WIN 66,306 is a cyclic heptapeptide antagonist of neurokinin-1 (NK1) and NK2 receptors originally isolated from A. flavipes.1 It binds to NK1 and NK2 receptors (Kis = 8 and 3.8 µM, respectively, for the human receptors) and inhibits contractions induced by substance P in isolated guinea pig ileum in a concentration-dependent manner.
1.Barrow, C.J., Doleman, M.S., Bobko, M.A., et al.Structure determination, pharmacological evaluation, and structure-activity studies of a new cyclic peptide substance P antagonist containing the new amino acid 3-prenyl-β-hydroxytyrosine, isolated from Aspergillus flavipesJ. Med. Chem.37(3)356-363(1994)