A 60-year-old woman with ER-positive, HER2-negative metastatic breast cancer is started on letrozole and palbociclib. What is the primary mechanism of action of palbociclib?
- A Aromatase inhibition
- B CDK4/6 inhibition ✓
- C HER2 receptor blockade
- D Selective estrogen receptor degrader
Correct answer: B. CDK4/6 inhibition
Explanation
Palbociclib is a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor that blocks cell cycle progression from G1 to S phase. It is used in combination with aromatase inhibitors for metastatic ER-positive breast cancer. Letrozole is the aromatase inhibitor, while trastuzumab and fulvestrant have different mechanisms.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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