London, United Kingdom, October 24, 2026
GSK has reported encouraging clinical data showing that 76% of evaluable patients with microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) locally advanced rectal cancer achieved a complete response with Jemperli (dostarlimab) alone. The latest interim results from the Phase 2 AZUR-1 trial were announced ahead of presentation at the European Society for Medical Oncology (ESMO) Congress 2026. Among 144 evaluable patients with previously untreated stage II or III disease, 110 achieved a complete response following treatment with dostarlimab. Notably, no disease recurrences had been reported among responders after a median follow-up of more than two years, according to the company. The findings strengthen the evidence supporting immunotherapy as a potential organ-preserving treatment option for appropriately selected patients. The results also build on the recent U.S. regulatory approval of Jemperli for this indication, representing a significant development in the management of a molecularly defined subgroup of rectal cancer.
AZUR-1 Trial Demonstrates Complete Response Potential
The global, open-label AZUR-1 Phase 2 clinical trial evaluates Jemperli as a standalone treatment for adults with previously untreated stage II and III MSI-H/dMMR locally advanced rectal cancer. In the latest exploratory analysis, 76% of evaluable patients (110 of 144) achieved a complete response, meaning that no evidence of cancer was identified through the relevant clinical assessments. This group included 98 patients, or 68% of those evaluated, who achieved a clinical complete response sustained for at least 12 months without surgery. Another 12 patients had their complete response confirmed through tissue analysis following surgery, known as a pathological complete response. The trial’s primary endpoint focuses on a sustained clinical complete response at 12 months, assessed through independent central review. At the time of analysis, 54 of 116 evaluable patients, or 47%, had achieved this endpoint, while another 38 patients had already achieved a clinical complete response but had not yet completed the required 12-month assessment period. These results indicate substantial clinical activity, although the different response measures and assessment populations should not be treated as interchangeable. Continued follow-up will be important for confirming the durability of responses and understanding long-term outcomes.
Jemperli May Help Eligible Patients Avoid Major Surgery
Jemperli contains dostarlimab, a monoclonal antibody that blocks the programmed cell death protein 1 (PD-1) immune checkpoint. By blocking this pathway, the medicine helps restore immune-cell activity against cancer cells. The approach is particularly relevant to MSI-H/dMMR tumors, which have defects in their DNA mismatch repair system and tend to accumulate genetic mutations. These mutations can make tumors more recognizable to the immune system and potentially more responsive to immunotherapy. Standard treatment for locally advanced rectal cancer commonly involves chemotherapy, radiation therapy and surgery. Although these treatments can control disease, they may also cause lasting effects on bowel, urinary and sexual function, fertility and quality of life. Dostarlimab alone may allow some eligible patients to avoid or delay these interventions if they achieve a sustained complete response and are managed through appropriate specialist monitoring. However, a complete response does not automatically establish a cure, and non-operative management requires careful follow-up to detect any returning disease. Treatment decisions must be individualized by a qualified multidisciplinary oncology team.
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Safety Findings and Regulatory Progress
The safety profile reported in AZUR-1 was generally consistent with the established safety profile of dostarlimab across solid tumors. Serious adverse reactions occurred in 20% of patients, while the most commonly reported adverse reactions included fatigue, rash, diarrhea and itching. The medicine was permanently discontinued because of adverse reactions in 3% of patients. As with other immune checkpoint inhibitors, clinicians must monitor for immune-mediated adverse reactions that can affect different organs and may require prompt treatment. GSK reported that the AZUR-1 findings supported the recent U.S. approval of Jemperli for adults with MSI-H/dMMR locally advanced rectal cancer. Regulatory reviews in other participating countries are ongoing through Project Orbis, which facilitates coordinated reviews by international health authorities. The trial remains important for generating additional evidence about response durability, safety and the potential to preserve rectal function without conventional chemoradiotherapy and surgery. The 76% complete response finding is promising, but it should be interpreted in the context of the study design, response definitions and ongoing follow-up. Further clinical evidence will help clarify which patients are most likely to benefit from this immunotherapy-based approach.
Source: GSK press release
