Accessing the cancer DUBome with UbiPlex: A bespoke drug discovery platform for deubiquitinase enzymes

Abstract Over the past decade, protein ubiquitination has emerged as an important post-translational modification with regulatory functions in all important cellular processes. Deubiquitinating enzymes (DUBs) including ubiquitin specific proteases (USPs) are cysteine proteases that catalyse the de-ubiquitination of protein substrates. As a result of their increasing implications in the etiology of numerous pathological conditions including cancer and immuno-oncology, DUBs have emerged as an attractive and promising target class for the development of first-in-class medicines with high therapeutic impact. However, despite 15 years of intense research DUBs have proven largely refractory to drug discovery efforts. Herein, we further describe the application of UbiPlex™, our purpose-built drug discovery platform for the identification and development of DUB inhibitors. In particular, we will highlight the versatility and robustness of UbiPlex™ by reporting the outcome of our focussed library screening campaign on multiple DUBs in parallel and by describing the de novo hit ID, orthogonal validation and hit optimization activities on two USPs of relevance to cancer. Multiple series of novel, highly potent (e.g. IC50 < 20 nM) and non-covalent inhibitors have been developed. Excellent selectivity profiles against a large panel of DUBs and other non-related enzymes (e.g. proteases) will be described. Further profiling indicated that these inhibitors are cell-permeable and exhibit potent target engagement in cells (e.g. EC50 < 30 nM). Finally, we will describe our progress towards the development of lead molecules with drug-like properties with the aim of rapidly establishing proof-of-concept studies in vivo. In summary, this work further exemplifies the broad tractability and druggability of the DUBome and reports the discovery and profiling of novel highly potent and selective inhibitors beyond USP7. These molecules may provide opportunities for the development of new therapeutics for cancer and associated disorders. Citation Format: Gerald Gavory, Colin O'Dowd, Oliver Barker, Christina Bell, Frank Burkamp, Stephanie Burton, Eamon Cassidy, Joana Costa, Anthony Dossang, Matt Helm, Ashling Henderson, Peter Hewitt, Caroline Hughes, Mary McFarland, Hugues Miel, Natalie Page, Lauren Proctor, Shane Rountree, Ewelina Rozycka, Steven Shepherd, Adam Treder, Mark Wappett, Steven Whitehead, Tim Harrison. Accessing the cancer DUBome with UbiPlex: A bespoke drug discovery platform for deubiquitinase enzymes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1935.