BioNTech and DualityBio Report Clinically Meaningful Efficacy for Trastuzumab Pamirtecan in HER2-Expressing Endometrial Cancer

BioNTech and DualityBio reported clinically significant efficacy for trastuzumab pamirtecan in patients with HER2-expressing recurrent endometrial cancer, based on updated results from an ongoing Phase 1/2 trial.¹

Bhavana Pothuri, MD, gynecologic oncologist at NYU Langone in New York City, reported the results at the Society of Gynecologic Oncology (SGO) Annual Meeting on Women’s Cancer 2026.

“Endometrial cancer is one of the few cancers with an increasing mortality rate, 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 Dr. Pothuri in a press release. “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.”

In the evaluable population, the antibody–drug conjugate (ADC) achieved an objective response rate (ORR) of approximately 50%, including complete and partial responses, with a disease control rate (DCR) exceeding 90%. Median duration of response had not yet been reached at the time of data cutoff, indicating the potential for durability.

Notably, responses were observed across patients with varying levels of HER2 expression, suggesting activity beyond a narrowly defined biomarker subset. The findings are particularly relevant given that enrolled patients were heavily pretreated, underscoring the agent’s potential in later-line settings.

What differentiates this ADC in a crowded HER2 landscape?
Trastuzumab pamirtecan is a next-generation HER2-targeting ADC developed using DualityBio’s platform technology. The candidate combines a HER2-directed monoclonal antibody with a topoisomerase I inhibitor payload via a cleavable linker, a design intended to improve intracellular drug delivery and enhance antitumor activity.

Compared with earlier HER2-directed ADCs, this construct aims to balance potency with tolerability, an ongoing challenge in the class. In endometrial cancer—where HER2 targeting has historically lagged behind its use in breast and gastric cancers—the agent may broaden the applicability of HER2 as a therapeutic target, particularly in tumors with heterogeneous or lower levels of expression.

How does this address an unmet need in endometrial cancer?
Patients with recurrent endometrial cancer face limited treatment options following progression on standard therapies, including platinum-based chemotherapy and immune checkpoint inhibitors. Outcomes in this setting remain poor, with modest response rates and short durations of benefit from available treatments.

HER2 overexpression is observed in a subset of endometrial tumors, particularly in more aggressive histologies, but targeted therapies have only recently begun to demonstrate meaningful clinical activity. The reported ORR and DCR for trastuzumab pamirtecan compare favorably with historical benchmarks in this population, supporting its potential role as a targeted option in later lines of therapy.

What are the regulatory and development implications?
Trastuzumab pamirtecan has received Breakthrough Therapy designation from the FDA for advanced endometrial cancer, reflecting both the unmet need and the strength of preliminary clinical data. The safety profile observed to date has been manageable and consistent with other ADCs utilizing topoisomerase I inhibitor payloads, with no new safety signals reported.

BioNTech and DualityBio are advancing the program into a global Phase 3 trial² to further evaluate efficacy and safety in a larger patient population. Beyond endometrial cancer, the agent is also being investigated in other HER2-expressing solid tumors, including breast cancer, where it has demonstrated positive results in late-stage studies.

Together, these efforts position trastuzumab pamirtecan as a potentially important addition to the evolving HER2-targeted treatment landscape.

References

1. A Phase 1/​2a Study of DB-1303/​BNT323 in Advanced/​Metastatic Solid Tumors. National Library of Medicine. Clinicaltrials.gov. https://clinicaltrials.gov/study/NCT05150691

2. BioNTech and DualityBio’s Antibody-Drug Conjugate Trastuzumab Pamirtecan Demonstrated Clinically Meaningful Efficacy in Patients with HER2-Expressing, Recurrent Endometrial Cancer.(2026, April 11). Bionech.com. https://investors.biontech.de/news-releases/news-release-details/biontech-and-dualitybios-antibody-drug-conjugate-trastuzumab