A Study of Belrestotug Plus Dostarlimab Compared With Placebo Plus Pembrolizumab in Previously Untreated Participants With Programmed Death Ligand 1 (PD-L1) High Non-small-cell Lung Cancer (NSCLC)

September 3, 2025 updated by: GlaxoSmithKline

A Randomized, Multicenter, Double-blind, Phase 3 Study to Investigate the Safety and Efficacy of Belrestotug in Combination With Dostarlimab Compared With Placebo in Combination With Pembrolizumab in Participants With Previously Untreated, Unresectable, Locally Advanced or Metastatic PD-L1 Selected Non-small Cell Lung Cancer (GALAXIES Lung-301)

The goal of this clinical trial is to evaluate the safety and tolerability profile of dostarlimab in combination with belrestotug when compared with pembrolizumab and placebo in participants with previously untreated, unresectable, locally advanced or metastatic PD-L1 high NSCLC.

Study Overview

Status

Active, not recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

88

Phase

  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

      • Buenos Aires, Argentina, 1425
        • GSK Investigational Site
      • Cipoletti Rio Negro, Argentina, R8324CVE
        • GSK Investigational Site
      • Ciudad Autonoma de Bueno, Argentina, C1056ABI
        • GSK Investigational Site
      • Ciudad Autonoma de Buenos Aire, Argentina, C1426AGE
        • GSK Investigational Site
      • Córdoba, Argentina, 5000
        • GSK Investigational Site
      • Florida, Argentina, 1602
        • GSK Investigational Site
      • Mendoza, Argentina, M5500AYB
        • GSK Investigational Site
      • Rosario, Argentina, S2002
        • GSK Investigational Site
      • Rosario, Argentina, S2002KDT
        • GSK Investigational Site
      • San Miguel de Tucumán, Argentina, T4000
        • GSK Investigational Site
      • Hasselt, Belgium, 3500
        • GSK Investigational Site
      • Mont Gaston, Belgium, 5530
        • GSK Investigational Site
      • Barretos, Brazil, 14784-400
        • GSK Investigational Site
      • Belém, Brazil, 66.073-005
        • GSK Investigational Site
      • CuritibaPR, Brazil, 80810-050
        • GSK Investigational Site
      • Florianópolis, Brazil, 88034-000
        • GSK Investigational Site
      • Fortaleza, Brazil, 60336-232
        • GSK Investigational Site
      • Londrina, Brazil, 86015-520
        • GSK Investigational Site
      • Porto VelhoRondOnia, Brazil, 76.834-899
        • GSK Investigational Site
      • SAo JosE Do Rio PretoSP, Brazil, 15090-000
        • GSK Investigational Site
      • Salvador, Brazil, 40414-120
        • GSK Investigational Site
      • São Paulo, Brazil, 04312903
        • GSK Investigational Site
      • Vitória, Brazil, 29043-260
        • GSK Investigational Site
      • Haskovo, Bulgaria, 6300
        • GSK Investigational Site
      • Plovdiv, Bulgaria, 4004
        • GSK Investigational Site
    • Nova Scotia
      • Halifax, Nova Scotia, Canada, B3H 1V7
        • GSK Investigational Site
      • Chengdu, China, 610000
        • GSK Investigational Site
      • Hangzhou, China, 310006
        • GSK Investigational Site
      • Hangzhou, China
        • GSK Investigational Site
      • Hefei, China, 230001
        • GSK Investigational Site
      • Nanjing, China, 210006
        • GSK Investigational Site
      • Shanghai, China, 200030
        • GSK Investigational Site
      • Kuopio, Finland, 70210
        • GSK Investigational Site
      • Turku, Finland, 20520
        • GSK Investigational Site
      • Angers, France, 49000
        • GSK Investigational Site
      • Boulogne-Billancourt, France, 92100
        • GSK Investigational Site
      • Limoges, France, 87042
        • GSK Investigational Site
      • Lorient, France, 56100
        • GSK Investigational Site
      • Pessac, France, 33064
        • GSK Investigational Site
      • Rennes, France, 35033
        • GSK Investigational Site
      • Hamburg, Germany, 20251
        • GSK Investigational Site
      • Shatin, Hong Kong
        • GSK Investigational Site
      • Ahmedabad-380016, India, 380 016
        • GSK Investigational Site
      • Apex Wellness Hospital, India, 422005
        • GSK Investigational Site
      • Bangalore, India, 560066
        • GSK Investigational Site
      • Bangalore, India, 560085
        • GSK Investigational Site
      • Belagavi, India, 590010
        • GSK Investigational Site
      • Bhubaneshwar, India, 751007
        • GSK Investigational Site
      • Bhubaneswar, India, 751019
        • GSK Investigational Site
      • Gūrgaon, India, 122001
        • GSK Investigational Site
      • Kolkata, India, 700020
        • GSK Investigational Site
      • New Delhi, India, 110075
        • GSK Investigational Site
    • Kolhapur
      • Gokul Shirgoan, Kolhapur, India, 416234
        • GSK Investigational Site
      • Aichi, Japan, 466-8560
        • GSK Investigational Site
      • Chiba, Japan, 273-8588
        • GSK Investigational Site
      • Ehime, Japan, 790-0024
        • GSK Investigational Site
      • Ehime, Japan, 791-0280
        • GSK Investigational Site
      • Fukuoka, Japan, 812-8582
        • GSK Investigational Site
      • Fukuoka, Japan, 814-0180
        • GSK Investigational Site
      • Gifu, Japan, 503-8502
        • GSK Investigational Site
