Relamorelin (RM-131), a selective and potent growth hormone-releasing peptide/growth hormone secretagogue receptor (GHSR) agonist, is a potent growth hormone-releasing peptide mimetic with a high affinity for the GHS-1a receptor Relamorelin is a centrally permeable pentapeptide that increases growth hormone levels and accelerates gastric emptying and has potential for studying malignant disease.

GHS-1a:0.42 nM (Ki), native ghrelin:1.12 nM (Ki), native ghrelin:4.2 nM (EC50), GHS-1a receptor:0.71 nM (EC50)

Relamorelin (RM-131) exhibits approximately 3 times greater affinity for GHS-1a (Ki=0.42 nM) compared to native ghrelin (Ki=1.12 nM). In vitro, as evaluated by calcium mobilization, Relamorelin is 6 times more potent (EC50=0.71 nM) in activating the GHS-1a receptor than native ghrelin (EC50=4.2 nM)[2].

Continuous infusion of Relamorelin (RM-131) at doses ranging from 50 to 500 nmol/kg/day via subcutaneous administration for 5 days results in a reduction in the loss of body mass and fat mass. In rats, when administered at a dose of 500 nmol/kg/day through continuous infusion for 5 days, Relamorelin increases food intake and promotes weight gain[1].A single subcutaneous injection of RM-131 at doses ranging from 250 to 500 nmol/kg stimulates acute food intake in wild-type mice but not in mice lacking the growth hormone secretagogue receptor (GHR)[1].