Background: Niraparib is a potent, oral poly(ADP-ribose)polymerase (PARP)1/2 inhibitor with efficacy in both germline BRCA mutation (gBRCAmut) ovarian cancer (OvCa) and BRCA negative (nongBRCAmut) high grade serous OvCa (HGSC). Ph I data established a RP2D of 300 mg with anti-OvCa activity and is well-tolerated. Methods: The ENGOT-OV16/NOVA study is a double-blind, 2:1 randomized, placebo controlled international ph III study of oral niraparib versus placebo in patients (pts) with platinum (plat) sensitive recurrent OvCa. Primary objective is to evaluate efficacy of niraparib as maintenance therapy in pts who have plat sensitive OvCa as assessed by the prolongation of progression free survival (PFS). PFS will be independently evaluated in a cohort of gBRCAmut pts and in pts who have HGSC histology and are nongBRCAmut. Secondary objectives are: (1) bridge the centralized BRCA mutation test method to the candidate companion diagnostic test, if needed; (2) evaluate add'l measures of clinical benefit including pt reported outcomes, PFS2, chemotherapy free interval, overall survival; (3) evaluate the safety/tolerability of niraparib vs placebo; (4) evaluate QTc in a subset of niraparib-treated OvCa pts. A recent food effect sub study in 15 pts demonstrated no effect of a high fat meal on the PK's of a single 300 mg dose of niraparib in OvCa pts. Main study eligibility includes: histologically confirmed OvCa, fallopian tube or peritoneal cancer, HGSC histology or known gBRCAmut, plat sensitive recurrence, completion of at least 2 previous courses of plat-containing therapy and sensitivity to both via radiographic imaging, normal or CA125 decrease by 90% after last plat, agreement by pt to undergo gBRCA status prior to randomization, availability of FFPE archival tumor, ECOG PS 0-1, normal organ function, and can take PO. The main study is sized to address PFS endpoint w/ an accrual goal of 360 pts. As of 04 February 2014, 37 pts have been enrolled and randomized in the study. The trial will be open at >100 sites in 15 countries in collaboration with ENGOT (NSGO, AGO, NCRI, GEICO, BGOG, GINECO, MaNGO, AGO Austria, MITO). Clinical trial information: NCT01847274.