XL888 is an ATP-competitive inhibitor of Hsp90 ( IC50: 24 nM). Heat shock protein 90 (Hsp90) is a chaperone that maintains the functionality of client proteins involved in cell proliferation, cell cycling, and apoptosis. Through this action, specific client proteins are degraded, resulting in cell cycle arrest or apoptosis. XL888 is orally bioavailable and shows efficacy in tumor regression in gastric carcinoma and melanoma xenografts in mice.

HSP90:24 nM

XL888在NCI-N87细胞中诱导HER2的降解，IC50为56nM。XL888抑制HER2过表达的NCI-N87、BT-474、MDA-MB-453，突变的MET MKN45，B-Raf Colo-205，B-Raf SK-MEL-28，EGFR HN5，EGFR NCI-H1975，PI3K MCF7以及K-Ras A549的细胞增殖，其IC50分别为21.8、0.1、16.0、45.5、11.6、0.3、5.5、0.7、4.1和4.3nM。[1]XL888导致剂量依赖性的减少，在维米拉非尼初始和耐药的黑色素瘤细胞系以及天生耐药的黑色素瘤细胞系的生长中，IC50均约为0.1μM。XL888的生长抑制效应与WM164、M229、M229R、M249、M249R、1205Lu和WM39细胞系的G1期细胞周期阻滞或WM164R、1205LuR和RPMI 7951细胞系的G2-M期细胞周期阻滞相关。XL888（300nmol）在这些细胞系中诱导高水平（>66%）的凋亡和线粒体膜电位（TMRM）的丧失。XL888的细胞毒效应是持久的，在任何细胞系中即使培养至4周也未观察到集落形成。XL888处理（300nM，48小时）导致IGF1R、PDGFRβ、ARAF、CRAF和cyclin D1的降解，并抑制所有获得BRAF抑制剂耐药的细胞系中AKT、ERK和S6信号的活性。处理对于维米拉非尼初学者、天生耐药和获得耐药的细胞系均有效。XL888（300nM）处理导致HSP70同型体1表达的强烈时间依赖性增加。XL888（48小时，300nM）处理在M229R、1205LuR、RPMI7951和WM39细胞系中增加了BIM-EL、BIM-L和BIM-S的表达，在WM164R细胞系中诱导了BIM-L和BIM-S的表达，在M249R细胞系中诱导了BIM-EL的表达。[2]

XL888 (100 mg/kg) 显著诱导 SCID 小鼠中已建立的 M229R 和 1205LuR 移植瘤的回归或生长抑制（50%）。15天的 XL888 处理显示与对照组相比，肿瘤内 HSP70 表达显著增加（8.6倍）。XL888 处理在体内显示促凋亡作用，导致 M229R 移植瘤中 TUNEL 染色增加，与 BIM 表达增加和 Mcl-1 表达减少相关。[2]

The PTP1B enzymatic assay, the total volume of 100 μL per well contains15 nM recombinant PTP1B protein, 2 mM p-nitrophenylphosphonic acid (pNPP), 1 mM dithiothreitol and 1 mM EDTA (pH 6.5). After 30 min incubation at 37℃, end the reaction by addition of 2.5 M NaOH. The hydrolysis product, pNP, is detected at the absorbance at 405 nm.

Cells are plated at a density of 2×105 per mL and left to grow overnight before being treated with increasing concentrations of XL888. After incubation with XL888 for 3 days, Methylthiazolyldiphenyl-tetrazolium bromide (MTT) assays are performed.(Only for Reference)