In T2DM, the first-line therapy is metformin; second-line therapies include dipeptidyl peptidase-4 (DPP-4) inhibitors, glucagon-like peptide-1 (GLP-1) receptor agonists, sodium-glucose transport protein 2 (SGLT2) inhibitors, insulin secretagogues, and insulin [6]. The gene discussed is GCG; the disease is type 2 diabetes mellitus.