The BELLE-2 (NCT01610284) and BELLE-3 (NCT01633060) trials reported that buparlisib plus fulvestrant was effective in hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, advanced breast cancer, with a median PFS of 6.9 months and 3.9 months, respectively. The gene discussed is ERBB2; the disease is breast cancer.