in this discussion includes forward-looking statements that involve risks and uncertainties. As a result of many factors, including those factors set forth in the Special note regarding forward-looking statements included in this Quarterly Report on Form 10-Q, and the "Risk factors" section of this Quarterly Report on Form 10-Q, our actual results could differ materially from the results described in or implied by the forward-looking statements contained in the following discussion and analysis.

Overview

We historically focused on pioneering the discovery and development of a new generation of immuno-oncology therapeutics for people living with cancer. We historically designed novel product candidates with optimized pharmacologic properties to improve clinical outcomes by restoring the immune response against cancer.

We previously focused on advancing our innovative pipeline, which includes monoclonal antibodies (mAbs) and small molecules for the treatment of cancer, especially solid tumors. Our immuno-oncology programs target three different key cancer resistance mechanisms: the TIGIT/CD226 pathway, which we target with an antibody to TIGIT (T cell immunoreceptor with lg and ITIM domains); the adenosine pathway, where we used a small molecule to inhibit ENT1 (equilibrative nucleoside transporter 1); and the reprogramming of immunosuppressive macrophages, where we are antagonizing triggering receptor expressed on myeloid cells 2 ("TREM2"), a critical receptor key to driving the tumor promoting functions of tumor resident macrophages.

Our lead clinical-stage antibody product candidate, belrestotug, was an antagonist of TIGIT, an immune checkpoint with multiple mechanisms of action.

On June 11, 2021, our wholly owned subsidiary, iTeos Belgium, and GlaxoSmithKline Intellectual Property (No. 4) Limited ("GSK"), executed a Collaboration and License Agreement (the "GSK Collaboration Agreement"), which became effective on July 26, 2021. Pursuant to the GSK Collaboration Agreement, we granted GSK a license under certain of our 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. We and GSK intended to develop belrestotug in combination, including with other oncology assets of GSK, and we and GSK would jointly own the intellectual property created under the GSK Collaboration Agreement that covers such combinations.

In partnership with GSK, we had multiple clinical trials:

On May 13, 2025, we reported topline results from an updated interim analysis of GALAXIES Lung-201. We reported that the GALAXIES Lung-201 data continued to demonstrate clinically meaningful improvements in the trial's primary endpoint of ORR, but the analysis did not meet established criteria for clinically meaningful improvements in the secondary endpoint of progression free survival in the belrestotug + dostarlimab combination cohorts versus dostarlimab monotherapy. Additionally, an interim analysis of the GALAXIES H&N-202 Phase 2 trial showed a trend below the

meaningful threshold for ORR in the belrestotug combination cohorts versus dostarlimab monotherapy in PD-L1 positive head and neck squamous cell carcinoma.

Based on the results described above, we and GSK made the decision to terminate the belrestotug development program and end the collaboration, ending all belrestotug-containing cohorts and any new enrollment in the GALAXIES Lung-201 trial. On May 13, 2025, iTeos Belgium received written notice from GSK electing to terminate the GSK Collaboration Agreement.

Our second clinical program was 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 extracellular adenosine, expressed on intratumoral T cells, which allows adenosine entry into the cell, disturbing T cell metabolism, expansion, effector function, and survival. We were evaluating EOS-984 in a Phase 1 Trial in advanced malignancies.

Our most recent program to initiate a clinical trial was EOS-215, a potential best-in-class monoclonal antibody which antagonizes TREM2. Macrophages expressing TREM2 in tumors promote tumor growth and survival. The antibody is designed to block ligand binding and alter tumor resident macrophage function resulting in anti-tumor effects. EOS-215 has been shown preclinically to have a meaningful impact on macrophage function, promoting multiple anti-tumor mechanisms including T cell activation. The therapeutic candidate's multiple mechanisms of action have been shown to translate to activity in highly immune resistant models.

On May 28, 2025, we announced our intention to wind down our clinical and operational activities. The action was taken as part of our review of strategic alternatives to maximize shareholder value following our decision to terminate the belrestotug development program and the termination of our collaboration with GSK. We are currently in the process of winding down our clinical activities and expect to complete the wind down in the third quarter of 2025.

Since our inception in August 2011, we have devoted substantially all of our resources to organizing and staffing our company, business planning, raising capital, conducting discovery and research activities, filing patent applications, identifying potential product candidates, undertaking preclinical studies and clinical trials and establishing arrangements with third parties for the manufacture of initial quantities of our product candidates and component materials. To date, we have financed our operations primarily through license and collaboration revenue generated through the GSK Collaboration Agreement and through our Initial Public Offering ("IPO"). Through June 30, 2025, we had raised an aggregate of $210.6 million of net proceeds from the IPO, $177.1 million from the sale of preferred stock, received an up-front payment of $625.0 million with respect to the GSK Collaboration Agreement, and received net proceeds of $119.7 million from the RDO. As of June 30, 2025, our principal sources of liquidity were cash and cash equivalents, which totaled $207.8 million, and available-for-sale securities, which totaled $382.2 million. In the event that the Merger (as defined below) is not consummated and we are unable to realize a strategic alternative and until such time as we are fully wound down, we expect to incur additional losses. Failure to manage discretionary spending or execute on a strategic alternative, including the Merger, will adversely impact our ability to achieve our intended business objectives. If we do not successfully consummate the Merger or other strategic transaction, the Board of Directors may decide to pursue a dissolution and liquidation of the Company.

