A drug used with fulvestrant to treat breast cancer that is advanced or has spread to other parts of the body and got worse during or after treatment with hormone therapy. It is used in postmenopausal women, and men, whose cancer is hormone receptor positive and HER2 negative and has a mutation in the PIK3CA gene. It is also being studied in the treatment of other types of cancer. Alpelisib blocks certain proteins, which may help keep cancer cells from growing and may kill them. It is a type of kinase inhibitor. Also called Piqray.