Trastuzumab pamirtecan demonstrated clinically meaningful activity and a manageable safety profile in patients with HER2-expressing recurrent endometrial cancer (EC), according to a recently published press release.
These results suggest trastuzumab pamirtecan may become a new treatment option for a disease with limited effective therapies.
In a Phase 2 cohort of a global trial, the investigational antibody-drug conjugate met its primary endpoint in patients whose cancer progressed after prior treatments. Among centrally tested patients, the confirmed objective response rate was 47.9%, and 49.3% in those who had previously received immune checkpoint inhibitors. Median progression-free survival reached 8.1 months, indicating that many patients experienced a delay in disease worsening.
“Endometrial cancer is one of the few cancers with an increasing mortality rate,1 and there is an urgent need for new treatment options, especially for patients with recurrent disease with lower HER2 expression levels where current standard-of-care chemotherapy offers only a 15 % response rate2,” said Bhavana Pothuri, M.D., Medical Director of the Clinical Trials Office (CTO) and Director of Gynecologic Oncology Research at the NYU Langone Perlmutter Cancer Center.
The study included 145 patients with advanced or metastatic disease who had already undergone at least one line of therapy. Across all evaluable patients, the objective response rate was 44.1% based on local testing. Responses were observed regardless of HER2 expression level, with rates of 33.9% in IHC1+, 40.4% in IHC2+, and 73.1% in IHC3+ tumors. The median duration of response was 10.3 months, suggesting that when tumors responded, the benefit often lasted several months.
Read more about therapies for EC
Importantly, the results reflect a population similar to real-world patients, including those with prior immunotherapy exposure and those with more advanced disease. Current chemotherapy options in this setting typically achieve response rates of about 15%, highlighting the potential improvement offered by trastuzumab pamirtecan.
The treatment’s safety profile was consistent with similar therapies. Common side effects included nausea, anemia, fatigue, and low platelet counts, mostly at lower severity. However, 46.9% of patients experienced grade 3 or higher treatment-related adverse events. Serious lung-related complications such as interstitial lung disease or pneumonitis occurred in 4.8% of patients, but most side effects were considered manageable with appropriate care.
For patients, these findings may signal a meaningful shift in treatment possibilities. A therapy that works across different HER2 levels and after prior treatments could expand access to effective care. Ongoing Phase 3 trials will help determine whether trastuzumab pamirtecan can become a standard option, and a regulatory filing is planned in 2026.
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