PCI-24781 (Abexinostat (PCI24781)) is a new pan-HDAC inhibitor mainly targeting HDAC1 (Ki: 7 nM), also have moderate inhibitory for HDACs 2, 3, 6, and 10 and greater than 40-fold selectivity against HDAC8. Phase 1/2.

HDAC1:7 nM(Ki)

每星期连续四天给药三天不给药处理HCT116移植小鼠模型,给药浓度分别为20 mg/kg, 40 mg/kg, 80 mg/kg和160 mg/kg PCI-24781,抑制效果分别是48%, 57%, 82.2%,和80.0%.隔一天一次200 mg/kg PCI-24781作用于移植小鼠,HCT116 和 DLD-1肿瘤细胞生长受到明显抑制,抑制效果分别是69%和59%.

在CHO细胞中,PCI-24781与抑制HR效果 一致,导致同源定向修复（I-SceI诱导染色质断裂引起）能力下降。PCI-24781对多种肿瘤细胞系均有明显的抗肿瘤活性,GI50范围为0.15 μM~3.09 μM。PCI-24781处理使HCT116和DLD-1细胞系中组蛋白/微管蛋白乙酰化呈剂量依赖性积累,同时诱导PARP的剪切,p21表达和γH2AX累积。PCI-24781诱导软组织细胞的凋亡,引起S期缺失和G2期细胞周期停滞。在STS细胞中,PCI-24781极可能通过增强E2F1在Rad51近端启动子区域的结合诱导Rad51 转录抑制。PCI-24781还诱导非霍奇金淋巴瘤和Hodgkin淋巴瘤中蛋白酶和活性氧依赖的NF-κB信号通路介导的细胞凋亡过程。PCI-24781也抑制人脐静脉内皮细胞内皮细胞的增值,GI50为0.43 μM。PCI-24781抑制HDACs酶活导致HR 相关基因的转录水平出现明显下降,其中包括RAD51。

HDAC Activity: HDAC activity is measured using a continuous trypsin-coupled assay. For inhibitor characterization, measurements are done in a reaction volume of 100 μL using 96-well assay plates. For each isozyme, the HDAC protein in reaction buffer [50 mM HEPES, 100 mM KCl, 0.001% Tween 20, 5% DMSO (pH 7.4), supplemented with bovine serum albumin at concentrations of 0% (HDAC1), 0.01% (HDAC2, 3, 8, and 10), or 0.05% (HDAC6)] is mixed with PCI-24781 at various concentrations and allowed to incubate for 15 minutes. Trypsin is added to a final concentration of 50 nM, and acetyl-Gly-Ala-(N-acetyl-Lys)-AMC is added to a final concentration of 25 μM (HDAC1, 3, and 6), 50 μM (HDAC2 and 10), or 100 μM (HDAC8) to initiate the reaction. Negative control reactions are done in the absence of PCI-24781 in replicates of eight. Reactions are monitored in a fluorescence plate reader. After a 30-minute lag time, the fluorescence is measured over a 30-minute time frame using an excitation wavelength of 355 nm and a detection wavelength of 460 nm. The increase in fluorescence with time is used as the measure of the reaction rate. Inhibition constants Ki(app) are obtained using the program BatchKi.

Cells are cultured for at least two doubling times, and growth is monitored at the end of PCI-24781 exposure using an Alamar blue fluorometric cell proliferation assay. PCI-24781 is assayed in triplicate wells in 96-well plates at nine concentrations using half-log intervals ranging from 0.0015 μM to 10 μM. The final DMSO concentration in each well is 0.15%. The concentration required to inhibit cell growth by 50% (GI50) and 95% confidence intervals are estimated from nonlinear regression using a four-parameter logistic equation.(Only for Reference)