3. PARP inhibitor MK4827
Abstract 
An inhibitor of Poly (ADP-ribose) polymerase (PARP) with potential Antineoplastic Activity. PARP Inhibitor MK4827 inhibits PARP Activity, ENHANCING the accumulation of DNA Strand Breaks and promoting genomic instability and apoptosis. The PARP family of Proteins detect and repair single strand DNA breaks by the base-excision repair (BER) pathway.

4. Glendenning J, Tutt A. PARP inhibitors – Current Status and the Walk towards Early Breast cancer. Breast. 2011 Oct; 20 Suppl 3: S12-9.
Abstract 
… Early Phase Trials with efficacy endpoints have been presented for the PARP inhibitors AG014699, olaparib, veliparib, iniparib and MK4827. The results of the first phase II trials exploring monotherapy PARP inhibitor strategies, which are based on revisiting the concept of synthetic lethality, have emerged and are reviewed herein. The clinical trials that have or are exploring combinations with DNA damaging therapy in these contexts are discussed with particular reference to breast cancer, as are biomarkers that have been proposed and are being investigated to develop optimal drug schedule and patient selection criteria for these DNA repair targeting approaches.

5. Jones, Philip; Altamura, Sergio; Boueres, Julia et al. Discovery of 2 – {4 – [(3S)-Piperidin-3-yl] phenyl}-2H-INDAZOLE-7-carboxamide (MK-4827): A Novel Oral Poly (ADP-ribose) polymerase (PARP) Inhibitor efficacious in BRCA-1 and -2 Mutant Tumors. Journal of Medicinal Chemistry (2009), 52 (22), 7170-7185.
Abstract 
… We Disclose the Development of a novel series of 2-phenyl-2H-indazole-7-carboxamides as poly (ADP-ribose) polymerase (PARP) 1 and 2 inhibitors. This series was optimized to improve enzyme and cellular activity, and the resulting PARP inhibitors display antiproliferation activities against BRCA-1 and BRCA-2 deficient cancer cells, with high selectivity over BRCA proficient cells. Extrahepatic oxidation by CYP450 1A1 and 1A2 was identified as a metabolic concern, and strategies to improve pharmacokinetic properties are reported. These efforts culminated in the identification of 2 – {4 – [(3S)-piperidin-3-yl] phenyl}-2H-indazole-7-carboxamide 56 (MK-4827), which displays good pharmacokinetic properties and is currently in phase I clinical trials. This compound displays excellent PARP 1 and 2 inhibition with IC50 = 3.8 and 2.1 nM, respectively, and in a whole cell assay, it 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. Compound 56 was well tolerated in vivo and demonstrated efficacy as a single agent in a xenograft model of BRCA-1 deficient cancer.