Enhertu improves both progression-free and overall survival in Destiny-Breast04 trial in patients with HER2-low metastatic breast cancer

Positive high-level results from Destiny-Breast04 phase-III trial showed Enhertu (trastuzumab deruxtecan) demonstrated improvement in both Progression-Free Survival (PFS) and overall survival (OS) in patients with HER2-low unresectable and/or metastatic breast cancer regardless of Hormone Receptor (HR) status versus physician’s choice of chemotherapy, AstraZeneca notified in a statement.

All patients in the trial received a HER2 test, and the results were centrally confirmed. HER2-low status was defined as an immunohistochemistry (IHC) score of 1+ or IHC 2+ with a negative in-situ hybridisation (ISH) score, added the statement.

It also informed that up to 55 per cent of all patients with breast cancer have tumours with a HER2 IHC score of 1+, or 2+ in combination with a negative ISH test, a level of HER2 expression not currently eligible for HER2-targeted therapy. HER2-low expression occurs in both HR-positive and HR-negative disease.

HER2 testing is well-established to determine an appropriate treatment strategy in metastatic breast cancer. Targetting the lower range of HER2 expression may offer another approach to delay disease progression and extend survival in patients with metastatic breast cancer. Currently, chemotherapy remains the only treatment option both for patients with HR-positive tumours following progression on endocrine (hormone) therapy, and for those who are HR-negative, the statement further said.

Destiny-Breast04 met its primary endpoint, where Enhertu demonstrated superior PFS in previously treated patients with HR-positive HER2-low metastatic breast cancer compared to the standard-of-care chemotherapy. The trial met the key secondary endpoint of PFS in patients with HER2-low metastatic breast cancer regardless of HR status (HR-positive or HR-negative). The trial also met the key secondary endpoints of OS in patients with HR-positive disease and in patients regardless of HR status at interim analysis, it added.

The safety profile of Enhertu was consistent with previous clinical trials, with no new safety concerns identified. Overall Interstitial Lung Disease (ILD) rates were consistent with that observed in late-line HER2-positive breast cancer trials of Enhertu, with a lower rate of Grade 5 ILD observed as determined by an independent adjudication committee, it also said.

The data will be presented at a forthcoming medical meeting and shared with global health authorities. Enhertu is being further assessed in a comprehensive clinical development programme evaluating efficacy and safety across multiple HER2-targettable cancers, including breast, gastric, lung and colorectal cancers.