Trastuzumab Pamirtecan Produces Durable Responses Across HER2 Expression Levels in Advanced Endometrial Cancer
Clinical Summary:
- Design/Population: Phase 1/2 dose-escalation and expansion study evaluating trastuzumab pamirtecan, a HER2-targeted antibody-drug conjugate, in 145 patients with previously treated HER2-expressing advanced or metastatic endometrial cancer.
- Key Outcomes: Median progression-free survival was 8 months and median overall survival was 15 months. Confirmed objective response rates were consistent across key subgroups, including prior immune checkpoint inhibitor exposure and number of prior therapies, with the highest response rate observed in HER2 IHC 3+ tumors (73.1%). Black/African American patients achieved an objective response rate of 56.5%.
- Clinical Relevance: These findings demonstrate meaningful activity of trastuzumab pamirtecan in heavily pretreated endometrial cancer and support ongoing phase 3 evaluation of this HER2-targeted antibody-drug conjugate.
Kathleen Moore, MD, Fred and Pamela Buffett Cancer Center, Omaha, Nebraska, discusses updated efficacy and survival results from a phase 1/2 study evaluating trastuzumab pamirtecan in patients with previously treated HER2-expressing advanced endometrial cancer.
Results demonstrated durable antitumor activity regardless of prior treatment history, with response rates remaining consistent across racial groups, prior lines of therapy, and prior immunotherapy exposure. The strongest activity was observed in HER2 IHC 3+ tumors, where response rates exceeded 70%, while median overall survival reached 15 months in this heavily pretreated population, supporting continued investigation in the ongoing phase 3 FERN-EC01 trial.
Dr Moore presented these results at the European Society for Medical Oncology (ESMO) Gynecological Cancers Congress in Copenhagen, Denmark.
Source:
Moore K, Wu X, Makker V, et al. Trastuzumab pamirtecan (T-Pam/DB-1303/BNT323) in patients (pts) with previously treated, HER2-expressing, advanced endometrial cancer (EC): Overall survival (OS) and efficacy in pt subgroups of a phase II dose-expansion cohort. Presented at ESMO Gynecological Cancers Congress. June 17-19, 2026. Copenhagen, Denmark. Abstract 83RO.
