A Study of the Duration of Dostarlimab in Untreated Mismatch Repair Deficient (dMMR)/ Microsatellite Instability-high (MSI-H) Locally Advanced Rectal Cancer

NCT07740720 | Not Yet Recruiting Phase 3 FDA Drug

• 2 other identifiers: 3083602026-526683-21
• Study Type: interventional
• Target: 90
• Locations: 0 countries
• Sites: N/A

Brief Summary

This study is conducted in adults with rectal cancer that has a certain genetic type. The main goal is to find out whether a longer treatment period with dostarlimab can help more participants have a complete response to treatment and avoid standard treatments like chemotherapy, radiation treatment, or surgery. Scans and endoscopy tests will be conducted to see if the tumor disappears and how long the cancer stays under control. The study will also collect information on side effects and health outcomes after dostarlimab.

Conditions

Neoplasms, Rectal

Keywords

GSK4057190; Dostarlimab; dMMR; MSI-H; Locally advanced rectal cancer; DuraSTAR; PD-1; LARC; Anti-PD1

Outcome Measures

Primary Outcomes (1)

• Percentage of participants who achieve clinical complete response (cCR) amongst participants who receive > 9 cycles (> 6 months) of dostarlimab monotherapy by investigator assessment

  Up to 168 weeks

Secondary Outcomes (6)

• Overall cCR rate by investigator assessment

  Up to 171 weeks

• Number of participants with sustained clinical complete response at 12 months (cCR12) as assessed by investigator

  Up to 171 weeks

• Objective response rate (ORR) as assessed by investigator

  Up to 171 weeks

• Number of participants with composite cCR12 and pathologic complete response (pCR) as assessed by investigator

  Up to 171 weeks

• Time to cCR

  Up to 171 weeks

Study Arms (1)

Dostarlimab

EXPERIMENTAL

Biological: Dostarlimab

Interventions

Dostarlimab BIOLOGICAL

Dostarlimab will be administered.

Also known as: GSK4057190, dostarlimab-gxly, TSR-042

Dostarlimab

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Has histologically confirmed Stage II to III (T3-T4, N0, or T any, N+) locally advanced rectal adenocarcinoma.
• Has radiologically and endoscopically evaluable disease.
• Has a tumor demonstrating the presence of either:
• dMMR status; MMR status must be assessed by immunohistochemistry for MMR protein expression (MLH1, MSH2, MSH6, PMS2) where loss of 1 or more proteins indicates dMMR; MMR status will be determined locally; or
• MSI-H phenotype as determined by polymerase chain reaction or by tissue next generation sequencing; MSI-H will be determined locally.
• Has an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
• Has adequate organ function.

You may not qualify if:

• Has received prior radiation therapy, systemic therapy, or surgery for management of rectal cancer.
• Has a tumor that, in the investigator's judgment, is causing symptomatic bowel obstruction or otherwise requires urgent/emergent local intervention. Participants with a history of bowel obstruction are eligible after obstruction is relieved by a diverting stoma (defunctioning colostomy). Patients with a history of bowel obstruction in the context of current rectal cancer diagnosis and treated with stenting are not eligible.
• Has an active autoimmune disease that has required systemic treatment in the past 2 years (i.e., with use of disease-modifying agents, corticosteroids, or immunosuppressive drugs). Replacement therapy (e.g., thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency) is not considered a form of systemic treatment.
• Has undergone any major surgical procedure, open biopsy, or experienced significant traumatic injury within 28 days prior to enrollment.
• Is receiving any other anticancer or experimental therapy.

Sponsors & Collaborators

• GlaxoSmithKline: lead

MeSH Terms

Conditions

Rectal Neoplasms

Interventions

dostarlimab

Condition Hierarchy (Ancestors)

Colorectal Neoplasms; Intestinal Neoplasms; Gastrointestinal Neoplasms; Digestive System Neoplasms; Neoplasms by Site; Neoplasms; Digestive System Diseases; Gastrointestinal Diseases; Intestinal Diseases; Rectal Diseases

Central Study Contacts

US GSK Clinical Trials Call Center

CONTACT

877-379-3718; GSKClinicalSupportHD@gsk.com

EU GSK Clinical Trials Call Center

CONTACT

+44 (0) 20 89904466; GSKClinicalSupportHD@gsk.com

Study Design

• Study Type: interventional
• Phase: phase 3
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: July 24, 2026
• First Posted: August 3, 2026
• Study Start (Estimated): September 17, 2026
• Primary Completion (Estimated): December 12, 2029
• Study Completion (Estimated): December 31, 2029
• Last Updated: August 3, 2026

Record last verified: 2026-07

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ICF, CSR
• 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 asset(s) with development terminated across all indications.
• 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.