– NBI 31772 is a nonpeptide ligand that releases insulin-like growth factor-1 (IGF-1) from its binding protein (IGFBP; Kis = 1-24 nM for the six human subtypes of IGFBP).1,2 As the released IGF-1 is biologically active, NBI 31772 is used to assess the role of IGF-1 in cells and animals, including in neuron survival, skeletal muscle regeneration, and glucose homeostasis.3,4,5