Palbociclib – CDK4/6 Inhibitor Therapy
Palbociclib is an innovative targeted anti-cancer medication and a highly selective reversible inhibitor of cyclin-dependent kinases 4 and 6 (CDK4/6). The drug represents a breakthrough in the treatment of the most common type of breast cancer, significantly slowing the division of malignant cells and delaying the need for aggressive chemotherapy.
The mechanism of action involves blocking the transition of the cell cycle from the G1 phase to the S-phase. Normally, CDK4 and CDK6 proteins bind with cyclin D, leading to the phosphorylation of the retinoblastoma (Rb) protein and initiating the DNA replication process. In tumor cells, this mechanism is often hyperactive. Palbociclib suppresses the activity of these kinases, thereby arresting cell division and inducing senescence in tumor tissue. The drug is most effective when combined with hormonal therapy (endocrine therapy), as simultaneously targeting estrogen signaling pathways and the cell cycle provides a synergistic effect in inhibiting tumor growth.
The medication is taken orally in the form of capsules or tablets in cyclic regimens, allowing the body to recover blood counts during breaks.
Indications
Palbociclib is indicated for the treatment of adult patients with the following diagnosis:
- HR-positive, HER2-negative breast cancer: locally advanced or metastatic cancer.
- First-line Therapy: in combination with an aromatase inhibitor (e.g., letrozole) for postmenopausal women or men.
- Subsequent Lines of Therapy: in combination with fulvestrant for patients whose disease has progressed following prior endocrine therapy.
Dosage and administration
The palbociclib dosing schedule is based on a cyclic regimen to manage drug tolerability.
- Standard Dose: 125 mg taken once daily.
- Treatment Cycle: the drug is taken for 21 consecutive days, followed by a 7-day break (a complete 28-day cycle).
- Administration: capsules should be taken with food, while tablets may be taken with or without food. The medication should be taken at the same time each day.
- Interactions: avoid grapefruit and grapefruit juice, as they can increase the concentration of the drug in the bloodstream.
- Dose Modification: in cases of significant neutropenia, the dose may be reduced to 100 mg or 75 mg per day.
