DPP4 and type 1 diabetes mellitus: While insulin is the only therapy for T1DM, patients with T2DM rely primarily on one or more of a range of oral hypoglycemic drugs that include α–glucosidase inhibitors, metformin, sulfonylureas, meglitinides, thiazolidinediones, amylin analogs, SGLT-2 inhibitors, dipeptidyl peptidase-4 (DPP-4) inhibitors, GLP-1 mimetics, and incretin receptor dual agonists.