Class:
- Cyclin-Dependent Kinase (CDK) 4/6 Inhibitor
Mechanism of Action:
- Selectively inhibits CDK4 and CDK6, key regulators of cell cycle progression from G1 to S phase, leading to cell cycle arrest and inhibition of tumor cell proliferation in hormone receptor–positive (HR+), HER2-negative breast cancer.
Indications:
- HR+/HER2− advanced or metastatic breast cancer, in combination with endocrine therapy (e.g., aromatase inhibitors or fulvestrant).
- Also approved for high-risk early breast cancer in the adjuvant setting (in combination with endocrine therapy).
Dosing:
- Typically 150 mg orally twice daily with continuous dosing. Dose adjustments required for toxicity.
Common Adverse Effects:
- Diarrhea (most common; usually manageable with antidiarrheals)
- Neutropenia (less severe than other CDK4/6 inhibitors)
- Fatigue
- Nausea and vomiting
- Elevated liver enzymes
Pharmacist Considerations:
- Counsel patients on proactive diarrhea management.
- Monitor CBC for neutropenia regularly.
- Monitor liver function tests periodically.
- Assess for drug interactions, especially CYP3A inhibitors or inducers (abemaciclib is metabolized by CYP3A4).
- Emphasize adherence to twice-daily dosing schedule.