Palbociclib is an oral targeted therapy classified as a CDK4/6 inhibitor, used primarily in hormone receptor-positive (HR+), HER2-negative advanced or metastatic breast cancer.
Overview
| Feature | Details |
|---|---|
| Class | Cyclin-dependent kinase (CDK) 4 and 6 inhibitor |
| Mechanism of Action | Blocks CDK4/6 → prevents phosphorylation of retinoblastoma protein → G1 cell cycle arrest → inhibits tumor cell proliferation |
| Indications | – HR+, HER2- advanced or metastatic breast cancer, usually combined with endocrine therapy (e.g., letrozole, fulvestrant) |
| Formulation | Oral capsules |
| Typical Dosing | 125 mg once daily for 21 days, followed by 7 days off (28-day cycle) |
| Pharmacokinetics | Metabolized primarily by CYP3A4; dose adjustments may be needed with strong CYP3A4 inhibitors/inducers |
Common side effects:
- Neutropenia (most frequent dose-limiting toxicity)
- Leukopenia, anemia, fatigue
- Infections (due to neutropenia)
- Diarrhea, nausea, alopecia
- Monitoring: Complete blood count (CBC) before starting and monthly during treatment. Monitor for signs of infection
- Drug Interactions: Avoid strong CYP3A4 inhibitors (e.g., clarithromycin) or inducers (e.g., rifampin); dose modifications may be necessary
- Special Considerations: Neutropenia is usually uncomplicated and reversible; dose holds or reductions are common.