MC4R and obesity due to melanocortin 4 receptor deficiency: Oral (per os) administration of this PC promoted the restoration of the anorexic effect of the MC4R agonist, melanotan II (MTII), in mice harboring the obesity-causing mutant form R165W-hMC4R but not in the loxP-flanked transcriptional blocking (loxTB) MC4R-null mice.