In vitro activity: In a whole cell assay, MK-4827 inhibited PARP activity with EC50 = 4 nM and inhibited proliferation of cancer cells with mutant BRCA-1 and BRCA-2 with CC50 in the 10-100 nM range. It was demonstrated to be a potent and selective PARP-1 and PARP-2 inhibitor with IC50=3.8 and 2.1 nM, respectively. Furthermore, it displayed at least a 100-fold selectivity over PARP-3, V-PARP, and tankyrase-1, with IC50 = 1300, 330, and 570 nM, respectively. As well as inhibiting the growth of HeLa cell lacking BRCA-1 because of silencing by RNA interference, MK-4827 is able to inhibit the proliferation of cancer cell lines carrying natural BRCA-1 or BRCA-2 mutations. In MDA-MB-436 human mammary gland adenocarcinoma cells carrying BRCA-1 mutations, MK-4827 displayed CC50 = 18 nM, while in CAPAN-1 human pancreatic adenocarcinoma cells, which are BRCA-2 mutant, MK-4827 displayed CC50 = 90 nM. In contrast, normal human prostate and mammary epithelial cells are resistant to MK-4827, displaying antiproliferative effects in the micromolar range, thereby demonstrating the very high selective cytotoxicity from these PARP inhibitors in BRCA-1 and -2 mutant cancer cells compared to surrounding tissue.

Kinase Assay: MK-4827 displays excellent PARP 1 and 2 inhibition with IC(50) = 3.8 and 2.1 nM, respectively, and in a whole cell assay, it inhibits PARP activity with EC(50) = 4 nM and inhibits proliferation of cancer cells with mutant BRCA-1 and BRCA-2 with CC(50) in the 10-100 nM range.

Cell Assay: Proliferation assays were conducted in 96-well black viewplates, and 300 cells/well (250 cell/well for BRCA-1 wt) in culture medium, 190 μL/well (DMEM containing 10% FCS, 0.1 mg/mL penicillin-streptomycin, and 2 mM L-glutamine), were plated and incubated for 4 h at 37℃ under 5% CO2 atmosphere. Inhibitors were then added with serial dilutions, 10 μL/well to obtain the desired final compound concentration in 0.5% DMSO. The cells were then incubated for 7 days at 37℃ in 5% CO2 after which time viability was assessed. Briefly, with CellTiter-Blue solution prediluted 1:10 in medium, 100 μL/well was added and the cells left for 45 min at 37℃ under 5% CO2 and then a further 15 min at room temperature in the dark. The number of living cells was determined by reading the plate at fluorimeter, excitation at 550 nm and emission at 590 nm. Cell growth was expressed as the percentage growth with respect to vehicle treated cells. The concentration required to inhibit cell growth by 50% (CC50) was determined.

Invest New Drugs. 2012 Dec;30(6):2113-20; J Med Chem. 2009 Nov 26;52(22):7170-85.