The Food and Drug Administration (FDA) has granted Enhertu (trastuzumab deruxtecan), Breakthrough Therapy Designation (BTD) in the US for the treatment of adult patients with unresectable or metastatic HER2-positive breast cancer who have received one or more prior anti-HER2-based regimens. Enhertu is a HER2-directed antibody drug conjugate (ADC) jointly developed by AstraZeneca and Daiichi Sankyo Company, Limited (hereafter, Daiichi Sankyo).
The FDA granted BTD based on data from the DESTINY-Breast03 Phase III trial presented during the European Society for Medical Oncology (ESMO) Congress 2021. This is the second BTD for Enhertu in breast cancer and now brings the total number of BTDs to four for this medicine.
The US FDA’s BTD is designed to accelerate the development and regulatory review of potential new medicines that are intended to treat a serious condition and address a significant unmet medical need. The new medicine needs to have shown encouraging preliminary clinical results that demonstrate substantial improvement on a clinically significant endpoint over available medicines.
Breast cancer remains the most common cancer worldwide, with more than two million cases diagnosed in 2020, resulting in nearly 685,000 deaths globally.1 Approximately one in five cases of breast cancer are considered HER2-positive.2
Despite initial treatment with trastuzumab and a taxane, patients with HER2-positive metastatic breast cancer will often experience disease progression.3 More effective options are needed to further delay progression and extend survival.3-5
Susan Galbraith, Executive Vice President, Oncology R&D, AstraZeneca, said: “This is an important step in bringing Enhertu as a potential new option in earlier lines of treatment for HER2-positive metastatic breast cancer, given the urgent need to improve outcomes. This recognition by the FDA underscores the transformative possibility of Enhertu seen with the remarkable DESTINY-Breast03 results presented at ESMO just two weeks ago.”
Ken Takeshita, Global Head, R&D, Daiichi Sankyo, said: “By granting a fourth Breakthrough Therapy Designation to Enhertu, the FDA continues to recognise the significant potential of this medicine across multiple HER2-targetable tumours. With the unprecedented data recently reported from the DESTINY-Breast03 trial, we look forward to working closely with the FDA to bring Enhertu to patients who have been previously treated for HER2-positive metastatic breast cancer as soon as possible.”
In DESTINY-Breast03, Enhertu demonstrated a 72% reduction in the risk of disease progression or death compared to T-DM1 (hazard ratio [HR] 0.28; 95% confidence interval [CI] 0.22-0.37; p=7.8×10-22) in patients with HER2-positive unresectable and/or metastatic breast cancer previously treated with trastuzumab and a taxane. Nearly all patients treated with Enhertu were alive at one year (94.1%) compared to 85.9% of patients treated with T-DM1. Confirmed objective response rate (ORR) more than doubled in the Enhertu arm versus the T-DM1 arm (79.7% vs. 34.2%). 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.
Previous BTDs for Enhertu were in late-line HER2-positive metastatic breast cancer in 2017 and HER2-mutant metastatic non-small cell lung cancer (NSCLC) and HER2-positive metastatic gastric cancer in 2020.
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 cases of 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.6 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.7
Despite initial treatment with trastuzumab and a taxane, people with HER2-positive metastatic breast cancer will often experience disease progression.3 More effective options are needed to further delay progression and extend survival.3-5
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 progression-free survival (PFS) based on blinded independent central review. Secondary efficacy endpoints include overall survival, objective response rate, duration of response, PFS based on investigator assessment and safety.
