(D-Arg1,D-Phe5,D-Trp79,Leu11)-Substance P initially described as a low potency ghrelin receptor antagonist has surprisingly been found to be a full inverse agonist (EC50 = 5.2 nM). In COS-7 cells transiently transfected with the ghrelin receptor the substance P analog rPKPfQwFwLL decreased the constitutive signaling down to levels observed in untransfected cells. Assuming that constitutive signaling of the ghrelin receptor is of physiological relevance in the regulation of appetite control, inverse agonists of the ghrelin receptor could be interesting for the treatment of obesity. So, Asakawa et al. found that peripherally administered H-6395 decreased food intake in lean mice, in mice with diet induced obesity, and in ob/ob obese mice.