Acetyl-(D-Arg10,Cys11,D-Phe14,Cys17)-β-MSH (10-17) amide, a selective and highly potent β-MSH-derived melanocortin-4 receptor (MC-4R) agonist, has sub-nanomolar potency with the binding affinities of 0.55±0.06, 16.78±1.53, 56.79±4.66 and <500 nM for human MC-4R, MC-1R, MC-3R and MC-5R, respectively.