ME0328 is a potent, selective PARP inhibitor with an IC50 of 0.89 μM for PARP3, showing approximately 7-fold selectivity over PARP1.

ARTD1/PARP1:6.3 μM, ARTD5/TNKS1:47.3 μM, ARTD6/TNKS2:34.3 μM, ARTD10/PARP10:71.3 μM, ARTD2/PARP2:10.8 μM, PARP3:0.89 μM

ME0328 is soluble, cell permeable, and metabolically stable in human liver microsomes and rat hepatocytes. ME0328 (10 μM) results in a significant delay of γH2AX-foci resolution by affecting ARTD3 in A549 and MRC5 cells without significant toxicity. [1]

Enzymatic Assays: Protein ADP-ribosylation is measured using hexahistidine-tagged ARTD proteins and recombinant histone proteins captured on 96-well Ni2+-chelating plates (5-PRIME). ADP-ribosylation reactions are initiated by addition of NAD+ (2% biotinylated), and modified reaction products are detected by chemiluminescence. Km values are estimated using plots of initial rates vs. NAD+ concentrations and linear curve fitting with GraphPad Prism. All compounds are dissolved in dimethyl sulfoxide (DMSO) to a stock concentration of 50 mM. Experiments to determine IC50 values are conducted with compound concentrations in the range between 10 nM and 450 μM with a DMSO concentration of 1% (v/v). Measurements are carried out at an NAD+ concentration below Km for each transferase. IC50 values are estimated using curve fitting with GraphPad Prism. Reported values represent means ± SE of the fits of the curves based on duplicate or triplicate experiments, each determined based on three replicates.

Compound cytotoxicity in A549 and MRC5 cells is evaluated using WST-1 assays. A549 cells are cultured in Dulbecco’s Modified Eagle’s Medium supplemented with 10% fetal calf serum (FCS), penicillin, and streptomycin. MRC5 cells are cultured in Minimal Essential Medium supplemented with 10% FCS, penicillin, streptomycin, and l-glutamine. Both cell lines are maintained in a humidified incubator at 37°C and 5% CO2. (Only for Reference)