Clinical trials have combined fulvestrant with CDK4/6 inhibitors, such as ribociclib in men and postmenopausal women with advanced breast cancer [NCT02422615] and palbociclib in hormone receptor+HER2-metastasized breast cancer after endocrine failure [NCT01942135], as well as phosphatidylinositol 3-kinasitol kinase (PI3K)/AKT/mTOR pathway inhibitors, such as pictilisib, in advanced or metastatic breast cancer in participants resistant to aromatase inhibitor therapy [NCT01437566]. Here, ERBB2 is linked to breast cancer.