Niraparib tosylate (MK-4827 (tosylate))(with IC50 of 3.8 nM/2.1 nM) is a selective PARP1/PARP2 inhibitor.

PARP1:3.8 nM, PARP2:2.1 nM

微摩尔浓度的Niraparib（尼拉帕利）对来源于肺癌、乳腺癌和前列腺癌的肿瘤细胞系进行放射增敏，其作用与p53状态无关，但对来源于正常组织的细胞系无效。Niraparib还能使肿瘤细胞对Water2敏感，并在DNA复制过程中将Water2引起的单链断裂（SSBs）转化为双链断裂（DSBs）[5]。

Niraparib tosylate显著增强了放射线对各种人类肿瘤异种移植物（包括p53野生型和p53突变型）的作用效果。Niraparib tosylate在给药后1小时内降低了肿瘤中的PAR水平，并且这种效果持续了至多24小时[1]。与单一疗法相比，联合使用Niraparib tosylate和放射线治疗能显著延长存活时间（p<0.01）。通过与单一疗法组相比，联合治疗组肿瘤中裂解的caspase-3和γ-H2AX显著升高，进一步证明了Niraparib tosylate加放射线治疗的体内优势[4]。

Enzyme assay is conducted in buffer containing 25 mM Tris, pH 8.0, 1 mM DTT, 1 mM spermine, 50 mM KCl, 0.01% Nonidet P-40, and 1 mM MgCl2. PARP reaction contains 0.1 μCi [3H]NAD+ (200 000 DPM), 1.5 μM NAD+, 150 nM biotinylated NAD+, 1 μg/mL activated calf thymus, and 1?5 nM PARP-1. Autoreactions utilizing SPA bead-based detection are carried out in 50 μL volumes in white 96-well plates. Compounds (e.g., MK-4827) are prepared in 11-point serial dilution in 96-well plate, 5 μL/well in 5% DMSO/Water (10× concentrated). Reactions are initiated by adding first 35 μL of PARP-1 enzyme in buffer and incubating for 5 min at room temperature and then 10 μL of NAD+ and DNA substrate mixture. After 3 h at room temperature, these reactions are terminated by the addition of 50 μL of streptavidin-SPA beads (2.5 mg/mL in 200 mM EDTA, pH 8). After 5 min, they are counted using a TopCount microplate scintillation counter. IC50 data is determined from inhibition curves at various substrate concentrations[1].

V-C8 (BRCA2-negative) Chinese hamster cells are treated with the PARP inhibitor MK-4827 for 24 h, washed and incubated in drug-free medium for 5-7 days until colonies formed. (Only for Reference)