European Commission approves Orserdu (elacestrant) for the treatment of patients with ER+, HER2- locally advanced or metastatic breast cancer with an activating ESR1 mutation

The European Commission’s approval follows the positive opinion of the Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA), which was issued in July 2023.

With this approval, Orserdu is the first and only therapy specifically indicated for the treatment of ER+, HER2- tumors that harbor ESR1 mutations. ESR1 mutations are acquired mutations that develop as a result of exposure to endocrine therapy, and they are found in up to 40% of patients with ER+, HER2- mBC. ESR1 mutations 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.

“With a significant number of ER+ HER2- patients ultimately developing ESR1 mutations at some point in their metastatic journey, it is important to test for ESR1 each time an mBC patient experiences disease progression, to understand what is fueling their breast cancer. This approval gives us the first-ever treatment option that directly acts against the very mutations that make this form of breast cancer more difficult to treat, and provides hope to our patients and their families,” said Giuseppe Curigliano, MD, PhD, Professor of Medical Oncology at the University of Milano and the Head of the Division of Early Drug Development at the European Institute of Oncology, IRCCS, Italy.

The approval of Orserdu is supported by data from the Phase III EMERALD trial, which demonstrated statistically significant progression-free survival (PFS) with elacestrant versus standard-of-care (SOC), defined as investigator’s choice of an approved endocrine monotherapy. The primary endpoints of the study were PFS in the overall patient population and in patients with ESR1 mutations. In the group of patients whose tumors had ESR1 mutations, elacestrant achieved a median PFS of 3.8 months vs 1.9 months on the SOC, and reduced the risk of progression or death by 45% (PFS HR=0.55, 95% CI: 0.39, 0.77) vs SOC.

A post hoc subgroup analysis of the EMERALD PFS results, which was presented at the San Antonio Breast Cancer Symposium (SABCS) 2022, demonstrated that the duration of prior CDK4/6i treatment was positively associated with longer PFS on elacestrant but not with SOC. For patients with ESR1 mutations who were treated with CDK4/6i for greater than 12 months prior to randomization on EMERALD, elacestrant achieved a median PFS of 8.6 months versus 1.9 months on SOC, with a 59% reduction in the risk of progression or death (HR=0.41 95% CI: 0.26-0.63).

Safety data were consistent with previously reported results. The most common ( greater than 10%) adverse reactions with Orserdu were nausea, triglycerides increased, cholesterol increased, vomiting, fatigue, dyspepsia, diarrhoea, calcium decreased, back pain, creatinine increased, arthralgia, sodium decreased, constipation, headache, hot flush, abdominal pain, anaemia, potassium decreased, and alanine aminotransferase increased.

Stemline and its affiliates will commercialize the product within Europe.

About the EMERALD Phase III Study (NCT03778931): The EMERALD Phase III trial is a randomized, open label, active-controlled study evaluating elacestrant as second- or third-line monotherapy in ER+, HER2- advanced/metastatic breast cancer patients. The study enrolled 478 patients who had received prior treatment with one or two lines of endocrine therapy, including a CDK4/6 inhibitor. Patients in the study were randomized to receive either elacestrant or the investigator's choice of an approved hormonal agent. The primary endpoints of the study were progression-free survival (PFS) in the overall patient population and in patients with estrogen receptor 1 gene (ESR1) mutations. In the group of patients whose tumors had ESR1 mutations, elacestrant achieved a median PFS of 3.8 months vs 1.9 months on the SOC, and reduced the risk of progression or death by 45% (PFS HR=0.55, 95% CI: 0.39, 0.77) vs SOC.