ERBB2 and breast cancer: MONALEESA-1 (NCT01919229) [41] is a phase II study to assess the biological activity of 14 days of neoadjuvant treatment with ribociclib (400 or 600 mg, daily) plus letrozole (2.5 mg, daily), compared with single-agent letrozole (2.5 mg, daily) in postmenopausal patients with newly diagnosed, resectable, HR+, HER2− early breast cancer.