Talazoparib (LT-673) is a PARP inhibitor that inhibits PARP 1 and PARP 2 (Ki=1.2/0.87 nM) and is orally active. Talazoparib has anti-tumorigenic activity and induces tumor cell death by blocking PARP enzyme activity and by trapping PARP at DNA damage sites.

PARP2:0.87 nM (Ki, cell free), NCI-H146 cells:4.35 nM (EC50), PARP1:1.2 nM (Ki, cell free), MDA-MB-468 cells:1 mM, NCI-H446 cells:EC50 (EC50), BT-20 cells:91.6 µM

方法：12 种 OCCC 细胞系用 Talazoparib (0-100 nM) 处理 14 天，使用 colony formation assays 检测化合物敏感性。
结果：除 KOC-7c 外，所有 HR 缺陷细胞系对 Talazoparib 均显示出具有敏感性的剂量反应曲线。而所有 HR 活性细胞系 (OVTOKO除外) 均显示具有耐药性的剂量响应曲线。[1]
方法：人结肠癌细胞 LoVo 用 Talazoparib (10-40 nM) 和 temozolomide (0-400 µM) 处理 5 天，使用 CellTiterGlo assay 检测细胞活力。
结果：单剂 Talazoparib 暴露导致约 15% 的细胞生长抑制。将 temozolomide 与 Talazoparib 组合可显著增强 temozolomide 的细胞毒性。[2]

方法：为测试体内抗肿瘤活性，将 Talazoparib (0.166-0.33 mg/kg) 口服给药给携带人乳腺癌肿瘤 MX-1 的 athymic nu/nu 小鼠，每天一次或每天两次，持续四周。
结果：Talazoparib 在小鼠异种移植物模型中以 0.165 mg/kg 剂量每天两次给药比 0.33 mg/kg 剂量每天一次给药更有效。在 MX-1 模型中，不仅用 0.165 mg/kg/dose 2X/天方案治疗的所有 6 只小鼠都达到了完全反应，而且直到研究结束，即给药停止 8 周后，没有一只小鼠出现肿瘤再生长。[2]

The ability of a test compound to inhibit PARP1 enzyme activity was assessed using the PARP Assay Kit following the manufacturer's instruction. IC50 values were calculated using GraphPad Prism5 software. For PARP inhibitor Ki determination, enzyme assays were conducted in 96-well FlashPlate with 0.5 U PARP1 enzyme, 0.25× activated DNA, 0.2 μCi [3H] NAD, and 5 μmol/L cold NAD in a final volume of 50 μL reaction buffer containing 10% glycerol (v/v), 25 mmol/L HEPES, 12.5 mmol/L MgCl2, 50 mmol/L KCl, 1 mmol/L dithiothreitol (DTT), and 0.01% NP-40 (v/v), pH 7.6. Reactions were initiated by adding NAD to the PARP reaction mixture with or without inhibitors and incubated for 1 minute at room temperature. Fifty microliter of ice-cold 20% trichloroacetic acid (TCA) was then added to each well to stop the reaction. The plate was sealed and shaken for a further 120 minutes at room temperature, followed by centrifugation. Radioactive signal bound to the FlashPlate was determined using TopCount. PARP1 Km was determined using Michaelis–Menten equation from various substrate concentrations (1–100 μmol/L NAD). Compound Ki was calculated from enzyme inhibition curve according to the formula: Ki = IC50/[1+(substrate)/Km]. Km for PARP2 enzyme and compound Ki were determined with the same assay protocol except 30 ng PARP2, 0.25× activated DNA, 0.2 μCi [3H] NAD, and 20 μmol/L cold NAD were used in the reaction for 30 minutes at room temperature [2].

Colony formation assays were conducted as described previously. In brief, cells were seeded into 6-well plates at a concentration of 500 to 2,000 cells per well. After 24 hours, media was replaced with fresh media containing PARP1/2 inhibitor. This procedure was repeated twice weekly for 14 days, at which point colonies were fixed with TCA and stained with sulforhodamine B. Colonies were counted and surviving fractions calculated by normalizing colony counts to colony numbers in vehicle-treated wells. Survival curves were plotted using a four-parameter logistic regression curve fit [2].

Female athymic nu/nu mice (8–10-week old) were used for all in vivo xenograft studies. Mice were quarantined for at least 1 week before experimental manipulation. Exponentially growing cells (LNcap and MDA-MB-468) or in vivo passaged tumor fragments (MX-1) were implanted subcutaneously at the right flank of nude mice. When tumors reached an average volume of approximately 150 mm^3, mice were randomized into various treatment groups (6–8 mice/group) in each study. Mice were visually observed daily and tumors were measured twice weekly by calliper to determine tumor volume using the formula [length/2] × [width^2]. Group median tumor volume (mm^3) was graphed over time to monitor tumor growth. In single-agent studies, olaparib (100 mg/kg), BMN 673 (various doses as indicated), or vehicle (10% DMAc, 6% Solutol, and 84% PBS) was administered by oral gavage (per os), once daily or BMN 673 (0.165 mg/kg) twice daily for 28 consecutive days. Mice were continuously monitored for 10 more days after last day of dosing. In cisplatin combination study, BMN 673, olaparib, or vehicle was administered per os once daily for 8 days starting on day 1. Cisplatin at a dosage of 6 mg/kg or its vehicle (saline) was administered intraperitoneally as a single injection on day 3, 30 minutes after PARP inhibitor was administered. Combination with carboplatin was conducted in a similar way in MX-1 model in which BMN 673 was administered per os once daily for either 8 days or 5 days and carboplatin was injected intraperitoneally at single dose of 35 mg/kg, 30 minutes after BMN 673 on day 3 [2].