DPP4 cleavage of the incretin peptides, glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP), have led to the development of DPP4 selective inhibitors as a successful type 2 diabetes mellitus (T2DM) therapy [4,15,16,17,18]. The gene discussed is GCG; the disease is type 2 diabetes mellitus.