FDA grants Breakthrough Therapy to a HER2-low ADC in breast cancer

A Phase II readout strong enough to earn Breakthrough Therapy designation — and put the broader HER2-low ADC field on notice.

The FDA has granted Breakthrough Therapy Designation (BTD) to an undisclosed HER2-low antibody-drug conjugate for adult patients with previously treated breast cancer. The designation follows Phase II data showing meaningful objective response rates in a population previously considered difficult to treat with HER2-directed therapies.

The BTD will accelerate development through intensive FDA guidance and rolling review eligibility. The crowded ADC landscape — already featuring T-DXd from AstraZeneca/Daiichi and several pipeline entrants — makes the differentiation of HER2-low versus HER2-positive targeting increasingly critical for market access. Track all BTD activity and ADC pipeline moves in BIO 360.