GSK Reports 76% Complete Response Rate in Exploratory Analysis of Rectal Cancer Drug
Key Facts
On October 24, GSK announced interim Phase 2 results from the AZUR-1 trial, showing a complete response in 76% of evaluable patients who received Jemperli, known as dostarlimab, alone to treat locally advanced stage II or III rectal cancer with MSI-H or dMMR. The rate covered 110 of 144 evaluable patients, with a 95% confidence interval of 69% to 83%. The company said the result came from an exploratory analysis, while the study focused on adults who had not received prior treatment. The U.S. Food and Drug Administration had granted the drug accelerated approval for this group on October 19. The results carry therapeutic significance because they point to the possibility of avoiding standard treatments for some patients, while approval remains limited by tumor characteristics and stage.
The exploratory analysis results distinguish complete response from its sustained component without surgery: 98 of 144 patients, or 68%, achieved a clinical complete response lasting at least 12 months, according to investigators' assessment. Histological examination after surgery also confirmed a complete response in 12 additional patients. According to an independent central review, 54 of 116 evaluable patients achieved a clinical complete response at 12 months, a rate of 47%, while 38 additional patients had achieved a complete response but had not yet reached the 12-month assessment. In the FDA analysis, the objective response rate according to central review was 79% among 116 patients. GSK said no recurrence had been recorded among responders as of the statement date, after a median follow-up exceeding two years; the FDA report cited a median follow-up of 26.3 months, with no disease progression among those who achieved a sustained, complete or near-complete response.
A total of 154 participants received treatment in AZUR-1, a global, open-label, single-arm trial, over 9 cycles across six months, at an intravenous dose of 500 mg every three weeks. According to FDA data, 110 patients, or 71% of all those treated, received no additional treatment and had no disease progression after dostarlimab alone. By contrast, 26 patients underwent surgery, 13 received additional systemic therapy or radiation, one patient had disease progression without subsequent treatment, and 4 patients withdrew or were lost to follow-up. The clinical result remains tied to a specific group: GSK says about 5% to 10% of rectal cancers have an MSI-H or dMMR profile, while published estimates cited by the FDA put the figure at about 3% of locally advanced cancer cases. The differing estimates show the target group is limited in scope, with the proportion varying according to the estimate's source and the group's definition.
The results are part of a treatment approach that may reduce the need for chemotherapy, radiation and surgery, which are components of standard treatment for locally advanced rectal cancer. These interventions may be associated with long-term consequences including bowel, urinary and sexual dysfunction, infertility and secondary cancers. Hasham Abdullah, GSK's Senior Vice President and Global Head of Oncology, said, "Avoiding chemotherapy, radiation and surgery may now be possible for some patients." In earlier data cited by the FDA, an investigator-led study included 50 patients in the same group, with a sustained complete response rate at 12 months of 93% and an objective response rate of 100%. Participants in that study did not receive chemoradiation or rectal surgery as part of their rectal cancer treatment; among 27 patients followed for at least three years, one local recurrence was recorded and treated with lymph node dissection.
Safety data showed serious adverse reactions in 20% of patients receiving Jemperli. Fatigue was the most common of the reported reactions, recorded in 32%, followed by rash in 22%, diarrhea in 18% and itching in 17%. Treatment was permanently discontinued because of adverse reactions in 3% of patients. These figures make safety one element in assessing the treatment alongside response, in a trial in which participants received the drug alone. The results in the statement did not provide a randomized comparison with standard treatments, as AZUR-1 had a single-arm design. U.S. approval remains accelerated, linking completion of the response characterization and disease follow-up to post-marketing requirements.
The FDA requires completion of AZUR-1 to characterize the duration of complete response at 12, 24 and 36 months, the organ preservation rate after three years, the rate of relapse or metastatic disease during the same period, and five-year survival follow-up; the expected date for completing the requirement is July 31, 2030. GSK said the results will be presented in a late-breaking oral session at the European Society for Medical Oncology congress, held in Madrid from October 23 to 27, 2026. The company also said the application is under review by other regulators through Project Orbis, without further details on decisions or their timing in the available information. The FDA report had noted that review of the Jemperli application was completed about four months ahead of the target date. Long-term follow-up remains part of the process for verifying the durability of response and organ preservation after accelerated approval.