Fz7-21 is a potent and selective peptide antagonist of Frizzled 7 (FZD 7) receptor which selectively binds to FZD7 cysteine rich domain (CRD) subclass at the cysteine rich region proximal to the lipid-binding groove. Binding alters the conformation of the CRD and the architecture of its lipid-binding groove and impairs Wnt/β-catenin signalling. Peptide Fz7-21 also shows cross-species binding to both the human and mouse FZD7 CRD.

The FZD7 receptor is enriched in intestinal stem cells which express the LGR5 receptor and plays a critical role in the cells self-renewal. FZD7 is essential for maintaining human embryonic stem cells in their undifferentiated state and is therefore an attractive pharmacological target for diseases associated with stem cell dysfunction and cancer biology.

FZD7 is also upregulated in subsets of colon, pancreatic and gastric tumours, therefore Fz7-21 serves as a pharmacological probe to explore further the function of FZD7 in stem cell and cancer biology.

Peptide is labelled with an N-terminal 5-carboxyfluorescein (5-FAM), a widely used green fluorescent tag.