Fibroblast growth factor 21 (FGF21) is a promising therapeutic agent for T2D/obesity, but the native FGF21 protein has poor pharmacokinetic properties, including a short half‐life and susceptibility to in vivo proteolytic degradation, which have hampered the pharmacological development of FGF21‐based drug products. This evidence concerns the gene FGF21 and obesity due to melanocortin 4 receptor deficiency.