Dostarlimab approved in the US for MSI-H/dMMR rectal cancer
GSK has received US Food and Drug Administration approval for dostarlimab (Jemperli) as a treatment for adults with stage II and III microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) locally advanced rectal cancer. The agency granted the antibody Fast Track and Breakthrough Therapy designations for the indication, and the supplemental biologics licence application also received Priority Review and a National Priority Voucher, bringing the approval forward from a February 2027 PDUFA date.
The approval marks the first time an immunotherapy has received a dedicated US label in this rectal cancer setting. The MSI-H/dMMR biomarker is present in roughly 5% to 10% of rectal cancers, meaning only a subset of patients will be eligible, but the potential to spare those patients from the standard-of-care sequence of chemotherapy, radiation and surgery is clinically significant. Long-term consequences of conventional treatment can include bowel, urinary and sexual dysfunction, secondary malignancies and infertility.
AZUR-1 trial results
The approval rests on data from the AZUR-1 trial. Investigator-assessed results showed 68% of evaluable patients (98 of 144; 95% confidence interval: 60% to 76%) achieved a sustained clinical complete response at 12 months, the study's primary objective. An exploratory analysis found 76% of evaluable patients (110 of 144; 95% CI: 69% to 83%) had no evidence of disease one year or more after treatment, incorporating patients who achieved a complete response without surgery and those confirmed by post-surgical tissue analysis. Notably, no disease recurrences have been reported among responders after a median follow-up of more than two years, though independent central review data on the primary endpoint continue to mature, with 47% of evaluable patients having met the cCR12 threshold in that analysis so far.
The safety profile was broadly consistent with dostarlimab's established record across solid tumours. Serious adverse reactions occurred in 20% of patients; the most frequently reported events were fatigue (32%), rash (22%), diarrhoea (18%) and pruritus (17%). Permanent discontinuation due to adverse reactions was recorded in 3% of patients.
GSK plans to present the full AZUR-1 interim analysis as a late-breaking abstract at ESMO Congress 2026 in Madrid on 25 October 2026. The supplemental BLA is also being reviewed under Project Orbis, the FDA Oncology Center of Excellence initiative that facilitates simultaneous review by international regulatory bodies; those reviews remain ongoing.
Market context and competitive landscape
Dostarlimab's approval in rectal cancer broadens a label that already covers dMMR endometrial cancer and dMMR solid tumours more broadly, deepening its position in the PD-1 inhibitor market alongside established competitors including pembrolizumab (Merck) and nivolumab (Bristol Myers Squibb). The MSI-H/dMMR patient segment has become a focal point for checkpoint inhibitor strategies across multiple tumour types, and the rectal cancer data add a particularly compelling narrative: the prospect of organ preservation and avoidance of major surgery at high response rates is likely to resonate with both clinicians and payers.
Dostarlimab was originally discovered by AnaptysBio and licensed to Tesaro, later acquired by GSK, under a 2014 collaboration agreement. AnaptysBio retains royalty interests and issued the announcement in the context of its financial collaboration with GSK, which continues to lead development and commercialisation.
The AZUR-1 data, particularly the zero recurrence signal at two-plus years of follow-up among responders, will face scrutiny as full results emerge at ESMO and in subsequent peer-reviewed publication. Longer follow-up will be required to determine durability and to understand outcomes in the subset of patients whose central review responses are still maturing.