The Menarini Group and Stemline Therapeutics Inc. presented results from a new post hoc analysis of the pivotal EMERALD clinical study that demonstrated a clinically meaningful improvement in progression-free survival (PFS) across all relevant subgroups. The data show favorable PFS for single-agent ORSERDU (elacestrant) compared to standard-of-care (SOC) for patients with ER+, HER2- advanced or metastatic breast cancer (mBC) with tumors that are endocrine sensitive and which harbor ESR1 mutations, when prior treatment duration with CDK4/6 inhibitors was at least 12 months. This data is being presented at the 2023 San Antonio Breast Cancer Symposium (SABCS), December 5-9, 2023.

EMERALD is a Phase 3 registrational trial that demonstrated statistically significant PFS with ORSERDU versus SOC endocrine monotherapy (fulvestrant, letrozole, anastrozole, exemestane). Based on these results, the FDA approved ORSERDU on January 27, 2023, for the treatment of postmenopausal women or adult men with ER+, HER2-, HER2 mutated advanced or metastatic breast cancer with disease progression following at least one line of endocrine therapy. ESR1 mutations are present in up to 40% of ER+, HER2- advanced and mBC.

They are a known driver of resistance to standard endocrine therapy, and until now, the tumors that harbor these mutations have been more difficult to treat. ORSERDU showed significantly greater PFS when prior treatment duration with CD K4/6 inhibitors was at least 12 months, indicating that when ESR1 mutated tumors remain endocrine sensitive, the ER pathway could be a key driver of disease, regardless of the metastatic site, concomitant PIK3CA or TP53 mutations, or HER2-low expression.