Design of a Potent, Selective, and Brain-Penetrant Inhibitor of Wnt-Deactivating Enzyme Notum by Optimization of a Crystallographic Fragment Hit

Abstract

Notum is a carboxylesterase that suppresses Wnt signaling through deacylation of an essential palmitoleate group on Wnt proteins. There is a growing understanding of the role Notum plays in human diseases such as colorectal cancer and Alzheimer's disease, supporting the need to discover improved inhibitors, especially for use in models of neurodegeneration. Here, we have described the discovery and profile of <b>8l</b> (ARUK3001185) as a potent, selective, and brain-penetrant inhibitor of Notum activity suitable for oral dosing in rodent models of disease. Crystallographic fragment screening of the Diamond-SGC Poised Library for binding to Notum, supported by a biochemical enzyme assay to rank inhibition activity, identified <b>6a</b> and <b>6b</b> as a pair of outstanding hits. Fragment development of <b>6</b> delivered <b>8l</b> that restored Wnt signaling in the presence of Notum in a cell-based reporter assay. Assessment in pharmacology screens showed <b>8l</b> to be selective against serine hydrolases, kinases, and drug targets.