FCN-437c + fulvestrant + goserelin acetate

This is a combination therapy consisting of three agents: FCN-437c, fulvestrant, and goserelin acetate. **FCN-437c** is an oral, second-generation, potent and selective cyclin-dependent kinase 4/6 (CDK4/6) inhibitor developed for the treatment of hormone receptor-positive (HR+), HER2-negative advanced or metastatic breast cancer. It acts by inhibiting CDK4 and CDK6, thereby blocking cell cycle progression from G1 to S phase in tumor cells[3][5][8]. **Fulvestrant** is a selective estrogen receptor degrader (SERD) that binds to estrogen receptors and accelerates their degradation, leading to downregulation of estrogen signaling in breast cancer cells. **Goserelin acetate** is a synthetic luteinizing hormone-releasing hormone (LHRH) agonist that suppresses ovarian function and reduces circulating estrogen levels by downregulating pituitary gonadotropins. The combination targets multiple pathways involved in HR+ breast cancer growth: cell cycle regulation via CDK4/6 inhibition (FCN-437c), direct blockade/degradation of the estrogen receptor pathway (fulvestrant), and suppression of endogenous estrogen production through ovarian suppression (goserelin acetate). This multi-pronged approach aims to overcome resistance mechanisms seen with single-agent therapies.