We are also party to other collaboration and license agreements in addition to the GSK Collaboration Agreement pursuant to which we may be required to make future royalty and milestone payments. In January 2017, we entered into a collaboration agreement with Adimab, LLC ("Adimab"), pursuant to which we paid $1.0 million in 2018 to exercise an option to acquire certain licenses from Adimab. One of the antibodies licensed under this agreement is what we now refer to as belrestotug. In February 2021, we entered into an amendment to this 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, we 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. In 2022, we made a payment of $2.0 million due to reaching an additional milestone (dosing of first patient for Phase 2 clinical trial). In the fourth quarter of 2023, we obtained an exclusive licensing option from Adimab and incurred a $1.0 million option fee. We also paid a $3.0 million milestone payment in connection with the dosing of the first patient in a Phase 3 trial, which occurred in July 2024. We also paid $1.0 million to Adimab in the six months ended June 30, 2025. We will also pay Adimab low to mid single-digit percentage royalties on a country-by-country and product-by-product basis on worldwide net sales of licensed products. Through June 30, 2025, we have paid a total of $10.4 million to Adimab relating to milestones, option and other fees pursuant the Adimab Agreement.The Adimab Agreement will survive the Merger.

We are also party to a biologics master services agreement (the "WuXi Agreement"), with WuXi Biologics Hong Kong Limited ("WuXi"), pursuant to which we will pay WuXi, at our election, either a low single-digit percentage royalty on

global net sales of manufactured products or a one-time milestone payment in the low tens of millions. The WuXi Agreement will survive the Merger.

Merger Agreement with Concentra

On July 18, 2025, the Company entered into an Agreement and Plan of Merger (the "Merger Agreement") with Concentra Biosciences, LLC, a Delaware limited liability company ("Concentra"), and Concentra Merger Sub VIII, Inc., a Delaware corporation and a wholly owned subsidiary of Concentra ("Merger Sub"). The Merger Agreement provides for, among other things: (i) the acquisition of all of the Company's outstanding shares of common stock by Concentra through a tender offer (the "Offer"), for a price per share of common stock of (A) $10.047 in cash (the "Cash Amount"), subject to applicable tax withholding and without interest, plus (B) one contingent value right (a "CVR") (together with the Cash Amount, the "Offer Price"), which represents the contractual right to receive contingent payments equal to (y) 100% of the amount by which Closing Net Cash (as defined in the Merger Agreement and as finally determined pursuant to the Merger Agreement) exceeds $475 million, subject to adjustment downward for any claims or downward or upward, as applicable, for any changes in amounts accrued in the Closing Net Cash that, in each case, are not accounted for in such Closing Net Cash, and (z) 80% of the Net Proceeds (as defined in the agreement governing the CVR (the "CVR Agreement")), if any, from any sale, transfer, license or other disposition by Concentra or any of its affiliates, including the Company after the Merger, of all or any part of the Company's and its subsidiaries' (1) product candidates known as EOS-984 and EOS-215, including, in each case, any form or formulation, and any improvement or enhancement, of any such product candidate, (2) preclinical obesity program targeting ENT1, including EOS-518 and EOS-855 and any product candidate contained in or arising from such program, (3) program developing a small molecule inhibiting PTPNI1/2, and any product candidate contained in or arising from, such program, and (4) any product or product candidate covered by the claims of a patent, patent application, provisional patent application or similar instrument owned by the Company or a subsidiary of the Company as of the closing date of the Merger ((1)-(4), collectively, the "CVR Products", and the closing date of the merger, the "Merger Closing Date"), in each case that occurs within the period beginning on the Merger Closing Date and ending on the six month anniversary following the Merger Closing Date (the "Disposition Period") and (ii) the merger of Merger Sub with and into the Company (the "Merger"), with the Company surviving the Merger.

Following the completion of the Offer, upon the terms and subject to the conditions of the Merger Agreement, Merger Sub will merge with and into the Company, with the Company surviving as a wholly owned subsidiary of Concentra, pursuant to the procedure provided for under Section 251(h) of the Delaware General Corporation Law ("DGCL"), without any additional Company stockholder approvals. The Merger will be effected as soon as practicable following the time of purchase by Concentra of shares of Common Stock validly tendered and not withdrawn in the Offer.

