Summary: The purpose of this study is to investigate the efficacy and safety of BGB-43395 in combination with letrozole compared with investigator's choice of cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) in combination with letrozole in patients with advanced or metastatic hormone receptor positive (HR+)/human epidermal growth factor receptor 2 negative (HER2-) breast cancer (BC) who have not received p...

Summary: This phase III trial compares standard of care hormone therapy plus ribociclib to chemotherapy followed by hormone therapy plus ribociclib for the treatment of patients with high anatomic stage breast cancer with low risk of the cancer returning (low risk recurrence). Ribociclib may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Hormone therapy, with letrozo...

Summary: This is an umbrella study evaluating the efficacy and safety of multiple treatment combinations in participants with metastatic or inoperable locally advanced breast cancer. The study will be performed in two stages. During Stage 1, seven cohorts will be enrolled in parallel in this study: Cohort 1 will consist of programmed death-ligand 1 (PD-L1)-positive participants who have received no prior s...