Kisqali mechanism of action?

Kisqali (ribociclib) works by inhibiting CDK4 and CDK6 (cyclin-dependent kinases) — key drivers of the cell cycle in hormone receptor–positive (HR+), HER2-negative breast cancer.

Mechanism of action (MOA):

• Ribociclib blocks CDK4/6, which prevents phosphorylation of the retinoblastoma (Rb) protein.
• Without Rb phosphorylation, cells stay in the G1 phase and don’t progress to S phase, slowing or stopping tumor cell proliferation.

Why it matters:

• This CDK4/6 blockade is often used in combination with endocrine therapy (e.g., letrozole, fulvestrant) to enhance control of HR+ cancers.

If you want, tell me the indication (e.g., early breast cancer vs metastatic) and I can summarize how the MOA ties into the specific use.