BEBT-209 + letrozole

BEBT-209 + letrozole is an investigational oral combination therapy for hormone receptor-positive, HER2-negative advanced breast cancer in women. BEBT-209 is a **highly selective cyclin-dependent kinase 4 (CDK4) inhibitor** developed to minimize hematologic toxicity and improve tolerability compared to pan-CDK4/6 inhibitors. Letrozole is a **non-steroidal aromatase inhibitor** that suppresses estrogen synthesis, widely used in hormone receptor-positive breast cancer. This combination leverages the cell cycle arrest induced by CDK4 inhibition and the anti-estrogenic action of letrozole. In phase 1b clinical studies, BEBT-209 plus letrozole demonstrated favorable pharmacokinetics, promising efficacy (median PFS ~25 months), and a manageable safety profile (predominantly neutropenia). Both agents are administered orally. The developer and primary sponsor is BeBetter Med.