GSK Wins FDA Approval for its Locally Advanced Rectal Cancer Immunotherapy

The accelerated approval of dostarlimab (Jemperli) could allow eligible patients with biomarker-defined rectal cancer to avoid chemotherapy, radiotherapy, and surgery.

GSK has announced that it has secured U.S. approval for dostarlimab (Jemperli) as the first and only immunotherapy for adults with stage II or III microsatellite instability-high/mismatch repair-deficient (MSI-H/dMMR) locally advanced rectal cancer. The U.S. FDA granted the indication under its accelerated approval pathway (1).

MSI-H/dMMR tumors carry defects in DNA mismatch repair and causing mutations to accumulate. The biomarker is present in an estimated 5–10% of rectal cancers and is associated with strong responses to PD-1-blocking immunotherapies such as dostarlimab.

The regulatory decision has been based on the Phase II AZUR-1 trial, which evaluated dostarlimab monotherapy in 154 patients with previously untreated disease. In investigator-assessed data, 68% of evaluable patients achieved a clinical complete response sustained for 12 months, while an exploratory analysis found that 76% had no detectable evidence of cancer one year or more after treatment.

Notably, 98 patients achieved a 12-month complete response without surgery, while 12 others had a pathological complete response confirmed through tissue analysis after surgery. GSK said no disease recurrences had been reported among responders after a median follow-up of more than two years, although data from the trial’s independently assessed primary endpoint are still maturing.

“[With this decision], Jemperli becomes the first and only approved immunotherapy for adults in the U.S. with MSI-H/dMMR locally advanced rectal cancer,” said Tony Wood, Chief Scientific Officer, GSK, in a company press release (1). “For decades, treatment [for MSI-H/dMMR] has relied on chemotherapy, radiation, and surgery. This approval offers a new treatment approach and represents an important step towards more personalized care for these patients.”

The approval of dostarlimab is expected to be welcomed by patients with the disease, who, until now, could only undergo chemotherapy, radiotherapy, and surgery as treatment options. These interventions are known to cause long-term bowel, urinary and sexual dysfunction, infertility, and secondary cancers, making an organ-preserving, biomarker-guided approach potentially significant for eligible patients.

Jemperli is a PD-1-blocking antibody that helps the immune system recognize and attack cancer cells. In the AZUR-1 trial, patients received nine intravenous 500 mg doses every three weeks over the course of six months. The safety profile was broadly consistent with Jemperli’s established profile in solid tumors: serious adverse reactions occurred in 20% of patients, with fatigue, rash, diarrhea, and pruritus among the most common adverse reactions.

“The AZUR-1 results demonstrate the potential for a fundamentally different treatment approach in this biomarker-defined patient population, and [this] approval means MSI-H/dMMR patients can now access a licensed treatment tailored to the biology of their disease,” added Dr. Andrea Cercek, MD, Principal Investigator of AZUR-1, Section Head of Colorectal Cancer and Co-Director of the Center for Young Onset Colorectal and Gastrointestinal Cancer, Memorial Sloan Kettering Cancer Center, in the press release (1).

FDA granted the program Fast Track and Breakthrough Therapy designations, along with Priority Review and a National Priority Voucher. The supplemental biologics license application is also being reviewed through Project Orbis — an FDA Oncology Center of Excellence initiative that enables concurrent review by international health authorities.

This regulatory decision reinforces GSK’s push to broaden its oncology presence beyond blood cancers and women’s cancers into gastrointestinal and other solid tumors. The company has recently expanded its oncology pipeline through partnerships and acquisitions, including last year’s deal with LTZ Therapeutics to develop next-generation immunotherapies (2), and a recent agreement to acquire Nuvalent for late-stage lung cancer assets (3).

References

1. GSK. Jemperli (Dostarlimab) Approved in US as First and Only Immunotherapy for Adults with MSI-H/dMMR Locally Advanced Rectal Cancer. Press Release, Oct. 19, 2026.
2. GSK. GSK and LTZ Announce Strategic Collaboration to Advance Novel Myeloid Cell Engagers in Oncology. Press Release, Nov. 19, 2025.
3. GSK. GSK Completes Acquisition of Nuvalent, Inc. Press Release, July 15, 2026.