      • Gunma, Japan, 377-0280
        • GSK Investigational Site
      • Hiroshima, Japan, 737-0023
        • GSK Investigational Site
      • Hokkaido, Japan, 062-0931
        • GSK Investigational Site
      • Hyōgo, Japan, 665-0827
        • GSK Investigational Site
      • Hyōgo, Japan, 670-8520
        • GSK Investigational Site
      • Kanagawa, Japan, 236-0051
        • GSK Investigational Site
      • Kyoto, Japan, 612-8555
        • GSK Investigational Site
      • Mie, Japan, 515-8544
        • GSK Investigational Site
      • Miyagi, Japan, 981-1293
        • GSK Investigational Site
      • Miyagi, Japan, 981-0914
        • GSK Investigational Site
      • Nagasaki, Japan, 852-8501
        • GSK Investigational Site
      • Niigata, Japan, 951-8566
        • GSK Investigational Site
      • Okayama, Japan, 710-8602
        • GSK Investigational Site
      • Osaka, Japan, 596-8501
        • GSK Investigational Site
      • Osaka, Japan, 591-8555
        • GSK Investigational Site
      • Tochigi, Japan, 329-0498
        • GSK Investigational Site
      • Tokyo, Japan, 104-0045
        • GSK Investigational Site
      • Tokyo, Japan, 162-8655
        • GSK Investigational Site
      • Tokyo, Japan, 113-8603
        • GSK Investigational Site
      • Tottori, Japan, 683-8504
        • GSK Investigational Site
      • Wakayama, Japan, 641-8510
        • GSK Investigational Site
      • Guadajalara, Mexico, 44280
        • GSK Investigational Site
      • La Paz BCS, Mexico, 23040
        • GSK Investigational Site
      • Mexico City, Mexico, 06700
        • GSK Investigational Site
      • San Luis Potosí City, Mexico, 78209
        • GSK Investigational Site
      • Alkmaar, Netherlands, 1815 JD
        • GSK Investigational Site
      • Enschede, Netherlands, 7512 KZ
        • GSK Investigational Site
      • Panama City, Panama
        • GSK Investigational Site
      • Punta Pacifica Panama City Panama, Panama
        • GSK Investigational Site
      • Daegu, South Korea, 41404
        • GSK Investigational Site
      • Incheon, South Korea, 21565
        • GSK Investigational Site
      • Seoul, South Korea, 02841
        • GSK Investigational Site
      • Seoul, South Korea, 03312
        • GSK Investigational Site
      • Seoul, South Korea, 05505
        • GSK Investigational Site
      • Seoul, South Korea, 08308
        • GSK Investigational Site
      • Seoul, South Korea, 120-752
        • GSK Investigational Site
      • A Coruña, Spain, 15006
        • GSK Investigational Site
      • Aravaca, Spain, 28013
        • GSK Investigational Site
      • BaracaldoVizcaya, Spain, 48903
        • GSK Investigational Site
      • Barcelona, Spain, 08025
        • GSK Investigational Site
      • Barcelona, Spain, 08035
        • GSK Investigational Site
      • Barcelona, Spain, 08003
        • GSK Investigational Site
      • Barcelona, Spain, 08023
        • GSK Investigational Site
      • Cartagena Murcia, Spain, 30202
        • GSK Investigational Site
      • Córdoba, Spain, 14004
        • GSK Investigational Site
      • Jaén, Spain, 23007
        • GSK Investigational Site
      • Las Palmas de Gran Canar, Spain, 35016
        • GSK Investigational Site
      • Madrid, Spain, 28007
        • GSK Investigational Site
      • Madrid, Spain, 28033
        • GSK Investigational Site
      • Madrid, Spain, 28010
        • GSK Investigational Site
      • Madrid, Spain, 28222
        • GSK Investigational Site
      • Málaga, Spain, 29016
        • GSK Investigational Site
      • Oviedo, Spain, 33006
        • GSK Investigational Site
      • Pamplona, Spain, 31008
        • GSK Investigational Site
      • Salamanca, Spain, 37007
        • GSK Investigational Site
      • Santander, Spain, 39008
        • GSK Investigational Site
      • Seville, Spain, 41014
        • GSK Investigational Site
      • Valladolid, Spain, 47003
        • GSK Investigational Site
      • Gävle, Sweden, SE-801 87
        • GSK Investigational Site
      • Kaohsiung City, Taiwan, 807
        • GSK Investigational Site
      • Taipei, Taiwan, 23561
        • GSK Investigational Site
      • Adana, Turkey (Türkiye), 1120
        • GSK Investigational Site
      • Ankara, Turkey (Türkiye), 06560
        • GSK Investigational Site
      • Ankara, Turkey (Türkiye), 06800
        • GSK Investigational Site
      • Istanbul, Turkey (Türkiye), 34722
        • GSK Investigational Site
    • Florida
      • Ocala, Florida, United States, 34474
        • GSK Investigational Site
    • Hawaii
      • Honolulu, Hawaii, United States, 96819
        • GSK Investigational Site
    • Kentucky
      • Lexington, Kentucky, United States, 40509
        • GSK Investigational Site
      • Lexington, Kentucky, United States, 40503
        • GSK Investigational Site
    • Michigan
      • Ann Arbor, Michigan, United States, 48106
        • GSK Investigational Site
    • Nebraska
      • Omaha, Nebraska, United States, 68114
        • GSK Investigational Site
    • Tennessee
      • Nashville, Tennessee, United States, 37203
        • GSK Investigational Site
    • Texas
      • Fort Worth, Texas, United States, 76104
        • GSK Investigational Site
    • Washington
      • Olympia, Washington, United States, 98506
        • GSK Investigational Site

