Relamorelin (RM-131) acetate is a pentapeptide ghrelin analog that acts as a selective agonist for the ghrelin/growth hormone secretagogue receptor (GHSR). It exhibits a high affinity for the GHS-1a receptor, with a Ki value of 0.42 nM. Notably, Relamorelin acetate can cross the blood-brain barrier and target the central nervous system. This compound effectively increases growth hormone levels and promotes faster gastric emptying. Due to these properties, Relamorelin acetate holds promise for its potential applications in research related to cachexia, gastroparesis, and gastric/intestinal dysmobility disorders [4] [5].

Relamorelin acetate, also known as RM-131, exhibits approximately threefold higher affinity for the GHS-1a receptor (K i = 0.42 nM) compared to native ghrelin (K i = 1.12 nM). Furthermore, it is sixfold more potent (EC 50 = 0.71 nM) in activating the GHS-1a receptor than native ghrelin (EC 50 = 4.2 nM), as demonstrated by in vitro calcium mobilization assays[1].

Relamorelin (RM-131; 50-500 nmol/kg/day; subcutaneously [s.c.] via continuous infusion for 5 days) acetate effectively reduces the loss of both body and fat mass. At a dosage of 500 nmol/kg/day administered subcutaneously through continuous infusion over a 5-day period, relamorelin acetate notably enhances food consumption and promotes weight gain in rats[1]. Furthermore, RM-131 (250-500 nmol/kg; single s.c. dose) acetate has been demonstrated to acutely increase food intake in wild-type mice, but this effect is not observed in mice lacking growth hormone secretagogue receptor (GHR) [2]. This research utilized F344/NTacfBR male rats implanted with tumors as the animal model[1], with dosages administered at 50 and 500 nmol/kg/day, subcutaneously, at a continuous infusion rate of 0.5 μL/h for 5 days. The outcomes revealed a significant increment in food intake (comparing tumor/saline at 41.4g with tumor/BIM-28131 at 72.5g) and an increase in weight (from tumor/saline -10.3% to tumor/BIM-28131 +19.5%).