Positive high-level results from the DESTINY-Breast06 Phase III trial showed that ENHERTU^® (fam-trastuzumab deruxtecan-nxki) demonstrated a statistically significant and clinically meaningful improvement in progression-free survival (PFS) compared to standard-of-care chemotherapy in the primary trial population of patients with HR-positive, HER2-low (IHC 1+ or 2+/ISH-) metastatic breast cancer following one or more lines of endocrine therapy.

A statistically significant and clinically meaningful improvement in PFS was also observed in the overall trial population (patients with HER2-low and HER2-ultralow [defined as IHC 0 with membrane staining; IHC >0<1+] metastatic breast cancer). A prespecified subgroup analysis showed the clinically meaningful improvement was consistent between patients with HER2-low and HER2-ultralow expression.

Overall survival (OS) data were not mature at the time of the analysis; however, ENHERTU showed an early trend towards an OS improvement versus standard-of-care chemotherapy in patients with HER2-low metastatic breast cancer and in the overall trial population. The trial will continue as planned to further assess OS and other secondary endpoints.

Susan Galbraith, Executive Vice President, Oncology R&D, AstraZeneca, said: “DESTINY-Breast06 shows that ENHERTU could become a new standard of care for patients with HER2-low and HER2-ultralow metastatic breast cancer following one or more lines of endocrine therapy. These data underscore the potential for treatment with ENHERTU across the spectrum of HR-positive breast cancer, further redefining the treatment of metastatic breast cancer.”

Ken Takeshita, Global Head, R&D, Daiichi Sankyo, said: “The topline results from DESTINY-Breast06 highlight the importance of continuing to challenge current treatment paradigms and established breast cancer classifications to evolve how we treat patients with HR-positive, HER2-expressing metastatic breast cancer. Building on the practice-changing data seen in DESTINY-Breast04, these results reinforce the potential for use of ENHERTU earlier in the treatment landscape and in an even broader patient population.”

ENHERTU is a specifically engineered HER2-directed DXd antibody drug conjugate (ADC) discovered by Daiichi Sankyo and being jointly developed and commercialized by AstraZeneca and Daiichi Sankyo.

It is estimated that approximately 60-65% of HR-positive, HER2-negative breast cancers are HER2-low and potentially an additional 25% may be HER2-ultralow.^1,2 Endocrine therapies are widely used in the early lines of treatment for HR-positive metastatic breast cancer; however after two lines of treatment, further efficacy from endocrine therapy is often limited.³ The current standard of care following endocrine therapy is chemotherapy, which is associated with poor response rates and outcomes