For example, metformin and dipeptidyl peptidase IV (DPP4) inhibitors, such as vildagliptin and alogliptin, which is a well-known anti-diabetic drug for type 2 diabetes mellitus (T2DM), had no effect on blood glucose in the T1DM animal model [52–54]. The gene discussed is DPP4; the disease is type 1 diabetes mellitus.