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Has a histologically or cytologically confirmed diagnosis of locally advanced, unresectable NSCLC (not eligible for curative surgery and/or definitive radiotherapy with or without chemotherapy), or Metastatic NSCLC
  • Has not received prior systemic therapy for their locally advanced or metastatic NSCLC.
  • Provides a fresh tumor tissue sample obtained at the time of or after the initial diagnosis of locally advanced or metastatic NSCLC.
  • Has a PD-L1-high (Tumor cells [TC] ≥50%) tumor
  • Has measurable disease (at least 1 target lesion) based on RECIST 1.1
  • Has an Eastern Cooperative Oncology Group (ECOG) Performance status (PS) score of 0 or 1.
  • Has adequate organ function

Exclusion Criteria:

  • Has NSCLC with a tumor that harbors any of the following molecular alterations:

    1. Epidermal growth factor receptor (EGFR) mutations that are sensitive to available targeted inhibitor therapy
    2. Anaplastic lymphoma kinase (ALK) translocations that are sensitive to available targeted inhibitor therapy
    3. Any other known genomic aberrations or oncogenic driver mutations for which a locally approved targeted therapy is available for first line treatment of locally advanced or metastatic NSCLC.
  • Has had surgery within 4 weeks of the first dose of study intervention and has not recovered from AEs (i.e., has any ongoing surgery-related events ≥ Grade 1)/complications related to surgery or has received lung radiation therapy of >30 gray (Gy) within 6 months
  • Has received prior therapy with any immune checkpoint inhibitors, including antibodies or drugs targeting PD-(L)1, Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), T cell immunoglobulin and ITIM domain (TIGIT), or other checkpoint pathways.
  • Has never smoked, defined as smoking <100 tobacco cigarettes in a lifetime.
  • Has an invasive malignancy or history of invasive malignancy other than the disease under study within the last 5 years, with the exception of those with a negligible risk of metastasis or death and/or treated with expected curative outcome.
  • Has symptomatic, untreated, or actively progressin g brain metastases or leptomeningeal disease
  • Has autoimmune disease or syndrome (current or history thereof) that required systemic treatment within the past 2 years.
  • Has received any live vaccine within 30 days prior to first dose of study intervention.
  • Has any history of idiopathic pulmonary fibrosis, organizing pneumonia, drug induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis.
  • Has symptomatic ascites, pleural effusion, or pericardial effusion.
  • Has active inflammatory bowel disease
  • Has a history of significant acute or chronic cardiac diagnosis requiring intervention/treatment in the last 6 months.
  • Has severe infection or complication thereof 4 weeks prior to randomisation including active tuberculosis.
  • Has a history of allogeneic tissue/stem cell transplant or solid organ transplant.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: Dostarlimab plus belrestotug
Dostarlimab will be administered.
Belrestotug will be administered.
Active Comparator: Pembrolizumab plus placebo
Placebo will be administered.
Pembrolizumab will be administered.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
Number of Participants with Treatment Emergent Adverse Events (TEAEs) and Serious Adverse Events (SAEs)
Time Frame: Up to approximately 138 weeks
Up to approximately 138 weeks
Number of Participants with TEAEs or SAEs leading to dose withdrawals or treatment discontinuation
Time Frame: Up to approximately 138 weeks
Up to approximately 138 weeks

