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AstraZeneca, Daiichi Sankyo Advance Regulatory Plans for Enhertu in Metastatic Breast Cancer

NEW YORK – AstraZeneca and Daiichi Sankyo are readying global regulatory submissions for trastuzumab deruxtecan (Enhertu) after it bested Genentech's trastuzumab emtansine (T-DM1/Kadcyla) as a treatment for HER2-positive, previously treated, metastatic breast cancer patients in a Phase III trial.

In the DESTINY-Breast03 study, researchers randomized around 500 unresectable or metastatic, HER2-positive breast cancer patients to either trastuzumab deruxtecan or T-DM1. Patients had to have previously received the standard of care trastuzumab (Genentech's Herceptin) and a taxane.

An independent data monitoring committee concluded based on a planned interim analysis that the study had met its primary endpoint after trastuzumab deruxtecan statistically significantly improved progression-free survival in patients compared to T-DM1. In the study, trastuzumab deruxtecan also trended toward improving patients' overall survival compared to T-DMI. There were no new safety concerns related to AstraZeneca and Daiichi Sankyo's drug in the study.

In a statement, Ken Takeshita, global head of R&D at Daiichi Sankyo, said the DESTINY-Breast03 is the first trial where trastuzumab deruxtecan is compared to an active drug in the control arm, and based on the data it may become the new standard of care in HER2-positive breast cancer patients who have already received the standard treatment. The company said it will share the results from the study at an upcoming medical meeting, as well as with regulators globally.

The US Food and Drug Administration in December 2019 granted accelerated approval to trastuzumab deruxtecan for unresectable or metastatic, HER2-positive breast cancer patients following two or more HER2-targeted regimens for metastatic disease. That expedited approval was based on the results from a single-arm trial of 184 heavily pretreated, metastatic breast cancer patients, in which the overall response rate for trastuzumab deruxtecan was around 60 percent.

"There is a continued need for new options and better outcomes for patients with HER2-positive metastatic breast cancer who often experience disease progression after initial treatment with available standards of care," Susan Galbraith, executive VP of Oncology R&D, said in a statement. "These transformative progression-free survival results demonstrate the superiority of Enhertu compared to T-DM1, and the encouraging safety data may open future opportunities to bring this benefit to patients in earlier treatment settings."