DNA repair is a critical process for the survival and normal proliferation of healthy cells. However, given the enhanced levels of cellular stress and genomic instability, these repair processes are even more critical to the survival of malignant cells, where rates of DNA damage are considerably increased. Given this, inhibitors of DNA damage repair have seen a resurgence of interest in recent years in an effort to exploit tumour cell vulnerabilities. One such example of this approach has resulted in the recent approval of the PARP inhibitor olaparib (Lynparza™) for women with advanced ovarian cancer associated with defective BRCA genes.

Olaparib acts against the poly(ADP-ribose)polymerase (PARP) enzymes, more recently re-defined as the ARTD (Diphtheria toxin-like human ADP-ribosyltransferase) enzyme class. Whilst PARP is widely known to play critical and well-understood roles in DNA repair, poly(ADP ribose) glycohydrolase (PARG) is less well known but equally essential for effective DNA repair, degrading PAR chains and facilitating effective DNA repair. However, its inhibition may offer several key advantages over PARP inhibition. Most critically, whilst there are 18 isoforms, there exists only a single PARG protein, offering a specific point of therapeutic intervention. However, due to the open nature of the PARG binding cleft and the nature of the binding site, this protein has been considered to be difficult to inhibit with small, drug-like small molecules, particularly in the cellular context.

This poster will describe our efforts to overcome these challenges against this challenging target and report our early successes achieved through innovative computational chemistry strategies. These efforts have delivered several credible, drug-like startpoints for further medicinal chemistry optimisation.

Citation Format: Bohdan Waszkowycz, Dominic James, Steven Durant, Nicola Hamilton, Cliff Jones, Stuart Jones, Allan Jordan, Alan Lau, Alison MGonagle, Mark O’Connor, Kate Smith, Alex Stowell, Julie Tucker, Ian Waddell, Donald Ogilvie. Discovery of the first cell-active inhibitors of poly(ADP Ribose) glycohydrolase through high-throughput screening and computational approaches. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4352.