Daiichi Sankyo Company, Limited (hereafter, Daiichi Sankyo) today announced that the first patient was dosed in the global TROPION-Breast01 phase 3 trial evaluating the efficacy and safety of datopotamab deruxtecan (Dato-DXd), a TROP2 directed DXd antibody drug conjugate (ADC) being jointly developed by Daiichi Sankyo and AstraZeneca (NASDAQ:AZN), in patients with hormone receptor (HR) positive, human epidermal growth factor 2 receptor (HER2) negative inoperable or metastatic breast cancer previously treated with chemotherapy.

Breast cancer is the most common cancer worldwide with more than two million cases diagnosed in 2020, resulting in nearly 685,000 deaths globally.1 Approximately 70% of all breast cancers are considered HR positive, HER2 negative.2 For patients with HR positive, HER2 negative metastatic breast cancer that progresses on or is not suitable for hormone therapy-based regimens, current standard of care is single-agent chemotherapy, which demonstrates diminishing efficacy with each subsequent line of treatment.3

"There are no TROP2 directed therapies currently approved for HR positive, HER2 negative breast cancer and we are encouraged by the emerging clinical profile of datopotamab deruxtecan in patients with breast cancer," said Gilles Gallant, BPharm, PhD, FOPQ, Senior Vice President, Global Head, Oncology Development, Oncology R&D, Daiichi Sankyo. "TROPION-Breast01 is the first pivotal trial of datopotamab deruxtecan in breast cancer and the third pivotal study in our clinical development program, underscoring our efforts to accelerate development of this TROP2 directed ADC in breast and lung cancer."

"Most patients with HR positive, HER2 negative metastatic breast cancer will inevitably progress on available treatments, including hormonal therapy and standard of care chemotherapy. In this setting, the unmet need is high, and new therapeutic approaches are necessary to delay disease progression and extend survival," said Cristian Massacesi, MD, Chief Medical Officer and Oncology Chief Development Officer, AstraZeneca. "The TROPION-Breast01 trial will evaluate whether datopotamab deruxtecan may be a more effective treatment than chemotherapy for patients with previously treated HR positive, HER2 negative advanced breast cancer previously treated with one to two lines of chemotherapy."