iTeos Therapeutics and GSK have begun the GALAXIES Lung-301 Phase III clinical trial of belrestotug in combination with dostarlimab for the treatment of non-small cell lung cancer (NSCLC).

The double-blind, placebo-controlled study aims to compare the combination of belrestotug and dostarlimab against placebo plus pembrolizumab in patients with previously untreated, unresectable, locally advanced or metastatic PD-L1 selected NSCLC.

It will enrol around 1,000 patients in North and South America, Asia and Europe.

Progression-free survival and overall survival are the trial’s primary endpoints.

Participants will be randomised at a 1:1 ratio to receive either an intravenous infusion of the belrestotug plus dostarlimab regimen or placebo plus pembrolizumab.

Last month, iTeos published interim analysis data from the Phase II GALAXIES Lung-201 study showing that the belrestotug-dostarlimab combination surpassed the pre-defined efficacy criteria for clinically relevant activity.

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It also demonstrated an acceptable safety profile consistent with the TIGIT:PD-1 class.

In addition, the treatment regimen offered “clinically meaningful” tumour reduction at every dose compared with dostarlimab monotherapy.

iTeos Therapeutics president and CEO Michel Detheux said: “With the initiation of the first Phase III 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.

“Based on our high-quality doublet exceeding its pre-defined efficacy criteria for clinically relevant activity in an interim assessment from the Phase II GALAXIES Lung-201 study, we believe initiating the Phase III programme with this patient population will serve as the foundation to our broader strategy and marks our first step in building a franchise.”

Based in Massachusetts, iTeos currently has three clinical-stage programmes targeting novel and validated immunosuppressive pathways in its pipeline.

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