DPP4 and type 2 diabetes mellitus: Although the FDA has not yet approved some other gliptins (e.g., vildagliptin, teneligliptin, trelagliptin), at least eight additional DPP-4 inhibitors have received approval from different regulatory agencies worldwide and are widely prescribed for T2DM treatment, coinciding with ongoing efforts yielding at least ten novel DPP-4 inhibitors in clinical development [5].