Class:
- Poly (ADP-ribose) polymerase (PARP) inhibitor
Mechanism of Action:
- Inhibits PARP enzymes involved in DNA single-strand break repair.
- In tumor cells with BRCA1/2 mutations (defective homologous recombination repair), PARP inhibition causes accumulation of DNA damage leading to synthetic lethality and cancer cell death.
Indications:
- BRCA-mutated, HER2-negative metastatic breast cancer after chemotherapy.
- Maintenance therapy for BRCA-mutated ovarian, pancreatic, and prostate cancers.
- Early-stage BRCA-mutated breast cancer (adjuvant setting) in some guidelines.
Dosing:
- Oral capsules/tablets, typical dose 300 mg twice daily (varies by formulation).
Common Adverse Effects:
- Anemia, fatigue, nausea, vomiting, diarrhea
- Risk of myelodysplastic syndrome/acute myeloid leukemia (rare)
- Elevated creatinine (benign and reversible)
Pharmacist Considerations:
- Counsel on adherence with twice-daily oral dosing.
- Monitor CBC regularly for cytopenias.
- Assess renal function before and during therapy.
- Educate patients on GI side effects and management strategies.
- Check drug interactions (CYP3A4 substrates; avoid strong inhibitors/inducers).