Concentra's obligation to accept shares of common stock tendered in the Offer is subject to conditions, including: (i) that the number of shares of voting common stock validly tendered (and not properly withdrawn) prior to the expiration of the Offer (excluding shares tendered pursuant to guaranteed delivery procedures that have not yet been "received" by the "depository," as such terms are defined by Section 251(h) of the DGCL) that, when considered together with all other shares of the voting common stock (if any) owned by Concentra and its "affiliates" (as defined in Section 251(h)(6)(a) of the DGCL), equals at least one share more than 50% of all shares of voting common stock then issued and outstanding as of the expiration of the Offer; (ii) the absence of any Legal Restraint (as defined in the Merger Agreement) in effect preventing or prohibiting the consummation of the Offer, the Merger or any of the other transactions contemplated by the Merger Agreement or the CVR Agreement; (iii) the accuracy of the representations and warranties made by the Company in the Merger Agreement, subject to specified materiality qualifications and exceptions; (iv) compliance by the Company with its covenants under the Merger Agreement in all material respects; and (v) the Closing Net Cash (as defined in the Merger Agreement) shall be no less than $475 million, unless following a final determination in accordance with the Merger Agreement that Closing Net Cash is less than $475 million, the Merger Agreement has not been terminated by Concentra within five (5) business days thereafter. The obligations of Concentra and Merger Sub to consummate the Offer and the Merger under the Merger Agreement are not subject to a financing condition.

The Merger Agreement contains representations and warranties from both the Company, on the one hand, and Concentra and Merger Sub, on the other hand, customary for a transaction of this nature. The Merger Agreement also contains customary covenants and agreements, including with respect to the operations of the business of the Company between the date of the Merger Agreement and the closing of the Merger. The Merger Agreement contains customary termination rights for both Concentra and Merger Sub, on the one hand, and the Company, on the other hand, including, among others, for failure to consummate the Offer on or before October 16, 2025. If the Merger Agreement is terminated under certain circumstances specified in the Merger Agreement, including in connection with the Company's entry into an agreement with respect to a Superior Company Proposal (as defined in the Merger Agreement), the Company will be required to pay Concentra a termination fee of $8.4 million. If Concentra terminates the Merger Agreement due to the Company having Closing Net Cash of less than $475.0 million, the Company will be required to reimburse expenses incurred by Concentra up to a maximum amount of $0.5 million.

Components of our results of operations

Revenue

To date, our revenues have been derived from the upfront payment associated with the GSK Collaboration Agreement and a milestone payment achieved through this agreement. For all collaboration agreements, no development or commercial milestones were included in the transaction price at inception, as all milestone amounts were fully constrained. As part of our evaluation of the constraint, we considered numerous factors, including that receipt of the milestones is outside our control 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 were also excluded from the transaction price. We applied the royalty exception for sales-based royalties and did not recognize revenue relating to any subsequent sales of product.

Research and development expenses

Research and development expenses have consisted primarily of costs incurred for the development of our product candidates, which include:

We expense research and development costs as incurred. We recognize costs for certain development activities, such as preclinical studies and clinical trials, based on an evaluation of the progress to completion of specific tasks using information provided to us by our vendors, such as patient enrollment or clinical site activations for services received and efforts expended.

Research and development activities were central to our business model. To the extent we pursue further clinical development of any of our product candidates or any future product candidate, we would expect research and development costs to increase significantly for the foreseeable future as development programs progress and new programs are added.

Because of the numerous risks and uncertainties associated with product development, if we pursue product development in the future, we cannot determine with certainty the duration and completion costs of the current or future preclinical studies and clinical trials or if, when, or to what extent we will generate revenues from the commercialization and sale of any product candidates that receive regulatory approval. If we pursue product development in the future, we may never succeed in achieving regulatory approval for our product candidates.To the extent we pursue further clinical development of any of our product candidates or any future product candidate, the duration, costs and timing of preclinical studies and clinical trials and development of our product candidates will depend on a variety of factors, including, but not limited to:

A change in the outcome of any of these factors could mean a significant change in the costs and timing associated with the development of our current and future preclinical and clinical product candidates. For example, if the FDA or comparable foreign regulatory authority were to require us to conduct clinical trials beyond those that we currently anticipate will be required for the completion of clinical development, or if we experience significant delays in execution of or enrollment in any of our preclinical studies or clinical trials, we could be required to expend significant additional financial resources and time on the completion of preclinical and clinical development.

The following table summarizes our principal product development programs, including allocated research and development expenses allocated to each clinical product candidate:

General and administrative expenses

General and administrative expenses consist primarily of employee-related expenses, including salaries, benefits and stock-based compensation, for personnel in executive, finance, business development, facility operations and administrative functions. Other significant costs include facility costs not otherwise included in research and development expenses, legal fees relating to patent and corporate matters and fees for accounting, tax and consulting services. We expect to maintain the general and administrative function for the foreseeable future to support our operations pending the completion of the Merger, or in the event we do not complete the Merger, our planned wind down.

Grant income

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

Subsequent to June 30, 2025, we received communication from the government authorities in the Walloon Region relieving us of the substantial majority of the $7.0 million grants repayable liability. We will be required to repay $0.2 million with respect to the repayable liability, as well as a $1.5 million reimbursement for cash received in advance of related expenditures, which is recorded under deferred income on the balance sheet as of June 30, 2025.

