Positive high-level results from the head-to-head DESTINY-Breast03 Phase III trial showed that Enhertu (trastuzumab deruxtecan), the AstraZeneca and Daiichi Sankyo Company, Limited (Daiichi Sankyo) HER2-directed antibody drug conjugate (ADC), demonstrated superiority over trastuzumab emtansine (T-DM1).
At a planned interim analysis, the Independent Data Monitoring Committee (IDMC) concluded that DESTINY-Breast03 met the primary endpoint of progression-free survival (PFS) showing a highly statistically significant and clinically meaningful improvement for patients with HER2-positive, unresectable and/or metastatic breast cancer previously treated with trastuzumab and a taxane.
In DESTINY-Breast03, Enhertu also showed a strong trend toward improved overall survival (OS) compared to T-DM1 in a key secondary endpoint, although the OS data are still immature. The safety profile of Enhertu was consistent with previous clinical trials, with no new safety concerns identified and no Grade 4 or 5 treatment-related interstitial lung disease events.
Susan Galbraith, Executive Vice President, Oncology R&D, said: "There is a continued need for new options and better outcomes for patients with HER2-positive metastatic breast cancer who often experience disease progression after initial treatment with available standards of care. These transformative progression-free survival results demonstrate the superiority of Enhertu compared to T-DM1, and the encouraging safety data may open future opportunities to bring this benefit to patients in earlier treatment settings."
Ken Takeshita, Global Head, Research and Development, Daiichi Sankyo, said: "DESTINY-Breast03 is the first global Phase III head-to-head trial of Enhertu against an active control and supports the potential of this medicine to become the new standard of care for patients with HER2-positive metastatic breast cancer following initial treatment with trastuzumab and a taxane. We believe this highly sophisticated and specifically engineered ADC is fulfilling its promise to reshape the treatment of HER2-positive metastatic breast cancer, with the goal to move into earlier lines of treatment for HER2-positive breast cancer and many other HER2-expressing tumour types across our broad clinical trial programme."
The data will be presented at an upcoming medical meeting and shared with health authorities.
Enhertu is approved for the treatment of adult patients with unresectable or metastatic HER2-positive breast cancer who have received two or more prior anti-HER2-based regimens in the metastatic setting in the US, Japan, the EU and several other countries based on the results from the DESTINY-Breast01 trial.
Enhertu is being further assessed in a comprehensive clinical development programme evaluating efficacy and safety across multiple HER2-targetable cancers, including breast, gastric, lung and colorectal cancers.
HER2-positive breast cancer
Breast cancer remains the most common cancer and is one of the leading causes of cancer-related deaths in women worldwide.1 More than two million patients with breast cancer were diagnosed in 2020, resulting in nearly 685,000 deaths globally.1 Approximately one in five patients with breast cancer are considered HER2-positive.2
HER2 is a tyrosine kinase receptor growth-promoting protein expressed on the surface of many types of tumours, including breast, gastric, lung and colorectal cancers.3 HER2 protein overexpression may occur as a result of HER2 gene amplification and is often associated with aggressive disease and a poor prognosis in breast cancer.4
Despite initial treatment with trastuzumab and a taxane, patients with HER2-positive metastatic breast cancer will often experience disease progression.5 More effective options are needed to further delay progression and extend survival.5-7
DESTINY-Breast03
DESTINY-Breast03 is a global head-to-head, randomised, open-label, registrational Phase III trial evaluating the safety and efficacy of Enhertu (5.4mg/kg) versus T-DM1 in patients with HER2-positive unresectable and/or metastatic breast cancer previously treated with trastuzumab and a taxane. The primary efficacy endpoint of DESTINY-Breast03 is PFS based on blinded independent central review. Secondary efficacy endpoints include OS, objective response rate, duration of response, clinical benefit rate, PFS based on investigator assessment and safety.
