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

Inclusion Criteria: * Japanese man or postmenopausal woman * Participant has adequate tumor tissue for the analysis of PIK3CA mutational status by a Novartis designated laboratory. * Participant has identified PIK3CA mutation (as determined by a Novartis designated laboratory) * Participant has a histologically and/or cytologically confirmed diagnosis of ER+ and/or PgR+ breast cancer by local laboratory * Participant has HER2-negative breast cancer defined as a negative in situ hybridization test or an IHC status of 0, 1+ or 2+. If IHC is 2+, a negative in situ hybridization (FISH, CISH or SISH) test is required by local laboratory testing * Participant has measurable disease, i.e., at least one measurable lesion as per RECIST 1.1 * Participant has advanced breast cancer * Participant has ECOG performance status 0 or 1 Exclusion Criteria: * Participant with symptomatic visceral disease or any disease burden that makes the participant ineligible for endocrine therapy per the investigator's best judgment * Participant has received prior treatment; * with chemotherapy (except for neoadjuvant/ adjuvant chemotherapy), fulvestrant, any PI3K, mTOR or AKT inhibitor for Cohort 1 and 3 * with chemotherapy (except for neoadjuvant/ adjuvant chemotherapy), fulvestrant, any PI3K, mTOR, AKT inhibitor or CDK 4/6 inhibitor for Cohort 2 * Participant has a known hypersensitivity to alpelisib or fulvestrant, or to any of the excipients of alpelisib or fulvestrant * Participant with inflammat…