Presently, there are three important DPP-4 inhibitors, namely Sitagliptin, Vidagliptin, and Saxagliptin, that are commercially available in the international market and used for the treatment of type-2 diabetes and Alzheimer’s disease (Type-2 diabetes is one of the major risk factors associated with Alzheimer’s disease). The gene discussed is DPP4; the disease is type 2 diabetes mellitus.