Linagliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor discovered by Boehringer Ingelheim and being developed as an oral once-daily tablet for the treatment of Type 2 diabetes. Linagliptin was first approved by FDA in 2011 under the trade name Tradjenta as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus. Linagliptin binds to DPP-4 (an enzyme that degrades the incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP)) in a reversible manner and thus increases the concentrations of incretin hormones. Linagliptin glucose dependently increases insulin secretion and lowers glucagon secretion, thus resulting in better regulation of glucose homeostasis. Linagliptin binds selectively to DPP-4, and selectively inhibits DPP-4 but not DPP-8 or DPP-9 activity in vitro at concentrations approximating therapeutic exposures.