PG-931, an analog of SHU 9119 (HY-P0227), is a potent melanocortin 4 (MC4) receptor (IC50=0.58 nM) agonist and is more selective than for the hMC3R (IC50=55 nM) or the hMC5R (IC50=2.4 nM). PG-931 can reverse haemorrhagic shock and prevent multiple organ damage in vivo.