MC4R and obesity due to melanocortin 4 receptor deficiency: Since then, several oral small molecules and injectable peptide agonists of MC4R have been clinically evaluated for treating obesity, including oral small molecule MK-0493 (Merck) [211] and peptide agonists LY2112688 (Eli Lilly) [138], MC4-NN-0453 (Novo Nordisk) [212], AZD2820 (Astra Zeneca) [213], and setmelanotide (Rhythm Pharmaceuticals) [214,215,216,217,218].