On July 13, 2026 GSK plc (LSE/NYSE: GSK) reported positive interim results from the registrational phase II AZUR-1 trial of Jemperli (dostarlimab) in patients with stage II/III mismatch repair deficient/microsatellite instability-high (dMMR/MSI-H) locally advanced rectal cancer. The single arm trial met its primary objective, showing a meaningful and sustained clinical complete response rate at 12 months (cCR12).
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These results support the potential for dostarlimab, if approved, to become the first immunotherapy capable of eliminating or delaying the need for chemotherapy, radiation and surgery for some patients in this population.
Rectal cancer, a type of bowel cancer, affects around 730,000 people globally each year1 and approximately 5-10% of all rectal cancers have the dMMR/MSI-H subtype2. Current standard of care typically includes chemotherapy, radiation, and surgery3. While often effective, these treatments can profoundly impact a patient’s quality of life, potentially leading to lifelong use of a colostomy bag, significant physiological dysfunction, and infertility4,5,6.
Hesham Abdullah, Senior Vice President, Global Head Oncology, R&D, GSK, said: "The AZUR-1 results support the potential for dostarlimab to transform treatment for dMMR/MSI-H locally advanced rectal cancer. For many patients today, rectal cancer treatment comes with the tolerability burden and lasting impacts from chemotherapy, radiation and surgery. These data demonstrate that some patients may be able to avoid those interventions while remaining free of detectable signs of cancer."
AZUR-1 results represent a substantial improvement compared to the historical standard of care7 and build on earlier research conducted in collaboration with Memorial Sloan Kettering Cancer Center, which first demonstrated the potential for dostarlimab to achieve clinical complete responses without other treatments in patients with dMMR/MSI-H locally advanced rectal cancer.
In interim data, the safety and tolerability profile of dostarlimab was consistent with its well-characterised and manageable safety profile observed across solid tumours.
Dostarlimab has received both Breakthrough Therapy and Fast Track designations from the US Food and Drug Administration (FDA) in this setting. GSK plans to share interim AZUR-1 data with global regulatory authorities to support review. Detailed results will be presented at a future scientific congress.
About stage II/III dMMR/MSI-H locally advanced rectal cancer
Around 5–10% of rectal cancers are mismatch repair-deficient (dMMR) or microsatellite instability-high (MSI-H)8. These tumours have a specific genetic characteristic where they are unable to properly repair DNA damage, leading to an accumulation of mutations. This unique biological feature often makes them highly responsive to immunotherapies like dostarlimab9,10. These biomarkers are most commonly found in colorectal, endometrial and other gastrointestinal cancers, but can also be present in other solid tumours11.
About AZUR-1
AZUR-1 is a global, open-label, single-arm, registrational phase II trial evaluating dostarlimab monotherapy in patients with stage II/III dMMR/MSI-H locally advanced rectal cancer. The trial was designed to assess sustained clinical complete responses for 12 months (cCR12) and determine whether dostarlimab alone could enable patients to avoid chemotherapy, radiation and/or surgery. A total of 154 participants received nine cycles of dostarlimab over six months, administered as a 500 mg intravenous infusion every three weeks.
About Jemperli (dostarlimab)
Jemperli, a programmed death receptor-1 (PD-1)-blocking antibody, is the backbone of GSK’s ongoing immuno-oncology-based research and development programme. A robust clinical trial programme includes studies of Jemperli alone and in combination with other therapies in gynaecologic, colorectal and head and neck cancers, as well as where there are opportunities for transformational outcomes.
Jemperli was discovered by AnaptysBio, Inc. and licensed to TESARO, Inc., under a collaboration and exclusive license agreement signed in March 2014. Under this agreement, GSK is responsible for the ongoing research, development, commercialisation, and manufacturing of Jemperli.
More information about Jemperli, its indications and complete important safety information is available at EU product information12 and US product information13. Jemperli is not currently approved anywhere in the world for rectal cancer.
(Press release, GlaxoSmithKline, JUL 13, 2026, View Source [SID1234669169])