The European Commission has approved AstraZeneca (NASDAQ: AZN) and Daiichi Sankyo's (TSE: 4568) Enhertu (trastuzumab deruxtecan) in combination with pertuzumab for the first-line treatment of adult patients with unresectable or metastatic HER2-positive breast cancer.

The approval is based on results from the DESTINY-Breast09 Phase III trial, which were presented at the 2025 American Society of Clinical Oncology Annual Meeting and published in The New England Journal of Medicine. In the trial, Enhertu combined with pertuzumab reduced the risk of disease progression or death by 44% compared to a taxane, trastuzumab, and pertuzumab regimen, based on a hazard ratio of 0.56 (95% CI 0.44–0.71; p<0.00001).

Median progression-free survival was 40.7 months with the Enhertu combination versus 26.9 months with the comparator regimen, as assessed by blinded independent central review. No new safety concerns were identified.

Based on these results, the European Society for Medical Oncology has included Enhertu plus pertuzumab in its Clinical Practice Guidelines as a Category IA first-line treatment option for patients with metastatic HER2-positive breast cancer, regardless of hormone receptor status.

Following the approval, AstraZeneca will pay Daiichi Sankyo a $100 million milestone payment for the first-line unresectable or metastatic HER2-positive breast cancer indication. Sales of Enhertu in most EU territories are recognized by Daiichi Sankyo.

Enhertu is also under review in the EU for patients with HER2-positive breast cancer who have residual invasive disease following neoadjuvant HER2-targeted treatment, based on data from the DESTINY-Breast05 trial.