LONDON, United Kingdom, July 13, 2026
GSK has announced positive interim results from the registrational Phase II AZUR-1 clinical trial, demonstrating that Jemperli (dostarlimab) achieved sustained clinical complete responses (cCR) in patients with stage II/III mismatch repair-deficient/microsatellite instability-high (dMMR/MSI-H) locally advanced rectal cancer. The study successfully met its primary endpoint, showing a clinically meaningful proportion of patients remained free of detectable cancer for at least 12 months following treatment with dostarlimab monotherapy. These findings suggest that Jemperli has the potential to become the first immunotherapy capable of eliminating or delaying chemotherapy, radiation therapy, and surgery for selected patients with this difficult-to-treat cancer subtype. GSK plans to submit the interim data to global regulatory authorities, including the U.S. Food and Drug Administration (FDA) under its accelerated review pathway, marking an important milestone in the advancement of precision immunotherapy for gastrointestinal cancers.
AZUR-1 Trial Demonstrates Sustained Complete Responses
The AZUR-1 study is a global, open-label, single-arm, registrational Phase II clinical trial evaluating Jemperli (dostarlimab) as a standalone treatment for patients with stage II/III dMMR/MSI-H locally advanced rectal cancer. A total of 154 participants received nine treatment cycles over six months through intravenous administration every three weeks. The trial achieved its primary objective by demonstrating sustained clinical complete responses at 12 months (cCR12), indicating that many patients experienced no detectable evidence of cancer after completing immunotherapy. Investigators also reported that the safety and tolerability profile remained consistent with previously established data across multiple solid tumors, with no unexpected safety concerns observed during the interim analysis. These encouraging findings build upon earlier clinical research conducted with Memorial Sloan Kettering Cancer Center, which first highlighted the transformative potential of PD-1 blockade in this patient population.
Potential to Transform Standard Rectal Cancer Treatment
Approximately 730,000 people worldwide are diagnosed with rectal cancer annually, with 5–10% of tumors classified as dMMR/MSI-H, a molecular subtype highly responsive to immune checkpoint inhibition. Current standard treatment generally combines chemotherapy, radiation therapy, and surgery, interventions that can result in permanent colostomy, bowel dysfunction, infertility, and substantial reductions in long-term quality of life. The positive AZUR-1 results suggest that Jemperli could fundamentally change this treatment paradigm by enabling some patients to avoid these invasive therapies while maintaining durable cancer control. The investigational therapy has already received Breakthrough Therapy Designation and Fast Track Designation from the U.S. FDA for this indication, reflecting the urgent need for innovative treatment options capable of improving survival while preserving patient quality of life.
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Strengthening GSK’s Leadership in Immuno-Oncology
The successful interim analysis reinforces GSK’s expanding leadership in precision oncology and immunotherapy innovation. Jemperli, a PD-1 immune checkpoint inhibitor, serves as a cornerstone of GSK’s growing oncology pipeline, with ongoing development across gynecologic, colorectal, head and neck, and other solid tumors. By targeting tumors characterized by mismatch repair deficiency and microsatellite instability, the therapy leverages the body’s immune system to generate durable anti-cancer responses while minimizing the need for conventional treatment modalities. Although Jemperli is not yet approved for rectal cancer, the compelling AZUR-1 data provide strong clinical evidence supporting future regulatory submissions and broader clinical adoption. If approved, the therapy could redefine the treatment landscape for dMMR/MSI-H locally advanced rectal cancer, offering patients a highly effective, organ-preserving immunotherapy option capable of transforming long-term clinical outcomes and improving quality of life.
Source: GSK press release
