ESR1 and breast cancer: Theα-specific PI3K inhibitor Alpelisib (PIQRAY, Novartis) has received accelerated approval by the Food and Drug Administration (FDA) in May 2019 for the treatment of patients with estrogen receptor–positive (HR +)/human epidermal growth factor receptor 2-negative (HER2-) PIK3CA-mutated advanced or metastatic BC based on the SOLAR-1 trial [10].