BioNTech and DualityBio disclosed that their trastuzumab pamirtecan antibody-drug conjugate delivered only “modest” benefit in a breast cancer study in HER2-low disease, with the companies characterizing the impact as “limited.” The update comes as the HER2-low segment intensifies following AstraZeneca and Daiichi Sankyo’s Enhertu benchmark. The companies’ remarks raise questions about where the ADC fits in the treatment sequence and what further development focus—such as patient selection or combination strategies—may be needed to improve differentiation. Separately, BioNTech’s broader post-data planning is now tied to the commercial bar set by established HER2-targeting ADCs, with investors likely watching for whether the next readouts can move efficacy beyond incremental gains.