5-Phenyl-1,3,4-oxadiazol-2(3 H)-ones Are Potent Inhibitors of Notum Carboxylesterase Activity Identified by the Optimization of a Crystallographic Fragment Screening Hit

J Med Chem. 2020 Nov 12;63(21):12942-12956. doi: 10.1021/acs.jmedchem.0c01391. Epub 2020 Oct 30.


Carboxylesterase Notum is a negative regulator of the Wnt signaling pathway. There is an emerging understanding of the role Notum plays in disease, supporting the need to discover new small-molecule inhibitors. A crystallographic X-ray fragment screen was performed, which identified fragment hit 1,2,3-triazole 7 as an attractive starting point for a structure-based drug design hit-to-lead program. Optimization of 7 identified oxadiazol-2-one 23dd as a preferred example with properties consistent with drug-like chemical space. Screening 23dd in a cell-based TCF/LEF reporter gene assay restored the activation of Wnt signaling in the presence of Notum. Mouse pharmacokinetic studies with oral administration of 23dd demonstrated good plasma exposure and partial blood-brain barrier penetration. Significant progress was made in developing fragment hit 7 into lead 23dd (>600-fold increase in activity), making it suitable as a new chemical tool for exploring the role of Notum-mediated regulation of Wnt signaling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Animals
  • Binding Sites
  • Blood-Brain Barrier / drug effects
  • Blood-Brain Barrier / metabolism
  • Crystallography, X-Ray
  • Drug Design
  • Enzyme Inhibitors / chemistry*
  • Enzyme Inhibitors / pharmacokinetics
  • Enzyme Inhibitors / pharmacology
  • Esterases / antagonists & inhibitors*
  • Esterases / metabolism
  • Half-Life
  • Humans
  • Inhibitory Concentration 50
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Microsomes, Liver / metabolism
  • Molecular Dynamics Simulation
  • Oxadiazoles / chemistry*
  • Oxadiazoles / pharmacokinetics
  • Oxadiazoles / pharmacology
  • Structure-Activity Relationship
  • Wnt Signaling Pathway / drug effects


  • Enzyme Inhibitors
  • Oxadiazoles
  • Esterases
  • Notum protein, human