question: What are 'vildagliptin', 'sitagliptin', 'saxagliptin', 'alogliptin', 'linagliptin', and 'dutogliptin'?
answer: "Sitagliptin," "vildagliptin," "saxagliptin," "alogliptin," "linagliptin," and "dutogliptin" are dipeptidyl peptidase-4 (DPP-4) inhibitors.