GSK's Jemperli produced a complete response in 76 percent of evaluable patients with MSI-H/dMMR locally advanced rectal cancer in the AZUR-1 trial, with full data presented at ESMO days after FDA approval.
GSK reported full interim results from the Phase II AZUR-1 trial showing that its immunotherapy Jemperli, given alone, produced a complete response in 76 percent of evaluable patients with stage II and III microsatellite instability-high, mismatch repair deficient locally advanced rectal cancer. The data were presented as a late-breaking abstract at the European Society for Medical Oncology Congress in Madrid on October 25, a week after the US Food and Drug Administration approved the drug for this use on October 19.
The trial enrolled 154 patients, of whom 144 could be evaluated. Investigators found that 68 percent, or 98 of 144, achieved a sustained clinical complete response for at least twelve months without surgery, and a further 12 patients had a pathological complete response confirmed through tissue analysis after surgery, taking the overall complete response figure to 76 percent. No disease recurrences have been reported among responders after a median follow-up of more than two years. Patients received nine cycles of dostarlimab, 500 milligrams every three weeks over six months.
The approval makes Jemperli the first and only immunotherapy for adults with this form of locally advanced rectal cancer in the United States, granted under fast track and breakthrough therapy designations with priority review and a national priority voucher, ahead of a February 2027 action date. The current standard treatment for this disease is chemotherapy, radiation and surgery, which can leave lasting bowel, urinary and sexual problems, secondary cancers and infertility, according to the approval announcement. MSI-H and dMMR tumours account for around 5 to 10 percent of rectal cancers.
The numbers here follow the companies' own filings and the approval announcement, which agree on the 68 percent and 76 percent figures and on the distinction between them, and that distinction matters: some coverage of the weekend announcement described all 76 percent as avoiding surgery, which the underlying data do not say, since 12 of the 110 responders had surgery before their complete response was confirmed. The safety picture is also narrower than a headline suggests: serious adverse reactions occurred in 20 percent of patients and the drug was permanently stopped for adverse reactions in 3 percent, while the primary endpoint assessed by independent central review is still maturing.
For the small group of rectal cancer patients whose tumours carry this biomarker, the result points to treatment without chemotherapy, radiation or surgery in many cases, which is why GSK's oncology research head, Hesham Abdullah, said avoiding those interventions may now be possible for some patients. The approval is accelerated rather than full, and regulatory reviews are continuing in other countries through the FDA's Project Orbis programme, so the next evidence that will shape this story is longer follow-up on whether the responses hold and whether other regulators follow the FDA.