AstraZeneca and Daiichi Sankyo have announced that the U.S. Food and Drug Administration (FDA) has approved Enhertu (trastuzumab deruxtecan) for the treatment of adult patients with unresectable or metastatic hormone receptor (HR)-positive, HER2-low or HER2-ultralow breast cancer, who have experienced disease progression following one or more endocrine therapies in the metastatic setting.
This approval is based on the results from the DESTINY-Breast06 Phase III trial, which demonstrated that Enhertu significantly improved progression-free survival (PFS) compared to standard-of-care chemotherapy.
In the trial, Enhertu showed a 36% reduction in the risk of disease progression or death versus chemotherapy in the overall trial population of patients with chemotherapy-naïve HER2-low or HER2-ultralow metastatic breast cancer. A median PFS of 13.2 months was observed in patients treated with Enhertu compared to 8.1 months in those receiving chemotherapy. The confirmed objective response rate (ORR) was 62.6% for Enhertu versus 34.4% for chemotherapy.
An exploratory analysis indicated that the benefits of Enhertu were consistent among patients with both HER2-low and HER2-ultralow expression. HER2 status in the trial was confirmed by a central laboratory using tumor samples obtained at the time of initial metastatic diagnosis or later. Approximately 85-90% of patients with HR-positive, HER2-negative metastatic breast cancer were determined to have actionable levels of HER2 expression. Additionally, nearly two-thirds of patients previously assessed as IHC 0 at a local laboratory were reclassified as HER2-low or HER2-ultralow upon central analysis.
The safety profile of Enhertu in DESTINY-Breast06 was consistent with previous clinical trials, with no new safety concerns identified.
Enhertu is the first HER2-directed therapy approved for patients with HER2-ultralow breast cancer, expanding treatment options for this subset of patients.
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