BGB-21447 + fulvestrant + BGB-43395

BGB-21447 + fulvestrant + BGB-43395 is an investigational **combination therapy** for hormone receptor-positive, HER2-negative (HR+/HER2-) metastatic breast cancer. - **BGB-21447** is a small molecule inhibitor of B-cell lymphoma 2 (Bcl-2), developed to promote apoptosis in cancer cells by disrupting the survival signals mediated by Bcl-2. - **BGB-43395** is a highly selective **cyclin-dependent kinase 4 (CDK4) inhibitor**, designed to target CDK4-dependent tumors and minimize off-target toxicities seen with existing CDK4/6 inhibitors. - **Fulvestrant** is a well-established estrogen receptor antagonist that induces degradation of the estrogen receptor, thereby suppressing estrogen-driven tumor growth. This combination aims to address endocrine resistance and enhance anti-tumor effects through simultaneous inhibition of multiple cancer-promoting pathways. The combination is in Phase 1 trials to evaluate safety, tolerability, pharmacokinetics, and preliminary efficacy in patients with HR+/HER2- metastatic breast cancer who have previously received at least two lines of therapy, including a CDK4/6 inhibitor and endocrine therapy[5][4][7][2].