Research and development tax credits

Our wholly owned subsidiary iTeos Belgium, as a Belgian biotechnology company, qualifies for a cash-based tax credit on research and development expenses. The credit is calculated based on a percentage of eligible research and development expenses defined by the Belgian government for each fiscal year (20.5% for 2024 and 2023) and then applying the effective tax rate to that result. The research and development tax credits are refundable to us if we are unable to use the credits to offset income taxes for the five subsequent tax years. We record a receivable and other income as the qualified expenses are incurred, as we are reasonably assured that the credit will be received, based upon our history of filing for the tax credits. Research and development tax credits receivable where we expect to receive refunds more than one year after the balance sheet date are classified as noncurrent in the condensed consolidated balance sheet.

Interest income

Interest income consists of interest earned on our available-for-sale securities, money market funds, and bank sweep accounts.

Other income (expense), net

Other income (expense), net includes income and expenses that do not fall within other categories of the statement of operations and comprehensive loss. Items included are bank fees, investment expenses, and gain or loss on foreign currency transactions.

Income taxes

We are subject to income taxes in the U.S. and Belgium. Belgium has a statutory tax rate different from the U.S. Accordingly, our effective tax rates will vary depending on the relative proportion of foreign to U.S. income, the utilization of foreign tax credits and changes in tax laws. Deferred tax assets are reduced through the establishment of a valuation allowance, if, based upon available evidence, it is determined that it is more likely than not that the deferred tax assets will not be realized.

Results of operations

Comparison of the three months ended June 30, 2025 and 2024

The following table summarizes our results of operations for the three months ended June 30, 2025 and 2024, together with the dollar change in those items:

License and collaboration revenue

We did not recognize any license and collaboration revenue for the three months ended June 30, 2025; we recognized $35.0 million of revenue in the three months ended June 30, 2024 in connection with the milestone achieved with the first dosing in the GAL-301 Phase 3 study.

Research and development expenses

Research and development expenses increased by $20.5 million to $57.3 million for the three months ended June 30, 2025, from $36.7 million for the three months ended June 30, 2024. This increase was primarily related to a $21.7 million increase in clinical and related expenses which was driven mostly by the termination payment owed to GSK. The increase was also due to a $1.5 million increase in payroll and related costs due to the research and development function's growth compared to the prior year. These increases were partially offset by a $2.0 million decrease in milestone expenses, a $0.5 million decrease in professional related fees, a $0.2 million decrease in stock-based compensation, and a $0.1 million decrease in other research and development expenses.

General and administrative expenses

General and administrative expenses decreased by $2.3 million to $10.2 million for the three months ended June 30, 2025, from $12.5 million for the three months ended June 30, 2024. This decrease was primarily related to a $2.0 million decrease in stock-based compensation, and a $0.9 million decrease in facilities and other expenses. These decreases were partially offset by an increase in professional fees of $0.3 million, and $0.2 million increase in payroll and related expenses, and a $0.1 million increase in commercial activities expense.

Restructuring costs

In the three months ended June 30, 2025, $16.4 million of restructuring costs were recorded related to severance costs incurred in the period relating to the wind-down of operations and the planned Merger.

Grant income

Grant income decreased by $0.3 million in the three months ended June 30, 2025 compared to the three months ended June 30, 2024. The decrease was due to the substantial conclusion of a recent grant in 2024 and decrease of activity for other active grants.

Interest income

Interest income decreased by $1.4 million for the three months ended June 30, 2025 compared to the three months ended June 30, 2024. The decrease was driven by decreased interest rates in the three months ended June 30, 2025 compared to the prior year, as well as a decrease in our investment base due to cash used since the prior year period.

Other (expense) income, net

The $0.6 million decrease in other (expense) income, net in the three months ended June 30, 2025 compared to the prior year period is primarily due to an increase of foreign currency exchange losses recorded in the three months ended June 30, 2025. The U.S. Dollar had more significantly weakened relative to the Euro in the three months ended June 30, 2025, as compared to the three months ended June 30, 2024.

Income tax expense

Our effective tax rates were -(2.2)% and -(46.4)% for the three months ended June 30, 2025 and 2024, respectively, which differed from the federal and foreign statutory rates of 21% and 25%, respectively. The income tax expense for the three months ended June 30, 2025 resulted primarily from additional interest accrued on the unrecognized tax benefits liability. For the three months ended June 30, 2024, income tax expense resulted primarily from investment income generated by marketable investments held by iTeos LLC, which was not consolidated for U.S. income tax purposes during that period. The Company incurred income tax expense, despite a loss before income taxes, due to taxable interest income generated by a subsidiary of iTeos Belgium which could not be offset by the net operating losses of iTeos Inc. or iTeos Belgium. In addition, for the three months ended June 30, 2024, additional interest was recorded on the unrecognized tax benefits liability.

Comparison of the six months ended June 30, 2025 and 2024

The following table summarizes our results of operations for the six months ended June 30, 2025 and 2024, together with the dollar change in those items:

License and collaboration revenue

We did not recognize any license and collaboration revenue for the six months ended June 30, 2025; we recognized $35.0 million of revenue in the six months ended June 30, 2024 in connection with the milestone achieved with the first dosing in the GAL-301 Phase 3 study.

