Screening of a Custom-Designed Acid Fragment Library Identifies 1-Phenylpyrroles and 1-Phenylpyrrolidines as Inhibitors of Notum Carboxylesterase Activity

Abstract

The Wnt family of proteins are secreted signaling proteins that play key roles in regulating cellular functions. Recently, carboxylesterase Notum was shown to act as a negative regulator of Wnt signaling by mediating the removal of an essential palmitoleate. Here we disclose two new chemical scaffolds that inhibit Notum enzymatic activity. Our approach was to create a fragment library of 250 acids for screening against Notum in a biochemical assay followed by structure determination by X-ray crystallography. Twenty fragments were identified as hits for Notum inhibition, and 14 of these fragments were shown to bind in the palmitoleate pocket of Notum. Optimization of 1-phenylpyrrole <b>20</b>, guided by structure-based drug design, identified <b>20z</b> as the most potent compound from this series. Similarly, the optimization of 1-phenylpyrrolidine <b>8</b> gave acid <b>26</b>. This work demonstrates that inhibition of Notum activity can be achieved by small, drug-like molecules possessing favorable <i>in vitro</i> ADME profiles.