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A Chinese phase III trial found that trastuzumab rezetecan, an antibody-drug conjugate (ADC), dramatically cut the risk of disease progression or death in HER2-low metastatic breast cancer patients compared to standard chemotherapy. The drug more than doubled median progression-free survival — 16.4 vs. 6.8 months — across all patient subgroups. However, experts caution it hasn't been proven superior to the already-approved T-DXd (Enhertu).
A Chinese phase III trial (HORIZON-Breast06) has found that trastuzumab rezetecan, an investigational antibody-drug conjugate (ADC), significantly outperformed physician's choice of chemotherapy in patients with HER2-low metastatic breast cancer. The results, presented at the ESMO congress and published simultaneously in JAMA, showed the drug more than doubled median progression-free survival (PFS) — a benefit that held regardless of hormone receptor status, including in the notoriously hard-to-treat HR-negative subgroup.
The drug works by linking a HER2-targeted antibody to a potent topoisomerase I inhibitor and is already approved in China for non-small cell lung cancer and colorectal cancer. While the results are impressive, experts note that a similar drug — trastuzumab deruxtecan (T-DXd/Enhertu) — already holds FDA approval for HER2-low breast cancer with comparable trial outcomes. No head-to-head comparison exists, and editorialists suggest trastuzumab rezetecan's best role may be as a sequential option if T-DXd moves earlier in the treatment pathway.
By the Numbers:
Why it matters: HER2-low breast cancer represents a large and underserved patient population. While trastuzumab rezetecan won't immediately displace T-DXd in markets where the latter is approved, it could expand treatment options globally — especially in regions where T-DXd is inaccessible — and may carve out a role in sequential therapy strategies.
