Topline results from the TROPION-Breast01 phase 3 trial of datopotamab deruxtecan (Dato-DXd) compared to investigator's choice of chemotherapy, which previously met the dual primary endpoint of progression-free survival (PFS), did not achieve statistical significance in the final overall survival (OS) analysis in patients with inoperable or metastatic hormone receptor (HR) positive, HER2 low or negative (IHC 0, IHC 1+ or IHC 2+/ISH-) breast cancer previously treated with endocrine-based therapy and at least one systemic therapy.

Datopotamab deruxtecan is a specifically engineered TROP2 directed DXd antibody drug conjugate (ADC) discovered by Daiichi Sankyo (TSE: 4568) and being jointly developed by Daiichi Sankyo and AstraZeneca (NASDAQ:AZN).

This analysis follows the positive PFS results presented at the 2023 European Society for Medical Oncology Congress which showed datopotamab deruxtecan demonstrated a statistically significant and clinically meaningful improvement in PFS. An improvement in patient-reported outcomes was also seen.1 The PFS data and additional results for key secondary endpoints were published this month in the Journal of Clinical Oncology.

The safety profile of datopotamab deruxtecan was consistent with that observed in the previous analysis, including lower rates of grade 3 or higher treatment-related adverse events compared to chemotherapy, and no new safety concerns identified. All grade interstitial lung disease (ILD) rates remained low with no new grade 3 or higher ILD events observed.

With ADCs approved during the course of the trial, including ENHERTU (trastuzumab deruxtecan), subsequent treatment following patients' disease progression or treatment discontinuation is likely to have affected survival results.

"Datopotamab deruxtecan has previously shown a statistically significant progression-free survival benefit in TROPION-Breast01, a result supported by multiple meaningful secondary measures including patient-reported outcomes," said Ken Takeshita, MD, Global Head, R&D, Daiichi Sankyo. "We are proud to have brought forth a new standard of care for patients with metastatic breast cancer with ENHERTU and we remain committed to making datopotamab deruxtecan another potential option for patients who can benefit."

"The metastatic HR positive breast cancer treatment landscape has advanced remarkably in the last several years to the benefit of patients," said Susan Galbraith, MBBChir, PhD, Executive Vice President, Oncology R&D, AstraZeneca. "Based on the TROPION-Breast01 results, there is evidence of the clinical value of datopotamab deruxtecan in this setting. We will continue discussions with regulatory authorities and apply insights from these results to our clinical development program for datopotamab deruxtecan in breast cancer."

The data will be presented at an upcoming medical meeting and shared with regulatory authorities currently reviewing applications for this indication.

In addition to TROPION-Breast01, Daiichi Sankyo and AstraZeneca are evaluating datopotamab deruxtecan alone and with immunotherapy as treatment for patients with triple negative or HR low, HER2 negative breast cancers in the TROPION-Breast02, TROPION-Breast03, TROPION-Breast04 and TROPION-Breast05 phase 3 trials.