• ORSERDU is the first treatment specifically approved for patients with ER+, HER2- advanced or metastatic breast cancer tumors that harbor ESR1 mutations, representing the first innovation in endocrine therapy in nearly 20 years.
• 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.
• This agreement includes undisclosed upfront, milestone payments and sales royalties.

ORSERDU, a once-daily oral endocrine monotherapy, for the treatment of postmenopausal women or adult men, with ER+, HER2-, ESR1-mutated advanced or metastatic breast cancer with disease progression following at least one line of endocrine therapy, was approved by the U.S. Food and Drug Administration in January 2023 under its priority review and fast track designation. In September 2023, ORSERDU was approved by the European Commission. Stemline Therapeutics, a wholly-owned subsidiary of the Menarini Group, focused on bringing transformational oncology treatments to cancer patients, commercializes ORSERDU in the U.S. and E.U.

Under the Sub-Licensing agreement, SciClone will pursue the development and registration of ORSERDU in China and commercialise ORSERDU upon its regulatory approval in China.

"Patients living with metastatic breast cancer need effective and tolerable options," said Elcin Barker Ergun, CEO of the Menarini Group. "We are proud to partner with SciClone in an effort to register a new breast cancer treatment for patients in China that can offer efficacy in a once-daily pill."

Approximately 70% of breast cancer cases are ER+, HER2-, and up to 40% of ER+, HER2- advanced or mBC tumors harbor ESR1 mutations, which develop as result of exposure to endocrine therapy in the metastatic setting. These 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. 

"China accounts for 20% of breast cancer prevalence worldwide,¹ and we know that these patients need new therapeutic options, particularly in the metastatic setting," said Zhao Hong, Executive Director, President and CEO of SciClone. "We believe that this agreement will enable us to work toward providing oncologists with an important option in the treatment armamentarium for their ER+, HER2- mBC patients whose tumors have an ESR1 mutation."

The approval of ORSERDU in the U.S. and E.U. 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 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 ≥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).²

Safety data were consistent with previously reported results. The most common adverse reactions with ORSERDU were musculoskeletal pain, nausea, triglycerides increased, cholesterol increased, vomiting, fatigue, dyspepsia, diarrhea, calcium decreased, back pain, creatinine increased, arthralgia, sodium decreased, constipation, headache, hot flush, abdominal pain, anemia, potassium decreased, and alanine aminotransferase increased. Important Safety Information for ORSERDU is provided below.