The HER2-directed antibody-drug conjugate Enhertu (trastuzumab deruxtecan) has won FDA approval for patients with unresectable or metastatic HER2-low breast cancer.

Enhertu is now the first approved therapy for patients with HER2-low breast cancer subtype.

The recent approval covers patients with HER2-low breast cancer if they have had chemotherapy for metastatic cancer or if their cancer returned within 6 months of completing an adjuvant chemotherapy regimen.

Patients with low levels of the HER2 protein have traditionally had fewer treatment options than patients with HER2-positive breast cancer, according to the National Cancer Institute. Treatment options for such patients typically included endocrine therapy or chemotherapy.

Overall, about 2 million women per year are diagnosed with breast cancer.

FDA estimated that approximately 60% of patients with HER2-negative breast cancer qualify for the HER2-low designation.

AstraZeneca (LON:AZN) and Daiichi Sankyo (OTCMKTS: DSNKY) jointly developed Enhertu.

To win the approval, the companies provided data from the Phase 3 DESTINY-Breast04 trial.

In April, Enhertu won Breakthrough Therapy designation from the FDA for HER2-low breast cancer, marking the fifth such designation for the drug.

In 2019, Enhertu first won FDA approval for some patients with HER2-positive unresectable or metastatic breast cancer. Two years later, the drug won an indication for previously treated HER2-positive advanced gastric cancer. Enhertu won approval in May 2022 for patients with HER2-positive metastatic breast cancer treated with an anti-HER2-based therapy.