Dostarlimab Meets Primary End Point in Registrational AZUR-1 Trial for dMMR/MSI-H Rectal Cancer
Results from the Phase 2 AZUR-1 Trial
Results from the Phase 2 AZUR-1 Trial
Clinical Summary:
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Design/Population: The registrational phase 2 AZUR-1 trial evaluated dostarlimab monotherapy in patients with stage II/III mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) locally advanced rectal cancer.
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Key Outcomes: At the prespecified interim analysis, the trial met its primary end point, demonstrating a durable 12-month clinical complete response. The safety profile was consistent with previous studies of dostarlimab, with no new safety signals identified.
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Clinical Relevance: These findings support dostarlimab as a potential organ-preserving treatment strategy for patients with dMMR/MSI-H locally advanced rectal cancer and may allow selected patients to avoid chemotherapy, radiation, and surgery pending regulatory review.
Interim results from the registrational phase 2 AZUR-1 trial demonstrated that dostarlimab (Jemperli; GSK) monotherapy achieved durable clinical complete responses in patients with stage II/III mismatch repair-deficient (dMMR)/microsatellite instability-high (MSI-H) locally advanced rectal cancer, supporting the PD-1 inhibitor as a potential organ-preserving treatment strategy.
In this open-label, single-arm trial, 154 patients received 500 mg of intravenous dostarlimab every 3 weeks for 9 cycles over a 6-month treatment period. The primary end point was sustained clinical complete response at 12 months, assessing whether treatment with dostarlimab alone could enable patients to avoid chemotherapy, radiotherapy, and surgery.
At the prespecified interim analysis, the study met its primary end point by demonstrating a durable 12-month clinical complete response. According to GSK, the findings exceeded historical outcomes reported with standard multimodality therapy and build on earlier investigator-initiated research from Memorial Sloan Kettering Cancer Center evaluating PD-1 blockade in this molecular subtype.
The safety profile of dostarlimab was consistent with previous studies across solid tumors, and no new safety signals were identified.
Based on these findings, GSK plans to submit the interim AZUR-1 data to global regulatory authorities, including the US Food and Drug Administration (FDA), to support regulatory review. Dostarlimab has previously received Breakthrough Therapy and Fast Track designations from the FDA for patients with dMMR/MSI-H locally advanced rectal cancer.
If approved, dostarlimab would become the first immunotherapy specifically indicated to potentially eliminate or delay the need for chemotherapy, radiation, and surgery in selected patients with dMMR/MSI-H locally advanced rectal cancer.
Source:
GSK. Jemperli (dostarlimab) achieves sustained clinical complete responses in dMMR/MSI-H locally advanced rectal cancer. Accessed on July 15, 2026. https://www.gsk.com/en-gb/media/press-releases/jemperli-dostarlimab-achieves-sustained-clinical-complete-responses-in-dmmrmsi-h-locally-advanced-rectal-cancer/
