c15-162: Phase IB trial of radium 223 and niraparib in patients with castrate resistant prostate cancer (NiraRad).

TPS385Background: PARP1 is a key regulator of the transition to lethal castrate resistant prostate cancer (CRPC); niraparib is a potent and selective PARP-1 and PARP-2 inhibitor that has shown single agent clinical activity in CRPC. Radium-223 is an alpha particle emitter that causes DNA double strand breaks and is FDA approved for use in CRPC. The addition of a PARP inhibitor (niraparib) may further enhance the clinical benefit of Radium-223 through inhibition of DNA repair and modifications in the bone microenvironment. We hypothesize that targeting the PARP1/androgen receptor (AR) axis in combination with radiopharmaceutical therapy will be safe and may improve clinical outcomes for men with advanced CRPC. Furthermore, combining clinical and pathologic features with correlative studies on tumor tissue, blood, and circulating tumor cells (CTCs) may help us develop biomarkers for future use in the treatment of CRPC. Methods: This is aphase IB dose finding study of patients with metastatic CRPC using a ti...