GlaxoSmithKline is advancing dostarlimab across multiple cancer indications with two significant clinical trials targeting colon and endometrial cancers, potentially expanding the therapeutic reach of this PD-1 inhibitor in oncology.
Phase 3 Colon Cancer Trial Shows Promise
GSK is currently recruiting for a Phase 3 clinical study evaluating perioperative dostarlimab monotherapy versus standard of care in participants with untreated T4N0 or Stage III dMMR/MSI-H resectable colon cancer. The open-label, randomized study follows a parallel assignment model with no masking, focusing on treatment as its primary purpose.
The study tests dostarlimab administered pre and post-surgery against standard of care treatments including FOLFOX or CAPEOX, or expectant observation post-surgery. Dostarlimab is intended to enhance treatment outcomes for patients with deficient mismatch repair (dMMR) or microsatellite instability-high (MSI-H) colon cancer.
The trial began on August 1, 2023, with an estimated completion date set for July 14, 2025. This timeline provides a clear framework for when results might influence clinical practices and market dynamics in colon cancer treatment.
Endometrial Cancer Study Explores Combination Approach
In parallel, GSK is conducting a Phase 2 clinical trial titled "A Study of Dostarlimab in Combination With Carboplatin-paclitaxel in Japanese Participants With Primary Advanced or Recurrent Endometrial Cancer." The study aims to evaluate the effectiveness of dostarlimab combined with carboplatin-paclitaxel, followed by dostarlimab monotherapy.
The intervention involves dostarlimab administered intravenously, initially at 500 mg for six cycles, then increased to 1,000 mg from the seventh cycle. Carboplatin and paclitaxel are also administered intravenously during the first six cycles. The study follows an interventional design with a single-group model and no masking.
This endometrial cancer study began on May 7, 2024, with an active but not recruiting status as of the last update on July 24, 2025.
Strategic Implications for Oncology Market
Both clinical trials represent significant opportunities for GSK to expand dostarlimab's therapeutic applications in oncology. Success in these trials could position GSK favorably against competitors in the pharmaceutical industry, particularly in the growing immunotherapy market.
The colon cancer study's focus on dMMR/MSI-H tumors aligns with the established understanding that these tumor types respond well to PD-1 inhibitors. The perioperative approach being tested could offer new treatment paradigms for resectable colon cancer patients.
For the endometrial cancer indication, the combination approach with standard chemotherapy agents carboplatin and paclitaxel represents a strategy to potentially enhance efficacy while maintaining manageable safety profiles.
