Ribociclib: Mechanism of Action and Approved Uses in Breast Cancer

　　Ribociclib(brand name Kisqali,developed by Novartis)is an oral targeted anticancer agent classified as a cyclin-dependent kinase 4/6(CDK4/6)inhibitor.Unlike conventional chemotherapy,which kills tumor cells by directly damaging DNA,ribociclib acts on specific cell cycle regulatory proteins to interrupt tumor cell proliferation.

　　Mechanism of action.​In some breast cancer cells,CDK4/6 binds to cyclin D and becomes activated,leading to phosphorylation of the retinoblastoma(Rb)protein and driving the transition from G1 to S phase.By inhibiting CDK4/6 activity,ribociclib reduces Rb phosphorylation,arresting tumor cells in the G1 phase and thereby suppressing proliferation.

　　Indications.​Ribociclib is indicated for HR-positive,HER2-negative breast cancer across several settings:in early breast cancer,it is combined with an aromatase inhibitor as adjuvant therapy for patients at high risk of recurrence;in the advanced setting,it is used with an aromatase inhibitor as initial endocrine-based therapy;and in the metastatic setting,it is combined with fulvestrant in appropriate patients.

　　How it differs from chemotherapy.​Conventional chemotherapy works mainly by damaging DNA,disrupting microtubule function,or inhibiting cell division.Ribociclib instead targets CDK4/6 to halt cell cycle progression.It is important to note that targeted therapy is not free of adverse effects:ribociclib can cause neutropenia,liver function abnormalities,and QT interval prolongation,so regular monitoring of blood counts,liver function,and ECG is required during treatment.

　　Combination use.​Ribociclib is generally administered alongside endocrine therapy,such as letrozole,anastrozole,or fulvestrant,and some patients also require ovarian function suppression.The specific regimen should be determined by a specialist based on disease stage,hormone receptor status,prior therapy,and individual tolerability.