This is a Phase III, randomized, double-blind, placebo-controlled, international, multi-center trial. Approximately 234 men and postmenopausal women will be randomized to either alpelisib plus fulvestrant or alpelisib-matching placebo plus fulvestrant. Randomization will follow a 1:1 randomization ratio and be stratified by presence of lung and/or liver metastases (yes vs. no) and setting at last prior CDK4/6 inhibitor therapy (adjuvant vs metastatic).~Study treatment with alpelisib plus fulvestrant or alpelisib-matching placebo plus fulvestrant will be initiated on Cycle 1 Day 1, and will continue until disease progression per RECIST v1.1 as per BIRC assessment, start of new antineoplastic therapy, death, lost to follow-up, or withdrawal of consent. A cycle is defined as 28 days.~Participants randomized to the alpelisib-matching placebo plus fulvestrant arm who have disease progression per RECIST v1.1 as assessed by BIRC will have the option to crossover to be treated with alpelisib plus fulvestrant.~Unblinding a single participant at a site will be permitted after disease progression confirmed by BIRC after discussion with the Novartis team to determine eligibility for cross-over to treatment with alpelisib plus fulvestrant.
The purpose of this study is to complement Study CBYL719C2301 (SOLAR-1) and obtain more comprehensive data on the efficacy and safety of alpelisib (BYL719) in combination with fulvestrant compared with placebo plus fulvestrant in men or postmenopausal women with HR-positive, HER2-negative advanced breast cancer with a PIK3CA mutation who progressed or relapsed on or after treatment with an AI plus a CDK4/6 inhibitor.