Niraparib: A PARP Inhibitor for Ovarian Cancer Maintenance Therapy

Niraparib is an oral poly (ADP-ribose) polymerase (PARP) inhibitor developed for the maintenance treatment of adult patients with advanced epithelial ovarian, fallopian tube, or primary peritoneal cancer. It is indicated for patients who are in a complete or partial response to platinum-based chemotherapy, regardless of their BRCA mutation status, significantly prolonging progression-free survival.

1. Mechanism of Action

Niraparib exerts its antitumor effect by inhibiting PARP enzyme activity. This prevents cancer cells from repairing damaged DNA, triggering apoptosis (cell death) and delaying tumor progression.

2. Indications and Patient Selection

• First-Line Maintenance (HRD Positive):​ For patients with HRD-positive tumors (defined by BRCA mutations or genomic instability) who responded to initial platinum chemotherapy.

• Recurrent Maintenance (gBRCAm):​ For patients with deleterious or suspected deleterious germline BRCA-mutated (gBRCAm) recurrent cancer who responded to platinum chemotherapy.

• Note:Patient selection relies on FDA-approved companion diagnostic testing.

3. Dosage and Administration

• Weight-Based Dosing:

  • Patients <77 kg OR Platelets <150,000/μL:​ 200 mg orally once daily.

  • Patients ≥77 kg AND Platelets ≥150,000/μL:​ 300 mg orally once daily.

• Hepatic Impairment:​ For moderate hepatic impairment, the dose is reduced to a flat 200 mg daily.

• Administration:​ Take once daily at approximately the same time, with or without food. Swallow tablets whole. If nausea occurs, taking it at bedtime may help. Do not double doses if one is missed.

4. Critical Safety and Monitoring

• Myelodysplastic Syndrome (MDS)/AML:​ Rare but fatal cases of MDS and AML have been reported. Patients with persistent cytopenias should be referred for hematologic evaluation.

• Bone Marrow Suppression:​ Thrombocytopenia (low platelets), anemia, and neutropenia are very common.

  • Monitoring Schedule:​ Weekly CBCs for the first month, monthly for the next 11 months, and periodically thereafter.

• Hypertension:​ Monitor blood pressure and heart rate frequently during the first two months of therapy.

• Posterior Reversible Encephalopathy Syndrome (PRES):​ Although rare, seek immediate medical attention for seizures, headaches, or visual disturbances.

5. Special Populations

• Pregnancy:​ Can cause fetal harm. Effective contraception is mandatory for females during treatment and for 6 months after the last dose.

• Lactation:​ Discontinue breastfeeding during treatment and for 1 month after the last dose.