Daiichi Sankyo and AstraZeneca's ENHERTU® (fam-trastuzumab deruxtecan-nxki) has been approved in the U.S. for the treatment of adult patients with unresectable or metastatic HER2 low (IHC 1+ or IHC 2+/ISH-) breast cancer who have received a prior chemotherapy in the metastatic setting or developed disease recurrence during or within six months of completing adjuvant chemotherapy. ENHERTU is a specifically engineered HER2 directed antibody drug conjugate (ADC) being jointly developed and commercialized by Daiichi Sankyo and AstraZeneca. The approval was granted under the FDA's Real-Time Oncology Review (RTOR) program following the recent Priority Review [1] and Breakthrough Therapy Designation [2] of ENHERTU in the U.S. in this setting.

The expanded approval for ENHERTU in the U.S. enables its use across a wide spectrum of HER2 expression, including patients with HER2 low disease. The approval by the U.S. Food and Drug Administration (FDA) was based on positive results from the DESTINY-Breast04 [3] phase 3 trial of previously treated patients with HER2 low metastatic breast cancer. In the trial, ENHERTU demonstrated a 49% reduction in the risk of disease progression or death versus physician's choice of chemotherapy in patients with HER2 low metastatic breast cancer with hormone receptor (HR) positive disease (hazard ratio [HR] = 0.51; 95% confidence interval [CI]: 0.40-0.64; pFinancial Considerations Following approval in the U.S., an amount of $200 million is due from AstraZeneca to Daiichi Sankyo as a milestone payment for an indication for ENHERTU in patients with HER2 low metastatic breast cancer who were previously treated with one or two lines of chemotherapy.