Trastuzumab pamirtecan, an investigational HER2‑targeted antibody-drug conjugate developed by BioNTech and DualityBio, has met the primary efficacy endpoint in a Phase II cohort of patients with advanced or metastatic endometrial cancer who had progressed after first‑line chemotherapy, with or without prior checkpoint‑inhibitor treatment. The results, presented at the 2026 Society of Gynecologic Oncology (SGO) Annual Meeting on Women’s Cancers, show a confirmed objective response rate of 49.3% in centrally HER2‑tested patients with prior immune checkpoint‑inhibitor exposure and 47.9% across all centrally tested evaluable patients, with a median progression‑free survival of 8.1 months.
“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 rate,” 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. “We are encouraged by these results for trastuzumab pamirtecan, which showed clinically meaningful responses across all HER2 levels. Importantly, these results were seen in a broad patient population that reflects real‑world clinical practice, including patients who have received prior immune checkpoint‑inhibitor treatment and those with visceral metastases.”
“These positive results in patients with endometrial cancer, including those with lower HER2 expression levels, support the potential of trastuzumab pamirtecan,” added Özlem Türeci, Co‑Founder and Chief Medical Officer at BioNTech, who recently announced he and Özlem Türeci plan to step aside from the company. “HER2 remains an important therapeutic target, particularly in gynaecologic cancers and breast cancer. We are continuing to advance trastuzumab pamirtecan, both as a monotherapy and in novel treatment‑combination approaches, with the aim of addressing the significant unmet medical needs in the treatment of patients with HER2‑driven tumours.”
For BioNTech, regulatory momentum is already building: the US FDA granted trastuzumab pamirtecan Fast Track and Breakthrough Therapy designations for endometrial cancer in 2023. A global confirmatory phase 3 trial, Fern‑EC‑01, is ongoing, comparing trastuzumab pamirtecan with investigator‑chosen single‑agent chemotherapy in previously treated patients with HER2‑expressing recurrent endometrial cancer. BioNTech and DualityBio plan to file a biologics licence application in 2026, subject to regulatory feedback.
For the broader oncology community, the data represent one of the largest cohorts reported to date for a HER2‑targeted ADC in endometrial cancer, highlighting that a HER2‑directed payload can deliver meaningful benefit even in lower‑expression settings that are typically underserved by existing targeted therapies.