VR23 is a potent proteasome inhibitor. Data shows IC50 =1 nM for trypsin-like proteasomes, IC50=50-100 nM for chymotrypsin-like proteasomes, and IC50=3 μM for caspase-like proteasomes.

Trypsin like proteasomes:1 nM, Caspase-like proteasomes:3 μM, Chymotrypsin-like proteasome:50-100 nM

在HeLa细胞中，VR23促使泛素化蛋白质积累。在RPMI 8226和KAS 6细胞中，VR23抑制细胞增长，其IC50分别为2.94和1.46μM。VR23对于bortezomib (BTZ)敏感和耐药的RPMI 8226及ANBL6细胞均具有等效的抑制作用。当与bortezomib联合使用时，VR23在上述细胞中显示出对细胞增长抑制的协同效应。此外，VR23通过促进泛素化cyclin E的积累，选择性地诱导癌细胞凋亡。[1]

在ATH490裸鼠中，接种MDA-MB-231转移性乳腺癌细胞后，VR23（30 mg/kg, i.p.）展现出有效的抗肿瘤和抗血管生成活性。VR23还能减轻紫杉醇在小鼠体内引起的不良反应。[1]

Proteasome assay: Exponentially growing cells on a 96-well clustered plate are treated with different concentrations of drugs or left untreated (control) for 6 hours. Proteasomes extracted with 0.5% NP40 buffer are mixed with equal amounts of samples in 100 μL total volume, and then incubated with 25 μmol/L of fluorogenic substrates (LRR- specific for trypsin-like activity, LLE-specific for caspase-like activity, and SUVY-specific for chymotrypsin-like activity) in black-bottom 96-well plates at 37°C. Fluorescence is monitored every 5 minutes at the wavelength of 360 nm (excitation) and 480 nm (emission).