GSK reports that dostarlimab (Jemperli) monotherapy achieved sustained clinical complete responses in the phase 2 AZUR-1 trial for dMMR/MSI-H locally advanced rectal cancer, with data to be submitted for regulatory review.
GSK has reported positive interim results from AZUR-1, a registrational
The July 13, 2026, announcement raises the possibility that dostarlimab could become the
"The AZUR-1 results support the potential for dostarlimab to transform treatment for dMMR/MSI-H locally advanced rectal cancer," said
AZUR-1 is a global, open-label, single-arm trial that enrolled 154 participants with stage II/III dMMR/MSI-H locally advanced rectal cancer. Participants received 9 cycles of dostarlimab, administered as a 500-mg intravenous infusion every 3 weeks over 6 months. The primary objective, cCR12, was designed to determine whether dostarlimab monotherapy could allow patients to forgo chemoradiation and surgery entirely.
GSK reported that the interim safety profile was consistent with dostarlimab's established profile across solid tumors, with no new safety signals identified. The company plans to share interim data with global regulators, including for accelerated review in the United States, with full results expected at a future scientific congress.¹
Rectal cancer affects an estimated 730,000 people worldwide annually, with the dMMR/MSI-H subtype accounting for roughly 5% to 10% of cases.¹ Standard treatment, such as neoadjuvant chemotherapy, radiation, and surgery, is often curative but can leave patients with permanent colostomies, urinary and sexual dysfunction, and infertility.2 This subtype is also known to respond poorly to conventional chemotherapy, making biomarker-driven alternatives clinically relevant.3
Dostarlimab is a programmed cell death protein 1 (PD-1)-blocking antibody that restores T-cell activity against dMMR/MSI-H tumors, which typically carry a high mutational burden. It first received FDA accelerated approval in April 2021 for dMMR endometrial cancer, was expanded to other dMMR solid tumors later that year, and gained additional endometrial cancer approvals in 2023 and 2024.⁴
Dostarlimab is
The reported cCR12 rate represents a substantial improvement over historical complete-response rates with standard neoadjuvant therapy in this chemotherapy-resistant subtype.²,³ However, AZUR-1 is single-arm and non-randomized, without a concurrent chemoradiation comparator. GSK has not yet released detailed response, duration, or organ-preservation data. Whether cCR12 translates into durable long-term avoidance of surgery, the outcome of which is most relevant to patients, remains to be established.
Patient-level efficacy and safety tables have not been published, which limits independent analysis ahead of peer-reviewed presentation. The single-arm design constrains causal comparison with standard care, and interim 12-month data typically require longer follow-up to confirm durability. Regulatory review, including a potential