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Objective Response Rate (ORR)
Time Frame: Up to approximately 5 years
ORR is defined as the percentage of participants achieving confirmed complete response (CR) or confirmed partial response (PR) per RECIST version 1.1 by investigator assessment.
Up to approximately 5 years
Molecular Response Rate (MRR)
Time Frame: Up to approximately 5 years
MRR is defined as the percentage of participants with a molecular response (i.e., a greater than or equal to 50% reduction in Circulating tumor deoxyribonucleic acid (ctDNA) levels relative to baseline).
Up to approximately 5 years
PFS per RECIST 1.1 by investigator assessment
Time Frame: Up to approximately 5 years
PFS per RECIST 1.1 by investigator assessment, defined as the time from the date of randomization to the date of first documented PD or death due to any cause, whichever comes first.
Up to approximately 5 years
Duration of Response (DOR)
Time Frame: Up to approximately 5 years
DOR per RECIST v 1.1 by investigator assessment, defined as the time from the date of first confirmed response (CR or PR) to the date of first documented PD or death due to any cause, whichever comes first.
Up to approximately 5 years
Time to first subsequent therapy (TFST)
Time Frame: Up to approximately 5 years
TFST is defined as the time from the date of randomization to the date of the first subsequent anticancer therapy or death, whichever occurs first.
Up to approximately 5 years
Number of Participants with Treatment Emergent Adverse Events (TEAEs), Serious Adverse Events (SAEs) and Adverse Events of Special Interest (AESIs)
Time Frame: Up to approximately 5 years
Up to approximately 5 years
Number of Participants with TEAEs or SAEs leading to dose modifications or study intervention discontinuation
Time Frame: Up to approximately 5 years
Up to approximately 5 years
Time to Deterioration (TTD) of lung cancer symptoms
Time Frame: Up to approximately 5 years
TTD of lung cancer symptoms is defined as time from randomization to the first confirmed clinically meaningful deterioration as assessed by the Non-Small Cell Lung Cancer Symptom Assessment Questionnaire (NSCLC SAQ) total score. The NSCLC-SAQ is a 7-item instrument that assesses symptoms relevant to NSCLC. It contains five domains and accompanying items that are identified as symptoms of NSCLC: cough (1 item), pain (2), dyspnea (1), fatigue (2), and appetite (1). The (total) lowest score possible is 0, and the highest (total) score possible is 20. Higher scores indicate more severe symptoms.
Up to approximately 5 years
TTD in physical functioning
Time Frame: Up to approximately 5 years
TTD in physical functioning is defined as time from randomization to the first confirmed clinically meaningful deterioration as assessed by the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire 30-item Core Module (EORTC QLQ C30). The EORTC QLQ C30 is a 30-item questionnaire. Participant responses will be scored in a range of 0-100. A higher value indicates a better level of physical function.
Up to approximately 5 years
Number of participants with anti-drug antibodies (ADA) against Dostarlimab
Time Frame: Up to approximately 5 years
Up to approximately 5 years
Number of participants with ADA against Belrestotug
Time Frame: Up to approximately 5 years
Up to approximately 5 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Collaborators

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

June 10, 2024

Primary Completion (Estimated)

February 2, 2027

Study Completion (Estimated)

February 2, 2027

Study Registration Dates

First Submitted

June 18, 2024

First Submitted That Met QC Criteria

June 18, 2024

First Posted (Actual)

June 24, 2024

Study Record Updates

Last Update Posted (Estimated)

September 10, 2025

Last Update Submitted That Met QC Criteria

September 3, 2025

Last Verified

September 1, 2025

More Information

Terms related to this study

Other Study ID Numbers

  • 213823

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Qualified researchers may request access to anonymized individual patient-level data (IPD) and related study documents of the eligible studies via the Data Sharing Portal. Details on GSK's data sharing criteria can be found at: https://www.gsk.com/en-gb/innovation/trials/data-transparency/

IPD Sharing Time Frame

Anonymized IPD will be made available within 6 months of publication of primary, key secondary and safety results for studies in product with approved indication(s) or terminated asset(s) across all indications.

IPD Sharing Access Criteria

Anonymized IPD is shared with researchers whose proposals are approved by an Independent Review Panel and after a Data Sharing Agreement is in place. Access is provided for an initial period of 12 months but an extension may be granted, when justified, for up to 6 months.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • ICF
  • CSR

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

Yes

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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