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AstraZeneca Plc (NASDAQ:AZN) on Monday released topline data from the DESTINY-Breast09 Phase 3 trial of Enhertu (5.4mg/kg) either alone or in combination with pertuzumab versus standard of care THP (a taxane [docetaxel or paclitaxel], trastuzumab, and pertuzumab) as a first-line treatment in patients with HER2-positive metastatic breast cancer.
High-level results from a planned interim analysis showed Enhertu pertuzumab combination demonstrated a statistically significant and clinically meaningful improvement in progression-free survival (PFS) compared to THP.
The PFS improvement was seen across all pre-specified patient subgroups with Enhertu in combination with pertuzumab.
The key secondary endpoint of overall survival (OS) was not mature at this planned interim analysis; however, interim OS data showed an early trend favoring the Enhertu combination compared with THP.
The second arm assessing Enhertu monotherapy versus THP remains blinded to patients and investigators and will continue to the final PFS analysis.
HER2-positive metastatic breast cancer is an aggressive disease driven by overexpression or amplification of HER2, affecting 15-20% of patients with metastatic breast cancer.
While HER2-targeted therapies have improved outcomes, prognosis remains poor, with most patients experiencing disease progression within two years of 1st-line treatment with THP, which has been the standard of care for more than a decade.
Further, approximately one in three patients never go on to receive treatment following 1st-line therapy due to disease progression or death.
The safety profile of Enhertu in combination with pertuzumab was consistent with the known profiles of each therapy.
Enhertu is a specifically engineered HER2-directed DXd antibody-drug conjugate (ADC) discovered by Daiichi Sankyo (OTC:DSNKY) (OTC:DSKYF) and being jointly developed and commercialized by AstraZeneca and Daiichi Sankyo.
Data from the combination arm of DESTINY-Breast09 will be presented at an upcoming medical meeting and shared with regulatory authorities.
Enhertu is already approved in more than 75 countries as the 2nd-line treatment for patients with HER2-positive breast cancer based on the results from the DESTINY-Breast03 trial.
In January, the U.S. Food and Drug Administration (FDA) approved Enhertu for adult patients with breast cancer that has progressed on one or more endocrine therapies in the metastatic setting.