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PARP Inhibitor Pregnancy: Contraindicated — genotoxic; female partners of male patients must also use effective contraception; male patients must use condoms during and for 3 months after treatment

Niraparib

Brand names: Zejula

Adult dose

Dose: 200 mg once daily (weight <77 kg or platelets <150,000/μL) or 300 mg once daily
Route: Oral
Frequency: Once daily
Max: 300 mg/day
mCRPC with BRCA1/2 or other HRR gene mutations (in combination with abiraterone + prednisone — BRAVO/MAGNITUDE trials); also ovarian cancer (NICE TA620); weight-based dosing reduces haematological toxicity

Paediatric dose

Dose: Not established N/A/kg
Route: N/A
Frequency: N/A
Max: N/A
Not licensed in paediatrics

Dose adjustments

Renal

No dose adjustment for mild-moderate impairment; limited data in severe

Hepatic

Mild: no adjustment; moderate-severe: avoid

Paediatric weight-based calculator

Not licensed in paediatrics

Clinical pearls

  • MAGNITUDE trial (Chi et al. NEJM 2022): niraparib + abiraterone significantly improved rPFS in BRCA1/2-mutated mCRPC vs abiraterone alone (16.6 vs 10.9 months) — MHRA approved for this combination; BRCA1/2 testing mandatory (germline or somatic via tumour NGS)
  • PARP inhibitor mechanism in prostate cancer: BRCA1/2 and other HRR (homologous recombination repair) gene mutations create 'BRCAness' — dependence on PARP for DNA repair; PARP inhibition causes catastrophic DNA damage and synthetic lethality in HRR-deficient tumour cells
  • Weight-based dosing (200 vs 300 mg): PRIMA trial data led to individualised dosing — patients <77 kg or with platelets <150,000/μL start at 200 mg; reduces grade 3-4 thrombocytopenia from 28% to 13% while maintaining efficacy
  • MDS/AML risk: class effect of all PARP inhibitors — cumulative incidence ~1-2% with prolonged use; monitor FBC; if unexplained cytopenias persist, bone marrow biopsy to exclude MDS
  • HRR testing beyond BRCA: ATM, CDK12, FANCA mutations confer variable sensitivity to PARP inhibitors — BRCA1/2 mutations have highest predictive value; broader HRR panel may identify additional responders but clinical significance of non-BRCA HRR mutations is less established

Contraindications

  • Known hypersensitivity
  • Myelodysplastic syndrome/AML (exclude before starting)

Side effects

  • Thrombocytopenia (dose-limiting — weight-based dosing reduces risk)
  • Anaemia
  • Neutropenia
  • Nausea
  • Fatigue
  • Hypertension
  • Palpitations
  • MDS/AML (rare — class effect of PARP inhibitors with prolonged use)

Interactions

  • Myelosuppressive agents — additive haematotoxicity
  • Anticoagulants — monitor carefully given thrombocytopenia risk

Monitoring

  • FBC (weekly ×4, then monthly)
  • Blood pressure (weekly ×4, then monthly)
  • LFTs
  • Creatinine
  • BRCA/HRR mutation status confirmation before starting
  • MDS monitoring (FBC pattern — unexplained persistent cytopenias)

Reference: BNFc; BNF 90; MAGNITUDE trial (Chi et al. NEJM 2022); PRIMA trial (González-Martín et al. NEJM 2019); MHRA SPC Zejula; NICE TA620; EAU Prostate Cancer Guidelines 2024. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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