Structural Analysis and Development of Notum Fragment Screening Hits

The Wnt signaling
suppressor Notum is a promising target for osteoporosis,
Alzheimer’s disease, and colorectal cancers. To develop novel
Notum inhibitors, we used an X-ray crystallographic fragment screen
with the Diamond-SGC Poised Library (DSPL) and identified 59 fragment
hits from the analysis of 768 data sets. Fifty-eight of the hits were
found bound at the enzyme catalytic pocket with potencies ranging
from 0.5 to >1000 μM. Analysis of the fragments’ diverse
binding modes, enzymatic inhibitory activities, and chemical properties
led to the selection of six hits for optimization, and five of these
resulted in improved Notum inhibitory potencies. One hit, 1-phenyl-1,2,3-triazole 7, and its related cluster members,
have shown promising lead-like properties. These became the focus
of our fragment development activities, resulting in compound 7d with IC50 0.0067 μM. The large number
of Notum fragment structures and their initial optimization provided
an important basis for further Notum inhibitor development.