The U.S. has granted approval for Enhertu as the first HER2-targeted treatment for patients with HER2-low or HER2-ultralow metastatic breast cancer after progression on one or more endocrine therapies.
AstraZeneca and Daiichi Sankyo have received approval from the U.S. Food and Drug Administration (FDA) for Enhertu as a treatment for individuals with HER2-positive breast cancer that has spread or cannot be surgically removed. This approval applies specifically to patients whose cancer has progressed after prior endocrine therapy.
The decision is based on findings from the DESTINY-Breast06 study, which revealed that Enhertu significantly delayed disease progression compared to standard chemotherapy in individuals with low and ultra-low HER2 expression. The results underscore Enhertu’s effectiveness as a targeted therapy for patients who previously had limited treatment options after endocrine therapy.
In the clinical study, Enhertu demonstrated a 36% decrease in the likelihood of disease progression or death compared to chemotherapy (hazard ratio [HR] 0.64; 95% confidence interval [CI]: 0.54-0.76; p<0.0001) among patients with chemotherapy-naïve HER2-low or HER2-ultralow metastatic breast cancer. The median progression-free survival (PFS) was 13.2 months for those treated with Enhertu, whereas patients who received chemotherapy had a median PFS of 8.1 months. The confirmed objective response rate (ORR) for Enhertu was 62.6%, significantly higher than the 34.4% observed in the chemotherapy group.
An exploratory analysis of individuals with HER2-ultralow expression indicated that treatment outcomes were comparable between patients with HER2-low and HER2-ultralow expression levels.
HER2 classification in the trial was verified by a central laboratory using a tumor sample collected at the time of initial metastatic diagnosis or later. Approximately 85-90% of patients with HR-positive, HER2-negative metastatic breast cancer were found to have detectable levels of HER2 expression. Additionally, nearly two-thirds of patients initially categorized as IHC 0 in local laboratory testing were later reclassified as HER2-low or HER2-ultralow upon central laboratory evaluation.
Enhertu is an advanced antibody-drug conjugate (ADC) that precisely targets HER2-expressing cancer cells while limiting harm to surrounding healthy tissues. Its mechanism of action allows for more effective drug delivery, which has been shown to improve outcomes for certain breast cancer patients.
The FDA’s approval marks an important milestone in expanding treatment choices for people with HER2-positive breast cancer. AstraZeneca and Daiichi Sankyo remain dedicated to further exploring Enhertu’s potential in other types of cancer and will continue research to enhance targeted treatment options.
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