In vitro activity: ABT-888 is inactive to SIRT2 (>5 μM). ABT-888 inhibits the PARP activity with EC50 of 2 nM in C41 cells. ABT-888 could decrease the PAR levels in both irradiated and nonirradiated H460 cells. ABT-888 also reduces clonogenic survival and inhibits DNA repair by PARP-1 inhibition in H460 cells. ABT-888 increases apoptosis and autophagy in H460 cells when combination with radiation. ABT-888 also inhibits PARP activity in H1299, DU145 and 22RV1 cells and the inhibition is independent of p53 function. ABT-888 (10 μM) suppresses the surviving fraction (SF) by 43% in the clonogenic H1299 cells. ABT-888 shows effective radiosensitivity in oxic H1299 cells. Furthermore, ABT-888 could attenuate the SF of hypoxic-irradiated cells including H1299, DU145 and 22RV1.

Kinase Assay: PARP assays are conducted in a buffer containing 50 mM Tris (pH 8.0), 1 mM DTT, 1.5 μM [3H]NAD+ (1.6 μCi/mmol), 200 nM biotinylated histone H1, 200 nM slDNA, and 1 nM PARP-1 or 4 nM PARP-2 enzyme. Reactions are terminated with 1.5 mM benzamide, transferred to streptavidin Flash plates, and counted using a TopCount microplate scintillation counter.

Cell Assay: In HCT-116 and HT-29 cell lines, the ability of ABT-888 to synergize the effect of the anti-cancer agents, SN38 or oxaliplatin, was determined using the SRB assay. PARP activity was significantly reduced in samples treated with SN38 in combination with ABT-888 (>4 fold at 24 h).