Newly published data from the MONALEESA-3 trial demonstrate that ribociclib is effective in patients with HR+/ HER2– breast cancer. In this trial, 726 postmenopausal women with disease relapse >12 months after completion of endocrine therapy were randomized in a 2:1 ratio to receive fulvestrant plus ribociclib or fulvestrant alone. Patients in the ribociclib plus fulvestrant group had a median progression-free survival (PFS) duration of 20.5 months versus 12.8 months (hazard ratio 0.59, 95% CI 0.48–0.73; P < 0.001). Improvements in PFS in the ribociclib group were accompanied by increased risks of several grade 3 adverse events including neutropenia (46.6% versus 0%) and leukopenia (13.5% versus 0%), in addition to grade 4 neutropenia (6.8% versus 0%). These findings demonstrate the superiority of the addition of ribociclib to fulvestrant monotherapy in this setting.