Fz7-21 (Ac-LPSDDLEFWCHVMY-NH2) TFA is a potent peptide antagonist of FZD7 receptors , selectively binds to FZD7 CRD subclass and alters the conformation of the CRD and the architecture of its lipid-binding groove. The EC50 values are 58 and 34 nM for human and mouse FZD7 CRD, respectively. Fz7-21 TFA impairs the function of FZD7 in Wnt-β-catenin signalling and stem cell function in intestinal organoids.