Linagliptin (1, Figure 1), a highly potent, selective, long-acting and orally bioavailable DPP-4 inhibitor for the treatment of type 2 diabetes, is chemically known as (R)-8-(3-aminopiperidin-1-yl)-7-(but-2-yn-1-yl)-3-methyl-1-((4-methylquinazolin-2-yl)methyl)-1H-purine-2,6(3H,7H)-dione [3]. This evidence concerns the gene DPP4 and type 2 diabetes mellitus.