Sermonix Pharmaceuticals Inc. and Shanghai Henlius Biotech, Inc. announced a strategic collaboration agreement in which Henlius will receive exclusive rights to develop, manufacture and commercialize Sermonix's lead investigational drug, Lasofoxifene, in China. Under the terms of the agreement, Henlius will receive exclusive Rights and sublicenses to Lasofoxifene for at least two estrogen receptor-positive (ER+)/HER2- breast cancer indications in the territory, with Sermonix retaining all other global rights. Sermonix received an upfront payment and is further eligible to receive up to $58 million in certain predetermined milestones, in addition to royalties upon Henlius commercialization in China.

Breast cancer is the cancer with the incidence rate in the world, according to GLOBOCAN 2020. There were 2.26 million new cases of breast cancer in 2020 globally, including more than 410,000 in China. Endocrine therapy remains the mainstay treatment for ER+ breast cancer and the most widely used class of aromatase inhibitor (AI) has been recommended by the National Comprehensive Cancer Network (NCCN) and Chinese Society of Clinical Oncology (CSCO) guidelines to be the adjuvant and first-line standard of care for patients with ER+/HER2- breast cancer.

However, almost all patients treated with AIs develop primary or acquired resistance, with acquired mutations in the estrogen receptor a gene (ESR1) being the most prevalent (up to 40%). This is a significant mechanism of resistance to endocrine therapy. Currently, there are limited treatment options for ER+/HER2- Breast cancer with ESR1 mutations, and thus a large clinical need exists.

The Phase 3 ELAINE-3 multi-regional clinical trial (NCT05696626) is the third of Sermonix?s Evaluation of Lasofoxifene in ESR1 Mutations (ELAINE) studies. With the Phase 2 ELAINE-1 and ELAINE-2 studies both completed and having shown compelling anti-tumor activity against tumors with increasingly prevalent ESR1 mutations, Sermonix in December 2023 activated and began enrollment for ELAINE-3 in the U.S. ELAINE-3 will assess the efficacy of lasofoxifene and Eli Lilly and Company?s CDK4/6 inhibitor abemaciclib (Verzenio®) compared to fulvestrant and abemaciclib in 400 pre- and post-menopausal subjects with locally advanced or metastatic ER+/HER2- breast cancer with an ESR1 mutation. Henlius will fund the clinical development and patient enrollment of the ELAINE-3 study in China, and be responsible for regulatory approval and post-marketing manufacturing and commercialization in the region.