Menarini Group Receives Positive CHMP Opinion Recommending EC Approval of ORSERDU® (Elacestrant) for the Treatment of Patients with ER+, HER2- Locally Advanced or Metastatic Breast Cancer with an Activating ESR1 Mutation

• Each year in Europe more than 550,000 patients are diagnosed with breast cancer, of whom 70% have estrogen receptor (ER)-positive disease¹; more than 147,000 breast cancer patients in Europe die annually from the disease²

• If approved by the European Commission, ORSERDU would be the first and only treatment specifically indicated for patients with ER+, HER2- advanced or metastatic breast cancer tumors that harbor ESR1 mutations

• ESR1 mutations are present in up to 40% of ER+, HER2- advanced or metastatic breast cancers, and are a known driver of resistance to standard endocrine therapy, making these tumors more difficult to treat

The Menarini Group (“Menarini”), a leading international pharmaceutical and diagnostics company, and Stemline Therapeutics Inc. (“Stemline”), a wholly-owned subsidiary of the Menarini Group, announced today that the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) has adopted a positive opinion on the approval of ORSERDU^® (elacestrant) monotherapy, indicated for the treatment of postmenopausal women, and men, with estrogen receptor (ER)‑positive, HER2-negative, locally advanced or metastatic breast cancer with an activating ESR1 mutation who have disease progression following at least one line of endocrine therapy including a CDK 4/6 inhibitor.

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The CHMP opinion will now be reviewed by the European Commission, which has the authority to grant marketing authorization for human medicines throughout the European Union (EU). If approved, Stemline and its affiliates will commercialize the product within Europe. ORSERDU would be 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.

“Patients living with metastatic breast cancer are in need of efficacious and tolerable treatment options. ORSERDU may become the first product, if approved by the European Commission, indicated in ER+, HER2- advanced breast cancer with ESR1 mutations, which are a strong driver of resistance to treatment in up to 40% of patients in second line mBC. ORSERDU, if approved, will also provide a convenient daily oral treatment,” said Elcin Barker Ergun, CEO of the Menarini Group. “We are proud of today’s positive CHMP opinion as it reflects our commitment to developing innovative solutions that address the greatest unmet needs in cancer treatment, and brings us one step closer to providing an important new option to the patients and families impacted by ESR1-mutated, ER+, HER2- metastatic breast cancer.”

The positive CHMP opinion for ORSERDU is supported by data from the Phase 3 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 were 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 ≥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).³

“As an oncologist, it is remarkable that we are on the cusp of having the first treatment option for patients with advanced or metastatic ER+, HER2- breast cancer harboring ESR1 mutations, which occur in up to 40% of patients in the metastatic setting,” 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. “Elacestrant has demonstrated efficacy and a manageable safety profile, underscoring the potential benefit this therapy may soon bring to the patients we care for, and to the broader oncology community.”

Safety data were consistent with previously reported results. Serious adverse reactions reported in ≥ 1% of patients included nausea, dyspnoea, and thromboembolism (venous). The most common (≥ 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. The most common Grade ≥3 (≥2%) adverse reactions of elacestrant were nausea (2.7%), AST increased (2.7%), ALT increased (2.3%), anaemia (2%), back pain (2%), and bone pain (2%).

About the EMERALD Phase 3 Study (NCT03778931)

The EMERALD Phase 3 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.

Elacestrant is also being investigated in several clinical trials in metastatic breast cancer disease, alone or in combination with other therapies: ELEVATE (NCT05563220); ELECTRA (NCT05386108); and ELCIN (NCT05596409). Elacestrant is also planned to be evaluated in early breast cancer disease.

The Menarini Group obtained global licensing rights for elacestrant in July 2020 from Radius Health, Inc. The Menarini Group is now fully responsible for global registration, commercialization, and further development activities for elacestrant.

About The Menarini Group

The Menarini Group is a leading international pharmaceutical and diagnostics company, with a turnover of over $4.4 billion and over 17,000 employees. Menarini is focused on therapeutic areas with high unmet needs with products for cardiology, oncology, pneumology, gastroenterology, infectious diseases, diabetology, inflammation, and analgesia. With 18 production sites and 9 Research and Development centers, Menarini’s products are available in 140 countries worldwide. For further information, please visit www.menarini.com.

About Stemline Therapeutics Inc.

Stemline Therapeutics, Inc. (“Stemline”) a wholly-owned subsidiary of the Menarini Group, is a commercial-stage biopharmaceutical company focused on the development and commercialization of novel oncology therapeutics. Stemline commercializes ORSERDU^® (elacestrant) in the United States, an oral endocrine therapy indicated for the treatment of postmenopausal women or adult men with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative, ESR1-mutated advanced or metastatic breast cancer with disease progression following at least one line of endocrine therapy. Stemline also commercializes ELZONRIS^® (tagraxofusp-erzs), a novel targeted treatment directed to CD123 for patients with blastic plasmacytoid dendritic cell neoplasm (BPDCN), an aggressive hematologic cancer, in the United States and Europe, which is the only approved treatment for BPDCN in the US and EU to date. Stemline also commercializes Nexpovio^® in Europe, an XPO1 inhibitor for multiple myeloma. Stemline also has an extensive clinical pipeline of small molecules and biologics in various stages of development for a host of solid and hematologic cancers.

¹ Decision Resource Group / Clarivate Breast Cancer Landscape / Epidemiology – June 14, 2023

² International Agency for Research on Cancer, World Health Organization – Globocan – 2020

³ Bardia et al. EMERALD phase 3 trial of elacestrant versus standard of care endocrine therapy in patients with ER+/HER2- metastatic breast cancer: Updated results by duration of prior CDK4/6i in metastatic setting. SABCS 2022. GS3-01

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