A new pharmacological class mimicking the actions of natural incretin hormones (principally glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP)), potentiating both meal-stimulated insulin and glucagon secretion (Drucker and Holst, 2023), arouses keen interest for the treatment of T2DM and obesity. The gene discussed is GLP1R; the disease is obesity due to melanocortin 4 receptor deficiency.