SIM0270 + palbociclib

**SIM0270 + palbociclib** is a combination under clinical investigation for the treatment of advanced or metastatic breast cancer that is estrogen receptor-positive (ER+) and human epidermal growth factor receptor 2-negative (HER2-). SIM0270 is a novel oral selective estrogen receptor degrader (SERD), while palbociclib is a small molecule cyclin-dependent kinase 4/6 (CDK4/6) inhibitor approved for HR+/HER2- breast cancer. The combination aims to block estrogen receptor signaling and inhibit cellular proliferation by halting cell cycle progression via CDK4/6 inhibition. Preliminary phase 1 trial data show acceptable safety, tolerability, and promising anti-tumor activity in ER+/HER2- advanced breast cancer, including patients with ESR1 mutations[1][3][5][7].