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FDA Approves Enhertu as Second-Line Therapy for Advanced HER2-Positive Breast Cancer

NEW YORK – AstraZeneca and Daiichi Sankyo said Wednesday that the US Food and Drug Administration has approved Enhertu (trastuzumab deruxtecan) as a second-line therapy for patients with unresectable or metastatic HER2-positive breast cancer, building on its original accelerated approval in 2019 as a third-line therapy in that indication.

The agency's latest action through its Real-Time Oncology Review program converts Enhertu's earlier accelerated approval to a full approval. HER2-positive metastatic breast cancer patients can now receive Enhertu after they've received an anti-HER2-based regimen either in the metastatic setting or in the neoadjuvant or adjuvant setting and have relapsed within six months of completing therapy. Under accelerated approval, advanced breast cancer patients could receive Enhertu after having two or more prior anti-HER2-based regimens in the metastatic setting.

The FDA granted full approval based on data from the DESTINY-Breast03 Phase III clinical trial, in which Enhertu treatment reduced the risk of disease progression or death by 72 percent compared to Genentech's competing agent Kadcyla (trastuzumab emtansine).

In a preliminary analysis presented at the European Society for Medical Oncology Congress in September 2021, the overall survival rate for patients treated with Enhertu after a year of follow-up was 94 percent compared to 85.9 percent for Kadcyla. The overall response rates were 79.7 percent and 34.2 percent, respectively.

"Enhertu has demonstrated significant progression-free survival in the earlier metastatic setting, potentially establishing it as a new standard of care in previously treated patients with HER2-positive metastatic breast cancer," Erika Hamilton, a DESTINY-Breast03 investigator and director of breast and gynecologic cancer research at the Sarah Cannon Research Institute, said in a statement. "Today's approval is an important milestone for the clinical community as we will now be able to offer Enhertu to these patients earlier in their treatment."

Enhertu and Kadcyla are both HER2-directed antibody-drug conjugates that comprise Genentech's monoclonal antibody Herceptin (trastuzumab) but are linked to different cyto-toxic agents.

In the HER2-positive metastatic breast cancer setting, Kadcyla is approved in the US for patients who have received Herceptin and a taxane, alone or in combination. Patients must have received prior treatment for metastatic breast tumors or recurred within six months of adjuvant treatment.

Enhertu is also approved in the US as a second-line therapy for patients with locally advanced or metastatic HER2-positive gastric adenocarcinomas. AstraZeneca and Daiichi Sankyo are also studying the agent in a Phase II trial in patients with HER2-mutated non-small cell lung cancer.