ITOS iTeos Therapeutics Inc

iTeos Therapeutics, Inc. (Nasdaq: ITOS) (“iTeos”), a clinical-stage biopharmaceutical company pioneering the discovery and development of a new generation of immuno-oncology therapeutics for patients, and its development partner GSK, have initiated the first, global Phase 3 registration study of belrestotug + dostarlimab doublet versus placebo + pembrolizumab in patients with previously untreated, unresectable, locally advanced or metastatic PD-L1 selected non-small cell lung cancer (NSCLC).

“With the initiation of the first Phase 3 study for belrestotug, we are entering a monumental stage in our journey to develop a world-leading oncology company. Nearly 70% of patients with first-line PD-L1 high non-small cell lung cancer rely upon a chemotherapy-free regimen. We believe belrestotug + dostarlimab are poised to potentially advance the therapeutic regimen in this setting and establish new benchmarks,” said Michel Detheux, Ph.D., president and chief executive officer of iTeos. “Based on our high-quality doublet exceeding its pre-defined efficacy criteria for clinically relevant activity in an interim assessment from the Phase 2 GALAXIES Lung-201 study, we believe initiating the Phase 3 program with this patient population will serve as the foundation to our broader strategy and marks our first step in building a franchise.”

The randomized, double-blind, placebo-controlled, multicenter trial will enroll approximately 1,000 patients with previously untreated, unresectable, locally advanced or metastatic PD-L1 selected NSCLC in North America, South America, Europe and Asia. The primary endpoints of the trial are progression free survival and overall survival. In the GALAXIES Lung-301 trial, patients will be randomized 1:1 to either an intravenous infusion of the belrestotug + dostarlimab doublet or placebo + pembrolizumab.

In May 2024, iTeos announced an interim assessment of the Phase 2 GALAXIES Lung-201 study of the belrestotug + dostarlimab doublet in previously untreated, locally advanced, or metastatic PD-L1 selected NSCLC exceeded pre-defined efficacy criteria for clinically relevant activity and showed an acceptable safety profile in line with the TIGIT:PD-1 class. Clinically meaningful tumor reduction was observed at every belrestotug + dostarlimab dose vs dostarlimab monotherapy.

About iTeos Therapeutics, Inc.iTeos Therapeutics is a clinical-stage biopharmaceutical company pioneering the discovery and development of a new generation of immuno-oncology therapeutics for patients. iTeos Therapeutics leverages its deep understanding of tumor immunology and immunosuppressive pathways to design novel product candidates with the potential to restore the immune response against cancer. The Company’s innovative pipeline includes three clinical-stage programs targeting novel, validated immunosuppressive pathways designed with optimized pharmacologic properties for improved clinical outcomes, including the TIGIT/CD226 axis and the adenosine pathway. iTeos Therapeutics is headquartered in Watertown, MA with a research center in Gosselies, Belgium.

About Belrestotug (EOS-448/ GSK4428859A)Belrestotug is an Fc active human immunoglobulin G1, or IgG1, monoclonal antibody (mAb) targeting T cell immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT), an important inhibitory receptor which contributes to the suppression of innate immune responses against cancer. As an optimized high-affinity, potent anti-TIGIT mAb, belrestotug is designed to enhance the antitumor response through a multifaceted immune modulatory mechanism by engaging with TIGIT and FcγR, a key regulator of immune responses which induces cytokine release and antibody dependent cellular cytotoxicity (ADCC). The therapeutic candidate is progressing in multiple indications in collaboration with GSK.

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Forward-Looking StatementsThis press release contains forward-looking statements. Any statements that are not solely statements of historical fact are forward-looking statements. Words such as “believe,” “anticipate,” “plan,” “expect,” “will,” “may,” “intend,” “prepare,” “look,” “potential,” “possible” and similar expressions are intended to identify forward-looking statements. These forward-looking statements include statements relating to our belief that belrestotug + dostarlimab are poised to potentially advance the therapeutic regimen in the first-line PD-L1 high non-small cell lung cancer setting and establish new benchmarks; and our belief that initiating the Phase 3 program with this patient population will serve as the foundation to our broader strategy and building a franchise.

These forward-looking statements involve risks and uncertainties, many of which are beyond iTeos’ control. Actual results could materially differ from those stated or implied by these forward-looking statements as a result of such risks and uncertainties. Known risk factors include the following: success in early clinical trials does not ensure that later clinical trials will be successful, and early results from a clinical trial do not necessarily predict final results; interim and early data may change as more patient data become available and are subject to audit and verification procedures; the expected benefits and opportunities related to the agreement between iTeos and GSK may not be realized or may take longer to realize due to a variety of reasons, including challenges and uncertainties inherent in product research and development and manufacturing limitations; and those risks identified under the heading “Risk Factors” in iTeos’ Quarterly Report on Form 10-Q for the period ended March 31, 2024 filed with the Securities and Exchange Commission (SEC) as well as other SEC filings made by the Company which you are encouraged to review.

Any of the foregoing risks could materially and adversely affect iTeos’ business, results of operations and the trading price of iTeos’ common stock. We caution investors not to place undue reliance on the forward-looking statements contained in this press release. iTeos does not undertake any obligation to publicly update its forward-looking statements other than as required by law.

For further information, please contact:

Investor Contact:Carl MauchiTeos Therapeutics, Inc.carl.mauch@iteostherapeutics.com

Media Contact:media@iteostherapeutics.com