Ribociclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor, is Food and Drug Administration (FDA) approved in combination with endocrine therapy for treatment of HR+/HER2- advanced or metastatic breast cancer in premenopausal/perimenopausal and postmenopausal women. Three phase III trials have evaluated ribociclib in combination with endocrine therapy, including letrozole, anastrozole, tamoxifen, and fulvestrant. These studies found that ribociclib 600 mg/d, 21 days on, 7 days off, leads to a significantly greater median progression-free survival (PFS), ranging from 8 to 13 months. Ribociclib is well tolerated in elderly patients, maintains health-related quality of life, and significantly reduces pain scores. The dose-limiting toxicities found in phase I studies were neutropenia, thrombocytopenia, and QTc prolongation. Common adverse effects seen in phase III trials include neutropenia, leukopenia, nausea, diarrhea, vomiting, and fatigue. Relevance to Patient Care and Clinical Practice: Literature on the safety and efficacy of ribociclib as well as its place in therapy in comparison to other FDA-approved CDK4/6 inhibitors for breast cancer is discussed., FDA Approves Kisqali for Early-Stage Breast Cancer. FDA Approves Kisqali for Early-Stage Breast Cancer September 17, 2024 Kisqali (chemical name: ribociclib) can now be used after surgery in combination with an aromatase inhibitor to treat stage II or stage III hormone receptor-positive, HER2-negative breast cancer with a high risk of recurrence., *Time spent living with breast cancer is called overall survival, or OS, in clinical trials. Median OS is the length of time when half of the people in the trial were still alive. At an 80-month check-in, median OS was 63.9 months with KISQALI + an AI vs 51.4 months with placebo + an AI..