Ipamorelin (NNC 26-0161) is a synthetic pentapeptide growth hormone secretagogue, Aib-His-D-2Nal-D-Phe-Lys-NH2. It emerged from a chemistry programme based on growth hormone-releasing peptide-1 (GHRP-1) and was identified within a series of compounds lacking the central Ala-Trp dipeptide of GHRP-1. It is an agonist of the ghrelin receptor (growth hormone secretagogue receptor). Published work includes in vitro and in vivo pharmacology in rats and swine, pharmacokinetics in rats, rodent studies of bone growth, bone mineral content and adiposity, a rodent model of postoperative ileus, and a registered phase 2 trial.