Research and development expenses

Research and development expenses increased by $15.1 million to $86.3 million for the six months ended June 30, 2025, from $71.2 million for the six months ended June 30, 2024. This increase was primarily related to a $14.7 million increase in clinical and related expenses which was driven mostly by the termination payment owed to GSK. The increase was also due to a $3.1 million increase in payroll and related costs due to the research and development function's growth compared to the prior year. The increases were also driven by a $0.6 million increase in stock-based compensation and a $0.1 million increase in facilities expenses. These increases were partially offset by a $2.0 million decrease in milestone expenses, a $0.7 million decrease in professional related fees, and a $0.7 million decrease in other research and development expenses.

General and administrative expenses

General and administrative expenses decreased by $4.0 million to $21.2 million for the six months ended June 30, 2025, from $25.2 million for the six months ended June 30, 2024. This decrease was primarily related to a $3.4 million decrease in stock-based compensation, a $0.6 million decrease in payroll costs, a $0.4 million decrease in professional fees, and a $0.2 million decrease in facilities expense. These decreases were partially offset by an increase in commercial related and other general expenses of $0.6 million.

Restructuring costs

In the six months ended June 30, 2025, $16.4 million of restructuring costs were recorded related to severance costs incurred in the period relating to the wind-down of operations and the planned Merger.

Grant income

Grant income decreased by $0.9 million in the six months ended June 30, 2025 compared to the six months ended June 30, 2024. The decrease was due to the substantial conclusion of a recent grant in 2024 and decrease of activity for other active grants.

Interest income

Interest income decreased by $1.9 million for the three months ended June 30, 2025 compared to the three months ended June 30, 2024. The decrease was driven by decreased interest rates in the three months ended June 30, 2025 compared to the prior year, as well as a decrease in our investment base due to cash used since the prior year period.

Other (expense) income, net

The $4.1 million decrease in other (expense) income, net in the three months ended June 30, 2025 compared to the prior year period is primarily due to an increase of foreign currency exchange losses recorded in the six months ended June 30, 2025. The U.S. Dollar had significantly weakened relative to the Euro in the six months ended June 30, 2025, as compared to the six months ended June 30, 2024.

Income tax expense

Our effective tax rates were -2.5% and -10.9% for the six months ended June 30, 2025 and 2024, respectively, which differed from the federal and foreign statutory rates of 21% and 25%, respectively. The income tax expense for the six months ended June 30, 2025 resulted primarily from additional interest accrued on the unrecognized tax benefits liability. For the six months ended June 30, 2024, income tax expense resulted primarily from investment income generated by marketable investments held by iTeos LLC, which was not consolidated for U.S. income tax purposes during that period. The Company incurred income tax expense, despite a loss before income taxes, due to taxable interest income generated by a subsidiary of iTeos Belgium which could not be offset by the net operating losses of iTeos Inc. or iTeos Belgium. In addition, for the six months ended June 30, 2024, additional interest was recorded on the unrecognized tax benefits liability.

Our uncertain tax position relates to our allocation of revenue between the U.S. and Belgium under the GSK Agreement. As the uncertain tax position relates to our allocation of that revenue between the U.S. and Belgium under the GSK Agreement, the additional recognition of revenue under that agreement may increase the liability for the uncertain tax position. The unrecognized tax benefits liability increased by $1.1 million and $2.1 million during the three months ended June 30, 2025 and 2024, respectively, related to the accrual of interest expense on the liability. The unrecognized tax benefits liability increased by $2.1 million during the six months ended June 30, 2025 and 2024, related to the accrual

of interest expense on the liability. As of June 30, 2025, we had accrued interest and penalties relating to uncertain tax positions of $10.3 million, all of which was included in unrecognized tax benefits liability in the condensed consolidated balance sheet as of June 30, 2025.

Liquidity and capital resources

In June 2021, our wholly owned subsidiary, iTeos Belgium S.A., and GSK executed the GSK Collaboration Agreement, pursuant to which we agreed to grant GSK a license under certain of our intellectual property rights to develop, manufacture, and commercialize products comprised of or containing our antibody product, belrestotug. Under the GSK Collaboration Agreement, GSK made an upfront payment of $625.0 million on August 5, 2021. On May 13, 2025, we received the GSK Termination Notice. On July 18, 2025, iTeos Belgium and GSK entered into a Mutual Termination Agreement, pursuant to which iTeos Belgium will pay GSK a settlement payment of $32.0 million no later than 20 business days after receipt of an invoice from GSK. 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.

