Japanese healthcare company Daiichi Sankyo Co Ltd (TYO:4568) and British-Swedish biopharmaceutical company AstraZeneca plc (STO:AZN) (LON:AZN) (Nasdaq:AZN) announced on Wednesday that the US.Food and Drug Administration (FDA) has accepted and granted Priority Review for a supplemental Biologics License Application of ENHERTU in combination with pertuzumab.

The application seeks approval for use as a first-line treatment for adult patients with unresectable or metastatic HER2 positive breast cancer.

This filing is supported by results from the phase 3 DESTINY-Breast09 trial, which showed that ENHERTU plus pertuzumab reduced the risk of disease progression or death by 44% compared to the standard taxane, trastuzumab, and pertuzumab regimen. Median progression-free survival exceeded three years with the ENHERTU-based therapy, versus 26.9 months for the comparator arm.

The FDA designated the combination for Priority Review following a Breakthrough Therapy Designation in July 2025. A regulatory decision is expected by 23 January 2026, under the Prescription Drug User Fee Act timeline. The review is being conducted under the FDA's Real-Time Oncology Review programme, designed to accelerate access to promising cancer therapies.

The DESTINY-Breast09 data also showed an objective response rate of 85.1% for ENHERTU plus pertuzumab, including 58 complete responses, compared with 78.6% for the standard regimen. Median duration of response surpassed three years, with safety findings consistent with the known profiles of each therapy.

ENHERTU, a specifically engineered HER2-directed antibody drug conjugate discovered by Daiichi Sankyo and jointly developed with AstraZeneca, is already approved in more than 85 countries for previously treated HER2 positive breast cancer.