Accordingly, in the light of these findings and the success of the unimolecular polypharmacy [106] for the development of a novel generation of drugs (e.g., tirzepatide) to treat obesity and diabetes [107], the development of dual agonists that include FGF21 may provide an interesting tool for the treatment of metabolic diseases. This evidence concerns the gene FGF21 and obesity due to melanocortin 4 receptor deficiency.