Study Assessing the Efficacy and Safety of Treatment With Alpelisib Plus Fulvestrant Versus Placebo Plus Fulvestrant in Chinese Men and Postmenopausal Women With Advanced Breast Cancer

This is a Phase II, randomized, double-blind, placebo-controlled, multi-center study conducted in Chinese men and postmenopausal women with HR- positive, HER2-negative, PIK3CA mutant advanced breast cancer which progressed on or after AI treatment. The study also includes a single arm, open-label cohort (the PK cohort) to conduct pharmacokinetic analysis. For the randomized cohort, in the randomized treatment phase, subjects will be randomized 1:1 to receive alpelisib or matching placebo plus fulvestrant. A total of approximately 120 subjects will be enrolled; randomization will be stratified by: 1. Lung and/or liver metastases (yes versus no) 2. Previous treatment with any CDK4/6 inhibitor (yes versus no) The total number of subjects pre-treated with any CDK4/6 inhibitor will be limited to 30% of the total number of subjects. Approximately 15 subjects meeting the same inclusion/exclusion criteria as the randomized cohort will be enrolled into the PK cohort. Subjects in the PK cohort will receive alpelisib plus fulvestrant. Subjects will continue to receive study treatment until disease progression as determined by investigator, unacceptable toxicity, or until discontinuation of study treatment due to any other reason.