A peptide antagonist of MC1R, MC3R, MC4R, and MC5R (IC50s = 19.5, 0.59, 13.58, and 8.07 nM, respectively, for the human receptors); an antagonist of dog MC1R, MC3R, MC4R, and MC5R receptors (IC50s = 53.64, 1.46, 7.14, and 11.22 nM, respectively); increases food intake and body weight in a rat model of LPS-induced cachexia at 10 mg/kg; increases body weight, muscle mass, blood urea nitrogen levels, and the mean heart rate in dogs with cachexia at 0.75 mg/kg per day