FDA Grants Enhertu a Priority Review for Metastatic HER2-Low Breast Cancer

The Food and Drug Administration (FDA) granted Enhertu (trastuzumab deruxtecan) a priority review for the treatment of patients with unresectable or metastatic HER2-low breast cancer that was previously treated with chemotherapy in the metastatic setting, according to AstraZeneca and Daiichi Sankyo, the manufacturers of the antibody drug conjugate.

By granting a priority review, the FDA is agreeing to speed up communications with the drug developers and potentially expedite the approval process, considering that clinical trial results show that the drug may improve outcomes for this patient population. The FDA plans on making an approval decision between October and December of 2022.

The priority review is based off findings from the phase 3 DESTINY-Breast04 clinical trial, which compared Enhertu to standard chemotherapy in patients with HER2-low metastatic breast cancer with HR-positive or HR-negative disease. Results showed that Enhertu improved progression-free survival (time from treatment until the disease gets worse) and overall survival (time from treatment until death of any cause) in patients with HER2-low metastatic breast cancer with HR-positive or HR-negative disease.

“The data from DESTINY-Breast04 represent the first time a HER2-targeted therapy has shown a survival benefit in patients with HER2-low metastatic breast cancer,” Susan Galbraith, executive vice president of Oncology R&D at AstraZeneca, said in a press release. “For more than two decades, only patients with HER2-positive breast cancer have been able to benefit from HER2-targeted therapies.”

Additionally, there were no new side effects of safety concerns seen on DESTINY-Breast04 that were not previously observed with Enhertu on other clinical trials. Interstitial lung disease (a group of lung disorders that makes it difficult for the lungs to get enough oxygen) or pneumonitis (lung inflammation) rates were similar to what was seen in studies of Enhertu in late-line HER2-positive breast cancer.

Most instances (10%) of these lung-related side effects were low grade (grade 1 or 2). There were five patients (1.3%) who experienced grade 3 interstitial lung disease/pneumonitis and no grade 4 side effects. Three patients (0.8%) died as a result of lung-related side effects.

Of note, the severity of side effects is graded on a 1 to 5 scale. A grade 1 or grade 2 side effect is considered mild to moderate in terms of severity. Grades 3 and 4 side effects are serious or severe in nature.

READ MORE: Enhertu Fulfills ‘Big Unmet Need’ for Patients With HER2-Low Metastatic Breast Cancer

“If approved, Enhertu will redefine how we classify and treat metastatic breast cancer, enabling patients whose tumors have lower levels of HER2 expression the opportunity to benefit from a HER2-directed therapy,” Galbraith said.

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