Trastuzumab pamirtecan, being developed under a 2023 partnership between BioNTech and DualityBio, elicited a 44.1% overall response rate in a Phase 2 trial.
BioNTech and DualityBio’s investigational antibody-drug conjugate demonstrated what the companies called “encouraging” efficacy in a mid-stage study of patients with HER2-positive endometrial cancer, giving the cancer collaborators another win.
Primary phase 2 findings, presented Saturday at the Society of Gynecologic Oncology’s annual meeting, demonstrated a 49.3% overall response rate (ORR) in 73 patients who had previously been treated with checkpoint inhibitor agents. In the overall readout sample, consisting of 143 patients, ORR dipped slightly to 44.1%.
Trastuzumab pamirtecan showed “encouraging antitumor activity” across all HER2 expression levels tested, the partners said. Median duration of response was 10.3 months, while median progression-free survival, regardless of prior checkpoint inhibition, was eight months.
Trastuzumab pamirtecan is an anti-HER2 antibody-drug conjugate (ADC) that carries a topoisomerase 1 inhibitor payload, which induces death in target tumor cells. Aside from the mid-stage endometrial cancer trial, BioNTech and DualityBio are running a Phase 1/2 study for the ADC in advanced/metastatic solid tumors.
The companies have also advanced trastuzumab pamirtecan into late-stage development for endometrial cancer in the Phase 3 Fern-EC-01 study, which is expected to wrap up in November 2029. The ADC is being studied in the Phase 3 DYNASTY-Breast02 trial in HER2-low, HR-positive metastatic breast cancer, with a completion date in July 2028.
BioNTech and DualityBio did not provide detailed updates for these trials in the Saturday news release, with BioNTech Chief Medical Officer Özlem Türeci saying only that they are “continuing to advance trastuzumab pamirtecan, both as a monotherapy and in novel-novel treatment combination approaches.”
Originally developed by Shanghai’s DualityBio, trastuzumab pamirtecan, along with another preclinical cancer asset, came to BioNTech in April 2023 for $170 million upfront. BioNTech also bet up to $1.5 billion in milestones across both programs, plus royalties.
The alliance has been successful. Just months after inking the agreement, in September 2023, the companies announced they would push trastuzumab pamirtecan, formerly DB-1303, into late-stage development for breast cancer.
In December 2024, BNT324/DB-1311—the second asset under the 2023 partnership—aced a Phase 1/2a solid tumor study, including patients with small cell lung cancer, non-small cell lung cancer and castration-resistant prostate cancer (mCRPC). The asset moved to Phase 3 for mCRPC earlier this year.
