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BioNTech, Duality Biologics Begin Pivotal Phase III ADC Trial in Advanced HER2-Low Breast Cancer

NEW YORK – BioNTech and Duality Biologics said on Monday that they have treated the first metastatic, hormone receptor-positive, HER2-low breast cancer patient in their Phase III trial of their investigational HER2-targeted antibody-drug conjugate.

The pivotal Phase III trial pits the antibody-drug conjugate, which is known as both BNT323 and DB-1303, against standard-of-care chemotherapy. BioNTech and DualityBio plan to enroll 532 HR-positive metastatic breast cancer patients whose cancers express low levels of HER2, defined as having an IHC score of 1+, or IHC 2+ and ISH negative by central laboratory testing.

To be eligible for the trial, patients have to be chemotherapy-naïve but treated previously with hormone therapy.

Mainz, Germany-based BioNTech and Shanghai-based DualityBio plan to begin their trial in China then expand it into the United States, Europe, and additional regions. The partnered firms will be looking at progression-free survival as the trial's primary endpoint and overall survival, objective response rate, duration of response, and safety as the trial's secondary endpoints.

The collaborative trial comes after BioNTech and DualityBio inked a $170 million antibody-drug conjugate licensing deal in April 2023. Following that deal, BioNTech has the rights to develop and commercialize BNT323/DB-1303 and another antibody-drug conjugate dubbed DB-1311 anywhere outside China, Hong Kong Special Administrative Region, and Macau Special Administrative Region, where DualityBio will retain rights to the agents.

The pivotal trial follows earlier Phase I/II data for BNT323/DB-1303, in which 38.5 percent of heavily pretreated patients with HER2-low breast cancer responded to BNT323/DB-1303 and the agent had a disease control rate of 84.6 percent.