To date, we have funded our operations primarily with proceeds from the IPO, the sales of preferred stock, grants and licenses and the upfront and milestone payments from the GSK Collaboration Agreement. As of June 30, 2025, we had $207.8 million in cash and cash equivalents and $382.2 million in available-for-sale securities. In addition, on May 10, 2023, we entered into a Sales Agreement (the "Sales Agreement") with Cowen and Company LLC ("Cowen") to offer and sell shares of our common stock having an aggregate offering price of up to $125,000,000, from time to time, through an at-the-market offering program. To date we have not made any sales pursuant to the at-the-market offering program. Under the Sales Agreement, Cowen will be entitled to compensation up to 3.0% of the gross proceeds of any shares of common stock sold under the Sales Agreement. Furthermore, to date we have not generated any revenue from product sales and do not expect to generate revenue from the sales of products for the foreseeable future.

In the second quarter of 2024, we entered into a SPA with RA Capital and Boxer Capital, LLC ("Boxer Capital"), pursuant to which we agreed to sell to RA Capital a pre-funded warrant to purchase up to an aggregate of 5,714,285 shares of our common stock, and to Boxer Capital 1,142,857 shares of our common stock (together, the "Securities"). The aggregate consideration for the pre-funded warrant sold to RA Capital was $100.0 million, or $17.499 per share of common stock underlying the pre-funded warrant, which, together with the exercise price per share of underlying common stock, was equal to $17.50 per share of common stock, and the aggregate consideration for the shares of common stock sold to Boxer Capital was $20.0 million, or $17.50 per share. In aggregate, the total proceeds from the sale of the Securities to the investors is $120.0 million, partially offset by $0.4 million of costs incurred to execute the offering. In the six months ended June 30, 2025, RA Capital exercised its pre-funded warrants in full with respect to 6,613,442 shares in cashless exercises.

In addition, in the event that we receive revenue from products or services related to the intellectual property developed arising from our recoverable cash advance agreements with the Walloon Region, we must pay to the Walloon Region a 0.33% royalty on revenue related to the inupadenant grant and a 0.15% royalty on revenue on the belrestotug grant (increased from 0.12% effectively December 2021). 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 grant received. We paid the royalty in 2024 and therefore did not record a royalty accrual as of June 30, 2025.

We have historically entered into contracts in the normal course of business with CROs and clinical sites for the conduct of clinical trials, professional consultants for expert advice and other vendors for clinical supply manufacturing or other services. These contracts are not included in the table above as they provide for termination on notice, and therefore are cancelable contracts and do not include any minimum purchase commitments.

In connection with the planned Merger and winding down of operations, we expect to make additional payments subsequent to June 30, 2025, including the $32.0 million settlement payment to GSK and $24.5 million of severance costs, in addition to other expected costs as we execute the wind down.

Cash flows

The following table provides information regarding our cash flows for the six months ended June 30, 2025 and 2024:

Net cash used in operating activities

Net cash used in operating activities increased by $9.9 million in the six months ended June 30, 2025 compared to the six months ended June 30, 2024, from $76.2 million to $66.3 million. An increase in net loss of $68.0 million, driven by the $35.0 million of license and collaboration revenue recognized in the prior year and no such revenue in the current year, was offset by a net increase of $15.2 million of accrued expense for clinical trials. The primary reason for this increase in clinical expenses accrued was due to the GSK termination payment. There was also a $12.5 million increase in accrued personnel costs primarily driven by the severance related restructuring costs incurred in connection with the planned Merger. Also offsetting the increased net loss was the reduction to the unbilled milestone receivable of $35.0 million in the prior year, which was since paid in late 2024. The increase was also due to an increased employee bonus payment in the three months ended March 31, 2025 compared to the prior year. The remaining difference was due to routine increases and decrease in the remaining relevant working capital balances.

Net cash provided by (used in) investing activities

Net cash provided by (used in) investing activities changed by $81.3 million for the six months ended June 30, 2025 compared to the six months ended June 30, 2024, from $53.3 million cash used in to $134.6 million provided by investing activities. The change was primarily due to the purchase of $90.0 million of fixed income securities in the six months ended June 30, 2025, compared to $245.1 million in the six months ended June 30, 2024. The increase in purchases was offset by $225.0 million of proceeds received upon the maturities of fixed income securities during the six months ended June 30, 2025, compared to $193.2 million of proceeds received upon the maturities of fixed income securities during the six months ended June 30, 2024. The increase of cash used in investing activities was also partially offset by the purchase of $0.4 million in property and equipment and other assets during the six months ended June 30, 2025, as compared to $1.4 million in the six months ended June 30, 2024. The overall decrease in purchases in the six months ended June 30, 2025 compared to the prior year was driven by the investing strategy to pause redeployment of matured investments in the second half of the six months ended June 30, 2025.

Net cash provided by financing activities

Net cash provided by financing activities was $4.5 million and $122.4 million during the six months ended June 30, 2025 and 2024, respectively. The decrease compared to the prior year period was due to the issuance of common stock and pre-funded warrants for proceeds of $120.0 million in the six months ended June 30, 2024, which did not recur in the current year period. The decrease was partially offset by an increase in cash proceeds from stock option exercises of $4.5 million in the six months ended June 30, 2025 compared to $2.4 million in the six months ended June 30, 2024.

