Niraparib is an oral poly(ADP ribose) polymerase (PARP) inhibitor that is 
currently approved by the United States Food and Drug Administration (US FDA) as 
well as recently approved by the European Medicines Agency (EMA) for the 
maintenance treatment of women with recurrent ovarian cancer who are in complete 
or partial response to platinum-based chemotherapy. The mechanisms of action of 
niraparib include inhibition of PARP enzymatic activity as well as increased 
formation of PARP-DNA complexes through "trapping" the PARP enzyme on damaged 
DNA. Phase I and III studies have demonstrated activity and benefit of niraparib 
in both BRCA mutated (BRCAm) and BRCA wild-type (BRCAwt) cancers. Phase I 
testing of niraparib established the maximally tolerated dose of 300mg by mouth 
(PO) daily, and the phase 3 ENGOT-OV16/NOVA study demonstrated the benefit of 
niraparib maintenance therapy compared to placebo after completion of and 
response to platinum-based chemotherapy in both BRCAm and BRCAwt ovarian cancer 
patient populations. Toxicities seen with niraparib include hematologic, 
gastrointestinal, fatigue, and cardiovascular. Hematologic toxicities include 
thrombocytopenia, anemia, neutropenia and leukopenia; upfront dose modification 
to 200mg niraparib for patients with baseline weight of ≤77kg and/or baseline 
platelets of ≤150,000K/uL should be considered to avoid significant hematologic 
toxicity, especially thrombocytopenia, based on recent analyses of the 
ENGOT-OV16/NOVA study. Cardiovascular toxicities include hypertension, 
tachycardia, as well as palpitations, and patients should be monitored for 
hypertension. PARP inhibitors have been associated with low risks of acute 
myelogenous leukemia (AML) and myelodysplastic syndrome (MDS), and the overall 
risk of AML and MDS is 0.9% of all patients treated with niraparib. Niraparib 
testing is ongoing in newly diagnosed ovarian cancer patients as maintenance 
therapy following completion of platinum-based chemotherapy, in BRCAwt cancers 
as treatment, as well as in combinations with other biologic drugs such as 
immunotherapy and anti-angiogenic agents.