 This is a two stage, open label, randomized-sequence, single-crossover Phase 1 study to evaluate the relative bioavailability BA of niraparib administered as a tablet formulation compared to the reference capsule formulation currently marketed in the United States. Specifically, a 300 mg niraparib tablet will be compared to 3 niraparib capsules 3 × 100 mg.The Extension Phase of this study is to enable patients enrolled in the study to continue to receive treatment with niraparib tablets if they are tolerating it and, in the Investigators opinion, may receive benefit. 