Information Niraparib tosylate (MK-4827, ZEJULA) is a selective inhibitor ofPARP1/PARP2withIC50of 3.8 nM/2.1 nM. Niraparib increases formation of PARP-DNA complexes resulting in DNA damage,apoptosis, and cell death. Targets PARP2 (Cell-free assay); PARP1 (Cell-free assay) 2.1 nM; 3.8 nM In vitro Micromolar concentrations of niraparib radiosensitizes tumor cell lines derived from lung, breast, and prostate cancers independently of their p53 status but not cell lines derived from normal tissues. Niraparib also sensitizes tumor cells to H2O2 and converts H2O2-induced single strand breaks (SSBs) into DSBs during DNA replication. In vivo MK-4827 strongly enhances the effect of radiation on a variety of human tumor xenografts, both p53 wild type and p53 mutant. MK-4827 reduces PAR levels in tumors by 1 h after administration which persisted for up to 24 h. In vivo treatment with MK-4827 and radiation prolonged survival (p Cell Research(from reference) Cell lines：V-C8 cells Concentrations：50 nM Incubation Time：24 h