Effects of exchange rate changes on cash, cash equivalents and restricted cash

The change from a $2.8 million reduction to an increase of $2.7 million due to the effects of exchange rate changes on cash, cash equivalents and restricted cash from June 30, 2024 to June 30, 2025, was primarily due to the absence of returns of capital made to the Belgian entity from its subsidiary as compared to the prior year. The decrease was also due to there being a significant weakening of the U.S. Dollar to the Euro in the six months ended June 30, 2025, as compared to a strengthening of the U.S. Dollar to the Euro in the six months ended June 30, 2024.

Funding requirements

Our primary use of cash is to fund operating expenses, which has historically consistent primarily of research and development expenditures related to our clinical stage programs, belrestotug and EOS-984, and our research and preclinical development efforts. In addition to the obligations set forth under "Liquidity and Capital Resources," we also expect to have near term cash requirements associated with supporting our operations pending completion of the Merger.

In June 2021, our wholly owned subsidiary, iTeos Belgium, and GSK executed the GSK Collaboration Agreement, pursuant to which we agreed to grant GSK a license under certain of our intellectual property rights to develop, manufacture, and commercialize products comprised of or containing our antibody product, belrestotug. Under the GSK Collaboration Agreement, GSK made an upfront payment of $625.0 million on August 5, 2021. On May 13, 2025, iTeos Belgium received the GSK Termination Notice, and on July 18, 2025, iTeos Belgium and GSK entered into 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

As of June 30, 2025, we had cash and cash equivalents of $207.8 million and available-for-sale securities of $382.2 million. We believe our existing cash and cash equivalents and available-for-sale securities will enable us to fund our operating expenses and capital expenditure requirements through 2027.

We have based our projections of operating capital requirements on assumptions that may prove to be incorrect and we may use all of our available capital resources sooner than we expect. If the Merger is not completed, we may choose to resume research and development of our current or future product candidates. However, at this time, we do not believe it is likely that we would choose to resume such efforts if the Merger is not completed, and instead we would either pursue an alternative strategic transaction, if available, or a dissolution and liquidation of the Company. Because of the numerous risks and uncertainties associated with product development, and the research, development and commercialization of other potential product candidates, we are unable to estimate the exact amount of our operating capital requirements. To the extent we pursue further clinical development of any of our product candidates or any future product candidates, our future capital requirements will depend on many factors, including:

Critical accounting policies and significant judgments and estimates

Our management's discussion and analysis of our financial condition and results of operations is based on our financial statements, which we have prepared in accordance with U.S. generally accepted accounting principles. We believe that several accounting policies are important to understanding our historical and future performance. We refer to these policies as critical because these specific areas generally require us to make judgments and estimates about matters that are uncertain at the time we make the estimate, and different estimates-which also would have been reasonable-could have been used. On an ongoing basis, we evaluate our estimates and judgments, including those described in greater detail below. We base our estimates on historical experience and other market-specific or other

relevant assumptions that we believe to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying value of assets and liabilities that are not readily apparent from other sources. Actual results may differ from these estimates under different assumptions or conditions.

There have been no significant changes to our existing critical accounting policies discussed in our Annual Report on Form 10-K for the year ended December 31, 2024. We believe the following accounting policies to be most critical to the judgments and estimates used in the preparation of our financial statements:

Revenue Recognition

We historically generated revenue from our GSK Collaboration Agreement. We recognized revenue in accordance with ASC 606, which applies to all contracts with customers, except for contracts that are within the scope of other standards. Under ASC 606, we recognize revenue when our customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that we determine are within the scope of ASC 606, we perform the following five steps:

We only apply the five-step model to contracts when it is probable that the entity will collect the consideration we are entitled to in exchange for the goods or services we transfer to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, we assess the goods or services promised within each contract and determine those that are performance obligations, and assess whether each promised good or service is distinct. We then recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. We do not include a financing component in our estimated transaction price at contract inception unless we estimate that certain performance obligations will not be satisfied within one year. Additionally, we recognize the incremental costs of obtaining a contract as an expense when incurred if the amortization period of the asset that we otherwise would have recognized is one year or less.

We must develop assumptions that require judgment to determine whether the individual promises should be accounted for as separate performance obligations or as a combined performance obligation, and to determine the stand-alone selling price for each performance obligation identified in the contract. Since the upfront license was bundled with other promises, we utilized judgment to assess the nature of the combined performance obligation and determined that the combined performance obligation was satisfied over time. Revenue was recognized using a percent complete method based on costs incurred compared with the total expected costs 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 provided 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. In accordance with ASC 606, constrained variable consideration is recognized when it is probable that there will not be a significant reversal of the revenue when the uncertainty associated with the variable consideration is resolved. Revenue relating to constrained variable consideration was recognized as a cumulative catch-up in the period in which the uncertainty was resolved if the performance obligation had already been fully satisfied.

