FDA Speeds Up Review of Enhertu for Previously Treated Unresectable/Metastatic HER2-Breast Cancer

The Food and Drug Administration (FDA) granted a priority review to Enhertu (trastuzumab deruxtecan) for the treatment of patients with unresectable or metastatic HER2-positive breast cancer who previously received an anti-HER2—based regimen.

Priority reviews are granted to treatments that prove to be promising in clinical trials. When the FDA gives a drug a priority review, the agency is agreeing to speed up the review process that can lead to the drug’s approval. Now, the FDA is expected to determine whether to approve the regimen by the end of the second quarter of 2022.

If approved, Enhertu will offer an exciting new treatment for patients with HER2-positive breast cancer — a population that makes up approximately 20% of all breast cancer cases. While there have been treatment advancements for this population in recent years, many patients will experience disease progression and need more options for their next line of therapy.

Some experts are even saying that Enhertu could be the next standard of care for the second-line treatment of patients with HER2-positive metastatic breast cancer.

The priority review is based off findings from the randomized, open-label, phase 3 DESTINY-Breast03 trial, which showed that treatment with Enhertu resulted in a 72% reduction in the risk of disease progression or death compared with Kadcyla (T-DM1; trastuzumab emtansine) in patients with HER2-positive unresectable and/or metastatic breast cancer that were previously treated with Herceptin (trastuzumab) and a taxane.

At the one-year mark in DESTINY-Breast03, there were also more patients in the Enhertu group who were alive compared with the Kadcyla group (94.1% and 85.9%, respectively). Additionally, more patients’ disease responded to Enhertu (79.7%) than Kadcyla (34.2%).

According to data presented at the 2021 San Antonio Breast Cancer Symposium (SABCS), at the data cutoff point, 58.9% of patients in the Kadcyla group experienced disease progression compared with only 32.2% of those in the Enhertu group.

The drug was also beneficial for patients who had brain metastases. In this group, 67.4% responded to treatment with Enhertu, compared with 20.5% for Kadcyla. A total of 48.8% and 69.2% of patients experienced disease progression on Enhertu and Kadcyla, respectively.

There were also no new side effects seen from DESTINY-Breast03 than what was seen on other previous clinical trials, and there were also no severe (grade 4 or 5) treatment-related interstitial lung disease events, which is when treatment causes scarring of the lung.

Previously documented side effects from Enhertu include nausea, fatigue, vomiting, hair loss, constipation, decreased appetite, anemia, decreased neutrophil count, diarrhea, leukopenia (decrease in a type of white blood cell involved in the immune system), cough and decreased platelet count.

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