GSK: Jemperli achieves 76% complete response in MSI‑H/dMMR locally advanced rectal cancer

Key results

In an exploratory analysis of the phase II AZUR‑1 trial, 76% of evaluable patients (110/144; 95% CI: 69%, 83%) with stage II/III MSI‑H/dMMR locally advanced rectal cancer had no evidence of cancer following dostarlimab monotherapy as confirmed by endoscopy, radiology and/or pathology. Of these, 98 patients (68% of 144; 95% CI: 60%, 76%) achieved a sustained clinical complete response for at least 12 months without surgery, and 12 additional patients had pathological complete responses after surgery. No disease recurrences have been reported among responders after a median follow-up of more than two years.

Efficacy details

AZUR‑1 met its primary objective of demonstrating a clinically significant proportion achieving cCR12. Independent central review data continue to mature: at the time of analysis 47% of evaluable patients (54/116; 95% CI: 37%, 56%) had achieved cCR12, and a further 38 participants had achieved clinical complete responses but had not yet reached the 12‑month assessment. The global, open‑label, single‑arm registrational trial enrolled 154 patients who received nine cycles of dostarlimab (500 mg IV every three weeks) over six months.

Safety

The safety profile was consistent with prior experience across solid tumours. Serious adverse reactions occurred in 20% of patients. The most common adverse reactions (≥15%) were fatigue (32%), rash (22%), diarrhoea (18%) and pruritus (17%). Jemperli was permanently discontinued for adverse reactions in 3% of patients.

Regulatory and next steps

These data supported a recent US approval of dostarlimab in this indication. Findings will be presented in a late‑breaking oral session at ESMO. Regulatory reviews are ongoing in participating countries through Project Orbis to enable concurrent international review.