Collaborative Arrangements

We analyze our collaboration arrangements to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and are, therefore, within the scope of ASC Topic 808, Collaborative Arrangements. This assessment is performed throughout the life of the arrangement and takes into consideration changes in the responsibilities of all parties to the arrangement. For collaboration arrangements that contain multiple elements, we first determine which elements of the collaboration are deemed to be within the scope of ASC 808. We also determine if there are any elements of the arrangement in which the third party meets the definition of a customer, and would therefore fall under the scope of ASC 606. The elements accounted for under ASC 808 may include

reimbursements from and payments to parties due to the activities performed by either party. Any reimbursement from parties involved in a collaboration agreement are recorded as a reduction to research and development expense. Payments made to parties involved in a collaboration agreement are recorded as research and development expense. For the elements accounted for under ASC 606, we apply the five-step model described above.

Research and development expenses

As part of the process of preparing our financial statements, we are required to estimate our accrued research and development expenses. This process involves reviewing open contracts and purchase orders, communicating with our personnel to identify services that have been performed for us and estimating the level of service performed and the associated cost incurred for the service when we have not yet been invoiced or otherwise notified of the actual cost. The majority of our service providers invoice us monthly in arrears for services performed or when contractual milestones are met. We make estimates of our accrued expenses as of each balance sheet date in our financial statements based on facts and circumstances known to us at that time, which we periodically confirm with the service providers and make adjustments if necessary. Examples of accrued research and development expenses include fees paid to:

The preceding estimates and judgments materially affect our recognition of revenue. Changes in our estimates of forecasted development costs could impact percentage complete and could have a material effect on revenue recorded in the period in which we determine that change occurs.

Stock-based compensation expense

The fair value of stock options and Employee Stock Purchase Plan awards we grant is estimated using the Black Scholes option pricing model. This option pricing model based on certain subjective assumptions, including (i) the expected stock price volatility, (ii) the expected term of the award, (iii) the risk-free rate of interest, and (iv) expected dividends. The fair value of our common stock utilized in the model is determined based on the quoted market price of our common stock. Expected volatility is estimated considering our own historical volatility, as well as that of identified peer companies. Expected term is estimated using the simplified method per SAB 107. The risk-free rate is estimated using daily treasury curve rates. We do not issue dividends.

The fair value of restricted stock units we grant is based on the quoted market price of our common stock on the date of grant.

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

We have agreements with granting agencies whereby we receive funding under grants, which partially or fully reimburse us for eligible research and development expenditures. Certain grant agreements require us to repay the funding wherein the repayment provision of the grants is predicated on whether we decide to pursue commercial development or out licensing of the drug candidate that is produced from the results of the research program. The repayment provision includes a portion that is fixed (corresponding to 30% of the grant) which is effective after we decide to pursue commercial development or out licensing of the drug candidate. The repayment provision also includes a potential obligation to pay a royalty that is contingent upon achieving sales of a product developed through the program. The maximum amount payable to the granting agency under each grant, including the fixed repayments, the royalty on revenue, and the interest thereon, is twice the amount of funding received.

Grant funding for research and development received under grant agreements where there is a repayment provision is recognized as other income to the extent there is no present obligation to repay such funding. We record the present value of the liability as a grant repayable in the accompanying condensed consolidated balance sheets. The grant repayable is subsequently recorded at amortized cost.

Income taxes

We are subject to taxes in the U.S. and Belgium. Significant judgment is required in determining our provision for income taxes, our deferred tax assets and liabilities and any valuation allowance recorded against our net deferred tax assets. We make these estimates and judgments about our future taxable income that are based on assumptions that are consistent with our future plans. Tax laws, regulations and administrative practices may be subject to change due to

economic or political conditions including fundamental changes to the tax laws applicable to corporate multinationals. The U.S. and many countries in the European Union are actively considering changes in this regard. As of June 30, 2025 and December 31, 2024, we had recorded a full valuation allowance on our net deferred tax assets because we expect that it is more likely than not that our deferred tax assets will not be realized. Should the actual amounts differ from our estimates, the amount of our valuation allowance could be materially impacted.

Furthermore, significant judgment is required in evaluating our tax positions. In the ordinary course of business, there are many transactions and calculations for which the ultimate tax settlement is uncertain. As a result, we recognize the effect of this uncertainty on our tax attributes or taxes payable based on our estimates of the eventual outcome. These effects are recognized when, despite our belief that our tax return positions are supportable, we believe that it is more likely than not that some of those positions may not be fully sustained upon review by tax authorities. We are required to file income tax returns in the U.S. and Belgium, which requires us to interpret the applicable tax laws and regulations in effect in such jurisdictions. Such returns are subject to audit by the various federal, state and foreign taxing authorities, who may disagree with respect to our tax positions. We believe that our consideration is adequate for all open audit years based on our assessment of many factors, including past experience and interpretations of tax law. We review and update our estimates in light of changing facts and circumstances, such as the closing of a tax audit, the lapse of a statute of limitations or a change in estimate. To the extent that the final tax outcome of these matters differs from our expectations, such differences may impact income tax expense in the period in which such determination is made. The eventual impact on our income tax expense depends in part on if we still have a valuation allowance recorded against our deferred tax assets in the period that such determination is made.