In vitro activity: PR-619 is a cell-permeable pyridinamine class broad-spectrum DUB inhibitor whose known targets include ATXN3, BAP1, JOSD2, OTUD5, UCH-L1, UCH-L3, UCH-L5/UCH37, USP1, 2, 4, 5, 7, 8, 9X, 10, 14, 15, 16, 19, 20, 22, 24, 28, 47, 48, VCIP135, YOD1, as well as deISGylase PLpro, deNEDDylase DEN1, and deSUMOlyase SENP6. PR-619 are shown to increase overall protein polyubiquitination in HEK293T cells in a dose- and time-dependent manner (20 to 150 μM, 0.5 to 20 h). PR619 treatment results in upregulation of both K 48 - and K63-linked polyUb chains. PR-619 induces HCT116 cell death with EC50 values of 6.3 μM.

Kinase Assay: Recombinant enzymes in 20 mM Tris-HCl, pH 8.0, 2 mM CaCl2 and 2 mM β-mercaptoethanol (DUB assay buffer) are preincubated with single doses or dose ranges of PR-619 or P22077 for 30 minutes in a 96 well plate before the addition of Ub-PLA2 and NBD C6-HPC. The liberation of a fluorescent product within the linear range of the assay is monitored at room temperature using a fluorescence plate reader. Vehicle (2%(v/v) DMSO) and 10 mM N-ethylmaleimide are included as controls. Where ≥60% inhibition is observed, EC50 values are determined using a sigmoidal dose response equation.

Cell Assay: 72 h hours later, 0.2 mg/mL resazurin prepared in phosphate-buffered saline is added to each well and the cells are incubated for an additional 3-6 h. The fluorescence of the resazurin reduction product is measured using Ex=535 nm and Em=590 nm filters on a fluorimeter. The EC50 values are calculated in Prism.

Chem Biol. 2011 Nov 23;18(11):1401-12.