An Experimental Tumor-Homing Drug Beat Chemotherapy in Returning Endometrial Cancer

CATEGORY: WOMEN’S HEALTH

When endometrial cancer comes back after chemotherapy and immunotherapy, the next treatment usually buys months, not years. A 776-woman international trial just moved that line: women who got an experimental drug called sacituzumab tirumotecan lived a median of 19 months, versus 12.1 months on standard chemotherapy, a 32% lower risk of death during the study.¹ The drug isn’t approved yet. US regulators have it under priority review, with a decision due by June 2027.

776 Women After the Standard Drugs Had Failed

Every woman in the trial had advanced or recurrent cancer of the endometrium, the lining of the uterus, and every one had already been through platinum chemotherapy and an immunotherapy drug. At 242 hospitals in 31 countries, a computer randomly sorted them into two groups. Half received the new drug by infusion every two weeks. The other half received whichever standard chemotherapy their own oncologist picked, doxorubicin or weekly paclitaxel. Nobody was blinded, so patients and doctors knew the assignment. The outcomes that mattered resist that knowledge: how long women lived, and tumor growth judged from scans by independent radiologists who didn’t know who got what. Follow-up ran a median of 14 months.¹

Sacituzumab tirumotecan is an antibody-drug conjugate. An antibody seeks out TROP2, a protein crowded onto the surface of most endometrial tumor cells, and releases its chemotherapy payload right there. It’s chemotherapy with a delivery address.

Seven More Months, and Tumors That Shrank Twice as Often

Median survival was 19.0 months with the new drug and 12.1 months with chemotherapy. A year in, 63.4% of the women on it were alive, versus 50.8% on chemotherapy. The cancer was also held still longer: a median of 7.2 months before growing, against 3.9, a 41% lower risk of progression or death. Tumors shrank in 35.1% of women on the new drug and 17.3% on chemotherapy, and those responses lasted longer too, 11.1 months against 6.9.¹

Who Didn’t Benefit

The gains weren’t spread evenly. Most participants, about 84%, had tumors whose DNA-repair machinery still works, called mismatch repair proficient, and the survival benefit showed up clearly there. It also showed up in the roughly 80% whose tumors carried medium or high levels of TROP2, the protein the drug homes in on. In the smaller groups the picture changed. Women whose tumors had faulty DNA repair saw no clear survival gain. Neither did women with low TROP2. And in the 48 women with carcinosarcoma, an aggressive rare subtype, chemotherapy actually did better. These subgroup readings come with wide error margins and no formal statistical test behind them, but they sketch who this drug is probably for.¹

Mouth Sores, Low Blood Counts, and a Decision Due in 2027

The targeting doesn’t make it gentle. Severe treatment-related side effects hit 54.4% of women on the new drug, versus 41.4% on chemotherapy, led by anemia, low levels of oxygen-carrying red blood cells, in 62.5%, and mouth sores in over half, which a preventive steroid mouthwash later blunted. Dry eye affected nearly one in five. Yet fewer women quit the new drug over side effects than quit chemotherapy, 3.1% versus 4.9%, and quality-of-life scores held steady in both groups. Three women in each group died of treatment-related causes. Merck, which is developing the drug, funded and ran the trial. The FDA’s deadline to decide on approval is June 15, 2027.¹

Key Takeaways

• This drug can’t be prescribed yet: it’s experimental, with a US approval decision expected by mid-2027.
• In previously treated advanced endometrial cancer, it extended median survival from 12.1 to 19.0 months and lowered the risk of death by 32% compared with standard chemotherapy.
• The benefit concentrated in the most common tumor types; women with DNA-repair-deficient tumors, low TROP2, or carcinosarcoma saw no clear gain, and the rare carcinosarcoma group fared better on chemotherapy.
• Side effects were frequent but manageable enough that fewer women stopped the new drug than stopped chemotherapy, and quality of life stayed level in both groups.

References

1. Lorusso D, Martin-Babau J, Backes F, et al. Sacituzumab tirumotecan versus treatment of physician’s choice in previously treated endometrial cancer (TroFuse-005/ENGOT-en23/GOG-3095): a randomised, open-label, phase 3 trial. The Lancet. 2026; DOI 10.1016/S0140-6736(26)02099-4 (published online October 26, 2026). link