PIK3CA and breast cancer: In preclinical models, Alpelisib inhibited the most common hotspot PIK3CAH1047R and PIK3CAE545K mutations at nanomolar concentration (4.6 nM/L) and interfered with PIK3CA-mediated downstream signaling; moreover, it induced a dose-dependent degradation of p110 protein levels in HR+/PIK3CA-mutated BC cell lines [33].