Merck: Experimental drug cuts risk of death by 32% in advanced endometrial cancer
Key Facts
Merck announced positive results from the Phase 3 TroFuse-005 trial of its investigational drug sacituzumab tirumotecan, known as sac-TMT, in patients with advanced or recurrent endometrial cancer. The company said the treatment reduced the risk of death by 32% compared with physician’s choice of chemotherapy. At the interim analysis, median follow-up was 14 months, and median overall survival reached 19 months with the drug versus 12.1 months with chemotherapy. That represents a difference of 6.9 months in median overall survival. The results apply to sac-TMT alone, an investigational drug targeting TROP2, and not to Keytruda or a combination of the two.
The trial included 776 patients, randomly assigned to sac-TMT or physician’s choice of chemotherapy, consisting of doxorubicin or paclitaxel. It was a global, multicenter, randomized, open-label study controlled with an active treatment. Before entering the trial, participants had received platinum-based chemotherapy and immunotherapy with a PD-1 or PD-L1 inhibitor, either together or separately. The results apply to patients whose disease progressed after these prior treatments. NYU Langone said all participants had previously received pembrolizumab, known as Keytruda, before starting subsequent treatment in the study.
On another measure of treatment efficacy, sac-TMT reduced the risk of disease progression or death by 41% compared with chemotherapy. Median progression-free survival was 7.2 months in the drug group versus 3.9 months in the chemotherapy group, a difference of 3.3 months. The trial also recorded an objective response rate of 35.1% with sac-TMT, compared with 17.3% with chemotherapy. Median duration of response was 11.1 months among patients receiving the drug, compared with 6.9 months in the other group. Merck said in its announcement that these results came from the trial’s prespecified interim analysis.
Safety data showed a higher rate of treatment-related adverse events of Grade 3 or higher with sac-TMT, occurring in 54.4% of recipients versus 41.4% in the chemotherapy group. The most notable severe clinical events included anemia in 23.7%, neutropenia in 20.1%, and oral mucositis or stomatitis in 9.9% of sac-TMT recipients. Merck said no new safety signals were observed. It added that health-related quality of life remained preserved over time among patients who received the drug. The results place the efficacy measures alongside the differences in adverse events recorded between the trial groups.
Merck said the TroFuse-005 results will be presented in a presidential session at the European Society for Medical Oncology Congress in Madrid, being held from 23 to 27 October 2026. The results were published simultaneously in The Lancet. The company described the data as the first results readout from the global TroFuse program. In August, it had announced that the trial achieved a statistically significant and clinically meaningful improvement in overall survival and progression-free survival compared with chemotherapy. The global results followed Phase 1 and Phase 2 data for the endometrial cancer cohort, whose participants were mostly from China; the response rate in the 4 mg/kg dose group was 36.9%, and median progression-free survival was 5.6 months.
Merck’s clinical program for the drug extends to 18 global Phase 3 trials, including 10 trials in gynecologic cancers, the company said. These include TroFuse-033, which is studying the treatment as first-line therapy for endometrial cancer in patients with mismatch repair-proficient tumors. Principal investigator Bhavana Pothuri said the results warrant a reassessment of clinical guidelines for endometrial cancer to include sac-TMT. That remains a research opinion, not a regulatory recommendation or a guideline update. Merck’s statement estimated that about 68,270 patients will be diagnosed with endometrial cancer in the United States during 2026, and that about 14,450 deaths will be attributed to it.
On the regulatory front, Merck said the U.S. Food and Drug Administration accepted the sac-TMT application for priority review and set 15 June 2027 as the target decision date. The company added that it will discuss the data with global regulatory authorities. Dean Li, president of Merck Research Laboratories, described the situation for patients whose disease progresses after platinum-based chemotherapy and a PD-1 inhibitor, saying they "face median survival of less than a year with current treatments." He described the survival gain of about seven months as an important advance. Merck shares closed at $145.27 on 23 October 2026, according to EL7 data.