Abstract LB-257: Discovery and characterization of novel, highly potent and selective USP7 inhibitors

Abstract

Abstract Over the past decade, protein ubiquitination has emerged as an important post-translational modification with roles in a plethora of cellular processes, and dysregulation in the ubiquitin proteasome system pathway (UPS) has been implicated in multiple human disorders including cancer. Ubiquitin specific proteases (USPs) are cysteine proteases that catalyse the de-ubiquitination of numerous protein substrates including tumor suppressors and oncogenes, hence regulating their levels and/or functions. USPs therefore represent a fast growing and attractive target class for pharmacological intervention. USP7 in particular has attracted considerable attention for its implications in multiple key oncogenic pathways including most notably MDM2/p53, PTEN and DNA damage. As part of a focussed effort towards targeting USPs, fragment screening was performed against a panel of family members, including USP7. Hits were identified by surface plasmon resonance and validated using orthogonal biophysical techniques (NMR, thermophoresis). Subsequent hit expansion identified molecules for which high-resolution co-crystal structures have been solved providing unique opportunities for structure-based design. Medicinal chemistry optimisation has yielded a series of novel, reversible and potent USP7 inhibitors (e.g. IC50 < 10 nM) with excellent selectivity profiles against deubiquitinating (DUBs) and other non-related enzymes. These inhibitors are cell-permeable and also exhibit potent target engagement in cells (e.g. EC50 < 30 nM). In line with the mechanism of action, further cellular profiling has demonstrated effects on p53, p21 and MDM2 levels in a concentration-dependant manner. From a translational viewpoint, initial studies aimed at identifying cell lines sensitive to these inhibitors will also be discussed. In summary, we report the discovery and detailed biochemical and cellular profiling of novel, potent and selective inhibitors of USP7. These molecules have drug-like properties and may provide opportunities for the development of new anticancer therapeutics. Citation Format: Gerald Gavory, Colin O'dowd, Keeva McClelland, Ewa Odrzywol, Alan Brown, Stephanie Burton, Oliver Barker, Frank Burkamp, Matt Helm, Iain James, Jakub Flasz, Elias Arkoudis, Tim Harrison. Discovery and characterization of novel, highly potent and selective USP7 inhibitors. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-257. doi:10.1158/1538-7445.AM2015-LB-257