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A new antibody-drug conjugate is turning heads in breast cancer treatment. Trastuzumab rezetecan more than doubled progression-free survival compared to standard chemo in HER2-low advanced breast cancer — 16.4 vs. 6.8 months — in the phase 3 HORIZON-Breast06 trial. But with T-DXd (Enhertu) already dominating this space, experts say its exact role in the treatment lineup is still up for debate.
A new antibody-drug conjugate (ADC) is making waves in breast cancer care. The phase 3 HORIZON-Breast06 trial found that trastuzumab rezetecan slashed the risk of disease progression or death by 73% compared to standard chemotherapy in patients with HER2-low advanced breast cancer. The results were presented at ESMO 2026 in Madrid and simultaneously published in JAMA.
A second trial, APEX-Breast01, also showed strong results for another novel biparatopic HER2-targeted ADC, rolditamig deuderuxtecan (TQB2102), with nearly identical PFS gains — 16.4 vs. 5.5 months — in the same patient population. Both drugs are currently investigational outside of China.
Despite the excitement, experts are urging caution. Neither drug has been tested head-to-head against trastuzumab deruxtecan (T-DXd/Enhertu), the current standard of care, which shows similar efficacy. Overlapping resistance mechanisms and a crowded ADC landscape mean sequencing strategies and biomarker-driven patient selection remain open questions.
By the Numbers:
Why it matters: These results expand the ADC toolkit for HER2-low breast cancer — a large and historically hard-to-treat population — but head-to-head trials are urgently needed to define which patients benefit most from each agent and how to sequence them optimally.
