<prompt> Answer this question truthfullyWhat is the class of drugs that includes Sitagliptin, Saxagliptin, Linagliptin, and Alogliptin, and what is their mechanism of action?  <response>: <reason> Sitagliptin, Saxagliptin, Linagliptin, and Alogliptin belong to the class of drugs called DPP-4 inhibitors, which work by inhibiting the enzyme DPP-4 to increase insulin secretion and lower blood glucose levels in patients with type 2 diabetes. 