SAG1.3-derived Frizzled-targeting small-molecule compounds.

Exaggerated Wingless/Int1 (WNT)-Frizzled (FZD) signaling contributes to pathologies, including fibrosis and different forms of cancer. Thus, targeting FZDs as WNT receptors for therapeutic purposes constitutes a promising intervention if the imminent risk of unwanted side effects caused by the involvement of WNT-FZD signaling in stem cell regulation and tissue homeostasis can be controlled. Here, we derivatize SAG1.3 (SMO agonist), which acts through FZD(6) as a partial agonist. Screening of SAG1.3 derivatives identified compound 11 that competed with BODIPY (boron-dipyrromethene)-cyclopamine binding at different FZDs and inhibited WNT-induced FZD dynamics and β-catenin signaling in human embryonic kidney 293 (HEK293) cells. Furthermore, compound 11 blocked WNT-3A-induced LGR5 gene expression in human primary hepatocyte spheroids and reduced the viability of RNF43-mutated but not RNF43-wildtype pancreatic cancer cells. Based on our data, we suggest that compound 11 acts on FZDs to limit WNT- and WNT-surrogate-induced receptor dynamics, providing a valid proof of concept for targeting FZDs with small-molecule compounds.