Numerous studies using recombinant FGF21 proteins, FGFR-activating antibodies or long-acting FGF21 analogues have been performed to evaluate the relevance of such therapies to treat metabolic disorders in classical animal models [21,22,25,129,130,131,132,133,134,135,136], leading to promising results and no serious deleterious side effects. The gene discussed is FGF21; the disease is metabolic disease.